Pigeon House TMDLs_final version approved by EPA

Total Maximum Daily Loads for Fecal Coliform Bacteria
and for Copper to Pigeon House Branch, North Carolina
Final Version Approved by EPA
June, 2003
Neuse River Basin
Prepared by:
NC Department of Environment and Natural Resources
Division of Water Quality
1617 Mail Service Center
Raleigh, NC 27699-1617
[phone]
Final version submitted to EPA
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TABLE OF CONTENTS
TMDL Summary Sheet ………………………………………………………….. 3
1.0 Introduction ……………………………………………………………….5
1.1 Watershed Description …………………………………………….7
1.2 Water Quality Monitoring Program…………………………………9
1.3 Water Quality Target ………………………………………………10
2.0 Source Assessment …………………………………………………………11
2.1 Point Source Assessment……………………………………………11
2.2 Nonpoint Source Assessment….……………………………………12
2.2.1 Livestock……………………………………………………12
2.2.2 Failed Septic Systems………………………………………..13
2.2.3 Urban Development…………………………..…………….13
2.2.4 Sanitary Sewer Overflows ………………………………….. 13
2.2.5 Wildlife …………………………………………………….14
2.3 Source Assessment Conclusion …………………………………….14
3.0 Modeling Approach………………………… ……………………………..14
3.1 Flow Duration Curves……………..……………………………….15
3.2 Load Duration Curves……………………………………………..16
4.0 Total Maximum Daily Load…………………………………………………18
4.1 Reduction Target…………. ………………………………………..19
4.1.1 Existing Conditions………………………………….……...19
4.1.2 Reduction Target Calculation……………….....……………. 20
4.1.3 Critical Conditions…………….……………………………. 21
4.2 Margin of Safety ….…………….…………………………………. 22
4.3 TMDL Allocation…….……………………………………………..22
4.3.1 Load Allocations…………………………………………….24
4.3.2 Wasteload Allocations……………………………………….24
4.4 Seasonal Variation………………………………………………….. 25
5.0 Summary and Future Considerations …………………….………………..25
5.1 Urban Sources of Pollutant Loading……………………………….26
6.0 Stream Monitoring…………………………………………………………27
7.0 Future Efforts……………………………………………………………….27
8.0 Public Participation………………………………………………………….28
9.0 Further Information…………………………………………………………28
References Cited……………………………………………………………………29
Appendix I.Observed Data …………………………….………………………..30
Appendix II.TMDL Calculations...……………………………………………… 37
Appendix III.Responsiveness Summary……………………………………………40
Final version submitted to EPA
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SUMMARY SHEET
Total Maximum Daily Load (TMDL)
1.303(d) Listed Waterbody Information
State: North Carolina
County:Wake
Major River Basin: Neuse River Basin
Watershed: Pigeon House Branch - in Upper Neuse Watershed HUC 03020201
Impaired Waterbody (2000 303(d) List):
Stream Index #Designated Use
Segment Name Partial
Support
[mi.]
Not
Support
[mi.]
27-33-18 Pigeon House Branch – source to
Crabtree Creek ---2.9
Constituent(s) of Concern:Fecal Coliform Bacteria, Copper
Designated Uses:Biological integrity, propagation of aquatic life, and recreation.
Applicable Water Quality Standards for Class C Waters:
Fecal coliforms shall not exceed a geometric mean of 200/100ml (membrane filter count)
based upon at least five consecutive samples examined during any 30 day period, nor exceed
400/100 ml in more than 20 percent of the samples examined during such period.
Copper: 7 ug/l.
2.TMDL Development
Analysis/Modeling:
Load duration curves based on cumulative frequency distribution of flow conditions in the
watershed. Allowable loads are average loads over the recurrence interval between the 95th
and 10th percent flow exceeded (excludes extreme drought (>95th percentile) and floods
(<10th percentile). Percent reductions expressed as the average value between existing loads
(calculated using an equation to fit a curve through actual water quality violations) and the
allowable load at each percent flow exceeded.
Critical Conditions:
Critical conditions are accounted for in the load curve analysis by determining the average
difference between the existing load violation trend line and the allowable load line. This
approach was chosen because existing load violations occur at all flow levels.
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Seasonal Variation:
Seasonal variation in hydrology, climatic conditions, and watershed activities are represented
through the use of a continuous flow gage and the use of all readily available water quality
data collected in the watershed.
3. Allocation Watershed/Stream Reach:
Pollutant LA WLA 1 MOS 2 TMDL Percent
Reduction3
Fecal Coliform 2.04 X 108
counts/day
7.63 X 109
counts/day Explicit 7.83 X 109
counts/day 78%
Copper 3.35 X 105
ug/day
1.26 X 107
ug/day Explicit 1.29 X 107
ug/day 66%
Notes:
WLA = wasteload allocation, LA = load allocation, MOS = margin of safety
1. WLA = TMDL – LA - MOS; where TMDL is the average allowable load between the 95th
and 10th percent flow exceeded.
2. Margin of safety (MOS) equivalent to 10 percent of the target concentration for fecal
coliform and 14 percent for copper.
3. Average reduction required over the range of flows between the 95th and 10th percent flow
exceeded, as estimated in Pigeon House Branch using the continuous streamflow gage from
nearby Rocky Branch.
4. Public Notice Date: April 15, 2003
5. Submittal Date:
6. Establishment Date:
7. Endangered Species (yes or blank):
8. EPA Lead on TMDL (EPA or blank):
9. TMDL Considers Point Source, Nonpoint Source, or both: both
Total Maximum Daily Loads
Final version submitted to EPA
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For Fecal Coliform Bacteria and Copper
To Pigeon House Branch
1.0 Introduction
On the draft 2002 North Carolina Integrated Report, the North Carolina Division of Water Quality
(DWQ) identified a 2.9-mile segment (27-33-18) of Pigeon House Branch in the Neuse Basin as
impaired by fecal coliform bacteria and copper. The impaired segment extends from the stream’s
source to its confluence with Crabtree Creek. This section of the stream is located in subbasin 03-
04-02. Pigeon House Branch is designated as a class C water. Class C waters are freshwaters that
are protected for secondary recreation, fishing, and propagation and survival of aquatic life.
Section 303(d) of the Clean Water Act (CWA) requires states to develop a list of waters not meeting
water quality standards or which have impaired uses. This list, contained within Categories 4
through 7 of the Integrated Report, is submitted biennially to the U.S. Environmental Protection
Agency (EPA) for review. The 303(d) process requires that a Total Maximum Daily Load (TMDL)
be developed for each of the waters appearing on Category 5 of the Integrated Report. A TMDL is
the maximum amount of a pollutant (e.g., fecal coliform or copper) that a waterbody can receive and
still meet water quality standards, and an allocation of that load among point and nonpoint sources.
The objective of a TMDL is to estimate allowable pollutant loads and allocate to known sources so
that actions may be taken to restore the water to its intended uses (USEPA, 1991). Generally, the
primary components of a TMDL, as identified by EPA (1991, 2000a) and the Federal Advisory
Committee are as follows:
Target identification or selection of pollutant(s) and endpoint(s) for consideration. An endpoint is an
instream numeric target. The pollutant and endpoint are generally associated with
measurable water quality related characteristics that indicate compliance with water quality
standards. North Carolina indicates known problem pollutants on the 303(d) list.
Source assessment. Sources that contribute to the impairment should be identified and loads
quantified, to the extent that that is possible.
Reduction target. Estimation of level of pollutant reduction needed to achieve water quality goal. The
level of pollution should be characterized for the waterbody, highlighting how current
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conditions deviate from the target endpoint. Generally, this component is identified through
water quality modeling.
Margin of safety. The margin of safety addresses uncertainties associated with pollutant loads,
modeling techniques, and data collection. Per EPA (2000a), the margin of safety may be
expressed explicitly as unallocated assimilative capacity (portion of TMDL) or implicitly
through conservative assumptions. The margin of safety should be included in the reduction
target.
Allocation of pollutant loads. Allocating available pollutant load (TMDL), and hence pollutant control
responsibility, to the sources of impairment. The wasteload allocation portion of the TMDL
accounts for the loads associated with existing and future point sources. The load allocation
portion of the TMDL accounts for the loads associated with existing and future nonpoint
sources. Any future nonpoint source loading should remain within the TMDL that is
calculated in this assessment; in other words, this TMDL does not leave allocation for future
sources.
Seasonal variation. The TMDL should consider seasonal variation in the pollutant loads and endpoint.
Variability can arise due to streamflows, temperatures, and exceptional events (e.g., droughts
and hurricanes).
Critical conditions. Critical conditions occur when fecal coliform levels exceed the standard by the
largest amount. If the modeled load reduction is able to meet the standard during critical
conditions, then it should meet the standard at all, or nearly all, times.
Section 303(d) of the CWA and the Water Quality Planning and Management regulation (USEPA,
2000a) require EPA to review all TMDLs for approval or disapproval. Once EPA approves a
TMDL, then the waterbody may be moved to Category 4a of the 2002 Integrated Report.
Waterbodies remain on Category 4a until compliance with water quality standards is achieved.
Where conditions are not appropriate for the development of a TMDL, management strategies may
still result in the restoration of water quality.
The goal of the TMDL program is to restore designated uses to water bodies. Thus, the
implementation of bacteria and copper controls will be necessary to restore designated uses in
Pigeon House Branch. Although an implementation plan is not included as part of this TMDL,
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reduction strategies are needed. The involvement of local governments and agencies will be critical
to developing an implementation plan and reduction strategy.
