£,EPA
United States
Environmental Protection
Agency
Environmental Impact and Benefits
Assessment for Final Effluent
Guidelines and Standards for the
Construction and Development Category
November 2009
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Environmental Impact and Benefits Assessment for the C&D Category
U.S. Environmental Protection Agency
Off ice of Water (4303T)
1200 Pennsylvania Avenue, NW
Washington, DC 20460
EPA-821-R-09-012
November 2009
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Environmental Impact and Benefits Assessment for the C&D Category
ACKNOWLEDGMENTS AND DISCLAIMER
This document was prepared by U.S. Environmental Protection Agency Office of Water staff. The
following contractor provided assistance in performing the analyses supporting the conclusions
detailed in this document.
Abt Associates, Inc.
Office of Water staff have reviewed and approved this document for publication. Neither the
United States Government nor any of its employees, contractors, subcontractors, or their
employees makes any warranty, expressed or implied, or assumes any legal liability or
responsibility for any third party's use of or the results of such use of any information, apparatus,
product, or process discussed in this document, or represents that its use by such a party would
not infringe on privately owned rights. References to proprietary technologies are not intended to
be an endorsement by the U.S Environmental Protection Agency.
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Environmental Impact and Benefits Assessment for the C&D Category
Table of Contents
Table of Contents v
List of Tables xi
List of Figures xvii
Acronyms and Abbreviations xix
1 Introduction 1-1
2 Overview of Environmental Impacts from Construction Site Sediment Discharges 2-1
2.1 Sediment and Turbidity Discharge to Surface Waters 2-2
2.2 Sediment and Turbidity Behavior in Surface Waters 2-5
2.2.1 Sediment Characteristics Affecting Surface Water Transport 2-6
2.2.2 Sediment and Turbidity Behavior in Specific Waterbody Types 2-7
2.3 Aquatic Life Impacts of Sediment and Turbidity 2-11
2.3.1 Primary Producers 2-13
2.3.2 Invertebrates 2-15
2.3.3 Fish 2-18
2.3.4 Other Wildlife Dependent on Aquatic Ecosystems 2-22
2.3.5 Threatened and Endangered Species 2-22
2.4 Sediment and Turbidity Impacts on Human Use of Aquatic Resources 2-25
2.4.1 Navigation on Surface Waters 2-25
2.4.2 Reservoir Water Storage Capacity 2-26
2.4.3 Municipal Water Use 2-26
2.4.4 Industrial Water Use 2-27
2.4.5 Agricultural Water Use 2-27
2.4.6 Stormwater Management and Flood Control 2-28
2.4.7 Recreational Uses and Aesthetic Value 2-28
2.4.8 Recreational and Commercial Fishing 2-29
2.5 Sediment and Turbidity Criteria 2-29
2.5.1 Federal Sediment Criteria 2-30
2.5.2 State Sediment Criteria 2-30
2.6 Surface Water Quality Impairment from Sediment and Turbidity 2-36
2.6.1 Current Total Suspended Solid Concentrations in U.S. Surface Waters 2-38
3 Other Pollutants in Construction Site Discharges 3-1
3.1 Introduction 3-1
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3.1.1 Pollution Discharge and Transport Pathways 3-1
3.1.2 National Scale and Cumulative Impact Concerns 3-2
3.2 Construction Site Sources of Pollutants Other Than Sediment and Turbidity 3-3
3.2.1 Construction Materials and Equipment 3-3
3.2.2 Historic Site Contamination 3-4
3.2.3 Natural Site Constituents 3-5
3.2.4 Altered Stormwater Discharge 3-6
3.3 Other Pollutants from Construction Activity 3-7
3.3.1 Nitrogen and Phosphorus 3-7
3.3.2 Organic Compounds and Materials 3-12
3.3.3 Metals 3-16
3.3.4 Dissolved Inorganic Ions 3-19
3.3.5 pH Level 3-20
3.3.6 Pathogens 3-21
4 Summary of Literature on Construction Site Discharges to Surface Waters 4-1
4.1 Overview of Impacts in Literature 4-1
4.2 Individual Study Summaries 4-17
4.3 State Reports of Construction Discharge Impacts 4-30
5 Overview of Benefits from Regulation 5-1
5.1 Conceptual Framework for Valuation of Environmental Services 5-1
5.1.1 Applicable Benefit Categories 5-3
5.1.2 Market Benefits 5-4
5.1.3 Nonmarket Benefits 5-6
5.2 Summary of Effects 5-9
6 Water Quality Modeling 6-1
6.1 SPARROW Model Documentation 6-1
6.1.1 General Overview 6-1
6.1.2 Modeling Concept 6-2
6.1.3 Model Infrastructure 6-3
6.1.4 Model Specification 6-4
6.1.5 Model Estimation 6-6
6.2 SPARROW Sediment Model 6-6
6.2.1 Sediment Model Data Sources 6-6
6.2.2 Model Estimation Results 6-8
6.2.3 Model Simulation 6-9
6.3 Extension of SPARROW to Estuaries and Coastal Waters 6-10
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6.4 Modeling Changes in Nutrient Concentrations 6-12
6.4.1 Modeling Approach Based on SPARROW Nutrient Models 6-13
6.5 Pollutant Load Modeling 6-15
6.6 Water Quality Modeling Results 6-17
6.6.1 Current Water Quality Impacts to Surface Water from Construction Site Discharges 6-26
6.6.2 Estimated Changes in TSS Concentrations in RF1 Watersheds with Most Developed
Acres (1992-2001) Receiving Sediment Loading from Construction Sites 6-31
6.6.3 Estimated Changes in TSS, TN, and TP Concentrations for all RF1 Watersheds
Receiving Loading from Construction Sites 6-35
6.6.4 Impacts on Reservoir Sedimentation 6-44
6.6.5 Estimated Changes in Nutrient Concentrations for all RF1 Watersheds Receiving
Loading from Construction Sites 6-44
7 Benefits to Navigation 7-1
7.1 Data Sources 7-1
7.2 Identifying Waterways That Are Dredged, the Frequency of Dredging, and the Quantity of
Sediment Dredged 7-3
7.2.1 Determining Dredging Job Locations 7-3
7.2.2 Identifying the Baseline Frequency of Dredging 7-3
7.2.3 Identifying the Amount of Sediment Dredged 7-5
7.3 Estimating the Navigational Maintenance Cost per Cubic Yard of Sediment Removed 7-5
7.4 Estimating the Total Cost of Navigable Waterway Maintenance Under Different Policy
Scenarios 7-6
7.4.1 Estimating the Reduction in Sediment Dredging in Navigable Waterways Due to the
Reduction in Discharge from Construction Sites 7-6
7.4.2 Estimating the Total Cost of Navigable Waterway Maintenance Under the Baseline and
Post-Compliance Scenarios 7-6
7.4.3 Sensitivity Analysis 7-7
7.4.4 Annualizing Future Dredging Costs 7-8
7.5 Estimating the Avoided Costs from Decreased Dredging of Navigable Waterways 7-10
7.6 Sources of Uncertainty and Limitations 7-13
8 Benefits to Water Storage 8-1
8.1 Review of Literature on Reservoir Sedimentation 8-1
8.2 Data Sources 8-3
8.3 Estimating the Unit Cost of Sediment Removal from Reservoirs 8-4
8.4 Estimating the Total Cost of Reservoir Dredging Under Different Policy Options 8-4
8.4.1 Estimating Sediment Accumulation in Reservoirs and the Amount of Sediment
Expected To Be Dredged 8-4
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8.4.2 Estimating the Total Cost of Reservoir Dredging Under the Baseline Scenario and
Policy Options 8-5
8.5 Estimating the Avoided costs from Reduced Reservoir Dredging 8-6
8.6 Sources of Uncertainty and Limitations 8-8
9 Benefits to Drinking Water Treatment 9-1
9.1 Construction Discharge Effects on Drinking Water Treatment Costs 9-1
9.1.1 Sediment 9-1
9.1.2 Nutrients 9-1
9.1.3 Increase in Primary Productivity and Associated Water Quality Impacts from Nutrient
Discharges (Eutrophication) 9-2
9.2 Avoided Costs of Drinking Water Treatment from Reducing Sediment Discharge from
Construction Sites 9-4
9.3 Data Sources 9-6
9.4 Modeling Sediment Concentrations and Reductions 9-6
9.5 Identifying Reaches with Drinking Water Intakes and Their Intake Volumes 9-7
9.6 Estimating the Cost of Chemical Turbidity Treatment 9-8
9.7 Estimating the Cost of Sludge Disposal 9-10
9.7.1 Estimating the Amount of Sludge Generated 9-10
9.7.2 Calculating the Probability That the Sludge Will Require Off-Site Disposal 9-11
9.7.3 Estimating the Distance to the Disposal Location 9-11
9.7.4 Calculating the Cost of Sludge Disposal 9-11
9.8 Sensitivity Analysis 9-12
9.9 Estimating the Total Costs of Drinking Water Treatment Under Different Policy Scenarios 9-13
9.10 Estimating Avoided costs from Lower Sediment and Turbidity in Drinking Water Influent 9-13
9.11 Sources of Uncertainty/Limitations 9-16
10 Nonmarket Benefits from Water Quality Improvements 10-1
10.1 Water Quality Index 10-1
10.1.1 Freshwater WQI for Rivers and Streams 10-3
10.1.2 WQI Methodology for Estuaries 10-5
10.1.3 Relation between WQI and Suitability for Human Uses 10-6
10.1.4 Sources of Data on Ambient Water Quality 10-7
10.1.5 Estimated Changes in Water Quality (AWQI) from the Regulation 10-9
10.2 Willingness to Pay for Water Quality Improvements 10-16
10.3 Estimating Total WTP for Water Quality Improvements 10-22
10.4 Uncertainty and Limitations 10-25
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11 Total Estimated Benefits 11-1
11.1 Summary of the Estimated Benefits 11-1
11.2 Sources of Uncertainty and Limitations 11-5
11.2.1 Water Quality Model Limitations 11-6
11.2.2Focus on Selected Pollutants of Concern (Sediment and Nutrients) 11-7
11.2.3 Omission of Several Benefit Categories from the Analysis of Monetized Benefits 11-7
11.2.4Limitations Inherent in the Estimate of Nonmarket Benefits 11-8
12 References 12-1
Appendix A- Status of Available Data on Waterbody Assessments A-l
Appendix B - Threatened and Endangered Aquatic Species B-l
Appendix C - SPARROW Model Documentation C-l
C.I General Overview C-l
C.2 Modeling Concept C-2
C.2.1 Objectives of SPARROW Modeling C-2
C.2.2 SPARROW Mass Balance Approach C-4
C.2.3 Time and Space Scales of the Model C-4
C.2.4 Accuracy and Complexity of SPARROW Models C-6
C.2.5 Comparison of SPARROW with Other Watershed Models C-7
C.2.6 Model Infrastructure C-8
C.2.7 Use of Monitoring Data C-10
C.2.8 Model Specification for Monitoring Station Flux Estimation C-ll
C.2.9 Tools for Flux Estimation C-ll
C.2.10 Guidance for Specifying Monitoring Station Flux Models C-12
C.2.11 Stream Network Topology C-13
C.2.12 Watershed Sources and Explanatory Variables C-15
C.3 Model Specification C-17
C.3.1 Model Equation and Specification of Terms C-17
C.3.2 Contaminant Sources C-19
C.3.3 Landscape Variables C-20
C.3.4 Stream Transport C-21
C.3.5 Reservoir and Lake Transport C-21
C.4 Model Estimation C-22
C.4.1 Evaluation of Model Parameters C-22
C.5 Model Prediction C-23
Appendix D - A Preliminary SPARROW Model of Suspended Sediment for the Coterminous
United States (Schwarz 2008a) D-l
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Appendix E - Estuary TSS Concentration Calculations Using Dissolved Concentration
Potentials E-l
Appendix F- TSS Subindex Curve Parameters F-l
Appendix G - Meta-Analysis Results G-l
G.I Literature Review of Water Resource Valuation Studies G-l
G.I.I Identifying Water Resource Valuation Studies G-2
G.I.2 Description of Studies Selected for Total WTP Meta-Analysis G-4
G.2 Total WTP Meta-Analysis Regression Model and Results G-7
G.2.1 Metadata Total WTP Regression Model G-8
G.2.2 Total WTP Regression Model and Results G-12
G.2.3 Interpretation of Total WTP Regression Analysis Results G-14
G.2.4 Model Selection G-18
G.3 Model Limitations G-19
Appendix H- Water Quality Index Tables H-l
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List of Tables
Table 2-1: Sediment and Turbidity Terminology 2-2
Table 2-2: Sediment Grade Scale 2-6
Table 2-3: Suspended Sediment and Turbidity Criteria for Surface Water Quality by State 2-32
Table 2-4: Surface Waters Impaired by "Sediment," by EPA Region 2-37
Table 2-5: Surface Waters Impaired by "Turbidity" and "Suspended Solids," by EPA Region 2-37
Table 2-6: SPARROW Distribution of TSS Concentrations in RF1 Reaches1 2-39
Table 3-1: Nutrient-Related Impairment in 305(b)-Assessed Waters, by EPA Region 3-11
Table 4-1: Studies Documenting Construction Site Discharges to Surface Waters and Their Impacts 4-4
Table 4-2: Summary of Suspended Sediment Concentrations from Selected Studies 4-13
Table 4-3: Summary of Sediment Yield Data from Selected Studies 4-15
Table 4-4: Summary of Turbidity Findings from Selected Studies 4-16
Table 4-5: Construction Impairment in 305(b)-Assessed Waters 4-31
Table 5-1: Summary of Benefits from Reducing Sediment and Other Pollutant Discharges from
Construction Sites 5-11
Table 6-1: Estimation Results for the SPARROW Suspended Sediment Model 6-9
Table 6-2: Nutrient-to-Sediment Ratios 6-14
Table 6-3: Literature Values of Nitrogen and Phosphorus in Soil and Sediment 6-14
Table 6-4: Baseline Construction Sediment Loading Summary and Post-Compliance Reductions 6-15
Table 6-5: Construction Sediment Loading Summary and Reductions by Option and EPA Region 6-16
Table 6-6: Distribution of TSS Concentrations based on SPARROW Output for 31,927 RF1 Reaches
Receiving Construction Sediment Discharges 6-26
Table 6-7: Summary of Baseline TSS Concentration in RF1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-27
Table 6-8: Summary of TSS Concentrations Under the Hypothetical No Discharge Scenario, by EPA
Region 6-27
Table 6-9: Water Quality Impacts: Improvements in TSS Concentrations Under the Hypothetical No
Discharge Scenario, by EPA Region 6-28
Table 6-10: Distribution of TN Concentrations based on SPARROW Output for 31,927 RF1 Reaches
Receiving Construction Sediment Discharges 6-29
Table 6-11: Summary of Baseline TN Concentration in RF1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-29
Table 6-12: Summary of TN Concentrations Under the Hypothetical No Discharge Scenario, by EPA
Region 6-29
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Table 6-13: Distribution of TP Concentrations based on SPARROW Output for 31,927 RF1 Reaches
Receiving Construction Sediment Discharges 6-30
Table 6-14: Summary of Baseline TP Concentration in RF1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-30
Table 6-15: Summary of TP Concentrations Under the Hypothetical No Discharge Scenario, by EPA
Region 6-30
Table 6-16: Reaches with Largest Increase in Developed Land Area (1992-2001) 6-32
Table 6-17: Distribution of RF1 Watersheds that Receive Direct Loadings by Increase in Developed
Land Area (1992-2001), by EPA Region 6-32
Table 6-18: Estimated Changes in RF1 Reach TSS Concentration by Policy Option: Top 1% of RF1
Watersheds Receiving Direct Construction Loadings by Increase in Developed Land Area
(1992-2001) 6-33
Table 6-19: Estimated Changes in RF1 Reach TSS Concentration by Policy Option: Top 10% of RF1
Watersheds Receiving Direct Construction Loadings by Increase in Developed Land Area
(1992-2001) 6-33
Table 6-20: Estimated Changes in RF1 Reach TSS Concentration by Policy Option: Top 25% of RF1
Watersheds by Increase in Developed Land Area (1992-2001) 6-34
Table 6-21: Distribution of TSS Concentration based on SPARROW Output for 31,927 RF1 Reaches
Receiving Construction Sediment Discharges 6-35
Table 6-22: Summary of Baseline TSS Concentration in RF1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-36
Table 6-23: Summary of Option 1 TSS Concentration in RF1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-36
Table 6-24: Summary of Option 2 TSS Concentration in RF1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-37
Table 6-25: Summary of Option 3 TSS Concentration in RF1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-37
Table 6-26: Summary of Option 4 TSS Concentration in RF1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-38
Table 6-27: Total RF1 Miles that Receive Direct Construction Loadings with Improvements in TSS
Concentrations 6-40
Table 6-28: Total RF1 Miles that Receive Direct Construction Loadings with Improvements in TSS
Concentrations from Option 1, by EPA Region 6-40
Table 6-29: Total RF1 Miles that Receive Direct Construction Loadings with Improvements in TSS
Concentrations from Option 2, by EPA Region 6-41
Table 6-30: Total RF1 Miles that Receive Direct Construction Loadings with Improvements in TSS
Concentrations from Option 3, by EPA Region 6-42
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Table 6-31: Total RF1 Miles that Receive Direct Construction Loadings with Improvements in TSS
Concentrations from Option 4, by EPA Region 6-43
Table 6-32: Sediment Accumulation in Reservoirs by Policy Option and EPA Region 6-44
Table 6-33: Distribution of TN Concentration Based on SPARROW Output for 31,927 RF1 Reaches
Receiving Construction Sediment Discharges 6-45
Table 6-34: Distribution of TP Concentration Based on SPARROW Output for 31,927 RF1 Reaches
Receiving Construction Sediment Discharges 6-45
Table 6-35: Summary of Baseline TN Concentration in RF1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-46
Table 6-36: Summary Option 1 TN Concentration in RF1 Reaches Receiving Construction Sediment
Discharges, by EPA Region 6-46
Table 6-37: Summary of Option 2 TN Concentration in RF1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-47
Table 6-38: Summary of Option 3 TN Concentration in RF1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-47
Table 6-39: Summary of Option 4 TN Concentration in RF1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-48
Table 6-40: Summary of Baseline TP Concentration in RF1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-48
Table 6-41: Summary of Option 1 TP Concentration in RF1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-49
Table 6-42: Summary of Option 2 TP Concentration in RF1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-49
Table 6-43: Summary of Option 3 TP Concentration in RF 1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-50
Table 6-44: Summary of Option 4 TP Concentration in RF1 Reaches Receiving Construction
Sediment Discharges, by EPA Region 6-50
Table 7-1: Dredging in U.S. Navigable Waterways, 1995-2008 7-2
Table 7-2: Dredging of Navigable Waterways Performed or Contracted by USAGE, 1995-2008 7-3
Table 7-3: Dredging Jobs and Recurrence Intervals, 1995- 2008 7-4
Table 7-4: Costs of Recurring Dredging, 1995-2006 7-5
Table 7-5: Annualized Dredging Costs Under the Baseline Scenario (millions of 2008$) 7-9
Table 7-6: Reductions in Dredging and Annualized Avoided Costs Under Option 1 7-11
Table 7-7: Reductions in Dredging and Annualized Avoided Costs Under Option 2 7-11
Table 7-8: Reductions in Dredging and Annualized Avoided Costs Under Option 3 7-12
Table 7-9: Reductions in Dredging and Annualized Avoided Costs Under Option 4 7-12
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Table 8-1: Average Annual Sedimentation Deposition Recorded by RESIS 8-3
Table 8-2: Estimated Cost of Reservoir Dredging Under the Baseline Scenario 8-6
Table 8-3: Reduction in Reservoir Dredging and Avoided Costs Under Option 1 8-7
Table 8-4: Reduction in Reservoir Dredging and Avoided Costs Under Option 2 8-7
Table 8-5: Reduction in Reservoir Dredging and Avoided Costs Under Option 3 8-8
