\ UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
o REGION
1650 Arch Street
Philadelphia, Pennsylvania 19103-2029
Decision Rationale
Total Maximum Daily Loads
Acid Mine Drainage Affected Segments
Wilson Creek Watershed
Somerset County, Pennsylvania
Signed
Jon M. Capacasa, Director
Water Protection Division
Date: 6/18/2008
Printed on 100% recycled/recyclable paper with 100% post-consumer fiber and process chlorine free.
Customer Service Hotline: 1-800-438-2474
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Decision Rationale
Total Maximum Daily Loads
Acid Mine Drainage Affected Segments
Wilson Creek Watershed, Somerset County, Pennsylvania
I. Introduction
The Clean Water Act (CWA) requires that Total Maximum Daily Loads (TMDLs) be
developed for those waterbodies identified as impaired by the state where technology based and
other controls will not provide for attainment of water quality standards. A TMDL is a
determination of the amount of a pollutant from point, nonpoint, and natural background sources,
including a Margin of Safety (MOS) that may be discharged to a waterbody without exceeding
water quality standards.
The Pennsylvania Department of Environmental Protection (PADEP) Bureau of
Watershed Management electronically submitted the Wilson Creek Watershed TMDL, Somerset
County, for Acid Mine Drainage Affected Segments (TMDL Report), dated February 29, 2008, to
the U.S. Environmental Protection Agency (EPA) for final Agency review on April 15, 2008.
This report includes the TMDLs for the three primary metals associated with acid mine drainage
(AMD) (i.e., iron, manganese, and aluminum and pH) and addresses one segment on
Pennsylvania's 1996 Section 303(d) List of impaired waters.
EPA's rationale is based on the TMDL Report and information contained in the
attachments to the report. EPA's review determined that the TMDL meets the following
seven regulatory requirements pursuant to 40 CFR Part 130:
1. The TMDL is designed to implement applicable water quality standards.
2. The TMDL includes a total allowable load as well as individual wasteload allocations
(WLAs) and load allocations (LAs).
3. The TMDL considers the impacts of background pollutant contributions.
4. The TMDL considers critical environmental conditions.
5. The TMDL considers seasonal environmental variations.
6. The TMDL includes a MOS.
7. The TMDL has been subject to public participation.
In addition, these TMDLs considered reasonable assurance that the TMDL allocations
assigned to the nonpoint sources can be reasonably met.
II. Summary
Table 1 presents the 1996, 1998 and 2002, Section 303(d) Listing and the 2004 and 2006
Integrated Report listing of information for the impaired segment first listed in 1996
(Pennsylvania's 1996, 1998, 2002 Section 303(d) Lists and 2004, 2006 Integrated Reports were
approved by the EPA. The 1996 Section 303(d) List provides the basis for measuring progress
under the 1997 lawsuit settlement of American Littoral Society and Public Interest Group of
Pennsylvania v. EPA).
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Table 1. 303(d) Listed Segments - State Water Plan (SWP) Subbasin: 19F
HUC: 05020006
Year
1996
1998
2002
2004
2006
2006
2006
2006
2006
2006
2006
Miles
1.0
0.91
0.9
0.9
1.33
0.64
1.86
0.48
0.63
0.37
1.05
Desig-
nated
Use
*
*
*
*
Aquatic
Life
Aquatic
Life
Aquatic
Life
Aquatic
Life
Aquatic
Life
Aquatic
Life
Aquatic
Life
Assessment
ID
*
*
*
*
7604
12724
12724
12724
12724
12724
12724
Segment
ID
4850
4850
4850
4850
*
*
*
*
*
*
*
DEP
Stream
Code
38947
38947
38947
38947
38947
38948
38949
38950
38951
38952
38953
Stream
Name
Wilson
Creek
Wilson
Creek
Wilson
Creek
Wilson
Creek
Wilson
Creek
Wilson
Creek,
Unt
Wilson
Creek,
Unt
Wilson
Creek,
Unt
Wilson
Creek,
Unt
Wilson
Creek,
Unt
Wilson
Creek,
Unt
Desig-
nated
Use
WWF
WWF
WWF
WWF
WWF
WWF
WWF
WWF
WWF
WWF
WWF
Data
Source
305(b)
Report
SWMP
SWMP
SWMP
SWMP
SWMP
SWMP
SWMP
SWMP
SWMP
SWMP
Source
RE
AMD
AMD
AMD
AMD
AMD
AMD
AMD
AMD
AMD
AMD
EPA
305(b)
Cause
Code
Metals
Metals
Metals
Metals
Metals
pH
Metals
pH
Metals
pH
Metals
pH
Metals
pH
Metals
pH
Metals
pH
* Denotes not applicable data for designated reporting year.