1.1 Watershed Description
Pigeon House Branch, located in the upper Neuse basin, drains into Crabtree Creek within the City
of Raleigh (see Figure 1). The creek’s watershed lies entirely within Wake County and is about 4
square miles in area. DWQ has an ambient water quality monitoring site (Storet number J3300000)
at Dortch St., about 2.5 miles from the confluence with the Crabtree Cr. The watershed at this
point is 1.15 square miles. This will be the evaluation point for the TMDL since fecal coliform and
copper data have been and will continue to be collected here.
Figure 1.
$
Cemetery Branch
Pigeon House Branch
CAPITAL BLVD
HILLSBOROUGH ST
WADE AV
GLENWOOD AV
Crabtree Creek
Major Roads
Reach File, V3 (03020201)
Pigeon House Branch Watershed$DWQ Ambient Monitoring Station at Dortch St.
1 0 1 2 Miles
$
S
N
EW
Pigeon House Branch Watershed
Pigeon House Branch
Vicinity Map
Note: watershed delineation in Fig. 1 is inexact, and has been used for display purposes only.
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The land use/land cover characteristics of the watershed were determined using 1996 land cover
data that were developed from 1993-94 LANDSAT satellite imagery. The North Carolina Center
for Geographic Information and Analysis, in cooperation with the NC Department of
Transportation and the United States Environmental Protection Agency Region IV Wetlands
Division, contracted Earth Satellite Corporation of Rockville, Maryland to generate comprehensive
land cover data for the entire state of North Carolina. Tabulated land cover/land use data for the
Pigeon House Branch Watershed are shown in Table 1. During the formation of this geographic
dataset, developed land was identified using the proportion of synthetic cover present; low density
developed was 50-80% synthetic cover, and high density developed was 80-100% synthetic cover.
Assuming that synthetic cover is impervious, and that all non-developed land cover classes have 1%
impervious cover, the Pigeon House Branch watershed is estimated to have 57-78% impervious
surface.
That the impervious cover estimate is so high is not surprising considering the watershed is entirely
within the City of Raleigh. For management purposes, DWQ will consider that there is only one
land class in Pigeon House Branch watershed – urban land. This land, however, may be drained by
a variety of means. These include storm pipes and sewers that are under the separate jurisdiction of
the City of Raleigh, Department of Transportation, federal government (railroad tracks), and Wake
County, as well as overland runoff and interflow from urban land into the stream network.
Table 1. Land use/land cover in Pigeon House Branch watershed
Land Use/Land Cover Pigeon House Branch Watershed Acres
High Density Developed 1314 (49.1%)
Low Density Developed 946 (35.4%)
Cultivated 0 (0.0%)
Managed Herbaceous 127 (4.7%)
Forest 289 (10.8%)
Total 2674
The USGS 14-digit hydrologic unit code (HUC) for Pigeon House Branch is 03020201090020.
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1.2 Water Quality Monitoring Program
There are two sources of fecal coliform and copper data for Pigeon House Branch: 1) data from the
North Carolina Division of Water Quality’s ambient monitoring program; 2) special study data
collected by the City of Raleigh. More information is provided below, and both of these datasets are
included in Appendix I.
Pigeon House Branch was listed as impaired based on data from the DWQ ambient monitoring
station, which is located at Dortch St. or approximately 2.5 miles from the stream’s confluence with
Crabtree Creek. Water samples collected at this site on a monthly basis are analyzed for fecal
coliform, copper and other water quality parameters.
DWQ used the ambient data as the basis for the TMDL calculation because those data have been
collected on a consistent basis, and will be used to assess compliance in the future. Furthermore,
DWQ conducts ambient monitoring using QAQC (quality assurance and quality control) protocols
established for sample collection and analysis. Raleigh undertook monitoring, as described below,
for their own source identification purposes; consequently, Raleigh did not follow formal QAQC
protocols for sample collection and transport. As a result, Raleigh data will be used in this TMDL
for source assessment and implementation strategy development purposes.
The City of Raleigh conducted synoptic sampling at 12 locations in the Pigeon House Branch
watershed. Raleigh sampled these sites on 8 days (approximately weekly) in June and July 2001. The
samples were analyzed for a number of water quality parameters, including fecal coliform and
copper. These data show extremely high fecal coliform levels, with noticeably higher counts at the
entrance to Equipment Service Depot off of West St., at the culvert between West St. and Peace St.,
and at Automotive Way past Crabtree Boulevard. More attention to these data may help to identify
specific sources of fecal coliform, possibly including leaky sewer lines and illicit discharges.
The copper data from Raleigh do not show the same level of impairment as DWQ’s copper data;
however, there are some sites, particularly the entrance to the Equipment Service Depot off of West
St. and the culvert between West St. and Peace St., which indicate copper impairment.
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1.3 Water Quality Targets
The North Carolina fresh water quality standard for fecal coliform in Class C waters (T15A:
02B.0211) states:
Organisms of the coliform group: fecal coliforms shall not exceed a geometric mean of
200/100ml (membrane filter count) based upon at least five consecutive samples examined
during any 30 day period, nor exceed 400/100 ml in more than 20 percent of the samples
examined during such period; violations of the fecal coliform standard are expected during
rainfall events and, in some cases, this violation is expected to be caused by uncontrollable
nonpoint source pollution; all coliform concentrations are to be analyzed using the
membrane filter technique unless high turbidity or other adverse conditions necessitate the
tube dilution method; in case of controversy over results, the MPN 5-tube dilution technique
will be used as the reference method.
The instream numeric target, or endpoint, is the restoration objective expected to be reached by
implementing the specified load reductions in the TMDL. The target allows for the evaluation of
progress towards the goal of reaching water quality standards for the impaired stream by comparing
the instream data to the target. For this TMDL the water quality target is the instantaneous
concentration of 400cfu/100ml. Cfu stands for colony-forming units; it may also be referred to as
simply ‘counts’ in this assessment. The geometric mean will not be considered because the method
used to develop the TMDL analysis method is incompatible with the available data; the method
relies on observed data, and, as previously mentioned, those are limited to a monthly frequency.
Typically in North Carolina, compliance with the instantaneous part of the fecal coliform criterion
has also meant compliance with the geometric mean part of the criterion.
For copper, the North Carolina freshwater action level for toxic substances in Class C waters
(T15A: 02B.0211) states:
If the Action Levels for any of the substances listed in this Subparagraph (which are generally not
bioaccumulative and have variable toxicity to aquatic life because of chemical form, solubility,
stream characteristics or associated waste characteristics) are determined by the waste load allocation
to be exceeded by a receiving water by a discharge under the specified low flow criterion for toxic
substances (Rule .0206 in this Section), the discharger shall monitor the chemical or biological
effects of the discharge; efforts shall be made by all dischargers to reduce or eliminate these
substances from their effluents. Those substances for which Action Levels are listed in this
Subparagraph shall be limited as appropriate in the NPDES permit based on the Action Levels listed
in this Subparagraph if sufficient information (to be determined for metals by measurements of that
portion of the dissolved instream concentration of the Action Level parameter attributable to a
specific NPDES permitted discharge) exists to indicate that any of those substances may be a
causative factor resulting in toxicity of the effluent. NPDES permit limits may be based on
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translation of the toxic form to total recoverable metals. Studies used to determine the toxic form
or translators must be designed according to “Water Quality Standards Handbook Second Edition”
published by the Environmental Protection Agency (EPA 823-B-96-007) which are hereby
incorporated by reference including any subsequent amendments. The Director shall consider
conformance to EPA guidance as well as the presence of environmental conditions that limit the
applicability of translators in approving the use of metal translators.
(a) Copper: 7 ug/l
For purposes other than consideration of NPDES permitting of point source dischargers as
described in this Subparagraph, the Action Levels in this Rule, as measured by an appropriate
analytical technique, per 15A NCAC 2B .0103(a), shall be considered as the numerical ambient water
quality standard(s). (emphasis added for this TMDL document)
In essence, the North Carolina TMDL criterion for copper is 7 ug/l. The term ‘action level’ refers
to a water quality standard for a parameter that is not highly bioaccumulative, and that has variable
toxicity to aquatic life due to chemical and environmental variables such as chemical form, solubility,
stream pH, and stream hardness. Instream toxicity testing and biological sampling may be used to
determine compliance with an action level parameter such as copper.
2.0 Source Assessment
A source assessment is used to identify and characterize the known and suspected sources of fecal
coliform bacteria and copper in the watershed. It is a qualitative assessment due to the requirements
of the simpler analysis method of this TMDL. Further source characterization may be done before
and/or during TMDL implementation.
2.1 Point Source Assessment
General sources of fecal coliform and copper are divided between point and nonpoint sources.
Currently, there are no facilities in the watershed that discharge wastewater through the National
Pollutant Discharge Elimination System (NPDES).
A recent EPA mandate (Wayland, 2002) requires NPDES permitted stormwater to be placed in the
wasteload allocation (WLA), which had previously been reserved for continuous point source
wastewater loads. The two entities that are permitted through Phase I of the NPDES stormwater
program to discharge in the Pigeon House Branch watershed are the City of Raleigh (NC0029033)
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and the North Carolina Department of Transportation (NCS000250). As part of Phase II of the
NPDES stormwater program, Wake County, which has jurisdiction over some land and storm pipes
in the Pigeon House Branch watershed, will be added.