Table 8-6: Reduction in Reservoir Dredging and Avoided Costs Under Option 4 8-8
Table 9-1: TN Concentrations Predicted by SPARROW for Reaches Serving as Drinking Water
Sources1 9-2
Table 9-2: Public Water Intakes and Estimated Average Daily Flow by EPA Region 9-8
Table 9-3: Drinking Water Turbidity Treatment Costs Under the Baseline Scenario 9-13
Table 9-4: Reduction in Drinking Water Treatment Costs Under Option 1 9-15
Table 9-5: Reduction in Drinking Water Treatment Costs Under Option 2 9-15
Table 9-6: Reduction in Drinking Water Treatment Costs Under Option 3 9-16
Table 9-7: Reduction in Drinking Water Treatment Costs Under Option 4 9-16
Table 10-1: Freshwater Water Quality Subindices 10-4
Table 10-2: Original and Revised Weights for Freshwater WQI Parameters 10-4
Table 10-3: Estuarine Water Quality Subindices 10-5
Table 10-4: Weights for Estuarine WQI Parameters 10-6
Table 10-5: Water Quality Classifications 10-6
Table 10-6: Percentage of Reach Miles in Coterminous 48 States by WQI Classification for EPA
Regions: Baseline Scenario 10-9
Table 10-7: Estimated Water Quality Improvements Under Option I1 10-12
Table 10-8: Estimated Water Quality Improvements Under Option 2: 10-13
Table 10-9: Estimated Water Quality Improvements Under Option 31 10-14
Table 10-10: Estimated Water Quality Improvements Under Option 4: 10-15
Table 10-11: Independent Variable Assignments 10-18
Table 10-12: Estimates of Annual Household Willingness to Pay for Water Quality Improvement by
Region and Policy Option (2008$) 10-21
Table 10-13 :Regional Willingness to Pay for Water Quality Improvement (Millions 2008$) 10-24
Table 11-1: Annual Total National Benefits by Benefits Category (millions of 2008$) 11-3
Table 11-2: Annual Total National Benefits Under Option 1 (millions of 2008$) 11-4
Table 11-3: Annual Total National Benefits Under Option 2 (millions of 2008$) 11-4
Table 11-4: Annual Total National Benefits Under Option 3 (millions of 2008$) 11-5
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Environmental Impact and Benefits Assessment for the C&D Category
Table 11-5: Annual Total National Benefits Under Option 4 (millions of 2008$) 11-5
Table A-1: Year of Available Waterbody Assessment Data, as of September 17, 2009 A-1
Table B-l: List of Federal Threatened and Endangered Aquatic Species Potentially Impacted by
Sediment B-l
Table E-l: TSS Concentrations (mg/L) Estimated by DCP, Southeastern Estuaries E-l
Table E-2: TSS Concentrations (mg/L) Estimated by DCP, Gulf of Mexico Estuaries E-l
Table E-3: TSS Concentrations (mg/L) Estimated by DCP, Northeastern Estuaries E-2
Table E-4: TSS Concentrations (mg/L) Estimated by DCP, West Coast Estuaries E-3
Table E-5: Total Number Reaches in the Analysis located in Southeastern Estuaries that Use DCP to
Calculate TSS by Estuary E-3
Table E-6: Total Number Reaches in the Analysis located in Gulf of Mexico Estuaries that Use DCP
to Calculate TSS by Estuary E-4
Table E-7: Total Number Reaches in the Analysis located in Northeastern Estuaries that Use DCP to
Calculate TSS by Estuary E-4
Table E-8: Total Number Reaches in the Analysis located in West Coast Estuaries that Use DCP to
Calculate TSS by Estuary E-4
Table F-l: TSS Subindex Curve Parameters, by Ecoregion F-l
Table G-l: Selected Summary Information for Studies G-5
Table G-2: Variables and Descriptive Statistics for the Total WTP Regression Model G-ll
Table G-3: Estimated Multilevel Model Results for the Trans-log and Semi-log Total WTP
Regression Models: WTP for Aquatic Habitat Improvements G-14
Table G-4: Comparison of WTP for Different Changes in WQI Based on Semi-log and
Trans-log Models G-19
Table H-l: Estimated Water Quality Improvements Under Option 1 H-2
Table H-2: Estimated Water Quality Improvements Under Option 2 H-5
Table H-3: Estimated Water Quality Improvements Under Option 3 H-8
Table H-4: Estimated Water Quality Improvements Under Option 4 H-ll
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Environmental Impact and Benefits Assessment for the C&D Category
List of Figures
Figure 2-1: EPA Regions 2-37
Figure 2-2: Extent of Stressors and Their Relative Risk to the Biological Condition of the Nation's
Streams 2-38
Figure 2-3: TSS Concentrations by Total RF1 Reach Miles as Predicted by SPARROW for Current
Conditions 2-39
Figure 3-1: Extent of Stressors and Their Relative Risk to the Biological Condition of the Nation's
Streams 3-12
Figure 5-1: Calculation of Monetized Benefits from the Regulation 5-12
Figure 6-1: Schematic of the Major SPARROW Model Components 6-3
Figure 6-2: Schematic Illustrating a Vector Stream Reach Network with Node Topology and
Water/Contaminant Reach-Node Routing Table 6-4
Figure 6-3: Location of 1,828 Water Quality Monitoring Stations Used in the SPARROW Sediment
Model, in Relation to the Reach File 1 (RF1) Reach Network 6-8
Figure 6-4: Plot of Construction Acres by RF1 Watershed Percentile Group (1992-2001) 6-18
Figure 6-5: Cumulative Plot of Construction Acres by RF1 Watershed (1992-2001) 6-19
Figure 6-6: EPA Region 1: Percent Urban Change 1992-2001 by RF1 Watershed 6-20
Figure 6-7: EPA Region 2: Percent Urban Change 1992-2001 by RF1 Watershed 6-20
Figure 6-8: EPA Region 3: Percent Urban Change 1992-2001 by RF1 Watershed 6-21
Figure 6-9: EPA Region 4: Percent Urban Change 1992-2001 by RF1 Watershed 6-21
Figure 6-10: EPA Region 5: Percent Urban Change 1992-2001 by RF1 Watershed 6-22
Figure 6-11: EPA Region 6: Percent Urban Change 1992-2001 by RF1 Watershed 6-22
Figure 6-12: EPA Region 7: Percent Urban Change 1992-2001 by RF1 Watershed 6-23
Figure 6-13: EPA Region 8: Percent Urban Change 1992-2001 by RF1 Watershed 6-23
Figure 6-14: EPA Region 9: Percent Urban Change 1992-2001 by RF1 Watershed 6-24
Figure 6-15: EPA Region 10: Percent Urban Change 1992-2001 by RF1 Watershed 6-24
Figure 9-1: Steps in Calculating the Cost of Treating Turbidity in Drinking Water 9-5
Figure 12-1: A Simple Continuum of Model Types Based on the Level of Statistical and Mechanistic
Descriptions of Contaminant Sources and Biogeochemical Processes C-7
Figure 12-2: Schematic of the Major SPARROW Model Components C-9
Figure 12-3: Location of 1,828 Water Quality Monitoring Stations Used in the SPARROW Sediment
Model, in Relation to the Reach File 1 (RF1) Reach Network C-10
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Environmental Impact and Benefits Assessment for the C&D Category
Figure 12-4: Schematic Illustrating a Vector Stream Reach Network with Node Topology and
Water/Contaminant Reach-Node Routing Table C-13
Figure 12-5: Schematic Illustrating Digital Overlay of Stream Reach Drainage Area and Polygonal
Areas Associated with Diffuse Sources C-15
Figure 12-6: Schematic Illustrating Digital Overlay of Stream Reach Drainage Area and Polygonal
Areas Associated with Landscape Properties C-16
Figure 12-7: Conceptual Illustration of a Reach Network for Five Incremental Watersheds. Model
Equation C-4 Describes the Supply and Transport of Load within an Individual Reach and its
Incremental Watershed C-17
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Environmental Impact and Benefits Assessment for the C&D Category
Acronyms and Abbreviations
AGNPS - Agricultural Nonpoint Source Model
ASCE - American Society of Civil Engineers
ATS - Active Treatment Systems
ATTAINS - Assessment TMDL Tracking and Implementation System
AWWA - American Water Works Association
BMP - Best Management Practices
BOD - Biological Oxygen Demand
BUVD - Benefits Use Valuation Database
C&D - Construction and Development
cfs - cubic feet per second
ChA - Chlorophyll-a
cm - centimeter
CPI - Consumer Price Index
CS - Compensating Surplus
CWA-Clean Water Act
DAF - Dissolved Air Flotation
DCPs - Dissolved Concentration Potentials
OEMs - Digital Elevation Models
DO - Dissolved Oxygen
EDA - Estuarine Drainage Area
EMAP-NCA - Environmental Monitoring & Assessment Program, National Coastal Assessment
Monitoring Data
EPA - Environmental Protection Agency
EPT - Ephemeroptera, Plectoptera, and Trichoptera
ERF - Enhanced Reach File
EVRI - Environmental Valuation Resource Inventory
FC - Fecal Coliform
ft/s - feet per second
FTUs - Formazin Turbidity Units
g - Gram
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GIS - Geographic Information System
HAB - Harmful Algal Bloom
HARC - The Houston Area Research Center
HSPF - Hydrologic Simulation Program-Fortran
HUC - Hydrologic Unit Code
JTU - Jackson Turbidity Units
kg/ha - Kilograms per hectare
LC - Lethal Concentration
LID - Low Impact Development
m - Meter
MCL - Maximum Contamination Limit
mgd - Millions of gallons per day
ug/L - Micrograms per liter
mg/L - Milligrams per liter
MIB - 2-methylisoborneol
mL/L - Milliliters per liter
mm - Millimeter
MRLC - Multi-Resolution Land Characteristics Consortium
NAWQA - National Water-Quality Assessment
NBER - National Bureau of Economic Research
NCEE - National Center for Environmental Economics
NEIWPCC - New England Interstate Water Pollution Control Commission
NERRS - The National Estuarine Research Reserve System
NHD - National Hydrogeography Dataset
NID - National Inventory of Dams
NLCD - National Land Cover Database
NMFS - National Marine Fisheries Service
NOAA - National Oceanic and Atmospheric Administration
NPDES - National Pollutant Discharge Elimination System
NRC - National Research Council
NRCS - Natural Resource Conservation Service
NRI - National Resources Inventory
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NSQAN - National Stream Quality Accounting Network
NTUs - Nephelometric Turbidity Units
NWIS - National Water Information System
NWLS - Nonlinear Weighted Least Squares
PAC - Powdered Activated Carbon
PAHs - Polycyclic Aromatic Hydrocarbons
POTWs - Publicly Owned Treatment Works
PPI - Producer Price Index
PTS - Passive Treatment Systems
RESIS - Reservoir Sedimentation Survey Information System
RF1 - Reach File Version 1.0
RFF - Resources for the Future
RMSE - Root Mean Squared Error
RR-River Reach
RUSLE - Revised Universal Soil Loss Equation
RUSLE k-factor- Soil Erodibility
RUSLE r-factor - Precipitation
SABS - Suspended and Bedded Sediments
SAS - Statistical Analysis System
SAS IML - Statistical Analysis System Interactive Matrix Language
SAV - Submerged Aquatic Vegetation
SCDHEC - South Carolina Department of Health and Environmental Control
SCDNR- South Carolina Department of Natural Resources
SDWIS - Safe Drinking Water Information System
SPARROW - Spatially Referenced Regressions on Watershed Attributes
SSC - Suspended Sediment Concentration
STATSGO - State Soil Geographic database
STORET - Storage and Retrieval data warehouse
SWAT - Soil Water Assessment Tool
T&E - Threatened and Endangered
TDS - Total Dissolved Solids
TESS - Threatened and Endangered Species System database
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TMDL - Total Maximum Daily Load
TM/ETM - Thematic Mapper/Embedded Trace Macrocells
TN - Total Nitrogen
TP - Total Phosphorus
TSS - Total Suspended Solids
U.S. OMB - United States Office of Management and Budget
USAGE - United States Army Corps of Engineers
USDA - United Stated Department of Agriculture
EPA - United States Environmental Protection Agency
USFWS - United States Fish and Wildlife Service
USGS - United States Geological Survey
USLE - Universal Soil Loss Equation
WATERS - Watershed Assessment Tracking & Environmental Results
WHO - World Health Organization
WQI - Water Quality Index
WQL - Water Quality Ladder
WSUT - Weak Structural Utility Theoretic
WTP - Willingness To Pay
WWF - World Wildlife Fund
WY-Water Year
yd3 - cubic yard
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Introduction
This document presents information on environmental impacts associated with construction site
discharges to surface waters and benefits associated with their reduction. Additional information on the
construction industry and construction site discharges to surface waters is provided in the U.S.
Environmental Protection Agency's (EPA's) Development Document for Final Effluent Guidelines and
Standards for the Construction and Development Category (USEPA 2009b) and Economic Analysis for
Final Effluent Guidelines and Standards for the Construction and Development Category (USEPA
2009c).
Construction takes place on approximately 853,000 acres in the coterminous United States and discharge
more than 5 billion pounds of sediment each year (USEPA 2009b). All major surface water types receive
construction discharges, including streams, rivers, wetlands, lakes, estuaries, and other coastal waters. In
any given year, some level of construction activity occurs in the majority of U.S. watersheds. However,
most construction acreage is concentrated in a relatively limited number of watersheds. Between 1992
and 2001, more than half of all construction activity took place in less than 5 percent of U.S. watersheds.1
A common development pattern is for new construction to concentrate in rural and suburban watersheds
adjacent to more densely developed urban areas. Because construction is a temporary activity, the
locations of the most highly impacted watersheds in the United States shift over time.
Construction activities significantly change the surface of the land. Typical activities include clearing
vegetation and excavating, moving, and compacting earth and rock. Consequences from these activities
include reduced stormwater infiltration, increased runoff volume and intensity, and higher soil erosion
rates.
Construction sites have been documented to increase pollutant discharges to surface waters. The most
thoroughly documented pollutants are sediment and turbidity. Nitrogen and phosphorus are common soil
constituents that can also pollute receiving waters. Other pollutants can derive from a wide variety of
construction equipment and materials or from historic contamination of construction sites. These
pollutants include metals, trash and debris, nutrients, organic matter, pesticides, petroleum hydrocarbons,
polycyclic aromatic hydrocarbons (PAHs), and other toxic organics. Construction activity can also impact
receiving waters by increasing the volume and intensity of stormwater runoff from a site. These flows can
erode receiving water banks and beds, particularly when pipes, ditches, or other stormwater conveyances
concentrate discharges. Surface water erosion can alter waterbody morphology and elevate sediment and
turbidity levels downstream.
Most pollutants enter surface waters when precipitation erodes soil and carries particulate matter to
receiving waters. A number of pollutants bind to soil particles and travel with them as they erode. Other
pollutants dissolve in precipitation and are carried to surface waters in solution. Construction site
pollutants can also enter surface waters during dry weather due to activities such as excavation
dewatering, construction equipment washout, wind erosion, and equipment operation in or near surface
waters.
1 Watersheds are those associated with the more than 62,000 surface water reaches in the coterminous United States in the
Reach File Version 1 (RF1) surface water network (USEPA 2007f). See Chapter 4 for additional information.
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Increases in pollutant and stormwater discharges from construction sites and subsequent increases in
waterbody pollutant levels can have adverse impacts on aquatic ecosystem function and human aquatic
resource use. Construction is a temporary activity in any given location, but impacts can range from
temporary to long-term. Impacts include both physical and chemical impacts on waterbodies and
biological impacts on aquatic organisms and communities. Impacts to human aquatic resource uses can
include impaired drinking water supplies, recreation, navigation, fishing, water storage, aesthetics,
property value, irrigation, industrial water supplies, and stormwater (including flood) management.
Though some surface waters can eventually recover from construction discharge impacts, they may
continue to be degraded by excess stormwater and pollutants from buildings, roads, and other structures
put in place by construction activity. This document, however, focuses solely on the impacts associated
with active construction sites. Chapters 2 and 3 provide additional information on the pollutants and
environmental impacts associated with construction site discharge to surface waters, with Chapter 2
focusing on sediment and turbidity and Chapter 3 presenting all other pollutants associated with
construction site stormwater discharges. Chapter 4 presents a review of literature documenting impacts of
construction site stormwater discharges.
EPA has established effluent limitations guidelines (ELGs) and new source performance standards
(NSPS) for stormwater discharges from the construction and development industry. These guidelines and
standards require discharges from certain construction sites to meet a numeric turbidity limit. The
guidelines and standards also require all construction sites currently required to obtain a National
Pollutant Discharge Elimination System (NPDES) permit to implement a variety of best management
practices (BMPs) designed to limit erosion and control sediment discharges from construction sites. EPA
evaluated four options in developing the final rule. These options are described below:
> Option 1 establishes minimum requirements for implementing a variety of erosion and
sediment controls and pollution prevention measures on all construction sites that are
required to obtain a permit.
> Option 2 contains the same requirements as Option 1. In addition, construction sites of 30 or
more disturbed acres would be required to meet a numeric turbidity limit in stormwater
discharges from the site. The technology basis for the numeric limit is Active Treatment
Systems (ATS). The numeric turbidity standard would be applicable to stormwater discharges
for all storm events up to the local 2-year, 24-hour event.
> Option 3 contains the same requirements as Option 1. Option 3 also requires all sites with 10
or more acres of disturbed land to meet a numeric turbidity standard based on the application
of ATS. The turbidity standard would apply to all stormwater discharges for all storm events
up to the local 2-year, 24-hour event.
> Option 4 contains the same requirements as Option 1. Option 4 also requires all sites with 10
or more acres of disturbed land to meet a numeric turbidity standard of 280 NTU based on the
application of Passive Treatment Systems (PTS). The turbidity standard would apply to all
stormwater discharges for all storm events up to the local 2-year, 24-hour event, although
only certain types of discharges would require monitoring.
