HUC 10280202 – Lower Chariton Subbasin Water body ID#: 0674 Pollutant(s): Pathogens as indicated by Escherichia coli Prepared by: Watershed Protection Section Total Maximum Daily Load (TMDL) for Mussel Fork Adair, Linn, Macon and Sullivan counties Pollutants of concern: Pathogens Completed: Feb. 8, 2017 Approved:
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HUC 10280202 – Lower Chariton Subbasin
Water body ID#: 0674
Pollutant(s): Pathogens as indicated by Escherichia coli
Prepared by: Watershed Protection Section
Total Maximum Daily Load (TMDL)
for
Mussel Fork Adair, Linn, Macon and Sullivan counties
Pollutants of concern: Pathogens
Completed: Feb. 8, 2017
Approved:
Mussel Fork E. coli TMDL - Missouri
i
WATER BODY SUMMARY
Mussel Fork – Water body ID No. 0674
Pollutant(s): Pathogens as indicated by E. coli
Name: Mussel Fork
Location: Adair, Linn, Macon and Sullivan counties
Hydrologic Unit Codes (HUC):1
8-digit HUC (subbasin):
10280202 – Lower Chariton
12-digit HUCs (subwatersheds):
102802020301 – Headwaters Mussel Fork
102802020302 – Little Mussel Creek-Mussel Fork
102802020303 – Painter Creek-Mussel Fork
Water Body Identification Number (WBID)
and Hydrologic Class:2
WBID 0674 – Class C
Designated Uses:3
Protection and propagation of fish, shellfish and wildlife – warm water habitat
Whole body contact recreation category B
Livestock and wildlife protection
Secondary contact recreation
Human health protection
Drinking water supply
Irrigation
Impaired Uses:
Whole body contact recreation category B
Secondary contact recreation
Pollutant Identified on the 303(d) List: Escherichia coli, or E. coli (fecal indicator bacteria)
Length and Location of Impaired Segment: 46.7 kilometer (29 miles), from Sec. 18, T58N, R17W to Sec. 2, T62N, R18W
1 Watersheds are delineated by the USGS using a nationwide system based on surface hydrologic features. This system divides
the country into 2,270 8-digit hydrologic units (USGS and NRCS 2013). A hydrologic unit is a drainage area delineated to nest in
a multilevel, hierarchical drainage system. A hydrologic unit code is the numerical identifier of a specific hydrologic unit
consisting of a 2-digit sequence for each specific level within the delineation hierarchy (FGDC 2003). 2 For hydrologic classes see 10 CSR 20-7.031(1)(F). Class C streams may cease to flow during dry periods, but maintain
permanent pools that support aquatic life. 3 For designated uses see 10 CSR 20-7.031(1)(C) and 10 CSR 20-7.031 Table H. Presumed uses are assigned per
10 CSR 20-7.031(2)(A) and (B) and are reflected in the Missouri Use Designation Dataset described at 10 CSR 20-7.031(2)(E).
2.1 Geology, Physiography and Soils ....................................................................................................... 3
2.2 Rainfall and Climate ............................................................................................................................ 5
2.3 Population ............................................................................................................................................ 7
2.4 Land Cover .......................................................................................................................................... 7
3. Applicable Water Quality Standards ......................................................................................................... 9
4. Defining the Problem .............................................................................................................................. 10
5. Source Inventory and Assessment .......................................................................................................... 12
5.1 Point Sources ..................................................................................................................................... 12
5.1.1 Municipal and Domestic Wastewater Discharge Permits ........................................................... 14
14. Public Participation ............................................................................................................................... 28
15. Administrative Record and Supporting Documentation ....................................................................... 29
Figure 5. Distribution of land cover in the Mussel Fork, WBID 0674, watershed
Mussel Fork E. coli TMDL - Missouri
9
3. Applicable Water Quality Standards
The purpose of developing a TMDL is to identify the pollutant loading that a water body can
assimilate and still attain and maintain water quality standards. Water quality standards are therefore
central to the TMDL development process. Under the federal Clean Water Act, every state must
adopt water quality standards to protect, maintain, and improve the quality of the nation’s surface
waters (U.S. Code Title 33, Chapter 26, Subchapter III). Water quality standards consist of three
major components: designated uses, water quality criteria to protect those uses, and an
antidegradation policy.