Resource Extraction = RE
Warm Water Fish = WWF
Surface Water Monitoring Program = SWMP
Abandoned Mine Drainage = AMD
See Attachment D of the TMDL Report, Excerpts Justifying Changes Between the 1996,
1998,2002 Section 303(d) Lists and the 2004, 2006 Integrated Report. The use designations
for the stream segments in this TMDL can be found in PA Title 25 Chapter 93.9v, Section IV.
Table 3 shows the TMDLs for the Wilson Creek Watershed.
In 1997, PADEP began utilizing the Statewide Surface Waters Assessment Protocol to
assess Pennsylvania's waters. This protocol is a modification of EPA's 1989 Rapid
Bioassessment Protocol II and provides for a more consistent approach to conducting biological
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assessments than previously used methods. The biological assessments are used to determine
which waters are impaired and should be included on the State's Section 303(d) List.
The TMDLs in this report were developed using a statistical procedure to ensure that
water quality criteria are met 99% of the time as required by Pennsylvania's water quality
standards at Pennsylvania Code Title 25, Chapter 96.3c. Table 3 of the TMDL Report lists the
TMDLs for the Wilson Creek Watershed, addressing metals and pH in the stream segments
listed as PADEP stream code 38947.
TMDLs are defined as the summation of the point source WLAs, plus the summation of
the nonpoint source, LAs plus a MOS and are often shown as follows:
TMDL = £WLAs + £LAs + MOS
The TMDL is a written plan and analysis established to ensure that a waterbody will
attain and maintain applicable water quality standards. The TMDL is a scientifically based
strategy which considers current and foreseeable conditions, utilizes the best available data, and
accounts for uncertainty with the inclusion of a MOS value. Since conditions, available data,
and the understanding of natural processes can change more than anticipated by the MOS, there
exists the option of refining the TMDL for resubmittal to EPA.
III. Background
The Wilson Creek Watershed is located in southwestern Pennsylvania, occupying the
southeastern part of Somerset County in Black Township. The watershed is found on the United
States Geological Survey Rockwood and Murdock 7.5 minute Quadrangles. The area within the
watershed consists of 8.0 square miles. Land uses within the watershed include woodland,
cropland, pastureland, rural residential, inactive and reclaimed mining sites, and coal refuse
piles.
The Borough of Rockwood is located 3,000 feet south of the mouth of Wilson Creek,
along S.R. 653. The headwaters can be reached by traveling on old S.R. 219, south of Somerset,
to the traffic light at the intersection of old S.R. 219 and Garrett Shortcut; turn right on Garrett
Shortcut Road and travel approximately three miles to the Shaffers crossroads intersection
turning right for 500 feet.
Wilson Creek is affected by pollution from AMD. This pollution has caused high levels
of metals and, in some cases, low pH in the watershed. Currently there are no known operations
that have National Pollutant Discharge Elimination System (NPDES) discharge points in the
Wilson Creek Watershed. The discharges that are contributing to the degradation in the Wilson
Creek water quality are associated with either long abandoned deep or surface mines and are not
being treated.
There are no active mining operations with WLAs in the watershed; however, three
segments have future allocations included for possible remining operations. All remaining
discharges in the watershed are resulting from abandoned mines and are treated as nonpoint
sources.
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PADEP treats each segment on the Section 303(d) List as a separate TMDL and
expresses each TMDL as a long-term average loading. See the Wilson Creek TMDL Report,
Attachment D, for the TMDL calculations.
