Bacteria total maximum daily loads for streams in upper Cimarron river area, Oklahoma

              FINAL
BACTERIA TOTAL MAXIMUM DAILY LOADS FOR STREAMS
IN THE UPPER CIMARRON RIVER AREA, OKLAHOMA
Prepared By:
OKLAHOMA DEPARTMENT OF ENVIRONMENTAL QUALITY
JULY, 2011
FINAL
BACTERIA TOTAL MAXIMUM DAILY LOADS FOR STREAMS
IN UPPER CIMARRON RIVER AREA, OKLAHOMA
OKWBID
OK720900000180_00 - Cimarron River
OK620930000010_00 - Cimarron River
OK620930000100_00 - Crooked Creek
Prepared by:
OKLAHOMA DEPARTMENT OF ENVIRONMENTAL QUALITY
JULY, 2011
Upper Cimarron River Area Bacteria TMDLs Table of Contents
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JULY, 2011
TABLE OF CONTENTS
EXECUTIVE SUMMARY ............................................................................................................ VI
SECTION 1 INTRODUCTION .................................................................................................... 1-1
1.1 TMDL Program Background ............................................................................................ 1-1
1.2 Watershed Description ...................................................................................................... 1-2
SECTION 2 PROBLEM IDENTIFICATION AND WATER QUALITY TARGET ............. 2-1
2.1 Oklahoma Water Quality Standards .................................................................................. 2-1
2.2 Problem Identification ....................................................................................................... 2-4
2.3 Water Quality Target ......................................................................................................... 2-5
TMDL required ................................................................................................................ 2-6
SECTION 3 POLLUTANT SOURCE ASSESSMENT .............................................................. 3-1
3.1 NPDES-Permitted Facilities .............................................................................................. 3-1
3.1.1 Continuous Point Source Discharges .................................................................... 3-1
3.1.2 NPDES No-Discharge Facilities and SSOs ........................................................... 3-2
3.1.3 NPDES Municipal Separate Storm Sewer Discharge ........................................... 3-2
3.1.4 Concentrated Animal Feeding Operations ............................................................ 3-2
3.2 Nonpoint Sources .............................................................................................................. 3-3
3.2.1 Wildlife .................................................................................................................. 3-3
3.2.2 Non-Permitted Agricultural Activities and Domesticated Animals ...................... 3-4
3.2.3 Failing Onsite Wastewater Disposal Systems and Illicit Discharges .................... 3-7
3.2.4 Domestic Pets ........................................................................................................ 3-8
3.3 Summary of Bacteria Sources ........................................................................................... 3-9
SECTION 4 TECHNICAL APPROACH AND METHODS ..................................................... 4-1
4.1 Using Load Duration Curves to Develop TMDLs ............................................................ 4-1
4.2 Development of Flow Duration Curves ............................................................................ 4-2
4.3 Estimating Current Point and Nonpoint Loading .............................................................. 4-3
4.4 Development of TMDLs Using Load Duration Curves .................................................... 4-4
SECTION 5 TMDL CALCULATIONS ....................................................................................... 5-1
5.1 Flow Duration Curves ....................................................................................................... 5-1
5.2 Estimated Loading and Critical Conditions ...................................................................... 5-4
5.3 Wasteload Allocation ........................................................................................................ 5-8
5.4 Load Allocation ................................................................................................................. 5-8
5.5 Seasonal Variability ........................................................................................................... 5-8
5.6 Margin of Safety ................................................................................................................ 5-9
5.7 TMDL Calculations ........................................................................................................... 5-9
5.8 Reasonable Assurances ................................................................................................... 5-15
Upper Cimarron River Area Bacteria TMDLs Table of Contents
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SECTION 6 PUBLIC PARTICIPATION ................................................................................... 6-1
SECTION 7 REFERENCES ......................................................................................................... 7-1
APPENDICES
Appendix A Ambient Water Quality Bacteria Data – 2000 to 2008
Appendix B Estimated Flow Exceedance Percentiles
Appendix C State of Oklahoma Antidegradation Policy
Appendix D Response to Comments
LIST OF FIGURES
Figure 1-1 Watersheds Not Supporting Primary Body Contact Recreation Use within the
Study Area ............................................................................................................ 1-5
Figure 1-2 Land Use Map by Watershed ............................................................................... 1-6
Figure 4-1 Flow Duration Curve for Cimarron River near Kenton ....................................... 4-3
Figure 5-1 Flow Duration Curve for Cimarron River near Kenton ....................................... 5-2
(OK720900000180_00) ........................................................................................ 5-2
Figure 5-2 Flow Duration Curve for Cimarron River above Ute Creek, near Boise City
(OK720900000010_00) ........................................................................................ 5-2
Figure 5-3 Flow Duration Curve for ..................................................................................... 5-3
Figure 5-4 Flow Duration Curve for Crooked Creek near Englewood, KS
(OK620930000100_00) ........................................................................................ 5-3
Figure 5-5 Load Duration Curve for Enterococci in Cimarron River near Kenton
(OK720900000180_00) ........................................................................................ 5-6
Figure 5-6 Load Duration Curve for Fecal Coliform in Cimarron River near Kenton
(OK720900000180_00) ........................................................................................ 5-6
Figure 5-7 Load Duration Curve for Enterococci in Cimarron River off US 64, Mocane
(OK620930000010_00) ........................................................................................ 5-7
Figure 5-8 Load Duration Curve for Fecal Coliform in Cimarron River off US 64, Mocane
(OK620930000010_00) ........................................................................................ 5-7
Figure 5-9 Load Duration Curve for Enterococci in Crooked Creek, near Englewood, KS
(OK620930000100_00) ........................................................................................ 5-8
LIST OF TABLES
Table ES-1 Excerpt from the 2008 Integrated Report – Comprehensive Waterbody
Assessment Category List ...................................................................................... vi
Table ES-2 Waterbodies Requiring TMDLs for Not Supporting Primary Body Contact
Recreation Use Contained in This Package ........................................................... vi
Upper Cimarron River Area Bacteria TMDLs Table of Contents
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Table ES-3 TMDL Percent Reduction Goals Required to Meet Water Quality Standards for
Impaired Waterbodies ............................................................................................. x
Table ES-4 TMDL Summaries Examples ................................................................................. xi
Table 1-1 Water Quality Monitoring Stations used for 2008 303(d) Listing Decision ........ 1-2
Table 1-2 County Population and Density ............................................................................ 1-2
Table 1-3 Average Annual Precipitation by Stream Segment .............................................. 1-3
Table 1-4 Land Use Summaries by Watershed ..................................................................... 1-4
Table 2-1 Excerpt from the Oklahoma 2008 303(d) List ..................................................... 2-2
Table 2-1a Designated Beneficial Uses for Each Impaired Waterbody in the Study Area .... 2-2
Table 2-2 Summary of Indicator Bacteria Samples from Primary Body Contact Recreation
Season, 2000-2008 ............................................................................................... 2-6
Table 2-3 Waterbodies Requiring TMDLs for Not Supporting Primary Body Contact
Recreation Use ..................................................................................................... 2-6
Table 3-1 Estimated Deer Populations ................................................................................. 3-4
Table 3-2 Estimated Fecal Coliform Production for Deer .................................................... 3-4
Table 3-3 Commercially Raised Farm Animals and Manure Application Area Estimates by
Watershed ............................................................................................................. 3-6
Table 3-4 Fecal Coliform Production Estimates for Commercially Raised Farm Animals
(x109 number/day) ................................................................................................ 3-6
Table 3-5 Estimates of Sewered and Unsewered Households .............................................. 3-8
Table 3-6 Estimated Fecal Coliform Load from OSWD Systems ........................................ 3-8
Table 3-7 Estimated Numbers of Pets .................................................................................. 3-9
Table 3-8 Estimated Fecal Coliform Daily Production by Pets (x 109) ................................ 3-9
Table 3-9 Estimated Major Source of Bacteria Loading by Watershed ............................... 3-9
Table 3-10 Summary of Daily Fecal Coliform Load Estimates from Nonpoint Sources to
Land Surfaces ..................................................................................................... 3-10
Table 5-1 TMDL Percent Reductions Required to Meet Water Quality Standards for
Impaired Waterbodies in the Upper Cimarron River Study Area ........................ 5-5
Table 5-2 Enterococci TMDL Calculations for Cimarron River near Kenton
(OK720900000180_00) ...................................................................................... 5-10
Table 5-3 Fecal Coliform TMDL Calculations for Cimarron River near Kenton
(OK720900000180_00) ...................................................................................... 5-11
Table 5-5 Fecal Coliform TMDL Calculations for Cimarron River off US 64, Mocane
(OK620930000010_00) ...................................................................................... 5-13
Table 5-6 Enterococci TMDL Calculations for Crooked Creek near Englewood, KS
(OK620930000100_00) ...................................................................................... 5-14
Table 5-7 Partial List of Oklahoma Water Quality Management Agencies ...................... 5-15
Upper Cimarron River Area Bacteria TMDLs Acronyms and Abbreviations
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ACRONYMS AND ABBREVIATIONS
ASAE American Society of Agricultural Engineers
BMP best management practice
CAFO Concentrated Animal Feeding Operation
CFR Code of Federal Regulations
cfs Cubic feet per second
cfu Colony-forming unit
CPP Continuing planning process
CWA Clean Water Act
DMR Discharge monitoring report
LA Load allocation
LDC Load duration curve
mg Million gallons
mgd Million gallons per day
mL Milliliter
MOS Margin of safety
MS4 Municipal separate storm sewer system
NPDES National Pollutant Discharge Elimination System
O.S. Oklahoma statutes
ODAFF Oklahoma Department of Agriculture, Food and Forestry
DEQ Oklahoma Department of Environmental Quality
OPDES Oklahoma Pollutant Discharge Elimination System
OSWD Onsite wastewater disposal
OWRB Oklahoma Water Resources Board
PBCR Primary body contact recreation
PRG Percent reduction goal
SSO Sanitary sewer overflow
TMDL Total maximum daily load
USDA U.S. Department of Agriculture
USEPA U.S. Environmental Protection Agency
USGS U.S. Geological Survey
WLA Wasteload allocation
WQM Water quality monitoring
WQS Water quality standard
WWTP Wastewater treatment plant
Upper Cimarron River Area Bacteria TMDLs Executive Summary
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Executive Summary
This report documents the data and assessment used to establish TMDLs for the pathogen
indicator bacteria fecal coliform and enterococci for certain waterbodies in the Upper Cimarron
River area. Elevated levels of pathogen indicator bacteria in aquatic environments indicate that
a receiving water is contaminated with human or animal feces and that there is a potential
health risk for individuals exposed to the water. Data assessment and TMDL calculations are
conducted in accordance with requirements of Section 303(d) of the CWA, Water Quality
Planning and Management Regulations (40 CFR Part 130), USEPA guidance, and Oklahoma
Department of Environmental Quality (DEQ) guidance and procedures. DEQ is required to
submit all TMDLs to USEPA for review and approval. Once the USEPA approves a TMDL,
then the waterbody may be moved to Category 4a of a state’s Integrated Water Quality
Monitoring and Assessment Report, where it remains until compliance with water quality
standards (WQS) is achieved (USEPA 2003).
The purpose of this report is to establish pollutant load allocations for indicator bacteria in
impaired waterbodies, which is the first step toward restoring water quality and protecting
public health. TMDLs determine the pollutant loading a waterbody can assimilate without
exceeding the WQS for that pollutant. A TMDL consists of a wasteload allocation (WLA),
load allocation (LA), and a margin of safety (MOS). The WLA is the fraction of the total
pollutant load apportioned to point sources, and includes stormwater discharges regulated under
the National Pollutant Discharge Elimination System (NPDES) as point sources. The LA is the
fraction of the total pollutant load apportioned to nonpoint sources. The MOS is a percentage
of the TMDL set aside to account for the uncertainty associated with natural process in aquatic
systems, model assumptions, and data limitations.