3.1 Designated Uses
Designated uses are the uses for a water body defined in the state Water Quality Standards at
10 CSR 20-7.031(1)(C) and assigned per 10 CSR 20-7.031(2) and Table H.6 These uses must be
maintained in accordance with the federal Clean Water Act. The following designated uses have been
assigned to WBID 0674 of Mussel Fork and are reflected in the Missouri Use Designation Dataset as
described at 10 CSR 20-7.031(2)E:7
Protection and propagation of fish, shellfish and wildlife – warm water habitat
Livestock and wildlife protection
Whole body contact recreation category B
Secondary contact recreation
Human health protection
Drinking water supply
Irrigation
The designated uses of Mussel Fork that are impaired due to high E. coli concentrations are whole
body contact recreation category B and secondary contact recreation. Whole body contact recreation
includes activities in which there is direct human contact with surface water that results in complete
body submergence, such as swimming. During such activities, accidental ingestion of the water may
occur and there is direct contact to sensitive body organs, such as the eyes, ears and nose. Category A
waters include water bodies that have been established by the property owner as public swimming
areas welcoming access by the public for swimming purposes and waters with documented existing
whole body contact recreation uses by the public (10 CSR 20-7.031(1)(C)2.A.(I)). Category B
applies to waters designated for whole body contact recreation, but are not contained within category
A (10 CSR 20-7.031(1)(C)2.A.(II)). Secondary contact recreation includes activities in which there is
limited, incidental or accidental contact with the water and the probability of ingesting appreciable
quantities of water is minimal. Such activities include boating, fishing and wading (10 CSR 20-
7.031(1)(C)2.B.).
3.2 Water Quality Criteria
Water quality criteria are limits on certain chemicals or conditions in a water body to protect
particular designated uses. Water quality criteria can be expressed as specific numeric criteria or as
general narrative statements. In Missouri’s Water Quality Standards at 10 CSR 20-7.031(5)(C) and
Table A, specific numeric bacteria criteria are given to protect whole body and secondary contact
6 The terminology used for naming designated uses varies from what is presented in the text of 10 CSR 20-7.031 and what is presented
in Table H. The terminology utilized in the text of the water quality standards rule is presented here. 7 The Missouri Use Designation Dataset documents the names and locations of the state’s rivers, streams, lakes and reservoirs, which
have been assigned designated uses (10 CSR 20-7.031 (1)(P)).
Mussel Fork E. coli TMDL - Missouri
10
recreation during the recreational season, which is defined as being from April 1 through October 31.
For category B waters, the E. coli count during the recreational season shall not exceed a geometric
mean of 206/100 mL of water. To be protective of secondary contact recreation, the E. coli count
during the recreational season must not exceed a geometric mean of 1,134/100 mL. In addition to
these specific criteria, the general criteria at 10 CSR 20-7.031(4) are narrative statements that provide
aesthetic and acute toxicity protections for all waters of the state.
3.3 Antidegradation Policy
Missouri’s Water Quality Standards include the EPA “three-tiered” approach to antidegradation, and
may be found at 10 CSR 20-7.031(3).
Tier 1 – Protects public health, existing in-stream water uses and a level of water quality necessary to
maintain and protect those uses. Tier 1 provides the absolute floor of water quality for all
waters of the United States. Existing instream water uses are those uses that were attained on
or after Nov. 28, 1975, the date of EPA’s first Water Quality Standards Regulation.
Tier 2 – Protects and maintains the existing level of water quality where it is better than applicable
water quality criteria. Before water quality in Tier 2 waters can be lowered, there must be an
antidegradation review consisting of: (1) a finding that it is necessary to accommodate
important economic and social development in the area where the waters are located; (2) full
satisfaction of all intergovernmental coordination and public participation provisions; and (3)
assurance that the highest statutory and regulatory requirements for point sources and best
management practices for nonpoint sources are achieved. Furthermore, water quality may
not be lowered to less than the level necessary to fully protect the “fishable/swimmable” uses
and other existing uses.
