Water Quality Analysis of the Blackstone River
Under Wet and Dry Weather Conditions
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Blackstone River Initiative:
Water Quality Analysis of the Blackstone River Under
Wet and Dry Weather Conditions
May 2001
by
Raymond M. Wright1 Ph.D., P.E., Peter M. Nolan2, David Pincumbe3, Elaine
Hartman4, and Oran J. Viator1
1 Civil and Environmental Engineering, University of Rhode Island,
Kingston, RI;2 Office of Environmental Measurement and Evaluation, EPA
New England Regional Laboratory, Lexington, MA;3 Office of Ecosystem
Protection, EPA Region I, Boston, MA;4 Massachusetts Department of
Environmental Protection, Worcester, MA
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Foreword
The Blackstone River is a valuable aquatic resource located in south central New England in the
states of Massachusetts and Rhode Island. The river basin has experienced a long history of
pollution dating back to the industrial revolution. Numerous water quality studies have been
conducted over the years by each state for a variety of flow and weather conditions. While much
has been learned from these studies, they were developed independently for their respective state
river segments. This has constrained the integration and use of the data for a comprehensive and
up-to-date analysis of the extent and nature of pollution and contamination within the watershed.
The Blackstone River Initiative (BRI) was organized by EPA at the request of the commissioners
of the Massachusetts Department of Environmental Protection and Rhode Island Department of
Environmental Management in 1990. The BRI was an inter-agency, inter-state project to monitor
and model water and sediment quality in the Blackstone River.
A draft of this report was first published in April 1996 and underwent a regional review by EPA.
In November 1997, the Region IU. S. EPA Administrator requested the EPA Science Advisory
Board (SAB) consider reviewing the BRI. The BRI incorporated the comments from the first
review and published a revised BRI report in February 1998. On March 24-25, 1998 the
Ecological Processes and Effects Committee (EPEC) of the EPA SAB and other EPA officials
met in Boston, MA to conduct a two day comprehensive review of the report.
Although the SAB rarely conducts regional reviews, the BRI presented an opportunity for the
Committee to assist a Regional office with peer review and to encourage Regional adoption of
integrated watershed assessment approaches. The Committee commended Region I and the other
BRI participants for initiating the study. Despite the limitations noted in the SAB report, the
Committee believes that the BRI study represents a significant advance for the Agency as an
initial attempt to integrate multi-agency, multi-scale, and multi-environmental stressor
considerations. They also noted that the contribution of volunteer and in-kind services was
impressive, and the BRI's accomplishments far surpass the dollars expended by the EPA.
The SAB review (EPA-SAB-EPEC-98-011) can be found on the U.S. EPA web page at
http://www.epa.gov/sciencel/fiscal98.htm. The response of the BRI authors to the SAB review
is also at this location. Many of the SAB's comments, questions and requests have been
incorporated and/or discussed in this final report (BRI 2001).
Raymond M. Wright1 Ph.D., P.E., Peter M. Nolan2, David Pincumbe3, Elaine Hartman4, and
Oran J. Viator1
1 Civil and Environmental Engineering, University of Rhode Island, Kingston, RI;2 Office of
Environmental Measurement and Evaluation, EPA New England Regional Laboratory,
Lexington, MA;3 Office of Ecosystem Protection, EPA Region I, Boston, MA;4 Massachusetts
Department of Environmental Protection, Worcester, MA
i
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Acknowledgment
The valuable contributions from the following individuals are gratefully acknowledged.
Michael Fanning, Rajat Roy Chaudhury, Sreenivas Makam, Anantha Karanam, Shahriar Mahbub
Alam, Srinivas Cheela, Qianqian Li, Mark Yeboah and Holly Olsen, Civil and Environmental
Engineering, University of Rhode Island.
Alan Cooperman, Robert Maietta, Gerald Szal, and Hilary Snook, Massachusetts Department of
Environmental Protection, Office of Watershed Management.
Celeste Barr, Arthur Clark, Ann Jefferies, Jack Paar, Diane Switzer, Patti Tyler, U.S.
Environmental Protection Agency, Office of Environmental Measurement and Evaluation,
Region I.
Gerald Potamis, U. S. Environmental Protection Agency, Office of Ecosystem Protection, Region
I.
Angelo Liberti, Charlene Newman and Connie Carey, Rhode Island Department of
Environmental Management.
A special note of gratitude goes to the many dedicated EPA, MADEP and URI personnel who
assisted with the dry and wet weather field collections and sample analyses.
The cooperation of the following industrial and municipal facilities along the river is gratefully
acknowledged: Massachusetts - Douglas WWTF, Grafton WWTF, Millbury WWTF,
Norihbridge WWTF, UBWPAD, Upton WWTF, Uxbridge WWTF, City of Worcester CSO
facility, Guilford Industries, New England Plating and Worcester Finishing and Spinning. Rhode
Island - Woonsocket WWTF, GTE, and Okonite. A special thanks to Adel Banoub for the use of
the Woonsocket WWTF for the wet and dry weather field laboratory.
Funding for this project was provided by the U.S. Environmental Protection Agency, Region I
through Section 104 (b) (3) - Water Quality and Wetlands Program and Section 319 - Nonpoint
Source Program of the Clean Water Act.
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TABLE OF CONTENTS
PAGE
Foreword i
Acknowledgments ii
TABLE OF CONTENTS iii
LIST OF FIGURES viii
LIST OF TABLES xvi
EXECUTIVE SUMMARY ESI
1.0 INTRODUCTION 1-1
1.1 The Blackstone River Study Area 1-1
1.2 Blackstone River Water Quality Issues: Dry and Wet Weather 1-3
1.3 Objectives 1-5
1.4 Program and Report Organization 1-5
2.0 PROGRAM DESCRIPTION 2-1
2.1 Field Program 2-1
2.1.1 Watershed Description 2-1
2.1.2 Water Quality Station Selection 2-1
2.1.3 Water Quality Sampling Frequency 2-2
2.1.4 Sample Collection and Handling 2-8
2.1.5 Flow Monitoring 2-9
2.1.6 Rainfall Monitoring 2-12
2.1.7 Storm Selection 2-13
2.2 Water Quality Computer Modeling 2-15
2.2.1 Data Collection 2-16
2.2.2 Model Construction 2-17
2.2.3 Model Application 2-17
2.3 Chemistry and Toxicity 2-18
2.3.1 Water Column Chemistry - Methods and Methodologies 2-18
2.3.2 Chemistry Quality Control and Quality Assurance 2-23
2.3.3 Toxicity Methods and Methodologies 2-24
3.0 SYSTEM HYDROLOGY AND HYDRAULICS 3-1
3.1 Dry Weather 3-1
3.2 Wet Weather 3-1
3.2.1 Rainfall Characteristics 3-1
3.2.1.1 Rainfall Network 3-1
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3.2.1.2 Rainfall Characteristics 3-4
3.2.1.3 Total Rainfall 3-4
3.2.2 System Flows 3-16
3.3 Hydraulic Structures or Controls 3-31
3.3.1 Dams and Impoundments 3-37
3.3.1.1 Fisherville Pond 3-37
3.3.1.2 Rice City Pond 3-39
3.3.1.3 Rochdale Impoundment 3-39
3.3.2 Hydropower Stations 3-42
3.3.3 Blackstone River Canal 3-43
DRY WEATHER WATER QUALITY INTERPRETATION 4-1
4.1 Dissolved Oxygen Dynamics 4-1
4.1.1 Dissolved Oxygen, Chlorophyll a, Chloride, pH, BODj 4-1
4.1.2 Nutrients ! 4-3
4.1.3 Historic Trends Related to Dissolved Oxygen 4-11
4.2 Total Suspended Solids 4-33
4.3 Total and Dissolved Trace Metals 4-38
4.3.1 Cadmium 4-38
4.3.2 Chromium 4-42
4.3.3 Copper 4-49
4.3.4 Lead 4-58
4.3.5 Nickel 4-58
4.4 Water Quality Criteria-Fecal Coliform 4-65
4.5 Water Quality Criteria-Toxicity 4-65
4.5.1 Acute and Chronic Criteria Violations 4-65
4.5.2 Actual Toxicity 4-76
4.5.2.1 Chronic Toxicity Testing of Ambient Blackstone River
Water 4-76
4.5.2.2 Discussion of Water Quality Criteria and Actual Toxicity ... 4-80
4.5.2.3 Blackstone River Whole Sediment Toxicity Tests 4-82
4.5.2.4 Blackstone River Sediment Pore Water Analysis 4-87
4.5.2.5 Effluent Toxicity Testing 4-87
4.5.2.6 Discussion of Blackstone River Sediment and Pore
Water Chemistry and Toxicity 4-90
4.6 Speciality Studies 4-107
4.6.1 Fish Toxics Monitoring 4-107
4.6.1.1 Field Methods and Results 4-108
4.6.1.2 Laboratory Methods and Results 4-109
4.6.1.3 Discussion 4-114
4.6.1.4 Conclusions 4-119
4.6.2 Benthic Macroinvertebrate Community Analyses at Select Stations . 4-120
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4.6.2.1 Design Overview 4-120
4.6.2.2 Methods and Station Locations 4-121
4.6.2.3 Results and Discussion 4-133
4.7 Dry Weather Data Summary and Conclusions 4-142
DRY WEATHER DISSOLVED OXYGEN MODELING SUMMARY 5-1
5.1 General Dissolved Oxygen Model Considerations 5-1
5.2 Blackstone River Model Representation 5-2
5.3 Flow Profile Development and Validation 5-7
5.4 Dissolved Oxygen Model Calibration 5-22
5.4.1 General Considerations 5-22
5.4.2 Incremental Inflow Concentrations 5-28
5.4.3 Atmospheric Reaeration Rate (K2) 5-28
5.4.4 BOD5 Simulations 5-29
5.4.5 Ammonia as Nitrogen 5-33
5.4.6 Sediment Oxygen Demand (SOD) 5-41
5.4.7 Algal Productivity 5-45
5.4.8 Final Dissolved Oxygen Profiles 5-58
5.5 Additional Model Validation 5-66
5.5.1 Massachusetts Waste Load Allocation (MA WLA) 5-66
5.5.2 Ecology and Environment (1988) 5-66
5.6 Sensitivity Analysis 5-73
5.6.1 Coefficient to Adjust Five-Day BOD to Ultimate BOD 5-73
5.6.2 Model Sensitivity for Selected Algal Coefficients Discussed in the
SAB Review 5-79
5.6.2.1 Algal Settling Velocity 5-79
5.6.2.2 Non-Algal Light Extinction Coefficient 5-88
5.6.2.3 Nutrient Half-Saturation Constants 5-93
5.6.2.4 Remineralization Rate of Organic Phosphorus (Organic
P Decay) 5-98
5.6.2.5 Organic Phosphorus Settling Rate 5-103
5.6.2.6 Chlorophyll a to Algal Biomass Ratio 5-108
5.6.2.7 Complete Algal Sensitivity Run 5-113
5.6.3 Model Sensitivity to the Sediment Oxygen Demand 5-127
5.7 Model Application with 7Q10 Flows 5-135
5.8 Dissolved Oxygen Modeling, Summary, Conclusions and
Recommendations 5-138
DRY WEATHER TRACE METAL MODELING SUMMARY 6-1
6.1 General Trace Metal Fate and Transport Considerations 6-1
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6.1.1 General Factors Governing the Distribution of Metals and
Total Suspended Solids in the Aquatic Environment 6-2
6.2 Trace Metal Model Description and Set-Up 6-4
6.3 Net Sediment Transport Coefficient 6-6
6.3.1 Model Simulations for Suspended Solids 6-11
6.4 Partition Coefficient of Metals 6-17
6.4.1 Development of Partition Coefficient/TSS Relationships 6-18
6.5 Calibration and Validation of Metals 6-20
6.5.1 Cadmium 6-32
6.5.2 Chromium 6-36
6.5.3 Copper 6-36
6.5.4 Lead 6-36
6.5.5 Nickel , 6-46
6.6 Trace Metal Modeling Summary and Conclusions 6-46
7.0 WET WEATHER WATER QUALITY INTERPRETATION 7-1
7.1 Water Quality Concentration 7-1
7.1.1 Comparison Between Dry and Wet Weather Concentrations 7-1
7.1.1.1 Nutrients 7-1
7.1.1.2 Trace Metals 7-9
7.1.2 Wet Weather Event Mean Concentrations (EMCs) 7-15
7.1.2.1 Nutrients 7-15
7.1.2.2 Conventional 7-15
7.1.2.3 Trace Metals 7-24
7.1.2.4 EMC Comparison With Other Rivers 7-24
7.1.3 Hardness, DO, Temperature, pH, Chloride and Sodium 7-26
7.2 Water Quality Criteria Violation 7-26
7.2.1 Fecal Coliform 7-26
7.2.2 Acute and Chronic Trace Metal Criteria 7-30
7.2.2.1 Lead 7-30
7.2.2.2 Copper 7-30
7.2.2.3 Cadmium 7-38
7.2.2.4 Chromium and Nickel 7-38
7.3 Wet Weather Toxicity 7-38
7.3.1 Toxicity Results 7-38
7.4 Wet Weather Pollutant Loadings 7-41
7.4.1 Mass Loading Estimates 7-42
7.4.2 Comparison of Wet and Total Loadings 7-42
7.4.2.1 Trace Metals 7-42
7.4.2.2 Conventional (TSS/VSS, BODs and FC/EC) 7-46
7.4.2.3 Nutrients 7-46
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7.4.3 Net Gain and Loss Per Reach 7-46
7.4.4 Major Point Sources vs Other Sources in the River 7-47
7.4.5 System Ranking 7-47
7.4.5.1 Nutrients 7-52 •
7.4.5.2 Conventional (TSS, BOD5 and FC) 7-52
7.4.5.3 Metals (Pb, Cu, Ni, Cd, Cr, Zn) 7-59
7.4.6 Comparison Between Wet Weather and Dry Weather Rankings 7-59
7.4.7 Comparison of Load for Different River Systems 7-62
7.5 Characterization of Nonpoint Loads - Runoff vs Resuspension 7-65
7.5.1 Previous Research 7-65
7.5.2 Blackstone River Application 7-67
7.6 Annual Loading Rates 7-68
7.6.1 Dry Weather Estimates 7-68
7.6.2 Wet Weather Estimates 7-72
7.6.3 Determination of Annual Load 7-77
7.6.4 Load at State Line and End of River 7-77
7.7 Summary of Wet Weather Interpretation 7-82
8.0 APPLICATION OF THE BLACKSTONE RIVER INITIATIVE 8-1
8.1 Rice City Pond (RCP) Study Site and Historical Background 8-1
8.2 RCPS Flow Analysis 8-4
8.3 RCPS Water Quality and Sediment Results 8-5
8.4 RCPS Remedial Options 8-7
9.0 SUMMARY 9-1
10.0 REFERENCES 10-1
APPENDIX
Dry Weather Water Quality Data
Wet Weather Water Quality Data
QUAL2E Directory and Input and Output Files
Pawtoxic Directory and Input and Output Files
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LIST OF FIGURES
Figure 1.1 Blackstone River Water Quality Initiative 1-7
Figure 2.1 Sampling Station Location 2-4
Figure 2.2 Blackstone River Watershed Sub-basins (MASS DEP/GIS Office) 2-5
Figure 2.3 Modeling Dissolved Oxygen on the Blackstone River 2-19
Figure 2.4 Modeling Trace Metals on the Blackstone River 2-20
Figure 3.1 Raingage Locations for the Blackstone River Wet Weather Studies 3-3
Figure 3.2 Rainfall For Blackstone River Wet Weather Studies 3-6
Figure 3.3 Rainfall Watersheds Distribution - Storm I 3-7
Figure 3.4 Rainfall Watersheds Distribution - Storm 2 3-8
Figure 3.5 Rainfall Watersheds Distribution - Storm 3 3-9
Figure 3.6 Thiessen Polygons - Storm 1 3-10
Figure 3.7 Thiessen Polygons - Storm 2 3-11
Figure 3.8 Thiessen Polygons - Storm 3 3-12
Figure 3.9 Contour Plot of Flow for Storm 1, September 22-24, 1992 3-25
Figure 3.10 Contour Plot of Flow for Storm 2, November 2-5, 1992 3-26
Figure 3.11 Contour Plot of Flow for Storm 3, October 12-16,1993 3-27
Figure 3.12 Hydrograph Comparison - Storm 1 3-28
Figure 3.13 Hydrograph Comparison - Storm 2 3-29
Figure 3.14 Hydrograph Comparison - Storm 3 3-30
Figure 3.15 Hydrograph Comparison - Headwaters 3-32
Figure 3.16 Hydrograph Comparison - State Line 3-33
Figure 3.17 Hydrograph Comparison-Mouth of River 3-34
Figure 3.18 Example of Concave Base Flow Separation 3-35
Figure 3.19 Aerial Photograph of Fisherville Pond 3-38
Figure 3.20 Aerial Photograph of Rice City Pond 3-40
Figure 4.1 Dissolved Oxygen July 10-11,1991 Survey 4-4
Figure 4.2 Dissolved Oxygen August 14-15, 1991 Survey 4-5
Figure 4.3 Dissolved Oxygen October 2-3,1991 Survey 4-6
Figure 4.4 Ammonia Concentration and Mass Loading Profiles 4-7
Figure 4.5 Point Source Versus Upstream and Downstream River Stations for
Ammonia 4-8
Figure 4.6 Comparison of the Two Major Point Sources Versus the Other Sources
for Ammonia 4-10
Figure 4.7 Nitrate as N Concentration and Mass Loading Profiles 4-12
Figure 4.8 Point Source Versus Upstream and Downstream River Stations for
Nitrate 4-13
Figure 4.9 Comparison of the Two Major Point Sources Versus the Other Sources
for Nitrate 4-15
Figure 4.10 Orthophosphate as P Concentration and Mass Loading Profiles 4-16
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Figure 4.11 Point Source Versus Upstream and Downstream River Stations for
Orthophosphate 4-17
Figure 4.12 Comparison of the Two Major Point Sources Versus the Other Sources for
Orthophosphate 4-19
Figure 4.13 Minimum DO Values for 1970, 1973, 1980, and 1991 Surveys 4-21
Figure 4.14 Average DO Values for 1970,1973,1980, and 1991 Surveys 4-22
Figure 4.15 BODs Mass Loading from 1973 to 1991 for UBWPAD 4-23
Figure 4.16 Ammonia Mass Loading from 1973 to 1991 for UBWPAD 4-24
Figure 4.17 Nitrate Mass Loading from 1973 to 1991 for UBWPAD 4-25
Figure 4.18 Average BODs Values for 1970,1973,1980, and 1991 Surveys 4-26
Figure 4.19 Average Ammonia Values for 1970,1973,1980, and 1991 Surveys 4-27
Figure 4.20 Average Nitrate Values for 1970,1973,1980, and 1991 Surveys 4-28
Figure 4.21 Ammonia and Nitrate Mass Loading for 1973 and 1991 Surveys 4-30
Figure 4.22 Blackstone River DO Deficit for 1973,1988, and 1991 4-32
Figure 4.23 History of DO Violations from 1969 to 1980 4-34
Figure 4.24 Total Suspended Solids (TSS) Concentration and Mass Loading Profiles ... 4-35
Figure 4.25 Point Source Versus Upstream and Downstream River Stations for TSS 4-36
Figure 4.26 Comparison of the Two Major Point Sources Versus the Other Sources
for TSS 4-39
Figure 4.27 Total Cadmium Concentration and Mass Loading Profiles 4-40
Figure 4.28 Dissolved Cadmium Concentration and Mass Loading Profiles 4-41
Figure 4.29 Point Source Versus Upstream and Downstream River Stations for Total
Cadmium 4-43
Figure 4.30 Total Cadmium Concentration - July 10-11,1991 Survey 4-45
Figure 4.31 Comparison of the Two Major Point Sources Versus the Other Sources
for Total Cadmium 4-46
Figure 4.32 Total Chromium Concentration and Mass Loading Profiles 4-47
Figure 4.33 Dissolved Chromium Concentration and Mass Loading Profiles 4-48
Figure 4.34 Point Source Versus Upstream and Downstream River Stations for Total
Chromium 4-50
Figure 4.35 Total Chromium Concentration - July 10-11,1991 Survey 4-52
Figure 4.36 Comparison of the Two Major Point Sources Versus the Other Sources
for Total Chromium 4-53
Figure 4.37 Total Copper Concentration and Mass Loading Profiles 4-54
Figure 4.38 Dissolved Copper Concentration and Mass Loading Profiles 4-55
Figure 4.39 Point Source Versus Upstream and Downstream River Stations for Total
Copper 4-56
Figure 4.40 Comparison of the Two Major Point Sources Versus the Other Sources
• for Total Copper- 4-59
Figure 4.41 Total Lead Concentration and Mass Loading Profiles 4-60
Figure 4.42 Dissolved Lead Concentration and Mass Loading Profiles 4-61
Figure 4.43 Point Source Versus Upstream and Downstream River Stations for Total
Lead 4-62
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Figure 4.44 Comparison of the Two Major Point Sources Versus the Other Sources
for Total Lead 4-64
Figure 4.45 Total Nickel Concentration and Mass Loading Profiles 4-66
Figure 4.46 Dissolved Nickel Concentration and Mass Loading Profiles 4-67
Figure 4.47 Point Source Versus Upstream and Downstream River Stations for Total
Nickel 4-68
Figure 4.48 Comparison of the Two Major Point Sources Versus the Other Sources
for Total Nickel 4-70
Figure 4.49 Acute Criteria Violations for Total Cadmium July 10-11,1991 Survey 4-75
Figure 4.50 Acute Criteria Violations for Total Lead July 10-11,1991 Survey 4-77
Figure 4.51 Results of the Whole Sediment Toxicity Test for Chironomus tentans 4-84
Figure 4.52 Results of the Whole Sediment Toxicity Test for Hyallela azteca 4-85
Figure 4.53 Cadmium in Blackstone River Sediments 4-91
Figure 4.54 Chromium in Blackstone River Sediments 4-92
Figure 4.55 Copper in Blackstone River Sediments 4-93
Figure 4.56 Nickel in Blackstone River Sediments 4-94
Figure 4.57 Lead in Blackstone River Sediments 4-95
Figure 4.58 Zinc in Blackstone River Sediments 4-96
Figure 4.59 Total Sediment Metals and Chironomus and Hyallela Mortality 4-97
Figure 4.60 Polynuclear Aromatic Hydrocarbons and Chironomus and C. dubia
Mortality 4-99
Figure 4.61 Total Aluminum in Sediment Pore Water and C. dubia and Fathead
Minnow Mortality 4-100
Figure 4.62 Total Cadmium in Sediment Pore Water and C. dubia and Fathead
Minnow Mortality 4-101
Figure 4.63 Total Chromium in Sediment Pore Water and C. dubia and Fathead
Minnow Mortality 4-102
Figure 4.64 Total Copper in Sediment Pore Water and C. dubia and Fathead
Minnow Mortality 4-103
Figure 4.65 Total Nickel in Sediment Pore Water and C. dubia and Fathead
Minnow Mortality 4-104
Figure 4.66 Total Lead in Sediment Pore Water and C. dubia and Fathead
Minnow Mortality 4-105
Figure 4.67 Total Zinc in Sediment Pore Water and C. dubia and Fathead
Minnow Mortality 4-106
Figure 4.68 Taxa Richness 4-125
Figure 4.69 Evenness 4-126
Figure 4.70 Shannon-Weaver Index 4-127
Figure 4.71 Biotic Index 4-128
Figure 4.72 Percent Scrapers 4-129
Figure 4.73 Percent Collector-Filterers 4-130
Figure 4.74 EPT Index 4-131
Figure 4.75 Mean Percent Composition 4-132
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Figure 5.1 Network of Computational Elements and Reaches 5-5
Figure 5.2 Flow Profiles for the 1991 Dry Weather Surveys 5-14
Figure 5.3 Flow Profile Validation for July 10-11,1991 5-16
Figure 5.4 Flow Profile Validation for August 14-15,1991 5-17
Figure 5.5 Flow Profile Validation for October 2-3,1991 5-18
Figure 5.6 Flows from the Woonsocket USGS Gage, July 10-11,1991 5-19
Figure 5.7 Flows from the Woonsocket USGS Gage, August 14-15,1991 5-20
Figure 5.8 Observed (Ries 1990) and Predicted Flows at Lonsdale Avenue,
Lonsdale, RI 5-21
Figure 5.9 Chloride Simulation for July 10-11,1991 5-24
Figure 5.10 Chloride Simulation for October 2-3,1991 5-25
Figure 5.11 Chloride Simulation for August 14-15,1991 5-26
Figure 5.12 Impact of Maximum and Minimum UB WP AD Chloride Concentrations
for August 14-15,1991 5-27
Figure 5.13 BODs Simulations for July 10-11,1991 5-30
Figure 5.14 BODs Simulations for October 2-3,1991 5-31
Figure 5.15 BODs Simulations for August 14-15,1991 5-32
Figure 5.16 Dissolved Oxygen Simulations for July 10-11,1991 with Reaeration
and CBOD 5-35
Figure 5.17 Dissolved Ammonia Simulations for July 10-11,1991 5-38
Figure 5.18 Dissolved Ammonia Simulations for October 2-3,1991 5-39
Figure 5.19 Dissolved Ammonia Simulations for August 14-15,1991 5-40
Figure 5.20 Dissolved Oxygen Simulations for July 10-11,1991 with
Reaeration, CBOD, and NBOD 5-42
Figure 5.21 Dissolved Oxygen Simulations for July 10-11,1991 with
Reaeration, CBOD, NBOD and SOD 5-44
Figure 5.22 Dissolved Nitrate Simulations for July 10-11,1991 5-51
Figure 5.23 Dissolved Nitrate Simulations for October 2-3,1991 5-52
Figure 5.24 Dissolved Nitrate Simulations for August 14-15,1991 5-53
Figure 5.25 Dissolved Orthophosphate Simulations for July 10-11,1991 5-55
Figure 5.26 Dissolved Orthophosphate Simulations for October 2-3,1991 5-56
Figure 5.27 Dissolved Orthophosphate Simulations for August 14-15,1991 5-57
Figure 5.28 Chlorophyll a Simulation for July 10-11,1991 5-59
Figure 5.29 Chlorophyll a Simulation for October 2-3,1991 5-60
Figure 5.30 Chlorophyll a Simulations for August 14-15,1991 5-61
Figure 5.31 Final Dissolved Oxygen Profile for July 10-11,1991 5-62
Figure 5.32 Final Dissolved Oxygen Profile for October 2-3,1991 5-63
Figure 5.33 Final Dissolved Oxygen Profile for August 14-15,1991 5-64
Figure 5.34 Dissolved Oxygen Profile for Validation Survey (MADEQE 1983),
June 9-12,1980 5-67
Figure 5.35 Dissolved Oxygen Profile for Validation Survey (MADEQE 1983),
August 4-7, 1980 5-68
Figure 5.36 Dissolved Oxygen Profile for Validation Survey (MADEQE 1983),
October 15-16, 1980 5-69
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Figure 5.37 Ammonia Profile for Validation Survey (MADEQE 1983),
June 9-12, 1980 5-70
Figure 5.38 Ammonia Profile for Validation Survey (MADEQE 1983),
August 4-7,1980 5-71
Figure 5.39 Ammonia Profile for Validation Survey (MADEQE 1983),
October 15-16,1980 5-72
Figure 5.40 Dissolved Oxygen Profile for Validation Survey, September 28-30,1987 ... 5-74
Figure 5.41 Dissolved Oxygen Sensitivity to K, Rates for July 10-11,1991 5-76
Figure 5.42 Dissolved Oxygen Sensitivity to K, Rates for August 14-15,1991 5-77
Figure 5.43 Dissolved Oxygen Sensitivity to K, Rates for October 2-3,1991 5-78
Figure 5.44 Dissolved Nitrate Sensitivity to Algal Settling Rates for July 10-11,1991 ... 5-80
Figure 5.45 Dissolved Orthophosphate Sensitivity to Algal Settling Rates
for July 10-11,1991 5-81
Figure 5.46 Chlorophyll a Sensitivity to Algal Settling Rates for July 10-11,1991 5-82
Figure 5.47 Dissolved Oxygen Sensitivity to Algal Settling Rates for July 10-11,1991 .. 5-83
Figure 5.48 Additional Dissolved Nitrate Sensitivity to Algal Settling Rates for
July 10-11,1991 5-84
Figure 5.49 Additional Dissolved Orthophosphate Sensitivity to Algal Settling Rates
for July 10-11,1991 5-85
Figure 5.50 Additional Chlorophyll a Sensitivity to Algal Settling Rates for July
10-11,1991 5-86
Figure 5.51 Additional Dissolved Oxygen Sensitivity to Algal Settling Rates for
July 10-11,1991 5-87
Figure 5.52 Dissolved Nitrate Sensitivity to Non Algal Light Extinction Coefficient
Changes for July 10-11,1991 5-89
Figure 5.53 Dissolved Orthophosphate Sensitivity to Non Algal Light Extinction
Coefficient Changes for July 10-11,1991 5-90
Figure 5.54 Chlorophyll a Sensitivity to Non Algal Light Extinction Coefficient
Changes for July 10-11,1991 5-91
Figure 5.55 Dissolved Oxygen Sensitivity to Non Algal Light Extinction Coefficient
Changes for July 10-11,1991 5-92
Figure 5.56 Dissolved Nitrate Sensitivity to Michaelis-Menton Nutrient Half Saturation
Constants 5-94
Figure 5.57 Dissolved Orthophosphate Sensitivity to Michaelis-Menton Nutrient Half
Saturation Constants 5-95
Figure 5.58 Chlorophyll a Sensitivity to Michaelis-Menton Nutrient Half Saturation
Constants 5-96
Figure 5.59 Dissolved Oxygen Sensitivity to Michaelis-Menton Nutrient Half Saturation
Constants 5-97
Figure 5.60 Dissolved Nitrate Sensitivity to Organic Phosphorus Remineralization Rates
for July 10-11,1991 5-99
Figure 5.61 Dissolved Orthophosphate Sensitivity to Organic Phosphorus
Remineralization Rates for July 10-11,1991 5-100
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Figure 5.62 Chlorophyll a Sensitivity to Organic Phosphorus Remineralization Rates
for July 10-11,1991 5-101
Figure 5.63 Dissolved Oxygen Sensitivity to Organic Phosphorus Remineralization
Rates for July 10-11,1991 5-102
Figure 5.64 Dissolved Nitrate Sensitivity to Organic Phosphorus Settling Rates for
July 10-11,1991 5-104
Figure 5.65 Dissolved Orthophosphate Sensitivity to Organic Phosphorus Settling Rates
for July 10-11,1991 5-105
Figure 5.66 Chlorophyll a Sensitivity to Organic Phosphorus Settling Rates for July
10-11,1991 5-106
Figure 5.67 Dissolved Oxygen Sensitivity to Organic Phosphorus Settling Rates for
July 10-11,1991 5-107
Figure 5.68 Dissolved Nitrate Sensitivity to Ratio of Chlorophyll a to Algal Biomass .. 5-109
Figure 5.69 Dissolved Orthophosphate Sensitivity to Ratio of Chlorophyll a to Algal
Biomass 5-110
Figure 5.70 Chlorophyll a Sensitivity to Ratio of Chlorophyll a to Algal Biomass 5-111
Figure 5.71 Dissolved Oxygen Sensitivity to Ratio of Chlorophyll a to Algal Biomass . 5-112
Figure 5.72 Dissolved Nitrate Simulations for July 10-11,1991: BRI vs SAB
Recommendations 5-114
Figure 5.73 Dissolved Nitrate Simulations for October 2-3,1991: BRI vs SAB
Recommendations 5-115
Figure 5.74 Dissolved Nitrate Simulations for August 14-15,1991: BRI vs SAB
Recommendations 5-116
Figure 5.75 Dissolved Orthophosphate Simulations for July 10-11,1991: BRI vs SAB
Recommendations 5-117
Figure 5.76 Dissolved Orthophosphate Simulations for October 2-3,1991: BRI vs SAB
Recommendations 5-118
Figure 5.77 Dissolved Orthophosphate Simulations for August 14-15,1991: BRI vs
SAB Recommendations 5-119
Figure 5.78 Chlorophyll a Simulations for July 10-11,1991: BRI vs SAB
Recommendations 5-120
Figure 5.79 Chlorophyll a Simulations for October 2-3,1991: BRI vs SAB
Recommendations 5-121
Figure 5.80 Chlorophyll a Simulations for August 14-15,1991: BRI vs SAB
Recommendations 5-122
Figure 5.81 Final Dissolved Oxygen Profiles for July 10-11,1991: BRI vs SAB
Recommendations 5-123
Figure 5.82 Final Dissolved Oxygen Profiles for October 2-3,1991: BRI vs SAB
Recommendations 5-124
Figure 5.83 Final Dissolved Oxygen Profiles for August 14-15,1991: BRI vs SAB
Recommendations 5-125
Figure 5.84 Dissolved Oxygen Profiles with Revised SOD Rates for July 10-11,1991 . 5-130
Figure 5.85 Dissolved Oxygen Profiles with Revised SOD Rates for October 2-3,1991 5-131
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Figure 5.86 Dissolved Oxygen Profiles with Revised SOD Rates for August 14-15,
1991 5-132
Figure 6.1 Comparison Plot of Model Predictions and Field Observations of
TSS on the Pawtuxet River 6-8
Figure 6.2 Example of a K^ and Velocity Relationship 6-13
Figure 6.3 Total Suspended Solids Profile for 1991 Blackstone River Dry Weather
Surveys (Cheela 1994) 6-14
Figure 6.4 Example of Validation Simulation for TSS August 1988 Blackstone
River Survey 6-15
Figure 6.5 Comparison Plot of Model Predictions and Field Observations of
TSS on the Blackstone River 6-16
Figure 6.6 Example of the EPA Relationship Between a Metal Partition
Coefficient and TSS (Kontaxis et al., 1982) 6-19
Figure 6.7 Revised Relationship Between Cadmium Partition Coefficient and
TSS (Kontaxis et al., 1982) 6-21
Figure 6.8 Revised Relationship Between Chromium Partition Coefficient and
TSS (Kontaxis etal., 1982) 6-22
Figure 6.9 Revised Relationship Between Copper Partition Coefficient and
TSS (Kontaxis et al., 1982) 6-23
Figure 6.10 Revised Relationship Between Lead Partition Coefficient and
TSS (Kontaxisetal., 1982) 6-24
Figure 6.11 Revised Relationship Between Nickel Partition Coefficient and
TSS (Kontaxis et al., 1982) 6-25
Figure 6.12 Cadmium Profiles for July 10-11,1991 6-33
Figure 6.13 Cadmium Profiles for October 2-3, 1991 6-34
Figure 6.14 Cadmium Profiles for August 14-15,1991 6-35
Figure 6.15 Chromium Profiles for July 10-11,1991 6-37
Figure 6.16 Chromium Profiles for October 2-3,1991 6-38
Figure 6.17 Chromium Profiles for August 14-15,1991 6-39
Figure 6.18 Copper Profiles for July 10-11,1991 6-40
Figure 6.19 Copper Profiles for October 2-3,1991 6-41
Figure 6.20 Copper Profiles for August 14-15,1991 6-42
Figure 6.21 Lead Profiles for July 10-11,1991 6-43
Figure 6.22 Lead Profiles for October 2-3,1991 6-44
Figure 6.23 Lead Profiles for August 14-15,1991 6-45
Figure 6.24 Nickel Profiles for July 10-11,1991 6-47
Figure 6.25 Nickel Profiles for October 2-3,1991 6-48
Figure 6.26 Nickel Profiles for August 14-15, 1991 6-49
Figure 7.1 Flow Chart Describing the Wet Weather Data Presentation and
Interpretation 7-2
Figure 7.2 Flow Chart Describing the Diy and Wet Weather Data Analysis and
Model Application 7-3
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Figure 7.3 Ammonia Concentration for Storm 2, November 2-5,1992 7-4
Figure 7.4 Nitrate Concentration for Storm 2, November 2-5,1992 7-5
Figure 7.5 Ammonia Concentration for Storm 1, September 22-24,1992 7-7
Figure 7.6 Nitrate Concentration for Storm 1, September 22-24, 1992 7-8
Figure 7.7 Orthophosphate Concentration for Storm 1, September 22-24,1992 7-10
Figure 7.8 Chromium Concentration for Storm 1, September 22-24,1992 7-13
Figure 7.9 Lead Concentration for Storm 1, September 22-24,1992 7-14
Figure 7.10 EMC Plots for N03-N and NH3-N for Storm 1, Storm 2 and Storm 3 7-19
Figure 7.11 EMC Plots for P04-P, FC, and EC for Storm 1, Storm 2 and Storm 3 7-20
Figure 7.12 EMC Plots for TSS, VSS, and Pb for Storm 1, Storm 2 and Storm 3 7-21
Figure 7.13 EMC Plots for Cd, Cr, and Cu for Storm 1, Storm 2 and Storm 3 7-22
Figure 7.14 EMC Plots for Ni, Zn, and BODs for Storm 1, Storm 2 and Storm 3 7-23
Figure 7.15 Fecal Coliform Loading for Storm 1, September 22-24,1992 7-27
Figure 7.16 Example Figure of Pb Showing Acute and Chronic Criteria Violations for
Storm 2 at Station BWW00 7-31
Figure 7.17 Acute Lead Violations for Storm 3, October 12-16,1993 7-32
Figure 7.18 Acute Copper Violations for Storm 2, November 2-5, 1992 7-33
Figure 7.19 Acute Cadmium Violations for Storm 1, September 22-24,1992 7-34
Figure 7.20 Example figure of Cr Showing Mass Loading Calculation for Storm 2
at Station BWW04 7-43
Figure 7.21 Example of Wet Load Showing Gain and Loss for TSS, Cu, and Pb for
Storm 2 7-48
Figure 7.22 Example Plot Showing a Comparison of the Two Major Point Sources
Versus the Other Sources for Lead in Wet Weather 7-49
Figure 7.23 Example Plot of Regression Line of Pb for Resuspended Load vs Flow
at Rice City Pond (Reach Between BWW07-BWW08) 7-69
Figure 7.24 Example of Resuspended and Runoff Load Calculation of Pb for Storm 2
at Rice City Pond (BWW07-BWW08) 7-70
Figure 7.25 Post Audit at MA/RI State Line (BWW13) 7-73
Figure 7.26 Post Audit at End of River (BWW21) 7-74
Figure 7.27 Example Plot of Model Regression, Nixon Regression and Six Data
Points from this Study for Pb at the End of River Station (BWW21) 7-76
Figure 7.28 Example Plot of Model Regression for Load vs Rainfall for Cu at the
End of River Station (BWW21) 7-79
Figure 7.29 Example Plot of Model Regression for Load vs Rainfall for Cu at the
State Line (BWW13) 7-80
Figure 8.1 Rice City Pond and Flood Plain 8-3
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LIST OF TABLES
Table 2.1 Water Quality Sampling Locations 2-3
Table 2.2 Summary of Analytical Methods 2-21
Table 2.3 Summary of Results for the Quality Assurance Project Plan for the
Blackstone River Wet and Dry Weather Surveys 2-25
Table 2.4 Trip Blank Analyses of the Measured Parameters in the Blackstone
River Dry and Wet Surveys 2-26
Table 2.5 Whole Sediment Toxicity Sample Sites 2-29
Table 3.1 Summary of Flows for the 1991 Diy Weather Surveys 3-2
Table 3.2 Precipitation Log of Three Storms for the Blackstone River Wet
Weather Studies 3-5
Table 3.3 Average Rainfall Characteristics 3-13
Table 3.4 Summary Table of Rainfall for Individual Subwatersheds 3-14
Table 3.5 Summary Table of Rainfall for Cumulative Subwatersheds 3-15
Table 3.6 Blackstone River Flow Summary (cfs) - Storm 1 3-17
Table 3.7 Blackstone River Flow Summary (cfs) - Storm 2 3-18
Table 3.8 Blackstone River Flow Summary (cfs) - Storm 3 3-19
Table 3.9 Average Survey Flow (cfs) 3-20
Table 3.10 Hydrograph Characteristics - Storm 1 3-22
Table 3.11 Hydrograph Characteristics - Storm 2 3-23
Table 3.12 Hydrograph Characteristics - Storm 3 3-24
Table 3.13 Dams and Impoundments along the Blackstone River 3-36
Table 4.1 Ammonia Dry Weather System Ranking 4-9
Table 4.2 Nitrate Dry Weather System Ranking 4-14
Table 4.3 Orthophosphate Dry Weather System Ranking 4-18
Table 4.4 TSS (1000 lbs/day) Diy Weather System Ranking 4-37
Table 4.5 Cadmium Dry Weather System Ranking 4-44
Table 4.6 Chromium Dry Weather System Ranking 4-51
Table 4.7 Copper Dry Weather System Ranking 4-57
Table 4.8 Lead Dry Weather System Ranking 4-63
Table 4.9 Nickel Dry Weather System Ranking 4-69
Table 4.10 Summary of Acute and Chronic Trace Metal Violations for the 1991
Surveys 4-72
Table 4.11 Blackstone River Aquatic Toxicity Test Results 4-78
Table 4.12 Blackstone River Sediment Stations 4-83
Table 4.13 Sediment Pore Water 48 Hour Toxicity (% Survival) Ceriodaphnia dubia .. 4-86
Table 4.14 Sediment Pore Water 48 Hour Toxicity (% Survival) Pimephalespromelas . 4-86
Table 4.15 Percent Survival (48 Hours) Pimephales promelas in Sediment Pore
Water from Two Stations 4-88
Table 4.16 Blackstone River Effluents Toxicity Test Results in Percent 4-89
Table 4.17 Great Lakes Sediment Classification Scheme 4-90
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Table 4.18 Location of Fish Toxics Monitoring 4-108
Table 4.19 Results of Metals Analysis (mg/kg wet weight) 4-111
Table 4.20 Quality Assurance/Quality Control Data: Metals (mg/kg wet weight) 4-115
Table 4.21 Quality Assurance/Quality Control Data: Mercury (mg/kg wet weight) 4-116
Table 4.22 Results of PCB (mg/kg), Organochlorine Pesticide, and % Lipids Analysis 4-117
Table 4.23 Benthic Macroinvertebrate Sampling Station Locations 4-122
Table 4.24 Benthic Macroinvertebrate Station Bottom Types and Current Velocity
Measurements 4-123
Table 4.25 Average Nutrient and TSS Rankings 1991 Blackstone River Dry
Weather Surveys 4-143
Table 4.26 Average Metal Rankings 1991 Blackstone River Dry Weather Surveys 4-144
Table 4.27 Percent Attributed to the Two Major Point Sources (MPS) versus all
Other Sources (OS) 4-145
Table 5.1 Reach Locations in the Blackstone River Model 5-3
Table 5.2 Wastewater Discharges Defined in the Blackstone River Model 5-8
Table 5.3 Reach Drainage Areas (mi2) Defined in the Blackstone River Model 5-9
Table 5.4 Dam Locations and Heights in the Blackstone River Model 5-10
Table 5.5 Reach Hydraulic Characteristics for the Blackstone River QUAL2E Model .5-11
Table 5.6 Summary of Flows (cfs) for the 1991 Dry Weather Surveys 5-12
Table 5.7 Summary of Estimated Blackstone River Flows at each Water Quality
Station for the 1991 Dry Weather Surveys in cfs 5-15
Table 5.8 Summary of Estimated Blackstone River Tributary Flows at each Water
Quality Station for the 1991 Dry Weather Surveys in cfs 5-15
Table 5.9 Chloride Concentrations (mg/L) of Point Sources and Tributaries in the
Blackstone River Model 5-23
Table 5.10 BOD, Concentrations (mg/L) of Point Sources and Tributaries in the
Blackstone River QUAL2E Model 5-34
Table 5.11 Ammonia Concentrations (mg/L) of Point Sources and Tributaries in the
Blackstone River QUAL2E Model 5-37
Table 5.12 SOD Rates in the BRI Final QUAL2E Blackstone River Model 5-43
Table 5.13 Dissolved Nitrate Concentrations (mg/L) of Point Sources and Tributaries
in the Blackstone River QUAL2E Model 5-46
Table 5.14 Dissolved Orthophosphate Concentrations (mg/L) of Point Sources and
Tributaries in the Blackstone River QUAL2E Model 5-47
Table 5.15 Final Values of Parameters Used in Algal Simulations 5-49
Table 5.16 Algal Parameters Defined in the QUAL2E Model for the
Blackstone River 5-50
Table 5.17 Results of the 7Q10 Flow Analysis for the UBWPAD WLA using
MADEP STREAM7 (MADEQE 1983) 5-136
Table 5.18 Boundary Conditions for the 7Q10 Flow Conditions of the
Blackstone River QUAL2E Model 5-137
Table 6.1 Blackstone River Flow (cfs) Data for Water Quality Surveys Since 1980 ... 6-10
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Table 6.2 K^- Velocity Relationships (Algal Growth Corrected) 6-12
Table 6.3 Summary of Metal Partition Coefficient and TSS Equations 6-26
Table 6.4 Summary of TSS (mg/L) and Metal (^g/L) Concentrations of Point
Sources in the Pawtoxic Model for July 10-11,1991 6-28
Table 6.5 Summary of TSS (mg/L) and Metal O^g/L) Concentrations of Point
Sources in the Pawtoxic Model for August 14-15,1991 6-29
Table 6.6 Summary of TSS (mg/L) and Metal Oug/L) Concentrations of Point
Sources in the Pawtoxic Model for October 2-3,1991 6-30
Table 6.7 Summary of Biomass Metals Analysis 6-51
Table 7.1 Summary of Ammonia Concentrations in mg/L at UBWPAD and
Woonsocket Treatment Facilities 7-6
Table 7.2 Average and Maximum Dry and Wet Weather Metal Concentrations for
UBWPAD 7-11
Table 7.3 Average and Maximum Dry and Wet Weather Metal Concentrations for
Woonsocket WWTF 7-12
Table 7.4 Event Mean Concentration (EMC) for Storm 1 7-16
Table 7.5 Event Mean Concentration (EMC) for Storm 2 7-17
Table 7.6 Event Mean Concentration (EMC) for Storm 3 7-18
Table 7.7 Event Mean Concentrations (EMCs) for Storms 1,2 and 3 for the
Blackstone River 7-25
Table 7.8 Event Mean Concentrations (EMCs) for the Blackstone, Moshassuck,
Woonasquatucket, Pawtuxet, and Ten Mile Rivers 7-25
Table 7.9 Fecal Coliform Violation in Accordance With Class B Water Criteria for
, Dry and Wet Weather 7-29
Table 7.10 Blackstone River Wet Weather Summary of Acute and Chronic Criteria
Violations (Storm 1, Storm 2 and Storm 3) 7-35
Table 7.11 Toxicity Testing Results - Ceriodaphnia dubia Survival and Reproduction.. 7-39
Table 7.12 TRC Concentrations for BWW23-25 7-41
Table 7.13 Average of all Storms for Wet Loads as Percent of Total Load 7-44
Table 7.14 Average of all Stations for each Storm for Wet Loads as Percent of
Total Load 7-45
Table 7.15 Wet Load Comparison Between the Two Major Point Sources and the
Other Sources along the River 7-50
Table 7.16 Total Load Comparison Between the Two Major Point Sources and the
Other Sources along the River 7-51
Table 7.17 Blackstone River Wet Weather Storm 1,2 and 3 Rankings, Wet Load (lbs) . 7-53
Table 7.18 Source Rankings by Wet Load Averaged for all Storms With Point
Sources in Percent 7-56
Table 7.19 Source Rankings by Wet Load Averaged for all Storms Without Point
Sources in Percent 7-57
Table 7.20 Top Five Source Rankings for Comparison Between Wet and Dry
Weather for Total Load in Percent 7-60
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Table 7.21 A Comparison Between Wet and Total Load for the Two Major Point
Sources and the Other Sources along the River in Percent 7-61
Table 7.22 Narragansett Bay Project 1988-89 Tributary Wet Loads and Rankings 7-63
Table 7.23 Narragansett Bay Project 1988-89 Tributary Wet Loads 7-64
Table 7.24 Providence River Tributaries - Wet Load Estimates and Rankings 7-66
Table 7.25 Resuspended Loading Predictive Equations for the Reach BWW07-
BWW08 (Load vs Flow) 7-69
Table 7.26 Runoff and Resuspended Loads Between BWW07 and BWW08 7-71
Table 7.27 Dry Weather Predictive Equations (Concentration vs Flow) 7-75
Table 7.28 Comparison of Dry Weather Load Predictive Equations at BWW21 7-76
Table 7.29 Wet Load Regression Data for Rainfall vs Load for BWW21 and BWW13 . 7-78
Table 7.30 Wet Weather Predictive Equations at BWW21 (Load vs Rainfall) 7-79
Table 7.31 Wet Weather Predictive Equations at BWW13 (Load vs Rainfall) 7-80
Table 7.32 Annual Mass Loading Forecast Summary for the Blackstone River at the
State Line (BWW13) and at the End of River (BWW21) 7-81
r
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Executive Summary
Rivers have long been important to the growth of a region. In the northeast United States
early in the 19th century, industry quickly grew relying on the rivers for storage, diversion and
hydro power. However, the downside to the industrial growth was the system of impoundments,
which were created by the construction of dams. These effectively eliminated movement of fish
along the river and provided ideal locations for settlement of contaminants, thereby establishing a
series of layered landfills behind the dams. With the loss of most of this industry, there is a real
concern about the dams and impoundments that have been left behind, and their current and
potential impact on water quality.
Although in the last 20 years there have been major successes with regards to the
reduction of municipal and industrial wastewater loadings into our rivers, present conditions still
create a challenging system for restoration, with many of the major influences associated with
rainfall including direct stormwater runoff, combined sewerage overflows, failed septic systems,
hydraulically inadequate wastewater treatment facilities, and resuspension and movement of
contaminated river sediments. It was the goal of this study to address these issues and
specifically answer the following questions:
1. What is the water quality of a river for dry weather, steady state conditions?
2. Where and how does wet weather impact the water quality of a river?
3. What are the major sources of wet and dry weather pollution in a watershed?
4. What is the relative importance between point and nonpoint sources of pollution
in a watershed, for both dry and wet weather conditions?
5. How do the water quality issues differ between wet and diy weather?
6. How can the information generated in this study be used to forecast annual
pollutant loading rates?
In order to accomplish the goals of this study the United States Environmental Protection
Agency (EPA) established the Blackstone River Initiative (BRI) as a multi-phased, interagency,
interstate project to conduct the sampling, assessment, and modeling work necessary for
restoration of the river system.
The objectives of the study were as follows:
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• Describe the steady state, dry weather water quality conditions in a watershed, including the
river, major tributaries, and major wastewater discharges;
• Measure sediment oxygen demand;
• Determine the toxicity of ambient water, sediments, and wastewater discharges;
• Calibrate and validate a dissolved oxygen and trace metal model for the river;
• Utilize the models and the field data to estimate the relative contribution of dry weather point
and nonpoint pollutant sources;
• Utilize the models to predict annual dry weather loadings of selected constituents to
Narragansett Bay;
• Describe the wet weather water quality conditions in a watershed to include the river, major
tributaries, and major wastewater discharges;
• Identify and rank the major wet weather pollutant "hot spots" in the watershed;
• Determine the toxicity of ambient water under wet weather conditions and compare the
results with criteria based toxicity;
• Determine the relative importance between wet weather nonpoint and point source pollutant
loadings;
• Determine the wet weather loading rate of pollutants, especially nitrogen, to Narragansett
Bay; and
• Forecast annual wet weather loading rates.
The report includes: (1) a general description of a watershed wide wet and dry weather
water quality study that will serve as a guideline for similar studies; (2) a detailed evaluation of
the Blackstone Rivers watershed hydrology and river hydraulics; (3) the dry weather data
interpretation; (4) dissolved oxygen and trace metal models including their calibration and
validation; (5) the wet weather data interpretation involving the evaluation of nonpoint and point
pollutant flows, system pollutant rankings and the development of annual loading rates; and (6)
the special extension to the BRI involving the detailed study of Rice City Pond. This report also
includes an appendix that is contained on a computer readable CD that includes; all data from the
dry and wet weather surveys and input and output files, the executable code, and a users manual
for the dissolved oxygen and trace metal models.
For the diy weather surveys there were 15 stations along the Blackstone River and 6 on
major tributaries. Dry weather stations are coded with the prefix BLK and wet weather stations
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are coded with the prefix BWW.
In addition to the river stations, two point source dischargers were sampled during the diy
weather surveys: the Upper Blackstone Water Pollution Abatement District (UBWPAD) and
Woonsocket Wastewater Treatment Facility (WWTF). For the wet weather study five point
source discharges were sampled. These included, from upstream to downstream, three direct
discharges to the Blackstone River including the CSO facility in Worcester, UBWPAD, and
Woonsocket WWTF, and two direct discharges to the Seekonk River below the mouth of the
Blackstone River including Bucklin Point Narragansett Bay Commission Facility (BP NBC) and
the BP NBC by-pass.
The dry weather program consisted of three 48 hour surveys in 1991 on July 10-11,
August 14-15, and October 2-3. Analyses included five-day biochemical oxygen demand
(CBOD), total suspended solids (TSS), volatile suspended solids (VSS), chloride, dissolved
ammonia-nitrogen (NH3 -N), dissolved nitrate-nitrogen (N03-N), dissolved orthophosphorous
(P04-P), total and dissolved metals (cadmium, chromium, copper, lead, and nickel), hardness
(calcium and magnesium), fecal coliform, chlorophyll a, and toxicity. Field measurements
included dissolved oxygen, temperature, pH, and conductivity.
Effluent analyses were conducted on 24-hour composite samples collected daily for five
days prior to the water quality surveys. Wastewater samples were handled and analyzed for the
same parameters as the river samples.
Effluent samples were also collected from the two largest dischargers as well as from 10
other dischargers in the Blackstone River Basin as part of the toxicity testing at these facilities.
The two additional facilities tested in RI were Okonite Industries and GTE. In MA, the eight
additional facilities tested were: Uxbridge WWTF, Northbridge WWTF, Millbury WWTF,
Guilford Industries in Douglas, Douglas WWTF, Grafton WWTF, New England Plating in
Worcester, and Worcester Spinning and Finishing in Leicester. Samples were not collected
concurrently with the river surveys conducted during this study. Instead, the facilities were
sampled once each during the summer of 1991, either during June or August, except for the two
largest facilities, which were sampled in both July and August. As part of this testing, the
samples were analyzed by a separate laboratory under contract to the EPA for aluminum,
cadmium, calcium, chromium, copper, lead, magnesium, nickel, zinc, ammonia, total solids,
TSS, total organic carbon, and alkalinity.
The wet weather program consisted of three storms. A total of 16 samples were taken at
each station for each storm. Field measurements included temperature, pH, conductivity and
DO. Laboratory chemical analysis included TSS, VSS, CBOD, chloride, sodium, dissolved NH3-
N, dissolved N03 -N, dissolved P04-P, total trace metals (cadmium, chromium, copper, lead,
nickel and zinc), hardness (calcium and magnesium), fecal coliform and E. coll Toxicity testing
was performed on samples representing first flush and peak flow for each station and discharge.
Samples at the five point source dischargers were collected at the same frequency as the river
samples and analyzed for the same set of constituents given above.
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Results of the Dry Weather Surveys
The interpretation of the ambient chemistry included a system ranking, where the major
point sources, tributaries and headwater loads were separated from individual reach gains. An
accounting of the two major point versus the other sources of pollutants was made by constituent
by survey. The following observations may be made from the data.
The loadings from the headwaters, as defined by BLK01, are small relative to other
sources along the Blackstone River with the exception of chromium and fecal coliform.
The flow in the river at the point of the UBWPAD discharge was very low, offering little
dilution. Therefore, the characteristics of the effluent often determined the characteristics of the
river at this point. The ratio of the UBWPAD flow to stream flow was 3:1 during the
July/August low flow surveys and about 1:1 in October. The UBWPAD is the single largest dry
weather source of nitrate, phosphorus, cadmium, nickel and copper to the Blackstone River.
Based on a comparison of mass loadings between the UBWPAD and BLK01, the UBWPAD
clearly dominates the Blackstone River at its point of discharge, especially with regards to all
three nutrients and three of the trace metals (cadmium, nickel, and copper).
High dilution at the point of Woonsocket's discharge makes it difficult to determine the
relative importance of this discharge based solely on concentration profiles. The ratio of the
Woonsocket WWTF flow to stream flow was 1:16 during the July/August surveys and 1:50 in
October. It is clear that the Woonsocket WWTF is the single largest dry weather source of
ammonia to the Blackstone River.
Chlorinated wastewater and instream residual chlorine from the UBWPAD has reduced
bacteria levels in the river at the next downstream station (BLK02) to near zero. There were also
elevated counts in the headwaters and at several locations along the mainstem.
The summer profile includes large daily swings in DO that are evident in the
impoundments. A comparison of the 1991 data for the UBWPAD with data from 1973 (before
secondary treatment) and 1980 (before nitrification) shows a substantial reduction in instream
CBOD and ammonia at the facility with a resulting improvement in DO in the reaches below its
discharge. Even with large daily swings of oxygen, few exceedences for DO outside of water
quality standards were evident in either the mainstem or the tributaries. Nitrification is evident
below the Woonsocket WWTF with a sharp decrease in ammonia, a comparable increase in
nitrate, and a loss of oxygen.
Three distinct profiles emerge from the evaluation of the five trace metals. The dominant
source is either (a) UBWPAD, (b) resuspending sediments; or (c) a combination of both. The
majority of the Blackstone River impoundments act as settling basins for solids and metals from
point and nonpoint sources at low flows. These impoundments then become significant sources
of these constituents with resuspension of deposited material during higher flows. It is not clear,
based on the dry weather data, what phenomena is causing the rapid dissolved metal losses for
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several of the trace metals including cadmium, copper and nickel in the reaches below
UBWPAD.
Violations of acute and chronic criteria in water column samples for cadmium, copper
and lead could be seen throughout the mainstem Blackstone River and along several tributaries.
During the low flow study, although the water quality criteria were exceeded for a number of
metals, only one toxic endpoint occurred along the mainstem. These results have prompted site
specific criteria studies for the Blackstone River in Massachusetts. It has also underscored the
importance of toxicity testing to be performed in conjunction with metals testing for
determination of water quality impacts and issuance of permits to municipalities and industry.
With regards to sediment toxicity testing, toxicity was only evidenced by the Hyallela azteca in
the Rice City Pond sample. Chironomus tentans survived fairly well in this sediment (64 and
82% survival in July and August). In July, when metal concentrations were measured, survival
of Hyallela and Chironomus were 70 and 72% in the Fisherville Dam sediment sample. Higher
mortality of one or both species occurred in the samples from Singing Dam, Manville Dam, and
Slater's Mill, and Gilboa and Grey's Pond, the background samples.
The study included the monitoring of the two largest point sources in the watershed,
defined as the "major point sources" in the analyses. All other sources, including the small point
discharges, tributaries, and reach nonpoint sources, were included in the term "other sources".
The Woonsocket WWTF was the major source of ammonia and the UBWPAD was the major
source of phosphorus. The single largest source of nitrate to the river was the UBWPAD in both
low and high flow conditions. The major sources of TSS, chromium and lead to the river were
from other sources, regardless of the flow condition. Under low flow, the stretch of river that
was most significant included Fisherville Pond and Rice City Pond (BLK.06-08). This reflected
the resuspension of sediments within the impoundments. For high flow, the highest loading
came from the reaches just below Rice City Pond (BLK08-13). In part, this reflected the
resuspension and transport of sediments from Rice City Pond. The major sources for cadmium
and copper for the low flow surveys were from the point sources (primarily UBWPAD). For
high flow, the nonpoint sources contributed more mass, with the highest loading from Rice City
Pond and the reach immediately below it (BLK07-11). The major sources of nickel for the low
flow surveys were from the point sources (primarily UBWPAD). For high flow, the nonpoint
sources contributed more mass, with the highest loading in the last reach in the river (BLK20-
21).
QUAL2E has been used to model dissolved oxygen in the Blackstone River from
Worcester, MA to its discharge into the Seekonk River in Pawtucket, RI. The major tributaries
and point sources have been included in the model. The model has been used to address daily
variations of dissolved oxygen. The major sources and sinks contributing to the DO balances
have been accounted for in the model including CBOD and Nitrogenous BOD (NBOD)
consumption, Sediment Oxygen Demand (SOD); reaeration; and algal productivity and
respiration. The following conclusions were determined from this analysis:
The model has been calibrated using the data collected in July and October 1991. The
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model was also successfully validated using the data collected in August 1991 and two
independent data sets: one collected in Massachusetts in 1980 and one in Rhode Island in 1987.
High levels of primary productivity in the Blackstone River result in impaired water
quality associated with significant daily swings of dissolved oxygen. The river reaches most
dramatically impaired are just above and below the MA/RI state line. High primary productivity
is a result of phosphorus additions from the municipal wastewater facilities on the river. The
major sources of phosphorus are from the UBWPAD and Woonsocket WWTF. The
impoundments along the river reduce velocities and increase the time of travel in the river
reaches directly behind the dams. These conditions compound the problems presented by high
levels of phosphorus by providing the appropriate hydraulic conditions for the growth of algae.
The river reaches with the highest nitrification rates are directly below the Woonsocket
WWTF. Instream nitrification governs the oxygen profiles in these reaches and causes a DO sag
below Woonsocket's discharge that often extends to the mouth of the river in Pawtucket, RI.
The 19 impoundments along the river are sediment traps. The sediments behind these
impoundments may be the single largest sink of oxygen in that reach. This is especially true in
the upstream reaches where productivity and instream nitrification are relatively small compared
with the lower reaches.
Based on a comparison of data from the early 1980s and this study and the model
application, it was clear that the advanced wastewater treatment implemented in the mid-1980s at
UBWPAD made a significant improvement to the DO concentration in the river. The
improvements are directly associated with a reduction in the facility's discharge of CBOD and
ammonia.
A one-dimensional, steady state model, called Pawtoxic, has been used to describe the
fate and transport of trace metals in the Blackstone River. The major tributaries and point
sources have been included in the model. The model has the option to simulate a maximum of
three conservative elements, total suspended solids, and five nonconservative elements. The
model adopts a simple approach to describe the fate and transport of metals in a river. The
model is based on two simplified equations involving net sediment transport and metal
partitioning.
Empirical relationships between average stream velocities and net sediment transport
coefficients were developed for most river reaches. Where relationships are significant, these
equations provide the modeler with the ability to establish the net sediment transport coefficient
at other stream velocities, and therefore, at other flows such as the waste load allocation flow.
Empirical relationships between metal partition coefficients and suspended solids were
expanded from equations from the literature to include the TSS range from 0-10 mg/L. The
equations provide the modeler with the ability to establish new partition coefficients as
suspended solids concentrations change in the river.
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The model has been calibrated to the flows observed in the three dry weather surveys of
1991. The model was validated with flow measurements from 6 independent measurements
conducted by USGS and the successful simulation of a conservative constituent.
The model was calibrated for suspended solids using the data collected in July and
October 1991. The model was also successfully validated using the data from August 1991 and
other independent surveys from 1980, 1985, 1988,1991 and 1992. The model adequately
describes TSS concentrations over the range of environmental conditions encountered (0-10
mg/L TSS). This is not to say that the model simulates the natural system on a micro scale.
Rather, the model's description of the external attributes of the environment agrees well with the
description obtained by making field measurements of the natural system.
Rapid decreases in dissolved metal concentrations for Cd, Cu, and Ni occurred in the
reaches below the UBWPAD through BLK06 in July and August. Model calibration for these
metals required adjustments to the net sediment transport and metal partitioning coefficients in
these reaches.
Two hypotheses were discussed to explain this rapid loss. Both focused on the
^ uniqueness of the high effluent-to-river ratios for flow and trace metal mass loadings in the low
flow surveys of 1991. Data suggests phenomena other than settling may be occurring in these
reaches. Lead had the highest variability of any metal in the reaches between BLK06 and
BLK11, especially in Rice City Pond. The highest Pb concentrations observed in these reaches
could not be simulated with the steady state model. The model successfully simulated the trace
metal profiles for Cd, Cr, Cu and Ni below BLK06 to the end of the river and for Pb from
BLK11 to the end of the river in the low flow surveys. The model successfully simulated all
metals for the October high flow survey.
Results of the Wet Weather Surveys
During the course of the wet weather data interpretation, one fact became very clear. The
location of Worcester in the headwaters of the Blackstone River had a strong influence on the
river's water quantity and quality during and after a storm. The magnitude and extent of the
impact were directly associated with the rainfall characteristics and the pre-storm flows.
Three storm events were monitored. Storm 1 (September 22-24,1992) was a short,
relatively light, well distributed rainfall. Storm 2 (November 2-5, 1992) was a long, moderate,
well-distributed rainfall. Storm 3 (October 12-14,1993) was a short, intense rainfall with several
localized thunderstorms. Storm 3 was not well distributed and had the heaviest rainfalls in the
northern part of the watershed.
Storm 1 - The runoff from Worcester resulted in a hydrograph that ranged from a base
flow of 15 cubic feet per second (cfs) to 185 cfs. This hydrograph was eventually attenuated in
Fisherville Pond. In general, all flows returned to pre-storm conditions within a 40-hour period.
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The peak flow at BWW21 was 302 cfs.
Storm 2 - The flows from the headwaters, including the UBWPAD, were highest between
the 6-12 hour runs. This peak arrived at Rice City Pond at 20-24 hours and at the mouth of the
river between 36 and 48 hours. The peak flow at BWW21 was 890 cfs.
Storm 3 - The flows from the headwaters reflect the intense thunderstorms that resulted in
over an inch of rainfall in less than 5 hours. The headwater flows reached BWW08 between 16-
20 hours and BWW21 at 28-36 hours. The peak flow at BWW21 was 646 cfs.
UBWPAD's ability to provide nitrification is inhibited under high storm flows. The
facility discharges significant levels of ammonia during these conditions. UBWPAD exceeded
their permit conditions in two out of three storms. These violations coincided with the maximum
runoff and river flows. Compared to the other metals, lead's (Pb) major source appears to be in
the headwaters (above BWW00). In fact, the headwater EMCs are typically the highest
concentration along the entire river. A consistent increase of lead does appear between BWW07
and BWW08 in Rice City Pond and is probably due to sediment resuspension. The other 5
metals (Cd, Cr, Cu, Ni and Zn) have similar EMC profiles in that there appears to be two distinct
peaks. The first occurs in the reaches below UBWPAD and is associated with the wastewater
facilities discharge and possibly other nonpoint sources of metals. A secondary peak consistently
occurs around BWW08; again the probable cause is sediment resuspension within Rice City
Pond. The fecal coliform concentrations and loads at the headwaters are the highest in the entire
watershed. The maximum concentrations coincide with peak runoff flows. In relatively
moderate flows, the residual chlorine from UBWPAD provides instream disinfection and
prevents the passage of the headwater concentrations. This is not the case at high peak flows,
where dilution in the facility and in the river reduces the chlorine residual, and instream
disinfection does not occur.
Higher storm flows resulted in lower hardness concentrations. Lower hardness values
resulted in stricter acute and chronic criteria. At the same time, higher flows typically caused
higher metal concentrations. The result was a short-term violation of acute criteria. High flows
moving through Rice City Pond cause violations in the reaches at and below the dam due to
resuspension. Cu is continually violated both with respect to chronic and acute criteria in dry and
wet weather, starting at station BWW02. Pb chronic violations occur for both dry and wet
weather. Cd violations are more limited, but also begin in and around BWW02. Ni and Cr had
no acute or chronic violations for either dry or wet weather. More stations had violations under
wet weather than dry weather, and the number of violations increased with larger storms.
Toxicity was observed in 35 out of 118 occasions during wet weather testing. Toxicity in
the first flush of the storm accounted for 14 toxic endpoints. The remaining 21 toxic end-points
occurred in the samples collected during the peak of the storm. Toxicity occurred at the same
stations for the most part during first flush and peak of the storm. Six stations had recurrent
toxicity in the peak storm conditions, thus the larger number of toxic endpoints observed during
peak rain. Only two stations were toxic for first flush and non-toxic during peak. Forty percent
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of all toxic endpoints occurred in the first two miles of the river in the Greater Worcester area.
Toxicity occurred in all of the dechlorinated WWTF effluents at least once and in the combined
sewer outfalls. The effluent of the Woonsocket WWTF was toxic during all three wet weather
events (three times during peak flow and once during first flush). The effluent of the
Narragansett Bay Commission Bucklin Point WWTF was also toxic during all three storm
events. All peak samples were toxic, and two of three first flush samples were toxic. This may
indicate bypassing during rain events. The chlorine concentrations in the effluents were
extremely high, and if left in the test solutions, would have caused acute toxicity. River stations
BWW01,02,05, and 11 on the Blackstone River and 09 on the Mumford River (a tributary
receiving municipal and industrial wastewater) experienced significant toxicity on more than one
occasion. By comparison to wet weather toxicity, testing conducted during low flow conditions
(near the 7Q10) indicate that there is no significant toxicity in the water column of the
Blackstone River. Only one toxic endpoint occurred in the mainstem during dry weather testing.
Compared with other tributaries, the Mumford River had the most toxic endpoints; Two were
observed in dry weather and two during wet weather. Little difference was observed between
toxicity occurring in first flush and peak storm samples. Toxicity was much more prevalent
during wet weather conditions. Acute toxicity, the more significant measure of toxicity, was the
predominant endpoint during wet weather toxicity testing.
The area under the mass loading curve defined the total pollutant load at a station. The
wet load was separated from the dry load (base load) for each constituent at each station for each
storm. The relative importance of the wet load was defined as a percentage of wet to total load.
All constituents had more than 50% of the total load as wet load, except for Ni and dissolved
N03-N. The trend of higher wet load as the storm intensity increases is true for all constituents,
except dissolved NH3-N. The headwaters had the highest percent wet load for most of the
constituents. The percent of wet load at each station generally decreases as one moves
downstream.
Similar to the dry weather analysis, the point sources were defined as the two "major
point sources" and the "other sources" included the small point sources, tributaries, runoff and
reach contributions. The result is the ability to compare the relative importance of the two major
point sources and the other sources in the watershed. The system ranking includes a comparison
by individual reach.
It is obvious, based on the analysis of the concentration data, that wet weather loadings
may dominate the river for days after the event, depending on the size of the storm and the
constituent. Specifically, wet weather can result in violations in effluents (ammonia/UBWPAD)
and in river reaches (fecal coliform criteria and acute and chronic criteria for trace metals). In all
cases, violations under wet weather were greater in magnitude, frequency and location.
Often times, more than one factor magnified the impact of wet weather. For instance,
during the height of the storm, instream hardness decreases due to dilution, thereby lowering the
acute criteria concentrations. The more stringent criteria typically coincided with maximum
instream concentrations due to peak flows. The results were instream violations.
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In general, the major nonpoint sources of wet weather pollutants appear to be runoff
related (new materials) although for several reaches sediment resuspension (old materials) was
significant. The headwaters did prove to be significant for several constituents. Pollutants
associated with wet weather may come from either new sources (runoff induced) or old sources
(river sediments). The water quality data coupled with stream flows allowed for the calculation
of mass loading curves. Each mass loading curve was integrated to obtain the total load for each
station for each storm. The total mass was divided by the time of the event to obtain the total
loading for that constituent for each station. Baseline loading rates were estimated for each
pollutograph from the initial (pre-storm) sample and the final (post-storm) samples. These rates
were multiplied by the time of the event to obtain the total dry load for that station. The wet load
per station per constituent was determined by subtracting the dry load from the total load. The
data indicate clearly that with only minor exceptions, more wet load entered the river during
these periods than dry load.
Based on the loading estimates, an estimate of pollutant gain or loss by reach was made.
Net pollutant changes in a reach help to identify locations of major pollutant sources. A
comparison of point and nonpoint pollutant sources was made. The results of this evaluation
also provided insight into the relative importance of each reach through a system ranking. A
system ranking was made using the net gains for each reach and loads from the point sources,
headwaters and tributaries. The result was a determination of reach hot spots.
The information collected during the wet weather sampling program provided insights
into the behavior of the sources during varying storm conditions. A relationship was developed
between rainfall and wet loadings using the data collected during the three storms and previous
wet weather data available for the state line (BWW13) and end of river (BWW21). These
equations were used to estimate the annual wet loading rates for the Blackstone River.
Similarly, dry weather predictions were estimated based on empirical relationships
developed for flow and concentration. The dry weather data was first used to calibrate and
validate models to describe trace metal and dissolved oxygen fate and transport. The dry weather
models were used to estimate baseline mass loadings under steady state flows. The relationships
developed were then used to estimate the annual dry weather contributions at MA/RI state line
(BWW13) and end of the river (BWW21).
Annual loading rates to the Providence River were developed for several constituents. Of
the five major tributaries to the Providence River, the Blackstone River is the major source of
most pollutants.
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1.0 INTRODUCTION
Rivers have long been important to the growth of a region. In the northeast United States,
early in the 19th century, industry quickly grew relying on the rivers for storage, diversion and
hydro power. However, the downside to the industrial growth was the system of impoundments,
which were created by the construction of dams. This effectively eliminated movement of fish
along the river and provided ideal locations for settlement of contaminants, thereby establishing a
series of layered landfills behind the dams. With the loss of most of this industry, there is a real
concern about the dams and impoundments that have been left behind, and their current and
potential impact on water quality.
Although in the last 20 years there have been major successes with regards to the
reduction of municipal and industrial wastewater loadings into our rivers, present conditions still
create a challenging system for restoration. Many of the major water quality issues are associated
with rainfall, including direct stormwater runoff, combined sewerage overflows, failed septic
systems, hydraulically inadequate wastewater treatment facilities, and resuspension and
movement of contaminated river sediments. It was the goal of this study to address these issues
and specifically answer the following questions:
1. What is the water quality of a river for dry weather, steady-state conditions?
2. Where and how does wet weather impact the water quality of a river?
3. What are the major sources of wet and dry weather pollution in a watershed?
4. What is the relative importance between point and nonpoint sources of pollution
in a watershed for both dry and wet weather conditions?
5. How do the water quality issues differ between wet and dry weather?
6. How can information generated in this study be used to forecast annual pollutant
loading rates?
1.1 The Blackstone River Study Area
The Blackstone River provides an excellent watershed for this study due to its historical
role in the industrialization of the northeast, and due to its present role in the environmental
health and future use of Narragansett Bay.
The Blackstone River is 48 miles long, flowing from south central Massachusetts into
northeastern Rhode Island. The river was the site of the first textile mill, Slater's Mill, in 1793.
Through the 1800's, the river became the hardest working river in the U.S., with 1 Hum for every
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mile of river. The Blackstone River has its headwaters in Worcester, MA. It flows south into RI,
where it discharges into the Seekonk River in Pawtucket. It is an important natural, recreational,
and cultural resource to both MA and RI. The river is a major source of freshwater to Rhode
Island's most important resource, Narragansett Bay, a productive and diverse estuary important
for fishing, shellfishing, tourism, and recreation.
The Massachusetts portion of the Blackstone River has been studied over the last 30 years
by the Massachusetts Department of Environmental Protection (MADEP). Reports have been
produced on the water quality in the river and tributaries, the wastewater discharge quality,
sediment analyses, wasteload allocations for dischargers, biological analyses, and management
plans. Several studies on the Rhode Island portion have been conducted by the Rhode Island
Department of Environmental Management (RIDEM) as recently as 1985 and 1989. These
studies included the fate and transport of metals from the state line to Slater's Mill Pond in
Pawtucket, RI.
A review of all available data on the Blackstone River took place in 1990 by the Civil and
Environmental Engineering Department at the University of Rhode Island (URI) and the United
States Environmental Protection Agency (EPA). It has been shown that the Blackstone River is a
major source of pollutants to Narragansett Bay. Specifically, the Blackstone has been identified
as the largest dry weather source of suspended solids, cadmium, lead, and nitrogen, and the
second largest dry weather source of copper, nickel, and chromium. It is important to recognize
that nitrogen driven productivity has been identified as the major component of the dissolved
oxygen depletion in Narragansett Bay.
Other water quality concerns in the Blackstone River watershed include the following:
(1) water quality criteria violations that have been documented throughout the river for cadmium,
copper, lead, and zinc, and at various locations for dissolved oxygen; (2) the potential water
quality problems associated with the operation of hydroelectric facilities and water withdrawals;
and (3) the resuspension at high flow of contaminated sediments located in the impoundments
behind many of the dams. These sediments were shown to be heavily laden with metals, organic
compounds, and hydrocarbons.
In order to provide perspective into the selection of the Blackstone River for this study, an
understanding of the evolution of work on the river and the receiving estuary system is necessary.
In 1987, the EPA created the Narragansett Bay Project (NBP) through the National Estuary
Program. The NBP produced a Comprehensive Conservation and Management Plan (CCMP)
which detailed present and future long-term management actions which are carried forward by
governmental and local agencies and authorities. A Management Committee was formed as part
of this project to develop the plan and to continue work over time in order to provide a forum for
cooperative actions. The present Management Committee is composed of representatives from
local, state, and federal agencies. One of the primary recommendations of the CCMP was a
coordinated assessment and sampling project for the Blackstone River in both Massachusetts and
Rhode Island. In order to support and implement some of the recommendations in the CCMP,
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the EPA established the Blackstone River Initiative (BRI) in 1991.
To further support the work on the BRI, the Governors of the Commonwealth of
Massachusetts and the State of Rhode Island signed a Memorandum of Understanding (MOU) in
1992. This MOU underscored the importance of the river system and estuary, the present
project, and the need for continued cooperation between the two states in order to attain the
restoration of the watershed system and the attenuation of pollutants to Narragansett Bay. In
response to the MOU, the MADEP selected the Blackstone River as one of four rivers to target in
the development of a total maximum daily load allocation (TMDL) management plan.
Additional national recognition to the importance of the river system was provided
through the United States Congress designating the Blackstone River Valley a National Heritage
corridor in 1993 for its historical importance. Also, the U.S. Army Corps of Engineers, through
their Coastal America's Program, has recently focused additional attention on the river.
In recognition of the primary importance of the Blackstone River to the future of
Narragansett Bay, the EPA established the BRI as a multi-phased, interagency, interstate project
to conduct the sampling, assessment, and modeling work necessary for restoration of the river
system and to prevent further deterioration of the resources of Narragansett Bay. The Initiative
was a collective effort between EPA, URI, MADEP and RIDEM. The basin-wide assessment of
the river, tributaries, and discharges was to be undertaken in two phases.
Phase I was completed for dry weather, steady state conditions. The primary effort of
Phase I was to monitor the chemistry and toxicity of the wastewater discharges and the river
water and sediments. Modeling of dissolved oxygen, nutrients and trace metals was
accomplished with the data from Phase I. The models provided the information necessary for
targeting point and nonpoint source reductions of contaminants. Phase II included a monitoring
of the major wastewater discharges and the river water during three rain storms. The BRI also
provided an umbrella under which other agencies and projects may coordinate efforts. Other
efforts conducted in parallel with this field program included an evaluation of fish and
macroinvertebrates.
The comprehensive BRI was a unique effort to provide a watershed evaluation under both
wet and dry weather water quality conditions. The possibility of conducting another project of
this scale is limited, therefore the BRI serves as a model for determining priorities for future
planning and study efforts.
1.2 Blackstone River Water Quality Issues: Dry and Wet Weather
From a historical perspective, water quality in the Blackstone River has improved
dramatically over the last 20 years as a result of requirements under the Clean Water Act. The
legislation mandated upgrading of municipal facilities and permitting of dischargers based upon
wasteload allocations. More recently, requirements to control stormwater runoff and combined
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sewerage overflows (CSOs) are also creating changes. These improvements should have brought
about significant reductions in conventional pollutants, producing changes in sanitary conditions,
aesthetics, and the ability to support aquatic life.
With these new regulatory measures in place, there is the need to characterize the current
water quality, document the changes and identify and quantify the existing water quality
problems which still must be solved. Specifically, the next stage of the cleanup will need to deal
with runoff, toxics and toxicity issues, eutrophication and movement of contaminants into
Narragansett Bay.
The Blackstone River is a river system that is characterized during low flow by the
effluent from many treatment plants and potential resuspension of contaminated sediments from
several impoundments. Studies conducted in the late 1980's indicated levels of trace metals well
above water quality standards at severed locations. The issue of instream toxicity still needs to be
resolved.
It is surmised, based on water quality evaluations of other rivers, that during wet weather
the conditions in the Blackstone River will be more complicated than under steady-state flows.
The variables influencing water quality that are unique to wet weather included rainfall
characteristics, runoff quality and quantity, river baseflow, river velocities and the potential for
sediment resuspension and the discharge from CSO and operating CSO facilities.
Results of previous dry weather surveys have showed sanitary conditions in the river had
improved significantly, based upon reductions in bacterial contamination from over 1 million
Coliform Forming Units (CFU)/100 mL for total coliforms and 200,000 CFU/100 mL for fecal
coliform, to near water quality standards for Class B waters.
The levels of solids and nutrients have been an issue in the past In the early 1980's,
ammonia was at toxic levels instream, but with the advent of nitrification at one of the largest
facilities in the watershed, this problem was resolved. However, nitrification in the facility results
in higher levels of nitrate below its discharge. The impact of the higher nitrate concentrations on
algal populations must be determined. Large algal growth creates dissolved oxygen problems.
This is true both in the river and in Narragansett Bay.
Phosphorus and its contribution to algal blooms in the river is a serious water quality
concern. Although the total phosphorus values may have been reduced due to better
management practices, the problems still exist with nutrient input from CSOs, bottom sediments
and the cumulative effect from the combined input of all municipal discharges.
In the past, many key regulatory decisions have been made around the need to improve
dissolved oxygen concentrations. The observed oxygen sags were typically found below the
major treatment facilities and within impoundments. Location and identification of current
problem areas is essential, as is the documentation of improved water quality due to recent
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regulatory actions.
1.3 Objectives
The Blackstone River is an interstate river, and as such has been studied for the most part
as separate segments. No coordinated effort existed prior to this study to determine sources of
pollution and river dynamics. Without a picture of the entire watershed, restoration of the river
and attenuation of impacts to Narragansett Bay could not be accomplished in a unified and
efficient manner. This initiative provided the forum and mechanism. The objectives of the study
were as follows:
1. Describe the steady-state, dry weather water quality conditions in a watershed to
include the river, major tributaries and major wastewater discharges;
2. Measure sediment oxygen demand;
3. Determine the toxicity of ambient water, sediments and wastewater dischargers;
4. Calibrate and validate a dissolved oxygen and a trace metal model for the river;
5. Utilize the models and field data to estimate the relative contribution of dry
weather point and nonpoint pollutant sources;
6. Utilize the models to predict annual dry weather loadings of selected constituents
to Narragansett Bay;
7. Describe the wet weather, water quality conditions in a watershed to include the
river, major tributaries and major wastewater discharges;
8. Identify and rank the major wet weather pollutant "hot spots" in the watershed;
9. Determine the toxicity of ambient water under wet weather conditions and
compare the results with criteria based toxicity;
10. Determine the relative importance between wet weather nonpoint and point source
pollutant loadings;
11. Determine the wet weather loading rate of pollutants, especially nitrogen, to
Narragansett Bay; and
12. Forecast annual wet weather loading rates.
1.4 Program and Report Organization
The responsibility of the dry weather field program design and execution was headed up
by the EPA and MADEP. The field program was a joint effort by URI, EPA and MADEP. All
samples were collected and analyzed under the control of URI with the exception of toxicity,
which was handled by the EPA Research Laboratory in Lexington, MA and fecal coliforms,
which were analyzed by MADEP at the Lawrence Experiment Station in Lawrence, MA. The
speciality studies involving macro invertebrates and fish were conducted by MADEP. A
preliminary assessment of the dry weather data was completed by MADEP. That assessment has
been expanded here by URI. The modeling efforts were completed by URI.
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The responsibility of the wet weather field program design and execution was headed up
by URL The field effort was a joint effort by URI, EPA, and MADEP. All samples were
collected and analyzed under the control of URI with the exception of toxicity, which was
handled by the EPA at Lexington. The interpretation of the wet weather data and the integration
of the results with the dry weather data was a joint effort between URI and MADEP. The
synthesis of this report was the responsibility of URI.
The report includes: (1) a general description of a watershed wide wet and dry weather
water quality study that will serve as a guideline for similar studies; (2) a detailed evaluation of
the Blackstone River's watershed hydrology and river hydraulics; (3) the dry weather data
interpretation; (4) dissolved oxygen and trace metal models including their calibration and
validation; (S) the wet weather data interpretation involving the evaluation of nonpoint and point
pollutant flows, system pollutant rankings and the development of annual loading rates; and (6)
the special extension to the BRI involving the detailed study of Rice City Pond. The report flow
chart is presented in Figure 1.1. The appendix is contained on a CD at the end of this report. It
includes all data from the dry and wet weather surveys, as well as input files, output files and the
models for dissolved oxygen and trace metal.
A draft of the BRI report was first published in April 1996. This was reviewed by
members of EPA, MADEP and RIDEM. In November 1997, the Region IU. S. EPA
Administrator requested the EPA Science Advisory Board (SAB) consider reviewing the BRI.
The BRI authors incorporated the comments, additions and corrections from the draft review in
the revised BRI report, which was published in February 1998 and sent to the SAB for review.
On March 24-25,1998 the Ecological Processes and Effects Committee (EPEC) of the EPA SAB
and other EPA officials met in Boston, MA to conduct the two day comprehensive review of the
BRI. The review team was made up of 14 members of the science and engineering community
from across the country. It included members from academics and the private sector.
Although the SAB rarely conducts regional reviews, the BRI presented an opportunity for
the Committee to assist a Regional office with peer review and to encourage Regional adoption
of integrated watershed assessment approaches. The Committee commended Region I and the
other BRI participants for initiating the study. Despite the limitations noted in the SAB report,
the Committee believed that the BRI study represented a significant advance for the Agency as
an initial attempt to integrate multi-agency, multi-scale, and multi-environmental stressor
considerations. They also noted that the contribution of volunteer and in-kind services was
impressive, and the BRI's accomplishments far surpass the dollars expended by the EPA.
The SAB review (EPA-SAB-EPEC-98-011) can be found on the U.S. EPA web page at
http://www.epa. eov/science 1 /fisca!98 .htm. The response of the BRI authors to the SAB review
is also at this location. All comments, questions and requests received, since the February 1998
publication, have been incorporated and/or discussed in this final report.
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Introduction
Chapter 1
Trace Metal
Modeling
Chapter 6
Program Description
Chapter 2
Application BRI Results
Chapter 8
Summary and Conclusions
Chapter 9
Dissolved Oxygen
Modeling
Chapter 5
Watershed Hydrology and River Hydraulics
Chapter 3
Dry Weather Water Quality Data
Collection and Interpretation
Chapter 4
Wet Weather Water Quality Data
Collection and Interpretation
Chapter 7
Blackstone River Water Quality Initiative
Wet and Dry Weather Data Analysis With Model Application
Chapter 7
Figure 1.1 Blackstone River Water Quality Initiative
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2.0 PROGRAM DESCRIPTION
2.1 Field Program
2.1.1 Watershed Description
General Considerations - The design of the BRI considered available information on the
river and its watershed including:
• the location, discharge history and permit requirements of all point sources;
• the location and history of known or potential nonpoint sources of pollution;
• the physical characteristics of the watershed including land use, river miles and
drainage areas;
• all political boundaries;
• the river uses including water supply, diversions, hydro power, navigation,
fisheries, waste assimilation; and
• a list of interested parties including regulatory agencies, municipalities and
conservation/citizen groups.
Blackstone River - For the Blackstone River, data was initially collected in an
independent study in 1990 conducted by URI and EPA.
2.1.2 Water Quality Station Selection
General Considerations - The selection of water quality sampling stations should meet
these objectives.
1. A sufficient number of river sampling sites should be selected to adequately
describe the impact of point and nonpoint sources of pollution on the river under
both wet and dry weather conditions.
2. The key point and nonpoint sources of pollution should be monitored.
The strategy is based on the following considerations:
a. a single sample at a cross section will adequately characterize the water quality
based on the assumption that the river at these sites is completely mixed;
b. the major sources of point and nonpoint pollution have been identified;
c. the location of all dams are known; and
d. the sampling stations are safely accessible at all times.
The location of the water quality stations should consider:
• the upstream and downstream boundaries (headwaters and mouth of the river);
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• the major tributaries as defined by size or anticipated water quality impact;
• other key locations such as political boundaries;
• the major pollutant point sources (if resources allow all point sources should be
sampled during the study);
• the boundaries of key modeling reaches;
• immediately above the major tributaries and pollutant point sources;
• sufficiently below the major tributaries and pollutant point sources to assure
complete mixing under both high and low flow conditions;
• further downstream below the major tributaries and pollutant point sources to
observe the fate of the pollutants and the response of the river;
• above and below expected sources of nonpoint pollutants;
• the locations where there is significant change in cross-section that will have an
impact on water quality and modeling decisions; and
• the locations that are accessible and safe 24 hrs a day in both wet and dry weather
conditions.
Blackstone River - A listing of the stations and a location map are provided in Table 2.1
and Figure 2.1 and a subwatershed areas are given in Figure 2.2. For the dry weather surveys
there were a total of 21 river stations: 15 along the Blackstone River and 6 near the mouth of the
major tributaries. Dry weather stations are coded with the prefix BLK. In addition, 2 point
source dischargers were sampled, in conjunction with the stream monitoring program. These
included the Upper Blackstone Water Pollution Abatement District (UBWPAD) and
Woonsocket WWTF for both pre and post chlorination.
For the wet weather surveys three stations were deleted due to budget constraints: 03,12,
and 19. One station was added; 00 to isolate the Worcester CSO outfall. Wet weather stations
are coded with the prefix BWW. In addition, five point source discharges were sampled. These
included from upstream to downstream, three direct discharges to the Blackstone River including
the CSO facility in Worcester (BWW22) (between BWW00 and BWW01), UBWPAD
(BWW23) (between BWW01 and BWW02), and Woonsocket WWTF (BWW24) (between
BWW17 and BWW18). Two direct discharges to the Seekonk River below the mouth of the
Blackstone River were also sampled, including Bucklin Point Narragansett Bay Commission
Facility (BP NBC) (BWW25) (below BWW21) and the BP NBC by-pass (BWW26) (below
BWW21). The NBC by-pass flowed over a weir at the northern end of the facility and received
no treatment.
2.1.3 Water Quality Sampling Frequency
General Considerations - The water quality sampling frequency should meet these
objectives.
1. A sufficient number of samples need to be taken to adequately describe the river's
water quality under both dry and wet weather conditions.
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Table 2.1 Water Quality Sampling Locations
Dry
Weather
Wet
Weather
River
Location
BWWOO
Blackstone
Greenwood St, Worcester, MA
BLK01
BWW01
Blackstone
Millbury St, Worcester, MA
BLK02
BWW02
Blackstone
McCracken Rd, Millbury, MA
BLK03
Blackstone
Riverlin St, Millbury, MA
BLK04
BWW04
Blackstone
Blackstone St (Singing Dam), Sutton, MA
BLK05
BWW05
Quinsigamond
Millbury St, Grafton, MA
BLK06
BWW06
Blackstone
Route 122A, Grafton, MA
BLK07
BWW07
Blackstone
Riverdale St, Northbridge, MA
BLK08
BWW08
Blackstone
Hartford St (Rice City Pond), Uxbridge, MA
BLK09
BWW09
Mumford
Mendon St (Rte 16), Uxbridge, MA
BLK10
BWWIO
West
Centerville (Off Rte 16), Uxbridge, MA •
BLK11
BWW11
Blackstone
Rte 122 Bridge, Uxbridge, MA
BLK12
Blackstone
Route 122 (near USGS Gage), Millville, MA
BLK14
BWW14
Branch
Route 146A, Slatersville, MA
BLK13
BWW13
Blackstone
Bridge St (State Boundary), Blackstone, MA
BLK15
BWW15
Mill
Winter St, Woonsocket, RI
BLK16
BWW16
Peters
Route 114, Woonsocket, RI
BLK17
BWW17
Blackstone
Hamlet Ave (Rte 122 and 126), Woonsocket, RI
BLK18
BWW18
Blackstone
Manville Hill Rd, Cumberland, RI
BLK19
Blackstone
School St/Albion Rd, Cumberland, RI
BLK20
BWW20
Blackstone
Lonsdale Ave, Lonsdale, RI
BLK21
BWW21
Blackstone
Main St (Slater's Mill), Pawtucket, RI
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LOCUS MAP
Worcester
Quinsigamond
River
llackstonci
: River
West
River
Mill
River
Mumford River
Peters
RHODE ISLAND
Branch River
Pawtucket 21
• Sampling Station
Providence
Figure 2.1 Sampling Station Location
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STOW
uMINGHAM
ASHLAfH
HOLLIS*
uptoi
FRANKLIN
Legend
iVIajor Roads
Hydrography
Towns Boundary
— State Boundary
Tributary Basin Boundary
1 1 IVIajor Basin Boundary
Figure 2.2 Blackstone River Watershed Sub-basins (Mass DEP/GIS Office)
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2. Sufficient information concerning the river and its pollutant sources should be
available to allow for water quality models to be calibrated and validated.