2.2 Nonpoint Source Assessment
Nonpoint sources of fecal coliform bacteria include those sources that can not be identified as
entering the waterbody at a specific location (e.g., an NPDES permitted pipe). In theory, nonpoint
source pollution includes urban, agricultural and background (e.g., forest, wildlife) sources. Fecal
coliform bacteria may originate from human and non-human sources. Table 2 lists the potential
human and animal nonpoint sources of fecal coliform bacteria (Center for Watershed Protection,
1999). The nonpoint sources of fecal coliform bacteria in Pigeon House Branch include runoff
from urban development (non-NPDES regulated stormwater), sewer line systems (leaky sewer lines
and sewer system overflows), wildlife, and probably illicit connections in unknown locations.
Nonpoint sources of copper in Pigeon House Branch watershed generally include urban
stormwater, and potentially sewer line systems (leaky sewer lines and sewer system overflows).
A more specific discussion of the nonpoint sources of fecal coliform and copper in the Pigeon
House Branch watershed is provided below.
2.2.1 Livestock
There is no known livestock in the Pigeon House Branch watershed.
Table 2. Potential sources of fecal coliform bacteria in urban watersheds (Center for Watershed
Protection, 1999).
Source Type Source
Human Sources Sewered watershed Combined sewer overflows
Sanitary sewer overflows
Illegal sanitary connections to
storm drains
Illegal disposal to storm drains
Non-human Sources Domestic animals and urban wildlife Dogs, cats
Rats, raccoons, opossum, squirrels
Pigeons, gulls, ducks, geese
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2.2.2 Failed Septic Systems
There are no septic systems in the Pigeon House Branch watershed.
2.2.3 Urban Development
Fecal coliform bacteria can originate from various urban sources. These sources include pet and
wildlife waste, illicit discharges/connections of sanitary waste, and leaky sewer systems.
Additionally, in the Pigeon House Branch watershed there may be a homeless human population,
which could account for additional fecal coliform loading.
Copper originates from various urban sources as well. The primary source of copper in urban
stormwater is deposition of abraded automobile brake linings (brake emissions) on roads (Davis et
al., 2001; Malmqvist, 1983; Hewitt and Rashed, 1990). Davis et al. (2001) estimated that copper
from brake wear composed at least 50% of copper in stormwater; this was from an analysis of a low
density residential area that assumed residents account for all vehicle traffic, or where all travel
outside the area is matched by non-resident travel inside. The proportion of copper from vehicle
brakes is likely to be significantly greater than 50% in the Pigeon House Branch watershed, where
major traffic thoroughfares with non-resident traffic are likely to increase vehicle copper loadings.
Secondary sources include building siding (possibly from wood preservative) and roofs (especially
commercial buildings), and wet and dry atmospheric deposition (Davis et al., 2001). Additional
sources may include leaky sewer systems and sanitary sewer overflows.
2.2.4 Sanitary Sewer Overflows
The city of Raleigh owns and operates a wastewater treatment plant and sewage collection system.
From 1997 through 2002, Raleigh reported five sanitary sewer overflows (SSOs) of greater than
1,000 gallons, including one SSO of greater than 50,000 gallons in the Pigeon House watershed.
There were also six SSOs of less than 1,000 gallons during that time. None of the SSOs appeared in
the monitoring data, as samples where not taken within 10 days of a spill, or in one case the spill
occurred outside of the monitoring station’s watershed. DWQ did not explicitly account for SSOs
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in the modeling. They are merely mentioned as a source of fecal coliform, and potentially copper,
that should receive further attention during development of an implementation strategy.
2.2.5 Wildlife
Wildlife is a source of fecal coliform bacteria throughout the watershed. Wildlife deposit feces
containing fecal coliform bacteria on the land surface; later, the bacteria may be transported to the
drainage network via runoff or shallow groundwater following a rain event. Direct deposition of
fecal coliform bacteria from wildlife into the stream is another avenue for loading. Wildlife in
Pigeon House Branch watershed is expected to include raccoons, opossum, squirrels, and birds
(pigeons in particular).
2.3 Source Assessment Conclusion
The source assessment for this TMDL is offered as a qualitative assessment of the potential sources
of fecal coliform and copper. For copper, it is highly likely that automobile brake deposits are the
leading source, followed by buildings and atmospheric deposition. Fecal coliform sources are less
certain. The primary sources are likely to be leaky sewer systems, and urban runoff containing fecal
coliform from pet waste, wildlife waste and potentially human waste. Other sources may include
sanitary sewer overflows, and illicit discharges/connections of sanitary waste. The specific entry
points to Pigeon House Branch from all of these sources are not currently known, though the City
of Raleigh has conducted some spatially intensive monitoring which may shed light on this (see page
9 and Appendix I).
Additionally, Raleigh and DWQ are collaborating on a bacterial source tracking project that will seek
to identify general fecal coliform sources (i.e., human, pets, or wildlife).
3.0 Analytical Approach
Since the allocation of the Pigeon House Branch TMDLs is essentially limited to one source, urban
stormwater (that regulated by NPDES, the City of Raleigh and the Department of Transportation as
of January 2003; and that which is not regulated by NPDES, State Government Complex and Wake
County land as of January 2003), a model to establish pollutant contribution by various sources is
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not required. Consequently, the primary analysis need is determining the TMDL, or amount of load
reduction. Rather than use a complex, mechanistic model such as HSPF, DWQ will employ a load
duration approach to determine these TMDLs. Using this approach provides a simplified and direct
manner to establish the relationship between water quality and streamflow. Load duration curves
are based entirely on observed data, and they employ a cumulative frequency distribution of
streamflow. The methodology used will be described further below and is based on work by Stiles
in Kansas (2002), Cleland (2002), and Sheely in Mississippi (2002).
3.1 Flow Duration Curves
In order to develop a load duration curve for TMDL development, the first step is to create a flow
duration curve, which displays the cumulative frequency distribution of daily flow data over the
period of record. The duration curve relates flow values measured at a monitoring station to the
percent of time the flow values were equaled or exceeded. Flows are ranked from lowest, which are
exceeded nearly 100 percent of the time, to highest, which are exceeded less than 1 percent of the
time.
Flow duration curves are limited to the period of record available at a monitoring station. The
confidence in the duration curve approach in predicting a realistic percent load reduction increases
when longer periods of record are used to generate the graphs. One of the shortcomings of using
this method to develop TMDLs is that many ambient monitoring locations, including that at Pigeon
House Branch, do not have a USGS gage. However, a nearby gage in a watershed of similar size
and land use as the ungaged watershed can be used to estimate flows. Flows at the ungaged location
can be estimated using a drainage area ratio, as explained below.
DWQ developed a flow duration curve using daily streamflow data collected at a continuous gage
on Rocky Branch (USGS 0208735012) between October 1996 and March 2003. There were other
alternatives that were not quite as useful as the Rocky Branch gage. Pigeon House Branch has a
gage (USGS 0208732534), but that drains only 0.27 square miles of the watershed and often reports
zero flow; at the ambient monitoring station, the watershed drains 1.15 square miles. Another
option was the USGS gage (0208732885) at Marsh Creek. The record for this extends as far back as
1984, but it drains 6.84 square miles. The flow per drainage area ratios for Marsh Creek and Rocky
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Branch are similar, though Rocky Branch’s ratio is slightly higher. After comparing the flow
duration curves using the various gages, DWQ chose the Rocky Branch gage because it is nearby,
and drains a nearly identical amount of land (1.17 square miles) as Pigeon House Branch at Dortch
St. The Rocky Branch watershed is slightly less urban than that of Pigeon House Branch, though it
still has a significant amount of impervious area.
To estimate Pigeon House Branch flows from Rocky Branch flows, DWQ completed the following
steps: 1) list the observed Rocky Branch flows chronologically during the entire period of record; 2)
calculate the daily flow per square mile by dividing the observed flows by the watershed area; 3)
order the results from 2) and rank them according to percentile; and finally, 4) multiply the result
from 3) by the area of the Pigeon House Branch watershed. The result may be seen in Figure 2
below.
Figure 2.
3.2 Load Duration Curves
Flow duration curves are transformed into load duration curves by multiplying the flow values along
the flow duration curve by the pollutant concentrations and the appropriate conversion factors. On
Flow Duration Curve for Pigeon House Branch based on
Rocky Branch at USGS 0208735012 - 1996 to 2003
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
1 10 100
Percent Flow Exceeded
F
l
o
w

(
c
f
s
)
High Flows
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the load duration curve, allowable and existing loads are plotted against the flow recurrence interval.
The allowable load is based on the water quality numerical criteria for fecal coliform and copper, less
the margin of safety, and on flow values from the flow duration curve. The line drawn through the
allowable load data points is called the target line.
The existing load is simply based on measured fecal coliform and copper concentrations and an
estimate of flow in the stream during sampling days, plus conversion factors. An example of this
calculation is provided:
1.28 cfs * 590 counts/100 ml * 1000 ml/l * 7.462 gallons/cfs * 3.785 l/gallon * 86400 sec./day
= 1.84 * 10^10 counts/day
In this TMDL, the estimate of flow comes from the USGS report of mean daily flow at Rocky
Branch (USGS 0208735012, see previous section). There is an exception to this statement, however;
between 1994 and 1996, DWQ used Marsh Cr. mean daily flow to calculate load on Pigeon House
Branch, as flow data did not become available until 1996 on Rocky Branch. The positioning of the
existing load on the plot is based on the recurrence interval (percent flow exceeded) of the estimated
flow. Existing loads that plot above the target line indicate a violation of the water quality criterion,
while loads plotting below the line represent compliance. The load duration plots for Pigeon House
Branch are shown in Figures 3 and 4.