This report does not stipulate specific control actions (regulatory controls) or management
measures (voluntary best management practices) necessary to reduce bacteria loadings within
each watershed. Watershed-specific control actions and management measures will be
identified, selected, and implemented under a separate process.
E.1 Problem Identification and Water Quality Target
A decision was made to place specific waterbodies in this Study Area, listed in Table ES-1,
on the DEQ 2008 303(d) list because evidence of nonsupport of primary body contact
recreation (PBCR) was observed.
Elevated levels of bacteria above the WQS for one or more of the bacterial indicators result
in the requirement that a TMDL be developed. The TMDLs established in this report are a
necessary step in the process to develop the bacteria loading controls needed to restore the
primary body contact recreation use designated for each waterbody.
Upper Cimarron River Area Bacteria TMDLs Executive Summary
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Table ES-1 Excerpt from the 2008 Integrated Report – Comprehensive Waterbody
Assessment Category List
Waterbody ID Waterbody Name
Stream Miles
Priority
TMDL Date
Primary Body
Contact
Recreation
Impairments
Enterococci
E. coli
Fecal
coliform
OK720900000180_00 Cimarron River near Kenton 19 3 2010 N X X X
OK720900000010_00
Cimarron River above Ute Creek,
near Boise City
47 2 2013 N X
OK620930000010_00 Cimarron River off US 64, Mocane 38 3 2016 N X X
OK620930000100_00
Crooked Creek near Englewood,
KS
6 3 2016 N X
N = Not Supporting; Source: 2008 Integrated Report, DEQ 2008
There was sufficient data collected between 2000 and 2008 to make an assessment of
the four segments for the three bacteria numeric criterion. Evidence of nonsupport of primary
body contact recreation beneficial uses was observed for fecal coliform and enterococci
indicators in two segments of Cimarron River (OK720900000180_00 &
OK620930000010_00). Nonsupport of PBCR was also observed for enterococci in Crooked
Creek (OK620930000100_00). There was no evidence of nonsupport of primary body contact
recreation beneficial uses observed for E. coli in two segments of Cimarron River
(OK720900000180_00 & OK720900000010_00) although both are listed on 2008 303(d) list.
Table ES-2 shows the bacteria TMDLs that will be developed in this report:
Table ES-2 Waterbodies Requiring TMDLs for Not Supporting Primary Body
Contact Recreation Use Contained in This Package
WQM Station Waterbody ID Waterbody Name
Indicator Bacteria
ENT E. coli FC
OK720900-00-0180C
OK720900-00-0180G OK720900000180_00 Cimarron River near Kenton X X
OK620930-00-0010G
OK620930-00-0010T OK620930000010_00 Cimarron River off US 64, Mocane X X
OK620930-00-0100G OK620930000100_00 Crooked Creek near Englewood, KS X
The definition of PBCR is summarized by the following excerpt from Chapter 45 of the
Oklahoma WQSs.
(a) Primary Body Contact Recreation involves direct body contact with the water where a
possibility of ingestion exists. In these cases the water shall not contain chemical,
physical or biological substances in concentrations that are irritating to skin or sense
organs or are toxic or cause illness upon ingestion by human beings.
Upper Cimarron River Area Bacteria TMDLs Executive Summary
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(b) In waters designated for Primary Body Contact Recreation...limits...shall apply only
during the recreation period of May 1 to September 30. The criteria for Secondary Body
Contact Recreation will apply during the remainder of the year.
To implement Oklahoma’s WQS for PBCR, OWRB promulgated Chapter 46,
Implementation of Oklahoma’s Water Quality Standards (OWRB 2008a). The excerpt below
from Chapter 46: 785:46-15-6, stipulates how water quality data will be assessed to determine
support of the PBCR use as well as how the water quality target for TMDLs will be defined for
each bacterial indicator.
(a) Scope. The provisions of this Section shall be used to determine whether the
subcategory of Primary Body Contact of the beneficial use of Recreation designated in OAC
785:45 for a waterbody is supported during the recreation season from May 1 through
September 30 each year. Where data exist for multiple bacterial indicators on the same
waterbody or waterbody segment, the determination of use support shall be based upon the use
and application of all applicable tests and data.
(b) Screening levels.
(1) The screening level for fecal coliform shall be a density of 400 colonies per 100ml.
(2) The screening level for Escherichia coli shall be a density of 235 colonies per 100 ml in
streams designated in OAC 785:45 as Scenic Rivers and in lakes, and 406 colonies per 100 ml
in all other waters of the state designated as Primary Body Contact Recreation.
(3) The screening level for enterococci shall be a density of 61 colonies per 100 ml in
streams designated in OAC 785:45 as Scenic Rivers and in lakes, and 108 colonies per 100 ml
in all other waters of the state designated as Primary Body Contact Recreation.
(c) Fecal coliform:
(1) The Primary Body Contact Recreation subcategory designated for a waterbody shall
be deemed to be fully supported with respect to fecal coliform if the geometric mean of 400
colonies per 100 ml is met and no greater than 25% of the sample concentrations from that
waterbody exceed the screening level prescribed in (b) of this Section.
(2) The parameter of fecal coliform is not susceptible to an assessment that Primary Body
Contact Recreation is partially supported.
(3) The Primary Body Contact Recreation subcategory designated for a waterbody shall
be deemed to be not supported with respect to fecal coliform if the geometric mean of 400
colonies per 100 ml is not met, or greater than 25% of the sample concentrations from that
waterbody exceed the screening level prescribed in (b) of this Section, or both such conditions
exist.
(d) Escherichia coli (E. coli):
(1) The Primary Body Contact Recreation subcategory designated for a waterbody shall
be deemed to be fully supported with respect to E. coli if the geometric mean of 126 colonies
per 100 ml is met, or the sample concentrations from that waterbody taken during the
Upper Cimarron River Area Bacteria TMDLs Executive Summary
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JULY, 2011
recreation season do not exceed the screening level prescribed in (b) of this Section, or both
such conditions exist.
(2) The parameter of E. coli is not susceptible to an assessment that Primary Body Contact
Recreation is partially supported.
(3) The Primary Body Contact Recreation subcategory designated for a waterbody shall
be deemed to be not supported with respect to E. coli if the geometric mean of 126 colonies per
100 ml is not met and any of the sample concentrations from that waterbody taken during the
recreation season exceed a screening level prescribed in (b) of this Section.
(e) Enterococci:
(1) The Primary Body Contact Recreation subcategory designated for a waterbody shall
be deemed to be fully supported with respect to enterococci if the geometric mean of 33
colonies per 100 ml is met, or the sample concentrations from that waterbody taken during the
recreation season do not exceed the screening level prescribed in (b) of this Section, or both
such conditions exist.
(2) The parameter of enterococci is not susceptible to an assessment that Primary Body
Contact Recreation is partially supported.
(3) The Primary Body Contact Recreation subcategory designated for a waterbody shall
be deemed to be not supported with respect to enterococci if the geometric mean of 33 colonies
per 100 ml is not met and any of the sample concentrations from that waterbody taken during
the recreation season exceed a screening level prescribed in (b) of this Section.
Compliance with the Oklahoma WQS is based on meeting requirements for all three
bacterial indicators. Where concurrent data exist for multiple bacterial indicators on the same
waterbody or waterbody segment, each indicator group must demonstrate compliance with the
numeric criteria prescribed (OWRB 2008).
As stipulated in the WQS, utilization of the geometric mean to determine compliance for
any of the three indicator bacteria depends on the collection of five samples within a 30-day
period. For most waterbodies in Oklahoma there are insufficient data available to calculate the
30-day geometric mean since most water quality samples are collected once a month. As a
result, waterbodies placed on the 303(d) list for not supporting the PBCR are the result of
individual samples exceeding the instantaneous criteria or the long-term geometric mean of
individual samples exceeding the geometric mean criteria for each respective bacterial
indicator. Targeting the instantaneous criterion established for the primary body contact
recreation season (May 1st to September 30th) as the water quality goal for TMDLs corresponds
to the basis for 303(d) listing and may be protective of the geometric mean criterion as well as
the criteria for the secondary contact recreation season. However, both the instantaneous and
geometric mean criteria for E. coli and enterococci will be evaluated as water quality targets to
ensure the most protective goal is established for each waterbody.
All TMDLs for fecal coliform must take into account that no more than 25 percent of the
samples may exceed the instantaneous numeric criteria. For E. coli and enterococci, no
samples may exceed instantaneous criteria. Since the attainability of stream beneficial uses for
E. coli and enterococci is based on the compliance of either the instantaneous or a long-term
geometric mean criterion, percent reductions goals will be calculated for both criteria. TMDLs
Upper Cimarron River Area Bacteria TMDLs Executive Summary
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JULY, 2011
will be based on the percent reduction required to meet either the instantaneous or the long-term
geometric mean criterion, whichever is less.
E.2 Pollutant Source Assessment
There are no NPDES permitted facilities of any type in the Study Area. There are no
continuous point source dischargers in the Study Area.
Nonpoint source bacteria loading to the receiving streams of each waterbody may emanate
from a number of different sources including wildlife, various agricultural activities and
domesticated animals, land application fields, urban runoff, failing onsite wastewater disposal
(OSWD) systems, and domestic pets. The data analysis and the load duration curves (LDC)
demonstrate that exceedances in stream segments are the result of a variety of nonpoint source
loading occurring during a range of flow conditions. Low flow exceedances are likely due to a
combination of non-point sources, uncontrolled point sources and permit noncompliance.
E.3 Using Load Duration curves to Develop TMDLs
The TMDL calculations presented in this report are derived from LDCs. LDCs facilitate
rapid development of TMDLs and as a TMDL development tool, may assist in identifying
whether impairments are associated with point or nonpoint sources.
Use of the LDC obviates the need to determine a design storm or selected flow recurrence
interval with which to characterize the appropriate flow level for the assessment of critical
conditions. For waterbodies impacted by both point and nonpoint sources, the “nonpoint
source critical condition” would typically occur during high flows, when rainfall runoff would
contribute the bulk of the pollutant load, while the “point source critical condition” would
typically occur during low flows, when treatment plant effluents would dominate the base flow
of the impaired water. However, flow range is only a general indicator of the relative
proportion of point/nonpoint contributions. It is not used in this report to quantify point source
or nonpoint source contributions. Violations that occur during low flows may not be caused
exclusively by point sources. Violations have been noted in some watersheds that contain no
point sources. Research has show that bacteria loading in streams during low flow conditions
may be due to direct deposit of cattle manure into streams and faulty septic tank/lateral field
systems.
The basic steps to generating an LDC involve:
· obtaining daily flow data for the site of interest from the USGS;
· sorting the flow data and calculating flow exceedance percentiles for the time period
and season of interest;
· obtaining the water quality data from the primary body contact recreation season (May
1 through September 30);
· matching the water quality observations with the flow data from the same date;
· display a curve on a plot that represents the allowable load determined by multiplying
the actual or estimated flow by the WQS for each respective indicator;
· multiplying the flow by the water quality parameter concentration to calculate daily
loads; then
Upper Cimarron River Area Bacteria TMDLs Executive Summary
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· plotting the flow exceedance percentiles and daily load observations in a load duration
plot.
LDCs display the maximum allowable load over the complete range of flow conditions by
a line using the calculation of flow multiplied by the water quality criterion. The TMDL can be
expressed as a continuous function of flow, equal to the line, or as a discrete value derived from
a specific flow condition.
E.4 TMDL Calculations
As indicated above, the bacteria TMDLs for the 303(d)-listed waterbodies covered in this
report were derived using LDCs. A TMDL is expressed as the sum of all WLAs (point source
loads), LAs (nonpoint source loads), and an appropriate MOS, which attempts to account for
uncertainty concerning the relationship between effluent limitations and water quality.
This definition can be expressed by the following equation:
TMDL = Σ WLA + Σ LA + MOS
For each waterbody the TMDLs presented in this report are expressed as a percent
reduction across the full range of flow conditions (See Table ES-3). The difference between
existing loading and the water quality target is used to calculate the loading reductions
required.