EPA expects that reduced discharges of pollutants from construction sites will enhance environmental
services provided by the affected water bodies and, as a result, human welfare. Chapter 5 provides an
overview of EPA's approach to assessing and quantifying the benefits of reducing construction site
discharges to surface waters. Chapter 6 describes the methodology EPA used to quantify improvements
in surface water quality associated with each of the evaluated regulatory options. EPA used the Spatially
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Referenced Regressions on Watershed Attributes (SPARROW) method, the Dissolved Concentration
Potential (DCP) method, and information on relationships between sediment and nutrient levels in surface
waters to quantify changes in surface water levels of total suspended solids (TSS), sedimentation, total
phosphorus (TP), and total nitrogen (TN) under each regulatory option. Chapter 6 also presents the results
of this analysis. EPA found available data on the location and magnitude of other types of construction
site pollutant discharges to be insufficient for inclusion in the water quality modeling analysis.
In analyzing benefits of the regulation, EPA quantified and monetized economic benefits from reduced
dredging of navigable waterways, reduced dredging of water storage facilities (reservoirs), and reduced
drinking water treatment costs. Chapters 7, 8, and 9 describe the methods EPA used to analyze these
benefit categories and present the results of EPA's analysis. Other benefit categories, including reduced
flood risk, increases in property values, industrial water use, agricultural water use, stormwater
management system management, and commercial fishing, are discussed qualitatively in Chapters 2 and
5. EPA estimates that Options 1, 2, 3, and 4 will reduce expenditures on navigable waterway dredging by
approximately $1.3, $2.6, $3.3, and $2.9 million per year respectively. Expenditures on reservoir
dredging are expected to decrease by $1.4 million per year under Option 1, $2.9 million per year under
Option 2, $3.6 million per year under Option 3, and $3.2 million per year under Option 4. Reductions in
drinking water treatment costs are estimated to amount to $1.2, $1.8 million, $2.1 million, and $1.8
million annually under Options 1, 2, 3 and 4, respectively. Overall, EPA expects this regulation to save
governments and private entities between $3.8 and $8.9 million in these three areas each year, depending
on the policy option.
EPA also expects that reductions in pollutant discharges to surface waters resulting due to regulation will
enhance or protect aquatic ecosystems. The drop in pollutant discharges is expected to improve the
protection of resident species; enhance the general health offish, invertebrate, plant and other aquatic
organism populations; increase their propagation in waters currently impaired; and expand fisheries for
both commercial and recreational purposes. Improvements in water quality such as decreased turbidity
will also favor increased recreational activities such as swimming, boating, nature observation, fishing,
camping and other outings, as well as overall aesthetic enjoyment. Improvements associated with reduced
nitrogen and phosphorus discharges include reduced eutrophication of surface waters, fewer beach
closings, greater fisheries productivity, and greater enjoyment of water resources. Finally, EPA expects
that the regulation will augment nonuse values (values that do not depend on use by humans, see Chapter
5 for details) of the affected water resources. EPA used a meta-analysis of surface water valuation studies
to estimate the total value of nonmarket benefits (values that arise outside of market transactions, such as
recreation at publicly accessible sites) stemming from the regulation. EPA estimates that mean total
willingness to pay (WTP) for water quality improvements resulting from regulation ranges from $210
million to $413 million, depending on the regulatory option under consideration. Chapter 10 of this report
provides details on EPA's analysis of nonmarket benefits. EPA expects that nonmarket benefits resulting
from Options 1, 2, 3, and 4 will be approximately $210, $353, $413, and $361 million per year,
respectively. Combining these nonmarket benefits estimates with the avoided cost estimate produces total
benefits estimates of $214 million per year for Option 1, $360 million per year for Option 2, $422 million
per year for Option 3, and $369 million per year for Option 4.
Sufficient data were available to monetize benefits for only a subset of:
> pollutants discharging from construction sites
> impacted surface waters
> ecological services from surface waters.
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The monetized benefits estimates therefore represent only a portion of the total benefits of each of the
regulatory options. The scope of the monetized benefits analysis is discussed in more detail in Chapter
11.
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2 Overview of Environmental Impacts from Construction Site
Sediment and Turbidity Discharges
This chapter summarizes information available from the literature and other sources on the pollutants and
environmental impacts associated with construction site discharges of sediment.
Construction sites have been documented to increase pollutant discharges to surface waters in a number
of studies. Sediment and turbidity are the most thoroughly documented pollutants. This chapter discusses
the process of sediment and turbidity discharge from construction sites, their behavior in surface waters,
and their potential impacts on aquatic organisms and human use of aquatic resources. Documentation of
these discharges and impacts can be found in the literature reviewed and summarized in Chapter 4. A
number of other pollutants can also discharge from construction sites including nitrogen, phosphorus,
metals, toxic organic compounds, and others. These are discussed in Chapter 3.
Suspended and bedded sediments (collectively referred to as "SABS" or "sediment" in this document)
and turbidity are natural components of many aquatic ecosystems. Sediments contribute to the physical
structure of surface waters and help to transport nutrients and organic matter. Natural turbidity can
modulate levels of aquatic photosynthetic activity and predator-prey relationships. Undisturbed
ecosystems contain species adapted to the sediment and turbidity levels naturally associated with those
ecosystems.
At excessive levels, however, sediment and turbidity become pollutants. Modifications to the physical and
chemical composition of sediment and turbidity discharges can also transform them into pollutants.
Sediment and turbidity are the most commonly documented pollutants in construction site discharges and
impacted surface waters. In a number of documented cases, sites have discharged sediment and turbidity
at very high levels (see Chapter 4).
Although suspended sediment, bedded sediment, and turbidity are distinct and separate water quality
properties, all describe impacts associated with eroded soil discharge to surface waters. For this reason,
many studies discuss these properties concurrently, as does this document. Soil and sediment are
composed of a variety of components including organic matter, phosphorus, nitrogen, metals, and other
compounds, both natural and anthropogenic. Many of these components travel with soil as it erodes and
discharges to surface waters. These components are discussed in more detail in Section 2.2.
There are multiple terms available to describe levels of sediment and turbidity in water. Table 2-1
presents terms and definitions used in this document.
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Table 2-1: Sediment and Turbidity Terminology
Sediment Metric Description
Bedded sediment A general term for sediment that, at any given time, settles from the water column onto surfaces
within a surface water (e.g., channel bed or aquatic plant leaves) in a process commonly known as
sedimentation or siltation. Measures of bedded sediments include depth of deposition within a given
time period, percent fines, geometric mean diameter, Fredle number (a permeability index) (Berry et
al. 2003), and others.
Settleable solids A measure of the solids that will settle to the bottom of a cone-shaped container (called an Imhoff
cone) in a 60-minute period. Settleable solids are primarily a measure of particles that can be
removed from water by sedimentation. Expressed as milliliters per liter (ml/L).
Suspended sediment A general term for sediment that, at any given time, is either maintained in suspension by a surface
water's turbulent currents or that exists in suspension as a colloid.
Suspended sediment The velocity-weighted concentration of suspended sediment in the sampled zone in a surface water
concentration (SSC) defined as extending from the water's surface to a point approximately 0.3 feet above the bed. It is
determined by measuring the dry weight of all sediment from a known volume of sample. Expressed
as milligrams of dry sediment per liter of water-sediment mixture (mg/L).
Total suspended A dry weight measure of suspended inorganic and organic material in the water column. It is
solids (TSS) measured by filtering a subsample of water and measuring the weight of the dried solids. Expressed
in milligrams of solids per liter of water-solids mixture (mg/L).
Turbidity A measure of the scattering and absorption of light when it enters a water sample. The quantity of
suspended particles in water helps to determine turbidity levels as do particle shape, size, and color
distributions. Suspended particles can include clay, silt, colloids, finely divided organic and
inorganic matter, soluble colored organic compounds, plankton, and other microscopic organisms. In
this document, turbidity levels are typically expressed in nephelometric turbidity units (NTUs).
Higher NTU levels indicate more turbid water.
Surface water turbidity levels are controlled by the quantity and nature of particulate matter suspended in
the water column. This particulate matter can consist of mineral particles (sediment), algae and other
organisms, and organic detritus. Particle shape, size, and color distributions influence total turbidity levels
as well. Suspended sediment contributes to surface water turbidity. However, because several factors
beyond the mass of suspended solids in the water column control surface water turbidity, the quantitative
relationship between suspended particle concentrations and turbidity levels has been found to vary among
watersheds, surface waters, and precipitation events.
The sections below provide additional information on the nature of construction site sediment and
turbidity discharges to surface waters (Section 2.1), their behavior and transport in surface waters (Section
2.2), their impacts on aquatic ecosystems (Section 2.3), their impacts on human use of aquatic resources
(Section 2.4), appropriate levels in surface waters as delineated by water quality criteria (Section 2.5), and
the extent to which they currently impair surface waters in the United States (Section 2.6).
2.1 Sediment and Turbidity Discharge to Surface Waters
Construction activities increase soil vulnerability to erosion. Typical construction site activities include
clearing vegetation and excavating, moving, and compacting earth and rock. Vegetation removal and
surface work loosens soil, removes protective root structures, and exposes soil directly to the erosive
powers of precipitation and stormwater runoff. Soil compaction reduces precipitation infiltration and
increases overland water flow, thereby increasing the quantity of stormwater runoff available to erode
soil. In addition, stockpiled construction materials such as stripped topsoil, fill material, and soil from
foundation excavation are often placed in steep, uncovered piles vulnerable to erosion. Construction
vehicles track soil onto roadways from which it can easily wash into storm sewer drainage systems and
subsequently to surface waters. Susceptibility to erosion remains high at construction sites until soil-
disturbing activities are complete and the land surface is revegetated or otherwise stabilized.
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Precipitation events are the primary cause of construction site sediment and turbidity discharges to surface
waters. Raindrop impact energy and overland water flow detach soil particles from the land surface,
suspend them in surface flow, and transport them to other locations on the construction site or to
discharge points. Suspended soil particles in the stormwater flow create turbidity.
Sediment erosion rates are highly variable among sites and depend on a number of factors including site
topography (slope length, steepness, and shape), precipitation intensity and quantity (i.e., rainfall
erosivity), soil type (particle size, credibility, land use (vegetation cover, erosion control practices), and
nature of the construction activity. Some phases of construction activity disturb soil more than others. For
a more detailed discussion of sediment and turbidity discharges from construction sites, see EPA's
Development Document for Final Effluent Guidelines and Standards for the Construction and
Development Category (USEPA 2009b).
Mobilization of soil particles is dependent on many factors including soil particle size, soil cohesiveness,
and rainfall energy and duration. As flows grow larger and more powerful, they are able to transport
larger particles. Sand-sized and larger particles are more easily detached from the soil surface because
they are generally not cohesive. However, once mobilized, they more easily settle from stormwater runoff
because of their greater mass. Smaller particles, such as clays, are generally harder to mobilize because
they are more likely to be cohesive. Once mobilized, however, individual smaller particles are more likely
to stay suspended in stormwater flow and be transported off-site because of their lesser mass (Reed 1980).
The soil fraction composed of smaller particles tends to contain a disproportionate quantity of the organic
matter and adsorbed materials and contaminants (e.g., metals, nutrients, pesticides, and other organic
compounds) found in soils. Smaller particles also contribute disproportionately to turbidity levels.
Suspended sediment and turbidity levels in construction site stormwater flows can be very high.
Suspended sediment concentrations up to 160,000 mg/L in construction site stormwater have been
documented (Daniel et al. 1979; Horner et al. 1990; Warner and Collins-Camargo 2001; Hedrick et al.
2006; USEPA 2009b). Turbidity levels up to 30,000 NTU have been documented (Lubliner and Golding
2005; Bhardwaj and McLaughlin 2008). These figures reflect suspended sediment and turbidity levels
prior to treatment on-site and/or prior to discharge to and dilution in surface waters.
In addition to elevated stormwater sediment and turbidity concentrations, stormwater runoff volume can
also increase on construction sites (Yorke and Davis 1972; Selbig et al. 2004; Clausen 2007; Line and
White 2007; Selbig and Bannerman 2008; Montgomery County DEP 2009) (see Chapter 4).
The path stormwater travels varies among construction sites. Stormwater can infiltrate soil, flow over
land, or travel through underground storm sewer systems. Vegetated areas can provide opportunities for
stormwater and pollutant capture on the land surface whereas paved surfaces tend to efficiently transport
stormwater downslope. Storm sewer systems can also very efficiently move water away from
construction sites (and into surface waters). Storm sewer systems are often installed early in site
development when large areas of earth are still disturbed and highly prone to erosion (NRC 2008).
Distance to surface water also varies among construction sites. Some sites are far from surface waters,
whereas others are adjacent to or, in some cases, directly in water (e.g., bridge construction, stream
channelization). Longer travel paths prior to surface water discharge can provide more opportunities for
stormwater and pollutant capture (Yorke and Herb 1978).
The combination of elevated sediment concentrations and elevated runoff volume results in higher total
export of sediment from a site. Erosion is a natural process; however, sediment yields from construction
sites can be many times higher than those from agricultural, forested, and mature developed sites.
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Forested watersheds in the United States are estimated to yield 0.02 to 1 tons/acre/year of sediment.
Cropland in the United States is estimated to yield 0.65 to 15 tons/acre/year (Vice et al. 1969; Yorke and
Herb 1978; Osterkamp et al. 1998; Faucette et al. 2007). Paul and Meyer (2001) state that construction
activity generally increases sediment yields 100 to 10,000 times over those from forested areas, with
larger increases possible in basins with steep topography. Studies summarized in Table 4-2 report
sediment yields of 0.009 to 219 tons/acre/year from catchments containing construction. All studies of
construction site sediment yield report that construction activity increases sediment discharges from sites.
Because of the importance of precipitation and its subsequent flow over land to the transport of soil, most
sediment and turbidity discharges take place during or shortly after precipitation events. Once a
precipitation event ceases, discharges from construction sites generally cease within a relatively short
time period unless site terrain or stormwater management systems, such as stormwater ponds, attenuate
discharge flows. This dynamic creates an intermittent discharge of pollutants from most construction
sites.
In addition to being an episodic discharger of pollutants, construction is a temporary activity at any one
site that typically lasts several months to several years. Individual construction sites are therefore transient
sources of pollutant discharges to surface waters. Sediment discharges from the land surface to surface
waters due to active construction at an individual site are greatly reduced once active construction ceases
and site soils have been stabilized (e.g., through revegetation or paving).
Surface water impacts such as elevated turbidity and suspended sediment levels generally cease
immediately downstream of construction sites soon after site discharges cease. Other impacts, however,
persist beyond the lifespan of individual precipitation events, individual construction sites, or even the
presence of construction activity in a watershed. This is due to the persistence of sediments and some
associated pollutants in surface waters as well as longer-term impacts on aquatic organism communities.
In addition, most construction activities in the United States are concentrated in a relatively small number
of watersheds during any single decade (see Chapter 6). Within these watersheds, the location of
individual construction sites changes from year to year, but the watershed's total annual construction
acreage remains elevated for a number of years until the watershed is "built out." Surface waters draining
these watersheds therefore experience a persistent, elevated level of impact from construction activity for
several years, despite the transient nature of individual sites in the watershed.
Sediment and turbidity discharges can also take place during dry weather at some construction sites.
Dewatering of site depressions and foundation excavations, slope failure, attenuated drainage from
stormwater basins, construction equipment operation or other activity directly in or near surface waters
(e.g., channelization, pipeline crossing, culvert emplacement, bridge construction), vehicle and other
construction equipment washing, 6ndscape irrigation, and overland flow from groundwater seeps can
create discharges during dry weather. Erosion of bare ground due to snowmelt in the spring can be high
(NRC 2008). Construction activity can also destabilize slopes under both dry and wet conditions. If
situated sufficiently close to a waterbody, slope failure can result in mass loading of sediment and
associated turbidity.
Requirements for construction site erosion and sediment control have gradually increased since the 1950s.
EPA, the U.S. Federal Highway Administration, the U.S. Federal Energy and Regulatory Commission,
the U.S. Department of Agriculture's Soil Conservation Service, states, counties, municipalities and other
entities have issued a variety of regulations and guidance. EPA has previously issued requirements for
construction sites under the National Pollutant Discharge Elimination System (NPDES) stormwater
program. Phase I of the stormwater program was promulgated in 1990 and addresses large construction
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activities disturbing 5 or more acres. Phase II of the stormwater program was promulgated in 1999 and
addresses construction sites disturbing 1 to 5 acres. EPA's Development Document for Final Effluent
Guidelines and Standards for the Construction and Development Category (USEPA 2009b) provides
additional information on the history of construction site erosion and sediment control requirements.
Under current practice, many construction site discharges are moderated to some degree by a variety of
sediment erosion and stormwater discharge control practices. Practices include the use of sedimentation
basins, silt fences, vegetative filter strips, grass swales, check dams, erosion control blankets, straw bale
barriers, gravel bag berms, sand bag barriers, straw mulch, hydraulic mulch, wood mulch, soil binders,
geotextiles and mats, rock filters, earth dikes and drainage swales, velocity dissipation devices,
sedimentation traps, and other methods. These practices and others are discussed in detail in EPA's
Development Document for Final Effluent Guidelines and Standards for the Construction and
Development Category (USEPA 2009b).
2.2 Sediment and Turbidity Behavior in Surface Waters
Sediment and turbidity movement within surface waters is highly variable. Factors influencing sediment
and turbidity movement and persistence in surface waters include the intensity, quantity, and composition
of sediment and turbidity discharges and the nature of the receiving waters. Important waterbody
characteristics include type, size, and flow rate.
Sediment discharges from construction sites typically contain a large proportion of inorganic material that
can persist in surface waters for long periods of time. Under appropriate conditions (e.g., anaerobic),
organic material in construction site discharges can also persist. For these reasons, impacts from
construction site discharges can last beyond the life span of a single precipitation event, an individual
construction site, and of the presence of construction activity in a watershed (Yorke and Herb 1978).
Several researchers have stated that long-term monitoring beyond the cessation of a construction project
is necessary in some cases to fully document its impacts (Barton 1977; Taylor and Roff 1986; Chen et al.
2009; Lee et al. 2009).
While in the surface water network, sediments can cycle many times between suspension in the water
column, where they contribute to turbidity levels, and deposition on waterbody beds. This process
depends on surface water currents and other disturbances. Larger sediment particles are more likely to
settle on surface beds, and smaller particles are more likely to remain suspended in the water column and
contribute to surface water turbidity. Because of this dynamic, larger particles tend to take longer to move
through surface water systems than smaller particles.
Construction sites discharge sediment and turbidity to all major surface water categories: wetlands;
streams and rivers; lakes, reservoirs, ponds, and other impoundments; and estuaries, bays, and other
coastal waters. Some waterbodies have flow regimes and physical structures that allow them to purge or
absorb excess sediment and turbidity inputs within relatively short time frames. Other surface waters
allow excess sediment and turbidity to persist for long periods of time. The ability of individual surface
waters to transport sediment varies as precipitation and other factors modify the nature of their flow.
Surface waters also vary widely in their size relative to construction site discharges. Larger surface waters
generally have more capacity for dilution of pollutant discharges. Sediment transport in several surface
water types are discussed in more detail in Section 2.2.