The Surface Mining Control and Reclamation Act of 1977 (SMCRA, Public Law 95-87)
and its subsequent revisions were enacted to establish a nationwide program to, among other
things, protect the beneficial uses of land or water resources, protect public health and safety
from the adverse effects of current surface coal mining operations, and promote the reclamation
of mined areas left without adequate reclamation prior to August 3, 1977. SMCRA requires a
surface mining permit for the development of new, previously mined, or abandoned sites for the
purpose of surface mining. Permittees are required to post a performance bond that will be
sufficient to ensure the completion of reclamation requirements by the regulatory authority in the
event that the applicant forfeits. Mines that ceased operating by the effective date of SMCRA
(often called "pre-law" mines) are not subject to the requirements of SMCRA.
Wilson Creek was on the 1996 Section 303(d) List of impaired waters and counts toward
the twelfth year (2009) TMDL milestone commitment under the requirements of the 1997
TMDL lawsuit settlement agreement. The twelfth year milestone is the development of TMDLs,
or delisting, for all remaining waters listed as impaired by AMD impacts on Pennsylvania's 1996
Section 303(d) List of impaired waters.
Computational Procedure
The TMDLs were developed using a statistical procedure to ensure that water quality
criteria are met 99% of the time as required by Pennsylvania's water quality standards. A two-
step approach was used for the TMDL analysis of impaired stream segments.
The first step used a statistical method for determining the allowable instream
concentration at the point of interest necessary to meet water quality standards. An allowable
long-term average instream concentration was determined at each sample point for metals and
acidity. The analysis was performed using Monte Carlo simulation to determine the necessary
long-term average concentration needed to attain water quality criteria 99% of the time, and the
simulation was run assuming the dataset was log normally distributed. Using @RISK2, each
pollutant source was evaluated separately by performing 5,000 iterations of the model where
each iteration was independent of all other iterations. This procedure was used to determine the
required percent reduction that would allow the water quality criteria to be met instream at least
99% of the time. A second simulation that multiplied the percent reduction by the sampled value
was run to ensure that criteria were met 99% of the time. The mean value from this dataset
represents the long-term average concentration that needs to be met to achieve water quality
standards.
2
@RISK - Risk Analysis and Simulation Add-in for Microsoft Excel, Palisade Corporation, Newfield,
NY.
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The second step was a mass balance of the loads as they passed through the watershed.
Loads at these points were computed based on average flow. Once the allowable concentration
and load for each pollutant was determined, mass-balance accounting was performed starting at
the top of the watershed and working downstream in sequence. This mass balance or load
tracking through the watershed utilized the change in measured loads from sample location to
sample location as a guide for expected changes in the allowable loads.
The existing and allowable long-term average loads were computed using the mean
concentration from @RISK multiplied by the average flow. The loads were computed based on
average flow and should not be taken out of the context for which they are intended. They are
intended to depict how the pollutants affect the watershed and where the sources and sinks are
located spatially in the watershed. A critical flow was not identified, and the reductions
specified in this TMDL apply at all flow conditions.
In addition to the above analysis, the WLAs for the NPDES permitted pit water treatment
ponds were determined. Typically, surface mining operations include an open pit where
overburden material has been removed to access the underlying coal, and this pit can accumulate
water primarily through direct precipitation and surface runoff. The pit water is pumped to a
nearby treatment pond where it is treated to the level necessary to meet effluent limitations.
However, precipitation events allow intermittent discharges from the treatment pond. If accurate
flow data are available for a treatment pond, they can be used to quantify the WLA by
multiplying the flow by the best available technology (BAT) effluent limitations for treatment
ponds. However, these flow data are typically not available. Alternatively, PADEP calculated a
total average flow for the water draining to the pit using average annual precipitation, the area of
the pit, and a runoff factor. Utilizing this value and BAT treatment pond effluent limits, the
WLAs were determined.
IV. Discussions of Regulatory Requirements
EPA has determined that these TMDLs are consistent with statutory and regulatory
requirements and EPA policy and guidance.
1. The TMDLs are designed to implement the applicable water quality standards.
Water quality standards are state regulations that define the water quality goals of a
waterbody. Standards are comprised of three components: (1) designated uses; (2) criteria
necessary to protect those uses; and (3) antidegradation provisions that prevent the degradation
of water quality. Wilson Creek has been designated by Pennsylvania as a cold water fishery
with criteria to protect the aquatic life use, and the designation can be found at Pennsylvania
Title 25 §93.9v. To protect the designated use as well as the existing use, the water quality
criteria shown in Table 2 apply to all evaluated segments. The table includes the instream
numeric criterion for each parameter and any associated specifications.
