SR
2008
Nutrient and Sediment TMDLs for the
Indian Creek Watershed, Pennsylvania:
Established by the U.S. Environmental
Protection Agency
i
Jon Capacasa, Director,
Water Protection Division
6/30/2008
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FINAL
Siltation and Nutrients TMDL Development for
the Indian Creek Watershed, Pennsylvania
June 2008
Prepared for:
United States Environmental Protection Agency, Region 3
Contract 68-C-02-108, Task Order #113
Prepared by:
Tetra Tech, Inc.
10306 Eaton Place, Suite 340
Fairfax, VA 22030
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June 2008 FINAL Indian Creek TMDLs
EXECUTIVE SUMMARY
Section 303(d) of the Clean Water Act and the U.S. Environmental Protection Agency's (USEPA) Water
Quality Planning and Management Regulations (Title 40 of the Code of Federal Regulations [CFR] Part
130) require states to develop Total Maximum Daily Loads (TMDLs) for impaired waterbodies. A TMDL
establishes the amount of a pollutant that a waterbody can assimilate without exceeding its water quality
standard for that pollutant. TMDLs provide the scientific basis for a state to establish water quality-based
controls to reduce pollution from both point and nonpoint sources to restore and maintain the quality of
the state's water resources (USEPA 1991).
A TMDL for a given pollutant and waterbody is composed of the sum of individual wasteload allocations
(WLAs) for point sources and load allocations (LAs) for nonpoint sources and natural background levels.
In addition, the TMDL must include an implicit or explicit margin of safety (MOS) to account for the
uncertainty in the relationship between pollutant loads and the quality of the receiving waterbody. The
TMDL components are illustrated using the following equation:
TMDL = X WLAs + X LAs + MOS
Indian Creek drains an area of approximately 7 square miles in Montgomery County, Pennsylvania. Its
watershed includes portions of eight municipalities and has three National Pollution Discharge
Elimination System (NPDES) permitted discharges. Various degrees of residential development (low
intensity residential, medium intensity residential and high intensity residential) are scattered thoughout
the watershed and the middle portion of the watershed is predominantly pasture.
This TMDL is developed to address segments in the Indian Creek watershed listed on the state's 303(d)
list as not meeting aquatic life uses and impaired by siltation (sediment) and nutrients. The TMDLs were
developed using the GWLF watershed model linked to the EFDC hydrodynamic model. The sediment
TMDL was developed to meet and loading targets established using a reference watershed, and the
nutrient TMDL was developed to meet the seasonal average concentration targets for total phosphorus
(TP) shown in table ES-1. Both TMDLs were developed to protect designated aquatic life uses.
Table ES-1. Nutrient Endpoints for Indian Creek TMDL
Parameter
TP
Period
April 1 - October 31
Target Concentration
0.040 mg/L
In addition to the seasonal average nutrient target, modeling analysis also demonstrates that the TMDL
complies with established water quality criteria for dissolved oxygen at all points in the stream as well as
with identified levels of acceptable periphyton densities.
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FINAL Indian Creek TMDLs
June 2008
Table ES-2. Summary of Sediment and Nutrient TMDLs for Indian Creek
Indian Creek Watershed
Existing
Allowable Load
MOS(10%)
Future Residential Growth (1%)
ZWLA
ZLA
TMDL
Sediment TMDL
(Ib/yr)
12,693,686
641,733
32,087
38,504
571,013
0
641,604
TPTMDL
(Ib/yr)
11,389
1,598
80
96
1,422
0
1,598
Allowable daily loads were also identified for all sources of sediment and nutrients. A statistical
approach was used to determine the maximum allowable daily load consistent with the long term loading
allocation.
Table ES-3. Allowable Daily Loads of Sediment and Nutrient TMDLs for Indian Creek
NPDES ID
PA0036978
PA0054950
PA0024422
MS4
MS4
MS4
MS4
Facility/Township
Telford Borough Authority
Pilgrim's Pride
Lower Salford Authority (Harleysville STP)
Lower Salford
Souderton
Telford
Franconia
Sediment
Maximum
Daily
(Ib/day)
523
35
533
497
45
104
1818
TP
Maximum
Daily
(Ib/day)
0.846
0.181
0.694
1.862
0.303
0.726
5.214
Because the entire Indian Creek watershed is covered by areas within 4 Municipal Separate Storm Sewer
Systems (MS4s), all allocated loads are assigned to the Waste Load Allocation (WLA) category. The
four MS4 jurisdictions are Lower Salford, Telford, Souderton, and Franconia. WLAs were assigned to
each of the three permitted point source facilities as well. Tables ES4-6 show WLAs for permittees in the
watershed.
Table ES-4. Sediment WLAs
NPDES ID
PA0036978
PA0054950
PA0024422
MS4
MS4
MS4
MS4
Facility/Township
Telford Borough Authority
Pilgrim's Pride
Lower Salford Authority
(Harleysville STP)
Lower Salford
Souderton
Telford
Franconia
Existing Load
(Ib/yr)
100,455
5,540
63,926
2,619,340
84,171
58,772
9,757,660
TMDL (Ib/yr)
100,455
5,540
63,926
80,950
7,272
16,864
296,005
Maximum Daily
(Ib/day)
523
35
533
497
45
104
1,818
% Reduction
0%
0%
0%
97%
91%
71%
97%
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June 2008
FINAL Indian Creek TMDLs
Table ES-5. TPWLAs
NPDES ID
PA0036978
PA0054950
PA0024422
MS4
MS4
MS4
MS4
Facility/Township
Telford Borough
Authority
Pilgrim's Pride
Lower Salford Authority
(Harleysville STP)
Lower Salford
Souderton
Telford
Franconia
Existing Load
(Ib/yr)
5695.66
791.53
1066.16
803.32
49.4
118.18
2863.44
TMDL (Ib/yr)
156.10
20.60
101.30
303.29
49.40
118.18
849.18
Maximum Daily
(Ib/day)
0.846
0.181
0.694
1.862
0.303
0.726
5.214
% Reduction
97%
97%
90%
62%
0%
0%
70%
III
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FINAL Indian Creek TMDLs June 2008
CONTENTS
1. Introduction and Background 1
1.1. Watershed Description 1
1.2. Impaired Waterbodies 3
1.3. Water Quality Standards 5
1.4. TMDL Targets 6
1.4.1. Sediment TMDL Target 6
Reference Watershed Approach 6
Selected Reference Watershed and TMDL Targets 6
1.4.2. Nutrient TMDL Targets 8
2. Data Inventory and Analysis 10
2.1. Stream Flow and Climate Data 10
2.2. PADEP Pre-TMDL Monitoring Data 11
3. Source Assessment 23
3.1. Nonpoint Sources 23
3.1.1. Agriculture 23
3.1.2. Biosolids 23
3.1.3. Urban Runoff 24
3.1.4. Septic Systems 25
3.2. Point Sources 25
3.2.1. MS4s 25
3.2.2. NPDES Permitted Facilities 26
Telford 26
Pilgrims Pride 28
Lower Salford 30
Ambient Sampling Above and Below Point Sources 32
3.3. Indian Valley Golf Course Water Withdrawals 33
3.4. Summary of Critical Water Quality Factors 33
4. TMDL Technical Approach 35
4.1. Sediment 35
4.1.1. Watershed modeling - Sediment 35
Land Use and Land Cover Data 35
Soils Data 36
Weather Data 36
4.1.2. Watershed Model Results - Sediment 36
4.2. Nutrients 37
4.2.1. Watershed Modeling - Nutrients 38
4.2.2. Model Setup 39
Land Use and Land Cover Data 41
Soils Data 42
Weather Data 43
Nonpoint Source Representation 44
4.2.3. Model Testing 48
4.2.4. Watershed Model Results - Nutrients 53
4.2.5. Receiving Water Model 55
4.2.6. EFDC Model Setup 56
Segmentation 57
Meteorological Data 58
Point Source Representation 58
Nonpoint Source Representation 59
IV
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June 2008 FINAL Indian Creek TMDLs
Linkage of GWLF to EFDC 59
4.2.7. EFDC Model Calibration 60
5. TMDL Allocation Analysis 64
5.1. Sediment TMDLs 65
Sediment WLAs 65
5.2. Nutrient TMDLs 68
Nutrient WLAs 68
5.3. Daily Load Expressions 70
5.4. Margin of Safety 71
5.5. Future Residential Growth 72
5.6. Critical Conditions and Seasonal Variations 72
6. Reasonable Assurance 73
7. Public Participation 74
References 76
Appendix A: Ambient Sampling Results Above and Below Municipal STPs 78
Appendix B: EFDC Calibration Plots 86
Appendix C: Results of EFDC Sensitivity Analysis 91
Appendix D: EFDC Results for Baseline Scenario 93
Appendix E: EFDC Results for Load Reduction Scenario 96
Appendix F: Suggested Adaptive Implementation Strategy for NPDES Point Sources Dischargers 98
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FINAL Indian Creek TMDLs
June 2008
TABLES
Table 1-1. Summary of 2004 303(d) Listings in the Indian Creek Watershed 3
Table 1-2. Impaired and reference watershed comparison 7
Table 1-3. Sediment Endpoints Established for Indian Creek Sediment TMDL 7
Table 1-4. Total Phosphorus Endpoint Development Approaches 8
Table 1-5. N:P Ratio statistics for streams in Northern Piedmont 9
Table 1-6. Nutrient Endpoint Established for Indian Creek Nutrient TMDL 10
Table 1-7. Applicable DO criteria 10
Table 2-1. Concentration of Various Constituents in Indian Creek Tributaries 22
Table 2-2. Comparison of Chemical Data (mg/1) at Rt 63, Salford Tributary, and Indian Creek Mouth ..22
Table 3 -1. Nutrient Permit Limits for NPDES Facilities in the Indian Creek Watershed 26
Table 4-1. Land Use in the Indian Creek Watershed (Sediment model) 36
Table 4-2. Modeled Sediment Loads and Landuse Loading Rates in the Indian Creek Watershed 37
Table 4-3. NLCD Landuse Coverage Category Crosswalked with Modeled Landuse Categories 41
Table 4-4. Land Use in the Indian Creek River Watershed 41
Table 4-5. Land Use in the East Branch Perkiomen Creek Watershed 42
Table 4-6. Meteorological Stations 44
Table 4-7. Assigned C and P Factor Values for the Indian Creek Watershed 45
Table 4-8. Nitrogen and Phosphorus Concentrations in Runoff 45
Table 4-9. Septic Inspection Results by Modeled Subbasin 47
Table 4-10. Septic Representation in GWLF 48
Table 4-11. Average Annual Watershed and Point Source Nutrient Loads for the Modeled Period 53
Table 4-12. Average Monthly Watershed Loads for the Modeled Period 53
Table 4-13. Modeled Landuse Loading Rates for Nutrients 53
Table 4-14. Width and Average Depth at the Cross-Sections 58
Table 4-15. Point source data used in Indian Creek EFDC model 58
Table 4-16. Ratio Used to Convert GWLF Constituents to EFDC Constituents 60
Table 4-17. Comparison of Measured and Modeled Depth on the Main Indian Creek 60
Table 4-18. Key Water Quality Parameters for Indian Creek EFDC Model 61
Table 5-1. Summary of Sediment TMDL Loads for Indian Creek Watershed 65
Table 5-2. Sediment WLAs for Continuous Point Sources in the Indian Creek Watershed 66
Table 5 -3. Existing, Reference and TMDL Landuse Loading Rates for Sediment 67
Table 5-4. MS4 Sediment WLAs (Ib/yr) 67
Table 5-5. Nutrient TMDL loads for Indian Creek Watershed 68
Table 5 -6. Summary of Continuous Discharger's TP Loading under the Indian Creek TMDL 69
Table 5-7. Existing, TMDL, and Maximum Daily Total Phosphorus WLAs for Permittees 69
Table 5-8. MS4 Related WLAs for Total Phosphorus 70
Table 5-9. Variables used in calculating the Daily Maximum Loads 71
FIGURES
Figure 1-1. Indian Creek watershed with municipalities, gauging station, and discharge points 2
Figure 1-2. 303(d) impaired reaches in the Indian Creek watershed 5
Figure 2-1. Historical precipitation (PA 3437) and flow (USGS 01472810) from 1995 to 2004 11
Figure 2-2. Diurnal monitoring locations 13
Figure 2-3. Diurnal DO (mg/1) patterns at Indian Creek monitoring locations 14
Figure 2-4. Diurnal DO (%) patterns at Indian Creek monitoring locations 14
Figure 2-5. Longitudinal DO patterns in different time intervals at monitoring locations 16
Figure 2-6. Longitudinal BOD patterns at Indian Creek sampling locations 17
Figure 2-7. Longitudinal total suspended solids patterns at Indian Creek sampling locations 17
VI
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June 2008 FINAL Indian Creek TMDLs
Figure 2-8. Longitudinal ammonia patterns at Indian Creek sampling locations 18
Figure 2-9. Longitudinal dissolved phosphorus patterns at Indian Creek sampling locations 18
Figure 2-10. Longitudinal dissolved nitrogen patterns at Indian Creek sampling locations 19
Figure 2-11. Longitudinal total nitrogen patterns at Indian Creek sampling locations 19
Figure 2-12. Longitudinal total ortho phosphorus patterns at Indian Creek sampling locations 20
Figure 2-13. Longitudinal dissolved ortho phosphorus patterns at Indian Creek sampling locations 20
Figure 2-14. Longitudinal total phosphorus patterns at Indian Creek sampling locations 21
Figure 2-15. Longitudinal nitrate + nitrite -N patterns at Indian Creek sampling locations 21
Figure 3-1. Land Application Sites (eMapPA) 24
Figure 3-2. Telford DMR data 27
Figure 3-3. Pilgrims Pride DMR data 29
Figure 3-4. Lower Salford DMR data 31
Figure 3 -5. Total Phosphorus concentration above and below Telford Discharge 33
Figure 4-1. Indian Creek subwatershed delineations 40
Figure 4-2. Soil distribution in the Indian Creek watershed 43
Figure 4-3. Septic Inspection Study Area and Results 46
Figure 4-4. East Perkiomen Creek watershed 50
Figure 4-5. Observed and Predicted Monthly Streamflow (centimeters) - East Branch Perkiomen Crk at
USGS 01493500 (1997-2004) 51
Figure 4-6. Observed and Predicted (centimeters) - East Branch Perkiomen Crk at USGS 01493500
(1997-2004) entire period 52
Figure 4-7. Comparing Annual PS andNPS Nutrient Loading in Indian Creek 54
Figure 4-8. EFDC model structure 55
Figure 4-9. EFDC hydrodynamics module structure 56
Figure 4-10. EFDC water quality module Structure 56
Figure 4-11. Indian Creek EFDC Modeling Domain 57
Figure 4-12. Temperature calibration results 61
VII
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June 2008 FINAL Indian Creek TMDLs
l. INTRODUCTION AND BACKGROUND
Section 303(d) of the Clean Water Act and the U.S. Environmental Protection Agency's (USEPA) Water
Quality Planning and Management Regulations (Title 40 of the Code of Federal Regulations [CFR] Part
130) require states to develop Total Maximum Daily Loads (TMDLs) for waterbodies that are not
supporting their designated uses even if pollutant sources have implemented technology-based controls. A
TMDL establishes the maximum allowable load (mass per unit of time) of a pollutant a waterbody is able
to assimilate and still support its designated use(s). The maximum allowable load is determined based on
the relationship between pollutant sources and in-stream water quality. A TMDL provides the scientific
basis for a state to establish water quality-based controls to reduce pollution from both point and nonpoint
sources to restore and maintain the quality of the state's water resources (USEPA 1991). The
development of TMDLs requires an assessment of streams' assimilative capacity, critical conditions, and
other considerations.
Several segments in the Indian Creek watershed have been listed on Pennsylvania's 303(d) list of
impaired waters for not meeting aquatic life uses and for impairments due to siltation and nutrients. This
report documents TMDLs developed to address the nutrient and siltation impairments in Indian Creek and
its tributaries.
1.1. Watershed Description
Indian Creek, a third-order stream with a drainage area of approximately 7 square miles, flows
approximately 6.1 miles, through areas of Montgomery County, Pennsylvania (Figure 1-1). Its watershed
includes portions of eight municipalities and has three National Pollution Discharge Elimination System
(NPDES) permitted discharges. About 19 tributaries (tributary 01182 through tributary 01200) drain to
Indian Creek, some of which are intermittent. Various degrees of residential development (low intensity
residential, medium intensity residential and high intensity residential) are scattered thoughout the
watershed. The middle portion of the watershed is predominantly pasture.
The mainstem of Indian Creek flows southwesterly and discharges to the East Branch Perkiomen Creek.
The nearest U.S. Geological Survey (USGS) stream gauging station (01472810) is located on East
Perkiomen Creek near Schwenksville.
National Land Cover Data (NLCD) are available through the Multi-Resolution Land Characteristics
Consortium (MRLC) as a joint effort between USEPA and USGS. NLCD data from 2001 were obtained
for the Indian Creek watershed and is presented in Figure 1-2.
Based on the 2001 NLCD, pasture is the dominant land use, comprising approximately of 36 percent,
followed by low and high intensity development (20 and 21 percent respectively). Agriculture comprises
of approximately 17 percent of the watershed, while forested areas comprise of only approximately 5
percent of the watershed area. Spatially these areas are scattered throughout the watershed. A golf course
is located in the northern half of the study area.
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FINAL Indian Creek TMDLs
June 2008
CKHILL
N
V
r-Satford)Twp Aulhot
1.5 Miles
SKIPPA
I
Weather Station (PA-
l)$GS Gauging Station,
Go'|f Course Water Withdrawal
Discharge Points
Weather Station (PA-343V)
Municipalities
Indian Creek
Indian Crqek Watershed
1>«veloped\Ppen Space
Developed Lpw Intensity
^H Developed Medium Intensity
^B Developed Hig"
| | Barren Land
Forest
Pasture/Hay
| Cultivated Crops
| | Wetlands
Stream Network
- Major Roads
Figure 1-1. Indian Creek watershed with municipalities, gauging station, and discharge points.
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June 2008
FINAL Indian Creek TMDLs
1.2. Impaired Waterbodies
Indian Creek was placed on Pennsylvania's 1996 303 (d) list of impaired waterbodies for not meeting the
designated aquatic life use due to various pollutants, including salinity, siltation, and nutrients.
Subsequent listing cycles (2004 and 2006) have included additional impairments, as shown in the
summary of the 2006 listings in Table 1-1. Attributed causes include municipal point sources, agriculture,
and urban and residential stormwater runoff (Figure 1-2). Based on PADEP field assessments, the stream
was also overwhelmed by sewage effluents in two locations. Available data show severe swings in
dissolved oxygen (DO), oxygen saturation levels and pH. Data also indicate phosphorous and nitrogen
concentrations in this system are elevated, likely contributing to the presence of thick algal mats that
frequently blanket the stream in various locations throughout the watershed.
Results of one specific field investigation conducted on the Unnamed Tributary to Indian Creek,
Stream Code 01182, on August 14, 2003 are included here for illustration of PADEP's impairment
assessment. During this investigation, PADEP conducted chemical and biological sampling at two
stations upstream and downstream of the Lower Salford Township Authority Harleysville STP
(PA0024422) outfall. Based on the results of this investigation, the invertebrate community at station
one was found to be "fair to poor" and the invertebrate community at Station two was found to be
"poor". Recommendations of the field staff conducting the investigation included the
recommendation "that the unnamed tributary to Indian Creek be listed as impaired from the Lower
Salford Township Authority, Harlyesville STP outfall to the mouth for municipal point source
nutrients." It was upon this recommendation and specific findings in the field as well as others similar
to it throughout the Indian Creek watershed, that the stream was included on PADEP's 303(d) list as
impaired. As another example, a second field form on which PADEP recorded results of the stream
assessment of Indian Creek at Indian Creek Road found: "Indian Creek is impaired based on the taxa
collected. This station lacked pollution sensitive taxa and was dominated by facultative taxa. The
cause of impairment is likely from storm water runoff from Harleysville and Telford and from sewage
effluent as the stream is effluent dominated."
This TMDL report establishes sediment and nutrient allocations to restore designated aquatic life uses in
all of the impaired segments of Indian Creek and its tributaries.
Table 1-1. Summary of 2004 303(d) Listings in the Indian Creek Watershed
Source
Cause
Assessment Unit
Miles
Date
Listed
Indian Creek
Agriculture
Small Residential Runoff
Urban Runoff/Storm Sewers
Agriculture
Municipal Point Source
Source Unknown
Municipal Point Source
Golf Courses
Siltation
Siltation
Nutrients
Cause Unknown
Salinity/TDS/Chlorides
Cause Unknown
NewlD:2851
Old 10:2001091 9-1 119-GLW
New ID:3372
Old 10:2002041 5-1 038-KAW
New ID:7958
Old ID:7007
New 10:10180
Old 10:990405-1 500-ACW
2.16
1.4
1.05
1.77
2004
2004
2004
2004
2004
1996
1996
2002
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FINAL Indian Creek TMDLs
June 2008
Source
Road Runoff
Small Residential Runoff
Cause
Siltation
Cause Unknown
Assessment Unit
Miles
Date
Listed
2002
2002
Indian Creek (Unt 00979)
Golf Courses
Road Runoff
Small Residential Runoff
Cause Unknown
Siltation
Cause Unknown
New 10:10180
Old 10:990405-1 500-ACW
1
2002
2002
2002
Indian Creek (Unt 01182)
Municipal Point Source
Nutrients
New 10:2948
Old 10:2001 101 0-1 320-GLW
0.3
2004
Indian Creek (Unt 01185)
Municipal Point Source
Nutrients
New 10:2948
Old 10:2001 101 0-1 320-GLW
0.3
2004
Indian Creek (Unt 01191)
Small Residential Runoff
Siltation
New 10:3373
Old 10:2002041 5-1 200-KAW
0.76
2004
Indian Creek (Unt 01192)
Small Residential Runoff
Siltation
New 10:3373
Old 10:2002041 5-1 200-KAW
0.25
2004
Indian Creek (Unt 01194)
Agriculture
Urban Runoff/Storm Sewers
Municipal Point Source
Small Residential Runoff
Siltation
Nutrients
Siltation
New 10:3372
Old 10:2002041 5-1 038-KAW
0.54
2004
2004
2004
2004
Indian Creek (Unt 01200)
Agriculture
Municipal Point Source
Small Residential Runoff
Urban Runoff/Storm Sewers
Municipal Point Source
Source Unknown
Siltation
Nutrients
Siltation
Salinity/TDS/Chlorides
Cause Unknown
New 10:3372
Old 10:2002041 5-1 038-KAW
New 10:7958
Old 10:7007
0.59
0.61
2004
2004
2004
2004
1996
1996
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June 2008
FINAL Indian Creek TMDLs
Municipal Point Source/Salinity/TDS/Chlorides 1996
Source Unknown/Cause Unknown 1996
Agriculture/Siltation 2004
Municipal Point Source/Nutrients 2004
Small Residential Runoff/Siltation 2004
Urban Runoff/Storm Sewers/SiItation 2004
Tributaries 01191 and 01192
Small Residential RunofT/Siltation 2004
Tributary 0118
LOWER SALFORD \ Municipal P«5int Source/Nutrients 2004
NPDES Permits
A Lower Salford Twp Authonty
A Pilgrim's Pride
A Telford Borough Authority
Municipalities
[ _ ] Indian Creek Watershed
l~~l East Branch Perkiomen Creek Subbasms
Indian Creek Impaired Reaches
^^ Not Attaining
Unassessed
Figure 1-2. 303(d) impaired reaches in the Indian Creek watershed.