The strategy is based on the following considerations:
a. for dry weather the river is steady-state;
b. for wet weather the river flows are steady before the start of runoff, and the river
will return to those conditions within a reasonable period of time after runoff
ends; and
c. in a river for wet weather the entire pollutograph is important, and peak
concentrations typically coincide with the peak flows.
The design of the dry weather sampling frequency should consider the following:
• each river survey should be conducted over a 24 hour period (if resources allow
the study should be extended for 48 hours for dissolved oxygen);
• each station should be sampled a minimum of 4 times in this period at 6 hour
intervals (start time should coincide with predawn hours to observe the lowest
oxygen concentrations);
• point sources should be sampled for five days leading up to and including the day
of river sampling (these samples should be 24 hour composites with samples
taken hourly and weighted by flow); and
• at least three surveys should be completed with significantly different flows.
Blackstone River - The dry weather program consisted of three 48 hour surveys: July 10-
11,1991 for Survey 1, August 14-15,1991 for Survey 2 and October 2-3,1991 for Survey 3.
Samples for dissolved oxygen (DO) determination were taken every six hours over the 48
hour period. The first sample was taken in the hours just before sunrise or around 0400. Field
measurements for temperature, pH, and conductivity readings were also taken at the same time.
Samples were taken four times in the first 24 hour period at six hour intervals for the
determination of the five-day biochemical oxygen demand (BODs), total suspended solids (TSS),
volatile suspended solids (VSS), chloride, Total Kjeldahl-Nitrogen (TKN), dissolved ammonia-
nitrogen (NH3-N), dissolved nitrate-nitrogen (N03-N), dissolved orthophosphate (P04-P), total
and dissolved metals (cadmium, chromium, copper, lead, and nickel), hardness (calcium and
magnesium) and toxicity. Nitrogen and phosphorus are reported as mg/L of N and mg/L of P,
respectively.
Fecal coliform samples were collected during the 0400 run on the first day of each
survey. Samples were also collected for chlorophyll a analyses on the 0400 and 1600 river runs
on the first day of each survey period.
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Effluent analyses were conducted on 24-hour composite samples collected daily for five
days prior to the water quality surveys. The effluents sampled included the UBWPAD and the
Woonsocket WWTF. Wastewater samples were handled and analyzed for the same parameters
as the river samples.
Effluent samples were also collected from the two largest dischargers, as well as 10 other
dischargers in the Blackstone River Basin as part of the toxicity testing at these facilities. The
two additional facilities tested in RI were Okonite Industries and GTE. In MA, the eight
additional facilities tested were: Uxbridge WWTF, Northbridge WWTF, Millbury WWTF,
Guilford Industries in Douglas, Douglas WWTF, Grafton WWTF, New England Plating in
Worcester, and Worcester Spinning and Finishing in Leicester. Samples were not collected
concurrently with the river surveys conducted during this study. Instead, the facilities were
sampled once each during the summer of 1991, either during June or August, except for the two
largest facilities, which were sampled in both July and August. As part of this testing, the
samples were analyzed by a separate laboratory under contract with the EPA, for aluminum,
cadmium, calcium, chromium, copper, lead, magnesium, nickel, zinc, ammonia, total solids,
TSS, total organic carbon, and alkalinity.
The design of the wet weather sampling frequency should consider the following:
• sampling should be conducted prior to the storm, during the storm and after the
storm until the river returns to baseflow conditions;
• the frequency of sampling will be dependent on the estimated time of
concentration in the watershed (this can be estimated in advance and monitored
during each storm);
• the frequency of sampling will also be dependent on the weather forecast,
specifically the magnitude and duration of the rainfall (for this reason the number
and timing of samples must remain flexible and may, in fact, be modified during
the storm if conditions change and sufficient sample bottles should be prepared to
accommodate a worst case scenario and assure adequate sampling for the entire
pollutograph);
• if the number of samples taken exceeds the budget for samples to be analyzed,
decisions to delete samples should only be made with careful consideration to the
rainfall hyetographs, river hydrographs and field water quality measurements;
• in the special case where a pollutant can not be sampled for the entire period due
to budget limitations, sampling must occur a minimum of three times: prestorm,
first flush and at peak flow;
• at the major pollutant point sources sampling should be at the same frequency as
the river sampling (if resources allow all point sources should be sampled during
the study); and
• at least three storms should be sampled with significantly different rainfall totals.
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Blackstone River - The wet weather program consisted of three storms: September 22,
1992, November 2,1992 and October 14,1993. Rainfall characteristics and stream flow
determinations are discussed in detail in Chapter 3.
A total of 16 samples were taken at each station for each storm. A prestorm sample was
collected 3-4 hours in advance of the storm to define the baseline dry weather loads. Initially^
sampling was set at a higher frequency to identify the local stormwater and first flush
contribution to the receiving water. Samples were taken starting at 3 hour intervals from time o
(observed runoff) and continuing through 12 hours, followed every 4 hours for the next 36 hours
with one sample on the third day to define the end of storm. Samples were transported to a field
laboratory located central to the watershed at the Woonsocket WWTF. Samples were processed
and distributed from the field lab.
Each station was sampled at the surface. Field measurements included temperature, pH,
conductivity and DO. Laboratoiy chemical analysis included TSS, VSS, BOD}, chloride,
sodium, NHj-N, N03-N, P04-P, total trace metals (cadmium, chromium, copper, lead, nickel and
zinc), hardness (calcium and magnesium), fecal coliform and E. coli. Toxicity testing was
performed on samples representing first flush and peak flow for each station and discharge.
Samples at the two WWTFs, UBWPAD and Woonsocket, were collected at the same
frequency as the river samples and analyzed for the same set of constituents given above.
2.1.4 Sample Collection and Handling
General considerations - In the collection of the water quality samples the following
should be considered.
1. A field laboratory needs to be set up central to the watershed.
2. Chain of command for field and laboratory crews must be clear. The decision to
sample, particularly in wet weather events, can be prolonged, frustrating, and may
not be made until right up to the point where the initial data collection has to be
started. Communication is crucial.
3. Location for sample collection should be clearly defined and consistent.
4. Procedures for sample collection and preservation must be defined and understood
by all field crews.
5. Laboratory analysis procedures and schedules should be available and understood.
6. Staffing levels need to be sufficient for expected sampling duration.
7. Field equipment needs to be inspected with adequate back-up equipment.
There should be appropriate notification of other agencies. Late night encounters with
police officers unaware of sampling events can be stressful and time consuming for all. If
qualified volunteer organizations exist, they should be welcomed.
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Staffing decisions can be important. Site locations, whether urban or rural, and
associated safety considerations may dictate staff assignments. Particular concerns are related to
the all night sampling situations that always seem to occur for wet weather events.
Blackstone River - Samples were collected using Teflon buckets and pre-cleaned plastic
bottles. Samples were stored in ice for transport. A field laboratory was set up at the
Woonsocket WWTF. All samples were processed through the field lab before distribution to the
designated laboratories. Details to the handling and preservation of the samples may be found in
a later section.
2.1.5 Flow Monitoring
General Considerations - Developing an understanding of the watershed hydrology and
hydraulics before the final design of the water quality surveys is essential to the success of any
study, given the typical constraints of time and money. One should allow a minimum of
coverage between high spring flows and low summer flows. This time period covers the months
that will be used to collect both the dry and wet weather water quality data. If resources allow a
1 year period is optimum.
The development of the river flows should include the following objectives.
1. Sufficient flow measurements should be determined at key locations to permit the
development of accurate flow profiles.
2. The ability to determine flows in real time quickly and easily under wet weather
conditions should be available.
3. Cost of data collection should be a consideration in the final design of the water
quality surveys.
4. The data should be adequate to allow for the calibration and validation of a
transport model.
The strategy i£ based on the following assumptions:
a. ground water inflow is not directly measured but instead is back calculated from
direct measurements of river and point source flows, assuming it is generally
proportional to the drainage area;
b. a dry weather survey is under steady-state conditions, which means that flows do
not change significantly over the period of the survey; and
c. flows in a wet weather survey may be determined based on a relationship between
river stage and discharge.
Some river systems will already have flow monitoring occurring. The obvious and most
extensive source of historic and current flows will be the United States Geological Survey's
(USGS) permanent gaging stations. In addition, several other sources including federal, state or
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municipal agencies (ie. fisheries) or industries (ie. hydro power) may have data. The quantity,
quality and format of this data needs to be determined. In addition to river flows, the quantity,
quality and format of all point source data will also need to be determined.
It will be unusual to find a watershed that has sufficient flow data. Therefore, flows will
need to be determined during the surveys. A procedure for the development of a supplemental
flow network is given below. The development of temporary flow sites, where stage/discharge
relationships will be determined, is necessary.
The determination of the number of temporary river flow sites requires the consideration
of the following:
• at the upstream and downstream boundaries (headwaters and mouth of the river);
• at a location(s) central to the watershed, for instance, one station for the watershed
to be divided in half or two stations for the watershed to be divided into thirds;
• at the major tributaries as defined by size or anticipated water quality impact;
• at other key locations such as political boundaries, critical water quality reaches,
and existing structures (ie. spillways, weirs); and
• at a location that coincides with a water quality sampling station for ease of access
and monitoring during water quality surveys.
The establishment of the river stage monitoring locations at the temporary flow sites
should consider the following:
• stage locations should be readily accessible even under high flows;
• stage locations should still be in the water even under low flows;
• one primary reading for this staff gage should be located either on a permanent
structure (ie. bridge) or at an installed reference point (ie. rebar) placed along the
side of the channel);
• one secondary reading from a mark located on a structure (ie. bridge) to the
surface of the water,
• both primary and secondary locations should be surveyed to a local bench mark to
assure accuracy throughout the course of the study (once established this should
be checked during the middle of the sample collection period and at the end of the
study); and
• the river stage monitoring locations should be filed with the local environmental
agency.
The development of the stage/discharge relationships at the temporary flow sites should
consider the following:
• the stage/discharge relationships require a minimum of six measurements of flow
and stage typically taken between April and October (if time and resources allow,
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the optimum is 12 measurements, with one taken every month for one year (the
data collection should cover the range of flows (high to low) expected during the
water quality monitoring program);
• selecting the cross-section for flow measurement should follow recommendations
as outlined by USGS with special attention to accessibility and minimum seasonal
interferences;
• flows should be determined using the USGS Velocity Area Method;
• flow/stage relationships should be developed through regression analysis; and
• the stage/discharge relationships should be filed with the local environmental
agency.
For dry weather surveys, when possible, flows should be directly measured once using the
USGS Velocity Area Method during each dry weather survey. These measurements are
independent of the stage/discharge relationships and can be used to validate them. Stage
readings should be taken when a water quality sample is taken. This will provide a confirmation
that the system is steady-state. Daily average point source flows should be obtained from each
facility for five days leading up to and including the survey date.
For wet weather surveys, stage readings are taken each time water quality is measured.
Flows are calculated from the stage/discharge relationships. The major pollutant sources should
have flow data at the same frequency and duration as the water quality sampling program. All
point sources should have both daily flows for the day before, during and after the storms, and
total discharge volumes that coincide with each storm's duration.
For continuous stage readings the following is recommended:
• a minimum of two continuous stage recorders located at the mouth of the river
and central to the watershed (stage/discharge relationships must be at these
locations); and
• additional locations to be considered would include the major tributaries and
headwaters.
The additional data that can be developed from the flow program includes the following:
• flow to flow relationships between the temporary stations and the permanent
gaging sites, which will allow the development of long term information, as well
as, average daily flows for the temporary sites (if a permanent gaging station is not
within the watershed, one can be selected from another watershed that is similar
with respect to geology, topography, land use and size); and
• flows can be determined for river locations not monitored by extrapolating from a
monitored site based on subwatershed drainage areas.
Blackstone River - Instream flow measurements were available at 9 sites. There are three
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USGS gaging stations in the watershed. These are located on the Quinsigamond River at North
Grafton, MA (upstream of 05), the Branch River at Forestdale, RI (upstream of 14) and the
Blackstone River at Woonsocket, RI (17). USGS also established six temporary gaging stations
for this study. These included four on the Blackstone River (01,04,11, and 20) and two on
tributaries (Mumford 09 and Peters 16). The system flows are discussed in detail in Chapter 3
and the development of the flow profile is detailed in Chapter 5.
2.1.6 Rainfall Monitoring
General Consideration - The development of the rainfall network should include the
following objectives.
1. Rainfall measurements should be sufficient to develop an accurate rainfall
watershed distribution for each storm.
2. The ability should be developed to monitor rainfalls in real time to support field
decisions.
3. The data should be adequate to allow for the calibration and validation of a
transport model.
The strategy is based on the following assumption:
a. average watershed rainfall characteristics can be represented by a network of
rainfall gages.
Some watersheds will already have rainfall monitoring in place. The obvious and most
extensive source of historic and current rainfall records will be the National Weather Service
(NWS) permanent rainfall stations often located at airports. In addition, several other sources
including federal, state or municipal agencies (ie. water supply groups, sewage treatment
facilities) may have data. The quantity, quality and format of this data needs to be determined.
An evaluation of existing data will be essential in determining the target rainfall characteristics
for the study.
It will be unusual to find a watershed that has sufficient rainfall data. Therefore, rainfall
will need to be determined during the surveys. A procedure for the development of a
supplemental rainfall network is given below.
To determine the number of temporary rainfall sites required the following should be
considered:
• the number of rainfall stations is driven by the study objectives (in the case of the
Blackstone River watershed 16 rainfall gages made up the network or about one
gage per 30 square miles); and
• rainfall recording sites should be uniformly distributed across the watershed (if
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this is not possible, at a minimum they should be located within the major
subwatersheds).
To determine the rainfall monitoring locations, the following should be considered:
• placement of continuous rainfall monitoring equipment should be in an elevated,
protected area, such as the roof of a municipal building for the duration of the
study (the drawback to this placement is that the gages may not be accessible at all
times); and
• as a storm develops, adjustment to the frequency and duration of the sampling
program will often have to be made, therefore, continuous access to key locations
in the rainfall network during the storm is essential. (Therefore, a rainfall gage at
the field headquarters is essential and inexpensive manual read gages should be
placed at most water quality stations to be recorded by water quality sampling
crews each time a sample is taken).
The rainfall and stream flow data should be applied in the following manner:
• rainfall can be averaged based on either the Thiessen or Isohetyl methods and can
be reported as an average for the entire watershed, averages for individual
subwatersheds or as a cumulative average as one proceeds from the headwaters to
the mouth of the river;
• for the flow monitoring period, a comparison of each storm and the continuous
stage/flow records before, during and after the storm will provide an illustration of
the response of the river to that storm;
• this analysis will be used to design the frequency and duration of the wet weather
sampling program; and
• this analysis will provide input for calibration of a hydraulic/hydrologic model.
Blackstone River - There were a total of 16 rain gages in the Blackstone River network: 7
operated by the National Weather Service; 3 maintained by cities and towns; 1 by the state and 5
added by URI.
2.1.7 Storm Selection
General Consideration - The selection of storms for a wet weather study should include
the following objectives.
1. The study should isolate the effect of a single storm on a river.
2. A storm should be selected to provide a measurable response of flow and water
quality in the river.
3. Storms should be selected that have different rainfall characteristics.
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Target rainfall characteristics should be set in advance including minimum and maximum
duration, minimum total rainfall, minimum antecedent dry period and minimum post storm diy
period.
• Minimum Duration (6 hours) - Convective storms should be avoided because
rainfall distributions will be significantly different across the watershed. A
drawback is the elimination of many storms during certain periods of the year,
such as June, July and August.
• Maximum Duration (24 hours) - This limitation is based on the cost of sampling
and analysis. The maximum number of samples to be taken at each site will be
set in advance.
• Minimum Total Rainfall (0.5 inches) - This value should be based on several
factors including the analysis of local rainfall data to determine a storm's
frequency of return, rainfall at which one would expect a response from an
important component of the system such as CSOs, magnitude of prestorm river
flows (large prestorm flows will quickly assimilate small storms) and the size of
the watershed versus the response of the river (a larger watershed requires a larger
storm).
• Minimum Antecedent Dry Period - This time period is needed to assure that the
system has returned to steady state conditions and to allow for a minimum buildup
of contaminants in the watershed.
• Minimum Post Storm Dry Period - This time period is needed to allow for the
return of the river to prestorm conditions.
The ability to forecast acceptable storms several hours in advance is critical.
• The support of professional meteorologists and real-time access to information on
the Internet is essential to the success of any wet weather field program.
• Field headquarters should be located central to the watershed. Communication
with field crews at strategic locations will allow for informed decisions.
• Since prestorm sampling is required at least 3 to 4 hours in advance of the rainfall,
storms with a leading edge that are well defined in time and space will reduce the
possibility of failure.
BJackstone River - Establishing rainfall criteria was critical to the success of the
monitoring program and the interpretation of the data. The goal was to isolate the effect of a
discrete event to permit the characterization of runoff and the determination of the impact on
receiving water quality. Rainfall criteria were set in advance of the field program and consisted
of the following: a minimum duration of six hours and a maximum of twenty-four hours; a
minimum of 0.5 inches of total rainfall; an antecedent dry period (ADP) of three days; and a post
storm period of three days. The criteria is designed to sample storms associated with frontal
systems that provide uniform rainfall over the watershed. Storm development and movement
were tracked by meteorologists with the final decision for the call of the storm provided by URL
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2.2 Water Quality Computer Modeling
General Considerations - Many watershed studies will include modeling of some
factor(s) affecting the quality of the water. Models can vary greatly in their level of
sophistication, ranging from simple spreadsheet calculations to complex computer models.
Perceived problems and regulatory mandates are the usual considerations central to the decision
to model. Cost, time, and data availability determine the magnitude of the study.
Occasionally a problem that initiates a model application may be identified during the
course of a study. A decision to apply a computer model usually is made in the study's design
phase. It is crucial that the aspects of the study described in the hydrology and hydraulics section
be designed to collect the data needed for the construction, calibration, and validation of a
model(s). When computer models for quantity and/or quality are to be applied, it is important
from a time and cost standpoint, that all the data necessary to support the model application is
collected from the start of the study. Additionally, the legitimacy of the calibrated and validated
models can be undermined by the lack of supporting data directly acquired. Site location, flow
data, and storm selection are important to both water quality and hydrologic data.
Many authors have addressed the issues involved in applying a computer model and the
appropriate applications for particular models. A means for identifying the most appropriate
model and its data requirements should be a significant part of a study design. Some general
recommendations include the following:
• an application of a computer model have an explicit goal;
• expertise in the model should be available (a large study should not be regarded as
an opportunity to learn how to use a model); and
• the model should be selected with a clear understanding of the study's goal and
the availability of data, with the understanding that additional model complexity
can always be added if conditions warrant (typically the more complex a model,
the more data intensive).
Blackstone River - For DO modeling, the EPA supported model, QUAL2E, was selected.
This model is a steady state model that simulates DO and all the constituents that impact DO
including BOD5, nutrients and productivity. The authors have had considerable experience with
the model which factored into its selection.
The computer modeling of trace metals is very complicated, since the number of variables
that account for the fate and transport of trace metals in a river system is large. In addition, the
more complex computer models require simulation of both the water column and sediment
compartments. For these models, data requirements are high and often times difficult to come by
for an entire river. The more complex a model, the more accurately its algorithms represent the
system, but the more difficult it is to calibrate and validate. A major disadvantage of most metal
fate and transport models is that few have been verified to real field data. The model selected for
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this study is a trace metal model that has been used by the authors in several stream systems in
Rhode Island. It adopts a very simple but effective approach to trace the dispersal pattern of
metals by considering two simplified equations involving net sediment transport and metal
partitioning.
2.2.1 Data Collection
General Considerations - As in the collection of hydrologic data (ie. flows and rainfall),
collection of data for quality modeling will include background research into many sources of
historic and current data. Federal, state, and municipal agencies may have data. Public and
private dischargers will have point source data.
The results of previous modeling efforts, whatever the degree of success, can be a
valuable reference tool. A more sophisticated modeling effort could be added onto the results of
previous efforts. Additionally, previous modeling attempts or preliminary sampling may have
highlighted a certain stream reach that has a particular problem worthy of further study. A more
sophisticated application of a model could focus on this reach, rather than the entire length of the
system, sharply reducing the number of samples to be taken.
Just as in the hydrologic data collection, data for quality models should, at a minimum, be
collected for a period of time that spans the expected range of water column chemistry. In both
dry and wet weather, it is important to capture data to the extremes of expected ranges.
Some supporting data for particular model applications may not be available from local
sources. Possible examples are solar values applied to plant growth, airborne pollutant
concentrations, and parameters related to snowmelt rates. Some data may be available from
federal agencies or private vendors at a price, but recent data from the immediate region of the
study may not be readily available. Models may have default settings recommended. In some
cases, judicious application of values obtained from other studies or extrapolation from historical
or spatially remote data may be necessary.
Special considerations must also be made for other complex sampling procedures. In
general, this would include anything outside the experience of the organization doing a study.
The study plan would then include consideration of using other resources with individuals more
familiar with the processes involved, or training of personnel and the purchase or building of new
equipment.
Some sampling and analysis is best left to specialty organizations. Costs associated with
certain analyses, safety, or specialized sample collection procedures would dictate that this data
collection be assigned to those best able to deal with these issues. Some data (ie. Sediment
Oxygen Demand [SOD]) has limitations, whether the data is collected in-situ or via sample
extraction and laboratory analysis. An understanding of the requirements and difficulties
associated with data collection has to be considered in modeling.
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Blackstone River - SOD rates were a parameter that was required in the wasteload
allocation model for the Blackstone River. Sampling was undertaken behind the existing
impoundments on the river because, it is hypothesized, that these are the areas of maximum DO
consumption. The sediment and overlying water cores were only sampled on one occasion.
Each station had five replicate cores taken. The SOD rate for the station is an average of the
rates measured in the five replicate cores.
2.2.2 Model Construction
General Considerations - As data is collected and tabulated, the quality of the data needs
to be evaluated. Values need to be compared to expected ranges and to the other data acquired.
Appropriate statistical analysis should be applied, and outliers identified and evaluated.
Deficiencies in the sampling plan can be corrected before needless expense is incurred.
Modifications needed to correct some possible skew in the data must be built into the study.
Construction of model applications should be accomplished in stages, rather than all at
once. Generally, a model should be proven hydraulically, then for conservative constituents, and
finally for non-conservative constituents. Conditions influencing the calculation of decay rates
must be understood.
In developing a water quality study to calibrate and validate a model, the following
questions should be asked during the study's design.
• What is an acceptable level of accuracy?
• How is that accuracy to be defined?
• Is the model sufficiently accurate for the purpose of the study (ie. 7Q10, first
flush) and over the full range of observed values?
• Will it support regulatory decisions, or worst case, a challenge?
Blackstone River - The procedures followed in the BRI for the steady state modeling are
given in the flow charts of Figures 2.3 and 2.4.
2.2.3 Model Application
General Considerations - After a computer model is satisfactorily calibrated and
validated, it may be applied for development of regulations, interpretation of current quality, and
prediction of future modifications. The final step to development of computer models could be a
critical review of the model. Does it answer the questions that were central to the initiation of
the study? Does it raise new questions that justify more sophisticated modeling?
2-17
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2.3 Chemistry and Toxicity
2.3.1 Water Column Chemistry - Methods and Methodologies
A summary of the methods used in the chemical analyses are presented in Table 2.2.
All polyethylene bottles and accessories used in the analysis of trace metals were pre-
soaked for three 48 hour periods in a 3% nitric acid solution and then rinsed with deionized (DI)
water. The polycarbonate filters were soaked in 3% nitric acid for 10 days and tested for
contamination by filtering DI water.
For the analyses of total metals, an experimentally determined volume of HNOj (Baker
Ultrex II) was added to 60 mL bottles containing dissolved trace metals, and 60 mL bottles
containing total trace metals. The acid volume was sufficient to leach the trace metals from the
particulate phase (one week) and keep the trace metals from adsorbing to surfaces or complexing.
Cadmium, chromium, copper, lead, nickel and zinc were analyzed in duplicate samples directly
using the Perkin-Elmer 5100 PC atomic absorption spectrophotometer (AAS) equipped with a
HGA Graphite Furnace. Analyses for magnesium and calcium were performed on a Perkin-
Elmer model 3030 B flame AAS. Quantification was based upon calibration curves of standard
solutions in the approximate acid proportions to the samples. The calibration curves were
plotted and all concentrations were calculated by Perkin-Elmer analytical software.
The Perkin-Elmer AAS, 5100 PC is equipped with a Zeeman/500 system designed to
provide the graphite furnace with background correction. Such systems enhance measurement
sensitivity by reducing any interferences in the sample background.
Analyses for dissolved N03 and dissolved P04 were conducted using a Technicon
Autoanalyzer II. All samples were run in duplicate. The sampler tray was loaded with a set of 5
prepared standards every 14 samples analyzed. Reagent blanks and continuing calibration
standards were also introduced for confirmation.
The basic method for nitrate and nitrite analysis is Technicon Industrial Method #158-71
W/tentative (1972). This procedure was adopted from the procedure used by the Marine
Ecosystem Research Laboratory (MERL) at the Graduate School of Oceanography at URI
(MERL 1972). The nitrate and nitrite analysis involved reduction of nitrate to nitrite by passage
through a copper-coated-cadmium column and used an alkaline-ammonium-chloride solution to
complex the oxidized cadmium ion. This complexation prevented precipitation of cadmium
hydroxide and thus restriction of flow. The generated nitrite reacted with acidified sulfanilamide
and N-(l -naphthyl) ethylene diamine dihydrochloride to form a red azo compound which was
measured at 540 nm in a flow cell. There are two primary differences between the EPA method
353.2 for nitrate analysis and this method. The first is the use of EDTA in the EPA method to
supplement the NH4C1 as complexing agent. The second difference is the concentration of the
reagents relative to sample volume. The Technicon Industrial Method uses 10 times less NH»C1
2-18
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Violations
Proposed Remediation
Time of Travel
Data
Nitrogen Data
Nitrification Rates
Water Quality Standards
Velocity/Depth Data
Reaeration Rates (Kj)
Sediment Oxygen
Demand (SOD) Rates
NH3-N Profile Development
Calibration & Validation
Flow Data & Profile Development
Calibration & Validation
Model Application for Critical Water Quality Conditions
Additional Data Collection in Specific
Stream Reaches - Specialty Studies
BODj Profile Development
Calibration & Validation
DO Profile Development
Calibration & Validation
Model Description
Physical Data & Stream Reach Network
Recalibrate, Modify or Change Models to Increase
Detail and Complexity in the Problem Area
Water Quality Problems
Stream Reach Identification
Point/Nonpoint Source Identification
NO3-N, P04-P, and Chi a Profile
Development
Calibration & Validation
Figure 2.3 Modeling Dissolved Oxygen on the Blackstone River
2-19
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Violations
Trace Metals Data
Proposed Remediation
Time of Travel
Data
Metal Partition
Coefficient (Kp)
Hardness Data
Acute & Chronic Criteria
Total & Volatile
Suspended Solids
Data (TSS/VSS)
TSS Profile Development
Calibration & Validation
Net Sediment Transport
Coefficients (K^)
Metal Partition Relationships
Kp vs TSS
Flow & Velocity Relationships
Flow & Depth Relationships
Trace Metal Profile Development
Calibration & Validation
Flow Data & Profile Development
Calibration & Validation
Model Application for Critical Water Quality Conditions
Net Sediment Transport Relationships
K,,, vs Velocity
Additional Data Collection in Specific
Stream Reaches - Specialty Studies
Model Description
Physical Data & Stream Reach Network
Recalibrate, Modify or Change Models to Increase
Detail & Complexity in the Problem Area
Water Quality Problems
Stream Reach Identification
Point/Nonpoint Source Identification
Figure 2.4 Modeling Trace Metals on the Blackstone River
2-20
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Table 2.2 Summary of Analytical Methods
Parameter
Units
Methodology
Reference
Maximum Holding
Time
Preservation
Total Metals
Cr, Cd, Cu, Ni, Pb, Zn
H g/L
Graphite AA
EPA
6 Months
Acidified with HN03 to a pH s 2
Dissolved Metals
Cr, Cd, Cu, Ni, Pb, Zn
Mg/L
Graphite AA
EPA
6 Months
Acidified with HN03 to a pH £ 2
Ca, Mg
mg/L
Flame AA
EPA
6 Months
Acidified with HN03 to a pH £ 2
Suspended Solids
mg/L
Gravimetric
STM
3 Days
Refrigerate at 4 °C
Chlorides
mg/L
Orion Probe
STM
28 Days
Refrigerate at 4 °C
bod5
mg/L
DO Probe
STM
2 Days
Refrigerate at 4 °C
Chlorophyll a
n g/L
Spectrophotometer
STM
2 Weeks
Freeze
TKN
mg/L
Block Digester
STM
2 Days
Refrigerate at 4 °C
NHj-N
mg/L
Spectrophotometer
STM
2 Days
Refrigerate at 4 °C
N03-N,P04-P
mg/L
Auto Analyzer
MERL
4 Weeks
Acidified with H2S04 to a pH ^ 2
EPA - USEPA (1979); STM - Standard Methods (APHA-AWWA-WPCF) 1989; MERL - Marine Ecosystem Research Laboratory,
Graduate School of Oceanography, The University of Rhode Island. MERL Series Report No. 1 "Manual of Biological and Geochemical
Techniques in Coastal Areas". Adapted from Technicon Industrial Method # 158-71 W/tentative (1972).
-------
and 4 times less color reagent.
The phosphate method followed the Technicon Industrial Method #155-71W, which is
also based on colorimetry. The sample was first diluted and then the mixed reagent was added to
the stream. This mixture was heated to 36 degrees Celsius (°C), after which the absorbance of
the phosphomolybdate complex was measured at 820 nm in the flow cell.
All glassware used in the Total Kjeldahl Nitrogen (TKN) analysis were pre-soaked in a
\% hydrochloric acid solution. The block digestion method was used for the TKN analysis. A
30 mL TKN sample was transferred into Kjeldahl tubes after which 5 mL of concentrated
sulfuric acid was added. A catalyst was then added to each tube along with 2 boiling chips. The
tubes remained quiescent for 15 minutes and then were mixed with a vortex mixer. The tubes
were then transferred to the pre-heated (200 °C) digestion block for one hour. The temperature
on the block was then reset to 380 °C and digested for another 2.5 hours. The tubes were then
removed from the block and allowed to cool to room temperature. Nitrogen free DI water was
then added to make-up the original volume of sample (30 mL) and the samples were analyzed for
ammonia.
All glassware used in the ammonia analysis were pre-soaked in a 1% hydrochloric acid
solution. Standard Methods method 4500-NH3 D. Phenate Method was utilized for ammonia
analysis. After preparation, absorbance was measured by utilizing a Milton Roy Spectronic 1001
Plus Spectrophotometer. According to Standard Methods, the phenate method has been proven
successful for samples with low interference background of alkalinity less than 500 mg/L as
CaC03 and acidity lower than 100 mg/L as CaC03. The automated Phenate method for
ammonia determination is typically used for drinking waters, and domestic and industrial wastes
in the range of 0.01 to 2.0 mg/L-N.
All glassware used in the Five Day Biochemical Oxygen Demand (BOD5) analysis were
washed using a phosphate free detergent and then rinsed with DI water. Standard Methods
method 5210 B. 5-day BOD Test procedures were followed. Seed was obtained from a local
WWTF and was used for the UBWPAD and Woonsocket WWTF samples only. Based on
recent research in other surface waters in RI and MA, BODs in stream concentrations were
typically below 7 mg/L. These lower concentrations permit the use of the direct method of
analysis. The direct method does not require dilution or seeding (Sawyer and McCarty 1978).
The Woonsocket WWTF and UBWPAD BODs samples were diluted 2 times. A series of
3 samples per survey were run with an extended time of 30 days. Nitrogenous inhibitor was
added to these extended time samples. A series of five glucose-glutamic standards were
analyzed. DO concentrations were measured by using a Yellow Springs Instrument (YSI) BOD
probe and DO meter. Before and after each survey, measurements by the DO probe were cross
checked with measurements by the Winkler method {Standard Methods, 4500-0 C.) for
confirmation.
2-22
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Chlorophyll a was analyzed by following Standard Methods method 10200 H.
Chlorophyll. Color absorbance was measured by utilizing a Milton Roy Spectronic 1001 Plus
Spectrophotometer. Gelman A/E glass fiber filters (0.45/um) were used for filtering the samples.
Filtered samples were frozen until analyzed.
TSS was analyzed by following Standard Methods method 2540 D. Total Suspended
Solids Dried at 103-105 °C, and VSS by method 2540 E. Fixed and Volatile Solids Ignited at
550 °C. The samples were refrigerated upon collection and filtered within 48 hours of collection
in the URI-CVE laboratory. Gelman A/E glass fiber filters (0.45 /zm) were first pretreated with
three successive 20 mL volumes of DI water. Filters were ignited for 15 minutes in a muffle
furnace at 550 °C and then cooled in a desiccator until ready for use. Filters were weighed
immediately prior to use. The volume of sample to be filtered was between 500-1000 mL.
Fecal coliform analyses were performed in a commercial laboratory (Biological
Analytical Laboratory). This laboratory followed the Standard Methods method 9213 D.3
Escherichia coli and method 9221 E. Fecal Coliform to confirm the previous results.
2.3.2 Chemistry Quality Control and Quality Assurance
Spiked samples were prepared and measured in five stream samples for each survey and
one sample each from the two WWTFs. The stream samples were selected at random and were
spiked with a known standard concentration. Percent recovery of spiked standards was expected
to be greater than 90%. If recovery was less than 90%, adjustments were made as indicated
above to take care of interferences.
Laboratory instrument calibration was performed by using a standard calibration curve,
which was a series of standards (at least three) and a reagent blank that resulted in a linear
relationship between the analyte signal and concentration. Standards were prepared using
laboratory grade chemicals. For automated analyses, calibration curves were run at least twice
for each sample tray loaded. Continuing calibration standards were run at least once between
each calibration curve.
The method of standard additions was run concurrently for one sample from 5 of the 21
river stations and for one sample from each of the treatment facility effluents. This was used as a
check for possible matrix interferences. This was also a measure of the recovery of standards.
If the slope of the standard calibration curve and method of addition curve were not
similar, matrix effects were considered to affect the analyses. In such cases, the methodology
was adjusted to take care of such interferences. Examples of such adjustments include using a
method of addition calibration curve for samples with similar matrices, dilution of the sample to
lower matrix effects, or an addition of matrix modifiers for metals.
The above procedure applies to the trace metals, Ca, Mg, dissolved N03-N, dissolved
2-23
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P04-P, and dissolved NH3-N. For TSS, VSS, BODs, CI, chlorophyll a, and TKN, the method of
addition was not used.
The precision of the procedures for the majority of constituents was measured as the
relative standard deviation (RSD). This test of precision was based on triplicate analyses carried
out on a minimum of 3 samples per survey which were selected at random. The RSDs were
typically better than 10% for both the dry and wet weather surveys (Table 2.3).
The completeness of the study was measured as the percentage of total samples collected
that were completely analyzed. This result has also been reported on Table 2.3.
All constituent concentrations were corrected by using reagent and procedural blanks.
The results of the trip blanks are given in Table 2.4 for the dry and wet weather surveys,
respectively.
2.3.3 Toxicity Methods and Methodologies
Water Column Toxicity - As part of the Blackstone River Initiative, chronic toxicity
testing was performed on water samples collected during both the dry and wet weather surveys.
The dry weather, low flow testing during the summer and fall surveys of 1991 included all 21
stations along the river. Each sample consisted of a composite of the four subsamples collected
at six hour intervals.
The wet weather testing during the three storms of 1992 and 1993 also included all 21
river stations. The samples collected at the time of the first flush, as well as the storm peak, were
analyzed individually for toxicity. First flush was defined as the early stages of the rising limb of
the hydrograph. The Woonsocket USGS gage was used to indicate flow at the midpoint of the
watershed. When the flow started to rise at this gage, the time was designated as first flush.
Peak flow sampling was keyed to the highest flow recorded at this gage.
The toxicity tests conducted were the fathead minnow, Pimephales promelas, larval
growth and survival test and the Ceriodaphnia dubia survival and reproduction test. The young
of P. promelas and C. dubia were exposed for seven days to the samples with renewals occurring
daily. The responses of the two organisms in the 21 samples were statistically compared to the
responses of the organisms in laboratory control water.
The test procedures used follow those outlined in the EPA manual, Short-Term Methods
For Estimating The Chronic Toxicity Of Effluents and Receiving Waters To Freshwater
Organisms, 2nd Edition, (Methods 1000.0 and 1002.0), EPA/600/489/001.
This method estimates the chronic toxicity of whole effluents and receiving water to C.
dubia in a 7-day, static-renewal test. This is an early life stage test, which focuses on the most
sensitive life-cycle stage. The samples are evaluated for toxicity through comparisons between
the survival and reproduction rates of C. dubia in the control group and those in the river water
2-24
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Table 2.3 Summary of Results for the Quality Assurance Project Plan for the Blackstone River
Wet and Dry Weather Surveys
Parameter
Accuracy
(%)
Precision
as RSD
Completeness
<%)
Accuracy
(%)
Precision
as RSD
Completeness
(%)
NHj-N
95.6
0.04
99
90.3
0.08
99
BODj
-
0.07
100
-
0.10
99
Ca
101.5
0.04
99
91.9
0.03
99
CI
98.2
0.05
99
106.8
0.04
100
Chi a
-
0.18
100
-
-
-
Mg
100.5
0.02
100
92.0
0.02
99
NO3-N
96.3
0.04
99
90.9
0.09
98
P04-P
92.4
0.05
99
92.7
0.08
99
TKN
-
0.04
99
-
-
100
TSS
-
0.06
99
-
0.06
100
VSS
-
0.11
99
-
0.11
99
Cd
97.8
0.12
100
89.6
0.06
100
Cr
100.1
0.13
100
106.5
0.06
100
Cu
103.3
0.11
100
95.9
0.05
100
Pb
95.6
0.14
100
92.9
0.11
100
Ni
95.6
0.12
100
108.2
0.05
100
Zn
-
-
-
109.1
0.05
100
Dry Weather Surveys
Wet Weather Surveys
RSD = Relative Standard Deviation; Accuracy = % Recovery of Spike; Completeness - Percent
of Samples Complete.
2-25
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Table 2.4 Trip Blank Analyses of the Measured Parameters in the Blackstone River Dry and Wet
Surveys
Dry Weather Surveys
Wet Weather Surveys
Parameter
Units
Survey 1
Survey 2
Survey 3
Survey 1
Survey 2
Survey 3
NHj-N
mg/L
NS
ND
ND
ND
ND
ND
BODs
mg/L
NS
ND
ND
ND
ND
ND
Ca
mg/L
ND
ND
ND
ND
ND
ND
CI
mg/L
NS
ND
ND
ND
ND
ND
Chi a
fj. g/L
NS
ND
ND
ND
ND
ND
Mg
mg/L
ND
ND
ND
ND
ND
ND
N03-N
mg/L
NS
ND
ND
ND
ND
ND
P04-P
mg/L
NS
ND
ND
ND
ND
ND
TKN
mg/L
NS
ND
ND
ND
ND
ND
TSS
mg/L
NS
ND
ND
ND
ND
ND
VSS
mg/L
NS
ND
ND
ND
ND
ND
Total Cd
M g/L
0.04
0.03
0.03
0.02
0.03
0.02
Total Cr
Mg/L
0.30
0.30
0.20
0.10
0.20
0.10
Total Cu
Mg/L
0.50
0.50
0.40
0.40
0.30
0.20
Total Pb
Mg/L
0.50
0.10
0.20
0.20
0.30
0.20
Total Ni
Mg/L
0.20
0.30
0.10
0.20
0.20
0.30
Total Zn
Mg/L
NA
NA
NA
0.40
0.40
0.50
ND = Non Detectable; NS = No Sample Taken; NA = Not Analyzed
2-26
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that is being tested.
Young organisms for the test were obtained by setting out adult C. dubia in test tubes 24
to 48 hours before the start of the test. All neonates were removed from the vessels 24 hours
prior to the start of the test. Neonates used for the test were removed and sorted by brood size.
Only neonates from broods of six or more were used for testing. Neonates must be less than 24
hours old at the test start.
A minimum of 10 organisms per sample were used for these tests. Each individual
organism is placed in a 20 mL test tube of test water and considered a replicate. Reconstituted
distilled laboratory water with a hardness of 60 mg/L as CaC03 was used as the control and all
river water samples were compared to the control to determine effects.
Every twenty-four hours, the test tubes were inspected to count organisms that had died,
and the number of young born per adult. During daily examination, any young found in the test
tube were pipetted into a watch glass for purposes of exact counting. After counting, they were
rinsed into a waste container. These counts were recorded on laboratory data sheets. DO, pH,
conductivity and temperature were recorded at these intervals as well. These data were
maintained in a bound chemistry logbook. The adult Ceriodaphnia were transferred to a new test
tube containing a new aliquot of the same sample every day.
All organisms were maintained at 25 °C +/-1 degree and 16 to 8 hour light to dark cycle.
Hardness was measured at the beginning of the test. Total residual chlorine (TRC) was measured
at the beginning of the test only in samples from WWTFs, CSOs and as far downstream as
necessary to reach a no detection level. Samples with detectable chlorine (>10 ppb) were
dechlorinated with sodium thiosulfate according to the microbiological method in Standard
Methods.
The test was ended when 60% of the control females had produced three broods. This
occurred after seven days. The other criterion for test validity was that 80% of the control
organisms must survive until the end of the test.
The survival data from the Ceriodaphnia dubia test was analyzed, using Fisher's Exact
Test, to determine whether a significant difference, relative to the control, existed for the river
station samples. The reproduction data from stations with no significant survival effects were
analyzed using an unpaired t-test.
Fathead minnow, Pimephales promelas, larval survival and growth test estimates the
chronic toxicity of whole effluents and receiving water to larvae of P. promelas in a seven-day,
static-renewal test. This is a survival and growth test, in which the toxicity of the effluent was
determined through comparisons of the survival and mean weight of minnows in the control
group and those in the effluent solutions. Daily observations on mortality make it possible to
also calculate the acute toxicity for specific exposure periods.
2-27
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Minnows that were less than 24 hours old were received from a supply house, not
cultured in the laboratory. They were acclimated to laboratory water with a hardness of 60 mg/L
CaC03, prepared according to the EPA protocol for chronic toxicity testing. Each river sample
had four replicate test chambers of fish. The test chambers used for the chronic tests were 2S0
mL beakers containing 200 mL of sample. Laboratory water was used as the test control
solution. Test chambers are randomized through the use of cardboard "chips", marked A, B, C
.... AA, BB, CC. The chips are shaken in a beaker and picked out one at a time. One chip was
placed in each test vessel, and the vessel was marked with the letter corresponding to that chip.
Prior to organism introduction and throughout the test period, the vessels were placed in
alphabetical order on the environmental chamber shelf. This minimized any error or bias in the
addition of organisms in feeding during the test, in lighting or positioning in the environmental
chamber.
The fish were placed in the test vessels in the following manner. A small amount of test
solution was scooped out of the test chamber with a plastic cup. The fish were then captured out
of the crystallization dish with a 3.5 mL plastic pipette and placed in the plastic cup. Hie fish
were then transferred into the test chamber. This same process is repeated until a total of 10 fish
per chamber was reached. Each beaker of ten fish were fed 0.1 mL of newly hatched brine
shrimp (Artemia) twice a day.
Daily renewals of the test solution were made. This was performed using a 25 mL plastic
pipette. The old solution, including old Artemia and cysts, was sucked out of the test vessel to
allow for 80% renewal and refilled to approximately 200 mL. The fish were counted prior to and
after renewal to ensure that no organisms were accidentally removed.
DO, pH, conductivity and temperature were measured daily. All counts of mortality and
test chemistry results were kept on laboratory data sheets. The weights of the weighing pans
before and after addition of fish were recorded in a lab book entitled "Fish Weights".
At the end of seven days, the contents of each beaker were poured through a fine mesh
sieve. The fish were retained in the sieve. They were rinsed well with distilled water and placed
on a pre-weighed pan. The fish in pans were dried at 100 °C for a minimum of two hours. The
pans were weighed the next day and the fish weight per replicate calculated and recorded in a
logbook.
From the fathead minnow test, the percentage of fish surviving was transformed using the
arc sine square root transformation and then tested for normality using Shapiro-Wilk's test and
for homogeneity of variance using Bartlett's test. Based on these two tests, the data was analyzed
with a t-test with a Bonferroni adjustment (because the number of replicates was not the same for
all stations). If any station showed significant impairment in comparison to the controls, this
station was selected for further tests for growth effects. The weight data was analyzed in the
same manner excluding the transformation procedure.
2-28
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Whole Sediment Toxicity - In addition to the water column toxicity testing, Blackstone
River sediments were analyzed twice in 1991 and once in 1993 by the EPA Region I, ESD
Biology. Sediment (SED) station names and identification numbers are given in Table 2.5.
Table 2.5 Whole Sediment Toxicity Sample Sites
SED
ID
Station Name
Sample or
Reference
SED
ID
Station Name
Reference
1
Singing Dam
Sample
7
Slater's Mill
Sample
2
Fisherville Pond
Sample
Ml
Gilboa Pond,
Mumford River
Reference
.3
Sutton St, Rochdale
Pond
Sample
M2
Grey's Pond,
Mumford River
Reference
4
Rice City Pond
Sample
LC
Lexington Pond
Control
Reference
5
Blackstone Dam
Sample
S
Saw Mill Brook,
Concord, MA
Reference
6
Manville
Sample
0
Lab Culture Water
Lab Control
Samples were collected from SED 1-4, Gilboa Pond on the Mumford River and Lexington
Pond on July 18,1991. Testing began July 22, 1991. The remaining samples were collected
from SED 5-7, Gilboa and Lexington Ponds September 3 and 4,1991. Testing began September
4,1991. The test species utilized were Chironomus tentans and Hyallela azteca.
A second round of samples was collected from SED 1-7, Grey's Pond on the Mumford
River and Lexington Pond on October 23 and 24, 1991. After the first sampling was completed,
a sample was collected at Grey's Pond (M2) because of suspected organic chemical
contamination at the Ml location. Testing began on October 30,1991.
Blackstone River sediments were again collected and analyzed in December 1993. The
ASTM sediment methods (ASTM 1991) had been refined and adopted by EPA (EPA 1993a) and
it was felt that it would be worthwhile to retest the sediments using the most recent methods.
Samples were collected from SED 1,3,4, 5,6, 7, Gilboa Pond (M2) and Saw Mill Brook, the
new reference sediment location, on December 6,1993. Fisherville Pond, station 2 was
inundated due to heavy rains and could not be sampled. Testing began December 10,1991.
Sediment samples were collected using a petit ponar dredge from a boat or while wading,
depending oh the location. Collection included sediments from the upper four inches of aquatic
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substrate. Sediments were emptied from the dredge into a shallow plastic pan. Any surface
water obtained with the sample was poured off, and sediments were deposited in an airtight, five
gallon pail. Approximately 18 liters of sediment were collected at each station. This volume
would be used for whole sediment, pore water tests and chemical analyses. Samples were kept
on ice in coolers and then stored in the ESD Biology Laboratory sample refrigerator which is
maintained at 3 °C.
Before the sediment samples were distributed to test chambers, they were homogenized.
This was necessary since the samples were composites of multiple dredgings. A uniform
distribution of sediment was obtained by stirring the sample for at least three minutes in the five
gallon pail using a masonry mixing blade and a drill press with motor.
Sieving was necessary to remove large stones, debris and predators. The sieve size used
prior to toxicity testing is 500 microns. Sieving was performed on all samples tested including
control and reference sediments.
The day before the toxicity tests started (Day-1) each test sediment and the reference
sediment (Lexington Pond) were mixed and an aliquot was added to the test chambers. The
sediment in each chamber was smoothed using a spoon or spatula. Overlying water was added
by pouring it into a petri dish laid on top of the sediment. This reduced resuspension. To allow
sediments to settle, no organisms were added to the test vessels for 12-24 hours. Water quality
parameters were measured prior to the addition of the test organism.
The beakers were covered with watch glasses to prevent evaporation. Aeration was
provided to each test chamber through a 1-mL glass pipette which extended between the beaker
spout and the watch glass cover to a depth not closer than 2 cm from the sediment surface. The
air was bubbled into test chambers at a rate that does not cause turbulence or disturb the sediment
surface. Water lost to evaporation was replaced as needed with temperature acclimated DI water
or overlying water. The tests were conducted for ten days.
The DO in each test chamber was measured in at least one test chamber in each treatment
at the beginning and end of the test, at least weekly during the test, and if the behavior of the
organisms suggested DO might be low. A measured DO concentration should be >40% and
<100% saturation. Conductivity, hardness, pH and alkalinity were measured every day.
The test chambers with sediment were set into an environmental chamber at the initiation
of a test. The temperature of the chamber was 25 °C. Overlying water was partially replenished
by pouring off 50% and adding new culture water.
Sediment Pore Water Toxicity Analysis - Pore water from the seven Blackstone River
sediment stations listed above were analyzed for toxicity using Ceriodaphnia dubia and the
fathead minnow, Pimephales promelas. Forty-eight hour acute toxicity tests compared organism
response in Blackstone River sediment pore water with lab culture water and reference pore
2-30
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water obtained from sediments in Gilboa Pond, Grey's Pond and Lexington Pond.
Blackstone River pore water toxicity was analyzed twice in 1991 by the U.S. EPA Region
I, ESD Biology Section. The first round (I) of tests were conducted in two parts. Samples were
collected from stations 1 - 4, Ml and LC, July 18,1991. Pore water was extracted by
centrifugation July 23 and 24,1991. Testing began July 24,1991. The remaining samples were
collected from stations 5-7, Ml and LC September 3 and 4,1991. Pore water was extracted
September 10 and 11 and testing began September 12,1991.
Samples for the second round (II) of tests were collected from stations 1-7, Grey's Pond
(M2) and Lexington Pond October 23 and 24,1991. After Round I was completed a reference
sample was collected at Grey's Pond in the Mumford River, because of suspected organic
chemical contamination at the Gilboa Pond (Ml) location. Pore water was extracted from these
samples November 5,6, and 7 and testing began November 7,1991.
Composite sediment samples were collected, either from a boat or by wading, using a
petite ponar dredge. Approximately 2 liters of sediments were emptied from the dredge into a
shallow plastic pan. Any surface water obtained with the sample was poured off, and sediments
were deposited in an airtight, five gallon pail. Approximately 18 liters were collected at each
station, as this volume was sufficient for whole sediment and pore water tests. Samples were
kept on ice in coolers and then stored in the ESD Biology Laboratory sample refrigerator which
was maintained at 3 °C.
There are three widely accepted methods used to extract the interstitial water which fills
the space between the solid portion of sediment. This liquid, known as pore water, can be
extracted by vacuum filtration, mechanical compression through a filter or by centrifugation.
High speed centrifugation effectively squeezes water out of sediments as larger particles are
forced to the bottom of the sample container. Lighter particles, including water, remain above
the settled particles and can be siphoned or poured off for collection. This method has been
shown to be one of the most efficient methods and was chosen for this study.
Before sediments could be centrifuged for pore water extraction, they had to be
homogenized. This was necessary since samples were composited by multiple dredgings. A
uniform distribution of sediment was obtained by stirring the sample for at least three minutes in
the five gallon pail using a masonry mixing blade and a drill press with motor.
Once homogenized, 1000 mLs of sediments were scooped into Nalgene centrifuge
bottles. An IEC PR-7000 centrifuge was used with a number 966 rotor with six (6) 1000 mL
capacity swinging buckets. To maintain balance, care was taken to match, by weight or volume,
the opposing samples in the centrifuge. Samples were centrifuged at 5200 rpms for 120 minutes
at 3 °C. This configuration of speed and rotor applied a force of 7406.53 x gravity (relative
centrifugal force) to the sediments. Since some sediments were dryer than others, additional
samples needed centrifugation in order to yield the minimum amount of pore water (750 mLs) to
2-31
-------
conduct the test. Centrifuged sediments were carefully removed from the centrifuge to prevent
resuspension of particles. Pore water from each station was composited in 1 and 2 liter
Erlenmeyer flasks and then, to prevent decomposition, stored in the sample refrigerator at 3°C.
Just prior to test time, the pore water temperature was raised to 25 °C by immersing the
flasks in a water bath. This was done to prevent thermal shock to the test organisms. Once the
temperatures were raised, the fathead minnow larvae, less than seven days old, and Ceriodaphnia
neonates, less than 24 hours old, were randomly distributed and assigned to the various testing
chambers. Fish were tested in 300 mL beakers containing approximately 200 mL of pore water.
Ceriodaphnia were exposed in 30 mL glass test tubes containing approximately IS mL of pore
water.
Three replicates of ten fish each were exposed for 48 hours to each of the seven pore
water stations, the reference, control and the culture water. For each pore water sample, thirty
Ceriodaphnia were exposed (fifteen test tubes containing two each).
2-32
-------
3.0 SYSTEM HYDROLOGY AND HYDRAULICS
For both the dry and wet weather surveys, river flows were measured at several water
quality stations along the mainstem Blackstone River and its tributaries. The data are
summarized in this chapter. The procedure for developing the complete system flows for both
dry and wet weather are discussed. A series of rainfall gages, located throughout the Blackstone
River watershed, provided data for each storm. The analysis of this data included the
determination of average rainfall characteristics for the entire watershed as well as the individual
watersheds associated with each water quality station. The Thiessen method for weighting
rainfall stations by area was used in the analysis. This data are summarized in this chapter. A
brief overview of the hydraulic structures and controls on the river are discussed.
3.1 Dry Weather
The three dry weather surveys occurred on July 10-11,1991 (Survey 1), August 14-15,
1991 (Survey 2) and October 2-3,1991 (Survey 3).
There are three active USGS gaging stations in the watershed. These are located on the
Quinsigamond River at North Grafton, MA (upstream of BLK05), Branch River at Forestdale, RI
(upstream of BLK14) and Blackstone River at Woonsocket, RI (upstream of BLK17). USGS
also established six temporary gaging stations for this study. These included four on the
Blackstone River (BLK01, BLK04, BLK11, and BLK20) and two on tributaries (Mumford
(BLK09) and Peters (BLK16)). All flows observed during the dry weather water quality surveys
fell within the range of flows used for the stage/discharge relationships.
The survey flows at the three river gages and at six wastewater treatment facilities
(WWTFs) are listed in Table 3.1.
For the remaining water quality stations, flows were estimated based on the determination
of an incremental flow factor in cfs/mi2. The survey flow profiles were validated by the
temporary gaging stations and by the successful mass balance of a conservative constituent. The
procedure is discussed in detail in Chapter 5.
3.2 Wet Weather
3.2.1 Rainfall Characteristics
The three wet weather surveys occurred on September 22-24,1992 (Storm 1); November
2-5, 1992 (Storm 2); and October 12-16,1993 (Storm 3).
3.2.1.1 Rainfall Network
3-1
-------
Table 3.1 Summaiy of Flows for the 1991 Diy Weather Surveys
USGS Gage Location
7/10/91
7/11/91
July
Average
8/14/91
8/15/91
August
Average
10/2/91
10/3/91
October
Average
Woonsocket
142
132
137
157
146
152
676
595
635.5
Quinsigamond River
7.7
6.9
7.3
8.6
8.5
8.6
56
48
52
Branch River
28
24
26.0
32
29
30.5
110
98
104
WWTF
7/10/91
8/14/91
10/2/91
WWTF
7/10/91
8/14/91
10/2/91
UBWPAD
38.4
44.6
64.7
Uxbridge
3.875
3.875
3.875
Millbury
0.6
0.8
1.3
Northbridge
1.8
1.2
1.8
Grafton
1.6
1.6
1.6
Woonsocket
8.3
11.5
13.4
-------
R2U
R1N
R3U
R4M ^
R6N
R7N
R5N
RHODE ISLAND
R9UA (
R11N
R12U
R8N
R10M
R13N
R14N
R15U
Legend
Rainfall Monitoring Stations
R16N
Figure 3.1 Raingage Locations for the Blackstone River Wet Weather Studies
3-3
-------
There were a total of 16 rain gages in the rainfall network (Figure 3.1). Not all of these
gages were available for each storm. Each station is coded by the following: R1N, where R =
rainfall station; 1 = station identification numbered from north to south; and N = the group
responsible for the gage (for instance, N = National Weather Service (NWS), U = URI, M =
Municipal, S = State).
The National Weather Service operates seven stations, either in, or just outside, the
watershed. Two of these stations are located at major airports (R1N and R16N) and log
precipitation continuously. The other five stations are managed by the NWS's Northeast River
Forecast Center. The data at these stations is manually collected daily by 0900 and is reported as
a total precipitation amount pertaining to the previous 24 hour period. Three of these stations are
inside the watershed (R6N, R7N and R1 IN), and two are to the east (R5N and R8N). Three
gages were maintained by municipalities at WWTFs (R4M, R10M, and R13M) and one station
(RMS) by the RIDEM. These data were also daily totals typically collected by 0700 each day.
To complete the rainfall network, URI established five additional stations with
continuous measurements from automatic tipping bucket rain gages (R2U, R3U, R9U, R12U and
R15U).
3.2.1.2 Rainfall Characteristics
A summary of the total rainfall records at each station is also given in Table 3.2. The
pattern of each storm has been represented by a series of hyetographs (Figure 3.2). The three
gages presented on this figure include the most northern station (R1N), a central station (R12U)
and the most southern station (R16N). Each storm's distribution across the watershed is
illustrated by total rainfall lines of equal precipitation (Isohyetal lines). These are presented in
Figures 3.3 to 3.5.
3.2.1.3 Total Rainfall
The simplest approach to developing equivalent uniform depth of precipitation over an
area is to approximate the depth with an average of all rain gages. However, this procedure is not
acceptable if the gages are not evenly spaced, or if the precipitation is irregularly distributed over
the drainage area. The Thiessen method provides a means of weighting the precipitation at gages
in proportion to a representative area. Each gage is assumed to represent all points closer to it
than to any other gage. These areas are determined by connecting adjacent gages by lines, and
then constructing perpendicular bisectors to these lines. The area contained in the resulting
polygons are then determined, and each gage reading is weighted by the area.
The Thiessen figures developed for the three storms are given in Figures 3.6 to 3.8. The
watershed weighted average is included in the storm summaries of Table 3.3. Each storm met
the minimum rainfall criteria as described in Chapter 2. Storm 1 had the lowest watershed total
rainfall of 0.56 inches. Storms 2 and 3 were similar with 0.88 and 0.81 inches, respectively,
3-4
-------
Table 3.2 Precipitation Log of Three Storms for the Blackstone River Wet Weather Studies
Gage Name
Location
Maintained
By
Type
Rainfall in inches
Storm 1
Storm 2
Storm 3
R1N
Worcester Airport, MA
NWS
1
0.44
0.98
1.30
R2U
Westborough WWTF, MA
URI
1
NA
0.83
0.85
R3U
Millbury WWTF, MA
URI
1
NA
0.77
NA
R4M
Millbury WWTF, MA
WWTF
2
0.66
0.62
NA
R5N
Buffumville, MA
NWS
2
0.63
0.99
1.15
R6N
Northbridge, MA
NWS
2
0.54
0.94
0.69
R7N
West Hill Dam, MA
NWS
2
0.53
0.89
0.90
R8N
Putnam, CT
NWS
2
0.63
0.84
1.15
R9U
Burriville WWTF, RI
URI
1
NA
0.85
NA
R10M
Burriville WWTF, RI
WWTF
2
0.74
NA
0.48
R11N
Woonsocket, RI
NWS
2
0.56
0.86
0.61
R12U
Woonsocket WWTF, RI
URI
1
0.46
0.78
NA
R13M
Bucklin Pt. WWTF.RI
WWTF
2
0.49
NA
NA
R14S
Providence, RI
RIDEM
2
0.51
NA
NA
R15U
Fields Point WWTF, RI
URI
1
0.62
0.76
NA
R16N
TF Green Airport, RI
NWS
1
0.62
0.80
0.27
R1N: R = Rainfall; 1= Station ID; N = National Weather Service (NWS); U = URI;
S = State; and M = Municipal; RIDEM = RI Department of Environmental Management;
Type 1 = Continuous Recorder; Type 2 = Daily Total; NA = Not Available.
3-5
-------
u>
0\
i r
JZ
o
c
0.40
0.30
£
c
¦«0
11:
= 0.20
0.10
0.00
¦H R1N (Worcester)
505SS R16N (T.F. Green Airport)
R12U (Woonsocket)
STORM-1
Time 0 = 2200
STORM-2
Time 0 = 2200
1
I
ii alaliiJi
w
1
mmi
3 4
STORM-3
Time 0 = 0900
Time 0 = Start of Storm
5 6 7 8 9 10 11 12 13 14 15 16 17 18
Time (hour)
Figure 3.2 Rainfall For Blackstone River Wet Weather Studies
-------
0.45
0.50
0.55
0.45
Storm 1
September 22-24,1992
± Rainfall Monitoring
Stations
0.60
0.65
0.70
0.60
0.55
Rainfall in inches
0.50
Figure 3.3 Rainfall Watersheds Distribution - Storm 1
3-7
-------
I
Storm 2
November 2-5,1992
± Rainfall Monitoring
Stations
Rainfall in inches
Figure 3.4 Rainfall Watersheds Distribution - Storm 2
-------
Storm 3
October 12-16, 1993
* Rainfall Monitoring
Stations
Rainfall in inches
Figure 3.5 Rainfall Watersheds Distribution - Storm 3
-------
Storm I
luinsigamom
River
0.54
44
R2U
R1N
R3U
Blackstone
River
West
Rivet/
0.53
R4M ^
R6N
Mumford River
0.63
R7N
R5N
0.56
Mill
River
0.63
RHODE ISLAND
R9U ~
R11N
R12U
Branch River
R8N
R10M
0.62
0.74
Legend
— — Thiessen Polygons
Rainfall Monitoring Stations
Figure 3.6 Thiessen Polygons - Storm 1
3-10
-------
Storm li
0.98
N
West
River/
/
\ R4mA '
Y-
. ^.MASSACHU5FTfS_^.'.^
J RHODE ISLAND »
R9U^
~> Arun |
V- l
(Branch Rive^
/I R10M
R13N
R14N A
R15uA.
Legend
Thiessen Polygons
Rainfall Monitoring Stations
Figure 3.7 Thiessen Polygons - Storm 2
3-11
-------
Storm III
A
1.30
N
| R4M ^
MASSACHUSETTS
RHODE ISLAND
R11N
R9Uj^
feranch River
R12U
R10M
R13N
R14N A
0.27 risuA
Legend
— — Thiessen Polygons
A Rainfall Monitoring Stations
Figure 3.8 Thiessen Polygons - Storm 3
3-12
-------
Table 3.3 Average Rainfall Characteristics
Characteristic
Storm 1
Storm 2
Storm 3
TR (inch)
0.56
0.88
0.81
D (hrs)
6.0
16.0
8.5
ADP (days)
11.0
8.0
8.0
PI (in/hr)
0.20 (R12U)
0.23 (R1N)
0.52 (R1N)
AI (in/hr)
0.09
0.06
0.10
TR = Total Rainfall Based on Thiessen Method; .
D = Rainfall Duration; ADP = Anticedent Dry Period;
PI = Peak Intensity (R1N = Station ID); AI = Average Intensity
3-13
-------
Table 3.4 Summary Table of Rainfall for Individual Subwatersheds
Station
Area
(square mile)
Rainfall (inch)
Storm 1
Storm 2
Storm 3
BWWOO
60.5
0.494
0.955
1.253
BWW01
15.5
0.440
0.857
1.300
BWW02
6.2
0.461
0.784
1.129
BWW04
16.7
0.534
0.792
0.864
BWW05
34.2
0.473
0.857
0.944
BWW06
16.5
0.540
0.848
0.713
BWW07
6.0
0.540
0.940
0.690
BWW08
6.1
0.533
0.907
0.827
BWW09
68.5
0.560
0.928
0.881
BWW10
37.4
0.535
0.899
0.827
BWW11
2.3
0.530
0.890
0.900
BWW14
93.1
0.723
0.850
0.513
BWW13
13.4
0.617
0.861
0.665
BWW15
23.0
0.525
0.883
0.820
BWW16
11.6
0.510
0.860
0.610
BWW17
20.0
0.510
0.860
0.603
BWW18
12.2
0.510
0.860
0.610
BWW20
13.6
0.495
0.860
0.610
BWW21
23.3
0.502
0.844
0.594
3-14
-------
Table 3.5 Summary Table of Rainfall for Cumulative Subwatersheds
Station
Area
(square mile)
Rainfall (inch)
Storm 1
Storm 2
Storm 3
BWWOO
60.5.
0.494
0.955
1.253
BWW01
75.9
0.483
0.935
1.263
BWW02
82.1
0.481
0.923
1.253
BWW04
98.8
0.490
0.901
1.187
BWW06
149.5
0.492
0.885
1.079
BWW07
155.5
0.493
0.887
1.064
BWW08
161.6
0.495
0.888
1.055
BWW11
269.8
0.517
0.900
0.978
BWW13
376.3
0.572
0.886
0.852
BWW17
430.9
0.565
0.884
0.832
BWW18
443.1
0.563
0.883
0.826
BWW20
456.7
0.561
0.883
0.819
BWW21
480.0
0.558
0.881
0.809
3-15
-------
however the range and distribution of rainfall in the watershed was dramatically different
Total rainfall was also determined as it relates to the direct drainage for each water
quality station. First, subbasin areas were determined for each station and the Thiessen polygons
were drawn. Total rainfalls for these subbasins between stations were determined (Table 3.4).
Second, the total rainfalls were determined for the cumulative drainage area from headwaters to
the river mouth (Table 3.5).
Storm 1 had a relatively uniform distribution of rainfall ranging from 0.44 inches in the
north to 0.74 inches at a location central to the watershed. The lowest rainfall total in a
subwatershed was 0.46 inches in the watershed area between BWW01 and BWW02 and the
largest was 0.72 for the area in the Branch River watershed above BWW14. In general, the
cumulative rainfall totals increased from Worcester, MA to Pawtucket, RI (0.49 to 0.56 inches).
The rainfall distribution for Storm 2 also had a relatively uniform distribution. Rainfall
ranged from a high in the north of 0.99 inches to the low in the south of 0.76 inches. The lowest
rainfall total in a subwatershed was 0.78 inches in the watershed area between BWW01 and
BWW02 and the largest was 0.96 in the headwaters above BWW01. In general, the cumulative
rainfall totals decreased as you proceeded down the watershed (0.96 to 0.88 inches).
In contrast, Storm 3 had within it several intense thunderstorms which affected the
drainage area along the western boundary and the headwaters to the north in Worcester (Figure
3.5). As a result, rainfall totals ranged from 0.27 inches along the southern border in Providence
to 1.3 inches in the headwaters. The lowest rainfall total in a subwatershed was 0.59 inches in
the watershed area between BWW20 and BWW21 and the largest was 1.30 in the watershed area
between BWW00 and BWW01. There was a significant decrease in the cumulative rainfall
totals as you proceeded down the watershed (1.25 to 0.81 inches).
These rainfall characteristics, especially the quantity and time distribution of the
precipitation, will be one of the factors in governing the rate and distribution of runoff.
3.2.2 System Flows
Flows were determined directly at 3 permanent and 6 temporary USGS gaging stations.
All flows observed during the wet weather water quality surveys were within the range of flows
used for the stage-discharge relationships.
For the remaining stations, URI established reference points at each location for
measurement of river stage. These reference points were monitored under a wide range of flow
conditions. River flow profiles were developed for each measurement following the procedure
described later in Chapter 5 using the model, QUAL2E. The flow estimates and river stages
were used to develop stage-discharge relationships at these stations. All flows observed during
the water quality surveys fell within this flow range.
3-16
-------
Table 3.6 Blackstone River Flow Summary (cfs) - Storm 1
Run
BWW00
BWW01
BWW02
BWW04
BWW05
BWW06
BWW07
BWW08
BWW09
BWW10
P
15.3
16.5
73.3
79.0
4.50
79.7
107
109
11.5
7.64
0
38.3
41.2
107
93.0
3.80
67.4
95.0
124
12.0
7.94
3
172
185
268
182
6.20
111
99.0
129
14.2
9.42
6
59.5
64.0
156
245
6.20
111
101
115
14.8
9.07
9
53.7
57.8
142
163
7.90
141
103
111
13.6
9.07
12
43.1
46.4
118
144
9.30
166
104
108
12.5
9.24
16
33.8
36.3
88.9
116
9.30
166
111
125
12.0
9.24*
24
21.9
23.5
49.6
80.0
6.70
120
123
130
11.5
9.24
32
15.3
16.5
49.6
53.0
5.60
100
120
136
11.0
8.74
40
21.9
23.5
80.8
66.0
5.10
90.0
123
136
9.29
8.90
Run
BWW11
BWW13
BWW14
BWW15
BWW16
BWW17
BWW18
BWW20
BWW21
P
133
169
32.8
6.30
2.37
162
181
210
239
0
142
188
42.0
5.80
3.61
163
205
220
250
3
173
232
54.7
12.4
13.2
292
250
253
253
6
160
214
50.1
12.4
11.0
250
210
241
241
9
155
205
46.1
12.4
7.23
205
226
259
259
12
162
209
42.8
10.2
10.5
214
226
265
265
16
155
200
41.5
8.72
6.25
215
186
215
215
24
148
192
40.6
16.7
4.00
209
226
247
247
32
166
210
39.8
16.7
4.00
209
226
271
271
40
177
218
36.4
15.0
4.00
289
315
253
253
-------
Table 3.7 Blackstone River Flow Summary (cfs) - Storm 2
Run
BWW00
BWW01
BWW02
BWW04
BWW05
BWW06
BWW07
BWW08
BWW09
BWW10
P
72.0
77.4
107
108
2.41
111
100
206
33.6
12.8
0
72.0
77.4
107
108
2.55
153
100
160
33.6
3
62.0
70.5
130
135
3.01
175
120
106
33.6
13.2
6
172
185
245
220
4.09
194
149
139
44.4
14.4
9
228
245
453
320
7.60
240
225
171
60.8
17.9
12
163
175
264
380
10.7
286
302
211
76.7
19.4
16
193
208
268
320
13.7
334
367
269
86.1
21.0
20
116
125
222
273
15.3
286
339
393
104
20.0
24
118
122
177
231
15.8
245
250
437
96.5
20.7
28
128
138
150
202
15.8
217
235
287
104
22.0
32
126
135
142
172
15.8
179
221
283
104
22.7
36
126
135
142
142
15.3
141
215
287
104
23.4
40
181
130
156
142
15.3
141
205
283
104
25.2
44
121
130
156
165
14.8
179
200
287
100
26.8 -
48
113
122
177
191
14.8
245
208
269
92.9
27.2
72
57.0
61.5
103
108
15.8
126
183
279
73.8
28.8
Run
BWW11
BWW13
BWW14
BWW15
BWW16
BWW17
BWW18
BWW20
BWW21
P
252
321
67.6
9.82
6.20
259
295
327
294
0
207
274
66.2
9.44
5.91
286
272
302
311
3
152
221
68.4
9.82
5.62
282
265
294
302
6
198
273
74.2
11.5
8.27
288
272
302
208
9
250
352
101
19.7
29.9
310
451
500
410
12
307
408
99.4
21.6
27.5
328
395
438
458
16
376
482
105
20.1
27.5
365
500
554
458
20
517
635
116
16.1
19.6
445
451
500
446
24
553
676
121
18.0
21.3
529
526
583
564
28
412
541
127
21.6
17.9
675
597
662
684
32
409
540
129
24.0
17.9
693
767
851
890
36
413
545
129
24.0
16.4
663
712
790
820
40
412
545
130
23.2
16.4
640
712
790
820
44
414
546
130
30.7
13.7
660
730
810
799
48
389
519
128
20.8
11.5
600
628
697
956
72
382
497
113
18.0
10.9
569
568
631
702
-------
Table 3.8 Blackstone River Flow Summary (cfs) - Storm 3
Run
BWW00
BWW01
BWW02
BWW04
BWW05
BWW06
BWW07
BWW08
BWW09
BWW10
P
38.0
41.2
60.4
109
8.26
98
144
152
16.6
9.07
0
38.0
41.2
73.3
109
8.62
98
144
229
23.1
9.24
9
530
570
829
746
20.2
229
201
127
38.8
11.9
12
407
438
637
541
20.8
456
421
184
41.2
12.8
16
140
150
165
378
25.8
456
570
364
37.1
12.6
20
128
138
153
246
26.9
216
300
414
17.8
12.1
24
122
131
147
271
29.9
244
278
352 ¦
29.5
12.6
28
109
117
130
277
28.8
229
287
332
29.5
11.7
32
48.4
52.0
130
230
26.5
229
265
294
25.8
11.7
36
160
108
107
215
24.7
260
249
301
25.8
12.1
44
76.0
81.7
103
173
22.7
224
238
283
27.3
13.0
52
76.0
81.7
105
187
21.9
110
144
283
25.1
72
266
26.6
Run
BWW11
BWW13
BWW14
BWW15
BWW16
BWW17
BWW18
BWW20
BWW21
P
202
228
40.6
1.87
1.61
165
240
255
254
0
149
177
43.2
1.80
1.52
172
280
300
264
9
372
423
62.1
7.60
6.51
204
218
231
385
12
143
186
58.2
5.10
4.39
246
280
300
314
16
188
223
54.4
4.20
3.58
207
236
250
290
20
341
378
48.4
223
302
323
314
24
494
580
45.0
4.20
3.58
420
403
437
302
28
460
530
44.5
3.80
3.23
797
682
746
485
32
346
495
45.0
3.60
3.06
551
429
464
668
36
288
379
45.0
3.80
3.23
416
420
455
558
44
267
320
45.0
3.60
3.06
416
338
363
429
52
235
299
44.5
5.90
5.09
406
395
427
402
72
228
259
280
314
327
-------
: ! ' / •'
Table 3.9 Average Survey Flow (cfs)
Survey
BWW22
BWW23
BWW24
BWW25
BWW26
Storm 1
0.0
50.1
9.5
34.9
31.0
Storm 2
97.2
51.9
10.0
35.6
38.6
Storm 3
246.0
49.6
9.9
32.8
34.2
BWW22 (Worcester CSO) flow average for 2.17 and 2.93 hrs for Storms 2 and 3, respectively;
BWW23 (UBWPAD), BWW24 (Woonsocket WWTF); BWW25 (BP NBC); BWW26 (BP NBC
By-Pass)
3-20
-------
During the wet weather surveys, river stage was recorded at each station for each water
quality sample. Flows were then determined from the USGS or URI stage-discharge
relationships for each station. The flows are summarized in the Tables 3.6 to 3.8.
Flows from UBWPAD, the Woonsocket WWTF and the Worcester CSO facility were
obtained from facility personnel. These are summarized in Table 3.9. The CSO facility
discharged during Storms 2 and 3.
In general, there are several rainfall and watershed characteristics which influence the
shape of the hydrograph. These include, but are not limited to: (a) rainfall distribution or pattern;
(b) hourly intensity; (c) watershed time to concentration (including all variables impacting this
calculation, i.e. watershed slope and percent impervious); and (d) upstream regulation.
The classic shape of a hydrograph includes a rising limb, peak flow, and falling limb.
Often times the hydrograph is directly a reflection of a dominant watershed characteristic. For
instance, different types of flow regulation, such as river reservoirs, leave an obvious imprint on
the downstream flow profiles, usually dampening the runoff hydrograph and extending the time
of its impact. An unusual hydrograph response speed (fast or slow) would be a direct indication
of the shape of the watershed and/or the percent of area that is impervious.
A summary of the hydrograph characteristics are given in Tables 3.10 to 3.12. Several
general observations can be made from the tables, the three-dimensional flow plots (Figures 3.9
to 3.11) and the individual hydrograph comparisons (Figures 3.12 to 3.14).
* Storm 1 (Figures 3.9 and 3.12) - Storm 1 was a short (6 hrs), relatively light, well
distributed rainfall (0.56 inches). The runoff from the headwaters in Worcester resulted in a
hydrograph at BWW01 with flows increasing from baseline of about 15 cfs to a maximum of 185
cfs at run time 3 hours (Point A). The hydrograph at BWW06 was impacted by local runoff
during run times 3 and 6 hrs. By run time 9 hrs, the hydrograph from the headwaters had arrived
at BWW06. The peak flow had decreased, and the hydrograph showed attenuation due to
channel storage over the 7.5 miles. In Fisherville Pond between BWW06 and BWW07, the
hydrograph from Worcester was completely attenuated, adding to the base flow of the river. The
storm track placed the headwater flows between BWW07 and BWW08 at the end of the
sampling period (Point B). The additional flows from the three major tributaries central to the
watershed (Mill, Peters and Branch) are observed at Point C. The hydrograph signatures below
this station typically reflected local drainage area runoff. The most prominent of these is the flow
from the Mill and Peters Rivers identified as Point D. In most cases, flows returned to prestorm
conditions within the 40 hour sampling period.
* Storm 2 (Figures 3.10 and 3.13) - Storm 2 was a long (16 hrs), moderate, well
distributed rainfall (0.88 inches). The peak flows and volumes steadily increase along the
watershed. The flows from Worcester were highest between the 6-12 hour runs (Point A). The
track of the storm can be seen arriving at BWW08 between 20-24 hours. The arrival of the
3-21
-------
Table 3.10 Hydrograph Characteristics - Storm 1
Station
Wet Volume
Total Volume
N
(106cf)
(106 cf)
(hrs)
BWW00
3.63
5.77
36.2
BWW01
3.63
5.82
36.0
BWW02
4.07
15.5
37.3
BWW04
5.31
16.9
38.0
BWW05
0.43
1.03
34.2
BWW06
9.39
20.7
39.6
BWW07
5.36
27.0
39.8
BWW08
4.20
34.7
39.9
BWW09
0.10
1.63
36.6
BWW10
0.07
1.34
34.5
BWW11
1.37
24.4
42.0
BWW13
2.91
31.1
43.4
BWW14
1.46
6.45
37.8
BWW15
1.24
2.54
32.8
BWW16
0.44
0.80
30.7
BWW17
5.60
35.4
44.0
BWW18
3.43
36.1
44.1
BWW20
5.32
48.3
44.3
BWW21
6.41
56.1
44.5
3-22
-------
Table 3.11 Hydrograph Characteristics - Storm 2
Station
Wet Volume
Total Volume
N
(106 cf)
(106 cf)
(hrs)
BWWOO
8.09
22.6
36.2
BWW01
8.66
23.9
36.0
BWW02
11.7
34.4
37.3
BWW04
15.0
39.4
38.0
BWW05
1.39
2.75
34.2
BWW06
17.4
44.5
39.6
BWW07
19.6
46.4
39.8
BWW08
26.1
62.1
39.9
BWW09
7.45
17.4
36.6
BWW10
34.5
BWW11
35.5
88.7
42.0
BWW13
43.1
116
43.4
BWW14
11.2
31.3
37.8
BWW15
2.75
5.57
32.8
BWW16
1.31
2.68
30.7
BWW17
49.7
145
44.0
BWW18
68.3
155
44.1
BWW20
75.3
172
44.3
BWW21
85.1
179
44.5
3-23
-------
Table 3.12 Hydrograph Characteristics - Storm 3
Station
Wet Volume
Total Volume
N
(106 cf)
(106 cf)
(hrs)
BWWOO
21.5
30.2
36.2
BWW01
22.7
32.5
36.0
BWW02
29.6
41.9
37.3
BWW04
30.4
53.6
38.0
BWW05
2.24
4.58
34.2
BWW06
27.0
47.5
39.6
BWW07
25.2
55.6
39.8
: BWW08
23.7
65.2
! 39.9
BWW09
1.63
5.39
36.6
BWW10
0.27
1.91
34.5
BWW11
30.2
73.6
42.0
BWW13
31.2
90.7
43.4
BWW14
1.18
8.40
37.8
BWW15
0.26
0.63
32.8
BWW16
0.25
0.53
30.7
BWW17
39.0
91.6
44.0
BWW18
27.7
73.1
44.1
BWW20
28.3
107
44.3
BWW21
34.4
113
44.5
3-24
-------
o
E2 ^
ffl
-------
BLACKSTONE RIVER INITIATIVE
FLOW - STORM 2
UBWPAD
Fisherville
Pond
Rice City
Pond
MA I RI
Woonsocket
VVWT F
46.0
Worcester,
Flow(cfs)
I 900-1000
800-900
i 700-800
I 600-700
i 500-600
400-500
300-400
i 200-300
100 200
0-1 OO
20 21 STATION ID
3.8 0.1 RIVER MILES
Pawtucket, RI
Figure 3.10 Contour Plot of Flow for Storm 2, November 2-5, 1992
-------
BLACKSTONE RIVER INITIATIVE
WWTF
Fisherville
UBWPAD PnnH
FLOW - STORM 3
Rice City MA I RI Woonsocket
STATION ID
RIVER MILES
RI
ro
I
o
<3\
CM
^ o
£ oj
Is
oo
H ^
rv)
ro
CO
Tt*
(N
10
(N
^00 01
46.0 45.8
Worcester, MA
20 21
3.8 0.1
Pawtucket,
Flow(cfs)
700-800
¦ 600-700
¦ 500-600
¦ 400-500
m 300-400
El 200-300
H 100-200
¦ 0-100
Figure 3.11 Contour Plot of Flow for Storm 3, October 12-16, 1993
-------
300
Storm 1
September 22-24,1992
- BWW01
- BWW06
- BWW07
200
100
x
X
A
X
X
X
X
X
X
X
X
X
-10 0 10 20 30 40
Hours
Figure 3.12 Hydrograph Comparison - Storm 1
-------
Storm 2
November 2-5, 1992
800
- BWW01
- BWW07
- BWW11
- BWW17
600
400
200
j L
0
J L
J.
J L
1
X
X
¦4
X
X
X
X
X
-10 0 10 20 30 40 50 60 70
Hours
Figure 3.13 Hydrograph Comparison - Storm 2
-------
1000
Storm 3
October 12-16,1993
- BWW01
- BWW07
- BWW17
750
500
250
60
-10
20
40
50
0
10
30
Hours
Figure 3.14 Hydrograph Comparison - Storm 3
-------
headwaters flows at BWW21 were between 36-48 hours (Point B). Unlike Storm 1, baseflows
remained high even in the post storm period. This was attributed to the storm's characteristics
(long duration, moderate rainfall and, therefore, high infiltration). The influence of the central
tributaries is evident again at Point C. The extended high flows beyond the storm track are due
to the longer, more gradual release of flows from the tributary watersheds. Local drainage runoff
is again seen in the Woonsocket area, as well as the downstream stations bracketing Central Falls
and Pawtucket (Point D).
* Storm 3 (Figure 3.11 and 3.14) - Storm 3 was a convective storm with most of the
rainfall occurring in a 5 hour period. It was not well distributed, with the heaviest rainfall in
Worcester. This resulted in a runoff signal from the headwaters in Worcester (Point A) that
dominated the runoff profiles throughout the entire length of the Blackstone. The Worcester
signal appeared at BWW08 between hours 16-20. The peak flows arrived at BWW21 between
hours 28 and 36 (Point B). The rainfall from the local drainage areas in the lower sections of the
watershed were evident, especially between BWW11 and BWW17 (Point C), but had a relatively
minor impact on the hydrographs.
Hydrographs have been compared at three key locations: headwaters BWW01; MA/RI
state line BWW13 and mouth of the river BWW21 in Figures 3.15 to 3.17, respectively.
Several procedures are available for separation of the hydrographs into baseflow and
direct runoff. These are well documented (McCuen 1989; Viessman, Lewis and Knapp 1990;
Wanielista 1990). The procedures include straight-line baseflow separation, constant slope
baseflow separation, concave baseflow separation and the master depletion curve method.
Caution must be used when interpreting direct runoff volumes in downstream reaches for as
hydrographs are routed downstream, runoff flows become attenuated, and some of the direct
runoff volume will begin to appear as river baseflow.
The concave baseflow separation method was used in this study. An example of this
method is given in Figure 3.18. The initial recession curve is projected downward from A to C,
which lies directly under the peak flow. The curve is then extended from C to a point D on the
falling limb of the hydrograph N days after the peak. The value of N is determined from an
empirical relationship provided in the references listed above. It takes the general form of N =
1.0 Ab where A is in square miles and b is a constant that may be determined specific to the
watershed. The default value for b is typically taken as 0.2, however, based on the response of
the hydrographs in Storm 1, b was set at 0.1. The results are summarized in Tables 3.10 to 3.12
including the wet volume (millions of cubic feet (106 cf)) and the total volume (106 cf) during the
period of runoff.
3.3 Hydraulic Structures or Controls
Historically, the Blackstone River has been a river in constant demand for its ability to
supply energy, water supply or waste transport. The result was the construction of major
3-31
-------
700
Blackstone River Headwaters - BWW00
600
Storm 1
Storm 2
Storm 3
500
o 400
300
200
100 -
50
60
40
30
-10
Hours
Figure 3.15 Hydrograph Comparison - Headwaters
-------
1000
Blackstone River MA/RI State Line - BWW13
- Storm 1
- Storm 2
- Storm 3
750
500
250
-10 .0 10 20 30 40 50 60 70
Hours
Figure 3.16 Hydrograph Comparison - State Line
-------
1250
Blackstone River Mouth of River - BWW21
1000
- Storm 1
- Storm 2
- Storm 3
750
500
250
-10
0
10
20
30
50
40
60
70
Hours
Figure 3.17 Hydrograph Comparison - Mouth of River
-------
500
Storm 2
November 2-5,1992
Station BWW07
400
300
200
100
0
-10
0
10
20
30
60
40
50
70
Hours
Figure 3.18 Example of Concave Base Flow Separation
-------
Table 3.13 Dams and Impoundments along the Blackstone River
No.
Name
River Mile
Code®
Storage
(acre-feet)
Source
1
McCracken Rd.
43.9
NA
NA
2
2
Millbury
41.0
MA00578
77
3
3
Singing Dam
39.8
MA01180
60
2
4
Wilkinsonville
39.2
NA
NA
3
5
Saundersville
38.7
NA
NA
3
6
Fisherville
36.5
MA00577
250
2
7
Famumsville
35.6
MA00576
85
3
8
Riverdale
31.9
MA00942
88.5
2
9
Rice City Pond
27.8
MA00935
1762
2
10
Tupperware
17.8
MA00096
305
2
11
Blackstone
16.5
NA
NA
3
12
Thundermist
14.3
RI03902
300
2
13
Manville
9.9
R100809
58
2
14
Albion
8.2
RI00808
495
2
15
Ashton
6.8
RI00807
NA
3
16
Lonsdale
4.1
RIO1705
NA
1
17
Central Falls
2.0
RI00401
80
1
18
Pawtucket
0.8
RI00402
150
1
19
Slaters Mill
0.0
RI04270
NA
1
i
1 = United States Army Corps of Engineers (1994); 2 = MADEP; 3 = Field
Survey;8 = United States Army Corps of Engineers (1994); NA = Not Available
3-36
-------
hydraulic structures to control the river flow on the order of one per mile. Today, many of these
structures have been removed. The ones that remain today (Table 3.13) have an impact on the
river's water quality.
3.3.1 Dams and Impoundments
Nearly 45 dams and impoundments once existed on the Blackstone River. Today only 19
remain. Some of them are still utilized for hydro power generation, but the majority no longer
serve their original purpose. Many of these dams are in poor condition.
Three of the major impoundments along the river are Fisherville, Rice City and Rochdale
Ponds.
3.3.1.1 Fisherville Pond
Fisherville is located immediately downstream of the confluence of the Blackstone and
Quinsigamond Rivers. It consists of an earthen dam 10 feet high and 650 feet long, with a 200
foot long stone masonry spillway.
The dam was constructed in 1882, creating a 185 acre pond, to supply water to the now-
abandoned Fisherville Mill Complex. The maximum storage of the pond is 1360 acre-feet, and
the drainage area at the dam is 134 square miles. A diversion structure (no longer in operation)
connected the pond to the Blackstone Canal.
The pond was drained in 1982 and the area has not been reflooded due to questions raised
by the Massachusetts Department of Environmental Management concerning the safety of the
dam. Partial reflooding of the pond happens periodically due to obstructions at the outlet from
floating debris. An aerial photograph taken of the impoundment area is shown in Figure 3.19.
The outline of the original impoundment is clearly visible (Point A). The confluence between
the Blackstone River and Quinsigamond River is highlighted (Point B).
The future use and disposition of the Fisherville Dam and Pond has been under debate for
a number of years. The sluice gate has been welded open since 1986. The debate centers on two
issues: reflooding the pond and the cleanup of the hazardous waste site at the dam.
The Massachusetts Division of Fisheries and Wildlife (MDFW) considers the pond one
of the more important flyways and waterfowl habitat for the northeast for species, such as the
black duck, wood duck, mallards and Canada geese. The MDFW is considering purchasing the
dam for reconstruction, and then reflooding the impoundment, thereby changing the hydraulics.
The sediments behind the dam are highly contaminated with metals and organics, and
have begun to compact over the last several years due to exposure to the air. However, concerns
exist over the potential for resuspension, and erosion from bank slumping should the
3-37
-------
Figure 3.19 Aerial Photograph of Fisherville Pond
QUINSIGAMOND RIVER
BLK06 (BWW06)
BLACKSTONE RIVER
-------
impoundment be reflooded. Also, there is the potential for water quality changes due to longer
retention times behind the dam. Since the effluent from the UBWPAD and runoff from the City
of Worcester form the majority of river flow at this point, algal blooms could occur with
subsequent dissolved oxygen problems.
Also of importance to water quality at the dam is the canal which begins on the western
edge of the dam and travels under the old factory, and then emerges across the street. This area is
designated a 2IE site (Omni-Duralite) due to oils and solvents leaching into the canal from the
site. Booms have been placed in the canal to retain the oils which stain the surface of the water
and the rock sides of the canal. The canal itself is under consideration for National Historic
Register status. If the canal is restored, the potential exists for diversion around the ponded area.
3.3.1.2 Rice City Pond
Rice City Pond Dam embodies two structures of control. The main spillway is about 50
feet long and about 6 feet high. A second spillway, or emergency spillway, is about 5 feet high
and 75 feet long. The reservoir area is 800 feet wide and 4000 feet long. A gate control structure
located adjacent to the emergency spillway served as part of the Blackstone Canal System. The
drainage area at the dam is 204 square miles. The maximum pool storage is 1762 acre-feet.
The original purpose of the dam was to impound water to supply the Blackstone Canal
during low flow periods. Today the dam provides wetlands for wildlife.
Similar to Fisherville, the elevation of Rice City Pond has dropped in recent years due to
a change in crest elevation at the outlet structures. The result is an exposure of historic sediments
clearly evident in the aerial photograph of Figure 3.20 (Point A). It is important to recognize that
this photograph was taken in April 1991 at a time of average flow. With the lowering of the
impoundment, the river has carved channels through the soft sediments. The result is a
movement of this sediment into the water column and down river, even under average flow
conditions (Point B). The impoundment has the potential for being a significant nonpoint source
of any constituent either recently or historically deposited in the impoundment. Reference will
be made to this impoundment in subsequent sections by the bordering stations BLK07-08 for dry
weather and BWW07-08 for wet weather. A more detailed evaluation of this impoundment was
completed in a specialty study discussed in Chapter 8 of this report.
3.3.1.3 Rochdale Impoundment
Control of the sediments of the Rochdale Impoundment portends to be a significant factor
in the future use of the Blackstone River. The former dam at the Rochdale impoundment site
(historically called the Northbridge Mill Dam) was removed by the present owners of COZ
Chemical Corporation during the 1960's. At that time, the 7 foot high granite block structure
with a 40 foot wide spillway had been damaged during the hurricane several years earlier, and
had silted in over the last several decades to from a very shallow pool. Concerns existed on the
3-39
-------
Figure 3.20 Aerial Photograph of Pace City Pond
BLK08 (BWW08) ?
3-40
-------
usefulness and.stability of the dam.
The present site is characterized by an extensive plain of sediments in various stages of
compaction and drying, divided by a riverbed varying in width from 80 to 125 feet (McGinn
1981). The surface of the sediments resembles a moon scape of light dusty particles with a
metallic orange coloration. A cross-sectional view of the sediments from the river channel,
which has cut through this plain to a depth of several feet, exhibits a dramatic layering of various
types of contaminants. These layers form a historical view of discharges, from textile remnants
to oils, metals, and other organics and provide a good case study for the documentation of the
extensive sediment buildup in the river.