Sediments and turbidity migrate with surface water flow downstream and therefore affect waters beyond
the initial receiving water. Migration of construction sediment typically benefits the initial receiving water
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but impacts downstream waters. Several studies have documented improvements in stream conditions
once construction site sediment and turbidity discharges cease and accumulated sediments migrate
downstream from the initial point of entry. The sediments, however, remain within the surface water
network and are redistributed to new waterbodies downstream. Because of sediment's ability to persist
and migrate downstream, surface waters downstream of a watershed containing a consistent level of
construction activity from year to year can experience a relatively consistent level of impact from
construction sediment and turbidity discharges, even though the timing of individual precipitation events
and the locations of individual construction sites within the watershed change from year to year.
2.2.1 Sediment Characteristics Affecting Surface Water Transport
Important sediment characteristics that influence transport and fate include the size, shape, density, fall
velocity, and concentration of sediment particles (Shen and Julien 1993). Multiple size scales exist. Table
2-2 presents the broad size categories of one scale.
Table 2-2: Sediment Grade Scale
Category
Size range (mm)
Boulders,
Cobbles
64 - 4,000
Gravel
2-64
Sand
0.062-2
Silt
0.004-0.062
Clay
0.00024 - 0.004
Source: Julien (1995).
Sediment size is also loosely discussed in terms of "fine sediment" and "coarse sediment." Fine sediment
consists primarily of particles smaller than 0.85 mm. Coarse sediment consists primarily of particles from
0.85 to 9.5 mm (USEPA 2006b). Particles smaller than 1 micron (0.001 millimeter) in diameter are
sometimes referred to as colloids.
Sediment samples rarely contain particles of a single size. Particle size distributions describe the
percentage by weight of sediment materials in each size category for a given sediment sample.
Particle size helps to determine how quickly a particle will settle out of suspension in the water column
onto the bed of a waterbody. The fall or settling velocity of sediment particles can be estimated using a
form of Stokes' law (Julien 1995; Chapra 1997):
(Eq. 2-1)
Where:
co = settling velocity (em's"1)
a = dimensionless form factor accounting for geometry (a=l for sphere)
g = gravitational acceleration (g=981 cm»s"2)
ps = density of sediment particle (g»cm~3)
pw = density of water (g» cm"3)
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/um = dynamic viscosity (g'cm'^s"1)
ds = particle diameter (cm)
This formula indicates that settling velocity increases as particle size increases, assuming all other factors
are equal. Stokes-type settling is most directly applicable to the behavior of sediment in detention basins
and some reservoirs and lakes, in which flow velocities are low and turbulent energy in the water column
is minimal. In streams and rivers, settling velocity operates in conjunction with turbulent energy affecting
particle suspension to determine sediment settling dynamics. Since turbulent energy is required to offset
the force of gravity (settling) in order to keep a particle in suspension, a greater amount of turbulent
energy is required to suspend larger, heavier particles than for smaller particles.
The degree to which a particle remains suspended helps to determine the degree to which it will be able to
move with water flow within a surface water or whether it will be deposited on a surface water bed. It
also determines whether or not a sediment particle will contribute to surface water turbidity, since only
suspended particles increase turbidity levels. Particles smaller than 0.063 mm (silt and clay) tend to
remain suspended in flowing freshwater systems and are the primary contributors to water turbidity
(USEPA 2006b). However, small sediments can also be transported in the aquatic environment in the
form of aggregates bound together by living (e.g., bacteria and algae) and nonliving (e.g., organic detritus,
extra-cellular polymeric substances) material (Bilotta and Brazier 2008). These aggregates have transport
behaviors closer to particles coarser than the particles composing the aggregate. Coarser particles are
more likely to settle from the water column, with the coarsest particles settling closest to their discharge
point to surface water.
The sections below provide additional information on transport dynamics associated with several surface
water types.
2.2.2 Sediment and Turbidity Behavior in Specific Waterbody Types
2.2.2.1 Sediment and Turbidity in Streams and Rivers
A distinguishing characteristic of streams and rivers is their strong, primarily unidirectional flow. Their
transport of sediment is predominantly controlled by stream transport capacity and sediment
physiochemical characteristics and supply rate. Larger sediments generally experience more episodic
movement over longer time scales through watersheds. Smaller sediments generally move more
continuously and within a shorter time scale. This difference is due to the fact that larger sediments rely
on larger, more powerful flows for transport, which occur episodically and less frequently than flows able
to move smaller particles.
Sediments transported by river and stream channels are typically described as bed load and suspended
load. The boundary separating these categories changes with flow conditions. Sediments not in transport
at a given time are often referred to as bedded sediments. If flow conditions change, these sediments can
become bed load or suspended load. Sediment particle size is the primary distinguishing factor among
these categories, with the largest particles deposited as bedded sediments, larger particles moving as bed
load, and finer particles moving as suspended load. Total sediment load consists of the sum of bed load
and suspended load.
Bed load consists of the movement of particles along the streambed by rolling, sliding, and a hopping
process known as saltation which involves the brief suspension of sediment particles by turbulent flow.
Particles moving as bed load often consist of sand and coarser size fractions. Bed load movement is
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intermittent in most settings, and bed load particles may not move for long periods between high flow
events.
Suspended sediment load is the movement of sediment particles supported by turbulent motion in stream
or river flow and often consists primarily of clay and silt size particles. Suspended sediment (and the
turbidity it creates) move more quickly downstream with streamflow than bed load from a given
discharge point. If the suspended sediment input to the stream or river is a single pulse, rather than
continuous, the stream or river can often move it downstream within a relatively short time period.
Several hydraulic and geomorphologic factors determine stream transport capacity including channel
width, flow depth and cross-sectional geometry, bed slope and roughness, and discharge velocity and
volume. In general, the more turbulent energy available for suspension and mobilization of sediment, the
greater the sediment transport capacity per unit of stream width and the larger the size of sediment
particles that can be moved. Several empirical formulas have been developed to estimate sediment
transport capacity on the basis of flow- and channel- related variables. One example, developed by
Simons et al. (1981), takes the form of a power law:
qs=Cl-hc>-Vci (Eq.2-2)
Where:
qs = sediment transport per unit stream area (ft2/s)
h = depth of flow in ft
V = flow velocity in ft/s
ci, c2, c3 = empirical coefficients calibrated to reflect channel slope (gradient) and median
particle size diameter.
The unit transport capacity is strongly related to flow velocity (V). Higher velocity flows are able to move
more sediment. Channels with lower stream gradients have, for a given volume of stream flow, lower
stream water velocities which allow more time for settlement of sediment in that channel. Many, if not
most, of the hydraulic factors controlling sediment transport capacity, including channel geometry, depth,
slope, and velocity of flow, vary in time and space within a given river system.
Many North American rivers and streams possess a strong seasonal discharge cycle with spring discharge
volumes typically many times larger than those of late summer and autumn flows. Intense or prolonged
rainfall events can also generate flood pulses of hourly to daily duration, which often have significant
turbulent energy. In addition, as Equation 2-2 indicates, sediment transport capacity is a nonlinear
function of flow-related variables, so large flows have significantly greater transport energy. The
movement of sediments, both as bed load and as suspended load, is thus highly nonuniform in time for
most river systems. The majority of annual sediment flux, particularly the movement of coarse or highly
cohesive sediment particles, may occur over a relatively short period of time during a single flood event.
Between such events, sediments are typically stored within the stream or river channel. Episodic
movement and deposition in stream channels between periods of movement has been documented for
sediments in watersheds whose total sediment load has been substantially increased by construction
activity. Sediment inputs from construction sites can outpace the immediate transport capacity of the
stream and may not migrate downstream until a major flow event occurs (Lee et al. 2009).
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Erosion and deposition of sediments within a river course also exhibit spatial patterns strongly related to
stream morphology. River reaches with smaller cross-sectional flow area, steeper slopes, and higher flow
velocities discourage the deposition of sediments. These traits tend to be characteristic of smaller streams
and rivers in upper elevation catchments, often at the headwaters of larger watersheds. These higher-
gradient streams may decrease their construction-associated sedimentation levels more quickly than other
aquatic ecosystems due to the occurrence of high flows, particularly in spring or after large storms, that
can resuspend and transport finer sediments downstream. Assuming cessation of additional sediment
input upstream, these stream dynamics may eventually restore a naturally coarse-grained channel bed
(Barton 1977; Berry et al. 2003), though some sediment may continue to persist in low-energy areas of
the stream (e.g., shallow side pools). By contrast, wider channels with lower bed slopes and flow
velocities act as regions of relative sediment deposition. Channel bottoms may be covered with finer
sediments, in contrast to the exposed rocks, boulders, and gravels seen in the channel beds of higher-
energy streams and rivers. Natural sediment deposition is more characteristic of channels at lower
elevations in a watershed.
Stream and river hydraulic and geomorphologic variables provide one set of controls on sediment
transport capacity. Sediment transport is also be regulated by the rate and quality of sediment supply
(Julien 1995). Sediment supply can outpace, match, or fall below the ability of a channel to transport it.
Within a particular reach, sediment fluxes can originate from land surface erosion, streambank erosion,
upstream reach sediment input, or remobilization of sediments previously deposited within the reach.
Channels whose sediment supplies outpace their transport capacity will accumulate sediments. The size of
a channel can decrease as sediments accumulate, increasing the likelihood of flooding and other overbank
flow events. Channels with sediment supplies falling below transport capacity will work to mobilize
additional material from channel beds and banks.
In all streams, sediments are preferentially deposited in regions of low-energy flow, including pools and
the inside of bends (Chapra 1997). If sufficient quantities of sediment are deposited, the deposition
features can alter channel morphology and flow patterns, obstruct flow, and exacerbate flood events.
Increased sediment supply during construction activity has converted some naturally meandering streams
to braided or straighter, more channelized forms (Paul and Meyer 2001). Fine sediments deposited on
stream and river beds may also impede water exchange with groundwater sources (both recharge and
discharge) (USFWS 1998). Sediment deposits can also provide substrate for the growth of plants in
channels in locations where they would normally not occur. King and Ball (1964) and Taylor and Roff
(1986) documented this effect downstream of highway construction sites.
Individual sediment deposits are often not permanent features of streams and rivers, since they can be
scoured and moved downstream during major flow events. Streams and rivers can also flow outside their
normal channels during major flow events and deposit sediments on low-lying areas adjacent to the
channel such as banks, floodplains, and terraces. These sediments may, at a later time, be remobilized
during an even larger flow event.
Lee et al. (2009) documented that watersheds undergoing construction activity may take many years or
even decades to move sediments discharged from construction sites fully through watersheds. Sediment
yields from larger watersheds may therefore remain elevated for some time after the implementation of
enhanced sediment and erosion control measures and after the completion of most construction in the
watershed.
Within the time scale of a single precipitation event, a certain amount of time is also necessary to move
suspended sediment and turbidity from its original point of entry into the surface water network to
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downstream waters. If construction is occurring primarily in the headwaters of a watershed, turbidity and
suspended sediment levels immediately downstream of construction sites will often decline within
relatively short periods of time following the cessation of precipitation events (assuming discharge from
the site is primarily precipitation-driven and not significantly attenuated). Turbidity and suspended
sediment levels further downstream, however, can remain elevated even after flow levels return to normal
because of the time required for their transport downstream.
An additional dynamic influencing short-term observation of impacts from upstream construction activity
is that levels of turbidity and sediment deriving from construction activity tend to decrease as they move
downstream from a construction site through the surface water network. This decrease is due to sediment
deposition during transport and dilution by waters containing lower levels of sediment and turbidity than
construction site discharges (Wolman and Schick 1967; Lee et al. 2009).
2.2.2.2 Sediment and Turbidity in Lakes, Reservoirs, and Ponds
A number of lakes, ponds, and reservoirs have a unidirectional flow component and therefore have some
of the basic dynamics described for rivers and streams. However, most lakes, ponds, and reservoirs have
lower flow velocities, greater depth of flow, and longer water residence times than streams and rivers and
therefore act as deposition zones (sinks) for sediments. Longer flow residence times also mean that
influxes of turbid water can linger for longer periods of time than they would in a stream or river.
Residence times vary widely among lakes, ponds, and reservoirs.
The lake and reservoir flow environment more closely approximates the still-water conditions under
which Stokes' law (Section 2.2.1} applies to sediment particles to predict settling velocity. The
assumption of Stokes-type settling is often used to predict the rate of sedimentation in lakes and
reservoirs by comparing the time required for a particle to settle with the particle's transit time through
the waterbody. Several surface water characteristics influence settling and transit times, including size,
shape, depth, and regulation of outflow (Chapra, 1997). These characteristics vary widely among lakes,
ponds, and reservoirs.
Particle transit time also varies with flow. Higher flows generally create shorter transit times as higher
volumes of water move more quickly through a surface water. Higher flows often transport both coarser
particles, which are more likely to settle in a lake, pond, or reservoir, and large quantities of fine
sediments, which may not have sufficient time to settle during a higher flow period. Sediments unable to
settle in lakes, ponds, and reservoirs due to insufficient settling time or turbulence from water flow, wind,
or human activity can continue their transport downstream.
Given sufficient residence time for incoming flows, however, these waters can remove significant
quantities of sediment and turbidity from incoming waters (Barton 1977). The deposition process
decreases sediment and turbidity loads to streams and rivers and other surface waters downstream
(Renwick et al. 2005; Lee et al. 2009), though it increases sedimentation in the lake, reservoir, or pond.
Over time, sediment accumulation reduces a waterbody's volume and decreases its capacity for sediment
removal.
Sediment deposition in lakes and reservoirs often begins with the formation of deltas at the point of water
inflow, where incoming stream flow decelerates and the heaviest particles settle (Julien 1995).
Turbulence from wind, currents, and human activity can keep finer sediments in suspension, creating a
deposition pattern called focusing in which coarser particles are deposited in shallower waters and finer
particles in deeper waters, often in the centers of lakes (Chapra 1997). Given sufficient sediment
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deposition, ponds and shallow areas in lakes and reservoirs may be transformed into wetland
environments.
2.2.2.3 Sediment and Turbidity in Wetlands
Wetlands are natural sediment deposition zones. Water flow volumes and velocities are smaller than in
most other surface water types, allowing time for settling of sediment from the water column. Because of
lower flow-through volumes and speeds, influxes of turbid and sediment-laden water typically remain for
a longer period of time in a wetland than they do in a stream or river channel.
Wetland ecosystem structure is heavily influenced by the type of vegetation a wetland supports, which in
turn is influenced by water and sediment distribution in the wetland. Elevated sedimentation levels can
change the type of vegetation able to persist in a given wetland, with consequences for the organisms it no
longer supports. In severe sedimentation cases, excess sediment may partially or completely fill in a
wetland, creating dry land conditions.
2.2.2.4 Sediment and Turbidity in Estuaries
Estuaries are like lakes and reservoirs in that they vary widely in benthic geometries, residence times,
flushing rates, vertical mixing, stratification, wave exposure, and other factors that govern sediment
transport and deposition. Estuarine flows transition first from unidirectional turbulent channel flow
controlled primarily by topographic gradient and discharge rate to a tidal river reach zone in which
downstream flow is influenced by the tidal cycle. The flow regime transitions again in the estuary proper,
in which water discharge and tidal forces offset each other. Flow regime changes again in the bay or open
ocean where tidal, wave, or a combination of these forces dominate.
As turbidity and sediment-laden freshwater decelerates and encounters tidal cycles in the estuary, a null
zone is formed in which channel discharge and tidal action largely cancel each other, favoring the
deposition of suspended sediment (Chapra 1997). In addition, increasing salinity levels favor flocculation
of fine sediments. Large deltas may form where rivers deposit sediments in coastal waters. Sediment
deposited in estuaries can be disturbed and redistributed due to natural events (e.g., floods, high winds,
tidal action) or by human activity (e.g., dredging).
2.3 Aquatic Life Impacts of Sediment and Turbidity
Numerous aquatic ecosystem impacts from construction site discharges have been documented (see
Chapter ¥).This section summarizes studies of aquatic organism and ecosystem impacts associated with
elevated sediment and turbidity levels in surface waters. EPA has reviewed available literature on the
biological effects of suspended and bedded sediments (SABS) and turbidity. This review is not an
exhaustive summary of the available literature, which is extensive, but instead provides an overview of
more commonly noted impacts.
A variety of organisms, including aquatic plants, invertebrates, amphibians, and fish, are affected by
elevated sediment and turbidity levels. High levels of sediment and turbidity affect aquatic ecosystems by
reducing photosynthetic activity, reducing food availability, burying habitat, and directly harming
organisms. Organisms may relocate, sicken, or die. Organism loss can alter the composition of the aquatic
community.
Both the magnitude and duration of sediment and turbidity exposure are important. Organisms vary in
their ability to tolerate and recover from exposure. The proportion of organisms able to tolerate (or
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escape) periods of elevated sediment and turbidity levels can increase in impacted surface waters, while
the proportion of sensitive species declines.
The appropriate level of sediment or turbidity varies from waterbody to waterbody. Some aquatic
ecosystems contain organisms adapted to higher levels of sediment or turbidity (e.g., some large coastal
floodplain rivers), whereas other ecosystems contain organisms adapted to lower levels of sediment or
turbidity (e.g., alpine lakes, headwater streams). Smaller streams tend to have naturally clearer water,
particularly those in forested watersheds. Short-term increases in suspended sediment and turbidity levels
can naturally occur during spring thaws, storms, and other high flow events. However, even organisms
adapted to sediment or turbidity influx (whether episodic or constant) can be harmed if input levels rise
excessively and/or if their resiliency is taxed by other stressors.
A construction project can change natural sediment and turbidity dynamics by elevating sediment and
turbidity levels significantly beyond those associated with natural events, for longer periods of time, and
at times when an aquatic ecosystem and its organisms are unaccustomed to receiving such inflows (e.g.,
late summer low flow periods). Some waterbody types are better able to flush excess suspended sediment,
turbidity, and deposited sediment (e.g., high energy streams), whereas others may retain accumulated
sediments for years (e.g., lakes and wetlands) (see Section 2.2).
Sediment impacts have been researched through both laboratory dose-response and in-stream field
studies. Much research has been done on the effects of sediment on fish (salmonids, in particular, because
of their economic importance and sensitivity). More studies have been conducted on suspended sediment
versus bedded sediment effects on organisms. Stream and coral reef habitats have been studied more
intensively than river, lake, and estuarine habitat, though available data indicate that biota sensitive to
elevated sediment levels exist in all of these environments. Many habitats with moderate and variable
levels of sediment also need additional research (Berry et al. 2003).
Though not addressed in detail in this discussion, sediments and turbidity can also affect chemical, fungal,
and microbial decomposition processes in aquatic ecosystems. Depending on the source and nature of the
sediments, sedimentation can change the organic content of surface water sediment, which can alter
fungal and microbial community activity. Rapid sediment deposition over an organic sediment layer can
also cause a shift to anaerobic conditions in the isolated strata and an accompanying shift in microbial
metabolism, methane generation, and nutrient dynamics (Tornblom and Bostrom 1995). In wetlands,
depressed levels of algal and microbial biomass and density can indicate chronically elevated
sedimentation levels (USEPA 1995).