1.3. Water Quality Standards
Applicable water quality standards for streams across Pennsylvania are included in Pennsylvania's Water
Quality Standards at 25 PA Code, Chapter 93. The designated use for streams in the Indian Creek
Watershed is to provide habitat and appropriate ecological services as a trout stocking fishery (TSF).
Numeric criteria applicable to Indian Creek and its tributaries and the related impairments include the
following DO criteria:
• February 1-July 31: Maintain a minimum daily average of 6.0 mg/1 with a daily minimum of 5.0
mg/1
• August 1-January 31: Maintain a minimum daily average of 5.0 mg/1 with a daily minimum of
4.0 mg/1
Pennsylvania does not currently have specific numeric water quality criteria for nutrients and sediments.
However, narrative water quality criteria exist (25 PA Code Chapter 93.6 (a and b)) which state: "Water
may not contain substances attributable to point or nonpoint source discharges in concentration or
amounts sufficient to be inimical or harmful to the water uses to be protected or to human, animal, plant
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FINAL Indian Creek TMDLs June 2008
or aquatic life;" and "In addition to other substances listed within or addressed by this chapter, specific
substances to be controlled include, but are not limited to, floating materials, oil, grease, scum and
substances which produce color, tastes, orders, turbidity or settle to form deposits." Excessive nutrient
concentrations in streams and rivers contribute to algal blooms and other conditions associated with
eutrophication.
1.4. TMDL Targets
To meet the designated aquatic life uses of Indian Creek and its tributaries, numeric endpoints for
sediment and for nutrient related parameters were identified. A reference approach was used for
identifying the sediment target. Nutrient targets were developed based on a separate study that applied a
weight of evidence approach, combining multiple analytical techniques to identify appropriate nutrient
endpoints for the TMDL as discussed in Section 1.4.2. The nutrient endpoint for this TMDL consists of
the average seasonal total phosphorus (TP) concentration associated with unimpaired aquatic life uses.
Additional detail regarding derivation of the TMDL endpoints is provided in the following paragraphs.
1.4.1. Sediment TMDL Target
Because Pennsylvania water quality standard regulations do not currently include numeric criteria for
sediment, EPA used the "reference watershed" approach to develop the allowable loading rates to protect
designated uses in Indian Creek.
Reference Watershed Approach
The reference watershed approach is used to estimate the necessary load reduction of sediment that would
be needed to restore a healthy aquatic community and allow the streams in the watershed to achieve their
designated uses. The reference watershed approach is based on determining the current loading rates for
the pollutants of interest from a selected unimpaired watershed that has similar physical characteristics
(i.e., land use, soils, size, geology) to those of the impaired watershed.
The reference watershed approach pairs two watersheds, one attaining its uses and one that is impaired
based on biological assessment. Both watersheds must have similar land cover and land use
characteristics. Other features, such as base geologic formation, soils, percent slope, land use, and
ecoregion, should be matched to the extent possible. The objective of this process is to reduce the loading
rate of sediment (or other pollutant) in the impaired stream segment to a level equivalent to or slightly
lower than the loading rate in the unimpaired reference stream segment. Achieving the sediment loadings
set forth in the TMDLs will ensure that the designated aquatic life of the impaired stream is achieved.
Selected Reference Watershed and TMDL Targets
The TMDL targets established for the Indian Creek sediment TMDL were determined using Ironworks
Creek as the reference watershed. Ironworks Creek is a subwatershed of the Wissahickon Creek
watershed and was also used to establish the reference conditions for the Wissahickon Creek sediment
TMDL. The TMDL process uses loading rates in the non-impaired watersheds as targets for loading
reductions in the impaired watersheds. The reference watershed was chosen based on the fact that it was
an urban watershed that was not impaired by siltation and had similar physical characteristics to the
Indian Creek watershed (i.e., watershed size, land use/cover, soils, geology, ecoregion). Table 1-2
presents the characteristics of both the Indian Creek and Ironworks Creek watersheds.
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June 2008
FINAL Indian Creek TMDLs
The sediment delivery ratios for the Indian Creek watershed and its reference watershed were 0.19 and
0.18, respectively. Table 1-3 shows the sediment endpoints used to develop the sediment TMDL for
Indian Creek.
Table 1-2. Impaired and reference watershed comparison
Characteristic
Watershed Type
Watershed Size (acres)
Geologic Province
Dominant Rock Types
Dominant Soils
Ecoregions
Percent Slope of Watershed
Point Sources
Percent Urban
Percent Forested
Percent Land Use:
Low Intensity Development
High Intensity Development
Hay/Pasture
Cropland
Conifer Forest
Mixed Forest
Deciduous Forest
Bare Rock/Sand/Clay
Wetlands
Transitional
Indian Creek
Impaired Watershed
4,480
Piedmont
Shale
C
Triassic Lowlands
Piedmont Uplands
0.71%
3
40.35%
4.94%
19.16%
22.52%
36.13%
16.76%
0.04%
0.0%
4.9%
0.27%
0.23%
Ironworks Creek
Reference Watershed
11,114
Piedmont
Sandstone/Metamorphic-lgneous
C&B
Triassic Lowlands
Piedmont Uplands
0.63%
0
44%
31%
39.8%
4.2%
11.7%
10.9%
1.8%
10.3%
19.6%
0.0%
0.0%
0.1%
Table 1-3. Sediment Endpoints Established for Indian Creek Sediment TMDL
Land Use
Low-Intensity Residential
High-Intensity Residential/Urban
Hay/Pasture
Row Crops
Coniferous Forest
Mixed Forest
Deciduous Forest
Quarry
Coal Mines
Unit Area Loading (Ib/ac/yr)
124.12
105.12
51.60
464.28
3.13
3.99
5.43
0.00
0.00
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FINAL Indian Creek TMDLs
June 2008
1.4.2. Nutrient TMDL Targets
There are presently no numeric water quality criteria for nutrients defined by PADEP water quality
standards for streams. As a result, adequately protective numeric endpoints for the TMDL were derived
through a separate nutrient endpoint identification study supported by EPA to develop scientifically valid
TMDL targets. The endpoint identification methodology relied on a multiple lines of evidence approach
using frequency distribution based analysis, stressor-responses analyses, and literature based values. The
resulting candidate values were then considered and a weight-of-evidence selection process applied to
select the final endpoints. The endpoint development approach used was similar to that applied for
nutrient criteria development to identify nutrient targets that would protect aquatic life uses. Data for the
effort were collected from sites in Pennsylvania, Maryland and New Jersey, in the same ecoregion
(Northern Piedmont) as Indian Creek.
For the frequency distribution based approach, water quality data was drawn from a variety of databases
including the EPA STORET and Ecological Monitoring and Assessment Program (EMAP) databases,
United States Geological Survey (USGS) National Water Inventory System (NWIS) and National Water
Quality Assessment (NAWQA) program, and the Maryland Biological Stream Survey (MBSS) database.
Two populations of sites were developed: sites for which nutrient samples were available (all sites), and
sites for which watershed land cover was available and for which reference criteria could be applied
(reference sites). Based on these populations, a 25th percentile nutrient concentration of TN and TP were
calculated from all sites, and a 75th percentile of for TN and TP concentrations were calculated from
reference sites. Results ranged from 1.3-1.5 mg/L for TN and 16-17 ug/L for TP.
Another approach used was the modeled reference expectation approach, under which reference
conditions were predicted from current conditions. Using data from the MBSS, USGS NAWQA and
EPA EMAP programs, and based on natural molar N:P ratios, a range between 2-37 ug/L of total
phosphorus was identified.
Stressor-response approaches, which explore the relationships between response variables and nutrient
concentrations, were used as another line of evidence to derive appropriate nutrient endpoints. Data (i.e.,
nutrients, periphyton, macroinvertebrate composition data, algal biomass, etc.) from EPA EMAP, USGS
NAWQA, USGS National Water Information System (NWIS), EPA STORET, EPA national nutrient
center (NNC) database, MBSS, and PADEP periphyton biomass data were used. Application of various
data analysis techniques resulted in TP thresholds as identified in Table 1-4.
A literature review of several studies was also conducted in support of this effort. Various studies, EPA
recommended nutrient thresholds, state nutrient criteria studies, etc. showed TP endpoints ranging
between 13-100 ug/L TP.
Table 1-4. Total Phosphorus Endpoint Development Approaches
Approach
Category
Reference Approach
Stressor-Response
Name
Reference Site 75th Percentile
All Sites 25th Percentile
Modeled Reference Expectation
Conditional Probability - EPT
Conditional Probability - Clinger Taxa
Total Phosphorus
Endpoint (ug/L)
16-17
17
2-37
38
39
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June 2008
FINAL Indian Creek TMDLs
Conditional Probability - % Urban Intolerant
Conditional Probability - Diatoms TSI
64
36
Mechanistic Models
Indian Creek
40
Other Literature
USEPA Recommended Regional Criteria
36
Summarization of Several Studies
13-100
Using a weight-of-evidence approach, the above analyses were weighted based on their applicability and
the strength of the analysis. The stressor-response analyses were weighted more heavily than the
reference-approach analyses due to the linkage between nutrient concentrations to specific aquatic life
(both invertebrate and algal) endpoints. Using invertebrate taxa metrics, conditional probability analyses
evaluated those TP concentrations which increased the risk of exceeding degradation thresholds
developed for these macroinvertebrate metrics in comparable piedmont streams in Maryland. For the
diatom Tropic State Index (TSI), the same analysis was used to identify TP concentration associated with
a shift from meso- to eutrophic conditions. The scientific literature was variably weighted, since it
included data from regions proximate to Pennsylvania. Based on greater weight to stressor-response
models, a TP endpoint of 40 ug/L was selected. This value is comparable to the majority of stressor-
response analyses, on the high end of the reference approaches, and intermediate to the scientific
literature values, but comparable to regionally relevant literature values.
Potential nitrogen endpoints for the TMDL were evaluated; however, the principal effort of the endpoint
determination work was the development of total phosphorus endpoints. This was principally due to the
fact that TP was assessed as the cause of impairment. Analyses support the conclusion that these streams
are P limited, based on instream N:P molar ratios evaluated against Redfield. The distributional statistics
of N:P ratios taken from more than 552 stream sites across the northern piedmont region in Pennsylvania
and Maryland are shown in Table 1-5.
Table 1-5. N:P Ratio statistics for streams in Northern Piedmont
Statistics for N:P Ratios in Northern Piedmont Sites in Pennsylvania and Maryland (N=552)
Minimum
5th Percentile
10thPercentile
25th Percentile
Median
Average
N:P Ratio
5
17
25
57
158
259
The critical Redfield ratio is 16:1, values below indicating N limitation and those above, P limitation.
Ratios have to be considered in relation to supply and become less meaningful as nutrient supplies exceed
uptake capacity of streams. Even so, clearly more than 95 percent of the streams are P limited.
Because these systems are not N limited, relationships between TN and response measures are more
questionable. The fact that N is not limiting also means that TN contributes less to use impairment in this
region. Endpoints are best derived when clear connections to use impairment can be made. Seeing that
there are less clear connections with TN and stream impairment in this region, enpoints for TN were not
specified for the TMDL.
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FINAL Indian Creek TMDLs June 2008
The selected TP endpoint would be applied as an average concentration during the growing season from
April to October, which in streams is typically the time during which the greatest risk of deleterious algal
growth exists. A seasonal sample period is more appropriate than an annual or daily timeframe for this
reason.
A more detailed description of the analyses and conclusions described above can be found in a summary
report entitled, Development of Nutrient Endpointsfor the Northern Piedmont Ecoregion of
Pennsylvania: TMDL Application (Paul and Zheng, 2007).
Based on results and recommendations of the nutrient endpoint identification study, the TP endpoint for
the Indian Creek TMDL is listed in Table 1-6.
Table 1-6. Nutrient Endpoint Established for Indian Creek Nutrient TMDL
Parameter
TP
Average Concentration
40 ug/L
Applicable Period
April 1- October 31
In addition, water quality must also meet applicable dissolved oxygen criteria in stream.
Table 1-7. Applicable DO criteria
Daily Average
6.0 mg/L
5.0mg/L
Daily Minimum
5.0 mg/L
4.0 mg/L
Period
February 1-July 3 1
August 1- January 3 1
2. DATA INVENTORY AND ANALYSIS
To evaluate conditions throughout the watershed, chemical and physical data collected at various
locations along the mainstem and tributaries were analyzed. USGS flow gauging station data and weather
station data were also evaluated to support this analysis. To evaluate point source contributions in greater
detail, discharge monitoring reports (DMR) were obtained for active point source dischargers in the
watershed. Chemical and biological ambient monitoring data collected by PADEP upstream and
downstream of these point sources were also evaluated; the results of these efforts are summarized in
Appendix A.
2.1. Stream Flow and Climate Data
Flow likely affects water quality in streams, by regulating concentrations and in stream processes. Most
of the time, stream flow is driven by precipitation patterns and ground water contributions. Precipitation
plays a critical role in nonpoint source pollution, where it washes away the unassimilated nutrients from
the terrestrial environment to streams during wet weather conditions. However, during dry weather
periods, the system behaves differently. As a result, assessment of stream flow and precipitation pattern
is a critical link in TMDL development and water quality analysis.
To assess hydrologic conditions of the Indian Creek Watershed, flow data were obtained from the USGS
gauging station 01472810, one of the nearest gauging stations to the Indian Creek watershed. It is located
on East Branch Perkiomen Creek near Schwenksville, Pennsylvania, and drains approximately 58.7
square miles. Rainfall data were obtained from the National Climate Data Center (NCDC) Station PA-
3437, the nearest weather station to the Indian Creek watershed outlet. Figure 2-1 shows the monthly
average values of precipitation and flow for a ten year period from 1995 to 2004. It can be seen that the
lowest flows are during the summer period (July-August) and high flows are experienced during winter
and early spring.
10
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June 2008
FINAL Indian Creek TMDLs
40.0
tr:l>trOtr:l>trOtr:l>trOtr:l>trOtr:l>trOtr:l>trOtr:l>trOtr:l>trOtr:l>trOtr:l>trO
Month
300
250
"TT| | I | | | I |
30
10 11
12
Figure 2-1. Historical precipitation (PA 3437) and flow (USGS 01472810) from 1995 to 2004.
2.2. PADEP Pre-TMDL Monitoring Data
A review of available data in the Indian Creek watershed (DMR data and the ambient monitoring above
and below the Telford and Salford NPDES facilities) resulted in the determination that additional
monitoring was needed to support TMDL development. EPA provided a monitoring strategy to PADEP
for additional data collection. On May 9, 10, and 11, 2006 additional data were collected by PADEP for
the Indian Creek Watershed at various locations (Figure 2-2). Various physical parameters such as
dissolved oxygen (DO) (mg/1), Temperature (C), pH, Conductivity (mS/cm), Salinity (ppt), and TDS (g/1)
were collected by YSI sondes at 3 minute intervals during a 48-hour period. This section discusses the
DO and nutrient data collected in Indian Creek.
11
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FINAL Indian Creek TMDLs June 2008
Plotting DO (mg/1) against time (hours) shows a clear diurnal pattern (Figure 2-3) for all of the sites. The
Pilgrims Pride site was the only sampling site where DO was always above daily average DO criteria. For
all sites in the watershed, minimum DO concentrations tend to occur between the hours of 11:00 PM and
7:00 AM. DO concentrations rise from approximately 6:00/7:00 AM until about noon, after which they
begin to fall. These fluctuations indicate that biological activity is likely a factor because minimum DO
levels at two stations, Bergey and Godshall, were significantly lower than the rest of the stations on the
second day of monitoring. These two stations bracket the golf course upstream and downstream,
respectively.
Similarly, DO saturation was plotted against time (Figure 2-4). A clear diurnal cycle was noted for all of
the sites. DO saturation was above 100% during most of the day time, suggesting high biological activity
(i.e., aquatic plant/algae growth). During the day, algae use CO2, releasing O2 to the stream, and use O2 at
night, releasing CO2 to the stream. Anecdotal reports by PADEP sampling staff indicated that significant
algal biomass was present throughout the watershed at the time of sampling. DO saturation was less than
100% during nighttime hours. Minimum DO saturation levels at two stations, Bergey and Godshall, were
significantly lower than the rest of the stations on the second day of monitoring.
12
-------
June 2008
FINAL Indian Creek TMDLs
N
A
SALFORD
WEST ROCKHILL
-IILLTOWN
TELFORD
At Keller Creamery
LOWER SALFORD
0.5 1
1.5 Miles
| | Indian Creek Watershed
Indian Creek
Municipalities
• Sampling Stations
Figure 2-2. Diurnal monitoring locations.
13
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FINAL Indian Creek TMDLs
June 2008
O)
O
Q
p
DTCOINJ
Ind Mouth
Minimum Criteria
for DO
Figure 2-3. Diurnal DO (mg/1) patterns at Indian Creek monitoring locations.
250.00
§ 100.00
Bergey
Godshall
Rlgrims
RT63IN
Saltrib
IndMouth
Date-Time
Figure 2-4. Diurnal DO (%) patterns at Indian Creek monitoring locations.
14
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June 2008 FINAL Indian Creek TMDLs
Longitudinal analysis of the water quality data was conducted to assess the variation in these parameters
from the headwaters to the mouth. For this analysis, each 3 minute interval of data was averaged over
three hours (for better graphical representation) to represent one data point. As shown in Figure 2-5, there
is an apparent decrease in DO (mg/1) concentration at the Godshall sampling site. Concentrations then
rebounded or remained similar moving downstream of the Godshall site until the next sampling site at the
mouth of Indian Creek. The drop in DO concentration at this location indicates that the golf course
activities are likely impacting water quality. Either water use by the golf course or other conditions
related to golf course operations could be contributing to the DO drop. At the time of sampling, PADEP
staff witnessed grass clippings having been disposed of directly in the stream (personal communication
with PADEP staff). Longitudinally, most DO concentrations remained above the minimum DO criteria of
5 mg/1.
Chemical data were collected along with physical data. Samples were collected for chemical analysis on
May 11, 2006 at various sites in Indian Creek. Longitudinal analysis was conducted for various water
quality constituents such as BOD, total suspended solids, dissolved phosphorous, dissolved nitrogen, total
nitrogen, alkalinity, total ortho phosphorous, dissolved ortho phosphorous, total phosphorous, nitrate +
nitrite, and ammonia.
Figure 2-6 presents the longitudinal analysis of BOD data collected on May 11, 2006, showing the
highest level of BOD at the Bergey Road site (possibly related to discharge associated with the Telford
facility). BOD then decreases downstream. Total suspended solids remained similar from the headwaters
until the Keller Creamery site, and then exhibited a slight increase at the Rt. 63 site (Figure 2-7). The
ammonia-N concentration increased at Godshall but was relatively consistent for the rest of the creek
(Figure 2-8). Longitudinal analysis for the sampling period shows similar patterns for dissolved
phosphorous, dissolved nitrogen, total nitrogen, total ortho phosphorous, dissolved ortho phosphorous,
total phosphorous, and nitrate + nitrite (Figures 2-9 to 2-15). After seeing high values at the Bergey Road
site, levels tend to decrease along the mainstem to the sampling station at Rt. 63. Then, an increase is
seen in nutrient levels between the Rt. 63 station and the sampling station at the mouth of Indian Creek.
This increase may be attributable to inputs from the tributary on which the Lower Salford facility is
located (trib 01182).
15
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FINAL Indian Creek TMDLs
June 2008
-5/9/2006 1400-1600 Mrs
-5/9/2006 1700-1900 Mrs
- 5/9/2006 2000-2200 Mrs
- 5/9/2006 2300-
5/10/2006 0100 Mrs
- - - Mnimum Criteria for DO
10000 8000 6000 4000 2000 0
Distance in meters
Longitudinal Pattern of DO
-5/10/2006 0200-0400 Mrs
-5/10/2006 0500-0700 Mrs
-5/10/2006 0800-1000 Mrs
-5/10/2006 1100-1300 Mrs
Mnimum Criteria for DO
10000 8000 6000 4000 2000 0
Distance in meters
-5/10/2006 1400-1600 Mrs
-5/10/2006 1700-1900 Mrs
-5/10/2006 2000-2200 Mrs
5/10/2006 2300-5/11/2006 0100
Mrs
- - - Mnimum Criteria for DO
10000 8000 6000 4000 2000 0
Distance in meters
Longitudinal Pattern of DO
5/11/2006 0200-0400 Mrs
5/11/2006 0500-0700 Mrs
5/11 /2006 0800-1000 Mrs
5/11/2006 1100-1300 Mrs
- Minimum Criteria for DO
10000 8000 6000 4000 2000 0
Distance in meters
Figure 2-5. Longitudinal DO patterns in different time intervals at monitoring locations.
16
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June 2008
FINAL Indian Creek TMDLs
BOD
8.00
Inflow from Pil aim's Pride trib
from Lower Salf >rd trib trib
0.00
10000
8000 6000 4000
Distance in meters from mouth
2000
Figure 2-6. Longitudinal BOD patterns at Indian Creek sampling locations.
A c:n
4.00 -
15 3.50 -
_§
% 3.00 -
"o
w 2.50 -
1 2.00 -
Q.
<7> 1.50 -
"ro
o 1.00 -
0.50 -
0 00 -
Bergey
IX ^
r\c
spended Soilds
Her
\|Godshall Creameryl
\l
\
I
\ \
1 ^
,*- -A.
Il
" -^
iflow from Pil"
\
RT 63 Mouth of 1C
\
\
\
\
~L
N
/
/
/
Inf
k
A
t\
\i
i V
ow from Lowe
1
—•—Total
Suspended
Solids
• Salford trib trib
10000 8000 6000 4000 2000 0
Distance in meters from mouth
Figure 2-7. Longitudinal total suspended solids patterns at Indian Creek sampling locations.
17
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FINAL Indian Creek TMDLs
June 2008
Ammonia-N
Inflow fiom Lower Saliord trib trib
0
10000
8000
6000 4000
Distance (m)
2000
Figure 2-8. Longitudinal ammonia patterns at Indian Creek sampling locations.
n «n
i Phosphorous (mg/l)
3 O O O O C
0 Ji. Ol
§ 0.20 -
b
0.10 -
0 00
Bergey
\
*
Inflow froi
Dissolved Phosphorous
Godshall
» \ Kelle
\ \ Crea
\\
\\
\
^^.