Table 2. Applicable Water Quality Criteria
Parameter
Aluminum (Al)
Criterion
Value (mg/1)
0.75
Duration
Maximum
Total Recoverable/
Dissolved
Total Recoverable
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Parameter
Iron (Fe)
Manganese (Mn)
pH
Criterion
Value (mg/1)
1.50
0.30
1.00
6.0-9.0
Duration
30-day Average
Maximum
Maximum
Inclusive
Total Recoverable/
Dissolved
Total Recoverable
Dissolved
Total Recoverable
N/A
Pennsylvania Title 25 §96.3c requires that water quality criteria be achieved at least
99% of the time, and TMDLs expressed as long-term average concentrations are expected to
meet these requirements. That is, the statistical Monte Carlo simulation used to develop TMDL
WLAs and LAs for each parameter resulted in a determination that any required percent
pollutant reduction would assure that the water quality criteria would be met instream at least
99% of the time. The Monte Carlo analysis performed 5,000 iterations of the model where each
iteration was independent of all other iterations and the dataset was assumed to be log normally
distributed.
EPA finds that these TMDLs will attain and maintain the applicable narrative and
numeric water quality standards.
The pH values shown in Table 2 were used as the endpoints for these TMDLs. In the
case of freestone streams with little or no buffering capacity, the allowable TMDL endpoint for
pH may be the natural background water quality, and these values can be as low as 5.4
(Pennsylvania Fish and Boat Commission). However, PADEP chose to set the pH standard
between 6.0 to 9.0, inclusive, which is presumed to be met when the net alkalinity is maintained
above zero. This presumption is based on the relationship between net alkalinity and pH, on
which PADEP based its methodology to addressing pH in the watershed (see the Wilson Creek
Watershed TMDL Report, Attachment B). A summary of the methodology is presented as
follows:
The parameter of pH, a measurement of hydrogen ion acidity presented as a negative
logarithm of effective hydrogen ion concentration, is not conducive to standard statistics.
Additionally, pH does not measure latent acidity that can be produced from the hydrolysis of
metals. PADEP has been using an alternate approach to address the stream impairments noted
on the Section 303(d) List due to pH. Because the concentration of acidity in a stream is
partially dependent upon metals, it is extremely difficult to predict the exact pH values which
would result from treatment of AMD. Therefore, net alkalinity will be used to evaluate pH in
these TMDL calculations. This methodology assures that the standard for pH will be met
because net alkalinity is able to measure the reduction of acidity. When acidity in a stream is
neutralized or is restored to natural levels, pH will be acceptable (>6.0). Therefore, the
measured instream alkalinity at the point of evaluation in the stream will serve as the goal for
reducing total acidity at that point. The methodology that is used to calculate the required
alkalinity (and therefore pH) is the same as that used for other parameters such as iron,
aluminum, and manganese that have numeric water quality criteria. EPA finds this approach to
addressing pH to be reasonable.
PADEP also has an alkalinity standard. Alkalinity (of a minimum 20 mg/1 calcium
carbonate except where natural conditions are less) is related but not identical to pH. Alkalinity
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is a measure of the buffering capacity of the water. Adequate buffering prevents large swings in
pH with additions of small amounts of acid. Although many of the AMD-impacted streams are
naturally low in alkalinity, available monitoring data does not always include upstream waters
not impacted by AMD. As PADEP does not list waters for inadequate alkalinity, TMDLs are
not being developed for alkalinity, but PADEP should monitor the waters for alkalinity and if,
after these TMDLs are implemented, alkalinity is less than 20 mg/1 or natural conditions,
PADEP should list the waters for alkalinity and develop TMDLs.
2. The TMDLs include a total allowable load as well as individual wasteload allocations and
load allocations.
For purposes of these TMDLs only, point sources are identified as permitted discharge
points or discharges having responsible parties, and nonpoint sources are identified as any
pollution sources that are not point sources. Abandoned mine lands were treated in the
allocations as nonpoint sources. As such, the discharges associated with these land uses were
assigned LAs (as opposed to WLAs). The decision to assign LAs to abandoned mine lands does
not reflect any determination by EPA as to whether there are unpermitted point source
discharges within these land uses. In addition, by approving these TMDLs with mine drainage
discharges treated as LAs, EPA is not determining that these discharges are exempt from NPDES
permitting requirements.