Table ES-3 presents the percent reductions necessary for each bacterial indicator causing
nonsupport of the PBCR use in each waterbody of the Study Area. Selection of the
appropriate PRG for each bacteria indicator for each waterbody in Table ES-3 is denoted by the
bold text. For Fecal Coliform, the PRG is determined based on instantaneous criteria. For E.
coli and enterococci, the TMDL PRG will be the lesser of that required to meet the geometric
mean or instantaneous criteria because WQ standards are considered to be met if 1) either the
geometric mean of all data is less than the geometric mean criteria, or 2) no samples exceed the
instantaneous criteria.
Table ES-3 TMDL Percent Reduction Goals Required to Meet Water Quality
Standards for Impaired Waterbodies
Waterbody ID Waterbody Name
Percent Reduction Required
FC ENT
Instantaneous Instantaneous Geo-mean
OK720900000180_00 Cimarron River near Kenton 28% 88% 56%
OK620930000010_00 Cimarron River off US 64,
Mocane
20% 99% 66%
OK620930000100_00 Crooked Creek near
Englewood, KS
94% 70%
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The TMDL, WLA, LA, and MOS vary with flow condition, and are calculated at every 5th
flow interval percentile. For illustrative purposes, the TMDL, WLA, LA, and MOS are
calculated for the median flow at each site in Table ES-4. The WLA component of each
TMDL is the sum of all WLAs within the contributing watershed of each waterbody. The sum
of the WLAs can be represented as a single line below the LDC. The LDC and the simple
equation of:
Average LA = average TMDL – MOS - ΣWLA
can provide an individual value for the LA in counts per day which represents the area under
the TMDL target line and above the WLA line. There are no permitted MS4s in the study area.
Where there are no continuous point sources the WLA is zero.
Federal regulations (40 CFR §130.7(c)(1)) require that TMDLs include a MOS. The MOS
is a conservative measure incorporated into the TMDL equation that accounts for the
uncertainty associated with calculating the allowable pollutant loading to ensure WQSs are
attained. USEPA guidance allows for use of implicit or explicit expressions of the MOS, or
both. When conservative assumptions are used in development of the TMDL, or conservative
factors are used in the calculations, the MOS is implicit. When a specific percentage of the
TMDL is set aside to account for uncertainty, then the MOS is considered explicit.
The use of instream bacteria concentrations to estimate existing loading is another
conservative element utilized in these TMDLs that can be recognized as an implicit MOS. This
conservative approach to establishing the MOS will ensure that both the 30-day geometric
mean and instantaneous bacteria standards can be achieved and maintained.
Table ES-4 TMDL Summaries Examples
Waterbody ID Waterbody Name
Indicator
Bacteria
Species
TMDL†
(cfu/day)
WLA†
(cfu/day)
LA†
(cfu/day)
MOS†
(cfu/day)
OK720900000180_00 Cimarron River
near Kenton
ENT 1.61E+09 0.00E+00 1.45E+09 1.61E+08
FC 5.97E+09 0.00E+00 5.37E+09 5.97E+08
OK620930000010_00 Cimarron River off
US 64, Mocane
ENT 1.32E+11 0.00E+00 1.19E+11 1.32E+10
FC 4.89E+11 0.00E+00 4.40E+11 4.89E+10
OK620930000100_00
Crooked Creek
near Englewood, ENT 2.91E+10 0.00E+00 2.62E+10 2.91E+09
Derived for illustrative purposes at the median flow value
E.5 Reasonable Assurance
As authorized by Section 402 of the CWA, DEQ has delegation of the NPDES in
Oklahoma, except for certain jurisdictional areas related to agriculture and the oil and gas
industry retained by the Oklahoma Department of Agriculture and Oklahoma Corporation
Commission, for which the USEPA has retained permitting authority. The NPDES program in
Oklahoma is implemented via Title 252, Chapter 606 of the Oklahoma Pollutant Discharge
Elimination System (OPDES) Act, and in accordance with the agreement between DEQ and
USEPA relating to administration and enforcement of the delegated NPDES program.
Implementation of WLAs for point sources is done through permits issued under the OPDES
program.
Upper Cimarron River Area Bacteria TMDLs Introduction
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SECTION 1
INTRODUCTION
1.1 TMDL Program Background
Section 303(d) of the Clean Water Act (CWA) and U.S. Environmental Protection Agency
(USEPA) Water Quality Planning and Management Regulations (40 Code of Federal Regulations
[CFR] Part 130) require states to develop total maximum daily loads (TMDL) for waterbodies not
meeting designated uses where technology-based controls are in place. TMDLs establish the
allowable loadings of pollutants or other quantifiable parameters for a waterbody based on the
relationship between pollution sources and in-stream water quality conditions, so states can
implement water quality-based controls to reduce pollution from point and nonpoint sources and
restore and maintain water quality (USEPA 1991).
This report documents the data and assessment used to establish TMDLs for the pathogen
indicator bacteria fecal coliform and enterococci for certain waterbodies in the Upper Cimarron
River Area of the Cimarron River Basin. Elevated levels of pathogen indicator bacteria in aquatic
environments indicate that a receiving water is contaminated with human or animal feces and that
there is a potential health risk for individuals exposed to the water. Data assessment and TMDL
calculations are conducted in accordance with requirements of Section 303(d) of the CWA, Water
Quality Planning and Management Regulations (40 CFR Part 130), USEPA guidance, and
Oklahoma Department of Environmental Quality (DEQ) guidance and procedures. DEQ is required
to submit all TMDLs to USEPA for review and approval. Once the USEPA approves a TMDL, then
the waterbody may be moved to Category 4a of a state’s Integrated Water Quality Monitoring and
Assessment Report, where it remains until compliance with water quality standards (WQS) is
achieved (USEPA 2003).
The purpose of this TMDL report is to establish pollutant load allocations for indicator bacteria
in impaired waterbodies, which is the first step toward restoring water quality and protecting public
health. TMDLs determine the pollutant loading a waterbody can assimilate without exceeding the
WQS for that pollutant. TMDLs also establish the pollutant load allocation necessary to meet the
WQS established for a waterbody based on the relationship between pollutant sources and in-stream
water quality conditions. A TMDL consists of a wasteload allocation (WLA), load allocation (LA),
and a margin of safety (MOS). The WLA is the fraction of the total pollutant load apportioned to
point sources, and includes stormwater discharges regulated under the National Pollutant Discharge
Elimination System (NPDES) as point sources. The LA is the fraction of the total pollutant load
apportioned to nonpoint sources. The MOS is a percentage of the TMDL set aside to account for the
uncertainty associated with natural process in aquatic systems, model assumptions, and data
limitations.
This report does not stipulate specific control actions (regulatory controls) or management
measures (voluntary best management practices) necessary to reduce bacteria loadings within each
watershed. Watershed-specific control actions and management measures will be identified,
selected, and implemented under a separate process involving stakeholders who live and work in the
watersheds, tribes, and local, state, and federal government agencies.
This TMDL report focuses on waterbodies that DEQ placed in Category 5 of the 2008
Integrated Report [303(d) list] for nonsupport of primary body contact recreation (PBCR):
Upper Cimarron River Area Bacteria TMDLs Introduction
1-2 FINAL
JULY, 2011
· Cimarron River (OK720900000180_00)
· Cimarron River (OK720900000010_00)
· Cimarron River (OK620930000010_00)
· Crooked Creek (OK620930000100_00)
Figure 1-1 is a location map showing the impaired segments of these waterbodies and their
contributing watersheds. This map also displays the locations of the water quality monitoring
(WQM) stations used as the basis for placement of these waterbodies on the Oklahoma 303(d) list.
These waterbodies and their surrounding watersheds are hereinafter referred to as the Study Area.
Elevated levels of bacteria above the WQS also result in the requirement that a TMDL be
developed. The TMDLs established in this report are a necessary step in the process to develop the
bacteria loading controls needed to restore the contact recreation use designated for each waterbody.
Table 1-1 provides a description of the locations of the WQM stations on the 303(d)-listed
waterbodies.
Table 1-1 Water Quality Monitoring Stations used for 2008 303(d) Listing Decision
Waterbody Name Waterbody ID WQM Station WQM Station Locations
Descriptions
Cimarron River near Kenton OK720900000180_00
OK720900-00-0180C
OK720900-00-0180G
SW¼NW¼SW¼ Section 11-5N-2E
SE¼ NE¼ SW¼ Section 4-5N-1E
Cimarron River above Ute
Creek, near Boise City
OK720900000010_00 OK720900-00-0010G SW¼ NE¼ NE¼ Section 9-5N-5E
Cimarron River off US 64,
Mocane
OK620930000010_00 OK620930-00-0010G
OK620930-00-0010T
SE¼NE¼SE¼Section23-29N-26W
SW¼NW¼NW¼Section24-6N-25E
Crooked Creek near
Englewood, KS OK620930000100_00 OK620930-00-0100G SW¼NW¼NW¼Section23-6N-27E
1.2 Watershed Description
General. Some parts of the watersheds in this TMDL are located in Cimarron and Beaver
Counties in Northwestern Oklahoma, Baca County in Colorado, Union County in New Mexico and
Meade County in Kansas. The vast majority of the drainage area for the waterbodies included in this
report is located in Cimarron County.
All watersheds in the Upper Cimarron River Study Area are in the Southwestern Tablelands and
High Plains eco-region. Table 1-2, derived from the 2000 U.S. Census, demonstrates that the
counties in which these watersheds are located are sparsely populated (U.S. Census Bureau 2000).
Table 1-2 County Population and Density
County Name Population
(2000 Census)
Area
(square miles)
Population Density
(per square mile)
Beaver 5,857 1,818 3
Cimarron 3,148 1,841 2
Harper 3,562 1,041 3
Upper Cimarron River Area Bacteria TMDLs Introduction
1-3 FINAL
JULY, 2011
Climate. Table 1-3 summarizes the average annual precipitation for each stream segment.
Average annual precipitation values among the stream segments in this portion of Oklahoma range
between 40.1and 42.1 inches (Oklahoma Climate Survey 2005).
Table 1-3 Average Annual Precipitation by Stream Segment
Waterbody Name Waterbody ID
Average
Annual
(Inches)
Cimarron River near Kenton OK720900000180_00 17.06
Cimarron River above Ute Creek, near Boise City OK720900000010_00 17.02
Cimarron River off US 64, Mocane OK620930000010_00 19.47
Crooked Creek near Englewood, KS OK620930000100_00 22.61
Land Use. Table 1-4 summarizes the acreages and the corresponding percentages of the land
use categories for the contributing watershed associated with each respective Oklahoma waterbody.
The land use/land cover data were derived from the U.S. Geological Survey (USGS) 2001 National
Land Cover Dataset (USGS 2001). The land use categories are displayed in Figure 1-2.
The dominant land use in the Study Area is grassland. The second most prevalent land use is
cultivated land for Cimarron River off US 64, Mocane (OK620930000010_00) and Crooked Creek
near Englewood, Kansas (OK620930000100_00). The second most prevalent land use is shrub land
for the other two Cimarron River segments (OK720900000180_00 &OK720900000010_00).