/
/
/
n Pilgrim' sPrii
r R
mery
\
\
\
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June 2008
FINAL Indian Creek TMDLs
0
10000
d trib trib
8000 6000 4000 2000
Distance in meters from mouth
Figure 2-10. Longitudinal dissolved nitrogen patterns at Indian Creek sampling locations.
19 00
10.00 -
I3 8.00 -
£=
o 6.00 -
iz
"ro
-5 4.00 -
H
2.00 -
0 00
Bergey
\
Total Nitrogen
Godshall Mouth of 1C
n
\
\
X
K
c
r
\
Inflow from Pil
eller
reamerv
1
,
>L
jrim'k Pride trib
RT63
\
\
\
—
Inflc
\
\
\
\
\ f
V
w from Lower S
— •— Total
Nitrogen
dford trib trib
10000 8000 6000 4000 2000 0
Distance in meters from mouth
Figure 2-11. Longitudinal total nitrogen patterns at Indian Creek sampling locations.
19
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FINAL Indian Creek TMDLs
June 2008
Phosphorous T Ortho
O
H
(/)
O
o
Q.
0.80
0.70 -
0.60 -
0.50 -
0.40 -
0.30 -
0.20 -
0.10 -
0.00
Inflow f'om Lower Saliord trib trib
Inflow from Pilgrim'£ Pride trib
10000 8000 6000 4000 2000
Distance in meters from mouth
Figure 2-12. Longitudinal total ortho phosphorus patterns at Indian Creek sampling locations.
o RO
^ 0.70 -
0)
"8 °-60 "
_>
§ 0.50 -
b
£ 0.40 -
-e
O
tn H QH
w U.oU -
£
1 0.20 -
en
o
Ql 0.10 -
0 00
Berg
I
4
Inflow from I
1 Phosphorous Ortho Dissolved Ipjgg I
OnHc
nail K<
/ °
;
\
\
u
\;
/
*
ilgrim's Pride 1
,
/
/
/
y
^r^*^^
rib
slier
reameryl
^—
Inflow fro:
^
^
~^
n Lower Salfoi
Mouth of 1C
/
/ + Phosphorous
Ortho
Dissolved
d tab tab
10000 8000 6000 4000 2000 0
Distance in meters from mouth
Figure 2-13. Longitudinal dissolved ortho phosphorus patterns at Indian Creek sampling locations.
20
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June 2008
FINAL Indian Creek TMDLs
Total Phosphorous
o
o
.£=
Q.
0.90
0.80 -
0.70 -
0.60 -
0.50 -
0.40 -
0.30 -
0.20 -
0.10 -
0.00
Iiflow from Pilgrim'& Pride trib
Inflow from Lower i
- Total
Phosphorous
>alford trib trib
10000 8000 6000 4000 2000
Distance in meters from mouth
Figure 2-14. Longitudinal total phosphorus patterns at Indian Creek sampling locations.
Nitrate + Nitrite - N
10.00
+ 4.00^
2.00 -
0.00
Inflow from Pilgrim's Pride trit
Inflow from Low er Salford trib trib
10000 8000 6000 4000 2000
Distance in meters from mouth
Figure 2-15. Longitudinal nitrate + nitrite - N patterns at Indian Creek sampling locations.
21
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FINAL Indian Creek TMDLs
June 2008
Table 2-1 shows concentrations of various constituents at the Pilgrims Pride and the Lower Salford
tributaries, which both receive discharges from point sources. The table shows higher total suspended
solids and alkalinity at Pilgrims Pride relative to the Lower Salford site; however, dissolved nitrogen,
total nitrogen, and nitrate + nitrite - N are higher at the Lower Salford site.
Table 2-1. Concentration of Various Constituents in Indian Creek Tributaries
Concentration (mg/l)
BOD
Total Suspended Solids
Dissolved Phosphorous
Dissolved Nitrogen
Total Nitrogen
Alkalinity
Phosphorous T Ortho
Phosphorous Ortho Dissolved
Phosphorous Total
Nitrate + Nitrite - N
Ammonia-N
Pilgrims Pride
2.400
6.000
0.155
5.840
5.810
140.000
0.163
0.146
0.173
5.200
0.020
Lower Salford Tributary
2.500
2.000
0.669
19.890
19.980
52.600
0.667
0.652
0.720
18.600
0.070
Table 2-2 shows concentrations of various constituents at Rt. 63, Lower Salford, and at the mouth of
Indian Creek. Concentrations of each of the listed constituents in the table increased from Rt. 63 to the
mouth of Indian Creek which may be attributed to input from the Lower Salford tributary. Concentrations
measured at Lower Salford trib were greater than concentrations at both Rt. 63 and at the mouth of Indian
Creek. Additionally, concentrations at the mouth of Indian Creek were greater than concentrations at Rt.
63.
Table 2-2. Comparison of Chemical Data (mg/l) at Rt 63, Salford Tributary, and Indian Creek Mouth
Parameter
Dissolved Phosphorous
Ammonia-N
Dissolved Nitrogen
Total Nitrogen
Phosphorous T Ortho
Phosphorous Ortho
Dissolved
Phosphorous Total
Nitrate + Nitrite - N
Rt63
0.176
0.030
1.520
1.700
0.183
0.166
0.188
1.100
Salford tributary
0.669
0.070
19.890
19.980
0.667
0.652
0.720
18.600
1C mouth
0.264
0.040
4.660
4.640
0.261
0.252
0.275
4.090
22
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June 2008 FINAL Indian Creek TMDLs
3. SOURCE ASSESSMENT
This section presents the information on point and nonpoint sources of nutrients and sediment in the
Indian Creek watershed.
3.1. Nonpoint Sources
In addition to point sources, nonpoint sources are expected to contribute to water quality impairments in
the Indian Creek watershed. Nonpoint sources represent contributions from diffuse, non-permitted
sources. Typically, nonpoint sources are precipitation driven and occur as overland flow, which carries
pollutants into streams. Nonpoint sources also include non-precipitation driven events such as
contributions from groundwater, septic systems, or direct deposition of pollutants from wildlife and
livestock.
3.1.1. Agriculture
Agricultural lands can be a significant source nutrient loading to streams. Runoff from pastures and crop
lands, livestock operations, improper land application of animal wastes and fertilizers, and erosion are all
agricultural sources of nutrients. Agricultural Best Management Practices (BMPs) such as buffer strips,
and the proper land application of manures and fertilizers reduce nutrient loading to waterbodies.
Based on the 2001 NLCD land use coverage available for the Indian Creek watershed, approximately
53% of the watershed can be classified as either row crop area or pasture. Manure and biosolids are
applied to agricultural lands in the watershed.
3.1.2. Biosolids
The application of bio-solids to lands in the watershed represents another potentially significant source of
phosphorous and other nutrients to Indian Creek. Such activities are permitted by PADEP through the
Waste Management Municipal Waste Program; a facility associated with the program is known as a
Municipal Waste Operation (MWO). Pennsylvania's eMap PA website
(http://www.emappa.dep.state.pa.us/emappa/viewer.htm) was accessed for an initial assessment of
locations in the Indian Creek watershed associated with MWOs. Sub-facility types related to MWOs that
are included in eMapPA are:
• Composting
• Land Application
• Abandoned Landfills
• Active Landfills
• Processing Facility
• Resource Recovery
• Transfer Station
Based on the eMapPA database, the Indian Creek watershed contains eight sites associated with MWOs,
only 3 of which are "Active" (Figure 3-1). All are categorized as land application activities, which may
include facilities that use agricultural utilization or land reclamation of waste. This category generally
applies to sewage sludge, which is land-applied for its nutrient value or as a soil conditioner. However,
based on a questionnaire provided to the Montgomery County Conservation District, there is limited
knowledge regarding application rates and practices.
23
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FINAL Indian Creek TMDLs
June 2008
N
NORMAN RITTENMOUSE FARM NUMBER 1
MWOs Land Application Sites
Site Status
ACTIVE
INACTIVE
Lower Saltbrd Twp Authority
Pilgrim's Pride
Telford Borough Authority
Not Attaining
Unassessed
Municipalities
Streams
Indian Creek Watershed
0.25 0.5
Figure 3-1. Land Application Sites (eMapPA).
These sites are associated with the Moyer Packing Company, a meat processing facility located to the east
of the watershed. Activities most likely associated with these sites include application of food processing
residual waste, which is required to be accomplished in accordance with the Food Processing Residuals
Manual. The Manual contains certain performance requirements, such as use of the waste in the course
of normal farming operations, nuisance prevention, metal loading rates, isolation distances, general site
criteria, and the need to have a farm conservation plan (PADEP 2005).
3.1.3. Urban Runoff
Urban areas constitute a potentially significant source of nutrients carried to receiving waters through
stormwater runoff. Due to the tendency of phosphorus to sorb to sediment particles, erosion may play a
significant role as a phosphorus source to receiving waters. Excessive rates of fertilizer application to
lawns, ballparks, and golf courses, etc., are another common source or nutrients to waterbodies from
urban and developed areas. Much of the loading from urban areas is due simply to the increase in
impervious surfaces relative to other land uses and the resulting increase in runoff. Higher percentages of
impervious areas decrease the time required to reach peak stormwater discharge rates, increase flow
velocities and exacerbate overland and in-stream erosion, further adding to potential sediment sorbed
nutrient loads. In areas where onsite wastewater treatment is provided by septic systems, failures and
malfunctioning systems may also pose a potential nutrient source. All of these are factors in the Indian
Creek watershed.
24
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June 2008 FINAL Indian Creek TMDLs
3.1.4. Septic Systems
On-site septic systems have the potential to deliver nutrients to surface waters due to system failure and
malfunction. Septic systems treat human waste using a collection system that discharges liquid waste into
the soil through a series of distribution lines that comprise the drain field. In properly functioning
(normal) systems, phosphates are adsorbed and retained by the soil as the effluent percolates through the
soil to the shallow saturated zone. Therefore, normal systems do not contribute phosphorus loads to
surface waters. A septic system failure occurs when there is a discharge of waste to the soil surface where
it is available for washoff As a result, failing septic systems can contribute high phosphorus and nitrogen
loads to surface waters. Short-circuited systems (those located close to streams) and direct discharges
also contribute significant nutrient loads.
Results from a sewer management study conducted by Franconia Township for its portion of the Indian
Creek watershed, which covers approximately the middle 2/3 of the basin, indicate that failing and
inadequate septic systems are a significant issue in portions of the Indian Creek basin (CMX 2008). Of
the 409 lots with inspected septic systems, study results indicated that slightly over 20% were confirmed
to be failing, with an additional 11% suspected of malfunctioning (i.e., show signs such as abnormally
green grass overlying drain fields or piped discharges). While approximately 68% did not exhibit signs of
failure at the time of inspection, given current permitting standards as well as soils and conditions in the
watershed, approximately 47 % are considered to have a strong potential for future failure. In sum, only
21% of the systems inspected as part of the study are thought to be properly sited and performing
adequately.
3.2. Point Sources
Point sources, according to 40 CFR § 122.3, are defined as any discernable, confined, and discrete
conveyance, including but not limited to, any pipe, ditch, channel, tunnel, conduit, well, discrete fissure,
container, rolling stock, concentrated animal feeding operation, landfill leachate collection system, vessel
or other floating craft from which pollutants are or may be discharged. The National Pollutant Discharge
Elimination System (NPDES) program, under Clean Water Act sections 318, 402, and 405, requires
permits for the discharge of pollutants from point sources.
3.2.1. MS4s
In 1990, USEPA developed rules establishing Phase I of the NPDES storm water program, designed to
prevent harmful pollutants from being washed by storm water runoff into Municipal Separate Storm
Sewer Systems (MS4s) (or from being dumped directly into the MS4) and then discharged from the MS4
into local waterbodies. Phase I of the program required operators of "medium" and "large" MS4s (those
generally serving populations of 100,000 or greater) to implement a storm water management program as
a means to control polluted discharges from MS4s. Approved storm water management programs for
medium and large MS4s are required to address a variety of water quality related issues including
roadway runoff management, municipal owned operations, and hazardous waste treatment. There are no
large or medium MS4s in the Indian Creek watershed.
Phase II of the rule extends coverage of the NPDES storm water program to certain "small" MS4s. Small
MS4s are defined as any MS4 that is not a medium or large MS4 covered by Phase I of the NPDES Storm
Water Program. Only a select subset of small MS4s, referred to as "regulated small MS4s," require an
NPDES storm water permit. Regulated small MS4s are defined as all small MS4s located in "urbanized
areas" as defined by the Bureau of the Census and those small MS4s located outside of an urbanized area
that are designated by NPDES permitting authorities. There are four such regulated MS4s in the Indian
25
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FINAL Indian Creek TMDLs
June 2008
Creek watershed: Telford, Souderton, Franconia, and Lower Salford. As a condition of the MS4 permit,
permittees are required to submit annual reports on permit activities in June of each year. The entire
Indian Creek watershed falls within regulated MS4 areas.
3.2.2. NPDESPermitted Facilities
The permitted point sources in the Indian Creek watershed include two municipal sewage treatment plants
(STP) in Telford and Lower Salford and a meat processing facility, Pilgrims Pride. PADEP provided
permit limits and discharge monitoring report (DMR) data for the three NPDES permitted facilities in the
Indian Creek watershed for the period of January 2001 to September 2005 for Telford (PA 0036978) and
Pilgrims Pride (PA0054950) and January 2001 to February 2005 for Lower Salford (PA0024422). The
three facilities and their nutrient and sediment limits are shown in Table 2-3. Spatially, the Telford STP is
located most upstream in the Indian Creek watershed, the Pilgrims Pride discharge in the middle (on Trib-
01194), and the Lower Salford STP is located most downstream on Trib-01182 (see Figure 1-1). While
there are seasonal limits for NH3-N for all three facilities PO4-P and TP limits exist only for the period of
April to October. Telford has a TP limit while Pilgrims Pride and the Lower Salford facilities have been
given limits for PO4-P (Table 3-1). Year round TSS limits also exist for all three facilities, with Pilgrims
Pride having the most stringent TSS limit of 10 mg/L compared to 30 mg/L for the other two facilities.
Table 3-1. Nutrient Permit Limits for NPDES Facilities in the Indian Creek Watershed
Facility Limits
Parameter
Flow(MGD)
Pas PO4 (mg/l)
TP (mg/l)
NH3-N (mg/l)
NH3-N (mg/l)
TSS (mg/L)
Period
January-December
April - October
April - October
May- October
November- April
January-December
Telford
(PA0036978)
1.1
No limit
1.7
1.5
3.0
30
Pilgrims Pride
(PA0054950)
Report
2.0
No limit
3.0
9.0
10
Lower Salford
(PA0024422)
0.7
0.5
No limit
1.5
3.0
30
Telford
For the period April 2001-October 2001, the Telford facility had a discharge limit for TP of 1.7 mg/L; no
TP limit exists for the rest of the year. Based on DMR data, in May 2002, July 2004, and June 2005, TP
concentrations violated permit limits by 0.1 mg/l, 0.4 mg/l, and 0.6 mg/l, respectively. NH3-N
concentrations were well within permit limits. The TSS limit was not exceeded. Figure 3-2 shows the
DMR data and permit limits for the Telford facility.
26
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June 2008
FINAL Indian Creek TMDLs
1.4 .
I Flow (mgd)
1 '2" 1_ULTFlow Limit ^mgd'
1.0
0.8-
0.6-
0.4
0.2
0.0
c-^c-^c-^c-^c-^a>'n>9>g-a>9>g-a>9>g-a> 9> ffl 0>
Or-iOOfU1oOfU1oOfU1oOfU1o
^2-MgMCo§co-^g^ai°ai
3'5 —I NH3-N (mg/L)
3.0-'—i— • — ••• "i— • NH3-N Limit (mg/L)
ii i i
2.5
2.0
1.5
1.0-
0.5-|
Q Q | I I I I I | I I I | I I I | I I I | I I I I I | I I I | I I I | I I I |
^^^^^^^^^^^^^^^^
8888888888888888
2.5
IIP (mg/L)
20i |- -' TPLimit (mg/L)
1.5
1.0
0.5
go-| 1 i I I | I I i 1 | I I I | I , L|_il
^cntD^cntD^cntD^aitD^aitD^
§§§§§§§§§§§§§§§§
oooooooooooooooo
Figure 3-2. Telford DMR data.
27
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FINAL Indian Creek TMDLs
June 2008
"Vi 0 -i
oU.U -
9^ n .
on n
m n .
m n
R n
n n -
i\
c
c
^^•TSS(mg/L)
- - - - TSS Limit (mg/L)
III ll|lll|lll| ih| I I, l| I III II II
1-OiCQ-i-OlCQ-i-OlCQ-i-OlCQ-i-OlCQ
SivSivSivSivSivSivSivSivSivSivSivSivSivSivS
3OOOOOOOOOOOOOO
3OOOOOOOOOOOOOO
*-^-^K>K>K>COCOCO.fc..&..&.OlOlOl
I
^
1/2006
Figure 3-2. Telford DMR data (continued).
Pilgrims Pride
In April 2001, May 2001, October 2001, and October 2004 discharges from the Pilgrims Pride facility
violated PO4-P limits by 0.14 mg/1, 0.14 mg/1, 1.39 mg/1, and 0.05 mg/1, respectively. NH3-N discharges
violated the permit limit in September 2002 by 2.7 mg/1. The TSS limits were exceeded at least once
every year and several times in 2001 and 2003. Figure 3-3 shows the DMR data and permit limits for the
Pilgrims Pride facility.
28
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June 2008
FINAL Indian Creek TMDLs
4 0
0 C _
•1C.
0 0 - -
c_
O
3> C—
0 0
Pas PCM (mg/L)
• • • -Pas PO4Limit (mg/L)
0
r f
v- 9
c_
o
,
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_|_
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o j-,
v- f
v- 9 '
- ^ v-
10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
c
c
f
•
1
•
•
I
D
t i
1
1
1
•
1
•
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,
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i
•
•
r
,
•
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•
v- 9
v- f
v- 9
^^m NH3-N (
mg/L)
- - - - NH3-NLmit(mg/L)
i
•
i
•
,
(
i
1
i
•
,
V- 3*
| |
v- 9
° 2
T }* V-
30.0
25.0
20.0
15.0
10.0
5.0
0.0
c
c
D
•
^TSS
- -TSS
> <-
- 9
(mg/L)
L mit (mg/L)
c_
c
IS
3
3
1
>
|
v- 9
V- 3*
1
v- 9
V- f
v- 9
° 2
T f V"
Figure 3-3. Pilgrims Pride DMR data.
29
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FINAL Indian Creek TMDLs June 2008
Lower Salford
In November 2001, April 2003, June 2003, July 2003, and April 2004, concentrations violated the PO4-P
limits by 1.0 mg/1, 0.06 mg/1, 0.41 mg/1, 0.53 mg/1, and 1.25 mg/1, respectively. No limits exist for TP.
NH3-N concentrations exceeded the specified limits in January 2002, February 2002, March 2002, April
2002, May 2002, and June 2002 by 9.7 mg/1, 2.3 mg/1, 9.6 mg/1, 10.3 mg/1, 6.5 mg/1 and 2.4 mg/1,
respectively. The TSS limit was not exceeded. Figure 3-4 shows the DMR data and permit limits for the
Lower Saford facility.
30
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June 2008
FINAL Indian Creek TMDLs
n R -.
0.7 •
0.6 •
0.5 •
0.4 -
0.3 •
0.2 •
0.1 -
n n .
^*
c_
o
6 0 -r
5.0 -
A n .
1.0 •
• • • • Flow Limit (mgdj
5 5
l
l
C_
O
1.8 -
1.6 -
1.4 -
1.2 -
1 n -
n R .
n R -
n A .
0.2 -
i
V
-
-
0 0
O V
o o
fO M
O
o
rO
1
I
1. ......
1
c_
8
o
CO
<- O <- > <- O <-
8 g g g g g 8
- - - - NH3-N Unit (mg/L)
1
1
> "r O
o o A
N) N) g
1
V
c_
O
CO
8
..
1 1 1
111
1
f
V- O "r > "r O "r
O r-i O O O f-. O
00 g 4^ g 4^ g 01
C_
O
6 6
^^H Pas PO4 (mg/L)
- - - - Pas PO4 Limit (mg/L)
o
5
D 6 O
0 M M
O
S
c_
O
CO
-
g
oo
•
c^ O "^ > "^ O "^
8 ° g g g g 8
Figure 3-4. Lower Salford DMR data.
31
-------
FINAL Indian Creek TMDLs
June 2008
35.0
30.0
25.0
20.0
15.0
10.0
ITSS (mg/L)
• TSS Limit (mg/L)
Figure 3-4. Lower Salform DMR data, (continued)
Ambient Sampling Above and Below Point Sources
Following an unassessed waters screening in the summer of 2001, PADEP determined that Indian Creek
was impaired from its source to the mouth by possible nutrient impairment. From this assessment,
biological habitat scores for locations throughout the Indian Creek watershed are available. They were
reviewed to support this effort; however the data are more suitable for qualitative descriptions of stream
conditions than for analysis of in-stream water quality as no chemical data were collected during the
biological surveys. Based on findings of the unassessed waters screening, investigations were conducted
to evaluate the possibility of Telford Borough Authority and Lower Salford Township Authority
Harleysville STP outfalls as the source of stream impairment. The Telford STP is listed as the source of
nutrient impairment to Indian Creek on the 2002 303(d) list. Chemical sampling was conducted in Indian
Creek at the Telford Borough Authority STP on October 24, 2001, April 14, 2003, and on May 14, 2003;
and at the Lower Salford STP on October 24, 2001, and April 14, 2003, by PADEP. In addition,
biological sampling was conducted at the two sites on all the listed dates, except May 14, 2003.
At each location, samples were collected upstream of the discharge (denoted as site 1), at the discharge
(effluent), and downstream of the discharge (denoted as site 2). See Appendix A for detailed discussion
of sampling results at each site. In general, the ambient sampling reveals a significant influence of the
point sources on the receiving streams during periods of dry weather. It also shows elevated background
nutrient levels following periods of rainfall which can be attributed to nonpoint source runoff from the
watershed. For example at the Telford site, sampling was conducted on October 24, 2001, under dry
conditions and on April 14, 2003, and May 14, 2003, under post-rainfall conditions. Analyses of total
phosphorous (TP) near the Telford discharge (Figure 3-5) suggest that the ambient concentration
(represented by site 1) remained approximately the same on the sampling dates of Oct. 24, 2001, Apr. 14,
2003, and May 14, 2003. TP concentration increased downstream of the effluent in Oct. 24, 2001,
decreased in Apr. 14, 2003, and remained approximately the same in May 14, 2003. Summation of the
ambient TP concentration (site 1) and effluent TP concentration (effluent) approximately equaled the
32
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June 2008
FINAL Indian Creek TMDLs
concentration of TP at Site 2 on Oct. 24, 2001. The summation of ambient concentration and effluent was
less than the TP concentration, however, at site 2 on Apr. 14, 2003 and on May 14, 2003. Since a greater
portion of the concentration at Site 2 was contributed by effluent on the October sampling date, the
effluent appears largely responsible for downstream (site 2) increased concentrations that day. Rainfall
data for the period indicated periods of precipitation preceded the April and May sampling dates. This
indicates that nonpoint source contributions, in addition to effluent, were affecting in-stream conditions
on those days.