The studies cited in this section attribute observed impacts to sediment and turbidity discharges in
general, rather than to the specific source materials from which the sediments and turbidity derived. The
discussion in this section provides a qualitative summary of the types of organism impacts associated with
elevated sediment and turbidity levels. Berry et al. (2003) discuss the possibilities, given available data,
for determining quantitative relationships (e.g., dose-response models) between sediment levels and
organism responses. For most organisms, there is insufficient information currently available to create
complete dose-response models (Berry et al. 2003). A model for clear water fish is discussed in Section
2.3.3.
The examples below discuss effects of elevated sediment and turbidity levels acting on organisms in
isolation. However, many construction sites have been documented to discharge other pollutants in
addition to sediment and turbidity such as nitrogen, phosphorus, metals, and other organic and inorganic
compounds (see Chapter 3). A number of these other pollutants travel with sediment as it erodes and
moves through the surface water network. In addition, many construction sites discharge to surface waters
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already impacted by stressors including pollutant discharges from other sources, invasive species, and
flow modification. Interactions among sediment, turbidity, and other stressors and their cumulative effects
on aquatic organisms have not been fully characterized (Berry et al. 2003).
Documented effects and relevant studies are organized in the discussion below by the type of aquatic
organism studied (primary producer, invertebrate, fish, and other wildlife) and by the type of organism
reaction. A section specific to threatened and endangered species follows this discussion (Section 2.3.5).
2.3.1 Primary Producers
Primary producers, including algae, phytoplankton, submerged aquatic vegetation, and other macrophytes
(plants with large leaves), are found in most aquatic ecosystems. Aquatic ecosystems vary in the degree to
which they derive energy and resources from primary producers. Some systems (e.g., small streams in
forested watersheds) derive a large proportion of their energy from external sources (e.g., leaf debris)
(Bilotta and Brazier 2008). Other systems are heavily dependent on the productivity of primary producers
(e.g., sea grass beds).
Primary producers can grow in a variety of forms: rooted to surface water substrate, free-floating, or
attached to rocks, aquatic plants, or other structures. The term periphyton refers to the algae, small plants,
bacteria, microbes, and detritus attached to submerged surfaces in aquatic ecosystems.
Primary producers transform sunlight into energy and provide food for other aquatic organisms. Aquatic
macrophytes and algae influence water column chemistry, including dissolved oxygen, pH, and nutrient
levels; provide important habitat for many organisms; and reduce waterbody flow velocity. Loss of algae
and macrophytes due to elevated sediment and turbidity levels can compound these pollutants' effects
because fewer plant structures are available to slow water flow and facilitate settling of suspended
sediment from the water column. This dynamic can allow elevated suspended sediment and turbidity
levels to persist further downstream (Wood and Armitage 1997).
Turbidity is an important parameter for aquatic ecosystems because of its influence on the compensation
point (the depth at which carbon production from photosynthesis equals consumption through respiration
in aquatic plants). A decrease in a surface water's compensation point can translate into a decline in an
aquatic ecosystem's primary producer community or a shift in its species composition. These changes can
affect the ecosystem's overall species composition, productivity, and health.
Impacts to primary producers have been noted in some studies of construction site impacts to surface
waters. Construction sites documented in these studies were discharging elevated levels of sediment and
turbidity. King and Ball (1964) documented a decline in primary productivity levels. Cline et al. (1982)
noted an increase in periphyton sediment content and a decline in periphyton abundance and algal
diversity.
Several ways in which turbidity and sediment affect primary producers are described below.
2.3.1.1 Light Reduction
The growth and distribution of macrophytes, algae, phytoplankton, and coral zooxanthellae can be limited
by excessive turbidity (Berry et al. 2003). Macrophytes with leaves that emerge above the water's surface
are much less affected by reduced light penetration than submerged species. Reduced primary production
due to light limitation from elevated turbidity is a common impact that has been documented by
LaPerriere et al. (1983), Rivier and Seguier (1985), and Lloyd (1987) (all as cited in Waters 1995), Meyer
and Heritage (1941) and Edwards (1969) (both as cited in Kerr 1995).
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LaPerriere et al. (1983) found that moderate turbidity levels of approximately 170 NTU reduced oxygen
production in a stream by 0.08-0.64 g/m2 per day relative to clear water conditions. Above 1,000 NTU,
primary production was undetectable. Lloyd (1987) developed a model relating turbidity and primary
production. The model indicated that in a clear, shallow stream, a turbidity increase of 5 NTU decreased
primary production 3 to 13 percent. A 25 NTU increase reduced primary production up to 50 percent. The
study documented stronger effects from turbidity in lakes due to greater water depths and the greater
importance of the phytoplankton community. Quinn et al. (1992, as cited in Bilotta and Brazier 2008)
found a 40 percent reduction in phytoplankton biomass exposed to suspended sediment concentrations of
lOmg/L for 56 days.
Guenther and Bozelli (2004) investigated whether lower light levels or increased sinking of
phytoplankton due to binding to sediment particles was the cause of their reduced photosynthetic activity
in turbid waters. The authors identified lower light levels as the primary cause.
Stony corals typically live in clear, oligotrophic waters where their symbiotic association with
photosynthetic zooxanthellae provides more than 100 percent of the coral's daily metabolic carbon
requirements (Muscatine et al. 1981; Grottoli et al. 2006). Corals exposed to elevated turbidity levels have
reduced photosynthesis rates and must compensate for this loss of resources (Philipp and Fabricius 2003).
Sediments can also reduce photosynthetic activity by settling on and coating macrophytes and periphyton.
Even a thin layer of sediment can block enough light to inhibit the growth of algae attached to surface
water substrates (Welsh and Ollivier 1998). Lower primary production by macrophytes and periphyton
can result in their decline and replacement with suspended algal communities. A shift in primary producer
community composition can alter a surface water's invertebrate and fish community composition.
2.3.1.2 Direct Physical Damage
Algae and aquatic macrophytes can suffer physical damage from elevated suspended sediment levels
(Waters 1995). Lewis (1973, as cited in Kerr 1995) conducted an experiment in which suspended coal
particle concentrations greater than 100 mg/L caused severe abrasive damage to the leaves of the aquatic
moss Eurhynchium riparioides over a period of 3 weeks. The damage substantially lowered the moss's
ability to produce chlorophyll and photosynthesize. Periphyton is also susceptible to being scoured from
stream substrate by suspended sediment particles (Welsh and Ollivier 1998). Francouer and Biggs (2006)
investigated the interaction of flow velocity and suspended solids in benthic algal communities and found
that high suspended sediment concentrations further increased algae removal above that due to flow
alone. Some taxa were more susceptible to removal than others. The results indicated that suspended
sediment scour may be an important mechanism for algae removal during flood events and that some
variability in biomass removal among flood events and benthic algal composition may be the result of
differences in suspended sediment load. Birkett et al. (2007, as cited in Bilotta and Brazier 2008) found
that suspended sediment levels of 100 mg/L stimulated periphyton growth and filament length under low
flow conditions, but levels of 200 mg/L significantly reduced biomass and filament length.
Macrophytes, algae, and periphyton can also be buried and damaged or killed by excessive sedimentation,
with different species having varying abilities to cope (Berry et al. 2003). Some organisms can outgrow
sediment damage, though this growth may consume additional organism resources. A reduction or
complete elimination of periphytic material and a reduction in component diversity due to elevated
sediment levels is described by Van Nieuwenhuyse and LaPerriere (1986), Pain (1987) (both as cited in
Waters (1995), and Samsel (1973, as cited in Kerr 1995).
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2.3.1.3 Substrate Modification
Sediment deposition in surface waters can change the types of algae (Wood and Armitage 1997) and
macrophytes able to grow in a waterbody by modifying nutrient availability and substrate chemistry,
texture, stability, and, depth. In many waterbodies, the locations of macrophyte beds are highly correlated
with the spatial distribution of fine-grained sediments since these often provide better rooting substrate.
Sediment deltas that form rapidly as a result of sediment runoff to a waterbody are often susceptible to
colonization by nuisance invasive macrophyte species.
Some established plants respond to elevated sedimentation levels by extending rhizome growth upwards,
but such growth patterns are abnormal for some species and consume plant energy (USFWS 1998). In
some cases, plants may not be able to grow quickly enough to adjust to increased sedimentation. Over
time, substrate may change to the extent that it no longer supports the original primary producer
community. Wetlands are particularly vulnerable to changes in sedimentation rate.
2.3.2 Invertebrates
Aquatic invertebrates, including zooplankton, insects, crustaceans, and bivalves (e.g., mussels and clams),
are widely distributed among aquatic ecosystems and can be found in even the smallest surface waters.
They provide an important link in the aquatic food chain between primary producers and larger organisms
such as amphibians, reptiles, fish, birds, and mammals (Waters 1995).
Because many benthic macroinvertebrates are relatively stationary and have limited powers to evade
polluted waters, their abundance, diversity, and species composition is widely used as an indicator for
overall aquatic ecosystem health (USEPA 2006d). The effects of elevated sediment and turbidity levels
on invertebrates, particularly on benthic macroinvertebrates, have been the focus of a large number of
studies over the past several decades.
Elevated sediment and turbidity levels impact invertebrates by reducing their health, disease and
parasitism resistance, and abundance, as documented in literature reviews conducted by Kerr (1995),
Waters (1995), and Henley et al. (2000). The density, diversity, and structure of aquatic invertebrate
communities can change as a consequence, to contain a higher proportion of sediment-tolerant species.
Gammon (1970, as cited in Kerr 1995) finds that TSS concentrations between 40 and 120 mg/L reduced
macroinvertebrate density by 25 percent, and greater TSS concentrations reduced density by 60 percent.
Organisms intolerant of turbid waters include mayflies and other Ephemeroptera, stoneflies (Plecoptera),
caddisflies (Trichoptera), clam, and bryozoan species (Cooper 1987, as cited in Kerr 1995).
The severity of sediment and turbidity impacts on invertebrate populations is related to the intensity and
duration of exposure (Anderson et al. 1996, as cited in USEPA 2004a). Some populations are adapted to
the short-term increases in suspended sediment and turbidity levels that can occur during spring thaws,
storms, and other natural high flow events. However, high or sustained elevated levels of sediment and
turbidity can alter long-term community structure by degrading habitat, food sources, organism health,
and increasing "drift" (i.e., voluntary/involuntary release of substrate by aquatic macroinvertebrates with
subsequent transport downstream)
If disturbance to a macroinvertebrate community is intense enough, it may impact the ability of the
community to recover its former condition, particularly if sensitive organisms are eliminated from
surrounding areas, as well, or habitat has been modified to the point where it is no longer able to support
the former community (Montgomery County DEP 2009). Healthy invertebrate populations in unaffected
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parts of a surface water system can provide organisms to recolonize disturbed areas once construction
activity has ceased.
Multiple studies have documented impacts to invertebrates from construction site sediment and turbidity
discharges (King and Ball 1964; Peterson andNyquist 1972; Barton 1977; Reed 1977; Chisholm and
Downs 1978; Extence 1978; Lenat et al. 1981; Tsui and McCart 1981; Cline et al. 1982; Taylor and Roff
1986; Young and Mackie 1991; Ohio EPA 1996a, 1997f, 1998d, 1999d, 2003a, 2006b; Reid and
Anderson 1999; Fossati et al. 2001; Levine et al. 2003, 2005; Hedrick et al. 2007; Chen et al. 2009;
Montgomery County DEP 2009).
Several categories of impact identified by Kerr (1995) and Wood and Armitage (1997) are described
below.
2.3.2.1 Loss of Habitat
Increased sediment and turbidity levels in waterbodies can degrade aquatic invertebrate habitat, including
pools and interstitial spaces in waterbody substrate and wetland areas. Habitat alteration due to changes in
substrate composition can modify the distribution and density of different invertebrate species and
therefore the structure of an invertebrate community (Waters 1995; Berry et al. 2003). Sediment settles
from the water column onto the substrate to which sedentary organisms attach and also fills small crevices
in waterbody beds (interstitial spaces) where a variety of species shelter, reproduce, feed, and seek
protection from predators, high flow velocities, and low flow conditions. Large accumulations of
sediment are also anoxic at depth. When interstitial spaces fill with sediment, the microhabitat diversity of
the substrate significantly declines, as does the diversity of organisms it can support (USEPA 2006d).
Embeddedness refers to the extent to which rocks or organic debris in a surface water are covered or
sunken into fine bottom sediments and is an important physical component of stream or river habitat
(USEPA 1999). Increased embeddedness due to sedimentation indicates habitat degradation. Studies have
found high correlations between benthic invertebrate response to depth and degree of embeddedness
(Berry et al. 2003). Correlations have also been found between benthic invertebrate abundance and
substrate particle size (Waters 1995). Even small increases in sedimentation levels can impact caddisfly
pupa survival (Berry et al. 2003). Ryan (1991, as cited in Henley et al. 2000), concludes that as little as a
12 to 17 percent increase in interstitial fine sediment could result in a 16 to 40 percent decrease in
macroinvertebrate abundance.
Siltation of previously coarse substrates is also implicated in the reduction of mussel populations by Ellis
(1936) and Marking and Bills (1980) (both as cited in Waters 1995). Very thin veneers of sediment can
decrease the settlement and recruitment of some bivalve larvae (Berry et al. 2003). One study postulates
that many of the more than 30 extinct species of North American mussels became extinct due to a loss of
habitat, most likely from sedimentation of surface water substrate (Henley et al. 2000). In coral reef
systems, most coral larvae seek firm substrates and will not settle and establish themselves on shifting
sediments (Berry et al. 2003).
Invertebrates can also be indirectly affected by impacts to primary producers in an aquatic community. A
shift in primary producers can impact the structure of invertebrate community by changing food and
shelter availability and quality. As discussed in the previous section, increased turbidity and sediment
levels can adversely affect the primary producer community and change its abundance and composition.
As turbidity increases, the contribution of primary production from aquatic macrophytes may decline,
while that associated with phytoplankton comes to dominate the system. Sediments and turbidity can
adversely affect the growth, abundance, and species composition of the periphytic algal community,
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reducing food availability for invertebrate grazers that feed predominantly on periphyton. A shift in
primary producers can impact the structure of the invertebrate community by changing food and shelter
availability and quality. This can lead to shifts in the relative proportion of various feeding guilds and
habitat preferences in the resulting aquatic invertebrate community (Vannote et al. 1980; Merritt and
Cummins 1996).
2.3.2.2 Altered Movement and Increased Drifting
Movement upstream or downstream ("drift") of benthic macroinvertebrates has been found to increase
with elevated suspended sediment and turbidity concentrations (Kerr 1995; Berry et al. 2003). Increases
in invertebrate drift have been shown to be specifically related to the turbidity caused by suspended
sediments (Waters 1995). One study found that suspended sediment levels of 120 mg/L were sufficient to
cause drift (Berry et al. 2003). Rosenberg and Wiens (1978, as cited in Bilotta and Brazier 2008) found
increased benthic macroinvertebrate drift after 2.5 hours of exposure to 8 mg/L suspended sediment.
Increased drift leads to increased predation on the displaced benthic invertebrates (Waters 1995) and
causes a decline in invertebrate abundance in the impacted surface water (White and Gammon 1977, as
cited in Waters 1995). Benthic macroinvertebrate drifting downstream of construction sites for pipeline
stream crossings has been documented in several studies (Tsui and McCart 1981; Reid and Anderson
1999).
2.3.2.3 Physiological Changes
The physical effects of elevated sediment levels on invertebrate species can be severe. Sediment particles
can clog an organism's filter feeding apparatus, filtration system, respiratory system, and digestive system
(Kerr 1995), resulting in compromised health or death of the organism. Affected organisms include taxa
with fragile or rudimentary gill structures, such as stoneflies (Merritt and Cummins 1996) and organisms
that primarily graze in the water column (e.g., zooplankton). Alabaster and Lloyd (1982, as cited in
Bilotta and Brazier 2008) found that Cladocera and Copepoda gills and guts were clogged after 72 hours
of exposure to suspended sediment levels of 300 to 500 mg/L.
Most species of coral are highly intolerant of sedimentation and will expend energy to flush excess
sediments. If a coral is unable to compensate for excess sedimentation, tissues can smother and die.
Sediments can also reduce zooxanthellae photosynthesis, reduce growth rates, cause temporary bleaching,
and eventually death. These impacts can affect other parts of the coral reef food web. Consequently,
increasing sedimentation levels are associated with reductions in coral reef diversity (Rogers 1990),
alterations in community composition by growth morphology (Rogers 1990, Stafford-Smith and Ormond
1992), decreased skeletal extension rates (Dodge et al. 1974, Miller and Cruise 1995, Heiss 1996), and
reduced coral recruitment (Rogers 1990, McClanahan et al. 2002, Fabricius et al. 2003). Other coral reef
organisms, such as sponges, are thought to be sensitive to sedimentation as well (Berry et al. 2003).
2.3.2.4 Impaired Feeding Activity
Another effect of elevated suspended sediment and turbidity levels on aquatic invertebrates is a reduction
in their feeding activity or the efficiency of their feeding. Kerr (1995) noted that this impact is
predominant in filter feeding species such as mussels and clams and cited Ellis (1936), who found that
under turbid conditions, mussels and clams reject silt-laden food and, under highly turbid conditions,
close their shells completely. Waters (1995) also discussed sediment's impact on feeding, citing Ellis
(1936) and Aldridge et al. (1987), who found that sediment additions impaired feeding in three species of
bivalves. Reactions to elevated sediment levels by freshwater mussels may be species specific. Mussels
compensate for increased suspended sediment levels by increasing filtration rates, increasing the
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proportion of filtered material that is rejected, and increasing the selection efficiency for organic matter.
This process increases the metabolic cost of feeding per unit of food and decreases resources available for
growth and reproduction.
Species that have evolved in turbid environments may be better able to select between organic and
inorganic particles during feeding. For example, one study found that a mussel from rocky coastal
environments (Mytilus californianus) was more sensitive to elevated suspended sediment levels than a
mussel of the same genus from a bay environment (Mytilus edulis), which is typically more turbid (Berry
et al., 2003). Many endangered freshwater mussel species evolved in fast flowing streams with
historically low levels of suspended sediment. Compared to other species that evolved in more turbid
environments, such rocky intertidal habitat species may not be able to differentiate between organic and
inorganic particles as well.
Light attenuation due to elevated turbidity can reduce feeding efficiency of invertebrates. Copepods and
daphnids have been found to reduce feeding activity in response to elevated suspended sediment levels
(Berry et al. 2003). Sediment coatings on macrophytes and periphyton can reduce their quality as food
sources because herbivores must consume elevated levels of sediment with the plant material (Ryan
1991).
Kerr (1995) cited three studies (Paffenhofer 1972; Appleby and Scarratt 1989; Kirk 1992) that found
reduced growth rates in invertebrates subjected to elevated sediment levels due, potentially, to reduced
feeding activity and/or reduced food value. Graham (1990, as cited in Waters 1995) finds that a decrease
in the percentage of organic matter in periphytic material may result from additional sediment particles
binding to the periphyton.