Upper Cimarron River Area Bacteria TMDLs Introduction
1-4
Table 1-4 Land Use Summaries by Watershed
Land Use Category
Stream Segments
Cimarron River near
Kenton
Cimarron River above Ute
Creek, near Boise City
Cimarron River off
US 64, Mocane
Crooked Creek near
Englewood, KS
Waterbody ID OK720900000180_00 OK720900000010_00 OK620930000010_00 OK620930000100_00
Barren 0.00% 0.05% 0.04% 0.02%
Cultivated 0.17% 4.73% 27.70% 31.81%
Deciduous Forest 0.05% 0.00% 0.09% 0.18%
Developed High Intensity 0.00% 0.00% 0.00% 0.00%
Developed Low Intensity 0.00% 0.00% 0.00% 0.00%
Developed Medium Intensity 0.00% 0.03% 0.15% 0.17%
Developed Open Space 0.41% 1.03% 3.32% 2.87%
Evergreen Forest 2.24% 0.04% 0.00% 0.00%
Grassland 64.55% 69.79% 64.56% 59.30%
Herbaceous Wetland 0.31% 0.65% 0.03% 0.01%
Mixed Forest 0.00% 0.00% 0.00% 0.00%
Pasture Hay 0.00% 0.93% 2.54% 4.89%
Shrub 31.80% 22.64% 0.26% 0.00%
Woody Wetland 0.37% 0.10% 0.30% 0.14%
Water 0.09% 0.01% 1.00% 0.60%
Total Percentage: 100% 100% 100% 100%
Units in Acres
Barren 5 207 137 2
Cultivated 246 21,523 100,624 3,347
Deciduous Forest 74 3 333 19
Developed High Intensity 0 0 12 0
Developed Low Intensity 0 0 0 0
Developed Medium Intensity 4 119 540 18
Developed Open Space 600 4,679 12,068 302
Evergreen Forest 3,311 187 1 0
Grassland 95,351 317,312 234,542 6,240
Herbaceous Wetland 464 2,970 103 1
Mixed Forest 0 0 0 0
Pasture Hay 0 4,247 9,214 514
Shrub 46,972 102,963 939 0
Woody Wetland 540 453 1,104 14
Water 139 28 3,648 63
Total (Acres) 147,706 454,692 363,266 10,522
Upper Cimarron River Area Bacteria TMDLs Introduction
1-5 FINAL
JULY, 2011
Figure 1-1 Watersheds Not Supporting Primary Body Contact Recreation Use within the Study Area
Upper Cimarron River Area Bacteria TMDLs Introduction
1-6 FINAL
JULY, 2011
Figure 1-2 Land Use Map by Watershed
Upper Cimarron River Area Bacteria TMDLs Problem Identification and Water Quality Target
2-1 FINAL
JULY, 2011
SECTION 2
PROBLEM IDENTIFICATION AND WATER QUALITY TARGET
2.1 Oklahoma Water Quality Standards
Title 785 of the Oklahoma Administrative Code includes Oklahoma’s water quality
standards (OWRB 2008). The OWRB has statutory authority and responsibility concerning
establishment of state water quality standards, as provided under 82 Oklahoma Statute [O.S.],
§1085.30. This statute authorizes the OWRB to promulgate rules …which establish
classifications of uses of waters of the state, criteria to maintain and protect such
classifications, and other standards or policies pertaining to the quality of such waters.
[O.S. 82:1085:30(A)]. Beneficial uses are designated for all waters of the state. Such uses are
protected through restrictions imposed by the antidegradation policy statement, narrative water
quality criteria, and numerical criteria (OWRB 2008). An excerpt of the Oklahoma WQS (Title
785) summarizing the State of Oklahoma Antidegredation Policy is provided in Appendix D.
Table 2-1a, an excerpt from the 2008 Integrated Report (DEQ 2008), lists beneficial uses
designated for each bacteria impaired stream segment in the Study Area. The beneficial uses
include:
· AES – Aesthetics
· AG – Agriculture Water Supply
· WWAC – Warm Water Aquatic Community
· FISH – Fish Consumption
· PBCR – Primary Body Contact Recreation
· PPWS – Public & Private Water Supply
· HQW – High Quality Water
Table 2-1 summarizes the PBCR and WWAC use attainment status and bacteria
impairment status for streams in the Study Area. The TMDL priority shown in Table 2-1 is
directly related to the TMDL target date. The TMDLs established in this report, which are a
necessary step in the process of restoring water quality, only address bacteria impairments that
affect the PBCR and WWAC-beneficial uses.
The definition of PBCR is summarized by the following excerpt from Chapter 45 of the
Oklahoma WQS.
(a) Primary Body Contact Recreation involves direct body contact with the water where a
possibility of ingestion exists. In these cases the water shall not contain chemical,
physical or biological substances in concentrations that are irritating to skin or sense
organs or are toxic or cause illness upon ingestion by human beings.
(b) In waters designated for Primary Body Contact Recreation...limits...shall apply only
during the recreation period of May 1 to September 30. The criteria for Secondary Body
Contact Recreation will apply during the remainder of the year.
Upper Cimarron River Area Bacteria TMDLs Problem Identification and Water Quality Target
2-2 FINAL
JULY, 2011
Table 2-1 Excerpt from the Oklahoma 2008 303(d) List
Waterbody ID Waterbody Name
Stream Miles
Priority
TMDL Date
Primary Body
Contact
Recreation
Impairments
Enterococci
E. coli
Fecal
coliform
OK720900000180_00 Cimarron River near Kenton 19 3 2010 N X X X
OK720900000010_00
Cimarron River above Ute Creek,
near Boise City
47 2 2013 N X
OK620930000010_00 Cimarron River off US 64, Mocane 38 3 2016 N X X
OK620930000100_00 Crooked Creek near Englewood,
KS
6 3 2016 N X
N = Not Supporting; Source: 2008 Integrated Report, DEQ 2008
Table 2-1a Designated Beneficial Uses for Each Impaired Waterbody in the Study
Area
Waterbody ID Waterbody Name AES AG WWAC FISH PBCR PPWS Limitation
OK720900000180_00 Cimarron River near Kenton F N N X N I HQW
OK720900000010_00 Cimarron River above Ute Creek, near
Boise City F F I X N F HQW
OK620930000010_00 Cimarron River off US 64, Mocane I N F I N I
OK620930000100_00 Crooked Creek near Englewood, KS I F I X N I
F – Fully supporting; N – Not supporting; I – Insufficient information; X – Not assessed
To implement Oklahoma’s WQS for PBCR, OWRB promulgated Chapter 46,
Implementation of Oklahoma’s Water Quality Standards (OWRB 2008a). The excerpt below
from Chapter 46: 785:46-15-6, stipulates how water quality data will be assessed to determine
support of the PBCR use as well as how the water quality target for TMDLs will be defined for
each bacterial indicator.
(a) Scope. The provisions of this Section shall be used to determine whether the
subcategory of Primary Body Contact of the beneficial use of Recreation designated in OAC
785:45 for a waterbody is supported during the recreation season from May 1 through
September 30 each year. Where data exist for multiple bacterial indicators on the same
waterbody or waterbody segment, the determination of use support shall be based upon the use
and application of all applicable tests and data.
(b) Screening levels.
(1) The screening level for fecal coliform shall be a density of 400 colonies per 100ml.
(2) The screening level for Escherichia coli shall be a density of 235 colonies per 100 ml in
streams designated in OAC 785:45 as Scenic Rivers and in lakes, and 406 colonies per 100 ml
in all other waters of the state designated as Primary Body Contact Recreation.
Upper Cimarron River Area Bacteria TMDLs Problem Identification and Water Quality Target
2-3 FINAL
JULY, 2011
(3) The screening level for enterococci shall be a density of 61 colonies per 100 ml in
streams designated in OAC 785:45 as Scenic Rivers and in lakes, and 108 colonies per 100 ml
in all other waters of the state designated as Primary Body Contact Recreation.
(c) Fecal coliform:
(1) The Primary Body Contact Recreation subcategory designated for a waterbody shall
be deemed to be fully supported with respect to fecal coliform if the geometric mean of 400
colonies per 100 ml is met and no greater than 25% of the sample concentrations from that
waterbody exceed the screening level prescribed in (b) of this Section.
(2) The parameter of fecal coliform is not susceptible to an assessment that Primary Body
Contact Recreation is partially supported.
(3) The Primary Body Contact Recreation subcategory designated for a waterbody shall
be deemed to be not supported with respect to fecal coliform if the geometric mean of 400
colonies per 100 ml is not met, or greater than 25% of the sample concentrations from that
waterbody exceed the screening level prescribed in (b) of this Section, or both such conditions
exist.
(d) Escherichia coli (E. coli):
(1) The Primary Body Contact Recreation subcategory designated for a waterbody shall
be deemed to be fully supported with respect to E. coli if the geometric mean of 126 colonies
per 100 ml is met, or the sample concentrations from that waterbody taken during the
recreation season do not exceed the screening level prescribed in (b) of this Section, or both
such conditions exist.
(2) The parameter of E. coli is not susceptible to an assessment that Primary Body Contact
Recreation is partially supported.
(3) The Primary Body Contact Recreation subcategory designated for a waterbody shall
be deemed to be not supported with respect to E. coli if the geometric mean of 126 colonies per
100 ml is not met and any of the sample concentrations from that waterbody taken during the
recreation season exceed a screening level prescribed in (b) of this Section.
(e) Enterococci:
(1) The Primary Body Contact Recreation subcategory designated for a waterbody shall
be deemed to be fully supported with respect to enterococci if the geometric mean of 33
colonies per 100 ml is met, or the sample concentrations from that waterbody taken during the
recreation season do not exceed the screening level prescribed in (b) of this Section, or both
such conditions exist.
(2) The parameter of enterococci is not susceptible to an assessment that Primary Body
Contact Recreation is partially supported.
(3) The Primary Body Contact Recreation subcategory designated for a waterbody shall
be deemed to be not supported with respect to enterococci if the geometric mean of 33 colonies
per 100 ml is not met and any of the sample concentrations from that waterbody taken during
the recreation season exceed a screening level prescribed in (b) of this Section.
Upper Cimarron River Area Bacteria TMDLs Problem Identification and Water Quality Target
2-4 FINAL
JULY, 2011
Compliance with the Oklahoma WQS is based on meeting requirements for all three
bacterial indicators. Where concurrent data exist for multiple bacterial indicators on the same
waterbody or waterbody segment, each indicator group must demonstrate compliance with the
numeric criteria prescribed (OWRB 2008).
As stipulated in the WQS, utilization of the geometric mean to determine compliance for
any of the three indicator bacteria depends on the collection of five samples within a 30-day
period. For most stream segments in Oklahoma there are insufficient data available to calculate
the 30-day geometric mean since most water quality samples are collected once a month. As a
result, waterbodies placed on the 303(d) list for not supporting the PBCR are the result of
individual samples exceeding the instantaneous criteria or the long-term geometric mean of
individual samples exceeding the geometric mean criteria for each respective bacterial
indicator. Targeting the instantaneous criterion established for the primary body contact
recreation season (May 1st to September 30th) as the water quality goal for TMDLs corresponds
to the basis for 303(d) listing and may be protective of the geometric mean criterion as well as
the criteria for the secondary contact recreation season. However, both the instantaneous and
geometric mean criteria for E. coli and enterococci will be evaluated as water quality targets to
ensure the most protective goal is established for each waterbody.
The specific data assessment method for listing indicator bacteria based on instantaneous
or single sample criterion is detailed in Oklahoma’s 2008 Integrated Report. As stated in the
report, a minimum of 10 samples collected between May 1st and September 30th (during the
primary recreation season) is required to list a segment for E. coli and enterococci.
A sample quantity exception exists for fecal coliform that allows waterbodies to be listed
for nonsupport of PBCR if there are less than 10 samples. The assessment method states that if
there are less than 10 samples and the existing sample set already assures a nonsupport
determination, then the waterbody should be listed for TMDL development. This condition is
true in any case where the small sample set demonstrates that at least three out of six samples
exceed the single sample fecal coliform criterion. In this case if four more samples were
available to meet minimum of 10 samples, this would still translate to >25 percent exceedance
or nonsupport of PBCR (i.e., three out of 10 samples = 33 percent exceedance). For E. coli and
enterococci, the 10-sample minimum was used, without exception, in attainment determination.
2.2 Problem Identification
Table 2-2 summarizes water quality data collected during primary body contact recreation
season from the stream segments between 2000 and 2008 for each indicator bacteria. All the
data within this time frame were used to support the decision to place specific waterbodies
within the Study Area on the DEQ 2008 303(d) list (DEQ 2008). Water quality data from the
primary and secondary contact recreation seasons are provided in Appendix A.
There was sufficient data collected between 2000 and 2008 to make an assessment of the
four segments for the three bacteria numeric criterion. Evidence of nonsupport of primary body
contact recreation beneficial uses was observed for fecal coliform and enterococci indicators in
two segments of Cimarron River (OK720900000180_00 & OK620930000010_00).