Tier 3 – Protects the quality of outstanding national and state resource waters, such as waters of
national and state parks, wildlife refuges and waters of exceptional recreational or ecological
significance. There may be no new or increased discharges to these waters and no new or
increased discharges to tributaries of these waters that would result in lower water quality. Waters in which a pollutant is at, near or exceeds the water quality criteria are considered in Tier 1
status for that pollutant. Therefore, the antidegradation goal for the impaired segment of Mussel Fork
is to restore stream water quality to levels that meet water quality standards.
4. Defining the Problem
Missouri’s Water Quality Standards use E. coli, bacteria found in the intestines of humans and warm-
blooded animals, as indicators of potential fecal contamination and risk of pathogen-induced illness to
humans. The department judges a stream to be impaired if the water quality criteria are exceeded in
any of the last three years for which there is a minimum of five samples collected during the
recreational season. This approach is detailed in the department’s 2016 Listing Methodology
Document, which is available online at dnr.mo.gov/env/wpp/waterquality/303d/303d.htm.
E. coli data for Mussel Fork has been collected since 1998 and was first listed as impaired on
Missouri’s combined 2004/2006 303(d) List. Most recently, Mussel Fork was included on the 2016
303(d) List due to documented exceedances of the whole body contact category B criterion in 2011,
2013 and 2016. In 2011, the criterion for the protection of secondary contact recreation was also
exceeded. Per federal regulations at 40 CFR§130.7(c)(1), TMDLs are required for all waters included
on a state’s approved 303(d) list.
Available recreational season E. coli data collected from water body 0674 of Mussel Creek is
summarized in Table 4. Although older data is available, only recreational season E. coli data available
since 2010 are presented. Data collected during this more recent period are expected to be the most
representative of current conditions that may be contributing bacteria loads to Mussel Fork. This data
is further summarized in the box plot presented in Figures 6. Individual E. coli measurements used to
calculate the values in Table 4 and Figure 6 are presented in Appendix A. These observed data are
used in this TMDL for illustration purposes only and were not used in the calculation of TMDL targets
or allocations for Mussel Fork.
Table 4. Summary of recreational season E. coli data for Mussel Fork, WBID 0674
Year
No. of
samples
Minimum
(count/100mL)
Maximum
(count/100mL)
Geometric Mean
(count/100mL)
2010 7 130 7,100 656
2011 6 250 33,000 1,172
2012 3 48 900 294
2013 5 19 10,000 511
2014 7 190 1,400 450
Figure 6. Monthly recreational season E. coli data from Mussel Fork (2010 – 2014)
Mussel Fork E. coli TMDL - Missouri
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5. Source Inventory and Assessment
Various sources may be contributing bacteria loads in varying degrees to Mussel Fork. For this
reason, a source inventory and assessment is included in this TMDL to identify and characterize
known, suspected and potential sources of pollutant loading specific to the Mussel Fork watershed.
Sources identified in this report are categorized as being either point (regulated) or nonpoint
(unregulated) in nature.
5.1 Point Sources
Point sources are defined under Section 502(14) of the federal Clean Water Act and are typically
regulated through the Missouri State Operating Permit program.8 Point sources include any
discernible, confined and discrete conveyance, such as a pipe, ditch, channel, tunnel or conduit, by
which pollutants are transported to a water body. Under this definition, permitted point sources
include permitted municipal and domestic wastewater dischargers, site-specific permitted industrial
and non-domestic wastewater dischargers, concentrated animal feeding operations, municipal
separate storm sewer systems, and general wastewater and stormwater permitted entites. In addition
to these permitted sources, illicit straight pipe discharges, which are illegal and therefore
unpermitted, are also point sources. The locations of each permitted outfall are presented on the
following page in Figure 7.
At the time of this writing, the Mussel Fork watershed contained eight permitted facilities. Two of
these facilities are municipal wastewater facilities, five are concentrated animal feeding operations,
or CAFOs, and one holds a stormwater land disturbance permit.9 There are no permitted municipal
separate storm sewer systems or industrial and non-domestic wastewater dischargers in the
watershed. The locations of the permitted structures and outfalls for the facilities present in the
Mussel Fork watershed are presented in Figure 7. More detailed discussions regarding these facilities
and their potential bacteria contributions appear in the following subsections.