The most noticeable feature of this area, aside from the definitive layering, is the virtually
nonexistent regrowth on this site. The McGinn (1981) report on sediment control in the river
cited high concentrations of contaminants, low pH, lack of fertilizer and lime, and elevated
position above groundwater recharge as possible reasons that either alone, or in combination,
have prevented regrowth. The recent chemistry and toxicity work performed on this site as part
of the Blackstone Initiative (and discussed in other chapters of this report) documents extensive
chemical contamination and toxicity as possible problems for regrowth.
In 1994, the USGS removed core samples from the site as part of a preliminary
investigation into the possible mining of this area. Analysis of chemical constituents in the cores
provided further evidence of nonpoint source impacts from this site, and also raised questions as
to the feasibility of removing the sediments. During core sampling, instability of the sediments
was noted. As the core sampling device was lowered into the sediments, a wave movement was
felt, indicating the possible existence of a petroleum layer which may be re-exposed if dredging
of the site were to take place. The USGS concluded their preliminary work by stating that prior
to any excavation, the sediments would need to be extensively mapped.
Ideas for restoration and/or stabilization of this site include dredging, rebuilding of the
dam with reflooding of the impoundment, possible reactivation of the old canal to reroute some
of the higher flows around the site, or biostabilization of the site. A number of questions arise as
to the effect of each of these activities on water quality.
Reflooding: A successful example on reflooding, stabilization and regrowth exist at the
Riverdale Impoundment site further downstream. The dam at this site has been rebuilt and
raised. Water quality testing at this site did not note the same types of impacts as seen at Rice
City Pond. A comparison of fish work performed at this site did not show any significant
bioaccumulation of contaminants from pre to post flooding of the site. However, there is no
certainty that reflooding at Rochdale would produce an impoundment with the characteristics of
Riverdale. Due to the shallowness that would exist, the impoundment may resuspend sediments,
similar to Rice City Pond.
Reactivation of the canal: Remnants of the old canal exist on-site. If the dam were
3-41
-------
restored, there would exist the possibility to redirect some of the higher flow through the canal,
thus avoiding the sediments in Rice City Pond. An analysis would need to be performed to
determine the feasibility and effects of this proposal.
Biostabilization: A nonpoint source, federally funded project investigated the possibility
of replanting the Rochdale site. However, this alternative was eliminated since it was believed
that the planted species would have a low probability of successful establishment. The
experience at the site showed that, with the extensive water level fluctuations due in part to hydro
power operation, the plants would not survive. A second biostabilization project is being
attempted at Rice City Pond.
The sediment in this impoundment is a major player with its potential for bank sloughing
and reintroduction of sediment bound contaminants into the water column. These sediments will
move downstream and have the potential to be accumulated in the biota. Higher velocities and
diurnal water level fluctuation due to hydro power facilities may accelerate the movement of the
contaminants. Extensive mapping of these sediments is needed to more fully detail existing
conditions prior to a decision on future action. A further analysis would need to be done using
the wasteload allocation models (Chapters 5 and 6) to determine effects on the river from
changes in time of travel and reaeration if this dam is modified.
3.3.2 Hydropower Stations
The Farnumsville Hydro Power Facility is located just upstream of the Riverdale
impoundment. It is a non-jurisdictional facility, since it was constructed prior to Federal Energy
Regulatory Commission (FERC) licensing, and, under this designation, has no FERC oversite, or
any other regulatory control. The daily fluctuations of the river, due to this facility, have been
shown to be significant.
The Riverdale facility is located in Northbridge, MA and mirrors and amplifies the
discharges from the upstream Farnumsville facility. In 1987, FERC issued a 30 year license to
operate the Riverdale facility for power generation. The concrete and steel dam is 142 feet long
and 14 feet high. The reservoir impounded is approximately 88.5 acre-feet with 1400 feet of
backwater. The original dam was built in 1955 after that years major hurricane, breached from
1976 to 1984, and then reconstructed. A 7Q10 of 44 cfs is specified in the application, but no
minimum flows appear to be in the permit. However, FERC has requested that the hydro power
facility operate as a run-of-the-river to maintain desired flows, and also states that fish passage
may be requested in the future.
Capacity of the Riverdale facility to generate more power and regulate flows will be
significantly increased once present construction is completed. Three tunnels with turbines exit
under the manufacturing plant. At present, only one tunnel is active. The other two are being
rebuilt and stabilized, and the turbines are being repaired. The original turbines were installed
around 1900. The three turbines will allow the facility to use all river flows, and thereby achieve
3-42
-------
maximum generating capacity.
In 1960, the old Thundermist Dam in Woonsocket, RI was replaced with a 266 foot long
40 foot high concrete overflow dam. For flood control purposes, four tainter gates were
constructed. The gross storage of the dam is 300 acre-feet, and the installed powerhouse capacity
is 1200 kilowatts (per FERC). Maximum flow diverted is 1000 cfs, according to EPA.
The Elizabeth Mill Dam, also known as Pawtucket (RI) Dam has a capacity of 670
kilowatts. It is a granite masonry dam 156 feet long and 10 feet high, with 12 inch flashboards on
it. The gross storage is ISO acre-feet. Minimal flow condition is reached during normal operation
in April and May. The rest of the year, the spillway is overflowing. The maximum diversion by
the hydro power plant is 1060 cfs (per license application).
3.3.3 Blackstone River Canal
The construction of the Blackstone Canal, which extended from Narragansett Bay to
Worcester, was finished in 1828. The Canal essentially channelized Mill Brook, from the basin
at Central Street to the Blackstone River, south of the Cambridge and Millbury Street
intersection. When the Canal was in operation, the number of industries in Worcester increased
as the transportation problems were diminished. The population increased by 37 percent from
1825 to 1830, and the value of manufactured goods expanded drastically. Hie Canal had a
significant influence on the cultural, social, and industrial development of Worcester. The rapid
growth of Worcester attracted many immigrants. Since Worcester was still a pedestrian city, the
settlement of the immigrants was based upon the proximity to many companies, which were
located near the Canal. Today the Canal is only watered for approximately 6 miles. A detailed
description of the canal and its history is provided elsewhere (BRVNHC 1993).
3-43
-------
4.0 DRY WEATHER WATER QUALITY INTERPRETATION
In this section, the spatial and seasonal variations of pollutants are discussed. The
complete listing of chemical data is given in the appendix. The loadings from the two major
treatment facilities, UBWPAD and Woonsocket WWTF, are defined in this chapter as "major
point sources". In addition a combination of the other smaller point sources along the river, the
nonpoint pollutant contributions in a given reach, the tributaries and the headwaters, are
identified in this report as "other sources".
Loading data for the entire system is also compiled and rankings are performed for each
constituent. This includes the two major point sources, each river reach (including both nonpoint
and small point sources), the headwater (defined as BLK01) and the tributaries. The reach hot
spots in the system are identified based on these rankings. System toxicity has been evaluated
with comparisons between ambient criteria and observed toxicity. Toxicity testing also included
the bottom sediments and biota. The speciality studies involving the fish toxicity monitoring and
the benthic macroinvertebrate community analyses is discussed in detail.
4.1 Dissolved Oxygen Dynamics
Dissolved oxygen (DO) is discussed in detail in Chapter 5 during the calibration and
validation of the DO model QUAL2E. A brief overview of water quality related to DO is given
below.
The two largest dischargers to the river, the UBWPAD and the Woonsocket WWTF,
were each discharging considerably less than permitted flow levels during the surveys. The
UBWPAD provides advanced treatment in the form of seasonal nitrification. Woonsocket
provides standard secondary treatment. During the two low flow surveys the oxygen demanding
load discharged from Woonsocket was less than one half of the permitted load, while the oxygen
demanding load discharged from UBWPAD was less than one sixth of the permitted load.
4.1.1 Dissolved Oxygen, Chlorophyll a, Chloride, pH, BOD5
Dissolved oxygen concentrations and percent saturation values met water quality
standards at all mainstem stations under low flow conditions (July and August surveys) with one
exception (Station BLK01 at Millbuiy Street during August at 4.9 mg/L). However, a number of
values approaching the water quality standard of 5 mg/L for Class B waters were measured at
several stations. In August, Rice City Pond had a low value of 5.6 mg/L during the night and a
high value of 10.3 mg/L during the day, showing the impact of productivity in the impoundment.
The highest value (12 mg/L) was seen at Riverdale Street (BLK07). Values above 10 mg/L were
also recorded at McCracken Road (BLK02), Singing Dam (BLK04) and at Fisherville Pond
(BLK06). For the tributaries, the Mumford River showed early morning values in August below
the 5 mg/L standard 4.4 and 4.7 mg/L, and the Peters River exhibited two values of 4.9 mg/L in
July. Most values in October were above 7 mg/L in the mainstem and tributaries due to higher
flows, cooler temperatures and decreased productivity.
4-1
-------
The Massachusetts and Rhode Island water quality standards for percent saturation for
DO differ. Massachusetts uses a value of 60%, while Rhode Island uses a value of 75%. The
Massachusetts value is applied as a daily minimum, while the Rhode Island value is applied as a
daily average. If the Massachusetts standard is used for the Massachusetts river segments, no
violations exist If the Rhode Island standard is used for the Rhode Island portion, BLK20 falls
below the water quality standard for the July and August surveys.
It should be noted that any DO sag that might have occurred below the Woonsocket
WWTF or the UBWPAD discharge would have been missed due to access restrictions on the
location of the sampling stations. The first two water quality sampling stations below the
Woonsocket discharge were located immediately downstream of dams, where any oxygen sag
would have recovered due to reaeration over the dam. Also, all DO samples were taken from
surface waters. Therefore, in deeper impoundments, any variability in DO values between
surface and bottom waters would have been missed. With regard to any DO sag, it must be
remembered that, although river flow was low, the study was not at critical conditions (i.e.
maximum load and low flow of 7Q10).
A comparison of DO values with data collected in 1988 by the Massachusetts Division of
Water Pollution Control (MDWPC) for the upper and middle reaches of the Blackstone River
show some improvement over the last few years. However, comparisons are difficult because
during the 1991 survey, the flows and the ultimate oxygen demanding load from the UBWPAD
were higher. The 1988 survey flows were slightly less than twice the 1991 flows. The 1988 data
indicate DO violations in June at Millbury Street, Worcester (<4 mg/L) and Hartford Street,
Uxbridge (<3 mg/L), and in August at Singleton Street, Woonsocket (<4 mg/L) and Hartford
Street, Uxbridge (<5 mg/L). A more detailed comparison with historic data is presented in a later
section.
Chlorophyll a levels indicated abundant growth during the months of July and August in
the impoundments, where river flows slowed, and the river widened. Growth was highest in the
Riverdale and Rice City Pond impoundments, at which points advanced eutrophication was
evident. Less growth was evident in the upper reaches where velocities were higher. The highest
levels were measured at the first two Rhode Island stations below the Woonsocket treatment
plant with values between 20 and 25 Mg/L. Overall, planktonic growth was abundant in July,
moderate in August, and low during the cooler, higher flow period of October.
Associated with the chlorophyll a levels were large diurnal swings of DO. Figure 4.1 is a
profile of oxygen concentrations for July 1991. The highest concentrations of oxygen can be
observed twice during the 48 hour survey coinciding with the afternoon periods monitored
between runs 2 and 3 and 6 and 7. The location of these highs occurred between BLK06 and
BLK08 (Fisherville, Riverdale and Rice City Ponds) (point A), between BLK12 and BLK13
(Tupperware Impoundment) (point B) and to a lesser extent between BLK19 and BLK21 (Albion
to Slater's Mill Impoundments). No immediate oxygen demand could be seen directly below the
UBWPAD (point C).
-------
The lowest oxygen concentrations occurred twice during the 48 hour survey, coinciding
with the late night/early morning period monitored with run 1 and runs 4 and 5. The locations of
these lows occurred in the reach between BLK07 and BLK12 where algal respiration would be a
major sink of oxygen at night, and below the Woonsocket WWTF, where instream nitrification is
no longer offset by photosynthesis as it is during the day. More moderate swings of DO occurred
in August (Figure 4.2). No significant fluctuations occurred in October, since the seasonal
productivity had ended (Figure 4.3).
Large diumal swings in pH, with some values outside of the Massachusetts water quality
standards range of 6.5-8.3 standard units for Class B waters, were recorded at a number of
stations on the mainstem with the largest ranges in the impoundments. In most instances, pH
measurements in the tributaries were within the acceptable range. The most notable exceptions
for the tributaries occurred in the August survey, where pH measurements were lower than 6.5
standard units. The pH standard used for Rhode Island was 6.5-8.0. Massachusetts standards
also state that values will vary by not more than 0.5 units outside of the background range. In
general, the highest pH values coincided with the highest DO concentrations and were measured
during the late afternoon. Lower values were measured in the early morning.
Chloride concentrations were highest in the upstream reaches during the July and August
surveys. A second peak was measured just over the state line in Rhode Island. During the
October survey, chloride concentrations were lower, showing the effects of dilution.
Five day biochemical oxygen demand (BOD5) was low to moderate throughout the river
length with highs in the Rice City Pond area and at the two stations below Woonsocket. The
highest value recorded was 3 mg/L.
4.1.2 Nutrients
Both of the wastewater treatment facilities discharge high levels of phosphorus and
nitrogen to the river. The nitrogen discharged from UBWPAD is mostly in the form of nitrate,
while the nitrogen discharged from Woonsocket includes high levels of ammonia. Ammonia can
result in toxicity to aquatic organisms and also contributes to the depletion of DO in the river.
Neither facility has a discharge limit for phosphorus or for nitrate. The UBWPAD has a stringent
discharge limit for ammonia, with which it is in compliance. The Woonsocket permit contains
no discharge limit for ammonia. Most Total Kjeldahl Nitrogen levels were below the limit of
detection of 1 mg/L.
Ammonia - Concentration and mass loading profiles are given in Figure 4.4 for ammonia.
The major source of ammonia is the Woonsocket WWTF, which is located between stations
BLK17 and 18. A comparison of the river loadings upstream of the two major dischargers is
given in Figure 4.5. The instream concentrations increased downstream of the Woonsocket
WWTF to over 1 mg/L and increased downstream of the UBWPAD to about 0.6 mg/L. Based
on the system ranking provided in Table 4.1, the Woonsocket WWTF is responsible for about
67% of the ammonia load on average for the study. Combined, the two major point sources
4-3
-------
BLACKSTONE RIVER INITIATIVE
DISSOLVED OXYGEN - JULY
Concentration
(mg/L)
H112.00-13.00
¦ 11.00-12.00
¦ 10.00-11.00
¦ 9.00-10.00
tea 8.00-9.00
~ 7.00-8.00
¦ 6.00-7.00
¦ 5.00-6.00
01 02 03 04 06
45.8 44.0 41.4 39.8 35.7
Worcester, MA
20 21 STATION ID
3.8 0.1 RIVER MILES
Pawtucket, RI
UBWPAD
Fisherville
Pond
Woonsocket
WWTF
Rice City
I Pond
Figure 4.1 Dissolved Oxygen July 10-11, 1991 Survey
-------
BLACKSTONE RIVER INITIATIVE
DISSOLVED OXYGEN - AUGUST
Concentration
(ing/L)
¦ 11.00-12.00
¦ 10.00-11.00
¦ 9.00-10.00
¦ 8.00-9.00
;7.00-8.00
¦ 6.00-7.00
¦ 5.00-6.00
Pond
01 02 03 04 06 07 08 11 12 13 17 18 19 20 21 STATION ID
45.8 44.0 41.4 39.8 35.7 32.0 27.8 23.2 19.2 16.6 12.8 10.0 8.2 3.8 0.1 RIVER MILES
Worcester, MA Pawtucket, RI
Rice City
Pond
MA | RI Woonsocket
M 5 ~ I WWTF
I T
UBWPAD Fisherville
Figure 4.2 Dissolved Oxygen August 14-15, 1991 Survey
-------
BLACKSTONE RIVER INITIATIVE
DISSOLVED OXYGEN - OCTOBER
UBWPAD
Fisherville
Pond
Rice City
Pond
Woonsocket
WWTF
••••} j 4 -
i
¦•j M
h
{$ j
I
i
! 1
• '
ffiri* nU'SyBv'^nr
01 02
45.8 44.0
Worcester, MA
Concentration
(mg/L)
¦ 9.00-10.00
8.00-9.00
~ 7.00-8.00
20 21 STATION ID
3.8 0.1 RIVER MILES
Pawtueket, RI
Figure 4.3 Dissolved Oxygen October 2-3, 1991 Survey
-------
2
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5
800
s?
Jr> eoo
400
200
—O— July 1991 Survey
—V— August 1991 Survey
• Q • October 1991 Survey
\
50 45 40 35 30 25 20 15 10
River Miles
Figure 4.4 Ammonia Concentration and Mass Loading Profiles
4-7
-------
1400
1200
1000
800
600
400
200
0
1000
800
600
400
200
0
1000
800
600
400
200
0
e4.5
JULY 1991
AUGUST 1991
I I WWTF
IZZ] River Station
VZA.
OCTOBER 1991
ZZZL
01 UBWPAD 02
17 Woon 18
>oint Source Versus Upstream and Downstream River Static
4-8
-------
Table 4.1 Ammonia Dry Weather System Ranking
Rank
Survey 1
Survey 2
Survey 3
Source
Load
%
Source
Load
%
Source
Load
%
1
Woon
1258
88.9
Woon
812
67.4
Woon
838
52.8
2
UBWPAD
91.1
6.4
BLK01-02
92.2
7.7
BLK01-02
266
16.8
3
BLK03-04
39.4
2.8
BLK20-21
85.5
7.1
BLK03-04
112
7.1
4
BLK14
12.2
0.9
UBWPAD
60.1
5.0
BLK18-19
108
6.8
5
BLK09
3.6
0.3
BLK14
45.8
3.8
UBWPAD
59.3
3.7
6
BLK05
3.4
0.2
BLK03-04
44.2
3.7
BLK20-21
44.5
2.8
7
BLK16
3.3
0.2
BLK09
16.9
1.4
BLK11-12
45.0
2.8
8
BLK10
1.6
0.1
BLK02-03
15.1
1.3
BLK04-06
43.6
2.7
9
BLK12-13
1.5
0.1
BLK05
12.8
1.1
BLK14
25.3
1.6
10
BLK15
1.3
0.1
BLK15
6.5
0.5
BLK12-13
13.6
0.9
11
BLK10
6.3
0.5
BLK15
13.1
0.8
12
BLK08-11
4.5
0.4
BLK09
7.7
0.5
13
BLK16
2.4
0.2
BLK16
5.2
0.3
14
BLK05
3.5
0.2
15
BLK10
3.0
0.2
Total
1415
1204
1588
Woon = Woonsocket WWTF; Load in lbs/day
-------
Ammonia % Contribution
Ammonia Load (lbs/day)
¦f
©
MAJOR
POINT
SOURCES
OTHER
SOURCES
PW1 LOW FLOW CONDITION
(JULY 1991 SURVEY)
HIGH FLOW CONDITION
(OCTOBER 1991 SURVEY)
MAJOR
POINT
SOURCES
OTHER
SOURCES
2000
Figure 4.6 Comparison of the Two Major Point Sources Versus the Other Sources for Ammonia
-------
deliver about 95% of the ammonia load to the river under July low flow conditions (Figure 4.6).
Nitrate - The concentration profiles for nitrate are given in Figure 4.7. For July and
August, nitrate concentrations were highest below the UBWPAD, approaching 4 mg/L at
McCracken Road (BLK02) and between 4 and 5 mg/L at the next two downstream stations.
The mass loading profiles are also presented in Figure 4.7. Nitrate increases due to
instream nitrification are evident in the two low flow surveys throughout the lower portion of the
river to BLK21.
A comparison of the river loadings upstream of the two major dischargers are given in
Figure 4.8. UBWPAD played a major role in the nitrate loading of the river. This is evident by
the system ranking, which has the UBWPAD as the number one source for all three surveys
(Table 4.2). The UBWPAD contributed about 49% on average for the study, with the highest
contribution coming in the August survey (about 65%).
The impact of the Woonsocket facility at the point of mixing was very small for July
(1.3%) and October (2.1%), but the combined impact of the downstream reaches below its
discharge due to instream nitrification was significant (over 17 and 28% for July and October,
respectively). In August, it appeared that the facility was achieving some form of nitrification.
The direct discharge from the facility was about 18%.
Considering the separation of the two major point sources from the other sources in the
system, as defined earlier, the percent breakdown in the low and high flow surveys was almost
identical (Figure 4.9). Other sources (58%) were higher than the two major point sources (42%).
However, since instream nitrification is ongoing, one might consider the contributions of nitrate
in the reaches immediately below the Woonsocket WWTF discharge (BLK18-21) as point source
loads. The combined loading of the two major WWTFs and these reaches would have been
about 60,90 and 70% for July, August and October, respectively.
Orthophosphate - Dissolved orthophosphate levels were very high in the upper reaches,
with values exceeding 1 mg/L downstream from the UBWPAD. The values remained high at the
next few stations, and then dropped to lower levels in the impoundments (Figure 4.10) where the
biological community removed the phosphorus to produce biomass. Levels of phosphorus in
these segments declined to 0.2-0.5 mg/L, while chlorophyll levels rose from <0.3 jug/L to around
20 /zg/L. The major peak in orthophosphate was evident at McCracken Road (BLK02), where
levels were 100 times the values measured at the nearest upstream station.
The mass loading profiles are also given in Figure 4.10. The significance of the two
facilities is evident in Figure 4.11 and Table 4.3. Combined the two facilities contribute about
80% of the loading to the river (Figure 4.12).
4.1.3 Historic Trends Related to Dissolved Oxygen
4-11
-------
5000
4000
3000
2000
« 1000
>-
a.
3
m
m =i
D
<
UJ
O
o
a.
m
d:
o
z
85 m ti
I S1 8
I ijO ffl
y K Q: Z
5 j Si! o
£ ^ts i
m 5 o. >
12 13 17 18 19
20
O- July 1991 Survey
V— August 1991 Survey
~ • October 1991 Survey
\
50 45 40 35 30 25 20 15 10
River Miles
Figure 4.7 Nitrates as N Concentration and Mass Loading Profiles
4-12
-------
1600
1400
1200
1000
800
600
400
200
0
6000
5000
4000
3000
2000
1000
0
6000
5000
4000
3000
2000
1000
0
4.8 I
JULY 1991
AUGUST 1991
CZZ1 WWTF
V/\ River Station
OCTOBER 1991
01 UBWPAD 02
17 Woon 18
Source Versus Upstream and Downstream River
4-13
-------
Table 4.2 Nitrate Dry Weather System Ranking
Rank
Survey 1
Survey 2
Survey 3
Source
Load
%
Source
Load
%
Source
Load
%
1
UBWPAD
1341
41.3
UBWPAD
4986
64.8
UBWPAD
4070
40.7
2
BLK02-03
462.2
14.2
Woon
1401
18.2
BLK20-21
2148
21.5
3
BLK06-07
330.5
10.2
BLK18-19
310.9
4.0
BLK11-12
845.8
8.5
4
BLK19-20
240.2
7.4
BLK 19-20
299.8
3.9
BLK17-18
631.5
6.3
5
BLK03-04
194.4
6.0
BLK11-12
198.3
2.6
BLK12-13
490.0
4.9
6
BLK18-19
148.2
4.6
BLK02-03
156.5
2.0
BLK01
452.5
4.5
7
BLK20-21
133.9
4.1
BLK06-07
66.8
0.9
BLK08-11
415.4
4.2
8
BLK12-13
133.4
4.1
BLK09
64.4
0.8
Woon
212.3
2.1
9
BLK11-12
62.1
1.9
BLK01
57.3
0.7
BLK04-06
159.8
1.6
10
BLK01
48.3
1.5
BLK14
44.2
0.6
BLK14
109.6
1.1
11
Woon
42.1
1.3
BLK03-04
41.1
0.5
BLK02-03
105.7
1.1
12
BLK17-18
39.7
1.2
BLK07-08
38.0
0.5
BLK06-07
95.4
1.0
13
BLK14
35.0
1.1
BLK16
9.3
0.1
BLK07-08
88.9
0.9
14
BLK09
10.6
0.3
BLK05
7.1
0.1
BLK09
54.4
0.5
15
BLK16
9.5
0.3
BLK15
5.8
0.1
BLK15
49.9
0.5
16
BLK15
7.7
0.2
BLK10
4.1
0.1
BLK16
49.3
0.5
17
BLK05
6.7
0.2
BLK05
18.5
0.2
18
BLK10
4.1
0.1
BLK10
8.67
0.1
19
Total
3250
7691
10006
Woon = Woonsocket WWTF; Load in lbs/day
-------
Nitrate % Contribution
i
<¦*
Nitrate Load (lbs/day)
MAJOR
POINT
SOURCES
OTHER
SOURCES
POT) LOW FLOW CONDITION
(JULY 1991 SURVEY)
HIGH FLOW CONDITION
(OCTOBER 1991 SURVEY)
MAJOR
POINT
SOURCES
OTHER
SOURCES
10000
8000
6000
4000
2000
Figure 4.9 Comparison of the Two Major Point Sources Versus the Other Sources for Nitrate
-------
r—>
s
Oh
I
cf
Ph
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CO
C/l
3
fc
D
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lli
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gi 2
i| 3
2 § 3
5 Li
(£
T ^ K O
S is S
5 _i E o
— t 5
m 5 o. §
750
12 13 17 18 19
—O— July 1991 Survey
—V— August 1991 Survey
• • October 1991 Survey
t 1 r
t r
i L.
5
CO
a.
LU
5
CO
45 40 35 30 25 20 15 10 5 0
•3
£ 500
¦8
£ 250
\
50 45 40 35 30 25 20 15 10
River Miles
Figure 4.10 Orthophosphate as P Concentration and Mass Loading Profiles
4-16
-------
600
JULY 1991
500
400
300
200
100
800
AUGUST 1991
600
I I WWTF
EZ3 River Station
400
o,
200
1200
OCTOBER 1991
1000
800
600
400
200
0
01 UBWPAD 02
17 Woon 18
Figure 4.11 Point Source Versus Upstream and Downstream River Stations for Orthophosphate
4-17
-------
Table 4.3 Orthophosphate Dry Weather System Ranking
Rank
Survey 1
Survey 2
Survey 3
Source
Load
%
Source
Load
%
Source
Load
%
1
UBWPAD
476
59.8
UBWPAD
567
63.6
UBWPAD
1057
64.6
2
Woon
151
19.0
Woon
208
23.3
Woon
289
17.7
3
BLK02-03
54.7
6.9
BLK13-17
55.4
6.2
BLK08-11
60.4
3.7
4
BLK12-13
40.2
5.0
BLK11-12
35.2
4.0
BLK12-13
59.3
3.6
5
BLK06-07
28.5
3.6
BLK19-20
15.2
1.7
BLK01
44.9
2.7
6
BLK11-12
12.7
1.6
BLK14
7.03
0.8
BLK11-12
40.1
2.5
7
BLK09
11.2
1.4
BLK09
0.78
0.1
BLK20-21
28.1
1.7
8
BLK20-21
8.98
1.1
BLK01
0.77
0.1
BLK02-03
26.7
1.6
9
BLK14
7.39
0.9
BLK10
0.63
0.1
BLK09
7.81
0.5
10
BLK05
3.20
0.4
BLK05
0.56
0.1
BLK 05
5.78
0.4
11
BLK15
0.99
0.1
BLK15
0.39
0.04
BLK14
5.75
0.4
12
BLK01
0.74
0.1
BLK16
0.35
0.04
BLK07-08
4.91
0.3
13
BLK10
0.52
0.1
BLK10
3.04
0.2
14
BLK16
0.26
0.03
BLK16
1.96
0.1
15
BLK15
1.87
0.1
Total
796
891
1637
Woon = Woonsocket WWTF; Load in lbs/day
-------
Orthophosphate % Contribution
MAJOR
POINT
SOURCES
OTHER
SOURCES
Orthophosphate Load (lbs/day)
MAJOR
POINT
SOURCES
OTHER
SOURCES
LOW FLOW CONDITION
(JULY 1991 SURVEY)
HIGH FLOW CONDITION
(OCTOBER 1991 SURVEY)
Figure 4.12 Comparison of the Two Major Point Sources Versus the Other Sources for Orthophosphate
-------
Water quality in the Blackstone River has improved dramatically over the last two
decades. The improvement is the result of better and more extensive treatment of the wastewater
discharges that enter the Blackstone. This more extensive treatment has reduced the amounts of
BOD, suspended solids, and ammonia that reach the river from these discharges. More recently,
dechlorination, or alternatives to chlorine, have been instituted to avoid any toxicity associated
with the disinfection of these effluents.
The reduction in suspended solids means that the water column is less turbid, and that
benthic organisms are less subject to being smothered by the deposition of this constituent.
Pretreatment and pollution prevention have reduced the amount of toxic substances being
discharged to sewer systems. Therefore, reduction in solids also means that remaining
contaminants associated with those solids, especially certain metals, are less likely to reach the
river. However, this is only an incidental aspect, which transfers the contaminant from one
medium (river water and sediment) to another (wastewater sludge).
There are five municipal wastewater treatment facilities in the Massachusetts portion of
the Blackstone River. The largest and dominant facility by far is the UBWPAD, which serves
Worcester, parts of Holden, Rutland and Auburn. This discharge, near the headwaters of the
Blackstone, constitutes about 90% of the 7Q10 river flow upon which the water quality standards
are based.
The improvement in water quality over the years is reflected in a comparison of DO
profiles for four surveys covering 21 years (1970,1973,1980 and 1991). Figures 4.13 and 4.14
show a clear increase of both minimum DO values and 24 hour DO averages. This increase in
DO is the direct result of less BOD and ammonia entering the river because of increased and
improved treatment as typified by data from the UBWPAD (Figures 4.15-4.17 for the plant and
Figures 4.18-4.20 for impacts instream). The impact of the reduction of ammonia entering the
river from the Upper Blackstone facility is reflected dramatically after nitrification was instituted
between the 1980 and 1991 surveys (Figures 4.16,4.17, and 4.19).
It should be noted that the nitrate concentrations, as well as those for ammonia at river
mile 16.6 (near the MA-RI state line), are not dramatically different for 1973 and 1991 when
compared to the sharp difference that was apparent just below the UBWPAD's discharge at mile
point 43.9 (Figures 4.19 and 4.20). The big difference is apparent in the interval between the
UBWPAD discharge and near the state line. Results from the surveys prior to 1991 show a large
spike in the ammonia concentration below the UBWPAD discharge, with a gradual decrease at
the downstream stations. This is mirrored in the concomitant increase in the concentration of
nitrate through those same stations.
Clearly, the ammonia is being oxidized to nitrate, and this process is consuming oxygen
resources in the river. In 1991, in contrast, this oxidation process is taking place in the
UBWPAD's facility, and thus is protecting the river's oxygen resources. This is reflected in the
relatively low and constant concentration of ammonia between the UBWPAD discharge and the
state line (Figure 4.19). It also is demonstrated by the high concentration of nitrate just below the
4-20
-------
UBWPAD
Completed 1976
Rice City
Pond
MA-RI
State Line
50
i
i
i
12 3 4
8 11
—1970 Minimum DO
• V - 1973 Minimum DO
—1980 Minimum DO
—O- 1991 Minimum DO
12 13
-------
UBWPAD
Completed 1976
Rice City
Pond
MA-RI
State Line
i
X
i
1 2 3 4 6
• Average DO 1970
• V Average DO 1973
—«— Average DO 1980
—O Average DO 1991
-------
18000
16000
14000
12000
I" 10000
C/5
£
0 8000
«
6000
4000
2000
0
1973 1976 1977 1979 1980 1982 1983 1984 1985 1991
Years
Note: Numbers at top of bar indicate the number of samples used in calculations
Figure 4.15 BOD5 Mass Loading from 1973 to 1991 for UBWPAD
SECONDARY
TREATMENT
1976
NITRIFICATION
1986
-------
4000
3500
3000
2500
2000
1500
1000
500
0
1973 1976 1977 1979 1980 1982 1983 1984 1985 1991
Years
Note: Numbers at top of bar indicate the number of samples used in calculations
Figure 4.16 Ammonia Mass Loading from 1973 to 1991 for UBWPAD
SECONDARY
TREATMENT
1976
NITRIFICATION
1986
-------
4500
NITRIFICATION
1986
SECONDARY
TREATMENT
1976
H
2
n
n
I |
12
1973
1976
1977
1979
1980 1982
Years
Note: Numbers at top of bar indicate the number of samples used in calculations
Figure 4.17 Nitrate Mass Loading from 1973 to 1991 for UBWPAD
1983
1984
1985
1991
-------
50
40
r—"S
S 30
m
Q
8
| 20
S>
<
10
UBWPAD
Completed 1976
Rice City
Pond
MA-RI
State Line
i
12 3 4
6 7
8
11
12 13
1970
•
•V- 1973
l\
-m- 1980
.
\
-0 1991
-
IV.
•
VI \
A
/ ^
1. •
[\
'v *
V „
. j . —
V
w
M—
—-¦
Or-o—o—j>-
« ¦ ¦ * 1 • * ¦ ¦ 1 ¦
t-<>rTY~r?'n"
H^>-
» »
•—- O-
-i—i i i i—i i
i
0
;o
Stations
50
45
40
35 30
River Miles
25
20
15
Figure 4.18 Average BOD5 Values for 1970, 1973,1980, and 1991 Surveys
4-26
-------
UBWPAD Rice City - MA-RI
Completed 1976 Pond State Line
5
Stations
1970
• v 1973
1980
-0 1991
4
3
2
1
0
50
30
15
River Miles
Figure 4.19 Average Ammonia Values for 1970, 1973, 1980, and 1991 Surveys
4-27
-------
UBWPAD
Completed 1976
Rice City
Pond
MA-RI
State Line
50
12 3 4
11
12 13
1970
•V 1973
—1980
-O 1991
Stations
45
40
35 30
River Miles
25
20
15
Figure 4.20 Average Nitrate Values for 1970,1973,1980, and 1991 Surveys
4-28
-------
UBWPAD's discharge and, while the concentration diminishes as one goes downstream, the
nitrate remains high for normal river water, at least until the state line (Figure 4.20). The overall
pattern is similar for the mass of ammonia and nitrate present (Figure 4.21) as well as for the
concentrations.
Since flow also is an important variable in the oxygen resources of a stream, and because
standards are based on a specified flow (7Q10), any comparison must be at the same flow or
adjusted to the same flow and design loads by using a mathematical model. Since the flow in
1973 and 1991 were close to each other and to the 7Q10, the results from these two surveys were
selected for the detailed analysis of the oxygen conditions in the Blackstone River.
These two times represent the extremes of just before treatment was expanded or
upgraded, and when the enhanced treatment was completed and its effects reflected in improved
water quality. Organic material, that can be metabolized by bacteria (BOD), and ammonia that
can be oxidized to nitrate, have an impact on the oxygen resources of a receiving water. In the
case of the Blackstone, the amounts of BOD, and ammonia instream and in the UBWPAD's
effluent show a drastic decrease when the 1991 results are compared to those from 1973. In
1973, 15,000 lbs/day of BOD5 and 2000 lbs/day of NH3-N were entering the river from the
UBWPAD. While each pound of BOD requires a pound of oxygen to satisfy the demand, each
pound ofNHj-N requires slightly more than 4.S pounds of oxygen to produce one pound of
nitrate. Thus the 2000 lbs of NH3 requires about 9,000 lbs of oxygen in accord with the
bacterially mediated reaction: NH3 + 202 = N03 + H + H20.
Thus, both BOD and NH3-N placed substantial demand on the oxygen resources in the
river. However, it is not only the magnitude of the demand, but the rate at which it is expressed
that is important because while the demand is being exerted, oxygen from the atmosphere is
entering the water column to make up the deficit caused by satisfying the demand. The mass of
BOD in the Blackstone diminished substantially immediately downstream from the discharge in
1973 while the ammonia remained relatively high and constant. Thus, the oxygen demand is
driven mainly by BOD in this section of the river. Further downstream, at about mile point 31.9,
ammonia begins to disappear. This disappearance could be caused by uptake of ammonia by
plants as a nutrient, or it could mean it is being oxidized to nitrate thereby consuming oxygen.
Because nitrate begins to increase at the same time and by approximately the same amount that
ammonia disappears, the inference is that oxidation is the mechanism causing the disappearance
of ammonia. Therefore, in this section of the river, the demand exerted by the oxidation of
ammonia to nitrate appears to be the dominant water column sink for oxygen.
Since the rate at which the oxygen demand is exerted is only half the picture, and the rate
of restoring oxygen to the river the other half, the variation in DO concentrations is the
combination of these two competing factors. Thus, while the exertion of 1 mg/L of oxygen
demand could result in a decrease of 1 mg/L DO instream, in general this is not the case because
of the counterbalance of reaeration from the atmosphere. The point is that the variation of DO
concentration is complex and not simply a mirror image of satisfying the demand. A more
detailed discussion of oxygen dynamics in the Blackstone River is presented in Chapter 5 of this
4-29
-------
UBWPAD
Completed 1976
Rice City
Pond
MA-RI
State Line
1973 Ammonia
v 1973 Nitrate
1991 Summer Ammonia
—O 1991 Summer Nitrate
1991 October Ammonia
A 1991 October Nitrate
:
Stations
50
45
40
35 30
River Miles
25
20
15
Figure 4.21 Ammonia and Nitrate Mass Loading for 1973 and 1991 Surveys
4-30
-------
report.
By 1991, the BODs and NH3 loads entering from the UBWPAD had decreased
substantially. This overall reduction is reflected not only in the decreased loads, but in the
increase of oxygen in the Blackstone River. The reduction of the ammonia load is accomplished
by converting it to nitrate in the treatment plant instead of in the river. Thus, the (approximately)
same amount of nitrate is discharged in place of ammonia. The nitrate added to the river in 1991
was approximately 3800 lbs/day, based on five 24 hour composites, while the ammonia was
about 200 lbs/day, based on those same samples. During the same interval, the BODs load from
UBWPAD was reduced from about 15,000 lbs/day to about 1000 lbs/day (Figure 4.15). One
major curiosity in the profile of nitrate in October 1991 (Figure 4.21) is that there is still an
increase comparable to that associated with nitrifying the ammonia in 1973. But, as was just
pointed out, not much ammonia was discharged at the plant, and therefore, another source of
nitrate must exist assuming the data are correct. It is possible that the wetlands are acting as a
buffer for nitrogen, perhaps passing it through in the late fall and winter (in fact, when only the
summer data are plotted (Figure 4.21) no increase in the mass of nitrate appears; only in October
is this phenomenon evident). Also, nitrogen may be lost from the water column during rapid
plant growth in the spring and summer and subsequently released in the fall as plant matter
begins to die and decay. It would be expected that the nitrogen would be released as ammonia
but given the relatively rich oxygen conditions that prevail, it is possible that the NH3 is quickly
oxidized to nitrate without a severe impact on the oxygen concentration in the water column.
Other aspects of the DO dynamics include the estimate of DO deficit (Figure 4.22) and
the diurnal variation in its concentration. Typically, the lowest concentrations occur in the early
morning hours when respiration has been continuing through the night, and photosynthesis is in
abeyance. The peaks normally occur later in the afternoon when the effects of photosynthesis
reach their maxima. In comparing the difference between the maxima and minima at each
station, no obvious difference was apparent between the 1973 and 1991 summer data. Clearly,
there are much smaller differences in October. This is consistent with being at or near the end of
the growing season. It also is consistent with the hypothesis that plant matter would be decaying
at this time and, therefore, might account for the substantial increase of nitrate in the section of
the river just above the Massachusetts-Rhode Island state line.
A final observation of DO is provided by the data collected at the USGS-Massachusetts
monitoring station that was located in Millville, near the state line. From 1970 to 1980,
temperature, DO, pH and conductivity were measured hourly by an automated system. While the
DO system was the most subject to failure, it nevertheless provided an abundant, long term data
base at this one location. A substantial improvement in the DO is documented by the records of
this station, as illustrated in Figure 4.23. The point of improving DO concentrations in the mid
1970s coincides with the improved treatment at UBWPAD.
In summary, the Blackstone River's major DO problems have been rectified by the
improved and expanded treatment of wastewaters being discharged to the water course. At the
same time, it must be kept in mind that the UBWPAD is well below its design flow with about
4-31
-------
MA-RI
UBWPAD Rice City Pond State Line
S31973 01988 B1991
45.7 43.9 41.3 39.8 36.3 31.9 27.8 23.2 19.1 16.6
River Miles
Figure 4.22 Blackstone River DO Deficit for 1973, 1988, and 1991
-------
30 MGD being processed on an average day, compared to its design of 56 MGD. Given that
some of this design capacity was included because this facility serves, in part, a combined sewer
system, the expectation is that the present average flows are likely to remain fairly stable in the
foreseeable future, with only the wet weather flows reaching the 56 MGD design.
4.2 Total Suspended Solids
In general, potential sources of TSS to the water column under dry weather conditions
include the headwaters, point sources, resuspension of bottom sediments and aquatic plant
growth. In the July low flow survey, the TSS concentrations were found to increase from BLK03
to BLK06 by a factor of 3.7. This increase was attributed to resuspension of the bottom
sediments, since point source loads and plant growth (chlorophyll) between these stations was
negligible. The increase from BLK06 to BLK08 (about a factor of 2.9) was a combination of
resuspension and plant growth (chlorophyll). The concentrations at BLK08 were 11 times
greater than at BLK03. The concentrations below BLK08 gradually decreased to the end of the
river (BLK21).
In August, TSS concentrations increased between BLK03 and BLK06 (about a factor of
2) and BLK06 and BLK08 (about a factor of 4). Between BLK08 and BLK12 TSS
concentrations declined slightly. Below BLK.12, the profile did not vary significantly (Figure
4.24).
For the October high flow survey, the maximum concentration was observed at BLK08.
A second major increase occurred between BLK12 and BLK13. October profiles were higher
than the July and August profiles. Mass loading profiles were plotted for all three surveys
(Figure 4.24).
The relative importance of any point source is directly related to the pollutant load of the
river at the point of mixing. The UBWPAD facility is located very close to the rivers's
headwaters. The ratio of the discharge flow to river flow is high, therefore, the impact of the
discharge on the river is expected to be significant. On the other hand, the Woonsocket facility is
located approximately 40 miles below the UBWPAD discharge. The ratio of discharge flow to
the river flow is low, therefore, the impact is expected to be less. To highlight the effect of point
sources, a comparison was made between the two major discharges and the river stations
immediately upstream and downstream. The UBWPAD input was about 8 times higher than
upstream station (BLK01) in July, 3 times in August, and 0.85 times in October (Figure 4.25). In
comparison, the Woonsocket WWTF input was 0.05 times the upstream station (BLK17) in July,
0.25 times in August, and 0.12 times in October.
The TSS contributions of the tributaries to the river were not significant.
The system ranking for sources of TSS is listed in Table 4.4. If the major point sources
and the all other sources are grouped together (i.e. major point sources = UBWPAD + WWWTF,
and other sources = headwaters + tributaries + sediment resuspension + plant growth + small
4-33
-------
Blackstone River Dissolved Oxygen Violations
Percentage of Days with DO < 5 mg/L - June to October
U>
4^
180
160-H
140 -H
C/3
a
.2
I 120
o
>
^ 100
"2
o
o
"i
&
Vh
O
t/5
&
Q
80 -H
60
40
20
0
S Number of Days DO
Measured
~ % Days in Violation
of Standard
h 123
1
|| 91
-m-
1
-Kg
I
96_
127
I
147
63
«4-
I
NEW / IMPROVED WWTFs
150
1
I
Mi.
64
39
I
TIT
96
139
J
I
60
142
|Sj
w
124
19
1969 1970 1971 1972 1973
1974 1975
Years
JZ6_
21
+
1976 1977 1978 1979 1980
Figure 4.23 History of DO Violations from 1969 to 1980
-------
12 13
20 21
X.
7
20000
16000
12000
jg
w 8000
4000
50
July 1991 Survey
-V— August 1991 Survey
d • October 1991 Survey
30 25 20
River Miles
Figure 4.24 Total Suspended Solids (TSS) Concentration and Mass Loading Profiles
4-35
-------
10
8
6
4
2
0
20
16
12
8
4
0
20
16
12
8
4
0
JULY 1991
AUGUST 1991
I I WWTF
1/ /I River Station
-J \7~7~A
7
A
/
A.
OCTOBER 1991
F777-
m
01 UBWPAD 02
17 Woon 18
int Source Versus Upstream and Downstream River Stations for TSS
4-36
-------
Table 4.4 TSS (1000 lbs/day) Dry Weather System Ranking
Rank
Survey 1
Survey 2
Survey 3
Source
Load
%
Source
Load
%
Source
Load
%
1
BLK07-08
2.34
19.9
BLK06-07
1.79
18.6
BLK04-06
2.76
14.8
2
BLK20-21
1.50
12.8
BLK20-21
1.42
14.7
BLK07-08
2.45
13.2
3
UBWPAD
1.27
10.8
BLK07-08
1.32
13.7
BLK12-13
2.35
12.6
4
BLK12-13
1.17
10.0
Woon
0.88
9.2
BLK08-11
1.96
10.6
5
BLK18-19
0.97
8.3
BLK12-13
0.88
9.2
BLK01
1.32
7.1
6
BLK04-06
0.97
8.3
BLK18-19
0.85
8.8
BLK02-03
1.24
6.7
7
BLK06-07
0.90
7.7
UBWPAD
0.78
8.1
BLK14
1.24
6.7
8
BLK13-17
0.90
7.6
BLK14
0.52
5.4
UBWPAD
1.09
5.9
9
BLK08-11
0.54
4.6
BLK04-06
0.29
3.0
BLK09
0.85
4.6
10
Woon
0.32
2.7
BLK01
0.27
2.8
BLK20-21
0.79
4.3
11
BLK14
0.20
1.7
BLK03-04
0.19
2.0
BLK15
0.50
2.7
12
BLK01
0.16
1.4
BLK15
0.12
1.3
BLK06-07
0.49
2.6
13
BLK03-04
0.13
1.1
BLK09
0.11
1.2
BLK10
0.44
2.4
14
BLK09
0.12
1.0
BLK05
0.07
0.7
BLK05
0.30
1.6
15
BLK10
0.07
0.6
BLK16
0.07
0.7
BLK01-02
0.30
1.6
16
BLK15
0.07
0.6
BLK10
0.06
0.6
Woon
0.29
1.6
17
BLK16
0.07
0.6
BLK16
0.21
1.1
18
BLK05
0.04
0.3
Total
11.73
9.60
18.56
Woon = Woonsocket WWTF; Load in lbs/day
-------
point sources), the result for the July survey was about 14% contribution from the major WWTFs
and 86% from the other sources. The single largest source of solids in the system was a 20%
contribution between BLK07 and BLK08 of which 65% is abiotic TSS and 35% is biotic TSS.
This source was most likely a combination of plant growth and resuspension of the bottom
sediments.
In August, the single major internal source was between BLK06 and BLK07, where about
19% of the total load was observed, of which 56% gain was abiotic and 44% biotic. The two
major point sources contributed about 17%, and the other sources totaled about 83%.
In October, the two major point sources contributed 7.5%, and the other sources totaled
92.5%. With regards to the other major sources, TSS increases were about 15% for BLK04 to
BLK06, and 13% for both BLK12 to BLK13 and BLK07 to BLK08.
A comparison between the two major point sources and the other sources in the river
under low and high flow conditions is shown in Figure 4.26. Under either condition, the other
sources contribute higher amounts than the two major point sources. These data indicate the
other sources contribute about 87% of the total load to the river on average. All three surveys
showed evidence of a major source of TSS between BLK07 and BLK08.
4.3 Total and Dissolved Trace Metals
A major purpose of the Blackstone River Initiative was the determination of the spatial
and seasonal trends of trace metals in the river system, the identification of reach hot spots in the
system, the determination of the relative contribution between the two major point sources and
the other sources in the river, and an estimation of the acute and chronic criteria violations based
on total and dissolved trace metal concentrations.
For the two major dischargers, there was no appreciable difference between their effluent
concentrations with the exception of nickel. On the other hand, UBWPAD typically discharged
higher amounts of metals.
4.3.1 Cadmium
In general, for the July and August low flow surveys, the total and dissolved Cd profiles
showed a low headwater concentration, a significant input from UBWPAD, a rapid loss from
BLK02 to BLK04, and a gradual decrease after BLK04 through to BLK21 (Figures 4.27 and
4.28). The high flow October survey showed a low headwater concentration, less of an impact
from the UBWPAD, although losses are still observed in the reaches directly below its discharge,
and a gradual decreasing profile below BLK07 to the mouth of the river (BLK21). The impact
from the Blackstone tributaries was negligible.
The input from the UBWPAD was higher than the Woonsocket WWTF. The relative
impact of the UBWPAD and Woonsocket facilities on Cd loadings were similar to that observed
4-38
-------
TSS % Contribution
TSS Load (lbs/day)
u>
vo
MAJOR
POINT
SOURCES
OTHER
SOURCES
FW1 LOW FLOW CONDITION
(JULY 1991 SURVEY)
HIGH FLOW CONDITION
(OCTOBER 1991 SURVEY)
MAJOR
POINT
SOURCES
OTHER
SOURCES
Figure 4.26 Comparison of the Two Major Point Sources Versus the Other Sources for TSS
-------
5
4
3
2
1
0
50 45 40 35 30 25 20 15 10 5 0
5
4
3
2
1
0
50 45 40 35 30 25 20 15 10 5 0
River Miles
Figure 4.27 Total Cadmium Concentration and Mass Loading Profiles
4-40
I
5
m
3
a.
0
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52
to
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2
(0
cc
1
(0
\
11 12 13 17 18 19 20 21
—0— July 1991 Survey
-V— August 1991 Survey
• -O • October 1991 Survey
45 40 35 30 25 20 15 10
River Miles
Figure 4.28 Dissolved Cadmium Concentration and Mass Loading Profiles
4-41
-------
with TSS.
In the July survey, the total metal input from UBWPAD compared to BLK01 was about
30 times higher, whereas, the Woonsocket facility was only 0.38 times that of BLK17. For the
August survey, UBWPAD input was 37 times higher than BLK01, and input from Woonsocket
was 0.75 times BLK17. For the October Survey, the UBWPAD input was 8.5 times BLK01 and
Woonsocket input was 0.03 times BLK.17 (Figure 4.29). Similar results were observed for
dissolved Cd.
Cd sources in the system are ranked and listed in Table 4.5. In July, the UBWPAD is
ranked first (51%). A source between BLK07 and BLK08 contributed about 14% of the total
river load. The overall contribution from the two major point sources was about 58%, with the
other sources contributing about 42%. Cadmium concentrations are shown in a 3-D plot in
Figure 4.30.
In August, the UBWPAD is again ranked first, contributing 52%. The input between
BLK07 and BLK08 was 8.6%. The contribution from the two major point sources was 66%,
compared to the contribution from the other sources of 34%.
Although the UBWPAD also ranked first for the high flow survey, the contribution was
only 18.4% of the cumulative source input. The relative importance of other sources to the two
major point sources was reversed. The other sources contributed about 80% of the total load to
20% from the two major point sources.
These data indicate Cd concentrations in the system are dominated by the two major point
sources, specifically the UBWPAD facility, under low flow conditions but, the other sources
under high flow conditions (Figure 4.31). Furthermore, the magnitude of the other sources
appear to be directly related to flow and velocity and would, therefore, suggest bottom sediment
resuspension as a major source.
4.3.2 Chromium
The total and dissolved chromium profiles are presented in Figures 4.32 and 4.33,
respectively. In July, a sharp rise at BLK08 was observed (about 4 times BLK07). This
observation was similar to the July TSS profile. The source above BLK08 appears to be related
to sediment resuspension.
In August, a significant loss in total Cr occurred between BLK01 and BLK04, followed
by a 2.64 fold increase between BLK07 and BLK08, and a gradual decline thereafter to BLK21.
The loss of the metal in the upper Blackstone River was similar to Cd in July and August,
although a major source of the Cr appears to be upstream of BLK01. The increase at BLK08
matches that observed in July. The concentration profile in October was relatively flat with the
exception of a small increase around BLK.11. In general, the profiles of dissolved Cr
concentrations were similar to the total Cr profiles.
4-42
-------
2
JULY 1991
2
AUGUST 1991
1/ y I River Station
1
0
4
OCTOBER 1991
3
2
1
0
01 UBWPAD 02
17 Woon 18
Figure 4.29 Point Source Versus Upstream and Downstream River Stations for Total Cadmium
4-43
-------
Table 4.5 Cadmium Diy Weather System Ranking
Rank
Survey 1
Survey 2
Survey 3
Source
Load
%
Source
Load
%
Source
Load
%
1
UBWPAD
0.882
50.8
UBWPAD
1.111
52.0
UBWPAD
0.942
18.4
2
BLK12-13
0.260
15.0
Woon
0.298
14.0
BLK08-11
0.807
15.8
3
BLK07-08
0.236
13.6
BLK17-18
0.223
10.4
BLK02-03
0.752
14.7
4
BLK01-02
0.133
7.7
BLK01-02
0.214
10.0
BLK04-06
0.716
14.0
5
Woon
0.127
7.3
BLK07-08
0.184
8.6
BLK12-13
0.529
10.3
6
BLK01
0.027
1.6
BLK14
0.043
2.0
BLK01-02
0.493
9.6
7
BLK20-21
0.018
1.0
BLK01
0.025
1.2
BLK07-08
0.488
9.5
8
BLK14
0.013
0.7
BLK12-13
0.013
0.6
BLK01
0.107
2.1
9
BLK08-11
0.013
0.7
BLK09
0.011
0.5
Woon
0.069
1.3
10
BLK09
0.010
0.6
BLK05
0.006
0.3
BLK09
0.061
1.2
11
BLK10
0.006
0.3
BLK15
0.005
0.2
BLK20-21
0.053
1.0
12
BLK16
0.006
0.3
BLK16
0.002
0.1
BLK14
0.046
0.9
13
BLK05
0.004
0.2
BLK10
0.001
0.0
BLK10
0.027
0.5
14
BLK15
0.002
0.1
BLK15
0.009
0.2
15
BLK05
0.007
0.1
16
BLK16
0.006
0.1
Total
1.74
2.14
5.11
Woon = Woonsocket WWTF; Load in lbs/day
-------
BLACKSTONE RIVER INITIATIVE
CADMIUM - JULY
Woonsocket
WWTF
UBWPAD
01 02 03 04 06 07 08 11 12 13 17 18 19 20 21 STATION ID
45.8 44.0 41.4 39.8 35.7 32.0 27.8 23.2 19.2 16.6 12.8 10.0 8.2 3.8 0.1 RIVER MILES
Worcester, MA Pawtucket, RI
¦ 4.0-5.0
H 3.0-4.0
~ 2.0-3.0
¦ 1.0-2.0
¦ 0.0-1.0
Concentration
(Mg/L)
Figure 4.30 Total Cadmium Concentration July 10-11, 1991 Survey
-------
Total Cadmium % Contribution
Total Cadmium Load (lbs/day)
MAJOR
POINT
SOURCES
OTHER
SOURCES
FTO LOW FLOW CONDITION
(JULY 1991 SURVEY)
HIGH FLOW CONDITION
(OCTOBER 1991 SURVEY)
MAJOR
POINT
SOURCES
OTHER
SOURCES
Figure 4.31 Comparison of the Two Major Point Sources Versus the Other Sources for Total Cadmium
-------
¦3
15
10
f2 5
—O— July 1991 Survey
—V— August 1991 Survey
• • October 1991 Survey
*~.
50 45 40 35 30 25 20 15 10 5 0
River Miles
Figure 4.32 Total Chromium Concentration and Mass Loading Profiles
4-47
-------
m d r) ^ o § x ^ ^ 5 >
o o z
co So. S
5
CO
O
"8
o
CO
CO
I
,o
0
1
4
3
2
1
1 2 3 4 6 7 8 11 12 13 17 18 19 20 21
—O- July 1991 Survey
—V— August 1991 Survey
¦ -O ¦ October 1991 Survey
50 45 40 35 30 25 20 15 10 5 0
P • • Q
50 45 40 35
30 25 20
River Miles
15 10
Figure 4.33 Dissolved Chromium Concentration and Mass Loading Profiles
4-48
-------
Figure 4.34 shows that, the UBWPAD input was 3.7 times higher than BLK01 in July,
1.4 times in August, and 0.5 times in October. For total Cr, the Woonsocket facility was 0.19
times BLK17 in July, 0.28 times in August, and 0.01 times in October.
The input from the UBWPAD was higher than the Woonsocket facility. The relative
impact of UBWPAD on the river was significant under low flow. Sources of Cr in the system
are ranked for all three surveys and listed in Table 4.6. The spatial and temporal plot of Cr is
given in Figure 4.35.
In July, a source between BLK07 and BLK08 was ranked first, contributing 58% of the
total load. The second highest source was UBWPAD with 12.7% contribution. The two major
point sources contributed 14.5% and other sources contributed 85.5% (Figure 4.36).
In August, sources between BLK07 and BLK08 contributed 45.7% and the UBWPAD
contributed 18.8%. The two major point sources contributed 25.4% and the other sources
contributed 74.6% of the total load.
In October, a source between BLK08 and BLK11 was ranked first contributing 29.4% of
the total input. The two major point sources contributed 5.1% and the other sources contributed
94.9%.
From this comparison, it can be concluded that, a major source was identified between
BLK07 and BLK08, with a 51.9% contribution on average under low flow conditions. Under
high flow conditions, the system was dominated by the other sources, with the largest source
between BLK08 and BLK11.
4.3.3 Copper
In July, a gradual decrease in Cu concentrations was observed (Figure 4.37) after BLK02
through BLK04, followed by a significant rise at BLK08 and a gradual decrease to BLK21. The
rise in concentration at BLK08 was due to resuspension of the bottom sediment. This was
supported by TSS and particulate Cu profiles. A similar trend was observed for dissolved Cu in
July (Figure 4.38). The August profiles were similar to July. In October, high concentrations
occurred around BLK08 with a gradual decrease after BLK11 through BLK21. Mass loading
curves for both total and dissolved Cu were plotted. October loads were high compared to the
low flow surveys.
UBWPAD load was 16 times higher than BLK01 in July, 9 times in August, and 3 times
in October. The Woonsocket facility load was 0.24 times BLK17 in July, 0.4 times in August,
and 0.02 times in October (Figure 4.39).
The sources of Cu were ranked based on a gain or loss in mass loadings between stations
for all three sources in Table 4.7. From Table 4.7 the UBWPAD impact on the system in the
4-49
-------
JULY 1991
WWTF
I / y\ River Station
10
OCTOBER 1991
01 UBWPAD 02
AUGUST 1991
1
1
1
17 Woon 18
Figure 4.34 Point Source Versus Upstream and Downstream River Stations for Total Chromium
4-50
-------
Table 4.6 Chromium Dry Weather System Ranking
Rank
Survey 1
Survey 2
Survey 3
Source
Load
%
Source
Load
%
Source
Load
%
1
BLK07-08
5.894
58.0
BLK07-08
3.014
45.7
BLK08-11
4.954
29.4
2
UBWPAD
1.292
12.7
UBWPAD
1.240
18.8
BLK07-08
4.565
27.1
3
BLK12-13
0.726
7.1
BLK01
0.865
13.1
BLK01
1.489
8.8
4
BLK06-07
0.550
5.4
Woon
0.435
6.6
BLK06-07
1.311
7.8
5
BLK17-18
0.434
4.3
BLK04-06
0.217
3.3
BLK12-13
1.127
6.7
6
BLK01
0.354
3.5
BLK14
0.171
2.6
BLK04-06
0.778
4.6
7
BLK04-06
0.267
2.6
BLK19-20
0.131
2.0
UBWPAD
0.732
4.3
8
Woon
0.188
1.8
BLK09
0.115
1.7
BLK09
0.546
3.2
9
BLK20-21
0.179
1.8
BLK06-07
0.115
1.7
BLK14
0.345
2.0
10
BLK03-04
0.070
0.7
BLK17-18
0.102
1.5
BLK02-03
0.325
1.9
11
BLK09
0.068
0.7
BLK12-13
0.069
1.0
BLK01-02
0.284
1.7
12
BLK14
0.068
0.7
BLK05
0.052
0.8
Woon
0.135
0.8
13
BLK10
0.048
0.5
BLK10
0.045
0.7
BLK 10
0.113
0.7
14
BLK16
0.014
0.1
BLK15
0.013
0.2
BLK05
0.070
0.4
15
BLK05
0.010
0.1
BLK16
0.007
0.1
BLK15
0.052
0.3
16
BLK15
0.006
0.1
BLK 16
0.026
0.2
Total
10.17
6.59
16.85
Woon = Woonsocket WWTF; Load in lbs/day
-------
BLACKSTONE RIVER INITIATIVE
CHROMIUM - JULY
UBWPAD
Fisherville
Pond
Rice City
Pond
Woonsocket
^ I WWII
02 03
45.8 44.0 41.4
Worcester, MA
Concentration
(Hg/L)
¦ 25-30
¦ 20-25
«15-20
~ 10-15
¦ 5-10
¦ 0-5
20 21 STATION ID
3.8 0.1 RIVER MILES
Pawtucket, RI
Figure 4.35 Total Chromium Concentration July 10-11, 1991 Survey
-------
Total Chromium % Contribution
Total Chromium Load (lbs/day)
MAJOR
POINT
SOURCES
OTHER
SOURCES
PW1 LOW FLOW CONDITION
(JULY 1991 SURVEY)
HIGH FLOW CONDITION
(OCTOBER 1991 SURVEY)
MAJOR
POINT
SOURCES
OTHER
SOURCES
Figure 4.36 Comparison of the Two Major Point Sources Versus the Other Sources for Total Chromium
-------
o
<
CL
5
m
=3
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a:
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m
d
1
12 3 4
a
uj
£
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§
CO
11 12 13 17 18 19 20 21
—O— July 1991 Survey
—V— August 1991 Survey
• • October 1991 Survey
50
45 40 35 30 25 20 15 10
30 25 20
River Miles
Figure 4.37 Total Copper Concentration and Mass Loading Profiles
4-54
-------
40
1
1
3
>-
DC
3
CD
(£.
UJ
>
0C
Q
Z
o
o o
z t
5 a?
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ss
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X
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0
tn
z
1
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0£
§
CO
12 3 4
6
11 12 13 17 18 19 20 21
—O- July 1991 Survey
—V- August 1991 Survey
• a • October 1991 Survey
"3
50 45 40 35 30 25 20 15 10
•8
50 45 40 35 30 25 20 15 10 5 0
River Miles
Figure 4.38 Dissolved Copper Concentration and Mass Loading Profiles
4-55
-------
20
15
10
5
0
20
I4 15
rO
o
8. io
a,
0
40
30
20
10
0
Figure 4.39 Point Source Versus Upstream and Downstream River Stations for Total
4-56
JULY 1991
AUGUST 1991
I I WWTF
l"7"7l River Station
OCTOBER 1991
01 UBWPAD 02
17 Woon 18
-------
Table 4.7 Copper Dry Weather System Ranking
Rank
Survey 1
Survey 2
Survey 3
Source
Load
%
Source
Load
%
Source
Load
%
1
UBWPAD
10.54
47.2
UBWPAD
7.52
36.5
BLK08-11
13.60
23.2
2
BLK07-08
5.05
22.6
BLK07-08
4.31
20.9
UBWPAD
10.29
17.5
3
Woon
1.83
8.2
Woon
2.41
11.7
BLK04-06
5.07
8.6
4
BLK14
1.01
4.5
BLK04-06
1.57
7.6
BLK20-21
4.66
7.9
5
BLK10
0.76
3.4
BLK17-18
l.ll
5.4
BLK07-08
4.44
7.6
6
BLK01
0.69
3.1
BLK20-21
0.77
3.7
BLK01
3.45
5.9
7
BLK06-07
0.59
2.6
BLK01
0.75
3.7
BLK17-18
3.33
5.7
8
BLK09
0.53
2.4
BLK02-03
0.66
3.2
BLK14
2.34
4.0
9
BLK20-21
0.46
2.1
BLK14
0.55
2.7
BLK06-07
2.22
3.8
10
BLK03-04
0.26
1.2
BLK19-20
0.42
2.0
BLK12-13
2.20
3.8
11
BLK16
0.21
0.9
BLK09
0.15
0.7
BLK09
2.15
3.7
12
BLK12-13
0.20
0.9
BLK05
0.14
0.7
BLK02-03
2.10
3.6
13
BLK05
0.12
0.5
BLK10
0.11
0.5
Woon
0.88
1.5
14
BLK15
0.09
0.4
BLK15
0.10
0.5
BLK05
0.60
1.0
15
BLK16
0.04
0.2
BLK10
0.57
1.0
16
BLK15
0.46
0.8
17
BLK16
0.29
0.5
Total
22.3
20.6
58.7
Woon = Woonsocket WWTF; Load in lbs/day
-------
July survey was clearly visible with a contribution of 47.2% of the total load. The source
between BLK07 and BLK08 was ranked second, contributing 22.6% of the total load to the
system. Similar to July, in August the UBWPAD was ranked first, contributing 36.5% and the
reach between BLK07 and BLK08 was ranked second with a contribution of 20.9%. In October,
the UBWPAD release was ranked second with 17.5%, and the reach between BLK08 and BLK11
was ranked first with 23.2% of the total load.
In general, the two major point sources contributed 55% of the total load under low flow
and the other sources contributed about 48%. The two major point sources contributed about
19% and the other sources contributed 81% (Figure 4.40) for high flow.
The UBWPAD point source release appears to be significant under low flow conditions
and the other sources dominate under high flow conditions. The source between BLK08 and
BLK11, which is ranked first for both Cu and Cr under high flow conditions, may indeed be Rice
City Pond. It was shown in a specialty study (Chapter 8) that high flows may bypass the primary
spillway when sampling occurred. The contributions from the source between BLK07 and
BLK08 are observed as a chronic source of Cu to the system.
4.3.4 Lead
Figures 4.41 and 4.42 show the spatial and seasonal variations of total and dissolved
concentrations as well as mass loads of lead. The large variability in the data near Rice City
Pond in July and August could be a result of hydro power release. This is discussed later in this
chapter and in Chapter 8.
Figure 4.43 shows that UBWPAD input was 4.2 times higher than BLK01 in July survey,
0.72 times in August and 0.37 times in October. The input from the Woonsocket facility was
0.06 times BLK17 in July, 0.18 times in August, and approximately equal in October. It is
evident that the two major point sources did not have a major impact on the water quality of the
Blackstone River.
The sources of Pb to the system are ranked and listed in Table 4.8. In the July survey, a
source between BLK06 and BLK07 was ranked first, with a contribution of 38%. In August, a
source between BLK07 and BLK08 was ranked first, contributing 28.2%. In October, the source
between BLK12 and BLK13 was ranked first, contributing 19.4%. The other sources were
dominant either under low or high flow conditions as shown in Figure 4.44.
4.3.5 Nickel
In July, there was a high input from UBWPAD, a significant loss in the total metal from
BLK02 to BLK06, and a gradual loss in the metal after BLK08 with a small rise in the
concentration at BLK08. Similar to Cd in July, the loss of the metal between BLK02-06
appeared to be due to uptake and/or sedimentation. A similar trend was observed in Ni
concentration profiles in August. In October, a high input from UBWPAD, and a gradual
4-58
-------
Total Copper % Contribution
Total Copper Load (lbs/day)
E22
MAJOR
POINT
SOURCES
OTHER
SOURCES
LOW FLOW CONDITION
(JULY 1991 SURVEY)
HIGH FLOW CONDITION
(OCTOBER 1991 SURVEY)
MAJOR
POINT
SOURCES
OTHER
SOURCES
Figure 4.40 Comparison of the Two Major Point Sources Versus the Other Sources for Total Copper
-------
& a: z
150
-O— July 1991 Survey
—V— August 1991 Survey
• • October 1991 Survey
75
50
25
5 0
0
50 45 40 35 30 25 20 15 10
40
50 45 40 35 30 25 20 15 10
5
0
River Miles
Figure 4.41 Total Lead Concentration and Mass Loading Profiles
4-60
-------
40
| 30
s 20
J
8
l/l
a 10
o
<
a
£
m
3
£
ffi
d
a:
LU
>
a:
a
z t
I $
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i
£
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o
z
a:
>
oe a:
o 8!
a. ~
O a
U- H
5 co
n
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o
g
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m
x
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a.
x
o
z
<5
m
s &
w a o
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(t a: z
_J £ O
¦ s t i
Q. S
5
(0
a:
§
12 3 4
6
8
> ^ UJ « a W
11 12 13 17 18 19 20 21
—O— July 1991 Survey
—V— August 1991 Survey
• •~ • October 1991 Survey
50 45 40 35 30 25 20 15 10 5
•8
45 40
35 30 25 20 15 10 5 0
River Miles
Figure 4.42 Dissolved Lead Concentration and Mass Loading Profiles
4-61
-------
10
8
6
4
2
0
10
8
6
4
2
0
40
30
20
10
0
¦>
JULY 1991
AUGUST 1991
I I WWTF
V7~A River Station
FT
V
OCTOBER 1991
01 UBWPAD 02
17 Woon 18
>urce Versus Upstream and Downstream River Stations for'
4-62
-------
Table 4.8 Lead Dry Weather System Ranking
Rank
Survey 1
Survey 2
Survey 3
Source
Load
%
Source
Load
%
Source
Load
%
1
BLK06-07
21.1
38.0
BLK07-08
4.58
28.2
BLK12-13
6.77
19.4
2
BLK04-06
16.3
29.2
BLK04-06
3.03
18.7
BLK04-06
6.09
17.4
3
BLK12-13
7.07
12.7
BLK01
1.62
10.0
BLK08-11
5.05
14.5
4
BLK08-11
6.07
10.9
UBWPAD
1.19
7.3
BLK07-08
3.20
9.2
5
BLK20-21
1.70
3.1
BLK06-07
1.19
7.3
BLK09
2.33
6.7
6
UBWPAD
1.29
2.3
BLK11-12
0.98
6.0
BLK01
1.97
5.6
7
BLK03-04
0.65
1.2
Woon
0.88
5.4
BLK13-17
1.86
5.3
8
BLK01
0.33
0.6
BLK03-04
0.71
4.4
BLK02-03
1.54
4.4
9
BLK09
0.28
0.5
BLK20-21
0.51
3.1
BLK06-07
1.40
4.0
10
BLK14
0.22
0.4
BLK14
0.43
2.6
BLK10
1.00
2.9
11
Woon
0.21
0.4
BLK05
0.28
1.7
BLK14
0.88
2.5
12
BLK10
0.12
0.2
BLK09
0.26
1.6
UBWPAD
0.73
2.1
13
BLK02-03
0.11
0.2
BLK18-19
0.24
1.5
BLK19-20
0.49
1.4
14
BLK16
0.11
0.2
BLK10
0.17
1.1
BLK05
0.47
1.4
15
BLK05
0.09
0.2
BLK15
0.06
0.4
BLK15
0.37
1.1
16
BLK15
0.04
0.1
BLK16
0.06
0.3
Woon
0.31
0.9
17
BLK02-03
0.04
0.3
BLK16
0.29
0.8
18
BLK17-18
0.01
0.1
BLK01-02
0.16
0.4
Total
55.7
16.2
34.9
Woon = Woonsocket WWTF; Load in lbs/day
-------
Total Lead % Contribution
MAJOR
POINT
SOURCES
OTHER
SOURCES
Total Lead Load (lbs/day)
FWI LOW FLOW CONDITION
(JULY 1991 SURVEY)
HIGH FLOW CONDITION
(OCTOBER 1991 SURVEY)
K~y
MAJOR
POINT
SOURCES
OTHER
SOURCES
Figure 4.44 Comparison of the Two Major Point Sources Versus the Other Sources for Total Lead
-------
decrease in the concentration of Ni were observed after BLK03 (Figures 4.45-46). Tributaries
did not play a major role in any survey.
There existed a distinct anomaly in the Woonsocket WWTF post chlorination data of Ni.
The post chlorination concentrations were 24 fold higher than the pre-chlorination
concentrations. Hence, the pre-chlorination data of Ni was considered for all calculation
purposes.
UBWPAD input was 13.2 times higher than BLK01 in July, 35.6 times in August, and
4.6 times in October. The Woonsocket facility was 0.11 times higher than BLK17 in July, 0.16
times in August, and 0.05 times in October (Figure 4.47).
Sources of Ni to the system were ranked based on gains or losses in mass loadings
between stations and listed in Table 4.9. The UBWPAD was ranked first with a contribution of
37.5% in July and 81.2% in August. In October, a source between BLK20 and BLK21 was
ranked first contributing 24.3%.
It may be concluded from the above discussion that, UBWPAD played a major role under
low flow conditions (Figure 4.48).
4.4 Water Quality Criteria-Fecal Coliform
High levels of fecal coliform bacteria above water quality standards (exceeding 400
CFU/100 mL for at least 10% of the samples) were seen at several locations along the mainstem
and tributaries. The mainstem stations included BLK01 with the highest levels (1800- 3500
CFU/100 mL), BLK03 (20-1060 CFU/100 mL), BLK04 (300-2300 CFU/100 mL), BLK06 (120-
900 CFU/100 mL) and BLK21 (140-560 CFU/100 mL). The tributary stations included the
Branch River (BLK14) (160-460 CFU/100 mL) and Peters River (BLK16) (260-1060 CFU/100
mL).
Levels above the water quality standards for geometric means (200 CFU/100 mL) were
recorded at the mainstem stations BLK01, 03,04, and 06 in Massachusetts, BLK17 and 20 in
Rhode Island and on two tributary stations, BLK14 and 16.
Of note is the abrupt change in fecal coliform levels between BLK01 (1800-3500
CFU/100 mL) and BLK02 (0-20 CFU/100 mL), showing the impact of chlorinated wastewater
from the UBWPAD.
4.5 Water Quality Criteria-Toxicity
4.5.1 Acute and Chronic Criteria Violations
Acute and chronic toxicity criteria are used as a tool to maintain, preserve and improve
the water quality of rivers. The criteria can also be used to prevent surface waters from
4-65
-------
5 W
July 1991 Survey
August 1991 Survey
•o • October 1991 Survey
30
•3
S 20
River Miles
Figure 4.45 Total Nickel Concentration and Mass Loading Profiles
4-66
-------
u.
U.
60
12 13
50
—O— July 1991 Survey
—
-------
10
8
6
4
0
30
-I
I 20
x>
o
3
e2
10
i/ / /
JULY 1991
Y/A
AUGUST 1991
WWTF
F71 River Station
OCTOBER 1991
UBWPAD
17 Woon 18
Figure 4.47 Point Source Versus Upstream and Downstream River Stations for Total Nickel
4-68
-------
Table 4.9 Nickel Dry Weather System Ranking
Rank
Survey 1
Survey 2
Survey 3
Source
Load
%
Source
Load
%
Source
Load
%
1
UBWPAD
4.89
37.5
UBWPAD
21.8
81.2
BLK20-21
9.22
24.3
2
BLK01-02
3.38
25.9
Woon
1.69
6.3
UBWPAD
7.71
20.3
3
BLK12-13
1.45
11.2
BLK20-21
0.91
3.4
BLK08-11
4.34
11.4
4
BLK18-19
0.98
7.5
BLK01
0.60
2.2
BLK13-17
3.09
8.2
5
BLK07-08
0.77
5.9
BLK18-19
0.54
2.0
BLK12-13
2.62
6.9
6
Woon
0.56
4.3
BLK19-20
0.48
1.8
BLK02-03
2.27
6.0
7
BLK01
0.38
2.9
BLK17-18
0.41
1.5
BLK01
1.70
4.5
8
BLK14
0.17
1.3
BLK14
0.13
0.5
BLK14
1.61
4.2
9
BLK20-21
0.15
1.2
BLK05
0.08
0.3
BLK04-06
1.48
3.9
10
BLK10
0.13
1.0
BLK09
0.08
0.3
BLK07-08
1.47
3.9
11
BLK09
0.08
0.6
BLK12-13
0.07
0.3
Woon
1.12
3.0
12
BLK16
0.05
0.4
BLK10
0.04
0.1
BLK15
0.29
0.8
13
BLK05
0.03
0.2
BLK15
0.02
0.1
BLK16
0.27
0.7
14
BLK15
0.02
0.1
BLK10
0.24
0.6
15
BLK05
0.21
0.6
16
BLK09
0.17
0.4
17
BLK06-07
0.13
0.3
Total
13.0
26.8
37.9
Woon = Woonsocket WWTF; Load in lbs/day
-------
Total Nickel % Contribution
P
11
It
¦
m
MAJOR
POINT
OTHER
SOURCES
Total Nickel Load (lbs/day)
POT! LOW FLOW CONDITION
(JULY 1991 SURVEY)
HIGH FLOW CONDITION
(OCTOBER 1991 SURVEY)
SOURCES
MAJOR
POINT
SOURCES
OTHER
SOURCES
50
Figure 4.48 Comparison of the Two Major Point Sources Versus the Other Sources for Total Nickel
-------
becoming unsuitable for fishing, swimming and other beneficial uses, thus protecting the public
health and the environment
A comparison of concentration data to these criteria may be used to assess the suitability
of environmental conditions for aquatic life, establish acceptable receiving concentrations; and
assess the degree of wastewater treatment needed to meet water pollution control requirements.
EPA Water Quality Criteria for total metals were adjusted using the 1993 EPA Guidance
Document on Dissolved Criteria, for comparison against dissolved metal concentrations
measured in the Blackstone River. Dissolved metal concentrations more closely approximate the
bioavailable fraction of metals in the water column than does measurement of total recoverable
metals. The toxicity criteria were calculated based on average hardness numbers. These values
are given in the appendix for all the metals. A summary of the violations for all the metals for all
three surveys is given in Table 4.10.
Cadmium - Of the ten sampling stations located in MA, on the mainstem of the
Blackstone River, concentrations at three sampling stations after the UBWPAD were above acute
criteria, and concentrations at eight sampling stations were above chronic criteria in July;
concentrations at four sampling stations after the UBWPAD were above acute criteria in August;
and in October, the concentrations at seven sampling stations were above acute and chronic
criteria. Figure 4.49 shows acute violations as they relate to time and station.
The acute criteria violations in the upper reaches were due to the UBWPAD. The
violations occurring at BLK08 in October emphasize the impact of the other sources under high
flow conditions.
Of the five sampling stations located in RI on the mainstem of the Blackstone River, none
were above acute and chronic criteria during the July survey. In August, none were above acute
criteria, but concentrations at three sampling stations were above chronic criteria. In October four
sampling stations were above acute criteria and all five sampling stations in RI were above
chronic criteria.
Chromium - Unlike Cd, Cr concentrations at all stations on the mainstem of the
Blackstone River were well below the acute and chronic criteria.
Copper - Similar to Cd, the UBWPAD dominated the upper reaches. In July, the
concentrations at nine sampling stations in MA were above acute criteria, and concentrations at
all ten sampling stations were above chronic criteria. In August, concentrations at nine sampling
stations on the mainstem of the Blackstone River were above acute criteria and concentrations at
all sampling stations on the mainstem were above chronic criteria. In October, nine of the ten
mainstem stations were above acute criteria and all ten were above chronic criteria. The greatest
violations were located just below the UBWPAD and the impoundment above BLK08.
In RI, concentrations at two stations exceeded the acute criteria and concentrations at all
4-71
-------
Table 4.10 Summaiy of Acute and Chronic Trace Metal Violations for the July 10-11,1991 Survey
Total Metals Dissolved Metals
-sj
N)
Station
Cd
Cu
Pb
Acute
Chronic
Acute
Chronic
Acute
Chronic
BLK01
—
—
—
YES
—
YES
BLK02
YES
YES
YES
YES
—
YES
BLK03
YES
YES
YES
YES
—
YES
BLK04
YES
YES
YES
YES
—
YES
BLK05
—
YES
YES
YES
YES
YES
BLK06
—
YES
YES
YES
YES
YES
BLK07
—
YES
YES
YES
—
YES
BLK08
—
YES
YES
YES
—
YES
BLK11
—
YES
YES
YES
—
YES
BLK.12
—
—
YES
YES
—
YES
BLK13
—
YES
YES
YES
—
YES
BLK17
—
—
YES
YES
—
YES
BLK18
—
—
YES
YES
—
YES
BLK19
—
—
—
YES
—
YES
BLK20
—
—
—
YES
—
YES
BLK21
—
—
—
YES
—
YES
Cd
Cu
Pb
Acute
Chronic
Acute
Chronic
Acute
Chronic
—
—
—
—
—
YES
YES
YES
YES
YES
—
YES
YES
YES
YES
YES
—
YES
—
YES
YES
YES
—
YES
—
YES
YES
YES
YES
YES
—
—
—
YES
—
YES
—
—
—
YES
—
YES
—
—
—
YES
—
YES
—
—
—
YES
—
YES
—
—
—
YES
—
YES
—
—
—
—
—
YES
—
—
—
—
—
YES
—
—
—
YES
—
YES
—
—
—
YES
—
YES
—
—
—
—
—
YES
—
—
—
—
—
YES
BLK05
—
—
—
—
—
YES
BLK09
—
—
YES
YES
—
YES
BLK10
—
—
YES
YES
—
YES
BLK14
—
—
YES
YES
—
YES
BLK15
—
—
YES
YES
—
YES
BLK16
—
—
—
YES
—
YES
TRIBUTARIES
—
—
—
—
—
YES
—
—
—
—
—
YES
—
—
—
—
—
YES
—
—
—
—
—
YES
—
—
—
—
—
YES
—
—
—
YES
—
YES
-------
Table 4.10 Summary of Acute and Chronic Trace Metal Violations (continued) for the August 14-15,1991 Survey
Total Metals Dissolved Metals
4^
I
Station
Cd
Cu
Pb
Acute
Chronic
Acute
Chronic
Acute
Chronic
BLK01
—
—
—
YES
—.
YES
BLK02
YES
YES
YES
YES
—
YES
BLK03
YES
YES
YES
YES
—
YES
BLK04
YES
YES
YES
YES
—
YES
BLK05
YES
YES
YES
YES
—
YES
BLK06
—
YES
YES
YES
—
YES
BLK07
—
YES
YES
YES
—
YES
BLK08
—
YES
YES
YES
—
YES
BLK11
—
YES
YES
YES
—
YES
BLK12
—
YES
YES
YES
—
YES
BLK13
—
YES
YES
YES
—
YES
BLK17
—
YES
YES
YES
—
YES
BLK18
—
YES
YES
YES
—
YES
BLK19
—
YES
YES
YES
—
YES
BLK20
—
—
YES
YES
—
YES
BLK21
—
—
—
YES
—
YES
Cd
Cu
Pb
Acute
Chronic
Acute
Chronic
Acute
Chronic
—
—
—
—
—
YES
YES
YES
YES
YES
—
YES
YES
YES
YES
YES
—
YES
YES
YES
YES
YES
—
YES
YES
YES
YES
YES
—
YES
—
YES
YES
YES
—
YES
—
YES
YES
YES
YES
YES
—
YES
YES
YES
—
YES
—
YES
YES
YES
—
YES
—
—
YES
YES
—
YES
—
—
—
YES
—-
YES
—
YES
YES
YES
—
YES
—
YES
YES
YES
—
YES
—
—
—
YES
—
YES
—
—
—
—
—
YES
—
—
—
—
—
YES
TRIBUTARIES
BLK05
—
—
—
—
—
YES
—
—
—
—
YES
BLK09
—
—
—
—
—
YES
—
—
—
—
—
YES
BLK10
—
—
—
—
—
YES
—
—
—
—
—
YES
BLK14
—
—
—
YES
—
YES
—
—
—
—
—
YES
BLK15
—
— .
—
YES
—
YES
—
—
—
—
—
YES
BLK16
—
—
—
—
—
YES
—
—
—
—
—
YES
-------
Table 4.10 Summary of Acute and Chronic Trace Metal Violations (continued) for the October 2-3,1991 Survey
Total Metals Dissolved Metals
¦r
Station
Cd
Cu
Pb
Acute
Chronic
Acute
Chronic
Acute
Chronic
BLK01
—
—
YES
YES
—
YES
BLK02
YES
YES
YES
YES
—
YES
BLK03
YES
YES
YES
YES
—
YES
BLK04
YES
YES
YES
YES
—
YES
BLK05
—
YES
YES
YES
—
YES
BLK06
—
YES
YES
YES
—
YES
BLK07
YES
YES
YES
YES
—
YES
BLK08
YES
YES
YES
YES
—
YES
BLK11
YES
YES
YES
YES
—
YES
BLK12
—
YES
YES
YES
—
YES
BLK13
—
YES
YES
YES
—
YES
BLK17
—
YES
YES
YES
—
YES
BLK18
—
YES
YES
YES
—
YES
BLK19
—
YES
YES
YES
—
YES
BLK20
—
YES
YES
YES
—
YES
BLK21
—
YES
YES
YES
—
YES
Cd
Cu
Pb
Acute
Chronic
Acute
Chronic
Acute
Chronic
—
—
—
YES
—
YES
—
YES
YES
YES
—
YES
YES
YES
YES
YES
—
YES
. —
YES
YES
YES
—
YES
—
YES
YES
YES
—
YES
—
YES
YES
YES
—
YES
—
YES
YES
YES
—
YES
—
YES
YES
YES
—
YES
—
YES
YES
YES
—
YES
—
YES
YES
YES
—
YES
—
—
YES
YES
—
YES
—
YES
YES
YES
—
YES
—
—
YES
YES
—
YES
—
—
YES
YES
—
YES
—
—
YES
YES
—
YES
—
—
YES
YES
—
YES
TRIBUTARIES
BLK05
—
—
—
—
YES
—
—
—
—
—
YES
BLK09
—
—
YES
YES
—
YES
—
—
—
—
—
YES
BLK10
—
—
YES
YES
—
YES
YES
BLK14
—
—
YES
YES
—
YES
—
—
YES
YES
—
YES
BLK15
—
—
YES
YES
—
YES
—
—
—
—
—
YES
BLK16
—
—
—
YES
—
YES
—
—
—
YES
—
YES
-------
a!
UBWPAD
BLACKSTONE RIVER INITIATIVE
ACUTE CADMIUM VIOLATIONS - JULY
Fisherville
Pond
I
Rice City
I Pond
I
I
MA , RI
L
Woonsocket
I WWTF
02 03 04 06 07 08 11 12
45.8 44.0 41.4 39.8 35.7 32.0 27.8 23.2 19.2
Worcester, MA
13 17 18 19
16.6 12.8 10.0 8.2
Concentration
(Hg/L)
¦ 1.5-2.0
~ 1.0-1.5
¦ 0.5-1.0
¦ 0.0-0.5
20 21
3.8 0.1
Pawtucket,
STATION ID
RIVER MILES
RI
Figure 4.49 Acute Criteria Violations for Total Cadmium July 10-11, 1991 Survey.
White Denotes No Violations
-------
five stations were above chronic criteria in July. For August, concentrations at all five sampling
stations were above both acute and chronic criteria.
Lead - observations at two stations in MA were above acute criteria during the July
survey. None of the observations in MA were above acute criteria during the August survey.
Observations at three sampling stations exceeded the acute criteria in October. Observations at
all sampling stations, including all the tributaries, were above the chronic criteria. Figure 4.50
shows acute violations with regards to time and station. The acute toxicity criteria violations
above BLK08 in July clearly highlight the impact of sediment resuspension. Similar
observations were noticed in October.
Nickel - Similar to Cr, all Ni observations were well below the acute or chronic criteria
both in MA and in RI.
4.5.2 Actual Toxicity
4.5.2.1 Chronic Toxicity Testing of Ambient Blackstone River Water
As part of the Blackstone River Initiative, chronic toxicity testing was performed on
water samples collected at the 21 stations along the river during the three surveys of 1991. Each
sample consisted of a composite of four subsamples collected at six hour intervals.
The tests utilized were the Fathead minnow, (Pimephales promelas) larval growth and
survival test, and the Ceriodaphnia dubia survival and reproduction test. The young of P.
promelas and C. dubia were exposed for seven days to the samples with renewals occurring
daily. The responses of the two organisms in the 21 samples were statistically compared to the
responses of the organisms in laboratory control water.
The test procedures used follow those outlined in the EPA manual, Short-Term Methods
For Estimating The Chronic Toxicity of Effluents and Receiving Waters To Freshwater
Organisms, 2nd Edition, (Methods 1000.0 and 1002.0), EPA/600/489/001.
All organisms were maintained at 25 degrees Celsius +/-1 degree and 16:8 hour
light/dark cycle. Survival was monitored every 24 hours and recorded on standard laboratory
data sheets. Temperature, pH, conductivity and DO were measured daily. Hardness was
measured at the beginning of the test. Total residual chlorine (TRC) was measured at the
beginning of the test only in samples collected at stations immediately downstream from
wastewater treatment plants.
Survival of fathead minnows was affected only in one sample on one of three occasions.
This occurred during July 1991 (Round I, at BLK09 in the Mumford River). The only significant
reduction in fish growth occurred during August 1991 (Round D) in the sample from BLK21
(Table 4.11).
4-76
-------
Pi
UBWPAD
-------
Table 4.11 a Blackstone River Aquatic Toxicity Test Results - Fathead Minnow
Fathead Minnow
Station
#
% Surviva
Mean Weight per Fish (mg)
Significant1
Effect
I
n
m
I
n
m
BLK01
81
90
80
0.623
0.401
0.428
BLK02
10
100
90
0.647
0.428
0.461
BLK03
90
90
100
0.663
0.405
0.489
BLK04
97
70
100
0.600
0.394
0.495
BLK05
93
80
100
0.683
0.343
0.381
BLK06
83
100
90
0.673
0.329
0.533
BLK07
80
70
100
0.663
0.413
0.583
BLK08
90
80
100
0.547
0.496
0.613
BLK09
87
68
100
0.620
0.373
0.333
*Round II
BLK10
97
100
100
0.623
0.505
0.793
BLK11
83
100
90
0.643
0.397
0.569
BLK12
100
90
90
0.613
0.420
0.455
BLK13
93
90
100
0.660
0.432
0.470
BLK14
87
100
80
0.690
0.450
0.480
BLK15
63
80
90
0.537
0.521
0.460
BLK16
97
100
100
0.590
0.429
0.447
BLK17
73
80
90
0.493
0.502
0.531
BLK18
83
100
100
0.537
0.447
0.547
BLK19
90
90
80
0.523
0.455
0.435
BLK20
87
87
90
0.553
0.452
0.491
BLK21
83
83
80
0.587
0.427
0.451
~Round HI
1 Significantly different from control treatment as determined by using either a t-test with
the Bonferoni adjustment or Wilcoxon rank sum test with the Bonferroni adjustment
because there were more control replicates than the number of replicates at each station;
• Fishers Exact Test (for survival).
4-78
-------
Table 4.11b Blackstone River Aquatic Toxicity Test Results - Ceriodaphnia Dubia
Species: Ceriodaphnia Dubia
Station
#
% Surviva
Mean # Young
Significant1
Effect
I
n
ffl
I
n
m
BLK01
100
90
80
32.8
24.3
22.1
BLK02
100
100
90
23.7
21.3
23.8
BLK03
100
90
100
24.7
24.6
21.4
BLK04
100
70
100
26.9
23.3
26.2
BLK05
100
80
100
23.3
15.6
22.0
BLK06
100
100
90
14.6+
28.4
25.0
BLK07
100
70
100
15.6+
18.8
26.3
BLK08
90
80
100
18.6+
25.2
24.6
BLK09
100
90
100
13.8+
14.4
8.5
~~Round IE
BLK10
100
100
100
10.7.
32.2
17.5
BLK11
100
100
90
22.3
29.3
23.6
BLK12
100
90
90
18.6
21.8
21.8
BLK13
100
90
100
15.3
27.7
21.9
BLK14
70
100
80
9.9
23.4
14.1
BLK15
100
80
90
12.0
21.2
21.6
BLK16
100
100
100
30.1
27.6
24.5
BLK17
100
80
90
36.4
20.1
21.3
BLK18
80
100
100
24.1
25.9
28.6
BLK19
100
90
80
37.8
28.2
26.8
BLK20
100
90
90
28.9
26.1
23.3
BLK21
100
90
80
30.1
24.6
27.3
1 Significantly different from control treatment as determined by using either a t-test with
the Bonferoni adjustment or Wilcoxon rank sum test with the Bonferroni adjustment
because there were more control replicates than the number of replicates at each station;
+ This rack accidentally discarded on Day 6, so mean # of young on day 6 compared to
mean # of control young on day 6 is significantly different from control treatment as
determined by ** Dunnetfs Test (for reproduction).
4-79
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Results of the Ceriodaphnia dubia chronic toxicity tests are also shown in Table 4.11.
Only BLK09, during October 1991 (Round EI), produced significantly different reproduction
results from the control.
During the first test, begun July 11,1991, BLK02 and BLK03 had TRC concentrations of
75 and 20 ppb, respectively. These samples were dechlorinated to avoid masking effects due to
chlorine toxicity. TRC was non-detectable in the other samples.