To determine the WLAs for the NPDES permitted pit water treatment ponds, PADEP
first calculated a total average flow for the water draining to the pit using average annual
precipitation, the area of the pit, and a runoff factor. The WLAs were then calculated using this
value and the BAT treatment pond effluent limits and were included in the mass balance along
with the LAs.
Once PADEP determined the allowable concentration and load for each pollutant, a mass
balance accounting was performed starting at the top of the watershed and working downstream
in sequence. Load tracking through the watershed utilizes the change in measured loads from
sample location to sample location as a guide for expected changes in the allowable loads.
PADEP used two basic rules for the load tracking between two ends of a stream segment:
(1) if the measured upstream loads are less than the downstream loads, it is indicative that there
is an increase in load between the points being evaluated, and no instream processes are
assumed; and (2) if the sum of the measured loads from the upstream points is greater than the
measured load at the downstream point, it is indicative that there is a loss of instream load
between the points, and the ratio of the decrease shall be applied to the allowable load being
tracked from the upstream point.
Tracking loads through the watershed provides a picture of how the pollutants are
affecting the watershed based on the available information. The analysis is performed to ensure
that water quality standards will be met at all points in the stream. EPA finds this approach
reasonable.
Table 3 presents a summary of the allowable loads, LAs, and WLAs for the Wilson
Creek Watershed.
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Table 3. Wilson Creek Watershed Summary Table
Parameter
Existing
Load
(Ibs/day)
TMDL
Allowable
Load
(Ibs/day)
WLA
(Ibs/day)
LA
(Ibs/day)
NFS Load
Reduction
(Ibs/day)
NFS
% Reduction
WILSON12 - Wilson Creek upstream of all Unnamed Tributaries
Aluminum (Ibs/day)
Iron (Ibs/day)
Manganese(lbs/day)
Acidity (Ibs/day)
2.83
2.00
0.23
38.71
1.33
2.00
0.23
0.77
-
.
.
-
1.33
NA
NA
0.77
1.50
NA
NA
11.39
53%
NA
NA
98%
WILSON10 - Wilson Creek upstream of WILSON9 Unnamed Tributary
Aluminum (Ibs/day)
Iron (Ibs/day)
Manganese(lbs/day)
Acidity (Ibs/day)
173.21
36.89
33.18
1672.53
8.66
24.35
16.26
0.00
1.68
6.78
4.50
-
6.98
17.57
11.76
0.00
163.05
12.54
16.92
1634.59
95%*
34%*
51%*
100%*
WILSON9 - Unnamed Tributary to Wilson Creek at mouth
Aluminum (Ibs/day)
Iron (Ibs/day)
Manganese(lbs/day)
Acidity (Ibs/day)
3.87
62.00
8.56
192.25
1.32
1.24
1.45
0.00
-
-
-
-
1.32
1.24
1.45
0.00
2.55
60.76
7.11
192.25
66%
98%
83%
100%
WILSONS - Unnamed Tributary to Wilson Creek at mouth
Aluminum (Ibs/day)
Iron (Ibs/day)
Manganese(lbs/day)
Acidity (Ibs/day)
1.24
1.59
1.06
17.71
0.26
0.52
0.56
0.00
-
-
-
-
0.26
0.52
0.56
0.00
0.98
1.07
0.50
17.71
79%
67%
47%
100%
WILSON? - Wilson Creek downstream of WILSONS Unnamed Tributary
Aluminum (Ibs/day)
Iron (Ibs/day)
Manganese(lbs/day)
Acidity (Ibs/day)
228.60
195.71
94.56
3170.75
20.57
43.06
30.26
0.00
1.68
6.78
4.50
-
18.89
36.28
25.76
0.00
39.95
78.28
39.77
1288.56
66%*
65%*
57%*
100%*
WILSON6 - Wilson Creek at mouth
Aluminum (Ibs/day)
Iron (Ibs/day)
Manganese(lbs/day)
Acidity (Ibs/day)
305.33
147.97
108.17
3257.38
15.27
62.15
35.70
0.00
1.68
6.78
4.50
-
13.59
55.37
31.20
0.00
82.03
0.00
8.17
86.63
85%*
0%*
19%*
100%*
NA = not applicable ND = not detected
* Takes into account load reductions from upstream sources.