8 The Missouri State Operating Permit program administers the federal National Pollutant Discharge Elimination System, or NPDES,
program for Missouri. The NPDES program requires all point sources that discharge pollutants to waters of the United States to obtain
a permit. 9 Permit numbers for Missouri are accurate as of Feb. 23, 2016. Permits associated with stormwater from land disturbance activities are
temporary and the number of effective permits of this type in a watershed may vary in any given year. Despite this variability, TMDL
targets and allocations will not change as a result of any changes in the number of these types of permits.
Mussel Fork E. coli TMDL - Missouri
13
Figure 7. Permitted features in the Mussel Fork, WBID 0674, watershed
Mussel Fork E. coli TMDL - Missouri
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5.1.1 Municipal and Domestic Wastewater Discharge Permits
Domestic wastewater dischargers include both publicly owned municipal wastewater treatment plants
and non-municipal treatment facilities. Domestic wastewater is primarily household waste, which
includes graywater and sewage. Untreated or inadequately treated discharges of domestic wastewater
can be significant sources of bacteria to receiving waters (EPA 1986). Influences of pollutant loading
from domestic dischargers are typically most evident at low-flow conditions when stormwater
influences are lower or nonexistent. Table 5 lists the two municipal wastewater lagoons located in the
Mussel Fork watershed along with their design flows as stated in Missouri State Operating Permits.10
Table 5. Municipal wastewater lagoons in the Mussel Fork watershed
Permit No.
Facility
Name
Receiving
Stream
Design Flow
m3/s (ft
3/s)
Permit
Expires11
(Mo/Day/Year)
MO-0103322
Greencastle Lagoon
System
An unnamed tributary to
Mussel Fork (WBID 3960) 0.001 (0.041) 03/31/2017
MO-0112135
Green City Wastewater
Treatment Facility
An unnamed tributary to
Mussel Fork (WBID 3960) 0.004 (0.155) 03/30/2017
These two domestic wastewater treatment facilities discharge treated wastewater into tributaries of
Mussel Fork, however neither one currently disinfects their effluent nor do their permits contain
effluent limits for E. coli. Due to a lack of E. coli monitoring data from either of these facilities, the
significance of any bacteria loading from these facilities cannot be determined. However, since
neither of these facilities disinfect their effluent, there is a potential for significant bacteria loading to
occur. It should be noted that historically these facilities had been exempted from bacteria
limitations and disinfection requirements due to conditions set forth in 10 CSR 20-7.015(9)(B)1.D.,
which only requires E. coli permit limitations if discharges are within two miles of a water
designated for whole body contact recreation. Since issuance of these facilities’ permits, water
quality standard revisions approved by EPA on Oct. 22, 2014, have expanded designations of whole
body contact recreation to streams in closer proximity to these facilities. Therefore, E. coli limits and
any applicable disinfection requirements will be included upon permit renewal. Such requirements
will maintain bacteria loads from these facilities to concentrations that meet water quality standards.
In addition to the direct discharges from these municipal wastewater treatment facilities, potential
bacteria contributions may also occur from overflows occurring from the adjoining sanitary sewer
system. A sanitary sewer system is a municipal wastewater collection system designed to convey
domestic, commercial and industrial wastewater to a municipal wastewater treatment facility. This
system can include limited amounts of inflow and infiltration from groundwater and stormwater, but
it is not designed to collect large amounts of runoff from precipitation events. Untreated or partially
treated discharge from a sanitary sewer system is referred to as a sanitary sewer overflow. Sanitary
sewer overflows can be caused by a variety of reasons including blockages, line breaks, sewer
defects, power failures and vandalism. Sanitary sewer overflows can occur during either dry or wet
weather and at any point in the collection system and can include overflows from manholes, or
backups into private residences. Such discharges are unauthorized by the federal Clean Water Act.