Figure 3.
Load Duration Curve for Copper - Pigeon House Branch at
Dortch St. (DWQ Ambient Site) - 1994 to 2003
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
1.00E+01
1.00E+02
10 100
Percent Flow Exceeded
Cu

L
o
a
d

(
k
g
/
d
a
y
)
Existing load violations
Existing load
Allowable Load
Final version submitted to EPA
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Figure 4.
Further explanation on how load duration curves are used to calculate the TMDLs is provided
below.
4.0 Total Maximum Daily Load
A Total Maximum Daily Load is the maximum amount of a pollutant that a water body can receive
and still meet water quality standards, and an allocation of that amount among point and nonpoint
sources. A TMDL comprises the sum of wasteload allocations (WLA) for point sources, load
allocations (LA) for nonpoint sources, and a margin of safety. This definition is expressed by the
equation:
TMDL = S WLA + S LA + MOS
The objectives of the TMDL are to estimate allowable pollutant loads, and to allocate to the general
pollutant sources in the watershed. Providing recommendations for regulatory or other actions to
be taken to achieve compliance with applicable water quality criteria based on the relationship
between pollution sources and in-stream water quality conditions is more the focus of an
implementation strategy, which will be done separately following this assessment.
Load Duration Curve for Fecal Coliform - Pigeon House Branch
at Dortch St. (DWQ ambient site) - 1994 to 2003
1.00E+09
1.00E+10
1.00E+11
1.00E+12
10 100
Percent Flow Exceeded
Fe
c
a
l

C
o
l
i
f
o
r
m

Lo
a
d

(
c
o
u
n
t
s
/
d
a
y
)
Allowable Load
Existing Load
Existing Load Violations
Final version submitted to EPA
19
40 CFR §130.2 (i) states that TMDLs can be expressed in terms of mass per time (e.g. pounds per
day), toxicity, or other appropriate measures. The fecal coliform TMDL will be expressed in terms
of counts per day, and represents the maximum one-day load the stream can assimilate and maintain
the water quality criterion. For copper, the TMDL is expressed as micrograms per day, and
represents the maximum one-day load the stream can assimilate and maintain the water quality
criterion.
The two main components of a TMDL, the reduction target, including a margin of safety, and the
allocation strategy, will be presented in the following sections.
4.1 Reduction Target
To determine the amount of fecal coliform and copper load reduction necessary to comply with the
water quality criteria, the period of critical conditions and the existing loading must be established.
4.1.1 Existing Conditions
The load duration curves for the impaired streams in the watershed are presented in Figure 5 and 6
on following pages. The criteria violations occur at both high and low flows, which indicate that
impairment occurs during wet and dry weather. This also means that the sources of fecal coliform
and copper are both near the stream channel, as evidenced by high concentrations during dry
weather/low flow, and distant from the stream channel, as evidenced by high concentrations during
high flows. The wet weather fecal coliform impairment appears to be more intractable as, at higher
flows, the proportion of samples in violation of the allowable load to samples below the allowable
load is greatest.
Superimposed on the graphs is a trend through the data points violating the water quality criterion.
A power curve provided the best fit, as determined by the correlation coefficient, R2 (see Figures 5
and 6 below). The trend equations appear above the curves in each of the figures. Due to the
scatter in the fecal coliform violations, the best R2, 0.58, remained somewhat low (see Figure 6).
To represent the TMDLs as a single value, the existing load was calculated from the trend as the
average of the load violations occurring when the flow (or load) was exceeded at a frequency greater
Final version submitted to EPA
20
than 10 percent and less than 95 percent. Additionally, the average load is calculated by using
percent flow exceeded in multiples of 5 percent. Consideration of violations of the one-day
maximum fecal coliform criterion for Pigeon House Branch when the flow frequency is between 10
and 95 percent, yields loads ranging between 9.49 X 109 and 1.63 X 1011 counts/day. The average of
these values, 3.61 X 1010 counts/day, represents the total existing load in the stream. For copper, the
range of one-day violations of the criterion includes loads of between 7.20 X 106 and 2.08 X 109
kg/day, and an average of 3.81 X 107 ug/day. See Appendix II for a further breakdown of the
existing load calculations.
4.1.2 Reduction Target Calculation
The next step is to determine the percent reductions needed to comply with the water quality
criteria. For both copper and fecal coliform in Pigeon House Branch, the allowable load was
exceeded during all – low, average and high - streamflows. To calculate the necessary reduction in
load, DWQ considered all violations through the use of the trend curve.
DWQ calculated the percent reduction as the difference between the average of the trend curve load
estimates and the average of the allowable load estimates. For example, at each recurrence interval
between 10 and 95 (again using recurrence intervals in multiples of 5) the equation of the trend
curve is used to estimate the existing load; the allowable load is calculated in a similar fashion by
substituting the allowable load curve. Next, DWQ took the average of these estimates and
calculated the percent difference between the averages. For fecal coliform, the averages were 3.16 X
1010 and 7.83 X 109 counts/day for the existing and target loads, respectively. This equates to a 78%
reduction required. For copper, the averages were 3.81 X 107 and 1.29 X 107 ug/day for the
existing and target loads, respectively. This equates to a 66% reduction in load. Detailed
calculations for estimating the percent reduction for each stream are provided in Appendix II.
Final version submitted to EPA
21
Figure 5.
Figure 6.
4.1.3 Critical Conditions
Critical conditions are accounted for in the load curve analysis by using an extended period of
streamflow and water quality data, and by examining at what flows (percent flow exceeded) the
Load Duration Curve for Fecal Coliform - Pigeon House Branch
at Dortch St. (DWQ ambient site) - 1994 to 2003
y = 3E+12x^-1.2334
R2 = 0.5811
1.00E+09
1.00E+10
1.00E+11
1.00E+12
10 100
Percent Flow Exceeded
Fe
c
a
l

C
o
l
i
f
o
r
m

Lo
a
d

(
c
o
u
n
t
s
/
d
a
y
)
Allowable Load
Existing Load
Existing Load Violations
Power (Existing Load Violations)
Load Duration Curve for Copper - Pigeon House Branch at Dortch
St. (DWQ Ambient Site) - 1994 to 2003
y = 6.4834x-1.4939
R2 = 0.8145
1.00E-03
1.00E-02
1.00E-01
1.00E+00
1.00E+01
1.00E+02
10 100
Percent Flow Exceeded
Cu

L
o
a
d

(
k
g
/
d
a
y
)
Existing load violations
Existing load
Allowable Load
Power (Existing load violations)
Final version submitted to EPA
22
existing load violations occur. In theory, the flow range (percent flow exceeded) with the greatest
difference between the existing load violations trend line and the allowable load line may be the
critical condition. However, in Pigeon House Branch, the existing load violations occur at all flows,
so DWQ elected to use the average difference between the exiting load violation trend line and the
allowable load line.
4.2 Margin of Safety
There are two methods for incorporating an MOS in a TMDL analysis: a) implicitly incorporate the
MOS using conservative model assumptions to develop allocations; or b) explicitly specify a portion
of the TMDL as the MOS and use the remainder for allocations. In these TMDLs, an explicit MOS
was used.
To provide an explicit margin of safety, the allowable load curves above (Figures 5 and 6) use
adjusted standards of 6 ug/L copper (versus the actual standard of 7 ug/L for copper) and 360
counts/100mL for fecal coliform (versus the actual instantaneous standard of 400 counts/100mL).
This provides a 14% margin of safety for copper and a 10% margin of safety for fecal coliform.
4.3 TMDL Allocation
The TMDLs determined above for fecal coliform and copper must be allocated to a wasteload
allocation (WLA) and a load allocation (LA).
The Pigeon House Branch watershed is, for the most part, an urban landscape that is drained by a
network of stormwater pipes and sewers. Additionally, most of this stormwater network is included
in NPDES stormwater permits for Municipal Separate Storm Sewer System (MS4s). Specifically, the
City of Raleigh and the North Carolina Department of Transportation have Phase I MS4 permits for
NPDES stormwater discharge. Wake County, which has jurisdiction over some of the stormwater
network, is expected to be added to this regulatory framework in Phase II. The State of North
Carolina Government Complex and some federal land has stormwater infrastructure within the
Pigeon House Branch watershed that is currently not scheduled to be permitted through NPDES.
This may change, however. Also, fecal coliform and copper reductions will be sought from these
lands.
Final version submitted to EPA
23
The assumption in this TMDL is that all fecal coliform and copper enters the drainage network
through the storm sewer system, or via leaks in the sanitary sewer system, except that which travels
overland in sheet flow. The latter is assumed to occur within 50 feet of open channels of the Pigeon
House drainage network. Based on mapping done for the City of Raleigh by contractors, DWQ
defines the open channel network in Figure 7. The rationale for this assumption is that property
adjacent to streams is not likely to be piped; it is more likely that stormwater will travel overland or
in shallow groundwater to the stream channel.
Figure 7.