4 no
3^n
.ou -
^~ o no -
05 O.UU
£
^ O EZCl
£- ^.ou -
o
~m o nn
ro ^.UU -
"E
(ii -i en
£J \ .OU -
d
o ^ nn
(j 1 .UU -
Oc r\
.ou -
0.00 -
i — r^B — i
—
=P
-
1 Effluent
~
2
I I l°tal
Phosphorous-
24-Oct-01
1 i l°tal
Phosphorous-
14-Apr-03
1 1 |otq|
Phosphorous-
14-May-03
Merrnn Limn
Upstream to Downstream
Figure 3-5. Total Phosphorus concentration above and below Telford Discharge
3.3. Indian Valley Golf Course Water Withdrawals
The Indian Valley Golf Course, located in the northern portion of the watershed. The golf course's
withdrawal point is from an impoundment that is adjacent to Indian Creek. The facility is known as a
"pre-compact" facility as it was in operation prior to the creation of the Delaware River Basin
Commission. Thus, no restrictions on water withdrawals by the facility from Indian Creek are in effect.
However, it is unclear if the water is drawn directly from the Indian Creek or if any of the water is
returned back to the Indian River. Historical data for water withdrawals were provided by the Delaware
River Basin Commission (DRBC). Based on review of the data provided, water withdrawals generally
increase from May until July and then decrease in subsequent months, with the month of July typically
experiencing the highest levels of withdrawals.
3.4. Summary of Critical Water Quality Factors
Based on a review of available data, the Indian Creek watershed appears subject to significant nutrient
loading from both point and nonpoint sources. Visual observations and diurnal monitoring of physical
water quality conditions in the watershed reveal evidence of significant levels of biological activity in the
form of primary productivity, algae blooms, and large swings in daily dissolved oxygen and pH levels.
Chemical monitoring data show elevated levels of nutrients. At times of low flow, considerable inputs of
nutrients are attributable to point source facilities in the watershed; particularly the Telford Borough
33
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FINAL Indian Creek TMDLs June 2008
Authority and Lower Salford Authority-operated municipal sewage treatment plants. Discharge from
these facilities cause receiving waters to exhibit elevated levels of nutrients over ambient concentrations
during periods of dry weather. It is expected that during times of extremely low flows and warm
conditions, these inputs to the watershed may contribute significantly to algal blooms and other
conditions associated with eutrophication.
Nonpoint source nutrient loading from watershed land uses is also evident during periods of wet weather,
as shown by the results of the ambient sampling above and below the two municipal treatment plants.
Following periods of rainfall, ambient levels of nutrients upstream of point sources appear elevated
relative to dry weather periods.
Land use activities in the Indian Creek watershed play an important role in water quality. Manure is
collected and applied to agricultural lands in the watershed. Food processing residual wastes are also
potentially applied to sites in the watershed. The watershed is suburbanizing, has multiple stormwater
outfalls, and experiences typical runoff conditions associated with urban stormwater runoff and discharge.
In addition, the golf course located in the headwaters region withdraws significant amounts of flow during
the summer months; however it is unclear if water is withdrawn directly from the Indian Creek. These
withdrawals likely compound critical low-flow periods where nutrient laden point source discharges may
already be overwhelming receiving streams.
An approach to develop TMDLs for the water quality impairments in the Indian Creek watershed should
be able to account for the varied nature of factors influencing problem conditions in the stream. These
include point source discharges, urban runoff, water withdrawals, and application of fertilizers and
manures. Such an approach should account for the various sources of nutrients to the watershed and their
influences on the watershed during both low-flow and high-flow conditions. The following section
describes the technical approach used to develop the Indian Creek watershed TMDL. The approach
accounts for the critical processes influencing Indian Creek and is also consistent with other TMDLs
developed for nearby waters.
34
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June 2008 FINAL Indian Creek TMDLs
4. TMDL TECHNICAL APPROACH
Two separate approaches were used to develop these TMDLs for Indian Creek. For sediment, a reference
watershed approach using a simplified Generalized Watershed Loading Function (GWLF) simulation was
applied. For nutrients (TP and TN), a separate GWLF watershed model was used to generate watershed
nutrient loadings and these were linked to a receiving water model to evaluate allowable nutrient inputs
from the watershed to meet the seasonal average nutrient targets.
4.1. Sediment
Section 4.2.1 provides details on the GWLF application and its underlying theory, as well as information
on how the model was configured to develop the nutrient TMDLs. There are several differences in how
GWLF was configured for the sediment and nutrient TMDLs; the sediment modeling is described here.
4.1.1. Watersh ed modeling - Sediment
For the sediment TMDL, a GWLF model was configured as a single subbasin as opposed to the multiple
subbasins used to feed the EFDC model for the nutrient TMDL. This was done since a single reference
watershed was used in developing the TMDL. A single modeled watershed for Indian Creek ensures that
the sediment delivery ratio for the Indian Creek subbasin was similar to the reference subwatershed.
Section 1.4 discusses the rational for the selected reference watershed and TMDL target.
Watershed data needed to run the GWLF model was similar to what was required for the nutrient TMDL
and included GIS spatial coverages, streamflow data, local weather data, and literature values. The Indian
Creek watershed was delineated into one subbasin to represent sediment loadings. The watershed was
delineated based on USGS Digital Elevation Model (DEM) data, USGS 7.5 minute digital topographic
maps (24K RG - Digital Rastar Graphics), and Pennsylvania's eMap stream coverage.
The following sections describe the data and information used for model setup, including watershed
conditions (e.g., land use, soils), weather inputs, simulation of streamflow and nonpoint source
representation.
Land Use and Land Cover Data
NLCD 2001 land use information from the MRLC was used for the Indian Creek watershed as was done
in the nutrient TMDL. The land use distribution is shown below in Table 4-1.
35
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FINAL Indian Creek TMDLs
June 2008
Table 4-1. Land Use in the Indian Creek Watershed (Sediment model)
Land Use
Low Intensity Residential
High Intensity Residential
High Intensity Commercial/Industrial/ Transportation
Paved_Roads
Bare Rock/Sand/Clay
Deciduous Forest
Evergreen Forest
Pasture
Agriculture
Wetlands
Total Area (mi2)
111
1.31
1.08
0.37
0.09
0.02
0.34
0.00
2.48
1.15
0.01
6.86
•Sw
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June 2008
FINAL Indian Creek TMDLs
Table 4-2. Modeled Sediment Loads and Landuse Loading Rates in the Indian Creek Watershed
SOURCE
Agriculture
Pasture
High Intensity Residential-Imp
Low Intensity Residential-Imp
High Intensity Commercial/lndustrial/Transportation-Imp
Low Intensity Residential
Paved_Roads
Bare Rock/Sand/Clay
High Intensity Residential
High Intensity Commercial/lndustrial/Transportation
Deciduous Forest
Evergreen Forest
Wetlands
Total
Loading Rate Ib/ac/yr
8,594.55
3,727.07
424.42
424.42
424.42
33.19
192.45
745.43
37.20
37.20
2.23
2.77
-
Existing Load (Ib/yr)
6,329,713.42
5,914,860.35
206,580.90
107,525.64
85,573.93
19,620.80
11,294.19
8,948.32
7,761.50
1,323.30
478.98
4.30
-
12,693,685.64
Average annual sediment loading is approximately 12,693,686 Ib/year. Of this, approximately 169,921
Ib/year, or about 1.3% of the total existing load are from the three continuously discharging point sources.
4.2. Nutrients
To evaluate the relationship between the time variable sources, their loading characteristics, and the
resulting water quality conditions in the stream, a combination of a watershed model and in-stream water
quality model was used for the Indian Creek nutrient and siltation TMDLs. Assessments of the nonpoint
source loading into the waterbody were developed using the GWLF (Haith and Shoemaker, 1987)
computer program. GWLF modeling was accomplished using the BasinSim 1.0 watershed simulation
program, a Windows-based modeling system that facilitates the development of model input data and
provides additional functionality for simulating daily flows and flow and pollutant routing (Dai et al.
2000).
The hydrodynamics and water quality processes in Indian Creek were simulated using the Environmental
Fluid Dynamics Code (EFDC) (Hamrick 1996,; Hamrick and Wu 1996). The EFDC model is a general
purpose modeling package for simulating one, two or three-dimensional flow, transport and
biogeochemical processes in surface water systems and can be used to simulate the physical, chemical,
and biological interactions related to DO and nutrients dynamics in the Indian Creek. The hydrodynamic
simulation module of EFDC can simulate the flow velocity, water depth, and temperature necessary for
driving the mass transport and DO re-aeration computation in a water quality model (Zou et al. 2006).
The water quality simulation module of EFDC is a flexible modeling framework allowing representation
of the kinetic structure in a water system at different levels of complexity. At a minimum, the EFDC
model can provide a representation of the water quality dynamics in the Indian Creek similar to that in the
Wissahickon Creek modeling effort where a linked EFDC-WASP model was developed. Because
EFDC's water quality modules are internally coupled with the hydrodynamic module, it offers a more
integrated and consistent numerical representation of the prototype than an externally linked EFDC-
WASP system. In addition, the flexible kinetic structure of the EFDC water quality model allows the
37
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FINAL Indian Creek TMDLs June 2008
modeling system to be extended to an even higher level of kinetic representation when the WASP level
representation is regarded insufficient.
The EFDC model was configured as a dynamic modeling system, representing the temporal and spatially
variable conditions in the stream. The model was used to simulate hydrodynamic and nutrient-algae
dynamics in Indian Creek in one single numerical framework and to represent seasonal and multiple year
variability in water quality. Its sediment digenesis module can be activated when necessary to account for
the response of benthic nutrient flux and oxygen demand in the TMDL process to enhance the
predictability of the model and the reliability of the resultant TMDL.
The combination of the linked GWLF and EFDC models established the relationship between the in-
stream water quality target and the source loading from the watershed to develop technically defensible
TMDL allocations.
The following sections discuss the modeling approach in more detail, including the setup, testing and
application of GWLF and EFDC to support development of the Indian Creek TMDLs.
4.2.1. Watersh ed Modeling - Nutrients
The nutrients watershed model for the Indian Creek watershed was developed using the GWLF model
and the BasinSim 1.0 interface. The GWLF model, which was originally developed by Cornell
University (Haith et al., 1992), provides the ability to simulate runoff, sediment, and nutrient loadings
from watersheds given variable-size source areas (e.g., agricultural, forested, and developed land). It also
has algorithms for calculating septic system loads and allows for the inclusion of point source discharge
data. GWLF is a continuous simulation model that uses daily time steps for weather data and water
balance calculations. Monthly calculations are made for sediment and nutrient loads based on daily water
balance totals that are summed to give monthly values.
GWLF is an aggregate distributed/lumped parameter watershed model. For surface loading, it is
distributed in the sense that it allows multiple land use/cover scenarios. Each area is assumed to be
homogeneous with respect to various attributes considered by the model. In addition, the model does not
spatially distribute the source areas, but aggregates the loads from each area into a watershed total. In
other words, there is no spatial routing. For subsurface loading, the model acts as a lumped parameter
model using a water balance approach. No distinctly separate areas are considered for subsurface flow
contributions. Daily water balances are computed for an unsaturated zone as well as for a saturated
subsurface zone, where infiltration is computed as the difference between precipitation and snowmelt
minus surface runoff plus evapotranspiration.
GWLF models surface runoff using the Soil Conservation Service Curve Number (SCS-CN) approach
with daily weather (temperature and precipitation) inputs. Erosion and sediment yield are estimated using
monthly erosion calculations based on the Universal Soil Loss Equation (USLE) algorithm (with monthly
rainfall-runoff coefficients) and a monthly composite of KLSCP values for each source area (e.g., land
cover/soil type combination). The KLSCP factors are variables used in the calculations to depict changes
in soil loss/erosion (K), the length/slope factor (LS), the vegetation cover factor (C), and the conservation
practices factor (P). A sediment delivery ratio based on watershed size and transport capacity based on
average daily runoff are applied to the calculated erosion to determine sediment yield for each source
area.
Surface nutrient losses are determined by applying dissolved nitrogen and phosphorus coefficients to
surface runoff and a sediment coefficient to the yield portion for each agricultural source area. Manured
areas, as well as septic systems, also can be considered. Urban nutrient inputs are all assumed to be solid
38
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June 2008 FINAL Indian Creek TMDLs
phase, and the model uses an exponential accumulation and washoff function for these loadings.
Subsurface losses are calculated using dissolved nitrogen and phosphorus coefficients for shallow
groundwater contributions to stream nutrient loads, and the subsurface submodel considers only a single,
lumped-parameter contributing area. Evapotranspiration is determined using daily weather data and a
cover factor dependent on land use/cover type. Finally, a water balance is performed daily using supplied
or computed precipitation, snowmelt, initial unsaturated zone storage, maximum available zone storage,
and evapotranspiration values. All the equations used by the model can be found in the original GWLF
paper (Haith and Shoemaker 1987) and GWLF User's Manual (Haith et al. 1992).
4.2.2. Model Setup
The GWLF model provides the ability to simulate surface water runoff, as well as sediment and nutrient
loads, from a watershed based on landscape conditions such as topography, land use/cover, and soil type,
characterized by user input. For execution, the model requires three separate input files containing
transport, nutrient, and weather-related data. The transport file (TRANSPRT.DAT) defines the necessary
parameters for each source area to be considered (e.g., area size, curve number) as well as global
parameters (e.g., initial storage, sediment delivery ratio, streambank erosion coefficient) that apply to all
source areas. The nutrient file (NUTRIENT.DAT) specifies the various loading parameters for the
different source areas identified (e.g., urban source area accumulation rates, manure concentrations). The
weather file (WEATHER.DAT) contains daily average temperature and total precipitation values for each
year simulated.
Watershed data needed to run the GWLF model were generated using GIS spatial coverages, streamflow
data, local weather data, and literature values. The Indian Creek watershed was subdivided into 12
subbasins to represent nutrient loadings (Figure 4-1). The watersheds were delineated based on USGS
Digital Elevation Model (DEM) data, USGS 7.5 minute digital topographic maps (24K RG - Digital
Rastar Graphics), and Pennsylvania's eMap stream coverage.
The following sections describe the data and information used for model setup, including watershed
conditions (e.g., land use, soils), weather inputs, simulation of streamflow and nonpoint source
representation.
39
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FINAL Indian Creek TMDLs
June 2008
A/ Streams
| I Subbasins
I I Municipalities
N
4 Miles
Figure 4-1. Indian Creek subwatershed delineations.
40
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June 2008
FINAL Indian Creek TMDLs
Land Use and Land Cover Data
NLCD 2001 land use information from the MRLC was available for the impaired and calibration
watersheds. Table 4-3 shows the 2001 NLCD landuse categories and the matching modeled landuse
category used to identify landuse specific loading rates. The NLCD land use coverage was used to
calculate the area of each land use category in the watersheds. The land use distribution in the impaired
and calibration watersheds is shown in Table 4-4 and Table 4-5.
Table 4-3. NLCD Landuse Coverage Category Crosswalked with Modeled Landuse Categories
2001 NLCD Category
Developed, Open Space
Developed, Low Intensity
Developed, Medium Intensity
Developed, High Intensity
Barren Land (Rock, Sand, Clay)
Deciduous Forest
Evergreen Forest
Pasture/Hay
Cultivated Crops
Woody Wetlands
Modeled Category
Low Intensity Residential
High Intensity Residential
High Intensity Commercial/lndustrial/Transportation
Paved_Roads
Bare Rock/Sand/Clay
Deciduous Forest
Evergreen Forest
Pasture
Agriculture
Wetlands
Table 4-4. Land Use in the Indian Creek River Watershed
Land Use
Low Intensity Residential
High Intensity Residential
High Intensity
Commercial/Industrial/
Transportation
Paved_Roads
Bare Rock/Sand/Clay
Deciduous Forest
Evergreen Forest
Pasture
Agriculture
Wetlands
Total Area (mi2)
Percent of Total (%)
Subbasin 1
0.06
0.07
0.02
0.00
0.00
0.01
0.00
0.10
0.02
0.00
0.27
3.97
Subbasin 2
0.21
0.09
0.02
0.00
0.00
0.01
0.00
0.20
0.12
0.00
0.66
9.61
Subbasin 3
0.20
0.10
0.02
0.00
0.01
0.03
0.00
0.36
0.16
0.00
0.88
12.87
Subbasin 4
0.05
0.07
0.05
0.03
0.00
0.01
0.00
0.14
0.12
0.00
0.47
6.89
Subbasin 5
0.08
0.03
0.00
0.00
0.00
0.04
0.00
0.27
0.18
0.00
0.61
8.83
Subbasin 6
0.06
0.08
0.01
0.00
0.00
0.05
0.00
0.19
0.12
0.00
0.51
7.48
Subbasin 7
0.09
0.04
0.01
0.00
0.00
0.04
0.00
0.33
0.16
0.00
0.68
9.84
Subbasin 8
0.06
0.08
0.02
0.00
0.00
0.01
0.00
0.15
0.08
0.00
0.41
6.03
Subbasin 9
0.06
0.02
0.00
0.00
0.00
0.03
0.00
0.23
0.09
0.00
0.44
6.37
Subbasin 10
0.21
0.21
0.09
0.03
0.00
0.02
0.00
0.32
0.07
0.00
0.95
13.82
Subbasin 11
0.01
0.01
0.00
0.00
0.00
0.06
0.00
0.07
0.02
0.00
0.17
2.49
Subbasin 12
0.21
0.27
0.13
0.03
0.00
0.02
0.00
0.13
0.02
0.00
0.81
11.81
cJ""'
E,
03
£
<
15
jS
1.31
1.08
0.37
0.09
0.02
0.34
0.00
2.48
1.15
0.01
6.86
Percent of
Total (%)
19.16
15.79
5.39
1.34
0.27
4.90
0.04
36.13
16.76
0.21
100
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FINAL Indian Creek TMDLs
June 2008
Table 4-5. Land Use in the East Branch Perkiomen Creek Watershed
Land Use
Water
Low Intensity Residential
High Intensity Residential
High Intensity Commercial/lndustrial/Transportation
Paved Roads
Bare Rock/Sand/Clay
Deciduous Forest
Evergreen Forest
Pasture
Agriculture
Wetlands
Total Area (mi2)
Area (mi^)
0.02
5.98
5.51
2.00
0.42
0.53
10.38
0.43
17.45
14.20
0.64
57.57
Percent of Total
0.03
10.39
9.57
3.48
0.73
0.92
18.03
0.75
30.32
24.67
1.12
100
Soils Data
Soils data were obtained from the Natural Resources Conservation Services (NRCS) State Soil
Geographic (STATSGO) database for the respective watersheds. There are two MUIDs within the Indian
Creek watershed and both have a hydrologic soil group of C soil type. Figure 4-2 shows the soil
distribution in the Indian Creek watershed.
42
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June 2008
FINAL Indian Creek TMDLs
PA062
/\y Streams
| | Municipalities
I | Indiancreekwatershed
STATSGO-MUID
| | PA062
| | PA063
• PA065
4 Miles
Figure 4-2. Soil distribution in the Indian Creek watershed.
Weather Data
Nonpoint source pollution is rainfall driven, therefore precipitation data are necessary to drive the
watershed model. Local rainfall and temperature data were used to simulate flow conditions in modeled
watersheds. Daily precipitation and temperature data were obtained from local National Climatic Data
Center (NCDC) weather stations. There were two precipitation stations in close proximity to the Indian
Creek watershed - Sellersville and Graterford. Since the Graterford station had good data coverage
43
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FINAL Indian Creek TMDLs
June 2008
(96%) for both precipitation and temperature, it was used to construct the weather file used in modeling.
Data gaps in the Graterford station were filled using the Sellersville station and a composite weather file
was developed. The Graterford station is located approximately 6.5 miles south of the Indian Creek
watershed, while the Sellersville station is located 4.2 miles north east of the Indian Creek watershed.
Since the NCDC summary of the day data at the two stations did not extend beyond 12/31/2004, the
Willow Grove NAS surface airways station (14793) located approximately 14 miles south east of the
Indian Creek was used to create another set of weather files. (Table 4-6 shows the weather stations used
in the watershed model.)
Table 4-6. Meteorological Stations
Station ID
PA7938
PA3437
14793
Station Name
Sellersville
Graterford 1 E
Willow Grove NAS
Data Begin Date
5/1/1948
1/1/1960
2/1/1945
Data End Date
12/31/2004
12/31/2004
Current
Percent
Coverage
20
96
99
Elevation (ft)
340
240
170
Nonpoint Source Representation
In the GWLF model, the nonpoint source load calculation is affected by terrain, such as the amount of
agricultural land, land slope, soil erodibility, farming practices used in the area, and by background
concentrations of nutrients (nitrogen and phosphorus) in soil and groundwater. Various parameters are
included in the model to account for these conditions and practices. Some of the more important
parameters are summarized in the following paragraphs.
Curve number: This parameter determines the amount of precipitation that infiltrates into the ground or
enters surface water as runoff. It is based on specified combinations of land use/cover and hydrologic soil
type and is calculated directly using digital land use and soils coverages. A GIS tool developed by Tetra
Tech was used to determine the CNs for each land use located in each subwatershed. The tool determines
the CN for each land use using a weighted average of the CNs for the soil types in each land use.
Universal Soil Loss Equation (USLE): The USLE is used in GWLF to estimate the sediment contribution
from the various land uses in the watershed. The USLE is calculated as:
A = R • K • LS • C • P
where A is soil loss (tons/acre/year). R is the rainfall and runoff factor in erosion index units. GWLF
calculates the R factor, but the remaining values must be entered as input. K is the soil erodibility factor,
which affects the amount of soil erosion on a given unit of land. The LS factor signifies the steepness and
length of slopes and directly affects the amount of soil erosion. The C factor is related to the amount of
vegetative cover in an area. C values range from 0 to 1.0, with the larger values indicating greater
potential for erosion. The P factor is directly related to the conservation practices used in agricultural
areas. P values range from 0 to 1.0, with larger values indicating a greater potential for erosion.
The R, K and LS values vary by subwatershed, and are estimated using a GIS tool/Arc View extension
developed by Tetra Tech. The values for C and P factors used for modeling the Indian Creek watershed
are presented in Table 4-7. Soil erodibility factor (K) values were derived from the STATSGO soil layer
and component database. The LS values were determined for each land use type within each
subwatershed using DEM data together with the subwatershed boundaries. The C value for each land use
44
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June 2008
FINAL Indian Creek TMDLs
was determined from the USLE guide book Predicting Rainfall Erosion Losses, A Guide to Conservation
Planning (USDA 537).