10 Issued and proposed operating permits are available online at dnr.mo.gov/env/wpp/permits/index.html. 11 When a permit expires, a facility remains bound by the conditions of that expired permit until either the permit is terminated or a
Concentrated Animal Feeding Operations, or CAFOs, are typically animal feeding operations that
confine and feed or maintain animals for 45 days or more in any 12-month period, and confine more
than 1,000 animal units. Facilities with fewer animal units may be permitted as CAFOs voluntarily, if
discharges occur or other water quality issues are discovered per 10 CSR 20-6.300. Animal wastes
generated from CAFOs that are carried through stormwater runoff or by wastewater discharges can
be a source of bacteria to water bodies (Rogers and Haines 2005). In general, CAFOs are permitted
as no discharge facilities with some allowances for certain catastrophic storm or chronic weather
conditions.12
In Missouri, CAFO facilities are permitted with either site-specific permits or under one
of two general permits; the MO-G01 CAFO permit or the MO-GS1 state no-discharge CAFO permit.
Under the MO-G01 permit, CAFO facilities are not permitted to discharge manure or process
wastewater, but exceptions are granted for discharges caused by excess stormwater runoff in
situations where the facility’s designed storage volume becomes exceeded by either a catastrophic
storm event or a chronic wet weather event as they are defined in the permit. Under the MO-GS1
permit, CAFO facilities are not allowed to discharge for any reason, without exception, and any
discharge is therefore a violation. One CAFO facility, Smithfield Hog Production, is permitted with a
site-specific permit. As with the generally permitted facilities, Smithfield is a no-discharge facility
and must land apply its wastewater. An exception for emergency discharge is allowed for specific
catastrophic storm conditions as defined in the permit under Special Condition #2 (see page 8 of
dnr.mo.gov/env/wpp/permits/issued/docs/0118478.pdf.) Per this special condition, only the portion
of stormwater flow that exceeds the defined catastrophic storm event may be discharged. CAFO
facilities operating in compliance with all specified permit conditions should not contribute
significant loads to surface waters. Table 6 describes the five CAFO facilities located within the
Mussel Fork watershed.
Table 6. CAFOs in the Mussel Fork watershed
Permit No. Facility Name Class13
Animal
Units
Manure Generated
(gallons/year)
MO-0118478 Smithfield Hog Production, Valley View Farm IA 49,459 80,287,225
MO-GS10083 L and D Farms IC 2,880 2,061,480
MO-GS10199 Lawrence Vasey IC 2,880 4,481,826
MO-GS10360 King Farms IC 1,920 1,982,717
MO-GS10490 Chris Dickell IC 1,984 1,589,575
Source: Missouri Clean Water Information System (MoCWIS)
Another potential source for bacteria loading from these operations is runoff from areas where animal
wastes are land applied as fertilizer. Land applications occurring on areas under the control of a
12
Storage structures should be properly designed, constructed, operated, and maintained to contain all manure, litter, process
wastewater plus the runoff and direct precipitation from the 25-year, 24-hour design storm event for the location of the CAFO. 13 An operation’s class size is a category that is based upon the total number of animal units confined at an operation. Class IA
facilities have 7,000 animal units or more. Class IC facilities have 1,000 or more animal units, but less than 3,000 animal units.
Stormwater runoff from lands used for agricultural purposes is a potential source of bacteria loading
to water bodies. Activities associated with agricultural land uses that may contribute pathogens to a
water body include manure fertilization of croplands or pastures, and livestock production.
Stormwater runoff from croplands and grasslands that are fertilized with animal manure may be
potential sources of pathogens to waters due to improper applications or from soil erosion. As noted
in Section 2.4 of this document, cropland comprises approximately 5.6 percent of the Mussel Fork
watershed and areas categorized as being hay or pasture account for about 57 percent of the area.
Bacteria inputs resulting from soil erosion are more likely to occur from cropland areas, but bacteria
carried through stormwater runoff is a potential problem for both land use types if application rates
are too high, are made prior to inclement weather, or are made to frozen ground or other conditions in
which the manure cannot be readily incorporated into the soil (Fulhage 2000). In this region of the
state, manure fertilizers (other than those from CAFOs) are most likely generated from cattle.
Application rates and timing vary depending upon a number of factors, such as crop type, manure
quality and soil need. However, a typical application is less than 10 tons per acre and can be as high
as 20 tons per acre. When poultry litter is used, application rates are less and range from two to four
tons per acre. (Zachary Erwin, University of Missouri Extension, email communication, March 16,
2016).