CA
LANE
JONES
WADE
T MARYS
PEACE
EDENTON EAST
GLENWOOD
BLOUNT
ELM
PARK
POLK
CLARK
BICKETT
FRANKLIWOODBURN
MORDECAI
SCALES
WEST
BLOODWORTH
JOHNSON
CAMERON
DANIELS
COLE
SALISBURY
WILLIAMSON
HARP
SMALLWOOD
COURTLAND
SUTTON
HARRINGTON
BENEHAN TUCKER
DAWSON
NASH
FILMORE
COLLEGE
POPLAR
GASTON
BOUNDARY
CEDAR
CALVIN
VIEW
GRAHAM
BOYLAN
SMEDES
NICHOLS
MCDOWELL
HILLCREST
HALIFAX
RAY
DALE
PACE
LINDEN
MORRI
CLAY
BRYAN
DEVEREUX
SEABOARD
ADAMS
HAYNES
NORTH
SWELL
PELL
BELLWOOD
FOREST
LAFAYE
WASHINGTON
TOWER
MULBERRY
HAWTHORNE
MARSHALL
HILLSBOROUGH
HINSDALE
BARDEN
EVERETT
FAISON
JAMES
MAIDEN
TILDEN
CLEVELAND
SNOW
PERSON
JEFFERSON
STAFFORD
EUCLID
CHEST
SYCAMO
MOS
MIMOSA
WILLARD
BROOKLYN
GROVELAND
BEDFORD
DELWAY
GLOVER
AMBLESIDE
FERNDELL
DORTCH
WILMINGTON
WILLS FOREST
WIREWOOD
CAMERON PARK
CLOVE
MORSON
OLD WILLIAMSON
BENJAMIN
PACE
JOHNSON
FRANKLIN
LANE WEST
BOYLAN
HARP
HARP
BLOUNT
NORTH
ELMOBERLIN
NORTH
CEDAR
MARSHALL
ELM
PERSON
ST MARYS
CDUMAS24-FEB-03
N
Phcntrln.shp
Pigeonhousebasin.shp
Phroads.shpPropertyClip1.shpRailroad.shpSubbasin.shpSub_rail.shpSub_county.shpSub_state.shpSub_city.shp
Ph_subwatershed.shp
Ph_sub_hydro.shp
Rail = .87County = 41.43
State = 108.76City = 63.22
ACREAGE
LEGEND
*Completely within ETJ and City Limits
City - County - State - Railroad
TOTAL ACREAGE: 798
Pigeon House Stormwater Jurisdiction
Information depicted hereon is for reference purposes only, and is compiled from the best available sources.The City of Raleigh assumes no responsibility for errors arising from the misuse of this map.
Notes on Figure 7: 1 “ = 1300 ft., watershed area is outlined
The area noted for the ‘rail’ category in Figure 7 is low because the area of all the railroad tracks and rights of way do not
show as parcels under the county’s property database. The true area for the ‘rail’ category is probably closer to 20 to 30
acres.
Final version submitted to EPA
24
Considering that the lion’s share of the watershed is drained by current or near future NPDES
stormwater permit holders, the lion’s share of the TMDL will be put in the WLA, per EPA guidance
(personal communication, EPA Region IV). In accordance with 40 CFR §130.2 (i), it is reasonable
to express allocations for NPDES-regulated stormwater discharges from multiple point sources as a
single waste load allocation (WLA), rather than assigning individual WLAs to each stormwater
outfall within the MS4 area. Additionally, DWQ will not attempt to separate NPDES regulated
stormwater from non-NPDES regulated stormwater; they will be lumped together in the WLA
because there is insufficient technical basis to separately quantify the NPDES and non-NPDES
stormwater loading.
4.3.1 Load Allocations
To calculate a load allocation, DWQ assumed that the 50 feet on either side of an open drainage
channel (see Figure 7 for display of open drainage channels) would drain directly to the stream
network (not via the storm sewer network) and hence should be included in the LA. The open
channel mapping comes from the City of Raleigh. Based on this, DWQ calculated that 0.03 square
miles (8600 feet in length times 50 feet on either side of drainage) drain by means other than
stormwater piping to open channels. 0.03 square miles is 0.026 percent of the 1.15 square miles in
the Pigeon House subwatershed (up to the monitoring station at Dortch St.), so the LA portion of
the TMDL, using the listed assumptions, is diminutive.
The LAs are 0.026 percent of the TMDLs, which equals 5.16 X 104 ug/day for copper, and 3.13 X
107 counts/day for fecal coliform.
4.3.2 Wasteload Allocations
For the Pigeon House Branch TMDL, the WLA consists of copper and fecal coliform loading from
the stormwater system, regardless of what entity has jurisdiction over the outfall. There are no
continuous NPDES discharges in the watershed. The WLA component was calculated as the
difference between the TMDL and the LA components. See Table 8 for the full TMDL allocation.
Final version submitted to EPA
25
Any future NDPES facility (in this case, continuous discharge) permitted to discharge fecal coliform
bacteria or copper in the watershed will be required to meet permit limits. Future facilities
discharging at concentrations less than the water quality standard should not cause or contribute
fecal coliform bacteria or copper impairment in the watershed.
Table 8. Pigeon House Branch Fecal Coliform and Copper TMDL Components
Pollutant WLA 1 LA 2 MOS 3 TMDL Percent
Reduction4
Fecal Coliform 7.63E+09
counts/day
2.04E+08
counts/day Explicit 7.83E+09
counts/day 78%
Copper 1.26E+07
ug/day
3.35E+05
ug/day Explicit 1.29E+07
ug/day 66%
Notes:
1. All future permitted discharges shall not exceed the water quality criteria for fecal coliform
bacteria maximum one-day concentration of 400 counts/100mL or a monthly average of 200
counts/100mL. WLA=TMDL – LA (see note 2).
2. LA = TMDL multiplied by area drained by unpiped flow (see 4.3.1), where TMDL is the
average allowable load between the 95th and 10th percent flow exceeded.
3. Margin of safety (MOS) equivalent to 10 percent of the target concentration for fecal
coliform and 14 percent for copper (see 4.2).
4. Average reduction required between the 95th and 10th percent flow exceeded estimated in the
stream. Used only DWQ ambient data in calculations (see Section 1.2).
4.4 Seasonal Variation
Seasonal variation was incorporated in the load curves by using the entire period of record of flow
recorded at the gages. Seasonality was also addressed by using water quality data that was collected
during multiple seasons.
5.0 Implementation Plan
The TMDL analysis was performed using the best data available to specify the percent reductions
necessary to achieve water quality criteria. The intent of meeting the criteria is to support the
designated use classifications in the watershed. As a class C water, the designated uses that apply to
Pigeon House Branch are aquatic life propagation and maintenance of biological integrity, and
secondary recreation.
Final version submitted to EPA
26
Achieving reductions in copper loading may be particularly challenging as changes to the sources
(brake linings, building siding and atmospheric loading) are not feasible in the near term. They
would require, for instance, changes to how automobile brakes are constructed. To reduce copper
loading a more likely, though still quite challenging, scenario is to treat stormwater before it enters
the stream network. Stormwater from roadways, in particular, will need to be treated to maintain
water quality standards. The good news in this case is that the copper impairment is not very severe.
According the synoptic surveys by the City of Raleigh (see Water Quality Monitoring section on p.
9, and Appendix I) several hot spots exist, including the entrance to the Equipment Service Depot
off of West St. and the culvert between West St. and Peace Street. Best management practice (BMP)
installation directed at reducing copper loading, and fecal coliform as well, should probably focus on
these areas.
An important component of the fecal coliform TMDL implementation plan will be the bacterial
source tracking project that DWQ and the City of Raleigh are scheduled to begin this year as part of
a larger EPA 319 project. Using antibiotic resistance techniques, the agencies and their contractor
will categorize the sources of the bacteria found in the stream. The source categories are expected
to be humans, pets and wildlife. This, along with Raleigh’s source assessment efforts (see Appendix
I), will provide better criteria for formulating a management strategy, and subsequently for installing
BMPs, to reduce fecal coliform loading. Of course, the overall goal is to meet the designated use of
allowing secondary recreation, and should the management strategy and initial BMPs fail to do that,
additional BMPs will be required.
5.1 Urban Sources of Pollutant Loading
The City of Raleigh and the NC Department of Transportation were issued a NPDES Municipal
Separate Storm Sewer System (MS4) permits under the Phase 1 storm water regulations. Each
permittee is required to develop a Storm Water Management Program (SWMP). The SWMP covers
the duration of the permit (5-year renewable) and comprises a comprehensive planning process
which involves public participation and intergovernmental coordination to reduce the discharge of
pollutants to the maximum extent practicable using management practices, control techniques,
public education, and other appropriate methods and provisions. With respect to fecal coliform and
Final version submitted to EPA
27
copper pollution reduction, additional activities and programs conducted by city, county, and state
agencies are recommended to support the SWMP:
· Field screening and monitoring programs to identify the types and extent of
fecal coliform and copper water quality problems, relative degradation or
improvement over time, areas of concern, and source identification.
· Requirements that all new and replacement sanitary sewage systems are
designed to minimize discharges from the system into the storm sewer
system.
· Mechanisms for reporting and correcting illicit connections, breaks,
surcharges, and general sanitary sewer system problems with potential to
release to the municipal separate storm sewer system.
6.0 Stream Monitoring
In order to evaluate the fecal coliform model, monitor water quality conditions and assess progress
of the TMDL, an evaluation location was established for the Pigeon House Branch watershed. The
evaluation location of this watershed is Pigeon House Branch at Dortch St., which is the DWQ
ambient monitoring station. DWQ should consider moving the ambient monitoring station closer
to Pigeon House Branch’s confluence with Crabtree Creek, which defines the extent of the fecal
coliform and copper impairments. Additionally, for this reason, reductions in copper and fecal
coliform loading should be sought from the entire Pigeon House Branch watershed to its
confluence with Crabtree Creek. Fixes (e.g. BMP installation) should be applied where sources
have been identified, and in subwatersheds where there are high levels of fecal coliform or copper.