Table 4-7. Assigned C and P Factor Values for the Indian Creek Watershed
Land Use
Low Intensity Residential
High Intensity Residential
High Intensity Commercial/lndustrial/Transportation
Paved_Roads
Bare Rock/Sand/Clay
Deciduous Forest
Evergreen Forest
Pasture
Agriculture
Wetlands
C
0.001
0.001
0.001
0.01
0.1763
0.0001
0.0001
0.0433
0.2067
0.005
P
1
1
1
1
0.989
1
1
0.88
0.725
1
Sediment delivery ratio: This parameter specifies the percentage of eroded sediment delivered to surface
water and is empirically based on watershed size.
Unsaturated available water-holding capacity: This parameter relates to the amount of water that can be
stored in the soil and affects runoff and infiltration.
Dissolved nitrogen and phosphorus in runoff: This parameter varies according to land use/cover type.
Reasonable values have been established in the literature. This rate, reported in milligrams per liter, can
be readjusted based on local conditions such as rates of fertilizer application and farm animal populations.
Default values reported in literature (tables B-15 and B-16 in the GWLF manual) were identified and used
for the various land uses in the Indian Creek watershed, as shown in Table 4-8.
Table 4-8. Nitrogen and Phosphorus Concentrations in Runoff
Land Use
Agriculture
Pasture
Bare Rock/Sand/Clay
Deciduous
Wetlands
Nutrient Concentration
N (mg/L)
2.9
3
0.24
0.19
0
P (mg/L)
0.26
0.25
0.15
0.006
0
Nutrient concentrations in runoff over manured areas: These concentrations are user-specified
concentrations for nitrogen and phosphorus that are assumed to be representative of surface water runoff
leaving areas on which manure has been applied. As with the runoff rates described above, these
concentrations are based on values obtained from the literature. They also can be adjusted based on local
conditions such as rates of manure application or farm animal populations. Limited information was
available related to local manure application rates and locations. Because agricultural lands in the
watershed are generally low-intensity, manure application was only simulated for cropland areas. The
45
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FINAL Indian Creek TMDLs
June 2008
default values reported in literature for cropland were used (Table B-15 from the GWLF manual for
manure left on soil surface for the land use category Corn - 12.2 mg/L N and 1.90 mg/L P).
Nutrient concentrations from septic system contributions: As part of Franconia Township's Sewer
Management Program, which was developed to address the township's Act 537 Plan, detailed information
on septic system performance was developed in the Indian Creek watershed. Two surveys were
conducted to gather information related to septic system functioning in the watershed, an initial mailed
census survey of residents' on-lot systems was conducted which included questions related to general
information, residents' current system, occupancy status, history of problems, lifestyle considerations and
water source information. The mail-in survey was sent to 323 Township residents served by onsite
systems within the watershed. The response rate for the mail in survey was 60% (195 responses). A
second survey was performed during onsite inspections. As of March 2008, 282 properties had been
inspected (81% of the total). Figure 4-3 shows the area of the watershed covered by the study.
Phase III Inspection Results. Sewer Myt. Study
Franconia Township
Not to be inspected
Vacant or Open Space, Vi/tiftbut Septic Systems
No Malfunctions
Potential Malfunctions, none noted
Suspected Malfunctions with Failure Characteristics
Figure 4-3. Septic Inspection Study Area and Results
Based on inspections, systems were placed into four categories:
Confirmed Malfunctions - malfunctions documented by dye testing, lab test results, and observation by
a certified Sewage Enforcement Officer. Also includes piped discharges with direct evidence of sewage,
reported backups, photographic documentation or other similar evidence.
46
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June 2008
FINAL Indian Creek TMDLs
Suspected Malfunctions - systems exhibiting some malfunction characteristics (e.g., abnormally green
grass in vicinity of absorption area, piped discharges without direct evidence of sewage, absorption areas
in known unsuitable soils, cesspools and pits.
Potential Malfunctions - systems appear to be operating satisfactorily but constructed prior to current
permitting requirements, located in areas unlikely to receive permitting by current standards, systems
constructed in areas mapped as unsuitable soils or located on exceptionally steep slopes greater than 25
percent.
No Malfunctions - systems appear to be operating satisfactorily.
Three additional categories were also used in the study:
Vacant or Open Space - includes properties that did not contain any onlot systems, such as vacant lots,
parks, cemeteries, etc.
Do Not Inspect - includes properties that were found to be connected to an existing public sewer system
or are scheduled to be connected in the near future.
Holding Tanks - include properties containing a holding tank.
Table 4-9 shows results of the study for each modeled subbasin. Note that results are not available for all
portions of subbasins 9, 10, 11, and 12.
Table 4-9. Septic Inspection Results by Modeled Subbasin
SUBBASIN
1
2
3
4
5
6
7
8
9
10
11
12
Total
Malfunctioning
1
5
38
6
12
7
23
11
Not surveyed
103
Suspected Malfunction
1
19
2
12
10
4
Not surveyed
48
Potential Malfunction
8
13
66
12
22
17
59
24
1
Not surveyed
222
Normal
1
5
29
5
7
8
38
7
Not surveyed
100
Data from this survey were compiled and used in parameterizing the GWLF model to represent septic
system loading to Indian Creek. Table 4-10 shows how the GWLF model was configured to represent
septic loading in Indian Creek. Because study results did not cover the entire portion of subbasins 9, 10,
11, and 12, certain assumptions were made with regard to the existences of onlot systems in those
subbasins. Subbasin 10 and the upper portion of subbain 12 were assumed to be largely sewered, while
subbasins 9 and 11 were assumed to be similar to subbasin 5 given similar landuse characteristics. This
was deemed to be a conservative assumption with respect to septic loading in subbasins 9 and 11 since
some of those areas are likely served by sewer connections. For purposes of model parameterization, the
conservative assumption that a single system serves 4 individuals was applied. Additionally, 50% of the
47
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FINAL Indian Creek TMDLs
June 2008
suspected and potential malfunctions were assigned to the "normal" category and 50% were assigned to
the direct discharge category.
Table 4-10. Septic Representation in GWLF; # Persons Served by Septic System Categories per Subbasin
Subbasin
1
2
3
4
5
6
7
8
9
10
11
12
Total
Normal
20
48
286
48
96
66
290
84
48
50
7
17
1060
Direct Discharge
20
48
322
52
116
62
230
100
58
50
9
17
1084
Background nitrogen and phosphorus concentrations in groundwater: Subsurface concentrations of
nutrients (primarily nitrogen and phosphorus) contribute to the nutrient loads in streams. Nutrient
concentrations in groundwater were based on the results from a nationwide study of mean dissolved
nutrients as measured in streamflow (as reported in Haith et al. 1992). For the Indian Creek watershed,
the groundwater concentrations were assumed to be approximately 0.021 mg/L for phosphorus and 0.71
mg/L for nitrogen, based on values for eastern U.S. watersheds (Table B-16 in the GWLF manual).
Background nitrogen and phosphorus concentrations in soil: Because soil erosion results in the transport
of nutrient-laden sediment to nearby surface waterbodies, reasonable estimates of background
concentrations in soil must be provided. Because there were no local soil concentration data to support
the modeling effort, literature values were used. The percent sediment weight of nitrogen and phosphorus
in the top 30 cm of soil was calculated based on maps in the GWLF manual (Figures B-3 and B-4 in the
GWLF manual) as 1,500 mg/kg and 660 mg/kg, respectively.
Other less important factors that can affect sediment and nutrient loads in a watershed also are included in
the model. More detailed information about these parameters and those outlined above can be obtained
from the GWLF User's Manual (Haith et al. 1992). Pages 15 through 41 of the manual provide specific
details that describe equations and typical parameter values used in the model.
4.2.3. Model Testing
Streamflow data are generally used to test or calibrate watershed hydrologic parameters for the GWLF
model. There are no active U.S. Geological Survey (USGS) gages in the Indian Creek watershed, nor is
there information available regarding historical stream flow data. The closest available gage is USGS
1472810 on East Branch Perkiomen Creek near Schwenksville, Pennsylvania (Figure 4-3). The Indian
Creek watershed drains to the East Branch Perkiomen Creek, which contributes drainage to the gage.
Therefore the East Branch Perkiomen creek watershed was modeled for calibration purposes. The East
Branch Perkiomen Creek watershed exhibits similar hydrologic properties such as soils, land use and
48
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June 2008 FINAL Indian Creek TMDLs
geology characteristics to the Indian Creek. Once calibrated, the hydrology parameters from the
calibration watershed were applied to the Indian Creek watershed.
GWLF predicted overall water balances in the calibration watershed. The East Branch Perkiomen Creek
watershed was modeled using the composite weather file created using the Greaterford and Sellersville
NCDC meteorological station for a time period 1997 through 2004. This modeling period was selected
based on the availability of weather and flow data that were collected during the same time period.
Although weather data were available prior to 1997 there were many data gaps. It was assumed that this
8-year time period would capture any seasonal variations in the watershed with a range of precipitation
and stream flow conditions being represented. Calibration plots for the East Branch Perkiomen Creek are
presented in Figures 4-4 and 4-5. In general, the seasonal trends and peaks are captured reasonably well
for the modeling period in the calibration watershed.
49
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FINAL Indian Creek TMDLs
June 2008
EASTROCKHILL \ cfEDM|NSTER
^J Municipalities
~^ Indian Crk Watershed
a USGS Gage Stations
East Branch Perkiomen Crk
East Branch Perkiomen Watershed
4
N
4 Miles
Figure 4-4. East Perkiomen Creek watershed.
50
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June 2008
FINAL Indian Creek TMDLs
J-97
J-98
J-04
20
18
y =0.7452x + 1.4274
R2 = 0.7504
8 10 12
Modeled
14
16
18
20
Figure 4-5. Observed and Predicted Monthly Streamflow (centimeters) - East Branch Perkiomen Crk at
USGS 01493500 (1997 - 2004)
51
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FINAL Indian Creek TMDLs
June 2008
10.00
9.50
9.00
8.50 J
8.00
7.50
7.00
6.50
6.00
5.50
5.00
4.50
4.00 -
3.50 -
3.00
2.50 H
2.00
1.50
1.00 J
0.50
0.00
10
9 -
8
7
•o 6
5
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June 2008
FINAL Indian Creek TMDLs
4.2.4. Watershed Model Results - Nutrients
For the nutrients simulation, the GWLF model was run for the period from April 2005 to December 2006
to obtain predicted loading values for TP and TN. This period was selected because it coincides with the
period during which monitoring data are available for various locations in Indian Creek. Average annual
and monthly predicted loads from the watershed (based on the modeled period) are shown in Table 4-11
and Table 4-12. These are loads from the watershed in total and represent the sum of subbasin loads. For
comparison, Table 4-11 also shows the permitted annual loads from the three continuously discharging
point sources in the watershed. Watershed loading values were used in conjunction with the EFDC
receiving water model to determine the necessary TMDLs for Indian Creek.
Table 4-11. Average Annual Watershed and Point Source Nutrient Loads for the Modeled Period
FN (Ib/yr)
TP (Ib/yr)
AVG. Annual Watershed Load
28,331
3,820
Total Point Source Loads
48,646.55
7,553.37
Table 4-12. Average Monthly Watershed Loads for the Modeled Period
TN (Ib)
TP (Ib)
JAN
62
8
FEB
29
1
MAR
19
1
APR
74
5
MAY
40
2
JUN
20
1
JUL
76
11
AUG
23
1
SEP
9
0
OCT
346
69
NOV
43
1
DEC
65
9
Predicted unit area loading rates by landuse are shown in Table 4-13
Table 4-13. Modeled Landuse Loading Rates for Nutrients
Landuse
Agriculture
Pasture
Paved Roads
Bare Rock/Sand/Clay
Deciduous Forest
Evergreen Forest
Wetlands
High Intensity Residential
High Intensity Commercial/lndustrial/Transportation
Low Intensity Residential
TN (Ib/acre/yr)
11.40
2.63
0.15
0.45
0.07
0.14
0.00
1.36
6.18
3.86
TP (Ib/acre/yr)
2.79
0.51
0.03
0.25
0.00
0.00
0.00
0.23
0.72
0.44
Landuse categories producing the highest loading rates for TP include agriculture, impervious areas
associated with low-intensity residential, and impervious areas associated with high-intensity
commercial/industrial/transportation. For TN, the highest loading categories include agriculture,
impervious residential and commercial areas, followed by pasture lands and pervious residential and
commercial areas. Because the entire watershed is an MS4, landuse loads, while modeled as nonpoint
source runoff, are subject to WLAs under the NPDES Phase II stormwater permitting program.
Because the critical condition in Indian Creek occurs during low flow periods, when point sources are the
dominant source of nutrients in the watershed, overall nonpoint loads were compared to overall point
source loads derived from DMR data (Table 4-8 compares predicted annual watershed loads with
53
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FINAL Indian Creek TMDLs
June 2008
permitted point source loads). For the period modeled, average point source TN loads far exceeded
nonpoint source loads while average point source TP loads were slightly less than nonpoint source loads.
However, the relationship varies depending on flow and season as well as on the values selected to
represent point source discharges.
Model results show highest nonpoint TP loading occurred during the month of October during the
simulation period; the same is true of TN loading. Figure 4-7 compares modeled nonpoint loads in Indian
Creek to typical annual loading values for point sources. Point source loading values were developed
from facility monitoring data from the three NPDES permitted facilities (see Table 4-15). These values
represent existing discharge levels and are actually less than baseline (permitted) loading levels, because
the facilities typically discharge at volumes lower than design flow volumes and at concentrations lower
than permitted concentration limits.
Ib/yr
Comparison of Annual PS and NFS Loading
NPSTN
PSTN NPSTP
Source Category
PSTP
Figure 4-7. Comparing Annual PS and NFS Nutrient Loading in Indian Creek
54
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June 2008
FINAL Indian Creek TMDLs
4.2.5. Receiving Water Model
EFDC (Environmental Fluid Dynamics Code) is used for the receiving water modeling of Indian Creek.
The EFDC model is a dynamic model that can simulate time-variable water quality constituents. In the
Indian Creek EFDC model, both time variable point sources and nonpoint sources are represented. The
nonpoint sources are estimated with the watershed model GWLF and the GWLF results are linked to
EFDC.
EFDC is a general purpose modeling package for simulating three-dimensional flow, transport, and
biogeochemical processes in surface water systems including rivers, lakes, estuaries, reservoirs, wetlands,
and coastal regions. The EFDC model is a widely tested model and is supported by USEPA. In addition
to hydrodynamic and salinity and temperature transport simulation capabilities, EFDC is capable of
simulating cohesive and noncohesive sediment transport, near field and far field discharge dilution from
multiple sources, eutrophication processes, the transport and fate of toxic contaminants in the water and
sediment phases, and the transport and fate of various life stages of finfish and shellfish. Special
enhancements to the hydrodynamic portion of the code, including vegetation resistance, drying and
wetting, hydraulic structure representation, wave-current boundary layer interaction, and wave-induced
currents, allow refined modeling of wetland marsh systems, controlled flow systems, and near-shore wave
induced currents and sediment transport. The EFDC model has been extensively tested and documented.
The model is presently being used by a number of organizations including universities, governmental
agencies, and environmental consulting firms.
The structure of the EFDC model includes four major modules: (1) a hydrodynamic model, (2) a water
quality model, (3) a sediment transport model, and (4) a toxics model (Figure 4-6). For Indian Creek, the
hydrodynamic and water quality modules are used; the sediment and toxics modules were not used. The
EFDC hydrodynamic model itself, which was used for this study, is composed of six transport modules
including dynamics, dye, temperature, salinity, near field plume, and drifter (see Figure 4-7). Various
products of the dynamics module (i.e., water depth, velocity, and mixing) are directly coupled to the
water quality, sediment transport, and toxics models. A schematic diagram for the water quality model is
included in Figure 4-8.
EFDC Model
Hydrodynamics
Water
Quality
Sediment
Transport
Toxics
Figure 4-8. EFDC model structure.
55
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FINAL Indian Creek TMDLs
June 2008
Figure 4-9. EFDC hydrodynamics module structure.
Hydrodynamic
Model
Figure 4-10. EFDC water quality module Structure.
The EFDC code includes a eutrophication submodel for water quality simulation (Park et al. 1995), which
is functionally equivalent to the CE-QUAL-ICM or Chesapeake Bay Water Quality model Cerco and
Cole 1993). The water column eutrophication models are coupled to a functionally equivalent
implementation of the CE-QUAL-ICM biogeochemical processes model (DiToro and Fitzpatrick 1993).
Figure 4-9 shows the schematic diagram. In addition to the phytoplankton, benthic algae or macroalgae
can be simulated in EFDC. The eutrophication models can be executed simultaneously with the
hydrodynamic component of EFDC. EFDC accepts an arbitrary number of point and nonpoint source
loadings as well as atmospheric and ground water loadings.
4.2.6. EFDC Model Setup
Indian Creek monitoring data, including water depth, DO, and nutrients, were available for 05/09/2006 to
05/11/2006. In addition, DO and nutrients data were collected in August, 2006. To develop a reliable
model for Indian Creek with limited data, a two-step approach was used to develop and calibrate the
model. In the first step, the model was setup for a 30-day period using the field data from May 2006 as a
pre-calibration run. This period was chosen to save computation time as it was anticipated that the model
would reach a pseudo steady state within a simulation period of 30 days. The model reached pseudo-
steady-state after 10 days simulation. In this step, the hydrodynamics were calibrated and the water
quality parameters were estimated. In the second step, the water quality parameters obtained in pre-
calibration were refined and finalized for TMDL development by linking it to the watershed model.
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FINAL Indian Creek TMDLs
Segmentation
To set up the EFDC model, the stream was divided into discrete cells for computation. The stream
network GIS coverage was cleaned to represent only the mainstem of Indian Creek and the two major
tributaries that include point sources (Pilgrims Pride and Lower Salford). The mainstem of Indian Creek
was divided into 49 segments. The tributary in subbasin 4 (Pilgrims Pride) was divided into eight
segments and the tributary in subbasin 10 (Lower Salford) was divided into nine segments. The lengths of
the segments were set to 200 meters for 63 segments among the total of 66 segments. The lengths for the
three upstream segments (one on the mainstem, two on tributaries) are less than 200 meters. Since Indian
Creek is a shallow stream, only one layer is used in the vertical direction. Figure 4-10 shows the EFDC
modeling domain for Indian Creek.
N
A Sampling Stations
Sub basins
Municipalities
Streams
IndianCreekEFDC
Figure 4-11. Indian Creek EFDC Modeling Domain.
Survey data from seven cross-sections were processed to obtain the width and average depth for the
modeled segments (Table 4-14). The locations of cross-sections are also shown in Figure 4-11. The
widths and depths of the segments on the mainstem were calculated by interpolating the surveyed data.
The widths and depths of the segment on the two tributaries were specified directly with the surveyed
data.
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FINAL Indian Creek TMDLs
June 2008
Table 4-14. Width and Average Depth at the Cross-Sections
Location
Sergey
Godshall
Pilgrims Pride (Tributary)
Keller Creamery
RT63
Salford (Tributary)
Indian Creek Mouth
Width (ft)
8.20
16.30
6.20
15.30
21.30
11.70
19.20
Average Depth (ft)
0.25
0.49
0.29
0.51
0.78
0.26
0.68
Width (meter)
2.50
4.97
1.89
4.66
6.49
3.57
5.85
Average Depth
(meter)
0.08
0.15
0.09
0.16
0.24
0.08
0.21
Meteorological Data
EFDC requires time-variable weather time series to drive the model. Weather data including wind, air
temperature, relative humidity, precipitation, and solar radiation are from the NCDC weather station
Willow Grove NAS. Raw data were processed to EFDC format. For the pre-calibration step, the weather
information from 05/09/2006 to 05/11/2006 was input to the model repeatedly for 30 days. For the
second step, weather data from 04/01/2005 to 10/31/2006 are input to the EFDC model.
Point Source Representation
In the pre-calibration step, which used field data collected in May 2006, representative point source
effluent flows were obtained by averaging the DMR flows for the month May for the period from 2001 to
2005. Nutrients and DO DMR data for the month of May for the same period were processed to estimate
the nutrients in the effluents from the point sources. It was assumed that the total amount of ammonia and
nitrate was identical among the three point sources since only one point source (Pilgrims Pride) had NO3
measurements. In addition, no data were available for the ratios of PO4 to TP in the effluents for the three
point sources. In-stream PO4 and TP measurements show that over 93 percent of TP is PO4. Therefore, it
was assumed that TP in the effluents was mainly PO4 and recorded TP concentrations were directly
assigned to the EFDC model as PO4. Since PO4 is the major phosphorus species that algae use for
growth, the assumption is conservative for TMDL development.
In the second step of calibration, if there were recorded data for both flow and nutrients within 2005, the
data were used directly. For the time period without any record, averaged data from 2001 to 2004 were
used. The assumptions for NO3 and PO4 are the same as in the pre-calibration step. Table 4-15 shows
the values used in the model for the three point sources.