In addition to manure spreading, livestock within the watershed may act directly as sources of
bacteria to streams due to either manure being deposited directly into a waterway or from manure
being carried by runoff from pasturelands or low density animal feeding operations that do not
require a CAFO permit. Although grazing areas are typically well vegetated, livestock tend to
concentrate near feeding and watering areas causing those areas to become barren of plant cover,
thereby increasing the possibility of erosion during a storm event (Sutton 1990). Stormwater runoff
can carry manure from these areas to nearby streams. Additionally, when livestock are not excluded
from a stream, direct manure contributions from cattle or other livestock to a water body become
more likely.
The permitted CAFO facilities in the Mussel Fork watershed are hog facilities and animal numbers
and manure rates are known as shown in Table 6. The number of other livestock that may be present
in the Mussel Fork watershed is unknown. Even so, an estimate of cattle numbers can be calculated
using the available land cover data in Section 2.4 and county cattle population numbers provided in
the U.S. Department of Agriculture’s 2012 Census of Agriculture. From these data, a number of
cattle per square mile of grassland for each county in the Mussel Fork watershed can be estimated.
And from these derived cattle densities, the number of cattle within the Mussel Fork watershed can
be estimated (Table 8). For beef cattle, the U.S. Department of Agriculture estimates that a 1,000
pound animal produces approximately 26.8 kilograms (59.1 pounds) of manure per day (USDA
1995).
Mussel Fork E. coli TMDL - Missouri
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Table 7. Cattle population estimates for pasture areas in the Mussel Fork, WBID 0674, watershed14
County
Cattle
(No. of animals)
Pasture
km2 (mi
2)
Cattle Density
No./km2 (No./mi
2)
Watershed Pasture
km2 (mi
2)
Watershed Cattle
(No. of animals)
Adair 37,295
674.02
(260.24)
55
(143)
34.14
(13.18) 1,878
Linn 46,905
850.12
(328.23)
55
(143)
17.38
(6.71) 956
Macon 42,691
916.73
(353.95)
47
(121)
39.63
(15.30) 1,863
Sullivan 40,638
979.27
(378.10)
41
(107)
106.01
(40.93) 4,346
TOTALS =
197.16
(76.12) 9,043
In addition to hogs and cattle, several other types of livestock operations may be present in the
Mussel Fork watershed. If present in the watershed, these other types of livestock could potentially
contribute bacteria loads to Mussel Fork. Table 8 summarizes the county-level data for these other
livestock that are noted in the 2012 Census of Agriculture. Some of these livestock may be confined
in lower-density animal feeding operations that may be acting as point sources, but are not regulated
under department regulations. There are no other data available to estimate the number or distribution
of these animals in the Mussel Fork watershed.
Table 8. Numbers of other livestock by county15
Livestock
Type
Adair County
(no. of animals)
Linn County
(no. of animals)
Macon County
(no. of animals)
Sullivan County
(no. of animals)
Sheep & Lambs 1,064 735 1,804 645
Goats 748 513 1,375 127
Equine 963 419 1,616 737
Poultry 9,456 891 2,003 754
5.2.2 Urban Stormwater Runoff
Urban stormwater runoff has been found to carry high levels of bacteria and can be expected to
exceed water quality criteria for bacteria during and immediately after storm events in most streams
throughout the country (EPA 1983). E. coli contaminated runoff can come from both heavily paved
areas and from open areas where soil erosion is common (Burton and Pitt 2002). Common sources of
E. coli contamination in urban stormwater have been documented as being from birds, dogs, cats, and
rodents (Burton and Pitt 2002). Therefore, in general, urban runoff is a potential contributor of
pathogens to surface waters. However, the Mussel Fork watershed is primarily a rural watershed with
very few urban spaces. Land cover data analyzed in Section 2.4 of this document identifies less than
5 percent of the watershed as being in a developed category. Of these areas categorized as being in
some level of development, the majority is contained within the boundaries of three small
municipalities. The largest of these municipalities is Green City with a population of 657, however
14 This analysis assumes all areas identified as being hay or pasture are being used for cattle grazing and that cattle are evenly
distributed on these areas. 15 Values that are “Not Given” were withheld by the U.S. Department of Agriculture to avoid disclosing data for an individual farm.