Continued monitoring of the fecal coliform concentration at multiple water quality sampling points
in the watershed is critical in characterizing sources of fecal coliform contamination and
documenting future reduction of loading. Monitoring should be expanded to provide water quality
information to characterize seasonal trends and refined source identification and delineation. In
addition, monitoring efforts should be refined and enhanced in order to characterize dry and wet
season base flow conditions (concentrations) and promote selective storm response (hydrograph)
characterization. The Storm Water Management Program (see previous page) is a good means for
achieving the continued and increased monitoring.
Final version submitted to EPA
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7.0 Future Efforts
This TMDL represents an early phase of a long-term restoration project to reduce fecal coliform
and copper loading to acceptable levels (meeting water quality standards) in the Pigeon House
Branch watershed. DWQ and the City of Raleigh should evaluate the progress of implementation
strategies, and refine the TMDL as necessary, in the next phase (five-year cycle). This will include
recommending specific implementation plans for identified problem areas. 319 nonpoint source
grants may be a good source of funding for BMP implementation.
8.0 Public Participation
DWQ will publish a notice in the Raleigh newspaper, The News & Observer, outlining information
on the development of this draft TMDL and will allow the public 30 days to comment on the draft.
Additionally, during this public notice period, DWQ will present the TMDL to the public on May 6,
2003 and offer opportunity for questions and comments.
9.0 Further Information
Further information concerning North Carolina’s TMDL program can be found on the Internet at
the Division of Water Quality website:
http://h2o.enr.state.nc.us/tmdl/
Technical questions regarding this TMDL should be directed to the following members of the
DWQ Modeling/TMDL Unit:
Chris Roessler, Modeler
e-mail: [e-mail]
Michelle Woolfolk, Supervisor
e-mail: [e-mail]
Final version submitted to EPA
29
References
Center for Watershed Protection. 1999. Microbes and Urban Watersheds: Concentrations, Sources
and Pathways. Watershed Protection Techniques 3(1): 554:565.
Cleland, B.R. 2002. TMDL Development from the “Bottom Up” – Part II: Using load duration
curves to connect the pieces. Proceedings from the WEF National TMDL Science and Policy 2002
Conference.
Davis, A.P., Shokouhian, M. and Ni, S. 2001. Loading estimates of lead, copper, cadmium and zinc
in urban runoff from specific sources. Chemosphere 44, 997-1009.
Hewitt, C.N., and Rashed, M.B. 1990. An integrated budget for selected pollutants for a major rural
highway. Sci. Total Environ. 93 (1), 375-384.
Malmqvist, P.A. 1983. Urban stormwater pollutant sources, Chaliners University Gothenberg, as
referenced by Hewitt, C.N., and Rashed, M.B. (1990) Sci. Total Environ. 93 (1), 375-384.
Sheely, L. H. July 2002. Load Duration Curves: Development and Application to Data Analysis for Streams in
the Yazoo River Basin, MS. Special Project – Summer 2002. Jackson Engineering Graduate Program.
Stiles, T.C. 2002. Incorporating hydrology in determining TMDL endpoints and allocations.
Proceedings from the WEF National TMDL Science and Policy 2002 Conference.
U.S. Environmental Protection Agency (USEPA). 1991. Guidance for Water Quality-Based
Decisions: The TMDL Process. Assessment and Watershed Protection Division, Washington, DC.
U.S. Environmental Protection Agency (USEPA). 2000a. Revisions to the Water Quality Planning
and Management Regulation and Revisions to the National Pollutant Discharge Elimination System
Program in Support of Revisions to the Water Quality Planning and management Regulation; Final
Rule. Fed. Reg. 65:43586-43670 (July 13, 2000).
U.S.Environmental Protection Agency (USEPA). 2001. Protocol for Developing Pathogen TMDLs.
Office of Water, Washington DC. EPA 841-R-00-001.
U.S. Environmental Protection Agency (USEPA). 2003. Draft Total Maximum Daily Load
Development for Fecal Coliform in the Duck River Watershed, Coffee and Bedford Counties,
Tennessee. USEPA Region IV, Atlanta, Georgia.
United States Geological Survey (USGS). 2001. Water Resources of the United States. NWIS web
online hydrologic data: http://water.usgs.gov.
Wayland, R. 2002. November 22, 2002 Memo from Robert Wayland of the U.S. Environmental
Protection Agency to Water Division Directors. Subject: Establishing TMDL Waste Load
Allocations for stormwater sources and NDPES permit requirements based on those allocations.
Final version submitted to EPA
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APPENDIX I.DWQ Ambient data for fecal coliform and copper
date fecal coliform (cfu/100 ml)data qualifier copper (ug/L)data qualifier
9/28/94 1200 26
10/26/94 1200 14
11/29/94 400 10
12/27/94 70 6
1/23/95 260 3
2/24/95 280 6
3/21/95 530 39
4/12/95 870 13
5/9/95 1700 6
6/8/95 10 K 380
7/26/95 7200 22
8/8/95 1200 28
9/12/95 430 13
10/26/95 420 12
12/21/95 36 4
1/26/96 9 4
2/6/96 10 12
4/24/96 400 24
5/1/96 1000 8
6/10/96 6900 19
7/1/96 230 21
8/8/96 1000 16
9/25/96 100 9
10/2/96 2500 12
11/5/96 240 5
12/4/96 1100 K 5
1/16/97 7300 32
2/11/97 810 7
3/5/97 690 6
4/8/97 160 5
5/8/97 100 3
6/11/97 1300 12
7/22/97 620 28
8/27/97 3000 12
9/25/97 6800 22
10/14/97 230 14
11/12/97 510 5.7
12/5/97 560 16
1/9/98 960 12
2/9/98 120 6.1
3/5/98 140 6.1
Final version submitted to EPA
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date fecal coliform (cfu/100 ml)data qualifier copper (ug/L)data qualifier
4/8/98 2300 4.6
5/11/98 6000 L 21
6/1/98 2200 20
7/7/98 6000 L 13
8/18/98 3100 17
9/8/98 13000 L 22
10/5/98 14000 L 8.1
11/10/98 2000 7.8
12/1/98 260 4.6
1/12/99 2300 5.4
2/8/99 650 3
3/3/99 580 7.5
4/16/99 6000 L 2 K
5/13/99 660 13
6/2/99 11000 L 12
8/11/99 210 14
9/8/99 2500 23
10/4/99 14000 L 8.4
11/10/99 590 3.8
12/6/99 600 L 29
1/20/00 1100 28
2/7/00 220 2 K
3/13/00 540 41
4/12/00 600 L 2
5/9/00 2700 7.4
6/19/00 4700 22
7/18/00 170 20
8/17/00 710 15
9/2/00 4100 10
10/23/00 3200 4.7
11/28/00 760 9.5
12/7/00 250
1/23/01 2600
2/28/01 710
5/8/01 660 B4,Q
6/21/01 200 Q
7/23/01 1900 B1,Q
9/24/01 2800 Q
10/11/01 810 Q,B4
11/29/01 370
Notes: Data qualifiers are: K - Actual value is known to be less than value given. L - Actual value is
known to be greater than value given. B4 – Filters have counts of both > 60 or 80 and <2. Data
Final version submitted to EPA
32
qualifier continued Reported value is a total of the counts from all countable filters reported per 100
ml. Q – Holding time exceeded.