Table 4-15. Point source data used in Indian Creek EFDC model
Time
Apr-05
May-05
Jun-05
Jul-05
Telford STP
Flow
(mgd)
0.848
0.519
0.527
0.577
PO4
(mg/L)
0.400
1.000
2.300
1.200
NH3
(mg/L)
0.100
0.100
0.100
0.100
NO23
(mg/L)
5.931
5.898
7.605
26.090
Pilgrims Pride
Flow
(mgd)
0.138
0.136
0.158
0.128
PO4
(mg/L)
0.925
0.740
0.793
1.230
NH3
(mg/L)
0.234
0.480
1.540
0.290
NO23
(mg/L)
5.798
5.518
6.165
25.900
Lower Salford STP
Flow
(mgd)
0.459
0.442
0.462
0.396
PO4
(mg/L)
0.246
0.126
0.164
0.178
NH3
(mg/L)
0.100
0.103
0.100
0.133
NO23
(mg/L)
5.931
5.894
7.605
26.057
58
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FINAL Indian Creek TMDLs
Time
Aug-05
Sep-05
Oct-05
Nov-05
Dec-05
Jan-06
Feb-06
Mar-06
Apr-06
May-06
Jun-06
Jul-06
Aug-06
Sep-06
Oct-06
Telford STP
Flow
(mgd)
0.511
0.405
0.583
0.705
0.810
0.713
0.840
0.958
0.848
0.519
0.527
0.577
0.511
0.405
0.583
PO4
(mg/L)
0.600
0.700
1.180
1.500
1.500
1.300
1.300
1.300
0.400
1.000
0.400
0.400
0.800
0.500
0.400
NH3
(mg/L)
0.100
0.100
0.323
0.220
0.353
0.670
0.585
0.592
0.100
0.100
0.050
0.050
0.900
0.050
0.050
NO23
(mg/L)
4.700
9.518
12.158
12.280
12.007
4.486
3.831
6.452
5.931
5.898
3.650
2.450
12.850
19.900
22.450
Pilgrims Pride
Flow
(mgd)
0.136
0.106
0.129
0.121
0.116
0.126
0.125
0.140
0.138
0.136
0.158
0.128
0.136
0.106
0.129
PO4
(mg/L)
0.360
0.100
1.580
1.580
1.580
0.360
0.360
0.360
0.925
0.740
0.010
0.090
0.320
0.045
0.030
NH3
(mg/L)
0.200
0.200
0.380
1.153
0.635
0.426
0.364
0.184
0.234
0.480
0.650
0.510
0.390
0.200
0.310
NO23
(mg/L)
4.600
9.418
12.100
11.347
11.725
4.730
4.053
6.860
5.798
5.518
3.050
1.990
13.360
19.750
22.190
Lower Salford STP
Flow
(mgd)
0.396
0.478
0.443
0.475
0.534
0.457
0.475
0.538
0.459
0.442
0.462
0.396
0.396
0.478
0.443
PO4
(mg/L)
0.110
0.103
0.126
0.479
0.479
0.246
0.246
0.246
0.246
0.126
0.100
0.090
0.130
0.120
0.120
NH3
(mg/L)
0.100
0.100
0.100
0.130
0.270
0.440
0.363
0.533
0.100
0.103
0.050
0.050
0.050
0.050
0.620
NO23
(mg/L)
4.700
9.518
12.380
12.370
12.090
4.716
4.054
6.510
5.931
5.894
3.650
2.450
13.70
19.90
21.880
Nonpoint Source Representation
In the pre-calibration simulation period, flows in Indian Creek were measured during the cross-section
survey between 05/09/2006 and 05/11/2006. Watershed inflows between the cross-section locations were
calculated and were distributed to corresponding EFDC model cells. Recorded water temperature time
series in Indian Creek at the cross-sections were averaged and were assumed to be the water temperature
in the watershed inflows. The temperature data were also repeated for the 30-day simulation period.
For the nutrients and organic carbon entering Indian Creek with watershed inflows, the GWLF model
results including TP and TN for the period from 05/09/2006 to 05/11/2006 were used. The TP and TN
results were processed to 12 nutrient and organic carbon species that are required by EFDC. DO in the
watershed inflows are assumed to be at the saturation level.
For the second step of calibration, watershed runoff generated by GWLF for the period from 04/01/2005
and 10/31/2006 were processed to EFDC format, and flows were distributed to corresponding EFDC
cells. The TP and TN generated by GWLF were processed and input to EFDC using the same approach as
for the pre-calibration step. DO in the watershed inflows were assumed to be at the saturation level. The
following section discusses the linkage between GWLF and EFDC.
Linkage of GWLF to EFDC
In the EFDC model, the variables for carbon and nutrients include labile particulate organic carbon
(LPOC), refractory particulate organic carbon (RPOC), dissolved organic carbon (DOC), labile
particulate organic phosphorus (LPOP), refractory particulate organic phosphorus (RPOP), dissolved
organic phosphorus (DOP), orthophosphate (PO4), labile particulate organic (LPON), refractory
particulate organic nitrogen (RPON), dissolved organic nitrogen (DON), ammonia (NH4), and nitrate
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FINAL Indian Creek TMDLs
June 2008
(NO3). To link the GWLF model to EFDC, GWLF-generated TP and TN were converted to the 12 EFDC
water quality variables.
To derive the conversion of TP and TN to LPOC, RPOC, DOC, LPOP, RPOP, OOP, PO4, LPON,
RPON, DON, NH4, and NO3, river and stream data from Montgomery County were obtained from
USEPA's STORET. Ratios were calculated using the monitoring data from all the stations. The ratios are
listed below in Table 4-16.
Table 4-16. Ratio Used to Convert GWLF Constituents to EFDC Constituents
EFDC Constituent
RPOC
LPOC
DOC
RPOP
LPOP
OOP
PO4
RPON
LPON
DON
NH4
NO3
GWLF Constituents
TN
TN
TN
TP
TP
TP
TP
TN
TN
TN
TN
TN
Conversion ratio
0.92
0.92
0.37
0.38
0.38
0.15
0.09
0.16
0.16
0.07
0.01
0.59
4.2.7. EFDC Model Calibration
Due to the limited data, the hydrodynamic calibration of the EFDC model was achieved by matching the
measured average depth and modeled depth. In addition, modeled temperature and measured temperature
were compared to insure correct thermal parameters. A comparison of depth is shown in Table 4-17.
Figure 4-12 shows the results of temperature calibration.
Table 4-17. Comparison of Measured and Modeled Depth on the Main Indian Creek
Location
1C Mouth
RT63
Keller Creamery
Godshall
Sergey
Measured Depth(m)
0.21
0.23
0.16
0.15
0.08
Modeled Depth (m)
0.24
0.23
0.17
0.12
0.14
60
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June 2008
FINAL Indian Creek TMDLs
30.00 -
_ 25.00 -
o
« 20.00 -
rf8jfrw0»
° Measured Temperature
"Modeled Temperature"
i»
/06 5/9/06 5/10/06 5/10/06 5/11/06 5/11/06 5/12/06
0:00 12:00 0:00 12:00 0:00 12:00 0:00
Time
Figure 4-12. Temperature calibration results.
The next step was to calibrate the water quality parameters in Indian Creek. In the pre-calibration step, the
flow and depth reach steady-state condition quickly. Although the flow and incoming nutrients are
constant, weather conditions and water temperature in the watershed inflows are time variable. PO4,
NH4, NO3 and DO were used as calibration targets, along with maximum, average, and minimum DO.
Parameters were adjusted until model results agreed reasonably well with data during pre-calibration.
After the pre-calibration, the model was run for the long-term simulation and parameters were calibrated
to observed data. Calibration plots showing longitudinal profiles of PO4, NH4, NO3, maximum DO,
average DO, and minimum DO from the mouth of Indian Creek to upstream are presented in Appendix B:
EFDC Calibration Plots. The comparison of modeled and monitored DO time series is also shown. The
key parameters for the Indian Creek water quality model are shown in Table 4-18. The original
calibration conducted in 2006 used only May 2006 data. The August 2006 data were also used in the
updated calibration to obtain more reliable values of the benthic macroalgae parameters. The major
change is the phosphorus half-saturation constant for macroalgae, which was changed from the original
estimation of 0.005 mg/L to 0.05 mg/L after using two sets of data for the updated calibration.
Modeled NH4 is slightly lower than data, especially around 7000 meters from the Indian Creek mouth,
where the golf course is located. Due to insufficient information on golf course irrigation, withdrawal
water is not included in the current model. The increase of NH4 at this location may be caused by golf
course irrigation. Modeled NO3 near Telford STP is strongly related to the NO3 in the effluent from
Telford STP. The low modeled NO3 at this location is caused by the low NO3 concentration from Telford
STP that is derived from Pilgrims Pride data. The modeled PO4 agrees well with the observed data. The
longitudinal and time variable plots of DO show that the model is able to catch the DO fluctuation fairly
well with slight over-predicting of minimum DO. Overall, the model is reasonably reliable to be used in
TMDL development.
Table 4-18. Key Water Quality Parameters for Indian Creek EFDC Model
Parameter
KHNm
KHPm
Parameter Description
nitrogen half-saturation for macroalgae (mg/L)
phosphorus half-saturation for macroalgae (mg/L)
Value
0.125
0.05
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FINAL Indian Creek TMDLs
June 2008
Parameter
DOPTm
TMm1
TMm2
KTG1m
KTG2m
TRm
KTBm
FCRPm
FCLPm
FCDPm
FCDm
KHRm
FPRPM
FPLPM
FPDPM
FPIPM
FPRm
FPLm
APCM
FPDm
FPIm
CPprml
CPprm2
CPprmS
FNRPM
FNLPM
FNDPM
FNRm
FNLm
FNDm
FNIm
ANCm
rNitM
AOCR
AONT
AOCRpm
PMm
BMRm
PRRm
Parameter Description
optimal depth (m) for macroalgae growth
lower optimal temperature for macroalgae growth (degC)
upper optimal temperature for macroalgae growth (degC)
suboptimal temperature effect coef. for macroalgae growth
superoptimal temperature effect coef. for macroalgae growth
reference temperature for macroalgae metabolism (degC)
temperature effect coef. for macroalgae metabolism
carbon distribution coef. for macroalgae predation: refractory POC
carbon distribution coef. for macroalgae predation: labile POC
carbon distribution coef. for macroalgae predation: DOC
carbon distribution coef. for macroalgae metabolism
half-sat, constant (gO2/m3) for macroalgae DOC excretion
phos. distribution coef. for macroalgae predation: RPOP
phos. distribution coef. for macroalgae predation: LPOP
phos. distribution coef. for macroalgae predation: OOP
phos. distribution coef. for macroalgae predation: Inorganic P
phos. distribution coef. of RPOP for macroalgae metabolism
phos. distribution coef. of LPOP for macroalgae metabolism
factor to modify APC for macroalgae
phosphorus distribution coef. of OOP for macroalgae metabolism
phosphorus distribution coef. of P4T for macroalgae metabolism
constant used in determining algae Phos-to-Carbon ratio
constant used in determining algae Phos-to-Carbon ratio
constant used in determining algae Phos-to-Carbon ratio
nitrogen distribution coef. for marcoalgae predation: RPON
nitrogen distribution coef. for marcoalgae predation: LPON
nitrogen distribution coef. for marcoalgae predation: DON
nitrogen distribution coef. of RPON for macroalgae metabolism
nitrogen distribution coef. of LPON for macroalgae metabolism
nitrogen distribution coef. of DON for macroalgae metabolism
nitrogen distribution coef. of DIN for macroalgae metabolism
nitrogen-to-carbon ratio for macroalgae
maximum nitrification rate (gN/m3/day)
stoichiometric algae oxygen-to-carbon ratio (gO2/gC)
stoichiometric algae oxygen-to-nitrate ratio (gO2/gN)
macroalgae photosynthesis oxygen-to-carbon ratio
max. growth rate for macroalgae (1/day)
basal metabolism rate for macroalgae (1/day)
predation rate on macroalgae (1/day)
Value
0.3
12
25
0.02
0.001
20
0.1
0.3
0.3
0.4
0.2
0.5
0.1
0.1
0.1
0.7
0.1
0.1
0.5
0.4
0.4
42
85
200
0.4
0.5
0.1
0.2
0.4
1
0
0.088
0.02
2.67
4.33
2.67
0.8
0.1
0.01
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June 2008 FINAL Indian Creek TMDLs
After the calibration, two scenarios were conducted to evaluate the impact of point sources and nonpoint
sources on the stream. The first scenario sets nutrient contributions from point sources to zero and the
second scenario sets nutrient contributions from nonpoint sources to zero. The results are shown in
Appendix C. Under the nonpoint source only scenario, modeled DO results achieve the water quality
standard (exhibiting less fluctuation due to algae) for the entire simulation period for all the stations. The
results support the assumption that point sources are the dominant factor controlling algae levels and DO
fluctuation.
To calculate the TMDL, two additional scenarios were run—baseline and the load reduction scenario.
The results for each are presented in Appendix D and E respectively. The baseline condition for the
Indian Creek TMDL uses the existing condition watershed runoff and nutrient loading generated with
GWLF and used in model calibration. The weather conditions were also identical to those used in model
calibration. Point sources were set at their permit limits (rather than existing discharges based on DMR
data). Among the three point sources, discharge flow limits of Telford STP and Lower Salford STP were
used in the baseline condition. Because there is no flow limit for Pilgrims Pride discharge, the recorded
flows were used. For nutrients discharged from the three point sources, TP and NH4 permit limits were
used forthe baseline condition. The simulation period is from 04/01/2005 to 10/31/2006. The first two
months were considered a stabilization period to eliminate the impacts of the model's initial conditions.
Beginning with the baseline condition, successive model runs were performed to evaluate the level of
instream nutrient concentrations during the target growing season period. Source loads were reduced
until the average instream nutrient concentration for the period from April 1 to October 31 was met.
The model results for the baseline conditions show that both modeled average TPconcentration is higher
than the TP target. In addition, modeled DO concentrations fall below the daily minimum of 5 mg/L and
daily average of 6 mg/. The phosphorus concentrations from both the watershed runoff and point sources
were reduced iteratively until TP met seasonal target levels and DO met the respective criteria. The
simulation period is the same as in baseline conditions. The load reduction results can be found in
Appendix E.
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FINAL Indian Creek TMDLs June 2008
5. TMDL ALLOCATION ANALYSIS
A TMDL is the total amount of pollutant that can be assimilated by the receiving waterbody while still
achieving water quality standards or goals. It is comprised of the sum of individual wasteload allocations
(WLAs) for point sources and load allocations (LAs) for both nonpoint sources and natural background
levels. In addition, the TMDL must include a margin of safety (MOS), either implicitly or explicitly, to
account for the uncertainty in the relationship between pollutant loads and the quality of the receiving
waterbody. Conceptually, this definition is represented by the equation:
TMDL = EWLAs + ELAs + MOS
In TMDL development, allowable loadings from pollutant sources that cumulatively amount to no more
than the TMDL must be established; this provides the basis to establish water quality based controls.
TMDLs can be expressed on a mass loading basis or as a concentration in accordance with 40 CFR
130.2(1).
The load allocation (LA) is the portion in the TMDL that is assigned to nonpoint sources. Since the entire
Indian Creek watershed is included in multiple MS4s regulated under the Phase II storm water program,
the municipalities within Indian Creek watershed received WLAs to address the land-based stormwater
loading. Therefore, the load allocation for sediment and nutrients in the Indian Creek watershed is zero.
Once a municipality delineates its MS4 area, the sediment and nutrient loads associated with nonpoint
sources may be parsed out of the WLA and allocated to the LA portion of the TMDL.
Federal regulations (40 CFR 130.7) require TMDLs to include individual WLAs for each point source. In
addition USEPA's stormwater permitting regulations require municipalities to obtain permit coverage for
all stormwater discharges from an urban municipal separate storm sewer system (MS4). A November 22,
2002 USEPA Memorandum from Robert Wayland and James Hanlon, Water Division Directors
(http://www.epa.gov/boston/npdes/stormwater/) clarified existing regulatory requirements for MS4s
connected with TMDLs. One key point is that NPDES-regulated MS4 discharges must be included in the
wasteload allocation component of the TMDL and may not be addressed by the load allocation
component of TMDL.
Based on this memorandum, MS4s within the Indian Creek watershed were treated as point sources for
TMDL allocation purposes, and the loading generated within the boundary of an MS4 area was assigned a
WLA.
There are three point source facilities and five MS4 communities within the Indian Creek watershed, all
requiring WLAs.
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June 2008
FINAL Indian Creek TMDLs
5.1. Sediment TMDLs
The sediment TMDL for the Indian Creek watershed was developed using the GWLF model and
identification of targets was based on a reference watershed. The GWLF model was used to establish
existing loading conditions for the Indian River watershed. The unit area loading rates established for the
reference watershed in the Wissahickon TMDL (i.e., Ironworks Creek) were used to identify the sediment
loading target; these rates were further refined to arrive at the final allocation for the landuse loading
derived (MS4) portion. Further information about selection of the sediment target can be found in
Section 1.4.
Model results show that existing sediment loading is approximately 12,693,686 Ib/year. The target
sediment values for the watershed were determined by multiplying the land use area of the Indian Creek
watershed by the target unit area loading rates established using Ironworks reference watershed in the
Wissahickon Creek TMDL (see Table 1-3). Based on this calculation, the target or allowable sediment
load for the Indian Creek watershed is 641,733 Ib/year.
From the allowable sediment load, a 5 percent MOS and a 6 percent future residential gross growth
wasteload allocation were subtracted. It was assumed that since point sources were not a significant
source of sediment in the watershed (approximately 1.3 percent of the existing loading), they would not
require a reduction. Therefore, the point source sediment total of 169,922 Ib/yr (calculated using permit
limits and corresponding flow limits) was also subtracted from the allowable load and this resulted in a
target value for the remaining portion of the watershed of 401,220 Ib/yr. Because the entire watershed is
considered an MS4, this remaining load is the amount allocated to the MS4 WLA. Finally, earlier
versions of the DRAFT TMDL inadvertently included a small portion of Upper Salford in the overall
allocation. For sediment, the Upper Salford MS4 area had been allocated 129 Ib/yr. Subtracting this from
the total allowable MS4 load leaves the target value for the remaining watershed as 401,091 Ib/yr. Not
counting the MOS or the Future Growth allocations, the WLA portions of the sediment TMDL is 571,013
Ib/yr, the TMDL is 641,604 Ib/yr, see Table 5-1 for a summary. The following sections describe in more
detail how the allocations for point source facilities and MS4 areas were identified.
Table 5-1. Summary of Sediment TMDL Loads for Indian Creek Watershed
Indian Creek Watershed
Existing Load
Allowable Load
MOS (5%)
Future Residential Growth (6%)
E WLA Point Sources
E WLA MS4
ELA
TMDL*
Sediment Loading (Ib/yr)
12,693,686
641,733
32,087
38,504
169,922
401,091
0
641,604
*Less 129 Ib/yr previously allocated to Upper Salford
Sediment WLAs
For the permitted facilities, the sediment WLA was calculated using permit limits and corresponding flow
limits. (Because the Pilgrims Pride facility does not have a flow limit, a maximum flow value based on
reported flow was used to compute the WLA for the Pilgrims Pride Facility.) Table 5-2 presents the
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FINAL Indian Creek TMDLs
June 2008
WLAs assigned to each of the point source facilities. The sediment WLA is an annual average based on a
seven year simulation period. A corresponding daily maximum load expression was developed using a
statistical approach outlined in EPA's Draft Options for Expressing Daily Loads in TMDLs (EPA 2007).
Calculation details are provided in Section 5.3. EPA did not impose reductions to permitted facility
discharge levels for sediment.
Table 5-2. Sediment WLAs for Continuous Point Sources in the Indian Creek Watershed
Point Source Facility
Telford
Pilgrims Pride
Lower Salford
NPDES ID
PA0036978
PA0054950
PA0024422
Total WLA
Sediment WLA (Ib/yr)
100,455
5,540
63,926
169,922
Sediment WLA
(mg/L)
30
10
30
-
Daily Maximum
(Ib/day)
523
35
533
-
To determine the allowable sediment loading associated with each MS4, the township boundary GIS layer
was overlaid with the watershed boundary and the MS4 WLA was proportionally assigned to each
municipality based on area and landuses contained.
The MS4 loadings were derived based on the modeled GWLF results after the EMPR reduction analysis.
First the GWLF model was used to estimate landuse specific unit area loadings for each subbasin. The
municipality total areas were then overlaid with the subbasins within GIS to estimate the MS4 area falling
within each subbasin. Next this unit area loading for each landuse within a particular subbasin was
multiplied by the area of the municipality that it falls into to estimate the MS4 loads.
In each municipality, the reference loading rate was applied to each appropriate landuse and multiplied by
the area of the landuse in the jurisdiction to determine the allowable sediment loading. The initial
reference loading rates were then adjusted downward for all categories except forest and wetlands until
the resulting loads for the MS4 portion of the WLA equaled the appropriate value, 401,220 Ib/yr. Table
5-3 shows existing, reference, and TMDL landuse loading rates. Table 5-4 provides the total and daily
maximum sediment loads allocated to each of the MS4 jurisdictions and the landuse breakdown.
At this time, EPA cannot determine what portion of the municipalities are designated/used for collection
or conveying stormwater, as opposed to portions that are truly nonpoint sources. As part of the Phase II
stormwater permit process, MS4s will be responsible for evaluating and mapping out areas that are
draining to or discharging to storm sewers. Since these systems have not yet been delineated, the TMDL
lumps nonpoint source loadings into the WLA portion of the TMDL. Once these delineations are
available, the nonpoint source loadings can then be separated out of the WLAs and moved under the LA.
After adjusting the WLAs and LAs based on MS4 service area delineation, Pennsylvania may initiate the
TMDL revision process.
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FINAL Indian Creek TMDLs
Table 5-3. Existing, Reference and TMDL Landuse Loading Rates for Sediment
SOURCE
Agriculture
Pasture
Paved_Roads
Bare Rock/Sand/Clay
Deciduous Forest
Evergreen Forest
Wetlands
High Intensity Residential*
High Intensity
Commercial/lndustrial/Transportation*
Low Intensity Residential*
Existing
Unit
Area
Load
(Ib/ac/yr)
8595
3727
192
745
2
3
0
37 / 424
37 / 424
33 / 424
Reference
Target Unit
Area
Loading
(Ib/ac/yr)
464
52
105
619
5.43
3.99
0
105
105.12
124.12
Final Target
Unit Area
Loading
(Ib/ac/yr)
291
32
66
388
5
3.99
0
66
66
78
denotes pervious / impervious estimated loading rates
Table 5-4. MS4 Sediment WLAs (Ib/yr)
Source
Agriculture
Pasture
Paved_Roads
Bare Rock/Sand/Clay
Deciduous Forest
Evergreen Forest
Wetlands
High Intensity Residential
High Intensity
Commercial/lndust rial/Transport
Low Intensity Residential
Total WLA (Ib/yr)
Maximum Daily (Ib/day)
Lower
Salford
35,033
13,326
1,405
345
414
6
-
11,503
3,849
15,068
80,950
497
Souderton
388
402
307
-
-
-
-
3,000
1,273
1,901
7,272
45
Telford
1,681
431
600
-
11
-
-
6,264
3,644
4,234
16,864
104
Franconia
176,524
37,068
1,551
4,312
744
-
-
24,850
6,805
44,150
296,005
1818
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FINAL Indian Creek TMDLs
June 2008
5.2. Nutrient TMDLs
The nutrient TMDL for the Indian Creek watershed was developed using a separate application of the
GWLF watershed model of the Indian Creek watershed linked to an in-stream EFDC model of Indian
Creek. The GWLF model was used to establish existing nonpoint loading conditions for the Indian Creek
watershed. The seasonal average TP target was used as the endpoint (Section 1.3). In addition, average
periphyton levels and daily minimum and average DO were also evaluated to ensure that reductions made
to comply with the seasonal nutrient endpoint will also adequately address necessary DO criteria and
nuisance algal levels.
As with the sediment TMDL, stormwater nutrient loads are covered under the Phase IINPDES
Stormwater Program and were considered waste loads. Since the entire watershed is considered an MS4,
and thus receives a waste load allocation, the load allocation is zero. Again, in earlier drafts of the
TMDL, 0.15 Ib/yr TP had been allocated to Upper Salford under the total MS4 allocation. That small
portion of load has been removed from this Final version of the report. Table 5-5 presents a summary of
the TMDL components for TP. The load reduction scenario required an approximately 70 percent
reduction in total phosphorus non-point sources.