During the August 1991 round of testing, TRC was detected in BLK01 (12 ppb) and
BLK02 (60 ppb). These samples were dechlorinated to eliminate chlorine as a likely toxicant
During the October 1991 testing round, TRC was detected at BLK02 (60 ppb) and
BLK03 (20 ppb). These samples were also dechlorinated. The concentrations measured in these
samples were above the EPA water quality criteria for chlorine, and so might have caused acute
or chronic toxicity to the test organisms. At these concentrations though, there is also the
possibility that the chlorine effects could be mitigated by other constituents of the river water.
Based on metals concentrations and the EPA water quality criteria alone (EPA 1991;
1993b), the water samples collected from the Blackstone River were predicted to produce greater
toxicity than actually occurred in the laboratory tests..
4.5.2.2 Discussion of Water Quality Criteria and Actual Toxicity
The development of national numerical water quality criteria for the protection of aquatic
organisms is a complex process that uses information from many areas of aquatic toxicology. To
derive a national criterion, all available toxicity data is amassed and evaluated for acceptability.
If enough acceptable data is available for 48 to 96 hour toxicity tests, these are used to derive an
acute criterion. The acute criterion is intended to estimate the highest one-hour concentration
that should not result in unacceptable effects on aquatic organisms. It is also referred to as the
Criterion Maximum Concentration (CMC). Ecosystems can tolerate some stress and occasional
adverse effects, so protection of all species all of the time is not considered necessary. If
acceptable data are available for a large number of taxa, a reasonable level of protection is
considered to be 95% of all species in the diverse data set (Stephen et al., 1985).
If enough data is available on the ratio of acute to chronic toxicity responses, a chronic
criterion is established. The chronic criterion is the highest four-day average concentration that
does not cause unacceptable toxicity. These criteria may be a function of pH, temperature or
hardness and, if so, it is expressed as an equation.
Another component of the criteria is the frequency of allowed exceedance. For both
chronic and acute criteria, the allowed frequency of exceedance is once every three years. This
frequency relates to the ability of the ecosystem to recover from excursions above the acceptable
concentration. EPA accepted that most aquatic ecosystems can recover from a variety of severe
stresses within three years.
4-80
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The national criteria must be protective of almost all water bodies. Thus for some, the
criteria will be overprotective, and for a few they will be under protective. In both of these
scenarios, there is the opportunity to derive site-specific criteria. Factors that are considered to
cause most of the difference between national and site-specific criteria are the species of
organisms that are exposed and the characteristics of the water. National water quality criteria
are based on tests conducted in water that is low in particulate and organic matter.
The criteria are also based on toxicity tests results conducted in laboratory water free of
metal-binding agents. The metals are then more bioavailable. The presence of metal-binding
agents in wastewater and ambient water prevent toxicity from occurring as expected. This
conservatism in criteria is probably reasonable as metals are very persistent chemicals, and the
criteria do not protect against sediment or food chain effects.
The results of toxicity tests using Blackstone River water and chemistry of these waters
are compared against the predicted toxicity using the national water quality criteria. In dry
weather, two species representing two different taxa of animals were used as test organisms.
There was fairly good agreement between the chronic responses of the two organisms. There
was only one station that produced toxicity in Ceriodaphnia and two stations that produced a
toxic response in fathead minnows.
Certain characteristics of the water alter biological availability and/or toxicity of
chemicals, particularly metals. Examples of this include hardness, alkalinity, pH, suspended
solids and organic carbon. Thus, the chemical concentrations may exceed the water quality
criteria, but because of one or more of the above mentioned characteristics, the chemical does not
exhibit toxicity during the conduct of the test.
Metals criteria were determined using the equations based on hardness described earlier.
These equations were developed with data that reflected high hardness conditions. The low
hardness range of the Mumford River could possibly explain the toxicity that occurred there
twice during dry weather. The EPA equations for estimating hardness-dependent metals criteria
do not accommodate hardness below 25 mg/L.
There are no modifying equations to account for total organic carbon, suspended solids
and other factors which attenuate metals toxicity.
EPA recognizes that laboratory-derived water quality criteria might not reflect site-
specific conditions, and so created procedures that can be used to develop site-specific criteria
that reflect the realities of natural and human-induced characteristics of receiving waters.
Biomonitoring, such as toxicity testing, is useful when specific numerical criteria are
absent, or when testing the effects of multiple contaminants. Biomonitoring integrates the total
processes affecting toxicity and therefore may be insensitive for studying the validity of
individual criteria. Biomonitoring can usually only detect changes of twenty percent or greater
(Stephen et al., 1985). Biological methods serve as a companion to numeric criteria in measuring
4-81
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water quality and predicting toxicity.
4.5.2.3 Blackstone River Whole Sediment Toxicity Tests
Blackstone River sediments were analyzed twice in 1991 by the EPA Region I, ESD
Biology Section. The first round of tests was conducted on two separate occasions. Samples
were collected from stations BSED 1-4, MSED 1 and LC in July 1991 (Table 4.12). The
remaining samples were collected from stations MSED 5-7, MSED 1, and LC in September
1991. Samples for the second round of tests were collected from stations BSED 1-7, MSED 1-2
and LC in October 1991.
The first Chironomus tentans test conducted on samples BSED 1-4 did not have adequate
survival in either reference station sample, the Mumford River or Lexington Pond. The
minimum acceptable control survival is 80% and only 64% was achieved. There appeared to be
no significant difference between survival at the BSED stations 1-4 (55-72%) and the reference
station, LSED (64%). Dry weights were also measured, but since the test was considered invalid,
these are not analyzed.
The tests conducted on the samples from BSED 5-7 had greater than 80% survival in the
Mumford River reference samples (MSED1 and MSED2). Lexington Pond sediment, however,
had a low survival rate of 57%. There was no significant difference between survival in samples
5- 7 and MSED samples.
The second round of sediment tests, which included all stations BSED 1-7, experienced
some significant mortality in samples from Singing Dam (BSED1) and Fisherville Pond
(BSED2) was recorded. The results of the Chironomus tentans tests are shown in Figure 4.51.
The Chironomus tentans test conducted in December 1993 exhibited toxicity at one
additional station not previously detected as toxic. This station was Rochdale Pond. Survival in
both the Singing Dam and Rochdale Pond samples was zero. Survival in the Mumford River
sample was 40%. All other stations experienced greater than 73% survival.
The first round of Hyallela azteca sediment toxicity tests demonstrated significant
mortality in samples from Singing Dam (BSED1) and Rice City Pond (BSED4). The subsequent
test, conducted on BSED stations 5-7, did not meet minimum survival requirements in the
reference station samples. At this point, the Mumford River was being used as a reference site.
It was learned later, that contaminant levels are high in this river and, as the toxicity tests
demonstrated, the tests organisms responded accordingly with high mortality.
During the second round of testing, minimum survival was achieved using Lexington
Pond as a reference sample. No Hyallela were retrieved in samples from Fisherville Pond,
Rochdale Pond and Rice City Pond (BSED 2,3, and 4, respectively). Only one organism was
retrieved in the samples from Singing Dam and Manville Dam (BSED 1 and 6, respectively).
Two live organisms were retrieved in the Mumford River sample (MSED2). Every station tested
4-82
-------
Table 4.12 Blackstone River Sediment Stations
Number
Station Location
Reference Stations
BSED1
Singing Dam
BSED2
Fisherville Pond
BSED3
Sutton St/Rochdale Pond
BSED4
Rice City Pond
BSED5
Tupperware Dam
BSED6
Manville Dam
BSED7
Slater's Mill
MSED1
Gilboa Pond, Mumford River
Reference
MSED2
Grey's Pond, Mumford River
Reference
LC
Lexington Pond Control
Reference
SM
Saw Mill Pond
Reference
4-83
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£> 40
o
^ 20
60 4
csf
1| 40
20
1
•
1
1
-
1
1
1
1
\\^j Significant Effect
M1 M2 LC
100
80
t3 60
§ o
c£ 40
20
0
I
1
¦
1
1
1
1
¦
1
1
H MRS iH a
1
H ¦
1 2 3 4 5 6 7 M1 M2 LC SM
Station
Figure 4.51 Results of the Whole Sediment Toxicity Test for Chironomus tent arts
4-84
-------
•a 23
§ S
o 5
& o
„ -4->
CN
c I
O 2
CT-
I I I I
7 M1 M2 LC
M1 M2 LC
100
80
&
£| 60
§ o
SI
c£ 40
20
0
¦
1
Significant Effect
•
-
i
is
FffP
n n "
mg
L: *
gplf]
m f:' •
1
2 3 4 5 6 7 M1 M2 LC SM
Station
Figure 4.52 Results of the Whole Sediment Toxicity Test for Hyallela azteca
4-85
-------
Table 4.13 Sediment Pore Water 48 Hour Toxicity (% Survival)
Ceriodaphnia dubia
Sediment Pore Water 48 Hour Toxicity (% Survival)
Ceriodaphnia dubia
Round I
Round II
Station
July
September
November
1
90
—
76
2
100
—
0
3
100
—
0
4
100
—
87
5
—
94
7
6
—
100
90
7
—
100
100
Ml
94
94
—
M2
—
—
97
LC
100
100
97
0
100
16
100
Table 4.14 Sediment Pore Water 48 Hour Toxicity (% Survival)
Pimephales promelas
Sediment Pore Water 48 Hour Toxicity (% Survival)
Pimephales promelas
Round I
Round II
Station
July
September
November
1
90
—
76
2
100
—
0
3
100
—
0
4
100
—
87
5
—
94
7
6
—
100
90
7
—
100
100
Ml
94
94
—
M2
—
—
97
LC
100
100
97
0
100
16
100
4-86
-------
showed a significant impact when compared against the LSED sample. The results of the
Hyallela azteca tests are shown in Figure 4.52.
When the sediments were retested in 1993 using the revised whole sediment toxicity
methods, only Singing Dam (BSED1) and Rochdale Pond (BSED3) produced significant
mortality of Hyallela. The growth of Hyallela was adversely affected in samples from Rice City
Pond (BSED4) and the Mumford River (MSED2).
4.5.2.4 Blackstone River Sediment Pore Water Analysis
Tables 4.13 and 4.14 list the survival for minnows and Pimephales and Ceriodaphnia,
respectively. The first round of pore water testing did not cause any adverse impact on
Ceriodaphnia. In the second round of testing, the samples exhibiting significant mortality were
from stations at Fisherville Pond, Rochdale Pond and Tupperware Dam (BSED 2,3 and 5).
Fisherville and Rochdale had been significantly toxic to the whole sediment test organisms, and
Tupperware Dam sediment was toxic to Hyallela once, but generally was lower in most chemical
concentrations than most of the upstream sites.
In the first round of pore water toxicity testing, Pimephales survival was zero in the
Singing Dam sample. This was the only sample that was adversely affected. In five out of six
occasions tested, whole sediments from Singing Dam were significantly toxic. In the second
round of testing, the fish were adversely affected by pore water samples from Singing Dam,
Fisherville Pond, Rochdale Pond, and Tupperware and Manville Dams (BSED 1,2,3,5 and 6).
The samples which significantly affected Ceriodaphnia survival were from stations 2,3 and 5.
Minnow survival was affected in samples from stations 1,2,3,5 and 6.
Additional tests were conducted in November on the same pore water samples from the
Rice City Pond and Rochdale Pond (BSED 2 and 3) because of the extreme toxicity exhibited
during previous Round II tests. Lethal concentrations (LC30s) were calculated by testing the
following percent dilutions of the pore water: 100,50,25, 10,5 and 1. Lab control water was
used as diluent. Table 4.15 lists the results of this examination. The LCS0s calculated for the
stations 2 and 3 samples were 32.6% and 10.6%, respectively.
4.5.2.5 Effluent Toxicity Testing
Chronic toxicity tests were conducted on a total of fourteen municipal and industrial
discharges to the Blackstone River or its tributaries. Most of these toxicity tests, employing
Ceriodaphnia dubia and Pimephales promelas, were conducted during the of summer of 1991.
These tests were performed by a contract laboratory for EPA. The samples were collected by
EPA. Test methods followed those in the EPA Short-Term Methods for Estimating the Chronic
Toxicity of Effluents and Receiving Waters to Freshwater Organisms (1989). Some earlier data
collected in 1990 is included for the Upton WWTF.
Seven-day Effective Concentrations (EC^), No Observed Effect Concentrations (NOEC)
4-87
-------
Table 4.15 Percent Survival (48 hours) Pimephales promelas in
Sediment Pore Water from Two Stations
Dilution
BSED2
BSED3
100
0
0
50
0
0
25
100
20
10
90
55
5
100
90
1
—
100
0
100
100
LCj„
32.6 %
10.6%
4-88
-------
Table 4.16 Blackstone River Effluents Toxicity Test Results in Percent
Ceriodaphnia/Fathead Minnow
Facility
LCjq
(48 hr)
ECjo
NOEC
LOEC
Permit
LCjo
UBWPAD
>100*
>100*
>100*
>100*
50/>100
100/>100
Millbury
>100*
82/>100
50/>100
100/>100
100
Grafton
>100*
25£>100
50/>100
100
Northbridge
>100*
6.25/>100
12.5/>100
Uxbridge
>100*
>100
>100
100
Douglas
62/66
62/68
25/50
50/100
Upton+
25*
50*
100*
o
o
*
100
12.5/50
25/100
12.5/100
25/>100
Woonsocket
30/100
66/63
50*
100*
66/60.4
29/>100
25/>100
50/>100
Worcester Finishing
70/86
35/65
6.25/50
12.5/100
NE Plating
7.4/76
<6.25/>100
<6.25/50
6.25/100
1/4 Monitor
Guilford Industries
>100*
50/100
100/>100
12
Okonite
>100*
>100*
>100*
No Permit
GTE 001A
18/17
6.25/12.5
12.5/25
GTE001B
100/64
50
100
Monitor Only
Data reported in percent as Ceriodaphnia/fathtad minnow; + From earlier sampling effort; *
Same result achieved with Ceriodaphnia and fathead minnow test.
4-89
-------
and Lowest Observed Effect Concentrations (LOEC), and 48 hour Lethal Concentrations (LCjqS)
were calculated for each sample tested. Table 4.16 displays all these results. Effluent from the
UBWPAD, Woonsocket and Upton WWTF'S were tested on more than one occasion.
The LCJ0 of the Millbury, MA sample was >100% effluent for both the Ceriodaphnia and
the Pimephales test. The LCjo for the Douglas WWTF was 62% and 66%, for Ceriodaphnia and
Pimephales, respectively. The LCJ0 for New England Plating was 7.4% and 76% for
Ceriodaphnia and Pimephales. The LCJ0s for Woonsocket were 29.5% and 60.4% for
Ceriodaphnia dubia on the two testing occasions. The Pimephales promelas LCjqS for
Woonsocket with these same effluent samples were >100% and 60.4%. Only five of the fourteen
dischargers tested have toxicity limits in their NPDES permits, and none of these exceeded the
toxicity limits of their permits.
4.5.2.6 Discussion of Blackstone River Sediment and Pore Water Chemistry and Toxicity
Sediments were analyzed on two occasions for six to nine metals. The values were
compared against National Oceanic and Atmospheric Administration (NOAA) values compiled
to indicate potential for biological effects from sediment bound contaminants (Long and Morgan
1991). The NOAA values named ER-L, the Effects Range-Low and ER-M, the Effects Range-
Median, represent contaminant concentrations in sediment that showed significant effects in 10
and 50 percent, respectively, of the studies evaluated.
Another comparative point used in evaluating contaminant levels (ppm dry weight) in the
Blackstone River were the Region V EPA Great Lakes Sediment Classification Scheme given
below.
Table 4.17 Great Lakes Sediment Classification Scheme
Metal
Nonpolluted
Moderately Polluted
Highly Polluted
Cadmium (/ig/L)
£25
25-75
*75
Chromium (/zg/L)
£25
25-50
*50
Copper (//g/L)
£40
40-60
*60
Lead Gug/L)
£40
40-60
*60
Nickel (/zg/L)
£20
20-50
*50
Zinc (/ig/L)
£90
90-200
*200
Metals (1991) - Figures 4.53 - 4.58 illustrate individual metal concentrations in sediment
for each station sampled during the July 1991 study (Round I) and the percent mortality for each
sediment toxicity test. Figure 4.59 illustrates the same but for total metals at each station. No
4-90
-------
VO
Cadmium (ng/L)
0 Hyallela % Sediment Mortality
mChironomus % Sediment Mortality
lb
ER-M
Singing Dam Fisherville Sutton St Rice City Tupperware Manville Slater's Mill Gilboa Pond Gilboa Pond Grey's Pond Lexington Lexington
Pond Pond Dam Pond Pond
Station
Figure 4.53 Cadmium in Blackstone River Sediments
-------
845 ng/L
Chromium (|ig/L)
BHyallela % Sediment Mortality
dChironomus % Sediment Mortality
- ER-M
Singing Dam Fisherville
Pond
Sutton St
Rice City
Pond
Tupperware
Dam
Manville Slater's Mill GilboaPond GilboaPond Grey's Pond
Lexington
Pond
Lexington
Pond
Station
Figure 4.54 Chromium in Blackstone River Sediments
-------
400
350
300
250
200
150
100
50
0
1730 ng/L
1040 ng/L
Copper (|ig/L)
0 Hyallela % Sediment Mortality
~ Chironomus % Sediment Mortality
ER-M
lerville Sutton St Rice City Tupperware Manville Slater's Mill Gilboa Pond Gilboa Pond Grey's Pond Lexington Lexington
'ond Pond Dam Pond Pond
Station
er in Blackstone River Sediments
-------
V©
100%
100%
260 ng/L
Nickel (ng/L)
E3 Hyallela % Sediment Mortality
~ Chironomus % Sediment Mortality
er-m - — — —
Singing Dam Fisherville Sutton St Rice City Tupperware Manville Slater's Mill Gilboa Pond Gilboa Pond Grey's Pond Lexington Lexington
Pond Pond Dam Pond Pond
Station
Figure 4.56 Nickel in Blackstone River Sediments
-------
-b.
I
VO
Ul
717 ug/L
723 ug/L
Lead (ug/L)
E3 Hyallela % Sediment Mortality
~ Chironomus % Sediment Mortality
ER-M
Singing Dam Fisherville Sutton St Rice City Tupperware Manville Slater's Mill Gilboa Pond Gilboa Pond Grey's Pond Lexington Lexington
Pond Pond Dam Pond Pond
Station
Figure 4.57 Lead in Blackstone River Sediments
-------
2150 (ig/L
851 Jig/L
Zinc (ng/L)
~ Hyallela % Sediment Mortality
~ Chironomus % Sediment Mortality
ER-M
Singing Dam Fisherviile Sutton St Rice City Tupperware Manville Slater's Mill Gilboa Pond Gilboa Pond Grey's Pond Lexington Lexington
Pond Pond Dam Pond Pond
Station
Figure 4.S8 Zinc in Blackstone River Sediments
-------
5500-
5000'
4500
4000'
3500
lb
a. 3000
CO
3
« 2500
2000
1500
1000'
500
I
Zinc (fig/g)
| Nickel (ug/e)
^ Lead (ng/g)
g Copper (ng/g)
Q Chromium (fig/g)
Cadmium (ue/e)
^ Chironomus % Sediment
Mortality
^ Hyallela % Sediment
Mortality
i
_BSL
100
90
80
70
60
50
40
30
20
10
Singing Fisherville Sutton St Rice City Tupperware Manville Slater's Mill Gilboa
Dam Pond Pond Dam Pond
Station
Gilboa Grey's Pond Lexington Lexington
Pond Pond Pond
£•
o
s
Figure 4.59 Total Sediment Metals and Chironomus and Hyallela Mortality
-------
chemical analyses were conducted on sediments collected and tested in November 1991.
Zinc concentrations exceeded the NOAA ER-M at Fisherville Dam, Sutton Street, Rice
City Pond, Blackstone Dam, Manville Dam, and Gilboa Pond. The concentration of zinc was
highest at Rice City Pond. According to the Great Lakes Sediment Classification Scheme, all
stations except Lexington and Grey's Pond would be considered highly polluted.
Nickel exceeded the ER-M only at Rice City Pond. Rice City Pond and Blackstone Dam
would be considered highly polluted by the Great Lakes Classification Scheme.
Lead concentrations greatly exceed the ER-M at Fisherville Pond and Rice City Pond.
Concentrations slightly exceeded the ER-M for lead at Blackstone Dam, Manville Dam, Slater's
Mill, and Gilboa Pond. Lead concentrations would classify all these sites as highly polluted
according to the Great Lakes Classification Scheme.
Copper concentrations exceeded the ER-M at Singing Dam, Fisherville Pond, and Rice
City Pond. The copper concentrations at Blackstone Dam were close to the ER-M. All sites
would be considered highly polluted except Grey's Pond and Lexington Pond.
Chromium concentrations exceed the ER-M at Fisherville Pond, Rice City Pond, and
Gilboa Pond. Nearly all sites fall into the highly polluted range.
Cadmium concentrations at Rice City Pond alone exceeded the ER-M. The concentration
at Blackstone Dam was close to the ER-M. Rice City Pond was the only site that would be
classified highly polluted under the Great Lakes Sediment Classification Scheme for cadmium.
Though metal concentrations at Rice City Pond and Fisherville Dam were the highest of
all stations analyzed, toxicity was only evidenced by the Hyallela azteca in the Rice City Pond
sample. Chironomus tertians survived fairly well in this sediment (64 and 82% survival in
Rounds I and II). In Round I, when these metal concentrations were measured, survival of
Hyallela and Chironomus were 70 and 72% in the Fisherville Dam sediment sample. Higher
mortality of one or both species occurred in the samples from Singing Dam (BSED1), Manville
Dam (BSED5), Slater's Mill (BSED7), and Gilboa and Grey's Pond, the background samples.
Figure 4.60 illustrates the total concentration of Polynuclear Aromatic Hydrocarbons
(PAHs) at each station, as well as ER-L and ER-M for total PAHs. Sediment samples from all
stations contained PAHs higher than the ER-L but lower than the ER-M. The highest
concentration of PAHs was in the first background station on the Mumford River at Gilboa Pond.
This is followed by Singing Dam (BSED1), Fisherville Pond (BSED2), and Rice City Pond
(BSED4). There is no strong correlation between PAH concentrations and the mortality
evidenced in the whole sediment toxicity tests.
Figures 4.61 - 4.67 illustrate individual metal concentrations found in the pore water
samples extracted from the sediment at each station. Percent mortality from the fathead minnow
4-98
-------
Polynuclear Aromatic Hydrocarbons and Chironomus
and G dubia Mortality
50
C? 40
Polynuclear Aromatic
Hydrocarbons (PAH)
Chironomus % Sediment
Mortality
C. dubia Pore Water
% Mortality
ER-M
£
3 20
ER-L
Singing Fisherville Sutton St Rice City Tupperware Manville Slater's Mill Gilboa Gilboa Grey's Pond Lexington Lexington
Dam Pond Pond Dam Pond Pond Pond Pond
Station
Figure 4.60 Polynuclear Aromatic Hydrocarbons and Chironomus and C. dubia Mortality
-------
Total Aluminum in Sediment Pore Water and C. dubia
and Fathead Minnow Mortality
5600 Jig/L H3100 (ig/L ¦5800^g/L
WXt Hardness (mg/L)
188881 C. dubia % Mortality
dlffj Fathead % Mortality
Singing Dam Fisherville Sutton St Rice City Tupperware Manville Slater's Mill OilboaPond Grey's Pond Lexington Lexington
Pond Pond Dam Pond Pond
Station
Figure 4.61 Total Aluminum in Sediment Pore Water and C. dubia and Fathead Minnow Mortality
-------
110
100
Cp 90
d1-
| 80
I-
B
w 60
50
40.
•o
W 30
20
10
0
Total Cadmium in Sediment Pore Water and C. dubia
and Fathead Minnow Mortality
ro
1 ©
8
CO
so
I
I
i
ja 11
I
I
132 mg/L
Cd (Hg/L)
Hardness (mg/L)
C. g/L)
~ WQC-C Qlg/L)
J
i
i
o
m z
Jstttt , ¦
2 :
,¦
Singing Dam Fisherville Sutton St Rice City Tupperware Manville Slater's Mill Gilboa Pond Grey's Pond Lexington Lexington
Pond Pond Dam Pond Pond
Station
Figure 4.62 Total Cadmium in Sediment Pore Water and C. dubia and Fathead Minnow Mortality
-------
180
£ 160
&
1 140
o
2
§ 120
| 100
1
m 80
J 60
h
u
40
20
0
Total Chromium in Sediment Pore Water and C. dubia
and Fathead Minnow Mortality.
Cr (Jlg/L)
Hardness (mg/L)
C. % Mortality
Fathead % Mortality
WQC-A(VI) (ng/L)
WQC-C(VI) (HR/L)
WQC-COn) (|ie/L)
Singing Fisherville Sutton St Rice City Tupperware Manville Slater's Mill Gilboa Grey's Pond Lexington Lexington
Dam Pond Pond Dam Pond Pond Pond
Station
k63 Total Chromium in Sediment Pore Water and C. dubia and Fathead Minnow Mortality
-------
Total Copper in Sediment Pore Water and C. dubia
and Fathead Minnow Mortality
160
140
I 120
I ioo-L
w
3
4>
^ 80
e3
ffl
3 60 -H
s
U 40
20--
0-M
260 lig/L
Cu (ng/L)
Hardness (mg/L)
C. rfufria % Mortality
Fathead % Mortality
O WQC-A (jig/L)
~ WQC - C (Ug/L)
Singing
Dam
Fisherville
Pond
Rice City Tupperware Manville Slater's Mill OilboaPond Grey's Pond Lexington Lexington
Pond Dam Pond Pond
Sutton St
Dati/1 TVim
Station
Figure 4.64 Total Copper in Sediment Pore Water and C. dubia and Fathead Minnow Mortality
-------
140
120
Total Nickel in Sediment Pore Water and C. dubia
and Fathead Minnow Mortality
S 100 -I—
i
I 80
i
a 60-1—4
g 40
o-
!~
~
¦
Ni (Hg/L)
m
Hardness (mg/L)
1
C. dubia % Mortality
H
Fathead % Mortality
~
WQC-C (Hg/L)
VO
Singing Dam Fisheryille Sutton St Rice City Tupperware Manville Slater's Mill Gilboa Pond Grey's Pond Lexington Lexington
Pond Dam Pond Pond
Station
Pond
Figure 4.65 Total Nickel in Sediment Pore Water and C. dubia and Fathead Minnow Mortality
-------
©
KJt
Total Lead in Sediment Pore Water and C. dubia
and Fathead Minnow Mortality
210|ig/L
Pb (jig/L)
Hardness (mg/L)
C. dubia % Mortality
Fathead % Mortality
O WQC-A (Jig/L)
~ WQC - C Oig/L)
60-
20--
Singing Dam Fisherville Sutton St Rice City Tupperware Manville Slater's Mill Gilboa Pond Grey's Pond Lexington Lexington
Pond Pond Dam Pond Pond
Station
Figure 4.66 Total Lead in Sediment Pore Water and C. dubia and Fathead Minnow Mortality
-------
Total Zinc in Sediment Pore Water and G dubia
and Fathead Minnow Mortality
U329 |ig/L
l-MCHSug/L
2 200
Zn Oig/L)
Hardness (mg/L)
C. (a % Mortality
Fathead % Mortality
~ WQC OigIL)
Singing Dam Fisherville Sutton St Rice City Tupperware Manville Slater's Mill GilboaPond Grey's Pond Lexington Lexington
Pond Pond Dam Station Pond Pond
Figure 4.67 Total Zinc in Sediment Pore Water and C. dubia and Fathead Minnow Mortality
-------
and Ceriodaphnia dubia acute toxicity tests are also illustrated.
The pore water from the Singing Dam sample exceeded acute EPA Ambient Water
Quality Criteria (AWQC) for chromium, copper, and cadmium. The criteria levels were adjusted
for hardness concentration. The fathead minnow acute toxicity test experienced 10% mortality in
this sample.
Pore water from Fisherville Dam exceeded acute AWQC for lead, chromium, copper, and
cadmium. No significant toxicity to either test species occurred in this sample.
The pore water from Sutton Street exceeded only the acute AWQC for copper and no
toxicity occurred in the same round of toxicity tests.
The pore water sample from Rice City Pond exceeded acute AWQC for chromium,
copper and cadmium. Only minor mortality occurred in the fathead minnow test (20%).
The pore water from the background stations of Gilboa and Grey's Pond, and from
Blackstone Dam, Manville Dam and Slater's Mill exceeded acute AWQC for chromium and
cadmium, but no significant mortality occurred.
No chemical analysis of the pore water accompanied the second round of acute toxicity
tests of pore water. Very significant mortality occurred during the second round in pore water
samples from Fisherville Pond and Sutton Street.
4.6 Specialty Studies
4.6.1 Fish T oxics Monitoring
During the summer of 1993, MADEP collected, prepared, and analyzed edible fillets of
fishes for selected metals, PCBs, and organochlorine pesticides as part of an extensive, interstate
evaluation of the water quality, and biological integrity of the Blackstone River.
Fish from the Blackstone River Basin have been analyzed for selected metals in the past
(1985 and 1986-1990). During the 1985 screening survey, seven stations were sampled. Five
stations were located on the Blackstone River (mainstem), one station was located on the Middle
River, and one station was located on Kettle Brook. Additional work was conducted at Riverdale
Impoundment in Northbridge from 1986-1990. This work was performed in order to monitor for
gross changes in metals concentrations, with the potential to occur as a result of the re-flooding
of parts of the Riverdale Impoundment around 1984. Fish were analyzed for metals only during
1986-1989. However, PCBs, Arsenic, and % Lipids were also measured during 1990 in an effort
to expand the database by including these parameters.
The evaluation of contaminant levels in resident fish was identified as a high priority goal
in the 1991 Blackstone River Initiative Program. As a result, the MADEP requested funding
4-107
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from the United States Environmental Protection Agency as Element 2 of a 104(b) 3 grant
application submitted in 1992. Funds were awarded to the MADEP, and equipment for
collection (electrofishing boat) and analysis (GC auto injector) were purchased.
The specific objectives of this speciality project were to:
1. Collect and analyze fish tissue samples from the Blackstone River Basin to provide
data for human health risk assessment, and to further define the fate and transport of
contaminants in the aquatic ecosystem; and
2. Provide fish toxics data for comparisons with existing statewide database.
Four of the major impoundments on the mainstem Blackstone River were chosen for the
1993 monitoring effort. In addition, Waite Pond in Leicester was chosen as a control or
reference site. Sampling stations are described by waterbody name followed by river mile in
parentheses (Table 4.18). River miles are measured increasingly upstream from Slater's Mill in
Rhode Island. This report summarizes methods and results of the Blackstone River fish tissue
monitoring effort conducted during 1993.
4.6.1.1 Field Methods and Results
All stations were sampled by MADEP personnel using a Coffelt electrofishing boat.
Electrofishing was performed by maneuvering the boat through the littoral habitat of each
waterbody and collecting most fish shocked. Fish collected were stored on board in a live well
filled with site water. Sampling continued until an "adequate" sample was collected. Fish which
were not included as part of the sample were released. Fish chosen as part of the sample were
Table 4.18 Location of Fish Toxics Monitoring
Station Name
USGS Quadrangle
Description
Waite Pond
Worcester South, MA
Waite Pond in Leicester, MA
Fisherville Pond
Milford, MA
Fisherville Pond (downstream of
confluence of Blackstone and
Quinsigamond Rivers in Grafton, MA)
Riverdale
Impoundment
Milford, MA
Riverdale Impoundment on Riverdale
Street in Northbridge, MA
Rice City Pond
Blackstone, MA-RI
Rice City Pond on Hartford Avenue in
Uxbridge, MA
Tupperware
Impoundment
Uxbridge, MA-RI
Tupperware Impoundment upstream of
Blackstone Gorge in Blackstone, MA
4-108
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stored in coolers on ice for subsequent preparation later in the day.
Water bodies were sampled on the following dates: Waite Pond-6/15/93; Tupperware
Impoundment (18.2)-6/17/93; Rice City Pond and Canal (28.0)-7/01/93; Fisherville Pond (37.0)-
7/07/93; Riverdale Impoundment (32.0)-7/26/93.
Sampling at Waite Pond resulted in the collection of five largemouth bass Micropterus
salmoides, one brown bullhead Ameiurns nebulosus, one yellow bullhead Ameiurus natalis, two
white perch Morone americana, three yellow perch Perca flavescens, and five bluegill Lepomis
macrochirus. Many other individuals of these species in various age classes were observed and
or collected and released.
Electrofishing at the Tupperware Impoundment resulted in the capture of one common
carp Cyprinus carpio, five largemouth bass, one chain pickerel Esox rtiger, four brown bullhead,
five bluegill, four yellow perch, and three white sucker Colostomas commersoni. Two additional
species were observed and/or captured but not included in the sample (black crappie Pomoxis
nigromaculatus and golden shiner Notemigonus crysoleucas). It was noted that one yellow perch
(BRF93-17) had a lesion on its right ventral area. Two of the four brown bullhead collected had
some type of anomaly. BRF93-9 had what looked to be a melanoma on the caudal peduncle and
what appeared to be a mouth lesion, and BRF93-11 had a lesion on its mandible.
Sampling in Rice City Pond was unsuccessful, while sampling of the canal resulted in the
collection of two common carp, five white sucker, one yellow bullhead, and one bluegill. The
canal was loaded with carp and suckers, however, the bullhead and bluegill which were collected
were the only two observed. The bullhead and the bluegill were prepared for metals analysis only
due to their small size and the tissue requirement to run the lull array of organics.
Fisherville Pond sampling was conducted downstream from the confluence of the
Blackstone and Quinsigamond Rivers. While this station is called Fisherville Pond, it was
actually a slow moving riverine segment due to the dam gates being partially open. Sampling
resulted in the capture of one common carp, four white sucker, one yellow bullhead, four
largemouth bass, five yellow perch and five bluegill. Fish were abundant in this reach, with
many other fish of these species observed.
Electrofishing in Riverdale Impoundment resulted in the capture of one common carp,
five bluegill, five yellow perch, two brown bullhead, three largemouth bass, and four white
sucker.
4.6.1.2 Laboratory Methods and Results
Fish were returned to the laboratory at OWM where they were identified to species,
measured, weighed, and notes were taken as to an individual fish's general condition.
Fish were filleted (skin off) on glass cutting boards and prepared for freezing. Fillers)
4-109
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targeted for metals analysis were placed in VWR 32 ounce, high density polyethylene (HPDE)
cups with covers. The opposite fillet(s) were wrapped in aluminum foil for % lipids, PCBs and
organochlorine pesticide analysis. Samples were wrapped or stored separately, in the case of
individual samples, or as groups of like-sized individuals, in the case of composite samples.
Fillets were tagged, bagged and frozen for subsequent delivery to the MADEP, Wall Experiment
Station (WES) on July 30, 1993.
All equipment used in the filleting process was rinsed in hot water to remove slime,
scales, and other fluids such as blood, then re-rinsed twice in deionized water before and/or after
each individual fish or composite.
Methods used at WES for metals analysis include the cold vapor method using a VGA
hydride generator for mercury, and Van an 1475 flame atomic absorption for all remaining
metals. PCB/organochlorine pesticide analysis was performed on a gas chromatograph equipped
with an electron capture detector. Additional information on analytical techniques used at WES
is available from the laboratory.
Results were received from WES on May 16,1994 and June 1,1994 for metals and
PCBs/organochlorine pesticide analysis (including lipid content), respectively.
All fish were analyzed for a total of seven metals. The complete set of metals data can be
found in Table 4.19. Cadmium was below the detection limit of 0.40 mg/L in all samples
analyzed. Arsenic, chromium, copper, and lead were below detection in most samples analyzed.
Mean (x) concentrations, ranges, and the number of samples below the method detection limit
(MDL) for all metals are listed below. Values below the method detection limit were factored by
0.5 and included in the calculation of the mean.
For the Blackstone River and Waite Pond 40 observations of fish were measured with the
following results: (Metal/x (mg/kg)/Range (min-max)/number below MDL); arsenic/0.034/<0.040
- 0.10/28; cadmium/0.30/<0.60/40; chromium/0.56/<0.60-2.8/30; copper/0.42/<0.60-1.4/31;
mercury/0.268/0.038 -1.04/0; lead/0.62/<1.0- 2.2/37; selenium/0.27/0.07-0.65/0
Note that in many cases, metals concentrations were below method detection limits with
the exception of a few high outliers. Fish from Waite Pond (control) had very high mercury
concentrations compared to fish from the Blackstone River itself.
The average mercury concentrations by station are given below: (Station/x total Hg
(mg/kg)/Range (min-maxk Waite Pond/0.817/0.457 -1.04; Fisherville Pond/0.195/0.074-0.302;
Riverdale Impoundment/0.101/0.058 - 0.156; Rice City Pond/0.096/0.077 - 0.118; Tupperware
Impoundment/0.207/0.038 - 0.487.
One sample from Waite Pond (WPF93-6+7) had a mercury concentration which exceeded
the United States Food and Drug Administrations1 (USFDA) Action Level of 1.0 mg/kg. The
average mercury concentration in Waite Pond was 0.817 mg/kg which is well above the
4-110
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Table 4.19 Results of Metals Analysis (mg/kg wet weight)
Sample Code
Species1
Code
Sample2
Type
As
Cd
Cr
Cu
Hg
Pb
Se
Waite Pond
WPF93-1
LMB
I
0.04
bdl3
1.2
0.6
0.810
bdl
0.26
WPF93-2
LMB
I
bdl
bdl
bdl
bdl
0.938
bdl
0.19
WPF93-3-5
LMB
C
0.10
bdl
1.2
bdl 1
0.948
bdl
0.21
WPF93-6+7
BB+YB
C
bdl
bdl
1.2
bdl
1.04
bdl
0.24
WPF93-8+9
WP
C
bdl
bdl
bdl
1.4
0.660
bdl
0.34
WPF93-10-12
YP
C
bdl
bdl
bdl
bdl
0.869
bdl
0.24
WPF93-13-17
B
C
bdl
bdl
bdl
0.6
0.457
bdl
0.28
Fisherville Pond (37.0)
BRF93-60
C
I
bdl
bdl
bdl
0.8
0.102
bdl
0.42
BRF93-61
WS
I
bdl
bdl
bdl
bdl
0.178
bdl
0.22
BRF93-62-64
WS
C
0.06
bdl
bdl
bdl
0.179
bdl
0.40
BRF93-65
YB
I
bdl
bdl
bdl
0.8
0.291
2.2
0.16
BRF93-66
LMB
I
bdl
bdl
bdl
bdl
0.280
bdl
0.20
BRF93-67
LMB
I
bdl
bdl
bdl
bdl
0.302
bdl
0.11
BRF93-68+69
LMB
c
0.85
bdl
bdl
bdl
0.179
bdl
0.14
BRF93-70-74
YP
c
bdl
bdl
1.2
bdl
0.074
bdl
0.65
BRF93-75-79
B
c
bdl
bdl
bdl
0.6
0.173
bdl
0.27
-------
Table 4.19 Results of Metals Analysis (mg/kg wet weight) (continued)
Riverdale Impoundment (32.0)
BRF93-100
C
I
bdl
bdl
bdl
bdl
0.081
bdl
0.38
BRF93-101-105
B
C
bdl
bdl
bdl
bdl
0.156
bdl
0.29
BRF93-106-110
YP
C
0.08
bdl
bdl
bdl
0.070
bdl
0.60
BRF93-111+112
BB
C
bdl
bdl
bdl
bdl
0.081
bdl
0.11
BRF93-113
LMB
I
bdl
bdl
bdl
bdl
0.155
bdl
0.30
BRF93-114+115
LMB
C
bdl
bdl
2.8
bdl
0.149
bdl
0.28
BRF93-116
WS
I
bdl
bdl
bdl
bdl
0.058
bdl
0.15
BRF93-117-119
WS
C
0.06
bdl
bdl
bdl
0.059
bdl
0.46
Rice City Pond (28.0)
BRF93-50
C
I
bdl
bdl
bdl
1.0
bdl
bdl
0.45
BRF93-51
C
I
0.06
bdl
bdl
bdl
0.042
bdl
0.46
BRF93-52
WS
I
bdl
bdl
bdl
bdl
0.094
bdl
0.31
BRF93-53
WS
I
0.07
bdl
1.4
bdl
0.118
bdl
0.36
BRF93-54-56
WS
C
0.08
bdl
bdl
bdl
0.086
bdl
0.42
BRF93-57
YB
I
bdl
bdl
bdl
0.8
0.160
bdl
0.23
BRF93-58
B
I
0.09
bdl
bdl
bdl
0.077
bdl
0.20
-------
Table 4.19 Results of Metals Analysis (mg/kg wet weight) (continued)
Tupperware Impoundment (18.2)
BRF93-1
C
I
bdl
bdl
bdl
bdl
0.068
bdl
0.35
BRF93-2
LMB
I
bdl
bdl
bdl
0.06
0.479
bdl
0.16
BRF93-3
LMB
I
bdl
bdl
bdl
bdl
0.487
1.8
0.15
BRF93-4-6
LMB
C
0.06
bdl
bdl
1.2
0.316
bdl
0.12
BRF93-7
CP
I
bdl
bdl
bdl
1.4
0.038
bdl
0.07
BRF93-8-11
BB
C
0.03
bdl
bdl
1.4
0.055
bdl
0.09
BRF93-12-16
B
C
bdl
bdl
bdl
bdl
0.226
2.2
0.28
BRF93-17-20
YP
C
bdl
bdl
1.2
bdl
0.097
bdl
0.25
BRF93-21-23
WS
C
bdl
bdl
bdl
bdl
0.100
bdl
0.31
1 Species Code: LMB - Large Mouth Bass; BB - Brown Bullhead; YB - Yellow Bullhead; WP - White Perch; YP - Yellow
Perch; B - Bluegill; C - Common Carp; CP - Chain Pickerel; WS - White Suckers
2 Sample Type: I - Individual; C = Composite.
3 bdl - below method detection limit
Metal Detection Limits in mg/L: As - 0.002; Cd - 0.03; Cr - 0.03; Cu - 0.03; Hg - 0.0002; Pb - 0.05; Se - 0.002
-------
Massachusetts Department of Public Health's (MDPH*s) health based trigger level of 0.5 ppm.
None of the fish from the Blackstone River had mercury concentrations in exceedance of the
MDPH's "trigger level". Quality Assurance/Quality Control data for metals can be found in
Tables 4.20 and 4.21.
PCBs/organochlorine pesticide/ % Lipid analysis resulted in the detection of PCB
Arochlors 1254 and 1260 in many of the samples from the Blackstone River, however, PCBs
were not present in samples from Waite Pond (Table 4.22).
The average PCB concentrations by station were: (Station/x Total PCBs (mg/kg/Range
(min-max)); Waite Pond/0.09/<0.089-<0.089; Fisherville Pond/0.24/<0.089- 0.71;
Riverdale Impoundment/1.08/0.089-2.8; Rice City Pond/2.09/0.24-4.4; Tupperware
Impoundment/0.87/<0.089-4.7.
Organochlorine pesticides were not detected in any samples. Pesticides analyzed for
included Aldrin, BHC, Lindane, DDD, DDE, DDT, Dieldrin, Endosulfan, Endosulfan sulfate,
Endrin, Endrin aldehyde, Heptachlor, Heptachlor epoxide, Methoxychlor, Toxaphene,
Chlordane, Hexachlorocyclopentadiene, Hexachlorobenzene, and Trifurlin. Of the thirty-one fish
analyzed from the Blackstone River, five samples had Total PCB concentrations which exceeded
the USFDA's Action Level of 2.0 ppm. Four of these fish were common carp and one was a
largemouth bass. Three additional fish had total PCB concentrations which were greater than 1
ppm. These concentrations were found in samples of white suckers. During the time frame that
PCBs and organochlorine pesticides were being analyzed by the laboratory, eighteen laboratory
"clam blanks" were analyzed as part of their quality assurance/quality control program. In all
cases for the clam blanks, PCBs are reported less than method detection limit (
-------
Table 4.20 Quality Assurance/Quality Control Data: Metals (mg/kg wet weight)
Sample Code
Sample Type
As
Cd
Cr
Cu
Hg
Pb
Se
BRF93-67
original
<0.040
<0.40
<0.60
<0.60
—
<1.0
0.09
BRF93-67
duplicate
<0.040
<0.40
<0.60
<0.60
—
< 1.0
0.12
BRF93-67
spike
2.0
20
20
20
—
20
2.0
BRF93-68
spike & sample
1.8
20.2
23
18
—
19
2.28
% Recovery
89
100
115
90
—
93
109
BRF93-60
original
<0.040
<0.40
<0.60
0.8
—
< 1.0
0.37
BRF93-60
duplicate
<0.040
<0.40
<0.60
0.8
—
< 1.0
0.46
BRF93-60
spike
2.0
20
20
20
—
20
2.0
BRF93-60
spike & sample
2.1
20
20
14.4
—
20
2.40
% Recovery
105
98
99
66
—
98
99
BRF93-23
original
<0.040
<0.40
<0.66
0.6
—
< 1.0
0.31
BRF93-23
duplicate
<0.040
<0.40
<0.60
0.6
—
<1.0
0.28
BRF93-23
spike
2.0
20
20
20
—
20
2.0
BRF93-23
spike & sample
1.4
20.2
21
14.4
—
20
2.1
% Recovery
70
101
105
72
—
98
90
-------
Table 4.21 Quality Assurance/Quality Control Data: Mercury (mg/kg wet weight)
Sample Code
Original
Duplicate
Spike
Spike & Sample
% Recovery
BRF93-62-64
0.179
0.179
0.364
0.529
96
BRF93-100
0.090
0.072
0.385
0.433
91
BRF93-117-119
0.058
0.059
0.118
0.183
106
BRF93-1
0.070
0.066
0.364
0.494
117
BRF93-21-23
0.102
0.098
0.408
0.612
125
BRF93-50
<0.02
<0.02
0.322
0.353
110
4-116
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Table 4.22 Results of PCB (mg/kg), Organochlorine Pesticide, and % Lipids Analysis
Sample Code
Species Code1
Sample Type2
% Lipids
PCB 1254
PCB 1260
Waite Pond
WPF93-1
LMB
I
0.12
-------
Table 4.22 Results of PCB (mg/kg), Organochlorine Pesticide, and % Lipids Analysis
(continued)
Riverdale Impoundment
BRF93-100
C
I
1.6
1.1
1.5
BRF93-101-105
B
C
0.20
< MDL
-------
arsenic data is well below criteria published in the EPA's Assessing Human Health Risks from
Chemically Contaminated Fish and Shellfish A Guidance Manual. The only exception to this is
in the case of Venezuela, which has a "legal limit" of 0.1 ppm.
Although chromium and lead were below method detection limits in most samples, high
outliers (>1.2 mg/kg) were reported in nine samples for chromium and three samples for lead.
The aforementioned document lists a legal chromium limit of 1.0 ppm for one country (Hong
Kong). Legal lead limits are listed for nineteen countries. These limits range from 0.5 to 10
ppm. The Canadian legal limit is listed at 0.S ppm. Selenium was detected in all samples
analyzed. Concentrations ranged from 0.07 to 0.60 mg/kg. There was no readily recognizable
relationship with regard to station or species differences with regard to selenium. The EPA
document cited earlier lists legal selenium limits for three countries including Australia (1.0,2.0
ppm), Canada (0.05,0.3 ppm) and New Zealand (2.0 ppm). California reports detecting
selenium concentrations of 1.0 to 2.0 ppm in edible fillets of freshwater fishes and compares
their data to a median international standard developed from the three data points cited in the
aforementioned EPA document.
PCBs, while absent from Waite Pond and at fairly low concentrations in Fisherville
Impoundment, appear to be a problem further downstream on the Blackstone River.
Concentrations increase dramatically between Fisherville Impoundment and Riverdale
Impoundment, the next major impoundment downstream. While there is potentially a source
somewhere between these two locations, it must be noted that the dam at Fisherville
Impoundment was open, and the Fisherville station was more like a stream station than a true
impoundment. The opening of the dam may have resulted in PCB laden fine sediments being
transported further downstream.
In June of 1994, the MDPH issued advisories regarding the PCB contamination. The
advisories were issued for Riverdale Pond, Rice City Pond, and the Blackstone River
Impoundment above Blackstone Gorge (Tupperware). The first part of each advisory is
consistent and reads: " 1. Children under 12, pregnant women and nursing mothers should refrain
from consuming any fish... in order to prevent exposure of developing fetuses, nursing infants
and young children to PCBs." The second recommendation of the advisories is somewhat
variable. The Riverdale Pond advisory goes on to recommend that "2. The general public should
limit consumption of Riverdale Pond fish to two meals per month." The Rice City Pond advisory
goes on to recommend that "2. The general public should refrain from consumption of Rice City
Pond carp." and the Blackstone River Impoundment above the Blackstone Gorge recommends
that "2. The general public should refrain from consumption of Blackstone River Impoundment
above the Blackstone Gorge carp and white suckers." Differences in the advisories can be
attributed to specific information included in each individual data set.
4.6.1.4 Conclusions
The PCB (Arochlors 1254 and 1260) concentrations in Blackstone River fish may be
coming from a number of potential sources. The Blackstone River received wastewater from a
4-119
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number of industrial sources for years. There is also a hazardous waste site (OMNI-DURALITE
Site) located just downstream of the Fisherville Impoundment. Site related contaminants include
many semi-volatile base/neutral and acid extractable compounds, and the presence of electrical
transformers on the site suggests the potential for PCBs as well. Another historic industrial site
is located one mile downstream of the Omni-Duralite Site at Farnumsville.
Sediments were not analyzed for PCBs during the 1991 Dry Weather Assessment (1991
Blackstone River Initiative). Results from the 1992 wet weather work indicate that there may
indeed be an increase in sediment PCBs between Singing Dam in Sutton (river mile 39.8) and
Riverdale Impoundment in Northbridge (river mile 32.0). One sample collected at each location
resulted in the detection of PCB Arochlor 1260 at concentrations of 0.10 and 1.1 mg/kg
respectively. A sediment sample collected at Tupperware Impoundment during the same survey
had a concentration of 0.36 mg/kg of PCB Arochlor 1260.
Sediment samples from Rice City Pond were analyzed for PCBs as part of a study by
MADEPs OWM examining potential solutions for remediating the Pond. PCBs (A1254 and
A1260) in five surface sediment samples (<12 inches in depth) ranged from 0.84-7.2 mg/kg. The
mean level was 2.8 mg/kg. Three additional samples will be collected as part of this ongoing
study. One sample will be collected from each of the following three stations; Fisherville
Impoundment, Farnumsville, and the Depot Street bridge. These samples should help to verify a
potential source located between Fisherville Pond and Riverdale Pond.
Regardless of the results from the ongoing DEP OWM study of Rice City Pond, it
appears that PCBs will continue to impact the recreational fisheries of the Blackstone River for
some time to come. Additional characterization of Blackstone River sediments will be necessary
to identify hot spots or potential sources of PCBs to the River. Periodic fish sampling could help
to identify any trends with regard to the bioaccumulation of PCBs in Blackstone River fishes.
The analysis of whole fish is necessary in order to perform any ecological risk assessment to
address potential impacts of PCBs to fish-consuming wildlife.
4.6.2 Benthic Macroinvertebrate Community Analyses at Selected Stations
4.6.2.1 Design Overview
Benthic macroinvertebrate communities were sampled in 1991 at eight stations on the
mainstem Blackstone River in Massachusetts and Rhode Island, and at one station in each of two
reference streams that are tributaries to the Blackstone River. Personnel from the Biology
Sections of the U.S. EPA, Environmental Services Division, Lexington, Massachusetts, and the
Massachusetts Department of Environmental Protection (MADEP) collaborated on the fieldwork
for this study. Two techniques were used to collect benthic invertebrate samples: artificial
substrate deployment and kick sampling. A number of metrics commonly used to evaluate
various components of invertebrate community structure were used to assess the samples. The
quality of community assemblages sampled at Blackstone mainstem stations was evaluated
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through a comparison of metric values from one station to the next. In addition, metric values
from the mainstem samples were compared to those from the two reference streams.
4.6.2.2 Methods and Station Locations
Rock Baskets: Rock baskets were deployed in riffle habitats in the Blackstone River and
two of its tributaries, the Mumford River and the Mill River, in late July 1991. Baskets were
recovered in late September of the same year. Station locations and specific dates of substrate
deployments are listed in Tables 4.23 - 24. EPA station codes, river miles and MADEP station
codes are assigned to each station. The latter are included to allow comparisons with past
MADEP surveys (Johnson, Nuzzo and Kennedy 1992; Fiorentino 2000). Baskets were placed in
stream sections where the water velocity at 5 cm from the bottom was 0.3 ±0.1 m/s. A low
velocity flow meter (Swoffer model 2100) was used to measure current speed. Three rock
baskets were deployed at each station and were anchored to the streambed with iron reinforcing
bar and wire.
To remove rock baskets from the substances, the investigators first placed a large plastic
container downstream of each rock basket while it was being dislodged from the streambed in
order to capture any organisms that might escape from the basket. Once the wire holding the
basket in place was removed, the basket was lifted out of the stream in the plastic container and
brought to the stream bank. Baskets were opened and each rock was gently rubbed (by hand)
clean of organisms. Cleaned rocks were discarded and the remaining sample was rinsed in a
Standard # 30 mesh sieve-bucket. Samples were subsequently removed from the sieve and
transferred to labeled glass jars filled with 95% ethanol.
Kick Nets: Kick net sampling was conducted on September 23 and 24,1991,
immediately prior to the removal of rock baskets from the substrates. Kick net sampling was
confined to areas immediately downstream of the rock baskets. At each station, investigators
disturbed one square meter of bottom substrates by foot while holding a D-frame net (30 mesh,
Standard Sieve Series) downstream of the area being worked to capture invertebrates released
from the stream substrates. Nets were picked clean of invertebrates and each kick net sample
was transferred to a labeled jar filled with 95% ethanol.
Sample Processing: Samples generated from the rock basket and kick sampling were sent
to Lotic, Inc. of Unity, Maine, where they were analyzed under an EPA contract. Personnel at
Lotic spread the contents of each sample on a gridded plan and used a random number table to
select a 100-organism subsample from each of the basket samples and three, 100-organism
subsamples from each kick-net sample. These 100-organism subsamples (called samples in the
remainder of the text) were identified to genus, and tabulated. Taxonomic lists generated for
each station were sent to the MADEP office for analysis.
Data Analysis: Aspects of the invertebrate community structure and feeding-function as
represented in samples taken from each of the stations were analyzed along with water quality
data to assess inter-station differences in the benthos. A number of metrics from the EPA Rapid
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Table 4.23 Benthic Macroinvertebrate Sampling Station Locations
DWPC
Station
ID
EPA
Station
ID
River
Mile
Description
Artificial
Substrates
Deployed
Artificial
Substrates
Collected
BS10
BIOl
44.0
Blackstone River in a riffle/run area located approximately 160 yds
upstream of McCracken Road bridge, Millbury
7/30/91
9/23/91
BS12
BI02
39.7
Blackstone River in a riffle/run area located approximately 70 yds
downstream from Singing Dam, Sutton
7/30/91
9/23/91
BS14
BI03
33.6
Blackstone River in a deep riffle area located behind the Coz Chemical
Company, upstream from the Sutton Street Bridge, Northbridge
7/30/91
9/23/91
BS16
BI04
27.4
Blackstone River in a run/pool/riffle area located behind an island
downstream from the outlet of Rice City Pond, Hartford Avenue,
Uxbridge
7/30/91
9/23/91
BS18
BI06
19.8
Blackstone River in a riffle/run area located approximately 90 yds
upstream of Central Street Bridge, Millville
7/30/91
9/23/91
BS19
BI08
16.5
Blackstone River in a riffle/run area located approximately 40 yds
downstream from the Bridge Street Dam, First Avenue, Blackstone
7/31/91
9/24/91
BSR11
BI09
9.8
Blackstone River in a riffle/run area located approximately 180 yds
downstream from the Manville Hill Road Bridge, Lincoln, RI
7/31/91
9/24/91
BSR12
BIOIO
0.0
Blackstone River in a riffle/run area located approximately 40 yds
downstream from Slater Mill Dam, Pawtucket, RI
7/31/91
9/24/91
MF02
BI05:MR
25.5/11.1
Mumford River in a riffle/run area located approximately 5 yds
downstream from an unnamed bridge off of Manchaug Street at the
outlet of Grays Pond, East Douglas
7/31/91
9/24/91
ML05
BI07:MI
13.3/3.0
Mill River in a riffle/run area located approximately 70 yds upstream of
Summer Street Bridge, Blackstone
7/31/91
9/24/91
-------
Table 4.24 Benthic Macroinvertebiate Station Bottom Types and Current Velocity
Measurements
DWPC
Station
ID
EPA
Station
ID
River
Mile
Bottom Type
Current Velocity
(m/s)
BS10
BIOl
44.0
Gravel
0.26
0.29
0.31
BS12
BI02
39.7
Cobble, Gravel, Boulder
0.37
0.38
0.21
BS14
BI03
33.6
Cobble, Gravel
0.41
0.38
0.38
BS16
BI04
27.4
Coarse, Gravel, Sand, Cobble
0.40
0.32
0.25
BS18
BI06
19.8
Gravel, Sand
0.20
0.33
0.44
BS19
BI08
16.5
Boulder
0.25
0.22
0.15
BSR11
BI09
9.8
Boulder, Cobble
0.19
0.21
0.39
BSR12
BIOIO
0.0
Boulder, Cobble, Sand
0.32
0.39
0.40
MF02
BI05:MR
25.5/11.1
Cobble, Gravel, Sand
0.26
0.26
0.39
ML05
BI07:MI
13.3/3.0
Boulder
0.21
0.36
0.28
Current meter measurements reported as a 30 second integrated period at each rock basket.
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Bioassessment Protocols (Plafkin et al., 1989) were used in addition to several others to evaluate
the invertebrate taxa lists. Each of the metrics chosen for this evaluation is a descriptor of a
particular aspect of the benthic community. Metrics results in this study are evaluated in
combination to obtain as unbiased a picture as possible of community structure and function.
Data from mainstem stations were also compared to those from the two reference streams
to assess trends, but were not used, per se, in a formal reference/test evaluation. We felt it was
inappropriate to conduct such an analysis because drainage area differences between available
reference stations and those on the Blackstone mainstem were substantial. Community
composition of invertebrate assemblages has been shown to change with increasing drainage area
(Allan 1975; Cummins 1979 and Minshall et al., 1992). Therefore, differences observed in taxa
lists between mainstem and reference stations might be complicated by those from drainage area.
Metrics used in this evaluation are described below.
Richness is the number of clearly different taxa from each sample. Since one most often
finds a wider variety of organisms at clean sites than at polluted sites, this index is usually
inversely correlated with anthropogenic disturbances and pollution.
Evenness is the relative distribution of sample specimens among different taxonomic
groups. The evenness index used here is calculated as die Shannon-Weaver diversity (1963;
computational formula from Poole 1974) of the sample divided by the maximum diversity, i.e.,
H'/H'max. The maximum value for H' is log(s), where s = the number of taxonomic groups in
the sample. Evenness is typically highest in unimpacted streams and lowest in heavily impacted
situations where one often sees dominance of a few highly tolerant taxa.
Shannon-Weaver diversity is composed of two elements: richness and evenness. H' is
positively correlated with both. Typically, one sees decreases in H' downstream of pollutant
impacts to streams, although in some low- productivity riverine systems, communities
downstream of organic waste inputs have been found to have a higher richness which increases
diversity (Courtemanch and Davies 1987).
Kick samples collected in this study are expected to provide higher values for richness
and diversity than are basket samples. This is due to the fact that a wider number of
microhabitats are usually encountered in kick sampling, in comparison to those existing in rock
baskets, which are filled with a fairly uniform size and shape of rock. This relationship should
hold unless evenness is differentially affected in the two sample types.
Biotic index values were calculated using tolerance values presented in Bode et al.,
(1991). To calculate this index, the researcher must ascribe a tolerance value between zero and
ten to each taxon. Tolerance values ascribed to a taxon are based on its history of occurrence in
association with certain types of pollution. Highly pollution-tolerant organisms are given high
tolerance values. Those found only in unpolluted environments that are highly oxygenated
receive the lowest tolerance values. The index is computed as the number of organisms in the
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18
16
14
BI01
BI02
BI03
BI04
BI06
BI08
BI09
BIO10
BI05:MR
BI07:MI
~ Kick#1
12
13
7
7
10
15
13
9
14
~ Kick#2
9
11
8
8
8
14
11
9
17
~ Kick#3
10
14
6
8
10
14
14
7
11
¦ Rock#1
11
9
5
7
8
9
6
5
11
11
1 Rock#2
13
10
6
8
7
7
6
6
10
10
¦ Rock#3
11
9
4
5
7
13
8
6
10
Biomonitoring Stations
Figure 4.68 Taxa Richness
-------
BI01
BI02
BI03
BI04
BI06
BI08
BI09
BIO10
BI05:MR
BI07:MI
~ Kick#1
0.59
0.68
0.50
0.48
0.59
0.69
0.64
0.35
0.76
~ Kick#2
0.55
0.70
0.52
0.51
0.64
0.72
0.64
0.56
0.72
~ Kick#3
0.46
0.74
0.58
0.47
0.56
0.66
0.56
0.50
0.77
¦ Rock#1
0.41
0.43
0.53
0.49
0.49
0.67
0.63
0.38
0.76
0.70
¦ Rock#2
0.60
0.38
0.54
0.49
0.46
0.76
0.56
0.31
0.68
0.77
¦ Rock#3
0.57
0.29
0.63
0.51
0.56
0.71
0.58
0.36
0.78
Biomonitoring Stations
Figure 4.69 Evenness
-------
X
CO
CD
£
1
c
o
c
c
ro
-C
W
2.50
2.00
1.50 --=
1.00
0.50 -
0.00
BI01
BI02
BI03
BI04
BI06
BI08
BI09
BIO10
BI05:MR
BI07:MI
~ Kick#1
1.47
1.74
0.97
0.93
1.35
1.88
1.65
0.78
2.00
~ Kick#2
1.21
1.68
1.09
1.06
1.32
1.90
1.53
1.23
2.05
~ Kick#3
1.05
1.96
1.03
0.97
1.30
1.75
1.48
0.97
1.85
¦ Rock#1
0.99
0.96
0.85
0.95
1.02
1.48
1.12
0.61
1.83
1.67
¦ Rock#2
1.53
0.88
0.97
1.02
0.90
1.47
1.00
0.55
1.58
1.77
¦ Rock#3
1.38
0.63
0.88
0.82
1.08
1.82
1.21
0.65
1.81
Biomonitoring Stations
Figure 4.70 Shannon-Weaver Index
-------
BI01
BI02
BI03
BI04
BI06
BI08
BI09
BI01C
BI05:MR
BI07.MI
~ Kick#1
6.78
5.12
4.42
4.70
4.40
4.27
4.68
4.90
3.72
~ Kick#2
6.20
5.21
4.55
4.66
4.31
4.17
4.55
5.00
3.57
~ Kick#3
6.05
5.30
4.54
4.63
4.26
4.26
4.49
4.92
3.77
¦ Rock#1
6.09
4.46
4.35
4.69
4.56
4.21
4.89
4.86
3.51
4.02
¦ Rock#2
6.11
4.32
4.53
4.54
4.67
3.99
4.79
4.87
3.97
3.92
¦ Rock#3
6.25
4.24
4.46
4.48
4.49
3.99
4.73
5.01
3.81
Biomonitoring Stations
Figure 4.71 Biotic Index
-------
B 010
BI05:MR
BI07:MI
~ Kick#1
~ Kick#2
~ Kick#3
Rock#1
Rock#2
S Rock#3
Biomonitoring Stations
Figure 4.72 Percent Scrapers
-------
I
~—*
U)
O
n mbB
~ Kick#1
~ Kick#2
~ Kick#3
Rock#1
Rock#2
Rock#3
Biomonitoring Stations
BIO10 BI05:MR
BI07:MI
Figure 4.73 Percent Collector-Filterers
-------
X
0
TJ
C
CL
111
BI01
BI02
BI03
BI04
BI06
BIOS
BI09
BIO10
BI05:MR
BI07MI
~ Kick#1
0
3
2
3
5
7
6
4
7
~ Kick#2
0
2
3
3
4
10
6
3
8
~ Kick#3
1
2
2
3
5
9
6
3
6
¦ Rock#1
0
2
2
2
5
7
3
3
6
7
¦ Rock#2
1
2
2
3
4
6
4
3
6
8
¦ Rock#3
0
2
2
2
4
8
3
3
7
Biomonitoring Stations
Figure 4.74 EPT Index
-------
¦ Mayflies 0 Hydropsychid Caddisflies EI Other Caddisflies HChironomids CD Tubificid Worms ~ Others 0 Crustaceans
100%
UJ
to
I
S
i
i
i
i
i
CU 60%
i
i
i
i
i
I
i
i
5 40%
1
i
m
II
I
1
I
BK BK BK BK BK BK BK BK BK B
BIOl BI02 BI03 BI04 BI06 BI08 BI09 BIO10 BI05:MR BI07:MI
Figure 4.75 Mean Percent Composition
-------
taxon multiplied by the pollution tolerance value for that taxon. The sum of these values over all
taxa is divided by the number of individuals in the sample and represents the mean tolerance
value for an organism in the sample. The Biotic index is most often positively correlated with
the degree of organic pollution.
The % Collector-Filterer index is the proportion of individuals in the sample that fall into
the collector-filterer functional feeding group. The feeding group assignments listed in Bode et
al., (1991) were used for this index as well as for the % Scrapers index (see below). The relative
abundance of collector-filterers is often positively correlated with the amount of fine-grained
organic material suspended in the water column. In Massachusetts streams, caddisflies of the
family Hydropsychidae often dominate benthic stream samples taken downstream of
impoundments where phytoplankton concentrations are high.
The % Scraper index is simply the proportion of individuals in each sample from the
scraper functional feeding group. Scrapers are often associated with waters that have a specific
type of periphytic growth most often found in clear, unimpacted streams. Typically, this index is
inversely correlated with organic pollution and turbidity.
The last index, EPT, is the number of distinctively different taxonomic groups from the
EPT orders found in each sample. A wider variety of EPT taxa has been found in pristine waters
with a high oxygen content than in areas subjected to anthropogenic disturbances.
4.6.2.3 Results and Discussion
The macroinvertebrate taxa lists and most metrics derived from them (Figures 4.68-75)
suggest the same general trend outlined here. The invertebrate community sampled at BIOl, the
most upstream station on the Blackstone (located about half a mile downstream of the
UBWPAD), is fairly degraded. The quality of the invertebrate assemblage improves
dramatically, however, between station BIOl and BI02 (located approximately four miles
downstream in Sutton). Between stations BI02 and BI04 (located in Uxbridge) the community
assemblages do not change as substantially, but still exhibit minor improvements. Between
stations BI04 and BI06 (in Millville), invertebrate community assemblages exhibit extensive
improvements compared to upstream stations. Between BI06 and BI08 (located in Blackstone,
MA, near the Massachusetts-Rhode Island border) the improvements are even more substantial.
Across the state line and downstream of the city of Woonsocket, Rhode Island, the quality of the
community assemblage degenerates. Metric values from samples collected from BI09 (located
in Lincoln, RI) all indicate a negative change in the quality of the benthic community when
compared to those for BI08; these regress even further at the second Rhode Island station, BIO 10
(in Pawtucket, RI).
Certain aspects of the suite of metrics from the Blackstone seem, at first, to counter the
trend outlined above. Shannon-Weaver diversity at BIOl and BI02 is higher than it is at the next
two stations. Due to the nearness of these two stations to the UBWPAD and the Worcester CSO
treatment facility, one might expect that the community diversity would be lowest at BIOl and
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BI02. Of the two elements of diversity, evenness and richness, the latter appears to be
responsible for the high values at BIOl. The overall evenness of the samples here is about equal
to that at BI02,3,4 and 6. Richness, however, is high at BIOl and BI02 but decreases at the
next three downstream stations.
High Richness values are often a sign of a healthy community. However, a review of
the other metric results shows that the community at BIOl is highly stressed. The Biotic Index
values at this station, much higher than all other mainstem stations, indicate that the invertebrate
taxa list for BIOl is primarily comprised of pollution-tolerant organisms. The preponderance of
pollution tolerant taxa is also reflected in the very low abundance of scrapers and EPT taxa. In
addition, this station is almost devoid of collector-filterers, a condition which is highly unusual
for the Blackstone. Although a low relative abundance of collector-filterers is often seen in low-
productivity, unpolluted streams, the near absence of this group from the benthic assemblage in
the Blackstone is highly unusual. This condition is more probably related to a toxic response
than to a lack of structural habitat or food materials (see below).
The taxonomic composition of the sample from station BIOl was heavily dominated by
chironomids: over 89% of die sample was made up of individuals from this one family of
dipterans. Many of the chironomids seen from this station were from taxonomic groups that are
fairly tolerant of organic pollution. Tubificid worms, also found at this station, were not found at
any of the other stations in substantial numbers. The latter are considered to be among the most
highly pollution-tolerant groups of macroinvertebrates. They are often found in areas that are
prone to heavy organic loading and oxygen stress.
Although tubificids were found in all kick samples collected at this station, none were
found in the basket samples. One explanation for this is that the kick sampling exposes
subsurface sediments. If these are poorly oxygenated, the likelihood of encountering tubificids or
other organisms adapted to living in low oxygen environments is increased by using the kick
sampling method when compared with the rock basket method. Rock baskets deployed in these
studies were placed on top of the stream substrates and the flow rate of oxygenated water through
these baskets was probably higher than through the natural substrates. Judging from the dry-
weather data set for oxygen (see Figures 4.1 - 4.3), this variable does not appear limiting in the
water column, but sediment oxygen demand may have been sufficient to create a depleted
oxygen layer just below the sediment/water interface.
At station BI02 and throughout the remainder of the mainstem stations, the invertebrate
assemblages undergo a dramatic change from chironomid-dominated to hydropsychid dominated.
The latter are commonly referred to as "net-spinning" caddisflies as they construct sizeable (up to
approximately 3 cm long) nets with which they filter and collect organic food matter from the
water column in the form of algae and fine suspended particulates.
It is likely that the large difference in the community assemblages between BIOl and
BI02 is related to the toxic effects of chlorine discharged from the Upper Blackstone wastewater
treatment plant or other more upstream sources such as the Worcester CSO treatment facility.
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Since there was no invertebrate station located upstream of BIOl, it is impossible to isolate the
exact source of the impacts found at this station. In at least two other macroinvertebrate studies
conducted by the Biology Section of Division of Water Pollution Control (DWPC) (Johnson et
al., 1986; and Nuzzo and Kennedy 1992), a similar change in community assemblages was
documented downstream of chlorinated discharges. In each of these, hydropsychids were either
eliminated or the percent composition of this group was drastically reduced. Midges and worms
predominated at the stations closest to the chlorinated discharges in both of the past studies while
hydropsychids and other groups began to appear farther downstream. As mentioned above,
dissolved oxygen levels did not appear to be a factor in these studies, and neither did toxicity due
to ammonia.
Chlorine toxicity was not directly evaluated in the wet or dry weather studies, but it
probably exerted an effect on benthos in the upper segments of the Blackstone due to the low
degree of dilution afforded to the UBWPAD by the Blackstone River. In addition, wet weather
chlorine releases from the Worcester CSO treatment facility have been known to be quite high
(see below). Studies conducted by the DWPC (Nuzzo and Kennedy 1992) and by DWPC in
coordination with EPA (Szal et al., 1991) have documented acute toxicity (mortality) of chlorine
to fathead minnows (Pimephales promelas) in 24-hr in situ studies downstream of chlorinated
WWTF discharges. In one of these studies, a zone of 100% mortality to deployed minnows
extended as far as 1.5 miles downstream of the chlorinated discharge. As a result, it is not
unreasonable to expect to see toxicity to the macroinvertebrate community at station BIOl due to
chlorine releases from nearby sources.
Total residual chlorine (TRC) concentrations downstream of the UBWPAD were
probably quite high judging from TRC concentrations of 24-hr composite stream samples
collected for the diy-weather toxicity evaluations of river water. TRC was detected in 24-hr
composite samples from stations BIOl, BI02 and BI03. Amperometric titrations for TRC were
conducted 4-6 hrs. after composite samples were collected. TRC concentrations in these samples
ranged from non-detect to 75 ppb (section 4.5.2). Because TRC rapidly decays with time,
especially in the presence of organic materials, dry-weather TRC levels in the Blackstone were
probably much higher than those reported here and may have greatly influenced community
composition at BIOl and at other stations close to the discharge.
Wet weather TRC concentrations from the UBWPAD discharged at first flush and peak
during Storm 1 were 290 and 640 ppb, respectively (section 7.3.1). Although TRC
concentrations in the Blackstone river were not measured, they are expected to have exceeded the
EPA acute ambient water quality criterion of 19 ppb during this storm event due to chlorine
additions from the UBWPAD. There was no release from the Worcester CSO treatment facility
during this storm, but chlorine discharges occurred during other wet weather events.
Chlorine was not the only toxicant acting on Blackstone benthic organisms during wet
weather events. Dechlorinated river water samples upstream of the Worcester CSO were toxic
(section 7.3.1), but on a less frequent basis than downstream of the Worcester CSO and
downstream of the UBWPAD discharge. Wet weather, dechlorinated samples collected from the
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UBWPAD discharge and the Worcester CSO discharge were toxic on a less frequent basis than
were the river water samples collected downstream of these facilities. Based on these data, it
seems logical to conclude that sources other than UBWPAD and the Worcester CSO were also
contributing to the river water toxicity seen in the upper section of the Blackstone.
Ammonia, another potential toxicant responsible for the disrupted community at BIOl,
probably did not exceed the 1999 EPA acute criteria (EPA 1999) levels during any of the
surveys. Ammonia toxicity is primarily dependent on the unionized fraction (NH3) of ammonia,
which increases dramatically with pH. Wet weather concentrations of ammonia, though high,
do not appear to have exceeded EPA acute criteria due to the low pH of the water column during
these events. During the three storm events, ambient pH levels ranged between 6.3 and 6.8
(section 7.1.3). The acute criterion for pH 6.8 in warm water streams is 42.0 mg/L as total
ammonia which is well above the wet weather total ammonia concentrations (maximum =
approximately 7 mg/L as N) seen in these surveys.
Ammonia concentrations during dry-weather periods ranged up to about 0.7 mg/L in
Massachusetts and up to about 1.2 mg/L in the Rhode Island segment of the river. The highest
and most persistent pH levels were seen in the first day of the 2-day July survey. Ambient water
column pH levels ranged well above 9.0 standard units on this day, and reached or exceeded 9.3
at five of the IS mainstem stations (all in Massachusetts) on the 1600 hr. run. The acute (1-hr)
criterion for total ammonia at pH=9.0 for warm water streams is 1.32 mg/L; the criterion for
pH=9.3 is 0.87 mg/L, so criteria levels do not appear to have been exceeded in Massachusetts.
As mainstem pH levels in Rhode Island did not reach above 9.3 on any of the surveys, criteria
levels were probably not exceeded during the surveys in this state either.
Even though EPA criteria levels for ammonia were probably not exceeded during dry or
wet weather surveys, the long-term absence of two common invertebrate species from the
mainstem leads one to wonder if ammonia toxicity might be the cause. Hyallela azteca (an
amphipod) and Musculium transversum (a fingernail clam) are two of the most sensitive taxa
listed in the EPA ammonia criteria document. H. azteca and species of Musculium other than M.
transversum are ubiquitous in Massachusetts streams. However, only one individual H. azteca
was found in the mainstem during the 1991 survey and no individuals of Musculium sp. were
found.
In four other surveys of the Blackstone and its tributaries that span a 25-year period, this
same trend is evident: both taxa appear in tributaries to the Blackstone but not in the mainstem.
The Massachusetts DEP has collected invertebrate samples in the Blackstone River and its
tributaries in five other years: 1973,1977,1985,1998. In each of these surveys, as well as in the
1991 survey, H. azteca was found in the West and/or Mumford rivers, tributaries to the
Blackstone. By contrast, the single H. azteca specimen found in the mainstem in 1991 was the
only specimen of this species found in all five mainstem surveys.
The particular species of fingernail clam (M transversum) used in the development of the
EPA ammonia criteria document is not found in Massachusetts. However, other species
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(Massachusetts has 3) in this genus often appear in benthic collections. As the criteria document
lists genus mean acute and chronic values for Musculium sp., this indicates that other species in
this genus are expected to respond similarly to M. transversum with regard to ammonia toxicity.
Two species of Musculium (M. partumeium, and M. securis, both formerly considered to be of
the genus Sphaerium) were found in mainstem stations in the 1977 survey, but were not reported
in the 1973 survey or in later surveys.
H. azteca is extremely sensitive to ammonia. The chronic EC20 given in the EPA
document for this amphipod at pH=8 and 25 °C is <1.45 mg/L as N. No acute data were listed for
H. azteca in the criteria document. The chronic ammonia criterion for pH=8 and 25'C is about
I.25 mg/L as N, so this species should be protected by the chronic criteria, although its toxic
threshold is very close to the criterion value.
Musculium sp. may be even more sensitive than H. azteca. The genus mean chronic
value for Musculium given in the criteria document is < 2.26 mg/L as N at pH=8 and 25°C. This
value is based on laboratory toxicity analyses. Field studies conducted by Zischke and Arthur
(1987), however, showed chronic effects at about 1 mg/L as N. Zischke and Arthur's field trial
results were not used in the criteria development because EPA decided not to use results of any
field experiments in the derivation of the final chronic values. As a result, one might expect
Musculium species to suffer toxic effects when long-term ammonia levels were near or even
slightly below the chronic criteria.
If ammonia toxicity is a problem in the Blackstone, it is most likely to occur as a
wintertime phenomenon. Both dry weather and wet weather ammonia levels appear to be well
below criteria levels for the survey dates reported. However, the UBWPAD does not achieve
year-round nitrification, nor does the Woonsocket WWTF. Wintertime ammonia levels in the
UBWPAD effluent reach 15 to 20 mg/L as N according to MA DEP personnel (Bryant Firmin,
MADEP, personal communication). Dilution at the UBWPAD is minimal. The design flow of
the UBWPAD is 56 MGD and the 7Q10 base flow of the Blackstone River directly upstream of
the facility is 4.4 MGD. The instream waste concentration of the effluent at these flows
approaches 93%. Even with dilution from wintertime flows we can expect water column
ammonia levels, at times, to exceed 10 mg/L as N in the Massachusetts segment of the river.
Ammonia criteria levels downstream of the Woonsocket WWTF reached close to 1.2
mg/L. during the summer 1991 survey, while above the Woonsocket WWTF the ammonia levels
were <0.1 mg/L even though instream dilution was high. Ammonia levels in the effluent reached
28.6 mg/L in the effluent during the first survey. The instream flow concentration of the effluent,
based on average plant flows and 7Q10 river flow is about 12%. Under design conditions (24.6
cfs plant flow, 102 cfs river flow at 7Q10) the RI DEM has determined that chronic ammonia
criteria exceedances will occur if the pH of the river is maintained at or above 7.4, river
temperatures are at 26°C or more, and the facility maintains ammonia levels above 10 mg/L as N.
EPA's 1999 chronic ammonia criteria have an inverse relationship with temperature.
For temperatures in the 0-7 C range, the criteria run between 4.36 to 10.8 mg/L as N in the pH
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range of 7.5-6.5, the expected cold-weather range in the Blackstone. As a result, criteria levels in
the upper Blackstone River may often be exceeded in the colder months if river flows are low.
Due to the extreme sensitivity of H. azteca and Musculium sp., ammonia concentrations during
the colder months throughout much of the Blackstone mainstem may be high enough to be toxic
to these two taxa. To address this question, chronic toxicity studies using these species could be
conducted in the laboratory at temperatures and pH levels matching those seen in the Blackstone
mainstem in the winter. UBWPAD effluent mixed with ambient water from an upstream source
could be diluted to match wintertime concentrations of effluent in the mainstem. Toxicity
studies using this mix would be compared with data from another effluent/diluent mix where
ammonia had been removed or substantially reduced. These studies were not conducted at
critical conditions of low river flow, pH and temperature, nor at design flows. The wasteload
allocation model should be utilized to determine ammonia criteria exceedances and potential
impacts.
Richness at BI02 is approximately the same as at BIOl. Tubificids have essentially
disappeared from the samples. Chironomids, although much reduced in relative abundance, are
still a major component of the community at this station. Two additional groups, the amphipods
and isopods (both crustaceans) are important in the assemblage here, but not at any other. Both
are collectors or gatherers of organic matter and are fairly tolerant of organic pollution and low
oxygen conditions. Due to a major reduction in the relative proportion of pollution-tolerant taxa
at this station compared with BIOl, the Biotic index exhibits its greatest improvement between
stations BIOl and BI02. Values for this index remain approximately the same until station BI08
where there is further improvement.
EPT organisms appear in substantial numbers at BI02, which denotes an improvement
over BIOl, but the EPT taxa at the former station (genera Hydropsyche, Cheumatopsyche and
Baetis) are not highly sensitive to organic wastes. Much more sensitive EPT taxa begin to appear
in samples collected farther downstream.
The relative proportion of hydropsychids found in the benthic samples increases between
stations BI02 and BI03 (located in Northbridge) and increases even further at station BI04
(downstream of Rice City Pond in Uxbridge).
Richness values decreased from station BI02 to BI03 and remained low at BI04,
probably as a result of high densities of hydropsychids. EPT essentially remains the same
through stations BI02, BI03 and BI04, although the proportion (approximately 1.3%) of the
total sample collected at BI04 composed of mayflies is higher than at BI03 and BI02. Only one
ephemeropteran was found in each of the 600-organism samples collected from the latter two
stations.
Organic solids appear to be the primary influence on benthic community structure
downstream of station BIOl. The proportion of the benthic samples composed of filter-
collectors, especially hydropsychid caddisflies, increases between stations BI02 and BI03 and
increases even further at BI04. These feeding-group changes reflect the rises in water column
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concentrations of VSS, chlorophyll a, as well as TSS. Each of these water quality variables
crescendos to a peak at Rice City Pond and BI04, located downstream of the pond. Although we
do not have information on secondary (invertebrate) productivity, the density of hydropsychids at
BI04 was extraordinary and must have been related to food availability. Hydropsychid densities
at this station were so great that, when investigators removed rock basket sampling devices from
the river bottom, small boulders stuck to the baskets and had to be removed. The boulders had
been cemented to the basket samplers by hydropsychid nets. Throughout this area, benthic
substrates were completely covered with hydropsychid nets.
Scrapers are essentially missing from the benthos in stations BI01-BI04 but appear in
fairly high proportions at station BI06. Chlorophyll a, TSS and TVS all decreased substantially
between BI04 and BI06. Much of this reduction may be due to the activity of the collector-
filterers found upstream of BI06. Lower concentrations of TSS and TVS are typically associated
with a decrease in turbidity and may have allowed periphyton to become established at BI06,
creating a food source for scrapers. In addition, lower organic solids concentrations would
decrease the food-base for hydropsychids and would have a negative effect on their densities. A
simple reduction in the hydropsychid density would allow colonization by other groups. To
evaluate these potential links, estimates of secondary productivity, turbidity and periphyton
productivity would have to be compared to densities of hydropsychids and scrapers at various
points along the mainstem.
Mayflies, an important component of most clean-water stream communities, first become
a major part of the invertebrate assemblage at station BI06 (located in Millville). Their
prevalence increases slightly at the next station BI08, where they account for over 20% of the
organisms collected. Most of the mayfly individuals found in these samples were scrapers, and
their presence may be linked with a decrease in TSS and TVS as described above.
Five of the seven metrics indicate improvements in the quality of the invertebrate
assemblage from BI06 to BI08. Four of these show substantive improvements. Whereas
richness increases only slightly from station BI03 to BI04, and then again slightly between
stations BI04 and BI06, it increases by an additional 50% between BI06 and BI08. One
component of this change in richness is the number of EPT taxa which increases approximately
60% between BI04 and BI06 and an additional 70% between BI06 and BI08. The overall
evenness of the distribution of individuals among the different taxonomic groups increases from
BI06 to BI08. As both evenness and richness increase, Shannon-Weaver diversity also
increases. EPT, Diversity and Evenness values at BI08 are more similar to those from the two
reference streams than are values for these metrics from other stations. The Biotic index scores
for station BI08, while still higher than those for the two reference streams, average lower (i.e.,
better) than scores for all the other mainstem stations. Without data from pristine streams in this
ecoregion that are similar in drainage area to mainstem stations, it is difficult to assess the degree
of impairment, if any, still remaining at station BI08.
The quality of the invertebrate community declines distinctly between stations BI08 and
the first Rhode Island station, BI09. All seven metrics undergo a negative change between the
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two stations. This trend continues between stations BI09 and BIO 10 (the most downstream
station located in Pawtucket, RI) where there is further degradation in all seven metrics. Major
changes between stations BI08 and the two Rhode Island stations include losses in sensitive EPT
taxa, an increase in hydropsychids, and an increase in the relative abundance of chironomids.
The relative abundance of mayflies decreases from a mean of 24% in the BI08 data set to a mean
of 9% at BI09 and is further reduced to a mean of 2% at BIOIO. This is accompanied by an
increase in the relative abundance of hydropsychids from 67% at BI08 to 79% at BI09 to 89% at
BIOIO.
Ambient water column toxicity during dry-weather sampling was observed only at station
BLK21, the most downstream station in Rhode Island (section 4.5.2). Station BLK21 was
located slightly upstream of BIOIO, and water column toxicity may account for the poor
condition of the invertebrate community at this station. The cause of the toxicity on this test
event was not determined but may be a combination of wastewater input from the Woonsocket
facility and CSO discharges.
Chlorine toxicity from the Woonsocket WWTF discharge may account for some of the
community changes in the more upstream of the two Rhode Island stations. The wet weather
TRC concentration in the 24-hr composite toxicity test sample from this facility was 3700 ppb
during the first-flush event, which is 195 times the EPA 1-hr acute toxicity criterion value. We
have no information on dry-weather TRC from the facility.
The community at BIOIO is very similar in structure to that at BI03. It is dominated by
hydropsychids with a much smaller midge (chironomid) comppnent. Both taxa groups are fairly
pollution-tolerant; the specific taxa found at BIOIO are slightly more tolerant than those at
BI03. TVS is higher here than at BI09 so food availability for collector-filterers may be more
abundant. As at BI03, a combination of water column toxicity and food abundance has probably
exerted a major effect on shaping this community.
During the summer of 1998, as a follow-up to the 1991 macroinvertebrate work,
additional sampling was conducted by the Division of Watershed Management of the
Massachusetts Department of Environmental Protection. Sampling was performed at some of
the same locations along the mainstem of the Blackstone River and at some of the same tributary
locations as well as some additional stations. One station was added above the UBWPAD and
the CSO facility in order to provide information for separating the effects of these two facilities
from the rest of the river system. A second station was located between the UBWPAD and the
CSO. A complete discussion of the sampling stations, strategy, and techniques is contained in
the memorandum, Blackstone River Watershed 1998 Biological Assessment 28 February, 2000,
from John Fiorentino, MADEP. A summary of the more relevant data is included below.
The impetus for this work was to determine the biological health of the benthic
macroinvertebrate community subsequent to the addition of dechlorination facilities at the
UBWPAD and after the 1991 sampling, as well as to provide assessment on some of the smaller
upstream headwater tributaries, and on a couple of the larger downstream tributaries. The
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UBWPAD was required to dechlorinate the effluent from the facility to meet new NPDES permit
limits in 1992. Early data from the BRI study had shown an impaired community downstream of
the effluent discharge. The chlorination and dechlorination is a seasonal process from April-
October, with dechlorination first becoming effective in August 1993.
Results were as follows:
Stations
Total Metric
Score
% Comparison to
Reference Station
Degree of Impairment
Assessed in 1998
BLKOOA
14
33
Moderate
BLK01
6
14
Severe
BLK02
8
19
Severe
BLK07
12
29
Moderate
BLK12A
10
24
Moderate
In comparison to the upstream reference station, which itself showed some impairment,
BLKOOA and BLK01 showed impairment from organic enrichment. Additionally, data from
BLK01 also indicated the continued present of a toxicant (potentially metals, ammonia, chlorine)
by the absence of filter-feeders and the extremely low abundance of invertebrates in general.
Although the UBWPAD had begun dechlorination procedures, the Worcester CSO facility which
discharges above BLK01 through the Mill Brook conduit still regularly discharged chlorinated
effluent with high levels of ammonia. The impact of this discharge, in combination with
stormwater runoff from the headwaters area, which contributed additional material, was still
evident. In early 1999, the Worcester CSO facility was refitted to also provide dechlorination.
Subsequent studies should be conducted to evaluate the instream improvements associated with
the combined removal of chlorine from these two facilities.
At BLK02, the community was still severely impaired as in 1991, and was responding to
the continued organic enrichment and presence of toxicants. This station also receives the
stormwater impact from the headwaters area, including the Worcester CSO facility, as well as the
storm effects on the UBWPAD discharge as discussed in the chapter on water quality. Of note,
is the data from comparison of this station (BLK02) with the upstream station (BLK01) used as a
reference, and the comparison of the data from BLK01 to its upstream station BLKOO. In these
cases, the degree of impairment of BLK02 to BLK01 was considered non-impaired (95%
comparable), and the degree of impairment from BLKOO to BLK01 was considered moderate
(30% comparable). The data indicates that the added impairment from the segment with the
UBWPAD is small in comparison to the impairment which still exists from the segment with the
CSO facility and Mill Brook conduit.
In addition, BLK07 and BLK12A communities showed some improvement since the 1991
survey but still displayed moderate impairment.
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4.7 Dry Weather Data Summary and Conclusions
Three dry weather surveys were completed in July, August and October 1991. Although
the river was not at critical conditions (i.e. low streamflow of 7Q10 and maximum effluent
discharge), flows were close to 7Q2 during the July and August surveys. The October survey
was at a much higher flow, thereby allowing for a comparison of river dynamics under baseline
and high flow conditions. During the 1991 study, the UBWPAD and the Woonsocket WWTF
were each discharging considerably less than permitted flows and were also within the NPDES
permit effluent guidelines.
The interpretation of the ambient chemistry included a system ranking, where individual
point sources, tributaries and headwater loads were separated from individual reach gains, and an
accounting of the two major point sources versus the other sources of pollutants was made by
constituent by survey. Tables 4.25 and 4.26 are averages for the study of the system ranking for
nutrients, TSS and trace metals. These values were determined in the following manner. The
results from the three surveys were averaged for each reach as well as the loads from the WWTFs
and the tributaries. A negative result, or loss, for a reach was counted as zero in the average.
The average loads for the each river reach and tributary, and the UBWPAD and Woonsocket
WWTFs, were totaled. Individual average loads were calculated as a percentage of the total load.
This percentage was used to rank the WWTFs, tributaries and river reaches for these tables:
Example - (Ave load BLK01-02 / Total Ave Load )* 100 = BLK01-02 % of total.
Table 4.27 is a summary of the contributions from the two major point sources and the
other sources by constituent by survey and then as an average for the study. In addition, the
relative importance of the two major point sources were discussed for each constituent for each
survey.
Headwaters
• The loadings from the headwaters, as defined by BLKO1, are small relative to other
sources along the Blackstone River with the exception of chromium and fecal coliform.
UBWPAD
• The flow in the river to which the plant discharges is very low in these upper reaches,
offering little dilution. Therefore, the characteristics of the effluent often determines the
characteristics of the river at this point. The ratio of WWTF flow to stream flow was 3:1
during the July/August low flow surveys and about 1:1 in October.
• Based on a comparison of mass loadings between the UBWPAD and BLK01, the
UBWPAD is clearly the dominant source in these upper reaches relative to nutrients
(orthophosphate 469:1 (UBWPAD:river), nitrate 42:1 and ammonia during periods of no
nitrification at UBWPAD) and to some trace metals (cadmium 31:1, nickel 18:1, and
copper 10:1).
• The UBWPAD is not a determining factor in the upper Blackstone River relative to TSS,
chromium and lead.