APPENDIX I. City of Raleigh - Refined Sampling Program Data
DATE LOCATION LAND
USE
Cu (mg/L)F. C.(CFU/100mL)
6/6/01 1. W Johnson St.comm/res.3 2800
6/6/01 2. West St.comm/res.2 1900
6/6/01 3. culvert - West St. to Peace St.comm/res.6 14000
6/6/01 4. entrance to ESD off West St.multi 2 11000
6/6/01 5. West St. (Thomas Concrete)multi 3 3100
6/6/01 6. connector - Wade Ave. to Glenwood Ave.res.1 1600
6/6/01 7. Harris Wholesale off Capital Blvd.multi 1 1200
6/6/01 8. Gravel Service Rd. parallel to Capital Blvd.multi 3 2200
6/6/01 9. Crabtree Blvd.multi 2 2100
6/6/01 10. Automotive Way res.1 5700
6/6/01 11. Frank St.res.1 2100
6/6/01 12. N Boundary St.res.5 950
6/13/01 1. W Johnson St.comm/res.2 9200
6/13/01 2. West St.comm/res.2 2900
6/13/01 3. culvert - West St. to Peace St.comm/res.5 39000
6/13/01 4. entrance to ESD off West St.multi 1 3800
6/13/01 5. West St. (Thomas Concrete)multi 4 1900
6/13/01 6. connector - Wade Ave. to Glenwood Ave.res.2 1800
6/13/01 7. Harris Wholesale off Capital Blvd.multi 2 11000
6/13/01 8. Gravel Service Rd. parallel to Capital Blvd.multi 2 1000
6/13/01 9. Crabtree Blvd.multi 2 920
6/13/01 10. Automotive Way res.1 1900
6/13/01 11. Frank St.res.1 3800
6/13/01 12. N Boundary St.res.63 3200
6/21/01 1. W Johnson St.comm/res.2 7500
6/21/01 2. West St.comm/res.2 860
6/21/01 3. culvert - West St. to Peace St.comm/res.10 1500
6/21/01 4. entrance to ESD off West St.multi 3 56000
6/21/01 5. West St. (Thomas Concrete)multi 5 1900
6/21/01 6. connector - Wade Ave. to Glenwood Ave.res.2 1700
6/21/01 7. Harris Wholesale off Capital Blvd.multi 2 29000
6/21/01 8. Gravel Service Rd. parallel to Capital Blvd.multi 3 1100
6/21/01 9. Crabtree Blvd.multi 2 1100
6/21/01 10. Automotive Way res.2 1400
6/21/01 11. Frank St.res.2 2200
6/21/01 12. N Boundary St.res.2 3800
6/27/01 1. W Johnson St.comm/res.2 2200
6/27/01 2. West St.comm/res.2 1600
Final version submitted to EPA
33
6/27/01 3. culvert - West St. to Peace St.comm/res.4 1600
6/27/01 4. entrance to ESD off West St.multi 4 32000
6/27/01 5. West St. (Thomas Concrete)multi 6 5000
6/27/01 6. connector - Wade Ave. to Glenwood Ave.res.1 600
6/27/01 7. Harris Wholesale off Capital Blvd.multi 1 9600
6/27/01 8. Gravel Service Rd. parallel to Capital Blvd.multi 4 2200
6/27/01 9. Crabtree Blvd.multi 3 8000
6/27/01 10. Automotive Way res.2 2800
6/27/01 11. Frank St.res.4 9800
6/27/01 12. N Boundary St.res.2 6000
7/5/01 1. W Johnson St.comm/res.4 5800
7/5/01 2. West St.comm/res.4 4300
7/5/01 3. culvert - West St. to Peace St.comm/res.7 21000
7/5/01 4. entrance to ESD off West St.multi 10 4100000
7/5/01 5. West St. (Thomas Concrete)multi 7 18000
7/5/01 6. connector - Wade Ave. to Glenwood Ave.res.4 6200
7/5/01 7. Harris Wholesale off Capital Blvd.multi 2 6800
7/5/01 8. Gravel Service Rd. parallel to Capital Blvd.multi 5 4800
7/5/01 9. Crabtree Blvd.multi 5 5800
7/5/01 10. Automotive Way res.3 8800
7/5/01 11. Frank St.res.2 12000
7/5/01 12. N Boundary St.res.2 4700
7/12/01 1. W Johnson St.comm/res.2 1500
7/12/01 2. West St.comm/res.2 3500
7/12/01 3. culvert - West St. to Peace St.comm/res.3 2000
7/12/01 4. entrance to ESD off West St.multi 3 58000
7/12/01 5. West St. (Thomas Concrete)multi 5 8000
7/12/01 6. connector - Wade Ave. to Glenwood Ave.res.1 2000
7/12/01 7. Harris Wholesale off Capital Blvd.multi 2 500
7/12/01 8. Gravel Service Rd. parallel to Capital Blvd.multi 2 1
7/12/01 9. Crabtree Blvd.multi 2 5500
7/12/01 10. Automotive Way res.5 3500
7/12/01 11. Frank St.res.2 3500
7/12/01 12. N Boundary St.res.2 2000
7/18/01 1. W Johnson St.comm/res.1 700
7/18/01 2. West St.comm/res.2 2200
7/18/01 3. culvert - West St. to Peace St.comm/res.3 700
7/18/01 4. entrance to ESD off West St.multi 26 31500
7/18/01 5. West St. (Thomas Concrete)multi 5 800
7/18/01 6. connector - Wade Ave. to Glenwood Ave.res.2 200
7/18/01 7. Harris Wholesale off Capital Blvd.multi 10 5600
7/18/01 8. Gravel Service Rd. parallel to Capital Blvd.multi 2 700
7/18/01 9. Crabtree Blvd.multi 2 500
7/18/01 10. Automotive Way res.2 600
7/18/01 11. Frank St.res.1 200
Final version submitted to EPA
34
7/18/01 12. N Boundary St.res.2 600
7/25/01 1. W Johnson St.comm/res.3 17000
7/25/01 2. West St.comm/res.5 17000
7/25/01 3. culvert - West St. to Peace St.comm/res.12 27000
7/25/01 4. entrance to ESD off West St.multi 7 270000
7/25/01 5. West St. (Thomas Concrete)multi 18 110000
7/25/01 6. connector - Wade Ave. to Glenwood Ave.res.5 12000
7/25/01 7. Harris Wholesale off Capital Blvd.multi 2 33000
7/25/01 8. Gravel Service Rd. parallel to Capital Blvd.multi 8 15000
7/25/01 9. Crabtree Blvd.multi 6 27000
7/25/01 10. Automotive Way res.2 18000
7/25/01 11. Frank St.res.2 20000
7/25/01 12. N Boundary St.res.2 10000
Pigeon House Branch Locations Index (provided by the City of Raleigh)
Location 1: Stream at West Johnson St. This location is at Edna Metz Wells Park at the intersection of
W. Johnson St and Peace St. This is a small park in an older residential neighborhood near
Cameron Village. Samples were taken in the stream just upstream of the culvert under E Forest Rd.
Grass, trees and other vegetation surround the creek, as well as numerous trash barrels. No sources
of pollution or contamination are visible, although higher fecal coliform levels may be a result of
neighborhood residents walking their dogs near the stream, as has been witnessed on numerous
occasions. Much, but not all, of the stream is shaded by trees during the day.
Location 2: Stream at West St. Samples were taken in the creek before it enters the culvert crossing
under West St; the culvert begins just north of the intersection of West St with Tucker St. This
location is in a commercial area with the creek paralleling a small parking lot on the southern side of
the creek. Throughout the day, trees shade the vast majority of the creek. No sources of pollution
are visible, however, evidence of homeless activity is clearly visible through old shirts and jackets
present, some hanging in trees, others lying in the water. Human contamination may be a partial
explanation for higher fecal coliform levels.
Location 3: Pipe discharging to culvert between West St. and Peace St. Samples were taken from a 60-in
concrete pipe approximately 450-ft into the box culvert (when measuring from the south to the
north end of the culvert) that collects stormwater from the State Government Complex. Flow from
this pipe is always steady and constant. No apparent pollution or contamination is visible, but
homeless activity is a possibility inside the culvert.
Location 4: Pipe discharging just upstream of entrance to ESD off West St. The creek parallels West St and
flows under the entrance to the Equipment Service Depot south of Dortch St. The sample is taken
immediately from a 54-in concrete pipe running perpendicular to Capital Blvd. Shade and other
factors surrounding the stream are not an influence on this sample because the sample is taken as
the water leaves the pipe. It has been suggested that there may be a sanitary sewer line running
Final version submitted to EPA
35
parallel to Capital Blvd (this has not been confirmed), and possible sanitary sewer leaks would
account for higher fecal coliform levels.
Location 5: Stream at West St. (Thomas Concrete). This site is located directly across the street from
Thomas Concrete on West St. The creek is shaded by trees and much other vegetation for the
majority of the day, if not all of the day. Thomas Concrete has an NPDES permitted storm drain
that outlets directly into the creek; residue and chunks of concrete are clearly visible and in the
morning hours, it is quite evident that this has an impact on the conditions immediately surrounding
the outfall. Due to this clear contamination, samples are taken immediately upstream of the Thomas
Concrete storm drainage site so the Thomas Concrete water may not contaminate the sample.
NOTE: The pH of water draining from Thomas Concrete is always at least above 10.0, usually around 11.5 and reaching
up to 12.2 on some days.
Location 6: Stream at connector ramp from Wade Ave to Glenwood Ave. This sample is taken from the
tributary flowing from the direction of Williamson Dr, just downstream from the Glenwood Ave
culvert—not from the direction of Cowper Dr (the tributaries are separate and then join together at
this site). This site is not shaded, as there are no large trees to offer shade nearby. This site is at
an island connector between two busy streets, which should limit the amount of human and animal
activity at the site. No evidence of human activity or domestic animals is visible.
Location 7: Pipe at Harris Wholesale off Capital Blvd. Harris Wholesale is located off northbound
Capital Blvd between Fairview Rd and Wake Forest Rd. Samples are taken from the 96-in concrete
pipe that runs perpendicular to Capital Blvd underneath Harris Wholesale; the samples are taken
directly from the pipe. No apparent causes of pollution or contamination are visible other than
wildlife present in the stream. Flow is not steady; it varies between a higher, steady flow and a low
flow, sometimes even a trickle.
Location 8: Stream at gravel service road parallel to Capital Blvd. As Atlantic Ave passes underneath
Capital Blvd, there is a gravel service road running under the overpass between the northbound and
southbound lanes of Capital Blvd above. At this point, the creek is surrounded by dense vegetation
with nearby trees shading the stream in various sections. No obvious sources of pollution or
contamination are visible.
Location 9: Stream at Crabtree Blvd. Samples are taken from the creek as it passes under Crabtree
Blvd near its intersection with Capitol Blvd., just downstream from the Gateway Plaza Shopping
Center. There are many trees and other vegetation that shade the sections of the stream. Large
boulders, rocks, and other riprap are on the slope leading from the parking lot on the east bank of
the stream. Many broken beer and liquor bottles can be seen along the rocks indicating possible
human contamination.
Location 10: Stream at Automotive Way. The sample site is in front of a car wash located on
Automotive Way as it merges into Capital Blvd. The stream flows from the direction of Plainview
Ave. and then into a culvert that passes under Capital Blvd for a short time. The samples are taken
from the stream before it enters the culvert. There are no trees at the site nor other vegetation
offering shade to the stream. Besides the hand car wash and a nearby house, there are no visible
pollution or contamination sources.