Table 5-5. Nutrient TMDL loads for Indian Creek Watershed
Indian Creek Watershed
Existing Load
Allowable Load
MOS (5%)
Future Growth (6%)
I WLA Point Source
I WLA MS4
I LA
TMDL
TP Loading (Ib/yr)
11,389.11
1,598.20
79.91
95.892
278
1,144.25
-
1,598.05
Nutrient WLAs
Since the entire watershed lies within MS4 areas, the entire allocated load is considered WLA. The two
types of WLA include the three continuous dischargers and the landuse based load originating from areas
within the jurisdictions responsible for implementing the MS4s in the watershed: Lower Salford,
Souderton, Telford and Franconia. Table 5-6 presents key loading information for the continuous
dischargers. Flows for the Pilgrims Pride facility were derived from monitored flows collected during the
critical summer period.
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FINAL Indian Creek TMDLs
Table 5-6. Summary of Continuous Discharger's TP Loading under the Indian Creek TMDL
NPDES ID
PA0024422
PA0054950
PA0036978
Facility
Name
Lower Salford
Pilgrims Pride
Telford
Flow
(MGD)
0.7
Report
1.1
Total
Baseline
Load
(Ib/yr)
1,066.16
791.53
5,695.68
7,553.37
TMDL Conditions
WLA
Annual
Load
(Ib/yr)
101.30
20.60
156.10
278.00
Growing
Seasonal
Load
(Ib/season)
59.40
12.30
91.50
163.20
Maximum
Daily Load
(Ib/day)
0.69
0.18
0.85
1.72
Concentration
(mg/L)
0.0475
0.052
0.04658
Landuse based, or MS4 associated WLAs are the second type of WLA specified in this TMDL. To
determine the phosphorus loading associated with each MS4, the township boundary GIS layer was
overlaid with the watershed boundaries and the land-based WLA was proportionally assigned to each
municipality based on area. Existing, TMDL, and Maximum Daily TP Loads for each permittee (point
source and MS4) are presented in Table 5-7. TP WLAs for each MS4 municipality are presented in Table
5-8 by landuse.
At this time, EPA cannot determine what portion of the municipalities are designated/used for collection
or conveying stormwater, as opposed to portions that are truly nonpoint sources. As part of the Phase II
stormwater permit process, MS4s will be responsible for evaluating and mapping out areas that are
draining to or discharging to storm sewers. Since these systems have not yet been delineated, the TMDL
lumps nonpoint source loadings into the WLA portion of the TMDL. Once these delineations are
available, the nonpoint source loadings can then be separated out of the WLAs and moved under the LA.
After adjusting the WLAs and LAs based on MS4 service area delineation, Pennsylvania may initiate the
TMDL revision process.
Table 5-7. Existing, TMDL, and Maximum Daily Total Phosphorus WLAs for Permittees
NPDES ID
PA0036978
PA0054950
PA0024422
MS4
MS4
MS4
MS4
Facility/Township
Telford Borough Authority
Pilgrim's Pride
Lower Salford Authority
(Harleysville STP)
Lower Salford
Souderton
Telford
Franconia
Existing
Load
(Ib/yr)
5695.66
791.53
1066.16
803.32
49.4
118.18
2863.44
TMDL
(Ib/yr)
156.10
20.60
101.30
303.29
49.40
118.18
849.18
Maximum
Daily
(Ib/day)
0.846
0.181
0.694
1.862
0.303
0.726
5.214
% Reduction
97%
97%
90%
62%
0%
0%
70%
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FINAL Indian Creek TMDLs
June 2008
Table 5-8. MS4 Related WLAs for Total Phosphorus
Land use/Source
Agriculture
Pasture
Paved Roads
Bare Rock/Sand/Clay
Deciduous Forest
Evergreen Forest
Wetlands
High Intensity Residential
High Intensity Commercial/lndustrial/Transport
Low Intensity Residential
Groundwater
Point Sources
LOWER
SALFORD
72.80
63.16
0.30
0.07
0.07
0.00
0.00
16.63
18.45
37.51
53.90
101.30
SOUDERTON
3.27
5.23
0.17
0.00
0.00
0.00
0.00
8.91
12.05
9.93
3.27
TELFORD
14.18
5.61
0.33
0.00
0.01
0.00
0.00
18.60
34.49
22.11
7.12
156.10
TMDL (Ib/yr)
5%MOS
6% FUTURE GROWTH
Total Allowable Load (Ib/yr)
Existing Load (Ib/yr)
FRANCONIA
208.31
176.95
0.31
0.99
0.21
0.00
0.00
35.77
30.63
105.35
177.57
20.60
1,422.25
79.91
95.892
1,598.05
11,389.11
5.3. Daily Load Expressions
Table 5-7 lists the maximum daily loads associated with the long-term allocations that have been
determined to meet the identified seasonal average TP target of .04 mg/L. A statistical approach based on
guidance provided in the Technical Support Document for Water Quality Based Toxics Control (EPA,
1991) was used to develop these daily maximum values. EPA's Draft Guidance Document, Options for
Expressing Daily Loads in TMDLs, (EPA, 2007) recommends this approach as an appropriate way to
develop daily maximum load values for TMDLs using allocation timeframes other than daily. The draft
guidance provides the following description of the rationale for using this approach to develop maximum
daily load values that correspond to long term loading values such as those identified in this TMDL:
In the case where the daily data are normally distributed about the mean, the maximum
daily load expressed as the/>th percentile of the distribution is calculated as
MDL =
Z
ju
where MDL is the maximum daily limit, O is the mean of the distribution (in this case,
the average load to achieve WQS), °" is the standard deviation of the daily loads, CVis
the coefficient of variation of the daily loads (standard deviation divided by the mean),
and Zp is thepth percentage point of the standard normal distribution. (Z-scores are
published in basic statistical reference tables and are often included as a spreadsheet
function [e.g., NORMSINV(y) in MS Excel]. For the 95th percentile, Zp = 1.645, and for
the 99th percentile, Zp = 2.326.)
In the case where the daily data are lognormally distributed about the mean—as is often
the case with loads that are dependent on flow magnitude—the MDL corresponding to a
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FINAL Indian Creek TMDLs
long-term average (LTA) calculated in the TSD relates the permit MDL to the desired
LTAas
MDL = LTA-exp (ZP ay - 0.5cry2)
;
where
Zp = pth percentage point of the standard normal distribution, as above
CV= coefficient of variation of the untransformed data
For the Indian Creek TMDL, daily maximums were calculated for each of the sources assuming a log-
normally distributed dataset, using the 95th percentile z-statistic. For the continuous dischargers, the
coefficient of variation was calculated based on monitoring data. Since no such data were available for
the MS4 sources, a coefficient of variation of 0.6 was assumed. Table 5-9 summarizes key parameters
used in each calculation. Note that using this method, the higher the coefficient of variation, the lower
the corresponding daily maximum value.
Table 5-9. Variables used in calculating the Daily Maximum Loads
Facility/Township
NPDES ID
Telford
Borough
Authority
PA0036978
Pilgrim's
Pride
PA0054950
Lower
Salford
Authority
PA0024422
Lower
Salford
MS4
Souderton
MS4
Telford
MS4
Franconia
MS4
Sediment
CV
ZP
ay
0.452
1.645
0.431
0.619
1.645
0.569
0.953
1.645
0.803
0.6
1.645
0.554
0.6
1.645
0.554
0.6
1.645
0.554
0.6
1.645
0.554
Total Phosphorus
CV
ZP
ay
0.487
1.645
0.461
1.03
1.645
0.8503
0.711
1.645
0.639
0.6
1.645
0.554
0.6
1.645
0.554
0.6
1.645
0.554
0.6
1.645
0.554
5.4. Margin of Safety
The margin of safety (MOS) is the portion of the pollutant loading reserved to account for any uncertainty
in the data. There are two ways to incorporate the MOS (USEPA 1991): (1) implicitly incorporate the
MOS by using conservative model assumptions to develop allocations or (2) explicitly specify a portion
of the TMDL as the MOS and use the remainder for allocations.
A five percent explicit MOS was used to account for uncertainty in the modeling process. This was based
on previous experience for TMDL development in Pennsylvania, professional judgment and published
literature.
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FINAL Indian Creek TMDLs June 2008
5.5. Future Residential Growth
An allocation of six percent of the total allowable load was made to future residential growth for each of
the parameters addressed in this TMDL. Both the MOS and the future growth allocations were taken
from the allowable portion of landuse related loadings.
5.6. Critical Conditions and Seasonal Variations
Federal Regulations (40 CFR 130.7(c)(l)) require TMDLs to consider critical conditions for streamflow,
loading, and water quality parameters. The intent of this requirement is to ensure that the water quality
and designated uses of the waterbodies are protected during periods when they are most vulnerable.
Critical conditions include combinations of environmental factors that result in attaining and maintaining
the water quality criteria and have an acceptably low frequency of occurrence (USEPA, 2001).
TMDLs for Indian Creek adequately address critical conditions for flow through the use of a dynamic
model and analysis of all flow conditions in the basin. In Indian Creek, critical conditions tend to occur
during warm weather months during periods of low flow. For nutrient impaired systems such as Indian
Creek, critical conditions can occur as a result of a combination of wet and dry weather conditions
depending on the system. Therefore the use of a dynamic modeling application capable of representing
conditions resulting from both low and high flow regimes is appropriate. The linkage to a dynamic
watershed loading model ensures that nonpoint source loads from the watershed delivered at times other
than the critical period were also considered in the analysis.
The TMDL was calculated based on the 7-month period from April to October as this was determined to
be the period during which most severe algal growth conditions are likely to occur. At times during this
period, much of the Indian Creek stream flow is dominated by point source flows.
Critical conditions for nutrient loads were also considered by determining WLAs based on maximum
flows from dischargers set by design flows specified in NPDES permits for each facility. Under normal
summer conditions, the combined discharge flows are approximately 40 percent of combined design
flows. Use of design flows in TMDL determination provides additional assurance that when design flows
are reached, the water quality in the stream will meet water quality criteria.
Model simulation of multiple complete years accounted for seasonal variations. Continuous simulation
(modeling over a period of several years that captured precipitation extremes) inherently considers
seasonal hydrologic and source loading variability. The constituent concentrations were simulated on a
sub-daily time step, capturing seasonal variation and allowing for evaluation of critical conditions.
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June 2008 FINAL Indian Creek TMDLs
6. REASONABLE ASSURANCE
EPA requires that there is reasonable assurance that TMDLs can be implemented. TMDLs represent an
attempt to quantify the pollutant load that may be present in a waterbody and still ensure attainment and
maintenance of water quality standards. Point source allocations will be implemented through the NPDES
program. MS4 allocations will be implemented by the respective municipalities and integrated into their
stormwater management programs.
WLAs will be implemented through the NPDES permit process. According to 40 CFR
122.44(d)(l)(vii)(B), the effluent limitations for an NPDES permit must be consistent with the
assumptions and requirements of any available WLA for the discharge prepared by the state and approved
by EPA. Furthermore, EPA has authority to object to issuance of an NPDES permit that is inconsistent
with WLAs established for that point source. Although TMDLs are not required to include an
implementation component, EPA has included for consideration an adaptive management NPDES
permitting approach in Appendix F.
It is worth noting that EPA has prepared a separate "Treatability Report" which summarizes the existing
treatment processes for the Indian Creek point source dischargers and discusses nutrient removal
techniques that are available and some costs. Included in this report is a summarization of BMPs that are
available for various land use types, including suburban/urban areas such as the Indian Creek Watershed,
for nutrient removal. There is information about treatment types and expected efficiencies, limitations,
costs, etc. that may be useful for MS4 communities.
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FINAL Indian Creek TMDLs June 2008
7. PUBLIC PARTICIPATION
As part of the TMDL development process, a public participation process is required. Each state must
provide for public participation consistent with its own continuing planning process and public
participation requirements.
To date, EPA has held two information meetings during the course of the TMDL development process.
On November 30, 2006 at the Lower Salford Township Building, EPA informed stakeholders of our
TMDL development plans and presented an overview of the TMDL process. And, on December 17, 2007
in EPA's Region 3 office, stakeholders were presented with the selected TMDL endpoints and
methodology used to derive such endpoints, as well as a conceptual adaptive management approach for
TMDL implementation.
In terms of the proposed TMDL, a notice of availability for comments on the draft TMDL was published
in The Philadelphia Inquirer on February 26, 2008 and on EPA Region 3's TMDL website and The
Souderton Independent Newspaper on February 27, 2008. EPA is accepting public comments from
February 27, 2008 through midnight on April 6, 2008. EPA will also be holding a public meeting to
present details and answer questions regarding the proposed TMDLs on March 18, 2008 from 7:00pm to
9:00pm at the Lower Salford Township Building, 379 Main Street, Harleysville, Pennsylvania.
EPA welcomes input from interested parties and the general public on the proposed TMDL document.
All comments must be postmarked no later than the close of the comment period, April 6, 2008. All
comments can be sent to Ms. Lenka Berlin at the address below. Electronic submission of comments is
encouraged. The TMDL report is available at the EPA Region III office or website
(http://www.epa.gov/reg3wapd/tmdl/index.htm). A copy of the report can also be requested through the
contact provided below. Please direct any questions about the proposed TMDL document or meeting to
Ms. Mary Kuo at (215) 814-5721 or kuo.mary@epa.gov.
berlin.lenka@epa.gov
or
Ms. Lenka Berlin (3WP30)
US EPA, Region III
1650 Arch Street, Philadelphia, PA 19103
Phone:215-814-5259
Following receipt of comments during the public comment period, EPA will finalize the TMDL and make
revisions as necessary. A document providing EPA's responses to public comments will also be prepared
as part of the final TMDL.
Note that EPA is seeking public comment on two scenarios: (1) whether TP and TN TMDL and
allocations are necessary to achieve necessary nutrient reductions within the Indian Creek Watershed, or
(2) if TP only allocations and controls are sufficient. To the extent that the commenters feel that both TP
and TN TMDLs are needed, EPA is also soliciting comment on whether the proposed TN endpoints are
appropriate.
Data analysis and modeling runs have established a clear linkage between phosphorus loading and
periphyton densities in the watershed; however, the linkage between nitrogen and periphyton in this
system is somewhat less well-established. Nevertheless, EPA is proposing TN endpoints in this TMDL
because of the potential downstream effects of excess nitrogen loading to coastal and estuarine waters,
such as the Delaware Bay. In a similar situation, NPDES permittees within Pennsylvania are currently
receiving both TP and TN effluent limits in order to help meet water quality standards in the Chesapeake
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June 2008 FINAL Indian Creek TMDLs
Bay. Additionally, PADEP is working on the development of numeric nutrient criteria development and
is considering criteria adoption for multiple indicators including nitrogen, as other states have. EPA
expects that establishment of nitrogen allocations at this time may enable permittees to address and plan
for treatment upgrades and capital expenditures for compliance with both TP and TN limits together
rather than requiring facilities to address phosphorus now and nitrogen at a later date.
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FINAL Indian Creek TMDLs June 2008
REFERENCES
Ambrose, R.B., T.A. Wool, and J.L. Martin. 1993. The water quality analysis and simulation program,
WASPS: Part A, model documentation version 5.1. U.S. Environmental Protection Agency,
Environmental Research Laboratory, Athens, GA, 210 pp.
Arnold, J. G., and P. M. Allen. 1999. Automated methods for estimating baseflow and groundwater
recharge from streamflow records. JAWRA 33:6 1010-1018.
Bingner, R. L, Theurer, F. D. 2000. Physics of suspended sediment transport in AnnAGNPS.
Proceedings of the 2002 Second Federal Interagency Hydrologic Modeling Conference, Las Vegas, NV,
July 28 - August 1, 2002. No page numbers, published as CD-ROM. 12 pp. 2002.
Carrick, H. and C. Godwin. 2006. TMDL Endpoint Estimates for an Urban-suburban Stream Based
Upon In-Stream Periphyton Biomass (Wissahickon Creek Watershed, Pennsylvania). School of Forest
Resources, The Pennsylvania State University, lip.
Cerco, C.F., and T. Cole. 19 93. T hree-dimensional eutrophication model of Chesapeake Bay. J. Environ.
Engnr. 119:1006-1025.
CMX. 2008. DRAFT Sewage Management Program Phase III, 2007 Annual Report. Prepared for
Franconia Township.
Dai, T., R.L. Wetzel, T. R. Christensen, and E.A. Lewis. 2000. BasinSiml.O: A windows-based
watershed modeling package. Virginia Institute of Marine Science. College of William and
Mary. Gloucester Point, VA.
DiToro, D.M ., and J.F. Fitzpatrick. 1993. Chesapeake Bay sediment flux model. Contract Report EL-93-
2. Prepared by HydroQual, Inc. for USEPA Chesapeake Bay Program, U.S. Army Engineer District,
Baltimore, MD, and U.S. Army Engineer Waterways Exp. Station.
Dodds, W.K. 2005. Eutrophication and Trophic State in Rivers and Streams. Limnol. Oceanogr. In
press.
Dodds, W.K., V.H. Smith, and K. Lohman. 2006. "Erratum: Nitrogen and phosphorus relationships to
benthic biomass in temperate streams". NRC Research Press Web site, (http://pubs.nrc-
cnrc.gc.ca/rp2 home e.html). April 21, 2006.
Haith, D.A., and L.L. Shoemaker. 1987. Generalized watershed loading functions for streamflow
nutrients. Water Resources Bulletin 23(3):471-478.
Hamrick, J.M. 1996. User's Manual for the Environmental Fluid Dynamics Code - EFDC. The College
of William and Mary, Virginia Institute of Marine Sciences.
Hamrick, J. M. and T.S. Wu, 1996. Computational Design and Optimization of EFDC/HEM3D Surface
Water Hydrodynamic and Eutrophication Models. Computational Methods for the Next Generation
Environmental Models. U.S. Environmental Protection Agency, National Environmental Supercomputer
Centre.
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June 2008 FINAL Indian Creek TMDLs
Matlock, M. D., M. E. Matlock, D. E. Storm, M. D. Smolen, and W. J. Henley. 1998. Limiting nutrient
determination in lotic ecosystem using a quantitative nutrient enrichment periphytometer. JAWRA 34:5
1141-1147.
PADEP 2005. Personal Communication, James Wentzel, Pennsylvania DEP.
PADEP 2005a. Equal Marginal Percent Reduction (EMPR) (An Allocation Strategy) and Watershed
EMPR for Point Source Discharges, January 20, 2005
Paul, M., and Lei Zheng 2007. Development of Nutrient Endpoints for the Northern Piedmont Ecoregion
of Pennsylvania: TMDL Application.
Shanaha, P. and M. Alam. 2001. The Water Quality Simulation Program, WASP5, Version 5.2-MDEP
Manual:Part A. Hydraulics and Water Resource Engineers, INC., Waltham, MA.
USEPA (U.S. Environmental Protection Agency). 1991. Technical Support Document for Water Quality
based Toxics Control. EPA/505/2-90-001. U.S. Environmental Protection Agency, Office of Water,
Washington, DC.
USEPA. 1999. Protocol for Developing Sediment TMDLs (First Edition), EPA 841-B-99-004. U.S.
Environmental Protection Agency, Office of Water, Washington, DC.
Welch, E.B., J.M. Jacoby, R.R. Homer, and M.R. Seeley. 1988. Nuisance Biomass Levels ofPeriphytic
Algae in Streams. Hydrobiologia 157: 161-168.
Zou, R., Carter, S., Shoemaker, L., Parker, A., and Henry, T., 2006. An Integrated Hydrodynamic and
Water Quality Modeling System to Support Nutrient TMDL Development for Wissahickon Creek.
Journal of Environmental Engineering, ASCE, 132(4), 555-566
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FINAL Indian Creek TMDLs June 2008
APPENDIX A: AMBIENT SAMPLING RESULTS ABOVE AND BELOW MUNICIPAL STPs
Following an unassessed waters screening in the summer of 2001, PADEP determined that Indian Creek
was impaired from its source to the mouth by possible nutrient impairment. From this assessment,
biological habitat scores for locations throughout the Indian Creek watershed are available. They were
reviewed to support this effort, however the data are more suitable for qualitative descriptions of stream
conditions than for analysis of in-stream water quality as no chemical data were collected during the
biological surveys. Based on findings of the unassessed waters screening, investigations were conducted
to evaluate the possibility of Telford Borough Authority and Lower Salford Township Authority
Harleysville STP outfalls as the source of stream impairment. The Telford STP is listed as the source of
nutrient impairment to Indian Creek on the 2002 303(d) list. Chemical sampling was conducted in Indian
Creek at the Telford Borough Authority STP on Oct. 24, 2001, Apr. 14, 2003, and on May 14, 2003; and
at the Lower Salford Township Authority Harleysville STP on Oct. 24, 2001 and Apr. 14, 2003 by
PADEP. Additionally, biological sampling was conducted in the above mentioned two sites on all the
above dates, except May 14, 2003.
At each location, samples were collected upstream of the discharge (site 1), at the discharge (effluent),
and downstream of the discharge (site 2).
Telford Ambient Sampling
Analyses of total phosphorous (TP) near the Telford discharge (Figure A-l) suggest that the ambient
concentration (represented by site 1) remained approximately the same on the sampling dates of Oct. 24,
2001, Apr. 14, 2003, and May 14, 2003. TP concentration increased downstream of the effluent in Oct.
24, 2001, decreased in Apr. 14, 2003, and remained approximately the same in May 14, 2003. Summation
of the ambient TP concentration (site 1) and effluent TP concentration (effluent) approximately equaled
the concentration of TP at Site 2 on Oct. 24, 2001. The summation of ambient concentration and effluent
was less than the TP concentration, however, at site 2 on Apr. 14, 2003 and on May 14, 2003. Since a
greater portion of the concentration at Site 2 was contributed by effluent on the October sampling date,
the effluent appears largely responsible for downstream (site 2) increased concentrations that day.
Rainfall data for the period indicated periods of precipitation preceded the April and May sampling dates.
This indicates that nonpoint source contributions, in addition to effluent, were affecting in-stream
conditions on those days.
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June 2008
FINAL Indian Creek TMDLs
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Analyses of total nitrogen (TN) near the Telford discharge (Figure A-2) suggest that concentrations
increased from site 1 to the effluent location and remained approximately the same at site 2 for Oct. 24,
2001, Apr. 14, 2003, and May 14, 2003. The increase in concentration on Oct. 24, 2001 at site 2 from
ambient (site 1) concentration was mostly due to the effluent discharge. Elevated TN concentration at site
2 on May 14, 2003 relative to the ambient concentration (site 1) could be attributed to the effluent, since
the ambient concentration was much lower than effluent.
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FINAL Indian Creek TMDLs
June 2008
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1 Effluent 2
Upstream to Downstream
Figure A-2. Total nitrogen concentration at the sampling sites.