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Table 4.25 Average Nutrient and TSS Rankings 1991 Blackstone River Dry Weather Surveys
nh3-n
N03-N
PO4-P
TSS
Ranking
Source
%
Source
%
Source
%
Source
%
1
Woon
67.32
UBWPAD
49.64
UBWPAD
63.18
BLK07-08
15.29
2
BLK01-02
8.28
BLK20-21
10.89
Woon
19.48
BLK12-13
11.01
3
UBWPAD
4.87
Woon
7.90
BLK12-13
2.99
BLK04-06
10.07
4
BLK03-04
4.52
BLK11-12
5.28
BLK11-12
2.65
BLK20-21
9.29
5
BLK20-21
3.01
BLK02-03
3.46
BLK02-03
2.45
BLK06-07
7.94
6
BLK01
2.62
BLK17-18
3.20
BLK08-11
1.82
UBWPAD
7.86
7
BLK18-19
2.49
BLK12-13
2.98
BLK13-17
1.67
BLK08-11
6.27
8
BLK14
1.93
BLK01
2.66
BLKOl
1.40
BLK14
4.89
9
BLK11-12
1.04
BLK19-20
2.58
BLK20-21
1.12
BLK18-19
4.56
10
BLK04-06
1.01
BLK06-07
2.35
BLK06-07
0.86
BLKOl
4.39
11
BLK09
0.65
BLK18-19
2.19
BLK14
0.61
Woon
3.75
12
BLK15
0.48
BLK08-11
1.98
BLK09
0.60
BLK02-03
3.10
13
BLK05
0.46
BLK03-04
1.12
BLK 19-20
0.46
BLK09
2.73
14
BLK12-13
0.35
BLK14
0.90
BLK05
0.29
BLK13-17
2.24
15
BLK02-03
0.35
BLK04-06
0.76
BLK07-08
0.15
BLK15
1.72
16
BLK10
0.25
BLK09
0.62
BLK10
0.13
BLK10
1.44
17
BLK16
0.25
BLK07-08
0.61
BLK15
0.10
BLK05
1.02
18
BLK08-11
0.10
BLK16
0.32
BLK16
0.08
BLK16
0.86
19
BLK15
0.30
BLK03-04
0.81
20
BLK05
0.15
BLKOl-02
0.75
21
BLK10
0.08
-------
Table 4.26 Average Metal Rankings 1991 Blackstone River Dry Weather Surveys
Cd
Cr
Cu
Ni
Pb
Ranking
Source
%
Source
%
Source
°/o
Source
%
Source
%
1
UBWPAD
32.66
BLK07-08
34.21
UBWPAD
27.91
UBWPAD
44.18
BLK04-06
23.78
2
BLK07-08
10.10
BLK08-11
16.18
BLK07-08
13.58
BLK20-21
13.22
BLK06-07
22.22
3
BLK01-02
9.36
UBWPAD
10.66
BLK08-11
13.39
BLK08-11
5.58
BLK12-13
12.96
4
BLK08-11
9.13
BLK01
8.84
BLK04-06
6.54
BLK12-13
5.32
BLK08-11
10.41
5
BLK12-13
8.93
BLK06-07
6.46
BLK20-21
5.80
BLK01-02
4.34
BLK07-08
7.28
6
BLK02-03
8.36
BLK12-13
6.28
Woon
5.04
Woon
4.33
BLK01
3.67
7
BLK04-06
7.97
BLK04-06
4.12
BLK01
4.82
BLK13-17
3.98
UBWPAD
3.01
8
Woon
5.49
Woon
2.48
BLK17-18
4.37
BLK01
3.44
BLK09
2.68
9
BLK17-18
2.48
BLK09
2.38
BLK14
3.84
BLK02-03
2.92
BLK20-21
2.07
10
BLK01
1.77
BLK14
1.91
BLK09
2.78
BLK07-08
2.88
BLK13-17
1.74
11
BLK14
1.14
BLK17-18
1.75
BLK06-07
2.77
BLK14
2.45
BLK02-03
1.58
12
BLK09
0.92
BLK02-03
1.06
BLK02-03
2.72
BLK18-19
1.95
BLK14
1.43
13
BLK20-21
0.80
BLK01-02
0.93
BLK12-13
2.36
BLK04-06
1.90
Woon
1.31
14
BLK10
0.38
BLK10
0.67
BLK10
1.42
BLK19-20
0.62
BLK03-04
1.27
15
BLK05
0.19
BLK20-21
0.58
BLK05
0.83
BLK17-18
0.53
BLK10
1.21
16
BLK15
0.18
BLK05
0.43
BLK15
0.63
BLK10
0.52
BLK11-12
0.91
17
BLK16
0.15
BLK19-20
0.43
BLK16
0.53
BLK09
0.42
BLK05
0.79
18
BLK15
0.23
BLK19-20
0.41
BLK15
0.42
BLK19-20
0.46
19
BLK03-04
0.23
BLK03-04
0.26
BLK05
0.41
BLK15
0.44
20
BLK16
0.16
BLK13-17
0.003
BLK16
0.41
BLK16
0.42
21
BLK06-07
0.17
BLK18-19
0.23
22
BLK01-02
0.15
23
BLK17-18
0.01
-------
Table 4.27 Percent Attributed to the Two Major Point Sources (MPS) versus all Other Sources (OS)
nh3-n
NOj-N
P04-P
TSS
MPS
OS
MPS
OS
MPS
OS
MPS
OS
Survey 1
94.4
5.7
42.6
57.4
78.7
21.3
13.6
86.4
Survey 2
70.1
29.9
83.0
17.0
87.0
13.0
17.3
82.7
Survey 3
54.5
45.5
42.8
57.2
82.2
17.8
7.5
92.5
Study
73.0
27.0
56.1
43.9
82.6
17.4
12.8
87.2
Cd
Cr
Cu
Ni
Pb
MPS
OS
MPS
OS
MPS
OS
MPS
OS
MPS
OS
Survey 1
58.1
41.9
14.6
85.4
55.4
44.6
41.8
58.2
2.7
97.3
Survey 2
65.9
34.1
25.4
74.6
48.2
51.8
87.5
12.5
12.7
87.3
Survey 3
19.8
80.2
6.3
93.7
19.0
81.0
23.3
76.7
3.0
97.0
Study
Average
47.9
52.1
15.4
84.6
40.9
59.1
50.8
49.2
6.1
93.9
MPS - Major Point Sources (UBWPAD and Woonsocket WWTF); OS - Other Sources (Tributaries, Small WWTFs, Nonpoint
Sources)
-------
Woonsocket WWTF
High dilution at the point of Woonsocket's discharge makes it difficult to determine the
relative importance of this discharge based solely on concentration profiles. The ratio of
WWTF flow to stream flow was 1:16 during the July/August surveys and 1:50 in
October.
Based on mass loadings, the Woonsocket treatment plant is clearly the determining factor
in the characteristics of the Rhode Island portion of the river relative to nitrogen
(ammonia loading rate 15:1 (WWTF to river) and nitrate 3:4) and phosphorus
(orthophosphate loading rate 2:1).
Since the river is transporting high levels of metals and solids at this point from upstream
sources, especially during high flow situations, the Woonsocket WWTF effluent is not
the determining factor in the characteristics of the Rhode Island portion of the river
relative to metals and TSS. The ratios of WWTF load to river load were on average less
than 1:5.
Dissolved Oxygen/Nutrients
Comparison with 1988 data shows substantial reduction in instream BOD, levels below
the UBWPAD, with a resulting improvement in DO concentrations in the these reaches.
Large diurnal swings in DO and pH are evident in the impoundments between BWW06
and BWW21. These result from an increased algal productivity (represented by increased
chlorophyll a concentrations). Along the river, the growth of algae is first stimulated by
the increase of nutrients from the UBWPAD, especially phosphorus, and the low
velocities in the impoundments. High phosphorus levels were also recorded from the
Woonsocket treatment plant and in the reaches below its discharge to Slater's Mill Dam.
Even with large diurnal swings, exceedance of DO outside of water quality standards
were evident in either the mainstem or the tributaries. Many more values outside water
quality standards were seen for pH.
Instream nitrification appears to be a determining factor in the levels of oxygen in the
reaches downstream of Woonsocket WWTF.
Fecal Coliform
High levels of fecal coliform bacteria above water quality standards were seen at several
locations along the mainstem and tributaries. Elevated fecal coliform counts in the water
above the UBWPAD result from sources in the city of Worcester. Further downstream,
unknown sources have resulted in high bacterial levels in several dams. Tributaries with
elevated counts included the Branch and Peters rivers.
Chlorinated wastewater and instream residual chlorine from the UBWPAD have reduced
bacteria levels in the river at the next downstream station to near zero.
4-146
-------
Trace Metals
In general, the instream water quality data demonstrate that the sediments and the two
treatment plants are major sources of metals. These sources contribute to metals levels
above water quality standards.
During periods of low flow, the Blackstone River impoundments, except for Rice City
Pond, may act as settling basins for solids and metals from point and nonpoint sources.
These impoundments then become significant sources of these constituents, with
resuspension of deposited material during higher flows. Rice City Pond acts as a source,
even during low flows.
It is not clear, based on the dry weather data, what phenomena is causing the rapid
dissolved metal losses (cadmium, copper and nickel) in the reaches below UBWPAD.
Toxicity
Violations of chronic criteria in water column samples for cadmium, copper and lead
could be seen throughout the mainstem Blackstone River. Violations of acute criteria for
these same metals occurred below UBWPAD and within and below Rice City Pond.
Several tributaries experienced violations of chronic criteria for copper and lead.
No acute or chronic criteria violations occurred for chromium and nickel in the
Blackstone River and its tributaries.
During the low flow study, although the water quality criteria were exceeded for a
number of metals, only one toxic endpoint occurred along the mainstem. These results
have prompted site specific criteria studies for the Blackstone River in Massachusetts,
and underscored the importance of toxicity testing to be performed in conjunction with
metals testing for determination of water quality impacts and issuance of permits to
municipalities and industry.
With regards to sediment toxicity testing, toxicity was only evidenced by the Hyallela
azteca in the Rice City Pond sample. Chironomus tentans survived fairly well in this
sediment (64 and 82% survival in July and August). In July, when metal concentrations
were measured, survival of Hyallela and Chironomus were 70 and 72% in the Fisherville
Dam sediment sample. Higher mortality of one or both species occurred in the samples
from Singing Dam (BSED1), Manville Dam (BSED5), Slater's Mill (BSED7), and
Gilboa and Grey's Pond, the background samples.
Other Sources (OS) vs the Two Major Point Sources (MPS)/NPS Reach Identification
Major Point Sources - The major sources of nutrients to the river were the two point
sources, UBWPAD and Woonsocket (Percentages have been rounded off):
• Ammonia - 73% MPS (68% Woonsocket and 5% UBWPAD)
• Phosphorus - 83% MPS (63% UBWPAD and 20% Woonsocket)
• Nitrate - 74% MPS (50% UBWPAD and 27% including Woonsocket at 8% and
instream nitrification in the reaches below its discharge at 19%).
4-147
-------
Other Sources - The major sources of TSS, chromium and lead to the river were from the
other sources in the river regardless of the flow condition. The reach hot spots are
identified below based on a percent of total load to the river (Percentages have been
rounded off):
TSS - 88% OS (BLK07-08, BLK12-13 and BLK04-06)
Chromium - 87% OS (BLK07-08 and BLK08-11)
Lead - 95% OS (BLK04-06, BLK06-07, BLK12-13 and BLK08-11)
Major Point and Other Sources - The major sources of the three metals, cadmium, copper
and nickel, were from the two major point sources under low flow conditions and other
sources under high flow conditions. The additional sources of metals under high flows
were typically associated with river reaches where sediment resuspension was occurring.
The reach hot spots are identified below based on a percent of total load to the river
(Percentages have been rounded off).
• Cadmium - 52% OS average for the entire study (BLK07-08); Low Flow Survey -
58% MPS; High Flow Survey - 80% OS.
• Copper - 58% OS average for the entire study (BLK07-08); Low Flow Survey -
53% MPS; High Flow Survey - 80% OS.
• Nickel - 52% OS average for the entire study (BLK20-21); Low Flow Survey -
65% MPS; High Flow Survey - 75% OS.
4-148
-------
5.0 DRY WEATHER DISSOLVED OXYGEN MODELING SUMMARY
5.1 General Dissolved Oxygen Model Considerations
QUAL2E is a steady state stream water quality model capable of simulating up to 15
constituents. The model primarily simulates dissolved oxygen (DO) and water quality
parameters that influence DO concentrations. It assumes that the major transport mechanisms
are significant only in the direction of flow. The model permits the input of waste water
discharges, tributary flows, incremental flows and withdrawals. A complete discussion of the
model's capabilities is available in the QUAL2E model documentation (Brown and Barnwell
1987).
The conceptual representation of the river involves a graphic idealization of the prototype
by dividing it into discrete elements in accordance with the modeling objectives. These elements
are defined through mathematical formulations and connected either physically or functionally,
as integral parts of the whole. Thus, a river can be generalized as a string of completely mixed
reactors or computational elements linked sequentially to one another. A sequential group of
these elements can be defined as reaches in which the computational elements have the same
hydraulic characteristics, stream slope, channel cross section, roughness and biological and
chemical rate constants (Brown and Barnwell 1987).
The steady state equations in QUAL2E allow the input of the hydraulic characteristics of
the river reaches as empirical equations:
u = aQb (5.1)
D = cQd (5.2)
where, u = stream velocity (ft/sec); Q = stream flow (cfs); D = stream depth (ft); and a, b, c and
d are empirical constants. Alternatively, given the relationship between depth and flow,
Manning's equation may be used to define the stream velocity.
The DO balance in a stream system is a function of the internal sources and sinks and is
represented by the differential equation shown below:
K,(0'-0) + (a3p-a4p)A - KJL - KJD - - agP2W2 (5 3)
where, O = the concentration of dissolved oxygen (mg/L); O* = the saturation concentration of
dissolved oxygen at the local temperature and pressure (mg/L); a3 = the rate of oxygen
production per unit of algal photosynthesis (mg-O/mg-A); a4 = the rate of oxygen uptake per unit
of algae respired (mg-O/mg-A); a5 = the rate of oxygen uptake per unit of ammonia nitrogen
5-1
-------
oxidation (mg-O/mg-N); a6 = the rate of oxygen uptake per unit of nitrite nitrogen oxidation
(mg-O/mg-N); fj. = algal growth rate, temperature dependent (day1); p = algal respiration rate,
temperature dependent (day*1); A = algal biomass concentration (mg-A/L); L = concentration of
ultimate carbonaceous BOD (mg/L); Kj= carbonaceous BOD deoxygenation rate, temperature
dependent (day*1); K2 = the reaeration rate, temperature dependent (day1); IC,= sediment oxygen
demand, temperature dependent (g-O/tf-day); p, = ammonia oxidation rate coefficient,
temperature dependent (day1); P2 = nitrite oxidation rate coefficient, temperature dependent
(day'1); N, = ammonia nitrogen concentration (mg-N/L); and N2 = nitrite nitrogen concentration
(mg-N/L).
The growth and decay kinetics of algae are complex and involve many parameters in the
mathematical formulations. Chlorophyll a, a component of algae, is used as an indicator to
simulate algal kinetics. The algal biomass is then estimated based on the ratio of chlorophyll a to
algal biomass. The change of algal biomass is represented in the model by:
dfl . » °i j»
— = uA - pA - — A
dt D
(5.4)
where o, = the local settling rate (ft/day). The algal settling rates can be input by reach.
The algal growth rate, |i, is a function of light, nitrogen, and phosphorus. These are
represented by Monod functions and each may limit growth. QUAL2E has three options
available to model The option used is presented below:
M = M-max(FL)(FN)(FP) (5.5)
where p.max= maximum specific growth rate (day1); FL = algal growth limitation factor for light;
FN = algal growth limitation factor for nitrogen; and FP = algal growth limitation factor for
phosphorus.
The algal respiration rate, p, is defined by a single parameter in the model and is constant
5.2 Blackstone River Model Representation
The Blackstone River was divided into 25 reaches as shown in Table 5.1. Computational
elements were 0.20 miles in length. The division of reaches represent contiguous sections of the
river with similar hydraulic or chemical characteristics. Reach divisions are consistent with
previous modeling efforts. Figure 5.1 is a representation of the river in the model. The location
or distances of strategic points from the mouth of the river were derived from the Geographical
Information System (GIS) data submitted to URI by MADEP. The locations of the five largest
5-2
-------
Table 5.1 Reach Locations in the Blackstone River Model
Reach
Upstream Boundary
Downstream Boundary
River
Mile
Reach
Length
1
Millbury St, Worcester,
MA
McCracken Rd, Millbuiy,
MA
45.8
1.8
2
McCracken Rd, Millbury,
MA
Riverlin St, Millbury, MA
44.0
2.6
3
Riverlin St, Millbury, MA
Millbury WWTF, Millbury,
MA
41.4
0.6
4
Millbury WWTF, Millbury,
MA
Singing Dam, Blackstone
St, Sutton, MA
40.8
1.0
5
Singing Dam, Blackstone
St, Sutton, MA
Pleasant St, Grafton, MA
39.8
1.6
6
Pleasant St, Grafton, MA
Quinsigamond River,
Grafton, MA
38.2
1.4
7
Quinsigamond River,
Grafton, MA
Grafton WWTF, Grafton,
MA
36.8
1.4
8
Grafton WWTF, Grafton,
MA
Riverdale St, Northbridge,
MA
35.4
3.4
9
Riverdale St, Northbridge,
MA
Northbridge WWTF,
Northbridge, MA
32.0
2.8
10
Northbridge WWTF,
Northbridge, MA
Rice City Pond Dam,
Hartford St, Uxbridge, MA
29.2
1.4
11
Rice City Pond Dam,
Hartford St, Uxbridge, MA
Rt.16, Mendon St,
Uxbridge, MA
27.8
1.8
12
Rt.16, Mendon St,
Uxbridge, MA
Confluence with Mumford
River, Uxbridge, MA.
26.0
0.4
13
Confluence with Mumford
River, Uxbridge, MA
Rt.122 (bridge), Uxbridge,
MA
25.6
2.4
14
Rt.122 (bridge), Uxbridge,
MA
Off Rt.122 (near USGS),
Millville, MA
23.2
4.0
5-3
-------
Table 5.1 Reach Locations in the Blackstone River Model (Continued)
Reach
Upstream Boundary
Downstream Boundary
River
Mile
Reach
Length
15
Off Rt. 122 (nearUSGS),
Millville, MA
Main St, Blackstone, MA
19.2
1.0
16
Main St, Blackstone, MA
Confluence of Branch
River, Smithfield, RI
18.2
0.8
17
Confluence of Branch
River, Smithfield, RI
St. Paul St, Blackstone, MA
17.4
0.8
18
St. Paul St, Blackstone,
MA
Thundermist Dam,
Woonsocket, RI
16.6
2.2
19
Thundermist Dam,
Woonsocket, RI
Hamlet Ave Dam,
Woonsocket, RI
14.4
1.6
20
Hamlet Ave Dam,
Woonsocket, RI
Manville Dam,
Cumberland, RI
12.8
2.8
21
Manville Dam,
Cumberland, RI
Albion Dam, Cumberland,
RI
10.0
1.8
22
Albion Dam, Cumberland,
RI
Washington Highway,
Cumberland, RI
8.2
1.4
23
Washington Highway,
Cumberland, RI
Lonsdale Ave, Pawtucket,
RI
6.8
3.0
24
Lonsdale Ave, Pawtucket,
RI
Broad St (bridge),
Pawtucket, RI
3.8
1.8
25
Broad St (bridge),
Pawtucket, RI
Exchange St, Pawtucket, RI
2.0
2.0
5-4
-------
Figure 5.1 Network of Computational Elements and Reaches - Massachusetts
1
BLK01
1
UBWPAD
2
3
4
5
6
7
8
9
10
BLK02
2
11
12
13
14
15
16
17
18
19
20
21
22
23
BLK03
3
24
25
26
MUXBURY WWTF
4
27
28
29
30
31
BLK04
5
32
33
34
35
36
37
38
39
6
40
41
42
43
44
45
46
47
48
49
SO
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
QUINSIGAMOND RIVER
BLK06
GRAFTON WWTF
BLK07
NORTHB RIDGE WWTF
10
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
BLK08
11
12
MUMFORD RIVER
13
WEST RIVER
BLKI1
UXB RIDGE WWTF
14
BLK12
15
State Line MA/RI
-------
i
Figure 5.1 Network of Computational Elements and Reaches - Rhode Island (continued)
139
180
BLX18
220
140
16
181
221
141
182
222
142
183
223
143
BRANCH RIVER
184
21
224
144
185
225
25
145
17
186
226
146
187
227
147
BLK13
188
228
148
189
BLK19
229
BLK21
149
190
End of River
ISO
191
151
192
22
152
18
193
153
194
154
195
155
196
156
197
157
198
158
199
159
200
160
201
161
19
202
162
203
23
163
MILL RIVER
204
164
PETERS RIVER
205
•
165
206
166
BLK17
207
167
WOONSOCKET WWTF
208
168
209
169
210
170
211
BLK20
171
212
172
213
173
214
174
20
215
24
175
216
176
217
177
218
178
219
179
5-6
-------
waste water treatment facilities (WWTF's) are given in Table 5.2.
Drainage areas for each of these reaches and tributaries were determined using both
available USGS estimates and planimeter computations from USGS topographic maps
(Table 5.3).
Nineteen dams were defined in the model. The location and heights of these dams are
shown in Table 5.4.
The system hydraulic characteristics, equations 5.1 and 5.2, were defined in earlier efforts
for the MA section of the river (Reaches 1-14) by MADEQE (1983), and for the RI section of the
river (Reaches 18-25) by Wright (1987) and Ecology and Environment (1988).
Time of travel studies are not available for the river sections at the state line of MA and
RI between the Route 122 bridge on the Blackstone River, Millville, MA and Main Street in RI
(Reach 15). Based on the USGS topographic maps and reconnaissance of the stream, the
hydraulic characteristics of Reach 15 were assumed to be similar to Reach 16 (Main Street to
Branch River).
A complete list of flow coefficients for the reaches is provided in Table 5.5.
5.3 Flow Profile Development and Validation
The average daily flows for the three permanent USGS gaging stations were calculated
from the recorded hourly flow data. The* locations of these gaging stations were as follows:
Blackstone River at Woonsocket, RI (BLK17); Quinsigamond River at North Grafton, MA; and
Branch River at Forestdale, RI (BLK14). Additional flows were measured at four temporary
locations along the main stem of the river. These are located at US Steel (BLK01), Northbridge
(BLK07), Millville (BLK12) and Lonsdale (BLK20).
Point source discharges were received from the environmental state agencies.
Flow profiles were developed for the three surveys using flow data from the three
permanent USGS gaging stations and the point sources. The resulting flow profiles were verified
with the flow data collected for the temporary stations at BLK01, BLK07, BLK12 and BLK20.
A summary of all measured flows are presented in Table 5.6. The first step in developing the
flow profile was the calculation of the incremental flow factor, q (cfs/mi2).
_ (Qq+@B + QfMTF^
DAw-(DAq+DAb)
(5.6)
-------
Table 5.2 Wastewater Discharges Defined in the Blackstone River Model
Point Sources
River Mile
Reach
Reach Element
UBWPAD
44.4
1
7
Millbury WWTF
40.6
4
1
Grafton WWTF
35.4
8
1
Northbridge WWTF
29.2
10
1
Uxbridge WWTF
22.0
14
7
Woonsocket WWTF
12.4
20
2
WWTF = Waste Water Treatment Facility
5-8
-------
Table 5.3 Reach Drainage Areas (mi2) Defined in the Blackstone River Model
Reach
Tributary
Blackstone
Cumulative Drainage
Drainage Area
Drainage Area
Area
Headwaters
75.9
75.9
1
6.2
82.1
2
8.9
91.0
3
6.4
97.4
4
1.4
98.8
5
15.7
114.5
6
Quinsigamond - 34.2
0.4
149.1
7
1.4
150.5
8
5.0
155.5
9
5.4
160.9
10
0.7
161.6
11
1.2
162.8
12
Mumford - 68.5 West-37.4
0.5
269.2
13
0.6
269.8
14
7.2
277.0
15
1.8
278.8
16
Branch - 93.1
0.04
371.9
17
4.5
376.4
18
4.5
380.9
19
Mill - 23.0 Peters - 11.6
15.6
431.1
20
12.2
443.3
21
3.6
446.9
22
6.7
453.6
23
3.3
456.9
24
1.3
458.2
25
22.0
480.2
5-9
-------
Table 5.4 Dam Locations and Heights in the Blackstone River Model
No.
Name
River
Mile
Reach
Reach
Element
Below
Dam
Height
(ft)
Source
1
McCracken Rd
43.9
2
2
4
2
2
Millbury Electric
41.0
3
3
4
3
3
Singing Dam
39.8
5
2
14
2
4
Wilkinsonville
39.2
5
4
4
3
5
Saundersville
38.7
5
7
4
3
6
Fisherville
36.5
7
3
18
2
7
Famumsville
35.6
7
7
4
3
8
Riverdale
31.9
9
2
10
2
9
Rice City Pond
27.8
11
2
10
2
10
Blackstone
16.5
18
2
4
3
11
Thundermist
14.3
19
2
18
2
12
Hamlet Avenue
12.8
20
2
10
2
13
Manville
9.9
21
2
17
2
14
Albion
8.2
22
2
6
2
15
Ashton
6.8
23
2
4
3
16
Lonsdale
4.1
23
15
4
1
17
Central Falls
2.0
25
2
4
1
18
Pawtucket
0.8
25
7
4
1
19
Slaters Mill
0.0
25
10
10
1
Source: 1 = United States Army Corps of Engineers (1994); 2 = Personal
communication (MADEP 1992); 3 = Field Survey
5-10
-------
Table 5.5 Reach Hydraulic Characteristics for the Blackstone River QUAL2E Model
Reach
a
b
c
d
Source
1
0.073
0.494
0.530
0.221
1
2
0.250
0.320
0.822
0.109
1
3
0.082
0.308
0.790
0.280
1
4
0.072
0.334
4.000
0.000
1
5
0.161
0.356
0.280
0.448
1
6
0.011
0.827
3.370
0.080
1
7
0.063
0.447
0.030
0.963
1
8
0.058
0.574
0.733
0.295
1
9
0.009
0.736
0.537
0.329
1
10
0.010
0.713
0.411
0.413
1
11
0.074
0.335
0.509
0.331
1
12
0.625
0.155
0.064
0.761
1
13
0.771
0.108
0.179
0.528
1
14
0.537
0.127
0.448
0.379
1
15
0.012
0.581
1.452
0.400
2,3
16
0.012
0.581
1.452
0.400
2,3
17
0.012
0.581
0.854
0.400
2,3
18
0.012
0.581
1.554
0.400
2,3
19
0.071
0.523
0.351
0.400
2,3
20
0.010
0.581
1.037
0.400
2,3
21
0.012
0.581
0.644
0.400
2,3
22
0.007
0.710
0.642
0.400
2,3
23
0.008
0.870
0.638
0.400
2,3
24
0.008
0.701
0.638
0.400
2,3
25
0.009
0.746
0.638
0.400
2,3
a, b = Velocity coefficients; c, d = Depth coefficients; 1 = MADEQE (1983); 2 =
Wright (1987) a, b only; 3 = Ecology and Environment (1988) c, d only
5-11
-------
Table 5.6 Summary of Flows (cfs) for the 1991 Dry Weather Surveys
Gaging Station
Flow
7/10-11/91
Flow
8/14-15/91
Flow
10/2-3/91
BR - Woonsocket8
137
152
635.5
Quinsigamond River*
7.3
8.6
52
Branch River"
26.0
30.5
104
UBWPAD
38.4
44.6
64.7
Millbury WWTF
0.6
0.8
1.3
Grafton WWTF
1.6
1.6
1.6
Northbridge WWTF
1.8
1.2
1.8
Uxbridge WWTF
3.875
3.875
3.875
Woonsocket WWTF
8.3
11.5
13.4
BR = Blackstone River; " = USGS permanent gaging station
5-12
-------
where Qw = flow at the Woonsocket USGS gage, RI (BLK17); Qq = flow at the Quinsigamond
River USGS gage in North Grafton, MA (upstream BLK05); QB = flow at the Branch River
USGS gage in Forestdale, RI (BLK14); Qwwtf - discharges from all waste water discharges
above the Woonsocket WWTF, (cfs); DAW = drainage area at the USGS Woonsocket gage (416
mi2); DAq = drainage area at the USGS Quinsigamond gage (25.6 mi2); and DAB= drainage area
at the USGS Branch River gage (91.2 mi2).
Once calculated, q, was multiplied by drainage area to develop the tributary and reach
flows. For example, the Quinsigamond River flow was equal to the USGS flow plus the
drainage area below the gage (8.6 mi2) times q.
The reach inflows were determined by multiplying drainage area and q.
The headwater flow for the model was determined by:
Qhw = 0.10 (Qw) (5.7)
where Qhw = flow at headwaters (BLK.01) (cfs). This relationship was developed between
observed flows at Woonsocket (BLK17) and U.S. Steel (BLK01) during the 1991 surveys. The
ratio of flows between BLK01 and BLK17 was 0.10,0.10 and 0.09 for the three surveys.
The incremental inflow, q, was estimated as 0.197,0.210 and 1.510 cfs/mi2 for the three
surveys. The flow profiles are presented in Figure 5.2 and predicted flows are given in Tables
5.7 and 5.8.
The measured flows for the four temporary stations are also plotted with the flow profiles
in Figures 5.3 to 5.5. Excellent accordance between model predictions and observed flows exists
for the 3 stations upstream of Woonsocket (BLK17) for all three surveys.
At Lonsdale (BLK20), the predicted flows for the two summer surveys were lower than
the observed values. In a previous study, Ries (1990) provided long-term average monthly flows
at Woonsocket and Lonsdale. This data provided an average ratio of 1.06 between the two
stations, with values ranging from 1.03 to 1.09. The ratio of flows between Lonsdale and
Woonsocket for the July, August and October surveys was calculated as 1.38, 1.36 and 1.06. The
two high ratios for the July and August surveys are explained with the hourly flow values at the
USGS Woonsocket gaging station for the July and August surveys that indicate, for the early part
of the surveys, the river was recovering from previous rain events (Figures 5.6 to 5.7). The
Lonsdale flows were measured once by the USGS between 0800 and 0900 hours (Hartman
1992). Since the travel time between Lonsdale and Woonsocket is between 8 to 12 hrs, it is
expected that the flow measurement was taken during the falling limb of the hydrograph. Using
q derived from equation 5.6, flows were predicted at Lonsdale. The ratio of these flows to the
Woonsocket flows was 1.06. A comparison was made between nine flow measurements by Ries
(1990) and model predictions at Lonsdale with excellent results (Figure 5.8). Thus, the use of a
5-13
-------
n-s
Flow (cfs)
UBWPAD
MILLBURY WWTF
QUINSIGAMOND RIVER
GRAFTON WWTF
NORTHBRIDGE WWTF
MUMFORD RIVER
WEST RIVER
UXBRIDGE WWTF
BRANCH RIVER
MILL RIVER
PETERS RIVER
WOONSOCKET WWTF
LI SLATER'S MILL
-------
Table 5.7 Summary of Estimated Blackstone River Flows at each Water
Quality Station for the 1991 Dry Weather Surveys in cfs
Station
7/10-11/91
8/14-15/91
10/2-3/91
BLK01
13.8
14.3
71.2
BLK02
53.4
60.2
145
BLK03
55.7
62.7
163
BLK04
57.4
64.7
173
BLK06
69.3
78.2
260
BLK07
72.2
81.2
271
BLK08
75.1
83.5
281
BLK11
96.5
106
445
BLK12
102
112
460
BLK13
129
144
576
BLK17
140
156
659
BLK18
151
170
691
BLK19
152
171
698
BLK20
154
172
711
BLK21
158
177
746
Table 5.8 Summary of Estimated Blackstone River Tributary Flows at each
Water Quality Station for the 1991 Dry Weather Surveys in cfs
Station
7/10-11/91
8/14-15/91
10/2-3/91
BLK05
8.99
10.4
65
BLK09
13.5
14.4
103
BLK10
7.37
7.85
56.5
BLK14
26.4
30.9
107
BLK15
4.53
4.83
34.7
BLK16
2.29
2.44
17.5
Note: These flows were used as input to the QUAL2E Model.
5-15
-------
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-------
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Figure 5.5 Flow Profile Validation for October 2 -3,1991
-------
<£UU
150
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-
50
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Woonsocket Gage Flow
-
Average Flow 137 cfs
• Time of Measurement at Lonsdale
0
10 11 12
July
Figure 5.6 Flows from the Woonsocket USGS Gage, July 10 -11,1991
-------
200
150
Survey II - August 14-15,1991
100
— Woonsocket Gage Flow
• • Average Flow 152 cfs
• Time of Measurement at Lonsdale
14
15
16
August
Figure 5.7 Flows from the Woonsocket USGS Gage, August 14 - 15,1991
-------
2000
Lonsdale Ave
Predicted flows = -25.6 +1.1 Observed flows
1500 -
1000 -
&
500 -
: 45 degree line
Dotted line is the regression of data with
95% confidence intervals
I i
500
1000
Observed Flows (cfs)
1500
2000
Figure 5.8 Observed (Ries 1990) and Predicted Flows at Lonsdale Avenue, Lonsdale, RI
-------
single q value for the surveys was adopted.
The flow profiles were also evaluated through the simulation of chloride. Chloride is a
conservative constituent which experiences no losses due to biological, physical, or chemical
actions. Dilution is the only mechanism that affects its concentration and, therefore, modeling
success supports the flow profile.
Since the Branch and Mumford had similar chloride concentrations, as well as the lowest
amongst the tributaries, their mean concentration from the calibration surveys of July and
October was adopted for all reach inflows. The headwater concentration of chloride was set to
BLK01. Point source contributions were taken from the 1991 survey data or MADEP records
(Table 5.9).
Figures 5.9 to 5.11 compare the observed chloride concentrations to the predictions for
the three surveys. In general, for July and October, the model predictions were excellent. For the
validation survey in August, chloride simulations were not as successful, possibly due to high
variations in the UBWPAD WWTF discharge over the 5 days leading to the survey. Figure 5.12
shows the chloride profiles for the highest and lowest chloride effluent concentrations from
UBWPAD. Based on the modeling efforts and its comparison to the temporary flow stations and
the chloride simulations, the flow profiles are considered calibrated and verified.
5.4 Dissolved Oxygen Model Calibration
The QUAL2E application to the Blackstone River was calibrated for the July and October
surveys, and validated with the August survey. The first step in model calibration considered
oxygen transfer from reaeration (Kj). This was followed by the evaluation of oxygen depletion
due to CBOD (KJ. The third step was the oxygen uptake due to nitrification (p, and Px).
Following nitrification, sediment oxygen demand (SOD or K«) was evaluated.
In systems without significant productivity, model calibration is finalized with the
addition of the SOD rates. For the Blackstone River, productivity is a major concern, and algal
simulations are evaluated in detail to complete the DO balance. Algal simulations are verified by
comparing model prediction to observation for chlorophyll a, dissolved orthophosphate and
dissolved nitrate.
The final evaluation of model calibration was performed by comparing the spatial
variations of the average DO values for all river locations, followed by a check of the temporal or
daily oxygen profiles at each station to address the impact of productivity.
5.4.1 General Considerations
5-22
-------
Table 5.9 Chloride Concentrations (mg/L) of Point Sources and Tributaries in the Blackstone River Model
Source
Observed Concentrations
July 10-11,1991
August 14 - 15,1991
October 2-3,1991
Mean
Maximum
Minimum
Mean
Maximum
Minimum
Mean
Maximum
Minimum
Headwater
114
114
114
107
116
106
58.7
60.0
57.0
UBWPAD
91.2
96.0
88.0
89.8
132
62.0
110
141
73.0
* Millbuiy WWTF
282
282
282
Quinsigamond River
68.1
72.5
65.0
71.0
77.6
64.8
54.4
70.0
. 47.0
* Grafton WWTF
102
102
102
* Northbridge WWTF
45.0
45.0
45.0
Mumford River
20.0
22.0
19.0
18.0
21.6
10.0
14.9
14.5
13.0
West River
43.0
48.0
35.0
44.3
49.2
40.8
27.4
29.0
26.0
* Uxbridge WWTF
102
102
102
Branch River
21.0
24.0
20.0
28.1
30.0
26.0
13.1
14.0
12.0
Mill River
24.0
24.0
23.9
27.2
28.2
25.2
27.7
31.0
27.5
Peters River
37.0
48.0
30.0
36.2
40.0
32.4
28.9
29.0
25.5
Woonsocket WWTF
128
154
100
231
290
175
281
440
191
* - MADEQE (1983); Sampling at UBWPAD & Woonsocket WWTF occurred for 5 days prior to survey dates
-------
1 i I I s IM 5 Is I s
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250
1 2 3 4 6 7 8 11 12 13 17 18 19 20 21
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150
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50 45 40 35 30 25 20 15 10
River Miles
Figure 5.9 Chloride Simulation for July 10-11, 1991
-------
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Sensitivity Analysis to the UBWPAD Discharge
150 t 89.8 mg/L (average)
132 mg/L (high)
T ^ 62 mg/L (low)
1001 rjL&4—I V
° , .1—
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i i i i i i i i i—1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 * 1 1 1 * ¦ 1 ¦ • 1 ¦ ¦ ' i ' ¦ ¦ ¦ ' ' ¦ ¦ ¦ ¦ i ¦ i
50 45 40 35 30 25 20 15 10 5 0
River Miles
Figure 5.12 Impact of Maximum and Minimum UBWPAD Chloride Concentrations for
August 14 -15, 1991
-------
All samples at UBWPAD were taken at the point of discharge into the concrete culvert,
which carries its wastewater approximately 0.4 miles before merging with the Blackstone River.
This channel is approximately 12 feet wide and appears to range between 2-4 feet deep. The
treatment that occurs in this channel is not known. The model has not taken into consideration
any treatment in the channel and has assumed that the discharge from the UBWPAD is directly
into the Blackstone River. This could be the reason adjustments to the UBWPAD had to be
made. In all cases a lower value was required. A project is now underway to evaluate the
treatment provided by the discharge channel. This is part of the research project funded by the
U.S. Army Corps of Engineers.
Initial model runs used the average or minimum concentration as inputs for the
UBWPAD and Woonsocket WWTF. If the minimum and average observations over-predicted
the concentration at BLK02, the concentrations were estimated for UBWPAD based on a mass
balance, using the observed concentrations and flows from BLK01 and BLK02 and the observed
flow at the UBWPAD. In the case of orthophosphate a value to best fit the values for the
upstream Blackstone (BLK02-BLK12) for the calibration runs was determined (84% of the mass
balance). Model runs with these concentrations were made for comparison with the mass
balance concentrations and the average and minimum observations from the facility. In all cases,
when this step was taken, the estimated concentration from the UBWPAD was less than the
minimum value observed in its discharge.
Woonsocket WWTFs average concentrations were used in all runs.
5.4.2 Incremental Inflow Concentrations
Based on the chloride simulations, the average concentrations of the Branch and the
Mumford Rivers for the July and October surveys were adopted to represent background
conditions for dissolved ammonia, nitrate and orthophosphate and were input for all surveys as
0.05 mg/L, 0.18 mg/L and 0.06 mg/L, respectively. DO concentrations for incremental inflows
were input at 75% of saturation, based on a previous DO modeling effort (Wright et al., 1985).
BOD, was set to zero, since the Branch and Mumford Rivers had concentrations for July and
October that were below the detection limit.
5.4.3 Atmospheric Reaeration Rate (K2)
The model has eight different options for calculating K2. Six of the options are based on
empirical relationships for specific conditions of depth and velocity. The range of velocities and
depths of the Blackstone River were compared to the range of values specified for each
reaeration equation in Bowie et al., (1985). For the three observed flow conditions, the equations
by Owens, Edwards and Gibbs (1964), O'Connor and Dobbins (1958) and Tsivoglou and Neal
(1972) were evaluated for the Blackstone River. This evaluation continued during the calibration
of the algal component of the model, leading to the final conclusion that the equation in
O'Connor and Dobbins (1958) was the most appropriate for use throughout the river.
5-28
-------
All the dams along the Blackstone River have been modeled as run of the river Hams
QUAL2E uses the relationship developed by Butts and Evans (1983) to simulate reaeration from
dams. All dams have been modeled as sharp crested weirs with moderate water quality. The
reaeration from the dams contributes towards maintaining DO concentrations in die river near the
DO saturation value. A further discussion on reaeration in this river will be addressed in the
conclusion of the model calibration.
5.4.4 BODj Simulations
The slope of the semi-log plot of BODs (lbs/day) and travel times is the rate of BOD
removal (KJ. For the majority of reaches, K,, could not be calculated, since a net increase of
BODj mass was indicated, instead of a net decrease due to BOD} decay. It should be noted that
BOD5 concentrations in the river were very small, typically ranging between 1-2 mg/L (BOD5
detection limit is 1.0 mg/L). Thus, a K,, of 0.10 day'1 base e at 20° C was used in all reaches of
the Blackstone River to represent a minimum decay rate in a stream system (Wright and
McDonnell 1979).
There were 24 hour composites taken at each discharge for the 5 consecutive days before
the July and August surveys and 8 consecutive days before the October survey. Figures 5.13 to
5.15 show the following model runs:
1. July 10-11,1991 -
2. October 2-3, 1991 -
3. August 14-15,1991
UBWPAD average and Woonsocket average
UBWPAD minimum and Woonsocket average.
UBWPAD average and Woonsocket average
UBWPAD minimum and Woonsocket average.
UBWPAD average and Woonsocket average
UBWPAD minimum and Woonsocket average
UBWPAD mass balance value and Woonsocket average
UBWPAD BOD,
Month
Average
Value
Minimum
Value
Maximum
Value
Model
Input
Comment on Model Input
July
3.60
2.00
5.00
2.00
Minimum Observation
October
3.07
1.73
4.70
1.73
Minimum Observation
August
4.48
3.75
5.70
2.30
Calculated by Mass Balance
5-29
-------
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UBWPAD Minimum, Woonsocket WWTF Average
UBWPAD Average, Woonsocket WWTF Average
— r •
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Figure 5.13 BODs Simulations for July 10 -11,1991
-------
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10 - Survey III - October 2 - 3,1991
o Observed with 95% confidence bars
UBWPAD Average, Woonsocket WWTF Average
UBWPAD Minimum, Woonsocket WWTF Average
I I I I—l—l—J—I I I I I I 11 i T" ¦ i ¦ V i i , A i i +¦ I i ¦ ¦ i l
50 45 40 35 30 25 20 15 10 5 0
River Miles
Figure 5.14 BOD, Simulations for October 2-3,1991
-------
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11
12 13 17 18 19 20 21
o Observed with 95% confidence bars
• • • • UBWPAD Average, Woonsocket WWTF Average
UBWPAD Minimum, Woonsocket WWTF Average
UBWPAD Mass Balance Value, Woonsocket WWTF Average
1 1 i i a i i i ... 11 i . .
50 45 40 35 30 25 20 15 10
River Miles
Figure 5.15 BOD, Simulations for August 14 -15,1991
/
-------
Woonsocket WWTF B0D5
Month
Average
Value
Minimum
Value
Maximum
Value
Model
Input
Comment on Model Input
July
5.75
3.70
7.60
5.75
Average Observation
October
13.8
7.65
20.0
13.8
Average Observation
August
9.72
6.15
14.4
9.72
Average Observation
BODj Summary: Average concentrations were run for all tributaries and the headwaters
(Table 5.10) for July and October. Average observations from UBWPAD's discharge into the
channel resulted in over-predictions of BOD5 at BLK02 (the first station monitored on the
Blackstone downstream of the discharge channel's confluence) for all three surveys. Minimum
observations at UBWPAD for July and October work well in providing a match of prediction to
observation at this station. In July, the model predictions begin to under predict the average
observations at BLK07 (at the point where algae growth increases). In October, the model
predictions are within the 95% confidence limits throughout the river. In August, the minimum
value from UBWPAD (3.75 mg/L) results in a high prediction of the average at BLK02 through
BLK06, however, all model values are within the 95 % confidence limits of the observations,
with minor exceptions in the lower reaches in Rhode Island. A value calculated by a mass
balance around BLK02 gave 2.3 mg/L at the discharge. The model run using the mass balance
value is shown for comparison, and it provided an excellent fit for stations 3LK03 through
BLK06. In all cases, the minimum observation at UBWPAD provided model predictions closer
to the average observations. Further study is recommended on the discharge channel to
determine its impact on the BODs concentrations that is discharged to the Blackstone River.
A major difference between the surveys is the variation of algae productivity. Algae
biomass, as it relates to chlorophyll a concentrations, is high in July and low in October. Since
the BODs samples were unfiltered, algae would increase the BOD5 determined in the laboratory
through respiration. In retrospect, filtered and unfiltered BODs samples should have been
analyzed.
The value of K, used for correction of BOD5 to ultimate CBOD was 0.25 day"1 base e.
This is approximately the default value in QUAL2E (0.23). Further discussion on this variable is
made later in this chapter. Figure 5.16 illustrates the change in the DO profile due to the
computed and uniform decay rates (Kj = 0.1 day"1). The low BOD3 concentrations and the low
Kj cause a minimal impact to instream DO depletion due to CBOD.
5.4.5 Ammonia as Nitrogen
The rate coefficients, B, and fi2, are used to represent the conversion of ammonia to nitrite
and nitrite to nitrate, respectively. Similar to CBOD deoxygenation rates, the ammonia loadings
5-33
-------
Table 5.10 BOD5 Concentrations (mg/L) of Point Sources and Tributaries in the Blackstone River QUAL2E Model
Source
Observed Concentrations
July 10-11,1991
August 14 -15,1991
October 2 - 3, 1991
Mean
Maximum
Minimum
Mean
Maximum
Minimum
Mean
Maximum
Minimum
Head water
ND
1.40
ND
1.61
2.80
ND
1.25
1.60
ND
UBWPAD
3.60
5.00
2.00
4.50
5.70
3.80
3.07
4.70
1.73
* Millbuiy WWTF
44.0
22.0
30.0
Quinsigamond River
ND
ND
ND
ND
1.95
ND
ND
1.20
ND
* Grafton WWTF
9.00
3.50
ND
* Northbridge WWTF
6.20
ND
6.20
Mumford River
ND
1.00
ND
1.09
1.75
ND
ND
1.40
ND
West River
ND
1.00
ND
1.05
2.10
ND
ND
1.80
ND
* Uxbridge WWTF
5.00
5.00
5.00
Branch River
ND
1.25
ND
1.39
2.10
ND
ND
1.35
ND
Mill River
1.00
1.50
ND
1.78
2.90
ND
ND
1.20
ND
Peters River
ND
1.60
ND
1.18
1.55
ND
ND
1.20
ND
Woonsocket WWTF
5.75
7.60
3.70
9.70
14.4
6.15
13.8
20.0
7.65
* = DMR Data 1991; Sampling at UBWPAD & Woonsocket WWTF occurred for 5 days prior to survey dates;
ND = Below the detection limit of 1.00 mg/L
-------
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: DO Saturation
8
11
12 13 17 18 19 20 21
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4 t DO Criteria
2
Reaearation Only
Reaeration & constant l^ of 0.1/ day
.... Reaeration & computed
i i i
i i i i i i i
50 45 40 35 30 25 20
River Miles
15
10
Figure 5.16 Dissolved Oxygen Simulations for July 10-11,1991 with Reaeration and CBOD
-------
were plotted against time of travel on semi-log plots for the summer survey in July. The slope of
the loadings is established as B,. Bj was estimated as twice the value of B„ as suggested in
QUAL2E.
Downstream of UBWPAD (BLK02), a gradual decrease of dissolved ammonia
concentrations to BLK08 from 0.36 to 0.11 mg/L permits a calculation of fl,. Also levels of
dissolved ammonia increase to 1.16 mg/L immediately downstream of Woonsocket WWTF
(BLK.18), rapidly decreasing to a value of 0.31 mg/L. For the remaining reaches, dissolved
ammonia concentrations are close to the detection limit of 0.05 mg/L, resulting in net increases
of dissolved ammonia in some reaches. A decision was made to maintain B, values within the
QUAL2E specified values of 0.1 to 1.0 day'1 base e at 20 °C. Calculated values less than the
lower limit would be input as 0.10 day'1 base e at 20 °C, while values greater than the upper limit
would be input as 1.0 day"1 base e at 20 °C.
Table 5.11 is a summary of the ammonia concentrations observed for the tributaries,
headwater and WWTF's. Average values for each survey are used as model input. Ammonia
and nitrate concentrations of 5 and 3 mg/L are used for Millbury, Northbridge, Uxbridge and
Grafton WWTF's. These values represent typical concentrations from secondary treatment
facilities (Thomann and Mueller 1987).
There were 24 hour composites taken at each discharge for the 5 consecutive days before
the July and August surveys and 8 consecutive days before the October survey. Figures 5.17 to
5.19 show the following runs.
1. July 10-11,1991 - UBWPAD average and Woonsocket average
2. October 2-3,1991 - UBWPAD average and Woonsocket average
3. August 14-15,1991 - UBWPAD average and Woonsocket average
UBWPAD Ammonia as Nitrogen
Month
Average
Value
Minimum
Value
Maximum
Value
Model
Input
Comment on Model Input
July
0.44
0.10
1.10
0.44
Average Observation
October
0.17
0.10
0.80
0.17
Average Observation
August
0.25
0.10
0.60
0.25
Average Observation
5-36
-------
Table 5.11 Ammonia Concentrations (mg/L) of Point Sources and Tributaries in the Blackstone River QUAL2E Model
Source
Observed Concentrations
July 10-11,1991
August 14 - 15, 1991
October 2-3, 1991
Mean
Maximum
Minimum
Mean
Maximum
Minimum
Mean
Maximum
Minimum
Headwater
0.20
0.24
0.14
0.51
1.37
0.02
0.15
0.17
0.11
UBWPAD
0.44
1.10
0.10
0.25
0.60
0.10
0.17
0.80
0.10
Millbury WWTF
* 5.00
* 5.00
* 5.00
Quinsigamond River
0.07
0.08
0.07
0.23
0.49
0.09
ND
ND
ND
Grafton WWTF
* 5.00
* 5.00
* 5.00
Northbridge WWTF
* 5.00
* 5.00
* 5.00
Mumford River
0.05
0.09
0.01
0.22
0.46
0.15
ND
0.03
ND
West River
0.04
0.09
0.01
0.15
0.55
0.13
ND
0.02
ND
Uxbridge WWTF
* 5.00
* 5.00
* 5.00
Branch River
0.09
0.12
0.09
0.28
0.62
0.22
0.04
0.19
0.08
Mill River
0.05
0.06
0.04
0.25
0.39
0.09
0.07
0.11
0.03
Peters River
0.27
0.33
0.22
0.19
0.28
0.18
0.06
0.06
0.04
Woonsocket WWTF
28.1
28.6
27.7
13.1
16.8
9.50
11.6
15.8
7.70
* = Thoman & Mueller (1987); Sampling at UBWPAD & Woonsocket WWTF occurred for 5 days prior to survey dates;
ND = Below the detection limit of 0.02 mg/L
-------
3.0
2.5
2.0
1.5
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0.0
i i i
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12 13 17 18 19 20 21
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Figure 5.17 Dissolved Ammonia Simulations for July 10-11,1991
-------
3.0
2.5
2.0
1.5
1.0
0.5
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i i i i •
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11111
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Figure 5.18 Dissolved Ammonia Simulations for October 2-3,1991
-------
u_
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a: a: z
3.0
12 13
2.5
Survey II - August 14-15, 1991
2.0
o Observed with 95% confidence bars
— UBWPAD Average, Woonsocket WWTF Average
1.5
1.0
0.5
0.0
50
45
40
35
30
25
20
15
10
5
0
River Miles
Figure 5.19 Dissolved Ammonia Simulations for August 14-15,1991
-------
Woonsocket WWTF Ammonia as Nitrogen
Month
Average
Value
Minimum
Value
Maximum
Value
Model
Input
Comment on Model Input
July
28.1
27.7
28.6
28.1
Average Observation
October
11.6
7.70
13.0
11.6
Average Observation
August
13.1
9.50
16.8
13.1
Average Observation
Ammonia Summary: The average values of ammonia were very low in the discharge of
the UBWPAD, a result of nitrification in the facility. Average and minimum values provide
essentially the same result. The July simulations indicate excellent model predictions
downstream of Woonsocket (Figure 5.17), where dissolved ammonia is most significant. The
October survey simulations, with the same fi, and 1^ values, produce excellent predictions at all
stations (Figure 5.18). The decay rates were validated with the August survey (Figure 5.19). The
model is considered calibrated and validated for dissolved ammonia with the decay rates
calculated in the July surveys.
Figure 5.20 illustrates the impact of nitrification to the DO profile. The reaches
immediately downstream of the Woonsocket WWTF show the greatest impact due to ammonia
oxidation.
5.4.6 Sediment Oxygen Demand (SOD)
SOD rates were measured at 10 stations along the Blackstone River in MA and RI,
between September 1-10, 1992 by the USEPA (Biological,Section, Lexington, MA). The study
area extended from Singing Dam in Sutton, MA to Albion Dam in Cumberland, RI.
The method involved confining a measurable volume of undisturbed sediment and
overlying water in a core cylinder and measuring the depletion of DO over time. All
measurements were performed at 21 ±2 °C.
The observed values were input by reach, as shown in Table 5.12. In general, the highest
values were found at impoundments and are typical of ranges found by Thomann and Mueller
(1987) for sections located in the vicinity of sewage outfalls.
The input of the SOD values has a significant impact, decreasing DO concentrations
upstream of dams for July (Figure 5.21). However, the reaeration over the dams causes the DO
concentration to recover. For October, the SOD impacts are not as significant, due to the higher
dilution, lower temperatures, and shorter detention times due to the higher velocities. As
expected, for the validation survey of August, DO impacts from SOD are similar to July.
5-41
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10
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8 11 12 13 17 18 19 20 21
o Observed with maximum and minimum bars
.ion . ... I. T I.
hi
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Reaeration Only
Reaeration & CBOD without settling
Reaeration, CBOD, and Nitrification only
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Figure 5.20 Dissolved Oxygen Simulations for July 10-11, 1991 with Reaeration, CBOD and NBOD
-------
Table 5.12 SOD Rates in the BRI Final QUAL2E Blackstone River Model
Reaches
Model Input
(g-02/ft2-day)
Observed by EPA
1
0.15
Minimum of observed values
2-6
0.55
Measured value at Singing Dam
7-8
0.37
Average of measured values at Riverdale Pond 0.22 & 0.53
9-10
0.23
Average of measured values above Rice City Pond 0.16 & 0.30
11-19
0.15
Average of measured values at Rte 122 near Railroad Bridge and
upstream of Tupperware Dam 0.15 & 0.14
20
0.37
Average of measured values downstream of Woonsocket WWTF
and upstream of Manville Dam 0.53 & 0.21
21-25
0.33
Measured value upstream of Albion Dam
5-43
-------
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o Observed with maximum and minimum bars
DO Saturation
\f\
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DO Criteria
Reaeration Only
Reaeration & CBOD without settling
Reaeration, CBOD, and Nitrification only
Reaeration, CBOD, Nitrification, and SOD only
50
45
40
35
30
25
20
15
10
River Miles
Figure 5.21
Dissolved Oxygen Simulations for July 10-11,1991 with Reaeration, CBOD,
NBOD, and SOD.
-------
5.4.7 Algal Productivity
The simulations of chlorophyll a constituted the final stage of the calibration process. A
calibrated algal productivity model should reflect the uptake of nitrates and phosphates in the
water column, while also producing diurnal DO variations resulting from photosynthesis and
respiration. Since many of the parameters required in the simulation of algal growth are not
measured, a range of values suggested in QUAL2E were tested in a systematic manner.
The light intensity, or total solar radiation for the three surveys, was obtained from the
URI Weather Station, Kingston, RI. The net solar radiation was calculated as 80% of the total
solar radiation, as suggested by Sawyer (1993). The model was run for a period approximately
equal to the time required for a particle of water to travel from the most upstream point to the
most downstream point in the river.
Tables 5.13 and 5.14 are summaries of the observed dissolved nitrate and orthophosphate
concentrations and model inputs for the tributaries, headwater and WWTF's.
Preliminary model simulations were performed for the July survey by using the average
values for all algal parameters given in the QUAL2E manual. Significant under predictions of
chlorophyll a between stations BLK06 and BLK11 occurred. Downstream of BLK11, significant
over predictions occurred. The observed chlorophyll a concentrations indicate the initiation of
algal growth at BLK06, with the highest concentrations at BLK08. Observed dissolved nitrate
and orthophosphate concentrations included rapid decreases from BLK06, down to values close
to the detection limits between BLK08 and BLK17, after which Woonsocket WWTF provided
additional nutrients.
Thus, the focus of the algal simulations was to initiate growth at BLK06 by maximizing |j.
in equation 5.4, consume nutrients by BLK08 with the appropriate increase in algal mass,
followed by stabilizing the growth downstream of BLK08.
An iterative procedure for the estimation of the ratio of algal biomass to chlorophyll a
(a0), the maximum algal growth rates (|imax), and the respiration rates (p) was adopted, aiming to
provide the initial growth between BLK06 and BLK08.
The ratio, a0, determines the algal biomass present from the chlorophyll a concentration.
This biomass then controls dissolved nitrate and orthophosphate concentrations that, in turn,
affect the growth factor, |i (equation 5.5). Initially, an average value of 3.0 was estimated by
calculating the algal biomass required to produce the observed DO swings for the July survey at
stations BLK08 and BLK11. This was then applied as a constant value for the river. This value
is within the range given in Bowie et al., (1985) for blue green algae.
The maximum growth rate, fi^, of 2.5 was settled on as a result of testing a range of
values in the QUAL2E manual from 1.5 to 3.0. Correspondingly, respiration rates were
5-45
-------
Table 5.13 Dissolved Nitrate Concentrations (mg/L) of Point Sources and Tributaries in the Blackstone River QUAL2E Model
Source
Observed Concentrations
July 10-11,1991
August 14-15,1991
October 2 - 3,1991
Mean
Maximum
Minimum
Mean
Maximum
Minimum
Mean
Maximum
Minimum
Headwater
0.65
1.00
0.45
0.75
0.71
0.16
1.18
2.19
0.73
UBWPAD
6.48
7.10
5.70
20.7
31.6
6.00
11.7
13.4
9.80
Millbury WWTF
* 3.00
* 3.00
* 3.00
Quinsigamond River
0.14
0.20
0.07
0.13
0.14
0.03
0.05
0.07
0.03
Grafton WWTF
* 3.00
* 3.00
* 3.00
Northbridge WWTF
~ 3.00
* 3.00
* 3.00
Mumford River
0.15
0.15
0.14
0.83
2.46
0.15
0.10
0.10
0.09
West River
0.10
0.17
0.03
0.10
0.98
ND
0.03
0.04
ND
Uxbridge WWTF
* 3.00
* 3.00
* 3.00
Branch River
0.25
0.27
0.23
0.27
0.31
0.22
0.19
0.24
0.15
Mill River
0.32
0.39
0.20
0.22
0.89
0.17
0.27
0.44
0.16
Peters River
0.77
0.77
0.76
0.71
0.95
0.56
0.52
0.69
0.42
Woonsocket WWTF
0.94
1.00
0.90
22.6
58.5
2.00
2.94
4.70
1.40
* — Thoman & Mueller (1987); Sampling at UBWPAD & Woonsocket WWTF occurred for 5 days prior to survey dates;
ND = Below the detection limit of 0.01 mg/L
-------
Table 5.14 Dissolved Orthophosphate Concentrations (mg/L) of Point Sources and Tributaries in the Blackstone River
QUAL2E Model
Source
Observed Concentrations
July 10-11,1991
August 14 - 15, 1991
October 2-3, 1991
Mean
Maximum
Minimum
Mean
Maximum
Minimum
Mean
Maximum
Minimum
Headwater
ND
0.11
ND
ND
0.50
ND
0.12
0.20
0.05
UBWPAD
2.30
3.00
1.60
2.36
3.00
1.90
3.03
3.40
2.40
Millbury WWTF
* 5.00
* 5.00
~ 5.00
Quinsigamond River
0.06
0.08
0.03
ND
0.06
ND
0.02
0.07
ND
Grafton WWTF
* 5.00
* 5.00
* 5.00
Northbridge WWTF
* 5.00
* 5.00
* 5.00
Mumford River
0.16
0.41
0.02
ND
2.46
ND
ND
West River
ND
0.15
ND
ND
0.98
ND
ND
Uxbridge WWTF
* 5.00
* 5.00
* 5.00
Branch River
0.05
0.14
ND
0.04
0.07
ND
ND
Mill River
0.04
0.05
ND
0.02
0.08
ND
ND
Peters River
0.02
0.05
ND
0.03
0.06
ND
ND
Woonsocket WWTF
3.37
3.90
3.00
3.35
4.90
0.01
4.00
4.20
3.70
* = Thoman & Mueller (1987); Sampling at UBWPAD & Woonsocket WWTF occurred for 5 days prior to survey dates;
ND = Below the detection limit of 0.01 mg/L
-------
evaluated from the QUAL2E range of 0.05 to 0.50, and a value of 0.20 was considered to be
representative for the river.
The chlorophyll a predictions, as a result of the above simulations, indicated that, unlike
the observed values, growth continued for the reaches downstream of BLK08. In order to
stabilize the growth, algal settling rates (o,) of 1.0 ft/day were introduced (QUAL2E suggests a
range of 0.5 to 6.0 ft/day) for reaches downstream of BLK08.
At this point, the nitrate and orthophosphate profiles for July were evaluated to determine
the rate of nutrient uptake by algae, otherwise known as the algal fractions of nitrogen (a,) and
orthophosphate (0(2). Since the nutrient concentrations impact the algal growth rates (equation
5.5), the process of determining the algal settling rates and nutrient uptake rates was an iterative
process. The convergent solution was then reviewed to ensure that rate coefficients were within
the range of literature values cited in Bowie et al., (1985). Values were initially set to the
average of the range reported in QUAL2E of 0.08 and 0.015 for a, and 04, respectively. The
result was an over prediction for both nutrients for the July and August surveys. After several
iterations of a„ e^, and o„ calibration was achieved with a, of 0.10 and otj of 0.05, while o,
remained unchanged at 1.0 ft/day. The final values of algal related parameters used for the
calibration and validation are listed in Tables 5.15 and 5.16, along with QUAL2E suggested
ranges and other literature values.
There were 24 hour composites taken at each discharge for the 5 consecutive days before
the July and August surveys but only 3 consecutive days before the October survey. Figures 5.22
to 5.24 show the following runs:
1. July 10-11,1991 -
2. October 2-3,1991 -
3. August 14-15,1991
UBWPAD average and Woonsocket average
UBWPAD minimum and Woonsocket average.
UBWPAD average and Woonsocket average
UBWPAD minimum and Woonsocket average.
UBWPAD mass balance value and Woonsocket average
UBWPAD average and Woonsocket average
UBWPAD minimum and Woonsocket average
UBWPAD minimum and Woonsocket minimum
UBWPAD Nitrate as Nitrogen
Month
Average
Value
Minimum
Value
Maximum
Value
Model
Input
Comment on Model Input
July
6.48
5.70
7.10
5.70
Minimum Observation
October
11.7
9.80
13.4
2.70
Calculated by Mass Balance
August
20.7
6.00
31.6
6.00
Minimum Observation
5-48
-------
Table 5.15 Final Values of Parameters Used in Algal Simulations
Variable
Units
EPA'
QUAL2E2
Other Sources
SAB5
Model Input6
Ratio of Chlorophyll a to
Algal Biomass
Hg/mg
2.5-100
10-100
2.0
3.00
Nitrogen Content to
Algal Biomass
mg/mg
0.006-0.16
0.07-0.09
0.02-1.03
0.10
Phosphorus Content to
Algal Biomass
mg/mg
0.0008-0.05
0.01-0.02
0.001-0.203
0.05
Maximum Algal
Growth Rate
day"1
0.58-9.2
1.0-3.0
2.50
Algal Respiration
Rate
day"1
0.02-0.92
0.05-0.50
0.20
Algal Settling
Rate
ft-day"1
0.0-2.92
0.5-6.0
0.89-3.614
0.25
0 and 1.0
1 Bowie et al., (1985); 2Brown and Barnwell (1987);3 Thomann and Mueller (1987);4 Chapra (1997);5 Recommended
by the SAB;6 Final Model Input
-------
Table 5.16 Algal Parameters Defined in the QUAL2E Model for the Blackstone River
Variable
Units
EPA1
QUAL2E2
SAB3
Model
Input4
Organic-N Hydrolysis
day"1
0.02-0.40
0.20
02 Production per Unit
of Algal Growth
mg-O/mg A
1.4-1.8
1.4-1.8
1.6
02 Uptake per Unit of
Algal Respiration
mg-O/mg A
1.6-2.3
1.6-2.3
2.0
02 Uptake per Unit of
NH3 Oxidation
mg-O/mg N
3.0-4.0
3.5
Michaelis-Mention Half
Saturation Constant for
Light
BTU/^-min.)
0.0066 - 0.235
0.02-0.10
0.06
Michaelis-Menton Half
Saturation Constant for
Nitrogen
mgN/L
0.001 -1.236
0.01-0.30
0.025
0.15
Michaelis-Menton Half
Saturation Constant for
Phosphorus
mgP/L
0.0025 - 0.475
0.001-0.050
0.002
0.025
Non Algal Light
Extinction Coefficient
ft"1
variable
0.2
0.01
Linear Algal Self-
Shading Coefficient
ft*'/(ng chl a!L)
0.002-0.020
0.011
Nonlinear Algal Self
Shading Coefficient
ft*'/(ng chl a/Lf3
0.0165
0.017
Algal Preference for
Ammonia
0.0-1.0
0.0
Benthos Source Rate for
Dissolved P
mg P/(fP-day)
Variable
0.50*
Organic P Settling Rate
day1
0.001-0.100
0.25
0.05
Organic P Decay
day"1
0.01-0.70
0.05
0.35
1 Bowie etal., (1985);2 Brown and Barnwell (1987);3 Final Model Input;4 Recommended by the SAB;
* Thomann and Mueller (1987)
5-50
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Survey I - July 10-11, 1991
o Observed with 95% confidence bars
— UBWPAD Minimum, Woonsocket WWTF Average
UBWPAD Average, Woonsocket WWTF Average
r
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Figure 5.22 Dissolved Nitrate Simulations for July 10 - 11,1991
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• ^ UBWPAD Mass Balance Value, Woonsocket WWTF Average
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Figure 5.23 Dissolved Nitrate Simulations for October 2-3, 1991
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UBWPAD Average, Woonsocket WWTF Average
• • • • UBWPAD Minimum, Woonsocket WWTF Minimum
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Figure 5.24 Dissolved Nitrate Simulations for August 14-15,1991
-------
Woonsocket WWTF Nitrate as Nitrogen
Month
Average
Value
Minimum
Value
Maximum
Value
Model
Input
Comment on Model Input
July
0.94
0.90
1.00
0.94
Average Observation
October
2.94
1.40
4.70
2.94
Average Observation
August
22.6
2.00
58.5
22.6
Average Observation
Nitrate Summary: In July, the average value for UBWPAD of 6.48 mg/L and the
minimum value of 5.7 mg/L provide a reasonablely good fit of model prediction to observation.
In October, only three days of data were analyzed, and the average (11.7 mg/L) and minimum
(9.8 mg/L) values were greater than July's average (6.48 mg/L) and minimum (5.7 mg/L). Runs
with the average and minimum values resulted in a significant over prediction at BLK02 of 3 and
2 times the observations, respectively. The over prediction continued throughout the Blackstone
(BLK.02 through BLK21). A value of 2.7 mg/L was necessary at the UBWPAD to produce the
observation at BLK02. This model run's predicted values passed through every 95 % confidence
limit for all observations along the Blackstone River. In August, there was a significant range of
nitrate concentrations reported in the UBWPAD effluent (6.0 to 31.6 mg/L), as compared to July
(5.7 to 7.1 mg/L). The model run with the average value of 20.7 mg/L resulted in a model
prediction at BLK02 about 4 times higher than reported. All model predictions were
significantly above the observations and the confidence limits. The minimum value of 6.0 mg/L
provided an excellent fit of prediction to observation.
Orthophosphate as Phosphorous: There were 24 hour composites taken at each discharge
for the 5 consecutive days before the July and August surveys but only 3 consecutive days before
the October survey. Figures 5.25 to 5.27 show the following runs:
1. July 10-11,1991 - UBWPAD average and Woonsocket average
UBWPAD minimum and Woonsocket average.
UBWPAD mass balance value and Woonsocket average
2. October 2-3,1991 - UBWPAD average and Woonsocket average
UBWPAD minimum and Woonsocket average.
UBWPAD mass balance value and Woonsocket average
3. August 14-15,1991 - UBWPAD average and Woonsocket average
UBWPAD minimum and Woonsocket average
UBWPAD mass balance value and Woonsocket average
UBWPAD 84% mass balance value and Woonsocket
average
5-54
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UBWPAD at 84% Mass Balance Value,
Woonsocket WWTF Average
UBWPAD Average, Woonsocket WWTF Average
UBWPAD Minimum, Woonsocket WWTF Average
UBWPAD Mass Balance Value,
Woonsocket WWTF Average
25 20
River Miles
10
Figure 5.25 Dissolved Orthophosphale Simulations for July 10-11,1991
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UBWPAD at 84% Mass Balance Value,
Woonsocket WWTF Average
UBWPAD Average, Woonsocket WWTF Average
UBWPAD Minimum, Woonsocket WWTF Average
UBWPAD Mass Balance Value,
Woonsocket WWTF Average
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Figure 5.26 Dissolved Orthophosphate Simulations for October 2-3, 1991
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UBWPAD at 84% Mass Balance Value,
Woonsocket WWTF Average
UBWPAD Average, Woonsocket
WWTF Average
UBWPAD Minimum, Woonsocket
WWTF Average
UBWPAD Mass Balance Value,
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Figure 5.27 Dissolved Orthophosphate Simulations for August 14-15, 1991
-------
UBWPAD Orthophosphate as Phosphorous
Month
Average
Value
Minimum
Value
Maximum
Value
Mass
Balance
Model
Input
Comment on Model
Input
July
2.28
1.56
2.97
1.09
0.9
84% of Mass Balance
October
3.03
2.40
3.40
1.03
0.9
84% of Mass Balance
August
2.36
1.89
2.97
1.48
1.2
84% of Mass Balance
Woonsocket WWTF Orthophosphate as Phosphorous
Month
Average
Value
Minimum
Value
Maximum
Value
Model
Input
Comment on Model Input
July
3.37
2.97
3.90
3.37
Average Observation
October
4.00
3.70
4.20
4.00
Average Observation
August
3.35
0.01
4.91
3.35
Average Observation
The orthophosphate simulations for the July and October surveys were made with the
average and minimum values observed at UBWPAD prior to each survey. The minimum values
(1.56 and 2.40 mg/L) resulted in slightly higher predictions than the observations in the river.
Based on the concentrations and flows at BLK01 and BLK02 and the flow at the UBWPAD, the
concentrations required at the point of UBWPAD discharge channel's confluence with the
Blackstone River to obtain the observed concentration at BLK02 were lower (0.9 and 0.9 mg/L).
The model results for both sets of values are presented on the figures. For the August survey, the
minimum UBWPAD orthophosphate concentration was 1.89 mg/L. The model runs for this
value, and the concentration back calculated to match BLK02 (1.2 mg/L), are presented in Figure
5.30.
For the August survey observed chlorophyll a concentrations were lower than those of the
July survey. Yet, at the same time, dissolved orthophosphate loss in the reaches where
productivity was greater, indicate that the algal biomass should be higher. It is not clear why
there was a significant over prediction of algae. One possibility is that samples at many of the
stations were taken below the dams. Flows were very low and the samples may not have
adequately represented the chlorophyll a content of samples just above the dam.
5.4.8 Final Dissolved Oxygen Profiles
With the model calibrated for algal productivity, the final chlorophyll a and DO profiles
are plotted for the three surveys in Figures 5.28 to 5.33.
The SAB requested a quantitative measure of goodness of fit with the determination of
5-58
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Figure 5.28 Chlorophyll a Simulation for July 10 - 11,1991
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Figure 5.30 Chlorophyll a Simulations for August 14-15, 1991
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Do Saturation
4 F- DO Criteria
2
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The DO profile with Reaeration, CBOD, Nitrification, SOD, & Algae
i i i
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Figure 5.31 Final Dissolved Oxygen Profile for July 10-11,1991
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The DO profile with Reaeration, CBOD, Nitrification, SOD, & Algae
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Figure 5.32 Final Dissolved Oxygen Profile for October 2-3,1991
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The DO profile with Reaeration, CBOD, Nitrification, SOD, & Algae
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Figure 5.33 Final Dissolved Oxygen Profile for August 14-15,1991
-------
root mean square error (RMS). This has been done for each variable for each survey. These are
reported below.
Root Mean Squared Errors for the BRI Final Runs
Survey
NOj-N
nh3-n
P04-P
Chlorophyll a
DO
July 1991
0.628
0.218
0.134
4.592
1.103
October 1991
0.255
0.107
0.091
1.001
0.575
August 1991
0.577
0.221
0.259
8.599
1.061
The relative error (e) is another statistical comparison that follows the following form:
e=|X-C|+X
where X is the average observation, and C is the predicted value. It provides a gross
measure of model adequacy. In Thomann (1980), a group of DO models were compared using
the median relative error. His article included the following quote: "As a crude measure,
therefore, of the present state of the art of DO models calibration/verification, one might suggest
an overall median relative error of 10%. It should, of course, be noted that this is not the error of
actual prediction but merely the error representative of a present level of understanding of
observed behavior of dissolved oxygen."
The value of 10% median relative error was brought up by the review team during the
SAB review. This measurement is used to (a) acknowledge the DO oxygen modeling effort
relative to the group of models presented in Thomann (1980) and, (b) it is used here to compare
the BRI model runs with the SAB revised runs for all three surveys.
The details .are presented below. There were 14 mainstem stations used for comparison.
They did not include the first station, which would be considered a boundary condition. The
results for the 7th and 8th ranking were averaged. The median relative errors in percent for the
BRI final DO profiles were as follows:
BRI Final DO Profiles - Median Relative Error
July
8
October
5
August
11
5-65
-------
5.5 Additional Model Validation
Model calibration is usually performed with two data sets, followed by validation with a
third data set For this model, additional validation is provided with previous water quality data
sets (MADEQE 1983; Ecology and Environment 1988). This evaluation also provides an
opportunity to post audit these previous modeling efforts.
5.5.1 Massachusetts Waste Load Allocation (MA WLA)
Monitoring for DO, BOD, dissolved ammonia and orthophosphate for the STREAM7
model calibration occurred on June 9-13,1980, August 4-8,1980 and October 15-16, 1980.
Sampling included stations BLK01 to BLK12 and UBWPAD. DO was monitored for 2 days at 6
hour intervals, while dissolved ammonia and orthophosphate samples were collected twice for
each survey. Flow profiles were developed using the average flows at the three USGS stations,
by the method defined in Section 5.3. All boundary conditions to the QUAL2E model are given
as the mean of the observed values (MADEQE 1983). The model was run in the dynamic mode
to include the impact of algal productivity, and the results are given as a daily average of four, six
hour interval simulations (similar to observed values). Observed and simulated DO profiles are
shown in Figures 5.34 to 5.36 and represent the mean DO values for the day.
The figures also include the STREAM7 predictions, derived from MADEQE (1983). DO
simulations by QUAL2E are similar to STREAM7 and, in some cases, better in defining the
impacts immediately upstream of dams. It should be noted that STREAM7 simulations had been
performed without productivity.
The results of the MADEQE 1983 study resulted in the UBWPAD expanding their level
of treatment to include seasonal nitrification. Thus, ammonia profiles (Figures 5.37 to 5.39) are
also included to evaluate the model performance. QUAL2E model simulations indicate excellent
predictions of instream observations of ammonia for conditions prior to UB WPAD's upgrade to
nitrification.
While a comprehensive post audit of the STREAM7 model is not performed here, the
ability of the QUAL2E model to predict conditions, before and after UB WPAD's improvement,
suggests that the 1983 modeling effort, and consequently the advanced treatment, has had a
significant impact on DO concentrations in the river.
5.5.2 Ecology and Environment (1988)
One survey, on September 28-30,1987, was conducted on the Blackstone River between
stations BLK13 and BLK19. Parameters included DO, BOD, and temperature. The data had
been used to develop a QUAL2E model to evaluate the feasibility of the withdrawal of water
from the Blackstone River for a thermal electricity facility.
For the current modeling effort, flow profiles were developed for the river with USGS
data and data from the state agencies. Observed values for Woonsocket WWTF and mean
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Figure 5.34 Dissolved Oxygen Profile for Validation Survey (MADEQE 1983), June 9-12,1980
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DO Saturation
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Figure 5.35 Dissolved Oxygen Profile for Validation Survey (MADEQE 1983), August 4-7, 1980
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DO Criteria
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Figure 5.36 Dissolved Oxygen Profile for Validation Survey (MADEQE 1983), October 15-16,1980
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• Observed
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Figure 5.37 Ammonia Profile for Validation Survey (MADEQE 1983), June 9-12,1980
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Figure 5.38 Ammonia Profile for Validation Survey (MADEQE 1983), August 4-7,1980
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concentrations (Wright 1991) for the remaining boundary conditions are given. The QUAL2E
model was run in the dynamic mode. The average model simulations for the day indicate
excellent predictions (Figures 5.40).
5.6 Sensitivity Analysis
The primary objective of this analysis is to investigate the relative importance of different
factors contributing to the DO concentrations in the Blackstone River. Sensitivity of model
parameters, chosen during the simulation process, is also studied to investigate the impact of a
calibration parameter on the water column DO concentrations, while also addressing the
uncertainty of model parameter selection.
All the sensitivity simulations were done on the data set of July 1991, since the flows
were similar to 7Q10 conditions, and the productivity is the highest amongst the three surveys.
The diurnal/dynamic model predictions of DO at 0400 hours was taken as the basis for studying
the sensitivity.
5.6.1 Coefficient to Adjust Five-Day BOD to Ultimate BOD
A major concern of the SAB was the use of a default value for the adjustment (K,) of
BODj to ultimate BOD. The conversion coefficient (BOD5 to BODJ used in the original BRI
model was 0.25 day"1 base e at 20 °C. QUAL2E suggests a default value of 0.23 day"1 base e at
20 °C. No values were suggested by the SAB.
The value of K, is expected to be less than the value of the instream K,,. From Thomann
and Mueller (1987):
"It should be noted that the "bottle rate," K„ in general, is not equal to the deoxygenation
rate for the BOD that occurs in natural waters, although, for deep bodies of water, K, is a useful
first approximation to the deoxygenation rate."
"In addition to the possible settling of BOD, the estimation of Kj cannot usually be made
from incubation of effluent to determine the BOD bottle rate, because the oxidation of BOD in a
natural body of water includes phenomena that are not part of the BOD bottle rate. Such
phenomena include biosorption by biological slimes on river bottoms. Stream turbulence and
roughness, and the density of attached organisms also affect the degree of this type of BOD
removal."
SAB did present a K,, value of 0.091 day'1 base e at 25.5 0 C for the Upper Mississippi
River with a flow of2024 cfs (This is compared to the Blackstone River flow in July and August
of about 100 cfs). The value of K,, was based on a semi-log regression of filtered BOD ultimate
vs travel time for 5 data points. Adjustment of this value, using a temperature coefficient of 1.04
as suggested by Thomann and Mueller (1987), yields a Kj value of 0.07 day"1 base e at 20 0 C.
This value is more appropriate for the size of the Upper Mississippi.
5-73
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Figure 5.40 Dissolved Oxygen Profile for Validation Survey September 28-30,1987
-------
"As an approximate guide, values of Kj range from about 0.1 to 0.5 day*1 for deeper
bodies of water (depths greater than about 5 ft) to 0.5 to 3.0 day'1 for shallow streams (depths less
than about 5 ft)." (Thomann and Mueller 1987)
In Bowie et al., (1985) there is a comprehensive list of instream deoxygenation
coefficients. There were a total of 43 studies identified, and 80% of these had minimums of at
least 0.1 day'1 base e at 20 °C.
Numerous model runs were made for coefficients in a range that seems reasonable based
on the literature referenced: 0.1 to 0.5 day'1 base e at 20 °C. Based on the BODs values in the
system, any value greater than 0.5 will not result in significant changes to the BODs or the final
DO. The DO results are presented for the three surveys (Figures 5.41 to 5.43), and a
comparison has been made for four locations along the river. Changes are within 0.10 mg/L DO.
Survey
KBOD
DO
BLK02
Change
in DO
BLK02
DO
BLK08
Change
in DO
BLK08
DO
BLK17
Change
in DO
BLK17
DO
BLK21
Change
in DO
BLK21
July
0.10
7.58
-0.01
7.71
-0.09
8.27
-0.03
6.44
-0.03
0.25
7.59
-
7.80
-
8.30
-
6.47
-
0.50
7.59
0.00
7.82
+0.02
8.31
+0.01
6.48
+0.01
August
0.10
7.26
-0.01
7.45
-0.10
7.86
-0.02
6.20
-0.05
0.25
7.27
-
7.55
-
7.88
-
6.25
-
0.50
7.27
0.00
7.57
+0.02
7.89
+0.01
6.26
+0.01
October
0.10
8.63
-0.01
8.79
-0.04
9.53
-0.01
9.51
-0.01
0.25
8.64
-
8.83
-
9.54
-
9.52
-
0.50
8.64
0.00
8.84
+0.01
9.55
+0.01
9.52
0.00
Both at the SAB review and in the BRI 1998 report, there was discussion concerning the
simulation of BOD. The BRI clearly laid out the problems concerning the field and laboratory
work in the Dry Weather Studies and admits that the samples for BOD should have been filtered.
However, it also points out that the amount of BOD in the system is low. This is due to the
advanced treatment being provided at UBWPAD, and the secondary treatment being provided at
the other facilities in Massachusetts. Sensitivity runs were made in the BRI report and have also
been made here with regards to the concerns voiced in the SAB review. Based on the literature,
we believe that the range of K,s evaluated is a fair representation for a river like the Blackstone
River. The impact on the river's dissolved oxygen and BOD is insignificant for the range of K,s
evaluated. Therefore, the 1991 data does not indicate that BOD decay in the Blackstone is a
5-75
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11 12 13 17 18 19 20 21
o Observed with 95% confidence bars
Predicted with K1 = 0.10
I DO Saturation
- DO Criteria
Predicted with K,= 0.25
Predicted with K,= 0.50
The DO profile with Reaeration, CBOD, Nitrification, SOD, & Algae
I I I I—L.
50 45 40 35 30 25 20
River Miles
15
10
Figure 5.41 Dissolved Oxygen Sensitivity to Kj Rates for July 10 -11,1991
-------
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DO Saturation
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Predicted with K = 0.10
1 DO Criteria
The DO profile with Reaeration, CBOD, Nitrification, SOD, & Algae
Predicted with K, = 0.25
Predicted with K, = 0.50
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50 45 40 35 30 25 20
River Miles
15
10
Figure 5.42 Dissolved Oxygen Sensitivity to K, Rates for August 14-15,1991
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- DO Saturation
8 11 12 13 17 18 19 20 21
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Predicted with K, = 0.10
I DO Criteria Predicted with K, = 0.25
Predicted with K, = 0.50
The DO profile with Reaeration, CBOD, Nitrification, SOD, & Algae
I I I I
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50 45 40 35 30 25 20
River Miles
15
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Figure 5.43 Dissolved Oxygen Sensitivity to K, Rates for October 2-3,1991
-------
governing force in DO simulations.
5.6.2 Model Sensitivity for Selected Algal Coefficients Discussed in the SAB Review
Specifically, the SAB questioned the values used for the following parameters:
Algal settling velocity
Non-algal light extinction coefficient
Nutrient half-saturation constants
Remineralization rate of organic phosphorus
Organic phosphorous settling rate
Chlorophyll a to algal biomass ratio
Each variable, along with a model run with all coefficients changed as suggested, are
discussed below. The effect of the variable changes on model predictions are presented as a
series of figures for N03-N, P04-P, Chlorophyll a, and DO.
5.6.2.1 Algae Settling Velocity
QUAL2E recommended a range of 0.5 to 6.0 ft/day.
Bowie et al., (1985) gave a range for Green Algae of 0.02 to 0.89 m/day or 0.066 to 2.92
ft/day; for Blue Green Algae of 0 to 0.20 m/day or 0 to 0.656 ft/day; and for Total Phytoplankton
of 0 to 2.0 m/day or 0 to 6.56 ft/day.
Chapra (1997) (Page 301 Table 17.3 and the text on that page) stated in the text that the
"measured values for phytoplankton and organic solids average about 0.25 m/day with a range of
0.1 to 1 m/day." This gives an average rate of 0.82 ft/day and the range of 0.328 to 3.28 ft/day.
The tabled data for phytoplankton ranges from 0.08 to 1.9 m/day or 0.26 to 6.23 ft/day.
The BRI model presented above had, as input, 0.0 ft/day for the first 10 reaches and 1.0
ft/day for the last 15 reaches.
The SAB recommended that the entire river should have a single value: 0.25 ft/day.
Two sets of figures are provided for this variable. The first set (Figures 5.44 to 5.47),
compares the algal settling velocities of 0.0 and 1.0 with the final BRI model run that uses 0.0 for
the first 10 reaches and 1.0 for the rest of the river. The second set of figures (Figures 5.48 to
5.51), compares the QUAL2E (minimum-0.5 and maximum-6.0), SAB (0.25) and the final BRI
model run (0.0 for the first 10 reaches and 1.0 for the rest of the river).
The changes in RMS are given for the BRI (Final Runs of Part 1 above) and the SAB
(with the recommended value of 0.25 ft/day):
5-79
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2 -
O Observed with 95% confidence bars
Model input: First ten reaches - 0.0 ft-day'1;
Remaining reaches -1.0 ft-day"1
EPA minimum rate: 0.0 ft-day'1
Algal settling rate of 1.0 ft-day"
30 25 20
River Miles
Figure 5.45 Dissolved Orthophosphate Sensitivity to Algal Settling Rates for July 10-11,1991
-------
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EPA minimum rate: 0.0 ft-day"1
Algal settling rate of 1.0 ft-day"1
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2
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River Miles
Figure 5.46 Chlorophyll a Sensitivity to Algal Settling Rates for July 10 -11,1991
-------
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11 12 13 17 18 19 20 21
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¦ OO Saturation
DO Criteria
Model input: First ten reaches - 0.0 ft-day'1; Remaining reaches 1.0 ft-day"
EPA minimum rate: 0.0 ft-day'1
Algal settling rate of 1.0 ft-day
-I I I I I I I I I L.
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50 45 40 35 30 25 20
River Miles
15
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Figure 5.47 Dissolved Oxygen Sensitivity to Algal Settling Rates for July 10-11,1991
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Model input: First ten reaches - 0.0 ft-day"1;
Remaining reaches -1.0 ft-day'1
SAB recommended rate: 0.25 ft-day'1
QUAL2E minimum rate: 0.5 ft-day'1
QUAL2E maximum rate: 6.0 ft-day'1
River Miles
Figure 5.48 Additional Dissolved Nitrate Sensitivity to Algal Settling Rates for July 10-11,1991
-------
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Model input: First ten reaches - 0.0 ft-day'1;
Remaining reaches - 1.0 ft-day'1
SAB recommended rate: 0.25 ft-day"1
QUAL2E minimum rate: 0.5 ft-day"1
QUAL2E maximum rate: 6.0 ft-day"1
0
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50 45 40 35 30 25 20 15 10
River Miles
Figure 5.49 Additional Dissolved Orthophosphate Sensitivity to Algal Settling Rates for July 10-11,1991
-------
60
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Model input: First ten reaches - 0.0 ft-day'1; Remaining reaches -1.0 ft-day'
SAB recommended rate: 0.25 ft-day"1
QUAL2E minimum rate: 0.5 ft-day'1
QUAL2E maximum rate: 6.0 ft-day'1
Survey I - July 10-11, 1991
_l_l_
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50 45 40 35 30 25 20
River Miles
15
10
Figure 5.50 Additional Chlorophyll a Sensitivity to Algal Settling Rates for July 10 - 11, 1991
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DO Criteria
Model input: First ten reaches - 0.0 ft-day"1
Remaining reaches -1.0 ft-day'1
SAB recommended rate: 0.25 ft-day'1
11 12 13 17 18 19 20 21
o Observed with 95% confidence bars
QUAL2E minimum rate: 0.5 ft-day'1
QUAL2E maximum rate: 6.0 ft-day"1
J—L.
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50 45 40 35 30 25 20
River Miles
15
10
Figure 5.51 Additional Dissolved Oxygen Sensitivity to Algal Settling Rates for July 10-11,1991
-------
RMS Comparison Between BRI and SAB Models for Algae Settling Velocity
Survey
N03-N
P04-P
Chloro
ihyll a
DO
BRI
SAB
BRI
SAB
BRI
SAB
BRI
SAB
July 1991
0.628
0.666
0.134
0.143
4.592
7.494
1.103
1.112
August 1991
0.577
0.619
0.259
0.287
8.599
12.03
1.061
1.185
October 1991
0.255
0.255
0.091
0.091
1.001
1.094
0.575
0.560
In almost all cases, the original BRI variables provided lower RMS values. In the 8 cases
where the change was significant (greater than 5 %; in Bold), the BRI had the lower RMS.
5.6.2.2 Non-Algal Light Extinction Coefficient
QUAL2E simply listed the coefficients as "Variable".
Literature values were not reported in Bowie et al., (1985), Chapra (1997), Thomann and
Mueller (1987) or other sources referenced.
The BRI model presented above had, as input, a value of 0.01 per ft.
The SAB suggested a range of 0.1 to 0.4 per ft for riverine systems. They recommended
a value of 0.2 per ft for the entire Blackstone River.
The sensitivity of the model to the non-algal extinction coefficient is shown in Figures
5.52 to 5.55. The four plots on each figure represent the SAB recommendation (0.2), minimum
(0.1), and maximum (0.4), along with the final BRI model run (0.01).
The changes in RMS are given for the BRI (Final Runs of Part 1 above) and the SAB:
RMS Comparison Between BRI and SAB Models for Non-Algal Light Extinction Coefficients
Survey
NO3-N
P04-P
Chloro
jhyll a
DO
BRI
SAB
BRI
SAB
BRI
SAB
BRI
SAB
July 1991
0.628
0.634
0.134
0.133
4.592
4.776
1.103
0.987
August 1991
0.577
0.921
0.259
0.227
8.599
8.494
1.061
1.461
October 1991
0.255
0.250
0.091
0.093
1.001
0.935
0.575
0.541
5-88
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8 11 12 13 17 18 19 20 21
o Observed with 95% confidence bars
Model input: 0.01 ft'1
SAB recommended value: 0.20 ft'1
SAB minimumrecommended value: 0.10 ft"1
SAB maximum recommended value. 0.40 ft"1
i . .
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River Miles
10
Figure 5.52 Dissolved Nitrate Sensitivity to Non Algal Light Extinction Coefficient Changes for
July 10-11,1991
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Model Input: 0.01 ft"1
SAB recommended input: 0.25 ft'1
SAB minimum recommended rate: 0.10 ft'1
SAB maximum recommended rate: 0.40 ft'1
r-
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50 45 40 35 30 25 20
River Miles
15
10
Figure 5.53 Dissolved Orthophosphate Sensitivity to Non Algal Light Extinction Coefficient Changes
for July 10-11, 1991
-------
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Model input 0.01 ft"1
SAB recommended value 0.2 ft'1
SAB minimum recommended value 0.1 ft"1
SAB maximum recommended value 0.4 ft'1
Survey I - July 10-11, 1991
Q
30 25 20
River Miles
Figure 5.54 Chlorophyll a Sensitivity to Non Algal Light Extinction Coefficient Changes for July 10 - 11,1991
-------
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DO Saturation
DO Criteria
Model input: 0.01 ft'1
SAB recommended input: 0.20 ft"1
SAB minimum recommended value:
o Observed with 95% confidence bars SAB maximum recommended value
i i i
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: 0.40 ft*1
50
45
40
35
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25
20
15
10
River Miles
Figure 5.55 Dissolved Oxygen Sensitivity to Non Algal Light Extinction Coefficient Changes
for July 10-11, 1991
-------
In 6 of the 12 cases, the change was significant (greater than 5 %; in Bold). However,
the results were divided between the two options (BRI3 and SAB 4), and there was no consistent
improvement with either option.
5.6.2.3 Nutrient Half-Saturation Constants
Both the Phosphorous and Nitrogen Half-Saturation constants are evaluated in Figures
5.56 to 5.59.
Phosphorous
QUAL2E gave a range of 0.001 to 0.05 mg/L as P.
Bowie et al., (1985) gave a range for Green Algae of 0.002 to 0.03 mg/L, for Blue Green
Algae of 0.0025 to 0.06 mg/L, and for Total Phytoplankton of 0.0005 to 0.08 mg/L.
Chapra (1997) (Table 33.1 page 607) and Thomann and Mueller (1987) (Table 7.12 page
427) recommended 0.001 to 0.005 mg/L P.
The BRI model presented above had, as input, Vi the maximum value reported in
QUAL2E: 0.025 mg/L P.
The SAB recommended 0.002 mg/L.