Nonsupport of PBCR was also observed for enterococci in Crooked Creek
(OK620930000100_00). There was no evidence of nonsupport of primary body contact
recreation beneficial uses observed for E. coli in two segments of Cimarron River
Upper Cimarron River Area Bacteria TMDLs Problem Identification and Water Quality Target
2-5 FINAL
JULY, 2011
(OK720900000180_00 & OK720900000010_00) although both are listed on 2008 303(d) list.
Table 2-3 summarizes the waterbodies requiring TMDLs for not supporting PBCR.
2.3 Water Quality Target
The Code of Federal Regulations (40 CFR §130.7(c)(1)) states that, “TMDLs shall be
established at levels necessary to attain and maintain the applicable narrative and numerical
water quality standards.” For the waterbodies requiring TMDLs in this report, defining the
water quality target is somewhat complicated by the use of three different bacterial indicators
with three different numeric criteria for determining attainment of PBCR use as defined in the
Oklahoma WQS. An individual water quality target is established for each bacterial indicator
since each indicator group must demonstrate compliance with the numeric criteria prescribed in
the Oklahoma WQS (OWRB 2008). As previously stated, because available bacteria data were
collected on an approximate monthly basis (see Appendix A) instead of at least five samples
over a 30–day period, data for these TMDLs are analyzed and presented in relation to the
instantaneous criteria for fecal coliform and both the instantaneous and a long-term geometric
mean for both E. coli and enterococci.
All TMDLs for fecal coliform must take into account that no more than 25 percent of the
samples may exceed the instantaneous numeric criteria. For E. coli and enterococci, no more
than 10 percent of samples may exceed instantaneous criteria. Since the attainability of stream
beneficial uses for E. coli and enterococci is based on the compliance of either the
instantaneous or a long-term geometric mean criterion, percent reductions goals will be
calculated for both criteria. TMDLs will be based on the percent reduction required to meet
either the instantaneous or long-term geometric mean criterion, whichever is less.
The water quality target for each waterbody will also incorporate an explicit 10 percent
MOS. For example, if fecal coliform is utilized to establish the TMDL, then the water quality
target is 360 organisms per 100 milliliters (mL), 10 percent lower than the instantaneous water
quality criteria (400/100 mL). For E. coli the instantaneous water quality target is
365 organisms/100 mL, which is 10 percent lower than the criterion value (406/100 mL), and
the geometric mean water quality target is 113 organisms/100 mL, which is 10 percent lower
than the criterion value (126/100 mL). For enterococci the instantaneous water quality target is
97/100 mL, which is 10 percent lower than the criterion value (108/100 mL) and the geometric
mean water quality target is 30 organisms/100 mL, which is 10 percent lower than the criterion
value (33/100 mL).
Each water quality target will be used to determine the allowable bacteria load which is derived
by using the actual or estimated flow record multiplied by the instream criteria minus a
10 percent MOS.
Upper Cimarron River Area Bacteria TMDLs Problem Identification and Water Quality Target
2-6 FINAL
JULY, 2011
Table 2-2 Summary of Indicator Bacteria Samples from Primary Body Contact Recreation Season, 2000-2008
Waterbody ID Waterbody Name
Indicator
Bacteria
Geo-Mean
(cfu/100ml)
# of
Samples
# of
Samples
Exceeding
Criterion
% of
Samples
Exceeding
Criterion
2008
303(d) Notes
OK720900000180_00 Cimarron River near Kenton
FC 161 8 3 38% X TMDL required
ENT 67 23 17 74% X TMDL required
EC 68 24 9 38% X Delist: Meets geo-mean
OK720900000010_00
Cimarron River above Ute
Creek, near Boise City
FC
ENT
EC 6 1 X Delist: Not enough data
OK620930000010_00
Cimarron River off US 64,
Mocane
FC 230 33 11 33% X TMDL required
ENT 86 49 37 76% X TMDL required
EC
OK620930000100_00
Crooked Creek near
Englewood, KS
FC
ENT 97 20 16 80% X TMDL required
EC
FC – Fecal Coliform, EC – E. coli, ENT – Enterococci Highlighted indicators are impaired
Table 2-3 Waterbodies Requiring TMDLs for Not Supporting Primary Body Contact Recreation Use
WQM Station Waterbody ID Waterbody Name
Indicator Bacteria
ENT E. coli FC
OK720900-00-0180C
OK720900-00-0180G OK720900000180_00 Cimarron River near Kenton X X
OK620930-00-0010G
OK620930-00-0010T OK620930000010_00 Cimarron River off US 64, Mocane X X
OK620930-00-0100G OK620930000100_00 Crooked Creek near Englewood, KS X
ENT = enterococci; FC = fecal coliform
Upper Cimarron River Area Bacteria TMDLs Pollutant Source Assessment
3-1 FINAL
JULY, 2011
SECTION 3
POLLUTANT SOURCE ASSESSMENT
A source assessment characterizes known and suspected sources of pollutant loading to
impaired waterbodies. Sources within a watershed are categorized and quantified to the extent
that information is available. Bacteria originate from humans and warm-blooded animals; and
sources may be point or nonpoint in nature.
Point sources are permitted through the NPDES program. NPDES-permitted facilities that
discharge treated wastewater are required to monitor for one of the three bacterial indicators
(fecal coliform, E coli, or enterococci) in accordance with its permit. Nonpoint sources are
diffuse sources that typically cannot be identified as entering a waterbody through a discrete
conveyance at a single location. These sources may involve land activities that contribute
bacteria to surface water as a result of rainfall runoff. For the TMDLs in this report, all sources
of pollutant loading not regulated by NPDES are considered nonpoint sources. The following
discussion describes what is known regarding point and nonpoint sources of bacteria in the
impaired watersheds.
3.1 NPDES-Permitted Facilities
Under 40CFR, §122.2, a point source is described as a discernable, confined, and discrete
conveyance from which pollutants are or may be discharged to surface waters. Certain
NPDES-permitted municipal plants are classified as no-discharge facilities. NPDES-permitted
facilities classified as point sources that may contribute bacteria loading include:
· NPDES municipal wastewater treatment plants (WWTP);
· NPDES municipal no-discharge WWTP;
· NPDES municipal separate storm sewer discharge (MS4); and
· NPDES Concentrated Animal Feeding Operation (CAFO).
Continuous point source discharges such as WWTPs, could result in discharge of elevated
concentrations of fecal coliform bacteria if the disinfection unit is not properly maintained, is of
poor design, or if flow rates are above the disinfection capacity. While the no-discharge
facilities do not discharge wastewater directly to a waterbody, it is possible that the collection
systems associated with each facility may be a source of bacteria loading to surface waters.
Stormwater runoff from MS4 areas, which is now regulated under the USEPA NPDES
Program, can also contain high bacteria concentrations. There are no permitted MS4s within
the study area. CAFOs are recognized by USEPA as significant sources of pollution, and may
have the potential to cause serious impacts to water quality if not properly managed. There are
no NPDES permitted CAFOs in the study area.
There are no NPDES permitted facilities of any type in any of the contributing watersheds
in the study area.
3.1.1 Continuous Point Source Discharges
There are no continuous point dischargers within the study area.
Upper Cimarron River Area Bacteria TMDLs Pollutant Source Assessment
3-2 FINAL
JULY, 2011
3.1.2 NPDES No-Discharge Facilities and SSOs
There is no NPDES no-discharge facility in any of the sub-watersheds in the study area.
There are no wastewater collection systems in the study area; hence no sanitary sewer
overflows (SSO).
3.1.3 NPDES Municipal Separate Storm Sewer Discharge
Phase I MS4
In 1990 the USEPA developed rules establishing Phase I of the NPDES Stormwater
Program, designed to prevent harmful pollutants from being washed by stormwater runoff into
MS4s (or from being dumped directly into the MS4) and then discharged into local water
bodies (USEPA 2005). Phase I of the program required operators of medium and large MS4s
(those generally serving populations of 100,000 or greater) to implement a stormwater
management program as a means to control polluted discharges. Approved stormwater
management programs for medium and large MS4s are required to address a variety of water
quality-related issues, including roadway runoff management, municipal-owned operations,
and hazardous waste treatment. There are no Phase I MS4 permits in the Study Area.
Phase II MS4
Phase II of the rule extends coverage of the NPDES Stormwater Program to certain small
MS4s. Small MS4s are defined as any MS4 that is not a medium or large MS4 covered by
Phase I of the NPDES Stormwater Program. Phase II requires operators of regulated small
MS4s to obtain NPDES permits and develop a stormwater management program. Programs are
designed to reduce discharges of pollutants to the “maximum extent practicable,” protect water
quality, and satisfy appropriate water quality requirements of the CWA. Small MS4
stormwater programs must address the following six minimum control measures:
· Public Education and Outreach;
· Public Participation/Involvement;
· Illicit Discharge Detection and Elimination;
· Construction Site Runoff Control;
· Post- Construction Runoff Control; and
· Pollution Prevention/Good Housekeeping.
The small MS4 General Permit for communities in Oklahoma became effective on
February 8, 2005. There are no permitted MS4s within the study area. DEQ provides
information on the current status of its MS4 program on its website, found at:
http://www.deq.state.ok.us/WQDnew/stormwater/ms4/
3.1.4 Concentrated Animal Feeding Operations
There are no NPDES-permitted CAFO facilities within the Study Area.
Upper Cimarron River Area Bacteria TMDLs Pollutant Source Assessment
3-3 FINAL
JULY, 2011
3.2 Nonpoint Sources
Nonpoint sources include those sources that cannot be identified as entering the waterbody
at a specific location. Bacteria originate from rural, suburban, and urban areas. The following
section describes possible major nonpoint sources contributing fecal coliform loading within
the Study Area.
These sources include wildlife, various agricultural activities, land application fields, urban
runoff, failing onsite wastewater disposal (OSWD) systems, and domestic pets.
Bacteria associated with urban runoff can emanate from humans, wildlife, commercially
raised farm animals, and domestic pets. Water quality data collected from streams draining
urban communities often show existing concentrations of fecal coliform bacteria at levels
greater than a state’s instantaneous standards. A study under USEPA’s National Urban Runoff
Project indicated that the average fecal coliform concentration from 14 watersheds in different
areas within the United States was approximately 15,000 /100 mL in stormwater runoff
(USEPA 1983). Water quality data collected from streams draining many of the non-permitted
communities show existing loads of fecal coliform bacteria at levels greater than the
State’s instantaneous standards. Best management practices (BMP) such as buffer strips, repair
of leaking sewage collection systems, elimination of illicit discharges and proper disposal of
domestic animal waste, can reduce bacteria loading to waterbodies.
3.2.1 Wildlife
Fecal coliform bacteria are produced by all warm-blooded animals, including wildlife such
as mammals and birds. In developing bacteria TMDLs it is important to identify the potential
for bacteria contributions from wildlife by watershed. Wildlife is naturally attracted to riparian
corridors of streams and rivers. With direct access to the stream channel, wildlife can be a
concentrated source of bacteria loading to a waterbody. Fecal coliform bacteria from wildlife
are also deposited onto land surfaces, where it may be washed into nearby streams by rainfall
runoff. Currently there are insufficient data available to estimate populations and spatial
distribution of wildlife and avian species by watershed. Consequently it is difficult to assess
the magnitude of bacteria contributions from wildlife species as a general category.
However, adequate data are available by county to estimate the number of deer by
watershed. This report assumes that deer habitat includes forests, croplands, and pastures.
Using Oklahoma Department of Wildlife Conservation county data, the population of deer can
be roughly estimated from the actual number of deer harvested and harvest rate estimates.
Because harvest success varies from year to year based on weather and other factors, the
average harvest from 1999 to 2003 was combined with an estimated annual harvest rate of
20 percent to predict deer population by county. Using the estimated deer population by county
and the percentage of the watershed area within each county, a wild deer population can be
calculated for each watershed. Table 3-1 provides the estimated number of deer for each
watershed.