Mussel Fork E. coli TMDL - Missouri
19
only 1.3 km2 (0.5 mi
2) of this municipality extend into the Mussel Fork watershed. Greencastle, a
municipality of 275 people accounts for 1 km2 (0.4 mi
2) of the watershed and Winigan, an
unincorporated community of only 44 people, covers 0.8 km2 (0.3 mi
2). Due to this small amount of
urban space in the watershed, urban stormwater runoff is not expected to be a significant contributor
of pathogens to Mussel Fork.
5.2.3 Onsite Wastewater Treatment Systems
Approximately 25 percent of homes in Missouri utilize onsite wastewater treatment systems,
particularly those in rural areas where public sewer systems may not be available (DHSS 2016).
Onsite wastewater treatment systems treat domestic wastewater and disperse it on the property where
it is generated, such as a home septic system. When properly designed and maintained, such systems
do not serve as a source of contamination to surface waters; however, onsite wastewater treatment
systems can fail for a variety of reasons. When these systems fail hydraulically (surface breakouts) or
hydrogeologically (inadequate soil filtration), there can be adverse effects to surface water quality
(Horsley & Witten 1996). Failing onsite wastewater treatment systems are known to be sources of
bacteria, which can reach nearby streams directly through surface runoff and groundwater flows,
thereby contributing bacteria loads under either wet or dry weather conditions. Onsite wastewater
treatment systems may contribute bacteria to waterbodies directly or as component of stormwater
runoff.
Unfortunately, the exact number of onsite wastewater treatment systems in the Mussel Fork
watershed is unknown. However EPA’s online input data server for the Spreadsheet Tool for
Estimating Pollutant Load, or STEPL, does provide estimates of septic system numbers by 12-digit
HUC watersheds based on 1992 and 1998 data from the National Environmental Services Center.16
Due to the relatively unchanged population estimates from 1990 to 2010 as described in Section 2.3
of this document, it is reasonable to assume that this older data can still provide a reasonable estimate
of septic system numbers in the Mussel Fork watershed. From this information, STEPL estimates that
there are approximately 117 septic systems in the Mussel Fork watershed. These STEPL derived
estimates are provided in Table 9 along with statewide estimated failure rates from the Electric
Power Research Institute (EPRI 2000). From this information, up to 59 onsite wastewater treatment
systems may be failing in the impaired watershed. For this reason, onsite wastewater treatment
systems are potential sources of bacteria loading; however the available data is inadequate to
determine the significance of such loading in relation to the impairment of Mussel Fork.
Table 9. Estimated numbers of septic systems in the Mussel Fork, WBID 0674, watershed
12-digit HUC
Subwatershed
name
Number of
Septic Systems
Statewide
Failure Rates
102802020301 Headwaters of Mussel Fork 80
30% – 50%
102802020302 Little Mussel Creek-Mussel Fork 24
102802020303 Painter Creek-Mussel Fork 13
Total = 117
16 The National Environmental Services Center is located at West Virginia University and maintains a clearinghouse for information
related to, among other things, onsite wastewater treatment systems. Available URL: www.nesc.wvu.edu/
Mussel Fork recreational season E. coli data (2010 – 2014)20,21
Site Code Site Name Date
Sample ID
E. coli (counts/100ml)
Flow m
3/s (ft
3/s)
674/28.8 Mussel Fork near Mystic 4/22/2010 200742 130 0.048 (1.70)
674/28.8 Mussel Fork near Mystic 5/19/2010 200743 800 0.623 (22.00)
674/28.8 Mussel Fork near Mystic 6/16/2010 200744 7,100 1.812 (64.00)
674/28.8 Mussel Fork near Mystic 7/29/2010 200745 310 0.048 (1.70)
674/28.8 Mussel Fork near Mystic 8/18/2010 200746 320 0.011 (0.40)
674/28.8 Mussel Fork near Mystic 9/23/2010 200747 2,100 1.614 (57.00)
674/28.8 Mussel Fork near Mystic 10/6/2010 200748 340 0.048 (1.70)