The predictions on the figures included changes in the variable for QUAL2E (minimum-
0.001 and maximum-0.05), SAB (0.002) and the final BRI model run (0.025).
Nitrogen
QUAL2E gave a range of 0.01 to 0.30 mg/L as N.
Bowie et al., (1985) gave a range for Green Algae of 0.001 to 0.15 mg/L, for Blue Green
Algae of 0 to 0.015 mg/L, and for Total Phytoplankton of 0.0014 to 0.4 mg/L.
Chapra (1997) (Table 33.1 page 607) recommended 0.005 to 0.020 mg/L N.
Thomann and Mueller (1987) (Table 7.12 page 427) recommended 0.010 to 0.020 mg/L
N.
The BRI model presented above had, as input, 14 the maximum value reported in
QUAL2E: 0.15 mg/L N.
The SAB recommended 0.025 mg/L.
The predictions on the figures included changes in the variable for QUAL2E (minimum-
5-93
-------
10
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12 3 4
Survey I - July 10-11, 1991
8 11 12 13 17 18 19 20 21
o Observed with 95% confidence bars
Model input: N = 0.15 mgN/L; P = 0.025 mgP/L
SAB recommended values: N = 0.025 mg N/L;
P = 0.002 mg P/L
QUAL2E minimum values: N = 0.01 mgN/L;
P = 0.001 mgP/L
QUAL2E maximum values: N = 0.30 mgN/L;
P = 0.05 mgP/L
30 25 20
River Miles
Figure 5.56 Dissolved Nitrate Sensitivity to Michaelis-Menton Nutrient Half Saturation Constants
-------
fN
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1 2 3 4 6 7
Survey I - July 10-11,1991
8
11 12 13 17 18 19 20 21
2 -
o Observed with 95% confidence bars
Model input: N = 0.15 mgN/L; P = 0.025 mgP/L
SAB recommended values: N = 0.025 mgN/L; P = 0.002 mgP/L
QUAL2E minimum values: N = 0.01 mgN/L; P = 0.001 mgP/L
QUAL2E maximum values: N = 0.30 mgN/L; P = 0.05 mgP/L
¦ ¦ ¦
50 45 40 35 30 25 20
River Miles
15
10
Figure 5.57 Dissolved Orthophosphate Sensitivity to Michaelis-Menton Nutrient Half Saturation Constants
-------
Q
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Model input: N = 0.15 mg N/L; P = 0.025 mg P/L
SAB recommended values: N = 0.025 mgN/L; P = 0.002 mgP/L
QUAL2E minimum values: N = 0.01 mgN/L; P = 0.001 mgP/L
QUAL2E maximum values: N = 0.30 mgN/L; P = 0.05 mgP/L
Survey I-July 10-11,1991
50
45
40
35
30
25
20
15
10
River Miles
Figure 5.58 Chlorophyll a Sensitivity to Michaelis-Menton Nutrient Half Saturation Constants
-------
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11 12 13 17 18 19 20 21
o Observed with 95% confidence bars
- DO Saturation
DO Criteria
Model input: N = 0.15 mgN/L; P = 0.025 mgP/L
SAB recommended values: N = 0.025 mgN/L; P = 0.002 mgP/L
QUAL2E minimum values: N = 0.01 mgN/L; P = 0.001 mgP/L
QUAL2E maximum values: N = 0.30 mgN/L; P = 0.05 mgP/L
_l u
¦ 1 '
1 1 1 1 1 1 ' 1
11111
50
45
40
35
30
25
20
15
10
River Miles
Figure 5.59 Dissolved Oxygen Sensitivity to Michaelis-Menton Nutrient Half Saturation Constants
-------
0.01 and maximum-0.30), SAB (0.025) and the final BR1 model run (0.15).
The changes in RMS are given for the BRI (Final Runs of Part 1 above) and the SAB
(with the recommended value for phosphorus of 0.002 mg/L and nitrogen of 0.025 mg/L):
RMS Comparison Between BRI and SAB Models for Nutrient Half-Saturation Constants
Survey
N03-N
P04-P
Chloro
phyll a
DO
BRI
SAB
BRI
SAB
BRI
SAB
BRI
SAB
July 1991
0.628
0.667
0.134
0.148
4.592
7.372
1.103
0.851
August 1991
0.577
0.339
0.259
0.206
8.599
12.923
1.061
0.972
October 1991
0.255
0.265
0.091
0.082
1.001
1.362
0.575
0.618
In 11 of the 12 cases, the change was significant (greater than 5 %; in Bold). However,
the results were divided between the two options (BRI 6 and SAB 5), and there was no consistent
improvement with either option. In all three surveys, the chlorophyll a predictions had lower
RMS values with the BRI model.
5.6.2.4 Remineralization Rate of Organic Phosphorus (Organic P Decay)
QUAL2E gave a range of 0.10 to 0.70 per day.
Literature values were not reported in Bowie et al., (1987), Chapra (1997), Thomann and
Mueller (1987) or other sources referenced.
The BRI model presented above had, as input, Vi the maximum value reported in
QUAL2E: 0.35 per day.
The SAB recommended a value of 0.05 per day, which is below the minimum suggested
in QUAL2E.
Figures 5.60 to 5.63 represent the sensitivity of the model predictions for the
remineralization rate of organic phosphorus. The predictions on the figures included rate
changes for QUAL2E (minimum-0.10 and maximum-0.70), SAB (0.05) and the final BRI model
run (0.35).
The changes in RMS are given for the BRI (Final Runs of Part 1 above) and the SAB
(with the recommended value of 0.05 per day):
5-98
-------
VO
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a:
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12 3 4
Survey I - July 10-11,1991
8 11 12 13 17 18 19 20 21
o Observed with 95% confidence bars
Model input: 0.35 day*1
SAB recommended rate: 0.05 day"1
QUAL2E minimum rate: 0.10 day'1
QUAL2E maximum rate: 0.70 day'1
0
' ' 1 1 1
1 I I I
11)1
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I .... I
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1 *
50 45 40 35 30 25 20
River Miles
15
10
Figure 5.60
Dissolved Nitrate Sensitivity to Organic Phosphorus Remineralization Rate for July 10-11,1991
-------
Q
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Survey I - July 10-11, 1991
2 -
5
o Observed with 95% confidence bars
Model input: 0.35 day"1
SAB recommended rate: 0.05 day"1
QUAL2E minimum value: 0.10 day"1
QUAL2E maximum value: 0.70 day"1
¦ i . QJl +¦ ¦ . . I
CO
a.
LU
5
CO
11 12 13 17 18 19 20 21
50 45 40 35 30 25 20
River Miles
15
10
Figure S.61 Dissolved Orthophosphate Sensitivity to Organic Phosphorus Remineralization Rate for
July 10-11,1991
-------
Ih
i
o
i
&
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3
CJ
60
50
40
30
20
10
50
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CO
K
111
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5
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12 3 4
Survey I - July 10-11, 1991
8 11 12 13 17 18 19 20 21
o Observed with 95% confidence bars
Model rate 0.35 day"1
SAB recommended rate 0.05 day1
QUAL2e minimum rate 0.10 day"1
QUAL2e maximum rate 0.70 day"1
I I I
45
30 25 20
River Miles
Figure 5.62 Chlorophyll a Sensitivity to Organic Phosphorus Remineralization Rates for July 10-11,1991
-------
f
Q
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12 3 4
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11 12 13 17 18 19 20 21
14 Survey I-July 10-11,1991
12
10
8
6
DO Saturation
4 I- DO Criteria
2
o Observed with 95% confidence bars
Model input 0.35 day"1
SAB recommended input 0.05 day'1
QUAL2E minimum value 0.1 day'
QUAL2E maximum value 0.7 day'
¦ 1 1 ¦ * ¦ ¦ 1
i i i
_i_i_
¦ ¦ ¦
50 45 40 35 30 25 20
River Miles
15
10
Figure 5.63 Dissolved Oxygen Sensitivity to Organic Phosphorus Remineralization Rates for July 10-11,1991
-------
RMS Comparison Between BRI and SAB Models for Remineralization Rate of Organic
Phosphorus
Survey
NOj-N
P04-P
Chloro
phyll a
DO
BRI
SAB
BRI
SAB
BRI
SAB
BRI
SAB
July 1991
0.628
0.620
0.134
0.137
4.592
4.377
1.103
0.977
August 1991
0.577
0.688
0.259
0.257
8.599
7.357
1.061
1.056
October 1991
0.255
0.255
0.091
0.091
1.001
1.001
0.575
0.560
The change was significant in only 3 of the 12 cases (greater than 5 %\ in Bold). The
results were divided between the two options (BRI2 and SAB 1), and there was no consistent
improvement with either option.
5.6.2.5 Organic Phosphorus Settling Rate
QUAL2E suggested a range of 0.001 to 0.100 per day.
Thomann and Mueller (1987) did report on Total Phosphorus (not organic phosphorus)
for lakes (not rivers). On page 406, information is discussed concerning the settling rate of Total
Phosphorus in lakes. A value of0.0274 m/day and values of 0.034 to 0.044 m/day from Chapra
and Tarapchak (1976) (0.039 average rate) are mentioned. Assuming a range of depths for the
Blackstone on the order of 1 to 10 ft the resulting settling rate in per day would be: Thomann
and Mueller (1987) 0.0274/[l/3.281] = 0.090 per day and 0.0274/[ 10/3.281] = 0.009 per day;
Chapra and Tarapchak (1976) 0.039/[l/3.281] = 0.128 per day and Chapra and Tarapchak
(1976) 0.039/[10/3.281] = 0.0128 per day. These ranges 0.009 to 0.09 and 0.0128 to 0.128 are in
the range reported by QUAL2E.
This coefficient was not reported in Bowie et al., (1985), Chapra (1997), or other sources
referenced.
The BRI model presented above had, as input, 54 the maximum value reported in
QUAL2E: 0.05 per day.
The SAB recommended a value of 0.25 per day, which is above the maximum suggested
in QUAL2E.
Figures 5.64 to 5.67 represent the sensitivity of the model predictions to the organic
phosphorus settling rate. The predictions on the figures included rate changes for QUAL2E
(minimum-0.001 and maximum-0.100), SAB (0.25) and the final BRI model run (0.05).
The changes in RMS are given for the BRI (Final Runs of Part 1 above) and the SAB
5-103
-------
8
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55
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12 3 4
6
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8 -
6 -
4
2
50
Survey I - July 10-11,1991
11 12 13 17 18 19 20 21
Observed with 95% confidence bars
Model input: 0.05 day'1
SAB recommended rate: 0.25 day"1
t
QUAL2E minimum rate: 0.001 day'1
QUAL2E maximum rate: 0.10 day"1
H~rx
I I
¦ I ¦
1 '
1 1 1 '
45
40
35
30
25
20
15
10
River Miles
Figure 5.64 Dissolved Nitrate Sensitivity to Organic Phosphorus Settling Rate for July 10-11,1991
-------
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1 2 3 4 6 7
Survey I - July 10-11,1991
8
11
12 13 17 18 19 20 21
o Observed with 95% confidence bars
Model input: 0.05 day'1
SAB recommended rate: 0.25 day'1
QUAL2E minimun rate: 0.001 day"1
QUAL2E maximum rate: 0.10 day-1
River Miles
¦? $
Figure 5.65 Dissolved Orthophosphate Sensitivity to Organic Phosphorus Settling Rate for
July 10-11,1991
-------
in
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60
50
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11 12 13 17 18 19 20 21
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o
Observed with 95% confidence bars
-
Model settling rate 0.05 day1
Survey I - July 10 -11,1991
SAB recommended rate 0.25 day"1
QUAL2E mimimum rate 0.001 day'1
-
QUAL2E maximum rate 0.10 day'1
-
§
o
(
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-
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50 45 40 35 30 25 20 15 10
River Miles
Figure 5.66 Chlorophyll a Sensitivity to Organic Phosphorus Settling Rate for July 10-11,1991
-------
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14
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DO Saturation
DO Criteria
o Observed with 95% confidence bars
11 12 13 17 18 19 20 21
_i_l.
¦ ¦ ¦
i i i
Model input 0.05 day
SAB recommended input 0.25 day
QUAL2E minimum value 0.001 day"1
QUAL2E maximum value 0.10 day"1
¦.¦.I'.
50 45 40 35 30 25 20
River Miles
15
10
Figure 5.67 Dissolved Oxygen Sensitivity to Organic Phosphorus Settling Rates for July 10-11,1991
-------
(with the recommended value of 0.25 per day):
RMS Comparison Between BRI and SAB Models for Organic Phosphorus Settling Rate
Survey
NOj-N
P04-P
Chloro
phyll a
DO
BRI
SAB
BRI
SAB
BRI
SAB
BRI
SAB
July 1991
0.628
0.625
0.134
0.134
4.592
4.451
1.103
0.972
August 1991
0.577
0.599
0.259
0.258
8.599
8.251
1.061
1.072
October 1991
0.255
0.255
0.091
0.091
1.001
1.001
0.575
0.560
In only one case was the change significant (greater than 5 %; in Bold).
5.6.2.6 Chlorophyll a to Algal Biomass Ratio
QUAL2E suggested a range of 10 to 100 /ig-Chl a/mg A.
Bowie et al., (1985) gave a range of 2.5 to 100 /zg-Chl a/mg A
The BRI model presented above had, as input, approximately the minimum value
reported in Bowie et al., (1985): 3.0 ^g-Chl a/mg A.
The SAB recommended a value of 2.0 /ug-Chl a/mg A.
Figures 5.68 to 5.71 represent the sensitivity of the model predictions to the chlorophyll a
to algal biomass ratio. The predictions on the figures included rate changes for QUAL2E
(minimum-10), SAB (2.0) and the final BRI model run (3.0).
The changes in RMS are given for the BRI (Final Runs of Part 1 above) and the SAB
(with the recommended value of 2.0 /ig-Chl a/mg A):
RMS Comparison Between BRI and SAB Models for Chlorophyll a to Algal Biomass Ratio
Survey
N03-N
P04-P
Chloro
)hyll a
DO
BRI
SAB
BRI
SAB
BRI
SAB
BRI
SAB
July 1991
0.628
0.584
0.134
0.144
4.592
5.909
1.103
0.924
August 1991
0.577
0.502
0.259
0.209
8.599
5.150
1.061
0.998
October 1991
0.255
0.269
0.091
0.081
1.001
0.994
0.575
0.608
5-108
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11
12 13 17 18 19 20 21
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Model input: 3.0 jog/mg
SAB recommended value: 2.0 fig/mg
Chlorophyll a to algal biomass ratio of 10 ng/mg ]
i i I i i i
i I i i i i I
1 * 1 1 1 1 *
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45 40 35 30
25 20 15 10
River Miles
Figure 5.68
Dissolved Nitrate Sensitivity to Ratio of Chylorophyll a to Algal Biomass
-------
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Survey I - July 10-11, 1991
2 -
Observed with 95% confidence bars
Model input: 3.0 ^g/mg
SAB recommended value: 2.0 iig/mg
Chlorophyll a ratio to algal biomass of 10 fig/mg
River Miles
Figure 5.69 Dissolved Orthophosphate Sensitivity to Ratio of Chlorophyll a to Algal Biomass
-------
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70
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Model input: 3.0 ng/mg
SAB recommended value: 2.0 ng/mg
Ratio of Chylorophyll a to algal biomass of 10 ng/mg
Survey I - July 10-11,1991
/
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frtn- n
River Miles
Figure 5.70 Chlorophyll a Sensitivity to Ratio of Chlorophyll a to Algal Biomass
-------
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Survey I - July 10-11,1991
- DO Saturation
DO Criteria
8
11 12 13 17 18 19 20 21
o Observed with 95% confidence bars
Model input: 3.0 jig/mg
SAB recommended value: 2.0 ng/mg
Chlorophyll a to algal biomass ratio of 10 jog/mg
i i i i
i tii i
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50 45 40 35 30 25 20
River Miles
15
10
Figure 5.71 Dissolved Oxygen Sensitivity to Ratio of Chlorophyll a to Algal Biomass
-------
In 11 of the 12 cases, the change was significant (greater than 5 %; in Bold). However,
the results were divided between the two options (BRI4 and SAB 7), and there was no consistent
improvement with either option for the calibration runs (BRI 4 vs SAB 3). In all cases, there was
an improvement during the validation run with the SAB values.
5.6.2.7 Complete Algal Sensitivity Run
All changes recommended by the SAB were incorporated in a single model run. These
included:
Summary of Algal Coefficients for the BRI Model and Recommended by
SAB
Variable
BRI
SAB
Algal Settling Rate
0 and 1.0
0.25
Non-Algal Light Extinction Coefficient
0.01
0.20
Michaelis-Menton Half-Saturation
Constant for Phosphorous
0.025
0.002
Michaelis-Menton Half-Saturation
Constant for Nitrogen
0.15
0.025
Remineralization Rate of Organic
Phosphorus
0.35
0.05
Organic Phosphorus Settling Rate
0.05
0.25
Chlorophyll a to Algal Biomass Ratio
3.0
2.0
The model runs included these changes for all three dry weather surveys. The output of
the adjusted model was compared against the output generated with the BRI variables (Section
1). A comparison between the original data set and the revised data set were made with, (a) plots
comparing the two model predictions Figures 5.72 to 5.83, (b) RMS, (c) Relative Errors, and (d)
the change of dissolved oxygen at each mainstem station.
Change in Root Mean Square (RMS) for the Final BRI Runs in Part 1. above compared to
model runs with all the SAB recommended changes are given below.
5-113
-------
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Final Dissolved Oxygen Profile for July 10 -
11, 1991: BRI vs SAB Recommendations
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Predicted with SAB changes
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Figure 5.83 Final Dissolved Oxygen Profile for August 14-15, 1991: BRI vs SAB Recommendations
-------
RMS Comparison for the Overall BRI and SAB Models
Survey
Run
NOj-N
nh3-n
P04-P
Chlorophyll a
DO
July
BRI
0.628
0.218
0.134
4.592
1.103
SAB
0.578
0.230
0.154
5.456
1.189
August
BRI
0.577
0.221
0.259
8.599
1.061
SAB
0.458
0.223
0.205
7.677
1.062
October
BRI
0.255
0.107
0.091
1.001
0.575
SAB
0.276
0.107
0.073
1.177
0.706
Bold numbers are the smaller RMS values for the BRI and SAB comparisons. As
before, RMS values that were below 5 % change were not highlighted. The BRI inputs resulted
in 7 runs with lower RMS values vs 5 runs with the SAB values. Three runs did not change.
The results were mixed and do not appear significant.
Median relative error was calculated as described earlier. A comparison of the two
models are given below:
Median Relative Error Comparison for the Overall BRI and SAB
Models
1991 Survey
BRI
SAB
July
8
12.5
October
5
8
August
11
10.5
In two of the three surveys, the median relative errors were lower for the BRI model
simulations and were below 10%. This test favors the BRI model.
/
In addition, the average absolute DO difference was determined between model
prediction and observation. The results are given below:
5-126
-------
Average Absolute DO Difference Between Model Prediction
and Observation
1991 Survey
BRI
SAB
July
0.80
1.04
October
0.52
0.64
August
0.87
0.96
In all three cases, the average absolute DO difference was less with the BRI model. The
differences were not significant, ranging between 0.09 and 0.24 mg/L.
In the SAB review, runs were made with their variables and the input files supplied in the
original BRI report (1998). These figures supplied in the review are attached. These figures
appear to be similar to those reported above. These figures also do not suggest major
improvements to the modeling as a result of the input of variables recommended by the SAB.
5.6.3 Model Sensitivity to the Sediment Oxygen Demand
The SAB did not comment on the SOD rates used in the model. The discussion was
received during the review of the WLA for the UBWPAD.
QUAL2E indicated SOD was variable.
Bowie et al., (1985) presented SOD ranges for 14 studies involving rivers and streams.
The overall range of the 14 studies was 0.002 to 4.09 g-Oj/f^-day. The averages of the ranges
for the 14 studies is 0.11 to 0.99 g-O^tf-day.
Schnoor (1996) reported the following SODs at 20 °C as a function of water quality.
Water Quality
g-O/f^-day
[g-0^m2-day]
Natural to Low Pollution
0.009 to 0.093
[0.1-1.0]
Moderate to Heavy Pollution
0.47 to 0.93
[5-10]
Chapra (1997) (Table 25.1 page 452) repeated the table from Thomann and Mueller
(1987) (Table 6.7 page 292), who repeated die table from Thomann (1972) (Table 5-4 page 104).
5-127
-------
Some of these values are reported below. All are at 20 °C.
Bottom type and location
g-Oj/f^-day
[g-(Vm2-day]
Approximate average
g-Oj/tf-day
Municipal sewage sludge-outfall
vicinity
0.186 to 0.929
[2 to 10]
0.37
Municipal sewage sludge-"aged",
downstream of outfall
0.092 to 0.185
[1-2]
0.14
Estuarine mud
0.092 to 0.185
[1-2]
0.14
Sandy bottom
0.019 to 0.093
[0.2-1.0]
0.047
Mineral soils
0.005 to 0.009
[0.05-0.10]
0.007
The details of the SOD measurements on the Blackstone River for the 1991 water quality
surveys were discussed in the BRI. The work was carried out by the U.S. EPA research
laboratory in Lexington, MA. The values measured ranged from a high of 0.55 to a low of 0.15
g-Cytf-day. All samples were taken in impoundments. Table 5.12 describes how these values
were applied in the BRI final model runs.
The extrapolation of the results to reaches above and/or below the impoundment was
questioned, as was the use of 0.15 for all other reaches because it was the minimum BRI
observation at any of the stations evaluated. The values measured on the Blackstone seem
reasonable based on the literature cited above. The values above the minimum, 0.23 to 0.55 g-
Oj/tf-day, fall within the ranges for water quality impaired reaches in all six references: Bowie
et al., (1985), Schnoor (1996) and Thomann (1972) [restated in Chapra (1997) and Thomann and
Mueller (1987)]. The BRI minimum of 0.15 is about equal [0.14] to the average value identified
for reaches downstream of a municipal sewage outfall (Municipal sewage sludge-"aged",
downstream of outfall) [after Thomann (1972) and restated in Chapra (1997) and Thomann and
Mueller (1987)].
Was this value reasonable? Since there are several municipal facilities (UBWPAD,
Millbury, Grafton, Northbridge, Uxbridge and Woonsocket WWTFs) on the Blackstone, most
reaches will be downstream of one or more municipal outfalls. Specific measurements at
Tupperware Impoundment would seem to support this. This location is in between the two major
cities on the river (ie. well below the City of Worcester and the UBWPAD discharge and several
miles above the City of Woonsocket.) Tupperware Impoundment is about 4 miles downstream
of the Uxbridge WWTF. There are no other discharges or large urban areas between the
Uxbridge WWTF and the Tupperware Impoundment.
5-128
-------
The following was done to evaluate SOD and provide an application of the values
measured on the BRI in a more conservative manner.
(1) Each measurement made by the U.S. EPA was applied only to the reach that it was
measured in, with one exception. The Fisherville and Farnumsville Impoundments are located in
Reaches 6 and 7, respectively. These impoundments are between two of the SOD measurements
(Reach 4 above BLK04 and Reach 8 above BLK07). The SOD in Reach 4 was 0.55 g-Oj/fP-day
and in Reach 8 was on average 0.37 g-Oj/f^-day. Over the years, the Fisherville and
Farnumsville Impoundments have provided similar sediment traps when compared to Singing
Dam (BLK04) and Riverdale Dam (BLK07). Therefore, it is assumed that the SOD in the
Fisherville and Farnumsville Impoundments would be greater than background. To be
conservative, both impoundments were run with the minimum for BLK07 of 0.22 g-O^tf-day.
(Although an average of 0.46 for those reaches between 4 and 8 would also be a logical
progression away from Worcester: 0.55 to 0.47 to 0.37). No other extrapolations of the SOD
observations occurred.
(2) Extrapolation of SOD data in a DO modeling study typically happens. SOD values
are not measured for every reach modeled. The Blackstone River is about 45 miles in length and
has been sectioned into a total of 25 modeling reaches. During the BRI, six locations were
monitored for SODs from Singing Dam (BLK04) to Albion Dam (BLK19). The SOD model
inputs for these six reaches, and for Reaches 6 and 7, have been discussed above. The remaining
17 reaches did not have SOD measurements. The discussion above supports the application of
0.14 g-02/ft2-day in these reaches. The results are presented for comparison to the BRI final runs
in Figures 5.84 to 5.86. The result of changes discussed above in 1 and 2 are summarized below:
The greatest impact is expected to occur in the following reaches:
Reaches
Original SOD Values
Revised SOD Values
2-3
0.55
0.14
5
0.55
0.14
6
0.55
0.22
7
0.37
0.22
9
0.23
0.14
22-24
0.33
0.14
5-129
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- DO Saturation
DO Criteria
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• DO profile with minimun literature SOD rate of 0.14 g02 ft"2-day'1
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4 I- DO Criteria
2
- DO Saturation
Observed with 95% confidence bars
DO profile with Reaeration, CBOD, Nitrification, SOD, & Algae
DO profile with mimimum literature SOD rate of 0.14 g02 ft"2-day'1
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• •• Predicted with minimum literature SOD rate 0.14 g02ft"2-day"1
50 45 40 35 30 25 20 15 10 5 0
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Figure 5.86 Dissolved Oxygen Profile with Revised SOD Rates for August 14-15,1991
-------
Reaches
Revised SOD
Values
(g-O/fP-day)
Comment
1-3
0.14
"For Municipal sewage sludge-"aged", downstream of outfall" [after
Thomann (1972)1
4
0.55
Measured value at Singing Dam
5
0.14
"For Municipal sewage sludge-"aged", downstream of outfall"
6-7
0.22
Minimum value measured at Riverdale Pond. This reaches include
Fisherville Pond and Farnumsville Impoundment
8
0.37
Average of measured values at Riverdale Pond 0.22 & 0.53
9
0.14
"For Municipal sewage sludge-"aged", downstream of outfall"
10
0.23
Average of measured values above Rice City Pond 0.16 & 0.30
11-15
0.14
"For Municipal sewage sludge-"aged", downstream of outfall"
16
0.15
Average of measured values at Rte 122 near Railroad Bridge and
upstream of Tupperware Dam 0.1S & 0.14
17-19
0.14
"For Municipal sewage sludge-"aged", downstream of outfall"
20
0.37
Average of measured values downstream of Woonsocket WWTF and
upstream of Manville Dam 0.53 & 0.21
21
0.33
Measured value upstream of Albion Dam
22-25
0.14
"For Municipal sewage sludge-"aged", downstream of outfall"
RMS changes for the dissolved oxygen simulations:
RMS Comparison for the BRI and SOD Revised Models
Survey
BRI
SOD
Revised
July 1991
1.103
0.703
August 1991
1.061
. 0.825
October 1991
0.575
0.616
No change in RMS occurred for N03-N, P04-P or Chlorophyll a. The RMS errors for the
July and August SOD revised runs were lower, and for October it was higher.
5-133
-------
The median relative error is used to, (a) acknowledge the DO oxygen modeling effort
relative to the group of models presented in Thomann (1980), and (b) to compare the BRI model
runs with the Revised SOD runs for all three surveys.
The details are presented below:
Median Relative Error Comparison for the BRI and SOD Revised
Models
1991 Survey
BRI
SOD Revised
July
8
6
October
5
6
August
11
7.5
In two of the three surveys, the median relative errors were lower for the Revised SOD
model simulations. All runs were below the 10% median relative errors described earlier, except
for the August BRI run. This test does favor the SOD revised model.
In addition, the average absolute DO difference was determined between model
prediction and observation. The results are given below:
Average Absolute DO Difference Between Model Prediction
and Observation for the BRI and SOD Revised Models
1991 Survey
BRI
SOD Revised
July .
0.80
0.58
October
0.52
0.60
August
0.87
0.62
Average absolute DO differences between the two models did not exceed 0.2S mg/L.
No other consideration in the assignment of these values has been made. Some concerns
may be raised for the following reaches. These concerns should result in higher SOD rates for
these reaches.:
1. Reaches 1-3 - Urban runoff from Worcester, MA
2. Reach 5 - Between Reach 4 (0.55 g-O/fP-day measured) and Reach 8 (0.37 g-O/fP-day
measured). The authors have settled on a background value for this reach. It could be
argued that the source of the SOD at Reach 4 will also impact Reach 5, raising the
assigned value above background.
3. Reach 22-24 - Urban runoff from Woonsocket, Central Falls and Pawtucket, RI. Also,
5-134
-------
below the Woonsocket WWTF values at Manville (0.37 g-O/tf-day measured) and
Albion (0.33 g-O/tf-day measured) were similar. Below Albion, we have set the
assigned value to background. This could be low.
5.7 Model Application with 7Q10 Flows
Preliminary model applications with the critical 7Q10 flow (the seven day low flow with
a ten year return period) are included in this section. The 7Q10 flow profile in Figure 5.2 has
been generated by determining the reach inflows using equation 5.6 with average discharges from
the WWTF's. Then, using the permitted discharges for WWTF's, and reach inflows, the flow
profile is generated. This ensures minimal flow from the tributaries and reaches for dilution.
The three conditions listed below evaluate the response of the river to changes in
discharge quality from UBWPAD, in addition to performing a post audit of STREAM7
(MADEQE 1983) simulations used in the UBWPAD WLA (Table 5.17). The UBWPAD WLA
evaluated various discharge conditions and lists the minimum DO prediction and the length of
the river violating the 5.0 mg/L DO criteria.
The baseline condition (Table 5.18) (Condition 1) simulated in QUAL2E has all WWTF
inputs to the model set at the maximum daily discharge permit concentrations. For Woonsocket
WWTF, the ammonia input represents the average of the July survey (28.1 mg/L). This was the
highest average concentration monitored during the three 1991 surveys. Tributary concentrations
represent the average of the July and August surveys (1991). Simulations are performed, with
and without productivity, in order to isolate the key sinks causing oxygen depletion, while also
addressing the issue involving the impact of limiting productivity through discharge regulation.
Condition 1
Violations of the DO criteria in MA occur at the impoundments upstream of Singing
Dam, Fisherville Dam, Riverdale Dam and Rice City Pond Dam, with and without productivity.
The DO loss occurs due to SOD and CBOD.
DO violations occur in RI downstream of the Woonsocket WWTF. The lowest DO
concentrations are predicted upstream of the Central Falls Dam (River Mile 2.0). DO violations
are greater without the presence of the productivity, indicating the dominance of photosynthesis
over respiration at all impoundments between Woonsocket WWTF and the Pawtucket Dam
(River Mile 0.8). The DO problems are caused by a combination of SOD, NBOD and CBOD.
Condition 2
The discharges for UBWPAD are set at 5.0 mg/L for BOD, and 1.0 mg/L for ammonia.
All other inputs are retained from condition 1. STREAM7 under this condition predicted no
violations of DO in MA. QUAL2E simulations support this prediction and minimum
concentrations predicted with QUAL2E equaled STREAM7 predictions. It is concluded that the
two models give similar results.
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Table 5.17 Results of the 7Q10 Flow Analysis for the UBWPAD WLA using MADEP STREAM7 (MADEQE 1983)
UBWPAD Effluent
Instream
Flow
(cfc)
BODs
(mg/L)
NHrN
(mg/L)
DO
(mg/L)
Minimum DO
Predicted (mg/L)
River Miles
in Violation of
5.0 mg/L
Percent of Total
Time in Violation
86.6
15.0
10.0
5.0
0.0
18.1
82.7
15.0
5.0
5.0
0.7
12.5
69.0
5.0
10.0
5.0
0.0
16.5
76.3
5.0
2.0
5.0
4.8
0.2
1.3
10.0
2.0
6.0
3.8
0.6
3.9
5.0
1.0
5.0
5.6
0.0
0.0
10.0
1.0
5.0
4.7
0.4
2.6
Headwater flow = 7.86 cfs, BOD5 = 3.0 mg/L, NH3-N = 0.06 mg/L, and DO = 7.0 mg/L and Temperature =
25°C
-------
Table 5.18 Boundary Conditions for the 7Q10 Flow Conditions of the Blackstone River QUAL2E Model
Sources
Flow
(cfs)
DO
(mg/L)
BODs
(mg/L)
NH3-N
(mg/L)
no3-n
(mg/L)
P04-P
(mg/L)
Chi a
(Mg/L)
Headwater1
6.53
6.75
1.25
0.36
0.70
0.01
2.05
Quinsigamond River1
3.03
7.27
0.68
0.15
0.14
0.04
1.50
Mumford River1
5.89
8.23
0.86
0.14
0.49
0.08
1.20
West River1
3.22
7.11
0.84
0.10
0.10
0.01
1.45
Branch River1
13.8
7.29
1.18
0.19
0.26
0.02
2.10
Mill River1
1.97
7.33
1.39
0.15
0.27
0.03
4.60
Peters River1
1.00
5.64
1.07
0.23
0.74
0.02
3.15
UBWPAD WWTF2
86.6
5.00
15.0
2.25
3.00
5.00
0.00
Millbury WWTF3
1.85
5.00
50.0
5.00
3.00
5.00
0.00
Grafton WWTF3
2.46
5.00
50.0
5.00
3.00
5.00
0.00
Northbridge WWTF3
2.77
5.00
15.0
5.00
3.00
5.00
0.00
Uxbridge WWTF3
3.87
5.00
30.0
5.00
3.00
5.00
0.00
Woonsocket WWTF4
24.6
5.00
30.0
28.13
3.00
5.00
0.00
1 = Average of July and August 1991 surveys;2 = Design flows and permitted concentrations for DO, BODs, and
NH3; 3 = Design flows, and permitted concentrations for DO and BOD5;4 = Design flows, and permitted
concentrations for DO, BOD5, and maximum observed for NH3-N; All WWTF's concentrations for N03-N, and
P04-P are typical of secondary treatment effluents (Thomann & Mueller 1987).
-------
1
DO concentrations in R1 are similar for conditions 1 and 2, indicating that CBOD and
ammonia changes in UBWPAD do not affect DO concentrations in RI. Also, UBWPAD's BOD
is completely assimilated when it reaches the interstate boundary during the 7Q10 flows.
Condition 3
UBWPAD concentrations are changed to 10.0 mg/L for BODs and 2.0 mg/L for
ammonia. This is a condition also tested by STREAM7 (MADEQE 1983), which might be the
basis for the current permits of 15.0 mg/L BOD3 and 2.25 mg/L ammonia for UBWPAD.
Violations for a 0.6 mile section of the river were predicted by STREAM7. QUAL2E
simulations again support the STREAM7 prediction, with DO violations for a 0.4 mile section
upstream of Fisherville Dam. This also supports the conclusion that the performances of
STREAM7 and QUAL2E are comparable to each other.
5.8 Dissolved Oxygen Modeling Summary, Conclusions and Recommendations
QUAL2E has been used to define the Blackstone River from Worcester, MA to it's
discharge into the Seekonk River in Pawtucket, RI. The major tributaries and point sources have
been included in the model.
The model has been used in the dynamic mode to address diurnal variations of oxygen.
The major sources and sinks contributing to the DO balance have been accounted for in the
model including: CBOD and NBOD consumption; SOD; reaeration; and algal productivity and
respiration.
The following conclusions were determined from this analysis:
Model Calibration and Validation
• The model has been calibrated using the data collected in July and October 1991 for the
Blackstone River Initiative - Dry Weather Study.
• The model was also successfully validated using the data collected in August 1991, and
two independent studies conducted in Massachusetts in 1980 and in Rhode Island in
1987.
System Observations (Productivity)
• High levels of primary productivity in the Blackstone River result in impaired water
quality associated with significant daily swings of oxygen. The river reaches most
dramatically impaired are just above and below the MA/RI state line.
• High primary productivity is a result of phosphorus additions from the municipal
wastewater facilities on the river. The major sources of phosphorus are from die
UBWPAD and Woonsocket facility.
• The impoundments along the river serve to reduce velocities and increase the time of
5-138
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travel in the river reaches directly behind the dams. These conditions compound the
problems presented by high levels of phosphorus by providing the appropriate hydraulic
conditions for the growth of algae.
System Observations (Nitrification)
• The river reaches with the highest nitrification rates are directly below the Woonsocket
WWTF. Instream nitrification governs the oxygen profiles in these reaches and causes a
dissolved oxygen sag below Woonsocket's discharge that often extends to the mouth of
the river in Pawtucket, RI.
System Observations (Sediment Oxygen Demand)
• The 19 impoundments along the river are sediment traps for both dry and wet weather
conditions. The sediments behind these impoundments are a major sink of oxygen and
often govern the oxygen profile. This is especially true in the upstream reaches, where
productivity and instream nitrification are relatively small compared with the lower
reaches.
Model Application (7Q10 flows and STREAM7 post audit)
• Model application to the 7Q10 flow indicated the potential of major violations of the
dissolved oxygen criteria of 5.0 mg/L downstream of the Woonsocket WWTF. The
major cause of these violations is the instream nitrification due to the high discharges of
ammonia from this facility.
• Model application to the 7Q10 flow indicated minor violations in Massachusetts
upstream of four impoundments. The major cause of these violations are high sediment
oxygen demands.
• Based on a comparison of data from the early 1980s and this study, it was clear that the
advanced wastewater treatment implemented in the mid 1980s at UBWPAD has made a
significant improvement to the dissolved oxygen concentrations in the river. The
improvements are directly associated with a reduction in the facility's discharge of CBOD
and ammonia.
• A post audit of the waste load allocation completed in 1983 with the STREAM7 Model
for the Massachusetts portion of the Blackstone River was successful. The model's
application and the modeler's interpretation of the results were appropriate.
Recommendations
The calibrated and validated model should be used in a comprehensive waste load
allocation. The following should be considered in the analysis:
• Dams and their current and future role in the Blackstone watershed are a complicated
issue. Dams are having a negative impact on the river oxygen profile, as related to the
discussion above on productivity and sediment oxygen demand. A ranking of the dams,
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based on their importance to dissolved oxygen, may be made. Those considered to be
significant may require a comprehensive study similar to Rice City Pond (Chapter 8).
• The QUAL2E model may be used to provide insight into the potential impact of dam
modification, or dam elimination on river oxygen profiles. At a minimum, the model
may be used to evaluate the impact of rerouting the river around the dams, for instance,
by utilizing the Blackstone Canal system around Fisherville Dam (BLK06) and Rice City
Pond (BLK08). The result would be a lowering of the detention times in these reaches,
which would have a positive impact on oxygen by decreasing the impacts of SOD, while
also reducing the time available for the initiation of algal productivity, thereby reducing
the potential of algae growth.
• QUAL2E should be modified to run in a continuous mode for annual simulations. This
data could then be used to address seasonal limits for point source discharges.
• The sampling program for the 1991 surveys did not include DO measurements upstream
of impoundments. The 7Q10 simulations indicate that there is the potential for violations
in a number of impoundments in MA and RI, caused mostly by the SOD values measured
during this initiative. A validation of these SOD rates is possible, through an inexpensive
DO monitoring effort during low flows upstream and downstream of these dams.
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6.0 DRY WEATHER TRACE METAL MODELING SUMMARY
6.1 General Trace Metal Fate and Transport Considerations
Surface water systems are a major carrier of metal pollution. Pollutants may be
transported in dissolved, colloidal or particulate forms. Reactions, including precipitation and
co-precipitation and complexation with organic or inorganic ligands, may alter the original
distribution of metal pollutants in shallow aquatic environments.
The mobility of metal pollutants, at large, depends on transport processes like advection,
and dispersion (Bourge 1988). Transport of metals increase because of complexation of metals
with organic or inorganic species. Adsorption onto solids and precipitation of metals tend to
delay the transport process. The dispersal patterns depend on rates of reaction between
particulate and dissolved forms of trace metals in natural aquatic systems (Wittman and Forstner
1983).
A thorough scientific understanding of metal fate in aquatic systems requires knowledge
of: sorption, aquatic plant growth, reaction kinetics of metals, characteristics of adsorbent
including biotic, abiotic, specific gravity, and grain size distribution, influence of humic and
fulvic acids, presence of hydrous oxide of iron and manganese, pH and temperature; quantity and
flow rates in aquatic systems and presence of salts.
Sorption by solid particulate matter is now widely recognized as the major mechanism
influencing metal fate. The rates of reaction between particulate and dissolved components are
dependent on physico-chemical factors and the resulting equilibrium conditions are determined
by nature and concentrations of adsorbing solids. The resulting equilibrium condition defines the
ratio between solid phase and dissolved concentrations, referred to as a partitioning coefficient
(Langmuirs Isotherm) (Goncalves, Sigg and Stumm 1985).
The partition coefficient (k„) is a function of various characteristics of the adsorbate and
adsorbent (Haque and Freed 1974; Karichoff, Brown and Scott 1979; O'Connor and Connolly
1980). Laboratory and field observations have shown that the partition coefficients decrease with
increasing adsorbent concentration (O'Connor and Connolly 1980). From a theoretical point of
view, the partition coefficient should be independent of the adsorbent concentration, but Di Toro
et al., (1982) indicated that the binding strength of all reversible sites might be decreased by
particle-particle interaction, causing desorption from reversible sites. Voice, Rice and Weber
(1983) proposed that the adsorbent mass phenomenon is due to the presence of micro-particles,
which are not removed in the solids separation process. This may cause a reduction in the
estimation of the partition coefficient.
Trace metal ions are accumulated by microorganisms that aid in removing metal ions
from natural water systems. The biological processes involved can be divided into two general
categories: (i) biosorption of metal ions onto the surface of microorganisms and (ii) intercellular
6-1
-------
uptake of metal ions (Darnall 1986). The range of environmental variables that affect the
accumulation of metals by algae include length of exposure period, type of metal, oxidation state,
pH, salinity and presence of organic pollutants. It was observed that chemical availability of
trace metals to plants was greater under acidic and oxidizing conditions.
One of the fundamental and most significant of the interactions in metals is the process of
adsorption and desorption. Adsorption is the concentration of molecules of a gas, solid or liquid
at a solid surface. The surface where the concentration takes place is called adsorbent, and the
molecules which adsorb are called adsorbate. The degree of partitioning is one of the most
important phenomenon, as it influences the transfer of metals to the biotic and abiotic
compartment. Scientific understanding of the variation of partition coefficients with other
environmental variables is of great use, because partition coefficients will have a role on the
amount of metal settled or resuspended in a river reach.
The computer modeling of trace metal is very complicated, as the number of variables
that account for the fate and transport of trace metals in a river system is large. In addition, the
computer models may require highly detailed information to develop oxide-solution interaction.
Computer models are useful devices to probe our understanding of the basic physico-chemical
nature of metal-particle interactions. In addition, such models enable one to predict the chemical
transport for any environmental situation. A major disadvantage of these computer models is
that few metal fate and transport models have been verified to real field data. Pawtoxic is a trace
metal model used to predict the transport and concentration of trace metals (Wright and
McCarthy 1985a). It adopts a very simple but effective approach to trace the dispersal pattern of
metals by considering two simplified equations involving net sediment transport and metal
partitioning.
The modeling of the fate and transport of trace metals in the Blackstone River has never
been performed in MA. However, the Rhode Island Department of Environmental Management
(RIDEM) did have a modeling study completed in 1985 for trace metals (Wright and McCarthy
1985a).
6.1.1 General Factors Governing the Distribution of Metals and Total Suspended Solids in the
Aquatic Environment
Cadmium (Cd) is a rare element that occurs in zinc-bearing sulfide ores (sphalerite), and
is often found in all zinc - containing products. Cd is more mobile compared to many metals and
is transported as either hydrated cations or as organic/inorganic complexes in aquatic systems.
The aquatic fate and transport of Cd is governed by the formation of complexes with organic
materials in highly polluted waters. Sorption processes are responsible for the removal of
dissolved Cd from die system (Ramamoorthy and Kushner 1975). As the pH increases, the
removal of dissolved Cd increases. Cd exists as a divalent cation up to a pH of 9. Humic acids
in solution, and other natural complexing agents, can maintain Cd ions in a bound form at a pH
below 3 (Guy and Chakrabarthi 1976). According to Suzuki, Miyazaki and Kawaeoc (1979)
6-2
-------
suspended solids of high organic content play a dominant role in deciding the fate of Cd. Humic
material, as well as phosphate, are the major components of sediment that are responsible for the
adsorption process of Cd (Gardiner 1974). According to Perhac (1972), Cd is distributed in the
water column in the dissolved state (77.4-95.4%), with only minor amounts in the particulate
form. Cd has less affinity for the common adsorbents than do Cu, Zn, and Pb, causing Cd to be
more mobile in the aquatic environment (Huang, Elliott and Ashmead 1977). Cd may be
strongly accumulated by all organisms at all trophic levels.
Chromium (Cr) is a transition element which is typically precipitated from magmas at an
early stage. It exists in two oxidation states in the aqueous system; hexavalent (Cr4*) and
trivalent (Cr+3). Cr is found in concentrations at about 0.01- 0.8 ppm in river waters (National
Academy of Sciences). The hexavalent Cr is more soluble than trivalent Cr and is not sorbed to
clays, ferric hydroxides, or oxides, or other particulate matter to a significant degree (Kharka,
Turekiar and Bertine 1968). However, trivalent Cr forms insoluble material when it reacts to
aqueous hydroxide ions. The hexavalent Cr adsorption process increases as pH decreases, but
adsorption of trivalent Cr increases as pH increases (Griffin, Au and Frost 1977). Compared to
the trivalent Cr, hexavalent Cr compounds are highly toxic in nature to the biological
compartment of an aqueous system. Trivalent Cr is highly stable in nature and precipitates
quickly when the pH of the system is above 5 (Cotton and Wilkinson 1972). Cr is accumulated
to a greater extent by the aquatic biota, as it is an essential nutrient. Researchers found that
phytoplankton concentrated a significant amount of Cr.
Copper (Cu) exists in the form of sulfide minerals (chalcocite) and as adsorbed ions. The
major source of copper pollution is the electrical industry (Ramamorthy and Kushner 1975).
Several processes determine the fate and transport of copper in aquatic system, including the
complex formation with humic substances, sorption to hydrous metal oxides, clays, organic
material, and strong accumulation by the biotic compartment of the aquatic system (Bourge
1988). Cu exists in the divalent form. As Cu is strongly adsorbed to many kinds of surfaces and
has a greater tendency to form complexes with both organic and inorganic ligands, the residence
time of Cu at a particular place in the aquatic environment is limited. The solid phase
concentration of Cu in the water column is enriched due to its strong affinity towards clays, iron
and manganese, carbonate minerals, and organic matter. Payne and Pickering (1975) found that
the total removal of copper from the system occun-ed in the presence of organic ligands and at a
pH greater than 6. However, in the presence of soluble organic matter, the sorption process is
ineffective, favoring the existence of the dissolved form of Cu in the system. Cu concentrations
are higher in the fall and winter, compared to the concentrations in the spring and summer, as Cu
is strongly accumulated by the biotic compartment.
Lead (Pb) ore is commonly accompanied by Cu, Zn, and Ag ores. Pb exists in three
oxidation states; 0, +2 and +4, and can only be solubilized by the presence of acids. Natural
compounds of Pb can be adsorbed by ferric hydroxides, or carbonate and sulfate ions to form
insoluble compounds. Therefore, Pb is not usually soluble in surface waters. The sorption
process of Pb is predominant in reducing the concentration of soluble Pb in surface waters,
6-3
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because the solubility of lead is relatively low with carbonates, sulfate and sulfides. Pb is
complexed by ligands of river water (Ramamoorthy and Kushner 1975). The transport of Pb in
natural waters is influenced by the sorption processes by organic material present in the surface
water (Jackson and Skippen 1978). Huang, Elliott and Ashmead (1977) suggested that the
adsorption of Pb is highly pH dependent Pb is desorbed at low pH, but almost all of the Pb
exists in the solid phase at a pH above 7. Pb in the sewage effluent entering polluted coastal
waters is most likely in the particulate form. The partition coefficient of lead is not affected by
the presence of other metals (Ramamoorthy and Rust 1978).
Literature emphasizes the ambiguous sorption behavior of Pb. Kubota, Mills and
Oglesby (1974) reported that the transport of Pb in river systems occurred in the particulate form.
Angino, Magnuson and Maugh (1974) suggested that the partitioning of Pb between dissolved
and particulate is about equal, and Pita and Hyne (1975) found that Pb is transported in the
dissolved form..
Nickel (Ni) is a rare element that is associated with pyrite and chalcopyrite. It is very
mobile in aquatic systems. Although in some cases, nickel has shown an affinity for organic
matter, hydrous iron and manganese oxides, sorption and precipitation do not appear significant
in the fate of nickel in the environment. It is almost always in the dissolved form, unless high
concentrations of organic matter exists, and the pH is above 9. Ni sulfide is quite insoluble and
occurs in the particulate form in natural waters. Although the biotic compartment accumulates
Ni, it is not a dominant process in determining the fate of Ni. Ni exists in the divalent form and
forms compounds with chlorides, phosphates, nitrates, oxides, hydroxides and organic ligands
(Cotton and Wilkinson 1972). Humic acids in natural water can increase the solubility of Ni,
thereby reducing the precipitation of Ni in natural waters. The dissolved concentration of Ni is
controlled by the presence of hydrous iron and manganese oxides (Angino, Magnuson and
Maugh 1974; Steele and Wagner 1975).
6.2 Trace Metal Model Description and Set-Up
The computational framework of the trace metal model, Pawtoxic (Wright and McCarthy
1985b), was developed by modifying the dissolved oxygen model QUAL-II. Pawtoxic is a
steady state, water quality model, applicable to well mixed river systems. The Pawtoxic model
has the capability to simulate a maximum of three conservative elements, total suspended solids,
and five non-conservative elements in each simulation. The physical representation and
input/output formats are similar to QUAL-II. The stream is represented as a chain of completely
mixed reactors linked together. Upstream inputs, sinks, incremental inflows, waste loads and
outflow through the final element in a reach are considered to perform the hydrologic and
material balances. The output of an element acts as an input to the downstream element, as the
transport mechanism is assumed to be controlled by advection in the direction of the flow.
The Pawtoxic model retained some of the options of QUAL-II that include, usage of
empirical relationships or Mannings formula to calculate velocities in order to represent stream
6-4
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hydraulics.
The fate and transport mechanism of suspended solids in the surface water column is
governed by the advection-dispersion mass transport equation. The equation for this transport
mechanism is given by the following equation, with advection being the primary process.
<^1 /r ^
V~te=-k3m l+kum2 (6,1)
where v = average stream velocity (ft/s); m, = concentration of suspended solids in the water
column (mg/L); x = distance traveled downstream (ft); k, = settling coefficient = YJD (1/s); V, =
settling velocity (ft/s); D = average depth of the stream (ft); k„ = resuspension coefficient = V„/D
(1/s); Vu = resuspension velocity (ft/s) and; m2 = concentration of suspended solids (mg/L).
Equation 6.1 represents a type II analysis of a mixed interactive bed. The calculation and
measurement of Vu, and m2 are difficult and the values used for these parameters are based on
modelers experience. The value of m2 is highly variable from reach to reach and a true average is
difficult to determine.
Wright and McCarthy (1985b) suggested that the estimation of Vu and V, can be
eliminated by introducing a net sediment transport coefficient, k,, (1/s):
dm1
0=~V ± ~km. re
dx ns 1 (6-2)
The steady state transport of the dissolved (c) and particulate (p) components of any toxic
chemical can be expressed as follows:
0=v^x~k>c*k'p (6.3)
0.vg*Jc1c-k1ptlc.j> (64)
where k, and k2 are the adsorption and desoiption coefficients, respectively, representing the
interactions between the dissolved and the particulate fractions of the contaminant. The total
concentration is (CJ given by:
Ct=c+p
(6.5)
-------
Combining equations 6.4 and 6.5, a relationship may be developed between and Ctas shown
by equation 6.6.
vdc
0—a<66>
The particulate fraction is equal to the product of the solid phase concentration of the
contaminant (r) and the solids concentration:
P=rmi
(6.7)
At equilibrium the ratio between the solid-phase and dissolved concentrations is referred
to as the partition coefficient according to Langmuirs isotherm. The magnitude of this
coefficient depends on the characteristics of the adsorbate and the adsorbing solids and varies
inversely with the adsorbate and directly with organic clay fractions of the solids. The equation
for partition coefficient can be written as:
m.
kP~ <6-8)
6.3 Net Sediment Transport Coefficient
A positive value of k„ indicates a net increase of solids in the water column, as
resuspension controls the process, while a negative value of indicates a net decrease in solids,
as settling controls the sediment concentration. The solution of equation 6.2 is:
jBj^expdJc^) (6.9)
where mo is an initial suspended solids concentration. A log plot of solids and time of travel of
the river (x/v) gives k„ as the slope. It was also shown in earlier work by Wright and McCarthy
that k„, may be related to average stream velocity through:
kns=a+t>V (6-10)
where a and b are empirical constants. This relationship may be used to estimate k„, for different
6-6
-------
stream velocities.
Total Suspended Solids (TSS) is a nonconservative constituent, subject to reductions due
to settling and increases due to scouring of the stream bed. Settling and resuspension are
dependent on shear velocities at the water-sediment interface. Shear velocities can be correlated
to average stream velocity in shallow river systems (Wright and McCarthy 1985b). In a river
system, a net increase or decrease in TSS concentration is dependent on the magnitude of stream
velocity.
By measuring river velocity and TSS concentrations at different flows, a semilog plot of
TSS loading versus time of travel yields a slope equal to k^. Using the calculated k,,, values and
the corresponding velocities for different surveys, a relationship between k,,, and stream velocity
can be found. The mathematical forms of these relationships were expressed in equations 6.9
and 6.10.
This procedure was followed in earlier application of this model on the Pawtuxet River in
Rhode Island (McCarthy 1986). More recently the relationship between and velocity were
checked for the Pawtuxet River for all available TSS data in mg/L. The results are summarized
in the comparison of model predictions to observation (Figure 6.1). For the 70 observations, the
coefficient of determination was 0.93. A test of the regression line to 95% confidence was
successful, in that the slope of the line approaches 1.0 (actual 1.03) and the intercept approaches
0.0 (actual 0.12). In general, the model did well in the typical ranges of TSS for the Pawtuxet
River (0-10 mg/L).
The system hydraulic characteristics for velocities and depths were defined by the
equations 5.1 and 5.2. These relationships were defined in earlier efforts: for Massachusetts by
MADEQE in 1983 and for Rhode Island by Ocean State Power in 1987 and Wright in 1987.
Time of travel studies are not available for the river sections at the state line of MA and
RI between the Route 122 bridge on the Blackstone River, MA and Main Street in RI (Reaches
15-17). After examination of the USGS topographic maps and field reconnaissance, the
hydraulic characteristics of Reaches 15 to 17 were assumed to be similar to Reach 18. A
complete list of flow/velocity coefficients for each reach was provided earlier in Table 5.5.
TSS exists in the water column as abiotic and biotic forms. Abiotic TSS such as silts,
sands, and clays are contributed due to headwaters, point sources releases, tributaries, and
settling/resuspension. Biotic TSS such as algae, periphyte, and macrophyte are primarily a
function of light and nutrient availability. Since k^-velocity relationships are based on a net
settling mechanism, the model predicts only abiotic TSS. Thus, the abiotic and biotic
components need to be separated before development of the k^ relationships.
Based on the evaluation of the chlorophyll a and oxygen profiles in Chapter 5, it was
concluded that plant growth is significant downstream of BLK06 to the point of discharge of the
6-7
-------
I 1 I
T r
—r
¦"—r
"^-7:
• June 7,1983
O June 5,1985
~ July 10,1985
V July 30,1985
¦ July 8.1993
~ August 2,1983
~ August 14, 1984
A
/>
/>
/>
/y
/>
/>
/y
/>
/>
Y = 1.03X + 0.12
R2 = 0.93
-------
river at BLK21 during the July and August 1991 surveys. No significant plant growth occurred
in October 1991. To calculate algal growth, the following method was used.
The algal biomass is mostly organic matter. A linear relationship was developed which
relates the volatile suspended solids (VSS) and chlorophyll a using river stations downstream of
BLK07 and formulated in equation 6.11. The intercept value with Y axis of this relationship
indicates the VSS concentration which was not contributed by algal biomass. This value is
called background VSS (BVSS). To get an organic matter content of algal growth at a station,
BVSS is deducted from actual VSS as formulated in equation 6.12.
VSS=a(Ca) +BVSS (6.11)
A0=VSS-BVSS
(6.12)
where VSS = volatile suspended solids (mg/L); Ca = chlorophyll a (^g/L); BVSS = background
VSS (intercept); and A0 = organic content of algal biomass.
The molecular formula for chlorophyll a is C5JH70N4O6Mg, of which 74% is organic
content. To obtain total algal biomass and abiotic TSS, the following formulas were used:
_ (VSS-BVSS) (6.13)
ATS=TSS-At (6.14)
where A, = total algal biomass and A^s = abiotic total suspended solids. Algal biomass
calculations and abiotic TSS concentrations for July and August 1991 surveys were determined.
In addition to 1991 data, other Blackstone River surveys were accessed for TSS information.
A complete listing of these surveys is given in Table 6.1. After evaluation of the data and
concurrent rainfall records, data from the June 9 and 10,1980 and June 18 and 19,1985 surveys
were disregarded due to storms within a few days of the study period. The flows on August 4
and 5, 1980 surveys were similar and, therefore, they were considered as one survey, and a two
day average TSS was taken. The same procedure was followed for October 15 and 16,1980.
Using the suspended solids data, stream velocities and time of travel estimates, k,,, values
were calculated. The coefficient, k,,,, and average stream velocity relationships were developed
for all reaches and are reported in Table 6.2, with the exception of reaches from 17 to 25. For
these reaches, no relationship could be determined and a constant k,,, term was selected based on
the average k^ observed. An example of the k^-velocity relationships is given in Figure 6.2. In
6-9
-------
Table 6.1 Blackstone River Flow (cfs) Data for Water Quality Surveys Since 1980
Source
Survey
Qw
Qq
Qb
UBWPAD
MWWTF
GWWTF
NWWTF
WWWTF
1
06/09/80
622
31.0
213
46.0
0.71
0.75
2.03
-
06/10/80
541
3.70
171
46.0
0.71
0.75
2.03
-
08/04/80 .
539
17.0
187
46.0
0.88
0.59
1.408
-
08/05/80
619
14.0
148
46.0
0.88
0.59
1.40a
-
10/15/80
217
10.0
37.0
40.7
0.77
0.56
1.08
-
10/16/80
201
8.70
36.0
40.7
0.77
0.56
1.08
-
2
06/18/85
505
15.0
121
37.1
1.04
0.96
1.24
-
06/19/85
403
16.0
100
41.8
1.03
0.96
1.39
-
06/14/88
286
21.5
64.0
55.7a
1.29®
1.43a
1.40°
-
08/02/88
496
25.0
77.0
55.7a
1.29"
1.43a
1.40"
-
08/03/88
349
21.0
66.0
55.7a
1.298
1.43a
1.40a
-
3
07/09/85
193
7.70
44.0
55.7a
1.29"
1.43a
1.40"
19.1
08/20/85
195
6.80
35.0
55.7a
1.29s
1.43"
1.40a
15.7
10/08/85
681
39.0
87.0
55.7a
1.29®
1.43a
1.40a
17.6
4
07/10/91
137
7.3
26.0
38.4
0.6
1.64
1.78
8.31
08/14/91
152
8.55
30.5
44.6
0.84
1.61
1.24
11.5
10/02/91
725
60.5
122
64.7
1.29
1.59
1.78
13.4
5
09/22/92
157
2.00
29.0
47.2
1.26
1.41
1.24
9.79
11/02/92
275
2.40
66.0
40.4
0.97
1.49
1.24
8.86
a = Flow data consists of daily average discharges. No survey specific data was utilized; Qw = USGS flow at Woonsocket;
Qq: USGS flow at Quinsigamond River; Qb: USGS flow at Branch River; UBWPAD = Upper Blackstone Water Pollution
Abatement District; WWTF = Waste Water Treatment Facility; MWWTF = Millbuiy WWTF; GWWTF = Grafton WWTF;
NWWTF = Northbridge WWTF; WWWTF = Woonscocket WWTF
Source: 1 UBWPAD WLA (1983) (MA Section); 2 Blackstone River Survey (MA Section); 3 URINBP Project (RI Section)
4 URI (Dry Weather)(MA and RI Sections); 5 URI (Wet Weather) Prestorms (MA and RI Sections)
-------
some cases, the relationships did not appear to be statistically significant. However, the model
appears not to be extremely sensitive to in reaches with short times of travel, or in reaches
were suspended solids concentrations are relatively small. The model's performance is evaluated
in the next section over a wide range of conditions.
6.3.1 Model Simulations for Suspended Solids
1991 Calibration Surveys: The TSS simulations for July and October 1991 surveys were
conducted using the following inputs into the model: the validated flows from Section 5.3; the
relationships presented in Table 6.2; TSS concentrations for the point source effluents; and zero
TSS concentration for the ground water flow. The biotic TSS component (algal biomass) was
calculated for each reach with the dissolved oxygen model described in Section 5. These values
were introduced in the model as reach inputs and added to the simulated abiotic TSS. Figure 6.3
shows the plot of TSS profiles for the Blackstone River. These plots show that the predicted
TSS values fall within the 95% confidence limits of observed values. Thus, the model was
calibrated successfully for TSS.
1991 August Validation Survey: The boundary conditions were set as in the calibration
surveys. The successfid results of the model simulation are given in Figure 6.3.
Other Surveys: Other independent surveys, which had been completed on the Blackstone
River, were used for validation. Without specific discharge data at the UBWPAD for these
surveys, TSS values at BLK03 (Reservoir Avenue) were set as the headwater boundary
condition for all other surveys, with the exception of August 1992. For this survey BLK04 (East
Avenue) was set as the headwater boundary condition, since information did not exist for
BLK03. An example of these validation runs is given in Figure 6.4 for the August 3,1988
survey.
A comparison plot of model predictions and field observations for all surveys are presented
in Figure 6.5. For the 121 observations, the coefficient of determination was 0.77. A test of the
regression line to 95% confidence was successful in that the slope of the line approaches 1.0
(actual 0.89), and the intercept approaches 0.0 (actual 1.03). In general, the model did well in the
typical ranges of TSS for the Blackstone River (0-10 mg/L). The model appears to under predict
at higher TSS values (greater than 10 mg/L).
The results reported for the Blackstone River are similar to those reported by Cheela (1994)
for the Pawtuxet River. The model has been adequately calibrated and validated for TSS.
The sensitivity of the model to the estimate of k,,, was determined by observing the response
of the model output due to variation in the model coefficient k„,. From the response of the July
1991 model to changes in k,,, for every reach, the percentage change in model output was
calculated by taking the average of the percent change in each element. Approximately a 10
percent change in the coefficient resulted in a 10 to 15 percent change in TSS.
6-11
-------
Table 6.2 Kns -Velocity Relationships (Algal Growth Corrected)
Reach
Station
n
a
b
1
1-UBWPAD
3
-7.55
12.0
2
2-3
8
-24.6
22.0
3
3-6
8
0.86
1.05
4
3-6
8
0.86
1.05
5
3-6
8
0.96
0.29
6
3-6
8
1.17
0.08
7
6-7
6
0.01
0.40
8
6-7
6
0.07
0.17
9
7-8
6
0.19
0.77
10
7-8
6
0.19
0.77
11
8-11
6
-2.08
5.25
12
8-11
6
-4.38
3.24
13
8-11
6
-5.61
4.10
14
11-12
3
-1.37
0.19
15
12-Branch River
3
-0.27
2.66
16
12-Branch River
3
-0.27
2.66
17
13-17
3
0.05
0.00
18
13-17
3
0.05
0.00
19
13-17
3
0.05
0.00
20
17-18
4
-0.10
0.00
21
18-19
4
-0.04
0.00
22
19-20
4
-0.01
0.00
23
19-20
4
-0.01
0.00
24
20-21
6
0.22
0.00
25
20-21
6
0.22
0.00
n = number of data points used in regression; Km = a + b(velocity)
6-12
-------
0.8
0.6
July 10,1991
September 22,1992
August 14,1991
August 16,1980
November 2,1992
October 2,1991
0.4
0.2
I 0.0
-0.4
Reach 12: Stations 8 to 11
Regression Line: Y = -4.38 + 3.24 X
R2 = 0.60
-0.6
-0.8
-1.0
1.6
1.2
1.3
1.4
1.5
1.1
Velocity (fps)
Figure 6.2 Example of a and Velocity Relationship
6-13
-------
^ 8
24 -
July 10-11,1991
20 -
16 -
12 -
28
2
T
T
24 -
o Observed TSS
— Predicted TSS
August 14-15,1991
20 -
oo
16 -
12 -
28
T
24 •
October 2-3,1991
20 -
16 -
12 -
50 45 40 35 30 25 20 15 10 5
0
River Miles
Figure 6.3 Total Suspended Solids Profile for 1991 Blackstone River
Dry Weather Surveys (Cheela 1994)
6-14
-------
15
Q
<
Q.
£
m
3
a:
LU
>
on
I
o
z
CD
mi LU
111 Ol
> CO CO
CO
0^
Ui
§
CO
12 3 4
8
11 12 13 17 18 19 20 21
August 3, 1988
o Observed TSS
10 |- Predicted TSS
Flow at USGS Gage, Woonsocket, Rl = 349 cfs
5 -
50 45 40 35 30 25 20 15 10 5 0
River Miles
Figure 6.4 Example of Validation Simulation for TSS August 1988 Blackstone River Survey
-------
T 1 | I I
• June 14-15,1988
O July 9,1985
~ July 10,1991
V August 4-5,1980
¦ August 2,1988
~ August 3,1988
ofi
-i | i i i i r
~
ft*
O
O
o
o
J L.
-i L
/
Y = 0.74X+ 1.14
R2 = 0.72
~ August 14,1991
O September 22,1992
G October 15-16,1980
~ October 2,1991
O November 2,1992
45° Line
Regression Line
1 » ¦ 1 '
I I
10 15
Observed TSS
20
25
Figure 6.5 Comparison Plot of Model Predictions and Field Observations of TSS on the Blackstone River
-------
TSS Modeling Summary - The success of the modeling of TSS on the Blackstone River in
this study, and the Pawtuxet River in earlier efforts (Cheela 1994) may be based on the response
to the following questions. Does the proposed model adequately represent the state of the natural
system it purports to describe, given the error and uncertainty associated with defining both the
natural system and the model?
The chloride simulations were successful for both the rivers and, therefore, provide the
validation of the flow profile and the procedure used to develop it. This is not an assertion that
the model mimics all aspects and components of the transport mechanism as they occur naturally.
Rather, it is a scientific deduction based on empirical evidence describing both the model's
output and the 'output' of the natural system. The model could now be developed for simulation
of selected nonconservative constituents.
The sediment transport in this model is based on an empirical relationship between average
stream velocity and a net sediment transport coefficient. The equations provide the modeler with
the ability to establish the net sediment transport coefficient at other stream velocities and,
therefore, at other flows, such as the WLA flow.
Examination of the spatial plots for simulation of the Pawtuxet and Blackstone Rivers
surveys indicates that TSS has been simulated successfully for both the rivers. Using the same
relationships, the model was applied successfully to historic surveys for both systems. The model
application to the Blackstone River requires consideration of plant growth. Since the Pawtuxet
River is a fast flowing river, plant growth was not a major concern on the river, thus, correction
was not needed for TSS.
One may state that the model adequately describes TSS concentrations over the range of
environmental conditions encountered. This leads to a conclusion that the methods used to
simulate TSS, namely the empirical approach utilizing the net sediment transport coefficients, is
valid. Again, this is not to say that the model mimics the natural system on a micro scale.
Rather, the model's description of the external attributes of the environment agree well with the
description obtained by making field measurements of the natural system. Thus, the ground
work has been laid for a model for simulation of particle-reactive metal concentrations.
6.4 Partition Coefficient of Metals
The partition coefficient for metals, which defines the degree of partitioning between
dissolved and adsorbed phases, is very important in simulating the transport dynamics of
dissolved and particulate forms of metals in surface water systems.
There exists a large body of literature explaining the significance of metal species and
particulate phases in aquatic system. Linear relationships between suspended solids and metal
partitioning coefficients had been observed in numerous adsorption studies (Suzuki, Miyazaki
6-17
-------
and Kawaeoc 1979; Karichoff, Brown and Scott 1979; Kontaxis, DiToro and O'Connor 1982).
The USEPA study (Kontaxis, DiToro and O'Connor 1982) recognized the importance of
determining a functional relationship between partition coefficients and environmental water
quality variables to realistically model both dissolved and particulate forms of a given metal.
Kontaxis, DiToro and O'Connor (1982) collected a large amount of data from various water
quality files, including STORET (USEPA); NASQAN (USGS); DIALOG, and databases
maintained by NOAA and STAR (Canadian Center for Inland Waters). These records contained
a vast amount of data of particulate and dissolved concentrations of various priority metals,
suspended solids, pH, alkalinity, hardness, temperature, COD, BOD, chlorophyll a, and flows.
Kontaxis, DiToro and O'Connor (1982) verified the consistent correlation of the partition
coefficient and suspended solids, but no correlation was observed among the partition
coefficients and pH, BOD, COD, temperature, alkalinity or chlorophyll a. The method followed
by Kontaxis, DiToro and O'Connor to evaluate the relationship among partition coefficient and
suspended solids is explained below.
As the data was very large, a specialized software was developed to select appropriate data
and to calculate partition coefficients. Partition coefficients were calculated using equation 6.8.
Progressive segmentation of data, defined by a specified range of suspended solids was followed.
The average of the suspended solids falling in these segmented parts, and their corresponding
partition coefficients were plotted on a log-scale to verify the correlation between the degree of
partitioning and suspended solids. An example of these results was given by Figure 6.6 along
with standard deviations.
Two things that are to be noted in this analysis were (i) concentrations of suspended solids
fell in the range between 10 mg/L and 600 mg/L, and (ii) partition coefficients may vary by four
orders of magnitude. As the EPA relationships did not include suspended solids concentrations
below 10 mg/L, the relationships were extended below 10 mg/L using the 1991 Blackstone River
Dry Weather Study data.
6.4.1 Development of Partition Coefficient/TSS Relationships
Outlier tests were performed on the 1991 survey data for suspended solids and metal
concentrations. Data falling outside the 95% confidence limits were deleted. Suspended solids
concentrations were regressed against corresponding partition coefficients. Large variations in
the data resulted in limited correlations for all metals.
The analysis was extended to account for seasonal variations in sorptive affinity of the
metals, as the degree of partitioning might vary with trophic status of the natural water system.
The partition coefficient values were calculated for each survey independently, and relationships
were evaluated. The results of this effort were inconclusive.
6-18
-------
10
100
1
1000
Total Suspended Solids (mg/L)
Figure 6.6 Example of the EPA Relationship Between a Metal Partition Coefficient
Kp and TSS (Kontaxis et al., 1982)
6-19
-------
Spatial variability of the partitioning coefficient was also checked. The Blackstone River
was spatially divided into two parts; upstream of BLK04 and downstream of BLK04. Again the
results were inconclusive.
Finally, the data groupings of Kontaxis, DiToro and O'Connor (1982) were used for the
Blackstone River data. The suspended solids data was divided into ranges of 0.0-2.5,2.5-5.0,
5.0-7.5, and 7.5-11.8 mg/L. The average suspended solids concentrations for the ranges were
regressed against corresponding average partition coefficients. Significant correlations were
determined.
These correlations were examined for higher ranges of suspended solids by considering both
the Blackstone River and data of Kontaxis, DiToro and O'Connor (1982). Figures 6.7 to 6.11
demonstrated significant correlations among suspended solids and the partition coefficients for
Cd, Cu, Cr and Pb. Table 6.3 summarized 'a' and W coefficients along with regression
coefficients. A lower correlation was evident for Ni (Figure 6.11).
These 'a' and V coefficients obtained using the combined data were used to simulate the fate
and transport mechanism of Cd, Cr, Cu, Pb, and Ni.
6.5 Calibration and Validation of Metals
The Pawtoxic model was used to simulate trace metal fate and transport in the Blackstone
River. The July and October 1991 EPA surveys were used for calibrating the model and the
August 1991 EPA survey for validating the model. Each observed data point was accompanied
by error bars. The error bars represent the 95% confidence limit for the observed data.
The input data used for the calibration and validation follows.
Hydraulic Coefficient: The calculation of hydraulic coefficients was discussed in detail in
Section 5.3. The coefficients given in Table 5.5 were used as input hydraulic coefficients.
Incremental Inflows and Metal Concentrations: The groundwater flow coefficients were
calculated based on equation 5.6. These coefficients were multiplied by the drainage areas
(Table 5.3) of respective reaches to get incremental inflows. The detailed discussion on the
calculation procedure was provided in Section 5.3. The average metal concentrations of
Mumford and Branch Rivers were given as input for all five metals.
kp Coefficients: The calculation procedure for kp was given in detail in Section 6.4. The kp
coefficients given in Table 6.3 were used as input data.
k„Coefficients: The a and b coefficients to calculate fusing equation 6.10 are in Table
6.2.
6-20
-------
Regression Line
¦ 1991 Blackstone River Dry Weather Study
~ EPA Report
10°
Total Suspended Solids (mg/L)
Figure 6.7 Revised Relationship Between Cadmium Partition Coefficient and TSS
(Kontaxis et al., 1982)
6-21
-------
10°
Regression Line
1991 Blackstone River Dry Weather Study
EPA Report
10°
Total Suspended Solids (mg/L)
Figure 6.8 Revised Relationship Between Chromium Partition Coefficient and TSS
(Kontaxis et al., 1982)
6-22
-------
Regression Line
¦ 1991 Blackstone River Dry Weather Study
~ EPA Report
10°
10°
Total Suspended Solids (mg/L)
Figure 6.9 Revised Relationship Between Copper Partition Coefficient and TSS
(Kontaxis et al., 1982)
6-23
-------
Regression Line
¦ 1991 Blackstone River Dry Weather Study
t EPA Report
10°
Total Suspended Solids (mg/L)
Figure 6.10 Revised Relationship Between Lead Partition Coefficient and TSS
(Kontaxis et al., 1982)
6-24
-------
Regression Line
¦ 1991 Blackstone River Dry Weather Study
~ EPA Report
ii ii
• 1 1 '
10-1
10°
101
102
Total Suspended Solids (mg/L)
Figure 6.11 Revised Relationship Between Nickel Partition Coefficient and TSS
(Kontaxis et al., 1982)
6-25
-------
Table 6.3 Summary of Metal Partition Coefficient and TSS Equations
Metal
a
b
R2
Cd
0.85
-0.72
0.84
Cr
1.07
-0.65
0.83
Cu
0.37
-0.47
0.77
Ni
0.08
-0.11
0.11
Pb
2.24
-0.74
0.91
Kp= a TSS b; a = intercept (L/mg); b = slope; R2 = coefficient of determination
6-26
-------
Headwater Flows and Concentrations: The BLK.01 flows given in Table 5.7 were used as
headwater flows. The TSS and metal concentrations for all five metals at BLK01 were used as
headwater concentrations.
Point Source Flows and Concentrations : The flows and concentrations of point sources
used as input were given in Tables 6.4 to 6.6.
In the simulations to follow, the conditions outlined above were considered to be the initial
conditions. There were two problems that were identified during the interpretation of the data
that have resulted in modification to these initial conditions.
First, for several metals, the mass balance around the UBWPAD was not successful. In a
few cases, the loading, as defined by the five day effluent sampling period, was either high or low
relative to the balance between BLK01, BLK02, and UBWPAD. This problem is reflected in the
initial model simulations with either an under or over prediction below BLK02. Model
simulations were made with a modification to the UBWPAD load based on the calculation from
a mass balance between BLK01, BLK02, and UBWPAD.
Second, there were several occurrences of rapid loss of dissolved and total metals in the
reaches immediately below the UBWPAD. This rapid loss is both interesting and perplexing.
Two hypotheses were introduced in Chapter 4. They have been restated and expanded in the
following discussion with specific reference to the calibration of the model:
(a) Rapid settling of metals attached to particles or formed as a precipitate - A major
argument against this hypothesis is the failure of either the TSS or particulate metal profiles to
reflect this. However, there were several observations which provide support:
There is a relatively unique situation occurring in the Blackstone River at the point of the
UBWPAD discharge. For the two summer surveys, the UBWPAD flow was about 3 times
higher than the river flow at the point of discharge: July UBWPAD flow = 38.4 cfs vs BLK01 =
13.8 cfs and for August UBWPAD flow = 44.6 cfs vs BLK01 = 14.3 cfs. This was not the case in
the fall survey where the flow balance was about 1 to 1: UBWPAD = 64.7 cfs vs BLK01 = 71.2
cfs. There is the real possibility that the effluent's impact on the river will be quite different
between the summer and fall flow conditions.
TSS concentrations are relatively small in the UBWPAD discharge, since it is an advanced
wastewater treatment facility. On the other hand, metal concentrations are relatively large.
Whereas, there are distinct trends below the UBWPAD relative to metals, because of the small
TSS loading from the facility there is not a comparable trend in solids.
Not all five metals have this sudden reduction between BLK02 and BLK06. The metals
which exhibit the sudden drop are cadmium, copper, and nickel. For these three metals, the
6-27
-------
Table 6.4 Summary of TSS (mg/L) and Metal (ng/L) Concentrations of Point
Sources in the Pawtoxic Model for July 10-11,1991
Point Sources
TSS
Cd
Cr
Cu
Ni
Pb
UBWPAD
6.13
4.26
6.24
50.9
23.6
6.24
~Millbury WWTF
24.0
3.55
5.22
45.9
18.0
5.46
~Grafton WWTF
0.76
3.55
5.22
45.9
18.0
5.46
~Northbridge WWTF
20.0
3.55
5.22
45.9
18.0
5.46
•Uxbridge WWTF
1.63
3.55
5.22
45.9
18.0
5.46
Woonsocket WWTF
7.20
2.84
4.20
40.9
12.4
4.68
WWTF = Wastewater Treatment Facility;
* = Average metal concentrations of UBWPAD and Woonsocket WWTF
6-28
-------
Table 6.5 Summary of TSS (mg/L) and Metal (|ig/L) Concentrations of Point
Sources in the Pawtoxic Model for August 14-15,1991
Point Sources
TSS
Cd
Cr
Cu
Ni
Pb
UBWPAD
3.24
4.62
5.16
31.3
90.5
4.94
*Millbury WWTF
14.0
4.71
6.09
35.1
53.1
8.71
* Grafton WWTF
1.0
4.71
6.09
35.1
53.1
8.71
*Northbridge WWTF
1.0
4.71
6.09
35.1
53.1
8.71
*Uxbridge WWTF
2.28
4.71
6.09
35.1
53.1
8.71
Woonsocket WWTF
14.20
4.8
7.02
38.9
27.3
14.2
WWTF = Wastewater Treatment Facility;
* = Average metal concentrations of UBWPAD and Woonsocket WWTF
6-29
-------
Table 6.6 Summary of TSS (mg/L) and Metal (ng/L) Concentrations of Point
Sources in the Pawtoxic Model for October 2-3,1991
Point Sources
TSS
Cd
Cr
Cu
Ni
Pb
UBWPAD
3.13
2.7
2.1
29.5
22.1
2.1
~Millbuiy WWTF
19.7
1.83
1.98
20.8
18.8
3.2
* Grafton WWTF
14.0
1.83
1.98
20.8
18.8
3.2
*Northbridge WWTF
0.8
1.83
1.98
20.8
18.8
3.2
~Uxbridge WWTF
1.8
1.83
1.98
20.8
18.8
3.2
Woonsocket WWTF
4.07
0.95
1.87
12.2
15.5
4.3
WWTF = Wastewater Treatment Facility;
* = Average metal concentrations of UBWPAD and Woonsocket WWTF
6-30
-------
UBWPAD loading is significantly larger than the headwater loading at BLK01. On the other
hand, for the two metals (chromium and lead) which do not exhibit this behavior, the headwater
loading (BLK01) is equal to or greater than the loading from UBWPAD.
For cadmium, copper and nickel, the sudden decrease in concentration was dramatic only in
the summer surveys, when the UBWPAD/BLKO1 flow comparison favored the effluent, and
were not significant for the fall survey, when the reverse was true. Again, this supports the
statement made earlier that the effluent's impact on the river will be quite different between the
summer and fall flow conditions.
In general, metals in a treatment plant effluent are more likely in the dissolved fraction
rather than the particulate. This is more a by-product of the settling processes built into the
system to remove suspended solids and biodegradable organics. This is true for the UBWPAD.
Depending on several factors, the partitioning in the river may be quite different Typically,
modelers make the assumption that the partitioning of metals in an effluent quickly take on the
partitioning behavior in a river. Therefore, the actual division between dissolved and particulate
metals in an effluent is typically ignored. This appears to be an acceptable assumption if the
river flow is large in comparison to the effluent flow. However, in the case of the 1991 summer
surveys, this condition obviously does not exist. The result is a mixture of effluent and river that
more reflects the effluent than the river. In this case, metals appear heavily partitioned to the
dissolved fraction.
Pawtoxic was developed to handle settling and resuspension. As a result, the application of
the model simulates the metals with modifications to the settling and partitioning coefficients in
the two reaches below the outfall. The modifications were made to provide an immediate shift in
the partitioning to the particulate fraction, followed by a rapid settling of the particulates. The
result is a loss of metals which reflect the trend. Although this improves the modeling
performance, the current data is not conclusive, and further study is warranted.
(b) Biological uptake - An alternative to rapid settling is the possibility of biological uptake.
Observations in the literature suggest that continuously high concentrations of metals in the water
column may result in a bioaccumulation of metals in the benthos at luxury levels. The result
would be a removal of dissolved metals and not necessarily particulates. This is certainly
supported by the data. The process is analogous to a trickling filter, which removes dissolved
biodegradable organics through contact of the organics with the biological slime on rocks or
other media.
In an attempt to support this hypothesis, a specialty study was designed late in the field
program to determine if there were significant differences in the metal concentrations on
materials readily removed from rocks above and below the UBWPAD effluent. This study is
discussed in more detail later. The results, although not conclusive, support this hypothesis. The
modifications to the Pawtoxic model to simulate biological uptake are not complete. Therefore,
the simulations to follow do not include biological uptake as a pathway for dissolved metal
6-31
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removal from the water column.
6.S.1 Cadmium
The most striking trends in the total concentration profiles of July and August were the
dramatic increase below the UBWPAD at BLK02, the rapid decrease between BLK02 and
BLK06, and the sharp increase between BLK07 and BLK08. There were no major variations or
spatial trends of Cd in the October survey.
For July the model did not adequately predicted the rapid decrease between BLK02 and
BLK06 for average total Cd. The result was an over prediction for the remainder of the river.
However, although the model over predicted the instream concentrations for the Blackstone
below BLK04, the profile predicted by the model was very similar to the profile observed.
To simulate the remainder of the river downstream of BLK04, the input file was modified.
The modifications in the input were listed below.
1. Input from UBWPAD was reduced by 25%.
2. kp coefficients were calculated specifically from the observed data following
equation 6.8 for Reaches 1-3. kp coefficients for all other reaches (Table 6.3) were
determined from the equations described earlier.
3. k„ coefficients were modified for Reaches 1-3 to represent the rapid loss of
metals due to settling, (Reach, Original k^, Modified lO'-1, -3.38,2.50; 2, -4.91,
-6.90; and 3,1.16, -25.5. The k^ coefficients for all other reaches (Table 6.2) were
determined from the equations described earlier.
The modifications in the input from UBWPAD were based on a mass balance between
BLK01 and BLK02. The model predictions are shown in Figure 6.12.
The simulation process was extended to dissolved and particulate Cd concentrations, and the
results of this effort also are shown in Figure 6.12. The model over predicted the dissolved
phase. The particulate phase prediction was excellent.
Input was not modified for the October simulations. The results are presented in Figure
6.13. The model successfully predicted the magnitudes and spatial variations for all phases of
Cd.
The results for August 1991 were similar to the original July simulations, in general, a
significant over prediction downstream of BLK04. This was not surprising given the similarity
in flows between the two summer surveys.
The input was modified as described above. The model predictions, given in Figure 6.14,
improved with the modified input, although the total and dissolved concentrations were still over
6-32
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Predicted Cd
¦ Q ,Q .3 o ¦ 6 $ o ¦ o r,
50 45 40 35 30 25 20 15 10 5
River Miles
Figure 6.12 Cadmium Profiles for July 10-11,1991
6-33
-------
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50 45 40 35 30 25 20 15 10 5 0
River Miles
Figure 6.13 Cadmium Profiles for October 2-3,1991
6-34
-------
(/) (/)
I I
0 °{0{{
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o Observed Cd
Predicted Cd
50 45 40 35 30 25 20 15 10 5
River Miles
Figure 6.14 Cadmium Profiles for August 14-15,1991
6-35
-------
predicted. The profile predicted by the model was very similar to the profile observed.
6.5.2 Chromium
The most dramatic change in total chromium for the summer surveys was the sudden
increase at BLK08. This was not observed in October.
In general, the model's performance for chromium was excellent for both calibration surveys
(Figures 6.15 - 6.16). The only exception was the inability of the model to reach the average
concentration at BLK08. However, the model prediction did fall within that station's 95%
confidence limit. No modification to the original model input was necessary.
The model was also successful in simulating the validation survey (Figure 6.17).
6.5.3 Copper
Similar to cadmium, the concentration profiles for July and August showed a rapid decrease
after UBWPAD through BLK06 and a sudden increase at BLK08.
The model output reflected the general trend of total copper, but the predictions were an
over prediction of the observations. The input parameters were modified in the same manner as
cadmium. The amount of the UBWPAD input reduction was based on a mass balance. Model
predictions improved with the modified input. The predictions for dissolved and particulate
phases were satisfactory (Figure 6.18). Model simulations for all three phases of Cu in October
were excellent (Figure 6.19).
The model predictions for August 1991 with modified input were comparable with observed
data and with the results of July (Figure 6.20).
6.5.4 Lead
The extremely high variability in the observed Pb concentration for all three 1991 surveys
between BLK06 and BLK011 was unexpected and not clearly understood. No other metal or
constituent exhibited the same variability.
The model did not emulate the highly variable averages shown in Figure 6.21. However,
where variability was similar to the other metals, the model predictions tracked the observed
averages. This is especially true for the October data (Figure 6.22). The original input was not
modified.
For the August data, the model predicted the average total and particulate Pb, however, the
predictions were obscured by high variability in the dissolved concentration of Pb between
BLK06 and BLK13 (Figure 6.23).
6-36
-------
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Figure 6.16 Chromium Profiles for October 2-3,1991
6-38
-------
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Figure 6.18 Copper Profiles for July 10-11,1991
6-40
-------
Ifa s
p f
12 13
40 -
50
o Observed Cu
— Predicted Cu
s 30
*90
•g 20
50 45 40 35 30 25 20 15 10
5
0
River Miles
Figure 6.19 Copper Profiles for October 2-3,1991
6-41
-------
12 13
20
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o Observed Cu
— Predicted Cu
Y° o—O
-L
L
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River Miles
Figure 6.20 Copper Profiles for August 14-15,1991
6-42
-------
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Figure 6.21 Lead Profiles for July 10-11,1991
6-43
-------
12 13 17 18 19 20 21
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— Predicted Pb
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Figure 6.22 Lead Profiles for October 2-3,1991
6-44
-------
50
12 13
40
20
10
0
50
T
T
T
T
40
O Observed Pb
— Predicted Pb
50
30
20
10
0
50 45 40 35 30 25 20 15 10 5
0
River Miles
Figure 6.23 Lead Profiles for August 14-15,1991
6-45
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6.5.5 Nickel
Similar to cadmium and copper, the average observed total and dissolved concentrations for
July and August 1991 surveys rapidly decreased below UBWPAD to BLK06.
Predictions did not match up with the sharp decrease observed between BLK02 and BLK06,
although a general trend was observed. Input values were modified in a similar manner as
discussed for Cd and Cu. Model predictions are given in Figure 6.24.
No modifications were run for the October simulation. The model predictions matched up
with the average observed data points and spatial variations for all three components of nickel in
October (Figure 6.25).
The same modifications made for the July simulations were made for the August runs.
Model predictions were satisfactory (Figure 6.26).
6.6 Trace Metal Modeling Summary and Conclusions
Pawtoxic, a one-dimensional, steady state trace metal model, has been used to define the
Blackstone River from Worcester, MA to its discharge into the Seekonk River in Pawtucket, RI.
The major tributaries and point sources have been included in the model. The model has the
ability to simulate a maximum of three conservative elements, total suspended solids, and five
nonconservative elements. The model adopts a very simple, but effective, approach to trace the
dispersal pattern of metals by considering two simplified equations involving net sediment
transport and metal partitioning. The model is available with input and output files.
• Net Sediment Transport - Empirical relationships between average stream velocities and net
sediment transport coefficients were developed for most river reaches. The equations
provide the modeler with the ability to establish the net sediment transport coefficient at
other stream velocities and therefore, at other flows, such as the waste load allocation flow.
• Metal Partitioning - Empirical relationships between metal partition coefficients and
suspended solids were developed for each metal. The equations provide the modeler with
the ability to establish new partition coefficients as suspended solids concentrations change
in the river.
The following conclusions were determined from this analysis:
Model Calibration and Validation - Flow Profile
• The model has been calibrated to the flows observed in the three dry weather surveys of
1991. The model was validated with flow measurements from 6 independent measurements
6-46
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River Miles
Figure 6.24 Nickel Profiles for July 10-11, 1991
6-47
-------
30
12 13
3 20
H 10
0
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T
T
T
T
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T
O Observed Ni
— Predicted Ni
20
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50 45 40 35 30 25 20 15 10 5 0
River Miles
Figure 6.25 Nickel Profiles for October 2-3,1991
6-48
-------
-I
o *
12 13
Z 40
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— Predicted Ni
40
CO
•a 20
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50 45 40 35 30 25 20 15 10 5
River Miles
Figure 6.26 Nickel Profiles for August 14-15,1991
6-49
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conducted by USGS and the successful simulation of a conservative constituent
• The model was also successfully validated using the data from August 1991 and other
independent surveys. The model adequately describes TSS concentrations over the range of
environmental conditions encountered (0-10 mg/L TSS). This is not to say that the model
mimics the natural system on a micro scale. Rather, the model's description of the external
attributes of the environment agree well with the description obtained by making field
measurements of the natural system.
Model Calibration and Validation - Trace Metals
• Rapid decreases in dissolved metal concentrations for Cd, Cu, and Ni occurred in the
reaches below the UBWPAD through BLK.06 in July and August. Model calibration for
these metals required adjustments to the net sediment transport and metal partitioning
coefficients in these reaches.
• Two hypothesis were discussed to explain this rapid loss. Both focused on the uniqueness
of the high effluent to river ratios for flow and trace metal mass loadings for the low flow
surveys of 1991. Data suggests a phenomena other than settling may be occurring iii these
reaches. Recommendations for further study have been made below.
• Lead had the highest variability of any metal in the reaches between BLK06 and BLK11,
especially in Rice City Pond. The highest Pb concentrations observed in these reaches could
not be simulated with the steady state model. A speciality study conducted on Rice City
Pond provides insight into this phenomena. This study is discussed in detail in Chapter 8.
• The model successfully simulated the trace metal profiles for Cd, Cr, Cu and Ni below
BLK06 to the end of the river and for Pb from BLK11 to the end of the river for the low
flow surveys.
• The model successfully simulated all metals for the October high flow survey.
• Metal concentrations entering Rhode Island via the Blackstone River are typically the
highest meted concentrations in the state.
Recommendations
Before this model is used in developing waste load allocations, the phenomena experienced
in the reaches below UBWPAD needs farther study. As discussed earlier, one possible
explanation is the removal of the dissolved metal through luxury uptake in the attached biomass
in the river downstream of the UBWPAD discharge. As microorganisms are continually exposed
to high concentrations of metals in the water column, they will gradually adjust to this difference
by the assimilation of the dissolved metal concentrations into their cell structures. The biological
process involved can be divided into two categories: (1) biosorption of metal ions onto the
surface of microorganisms and (2) intercellular uptake of metal ions (Darnall 1986). The range
of environmental variables that affect the accumulation of metals by algae include length of
exposure, type of metal, oxidation state, salinity, pH and the presence of organic pollutants.
Bottom rock samples were taken to determine if data would support the possibility of luxury
6-50
-------
uptake and to determine if additional study was warranted. Samples were taken at three points
along the upper Blackstone: above UBWPAD at BLK01 and below UBWPAD, between stations
BLK02 and BLK03 and between stations BLK03 and BLK04. Rocks and river water were
collected together in plastic containers. These samples were agitated to force the biomass and
sediment to sluff off into the water column. This water containing the biomass and sediment
was then transferred into another prepared plastic container and acidified to a pH of 2.0 to leech
the metals from the particulates. The analytical procedure followed was the same as presented in
Chapter 2. Results of this analysis are given below.