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Table 3-1 Estimated Deer Populations
Waterbody ID Waterbody Name Deer Acre
OK720900000180_00 Cimarron River near Kenton 50 147,706
OK620930000010_00 Cimarron River off US 64, Mocane 413 363,266
OK620930000100_00 Crooked Creek near Englewood, KS 1 10,522
According to a study conducted by ASAE (the American Society of Agricultural Engineers),
deer release approximately 5x108 fecal coliform units per animal per day (ASAE 1999).
Although only a fraction of the total fecal coliform loading produced by the deer population
may actually enter a waterbody, the estimated fecal coliform production for deer provided in
Table 3-2 in cfu/day provides a relative magnitude of loading in each watershed.
Table 3-2 Estimated Fecal Coliform Production for Deer
Waterbody ID Waterbody Name
Watershed
Area
(acres)
Wild Deer
Population
Estimated
Wild Deer
per acre
Fecal
Production
(x 109 cfu/day)
of Deer
Population
OK720900000180_00 Cimarron River near Kenton 147,706 50 0.0003 25
OK620930000010_00 Cimarron River off US 64,
Mocane 363,266 413 0.0011 206
OK620930000100_00 Crooked Creek near
Englewood, KS 10,522 1 0.0001 0
3.2.2 Non-Permitted Agricultural Activities and Domesticated Animals
There are a number of non-permitted agricultural activities that can also be sources of fecal
bacteria loading. Agricultural activities of greatest concern are typically those associated with
livestock operations (Drapcho and Hubbs 2002). The following are examples of commercially
raised farm animal activities that can contribute to bacteria sources:
· Processed commercially raised farm animal manure is often applied to fields as
fertilizer, and can contribute to fecal bacteria loading to waterbodies if washed into
streams by runoff.
· Animals grazing in pastures deposit manure containing fecal bacteria onto land
surfaces. These bacteria may be washed into waterbodies by runoff.
· Animals often have direct access to waterbodies and can provide a concentrated source
of fecal bacteria loading directly into streams.
Table 3-3 provides estimated numbers of commercially raised farm animals by watershed
based on the 2002 U.S. Department of Agriculture (USDA) county agricultural census data
(USDA 2002). The estimated animal populations in Table 3-3 were derived by using the
percentage of the watershed within each county. Because the watersheds are generally much
Upper Cimarron River Area Bacteria TMDLs Pollutant Source Assessment
3-5 FINAL
JULY, 2011
smaller than the counties, and commercially raised farm animals are not evenly distributed
across counties or constant with time, these are rough estimates only. Cattle generate the
largest amount of fecal coliform and often have direct access to the impaired waterbodies.
Detailed information is not available to describe or quantify the relationship between
instream concentrations of bacteria and land application of manure. The estimated acreage by
watershed where manure was applied in 2002 is shown in Table 3-3. These estimates are also
based on the county level reports from the 2002 USDA county agricultural census, and thus
represent approximations of the land application area in each watershed. Because of the lack of
specific data, for the purpose of these TMDLs, land application of animal manure is not
quantified in Table 3-4 but is considered a potential source of bacteria loading to the
waterbodies in the Study Area. Most poultry feeding operations are regulated by ODAFF, and
are required to land apply chicken waste in accordance with their Animal Waste Management
Plans or Comprehensive Nutrient Management Plans. While these plans are not designed to
control bacteria loading, best management practices and conservation measures, if properly
implemented, could greatly reduce the contribution of bacteria from this group of animals to
the watershed.
According to a study conducted by the ASAE, the daily fecal coliform production rates by
species were estimated as follows (ASAE 1999):
· Beef cattle release approximately 1.04E+11 fecal coliform counts per animal per day;
· Dairy cattle release approximately 1.01E+11 per animal per day
· Swine release approximately 1.08E+10 per animal per day
· Chickens release approximately 1.36E+08 per animal per day
· Sheep release approximately 1.20E+10 per animal per day
· Horses release approximately 4.20E+08 per animal per day;
· Turkey release approximately 9.30E+07 per animal per day
· Ducks release approximately 2.43E+09 per animal per day
· Geese release approximately 4.90E+10 per animal per day
Using the estimated animal populations and the fecal coliform production rates from
ASAE, an estimate of fecal coliform production from each group of commercially raised farm
animals was calculated in each watershed of the Study Area in Table 3-4. Note that only a
small fraction of these fecal coliform are expected to represent loading into waterbodies, either
washed into streams by runoff or by direct deposition from wading animals. Cattle appear to
represent the largest source of fecal bacteria.
According to data provided by Oklahoma Department of Agriculture, Food, and Forestry
(ODAFF), there are no CAFOs or poultry operations in the study area.
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JULY, 2011
Table 3-3 Commercially Raised Farm Animals and Manure Application Area Estimates by Watershed
Waterbody ID Waterbody Name Cattle &
Calves-all
Dairy
Cows
Horses &
Ponies Goats Sheep &
Lambs
Hogs
& Pigs
Ducks &
Geese
Chicken &
Turkeys
Acres of
Manure
Application
OK720900000180_00 Cimarron River near
Kenton 14,463 0 66 0 9 8 0 26 557
OK620930000010_00 Cimarron River off US 64,
Mocane
34,896 54 156 0 198 0 6 116 1,004
OK620930000100_00 Crooked Creek near
Englewood, KS 970 0 1 0 6 60 0 3 38
Table 3-4 Fecal Coliform Production Estimates for Commercially Raised Farm Animals (x109 number/day)
Waterbody ID Waterbody Name Cattle &
Calves-all
Dairy
Cows
Horses
&
Ponies
Goats
Sheep
&
Lambs
Hogs &
Pigs
Ducks
&
Geese
Chickens
& Turkeys Total
OK720900000180_00 Cimarron River near
Kenton 1,504,152 0 28 0 108 86 0 2 1,504,377
OK620930000010_00 Cimarron River off US 64,
Mocane 3,629,184 5,454 66 0 2,376 129,784 15 11 3,766,888
OK620930000100_00 Crooked Creek near
Englewood, KS 100,880 0 0 0 72 648 0 0 101,601
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3.2.3 Failing Onsite Wastewater Disposal Systems and Illicit Discharges
DEQ is responsible for implementing the regulations of Title 252, Chapter 641 of the
Oklahoma Administrative Code, which define design standards for individual and small public
onsite sewage disposal systems (DEQ 2008a). OSWD systems and illicit discharges can be a
source of bacteria loading to streams and rivers. Bacteria loading from failing OSWD systems
can be transported to streams in a variety of ways, including runoff from surface ponding or
through groundwater. Fecal coliform-contaminated groundwater discharges to creeks through
springs and seeps.
To estimate the potential magnitude of OSWDs fecal bacteria loading, the number of
OSWD systems was estimated for each watershed. The estimate of OSWD systems was
derived by using data from the 1990 U.S. Census because this data was not available in the
2000 U.S. Census. The estimate was then prorated based on the population data from both the
1990 and 2000 U.S. Census. The density of OSWD systems within each watershed was
estimated by dividing the number of OSWD systems in each census block by the number of
acres in each census block. This density was then applied to the number of acres of each
census block within a waterbody watershed. Census blocks crossing a watershed boundary
required additional calculation to estimate the number of OSWD systems based on the
proportion of the census tracking falling within each watershed. This step involved adding all
OSWD systems for each whole or partial census block.
Over time, most OSWD systems operating at full capacity will fail. OSWD system
failures are proportional to the adequacy of a state’s minimum design criteria (Hall 2002). The
1995 American Housing Survey conducted by the U.S. Census Bureau estimates that,
nationwide, 10 percent of occupied homes with OSWD systems experience malfunctions
during the year (U.S. Census Bureau 1995). A study conducted by Reed, Stowe & Yanke, LLC
(2001) reported that approximately 12 percent of the OSWD systems in northeast Texas
(adjacent to the study area) were chronically malfunctioning. Most studies estimate that the
minimum lot size necessary to ensure against contamination is roughly one-half to one acre
(Hall 2002). Some studies, however, found that lot sizes in this range or even larger could still
cause contamination of ground or surface water (University of Florida 1987). It is estimated
that areas with more than 40 OSWD systems per square mile (6.25 septic systems per
100 acres) can be considered to have potential contamination problems (Canter and
Knox 1986). Table 3-5 summarizes estimates of sewered and unsewered households for each
watershed in the study area.
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3-8 FINAL
JULY, 2011
Table 3-5 Estimates of Sewered and Unsewered Households
Waterbody ID Waterbody Name Public
Sewer
Septic
Tank
Other
Means
Housing
Units
%
Sewered
OK720900000180_00 Cimarron River near Kenton 2 61 0 63 3%
OK620930000010_00 Cimarron River off US 64,
Mocane 475 345 7 828 57%
OK620930000100_00 Crooked Creek near
Englewood, KS 12 9 0 21 57%
For the purpose of estimating fecal coliform loading in watersheds, an OSWD failure rate
of eight percent was used. Using this eight percent failure rate, calculations were made to
characterize fecal coliform loads in each watershed.
Fecal coliform loads were estimated using the following equation (USEPA 2001):
( )  

 

´ 


 ´  

 

´  


 


= ´
gal
ml
household
person
personday
gal
ml
counts
Failing systems
day
counts
# 3785.2
70
100
10
# #
6
The average of number of people per household was calculated to be 2.48 for counties in
the Study Area (U.S. Census Bureau 2000). Approximately 70 gallons of wastewater was
estimated to be produced on average per person per day (Metcalf and Eddy 1991). The fecal
coliform concentration in septic tank effluent was estimated to be 106 per 100 mL of effluent
based on reported concentrations from a number of published reports (Metcalf and Eddy 1991,
Canter and Knox 1985; Cogger and Carlile 1984). Using this information, the estimated load
from failing septic systems within the watersheds was summarized below in Table 3-6.
Table 3-6 Estimated Fecal Coliform Load from OSWD Systems
Waterbody ID Waterbody Name Acres Septic
Tank
# of Failing
Septic
Tanks
Estimated Loads
from Septic Tanks
( x 109 counts/day)
OK720900000180_00 Cimarron River near
Kenton 147,706 61 5 32
OK620930000010_00 Cimarron River off US 64,
Mocane 363,266 345 28 182
OK620930000100_00 Crooked Creek near
Englewood, KS 10,522 9 1 5
3.2.4 Domestic Pets
Fecal matter from dogs and cats, which is transported to streams by runoff from urban and
suburban areas can be a potential source of bacteria loading. On average nationally, there are
1.7 dogs per household and 2.2 cats per household (American Veterinary Medical
Association 2007). Using the U.S. census data at the block level (U.S. Census Bureau 2000),
Upper Cimarron River Area Bacteria TMDLs Pollutant Source Assessment
3-9 FINAL
JULY, 2011
dog and cat populations can be estimated for each watershed. Table 3-7 summarizes the
estimated number of dogs and cats for the watersheds of the Study Area.
Table 3-7 Estimated Numbers of Pets
Waterbody ID Waterbody Name Housing Units Dogs Cats
OK720900000180_00 Cimarron River near Kenton 63 107 139
OK620930000010_00 Cimarron River off US 64, Mocane 828 1,407 1,821
OK620930000100_00 Crooked Creek near Englewood, KS 21 36 46
Table 3-8 provides an estimate of the fecal coliform load from pets. These estimates are
based on estimated fecal coliform production rates of 5.4x108 per day for cats and 3.3x109 per
day for dogs (Schueler 2000).
Table 3-8 Estimated Fecal Coliform Daily Production by Pets (x 109)
Waterbody ID Waterbody Name Dogs Cats Total
OK720900000180_00 Cimarron River near
Kenton 353 75 428
OK620930000010_00 Cimarron River off US 64,
Mocane 4,644 983 5,628
OK620930000100_00 Crooked Creek near
Englewood, KS 118 25 143
3.3 Summary of Bacteria Sources
NPDES-permitted facilities operate in a few of the watersheds in the Study Area but most
of the point sources are relatively minor and for the most part tend to meet instream water
quality criteria in their effluent. Thus, nonpoint sources are considered to be the major source
of bacteria loading in each watershed. Table 3-9 summarizes the suspected sources of bacteria
loading in each impaired watershed.