Analysis of NH3-N concentration near the Telford discharge (Figure A-3) shows that the concentrations
remained similar on different sampling days (Oct. 24, 2001 and May 14, 2003) and up and downstream of
the effluent (site 1 and site 2). However, elevated concentrations were observed on Apr. 14, 2003 relative
to the other two dates. The increase is likely attributable to the rainfall that occurred within the 3 days
prior to sampling. Concentrations on Apr. 14, 2003 increased from site 1 to the effluent site, and remained
high at downstream site 2 although they were lower than those directly at the outfall (possibly due to
dilution from higher stream flows). Precipitation also occurred 3 days prior to the May sampling;
however, the magnitude of the rainfall was less than the magnitude of rainfall that occurred 3 days prior
to the April sampling. Therefore, the effluent was most likely responsible for the spike in concentration
from site 1 to the effluent, but the elevated ambient concentrations may have been related to nonpoint
source runoff related to the recent rainfall.
NO3-N concentration near the Telford discharge (Figure A-4) shows that concentrations increased from
site 1 to the effluent site and remained almost the same for site 2 on all the sampling dates (Oct. 24, 2001,
Apr. 14, 2003, and May 14, 2003). Increased concentrations of NO3-N at site 2 from ambient
concentration (site 1) are also likely attributable to the effluent discharge. However, the effluent does not
appear to be as dominant a factor as the in-stream nitrate concentrations under periods influenced by wet
weather.
80
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June 2008
FINAL Indian Creek TMDLs
3nn
.uu •
- — - o <^r\ -
^ ^l.OU
05
' — ' "~> nn
_ ^l.UU -
o
"2 -i en
i= 1 .OU -
CD
c 1 nn -
o n-uu
O
Oc.n
.ou
.00 -
_n_
=0=
I 1 I Ota I NhK3-N-.^4-
Oct-01
Apr-03
i i |ofq| NH-4-N-14-
May-03
- - - • Permit Limit for
May -October
— — Permit Limit for
November- A pril
1 Effluent 2.
Upstream to Downstream
Figure A-3. NH3-N concentration at the sampling sites.
1 n nn
9nn
.uu -
8nn -
• UU
? 7 nn -
i — c nn -
.0
§ 3.00 -
° 2.00-
1.00 -
Onn
n
il rr
^h
I
I
n Total NO3-N-24-Oct-01
• Total N03-N-14-Apr-03
in Total NO3-N- 14- May-
OS
1 Effluent 2
Upstream to Downstream
Figure A-4. NO3-N concentration at the sampling sites.
The increase in TN concentration on Apr. 14, 2003 is due largely to the increase proportionally, of NH3-N
concentrations on the sampling dates (Figures A-2 and A-3). Whereas, the TN increase on Oct. 24, 2001,
and May 14, 2003 was due to an increase in the proportion of NO3-N on the sampling dates (Figures A-2
and A-4). Control of nutrient concentrations at the effluent discharge would significantly control
81
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FINAL Indian Creek TMDLs
June 2008
downstream water quality; however, during wet weather periods, additional loading of nutrients will
occur due to nonpoint source runoff.
Lower Salford Ambient Sampling
Analysis of total phosphorous (TP) near the LowerSalford discharge (Figure A-5) showed that the in-
stream concentration substantially decreased downstream of the effluent discharge on the Oct. 24, 2001
sampling, suggesting the possibility of healthy in-stream nutrient processing. However, concentrations
were not decreased downstream of the effluent (site 2) on Apr. 14, 2003 suggesting influence of the
effluent discharge on that day to downstream concentrations. Ambient concentration (site 1) remained
similar for both the sampling dates.
A nn
.oU -
f — - »> nn
^ o.uu -
CD
' — ' o *^n
z.ou -
.0
~m o nn
2 ^.uu -
"c
o -i r;n
o 1 -oU
c
0
01 nn -
O 'SO -
Onn
. UU T
i — rm
__|— i
1 1 Intal
Phosphorous-24-
Oct-01
1 i l<~>tal
Phosphorous- 14-
Apr-03
MSI mi Limn
1 Effluent 2
Upstream to Downstream
Figure A-5. TP concentration at the sampling sites.
Figure A-6 shows that total nitrogen (TN) in Oct. 24, 2001 increased downstream. Concentrations at the
effluent and at site 2 remained similar, and greater than the ambient concentration, suggesting the
influence of the effluent discharge on downstream water quality. Similar to trends shown at the Telford
discharge, TN concentrations on Apr. 14, 2003 (following wet weather) increased at the effluent and
further decreased at site 2 suggesting elevated ambient concentrations due to nonpoint source runoff and
possible dilution at site 2 due to potentially higher stream flow.
82
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June 2008
FINAL Indian Creek TMDLs
1R on
Mnn -
' — - 1 9 on
CD
' — ' •! n nn .
IU.UU
.Q
~m Q r\r\
™ o.UU -
•E
o ^ on
o O.UU -
C
O
OA nn
*f.UU
2.00 -
Onn .
TTT
• Total Nitrogen-24-Oct-01
• Total Nitrogen- 14-Apr-
03
1 Effluent 2
Upstream to Downstream
Figure A-6. TN concentration at the sampling sites.
Figure A-7 shows NH3-N concentration at LowerSalford during the sampling. Lower concentrations were
observed across all the three sites (site 1, effluent, site 2), on all the sampling dates.
3C\C\
2cr\
•&
£ o nn -
^
.0
| 1.50 -
CD
O
C
O -i c\c\
o ' -uu
Occ\
.OO H
1 i 1 otal NH'-'-N-24-
Oct-O1
I 1 lotal NH3-N-14-
Apr-O3
• Permit Limit for
May - October
^— - - Permit Limit for
November to April
1 Effluent 2
Upstream to Downstream
Figure A-7. NH3-N concentration at the sampling sites.
83
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FINAL Indian Creek TMDLs
June 2008
Figure A-8 shows NO3-N concentration at LowerSalford. In Oct. 24, 2001, NO3-N concentrations appear
to be attributable to the input from the discharge. On the April sample date, again, ambient concentrations
appear elevated and dilution occurred at site 2, likely because of higher stream flows following the wet
weather.
Moo
-i o nn
1 Z.UU -
=Si 1 O OO -
c 55 nn _
o o.uu
IE
-£± c nn
C O.UU ~
0
o
c
O A OO -
0 4"UU
2.00 -
Ooo -
^TT
D Total NO3-N-24-Oct-01
• Total NO3-N-14-Apr-03
1 Effluent 2
Upstream to Downstream
Figure A-8. NO3-N concentration at the sampling sites.
On all the sampling dates, across all sites, the major portion of TN concentration was due to increased
levels of NO3-N concentration (Figures A-6 and A-8).
84
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June 2008 FINAL Indian Creek TMDLs
85
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FINAL Indian Creek TMDLs
June 2008
APPENDIX B: EFDC CALIBRATION PLOTS
1.0
0.8
0.6
0- 0.4
0.2
0.0
3
fO
O
May 10 PO4
10.0
30.0
25.0
20.0
15.0
10.0
0.0
2000 4000 6000 8000 10000 12000
Figure B-l. Longitudinal profile of PO4 in Indian Creek
n A
00
09 .
04
n n .
May 10 NH4
> r 5 — •»— —
0 2000 4000 6000 8000 10000 12000
Figure B-2. Longitudinal profile of NH4 in Indian Creek.
0 2000 4000 6000 8000 10000 12000
Figure B-3. Longitudinal profile of NO3 in Indian Creek.
0 2000 4000 6000 8000 10000 12000
Figure B-4. Longitudinal profile of maximum DO in Indian Creek.
86
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June 2008
FINAL Indian Creek TMDLs
30.0
25.0
20.0
15.0
10.0
5.0
0.0
May 10 DO
- • • — -_ —
^-
• *
0 2000 4000 6000 8000 10000 12000
Figure B-5. Longitudinal profile of average DO in Indian Creek
30.0
25.0
20.0
15.0
10.0
5.0
0.0
Min DO
0 2000 4000 6000 8000 10000 12000
Figure B-6. Longitudinal profile of minimum DO in Indian Creek
30.0
0.0
05/05/06 05/07/06 05/09/06 05/11/06 05/13/06 05/15/06
Figure B-7. Comparison of modeled and monitored DO at Bergey Rd. in Indian Creek
30.0
25.0
20.0
05/05/06 05/07/06 05/09/06 05/11/06 05/13/06 05/15/06
Figure B-8. Comparison of modeled and monitored DO at Godshall Rd. in Indian Creek
87
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FINAL Indian Creek TMDLs
June 2008
30.0
05/05/06 05/07/06 05/09/06 05/11/06 05/13/06 05/15/06
Figure B-9. Comparison of modeled and monitored DO at Pilgrim Pride (Tributary) in Indian Creek
30.0
25.0
20.0
05/05/06 05/07/06 05/09/06 05/11/06 05/13/06 05/15/06
Figure B-10. Comparison of modeled and monitored DO at Lower Salford (Tributary) in Indian Creek
30.0
05/05/06 05/07/06 05/09/06 05/11/06 05/13/06 05/15/06
Figure B-ll. Comparison of modeled and monitored DO at RT63 in Indian Creek
30.0
25.0
20.0
15.0
10.0
5.0
0.0
ICMouth DO
V/
05/05/06 05/07/06 05/09/06 05/11/06 05/13/06 05/15/06
Figure B-12. Comparison of modeled and monitored DO at the mouth of Indian Creek
88
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June 2008
FINAL Indian Creek TMDLs
Tt
o
0.
n P. .
n R
n A
n o
no. -
Aug2006 PO4
*^-V
• ^^^^^^^^\
* \
0 2000 4000 6000 8000 10000 12000
Figure B-13. Longitudinal profile of PO4 in Indian Creek in August 2006
0.5
0.4
0.3
Aug2006 NH4
0 2000 4000 6000 8000 10000 12000
Figure B-14. Longitudinal profile of NH4 in Indian Creek in August 2006
fO
O
on.
c: n
A n
o n
n n _
Aug2006 NO3
V
s\
^ \
— ^_» • "^ • \
0 2000 4000 6000 8000 10000 12000
Figure B-15. Longitudinal profile of NO3 in Indian Creek in August 2006
Qn n
O
a
oc; n
on n
•ic n _
m n -
en.
n n _
Max DO
, • -^^
^
0 2000 4000 6000 8000 10000 12000
Figure B-16. Longitudinal profile of maximum DO in Indian Creek in August 2006
•an n
O
a
oc n .
on n .
•ic n
100 -
c n
n n .
Aua2006 DO
1 .
0 2000 4000 6000 8000 10000 12000
Figure B-17. Longitudinal profile of average DO in Indian Creek in August 2006
89
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FINAL Indian Creek TMDLs
June 2008
8
30.0
25.0
20.0
15.0
10.0
5.0
0.0
Min DO
0 2000 4000 6000 8000 10000 12000
Figure B-18. Longitudinal profile of minimum DO in Indian Creek in August 2006
30.0
25.0
20.0
10.0
5.0
0.0
GODSHALL DO
-A A AT
07/25/06 07/27/06 07/29/06 07/31/06 08/02/06 08/04/06
Figure B-19. Comparison of modeled and monitored DO at Godshall Rd. in Indian Creek in August 2006.
§
oc; n
on n .
4 c n
1 n n -
c n .
nn -
SALTRIB DO
-^^x-/^^-^^"^ ^-^""-* — ^^^s^^^^^*^^\_-^*-.
07/25/06
07/27/06
07/29/06 07/31/06
08/02/06
08/04/06
Figure B-20. Comparison of modeled and monitored DO at Lower Salford (Tributary) in Indian Creek in
August 2006.
0
a
Oc; n
on n
•i c n .
1 n n
c n .
nn -
ICMouth DO
ujk ^*
^^P ^^^p V —• r —
07/25/06 07/27/06 07/29/06 07/31/06 08/02/06 08/04/06
Comparing Model results against the second set of data in 2006
Figure B-21. Comparison of modeled and monitored DO at the mouth of Indian Creek in August 2006.
90
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June 2008
FINAL Indian Creek TMDLs
APPENDIX C: RESULTS OF EFDC SENSITIVITY ANALYSIS
o>
E.
O
Q
o>
E,
O
Q
:>2«9?9S«9?
8888888.88.88888888888
o>
E,
O
Q
0.0
:>2«9?9S«9?
SS°°8SSSS88888888888
Figure C-l. Modeled DO with only point sources.
91
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FINAL Indian Creek TMDLs
:> 2 V v :> co o
Q Q § § o o 6
01 01
01 01 01
June 2008
"5)
E
8
on n -.
1 c n -
1 n n
c n -
n n .
BERGEN
.y-Ki,T .i,>it
•V '.- . . .. ' " ' '^ " '"•-• . . . .
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E
8
•i c n .
1 n n
c n .
n n .
GODS HALL
• f1-. >:"v'JV,
W V '».. x , . ,.**!* 'N1**1 'W^IHH** ' ' ""
3> 2 V V 3> CO O
6 o o o 6 6 o
01 01 01 01 01 01 01
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O
Q
*i ^ i i *i i
O o O O o O o
01 g 01 01 01 01 y,
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o
a
20.0
15.0
10.0
5.0
0.0
> OT
8 8 8 a 8 8 ° s
5"
"oi
E,
O
Q
20.0 -i
^ c n
m n -
c n
nn -
^___,_^^
,v '' •'"v'^W " I
|ty*yV ..... ,...«^ ^^ ..^v*tv*» ' |
3>2
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June 2008
FINAL Indian Creek TMDLs
APPENDIX D: EFDC RESULTS FOR BASELINE SCENARIO
LOLOLOCQCQCQroCQCQCQrQ
OOOOOOooo°O
8
CD CD
o o
< w o
< w o
o
a
0.0
IT) LO LO LO
g O O O
§
LOLOLOCDCDCDcoCDCDCDro
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8
CD CD
O O
< w o
..
Q —>
< W O
O
a
§§§§§§§§§88888888888
O
a
§§§§§§§§§88888888888
93
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FINAL Indian Creek TMDLs
June 2008
Figure D-l. Modeled DO under baseline condition.
20.0
15.0
10.0
5.0
0.0
BERGEY DO
»lr
lO
o
CO
o
opppooPPPPPPoPPPooPP
^S^^^WOZQ^LL^^S^^^WOZ
20.0
15.0
10.0
5.0
0.0
GODSHALL DO
§§§§§§§§§88889888808
---
20.0
15.0
Q 10.0
5.0
0.0
RlgrimTRIB DO
^S^^^WOZQ^LL.
W o
20.0 -r
15.0
SALTRIB DO
10.0
5.0
0.0
§§§§§§§§§88888888888
---
94
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June 2008
FINAL Indian Creek TMDLs
20.0
15.0
Q 10.0
0.0
§§§§§§§§§88888888888
20.0
15.0
10.0
5.0
0.0
ICMouth DO
'ft-
8LOLO LO in ID LO LOLOCDCD CDrnCDCD (QmCQCQ
ooooooooooooocpcpooo
Figure D-2. Modeled DO average under baseline condition.
95
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FINAL Indian Creek TMDLs
June 2008
APPENDIX E: EFDC RESULTS FOR LOAD REDUCTION SCENARIO
20.0 n
15.0
Q 10.0
5.0
0.0
BERGEY DO
. 1*' .'
minininminininincDCDCDcoCDCDCDcoCD
oOOOooOOOOOOoOOOoO
coco
oc
20.0
15.0
10.0
5.0
0.0
GODSHALL DO
§§§§§§§§§88888888888
0.0
minininminininincQCQCQcoCQCQCQcQCQCQCQ
ocpcpcpooocpcpcpcpcpocpcpcpooop
< w o ~z. Q —>
< W o
20.0
15.0
10.0
5.0
0.0
SALTRIB DO
§§§§§§§§§88888888888
20.0 n
15.0
RT63IN DO
10.0
5.0
0.0
in
o
CD
o
ocpcpcpooocpcpcpcpcpocpcpcpooocp
^S^^^WOZQ-^LL^^S^^^WOZ
20.0
15.0
10.0
5.0
0.0
ICMouth DO
§§§§§§§§§88888888888
Figure E-l. Modeled DO under load reduction scenario (hourly)
96
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June 2008
FINAL Indian Creek TMDLs
20.0 n
15.0
Q 10.0
5.0
0.0
BERGEY DO
8§§§8§§§§88888888888
^S^^^COOZa-^U-Ssts-^-^sfccOOZ
1 R n
1 n n
c n
n n .
GODSHALL DO
,,/V- A/,,V^V
*y\.% , - ' ' ' - ..-•**
§inininminininincDCDCD(oCDCDCD(o
9998099999989998
";>u.5-j >»"%.,
§inininminininincDCDCD(oCDCDCD(ocDCc
999889999998999899
^S^^^COOZQ^LL^^S^^^COO
CD CD
00
20.0 n
15.0
Q 10.0
5.0
0.0
RT63IN DO
r^v
^*^
8§§§8§§§§88888888888
^S^^^COOZQ-^U-Ssts-^-^stcOOZ
20.0
15.0
10.0
5.0
0.0
ICMouth DO
M* V S ,.
§inininininininincococO(oCococO(ocococo
0008900000089998900
Figure E-2. Modeled daily average DO under load reduction scenario
97
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FINAL Indian Creek TMDLs June 2008
APPENDIX F: SUGGESTED ADAPTIVE IMPLEMENTATION STRATEGY FOR NPDES
POINT SOURCES DISCHARGERS
• EPA regulations do not require an implementation plan to be established as part of or
with the establishment of the TMDLs. However, EPA provides this implementation
strategy to assist the National Pollutant Discharge Elimination System (NPDES) permit
issuing authority in the development and issuance of NPDES permits for point sources
with waste load allocations (WLAs) under this TMDL. The Pennsylvania Department of
Environmental Protection (PADEP) is the NPDES permitting authority in Pennsylvania,
and will make the final determination, subject to EPA review, on issuance of the NPDES
permits consistent with the assumptions and requirements of the approved TMDL WLAs.
This strategy provides guidance for PADEP to use in issuing, reissuing, or modifying
NPDES permits. This strategy should be considered where it may be appropriate to
allow interim effluent limits and a compliance schedule to achieve the final effluent
limits. This strategy may be appropriate to ensure that point source dischargers achieve
and maintain their prescribed nutrient loading levels to restore and protect the receiving
waters, while providing opportunities for reducing costs and improving efficiencies by
allowing the use of phased permit requirements based on interim technology-based
analysis. This process recognizes that PADEP has indicated that it may proceed with its
development of nutrient water quality standards/criteria by 2010. Any NPDES permit
issued by PADEP that contains such interim limits and/or compliance schedules must
explain the reasons and findings in the draft permit submittal for public comment and
EPA review. Any such permit with interim limits must include a compliance schedule
with a fixed date to implement the effluent limit consistent with the final WLA. Best
Management Practices should be considered as a means to address nutrient reductions
and can be reflected in the compliance schedules to meet the final TMDL WLAs. Final
compliance dates must be based on EPA regulations at 40 CFR 122.47.
During the TMDL development process, several categories of point source dischargers assigned
TMDL WLAs were identified as needing NPDES permit requirements to implement the Total
Phosphorus WLAs of this TMDL. EPA's Treatability Study provides additional information on
31 facilities in PA and options for removal of nitrogen and phosphorus.
• Category 1 - Dischargers where treatability considerations (i.e. ability to provide
chemical addition w or w/o filtration) could yield performance in the range of 0.5 - 1.0
mg/1 Total P. This may include facilities with design flows greater than or equal to
10,000 gpd.
• Category 2 - Dischargers where limitations on cost or technology have not been fully
explored during TMDL development. Interim technology-based limits could be in the
range of 1.0 - 2 mg/1 Total P. This may include dischargers with design flows greater
than or equal to 2,000 gpd and less than 10,000 gpd.
• Category 3 - Insignificant dischargers who are likely to have a minimal contribution to
the WLA (i.e. whose sum is equal to less than one percent of the total and are part of a
WLA assigned to insignificant sources). This may include dischargers with design flows
less than 2,000 gpd.
• Category 4 - Dischargers who existing limits were more stringent than those above
would maintain existing limits.
98
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June 2008 FINAL Indian Creek TMDLs
These categories should be utilized when establishing the interim technology-based requirements
in NPDES permits. In the event that a facility seeks to expand or increase its design capacity,
they should be capped at their existing load, consistent with the current design flow within that
relevant category.
The timeline for implementing WLA requirements into NPDES permits could follow a three
phased approach.
• Phase I - THRU June 2008 (TMDL Development and Establishment) - consists of
studies and analyses performed during the TMDL development process. These actions
include:
o Characterization of existing facilities
o Determination of nutrient endpoints in southeastern PA
o Treatability study of southeastern PA facilities
o Review of National Nutrient Study
o Review effectiveness of BMPs for MS4s
o EPA Office of Water study on retrofits for municipal WWTPs
• Phase II - June 2008 thru June 2013 (Progressive Improvement) - Optimization
phase which would implement interim nutrient control limitations along with a
compliance schedule to achieve the final effluent limit in NPDES permits based on
evaluation of reductions that can be achieved in the near term using existing technologies
while the long-term facilities planning process moves forward. This time period also
allows PADEP to consider any necessary changes in the TMDLs based on adoption of
nutrient criteria. PADEP may consider applying the discharge categories_mentioned
above. Based on the analysis from Phase I and applying existing regulations, permits
should require interim TP limits as follows:
o Category 1 - 0.5 - 1.0 mg/1 monthly average during the growing season.
• Basis - Nutrient Treatability study
o Category 2 - 1.0 - 2.0 mg/1 monthly average during the growing season.
• Basis - PA's existing Phosphorus regulations
o Category 3 - Existing effluent quality
o Category 4 - Existing limits more stringent than above.
EPA's Treatability Study identified an interim nitrogen value of 8 mg/1 as a monthly
average during the growing season as achievable through BNR processes. Along with
any interim effluent limits, compliance schedules to achieve final permit limitations
consistent with the WLAs in the TMDL must be incorporated into the permits in order to
address TMDL and water quality requirements. All permits issued during Phase II must
contain effluent limits consistent with the established TMDL.
Actions required during this phase include:
o Issue, reissue, or modify NPDES permits with requirements as specified above
o Collection of effluent data for TP and TN
o Optimization of treatment at individual facilities
o Implementation of BMPs
o Completion of wastewater facilities planning
99
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FINAL Indian Creek TMDLs June 2008
o Consideration of trading where appropriate
Phase III - Begins June 2013 (Final TMDL Implementation)
Actions required during this phase include:
o Continue to issue, reissue, or modify NPDES permits to reflect final water quality
based effluent limits and final compliance schedules
o Facility design and construction
o Compliance with final WQBELs consistent with the TMDLs.
If Pennsylvania adopts numeric nutrient criteria by 2013, it may be necessary to revise
the TMDLs and associated WLAs. If so, the revised criteria would serve as the basis for
the revised TMDLs and WLAs. NPDES permits would thereafter be modified
accordingly, including necessary revisions to compliance schedules, if allowed, requiring
dischargers to meet WLAs or revised WLAs based on criteria. If nutrient criteria do not
cause the TMDLs to be modified, the permits would not be modified and the existing
TMDL allocations would be governing. Final compliance dates must be based on EPA
regulations at 40 CFR 122.47.
100
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