Table 6.7 Summary of Biomass Metals Analysis
Trace
Metal
Wg)
Above
UBWPAD
Below BLK01
Below UBWPAD
Between
BLK02 and BLK03
Below UBWPAD
Between
BLK03 and BLK04
Surface Sediment
Maximum
Concentration1
Cr
6.96
44.1
193
630*
Cd
29.7
88.9
62.7
93#
Cu
84.4
494
735
1100*
Pb
4.35
32.9
617
590*
Ni
22.5
375
387
230*
1. Blackstone River Metals Summary, Personal Communication with John King,
URIGSO; * Rice City Pond; # Tupperware Pond
It is clearly evident in this table that metal concentrations in ^g/gm are significantly higher
in the stations below the UBWPAD, supporting the possibility of luxury uptake. In fact, these
concentrations are equal to, or higher than, those seen in sediments in downstream
impoundments considered to have high metals concentrations. These data alone are not
conclusive, but strongly suggest the need for further study.
6-51
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7.0 WET WEATHER WATER QUALITY INTERPRETATION
The two flow charts presented in Figures 7.1 and 7.2 outline the method followed in
interpreting the wet weather data Section 7.1 includes a presentation of individual
concentrations and event mean concentrations (EMCs). Section 7.2 deals with criteria and
violations. Actual toxicity is described in Section 7.3. Section 7.4 uses the concentration and
flow data to develop the mass loadings and gains/losses. Also, system rankings and hot spot
identification are provided in Section 7.4. A method for separating resuspended and runoff
loadings is described in Section 7.5. An estimate of annual loadings at the MA/RI state line and
end of river is provided in Section 7.6.
Three wet weather events were monitored for this study: September 22-24,1992 (Storm
1), November 2-5,1992 (Storm 2) and October 12-14,1993 (Storm 3). The total rainfall and
duration for each storm were 0.56 inches/6 hrs, 0.88 inches/16 hrs, and 0.81 inches/8.5 hrs,
respectively. Detailed discussions on each storm were provided in Chapter 3. Grab samples
were collected at specific time intervals throughout the Blackstone River watershed and analyzed
for 14 constituents. Details of the sampling protocol were given in Chapter 2. A complete listing
of all data is provided in the appendix. Mass loadings for each constituent, per station, per storm
were calculated using the stream flows of Chapter 3. Individual station concentration and mass
loading curves were developed for all nutrients, trace metals, fecal coliform and TSS. Mass and
concentration profiles representing a constituent in time and space for a single storm were
developed for the entire river.
7.1 Water Quality Concentration.
7.1.1 Comparison Between Dry and Wet Weather Concentrations
7.1.1.1 Nutrients
It was established in Chapter 4 that both the UBWPAD and Woonsocket wastewater
treatment facilities are the major sources of nitrogen and phosphorous under dry weather
conditions.
Advanced treatment (nitrification) is required for UBWPAD. The facility's discharge
permit divides the year into three time frames: November 1 to May 15; May 16 to May 31; and
June 1 to October 31. The maximum daily ammonia discharges allowed by the permit for the
three time periods are 12.5,7.5 and 2.5 mg/L, respectively. The Woonsocket facility is a
secondary facility, and therefore, typically discharges large quantities of ammonia and relatively
low levels of nitrate. There are no permit levels for ammonia for Woonsocket.
Nitrate and Ammonia - The ammonia and nitrate profiles for Storm 2 are given in Figures
7.3 and 7.4, respectively. For ammonia, Points A and B represent the location of the UBWPAD
discharge. Since the UBWPAD was not providing nitrification during the November storm, the
7-1
-------
Trace
Metals
Fecal
Coliform
Ceriodaphnia dubia
Pollutant Mass
River Reach
Mass Balance
Water Column
Chemistry
Water Column
Toxicity
Actual
Toxicity
Hyetographs, Hydrographs
and Point Source Flows
Event Mean
Concentrations
Pollutant
Source
Comparison
River System
Pollutant
Ranking
Criteria Based
Versus Actual
Toxicity
Pollutographs and
Point Source
Concentrations
Water Quality
Criteria
Comparison
Watershed
Hydrology
and River Hydraulics
Wet Weather Data Presentation and Interpretation
River Reach Pollutant Hot Spot Identification
Figure 7.1 Flow Chart Describing the Wet Weather Data Presentation and Interpretation
7-2
-------
River Flow
Pollutant Mass
Rainfall
Hyetographs
Trace Metals
Pawtoxic
Dissolved Oxygen
QUAL2E
Flow/Resuspension
Relationship
Wet Weather Mass Load
Pollutant
Resuspension
Previous Wet Weather
Studies
Flow/Quality
Dry Weather
Annual Loading
Rate Relationship
Wet Weather
Annual Loading
Rate Relationship
Fate and Transport
Pollutant Model Applications
Total Annual Loadings
RI/MA State Line
End of Blackstone River
Wet Weather Mass Load
Separation into
Resuspension and Runoff
Dry and Wet Weather Data Analysis and Model Application
Figure 7.2 Flow Chart Describing the Dry and Wet Weather Data Analysis
and Model Application
7-3
-------
BLACKSTONE RIVER INITIATIVE
AMMONIA - STORM 2
UBWPAD
Fisherville
Rice City
Woonsocket
WWTF
V2V;
07 08
46.0 45.8 44.0
Worcester, MA
Concentration
(mg/L)
¦ 6.00-7.00
!¦ 5.00-6.00
¦ 4.00-5.00
» 3.00-4.00
rn 2.00-3.00
¦ 1.00-2.00
m 0.00-1.00
21 STATIONED
39.8 35.7 32.0 27.8 23.2 16.6 12.8 10.0 3.8 0.1 RIVER MILES
Pawtucket, RI
Figure 7.3 Ammonia Concentration for Storm 2, November 2-5, 1992
-------
BLACKSTONE RIVER INITIATIVE
NITRATE - STORM 2
Concentration
(mg/L)
¦ 5.00-6.00
¦f 4.00-5.0Q
m 3.00-4.00
~ 2.00-3.00
m 1.00-2.00
m o.OO-1 .OO
Rice City
Pond
MA
A—
RI
—~
Woonsocket
WWTF
18 20 21 STATION ID
10.0 3.8 0.1 RIVER MILES
Pawtucket, RI
UBWPAD F,sherville
| "°"d|
Worcester, MA
Figure 7.4 Nitrate Concentration for Storm 2, November 2-5, 1992
-------
high levels of ammonia in their discharge were continuous and independent of the storm. The
nitrate profile indicated instream nitrification below UBWPAD. Both profiles clearly indicate
the storm track from the headwaters in Worcester, though the results were quite different. The
higher flows produced higher ammonia concentrations and extended these concentrations much
further downstream to BWW08 in Rice City Pond. Nitrate concentrations were smaller in this
same path suggesting that nitrification, which was occurring prior to the storm in these reaches,
was delayed due to the high flows and faster times of travel.
The ammonia and nitrate profiles for Storm 1 are given in Figures 7.5 and 7.6,
respectively. Storm 3 profiles are similar to Storm 1. For ammonia, Points A and B again
represent the UBWPAD discharge point. However, unlike Storm 2, ammonia concentrations do
not remain high in the post storm hours. This is as expected given that nitrification should have
been occurring in the facility. What is striking about this profile is the response of the facility to
the storm hydrograph that passed through the facility. The result was poorer treatment at the
facility, causing the discharge of a high, short term spike of ammonia.
As discussed earlier, there was no violation of the daily maximum ammonia discharge of
2.5 mg/L during the dry weather surveys. By comparison, under wet weather conditions,
violations of ammonia concentrations did occur in two out of three storms (Storm 1 and Storm
2). During Storm 1,3 out of 10 samples collected at UBWPAD violated the maximum limit of
2.5 mg/L ammonia. These violations coincided with peak storm flows. During Storm 2 when no
nitrification was required, 10 out of 16 samples collected at UBWPAD violated the maximum
limit of 12.5 mg/L ammonia. Again, these violations coincided with peak flows and the period
immediately after.
Table 7.1 Summary of Ammonia Concentrations in mg/L at UBWPAD and
Woonsocket Treatment Facilities
Facility
Average Dry
Average Wet
Maximum
Maximum
Weather
Weather.
Dry Weather
Wet Weather
UBWPAD
0.36
1.48*
0.60-1.1
2.1-4.3
13.2"
20.6
Woonsocket
0.74
25.1
15.8-28.6
33.6-34.3
* Storm 2 without nitrification at UBWPAD; *' Storm 1 and 3 with nitrification
at UBWPAD
Two other significant increases of ammonia appear in these figures (Figures 7.3 and 7.5).
Point C marks the reaches between BWW07-11 which encompasses the reaches above, within
and below Rice City Pond. The earlier peak between hours 3-6 is related to local drainage area
runoff or reach resuspension. The later peak at hour 12 is more reflective of the storm track
7-6
-------
BLACKSTONE RIVER INITIATIVE
AMMONIA - STORM 1
20 21 STATION ID
3.8 0.1 RIVER MILES
Pawtucket, RI
00 01
46.0 45.8
Worcester, MA
Figure 7.5
02 04 06 07 08 11 13 17 18
44.0 39.8 35.7 32.0 27.8 23.2 16.6 12.8 10.0
Ammonia Concentration for Storm 1, September 22-24, 1992
UBWPAD Flsherv,!,e
Rice City
MA . RI
Woonsocket
WWTF
Concentration
(mg/L)
¦ 4.00-4.50
~ 3.50-4.00
m 3.00-3.50
¦ 2.50-3.00
¦ 2.00-2.50
sa 1.50-2.00
~ 1.00-1.50
¦ 0.50-1.00
m 0.00-0.50
-------
BLACKSTONE RIVER INITIATIVE
WWTF
Concentration
(mg/L)
i i 3.50-4.00
¦ 3.00-3.50
¦ 2.50-3.00
¦ 2.00-2.50
m 1.50-2.00
~ 1.00-1.50
¦ 0.50-1.00
¦ 0.00-0.50
20 21 STATION ID
3.8 0.1 RIVER MILES
Pawtucket, RI
o
^ 00 01
46.0 45.8
Worcester, MA
Figure 7.6
02
44.0
Nitrate
04 06 07 08 11 13 17 18
39.8 35.7 32.0 27.8 23.2 16.6 12.8 10.0
Concentration for Storm 1, September 22-24, 1992
NITRATE - STORM 1
-------
from the Worcester headwaters. Point D marks the Woonsocket WWTF discharge. The signal is
relatively constant in space and time and supports the finding in Chapter 4 that Woonsocket is a
major source of ammonia.
At Point D (Figure 7.6), concentrations of nitrate decline due to both dilution from the 3
tributaries coming in between BWW08 and BWW13, as well as the nitrate uptake associated
with plant productivity (described in Chapter 5).
The ridge of higher concentrations at E occurs between BWW18 and BWW20 and is a
direct result of instream nitrification of Woonsocket's ammonia load. In both Figures 7.5 and 7.6,
the storm track from the headwaters in Worcester and the UBWPAD are evident. Storm 3
profiles are similar to Storm 1.
Phosphate - Similar to dry weather, under wet weather conditions, dissolved
orthophosphate profiles are dominated by UBWPAD and Woonsocket WWTF. An example of
the orthophosphate profile is presented in Figure 7.7 for Storm 1. The most striking feature of
this figure is the ridge line of high concentrations at UBWPAD, between stations BWW01 and
BWW02 (Points A and B). The high discharge of orthophosphate from UBWPAD is continuous
and independent of the storm events. In general, the orthophosphate profile shows a reduction in
concentration below Rice City Pond (BWW08), an increase due to the Woonsocket facility's
discharge and then a decline to station B WW21. The decrease in concentration below Rice City
Pond, as well as in the reaches below the Woonsocket facility, are related to dilution from
incoming tributaries and uptake due to plant productivity (described in detail in Chapter 5).
There is no permit requirement for orthophosphate for either UBWPAD or Woonsocket
WWTF. The maximum concentrations discharged by UBWPAD for the three dry weather
surveys of July, August, and October 1991 were 3.0,3.0, and 3.4 mg/L, respectively, and the
average concentrations discharged were 2.30,2.36, and 3.03 mg/L. In comparison, the maximum
concentrations discharged during the three storm events were 2.09,1.61 and 1.98 mg/L for
Storms 1,2, and 3, respectively, and the average concentrations discharged were 1.52,1.16, and
1.35 mg/L. The lower concentrations during the storm events are a result of dilution by higher
facility flows.
The maximum concentrations discharged by Woonsocket WWTF for dry weather were
3.9,4.9, and 4.2 mg/L, and the average concentrations discharged were 3.3,3.36, and 4.0 mg/L.
The maximum concentrations discharged during the three storm events were slightly higher:
5.97,7.16, and 6.86 mg/L, for Storms 1,2, and 3, respectively, as were the average
concentrations of 3.92,4.43, and 5.21 mg/L.
7.1.1.2 Trace Metals
In Chapters 4 and 6, the UBWPAD was shown to be a major source of most metals to the
Blackstone River under dry weather, steady-state conditions. The Woonsocket facility was also
7-9
-------
BLACKSTONE RIVER INITIATIVE
PHOSPHATE - STORM 1
UBWPAD
Fisherville
Woonsocket
WWTF
MA _ RI
Rice City
Pond
Pond
00 01 02 04 06 07 08 11 13 17
46.0 45 8 44.0 39.8 35.7 32.0 27.8 23.2 16.6 12.8
Worcester, MA
Figure 7.7 Phosphate Concentration for Storm 1, September 22-24, 1992
20 21 STATION ID
3.8 C.l RIVER MILES
Pawtueket, RI
Concentration
(mg/L)
¦ 1.00-1.25
IB 0.75-1.00
~ 0.50-0.75
¦ 0.25-0.50
¦ 0.00-0.25
-------
indicated as a significant source for several metals. A comparison between the two surveys (dry
vs wet) for these two facilities has been made below. Data has been presented as survey average
concentration, and as a maximum concentration range. The average dry weather survey
concentration was obtained by averaging all data from the three 1991 dry weather surveys to
provide a single dry weather average concentration for each constituent. Similarly, all wet
weather data from the three 1992/3 wet weather surveys were averaged to provide a single wet
weather average concentration for each constituent. The maximum concentration range includes
the maximum concentrations reported for each survey.
UBWPAD - For the UBWPAD (Table 7.2), several metals were influenced by the higher
storm flows through the facility. The following general observations can be made based on the
comparison of averages: under storm flows, chromium concentrations doubled; copper and
nickel concentrations did not change significantly; and cadmium and lead concentrations
decreased.
A comparison of maximum wet weather and dry weather concentrations lead to the
following observations: for chromium, the wet weather range was significantly higher; for lead,
copper, and nickel, the dry and wet weather maximum concentration ranges were slightly lower
and for cadmium, the wet weather range was significantly lower.
Table 7.2 Average and Maximum Dry and Wet Weather Metal Concentrations for
UBWPAD
Facility
Metal
(Hg/L)
Average
Dry Weather
Average
Wet Weather
Maximum
Dry Weather
Maximum
Wet Weather
UBWPAD
Cd
3.9
1.6
3.2-6.8
0.9-2.9
Cr
4.5
9.1
2.7-7.5
6.8-31.5
Cu
40
36
41.4-61.1
21.1-74.1
Pb
4.4
2.7
2.4-8.6
3.4-5.7
Ni
39
29
25.8-163
26.1-46.7
Woonsocket - For the Woonsocket WWTF (Table 7.3), several metals were influenced
by the higher storm flows through the facility. The following general observations can be made
based on the comparison of averages: under storm flows, copper and lead concentrations
increased significantly; chromium concentrations did not change significantly; and cadmium and
nickel concentrations decreased.
A comparison of maximum wet weather and dry weather concentrations lead to the
following observations: for cadmium, copper, and lead, the wet weather ranges were significantly
7-11
-------
higher; for chromium, the dry and wet weather maximum concentration ranges were similar; and
for nickel the wet weather range was significantly lower.
Table 7.3 Average and maximum Dry and Wet Weather Metal Concentrations for
Woonsocket WWTF
Facility
Metal
(Hg/L)
Average
Dry Weather
Average
Wet Weather
Maximum
Dry Weather
Maximum
Wet Weather
Woonsocket
Cd
2.9
1.5
1.7-5.9
2.7-11.5
Cr
4.4
5.3
3.3-14.7
6.7-8.0
Cu
31
51
20.0-46.2
61.9-97.1
Pb
7.2
16
6.0-21.0
21.6-31.4
Ni
160
5.4
79-256
5.6-10.6
No record or data support that metal loadings have changed between 1991 and 1993.
Therefore, one possible cause of the relatively high metal concentrations observed at UBWPAD
(chromium) and the Woonsocket WWTF (chromium, copper and lead) may be from sources in
the system triggered under wet weather conditions. On the other hand, the decrease in some
concentrations at UBWPAD (cadmium, copper, lead and nickel) and the Woonsocket WWTF
(cadmium) may be more a result of the dilution from runoff. The exception to this was the
unusually high post chlorination concentration of nickel at the Woonsocket facility in 1991.
River Profile - Under dry weather conditions, the metal concentrations along the river
were categorized into two general profiles (Chapter 4). Under wet weather, these same patterns
appear similar but magnified. The first pattern (Figure 7.8) generally describes cadmium,
chromium, copper, nickel and zinc. It was consistent with the dry weather surveys in that the
major increase occurred between BWW01-04. This reach includes UBWPAD and several other
potential nonpoint sources of metal pollution. The other consistent increase in metals occurred in
the reaches above, in, and immediately below Rice City Pond (BWW07-11), due most likely to
sediment resuspension.
The other pattern (Figure 7.9) was specific to lead and showed a significant source of the
metal in the headwaters above BWWOO. The UBWPAD was not significant relative to the
headwater source. A secondary source of lead was associated with resuspension in the river
reaches surrounding Rice City Pond (BWW07-11). The source of lead in the headwaters is not
known. Further investigation within the Worcester collection system is warranted.
The concentration profiles were developed for all trace metals, per station, per storm.
7-12
-------
BLACKSTONE RIVER INITIATIVE
WWTF
CHROMIUM -
_ Fisherville „.
STORM 1
MA RI
20 21 STATION ID
3.8 0.1 RIVER MILES
Pawtucket, RI
00 01
46.0 45.8
Worcester, MA
Figure 7.8
02 04 06 07 08 11 13
44.0 39.8 35.7 32.0 27.8 23.2 16.6
Chromium Concentration for Storm 1, September 22-24, 1992
Concentration
(Hg/L)
¦ 1 8-20
* 16-18
HI 14-16
¦ 12-14
¦ 10-12
¦ 8-10
m 6-8
,u3 4-6
¦ 2-4
¦ 0-2
-------
BLACKSTONE RIVER INITIATIVE
LEAD - STORM 1
Concentration
(Mg/L)
* 30-35
¦ 25-30
¦ 20-25
i£l 1 5-20
~ 10-15
m 5-10
¦ 0-5
STATION ID
UBWPAD F,sherv,lle
Rice City
MA . RI
Woonsocket
WWTF
46.0 45.8 44.0 39.8 35.7 32.0 27.8 23.2 16.6 12.8 10.0 3.8 0.1 RIVER MILES
Worcester, MA Pawtucket, RI
Figure 7.9 Lead Concentration for Storm 1, September 22-24, 1992
-------
7.1.2 Wet Weather Event Mean Concentrations (EMCs)
Since wet weather concentrations are time-varying one way to represent the data is to
develop event mean concentrations (EMCs). The EMC is used to represent a flow weighted
concentration for any water quality parameter during a single storm event. EMCs for each
station were calculated by summing the products of concentration and flow for each time
interval, and then dividing by the total flow. A watershed EMC for the Blackstone River was
determined by averaging the EMCs for all stations. Tables 7.4,7.5 and 7.6 represent the EMC
values for Storms 1,2 and 3, respectively, and Table 7.7 represents the EMCs for the entire
Blackstone River watershed. Figures 7.10 to 7.14 show the spatial variation of EMCs for the 14
constituents for the three storms.
7.1.2.1 Nutrients
The nutrient EMC profiles support the observations in section 7.1.1. In general, based
on the EMC profiles, the nutrient concentrations were dominated by direct discharge from the
two major point sources and/or instream nitrification resulting from their discharge.
7.1.2.2 Conventional
TSS and VSS EMC profiles are presented in Figure 7.12. In general, the headwater
concentrations are significant, often with concentrations that are amongst the highest for the
entire river. This was opposite to the findings of the dry weather surveys, evidence to the relative
importance of urban runoff as a major source of solid loadings.
There is an interesting pattern between BWW01 and BWW02, which again supports the
operation of nitrification in the UBWPAD. With nitrification providing a much higher retention
time within the facility, solids removal is often better. During Storms 1 and 3, where nitrification
was occurring, the TSS EMC profiles actually show a decline between BWW01 and BWW02.
Storm 2 provides a different result, reflecting a higher solids load from the UBWPAD when
nitrification was not occurring.
Also of interest is the increase of solids for Storm 3 between BWW02 and BWW04. It is
not clear what source or sources have caused this increase. Further discussion of this reach
occurs in a later section-
To a lesser degree, increases in solids could also be seen between BWW07 to BWW11.
This reflects the resuspension of bottom sediments from Rice City Pond described earlier.
Fecal Coliform (FC) and E. Coli (EC) concentrations in the headwaters (above BWW00)
are some of the highest concentrations along the entire river. This was especially true in Storm 3.
The sharp decreases in the instream FC and EC concentrations below the UBWPAD (between
BWW01 and BWW02) for Storms 1 and 3 are most likely due to residual chlorine in the
7-15
-------
Table 7.4 Event Mean Concentration (EMC) For Storm 1
Station
Cd
Cr
Cu
Ni
Pb
Zn
EC
Hg/L
Mg/L
Hg/L
Hg/L
Hg/L
Hg/L
CFU/lOOmL
BWWOO
0.61
2.47
6.45
3.10
19.7
33.5
2690
BWW01
0.35
4.08
9.36
3.89
14.2
46.4
3850
BWW02
0.90
10.8
14.3
10.4
13.2
64.1
0.55
BWW04
1.26
8.99
38.3
21.4
10.1
55.4
88.5
BWW06
1.00
7.15
31.8
18.3
9.83
38.5
173
BWW07
0.81
5.11
24.5
16.1
8.28
30.3
182
BWW08
1.10
8.40
28.4
16.4
12.4
41.3
41.5
BWW11
0.71
4.89
17.1
11.3
7.12
26.8
105
BWW13
0.45
2.86
11.0
8.28
4.34
17.5
139
BWW17
0.39
2.98
10.4
7.61
6.36
22.8
958
BWW18
0.43
2.16
11.8
5.85
4.82
35.0
49.1
BWW20
0.33
1.69
10.5
4.80
3.87
25.8
40.2
BWW21
0.38
2.05
10.4
4.62
6.76
25.1
319
Station
bod5
nh3-n
N03-N
PO4-P
TSS
vss
FC
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
CFU/lOOmL
BWWOO
4.16
0.17
0.32
0.02
6.41
2.76
6190
BWW01
5.42
0.22
0.43
0.02
13.1
5.10
11400
BWW02
5.99
1.54
1.14
0.73
7.55
4.50
340
BWW04
5.25
1.04
2.14
0.80
16.0
6.88
735
BWW06
4.33
0.49
3.25
0.74
7.40
3.42
607
BWW07
2.48
0.81
3.00
0.65
7.28
2.93
784
BWW08
2.85
0.83
2.54
0.64
9.80
3.30
189
BWW11
2.24
0.31
1.77
0.37
5.47
2.61
228
BWW13
1.75
0.05
1.29
0.28
3.67
2.07
594
BWW17
1.67
0.04
1.37
0.24
5.04
2.39
2230
BWW18
1.73
2.42
1.33
0.41
4.70
2.94
394
BWW20
1.67
0.55
1.99
0.26
2.74
1.86
117
BWW21
1.34
0.37
1.73
0.17
2.75
1.78
2290
7-16
-------
Table 7.5 Event Mean Concentration (EMC) For Storm 2
Station
Cd
Cr
Cu
Ni
Pb
Zn
EC
Hg/L
Hg/L
Hg/L
Hg/L
Hg/L
Hg/L
CFU/lOOmL
BWWOO
0.05
1.45
7.80
.2.23
11.4
27.6
2780
BWW01
0.09
3.27
10.6
4.60
11.9
45.3
3570
BWW02
1.12
7.02
15.9
12.3
11.7
46.9
8160
BWW04
1.85
9.07
23.0
13.9
15.9
56.3
4840
BWW06
1.41
5.62
17.5
10.5
13.2
43.7
3500
BWW07
1.20
3.93
14.1
9.72
7.36
41.6
1580
BWW08
1.72
6.69
18.6
11.8
11.4
45.0
1250
BWW11
1.23
6.91
17.2
7.68
10.6
41.1
350
BWW13
0.51
3.52
9.46
5.00
6.31
21.8
328
BWW17
0.54
2.49
8.68
5.39
5.21
19.3
402
BWW18
0.51
2.33
9.87
4.72
4.28
21.3
215
BWW20
0.48
1.85
8.73
6.05
4.79
24.6
88.8
BWW21
0.54
1.68
8.21
4.97
5.97
26.4
516
Station
BODs
NH3-N
NO3-N
P04-P
TSS
VSS
FC
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
CFU/lOOmL
BWWOO
6.30
0.07
0.12
0.04
11.8
6.51
4900
BWW01
7.19
0.17
0.24
0.03
13.6
6.32
5800
BWW02
7.80
3.87
0.28
0.41
19.6
13.9
22200
BWW04
9.13
3.21
0.43
0.47
17.8
11.8
26100
BWW06
7.54
3.27
0.74
0.42
10.7
5.51
17400
BWW07
5.37
2.75
0.94
0.43
6.05
3.09
8350
BWW08
4.89
2.49
1.07
0.45
8.83
3.83
7240
BWW11
4.51
1.17
1.23
0.27
11.4
4.24
3030
BWW13
2.62
0.79
1.50
0.18
4.10
2.07
764
BWW17
2.48
0.44
1.63
0.19
4.11
1.76
836
BWW18
3.31
1.20
1.45
0.28
6.83
3.93
895
BWW20
3.76
0.79
1.44
0.26
7.04
4.05
409
BWW21
4
0.79
1.69
0.23
4.81
2.33
2110
7-17
-------
Table 7.6 Event Mean Concentration (EMC) For Storm 3
Station
Cd
Cr
Cu
Ni
Pb
Zn
EC
Hg/L
Hg/L
Hg/L
Hg/L
Hg/L
Hg/L
CFU/lOOmL
BWWOO
0.36
7.28
19.2
3.94
41.1
35.8
9120
BWW01
0.40
6.12
19.1
5.35
33.5
91.6
5590
BWW02
0.79
7.60
29.0
11.6
30.6
52.7
781
BWW04
0.50
4.41
14.9
8.32
10.4
22.6
2040
BWW06
0.53
3.89
19.4
9.19
16.4
36.2
1510
BWW07
0.46
4.06
19.3
10.6
11.7
32.6
315
BWW08
0.54
8.83
25.6
11.4
19.1
51.0
486
BWW11
0.57
5.93
20.0
9.74
16.8
41.7
239
BWW13
0.36
2.77
10.6
8.24
6.17
16.5
120
BWW17
0.25
2.34
10.4
7.84
8.17
17.2
722
BWW18
0.25
1.85
10.7
7.18
5.74
17.9
282
BWW20
0.21
1.74
11.9
6.61
6.41
16.7
291
BWW21
0.24
1.77
9.81
5.34
5.68
15.0
1090
Station
BODs
NHs-N
NO3-N
PO4-P
TSS
VSS
FC
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
CFU/lOOmL
BWWOO
5.66
0.05
0.22
0.01
28.8
9.15
22200
BWW01
6.60
0.06
0.34
0.01
28.5
8.33
9850
BWW02
7.19
0.35
1.35
0.28
24.2
8.61
5910
BWW04
6.38
0.29
1.34
0.26
44.5
15.5
5280
BWW06
4.21
0.18
1.61
0.35
26.0
9.49
3170
BWW07
4.36
0.18
1.72
0.31
10.3
5.61
2350
BWW08
4.13
0.17
1.64
0.30
17.2
5.27
2250
BWW11
3.53
0.11
0.69
0.26
14.5
7.35
807
BWW13
2.02
0.06
1.81
0.30
5.93
3.80
201
BWW17
2.12
0.03
1.87
0.06
7.79
3.71
1490
BWW18
1.98
0.21
2.44
0.39
7.08
3.96
2460
BWW20
1.95
0.26
2.31
0.57
10.5
3.61
728
BWW21
1.79
0.11
2.27
0.40
8.64
4.70
1480
7-18
-------
!
£
£
l
i
S
w
I
Storm 1
Storm 2
&
1
t 1 1 1 1 1 1 1 1 1 1 r
Storm 3 v Nitrate
O Ammonia
00 01 02 04 06 07 08 11 13 17 18 20 21
Wet Weather Stations (BWW)
Figure 7.10 EMC plots for NO3-N and NH3-N for Storm 1, Storm 2, and Storm 3
7-19
-------
1.5
A Storm -1
O Storm - 2
~ Storm - 3
1.0
/—N
-------
Storm -1
Storm - 2
Storm - 3
\
5 20
00 01 02 04 06 07 08 11 13 17 18 20 21
Wet Weather Stations (BWW)
Figure 7.12 EMC plots for TSS, VSS and Pb for Storm 1, Storm 2, and Storm 3
7-21
-------
2.5
Cd
Storm -1
Storm - 2
Storm - 3
~ a—¦ -o-
—o:
—~
12
9
- Ck.
6
O-
3
0 u-1
50 r—J
Cu
40
Wet Weather Stations (BWW)
Figure 7.13 EMC plots for Cd, Cr, and Cu for Storm 1, Storm 2, and Storm 3
7-22
-------
25
20
/—"N
i
15
u
S
10
w
5
0
100
80
i
60
a
u
40
S
w
20
0
10
8
2
6
S
w
0
2
4
w
2
0
. 1 i I I I I 1 I I
: a Ni
1 1 i 1 .
A Storm -1
/
O Storm - 2 "
/ ^ A
~ Storm - 3
/\
' iiitiiiii
>— "O—-
1 1 1 1 -
\
00 01 02 04 06 07 08 11 13 17 18 20 21
Wet Weather Stations (BWW)
Figure 7.14 EMC plots for Ni, Zn, and BOD5 for Storm 1, Storm 2, and Storm 3
7-23
-------
facilities effluent. This was not the case in Storm 2, where higher stream flows resulted in lower
residuals. In fact, FC and EC concentrations increased to their highest levels in the reaches
immediately below UBWPAD. This impact could be felt as far downstream as BWW08.
Similar increases of FC and EC are evident in the Woonsocket area in the river reaches
above and below the Woonsocket facility. Fecal coliform are discussed in more detail in the
section that follows.
BODj has a similar trend for all three storms. Generally it peaks immediately after
UBWPAD discharge, and then decreases to the mouth of the river. BODs does not appear
strongly influenced by storm related sources but by the two major point sources.
7.1.2.3 Trace Metals
Compared to the other metals, lead's major source appeared to be in the headwaters
(above BWWOO). In fact, the headwater concentrations were typically the highest concentration
along the entire river.
Neither the UBWPAD nor Woonsocket facilities appeared to have a major impact on
these profiles. A consistent increase of lead did appear between BWW07 and BWW08 in Rice
City Pond and was probably due to sediment resuspension.
The other 5 metals (Cd, Cr, Cu, Ni and Zn) had similar profiles, in that there appeared to
be two distinct peaks (Figure 7.13 and 7.14). The first occurred in the reaches below UBWPAD
and was associated with the wastewater facilities discharge and possibly other nonpoint sources
of metals. In addition, concentrations, on average, typically continued to increase through
BWW04. This might reflect the resuspension, or sloughing, of material off the bottom that may
be an end result of the process of luxury metal uptake under steady state conditions.
A secondary peak consistently occurred around BWW08, again the probable cause was
sediment resuspension within Rice City Pond. Below BWW08, the profiles quickly decreased to
BWW13. As the Blackstone River enters and passes through Rhode Island, all the metal profiles
were either flat or declining, with only minor exceptions typically around the City of
Woonsocket. Concentrations in Rhode Island were generally either equal to, or slightly higher
than, the Worcester headwater concentrations. These data suggested that the metal EMC profiles
in Rhode Island were governed by concentrations entering at the state line.
7.1.2.4 EMC Comparison With Other Rivers
The data of this study have been summarized as average EMCs for the entire Blackstone
River watershed in Table 7.7. For comparison, results from an earlier wet weather study on five
tributaries to the Providence River, including the Blackstone River, are provided (Table 7.8).
Although the rainfall characteristics were quite different between studies, the EMCs for the
7-24
-------
Table 7.7 Event Mean Concentrations (EMCs) for Storms 1, 2, and 3, for
the Blackstone River
Storm
Cd
Cr
Cu
Ni
Pb
Zn
EC
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
CFU/lOOmL
Storm l
0.61
4.28
16.1
9.48
7.60
32.3
372
Storm 2
0.79
3.73
11.9
6.93
7.75
31.1
1430
Storm 3
0.40
4.04
15.8
8.11
13.6
30.2
1380
Storm
BOD5
NH3-N
NO3-N
PO4-P
TSS
VSS
FC
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
CFU/lOOmL
Storm 1
2.58
0.71
1.77
0.40
5.94
2.92
1270
Storm 2
4.60
1.36
1.23
0.27
8.07
4.30
5440
Storm 3
3.64
0.16
1.66
0.30
16.1
6.38
3670
Table 7.8 Event Mean Concentrations (EMCs) for the Blackstone, Moshassuck, Woonasquatucket,
Pawtuxet, and Ten Mile Rivers
Station
Code
Cd
Cr
Cu
Ni
Pb
NH3-N
NO3-N
PO4-P
TSS
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
mg/L
mg/L
mg/L
mg/L
Blackstone
a-l
0.60
4.00
14.6
8.20
9.60
0.70
1.60 -
0.30
10.0
Blackstone
a-2
0.40
1.80
9.50
5.00
6.10
0.40
1.90
0.30
5.40
Blackstone
b
0.94
6.82
12.5
10.7
8.25
0.25
5.42
0.67
10.1
Moshassuck
b
0.39
7.10
20.2
7.76
20.9
0.15
2.08
0.11
17.5
Woonasquatucket
b
0.31
3.39
8.98
6.13
8.06
0.10
3.26
0.22
10.5
Pawtuxet
b
1.06
4.43
11.9
12.7
7.53
1.04
4.03
0.52
21.0
Ten Mile
b
1.06
7.58
14.7
44.0
4.13
0.10
4.92
0.27
5.35
a-l: This study whole river, a-2: this study BWW21; b: NBP study Wright et al., (1991)
-------
Blackstone are similar. Rankings are not provided with the EMC data, since concentrations are
influenced by flow, and rankings have more meaning when presented as mass loads. This has
been done in a later section.
7.1.3 Hardness, DO, Temperature, pH, Chloride and Sodium
Hardness concentrations (mg/L as CaC03) were determined specific to each sample taken
for the three storms. Hardness-based equations were used to calculate the acute and chronic
toxicity criteria of each trace metal in the next section. Concentration profiles of hardness, along
with chloride, sodium, DO, temperature, and pH, were developed for each storm. All the profiles
for all stations and storms were evaluated.
In general, the concentrations of hardness decreased at, or near, the peak flows (peak
dilution from runoff) and increased again with time. This was most significant in the headwaters
and upper parts of the river for all three storms, declining in significance as one moves
downstream. At and near the mouth of the river, the decrease in hardness concentrations at peak
flows were not significant for two (Storms 1 and 2) out of three storms. The lower hardness
reduces the concentrations at which a particular metal becomes toxic.
Chloride and sodium showed similar trends, decreasing in concentration at or near the
peak flows.
The pH did not vary significantly with time and stations. The value of pH ranged
between 6.3 and 6.8 for all stations and storms.
Temperature varied according to the season and time. Storm 1 (September) had much
higher temperatures than Storms 2 and 3 (November and October).
Due to other sources and sinks of oxygen in the system, it was difficult to discern any
relevant impact of wet weather on DO. The DO profiles generally showed a slight decrease in
concentrations at the peak flows. There were no violations of DO criteria (5.0 mg/L) in the
mainstem stations of the Blackstone River at any time. However, tributary stations, BWW05 and
BWW15, had 1 violation (pre-storm sample) out of 16 samples collected for Storm 2, and 2
violations out of 13 samples collected for Storm 3, respectively.
7.2 Water Quality Criteria Violation
7.2.1 Fecal Coliform
The Blackstone River headwaters appear to be the major source of fecal coliform (FC)
under wet weather conditions. Other notable increases in concentration occur at Fisherville Pond,
Rice City Pond and some individual river reaches between stations BWW11 to BWW17. Figure
7.15 is an example of a 3-D FC profile. Residual chlorine from the UBWPAD appears to be an
7-26
-------
BLACKSTONE RIVER INITIATIVE
FECAL COLIFORM LOADING - STORM 1
Load - log (CFU)
¦ 13-14
Hi 12-13
ED 11-12
¦ 10-11
¦ 9-10
UBWPAD
WWTF
o
CO 01
46 0 45.8
Worcester, MA
20 21 STATION ID
3.8 0.1 RIVER MILES
Pawtucket, RI
Figure 7.15 Fecal Coliform Leading for Storm 1, September 22-24, 1992
-------
effective disinfectant in the reaches at, and below, its discharge (Points A to B), with one major
exception. At peak flow between time 0 and 6 hours, fecal coliforms pass by the UBWPAD
without instream disinfection. This is probably due to the lower instream chlorine residual
resulting from the higher flows in the river and in the facility.
FC concentrations increase between BWW11 and BWW17 (Point C in Figure 7.15). The
source appears to be independent of the storm, occurring before, during, and after rainfall. The
high FC concentrations from the Branch River (BWW14) and Peters River (BWW16) may be
responsible for this. The FC ranges for Branch River were: 280-6200,60-400, and 230-5800
CFU/100 mL for Storms 1,2, and 3, respectively, and the average FC concentrations were 2350,
249, and 1434 CFU/100 mL. The FC ranges for the Peters River were: 300-39000,14000-79000,
and 63-94000 CFU/100 mL for Storm 1,2, and 3, respectively, and the average FC counts were
9531,42909, and 26757 CFU/100 mL, respectively. The dry weather data also showed these two
tributaries had the highest FC concentrations.
The storm track of FC (Figure 7.15) matches perfectly with the storm track of the
hydrograph for Storm 1 (Figure 3.9), returning to background concentrations at BWW08 at 40
hours. Maximum FC loads were typically seen along the storm track for all three storms.
Table 7.9 shows the criteria violation for Storms 1,2, and 3. Two types of violations were
considered: Violation A was the log mean > 200 CFU/100 mL, and Violation B was 10% of
samples exceeding 400 CFU/100 mL.
Under dry weather conditions Type A violations occurred in the mainstem stations
BWW01, BWW04, BWW06 and in the tributary stations Branch River (BWW14) and Peters
River (BWW16). Type B violations occurred at the stations listed above and also at BWW17
and BWW21 (Section 4.4).
Under wet weather, all stations along the mainstem Blackstone River had violations of
both Type A and Type B for all three storms, with the exception of BWW02, BWW08, BWW11,
BWW18, and BWW20 for Storm 1 and BWW13 for Storm 3. BWW11 and BWW18 had only
Type B violations for Storm 1. The tributary stations BWW14 and BWW16 had both Type A and
Type B violations. BWW09 had no violations at any time. During wet weather, FC samples
were not collected at tributary stations BWW05 (Quinsigamond River), BWW10 (West River),
and BWW15 (Mill River).
Significantly more stations had violations of both Type A and Type B for wet weather
versus dry weather. This comparison is provided in Table 7.9. The high loading at the
headwaters seems to be the main cause of the FC problems under wet weather conditions. The
river benefits from the high residual chlorine discharged at UBWPAD during most time periods.
The exception is at or near peak storm flow. There are more violations in Storm 2 and 3 than in
Storm 1. This is probably due to the fact that Storm 1 was smaller (0.56 inches) than Storms 2
and 3 (0.81 and 0.88 inches).
7-28
-------
Table 7.9 Fecal Coliform Violation in Accordance With Class B
Water Criteria for Dry and Wet Weather
Stration ID
Violation-A
Violation-A
Violation-B
BWW/BLK
Dry Weather
Wet Weather
Wet Weather
Blackstone River Stations
00
No Samples
1,2,3
1,2,3
01
1,2,3
1,2,3
1,2,3
02
No Violation
2,3
2,3
03
1,2
No Samples
No Samples
04
1,2,3
1,2,3
1,2,3
06
1,2
1,2,3
1,2,3
07
3
1,2,3
1,2,3
08
2
2,3
2,3
11
No Violation
2,3
1,2,3
12
No Violation
No Samples
No Samples
13
No Violation
1,2
1,2
17
1,3
1,2,3
1,2,3
18
3
2,3
1,2,3
19
No Violation
No Samples
No Samples
20
1
2,3
2,3
21
1
1,2,3
1,2,3
Tributary Stations
05
No Violation
No Samples
No Samples
09
1
No Violation
No Violation
10
No Violation
No Samples
No Samples
14
2,3
1,2,3
1,2,3
15
No Violation
No Samples
No Samples
16
1,2,3
1,2,3
1,2,3
Violations A = Log Mean > 200 CFU/100 mL; Violations
B = 10% of Samples exceeding 400 CFU/100 mL; 1,2,3 = Surveys
(Dry Weather Surveys 1,2, 3; Wet Weather Storms 1,2, 3)
7-29
-------
7.2.2 Acute and Chronic Trace Metal Criteria
Acute and chronic toxicity criteria for metals are used to protect the public health and the
environment. These criteria prevent the surface waters from becoming unsuitable for fishing,
swimming and other beneficial uses. The acute and chronic criteria were initially discussed in
Chapter 4. Criteria used in the analysis to follow were calculated by using these hardness-based
equations. The hardness concentrations were determined specific to each sample taken.
Individual pollutographs were plotted by station, with the criteria for each metal. These
plots provide insight into the question of whether wet weather causes acute criteria violations.
Figure 7.16 is an example of a pollutograph and is an illustration of just such a violation. It
shows all 12 samples violated lead chronic criteria, but only 2 samples violated lead acute criteria
for Storm 3 at BWWOO. These violations occurred during the height of the storm, when instream
hardness declined, resulting in lower acute criteria. The more stringent criteria typically
coincided with maximum instream concentrations. Similar plots were developed, per station, for
all trace metals during the course of this analysis.
The acute and chronic violations can be represented for the entire storm and river.
Examples of these figures for acute criteria are given in Figures 7.17-7.19. These figures
represent the location, duration, and magnitude of acute violations, by constituent, by storm.
7.2.2.1 Lead
Chronic Criteria Violations - Chronic criteria violations occur at all stations for all three
dry weather surveys and all three wet weather storms. Violations are greater at the headwater
station and around Rice City Pond (Tables 4.10 and 7.10).
Acute Criteria Violations - The only violations under dry weather conditions occurred at
two stations (BWW06 and BWW07) during the first survey in July 1991. For wet weather, acute
violations start typically at the headwaters (BWWOO) in conjunction with runoff (peak
hydrograph flow) and decrease in frequency and magnitude downstream. Storm 3 (Figure 7.17) is
an excellent example of violations coinciding with the track of the storm hydrograph from the
headwaters in Worcester. The impact of the headwater peak storm flows are not limited to these
upper reaches. With the arrival of the higher flows from Worcester, lead concentrations
increase, and violations occur in Rice City Pond due to resuspension (Figure 7.17).
7.2.2.2 Copper
Chronic Criteria Violations - The chronic criteria violations occurred at all stations, at all
times, for all surveys and storms (dry and wet weather) along the mainstem and the tributaries of
7-30
-------
50 i'ii
|
1 50
o
Oh
25
-12
BWWOO
November 2-5,1992
TIME 0 = 2230 on November 2
Acute Criteria
Chronic Ctriteria
-• •
. i .
12
24 36
Hour
48
60
72
Figure 7.16 Example Figure of Pb Showing Acute and Chronic Criteria
Violations for Storm 2 at Station BWWOO
7-31
-------
BLACKSTONE RIVER INITIATIVE
ACUTE LEAD VIOLATIONS - STORM 3
Fisherville
Pond |
Woonsocket
WWTF
UBWPAD
46.0 45.8 44.0 39.8 35.7 32.0 27.8 23.2 16.6 12.8 10.0
Worcester, MA
Figure 7.17 Acute Lead Violations for Storm 3, October 12-16, 1993.
White Denotes No Violations
STATION ID
3.8 0.1 RIVER MILES
Pawtucket, RI
Concentration
(Hg/L)
m 70-80
¦ 60-70
¦ 50-60
¦ 40-50
« 30-40
20-30
¦ 10-20
¦ 0-10
-------
BLACKSTONE RIVER INITIATIVE
ACUTE COPPER VIOLATIONS - STORM 2
WWTF
Concentration
(Hg/L)
m 50-60
¦ 40-50
m 30-40
~ 20-30
¦ 1 0-20
¦ 0-10
STATION ID
46.0 45.8 44.0 39.8 35.7 32.0 27.8 23.2 16.6 12.8 10.0 3.8 0.1 RIVER MILES
Worcester, MA Pawtucket, RI
Figure 7.18 Acute Copper Violations for Storm 2, November 2-5, 1992.
White Denotes No Violations
-------
fO
vo
ON
-------
Table 7.10 Blackstone River Wet Weather Summary of Acute and Chronic Criteria
Violations, Storm 1
Stations
Samples
Pb
Pb
Cu
Cu
Cd
Cd
Acute
Chronic
Acute
Chronic
Acute
Chronic
Blackstone River Stations
BWW00
10
2
10
2
3
1
3
BWW01
10
0
10
1
3
0
0
BWW02
10
0
10
6
6
0
6
BWW04
10
0
10
10
10
1
10
BWW06
10
0
10
10
10
0
10
BWW07
10
0
10
10
10
0
5
BWW08
10
0
10
10
10
1
9
BWW11
10
0
10
10
10
0
5
BWW13
10
0
10
10
10
1
1
BWW17
10
0
10
10
10
0
0
BWW18
10
0
10
10
10
0
0
BWW20
10
0
10
9
10
0
0
BWW21
10
0
10
6
10
0
1
Tributaries
BWW05
10
0
2
0
0
0
0
BWW09
10
0
10
0
0
0
0
BWW10
10
0
6
0
0
0
0
BWW14
10
0
5
1
7
0
0
BWW15
10
0
10
1
1
0
0
BWW16
10
1
10
1
2
1
0
Note: Ni and Cr have no acute and chronic criteria violations
7-35
-------
Table 7.10 Blackstone River Wet Weather Summary of Acute and Chronic Criteria
Violations, Storm 2 (continued)
Stations
Samples
Pb
Pb
Cu
Cu
Cd
Cd
Acute
Chronic
Acute
Chronic
Acute
Chronic
Blackstone River Stations
BWW00
15
2
15
3
4
0
0
BWW01
16
2
16
5
7
0
0
BWW02
16
1
16
9
16
3
10
BWW04
16
2
16
9
14
3
12
BWW06
16
1
16
16
16
3
14
BWW07
15
0
15
16
16
1
15
BWW08
16
0
16
16
16
8
16
BWW11
16
1
16
16
16
6
16
BWW13
16
0
16
16
16
0
11
BWW17
16
0
16
15
15
1
7
BWW18
16
1
16
16
16
1
9
BWW20
16
0
16
10
15
0
7
BWW21
16
0
16
9
13
0
7
Tributaries
BWW05
15
0
10
0
0
0
0
BWW09
16
1
15
0
0
0
0
BWW10
16
0
16
0
0
0
0
BWW14
16
1
16
1
7
0
0
BWW15
16
0
16
1
2
0
0
BWW16
16
0
16
2
4
0
0
Note: Ni and Cr have no acute and chronic criteria violations
7-36
-------
Table 7.10 Blackstone River Wet Weather Summary of Acute and Chronic Criteria
Violations, Storm 3 (continued)
Stations
Samples
Pb
Pb
Cu
Cu
Cd
Cu
Acute
Chronic
Acute
Chronic
Acute
Chronic
Blackstone River Stations
BWW00
12
2
12
2
2
0
2
BWW01
12
3
12
5
6
0
4
BWW02
12
2
11
11
12
0
3
BWW04
11
3
9
9
12
1
3
BWW06
12
2
12
10
12
0
4
BWW07
13
1
12
13
13
0
1
BWW08
13
2
12
10
12
0
5
BWW11
13
2
11
11
12
0
4
BWW13
13
0
12
10
10
0
2
BWW17
13
1
13
12
12
0
0
BWW18
12
0
12
9
11
0
0
BWW20
12
0
12
11
11
0
0
BWW21
12
0
11
10
11
0
0
Tributaries
BWW05
12
0
6
0
0
0
0
BWW09
13
0
13
0
0
0
0
BWW10
13
0
11
0
0
0
0
BWW14
12
0
11
0
0
0
0
BWW15
13
0
12
0
0
0
0
BWW16
13
0
13
0
0
0
0
Note: Ni and Cr have no acute and chronic criteria violations
7-37
-------
the Blackstone River. The greatest violations occurred below UBWPAD and around Rice City
Pond (Tables 4.10 and 7.10).
Acute Criteria Violations - In the dry weather surveys violations typically began at
BWW02 (UBWPAD) and continued downstream reaching BWW18 or BWW21. The same
reaches are subject to violations under wet weather conditions, although the magnitude of the
violations were greater.
7.2.2.3 Cadmium
Chronic Criteria Violations - For all dry and wet weather surveys, the chronic violations
for Cd generally start directly below the UBWPAD discharge. The reaches with violations
typically extended at least to Woonsocket.
Acute Criteria Violations - Dry weather acute violations began at BWW02 and typically
continued downstream for 3 to 4 stations. The exception was for dry weather survey 3, which
also had several violations in the reaches below Rice City Pond. Similarly, under wet weather
conditions, most of the violations for Cd also occurred directly below UBWPAD and extended
for several stations downstream.
7.2.2.4 Chromium and Nickel
Cr and Ni concentrations were well below the acute and chronic criteria violations for all
stations under either wet weather or dry weather conditions.
7.3 Wet Weather Toxicity
7.3.1 Toxicity Results
Toxicity during the wet weather testing was significantly greater than during diy weather.
Toxicity was observed in 34 out of 118 possible occasions during the wet weather testing. Each
test had two possible endpoints: survival and reproduction. Toxicity during "first flush" portion
of the three rain events accounted for 14 toxic endpoints. The remaining 20 toxic occurrences
were during "peak flow" conditions. The results of dry weather and three wet weather toxicity
testing events are shown in Table 7.11. A large number of locations that were non-toxic during
dry weather were toxic during wet weather. The following discussion includes stations that had
adverse effects. Stations that experienced some toxicity, but were not statistically or biologically
significant, are not included in this discussion.
The results of the testing in Storm 1 indicate that toxicity was first present at Millbury
Street (BWW01) in Worcester and then downstream of UBWPAD. The effluent of UBWPAD
was not toxic. The CSO in Worcester was not tested until Storms 2 and 3. Samples from
Singing Dam (BWW04) and downstream of Singing Dam were toxic. The sample downstream
7-38
-------
Table 7.11 Toxicity Testing Results - Ceriodaphnia dubia Survival and Reproduction
Station
Dry Weather
Wet Weather
1st Flush
Wet Weather
Peak
BWWOO
S2
BWW01
S3
SI, S3
BWW02
S3, R1
R1,R3
BWW04
R1
BWW05
S2
R1
BWW06
S2
BWW07
S2
BWW08
S2
BWW09
R3
S3
S3
BWW11
S2, R1
BWW12
BWW13
BWW14
BWW15
BWW16
BWW17
BWW18
BWW20
S2
BWW21
BWW22
S2, S3
S2,R3
BWW23
R3
BWW24
R2
SI, S2, S3
BWW25
SI, S3
SI, S2, S3
BWW26
SI
Survival (S) or Reproduction (R) significantly affected; 1,2, 3 = three rounds of testing.
7-39
-------
of Rice City Pond (BWW08) in Uxbridge was toxic. No toxicity was detected below this until
the Woonsocket WWTF effluent, which was toxic.
During Storm 2, a sample upstream of the Worcester CSO was toxic, as was the CSO
(BWW22) discharge itself. Toxicity occurred at all stations between the Quinsigamond River
(BWW05) in Grafton and the Mumford River (BWW09). The sample downstream from Rice
City Pond (BWW08) in Uxbridge was toxic again. From Millville to Woonsocket no toxicity
was observed. The Woonsocket effluent was toxic. Only the sample from Lonsdale Avenue
(BWW20) in Cumberland was toxic. This station was downstream of Woonsocket.
Storm 3 produced more toxicity than either previous round of testing. The Worcester
CSO and the Millbury Street sample (BWWOO) upstream of the CSO were toxic. This was the
only event when UBWPAD effluent produced significant toxicity. At McCracken Road
(BWW02), downstream of UBWPAD, toxicity was evident again. No toxicity was observed at
either Singing Dam (BWW04) or Rice City Pond (BWW08). The Mumford River (BWW09)
was toxic. Downstream, the Woonsocket effluent was toxic.
Included in this study were two additional sources downstream of the Blackstone River
along the Seekonk River. They included the Narragansett Bay Commission's Bucklin Point
secondaiy discharge and its bypass. The secondary effluent was toxic for Storms 2 and 3. The
bypass was toxic for Storm 1 but was not tested during either Storms 2 or 3.
For the most part, toxicity occurred at the same stations during first flush and storm peak.
For more than one storm, six stations had recurrent toxicity in the peak storm conditions, thus the
larger number of toxic endpoints were observed during peak rain. Only four stations, that were
toxic at first flush, were non-toxic during peak rain.
During the September 1992 (Storm 1) wet weather testing, all three wastewater treatment
plant effluents contained total residual chlorine (TRC) concentrations (Table 7.12) that were
orders of magnitude greater than the EPA ambient water quality criteria. These samples were
dechlorinated with sodium thiosulfate before testing.
Due to the chlorine concentrations alone, these samples could be viewed as acutely toxic.
Dechlorination of these samples was performed to preclude the masking effects of chlorine
toxicity, and to test whether other constituents of the water were toxic.
Toxicity did occur in all of the dechlorinated WWTF effluents at least once and in the
combined sewer outfalls. The effluent of Woonsocket WWTF was toxic during all three wet
weather events (three times during peak flow and once during first flush). The effluent of the
Narragansett Bay Commission Bucklin Point WWTF was also toxic during all three storm
events. All peak samples at this facility were toxic, and two of three first flush samples were
toxic. This may indicate bypassing during rain events.
7-40
-------
Table 7.12 TRC Concentrations for BWW23-25
Station
Time of Sampling
TRC (|ig/L)
BWW23
1st Flush
290
BWW23
Peak
640
BWW24
1st Flush
300
BWW24
Peak
690
BWW25
1st Flush
3700
BWW25
Peak
1650
Millbury Street (BWW01), McCracken Road (BWW02), the Quinsigamond River
(BWW05), Route 122 (BWWi 1), and the Mumford River (BWW09) experienced significant
toxicity on more than one occasion.
Thirty eight percent of all toxic endpoints occurred in the first two miles of the river in
the Greater Worcester area.
Little difference was observed between toxicity occurring in first flush and peak storm
samples.
Acute toxicity, the more significant measure of toxicity, was the predominant endpoint
during wet weather toxicity testing. Twenty four of the toxic responses during wet weather
resulted in the mortality of the test organisms. Nine samples caused reproductive effects to the
test organisms.
The choice of a certain time to represent peak and first flush across the watershed, based
on the peak and first flush at the heart of the watershed, caused some potential toxicity data to be
lost. If one looks at the three dimensional graphs showing pollutant loadings throughout the river
basin over the duration of the storm, it can be seen that samples taken at approximately the same
time throughout the watershed, would not actually receive slugs of upstream pollution until much
later. So, if certain sources on the river are dominating the pollutant loadings, ie. runoff from the
City of Worcester, or historical pollutants in the sediments of Rice City Pond, these loadings will
not affect downstream stations for some time. The intensity and speed of the storm's movement
affects this as well.
7.4 Wet Weather Pollutant Loadings
7-41
-------
7.4.1 Mass Loading Estimates
The water quality data, coupled with stream flows, allow for the calculation of mass
loading curves. About 1000 mass loading profiles, along with concentrations profiles, were
generated during the course of this analysis. Each mass loading curve was integrated to obtain
the total load (e.g. lbs) for each station, for each storm. The total mass was divided by the time of
the event to obtain the total loading (e.g. lbs/day) for that constituent, for each station. Baseline
loading rates (dry load in lbs/day) were estimated for each pollutograph from the initial (pre-
storm) sample and the final (post storm) samples. These rates were multiplied by the time of the
event to obtain the total dry load for that station (lbs). The wet load (lbs), per station, per
constituent, was determined by subtracting the dry load from the total load. Figure 7.20 illustrates
the procedure for load calculations. Point source loadings, including the CSO, were calculated
using the average flow and average concentration during the event period.
7.4.2 Comparison of Wet and Total Loadings
Mass loadings provide insight into the question of whether wet loads are a major source
of metals during and immediately after storm events. The data clearly indicate that, with only
minor exceptions, more pollutants entered the river during wet weather than dry. One means of
highlighting this is to compare wet and diy loadings. This has been done by representing each
station's wet load as a % of total load (Table 7.13). These data represent the spatial variation for
all constituents along the mainstem Blackstone River and its tributaries. A simplification of these
data are presented as an average across all stations for each storm in Table 7.14. This table
illustrates the variation of wet load as a % of total load with the change of rainfall. The same
table summarizes the average wet loadings for each constituents under wet weather for the entire
watershed. A comparison by constituent is provided below.
7.4.2.1 Trace Metals
In general, there are two observations which were consistent for all six metals. First, the
highest percentage of wet load occurred at the headwaters. This reflects the importance of
Worcester as a source of metals under wet weather conditions. The reduction in the percentage of
wet load to total load downstream is attributed to the higher, more dominate, point source
loadings from the WWTFs, especially UBWPAD.
Second, either individually, by station, or based on the overall average for all stations by
storm, there is a positive correlation between the wet load percent of total and the rainfall
intensity observed at the headwaters. This is logical and certainly supportive of the hypothesis
that metal mobilization, whether by runoff or resuspension, is a function of the characteristics of
the event.
A notable decrease in wet load % at Fisherville Pond (between BWW04 and BWW06) is
seen for all metals. For example, Cu declined from 75.2% to 58.6% wet load, due most likely to
7-42
-------
Sampling Station BWW04
November 2-5, 1992
Time 0 = 2230, November 2
20
0
-12 -6 0 6 12 18 24 30 36 42 48 54 60 66 72 78
80
A
60
0.0
Wet Load
40
20
Base Load
End of Storm
Start of Storm
0
12
30 36 42
60 66 72 78
Hour
Figure 7.20 Example Figure of Cr Showing Mass Loading Calculation for
Storm 2 at Station BWW04
7-43
-------
Table 7.13 Average of all Storms for Wet Loads as Percent of Total Load
Station
Cd
Cr
Cu
Ni
Pb
Zn
BODs
EC
FC
NH3-N
NO3-N
PO4-P
TSS
vss
Blackstone River Stations
BWWOO
81.3
93.1
90.8
84.6
87.5
85.9
85.9
96.9
87.9
86.9
77.9
83.0
91.6
91.7
BWW01
84.9
74.3
84.3
69.7
88.1
80.4
86.9
96.4
81.0
64.9
56.3
81.2
93.6
81.8
BWW02
85.8
75.2
82.3
62.1
84.6
72.1
69.3
75.9
90.0
73.4
51.9
77.7
76.0
74.9
BWW04
73.1
81.2
75.2
48.8
88.9
69.9
80.8
90.2
84.9
80.6
43.7
62.8
94.3
91.4
BWW06
56.4
66.9
58.6
42.8
73.2
64.2
67.6
94.2
94.7
67.4
53.9
44.3
79.0
71.2
BWW07
38.6
59.1
50.1
37.2
63.3
54.9
58.2
88.4
87.7
67.4
34.5
47.2
69.3
65.5
BWW08
51.2
61.9
56.4
40.6
63.3
49.4
63.2
84.9
75.7
70.0
32.2
43.4
67.1
66.0
BWW11
54.0
60.2
56.8
43.2
67.0
59.1
58.4
88.1
82.1
81.6
45.9
39.2
66.9
72.7
BWW13
64.8
52.5
44.0
31.8
62.0
55.8
49.3
82.5
79.5
85.2
54.2
36.4
54.0
65.6
BWW17
52.6
51.5
52.3
40.9
56.2
54.2
60.0
95.9
85.9
82.1
40.5-
42.1
72.7
74.4
BWW18
53.8
55.7
48.8
34.8
51.0
47.6
59.1
90.4
83.6
69.3
32.1
40.3
55.6
69.9
BWW20
49.0
61.4
51.0
50.4
55.2
55.5
59.4
93.0
77.3
62.4
38.0
52.7
71.4
72.9
BWW21
52.2
53.1
46.1
47.9
62.0
60.3
69.3
95.3
95.8
70.9
42.2
48.3
64.6
72.2
Tributaries
BWW05
71.1
82.7
69.3
72.4
72.7
56.4
36.4
65.6
58.4
73.9
BWW09
72.1
61.2
74.5
43.9
68.3
43.2
60.9
68.9
72.0
55.9
55.4
45.4
64.3
77.3
BWW10
44.3
71.7
54.9
48.0
57.9
34.3
47.4
50.2
69.0
83.9
BWW14
53.8
57.1
51.2
59.2
50.2
36.8
66.0
81.5
75.4
81.3
40.7
22.9
63.3
62.6
BWW15
63.4
60.9
57.1
44.0
58.3
35.1
47.9
50.0
73.3
77.3
BWW16
71.0
63.8
64.2
68.6
70.2
81.5
67.9
83.9
90.9
71.4
49.3
62.4
77.2
66.2
-------
Table 7.14 Average of all Stations for each Storm for Wet Loads as Percent
of Total Load
Storm
Cd
Cr
Cu
Ni
Pb
Zn
EC
Storm 1
51.9
48.0
41.9
35.1
53.4
45.5
86.8
Storm 2
65.9
68.8
65.1
49.3
73.4
63.6
90.5
Storm 3
66.3
78.5
76.8
62.1
81.5
77.6
93.2
Average
61.4
65.1
61.3
48.8
69.4
62.2
90.2
Storm
bod5
NH3-N
N03-N
PO4-P
TSS
VSS
FC
Storm 1
48.3
75.1
37.2
41.9
56.5
68.7
76.6
Storm 2
78.2
69.5
49.0
64.6
81.7
68.8
85.9
Storm 3
73.7
77.4
53.1
54.7
82.5
86.4
92.7
Average
66.7
74.0
46.4
53.7
73.5
74.6
85.1
7-45
-------
settling. On the other hand, an increase in wet load % occurred in the Rice City Pond for all
metals, except for Zn, due to sediment resuspension, which occurred under the higher wet
weather flows.
All the tributaries had greater than 50% wet load, except for Zn and Ni. Other significant
increases in % wet load, which is an indication of a wet weather source, were: Pb between
BWW18-20 and BWW20-21; Cu between BWW13-17 and BWW18-20; Ni between BWW18-
20; Cd between BWW11-13, and BWW20-21; Cr between BWW02-04 and BWW18-20; Zn
between BWW18-20 and BWW20-21.
7.4.2.2 Conventional (TSS/VSS, BODs, and FC/EC)
With regards to the conventional constituents such as TSS, VSS, EC, FC, and BOD5, all
the mainstem and tributary stations of the Blackstone River had more than 50% wet load except
BWW13 for BODj. The highest percentage occurred for TSS/VSS at BWW04 (94%). The trend
of higher percent wet load as the storm intensity increases is true for all these constituents.
7.4.2.3 Nutrients
All ammonia loadings were above 50%, and most of the nitrate loadings were below 50%
for the mainstem and tributaries stations of the Blackstone River. Wet load as % total load for
nitrate ranged from 78% at the headwaters to about 40 % at the mouth of the river. For
ammonia, the values were greater than 70% for the whole length of the river, with the exception
of BWW01 and BWW20.
Orthophosphate wet loadings were above 50% at the headwaters but steadily declined to
below 50% at the mouth of the river.
7.4.3 Net Gain and Loss Per Reach
Based on the interpretation of the mass loading curves, mass balance around each reach
may be made, providing an estimate of pollutant gain or loss. Net pollutant changes in a reach
help to identify locations of major pollutant sources. The results of this evaluation also provides
insight into the relative importance of each reach through a system ranking. The following
decisions were made to establish the protocol for data evaluation.
The conditions between stations are dynamic. There are potentially multiple sources of
each constituents in each reach which may function differently depending on the rainfall
characteristics. Individual measurements within a reach were limited to a select group of the
major point sources (UBWPAD and Woonsocket) and tributaries. Station comparisons only
provide net gains or losses of pollutants. Specific identification of a source requires a more
detailed evaluation of each reach, which was beyond the scope of this project. However, reaches
identified as a hot spot may undergo a more detailed evaluation. An example of this is the
7-46
-------
identification of Rice City Pond (river reach BWW07-08) as a source of pollutant resuspension,
and the subsequent speciality study summarized in Chapter 8. Potential sources are usually
identified based on measured land use or observations (both past and present).
The UBWPAD and Woonsocket loads were subtracted from their respective reach mass
balance. The other WWTFs in the watershed were not considered in the balance, and, therefore,
their contribution remains as a part of the net gain in a reach.
The total load net gain and loss was calculated by reach by subtracting loadings from
consecutive stations along with other reach additions (the two major point sources and the
tributaries). For example:
Gains/Loss = BWW02 - BWW01 - UBWPAD (ie. BWW23)
or
Gains/Loss = BWW06 - BWW04 - BWW05 (ie. Quinsigamond River)
The wet load follows a similar procedure. An. example of net gain/loss profiles is given in
Figure 7.21. Trends may be observed in these types of figures. For instance, in Figure 7.21, a
major gain for all three constituents (TSS, Cu and Pb) may be seen in the reaches BWW00-04
and BWW07-11, and a major loss may be seen in the reaches BWW04-07 and BWW11-17, with
some rise and fall after station BWW17.
7.4.4 Major Point Sources vs Other Sources in the River
A point source is continuous and can be readily quantified. Nonpoint sources may be
difficult to identify and quantify. Surface runoff and resuspension from bottom sediment are
examples of nonpoint sources. Sources were grouped for comparison in the following manner:
Major Point Sources Loadings = UBWPAD + WOON + WOR CSO and; Other Source Loadings
= Headwaters (BWWOO) + Reach Gains + Tributary load + Small WWTFs.
Figure 7.22 is an example of the major point sources compared to the other sources in the
river. These figures illustrate the importance of the other sources during wet weather events.
The summary of the two categories are presented in Table 7.15 and 7.16 for wet and total loads.
In general, the other sources in the river are higher for most constituents. The exceptions are
ammonia and orthophosphate, which are governed by the major point sources. Pb had the
highest percentage of other sources (93%-98%). The highest loadings of Pb are from the
headwaters and in the reach that includes Rice City Pond.
7.4.5 System Ranking
A system ranking was made using the net gains for each reach and loads from the major
point sources, headwaters, and tributaries. UBWPAD and Woonsocket were only considered for
ranking calculations. The load and rankings, by storm, are presented in Table 7.17. The average
7-47
-------
Total Suspended Solids
20 -
15 -
CO 10 ~
S3
S 5-
Gain
IZZ
13
-15 - Loss
-20
15 -
Gain
Copper
/"™*\
CO
10 -
-5 -
<+-»
-------
% Contribution
%
MAJOR
POINT
SOURCES
OTHER
SOURCES
Wet Weather Mass (lbs)
STORM -1
| 1 STORM-2
T7\ STORM-3
MAJOR
POINT
SOURCES
I
//
/ /
XA.
OTHER
SOURCES
150
120
W
90 o
13
60
30
Figure 7.22 Example Plot Showing a Comparison of the Two Major Point
Sources Versus the Other Sources for Lead in Wet Weather
7-49
-------
Table 7.15 Wet Load Comparison Between the Two Major Point Sources and the Other Sources along the River
Storm
Cd
Cr
Cu
Pb
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
1
32.7
67.3
55.8
44.2
53.9
46.2
13.2
86.8
2
15.0
85.0
15.1
84.9
16.2
83.8
4.38
95.6
3
20.9
79.1
9.53
90.5
28.0
72.0
4.38
95.6
Storm
Ni
Zn
TSS
FC
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
1
69.6
30.4
48.3
51.7
23.3
76.7
2.72
97.3
2
28.9
71.1
15.0
85.0
28.4
71.6
68.2
31.8
3
35.6
64.5
14.3
85.7
7.42
92.6
0.26
99.7
Storm
NH3-N
NO3-N
PO4-P
BODs
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
1
58.6 •
41.4
41.3
58.7
72.3
27.7
36.2
63.8
2
68.0
32.0
1.89
98.1
77.2
22.8
26.2
73.9
3
31.1
68.9
54.5
45.5
39.3
60.7
39.6
60.4
Two Major Point Sources = UBWPAD + Woonsocket WWTF; Other Sources = Tributaries + Small Point Sources +
Nonpoint Sources (for instance, runoff, resuspension and groundwater).
-------
Table 7.16 Total Load Comparison Between the Two Major Point Sources and the Other Sources along the River
Storm
Cd
Cr
Cu
Pb
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
1
18.8
81.2
40.2
59.8
35.7
64.3
6.11
93.9
2
15.3
84.7
12.8
87.2
11.6
88.4
4.87
95.1
3
15.3
84.7
6.29
93.7
18.8
81.2
1.97
98.0
Storm
Ni
Zn
TSS
FC
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
1
41.7
58.3
24.9
75.1
16.9
83.1
1.85
98.2
2
29.7
70.4
13.9
86.1
19.2
80.8
66.2
33.8
3
30.3
69.8
8.66
91.3
2.42
97.6
0.07
99.9
Storm
NH3-N
NO3-N
PO4-P
BODs
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
1
49.2
50.8
27.2
72.8
81.1
18.9
39.4
60.6
2
82.6
17.4
1.57
98.4
59.4
40.6
35.8
64.2
3
20.1
80.0
31.5
68.5
35.9
64.1
25.9
74.1
Two Major Point Sources - UBWPAD + Woonsocket WWTF; Other Sources = Tributaries + Small Point Sources +
Nonpoint Sources (for instance, runoff, resuspension and groundwater).
-------
rankings for all storms are presented in Table 7.18.
To highlight individual reach contributions, a ranking without the major point sources for
the wet load was also calculated for each storm and is given in Table 7.19.
7.4.5.1 Nutrients
Wet and Total Load • UBWPAD is the most important source for nutrients for both wet
and total load and delivers almost 1/3 of the total loadings for ammonia. The second most
important source is Woonsocket.
UBWPAD is ranked first for nitrate loadings, while Woonsocket does not appear within
the first 10 positions for total load and only in the 6th position for the wet load.
V
UBWPAD and Woonsocket are the most important sources of phosphorus and together
deliver about 60% of the total loadings.
The headwaters were not an important source for nutrients.
Wet Load Without Major Point Sources - If we only consider the river reaches, the
important reaches are between BWW17-18 and BWW01-02. Since both reaches include the
discharge from the major point sources, the loading estimated may simply be an inaccurate
accounting of the major point source load, or a conversion of organic nitrogen to ammonia.
BWW17-18 delivers about 44% of the ammonia loadings, and BWW01-02 delivers about 20%.
Other relevant reaches are BWW02-04, BWW06-07, and BWW20-21.
BWW11-13, BWW18-20, and BWW20-21 have the major reach gains of nitrite totaling
about 62%. Other important sources are BWW04-06, BWW02-04, and BWW13-17. Instream
nitrification is most likely a component of the reaches below the facilities (BWW02-06 and
BWW18-21).
BWW18-20, BWW17-18 and Rice City Pond (BWW07-08) are the major reaches for
phosphate, delivering about 60% of the reach loadings. Other important sources are BWW02-04,
BWW06-07, and BWW01-02.
7.4.5.2 Conventional (TSS, BODs, FC)
Wet and Total Load - BWW02-04, the headwaters (BWW00), and Woonsocket are the
major sources for TSS, delivering greater than 50% of the loading.
UBWPAD, BWW00 and BWW01-02 are the most important sources of BOD5 delivering
more than 50% of the loading.
7-52
-------
Table 7.17 Blackstone River Wet Weather Storm - 1 Rankings, Wet Load (lbs)
Rank
Pb
Cu
Ni
Cd
Cr
Zn
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
1
BWW20-21
5.47
27.5
UBWPAD
30.7
47.1
UBWPAD
20.1
67.4
BWW02-04
1.30
31.5
UBWPAD
7.03
51.3
UBWPAD
31.6
36.9
2
BWW00
5.12
25.7
BWW02-04
13.5
20.6
BWW 18-20
3.75
12.6
UBWPAD
1.15
27.9
BWW01-02
1.86
13.6
BWW01-02
15.9
18.5
3
BWW01-02
2.92
14.7
BWW13-17
4.30
6.59
BWW02-04
1.65
5.53
BWW11-13
0.86
21.0
BWW13-17
1.66
12.1
WOON
9.74
11.4
4
BWW13-17
1.98
9.95
BWW07-08
4.20
6.44
BWW01-02
0.88
2.96
BWW07-08
0.26
6.25
BWW 18-20
0.77
5.58
BWWOO
9.12
10.7
5
UBWPAD
1.51
7.60
WOON
4.10
6.29
BWWOO
0.87
2.91
WOON
0.20
4.89
BWWOO
0.70
5.11
BWW13-17
7.57
8.85
6
WOON
1.12
5.62
BWW18-20
3.61
5.53
BWW07-08
0.69
2.30
BWWOO
0.17
4.21
WOON
0.62
4.51
BWWOO-Ol
5.41
6.31
7
BWW07-08
0.60
3.02
BWWOO
1.79
2.75
BWW04-06
0.59
1.97
BWW20-21
0.10
2.48
BWW00-01
0.40
2.89
BWW17-18
3.91
4.57
8
BWW14
0.33
1.67
BWWOO-Ol
1.27
1.95
WOON
0.48
1.61
BWW18-20
0.04
1.07
BWW06-07
0.38
2.76
BWW14
1.21
1.42
9
BWW16
0.27
1.36
BWW10
0.60
0.92
BWW05
0.27
0.91
BWW14
0.02
0.41
BWW14
0.15
1.09
BWW 16
0.52
0.61
10
BWW17-18
0.23
1.15
BWW09
0.50
0.77
BWW14
0.18
0.62
BWW09
0.00
0.10
BWW16
0.05
0.36
BWW15
0.23
0.27
U
BWW15
0.12
0.60
BWW14
0.38
0.58
BWW15
0.17
0.57
BWW05
0.00
0.10
BWW05
0.05
0.34
BWW08-11
0.21
0.24
12
BWW05
0.09
0.46
BWW16
0.14
0.21
BWW13-17
0.11
0.38
BWW15
0.00
0.07
BWW09
0.02
0.15
BWW05
0.12
0.14
13
BWW09
0.09
0.45
BWW15
0.12
0.18
BWW16
0.05
0.17
BWW16
0.00
0.07
BWW15
0.02
0.15
BWW09
0.05
0.06
14
BWW10
0.03
0.15
BWW05
0.04
0.06
BWW10
0.01
0.03
BWW10
0.00
0.02
BWW10
0.01
0.07
BWW10
0.05
0.06
15
BWW02-04
0.02
0.09
Total
19.9
65.2
29.8
4.11
13.7
85.6
Rank
TSS/1000
NO3-N/IOOO
PO4-P/IOOO
NHj-N/1000
BODs/1000
FC/(1E12)
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
1
BWW02-04
8.39
30.3
UBWPAD
2.29
37.9
UBWPAD
0.72
46.5
WOON
2.48
40.8
UBWPAD
3.11
29.3
BWW20-21
19.8
36.4
2
BWW13-17
4.48
16.2
BWW04-06
1.09
18.1
WOON
0.40
25.8
BWW17-18
1.85
30.4
BWW13-17
1.76
16.6
BWW13-17
11.4
20.9
3
UBWPAD
3.92
14.2
BWW11-13
0.70
11.6
BWW17-18
0.12
7.46
UBWPAD
1.08
17.8
BWW20-21
1.49
14.1
BW00-O1
7.00
12.8
4
WOON
2.53
9.15
BWW18-20
0.64
10.6
BWW07-08
0.11
6.75
BWW01-02
0.21
3.39
BWWOO
1.13
10.7
BWWOO
6.73
12.4
5
BWWOO-Ol
2.24
8.10
BWW02-04
0.52
8.54
BWW01-02
0.07
4.18
BWW07-08
0.20
3.32
BWW01-02
0.86
8.06
BWW14
3.29
6.05
6
BWWOO
1.91
6.91
BWW09
0.40
6.62
BWW02-04
0.06
4.11
BWW06-07
0.15
2.53
WOON
0.73
6.87
BWW16
3.03
5.57
7
BWW07-08
1.65
5.95
BWW17-18
0.15
2.55
BWW18-20
0.05
3.47
BWWOO
0.05
0.76
BW00-01
0.54
5.10
BWW02-O4
0.89
1.64
8
BWW06-08
1.00
3.61
BWWOO
0.07
1.17
BWW13-17
0.02
1.09
BWW14
0.03
0.56
BWW02-04
0.48
4.55
UBWPAD
0.83
1.53
9
BWW14
0.68
2.47
WOON
0.05
0.89
BWWOO
0.01
0.39
BWW13-17
0.01
0.18
BWW07-08
0.27
2.58
WOON
0.65
1.19
10
BWW15
0.42
1.50
BWWOO-Ol
0.04
0.66
BWW15
0.00
0.06
BWWOO-Ol
0.01
0.18
BWW14
0.15
1.39
BWW04-06
0.35
0.64
11
BWW10
0.23
0.83
BWW14
0.03
0.50
BWW14
0.00
0.06
BWW09
0.00
0.05
BWW16
0.06
0.53
BWW08-11
0.28
0.51
12
BWW16
0.18
0.63
BWW15
0.03
0.43
BWW09
0.00
0.06
BWW16
0.00
0.02
BWW09
0.03
0.27
BWW06-07
0.20
0.37
13
BWW09
0.03
0.12
BWW16
0.02
0.30
BWW16
0.00
0.06
BWW09
0.04
0.08
14
BWW05
0.00
0.03
15
BWW10
0.00
0.02
Total
27.6
6.04
1.56
6.09
10.6
54.5
WOON = Woonsocket WWTF, WOR CSO = Worcester CSO
-------
Table 7.17 Blackstone River Wet Weather Storm - 2 Rankings, Wet Load (lbs) (continued)
-j
I
Rank
Pb
Cu
Ni
Cd
Cr
Zn
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
1
BWW07-08
18.4
19.0
BWW04
21.7
16.8
UBWPAD
26.0
28.0
BWW07-08
2.06
18.0
BWW08-11
12.8
24.2
BWW18-20
89.4
21.7
2
BWW00
15.1
15.6
BWW08-11
20.7
16.0
BWW 18-20
21.6
23.3
BWW02-04
1.75
15.3
BWW02-04
9.74
18.5
BWW08-11
62.4
15.2
3
BWW20-21
13.2
13.6
BWW17-18
17.4
13.4
BWW13-17
13.5
14.5
BWW20-21
1.71
15.0
BWW07-08
9.65
18.3
BWW20-21
51.2
12.4
4
BWW02-04
12.1
12.5
BWW20-21
15.9
12.3
BWW02-04
8.96
9.67
UBWPAD
1.59
13.9
UBWPAD
7.43
14.1
BWW02-04
41.1
9.98
5
BWW08-11
11.5
11.8
UBWPAD
15.6
12.1
BWW01-02
6.20
6.69
BWW13-17
1.14
9.93
BWW01-02
5.10
9.67
BWWOO
38.1
9.25
6
BWW01-02
8.84
9.11
BWW07-08
13.3
10.3
BWW07-08
4.62
4.99
BWW01-02
1.10
9.61
BWW20-21
2.75
5.22
WOON
31.7
7.70
7
BWW18-20
8.00
8.24
BWW00
9.60
7.42
BWW08-I1
3.97
4.28
BWW08-11
1.07
9.37
BWW00
1.88
3.57
UBWPAD
29.7
7.20
8
UBWPAD
2.15
2.22
BWW01-02
6.01
4.65
BWW00
2.62
2.83
BWW 18-20
0.67
5.89
BWW17-18
0.97
1.84
BWW00-01
21.7
5.27
9
WOON
2.05
2.11
WOON
5.44
4.21
BWW00-01
2.18
2.35
WOON
0.12
1.03
BWW09
0.59
1.12
BWW09
13.9
3.37
10
BWW09
1.81
1.86
BWW09
1.00
0.77
BWW15
0.84
0.91
BWW00
0.05
0.46
WOON
0.52
0.98
BWW14
6.71
1.63
11
WOR CSO
1.31
1.35
WOR CSO
0.79
0.61
WOON
0.72
0.78
BWW00-01
0.04
0.38
BWW00-01
0.46
0.87
BWW07-08
5.65
1.37
12
BWW14
1.04
1.07
BWW00-01
0.50
0.39
BWW05
0.37
0.40
BWW09
0.04
0.35
BWW14
0.40
0.75
BWW16
5.26
1.28
13
BWW16
0.69
0.71
BWW16
0.48
0.37
BWW14
0.31
0.33
BWW16
0.02
0.17
WOR CSO
0.20
0.39
BWW01-02
4.85
1.18
14
BWW05
0.34
0.35
BWW15
0.30
0.23
WOR CSO
0.30
0.33
BWW15
0.02
0.17
BWW10
0.09
0.17
WOR CSO
4.47
1.09
15
BWW15
0.28
0.29
BWW10
0.29
0.22
BWW16
0.30
0.32
BWW10
0.02
0.17
BWW05
0.09
0.16
BWW06-07
3.02
0.73
16
BWWOO-Ol
0.16
0.16
BWW05
0.18
0.14
BWW09
0.19
0.21
BWW14
0.02
0.16
BWW15
0.06
0.11
BWW 10
1.72
0.42
17
BWW10
0.11
0.11
BWW14
0.14
0.11
BWW10
0.04
0.04
WOR CSO
0.01
0.11
BWW16
0.06
0.11
BWW15
0.97
0.24
Total
97.1
129
92.7
11.4
52.7
412
Rank
TSS/1000
NOj-N/1000
PO4-P/IOOO
NHj-N/1000
BODs/1000
FC/(1E12)
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
1
BWW8-11
27.9
22.6
BWW20-21
5.96
36.6
UBWPAD
1.01
44.9
UBWPAD
11.4
49.6
UBWPAD
12.8
15.6
UBWPAD
336
45.1
2
WOON
27.7
22.5
BWW11-13
5.01
30.8
WOON
0.72
31.9
WOON
4.21
18.2
BWW 18-20
10.7
13.1
BWW01-02
226
30.3
3
BWW01-02
15.7
12.7
BWW 18-20
1.66
10.2
BWW07-08
0.15
6.85
BWW02-04
1.97
8.54
BWW20-21
10.5
12.8
BWW02-04
47.9
6.4
4
BWWOO
14.3
11.6
BWW08-11
1.46
8.97
BWW17-18
0.07
3.16
BWW01-02
1.53
6.63
WOON
7.83
9.57
BWW20-21
41.1
5.5
5
BWW13-17
12.7
10.3
BWW04-06
0.39
2.41
BWW02-04
0.06
2.80
BWW20-21
1.11
4.81
BWW02-04
7.69
9.40
BWW16
34.3
4.6
6
UBWPAD
6.97
5.66
UBWPAD
0.29
1.75
BWW08-11
0.06
2.67
BWW04-06
1.10
4.77
BWWOO
7.14
8.72
BWWOO
20.8
2.8
7
BWW17-18
5.19
4.21
BWW07-08
0.27
1.65
BWWOO
0.05
2.27
BWW11-13
0.90
3.90
BWW01-02
6.61
8.08
WOON
13.7
1.8
8
BWWOO-Ol
3.37
2.74
BWW02-04
0.21
1.29
BWW13-17
0.05
2.22
BWW06-07
0.34
1.47
BWW17-18
5.43
6.63
BWW07-08
11.9
1.6
9
BWW07-08
2.85
2.31
BWW01-02
0.20
1.21
BWW20-21
0.04
1.69
BWW08-11
0.18
0.77
BWW07-08
4.02
4.91
WOR CSO
6.34
0.8
10
BWW14
1.43
1.16
BWW14
0.18
1.09
WOR CSO
0.01
0.44
BWW14
0.12
0.52
WOR CSO
2.98
3.64
BWW00-01
5.41
0.7
11
BWW09
1.41
1.14
BWW09
0.15
0.91
BWW14
0.01
0.31
WOR CSO
0.08
0.33
BWW14
1.95
2.38
BWW14
1.02
0.1
12
WOR CSO
1.13
0.92
BWWOO
0.15
0.90
BWW16
0.01
0.22
BWWOO
0.07
0.30
BWW08-11
1.76
2.15
BWW09
0.79
0.1
13
BWW16
0.85
0.69
BWW06-07
0.14
0.85
BWW10
0.00
0.18
BWW16
0.02
0.08
BWW09
1.34
1.64
14
BWW02-04
0.80
0.65
BWW16
0.07
0.42
BWW09
0.00
0.13
BWW00-01
0.01
0.04
BWW16
0.76
0.93
15
BWW15
0.56
0.45
BWW15
0.07
0.42
BWW15
0.00
0.13
BWW09
0.00
0.01
BWW00-01
0.34
0.42
16
BWW10
0.16
0.13
WORCSO
0.07
0.41
BWW05
0.00
0.09
17
BWW05
0.15
0.12
BWW10
0.02
0.10
Total
123
16.3
2.25
23.1
81.8
746
WOON « Woonsocket WWTF, WOR CSO = Worcester CSO
-------
Table 7.17 Blackstone River Wet Weather Storm - 3 Rankings, Wet Load (lbs) (continued)
Rank
Pb
Cu
Ni
Cd
Cr
Zn
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
1
BWW00
86.2
51.2
BWW00
40.1
22.3
UBWPAD
20.1
32.5
BWW01-02
1.33
33.2
BWW07-08
20.0
39.6
BWWOO-Ol
93.6
27.9
2
BWW07-08
35.3
20.9
UBWPAD
33.9
18.9
BWW07-08
15.6
25.1
BWW00
0.63
15.6
BWW00
15.0
29.8
BWW00
75.2
22.4
3
BWW01-02
26.3
15.6
BWW07-08
29.6
16.5
BWW00
7.83
12.6
BWW07-08
0.52
13.1
BWW01-02
9.70
19.3
BWW07-08
72.9
21.8
4
BWW13-17
6.02
3.57
BWW01-02
22.4
12.5
BWW01-02
6.90
11.1
UBWPAD
0.51
12.8
UBWPAD
3.46
6.87
WOON
22.2
6.62
5
BWW18-20
5.28
3.13
BWW13-17
17.8
9.92
BWW13-17
4.14
6.68
BWW08-11
0.37
9.33
WOON
1.07
2.12
BWW04-06
20.5
6.12
6
WOON
3.92
2.33
WOON
12.7
7.07
BWW06-07
2.11
3.40
WOON
0.27
6.76
BWW14
0.40
0.79
BWW20-21
14.4
4.30
7
WOR CSO
1.78
1.06
BWW18-20
10.7
5.99
BWW00-01
1.83
2.95
BWW20-21
0.22
5.46
WOR CSO
0.27
0.54
WOR CSO
13.1
3.89
8
UBWPAD
1.69
1.00
BWW06-07
7.50
4.18
WOON
1.15
1.85
WOR CSO
0.06
1.47
BWW09
0.27
0.54
UBWPAD
12.8
3.81
9
BWW14
0.60
0.36
WOR CSO
3.77
2.10
BWW 18-20
0.98
1.58
BWW0O-01
0.05
1.12
BWW05
0.07
0.14
BWW18-20
5.87
1.75
10
BWW09
0.39
0.23
BWW14
0.51
0.29
WOR CSO
0.75
1.21
BWW05
0.02
0.52
BWW 18-20
0.07
0.14
BWW08-11
1.39
0.41
11
BWW05
0.28
0.17
BWW09
0.25
0.14
BWW14
0.19
0.31
BWW09
0.02
0.47
BWW10
0.05
0.10
BWW09
0.94
0.28
12
BWW10
0.24
0.14
BWW05
0.13
0.07
BWW09
0.11
0.18
BWW16
0.00
0.07
BWW16
0.03
0.06
BWW05
0.83
0.25
13
BWW16
0.23
0.14
BWW16
0.09
0.05
BWW05
0.14
0.23
BWW10
0.00
0.05
BWW15
0.02
0.04
BWWI3-17
0.70
0.21
14
BWW04-06
0.16
0.09
BWW10
0.08
0.04
BWW10
0.08
0.13
BWW15
0.00
0.05
BWW16
0.51
0.15
15
BWW15
0.10
0.06
BWW15
0.03
0.02
BWW16
0.09
0.15
BWW10
0.25
0.07
16
BWW15
0.01
0.02
BWW15
0.12
0.04
Total
168.4
179.5
62.0
4.01
50.4
335
Rank
TSS/1000
NOj-N/1000
PO4-P/IOOO
NH3-N/IOOO
BODs/1000
FC/(1E12)
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
Source
Load
%
1
BWW02-04
107
41.0
UBWPAD
4.29
36.6
BWW 18-20
1.52
30.6
BWW17-18
0.98
38.8
BWW00
11.2
29.2
BWW00
200
79.7
2
BWW00
63.5
24.3
BWW11-13
2.36
20.2
UBWPAD
1.07
21.6
UBWPAD
0.63
25.0
UBWPAD
8.51
22.2
BWW17-18
16.7
6.66
3
BWW18-20
28.1
10.7
WOON
2.08
17.7
WOON
0.83
16.8
BWW01-02
0.48
19.0
BWW01-02
5.08
13.3
BWW13-17
11.2
4.47
4
BWW07-08
24.7
9.45
BWW18-20
0.84
7.14
BWW06-07
0.60
12.2
BWW06-07
0.12
4.76
WOR CSO
4.03
10.5
BWW02-04
6.80
2.71
5
WOR CSO
11.3
4.32
BWW13-I7
0.80
6.80
BWW17-18
0.51
10.2
WOR CSO
0.09
3.69
WOON
2.63
6.87
BWW06-07
5.04
2.01
6
BWW01-02
7.64
2.92
BWW02-04
0.39
3.34
BWW11-13
0.33
6.61
BWW00
0.07
2.90
BWW02-04
2.34
6.11
BWW16
4.39
1.75
7
BWW13-17
6.45
2.46
BWW00
0.32
2.75
WOR CSO
0.05
0.93
WOON
0.06
2.42
BWW17-18
1.73
4.52
BWW20-21
3.54
1.41
8
WOON
4.67
1.78
BWW07-08
0.27
2.26
BWW09
0.04
0.83
BWW14
0.04
1.47
BWW06-07
1.68
4.39
BWW14
2.35
0.94
9
UBWPAD
3.44
1.31
BWW14
0.15
1.26
BWW00
0.01
0.26
BWW15
0.03
1.03
BWW14
0.48
1.26
UBWPAD
0.33
0.13
10
BWW14
1.63
0.62
BWW00-01
0.12
1.03
BWW05
0.002
0.04
BWW08-11
0.01
0.36
BWW18-20
0.26
0.68
WOR CSO
0.32
0.13
11
BWW16
0.89
0.34
BWW15
0.04
0.32
BWW14
0.001
0.02
BWW05
0.01
0.28
BWW09
0.23
0.60
BWW09
0.20
0.08
12
BWW15
0.77
0.29
BWW04-06
0.03
0.27
BWW10
0.001
0.02
BWW09
0.002
0.08
BWW16
0.17
0.44
WOON
0.01
0.01
13
BWW09
0.66
0.25
BWW16
0.02
0.15
BWW16
0.002
0.08
14
BWW05
0.40
0.15
BWW09
0.01
0.10
BWW10
0.002
0.08
15
BWW10
0.27
0.10
BWW10
0.00
0.01
Total
262
11.7
4.96
2.52
38.3
250
WOON = Woonsocket WWTF, WOR CSO = Worcester CSO
-------
Table 7.18 Source Rankings by Wet Load Averaged for all Storms With Point Sources in Percent
I Rank |
Source
1 % 1
Source
1 % 1
Source
%
Source
1 % 1
Source
%
Source
%
Cd
Cr
Cu
Pb
Ni
Zn
1
UBWPAD
18.2
UBWPAD
25.7
UBWPAD
26.2
BWW00
31.1
UBWPAD
42.7
UBWPAD
16.0
2
BWW02-04
15.6
BWW01-02
15.1
BWW02-04
12.6
BWW07-08
14.5
BWW 18-20
12.5
BWWOO
14.2
3
BWW01-02
14.3
BWW07-08
14.1
BWW07-08
11.1
BWW01-02
13.9
BWW07-08
10.8
BWWOO-01
13.2
4
BWW07-08
12.4
BWW00
13.7
BWW00
10.9
BWW20-21
13.8
BWW13-17
7.22
WOON
8.60
5
BWW20-21
7.64
BWW08-11
8.63
WOON
5.88
BWW13-17
4.54
BWW01-02
6.94
BWW 18-20
7.90
6
BWW11-13
6.99
BWW02-04
6.58
BWW01-02
5.71
BWW02-04
4.27
BWW00
6.13
BWW07-08
7.73
7
BWW00
6.76
BWW13-17
4.31
BWW13-17
5.52
BWW18-20
3.85
BWW02-04
5.08
BWW01-02
6.58
8
BWW08-11
6.23
WOON
2.70
BWW08-11
5.37
UBWPAD
3.64
BWWOO-01
1.77
BWW20-21
5.62
9
WOON
4.22
BWW18-20
2.03
BWW17-18
4.50
WOON
3.38
BWW08-11
1.43
BWW08-11
5.32
10
BWW13-17
3.32
BWW20-21
1.86
BWW20-21
4.12
BWW08-11
2.80
WOON
1.42
BWW02-04
3.36
11
BWW18-20
2.32
BWW0O-01
1.33
BWW 18-20
3.85
BWW15+16
1.06
BWW06-07
1.14
BWW13-17
3.02
12
BWW00-01
0.50
BWW06-07
0.98
BWW06-07
1.39
BWW 14
1.05
BWW15+16
0.66
BWW04-06
2.05
13
WOR CSO
0.49
BWW14
0.93
BWW00-01
0.79
BWW09+10
1.00
BWW04-06
0.66
BWW17-18
1.52
14
BWW9+10
0.40
BWW9+10
0.76
WOR CSO
0.70
BWW17-18
0.39
BWW05
0.51
BWW09+10
1.44
15
BWW15+16
0.23
BWW17-18
0.65
BWW09+10
0.68
WOR CSO
0.35
BWW 14
0.42
WOR CSO
1.30
16
BWW05
0.21
BWW15+16
0.30
BWW15+16
0.36
BWW05
0.33
WOR CSO
0.40
BWW14
1.02
17
BWW14
0.19
BWW05
0.23
BWW14
0.33
BWWOO-01
0.06
BWW09+10
0.20
BWW15+16
0.80
18
WOR CSO
0.19
BWW05
0.09
BWW04-06
0.03
BWW06-07
0.25
19
BWW05
0.13
BODs
FC
NH3-N
NO3-N
PO4-P
TSS
1
UBWPAD
24.1
BWW00
32.69
UBWPAD
31.2
UBWPAD
26.2
UBWPAD
42.0
BWW02-04
242
2
BWW00
17.4
UBWPAD
16.24
BWW17-18
23.4
BWW11-13
21.1
WOON
27.7
BWWOO
14.4
3
BWW01-02
10.6
BWW20-21
14.44
WOON
20.8
BWW20-21
12.2
BWW17-18
7.72
WOON
11.3
4
BWW20-21
9.74
BWW01-02
10.55
BWW01-02
9.83
BWW 18-20
9.56
BWW07-08
5.06
BWW13-17
9.77
5
WOON
8.42
BWW13-17
8.73
BWW06-07
2.96
BWW04-06
7.29
BWW06-07
4.52
BWW08-11
7.68
6
BWW02-04
7.26
BWOO-Ol
4.68
BWW02-04
2.89
WOON
6.27
BWW02-04
2.57
UBWPAD
7.12
7
BWW13-17
5.90
BWW15+16
4.12
BWW20-21
1.63
BWW02-04
4.57
BWW11-13
2.45
BWW07-08
5.96
8
BWW17-18
4.06
BWW02-04
3.73
BWW04-06
1.61
BWW08-11
3.00
BWW01-02
1.55
BWW01-02
5.30
9
WOR CSO
3.73
BWW14
2.46
BWW00
1.34
BWW13-17
2.27
BWW18-20
1.29
BWWOO-01
3.65
10
BWW07-08
2.73
WOON
1.05
WOR CSO
1.25
BWW00
1.63
BWW13-17
1.23
BWW 18-20
3.61
11
BW 00-01
1.96
BWW06-07
0.82
BWW07-08
1.12
BWW07-08
1.31
BWWOO
1.09
WOR CSO
1.45
12
BWW14
1.82
BWW04-06
0.22
BWW14
0.86
BWW 14
0.96
BWW08-11
0.99
BWW14
1.43
13
BWW09+10
0.91
BWW08-11
0.18
BWW15+16
0.41
BWW17-18
0.90
BWW20-21
0.63
BWW17-18
1.43
14
BWW08-11
0.80
BWW09+10
0.09
BWW08-11
0.38
BWW 15+16
0.70
BWW14
0.45
BWW15+16
1.32
15
BWW15+16
0.69
BWW05
0.09
BWW00-01
0.58
WOR CSO
0.35
BWW06-08
1.21
16
BWW13-17
0.07
BWW09+10
0.58
BWW15+16
0.18
BWW09+10
0.07
17
BWW09+10
0.07
BWW01-02
0.41
BWW09+10
0.14
BWW05
0.07
18
BWW00-01
0.06
BWW06-07
0.28
BWW05
0.05
19
WOR CSO
0.08
20
BWW05
0.01
WOON = Woonsocket WWTF, WOR CSO = Worcester CSO
-------
Table 7.19 Source Rankings by Wet Load Averaged for all Storms Without Point Sources in Percent
Ranking
Source
%
Source
%
Source
%
Source
%
Source
%
Source
%
Cd
Cr
Cu
Pb
Ni
Zn
1
BWW02-04
15.6
BWW07-08
19.3
BWW07-08
11.1
BWW00
30.8
BWW18-20
12.5
BWWOO
14.1
2
BWW01-02
14.3
BWW01-02
14.2
BWW00
10.8
BWW07-08
14.3
BWW07-08
10.8
BWWOO-Ol
13.2
3
BWW07-08
12.4
BWW00
12.8
BWW02-04
6.87
BWW20-21
13.7
BWW13-17
7.20
BWW 18-20
7.82
4
BWW20-21
7.63
BWW08-11
8.07
BWW01-02
5.70
BWW01-02
13.1
BWW01-02
6.93
BWW07-08
7.71
5
BWW11-13
6.99
BWW02-04
6.16
BWW04
5.59
BWW13-17
4.51
BWW00
6.12
BWW01-02
6.58
6
BWW00
6.77
BWW13-17
4.05
BWW13-17
5.50
BWW02-04
4.19
BWW02-04
5.07
BWW20-21
5.58
7
BWW08-11
6.23
BWW18-20
1.91
BWW08-11
5.34
BWW08-11
3.94
BWWOO-Ol
1.77
BWW08-11
5.27
8
BWW13-17
3.31
BWW20-21
1.74
BWW17-18
4.48
BWW18-20
3.79
BWW08-11
1.43
BWW02-04
3.33
9
BWW18-20
2.32
BWWOO-Ol
1.25
BWW20-21
4.10
BWW14
1.03
BWW06-07
1.13
BWW13-17
3.02
10
WOR CSO
0.53
BWW06-07
0.92
BWW18-20
3.84
BWW09
0.85
BWW04-06
0.66
BWW04-06
2.04
11
BWW00-01
0.50
BWW14
0.88
BWW06-07
1.39
WOR CSO
0.80
WOR CSO
0.51
WOR CSO
1.66
12
BWW09
0.31
BWW17-18
0.61
WOR CSO
0.90
BWW16
0.74
BWW05
0.51
BWW17-18
1.52
13
BWW05
0.21
BWW09
0.60
BWWOO-Ol
0.78
BWW17-18
0.38
BWW15
0.50
BWW09
1.24
14
BWW14
0.19
WOR CSO
0.31
BWW09
0.56
BWW05
0.33
BWW14
0.42
BWW14
1.02
15
BWW15
0.10
BWW05
0.21
BWW10
0.39
BWW15
0.32
BWW16
0.21
BWW16
0.68
16
BWW16
0.10
BWW16
0.18
BWW14
0.33
BWW10
0.13
BWW09
0.13
BWW06-07
0.24
17
BWW10
0.08
BWW10
0.11
BWW16
0.21
BWWOO-Ol
0.05
BWW10
0.07
BWW10
0.18
18
BWW15
0.10
BWW15
0.14
BWW04-06
0.03
BWW15
0.18
19
BWW05
0.09
BWW05
0.13
WOR CSO = Worcester CSO
-------
Table 7.19 Source Rankings by Wet Load Averaged for all Storms Without Point Sources in Percent (continued)
Ranking
Source
%
Source
%
Source
%
Source
%
Source
%
Source
%
BODs
FC
NH3-J
N
NO3-N
PO4-P
TSS
l
BWW00
16.2
BWW00
31.6
BWW17-18
23.1
BWW11-13
20.9
BWW 18-20
11.3
BWW02-04
24.0
2
BWW01-02
9.80
BWW20-21
14.4
BWW01-02
9.69
BWW20-21
12.2
BWW17-18
6.93
BWWOO
14.3
3
BWW20-21
8.96
BWW01-02
10.1
BWW06-07
2.92
BWW18-20
9.33
BWW07-08
4.53
BWW13-17
9.66
4
BWW02-04
6.69
BWW13-17
8.45
BWW02-04
2.85
BWW04-06
6.92
BWW06-07
4.06
BWW08-11
7.54
5
BWW13-17
5.54
BW00-01
4.53
BWW20-21
1.60
BWW02-04
4.39
BWW02-04
2.30
BWW07-08
5.90
6
WOR CSO
4.72
BWW16
3.97
BWW04-06
1.59
BWW08-11
2.99
BWW11-13
2.20
BWW01-02
5.22
7
B WW 18-20
4.58
BWW02-04
3.59
WOR CSO
1.34
BWW09
2.54
BWW01-02
1.39
BWWOO-Ol
3.61
8
BWW17-18
3.72
BWW14
2.38
BWWOO
1.32
BWW13-17
2.27
BWW13-17
1.10
BWW 18-20
3.58
9
BWW07-08
2.50
BWW17-18
2.22
BWW11-13
1.30
BWWOO
1.61
BWWOO
0.97
WOR CSO
1.75
10
BW00-01
1.84
BWW06-07
0.79
BWW07-08
1.11
BWW07-O8
1.30
BWW08-11
0.89
BWW 14
1.42
11
BWW14
1.68
BWW07-08
0.53
BWW14
0.85
BWW 14
0.95
BWW20-21
0.56
BWW17-18
1.40
12
BWW06-07
1.46
WOR CSO
0.33
BWW08-11
0.38
BWW17-18
0.85
WOR CSO
0.46
BWW06-08
1.20
13
BWW09
0.84
BWW04-06
0.21
BWW15
0.34
BWWOO-Ol
0.56
BWW09
0.34
BWW15
0.75
14
BWW08-11
0.72
BWW08-11
0.17
BWW05
0.09
BWW01-02
0.40
BWW14
0.13
BWW16
0.55
15
BWW16
0.63
BWW09
0.09
BWW00-01
0.07
BWW 15
0.39
BWW16
0.09
BWW09
0.50
16
BWW13-17
0.06
BWW16
0.29
BWW10
0.07
BWW10
0.35
17
BWW16
0.06
BWW06-07
0.28
BWW15
0.06
BWW05
0.09
18
BWW09
0.05
WOR CSO
0.14
BWW05
0.04
19
BWW10
0.03
BWW10
0.04
20
BWW05
0.01
WOR CSO = Worcester CSO
-------
The headwaters are the major source for FC, delivering about 1/3 of the loadings.