Table 3-9 Estimated Major Source of Bacteria Loading by Watershed
Waterbody ID Waterbody Name Point
Sources
Nonpoint
Sources
Major
Source
OK720900000180_00 Cimarron River near Kenton No Yes Nonpoint
OK620930000010_00 Cimarron River off US 64, Mocane No Yes Nonpoint
OK620930000100_00 Crooked Creek near Englewood, KS No Yes Nonpoint
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JULY, 2011
Table 3-10 below provides a summary of the estimated fecal coliform loads in percentage
for the four major nonpoint source categories (commercially raised farm animals, pets, deer and
septic tanks) that are contributing to the elevated bacteria concentrations in each watershed.
Commercially raised farm animals are estimated to be the primary contributors of fecal
coliform loading to land surfaces. It must be noted that while no data are available to estimate
populations and fecal loading of wildlife other than deer, a number of bacteria source tracking
studies demonstrate that wild birds and mammals represent a major source of the fecal bacteria
found in streams.
The magnitude of loading to a stream may not reflect the magnitude of loading to land
surfaces. While no studies quantify these effects, bacteria may die off or survive at different
rates depending on the manure characteristics and a number of other environmental conditions.
Manure handling practices, use of BMPs, and relative location to streams can also affect stream
loading. Also, the structural properties of some manures, such as cow patties, may limit their
wash-off into streams by runoff. Because litter is applied in a pulverized form, it could be a
larger source during storm runoff events. The Shoal Creek report showed that poultry litter was
about 71% of the high flow load and cow pats contributed only about 28% of it (Missouri
Department of Natural Resources, 2003). The Shoal Creek report also showed that poultry litter
was insignificant under low flow conditions up to 50% frequency. In contrast, malfunctioning
septic tank effluent may be present in pools on the surface, or in shallow groundwater, which
may enhance its conveyance to streams.
Table 3-10 Summary of Daily Fecal Coliform Load Estimates from Nonpoint Sources
to Land Surfaces
Waterbody ID Waterbody Name
Commercially
Raised Farm
Animals
Pets Deer Septic
Tanks
OK720900000180_00 Cimarron River near Kenton 99.97% 0.03% 0.00% 0.00%
OK620930000010_00 Cimarron River off US 64, Mocane 99.85% 0.14% 0.00% 0.00%
OK620930000100_00 Crooked Creek near Englewood, KS 99.97% 0.03% 0.00% 0.00%
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SECTION 4
TECHNICAL APPROACH AND METHODS
The objective of a TMDL is to estimate allowable pollutant loads and to allocate these
loads to the known pollutant sources in the watershed so appropriate control measures can be
implemented and the WQS achieved. A TMDL is expressed as the sum of three elements as
described in the following mathematical equation:
TMDL = Σ WLA + Σ LA + MOS
The WLA is the portion of the TMDL allocated to existing and future point sources. The
LA is the portion of the TMDL allocated to nonpoint sources, including natural background
sources. The MOS is intended to ensure that WQSs will be met. Thus, the allowable pollutant
load that can be allocated to point and nonpoint sources can then be defined as the TMDL
minus the MOS.
40 CFR, §130.2(1), states that TMDLs can be expressed in terms of mass per time,
toxicity, or other appropriate measures. For fecal coliform, E. coli, or enterococci bacteria,
TMDLs are expressed as colony-forming units per day, where possible, or as a percent
reduction goal (PRG), and represent the maximum one-day load the stream can assimilate
while still attaining the WQS.
4.1 Using Load Duration Curves to Develop TMDLs
The TMDL calculations presented in this report are derived from load duration curves
(LDC). LDCs facilitate rapid development of TMDLs, and as a TMDL development tool are
effective at identifying whether impairments are associated with point or nonpoint sources.
The technical approach for using LDCs for TMDL development includes the four following
steps that are described in Subsections 4.2 through 4.4 below:
· Preparing flow duration curves for gaged and ungaged stream segments;
· Estimating existing bacteria loading in the receiving water using ambient water quality
data;
· Using LDCs to identify the critical condition that will dictate loading reductions
necessary to attain WQS; and
· Interpreting LDCs to derive TMDL elements – WLA, LA, MOS, and PRG.
Historically, in developing WLAs for pollutants from point sources, it was customary to
designate a critical low flow condition (e.g., 7Q2) at which the maximum permissible loading
was calculated. As water quality management efforts expanded in scope to quantitatively
address nonpoint sources of pollution and types of pollutants, it became clear that this single
critical low flow condition was inadequate to ensure adequate water quality across a range of
flow conditions. Use of the LDC obviates the need to determine a design storm or selected
flow recurrence interval with which to characterize the appropriate flow level for the
assessment of critical conditions. For waterbodies impacted by both point and nonpoint
sources, the “nonpoint source critical condition” would typically occur during high flows, when
rainfall runoff would contribute the bulk of the pollutant load, while the “point source critical
condition” would typically occur during low flows, when WWTP effluents would dominate the
base flow of the impaired water. However, flow range is only a general indicator of the
Upper Cimarron River Area Bacteria TMDLs Technical Approach and Methods
4-2 FINAL
JULY, 2011
relative proportion of point/nonpoint contributions. It is not used in this report to quantify point
source or nonpoint source contributions. Violations that occur during low flows may not be
caused exclusively by point sources. Violations have been noted in some watersheds that
contain no point sources. Research has shown that bacteria loading in streams during low flow
conditions may be due to direct deposit of cattle manure into streams and faulty septic
tank/lateral field systems.
LDCs display the maximum allowable load over the complete range of flow conditions by
a line using the calculation of flow multiplied by the water quality criterion. The TMDL can be
expressed as a continuous function of flow, equal to the line, or as a discrete value derived from
a specific flow condition.
4.2 Development of Flow Duration Curves
Flow duration curves serve as the foundation of LDCs and are graphical representations of
the flow characteristics of a stream at a given site. Flow duration curves utilize the historical
hydrologic record from stream gages to forecast future recurrence frequencies. Many streams
throughout Oklahoma do not have long term flow data and therefore, flow frequencies must be
estimated. The most basic method to estimate flows at an ungaged site involves 1) identifying
an upstream or downstream flow gage; 2) calculating the contributing drainage areas of the
ungaged sites and the flow gage; and 3) calculating daily flows at the ungaged site by using the
flow at the gaged site multiplied by the drainage area ratio. The more complex approach used
here in this TMDL report, also considers watershed differences in rainfall, land use, and the
hydrologic properties of soil that govern runoff and retention. More than one upstream flow
gage may also be considered. A more detailed explanation of the methods for estimating flow
at ungaged streams is provided in Appendix C.
Flow duration curves are a type of cumulative distribution function. The flow duration
curve represents the fraction of flow observations that exceed a given flow at the site of
interest. The observed flow values are first ranked from highest to lowest then, for each
observation, the percentage of observations exceeding that flow is calculated. The flow value
is read from the ordinate (y-axis), which is typically on a logarithmic scale since the high flows
would otherwise overwhelm the low flows. The flow exceedance frequency is read from the
abscissa, which is numbered from 0 to 100 percent, and may or may not be logarithmic. The
lowest measured flow occurs at an exceedance frequency of 100 percent, indicating that flow
has equaled or exceeded this value 100 percent of the time, while the highest measured flow is
found at an exceedance frequency of 0 percent. The median flow occurs at a flow exceedance
frequency of 50 percent. The flow exceedance percentiles for each stream segment addressed
in this report are provided in Appendix C.
While the number of observations required to develop a flow duration curve is not
rigorously specified, a flow duration curve is usually based on more than 1 year of
observations, and encompasses inter-annual and seasonal variation. Ideally, the drought of
record and flood of record are included in the observations. For this purpose, the long-term
flow gaging stations operated by the USGS are utilized (USGS 2007a).
A typical semi-log flow duration curve exhibits a sigmoidal shape, bending upward near a
flow exceedance frequency value of 0 percent and downward at a frequency near 100 percent,
often with a relatively constant slope in between. For sites that on occasion exhibit no flow, the
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curve will intersect the abscissa at a frequency less than 100 percent. As the number of
observations at a site increases, the line of the LDC tends to appear smoother. However, at
extreme low and high flow values, flow duration curves may exhibit a “stair step” effect due to
the USGS flow data rounding conventions near the limits of quantitation. An example of a
typical flow duration curve is shown in Figure 4-1.
Figure 4-1 Flow Duration Curve for Cimarron River near Kenton
(OK720900000180_00)
4.3 Estimating Current Point and Nonpoint Loading
Another key step in the use of LDCs for TMDL development is the estimation of existing
bacteria loading from point and nonpoint sources and the display of this loading in relation to
the TMDL. In Oklahoma, WWTPs that discharge treated sanitary wastewater must meet the
state WQSs for fecal bacteria at the point of discharge. However, for TMDL analysis it is
necessary to understand the relative contribution of WWTPs to the overall pollutant loading
and its general compliance with required effluent limits. The monthly bacteria load for
continuous point source dischargers is estimated by multiplying the monthly average flow rates
by the monthly geometric mean using a conversion factor. The current pollutant loading from
each permitted point source discharge is calculated using the equation below.
Point Source Loading = monthly average flow rates (mgd) * geometric mean of
corresponding fecal coliform concentration * unit conversion factor
Where:
unit conversion factor = 37,854,120 100-ml/million gallons
0.01
0.1
1
10
100
1000
10000
100000
0 10 20 30 40 50 60 70 80 90 100
Flow (cfs)
Flow Exceedance Frequency
Cimarron River - OK720900000180_00
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It is difficult to estimate current nonpoint loading due to lack of specific water quality and
flow information that would assist in estimating the relative proportion of non-specific sources
within the watershed. Therefore, existing instream loads minus the point source loads were
used as an estimate for nonpoint loading.
4.4 Development of TMDLs Using Load Duration Curves
The draft step in the TMDL calculation process involves a group of additional
computations derived from the preparation of LDCs. These computations are necessary to
derive a PRG (which is one method of presenting how much bacteria loading must be reduced
to meet WQSs in the impaired watershed).
Step 1: Generate Bacteria LDCs. LDCs are similar in appearance to flow duration
curves; however, the ordinate is expressed in terms of a bacteria load in cfu/day. The curve
represents the single sample water quality criterion for fecal coliform (400 cfu/100 mL), E. coli
(406 cfu/100 mL), or enterococci (108 cfu/100 mL) expressed in terms of a load through
multiplication by the continuum of flows historically observed at this site. The basic steps to
generating an LDC involve:
· obtaining daily flow data for the site of interest from the USGS;
· sorting the flow data and calculating flow exceedance percentiles for the time period
and season of interest;
· obtaining the water quality data from the primary body contact recreation season
(May 1 through September 30);
· matching the water quality observations with the flow data from the same date;
· display a curve on a plot that represents the allowable load multiplied by the actual
or estimated flow by the WQS for each respective indicator;
· multiplying the flow by the water quality parameter concentration to calculate daily
loads; then
· plotting the flow exceedance percentiles and daily load observations in a load
duration plot.
The culmination of these steps is expressed in the following formula, which is displayed on
the LDC as the TMDL curve:
TMDL (cfu/day) = WQS * flow (cfs) * unit conversion factor
Where: WQS = 400 cfu /100 ml (Fecal coliform); 406 cfu/100 ml (E. coli); or 108 cfu/100 ml
(Enterococci)
unit conversion factor = 24,465,525 ml*s / ft3*day
The flow exceedance frequency (x-value of each point) is obtained by looking up the
historical exceedance frequency of the measured or estimated flow, in other words, the percent
of historical observations that equal or exceed the measured or estimated flow. Historical
observations of bacteria concentration are paired with flow data and are plotted on the LDC.