2.3.2.5 Direct Mortality
Sediment can directly or indirectly increase invertebrate mortality levels. Forbes et al. (1981, as cited in
Kerr 1995) found that elevated suspended sediment levels increased amphipod (shrimp-like crustacean)
mortality. Henley et al. (2000) concluded from a literature review that increased sediment concentrations
have a negative effect on the survival rates of freshwater mussels with the magnitude of the impact being
species specific. Robertson (1957, as cited in Bilotta and Brazier 2008) found the survival and
reproduction of Cladocera to be harmed by 72 hours of exposure to suspended sediment concentrations of
82 to 392 mg/L.
Organisms can also be buried and smothered by heavy sedimentation. Large sediment accumulations
become anoxic at depth. Species vary in their ability to evade burial under moderate sedimentation
deposits. Sediment grain size, depth, and bulk density and species motility, living position, and tolerance
of anoxic conditions during burial affect this ability (Berry et al. 2003).
Sediment organic matter is an important food source for many benthic macroinvertebrates. A number of
toxic pollutants bind to and travel with sediment and can be ingested by invertebrates with the organic
matter (Paul and Meyer 2001). The aquatic organism effects associated with these toxic pollutants are
discussed in Chapter 3.
2.3.3 Fish
A substantial amount of research has been conducted to identify and quantify the effects of elevated
sediment and turbidity levels on a variety offish species, more so than other taxonomic groups (Berry et
al. 2003). Salmonids, in particular, have been well studied because of their commercial and recreational
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importance and because of the concerns and well-documented impacts arising from logging in the Pacific
Northwest and elsewhere (Waters 1995).
The level of impact from suspended sediments and turbidity is a function of the interaction of many
factors, including natural sediment and turbidity levels for the area in question; pollutant concentration;
exposure duration; particle size; ambient temperature; physical and chemical properties of the sediments;
associated toxins; co-occurring stressors; and fish acclimatization, life history stage, migration, and
breeding season (Anderson et al. 1996, as cited in USEPA 2004a). In general, longer duration and higher
level exposures produce greater effects. Milder, primarily behavioral effects are observed at lower
magnitude and duration exposure levels. As exposure and duration levels increase, effects become
sublethal and lethal (Berry et al. 2003). Several researchers have sought to construct models linking
varying levels and durations of sediment exposure to fish responses, but responses vary widely among
different species, and data are generally insufficient at this time to fully characterize many of them (Berry
et al. 2003).
Newcombe (2003) has created a model for clear water fishes that relates magnitude and duration of
exposure to turbid water to a variety of adverse effects. The model indicates that fish exposure to turbidity
levels of 7 to 1,100 NTU for 1 to 48 hours can create effects ranging from small behavioral impacts to
death of a portion of the exposed population. This model does not describe fish that typically inhabit more
turbid surface waters and that exhibit a different set of reactions to a given range of turbidity levels and
exposures.
Short-term increases in suspended sediment and turbidity levels can naturally occur during spring thaws,
storms, and other natural events. Aquatic ecosystems also vary in their natural sediment and turbidity
levels. Studies have found that, in general, fish typically found in environments with naturally high
turbidity preferred more turbid environments in the laboratory (Berry et al. 2003). Other fish species are
very sensitive to elevated sediment levels (e.g., entire salmonid fisheries have been destroyed by elevated
sediment levels) (Berry et al. 2003).
A construction project may produce sediment and turbidity levels significantly higher those associated
with natural events, for longer periods of time, and at times when an aquatic ecosystem is unaccustomed
to receiving such sediment inputs. Many fish species have seasonal migration and breeding behaviors
which can be disrupted by elevated sediment levels. Younger fish are more vulnerable to sediment
impacts and are more prevalent within a population at certain times of the year (Berry et al. 2003).
Observed impacts from elevated sediment and turbidity levels fall into several broad categories, discussed
below. The potential cumulative effect of these impacts includes reduced disease and parasite resistance,
reduced growth, and degraded health of individual organisms in the fish community. These impacts may
decrease fish population levels in affected areas. Reductions can take place both through direct mortality
in the short term and reduced reproductive success in the long term. Newcombe (1994) and Newcombe
and Jensen (1996) (both as cited in Henley et al. 2000) found that elevated sediment concentrations are
associated with increased mortality in at least 14 species offish. EPA (USEPA 2004a) states that
suspended sediment concentrations between 500 and 6,000 mg/L can result in significant (greater than 50
percent) mortality. Berkman and Rabeni (1987, as cited in Wood and Armitage 1997) noticed a decline in
the overall abundance offish stocks as sediment levels increased in a river in northeastern Missouri. The
overall impact of these effects can be a change in fish community composition to one composed
predominantly of species that are tolerant of sediment and turbidity, primarily bottom-feeders (Berry et al.
2003), or an overall reduction in fish abundance.
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Impacts to fish communities downstream of construction sites discharging elevated levels of sediment and
turbidity have been documented in multiple studies (King and Ball 1964, Graves and Burns 1970, Barton
1977, Garton 1977, Reed 1977, Werner 1983, Taylor and Roff 1986, Ohio EPA 1997f, Ohio EPA 1999c,
Reid and Anderson 1999, Hunt and Grow 2001, California Department of Fish and Game 2004,
Montgomery County DEP 2009).
2.3.3.1 Avoidance and Other Behavioral Responses
The severity of behavioral responses is associated with the timing of disturbance, the level of stress, fish
energy reserves, phagocytes, metabolic depletion, seasonal variation, and habitat alteration (USEPA
2006b).
Because fish are generally more mobile than aquatic plants, plankton, and invertebrates, some species are
capable of actively avoiding waters with high levels of suspended sediment or turbidity if migration
routes to alternative habitats are available (mobility may be limited by culverts, small dams, and other
obstacles). While larger, nonlarval fish are generally capable of avoidance behavior (Berry et al. 2003),
smaller and younger fish are generally less mobile and therefore more vulnerable to elevated sediment
and turbidity levels. Avoidance behaviors may reduce or eliminate fish populations in stream reaches with
sustained elevated sediment levels. Barton (1977) noted a relocation offish populations away from areas
with elevated TSS levels due to construction near a small stream. Servizi and Martens (1987, as cited in
Reid et al. 2003) determined that turbidity levels in excess of 37 NTU elicit avoidance behavior among
fish populations. Berg (1982, as cited in Bash et al. 2001) documented that juvenile coho salmon exposed
to a short-term pulse of 60 NTU water left the water column and congregated at the bottom of the test
tank, returning to the water column once turbidity was reduced to 20 NTU. Boubee et al. (1997, as cited
in Newcombe 2003) found inhibition of upstream migration of one species at turbidity levels of 15 to 20
NTU. Because of avoidance behaviors, some fish may be excluded from otherwise desirable habitat due
to increased turbidity (Berry et al. 2003).
Other fish behavioral responses to elevated sediment and turbidity levels include increased frequency of
the cough reflex and temporary disruption of territoriality (USEPA 2006b).
2.3.3.2 Feeding and Hunting
Elevated suspended sediment and turbidity levels have been shown to reduce feeding rates in several
species offish (Kerr 1995). Elevated turbidity reduces the prey reaction distance for trout and therefore
reduces foraging success (Hedrick et al. 2006). This effect is generally believed to be a result of decreased
visibility caused by turbidity because many fish use vision to locate food. De Robertis et al. (2003) found
that turbidity level increases affected piscivorous fish feeding more than planktivorous fish feeding.
Piscivorous fish visually locate food sources at much longer distances than planktivorous fish do. EPA
(USEPA 2004a) concluded that turbidities greater than 25 NTU or TSS levels of 2,000-3,000 mg/L or
greater are sufficient to reduce fish predation abilities. Sweka and Hartman (2001) observed that brook
trout prey reaction distance decreased curvilinearly as turbidities levels increased from 0 to 43 NTU.
Although most fish species' predation abilities are reduced by increased turbidity levels, some fish
species have been documented to hunt better as turbidity increases because of increased contrast between
the prey and surrounding water. This advantage deteriorates as turbidity levels further increase, however
(Berry et al. 2003). Some larval fish species (e.g., striped bass -Morone saxatilis) appear to be able to
feed under extremely turbid conditions (Berry et al. 2003).
Reduction in predation can benefit prey species able to use turbid water to hide from predators (Rowe et
al. 2003). However, a paper by the Canadian DFO (2000) suggests that as turbidity levels continue to
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increase, the advantage of reduced predation is outweighed by the prey species' own increased difficulty
in locating food.
An additional effect on feeding and hunting from elevated sediment and turbidity levels is decreased food
availability and quality due to invertebrate community impacts, decreased primary productivity, and
sediment coatings on macrophytes and periphyton, which increase the quantity of nonnutritive sediment
herbivores must consume (Waters 1995; Ryan 1991). Bottom-feeding fish can be adversely impacted if
sediment organic content and associated microbial and macroinvertebrate communities are degraded by
sedimentation.
2.3.3.3 Breeding and Egg Survival
Elevated sedimentation levels can reduce spawning habitat for multiple fish species, particularly benthic
spawners. Many fish species use well-aerated interstitial spaces in surface water beds to lay eggs.
Sedimentation impact levels vary with differences in species sensitivity, life stage impacted, sediment
particle size, and sedimentation rates and total magnitude. Eggs and larvae can be buried too deeply by
sediment to survive (Berry et al. 2003). Sediments that settle onto surface water beds, particularly finer-
sized particles, can reduce the level of dissolved oxygen available to eggs deposited in the substrate (Kerr
1995). Even thin layers of sediment only a few millimeters thick can disrupt the normal exchange of gases
and metabolic wastes between eggs and the water column (Berry et al. 2003). Bjornn et al. (1977), as
cited in Kerr (1995), found that successful emergence offish fry from eggs began to decline when fine
sediment levels in the substrate were in excess of 20 to 30 percent. Sediment deposition can result in
surface water substrate armoring, trapping larvae as they attempt to emerge after hatching (Berry et al.
2003). Emergence success of cutthroat trout was reduced from 76 percent to 4 percent when fine sediment
was added to spawning gravel redds (Weaver and Fraley, 1993).
Correlations have also been found between elevated suspended sediment and turbidity levels and reduced
breeding and hatching success. Saunders and Smith (1965, as cited in Kerr 1995) found that increased
suspended sediment levels reduced fish spawning activity. Other studies document lower survival rates
for eggs spawned in surface waters with elevated suspended sediment and turbidity levels (Chapman
1988, as cited in Canadian DFO 2000). Reynolds (1989, as cited in Henley et al. 2000) found that
increases in turbidity levels increased sac fry mortality in arctic grayling (Thymallus arcticus).
2.3.3.4 Habitat Loss
Like invertebrates, fish use crevices in waterbody beds for feeding, shelter from predators and high flow
events, and reproduction. Loss of these interstitial spaces degrades fish habitat (USEPA 2006b). Sediment
can also decrease the depth of or eliminate other important habitats such as stream pools and wetlands
adjacent to surface waters. Riparian wetlands are particularly important for fish spawning. Fish are also
affected by loss or decline in aquatic macrophytes, which are important sources of shelter and food for a
number offish species. Coral reef bleaching and decline severely impact fish habitat in coral reef
ecosystems.
2.3.3.5 Juvenile Growth and Survival
High sediment concentrations can impact juvenile fish more severely than adult fish. Smallmouth bass
reduced growth after a 24-hour exposure to suspended sediment levels as low as 11.4 mg/L (Berry et al.
2003). Reynolds et al. (1989, as cited in Bilotta and Brazier 2008) found 6 to 15 percent mortality of
arctic grayling sac fry after 24 hours of exposure to suspended sediment levels of 25 to 65 mg/L.
Mortality of 41 percent was documented after 72 hours of exposure to suspended sediment levels of 185
mg/L. Juvenile coho and Chinook salmon exhibited abnormal surfacing behavior under elevated
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suspended sediment concentrations, rendering them more vulnerable to avian predators (Canadian DFO
2000). This study also notes that excessive sediment levels can stress juvenile fish and consequently
increase their predation risk. These types of effects can reduce the strength of a year class (Berry et al.
2003).
2.3.3.6 Physical Damage
At high levels, suspended sediment, particularly more angular particles, are capable of causing physical
damage to fish by clogging gills (which impairs breathing) and by skin abrasion (Bell 1973, as cited in
Waters 1995). Kerr (1995) notes that fish can withstand short episodes of high sediment concentrations by
producing mucus to protect skin and gills, but this reaction stresses fish. Excessive gill mucus can cause
gill tissue traumatization and asphyxiation. The severity of damage appears to be related to sediment
dose, exposure duration, and particle size and angularity. Fish can release stress hormones (i.e., cortisol
and epinephrine) in response to decreased gill function. Reid et al. (2003) finds that elevated sediment
levels reduces the ability of rainbow trout to withstand hypoxic conditions and thereby reduces their
average life span.
2.3.4 Other Wildlife Dependent on Aquatic Ecosystems
Birds, mammals, reptiles, and amphibians that consume aquatic plants, invertebrates, fish, and other
aquatic organisms or otherwise utilize aquatic habitats for shelter and reproduction can also be affected by
elevated sediment and turbidity levels in surface waters. Some species are sufficiently mobile that they
can avoid impacted aquatic communities and seek substitutes, if available and accessible (Berry et al.
2003).
Welsh and Ollivier (1998) documented lower densities of two salamander species and one frog species in
streams impacted by sedimentation from a construction site. The authors postulated that sedimentation of
interstitial spaces in the stream's substrate was the cause because of the organisms' dependence on these
spaces. Interstitial spaces provide amphibians with shelter from predators and high flows and habitat for
food (e.g., diatoms and periphyton) production. Concerns have been raised about the potential impact of
sedimentation on the endangered Barton Springs salamander (Eurycea sosorum), which depends on a
coarse substrate and healthy aquatic macrophyte population (USFWS 2005).
Sedimentation can also affect or eliminate riparian wetlands, important habitats for the laying of
amphibian egg masses (USEPA 2006b).
There are few studies available on the effects of elevated sediment and turbidity levels in aquatic
ecosystems on fundamentally terrestrial wildlife that utilize aquatic ecosystems. Most available studies
examine effects on birds. Loons appear to need clear water for hunting fish and may avoid turbid waters
for nesting. Other studies documented birds modifying their fish hunting behaviors and distribution on a
surface water in order to avoid more turbid areas, probably because of increased foraging difficulty (Berry
et al. 2003).
2.3.5 Threatened and Endangered Species
Threatened and endangered (T&E) and other special status species can be adversely affected by elevated
turbidity and sediment levels. The multiple ways in which elevated sediment and turbidity levels impact a
variety of organisms are discussed above. These impacts can reduce organism growth, health, survival,
and reproduction, thereby leading to further decline in an impacted T&E species population. The potential
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further decline of listed species or critical habitat for these species from construction activity is
particularly important because these species are already rare and at risk of irreversible decline.
The federal trustees for T&E species are the Department of the Interior's U.S. Fish and Wildlife Service
(USFWS) and the Department of Commerce's National Marine Fisheries Service (NMFS). USFWS is
responsible for terrestrial and freshwater species (including plants) and migratory birds, and NMFS deals
with marine species and anadromous fish (USFWS 2008). Various state agencies and departments have
state-level jurisdiction over T&E species and habitats of concern.
A species is federally listed as "endangered" when it is likely to become extinct within the foreseeable
future throughout all or part of its range if no immediate action is taken to protect it. A species is listed as
"threatened" if it is likely to become endangered within the foreseeable future throughout all or most of
its range if no action is taken to protect it. The 1973 Endangered Species Act outlines detailed procedures
used by the Services to list a species, including listing criteria, public comment periods, hearings,
notifications, time limits for final action, and other related issues (USFWS 1996).
A species is considered to be federally threatened or endangered if one or more of the following listing
criteria apply (USFWS 2007):
> The species' habitat or range is currently undergoing or is jeopardized by destruction,
modification, or curtailment.
> The species is overused for commercial, recreational, scientific, or educational purposes.
> The species' existence is vulnerable because of predation or disease.
> Current regulatory mechanisms do not provide adequate protection.
> The continued existence of a species is affected by other natural or manmade factors.
States and the federal government have also included species of "special concern" on their lists. These
species have been selected because they are (1) rare or endemic, (2) in the process of being listed,
(3) being considered for listing in the future, (4) found in isolated and fragmented habitats, or
(5) considered a unique or irreplaceable state resource.
The federal government and individual states develop and maintain lists of species that are considered
endangered, threatened, or of special concern. The federal and state lists are not identical: a state does not
list a species that is on the federal list if it is extirpated in the state. States may also list a species that is
not on the federal list if the species is considered threatened or endangered at the state, but not federal,
level.
Information on federally listed T&E species is available from the USFWS Threatened and Endangered
Species System (TESS) database (USFWS 2009), available at
http://www.fws.gov/endangered/wildlife.html. Information on both federal and state listed species is
available online in the NatureServe database (NatureServe 2009) at http://www.natureserve.org/explorer/.
Additional information on state-listed species is available from state T&E species coordinators.
Numerous physical and biological stressors have resulted in the listing of multiple aquatic species as
threatened or endangered. Major factors include habitat destruction or modification, displacement of
populations by exotic species, dam building and impoundments, various point and nonpoint sources of
pollution, poaching, and accidental deaths due to human activity.
Because construction activity occurs in every state and in or near a variety of waterbody types, there are
many potentially affected T&E aquatic species. The current USFWS list of T&E species includes 255
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aquatic species in five species groups: fish, amphibians, mollusks, crustaceans, and corals (USFWS
2009). For a complete list of these species, see Appendix B. This list is only a partial representation of
potentially affected species because it does not include aquatic or aquatic ecosystem-dependent plants,
insects, arachnids, reptiles, birds, and mammals. Although the USFWS list of T&E species does not
provide information on causes of endangerment for each species, a review of the ecological literature
suggests that elevated sedimentation, turbidity, and suspended sediment levels may have adverse impacts
on species that are already in peril either directly or indirectly through impacts on supporting food chains
(Cloud 2004; NatureServe 2009; USFWS 2009).
Several T&E species are thought to be particularly susceptible to excessive sedimentation, turbidity, and
suspended sediment levels. One such example is Amblema neislerii, an endangered freshwater mussel
commonly known as the fat threeridge. As the NatureServe Explorer database notes, ".. .the species and
its habitats continue to be impacted by excessive sediment bed loads of smaller sediment particles,
changes in turbidity, [and] increased suspended solids..." (NatureServe 2009). Other similarly sediment-
susceptible species of mollusks include the oyster mussel (Epioblasma capsaeformis), purple bankclimber
(Elliptoideus sloatianus), Louisiana Pearlshell (Margaritifera hembeli), Alabama Heelsplitter (Potamilus
inflatus), and Ouachita rock pocketbook (Arkansia wheeleri) (USFWS 2009).