Final version submitted to EPA
36
Location 11: Stream at Frank St. Samples are taken near the intersection of Frank St and Norris St,
before the stream passes under Frank St. Nearby trees and vegetation do offer shade to some areas
of the stream but not all. The site is in a neighborhood and alongside a large patch of grass where
many people are likely to walk their dogs and other domestic pets.
Location 12: Stream at North Boundary St. This location is within Oakwood Cemetery. The creek
passes through a culvert under Oakwood Ave and flows north through the cemetery. No shade is
offered to the creek through the cemetery. The streambanks are covered by grass and more dense
vegetation. No apparent pollution or contamination is visible.
Final version submitted to EPA
37
Appendix II. TMDL Calculations
Copper load allocation at Pigeon House ambient site based on
trendline equation and percent flow exceeded.
Power Eqn. Trendline:y = 6.4834x^-1.4939
where: x = percent flow exceeded
Percent
Flow
Exceeded
Existing
Load
(kg/day)
Target load
(kg/day)
% Reduction
95 7.20E-03 3.28E-03 54.4%
90 7.80E-03 4.57E-03 41.5%
85 8.50E-03 4.99E-03 41.3%
80 9.31E-03 5.99E-03 35.6%
75 1.02E-02 6.46E-03 37.0%
70 1.14E-02 6.99E-03 38.5%
65 1.27E-02 7.56E-03 40.4%
60 1.43E-02 7.70E-03 46.1%
55 1.63E-02 8.42E-03 48.3%
50 1.88E-02 9.27E-03 50.6%
45 2.20E-02 9.84E-03 55.2%
40 2.62E-02 1.08E-02 58.6%
35 3.20E-02 1.20E-02 62.5%
30 4.03E-02 1.37E-02 66.0%
25 5.29E-02 1.57E-02 70.3%
20 7.38E-02 2.00E-02 72.9%
15 1.13E-01 3.00E-02 73.6%
10 2.08E-01 5.56E-02 73.2%
average reduction 53.7%
Target load based on estimated flow and target conc of 6 ug/L
Existing load based on trendline equation - power equation
Only used DWQ ambient data for these calculations (see
Section 1.2)
Final version submitted to EPA
38
avg existing load (95 to 10 interval)3.81E-02
avg target load (95 to 10 interval)1.29E-02
avg reduction 66%
Appendix II. TMDL Calculations continued
F.C. load allocation at Pigeon House ambient site based on trendline equation
and percent flow exceeded
Power Eqn. Trendline:3E+12* x^-1.264
where: x = percent flow exceeded
Percent
Flow
Exceeded
Existing Load
(cnts/day)
Target load
(cnts/day)
% Reduction
95 9.49E+09 1.99E+09 79.1%
90 1.02E+10 2.76E+09 72.8%
85 1.09E+10 3.02E+09 72.3%
80 1.18E+10 3.63E+09 69.2%
75 1.28E+10 3.91E+09 69.5%
70 1.40E+10 4.23E+09 69.7%
65 1.53E+10 4.58E+09 70.1%
60 1.70E+10 4.66E+09 72.5%
55 1.89E+10 5.10E+09 73.1%
50 2.14E+10 5.61E+09 73.7%
45 2.44E+10 5.96E+09 75.6%
40 2.83E+10 6.56E+09 76.8%
35 3.35E+10 7.25E+09 78.4%
30 4.07E+10 8.29E+09 79.7%
25 5.13E+10 9.50E+09 81.5%
20 6.80E+10 1.21E+10 82.2%
15 9.78E+10 1.81E+10 81.5%
10 1.63E+11 3.37E+10 79.4%
Average reduction 75.4%
Final version submitted to EPA
39
Target load based on estimated flow and target conc of 360 counts/100mL
Existing load based on trendline equation - power equation
Only used DWQ ambient data for these calculations (see Section 1.2)
avg existing load (95 to 10 interval)3.61E+10
avg target load (95 to 10 interval)7.83E+09
avg reduction 78%
Final version submitted to EPA
40
Appendix III.
Responsiveness Summary for TMDLs for fecal coliform and copper to Pigeon House Branch -
Raleigh, NC
NC Division of Water Quality
May, 2003
Comments from specified organizations are in italics as they appear in the delivered documents.
DWQ’s response follows in plain text.
The City of Raleigh would like to thank the State for the opportunity to comment on the draft
Pigeon House Branch TMDL prepared by Division of Water Quality staff. We have the
following comments:
1.The City of Raleigh takes exception to the placement of stormwater in the wasteload allocation (WLA) of the draft
TMDL. There is, and has always been, a clear distinction between wastewater, which is a point source, and
stormwater, which is a non-point source. Including stormwater in the WLA ignores this critical distinction.
Placement of stormwater in the WLA contradicts the established understanding of the nature of non-point source
pollution. In addition, including stormwater under the WLA may place limitations on issuance of new NPDES
permits in this impaired (303(d) listed) water; may prohibit the State from issuing an NPDES Phase II Stormwater
permit to Wake County; and could possibly be interpreted to require a moratorium on new development or expansions
within the watershed. Such a moratorium would apply to city, state, and federally owned properties as well as private
property.
DWQ agrees with the City of Raleigh that NPDES stormwater does not belong in the WLA.
However, EPA has mandated that NPDES stormwater shall be put in the WLA. As far as what
Raleigh has suggested for the effects of allocating the TMDL this way, DWQ will move forward by
using appropriate alternatives for the management of stormwater runoff in accordance with these
TMDLs. We anticipate that this will focus on the best management practices to meet these
requirements, while still allowing additional activities to occur in these areas.
2.The City of Raleigh takes exception to both NPDES and non-NPDES permitted stormwater discharges being
lumped together under the WLA primarily because this may become a significant issue during the implementation
phase of the TMDL. The City of Raleigh would only support this arrangement if the City could be assured that those
entities not identified as holding NPDES permits (such as the railroad and downtown NC Government complex)
would be subject to the same restrictions and would be held accountable
for reducing their pollutant loads similar to those entities that have NPDES permits.
Because there is insufficient technical basis to separately quantify the NPDES and non-NPDES
stormwater loading, DWQ, with EPA’s consent, decided to combine the two stormwater categories
Final version submitted to EPA
41
together. DWQ will seek pollutant load reductions from all sources within the watershed. Clearly,
however, the regulatory agencies have more control over sources that require NPDES permits. The
difference is that implementation of BMPs is mandatory for NPDES stormwater permit holders,
while TMDL required load reductions are more or less voluntary for non-NPDES sources.
3. The City of Raleigh takes exception to the inference that the Department of Transportation (NCDOT) is the only
State entity accountable under the State’s NPDES stormwater permit. Since there are other portions of the
Municipal Separate Storm Sewer System (MS4) outside of the jurisdiction of NCDOT that are owned and operated
by the State, such as the downtown government complex, these areas should be included under the State’s NPDES
stormwater permit. In addition, it would appear that the State’s
NPDES stormwater permit would legally have to be issued for the State MS4 as a whole, under the signature of the
State CEO, and that an individual department such as NCDOT would not qualify for separate permitting for just
their portion of the MS4.
DWQ understands this concern and is continuing to investigate the issue. DWQ wants to assure
that the best alternatives for addressing stormwater discharges from various activities in this area,
from both a management and permitting perspective, are used.
4. The City of Raleigh would argue that under section 2.2.5, birds and other wildlife are a source of fecal coliform
bacteria (FCB) throughout the watershed and not just in isolated urban areas as indicated.
This section has been changed to reflect Raleigh’s comment.
5.The City of Raleigh takes exception to the statement in the 3rd paragraph of 4.3 that “Raleigh defines” the open
channel network as illustrated. Raleigh has never “defined” the open channel system. There may be many more open
channels within the watershed than those noted on the map. The system shown is simply based on maps prepared by
contractors for the City of Raleigh.
Changed to ‘Based on mapping done for the City of Raleigh by contractors, DWQ defines the open
channel network in Figure 7’.
6.The City of Raleigh would take exception to the assumption in the 3rd paragraph of section 4.3 that “all fecal
coliform and copper enters the drainage network through the storm sewer system”. There is strong evidence from
Charlotte studies that some FCB is transported directly to streams through underground flows from leaking sewers and
failing septic systems. The magnitude of the contribution from these sources is unknown at this time.
Final version submitted to EPA
42
This sentence has been changed as follows: the assumption in this TMDL is that all fecal coliform
and copper enters the drainage network through the storm sewer system or via leaks in the sanitary
sewer system except that which travels overland in sheet flow.
7.The City of Raleigh believes that the acreage noted under the “rail” category in Figure 7 is far greater than the .87
acres noted.
The area noted for the ‘rail’ category in Figure 7 is low because the area of all the railroad tracks and
rights of way do not show as parcels under the county’s property database. The true area for the
‘rail’ category is probably closer to 20 to 30 acres. This will be noted below Figure 7.
8.The City of Raleigh believes that the 0.03 acres assigned to the Load Allocation in section 4.3.1 is incorrect due to
a math error.
Raleigh is correct; this is a mistake in the draft TMDL. It should read 0.03 square miles, not acres.
Corrections have been made in the final TMDL.
9.The City of Raleigh believes that the phrase “and the problem pollutants” in the last sentence of the 1st paragraph of
section 5.0 should be removed since this would indicate that uses apply to pollutants as opposed to streams.
The phrase “and other problem pollutants” has been removed.
END OF RESPONSIVENESS SUMMARY
END OF TMDL DOCUMENT