674/28.8 Mussel Fork near Mystic 4/7/2011 212196 250 0.071 (2.50)
674/28.8 Mussel Fork near Mystic 5/5/2011 212197 1,900 0.065 (2.30)
674/28.8 Mussel Fork near Mystic 6/9/2011 212198 650 0.054 (1.90)
674/28.8 Mussel Fork near Mystic 7/13/2011 212199 33,000 0.566 (20.00)
674/28.8 Mussel Fork near Mystic 8/17/2011 212200 980 0.017 (0.61)
674/28.8 Mussel Fork near Mystic 9/15/2011 212201 260 0.000 (0.01)
674/28.8 Mussel Fork near Mystic 4/18/2012 223020 900 0.238 (8.40)
674/28.8 Mussel Fork near Mystic 5/23/2012 223021 48 0.007 (0.25)
674/28.8 Mussel Fork near Mystic 6/6/2012 223022 590 0.002 (0.06)
674/28.8 Mussel Fork near Mystic 4/10/2013 238859 10,000 1.727 (61.00)
674/28.8 Mussel Fork near Mystic 5/22/2013 238860 1,100 0.031 (1.10)
674/28.8 Mussel Fork near Mystic 6/25/2013 238861 880 0.034 (1.20)
674/28.8 Mussel Fork near Mystic 7/9/2013 238862 190 0.002 (0.06)
674/28.8 Mussel Fork near Mystic 8/13/2013 238863 19 0.000 (0.01)
674/28.8 Mussel Fork near Mystic 4/8/2014 244017 190 0.008 (0.29)
674/28.8 Mussel Fork near Mystic 5/7/2014 244018 360 0.015 (0.53)
674/28.8 Mussel Fork near Mystic 6/10/2014 244019 1,400 0.311 (11.00)
674/28.8 Mussel Fork near Mystic 7/16/2014 244020 330 0.028 (1.00)
674/28.8 Mussel Fork near Mystic 8/19/2014 251023 790 0.340 (12.00)
674/28.8 Mussel Fork near Mystic 9/23/2014 251024 220 0.059 (2.10)
674/28.8 Mussel Fork near Mystic 10/7/2014 251025 680 0.079 (2.80)
20
Recreational season E. coli data was retrieved from the department’s Water Quality Assessment Database on Feb. 19, 2016. 21 All data was collected by the U.S. Geological Survey.
Mussel Fork E. coli TMDL - Missouri
33
Appendix B
Development of the Mussel Fork Bacteria Load Duration Curve
Overview
The load duration curve approach was used to develop the total maximum daily load, or TMDL, for
the impaired water body segment of Mussel Fork, WBID 0674. The load duration curve method
allows for characterizing water quality concentrations (or water quality data) at different flow
regimes and estimating the load allocations and wasteload allocations for each impaired segment.
This method also provides a visual display of the relationship between stream flow and loading
capacity. Using the duration curve framework, allowable loadings are easily presented.
Methodology
Using the load duration curve method requires a long time series of flow data, a numeric water
quality target, and bacteria data from the impaired streams. For the Mussel Fork TMDL, bacteria data
collected from the impaired segments was converted into an instantaneous load using measured
flows. These observed loads were plotted along with the load duration curve to illustrate conditions
when the water quality target may have been exceeded.
To develop a load duration curve, a long record of average daily flow data from a gage (or multiple
gages) that is representative of the impaired reach is used. The flow record should be of sufficient
length to be able to calculate percentiles of flow. If a flow record for an impaired stream is not
available, then a synthetic flow record is needed. For the Mussel Fork TMDL, flow gage data from
Dec. 11, 2002 to Jan. 27, 2016, was available from Mussel Fork via USGS gage 06906000. The
modeling approach assumes that discharge at the outlet of the impaired watershed is proportional to
the discharge from the USGS gage station. Therefore, average daily flow values were corrected based
on the proportion of the area draining to the impaired watershed to that draining to the flow gage
(Table B-1). The developed flow duration curve for the impaired water body is presented in Figure
B-1. These flows in units of ft3/second are then multiplied by the selected water quality target of 206
counts/100 mL and a conversion factor of 24,465,715 in order to generate the allowable load in units
of counts/day.22
Despite the varying load, the targeted concentration is constant at all flow percentiles
and reflects the static nature of the water quality standards.
Table B-1. Information used to calculate area corrected flows