UBWPAD and BWW20-21 together deliver more than 30% of the FC loadings.
Wet Load Without Major Point Sources - The headwaters are the most important source
for FC, BODj and second for TSS.
The reaches from the headwaters to BWW04 deliver about 60% of the other source
loadings of TSS. Other important reaches for TSS are BWW13-17, BWW08-11, and Rice City
Pond (BWW07-08).
The reaches from the headwaters to BWW04 together deliver more than 50% of the other
source loadings of BODs. Other important reaches for BOD5 are BWW20-21 and BWW13-17.
The reaches from the headwaters to BWW04 together deliver more than 60% of the other
source loadings of FC. BWW20-21 and BWW13-17 are other important reaches for FC.
7.4.5.3 Metals (Pb, Cu, Ni, Cd, Cr, Zn)
Wet and Total Load - The headwaters and resuspension in the Rice City Pond are the
most important sources of Pb, providing about 50% of the total load to the river. The UBWPAD
and Woonsocket are not important sources. Other reaches of significance include BWW01-02,
BWW20-21, and BWW13-17, delivering another 30% of the lead load.
UBWPAD is the major source for the other five metals, for both wet and total loadings.
Woonsocket is not a major source of Ni, Cd, or Cr, delivering less than 2% of the total loading.
It is an important source for Cu and Zn.
Both Rice City Pond and the headwaters are important sources for all trace metals
appearing within the first five positions for both total and wet load rankings.
Other reaches of significance include BWW02-04 for Cu and Cd and BWW01-02 for Cd
andCr.
Wet Load Without Major Point Sources - In general the headwaters, Rice City Pond,
BWW01-02, and BWW02-04 are the most important reaches for trace metals.
7.4.6 Comparison Between Wet Weather and Dry Weather Rankings
The comparison between dry weather and wet weather rankings for trace metals, TSS,
and nutrients for the top five position are provided in Table 7.20. A summary for the entire river
by constituent is given in Table 7.21.
UBWPAD is in the first position for nitrate and phosphate under both dry and wet
7-59
-------
Table 7.20 Top Five Source Rankings for Comparison Between Wet and Dry
Weather for Total Load in Percent
Rank
Source
%
Source
%
Source
%
Source
%
Source
%
Wet Weather
Cd
Cr
Cu
Ni
Pb
l
BWW02-04
15.1
BWW07-08
21.6
BWW02-04
22.3
UBWPAD
32.7
BWWOO
38.9
2
UBWPAD
14.5
UBWPAD
18.5
UBWPAD
17.8
BWW02-04
14.6
BWW07-08
15.3
3
BWW07-08
14.0
BWW00
18.3
BWW00
17.1
BWWOO
11.0
BWW01-02
11.1
4
BWW00
12.8
BWW01-02
14.2
BWW07-08
11.6
BWW07-08
9.89
BWW20-21
9.26
5
BWW01-02
11.2
BWW13-17
8.43
BWW01-02
8.46
B WW 18-20
8.31
BWW13-17
4.95
NH3-N
N03-N
PO4-P
TSS
1
UBWPAD
31.2
UBWPAD
16.3
UBWPAD
35.3
BWW02-04
28.3
2
BWW17-18
22.4
BWW11-13
11.1
WOON
22.8
BWWOO
25.3
3
WOON
19.4
BWW02-04
8.95
BWW 18-20
10.0
WOON
8.48
4
BWW01-02
12.8
BWW18-20
8.45
BWW17-18
6.09
BWW00-01
6.64
5
BWW18-20
4.13
BWW20-21
8.16
BWW07-08
5.61
BWW07-08
6.49
Dry Weather
Cd
Cr
Cu
Ni
Pb
1
UBWPAD
32.7
BLK07-08
34.2
UBWPAD
27.9
UBWPAD
44.2
BLK04-06
23.8
2
BLK07-08
10.1
BLK08-11
16.2
BLK07-08
13.6
BLK20-21
13.22
BLK06-07
22.2
3
BLK01-02
9.36
UBWPAD
10.7
BLK08-11
13.39
BLK08-11
5.58
BLK12-13
13.0
4
BLK08-11
9.13
BLK01
8.84
BLK04-06
6.54
BLK12-13
5.32
BLK08-11
10.4
5
BLK12-13
8.93
BLK06-07
6.46
BLK20-21
5.80
BLK01-02
4.34
BLK07-08
7.28
NH3-N
NOj-N
PO4-P
TSS
1
WOON
67.3
UBWPAD
49.6
UBWPAD
63.2
BLK07-08
15.3
2
BLK01-02
8.28
BLK20-21
10.89
WOON
19.5
BLK12-13
11.0
3
UBWPAD
4.87
WOON
7.90
BLK12-13
2.99
BLK04-06
10.1
4
BLK03-04
4.52
BLK11-12
5.28
BLK11-12
2.65
BLK20-21
9.29
5
BLK20-21
3.01
BLK02-03
3.46
BLK02-03
2.45
BLK06-07
7.94
WOON = Woonsocket WWTF
7-60
-------
Table 7.21 A Comparison Between Wet and Total Load for the Two Major Point Sources and the Other Sources
along the River in Percent
Cd
Cr
Cu
Pb
Survey
Load
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Wet
22.9
77.1
26.8
73.2
32.7
67.3
7.33
92.7
Total
16.5
83.5
19.8
80.2
22.1
78.0
4.32
95.7
Ni
Zn
TSS
FC
Survey
Load
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Wet
44.7
55.3
25.9
74.1
19.7
80.3
23.7
76.3
Total
33.9
66.1
15.8
84.2
12.8
87.2
22.7
77.3
\
NH3-N
NO3-N
PO4-P
BOD5
Survey
Load
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Two Major
Point Sources
Other
Sources
Wet
52.6
47.4
32.6
67.5
62.9
37.1
34.0
66.0
Total
50.6
49.4
20.1
79.9
58.8
41.2
33.7
66.3
Two Major Point Sources = UBWPAD + Woonsocket WWTF; Other Sources = Tributaries + Small Point Sources +
Nonpoint Sources (for instance, runoff, resuspension and groundwater).
-------
weather conditions.
Under dry weather, Woonsocket is ranked first for ammonia (68%). The UBWPAD,
which was providing nitrification, was not important.
The headwaters and Rice City Pond are not important sources of nutrients under either
dry or wet weather. Nutrients are mostly controlled by the major point sources under dry
weather and by a combination of the major point sources and ail other sources under wet weather
conditions.
UBWPAD is ranked first for TSS under dry weather. For wet weather, Woonsocket was
ranked first. The headwaters are an important source under wet weather. Rice City Pond was
important for both wet and dry weather.
River reach sources of Pb dominated the rankings for both dry and wet weather.
UBWPAD and Woonsocket were not important sources for Pb, under either wet or dry weather.
UBWPAD was the major source for Cu, Ni, Cd, and Cr under both wet and dry weather.
Woonsocket was a major source for Cu, Ni, and Cd under dry weather but did not appear within
the first five positions under wet weather.
The headwaters were an important source for all trace metals under wet weather but did
not appear within the first five rankings under dry weather.
BWW02-04 was a major source of Cu, Cd, and Ni under wet weather but did not appear
within first five rankings under diy weather.
BWW01-02 was an important source for Pb, Cu, Ni, Cd, and Cr under wet weather but
was only important for Ni and Cd under dry weather.
7.4.7 Comparison of Load for Different River Systems
Five major rivers contribute flows and pollutant loadings to the Providence River and
Upper Narragansett Bay. The wet weather study conducted in 1988-89 for the Narragansett Bay
Project provided a ranking for the five rivers for several pollutants. A similar ranking table is
reproduced here (Table 7.22). Blackstone River ranked first for all the constituents except
ammonia, where it was second. In general, the rankings for the other rivers in descending order
were: Pawtuxet, Woonasquatucket, Ten Mile, and Moshassuck. Blackstone River alone was
contributing 41-67% of the wet load delivered by the five tributaries.
Total rainfall for the NBP studies for three storms were in 0.90,1.94 and 0.37 inches, as
compared to this study, 0.56,0.88, and 0.81 inches. The data from this study have also been
summarized in Table 7.23. The wet loads (lbs) were calculated using the EMC values from Table
7-62
-------
Table 7.22 Narragansett Bay Project 1988-89 Tributary Wet Loads and Rankings
End of River
TSS NO3-N PO4-P NH3-N Cu
Pb
Cd
Cr
Ni
NBP Wet Loads in lbs, Total of the Three NBP 1988-89 Storms
Blackstone River
684000
127000
13700
7160
468
433
36.4
331
315
Moshassuck
68900
5980
241
419
45.7
46.2
0.84
29.5
30.7
Pawtuxet
643000
32900
5070
12100
148
127
9.52
87.1
143
Ten Mile
28800
20200
1260
856
92.8
28.5
5.79
92.2
217
Woonasquatucket
115000
6780
691
650
51.0
67.7
1.72
18.6
47.0
NBP Wet Load Rankings, Total of the Three NBP 1988-89 Storms
Blackstone River
1
1
1
2
1
1
1
1
1
Moshassuck
4
5
5
5
5
4
5
4
5
Pawtuxet
2
2
2
1
2
2
2
3
3
Ten Mile
5
3
3
3
3
5
3
2
2
Woonasquatucket
3
4
4
4
4
3
4
5
4
NBP Wet Loads in Percent, Total of the Three NBP 1988-89 Storms
Blackstone River
44.4
65.9
65.3
33.7
58.1
61.6
67.1
59.3
41.8
Moshassuck
4.48
3.09
1.15
1.97
5.67
6.58
1.55
5.28
4.08
Pawtuxet
41.8
17.0
24.2
57.2
18.3
18.1
17.5
15.6
19.0
Ten Mile
1.87
10.5
6.01
4.03
11.5
4.06
10.7
16.5
28.8
Woonasquatucket
7.49
3.51
3.30
3.06
6.33
9.64
3.17
3.33
6.24
NBP Study in Wright et al., (1991); Total rainfall for NBP studies for three storms observed were 3.21" (October
1988 - 0.90"; May 1989 - 1.94"; June 1989 - 0.37")
-------
Table 7.23 Narragansett Bay Project 1988-89 Tributary Wet Loads
NBP Wet Load Rate in lbs/Mft3, Total of the Three NBP 1988-89 Storms
End of River
Volume
TSS
NO3-N
PO4-P
NH3-N
Cu
Pb
Cd
Cr
Ni
Mft3
lbs/Mft3
lbs/Mft3
lbs/Mft3
lbs/Mft3
lbs/Mft3
lbs/Mft3
lbs/Mft3
lbs/Mft3
lbs/Mft3
Blackstone River
306
904
356
43.1
18.5
0.86
0.61
0.06
0.71
0.89
Moshassuck
23.7
2319
119
9.67
12.0
1.82
1.63
0.03
1.02
0.64
Pawtuxet
125
2342
226
47.9
105
1.05
0.54
0.08
0.31
1.36
Ten Mile
47.5
354
234
8.47
5.24
0.91
0.20
0.06
0.55
2.94
Woonasquatucket
31.3
1414
188
18.2
10.8
0.57
0.74
0.01
0.23
0.52
NBP Study in Wright et al., (1992); lbs/Mft3 = pounds/million cubic feet
-------
7.8 and the corresponding flows for those rivers. The wet loads were divided by the effective
runoff for each storm to obtain the lbs/million cubic ft (lbs/M-ft3) values for each storm. The
values were averaged for the three storms in each survey. The same flow ratios for the NBP study
(Blackstone:Moshassuck:Pawtuxet:Ten Mile:Woonasquatucket = 1.0 : 0.0776: 0.4091:
0.15527 : 0.1024) were used to determine an estimate of effective runoff for the tributaries for
the storms of this study. The wet loadings were then calculated using these runoff values (Table
7.24).
A ranking table, similar to the NBP study, has been prepared and presented in Table 7.24.
The 1992-93 data supports the earlier observation that the Blackstone River is the major
contributor of trace metals, nitrate and orthophosphate In general, the rankings for the other
rivers in descending order are: Pawtuxet, Woonasquatucket, Ten Mile, and Moshassuck.
7.5 Characterization of Nonpoint Loads - Runoff vs Resuspension
Loadings in a river can be divided into point and nonpoint sources. Nonpoint sources can
be broadly classified into two categories: runoff (new material to the river) and resuspension
(movement of previously deposited or old material). Runoff is due to overland flow and
pollutant washoff. The pollutant runoff characteristics are considered to be a function of total
rainfall, intensity of rain, duration of storm and antecedent dry period. Land characteristics such
as: land use, slope and width of catchment, also influences runoff characteristics of pollutants.
Resuspension is a result of high storm flows and velocities scouring the bottom sediments.
Bottom sediments are a reflection of the watershed history, and potential interactions of these
sediments during wet weather is important.
The need for reduction, or elimination of, nonpoint pollutants is difficult if the source of
the pollutants is not adequately identified. In this section a procedure is presented to illustrate
one method of providing a separation of a pollutograph into its three components: baseline
loadings, resuspension, and storm water runoff.
The separation of the wet load into its components is important, since the management
for runoff and resuspension is quite different. The distinction between runoff and resuspension
should require water quality modeling under unsteady wet weather conditions. However, the
field of unsteady state water quality modeling is still developing, and attempts at modeling have
proven to be data intensive and difficult to calibrate and validate. A empirical procedure is
discussed in this section to separate runoff and resuspension. This procedure is demonstrated for
the reach between BWW07 and BWW08 (Rice City Pond).
7.5.1 Previous Research
An attempt to assess the resuspension of materials in the Pawtuxet River due to wet
weather was completed by Roy Chaudhury (1991). Wet weather contributions from surface
runoff were evaluated using data collected during the 1988-89 NBP Wet Weather Study (Wright
7-65
-------
Table 7.24 Providence River Tributaries - Wet Load Estimates and Rankings
Wet Load Storm Average in lbs
Station
Flow1
TSS
NO3-N
PO4-P
NH3-N
Cu
Pb
Cd
Cr
Ni
BWW21®
42.0
21970
6080
1050
2600
37.4
34.8
1.80
7.85
20.8
Moshassuckb
3.26
7550
388
31.5
38.9
5.94
5.29
0.10
3.33
2.10
Pawtuxetb
17.2
40200
3880
823
1800
18.1
9.26
1.45
5.29
23.3
Ten Mileb
6.52
2310
1530
55.2
34.2
5.94
1.32
0.42
3.56
19.1
Woonasquatucketb
4.30
6080
806
78.2
46.5
2.47
3.18
0.06
0.99
2.25
Wet Load Rankings
br the Storm Average
Station
Flow1
TSS
NO3-N
PO4-P
NH3-N
Cu
Pb
Cd
Cr
Ni
BWW21
42.0
2
1
1
1
1
1
1
1
2
Moshassuck
3.26
3
5
5
4
4
3
4
4
5
Pawtuxet
17.2
1
2
2
2
2
2
2
2
1
Ten Mile
6.52
5
3
4
5
3
5
3
3
3
Woonasquatucket
4.30
4
4
3
3
5
4
5
5
4
Wet Load Storm Average in Percent
Station
Flow
TSS
NO3-N
PO4-P
NH3-N
Cu
Pb
Cd
Cr
Ni
BWW21
57.3
28.1
47.9
51.4
57.6
53.6
64.6
47.0
37.3
30.7
Moshassuck
4.45
9.66
3.07
1.55
0.86
8.50
9.82
2.64
15.9
3.10
Pawtuxet
23.5
51.5
30.6
40.5
39.8
25.9
17.2
37.8
25.2
34.5
Ten Mile
8.90
2.95
12.0
2.72
0.76
8.51
2.46
10.9
16.9
28.3
Woonasquatucket
5.87
7.78
6.36
3.85
1.03
3.53
5.90
1.60
4.71
3.32
""this study (EPA 1991-93) ;b = Estimates Using Flow ratios of NBP Study (Wright et al., 1992);1 Flow in million-ft3;
Total rainfall for NBP studies for three storms (October 1988 - 0.90", May 1989 -1.94", June 1989 - 0.37");
Total rainfall for EPA studies for three storms (September 1992 - 0.56", November 1992 - 0.88",
October 1993 - 0.81")
-------
et al., 1991). The sampling occurred over a period of five days, and the details of the sampling
procedures and rainfall characteristics can be found in the literature cited above. The first
attempt to assess the resuspension of material in the Pawtuxet River was made using the
procedure proposed by Raes (1989). The Pawtoxic model was used to develop the relationship
between flow and concentration for the range of 0 - 450 cfs. Raes suggested that if the
assumption is made that these relationship are valid for higher flows, then the equations may be
used to generate the mass of pollutant resuspension during a storm event. These results were not
conclusive.
Roy Chaudhury followed up Raes' work by developing a new set of flow and
concentration relationships for dry weather, steady state conditions, for the Pawtuxet River, for
actual flow periods, which ranged from 75 to 1600 cfs. The concentrations were determined
based on the application of the trace metal model, Pawtoxic, which had been calibrated and
validated to the Pawtuxet River. Input for each simulation required average point source
loadings and estimates of reach incremental inflows.
For a specific storm event with a hydrograph and pollutograph, the flows from the
hydrograph were used to determine the resuspension contribution from the relationships
developed above. The result was a second curve which included baseline loading and
resuspension. Separate integration of the original pollutograph curve and the baseline plus
resuspension curve gave the difference to runoff.
7.5.2 Blackstone River Application
Roy Chaudhury et al., (1993) first attempted the separation of the wet component on the
Blackstone River. They isolated runoff and resuspension loadings for TSS, Pb, Cu, and Cd for
the Reach BWW07 to BWW08 for Storm 2 of this study. Nomographs relating flow to
resuspended loads were generated for several constituents over a range of flows, using the
calibrated and validated model Pawtoxic (Chapter 6). The resuspended loads were estimated
from these curves for each wet weather sampling run. The difference between resuspended
loadings at BWW07 and BWW08 provided an estimate of the reach runoff for each sampling
run.
In this section, a similar procedure was followed, but the base data set for flow was
extended to the 1991-1993 USGS flow record for the Blackstone River. Both nomographs and
regression equations for flow vs resuspension for each constituent were developed.
The Pawtoxic model was run for monthly average flow conditions for the 3 year period.
Incremental inflows were calculated, based on the procedure discussed in Chapter 5.
Concentrations and flows at BWW07 and BWW08 for Cr, Cu, Pb, Ni, and TSS were taken from
the model output. Loadings at BWW08 and BWW07 were determined using the flow and
concentration data. Loadings due to groundwater were also determined. The resultant increase or
decrease in pollutant load in Rice City Pond is an estimate of resuspension:
7-67
-------
Mass resuspension = Mass at BWW08 - Mass at BWW07 - Incremental Groundwater
Mass
A regression was run on these data to determine a relationship for flow vs mass
resuspended for each constituent. Figure 7.23 is an example of these regressions. The regression
summaries are provided in Table 7.25.
The regression equations were then applied for the ranges of flows reported at the two
stations over the 3 storms to obtain the resuspended loadings. The resuspended load was then
added to the loading of BWW07 for each sample period to obtain the line of BWW07 plus
resuspension (an example figure is shown in Figure 7.24). The area under each curve was
integrated to determine the loadings. The difference between the load defined by BWW08 and
that defined by BWW07 plus resuspension was equal to the estimate of runoff. This was done
for a select group of constituents for all three storms. Table 7.26 represents the resuspended and
runoff loadings for each storm.
Resuspension of Cr varies between 20-39%, Cu between 47-96%, Pb between 20-46%,
Ni between 32-81% and TSS between 31-84% (Table 7.26). On average, the percent wet load
associated with resuspension for each metal was: Cr - 32.0%, Cu - 67.0%, Pb - 33.7%, Ni -
51.0%, and TSS-64.7%.
It was established in Section 7.2 that wet weather can cause acute criteria violations, and
the cause of higher metal concentrations may be resuspension of the bottom sediments, due to
high flow and velocity and runoff. If we can identify the type and cause of the problem, then the
regulatory agency can impose new regulations to solve the problem of pollution. This procedure
can be repeated for each hot spot identified in Section 7.4. The separation of the wet loads into
runoff and resuspension components will provide us with the information determining whether
the problem of pollution is new (runoff related), or old (resuspension of bottom sediments). The
solution will be different for different cases.
7.6 Annual Loading Rates
Information developed in earlier sections leads to the estimation of the annual loading
rates. The annual loads were divided into two parts: contribution by dry weather flows and
contribution by wet weather flows. Dry weather flow is defined as the baseflow and wet weather
flow is defined as the flow due to a rainfall event (flow above the baseflow on a hydrograph).
Annual loads were determined for the years 1991-92. USGS flow data were used for these
calculations.
7.6.1 Dry Weather Estimates
Linear relationships between flows at the Woonsocket USGS gage station (BWW17) and
7-68
-------
Table 7.25 Resuspended Loading Predictive Equations for
the Reach BWW07-BWW08 (Load vs Flow)
Constituents
n
a
b
R2
Pb
36
0.0044
1.14
0.95
Cu
36
0.54
0.39
0.63
Ni
36
0.10
0.50
0.67
Cd
36
0.02
0.60
0.85
Cr
36
0.013
0.84
0.86
TSS
36
3.68
1.20
0.93
Constituent (lbs/day)= a * [flow(cfs)]b; n = number
of observations, R2 = Coefficient of Determination
Reach BWW07-BWW08
95% confidence Line
1000 .
100
Flow at BWW08 (cfs)
Figure 7.23 Example Plot of Regression Line of Pb for Resuspended Load vs
Flow at Rice City Pond (Reach Between BWW07-BWW08)
7-69
-------
Storm - 2
November 2-5,1992
40
0.0
Time 0 = 2230 on November 2
i Vvv.
V",7v-
-O- BWW07 o—
• • V • BWW07 plus resupension
-a- BWW08
I i i—i I i i i I i—i i i i—i i i i i ¦ 1 ¦ ¦ ¦
i i i
-12 -6 0 6 12 18 24 30 36 42 48 54 60 66 72
Time (hrs)
Figure 7.24 Example of Resuspended and Runoff Load Calculation of Pb for
Storm 2 at Rice City Pond (BWW07-BWW08)
7-70
-------
Table 7.26 Runoff and Resuspension Loads Between BWW07 and BWW08
Storm-1
Constituent
Loadings Between
BWW07- BWW08, (lbs)
Resuspension
Runoff
(lbs)
%
(lbs)
%
Pb
4.55
2.07
45.5
2.48
54.5
Cu
7.05
6.80
96.5
0.25
3.55
Ni
2.67
2.15
80.5
0.52
19.5
Cr
3.81
1.49
39.1
2.32
60.9
TSS
2500
2089
83.6
414
16.6
Storm-2
Constituent
Loadings Between
BWW07- BWW08, lbs
Resuspension
Runoff
lbs
%
lbs
%
Pb
22.9
7.91
34.5
15
65.5
Cu
25.3
14.7
58.0
10.6
42.0
Ni
13.4
4.34
32.4
9.04
67.6
Cr
11.8
4.32
36.8
7.43
63.2
TSS
10100
7390
73.2
2162
21.4
Storm-3
Constituent
Loadings Between
BWW07- BWW08, lbs
Resuspension
Runoff
lbs
%
lbs
%
Pb
36.7
7.33
20.0
29.3
80.0
Cu
25.9
12.1
46.7
13.8
53.2
Ni
13.0
5.0
38.6
7.47
57.6
Cr
18.8
3.80
20.2
14.9
79.5
TSS
29300
9049
30.9
20320
69.4
7-71
-------
BWW13 and BWW21 were developed and compared with the measured flows at these stations
during the three storm events. These relationships provide the means for calculating the flow at
BWW13 and BWW21 for any day, using the USGS flow gage at Woonsocket. The relationships
were as follows:
Q21 = 1.053Qw +20.384
and Q13 =0.815QW+21.963
where, Qw = flow at Woonsocket USGS gage, cfs, Q21 = calculated flow at BWW21 (end of
river), cfs, and Q13 = calculated flow at BWW13 (MA/RI state line), cfs.
Nutrients - The calibrated and validated QUAL2E Model (Chapter 5) was run using the
same database as in section 7.5 (1991-1993 USGS data) for DO, N03-N, P04-P and NH3-N.
The post audit of the model by Carrelli et al., (1995) showed a very good fit for those
constituents at the MA/RI state line (BWW13) and end of river (BWW21) (Figures 7.25 and
7.26, respectively).
The model was then used to develop concentration/flow equations for the three nutrients
at BWW13 and BWW21. From each run of the model for a particular month and year, the flow
and concentration data for each constituent at these two stations were read from the output of
QUAL2E. These data were evaluated through least squared regression to find a relationship
between flow and concentration. The tests included arithmetic, log-log and semi-log
relationships. The most statistically significant results involved the log-log transformation. The
results of the regression analysis are presented in Table 7.27.
Trace Metals - The calibrated and validated Pawtoxic Model was run for trace metals
with the same flow database (1991-1993 USGS data). Using the output of the model for BWW13
and BWW21, concentration vs flow relationships were developed, as described above, for both
stations (Table 7.27). Again, log-log, semi-log, and arithmetic relationships were tried. The log-
log relationship proved to be the most statistically significant.
Previous work by Nixon (1991) also developed flow/concentration relationships for five
trace metals (Pb, Cu, Ni, Cd, and Cr) with data collected at BWW21 prior to 1990. The
relationships developed above by the model applications were converted to metric units (m3/day
and kg/day) for comparison to Nixon's equations (Table 7.28). An example plot of the Nixon
and model regression for lead at BWW21 is shown in Figure 7.27. The two sets of equations
were visually tested against the six independent data points from this study, including the 1991
dry weather surveys (3 surveys) and the baseflow (pre-storm) loadings for 1992-1993 wet
weather surveys (3 storms).
7.6.2 Wet Weather Estimates
7-72
-------
100.00
-J
Ul
10.00
*6b
s,
c
0
•3 1.00
1
4)
o
c
o
o
0.10
0.01
Chloride A->.
DO
A
"fltfi I, IV
X
+
B0Ds
—)T * *
. no3-n
X *
O
NH3-N ^
0
^SjL +
^ ^ 0
° 0 0
Epipa rij
Vh
>~
0
0
0
P04-P 0
10
100
1000
Flow (cfs)
Figure 7.25 Post Audit at MA/RI State Line (BWW13)
0
Ammonia
~
BOD
A
Chloride
X
DO
+
Nitrate
O
Orthophosphate
Ammonia
BOD
- - -
Chloride
m
DO
Nitrate
s
Orthophosphate
10000
-------
100.00
-J
-fct
10.00
I
§
•a 1.00
is
s
o
§
u
0.10
0.01
A
Chloride
A
A
* X ¦
"111 ^1, (j| n A
A
r
no3-n
£-¦
° ~
* DO
BODs
ET
0
" [P (B^+Q t*-1
0
+
. ^t;
ni O ^ +
O
UJ J-"EP Hj
+
— nh3-N
>
O
O
0 PO4-P
10
100
1000
10000
Flow (cfs)
Figure 7.26 Post Audit at End of River (BWW21)
0
Ammonia
~
BOD
A
Chloride
X
DO
+
Nitrate
0
Orthophosphate
Ammonia
BOD
- - -
Chloride
m
DO
Nitrate
Orthophosphate
-------
Table 7.27
Dry Weather Predictive Equations (Concentration vs Flow)
BWW21
Constituents
n
a
b
R2
Pb
36
1.17
0.21
0.86
Cu
36
45.7
-0.17
0.77
Ni
36
45.3
-0.36
0.91
Cd
36
7.57
-0.35
0.92
Cr
36
1.04
0.14
0.48
NO3-N
32
79.5
-0.73
0.88
PO4-P
32
7.36
-0.60
0.87
NH3-N
32
2.89
-0.37
0.59
BWW13
Constituents
n
a
b
R2
Pb
36
0.81
0.29
0.91
Cu
36
39.2
-0.14
0.71
Ni.
36
44.0
-0.35
0.90
Cd
36
6.17
-0.31
0.91
Cr
36
0.81
0.21
0.69
NO3-N
32
29.6
-0.60
0.96
PO4-P
32
3.77
-0.52
0.77
NH3-N
32
1.67
-0.40
.0.57
Constituent (ngfl)= a * [flow(cfs)]b ; [for Pb, Cu, Ni, Cd, and Cr]
Constituent (mg/l)= a * [flow(cfs)]b; [for NO3-N, PO4-P, and NH3-N]
n = number of observation, R2 - Coefficient of Determination
7-75
-------
Table 7.28 Comparison of Dry Weather Load Predictive Equations at B WW21
Pb
Cu
Ni
Cd
Cr
Model
log(a)
-6.65
-3.77
-3.12
-3.94
-6.47
b
1.21
0.83
0.64
0.65
1.14
R2
0.99
0.99
0.97
0.98
0.98
n
36
36
36
36
36
Nixon
log(a)
-5.15
-4.69
-3.07
-6.64
-6.6
b
0.93
0.94
0.7
1.09
1.15
R2
0.93
0.97
0.85
0.75
0.95
Constituent (kg/day) = log(a) + b * log [flow(m3/day)]; Nixon (1991);
The number of observations in the Nixon relationships is not known.
Model Regression
Nixon (1991) Regression
O Six Data Points From This Study
OO
CT
I I t 1 I
1 ' ' '
105
106
Flow (m3/day)
107
Figure 7.27 Example Plot of Model Regression, Nixon's Regression and Six Data
Points from This Study for Pb at the End of River Station (BWW21)
7-76
-------
Relationships were developed between rainfall and wet weather loadings using the data
collected during the three storms (1992-93, EPA), previous (1987-90) wet weather data available
for the state line (BWW13), and end of river (BWW21) (Table 7.29). The total rainfall of each
storm was different ranging from 0.21 to 1.94 inches. Log-log relationships were found to better
represent the data than semi-log or arithmetic relationships. Regression plots were done for trace
metals, nutrients and TSS. Summary tables for the regressions for BWW13 and BWW21 are
presented in Tables 7.30 and 7.31, and example plots for copper are shown in Figures 7.28 and
7.29 for each station, respectively. These equations were used to estimate the annual wet
weather loading rates for the Blackstone River. The equations are most appropriately applied
within the range of observed total rainfalls.
7.6.3 Determination of Annual Load
Annual loadings for 1991-92 were calculated using the equations developed above. Flows
at BWW21 and BWW13 were calculated using flow relationship developed above. Spreadsheets
were prepared to separate the base flow for each station for the whole year. For this purpose,
monthly hydrographs were drawn for each year per station. These hydrographs were compared
with the equivalent daily rainfall data to determine the influence of wet weather. During a storm
period, the baseflow was separated using the equation:
N = 1.0 A010
where, N = number of days from the peak flow and A = cumulative drainage area, square miles.
The equations developed in section 7.6.1 were applied to the base flow for each day of the
year to calculate the dry load for that day. The sum of the loadings gave the annual dry load.
Rainfall data for all the National Weather Service stations (Table 3.2) in the watershed
were available (Climatological Data of New England 1991-1992, NOAA). The equivalent
rainfall was calculated by using Thiessen Method (Chapter 3) for each day of rainfall. These
rainfalls were then used with the equations developed in section 7.6.2 to estimate each event's
wet loadings. All calculated wet loads for the year were summed to obtain wet load contributions
for the year.
Total loadings were determined by adding wet loads and dry loads for that year as
calculated above. Table 7.32 represents the summary of the annual loadings for 1991-92.
7.6.4 Load at State Line and End of River
Annual wet weather loads as a % of the total load at the state line (BWW13) were: Pb -
22-28%, Cu -16-24%, Ni - 23-32%, Cd -18-22%, Cr - 31-44%, NOa-N - 38-46%, P04-P - 21-
26%, and NH3-N - 30-37%.
7-77
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Table 7.29 Wet Load Regression Data for Rainfall vs Load for BWW21 and BWW13
BWW21
Project
Date
Rainfall
Cd
Cr
Cu
Pb
Ni
NO3-N
PO4-P
NH3-N
TSS
inch
lbs
lbs
lbs
lbs
lbs
lbs
lbs
lbs
lbs
This Study
09/22/92
0.56
0.33
1.30
6.64
9.07
3.89
936
218
596
2170
This Study
11/02/92
0.88
4.68
16.0
64.4
38.7
37.9
12100
1390
6970
4030
This Study
10/12/93
0.81
0.77
5.85
30.3
21.2
14.9
5020
836
374
40700
NBP
05/10/89
1.94
26.6
220
344
353
153
60100
2630
3500
590000
NBC
05/29/90
1.41
144
63.9
61.3
7870
1400
223000
NBC
06/29/90
0.21
0.77
4.82
0.97
167
25.5
612
NBC
07/12/90
1.56
36
18.2
12.2
4400
912
22300
BWW13
Project
Date
Rainfall
Cd
Cr
Cu
Pb
Ni
NO3-N
PO4-P
NH3-N
TSS
inch
lbs
lbs
lbs
lbs
lbs
lbs
lbs
lbs
lbs
This Study
09/22/92
0.55
1.12
0.73
2.70
2.28
2.08
845
72
92
2550
This Study
11/02/92
0.92
2.24
18.9
44.9
33.6
9.77
8150
673
6200
15000
This Study
10/12/93
0.80
1.36
11.5
33.2
21.1
22.8
4780
767
338
26900
NBP
05/10/89
1.94
30.5
155
350
148
204
46400
3600
40600
207000
NBP = Narragansett Bay Project Study Wright et al., (1991); NBC = Narragansett Bay Commission Study
Wright etal., (1992)
-------
Table 7.30 Wet Weather Predictive Equations at BWW21 (Load vs Rainfall)
Constituents
n
a
b
R2
Pb
7
35.3
1.52
0.67
Cu
7
42.1
2.53
0.90
Ni
7
21.1
2.02
0.80
Cd
4
2.93
3.55
0.92
Cr
4
16.3
4.06
0.99
NO3-N
7
5700
2.25
0.82
PO4-P
7
769
1.97
0.90
NH3-N
1680
1.55
0.34
TSS
7
38100
2.87
0.81
Constituent (lbs) = a * [rainfall (inch)]b
n = number of observation, R2 = Coefficient of Determination
1000
BWW21
O Data
100
\
CO
"3
5
u
95% Confidence Line
1
10
0.1
Rainfall (inch)
Figure 7.28 Example Plot of Model Regression for Load vs Rainfall for Cu at
the End of River Station (BWW21)
7-79
v
-------
Table 7.31 Wet Weather Predictive Equations - BWW13 (Load vs Rainfall)
Constituents
n
a
b
R2
Pb
4
26.7
3.10
0.90
Cu
4
43.0
3.63
0.93
Ni
4
21.6
3.45
0.91
Cd
4
3.78
2.79
0.93
Cr
4
15.9
4.00
0.92
NOa-N
4
7520
3.06
0.96
P04-P
4
718
2.85
0.88
NH3-N
4
1120
2.90
0.58
TSS
4
26200
3.29
0.92
Constituent (lbs) = a * [rainfall (inch)]b
n = number of observation, R2 = Coefficient of Determination
1000
BWW13
O Data
100
10
95% Confidence Line
1
1
Rainfall (inch)
Figure 7.29 Example Plot of Model Regression for Load vs Rainfall for Cu
at the State Line Station (BWW13)
7-80
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Table 7.32 Annual Mass Loading Forecast Summary for the Blackstone River
at the State Line (BWW13) and at the End of River (BWW21)
Constituent
Year
Equivalent
BWW13
BWW21
Yearly
Dry
Wet
Dry
Wet
Rainfall
Load
Load
Load
Load
(in)
(%)
(%)
(%)
(%)
Pb
1991
49.2
72.0
28.0
81.5
18.5
Cu
1991
49.2
76.4
23.6
89.3
10.7
Ni
1991
49.2
68.1
31.9
84.9
15.1
Cd
1991
49.2
78.1
21.9
74.7
25.3
Cr
1991
49.2
55.8
44.2
55.9
44.1
NO3-N
1991
49.2
53.5
46.5
75.3
24.7
PO4-P
1991
49.2
74.1
25.9
84.1
15.9
NH3-N
1991
49.2
62.8
37.2
82.2
17.8
Pb
1992
47.3
77.7
22.3
81.8
18.2
Cu
1992
47.3
83.9
16.1
91.1
8.9
Ni
1992
47.3
76.8
23.2
86.5
13.5
Cd
1992
47.3
82.4
17.6
82.6
17.4
Cr
1992
47.3
69.0
31.0
69.8
30.2
NO3-N
1992
47.3
62.2
37.8
78.8
21.2
PO4-P
1992
47.3
79.5
20.5
85.9
14.1
NH3-N
1992
47.3
69.6
30.4
83.0
17.0
7-81
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Wet weather related loadings, as a % of total load discharged to Narragansett Bay
(BWW21), were: Pb -18-19% Cu - 9-11%, Ni -13-15%, Cd -17-25%, Cr - 30-44%, N03-N -
21-25%, P04-P -14-16%, andNH3-N -17-18%.
The percentage of wet load at BWW13 was higher than that at BWW21 for all
constituents.
The determination of annual loadings is important. Estimation of the annual loadings at
BWW13 provide us with an estimate of pollutants delivered to Rhode Island from
Massachusetts. The estimate of loadings at BWW21 provide us information concerning
pollutants loads to Narragansett Bay by the Blackstone River. The division of the annual
loadings into dry and wet loadings provided the contribution by base loadings and the wet
weather loadings. The percentage of wet loads delivered by the Blackstone River to Narragansett
Bay were, on average, about 20%. The wet load's significance is magnified when one considers
the number of days this load is distributed, compared to the entire year for diy weather
contributions.
7.7 Summary of Wet Weather Interpretation
Three wet weather events were sampled: Storm 1 (September 22-24,1992), Storm 2
(November 2-5, 1992) and storm 3 (October 12-14, 1993). The concentrations and EMCs (event
mean concentration) for different constituents were determined. Violations to existing criteria
were determined for fecal coliform and trace metals. Actual toxicity was determined and
compared to predicted toxicity based on criteria.
Total and wet mass loads were determined, and net gains and losses per reach were
calculated. Major point sources and the other sources within a given river reach were compared
through system rankings, and pollutant source hot spots were identified. A procedure was
presented to separate resuspension for wet load estimates. This procedure was demonstrated for
the reach between BWW07 and BWW08 (Rice City Pond). An estimate of annual loadings at the
MA/RI state line and end of river was made based on a series of empirical equations developed
from observed data and model application.
The following conclusions/observations were determined from this analysis:
Nitrification
• UBWPAD's ability to provide nitrification is inhibited under high storm flows. The
facility discharges significant levels of ammonia under these conditions.
• In reaches experiencing nitrification under dry weather steady-state condition,
nitrification may be inhibited due to high storm flows.
• In reaches not experiencing nitrification under dry weather condition, nitrification may
occur due to transient storm related ammonia loads which occur in upstream reaches.
7-82
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Concentration
• Under high storm flows, high ammonia concentrations occurred in the reaches around
Rice City Pond.
• UBWPAD had no violation of maximum ammonia concentrations under dry weather
surveys, but under wet weather conditions, violations of ammonia did occur in two out of
three storms. These violations coincided with peak flows and the time period
immediately after.
• Orthophosphate concentrations are dominated by the two major point sources UBWPAD
and Woonsocket.
• The two treatment facilities are major contributors of metals to the Blackstone River. For
the UBWPAD, several metals were influenced by the higher storm flows through the
facility. A comparison of average concentrations between dry and wet weather conditions
lead to the following observations: chromium concentrations doubled under storm flows;
cadmium and lead concentrations decrease, under storm flows, and copper and nickel did
not change significantly.
• A comparison of maximum wet weather and dry weather concentrations lead to the
following observations: for chromium, wet weather was significantly higher; for
cadmium, dry weather was significantly higher; and for lead, copper, and nickel, the
ranges were similar.
• Since Woonsocket is located in the lower reaches of the Blackstone River, the flow in the
river is much higher compared to the flow discharged by the facility, therefore, the
dilution is much higher. As a result, the high concentrations discharged by this facility
have less effect on the river.
• Headwaters are a major source of Pb.
Event Mean Concentration (EMC)
• The EMC profiles reflect the operation of UBWPAD with respect to nitrification. It was
established earlier that nitrification was being provided at the facility during Storms 1 and
3. The instream data supports this with high nitrate EMCs below UBWPAD and
comparatively low ammonia levels. The reverse is true for Storm 2, when nitrification
was not being provided at the facility.
• The increase in ammonia EMCs between BWW17 and BWW18 are due to the
Woonsocket WWTF discharge.
• For orthophosphate, the headwater concentrations are generally very low. There are
major increases in the EMCs between BWW01 and BWW02 and between BWW17 and
BWW18, reflecting the two major treatment facilities.
• There is an interesting pattern for TSS profiles between BWW01 and BWW02, which
again supports the operation of nitrification in the UBWPAD. With nitrification
providing a much higher retention time within the facility, solids removal is often better.
During Storms 1 and 3, where nitrification was occurring, the TSS EMC profiles actually
7-83
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show a decline between BWW01 and BWW02. Storm 2 provides a different result,
reflecting the higher solids load from the UBWPAD when nitrification was not occurring.
TSS EMCs were the highest for Storm 2 just below the UBWPAD discharge.
• The sharp decreases in the instream Fecal Coliform (FC) and E. Coli (EC) EMCs below
the UBWPAD (between BWW01 and BWW02) for Storms 1 and 3 are most likely due to
residual chlorine in the facilities effluent. This was not the case in Storm 2. In fact, FC
and EC concentrations increased to their highest levels in the reaches immediately below
UBWPAD. The impact could be felt as far as BWW08.
• Similar increases of FC and EC are evident in the Woonsocket area that include the
WWTF and just below it.
• EMCs for BOD5 had a similar trend for all three storms. Generally, it increases after the
UBWPAD discharge and decreases to the mouth of the river. BOD5 does not appear
strongly influenced by the storm related sources, and therefore, appears governed by the
major point sources.
• Compared to the other metals, lead's (Pb) major source appears to be in the headwaters
(above BWWOO). In fact, the headwater EMCs are typically the highest concentration
along the entire river.
• A consistent increase of lead does appear between B WW07 and BWW08 in Rice City
Pond and is probably due to sediment resuspension.
• The other 5 metals (Cd, Cr, Cu, Ni and Zn) have similar EMC profiles in that there
appears to be two distinct peaks. The first occurs in the reaches below UBWPAD and is
associated with the wastewater facilities discharge and possibly other nonpoint sources of
metals. A secondary peak consistently occurs around BWW08, again the probable cause
is sediment resuspension within Rice City Pond.
Trace Metal Acute/Chronic Violations
• High flows moving through Rice City Pond cause violations in the reaches at and
below the dam due to resuspension.
• Cu is continually violated both with respect to chronic and acute criteria, in both dry and
wet weather, starting at station BWW02.
• Pb chronic violations occur for both dry and wet weather.
• Cd violations are more limited but also begin in and around BWW02.
• Ni and Cr had no acute and chronic violations under dry and wet weather.
• More stations had violations under wet weather than dry weather.
• More violations occurred if the storm event was larger.
Fecal Coliform Violation
• The high loading at the headwaters seems to be the main source of fecal coliform under
both dry and wet weather.
• Residual chlorine from UBWPAD is a major factor in instream disinfection, although its
impact is minimized at high storm flows.
7-84
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Wet Weather Actual Toxicity
• Toxicity was observed in 35 out of 118 occasions during wet weather testing. Toxicity in
the first flush of the storm accounted for 14 toxic endpoints. The remaining 21 toxic
endpoints occurred in the samples collected during the peak of the storm.
• Toxicity occurred at the same stations, for the most part, during first flush and peak of the
storm. Six stations had recurrent toxicity in peak storm conditions, thus the larger
number of toxic endpoints observed during peak rain. Only two stations were toxic for
first flush and non-toxic during peak.
• Forty percent of all toxic endpoints occurred in the first two miles of the river in the
Greater Worcester area.
• Toxicity occurred in all of the dechlorinated WWTF effluents at least once and in the
combined sewer outfalls. The effluent of Woonsocket WWTF was toxic during all three
wet weather events (three times during peak flow and once during first flush). The
effluent of the Narragansett Bay Commission Bucklin Point WWTF was also toxic during
all three storm events. All peak samples were toxic, and two of three first flush
samples were toxic. This may indicate bypassing during rain events. The chlorine
concentrations in the effluents were extremely high, and if left in the test solutions would
have caused acute toxicity.
• River stations BWW01,02,05,11 and 09 (in the Mumford River, a tributary receiving
municipal and industrial wastewater) experienced significant toxicity on more than one
occasion.
• By comparison to wet weather toxicity, testing conducted during low flow conditions
(near the 7Q10) indicate that there is no significant toxicity in the water column of the
Blackstone River. Only one toxic endpoint occurred in the mainstem during dry weather
testing.
• Compared with other tributaries, the Mumford River had the most toxic endpoints; Two
were observed in dry weather and two during wet weather.
• Little difference was observed between toxicity occurring in first flush and peak storm
samples.
• Toxicity was much more prevalent during wet weather conditions.
• Acute toxicity, the more significant measure of toxicity, was the predominant endpoint
during wet weather toxicity testing.
Mass Loading
• Most of the constituents had more than 50% wet loadings, except for Ni and N03-N.
• The trend of higher wet load as the storm intensity increases is true for almost all the
constituents, except NH3-N.
• Headwaters had the highest percent wet load to total load for most of the constituents.
Percent wet load generally decreases as one moves downstream.
• Compared to 4 other major tributaries to Narragansett Bay, the Blackstone River is the
7-85
-------
highest contributor of most pollutants.
Major Point Sources and all Other Sources in a River Reach
• Under wet weather conditions, NH3-N and P04-P are dominated by the two major point
sources.
• Under wet weather conditions, over 50% of the loadings to the river are from the other
sources in the river for Cd, Cr, Cu, Pb, Ni, Zn, TSS, FC, N03-N, and BOD5.
System Rankings
• Major sources of Pb in both wet and dry weather are in the headwaters.
• The first five positions on each ranking represents between 70-90% of the total loadings
for both wet and dry weather, except for dry TSS (51%), and wet N03-N (53%).
• UBWPAD is the major source of Cu (35% for dry, 18% for wet), Ni (47% for dry, 33%
for wet) and Cd (37% for dry, 15% for wet) for both dry and wet weather.
• Woonsocket is a significant source of trace metals under dry weather conditions but not
under wet weather.
• Resuspension in Rice City Pond is a major source of metals for both wet and dry weather.
• The UBWPAD and Woonsocket facility are major sources of nutrients.
Annual Loading Rate
• Log-log relationships are statistically significant for both wet weather - rainfall vs wet
load equations and dry weather - flow vs concentration equations.
• The percentage of wet load versus dry load is higher at B WW 13 than that at B WW21.
• The percentage of total annual load, which is wet load, that is delivered by the Blackstone
River to the Narragansett Bay, is about 20% on average.
• The wet load's significance is magnified if one compares the number of the days of the
year that wet weather events occur to the number of days in a year.
7-86
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8.0 APPLICATION OF THE BLACKSTONE RIVER INITIATIVE
The Blackstone River Initiative was designed to evaluate the entire watershed tinder both
dry and wet weather conditions. A major output of this study was the identification of reach hot
spots that contribute significant pollutant loadings to the system. One of the most important
reaches identified in this study was the reach between BLK07 and BLK08 (BWW07 and
BWW08).
I
This reach was first identified as a major source of pollutants during the dry weather
surveys in 1991. Data showed significant increases in water column pollutant concentrations
between stations even under steady, low flows (i.e. metals, TSS, etc.).
The major physical feature between these stations was Rice City Pond. From aerial
photographs it was determined that the elevation of Rice City Pond had dropped in recent years
exposing the historic sediments of the impoundment. With the lowering of the pond, the river
had carved channels through the soft sediments. The conclusion based on the 1991 dry weather
data was that resuspension of the pond's sediments was the source of the pollutants, that the
increase was significant and that the impact of this reach could be felt for several miles
downstream.
The wet weather studies confirmed the dry weather observations. In fact, under unsteady,
high flows the loadings from this reach were for some constituents the highest on the entire river
causing short term violations in aquatic criteria.
In an effort to further delineate the locations of contaminant sources between BLK07 and
BLK08, EPA funded a speciality study to examine the river segment in greater detail. Outputs
from this effort should determine the extent and degree of pollution, the mechanics for its
introduction into the water body, and the development and implementation of cost effective
remedial options for mitigation of these chronic nonpoint sources of pollution.
The major focus of the study was Rice City Pond (RCP). The RCP study should be
considered as a case study for other impacted impoundments along the Blackstone River with
potential transferability of recommended mitigation options to other impoundments on the river
and other river basins in the northeast. Remedial recommendations would be made on
appropriate and cost effective Best Management Practices.
The main study objectives of the RCPS were to determine the historical site background,
to describe the river segment hydraulics in greater detail and to locate and quantify contaminants
in the reach in both the water column and sediments.
8.1 Rice City Pond (RCP) Study Site and Historical Background
Rice City Pond is formed by the impoundment of the Blackstone River, whose flow is
8-1
-------
impeded by an earthen embankment which crosses the Blackstone River and makes up the
Hartford Avenue causeway. Two spillways and a small headgate structure provide the outlets for
RCP. The primary spillway, through which water flows during all conditions, is located midway
across the impoundment and is integrated into the Hartford Avenue causeway. A secondary or
emergency spillway is located just downstream of Hartford Avenue on the western side of the
impoundment, and a small headgate structure is located just West and adjacent to the secondary
spillway (Figure 8.1). The secondary spillway ceases to flow under low flow conditions, due to
the crest being at a higher elevation than the primary spillway. The headgates provide minimal
continuous flow (<12 cfs).
On the western side of RCP and the Blackstone River are remnants of the historic
Blackstone Canal and towpath, which runs underneath Hartford Avenue via a stone bridge before
exiting the impoundment over the secondary spillway.
About 1865, land upstream and adjacent to Hartford Avenue was purchased by the
owners of the Stanley Woolen Mill, located a mile downstream of Hartford Avenue, for the
purpose of providing additional water storage capacity for the mill, augmenting the flow that was
presently being provided by the canal. The Blackstone River was subsequently dammed and
RCP came into existence.
In 1917 additional pool storage needs became evident, and Rice City was again dammed,
this time to its highest elevation. The millpond remained unchanged from 1917 to 1955 and was
once again a major settling pond for raw sewage discharges, textile mill, metal plating, wire
manufacturing, orchard pesticides, soil erosion from poor agricultural practices, auto graveyards
and many other undocumented industrial and commercial wastes.
Continuous rains following an August 1955 hurricane (Diane) caused severe flooding in
the basin and subsequent failure of most of the dams along the Blackstone River, including Rice
City Pond. The flooding left a 200 foot wide breach in the Hartford Avenue embankment and
continued flood stage conditions washed out much of the remaining earthen causeway, carrying
with it significant quantities of once impounded contaminated sediments. The downstream
washout area can easily be seen on the aerial photograph (Figure 3.20).
Reconstruction of Hartford Avenue and the Rice City Pond Dam began shortly thereafter
with a lowering of spillway heights approximately five feet to their present elevations. No
development or flow control alterations have taken place in this area since that time.
Due to the 1955 hurricane, braided stream patterns exist throughout the RCP,
demonstrating the incapacity of the flood waters to carry the large sediment load that had
previously been contained by the impoundment. As the rains from the hurricane subsided and
river flows returned to normal, the river carved its way through the new fine, easily erodible
sediments, in order to reach the newly established base level.
8-2
-------
Rice Gty Pond and Roodplain
General Features Map
DATA SOURCES
HYEROGRAHiY: MA. DEP. Dgferri 6om
sramffri trrage of aerial photograph. Scale
agproxinBtely 1:12300. Source dale April
1991 (L5EPA/EHQ. Accuracy +/-50 fed.
WAIH&HED BC5LM1ARY: LSGS^VRDMssOS,
L240C0. Deroed &om MksGIS sub-toons
data layer: Source dates 19874993.
ROADS: MA DEP. Digitized from USGS 1:25000
qmctangle. &urce date 1980.
BLEVA3KK MA CEP. Digitized &om 15G5
K25000 quadrangle. Source (fate 1980.
FCUIICAL BOUNDAHIESc MssGS, L25C00L
Source cfete appoxirrBtely 1985,
HISTORIC PCKD LEVEL MA CEP, Estimated
from 1938- atrial photograph.
Qry raid
Watershed
Scale 1:8340
SCO
AML Ued:
dfekg; (^jden.vraio.barkEr.ricabcBe]tQiainl
Map Area
Barko- C8/L5i95
Goal Hill Lock\
Cedar Swamp
-ik.
MiirHl Surface Water
Elevation Contours
(15 meter interval)
DEM Bla^one>|
-------
The most significant depths of sediment which have been cut within the project area are
found at the most upstream end of the Rice City flood plain; this being the area of greatest and
coarsest deposition when Rice City was dammed to its greatest height. These depositional
stream banks are four to five feet in height above the original natural flood plain level.
"Natural" levees are also prevalent in the upper reaches of the RCP flood plain and are
indicative of the high frequency of over bankfull flood events in conjunction with high
suspended sediment loads. The coarser fractions settling out on the banks as velocity quickly
drops, building a "natural" berm. The finer sediments, having slower settling velocities, are
deposited farther from the edge of water and are especially noticeable on outside channel bends
and fringes of the flood plain. These levees are a result of the changing characteristics of the
watershed. Increased development upstream has increased the impervious percentage of the
watershed, particularly near die headwaters. Compounding the problem is the present lack of
flow controls in the river.
Approximately midway through the RCP flood plain, the river makes a sharp bend to the
west. Sediments here are mainly comprised of silts and clays, identifying the area where the finer
particulates settled out during the time of maximum ponding. The de-watered impoundment has
resulted in compacted silts and clays, which are more resistant to stream erosion processes than
the coarser materials in the upstream portion of the impoundment.
Within this same mid-region of the flood plain, the canal is breached by the natural path
of the Blackstone River, providing the majority of water to the canal. A less significant source of
water to the canal is located four hundred feet upstream from this breach. This "channel" is a
historic "feeder stream" which was constructed when the canal was built, to supply water to the
canal system. Water still flows into the canal through this feeder.
Rice City Pond historically provided an excellent settling basin for discharged pollutants,
but is now silted in to capacity with contaminated wastes. Rice City Pond, and similarly
impounded areas on the Blackstone, are the sites of major sources of contaminants.
8.2 RCPS Flow Analysis
Cursory flow studies were initiated during the RCPS to determine hydrologic interactions
between the canal and the pond, gain insight to river responses from precipitation and hydro
power release events, and for determining the contaminant loading contribution from the two
areas.
In order to assess the hydrologic interactions in the RCP segment, a USGS gage at
Northbridge, MA was reactivated. In conjunction with frequent stage height measurements at the
primary and secondary spillways, flow measurements were conducted at various cross sections in
the Rice City Pond flood plain.
8-4
-------
To ensure accurate measurements, factors potentially influencing flow along the 8.1 mile
segment were investigated. Land use along this stretch is predominantly rural undeveloped or
forested, no significant tributaries enter the river, and there are no groundwater withdrawals. The
Grafton municipal wastewater treatment plant is located just downstream of the Northbridge
USGS gage, and the Northbridge municipal treatment plant is located approximately a mile and a
half upstream of the Rice City Pond outlet. Review of plant strip charts and daily flow records
indicate their combined discharge on average is less than three million gallons per day with no
significant daily fluctuations. This makes up less than 10% of the total flow under 7Q10
conditions (45 cfs).
There are two hydro power facilities just upstream of RCP: Farnumsville and Riverdale.
The fluctuations in daily discharge caused by these facilities have a direct impact on the water
quality and the import of resuspended solids to the Blackstone River. Substantial fluctuations in
discharge rates are compensated for by increases in river stage height and channel velocity within
the narrow stream channels downstream of Farnumsville and Riverdale. In addition to these
narrow and vertically banked river sections, there exists numerous backwater sloughs, canal
remnants, and side channels between Riverdale and Rice City Pond. These areas are subjected to
daily submersion and re-exposure when the hydro facilities are in operation. Flooding of these
backwater areas loosens material which has dried overnight and imports it into the main river
channel during recession of the flood crest, behaving in much the same manner as an outgoing
tide.
The implications of these significant fluctuations in daily flow to the Rice City Pond river
segment are noteworthy. Main channel cross sections from Riverdale to Rice City (and in many
other segments of the Blackstone) are predominantly rectangular, with vertical banks comprised
of very porous and highly contaminated sediments. These channel characteristics are
representative of depositional flood sediments and debris which the river then cuts through to
return to its original npre-flood" base level. As river stage height increases significantly, in order
to accommodate large increases in flow through the narrow channel areas, water permeates the
highly porous soil matrix and reaches an equilibrium with the present river stage. Rapid
recession of the flood crest, as indicated by the hydrographs, results in head differentials between
the soil pore water and current river stage, forcing the movement of water out of the soil pore
space towards the stream bank, resulting in bank instability and subsequent bank slumping.
8.3 RCPS Water Quality and Sediment Results
Review of the Blackstone Initiative Dry Weather ambient water quality data indicated
consistent diurnal fluctuations of metals concentrations in the river during all three of the
Blackstone Initiatives1 ambient dry weather water quality surveys. This phenomena persisted
even though daily average flows increased by over 300% between the first and last survey. This
indicates that flow regulation by the hydro facilities can be suspected of impacting ambient water
quality.
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As part of the RCPS water quality assessment, four model 2700ISCO automatic samplers
were stationed on the Blackstone River to collect 2 hour composite samples over a 24 hour
sampling period. The samplers were located so two were upstream of Rice City Pond and two
just upstream of the primary spillway outlet. Positioning of the samplers in these locations would
determine if contaminants were being resuspended in the shallow pool area of the RCP, being
transported from an unknown source further upstream, or both.
Objectives of the Rice City Pond sediment sampling survey were to quantify types and
relative concentrations of contaminants present within the Rice City Pond flood plain and to
determine their areal and vertical distributions within the project area.
Sampling locations were randomly selected throughout the study area and varied from
perennially inundated sites to areas that were subject to annual or less frequent flooding events.
Twenty-one core samples (2lA" x 18") were extracted from the Rice City Pond flood
plain, canal, and ponded area, and the first 12" of sediment analyzed for nine different metals,
PCB's, TPH, and semi-volatiles. A Toxicity Characteristic Leaching Procedure (TCLP) was also
performed.
The RCPS water quality and sediment analysis led to several conclusions.
1. The highest concentrations of metals found occur predominantly in the organic
inundated silts and are mostly located within or in close proximity to historic river/canal channels
and backwater areas. These sediments presently occur predominantly at the permanent pool level
of the impoundment and are comprised of non-fibrous organic material, are black and saturated
with petroleum hydrocarbons, and have an odor of hydrocarbons and sulfides.
2. A gradual concentration gradient for most metals increases from the inlet of the
historic Rice City Pond to the spillways, with the exception of some low concentrations at a few
stations. The lower concentrations appear to be due to more recent fluvial deposition of coarser
grained (sand sized) sediments, which now overlay the historic lacustrine deposits.
3. The extremely high iron content of these sediments from historic wire and hoop
manufacturing, and the high total volatile solids from major pollutant discharges of wool/textile
manufacturing wastes and open sewer discharges, have provided the perfect substrates for
scavenging metal cations and organics. The precipitation and non-mobile characteristics of Fe
under oxidizing conditions scavenges those metals which are mobilized under oxidizing
conditions (i.e. Pb, Cu, Ni, Zn, Cd, Hg). They appear to have played a key role in providing a
significant sink for the immobilization and speciation of contaminants within the project area. In
essence, various pollutants of one type have mitigated the effects of others.
4. The highest concentrations of metals are located above and within the uppermost
portion of the oil sediment layers and concentrations decrease significantly below this layer.
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Surficial sediment cores showing higher concentrations of metals appear to be closely related to
the percentage of the black oil layer contained within the sample.
5. The upper flood plain, non-inundated sediments show the highest concentration of
metals to be located in the upper twelve inches of sediment, where they are not affected by
changing redox conditions. Areas frequently inundated by fluctuating water elevations show a
downward flux of metals by reflecting increasing concentrations with depth. It appears that this
is brought about by the introduction of oxygenated surface waters into otherwise reducing
environments and remobilizing metal from particulates and into the pore water to be re-adsorbed
further down in the sediment profile.
8.4 RCPS Remedial Options
Remedial options can be broken down into three general alternatives; no action, in-place
or on-site treatment of sediments, and offsite relocation and/or treatment.
The no action alternative would leave sediment highly contaminated with heavy metals,
hydrocarbon residuals, chlorinated organics, and historic wastewater sludges in the Rice City
project area (2 million cubic yards estimated basin wide). Under this option contaminated
sediments will be subjected to dynamic hydrologic interactions throughout the river system. No
action leaves upstream improvement to the river basin to natural processes, and as a result
contaminants will be chronically transported to and imported into Narragansett Bay.
The no action alternative may promote some temporary encapsulation of sediments, in
particular, directly behind the impoundment where the coarser fractions from bank erosion have
settled out (as is the case in Rice City); but the finer and higher percentage of fine silts will have
passed through the area and moved downstream. Natural encapsulation will be temporary and
will be partially lost during spring flooding or may be totally stripped when another significant
flood event occurs. Even if all sediments were remediated completely, there would still be a
74% contribution to flow from wastewater discharges under low flow conditions at RCP.
Dredging was one of the first remedial options to be considered. The fine and relatively
homogeneous nature of these sediments are very amenable to dredging, yet the uniqueness of the
site does not lend itself to successful removal by this method. Problems arise due to the sheer
volume and spatial area which would have to be covered by the dredging operation. Dredge
spoils would need to be piped three quarters of a mile in some instances to reach staging areas
where transport vehicles could be loaded and the material hauled. The fine silt sediments would
also have to be dewatered by on site settling ponds, or if left as is, transported via tanker truck.
Mechanical de-watering via hydro-cyclones was researched but proved technically infeasible as
the % solids removals was limited to the coarser fraction (ie. fine sands and larger). This
particulate size fraction is known to retain the least amounts of contaminants (ie. small surface
area/unit volume, cation exchange capacity).
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In addition to the above constraints, a large percentage of these sediments are non-
inundated, or are only submerged during high spring flows. This necessitates bringing in
excavating equipment into almost inaccessible areas to work on sediments that dredge booms
could not reach. Equipment would be operating on sediments which are peat like in consistency,
or where flooded are more like a fine silty muck, creating operational problems.
Estimates made by the Army Corps of Engineers for Blackstone sediments indicate an
approximate cost range from two to 5.2 million dollars to dredge/excavate and load half a million
cubic yards of sediments onto trucks. Material may have to be transported a considerable
distance to find a landfill willing to accept the sediment based on conversations with State solid
waste experts in the area; even though the Rice City sediments passed TCLP tests and is legally
acceptable for landfill cover material. Landfill tipping fees range between 45 to 65 dollars per ton
and a cubic yard of wet dredge spoil sediment ranges between one and two tons. This means
tipping fees can vary from 24.5 to 70.7 million dollars for Rice City if sediment weight
approximates two tons and tipping fees are high. If landfill operators are not willing to accept
the dredge material, than the alternative would be to contract a hazardous waste hauler, adding to
the cost of remediation.
In addition to these constraints, if a cost effective means to dredge the site could be
found, the practicality of dredging sediments at all impoundments remains in question. Upstream
of Rice City remains possibly hundreds of thousands of cubic yards of sediments which may be
even more contaminated than that found in Rice City. These sediments will continue to be
transported downstream through various hydrologic mechanisms only to settle out in the Rice
City impoundment, if control elevations remain the same. Based on seasonal visual observations,
sedimentation rates appear to be high.
On site relocation of sediments was considered early on as an remedial alternative.
Moving contaminated sediments to continuously inundated areas absent of dynamic flow
conditions would ensure that the majority of metals would remain immobile due to reduced
conditions within the sediment and non-erosive forces imparted by extremely slow moving
water.
The sheer volume of sediments within the project area revealed that there were no good
locations in which to place the sediments on site other than a small area on the east side of the
ponded area. Although the site location was appropriate, it could not possibly hold the volume
that is in Rice City. Other major constraints beside the most predominant one of volume is that
the sediment would need to be retained by using sheet pilings or some other like material. The
sediment itself would be difficult to control and would be deposited behind the pilings most
likely as a flocculent organic slurry, causing sedimentation and containment problems.
Once again, the fundamental feasibility of the option is limited because of site re-
contamination from upstream.
8-8
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Several in place treatment alternatives were briefly considered through the course of the
study but were discarded early on as being non-viable. These included sediment solidification
through the use of lime or resins, sediment capping, and bank rip-rap and channelization. None
of these alternatives appeared viable due to the hydrologic characteristics of the river, (ie. high
flows, frequent flooding), the nature of the existing sediments (ie. easily erodible), and the large
spatial area of contamination. These options were not considered further.
Bioengineering and bank stabilization methods which re-establish indigenous riparian
plant species provide one of the most viable cost effective and self sustaining options for
mitigating pollutant introduction and downstream transport impacts to the river segment. Present
project costs are approximately $7,000/5,000 square feet of bank area and result in long term
erosion control with limited to no long term maintenance costs. Bank/slope improvements result
in greater tolerance of fluctuating river stages and reduce flow velocities, create greater channel
carrying capacity, and increase riparian zone habitat. Installation is non-technical in nature with
minimal site disturbance and can be accomplished with non-skilled labor.
Bioengineering techniques will see their greatest success when used in conjunction with
flow management of upstream hydro power facilities and other control structures. Flow control
is imperative to stabilize contaminated stream banks through the project area while riparian
vegetation is taking hold, limiting exacerbating effects such as icing conditions with daily flow
fluctuations and limiting metals flux from flow induced redox changes.
Bioengineering appears to be the most feasible from a cost and practicality stand point.
Improvements to the stream bank will not be impacted by the continuous downstream transport
of materials from upstream sites, and if flow is controlled, erosive forces will be minimized.
Establishment of plants will by themselves slow stream edge velocities and help to reduce
erosion. However, bioengineering will not be a cure all for the elimination of resuspended
sediments, as they will continue to be transported into the area from upstream sources; but it will
greatly reduce contaminant transport emanating from the project area.
Since contaminated sediments are so ubiquitous upstream, the chances of seeing
noticeable changes in water quality within or immediately downstream of Rice City is limited.
Implementation of this option should be viewed as a demonstration in which site specific designs
can be implemented and show their utility for further implementation throughout the watershed,
which then would show improvements in water quality.
One of the most important features of this option will be to utilize plants that have deep
root systems or a design which will wick water up into the bank area, since the availability of
water to riparian vegetation appears to be the most limiting factor under low flow conditions.
(Design should also include stripping off the contaminant overburden in order to expose the
historic flood plain sediments, thus inviting historically buried plants to re-emerge and assist in
building an indigenous riparian edge).
8-9
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Minor renovation of control structure would also be facilitated under this proposed
option. Constructing the primary spillway to be uniform with the secondary spillway by utilizing
stop logs will eliminate breach flow resuspension processes in the impoundment and provide
ponded water during the low flow periods to support further wetland emergent plant
development.
The renovation of the Rice City impoundment by refurbishment of control structures
would be a viable option for containment of contaminated sediments and improvements of water
quality. Inundation of sediments would create reducing conditions which would assist
immobilizing the majority of metals within the impoundment. Further research should be
pursued to determine if the high organic material and Fe have sufficiently immobilized the other
metals under steady flow conditions.
8-10
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9.0 SUMMARY
This report is a summary of a comprehensive dry and wet weather water quality analysis
of the Blackstone River in Massachusetts and Rhode Island. Throughout this report, conclusions
and summary sections were presented in Chapters 3-8. This final section does not restate these
conclusions but in turn discusses the broader research questions this study was to address.
To what extent does wet weather impact the water quality of the Blackstone River?
It is obvious, based on the analysis of the concentration data, that wet weather loadings
may dominate the river for days after the event depending on the size of the storm and the
constituent. Specifically, wet weather can result in violations in effluents (ammonia/UBWPAD)
and in river reaches (fecal coliform criteria and acute and chronic criteria for trace metals). In all
cases violations under wet weather were greater in magnitude, frequency and location.
Often times more than one factor magnified the impact of wet weather. For instance,
during the height of the storm instream hardness decreases due to dilution, thereby lowering the
acute criteria concentrations. The more stringent criteria typically coincided with maximum
instream concentrations due to peak flows. The results were instream violations.
In general, the major nonpoint sources of wet weather pollutants appear to be runoff
related (new materials) although for several reaches sediment resuspension (old materials) was
significant. The headwaters did prove to be significant for several constituents.
What are the major contributors to wet weather loadings? What is the relative importance
between wet weather and point source loadings?
Pollutants associated with wet weather may come from either new sources (runoff
induced) or old sources (river sediments). The water quality data coupled with stream flows
allowed for the calculation of mass loading curves. Each mass loading curve was integrated to
obtain the total load for each station for each storm. The total mass was divided by the time of
the event to obtain the total loading for that constituent for each station. Baseline loading rates
were estimated for each pollutograph from the initial (prestorm) sample and the final (poststorm)
samples. These rates were multiplied by the time of the event to obtain the total dry load for that
station. The wet load per station per constituent was determined by subtracting the dry load from
the total. The data indicate clearly that with only minor exceptions more wet load entered the
river during these periods than dry load.
Based on the loading estimates an estimate of pollutant gain or loss by reach was made.
Net pollutant changes in a reach help to identify locations of major pollutant sources. A
comparison of point and nonpoint pollutant sources was made. The results of this evaluation
also provided insight into the relative importance of each reach through a system ranking. A
system ranking was made using the net gains for each reach and loads from the point sources,
9-1
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headwaters and tributaries. The result was a determination of reach hot spots.
How can the information generated in this study be used to forecast annual wet weather loading
rates? What is the wet weather loading rate of pollutants, especially nitrogen, to the Providence
River?
The information collected during the wet weather sampling program provided insights
into the behavior of the sources during varying storm conditions. A relationship was developed
between rainfall and wet loadings using the data collected during the three storms and previous
wet weather data available for the state line (BWW13) and end of river (BWW21). These
equations were used to estimate the annual wet loading rates for the Blackstone River.
Similarly, dry weather predictions were estimated based on empirical relationships
developed for flow and concentration. The dry weather data was first used to calibrate and
validate models to describing trace metal and dissolved oxygen fate and transport. The dry
weather models were used to estimate baseline mass loadings under steady state flows. The
relationships developed were used to estimate the annual dry weather contributions at MA/RI
state line (BWW13) and end of the river (BWW21).
Annual loading rates to the Providence River were developed for several constituents. Of
the five major tributaries to the Providence River, the Blackstone River is the major source of
most pollutants.
9-2
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Appendix
Blackstone River Initiative
A listing of the contents of the appendix are attached in the following order:
1. Dry Weather Data - Nonmetal Constituents
2. Dry Weather Data - Metal Constituents
3. Wet Weather Data
4. QUAL2E Directory
5. Pawtoxic Directory
The appendix is contained on the attached CD.
CD-I
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DRY WEATHER DATA
NONMETAL CONSTITUENTS
FILENAME
TITLE OF TABLE
BBOD.TXT
BCL.TXT
Biochemical Oxygen Demands (mg/L) for all three Blackstone River Dry
Weather Surveys
Chloride concentrations (mg/L) for all three Blackstone River Dry
Weather Surveys
BCHLA.TXT Chlorophyll a concentrations (ppb) for all three Blackstone River Dry
Weather Surveys
BDO.TXT
BNH3.TXT
BN03.TXT
BP04.TXT
BTKN.TXT
BTSS.TXT
BVSS.TXT
BPTBOD.TXT
BPTCL.TXT
Dissolved Oxygen concentrations (mg/L) for all three Blackstone River
Dry Weather Surveys
Dissolved Ammonia as N concentrations (mg/L) for all three Blackstone
River Dry Weather Surveys
Dissolved Nitrate as N concentrations (mg/L) for all three Blackstone
River Dry Weather Surveys
Dissolved Orthophosphate as P concentrations (mg/L) for all three
Blackstone River Dry Weather Surveys
Total Kjeldhal Nitrogen concentrations (mg/L) for all three Blackstone
River Dry Weather Surveys
TSS concentrations (mg/L) for all three Blackstone River Dry Weather
Surveys
VSS concentrations (mg/L) for all three Blackstone River Dry Weather
Surveys
Point Source Effluent BODs concentrations (mg/L) for all three
Blackstone River Dry Weather Surveys
Point Source Effluent Chloride concentrations (mg/L) for all three
Blackstone River Dry Weather Surveys
CD-2
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BPTNH3.TXT
BPTN03.TXT
BPTP04.TXT
BPTTSS.TXT
BPTYSS.TXT
BPTTKN.TXT
BPTINP.TXT
Point Source Effluent Dissolved Ammonia as N concentrations(mg/L) for
all three Blackstone River Dry Weather Surveys
Point Source Effluent Dissolved Nitrate as N concentrations(mg/L) for all
three Blackstone River Dry Weather Surveys
Point Source Effluent Dissolved Orthophosphate as P concentrations
(mg/L) for all three Blackstone River Dry Weather Surveys
Point Source Effluent TSS concentrations (mg/L) for all three Blackstone
River Dry Weather Surveys
Point Source Effluent VSS concentrations (mg/L) for all three Blackstone
River Dry Weather Surveys
Point Source Effluent TKN concentrations (mg/L) for all three Blackstone
River Dry Weather Surveys
Input Data used in the QUAL2E Dissolved Oxygen Model for Point
Sources and Tributaries in the Blackstone River
CD-3
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DRY WEATHER DATA
METAL CONSTITUENTS
FILENAME
BCD.TXT
BDCD.TXT
BPCD.TXT
BCR.TXT
BDCR.TXT
BPCR.TXT
BCU.TXT
BDCU.TXT
BPCU.TXT
BNI.TXT
TITLE OF TABLE
Total Cd concentrations (ppb), Ave. Hardness (ppm), Fresh Water Aquatic
Life Criteria (ppb) for all three Blackstone River Dry Weather Surveys
Dissolved Cd concentrations (ppb), Ave. Hardness (ppm) Fresh Water
Aquatic Life Criteria (ppb) for all three Blackstone River Dry Weather
Surveys
Particulate Cd concentration (ppb) for all three Blackstone River Dry
Weather Surveys
Total Cr concentrations (ppb), Ave. Hardness (ppm), Fresh Water Aquatic
Life Criteria (ppb) for all three Blackstone River Dry Weather Surveys
Dissolved Cr concentrations (ppb), Ave. Hardness (ppm), Fresh Water
Aquatic Life Criteria (ppb) for all three Blackstone River Dry Weather
Surveys
Particulate Cr concentration (ppb) for all three Blackstone River Dry
Weather Surveys <
Total Cu concentrations (ppb), Ave. Hardness (ppm), Fresh Water Aquatic
Life Criteria (ppb) for all three Blackstone River Dry Weather Surveys
Dissolved Cr concentrations (ppb), Ave. Hardness (ppm), Fresh Water
Aquatic Life Criteria (ppb) for all three Blackstone River Dry Weather
Surveys
Particulate Cu concentration (ppb) for all three Blackstone River Dry
Weather Surveys
Total Ni concentrations (ppb), Ave. Hardness (ppm), Fresh Water Aquatic
Life Criteria (ppb) for all three Blackstone River Dry Weather Surveys
CD-4
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BDNI.TXT
Dissolved Ni concentrations (ppb), Ave. Hardness (ppm), Fresh Water
Aquatic Life Criteria (ppb) for all three Blackstone River Dry Weather
Surveys
BPNI.TXT
Particulate Ni concentration (ppb) for all three Blackstone River Dry
Weather Surveys
BPB.TXT
Total Pb concentrations (ppb), Ave. Hardness (ppm), Fresh Water Aquatic
Life Criteria (ppb) for all three Blackstone River Dry Weather Surveys
BDPB.TXT
Dissolved Pb concentrations (ppb), Ave. Hardness (ppm), Fresh Water
Aquatic Life Criteria (ppb) for all three Blackstone River Dry Weather
Surveys
BPPB.TXT
Particulate Pb concentration (ppb) for all three Blackstone River Dry
Weather Surveys
TMCUBW.TXT
Total Metal Concentrations (ppb) - UBWPAD Wastewater Secondary
Effluent Post Chlorination
TMCWOON.TXT Total Metal Concentrations (ppb) - Woonsocket Wastewater Secondary
Effluent Post Chlorination
KPTM.TXT
Partition Coefficient Values for Cd, Cr, Cu, Ni, and Pb, for all Three. 1991
Blackstone River Dry Weather Surveys
CD-5
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FILENAME
STORMI.TXT
STORMH.TXT
STORMm.TXT
WET WEATHER DATA
TITLE OF TABLE
Water Quality Data for Storm I
Water Quality Data for Storm II
Water Quality Data for Storm III
CD-6
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QUAL2E DIRECTORY
INSTALL.EXE
Q2READ.TXT
BLKJMDO.DAT
BLKJMDO.OUT
BLKJRDO.DAT
BLKJRDO.OUT
BLKAMDO.DAT
BLKAMDO.OUT
BLKARDO.DAT
BLKARDO.OUT
BLKOMDO.DAT
BLKOMDO.OUT
BLKORDO.DAT
An executable file that de-archives the QUAL2E model.
Directions for installing the QUAL2E model and testing the performance
of the model after it is installed. It is recommended that the user follow the
these test procedures prior to running the Blackstone River files.
QUAL2E Dissolved Oxygen Model data file for the Massachusetts portion
of the Blackstone River for Survey I, July 10-11, 1991.
QUAL2E Dissolved Oxygen Model output file for the Massachusetts
portion of the Blackstone River for Survey I, July 10-11,1991.
QUAL2E Dissolved Oxygen Model data file for the Rhode Island portion
of the Blackstone River for Survey I, July 10-11,1991.
QUAL2E Dissolved Oxygen Model output file for the Rhode Island
portion of the Blackstone River for Survey I, July 10-11,1991.
QUAL2E Dissolved Oxygen Model data file for the Massachusetts portion
of the Blackstone River for Survey II, August 14-15,1991.
QUAL2E Dissolved Oxygen Model output file for the Massachusetts
portion of the Blackstone River for Survey II, August 14-15, 1991.
QUAL2E Dissolved Oxygen Model data file for the Rhode Island portion
the Blackstone River for Survey II, August 14-15,1991.
QUAL2E Dissolved Oxygen Model output file for the Rhode Island
portion the Blackstone River for Survey II, August 14-15, 1991.
QUAL2E Dissolved Oxygen Model data file for the Massachusetts portion
the Blackstone River for Survey III, October 2-3,1991.
QUAL2E Dissolved Oxygen Model output file for the Massachusetts
portion the Blackstone River for Survey III, October 2-3,1991.
QUAL2E Dissolved Oxygen Model data file for the Rhode Island portion
of the Blackstone River for Survey III, October 2-3,1991.
CD-7
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BLKORDO.OUT QUAL2E Dissolved Oxygen Model output file for the Rhode Island
portion of the Blackstone River for Survey HI, October 2-3,1991.
SRJULDO.DAT File containing the local climatology data for the dynamic (DIURNAL)
input for July, 1991.
SRAUGDO.DAT File containing the local climatology data for the dynamic (DIURNAL)
input for August, 1991.
SROCTDO.DAT File containing the local climatology data for the dynamic (DIURNAL)
input for October, 1991.
TURBO.EXE A DOS text editor that is able to assimilate the large output files generated
from the QUAL2E dynamic simulations. To execute, type, TURBO [file
name].
CD-8
-------
PAWTOXIC directory
PTOXMAN.TXT
FIGURE 1. WPG
FIG l.JPG
File containing a manual explaining the format of the PAWTOXIC Model.
A Corel Presentation 8 graphic schematic of how stream reaches are
labeled. The explanation of Figure 1 is in the PAWTOXIC manual.
A .JPG graphic of Figure 1 in a universal format.
PAWTOXIC.EXE The executable program for the PAWTOXIC Model. Transfer this file to a
hard drive to execute the model.
PAWTOXIC.FOR
BLKJTM.DAT
BLKJTM.OUT
BLKATM.DAT
BLKATM.OUT
BLKOTM.DAT
BLKOTM.OUT
7Q10TM.DAT
7Q10TM.OUT
A formatted copy of the file/card structure for the PAWTOXIC Model.
PAWTOXIC Model input file for trace metals from the Blackstone River
Dry Survey I, July 10-11,1991.
Output file from the PAWTOXIC Model for the Blackstone River Dry
Survey I, July 10-11,1991. The July 1991 data file was the input file used
to generate this file.
PAWTOXIC Model input file for trace metals from the Blackstone River
Dry Survey II, August 14-15,1991.
Output file from the PAWTOXIC Model for the Blackstone River Dry
Survey II, August 14-15,1991. The August 1991 data file was used.
PAWTOXIC Model input file for trace metals from the Blackstone River
Dry Survey III, October 2-3,1991.
Output file from the PAWTOXIC Model for the Blackstone River Dry
Survey III, October 2-3,1991. The October 1991 data file was used.
PAWTOXIC Model input file for trace metals from the Blackstone River
for the 7Q10 flow.
Output file of PAWTOXIC Model from the 7Q10 data file for the
Blackstone River.
QUIKSTRT.TXT Instructions for loading the PAWTOXIC Model onto a hard disk and how
to run the program.
PTOXDIR.TXT Disk directory with explanation of files.
CD-9
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/
// Blackstone River Initiative
/Y Civil and Environmental Engineering
/ University of Rhode Island \
Contents: Dry Weather Data Sets • Wet Weather Survey Data Sets
QUAL2E Dissolved Oxygen Model & Data Sets • FAWTOXIC Trace Metal Model & Data Sets
------- |