Many fish species are also vulnerable to sedimentation. Sedimentation is a risk factor for a number of
shiner species, including the Arkansas river shiner (Notropis girardi), Pecos bluntnose shiner (Notropis
simuspecosensis), and blue shiner (Cyprinella caeruled) (NatureServe 2009). The NatureServe Explorer
notes that the biggest protection need for the threatened blue shiner (Cyprinella caerulea), native to the
southeastern United States, is "...preventing] siltation of habitat, especially during the spawning
period..." (NatureServe 2009). Sedimentation is also listed as a threat factor to a number of minnow and
darter species, such as the loach minnow (Tiaroga cobitis), spikedace (Medafulgidd), fountain darter
(Etheostoma fonticola), leopard darter (Percina pantherind), watercress darter (Etheostoma nuchale), and
vermilion darter (Etheostoma chermocki) (USFWS 1998, 2009; Drennen 2003; Cloud 2004; NatureServe
2009).
Sedimentation has also contributed to the threatened status of some populations of rainbow trout and
several salmon species in the Pacific Northwest (NatureServe 2009). For example, California coho
salmon and steelhead trout are listed as threatened and endangered by the state of California. The state has
expressed concern about the impact of sediment discharges from construction sites on habitat throughout
these species' range (McEwan and Jackson 1996; California Department of Fish and Game 2004). The
state noted, for example, that discharges from the construction of Interstate 5 in California depleted
spawning gravels for coho salmon (California Department of Fish and Game 2004).
Construction activities have been noted as a source of stress for the endangered Barton Springs
salamander (Eurycea sosorum) (USFWS 2005). The U.S. Fish and Wildlife Service (2004) also issued a
biological opinion addressing potential harm to the Arkansas river shiner (Notropis girardi) from a bridge
construction project in Texas. While USFWS concluded that the project would not jeopardize the
continued existence of the species, it did note that the river's fish community would be adversely affected
by temporary loss of habitat, seining and handling of individual fish necessary to remove them from the
immediate vicinity of the construction site, increased turbidity in the river, and harassment due to
construction activity (e.g., equipment usage, materials storage, foot and vehicle traffic, installation of
sediment and erosion controls, incidental deposition of debris in river). USFWS stated that these impacts
might affect habitat access and seasonal movement of the fish.
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Environmental Impact and Benefits Assessment for the C&D Category
Texas has identified the threatened and endangered aquatic plants Texas wild-rice (Zizania texand) and
puzzle sunflower (Helianthus paradoxus) as vulnerable to siltation. Texas wild-rice also grows best in
water with little or no turbidity. Little Aguja pondweed (Potamogeton clystocarpus) was identified as
vulnerable to substrate texture modification (USFWS 1998).
2.4 Sediment and Turbidity Impacts on Human Use of Aquatic Resources
As sediment eroded from construction sites settles in surface waters or elevates sediment concentrations
and turbidity in the water column, human uses of surface waters and human-built elements of the
environment can be damaged. Damage from discharge of sediment and turbidity to surface waters has
been recognized in the literature for several decades (Wolman and Schick 1967). Impacts to several types
of human use of aquatic resources are described below.
2.4.1 Navigation on Surface Waters
Navigable waterways, including rivers, lakes, bays, shipping channels, and harbors, are an integral part of
the United States' industrial transportation network. Navigable channels are prone to reduced
functionality due to sediment build-up, which can reduce the navigable depth and width of the waterway
(Clark et al. 1985). Increased sedimentation can lead to increased navigational difficulties and
inefficiencies such as groundings and delays (Osterkamp et al. 1998). Shipping companies may switch to
lighter loads or smaller vessels, which are generally less efficient. Removing sediment to keep navigable
waterways passable requires dredging, which can be costly. The U.S. Army Corps of Engineers (USAGE)
spends an average of more than $572 million (2008$) every year to dredge waterways and keep them
passable (USAGE 2009).
Dredging is itself an environmentally disruptive activity because it significantly disturbs the physical
structure of a surface water's bed and because dredged material may contain significant quantities of toxic
substances and heavy metals. Dredging can disturb contaminants that have settled to the bottom of the
waterway, increasing the potential for their uptake by fish and other aquatic organisms. Dredged sediment
may be disposed of in another section of the waterbody or watershed, relocating the problem rather than
removing it. Additionally, if the sediment removed from a site is contaminated, it can add to pollution at
the disposal site (Clark et al. 1985).
In addition, unless there is overdredging to compensate or sedimentation is monitored so that dredging
activity may be timed optimally, waterbodies will be on average be less navigable than if sedimentation
rates were reduced.
In areas with significant sediment contamination, dredging may not be a feasible option because of high
disposal costs for the dredged sediment. This can lead to damage of shipping vessels or shipping
inefficiencies. An example is the Great Lakes Harbor and Indiana Harbor Ship Canal, where navigational
dredging has not been conducted since 1972 because of the difficulty of contaminated dredge spoil
disposal. Ships have trouble navigating the harbor and canal and must enter the harbor while loaded at
less than optimum vessel drafts. There is also restricted use of some docks, requiring unloading at
alternative docks and double handling of bulk commodities to the preferred dock. In 1995, the increased
transportation costs associated with the lack of dredging were estimated to be $12.4 million annually
(USEPA 2004c).
Chapter 7 of this report describes the methodology for and presents the results of EPA's analysis of
benefits to navigation from several alternative regulatory options.
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Environmental Impact and Benefits Assessment for the C&D Category
2.4.2 Reservoir Water Storage Capacity
Reservoirs are water impoundments, often manmade, that serve many functions, including providing
drinking water, flood control, hydropower supply, and recreational opportunities. The National Inventory
of Dams includes more than 75,000 dams (Renwick et al. 2005). Renwick et al. (2005) estimated the
presence of 375,000-750,000 additional manmade impoundments in the United States, of which the
majority are smaller than 1 acre in area. These smaller impoundments are used for recreation, livestock
water supply, sediment trapping and erosion control, and other purposes. Sediment in streams can be
carried into reservoirs and smaller impoundments, where it can settle and build up layers of silt overtime.
Historically, the United States Geological Survey (USGS) has recorded an average of 2.6 billion pounds
of sediment deposition settles in reservoirs each year (USGS 2007c). An increase in sedimentation rates
will reduce reservoir capacity and utility. To replace this capacity, sediment must be dredged from
reservoirs, or new reservoirs must be constructed (Clark et al. 1985). Both dredging and new reservoir
construction can have a variety of environmental impacts. Crowder (1987) estimated that the United
States was losing about 0.22 percent of its reservoir capacity each year due to sedimentation. Clark et al.
(1985) noted that total U.S. reservoir capacity is filling up slowly and has enough excess capacity
dedicated to hold sediment build-up over hundreds of years. However, the study went on to conclude that
while total reservoir sedimentation is manageable, sedimentation is far from uniform and that, in
approximately 15 percent of U.S. reservoirs, sedimentation rates exceeded 3 percent of capacity annually
and, in the more extreme cases, 10 percent per year (Clark et al. 1985).
Sediment can also affect reservoir evaporation rates. Turbid waters tend to be sharply stratified, with a
warm layer at the surface and a cooler layer below. Because warm water evaporates faster, turbidity can
cause higher rates of water loss from reservoirs. However, turbidity may also increase the reflectivity of
water, which makes water absorb solar heat more slowly than it otherwise would and reduces evaporation
rates (Clark et al. 1985). The overall effect from temperature stratification in an individual reservoir could
be positive or negative.
Wolman and Schick (1967) describe the loss of the use of a Massachusetts reservoir because of sediment
discharged from airport construction. Significant resources were expended over two successive years for
supply and pumping of water from alternative sources.
Chapter 8 of this report describes the methodology for and presents the results of EPA's analysis of
benefits from reduced sedimentation of larger reservoirs under several alternative regulatory options.
2.4.3 Municipal Water Use
Discharges from construction sites can affect the quality and cost of providing drinking water. Sediment,
turbidity, and other discharged pollutants negatively affect water quality and require increased spending
on treatment measures such as settlement ponds, filtration, and chemical treatment (Osterkamp et al.
1998). There is an additional cost associated with removing sludge that is created during the treatment
process (USEPA 2007b). The presence of pollutants or dissolved minerals in drinking water may also
affect the flavor and odor of water.
Surface water sedimentation can impede water flow into drinking water treatment facility intakes.
Facilities may need to expend resources to unblock intakes or rebuild them in a different part of the
drinking water supply surface water.
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Environmental Impact and Benefits Assessment for the C&D Category
Construction site discharge impacts on municipal water supplies have been documented in the literature.
Wolman and Schick (1967) noted that erosion and deposition of sediment had compromised use of
surface waters as municipal water supplies in Maryland. They stated that where storage facilities were
lacking and water was pumped directly from a river, sediment concentration spikes following rain events
could force facilities to temporarily cease water withdrawals. This practice was practicable for only a very
short period of time. Highway officials in the state had compensated municipalities for the construction of
additional water storage facilities and for changing water intake locations to cope with sediment
discharges from highway construction sites. Tan and Thirumurthi (1978) documented increases in
turbidity, suspended solids, nitrogen, and conductivity levels in water supply lakes due to highway
construction in Nova Scotia, Canada. Buckner (2002) described contamination of a municipal water
supply due to runoff from an upstream highway construction site.
Chapter 9 of this report describes the methodology for and presents the results of EPA's analysis of
benefits from reduced impacts to municipal water supplies under several alternative regulatory options.
2.4.4 Industrial Water Use
Elevated sediment and turbidity levels may have negative effects on industrial water users. Suspended
sediment increases the rate at which hydraulic equipment, pumps, and other equipment wear out, causing
accelerated depreciation of capital equipment. Sediment can also clog water intake systems at power
plants and other industrial facilities and possibly require their relocation to another part and/or depth level
of the surface water. Some industrial facilities treat water before use, and elevated sediment and turbidity
levels may require additional treatment (Osterkamp et al. 1998) or make a surface water source unusable.
Wolman and Schick (1967) noted that erosion and deposition of sediment had led to turbid waters
unsuitable for industrial uses in the state of Maryland. They stated that even small amounts of sediment
can cause problems for industrial operations such as vegetable processing or cloth manufacture. They also
noted that sediment had led to failure of pumping equipment. Excess sediment levels may require the use
of filters to improve water quality.
At least one positive effect from elevated turbidity levels is also possible, however. Since turbidity may
reduce the rate at which waterbodies absorb solar heat, more turbid waterbodies may supply cooler water,
which in turn could improve the efficiency of cooling water systems at power plants and other industrial
facilities (Clark et al. 1985).
2.4.5 Agricultural Water Use
Irrigation water that contains sediment or other pollutants from construction sites can harm crops and
reduce agricultural productivity. Suspended sediment can form a crust over a field, reducing water
absorption, inhibiting soil aeration, and preventing emergence of seedlings. Sediment can also coat the
leaves of plants, inhibiting plant growth and reducing crop value and marketability. Furthermore,
irrigation water that contains dissolved salts or pollutants can harm crops and damage soil quality (Clark
etal. 1985).
Wolman and Schick (1967) noted that erosion and deposition of sediment in surface waters in the state of
Maryland had led to failure of pumping equipment. Pumps are often used for the movement of irrigation
water. Excess sediment levels may require the use of filters to improve water quality.
Surface water sedimentation can block irrigation water intake structures or require their relocation to
another part of the surface water. Sedimentation can also cause sediment build-up in irrigation water
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Environmental Impact and Benefits Assessment for the C&D Category
canals and other transport systems (Osterkamp et al. 1998), reducing their efficiency. Sediment can also
accumulate in livestock water supply impoundments and reduce their capacity (see Section 2.4.2).
2.4.6 Stormwater Management and Flood Control
Sediment in discharges from construction sites can clog or fill ditches, culverts, storm sewer pipes and
basins, Stormwater detention ponds, infiltration basins, and other stormwater management structures
(Osterkamp et al. 1998). Sedimentation also decreases the capacity of natural stream and river channels,
ponds, lakes, and reservoirs, increasing the likelihood of overbank flow events and their magnitude (Paul
and Meyer 2001). Wolman and Schick (1967) noted that erosion and deposition of sediment in the state of
Maryland had led to sediment deposition in streams and overflow and clogging of storm drains.
If left in place, sedimentation can increase flooding. The U.S. Army Corps of Engineers (2007) stated that
channel sedimentation due to construction discharges contributed to flooding of a Virginia residential
neighborhood. Preventing flood damages from excessive sedimentation may require increased
maintenance efforts such as dredging (Clark et al. 1985), vacuuming, and other types of sediment removal
from stormwater management structures and surface waters. If sedimentation removal is performed in
surface waters or in structures directly adjacent to surface waters, it can create additional environmental
impacts such as resuspension of sediments and associated turbidity and contaminants in the water column
and disturbance of the physical structure of the surface water bed and the associated benthic aquatic
community.
Surface water and stormwater management system sedimentation can increase the severity of property
damages to bridges, roads, farmland, and other private and public property from flooding. Additionally,
sediments carried by flood waters can damage property and can be expensive to remove once deposited,
particularly in developed areas (Clark et al. 1985; Osterkamp et al. 1998). Clark et al. (1985) estimated
flooding damages attributable to all sediment discharges to be $1.5 billion (2008$), annually.
The quantity of sediment captured in stormwater control structures is unknown or could be very variable.
Nelson and Booth (2002) did not observe significant long-term sediment accumulation in the stormwater
retention/detention facilities (including the ditches and pipes connecting them to surface waters) of newer
residential developments in Issaquah, Washington. They did note, however, that a significant amount of
sediment was removed every year from catch-basins in the city of Issaquah, though a large fraction of this
sand may have derived from winter road sanding.
2.4.7 Recreational Uses and Aesthetic Value
Polluted water greatly reduces the aesthetic appeal of a variety of recreational activities that take place in
or near surface waters, including boating; swimming; hunting; and outings to hike, jog, picnic, camp, and
view wildlife. Turbidity and suspended sediments are highly visible pollutants. Murky and visually
unpleasant water and odors can detract from the enjoyment gained through outdoor activities.
Sedimentation of streams, reservoirs, lakes, and bottomlands can reduce their depth and thus their
capacity for boating and swimming (Osterkamp et al. 1998).
Turbidity caused by sediment discharges may affect the safety of boating. Turbidity may obscure
underwater obstacles, making collisions more likely. Increased sedimentation levels may create sandbars,
increasing the chances of running aground. Clark et al. (1985) estimated that turbidity (from all sources)
may be responsible for as many as 200 boating fatalities and many more injuries each year. Turbidity may
also create safety hazards for swimmers by reducing the ability to see underwater hazards, increasing the
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Environmental Impact and Benefits Assessment for the C&D Category
frequency of diving accidents by impairing the ability to gauge water depth, and making location of
swimmers in danger of drowning more difficult.
Wolman and Schick (1967) noted that erosion and deposition of sediment in the state of Maryland had
damaged recreation areas. Concern about potential highway construction impacts to aesthetic and
recreational values of a small lake was sufficient to motivate residents of an adjoining neighborhood to
initiate monitoring of lake water quality (Line 2009).
Aesthetic degradation of land and water resources resulting from sediment and turbidity discharges can
also reduce the market value of property near surface waters and thus affect the financial status of
property owners. For example, a hedonic price study by Bejranonda et al. (1999) found that "the rate of
sediment inflow entering the lakes has a negative influence on lakeside property rent." Sediment
discharges also have a significant impact on stream morphology. For example, higher coarse-sediment
load leads to an increase in width of the river bed and, as a result, bank erosion (Wheeler et al. 2003). A
1993 study of Lake Erie's housing market found that "erosion-prone lakeshore property will be
discounted" (Kriesel et al. 1993). Stabilization of stream banks leads to an increase in the value of
surrounding property (Streiner and Loomis 1996).
2.4.8 Recreational and Commercial Fishing
Pollutants can negatively affect local flora and fauna, negatively impacting aesthetic appeal, wildlife
viewing, and hunting for game (Osterkamp et al. 1998). By harming fish and shellfish communities,
sediment can reduce fish and shellfish numbers or cause more desirable fish and shellfish to be replaced
by less desirable fish and shellfish in a given location.
As discussed in Section 2.3, sediment, turbidity, and other discharges from construction sites can reduce
fish and shellfish populations by inhibiting their reproduction, growth, and survival. In some areas,
desirable sediment-sensitive fish may be replaced by less-desirable, sediment-tolerant fish and shellfish.
These population changes and reductions would reduce the size of commercial and recreational harvest by
lowering both the total abundance of organisms and their individual size. These changes negatively affect
recreational anglers, subsistence anglers, commercial anglers, fish and shellfish sellers, and consumers of
fish and shellfish products.
In addition, sediments, turbidity, and other pollutants reduce the aesthetics of a waterbody, which can
reduce anglers' enjoyment of their fishing experience and their choices of how often and where to fish.
Sediment and turbidity may also affect recreational anglers by reducing the distance over which fish can
see lures, resulting in lower catch rates (Clark et al. 1985).
2.5 Sediment and Turbidity Criteria
Natural levels of sediment and turbidity play important roles in aquatic ecosystems, providing habitat for
benthic species, protection from predators, nutrient transport, and other functions. Appropriate levels of
sediment are waterbody specific, as sediment levels vary naturally among different types of waterbodies
according to geology, topography, stream gradient, waterbody morphology, vegetative land cover,
climate, soil erodibility, and other landscape characteristics of the contributing watershed (USEPA
2006b). When sediment and turbidity enter surface water at elevated levels, they can raise TSS and
turbidity levels in the water column, increase deposition of sediment on the waterbody's bed, and degrade
overall water quality (USEPA 2006b). Elevated sediment and turbidity levels also negatively impact
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Environmental Impact and Benefits Assessment for the C&D Category
human use of aquatic resources for recreation, drinking water supply, agricultural use, industrial use, and
navigation and can impair stormwater management system function and surface water aesthetics.
EPA and many states have issued criteria that describe appropriate sediment and turbidity levels for
surface waters. Many of these criteria are narrative and provide a qualitative description of appropriate
levels. Other criteria are numeric.
2.5.1 Federal Sediment Criteria
In 1987, EPA published the following guidance for developing numeric water quality criteria for
sediment and turbidity:
Solids (Suspended, Settleable) and Turbidity - Freshwater fish and other aquatic life: Settleable and suspended solids
should not reduce the depth of the compensation point for photo synthetic activity by more than 10 percent from the
seasonally established norm for aquatic life (USEPA 1987).
This criterion has not been widely adopted by states. Guidance addressing primarily aesthetic properties,
however, has been adopted by several states.
Aesthetic Qualities - All waters shall be free from substances attributable to wastewater or other discharges that: settle
to form objectionable deposits; float as debris, scum, oil, or other matter to form nuisances; produce objectionable
color, odor, taste, or turbidity; injure or are toxic or produce adverse physiological response in humans, animals, or
plants; [or] produce undesirable or nuisance aquatic life (USEPA 1987).
EPA has not issued new sediment or turbidity criteria since 1987. However, EPA has published a
document providing guidance on setting sediment criteria: Framework for Developing Suspended and
Bedded Sediments (SABS) Water Quality Criteria (USEPA 2006b).