Numbers in italics are set aside for future mining operations.
PADEP allocated to nonpoint sources and point sources. There are no active mining
operations in the watershed. Where there are active mining operations, Federal regulations
require that point source permitted effluent limitations be water quality based subsequent to
TMDL development and approval.3 In addition, PA Title 25, Chapter 96, Section 96.4d requires
It should be noted that technology-based permit limits may be converted to water quality-based limits
according to EPA's Technical Support Document For Water Quality-based Toxics Control, March 1991,
recommendations.
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that WLAs serve as the basis for determination of permit limits for point source discharges
regulated under Chapter 92 (relating to NPDES permitting, monitoring, and compliance).
Therefore, no new mining may be permitted within the watershed without reallocation of the
TMDL. The Wilson Creek TMDL has allowed for future mining allocations on three segments
with three mining operations in each segment. Additionally, no required reductions of permit
limits are necessary at this time, as all necessary reductions have been assigned to nonpoint
sources.
3. The TMDLs consider the impacts of background pollutant contributions.
The TMDLs were developed using instream data, which account for existing background
conditions.
4. The TMDLs consider critical environmental conditions.
The reductions specified in these TMDLs apply at all flow conditions. A critical flow
condition was not identified from the available data.
5. The TMDLs consider seasonal environmental variations.
The dataset included data points from all seasons, thereby accounting for seasonal
variation implicitly.
6. The TMDLs include a Margin of Safety.
The CWA and Federal regulations require TMDLs to include a MOS to take into account
any lack of knowledge concerning the relationship between effluent limitations and water
quality. EPA guidance suggests two approaches to satisfy the MOS requirement. First, it can be
met implicitly by using conservative model assumptions to develop the allocations. Alternately,
it can be met explicitly by allocating a portion of the allowable load to the MOS.
PADEP used an implicit MOS in these TMDLs by assuming that the treated instream
concentration variability was the same as the untreated stream's concentration variability. This
is a more conservative assumption than the general assumption that a treated discharge has less
variability than an untreated discharge. By retaining variability in the treated discharge, a lower
average concentration is required to meet water quality criteria 99% of the time than if the
variability of the treated discharge is reduced.
Additionally, calculations were performed using a daily average for iron rather than the
30-day average, thereby, incorporating a MOS.
7. The TMDLs have been subject to public participation.
Public notice of the draft TMDL was published in the Pennsylvania Bulletin and the
Daily American on January 9, 2008, to foster public comment on the allowable loads calculated.
The public comment period on this TMDL was open from January 9, 2008 to March 19, 2008.
A public meeting was held on January 24, 2008, at the Cambria District Mining Office to discuss
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the proposed TMDL. No comments were received relating to Wilson Creek TMDL.
Although not specifically stated in the TMDL Report, PADEP routinely posts the
approved TMDL Reports on their web site: www.dep.state.pa.us/watermanagement_apps/tmdl/.
V. Discussion of Reasonable Assurance
Aside from PADEP's primary efforts to improve water quality in the Wilson Creek
Watershed through reclamation of abandoned mine lands and through the NPDES permit
program, additional opportunities for reasonable assurance exist. PADEP expects that activities
such as research conducted by its Bureau of Abandoned Mine Reclamation, funding from EPA's
§319 grant program, and Pennsylvania's Growing Greener program will help remedy abandoned
mine drainage impacts. PADEP also has in place an initiative that aims to maximize reclamation
of Pennsylvania's abandoned mineral extraction lands. Through Reclaim PA, Pennsylvania's
goal is to accomplish complete reclamation of abandoned mine lands and plugging of orphaned
wells. Pennsylvania strives to achieve this objective through legislative and policy land
management efforts and activities described in the TMDL Report.
Currently, there is no watershed organization interested in the Wilson Creek Watershed.
It is recommended that agencies work with local interests to form a watershed group that will be
dedicated to the remediation and preservation of these watersheds through public education,
monitoring and assessment, and improvement.
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