2.5.2 State Sediment Criteria
Many states have developed their own criteria to designate appropriate sediment levels for waters within
the state. Some criteria vary by waterbody type. Streams with hard substrates (e.g., gravel, cobble,
bedrock) or cold water fisheries typically have more stringent criteria than streams with soft substrates
(e.g., sand, silt, clay) or warm water fisheries. Hawaii has separate criteria for reefs (Berry et al. 2003). In
addition, Total Maximum Daily Loads (TMDLs) addressing sediment and turbidity have been developed
for some surface waters and contain information on acceptable levels specific to those waterbodies.
Many criteria are narrative statements describing the general nature of healthy sediment or turbidity levels
without attempting to provide numeric guidelines. Narrative criteria most frequently address turbidity or
surface water appearance (e.g., "free of substances that change color or turbidity"). Other criteria refer to
undesirable biological effects (e.g., "no adverse effects" or "no actions which will impair or alter the
communities") (Berry et al. 2003). EPA (USEPA 2006b) provides a summary of state narrative and
numeric criteria (though some criteria may have been modified since this information was compiled).
A number of states have also set numeric criteria for TSS or turbidity levels. Most of these numeric
criteria are for turbidity. Turbidity criteria exist as absolute values or ranges of values or as a permitted
exceedance beyond background turbidity levels. Some states have issued numeric criteria for suspended
sediments.
A number of states have criteria based on sedimentation levels over a time period or during a storm event.
Values are typically 5 mm during an individual event (e.g., during the 24 hours following a heavy
rainstorm) for streams with hard substrate bottoms and 10 mm for streams with soft bottoms. Hawaii's
reef criterion is 2 mm of deposited sediment after an event (Berry et al. 2003).
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Environmental Impact and Benefits Assessment for the C&D Category
Table 2-3 summarizes state suspended sediment and turbidity criteria for surface water quality. States
using narrative criteria are noted with a "Yes" in the "Narrative TSS" or the "Narrative Turbidity"
column. Values for numeric criteria and some details on their implementation are provided in the
"Numeric TSS" and "Numeric Turbidity" columns. This table is intended to provide an overview of state
numeric suspended sediment and turbidity water quality requirements and does not summarize all details
relevant to their applicability. In addition, states periodically update their water quality criteria. Readers
should consult individual state water quality criteria publications in order to obtain the most complete and
current requirements.
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Environmental Impact and Benefits Assessment for the C&D Category
Table 2-3:
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Suspended Sediment and Turbidity Criteria for Surface
Numeric TSS Narrative
(mg/L) TSS Numeric Turbidity Criteria
<50 NTU increase
<5 NTU increase
<10% increase (max. 25 NTU)3
10-50 NTU4
1 0-75 NTU 4 for baseflow values
<20% increase2
<10% increase3
Yes
<5 NTU increase
<10 NTU increase
Water Quality by State
Notes on Numeric Turbidity Criteria
Source: Alabama DEM (2009).
Source: Alaska DEC (2003)
Human Contact: 50 NTU in rivers, 25 NTU in lakes
Cold Water Fishery: 10 NTU
Warm Water Fishery: 50 NTU in rivers, 25 NTU in lakes
"Non-point source runoff shall not result in the
exceedance of the in stream all flows values in more
than 20% of the ADEQ ambient monitoring network
samples taken in not less than 24 monthly samples."
Source: Arkansas Pollution Control and Ecology
Commission (2007).
20% increase applies to Central Coast Region and is
measured in JTU
10% increase applies to San Francisco Region
Source: California EPA 2009a, b
Under ambient conditions. Class AA criteria
Source: Connecticut DEP (2002).
For all fresh waters and mixing zones
District of Columbia - -
Florida
Georgia
Hawaii
<29 NTU increase
Yes
Turbidity levels not to exceed NTU as specified below:
Water type , Geometric More than
mean 10° oof the time 2% of the time
Stream (wet 5 15 25
season)
Stream (dry 2 5.5 10
season)
1Q_557 yes 2"25 NTU f°r streams A11 Estuaries IZjTflll 3U> Il-PZZZ
0.1-15 NTU for coastal/marine waters Pearl Harbor 4.0 8.0 15.0
Embayment 0.4 1.0 1.5
Open Coastal 0.5 1.25 2.0
(wet season)
Open Coastal 6.02 0^05 1.6
(dry season)
Oceanic 0.03 0.1 0.2
Marine 1 0.1 1 1
Narrative
Turbidity
Yes1
Yes
Yes
Yes
Yes
-
-
-
Yes5
Yes
Yes
Yes
November 2009
2-32
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Environmental Impact and Benefits Assessment for the C&D Category
Table 2-3: Suspended Sediment
and
Turbidity Criteria for Surface Water Quality by State
Numeric TSS Narrative
State (mg/L) TSS Numeric Turbidity Criteria
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey 25
New Mexico
Yes
-
Yes
Yes
Yes
Yes
Yes
-
-
Yes
-
-
Yes
Yes
Yes
-
Yes
Yes
-
Yes
<50 NTU increase at any time, <25
NTU increase over 10 consecutive
days
-
-
25 NTU
-
-
25, 50, 150 NTU, or <10% increase4
-
150 NTU at any time
50 NTU monthly average
-
-
5, 10, or 25 NTU4
50 NTU
-
-
-
Waterbody specific
0-10 NTU increase4
10, 30, or 50 NTU4
<10 NTU increase2 or <20% increase3
Notes on Numeric Turbidity Criteria
For applicable mixing zones set by the department only
Source: Idaho DEQ (2008).
25 NTU: freshwater lakes, reservoirs, and oxbows;
designated scenic streams and outstanding natural
resource waters
50 NTU: Amite, Pearl, Ouachita, Sabine, Calcasieu,
Tangipahoa, Tickfaw, and Tchefuncte Rivers;
estuarine lakes, bays, bayous, and canals
1 50 NTU: Atchafalaya, Mississippi, and Vermilion
Rivers and Bayou Teche
10% Increase: All other waters
Domestic Consumption: Class A & B 5 NTU, Class C 24
NTU
Fisheries & Recreation: Class A 10 NTU, Class B & C
25 NTU
Industrial Consumption: Class A 5 NTU
Applicable to waters outside the limits of a 750-foot
mixing zone
Class A waters: No turbidity other than natural
Class B & C: 10 NTU increase over natural
Freshwater: 50 NTU any time, 15 NTU 30-day average
Saline water: 30 NTU any time, 10 NTU 30-day average
Coastal saline: 10 NTU
GA waterbody Turbidity shall not exceed 5 NTU
Source: New Mexico (2005)
Narrative
Turbidity
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
-
Yes
Yes
Yes
Yes7
Yes
Yes
-
Yes
November 2009
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Environmental Impact and Benefits Assessment for the C&D Category
Table 2-3:
State
New York
North Carolina
North Dakota
Suspended Sediment and Turbidity Criteria for Surface
Numeric TSS Narrative
(mg/L) TSS Numeric Turbidity Criteria
Yes Waterbody specific
5009 Yes 10,25, or 50 NTU4
30
Water Quality by State
Notes on Numeric Turbidity Criteria
10 NTU in trout waters
25 NTU in other lakes and reservoirs
50 NTU in other streams
If background exceeds these levels, no increase
Narrative
Turbidity
Yes8
-
-
Ohio
Oklahoma
Oregon
Pennsylvania
Puerto Rico
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
10 or 50 NTU4
Yes < 10% Increase
Yes 40-100 NTU
Specific to waterbody class
5 NTU or < 1 0 NTU increase4
Yes 10 NTU or < 1 0% increase
53-263 (at any time);
30-1 50 (monthly Yes
average)4
Yes
Yes
35-904 Yes 10 or 15 NTU4
10 or 25 NTU4
Yes
Cold water aquatic communities/trout fisheries: 10 NTU;
Lakes: 25 NTU; Other Surface Waters: 50 NTU
If background exceeds these levels, point sources may not
cause increases above ambient levels
Exception for temporary increases to do "legitimate
activities" including dredging and construction,
providing all practicable turbidity control techniques
are applied.
Specific limits only apply to Neshaminy Basin
Class SB shall not exceed 10 NTU, except by natural
causes; Class SC shall not exceed 10 NTU; Class SD
shall not exceed 50 NTU, except when due to natural
phenomena
Source: Puerto Rico EQB (2003).
Class A: 5 NTU
Class B & C: 10 NTU increase
Providing existing uses are maintained
Specific to freshwaters suitable for supporting trout stocks
10 NTU for cold and warm water game fish
1 5 NTU for nongame fish, waterfowl, and other wildlife
10 NTU for Class A(l) ecological waters and Class B
cold water fish habitats
25 NTU for Class B warm water fish habitats
-
Yes
Yes
Yes
-
Yes
Yes
Yes
Yes
Yes10
Yes
Yes
November 2009
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Environmental Impact and Benefits Assessment for the C&D Category
Table 2-3: Suspended Sediment and Turbidity Criteria for Surface Water Quality by State
State
Numeric TSS
(mg/L)
Narrative
TSS
Numeric Turbidity Criteria
Notes on Numeric Turbidity Criteria
Narrative
Turbidity
Class AA &A: 5 NTU2 or 10% increase3
Class B & C: 10 NTU2 or 20% increase3
Lakes: 5 NTU increase
m ,. , 5 or 10NTU2or<10%or<20% Also includes a flow-based criteria based on flow from
Washington - - -34 + +• •+ ^ • * m* i
increase construction site. Flows ranging trom 10 to above
100 CFS have turbidity measured at 100 to 300 feet
from downstream activity
Source: Washington (1997)
West Virginia - - 10 NTU2 or < 10% increase3
Wisconsin - Yes - Yes
<10 NTU increase for Class 1 and 2 waters that are cold
„, . ,, ,„ IC-K-TTTT- 4 water fisheries ,,
Wyoming - Yes <10 or 15 NTU increase IC-K-TTTT- c ™ i j ^ + a + Yes
J ° <15 NTU increase for Class 1 and 2 waters that are warm
water fisheries and all Class 3 waters
1 "There shall be no turbidity of other than natural origin that will cause substantial visible contrast with the natural appearance of waters or interfere with any beneficial uses which they serve."
2 If naturally less than 50 NTU.
3 If naturally greater than 50 NTU.
4 Varies based on waterbody classification.
5 May not "produce objectionable odor, color, taste, or turbidity."
6 Applies during dry season only. Geometric mean of 10 mg/L, not exceeding 30 mg/L 10% of the time and 55 mg/L 2% of the time.
"To be aesthetically acceptable, waters shall be free from human-induced pollution which causes: 1) noxious odors; 2) floating, suspended, colloidal, or settleable materials that produce
objectionable films, colors, turbidity, or deposits."
8 Waterbody types AA, A, B, C, D, SA, SB, SC, SD, I: no increase may cause substantial visible contrast from natural conditions.
9 Standard is for total dissolved solids (TDS).
10 For mixing zones.
Source: USEPA (2006b), unless otherwise noted.
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Environmental Impact and Benefits Assessment for the C&D Category
2.6 Surface Water Quality Impairment from Sediment and Turbidity
Section 305(b) of the Clean Water Act (CWA) requires states, territories, and other jurisdictions of the
United States to submit reports to EPA on the quality of their surface waters every two years. These
entities have determined the appropriate uses of each waterbody within their jurisdiction. Uses can
include recreation, drinking water source, navigation, cold water fishery, and wildlife habitat, among
others. States and other entities determine appropriate narrative and/or numeric water quality criteria for
each of the designated uses. The criteria describe the physical, chemical, and biological characteristics of
a surface water able to fulfill its designated uses. The sediment criteria described in the section above are
examples of such criteria. Typically, a surface water has criteria for multiple water quality parameters. If
a waterbody fails to meet any one of its designated uses, CWA Section 303(d) requires a state or other
entity to list the waterbody as "impaired." If a waterbody meets its designated uses but is in danger of
failing to do so in the future, the state or other entity must list the waterbody as "threatened" (USEPA
2005a).
The Assessment TMDL Tracking and Implementation System (ATTAINS) provides information on water
quality conditions reported by the states to EPA under Sections 305(b) and 303(d) of the Clean Water
Act. The information available in ATTAINS is updated as data are processed and are used to generate the
biennial National Water Quality Inventory Report to Congress. This information reflects only the status of
those waters that have been assessed. Appendix A provides information on the state water report year for
which data were available for populating the tables below as of September 17, 2009.
According to ATTAINS, 49 percent of assessed reach miles (or 458,209 miles) have been identified as
impaired; sediment contributes to impairment in 107,231 miles, and turbidity contributes to impairment in
26,278 miles. For lakes and reservoirs, 66 percent of assessed lake acres (or 11,545,337 acres) have been
identified as impaired; sediment contributes to impairment in 715,558 lake acres, and turbidity contributes
to impairment in 1,008,276 acres. For bays and estuaries, 63 percent of assessed square miles (or 11,222
square miles) have been identified as impaired; sediment contributes to impairment in 209 square miles,
and turbidity contributes to impairment in 240 square miles. It should be noted that individual waters may
be impaired by more than one pollutant. Although states tend to target their monitoring efforts to those
surface waters they believe to be impaired, the total area of impaired surface waters due to sediment and
turbidity is probably underestimated due to the low percentage of surface waters that were assessed. As of
September 17, 2009, states had assessed only 26 percent of the nation's reach miles, 42 percent of its lake
acres, and 20 percent of its bay and estuary square miles.
Table 2-4 and Table 2-5 present information on "sediment" and "turbidity and suspended solids"
impairment by EPA Region as reported by the states in ATTAINS. This information is presented by EPA
Region. Figure 2-1 provides a map of the EPA Regions.
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Environmental Impact and Benefits Assessment for the C&D Category
Table 2-4: Surface Waters Impaired by "Sediment," by EPA Region
EPA Region
1
2
3
4
5
6
7
8
9
10
Nation
Reach (miles)
236
1,123
8,188
11,126
34,410
3,567
9,659
9,597
198
29,127
107,231
Source: EPA ATTAINS database (USEPA 2009a)
Lake/Pond/Reservoir (acres)
443
39,277
193
23,333
57,965
153,478
144,125
147,592
-
149,152
715,558
as of 9/1 7/09.
Bay/Estuary (sq. miles)
4
0
12
-
-
193
-
-
-
-
209
Table 2-5: Surface Waters Impaired by "Turbidity" and "Suspended Solids," by EPA
Region
EPA Region
1
2
3
4
5
6
7
8
9
10
Nation
Stream/ River (miles)
339
3,539
229
732
9,278
6,880
84
2,304
904
2,439
26,728
Source: EPA ATTAINS database (USEPA 2009a)
Lake/Pond/Reservoir (acres)
43,735
1,539
-
13,814
134,427
626,642
38,173
3,168
136,980
9,798
1,008,276
as of 9/1 7/09.
Bay/Estuary (sq. miles)
5
8
-
4
-
195
-
-
28
-
240
Figure 2-1: EPA Regions
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American Samoa
northern Mariana
lalanda I
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Environmental Impact and Benefits Assessment for the C&D Category
Water quality in the United States has also been assessed through a series of national, probability-based
surveys known as the National Aquatic Resource Surveys. These surveys use randomized sampling
designs, core indicators, and consistent monitoring methods and laboratory protocols to provide
statistically defensible assessments of water quality at the national scale. The Wadeable Streams
Assessment (USEPA 2006d) is a statistical survey of the smaller perennial streams and rivers that,
according to the report, comprise 90 percent of all perennial stream miles in the United States. Excess
streambed sedimentation is ranked as one of the most widespread stressors examined in the survey. (The
survey did not analyze turbidity or suspended sediment levels.) According to the survey, 25 percent of
streams have "poor" streambed sediment condition, and 20 percent are in "fair" condition relative to
reference streams. The survey also examined the association between stressors and biological condition,
and found that high levels of sediments more than double the risk for poor biological condition (see
Figure 2-2).
tFigure 2-2: Extent of Stressors and Their Relative Risk to the Biological Condition of the
Nation's Streams
Relative Extent
Relative Risk to
Macroinvertebrate Integrity (IBI)
Nitrogen
Phosphorus
Riparian Distrubance
Streambed Sediments
In-stream Fish Habitat
Riparian Vegetative Cover
Salinity
Acidification
h-H 30.9%
h-H 25.5%
J -i jt no/
1 | 1 24.9%
h-H 19.5%
1 1 19.3%
•42.9%
J 2.2%
3 10 20 30 40
Percentage Stream Length in Most
1 1 1 2.1
t 1 ^ ••)
\ \ 2..2.
\— I— 11-4
1 1 104
h-H 1.4
1 1 1 1.6
b-n.7
234
Relative Risk
Disturbed Condition
Source: USEPA (2006c).
Another National Aquatic Resource Survey, the National Coastal Condition Report III (USEPA 2008b),
assesses coastal aquatic habitat and found water clarity (related to turbidity) to be poor in 17 percent of
coastal waters. Data on excessive sedimentation was not collected for the report.
2.6.1 Current Total Suspended Solid Concentrations in U.S. Surface Waters
TSS concentrations vary from waterbody to waterbody due to differences in their contributing watersheds
created by natural conditions and human activity. EPA used the SPARROW model to estimate current
TSS concentrations in the United States' Reach File Version 1 (RF1) surface water network (see Chapter
6 for more information). For this analysis, the RF1 network consists of approximately 650,000 miles of
the largest rivers and streams in the coterminous United States and associated lakes, reservoirs, and
estuarine waters. Due to data limitations, EPA did not model surface water turbidity levels. Table 2-6
summarizes the distribution of TSS concentrations found in individual RF1 reaches as estimated by
EPA's analysis. The median TSS concentration, weighted by reach length, is 302.9 mg/L. The range of
TSS concentrations falls between 26.7 mg/L and 6,154.5 mg/L at the 5th and 95th percentiles, respectively.
The average TSS concentration is 1,068.6 mg/L, indicating that concentrations in the 90th to 95th
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Environmental Impact and Benefits Assessment for the C&D Category
percentile range are high enough to shift the average concentration significantly higher than the median
concentration.
Table 2-6: SPARROW Distribution of TSS Concentrations in RF1 Reaches1
RFl
Reach
Count
62,370
RFl
Reach
Miles
650,043
Average
TSS
(mg/L)1
1,068.6
Distribution of TSS Concentrations in RFl Reaches1
5th
Percentile
26.7
25th
Percentile
102.9
50th
Percentile
302.9
75th
Percentile
1,079.6
95th
Percentile
6,154.5
Concentrations weighted by reach length. Concentration estimates reflect replacement of potential outliers (defined as values above the 95
percentile) with the 95th percentile value.
Figure 2-3 shows total RFl reach miles and their current TSS concentrations as predicted by SPARROW
(not weighted by reach length). As shown below, the majority of waters have TSS concentrations below
1,000 mg/L, though substantially higher average concentrations up to and exceeding 6,000 mg/L can be
found in some waters.
Figure 2-3: TSS Concentrations by Total RF1 Reach Miles as Predicted by SPARROW for
Current Conditions
225000
200000
175000
y,
150000
t125000
0)
1*100000
3
o
H 75000
50000
25000
0
Total: 62,370 River Reaches (650,043 River Miles)
95th Percentile: 6,154.51 mg/L
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