The fecal coliform load (or the y-value of each point) is calculated by multiplying the fecal
coliform concentration (colonies/100 mL) by the instantaneous flow (cubic feet per second) at
the same site and time, with appropriate volumetric and time unit conversions. Fecal
coliform/E. coli/enterococci loads representing exceedance of water quality criteria fall above
the water quality criterion line.
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Only those flows and water quality samples observed in the months comprising the
primary body contact recreation season are used to generate the LDCs. It is inappropriate to
compare single sample bacteria observations and instantaneous or daily flow durations to a
30-day geometric mean water quality criterion in the LDC.
As noted earlier, runoff has a strong influence on loading of nonpoint pollution. Yet flows
do not always correspond directly to local runoff; high flows may occur in dry weather and
runoff influence may be observed with low or moderate flows.
Step 2: Define MOS. Federal regulations (40 CFR §130.7(c)(1)) require that TMDLs
include a MOS. The MOS is a conservative measure incorporated into the TMDL equation that
accounts for the uncertainty associated with calculating the allowable pollutant loading to
ensure WQSs are attained. USEPA guidance allows for use of implicit or explicit expressions
of the MOS, or both. When conservative assumptions are used in development of the TMDL,
or conservative factors are used in the calculations, the MOS is implicit. When a specific
percentage of the TMDL is set aside to account for uncertainty, then the MOS is considered
explicit. The MOS may be defined explicitly or implicitly. A typical explicit approach would
reserve some specific fraction of the TMDL as the MOS. In an implicit approach, conservative
assumptions used in developing the TMDL are relied upon to provide an MOS to assure that
WQSs are attained.
Step 3: Calculate WLA. As previously stated, the pollutant load allocation for point
sources is defined by the WLA. A point source can be either a wastewater (continuous) or
stormwater (MS4) discharge. Stormwater point sources are typically associated with urban and
industrialized areas, and recent USEPA guidance includes NPDES-permitted stormwater
discharges as point source discharges and, therefore, part of the WLA.
The LDC approach recognizes that the assimilative capacity of a waterbody depends on the
flow, and that maximum allowable loading will vary with flow condition. TMDLs can be
expressed in terms of maximum allowable concentrations, or as different maximum loads
allowable under different flow conditions, rather than single maximum load values. This
concentration-based approach meets the requirements of 40 CFR, 130.2(i) for expressing
TMDLs “in terms of mass per time, toxicity, or other appropriate measures” and is consistent
with USEPA’s Protocol for Developing Pathogen TMDLs (USEPA 2001).
WLA for WWTP. WLAs may be set to zero for watersheds with no existing or planned
continuous permitted point sources. For watersheds with permitted point sources, WLAs may
be derived from NPDES permit limits. A WLA may be calculated for each active NPDES
wastewater discharger using a mass balance approach as shown in the equation below. The
permitted average flow rate used for each point source discharge and the water quality criterion
concentration are used to estimate the WLA for each wastewater facility. All WLA values for
each NPDES wastewater discharger are then summed to represent the total WLA for the
watershed.
WLA (cfu/day) = WQS * flow * unit conversion factor
Where:
Where: WQS = 200 cfu /100 ml (Fecal coliform); 126 cfu/100 ml (E. coli); or 33 cfu/100 ml
(Enterococci)
flow (106 gal/day) = permitted flow
Upper Cimarron River Area Bacteria TMDLs Technical Approach and Methods
4-6 FINAL
JULY, 2011
unit conversion factor = 37,854,120-106gal/day
Step 4: Calculate LA and WLA for MS4s. LAs can be calculated under different flow
conditions as the water quality target load minus the WLA. The LA is represented by the area
under the LDC but above the WLA. The LA at any particular flow exceedance is calculated as
shown in the equation below.
LA = TMDL - ΣWLA – MOS
WLA for MS4s. When there are permitted MS4s in the watershed, WLAs for MS4s will
be calculated based on area prorated LA. This WLA for MS4s may not be the total load
allocated for permitted MS4s unless the whole MS4 area is located within the study
watershed boundary. However, in most case the study watershed intersects only a portion
of the permitted MS4 coverage areas.
Step 5: Estimate WLA Load Reduction. The WLA load reduction was not calculated as
it was assumed that continuous dischargers (NPDES-permitted WWTPs) are adequately
regulated under existing permits to achieve water quality standards at the end-of-pipe and,
therefore, no WLA reduction would be required. All SSOs are considered unpermitted
discharges under State statute and DEQ regulations. For any MS4s that are located within a
watershed requiring a TMDL the load reduction will be equal to the PRG established for the
overall watershed.
Step 6: Estimate LA Load Reduction.
After existing loading estimates are computed for each bacterial indicator, nonpoint load
reduction estimates for each stream segment are calculated by using the difference between
estimated existing loading and the allowable load expressed by the LDC (TMDL-MOS). This
difference is expressed as the overall percent reduction goal for the impaired waterbody. For
fecal coliform the PRG which ensures that no more than 25 percent of the samples exceed the
TMDL based on the instantaneous criteria allocates the loads in a manner that is also protective
of the geometric mean criterion. For E. coli and enterococci, because WQ standards are
considered to be met if 1) either the geometric mean of all data is less than the geometric mean
criteria, or 2) no samples exceed the instantaneous criteria, the TMDL PRG will be the lesser of
that required to meet the geometric mean or instantaneous criteria.
Upper Cimarron River Area Bacteria TMDLs TMDL Calculations
5-1 FINAL
JULY, 2011
SECTION 5
TMDL CALCULATIONS
5.1 Flow Duration Curves
The USGS National Water Information System serves as the primary source of flow
measurements for the application. All available daily average flow values for all gages in
Oklahoma, as well as the nearest upstream and downstream gages in adjacent states, were
retrieved for use in the application. The application includes a data update module that
automatically downloads the most recent USGS data and appends it to the existing flow
database.
Some instantaneous flow measurements were available from various agencies. These were
not combined with the daily average flows or used in calculating flow percentiles, but were
matched to bacteria grab measurements collected at the same site and time. When available,
these instantaneous flow measurements were used in lieu of the daily average flow to calculate
instantaneous bacteria loads.
Figures 5-1 through 5-4 are flow duration curves for each impaired waterbody during the
primary body contact recreation season. The flow duration curve for Cimarron River near
Kenton (OK720900000180_00) was based on measured flows at USGS gage station 07154500.
The flow period used for this station was 1950 through 2010.
The flow duration curve for Cimarron River above Ute Creek, near Boise City
(OK720900000010_00) was based on measured flows at USGS gage station 07155000. The
flow period used for this station was 1905 through 1954. No flow data is available after 1954.
The flow duration curve for Cimarron River off US 64, Mocane (OK620930000010_00)
was estimated using watershed area ratio method based on measured flows at USGS gage
station 07157950 (Cimarron River near Buffalo). The flow period used for this station was
1960 through 2010.
The flow duration curve for Crooked Creek (OK620930000100_00) was based on
measured flows at USGS gage station 07177000 (Crooked Creek near Englewood, KS). The
flow period used for this station was 1942 through 2010.
Upper Cimarron River Area Bacteria TMDLs TMDL Calculations
5-2 FINAL
JULY, 2011
Figure 5-1 Flow Duration Curve for Cimarron River near Kenton
(OK720900000180_00)
Figure 5-2 Flow Duration Curve for Cimarron River above Ute Creek, near Boise City
(OK720900000010_00)
0.01
0.1
1
10
100
1000
10000
100000
0 10 20 30 40 50 60 70 80 90 100
Flow (cfs)
Flow Exceedance Frequency
Cimarron River - OK720900000180_00
0.1
1
10
100
1000
10000
0 10 20 30 40 50 60 70 80 90 100
Flow (cfs) Flow Exceedance Frequency
Cimarron River- OK720900000010_00
Upper Cimarron River Area Bacteria TMDLs TMDL Calculations
5-3 FINAL
JULY, 2011
Figure 5-3 Flow Duration Curve for Cimarron River off US 64, Mocane
(OK620930000010_00)
Figure 5-4 Flow Duration Curve for Crooked Creek near Englewood, KS
(OK620930000100_00)
1
10
100
1000
10000
100000
0 10 20 30 40 50 60 70 80 90 100
Flow (cfs)
Flow Exceedance Frequency
Cimarron River- OK620930000010_00
0.1
1
10
100
1000
10000
100000
0 10 20 30 40 50 60 70 80 90 100
Flow (cfs)
Flow Exceedance Frequency
Crooked Creek- OK620930000100_00
Upper Cimarron River Area Bacteria TMDLs TMDL Calculations
5-4 FINAL
JULY, 2011
5.2 Estimated Loading and Critical Conditions
USEPA regulations at 40 CFR 130.7(c) (1) require TMDLs to take into account critical
conditions for stream flow, loading, and all applicable water quality standards. To accomplish
this, available instream WQM data were evaluated with respect to flows and magnitude of
water quality criteria exceedance using LDCs.
To calculate the bacteria load at the WQS, the flow rate at each flow exceedance percentile
is multiplied by a unit conversion factor (24,465,525 ml*s / ft3*day) and the criterion specific to
each bacterial indicator. This calculation produces the maximum bacteria load in the stream
without exceeding the instantaneous standard over the range of flow conditions. The x-axis
indicates the flow exceedance percentile, while the y-axis is expressed in terms of a bacteria
load.
To estimate existing loading, bacteria observations for the primary body contact recreation
season (May 1st through September 30th) from 1999 to 2007 are paired with the flows measured
or estimated in that segment on the same date. Pollutant loads are then calculated by
multiplying the measured bacteria concentration by the flow rate and a unit conversion factor of
24,465,525 ml*s / ft3*day. The associated flow exceedance percentile is then matched with the
measured flow from the tables provided in Appendix C. The observed bacteria loads are then
added to the LDC plot as points. These points represent individual ambient water quality
samples of bacteria. Points above the LDC indicate the bacteria instantaneous standard was
exceeded at the time of sampling. Conversely, points under the LDC indicate the sample met
the WQS.
The LDC approach recognizes that the assimilative capacity of a waterbody depends on the
flow, and that maximum allowable loading varies with flow condition. Existing loading, and
load reductions required to meet the TMDL water quality target can also be calculated under
different flow conditions. The difference between existing loading and the water quality target
is used to calculate the loading reductions required. Percent reduction goals are calculated for
each watershed and bacterial indicator species as the reductions in load required in order that
no more than 10 percent of the existing instantaneous water quality observations would exceed
the water quality target. This is because for the PBCR use to be supported, criteria for each
bacterial indicator must be met in each impaired waterbody.
Table 5-1 presents the percent reductions necessary for each bacterial indicator in each of
the impaired waterbodies in the Study Area. Attainment of WQS in response to TMDL
implementation will be based on results measured in these stream segments. The appropriate
PRG for each bacteria indicator for each waterbody in Table 5-1 is denoted by the bold text.
Upper Cimarron River Area Bacteria TMDLs TMDL Calculations
5-5 FINAL
JULY, 2011
Table 5-1 TMDL Percent Reductions Required to Meet Water Quality Standards for
Impaired Waterbodies in the Upper Cimarron River Study Area
Waterbody ID Waterbody Name
Percent Reduction Required
FC ENT
Instantaneous Instantaneous Geomean
OK720900000180_00 Cimarron River near Kenton 28% 88% 56%
OK620930000010_00 Cimarron River off US 64, Mocane 20% 99% 66%
OK620930000100_00 Crooked Creek near Englewood, KS 94% 70%
LDCs for each impaired waterbody (for the contact recreation season from 2000 through
2008) for each bacteria indicator are shown in Figures 5-5 through 5-9. Observed data during
both primary body contact recreation season and secondary body contact recreation season are
shown on the load duration curves. However, only data from primary body contact recreation
season (May through September) are used to calculate percent reduction goal because this
calculated reduction is sufficient to ensure that the secondary body contact recreation criteria
are also met.
The LDCs for Cimarron River, segment OK720900000180_00 (Figure 5-5 & 5-6) shows
enterococci and fecal coliform bacteria measurements at WQM station OK720900-00-0180C
and OK720900-00-0180G. The LDCs indicates that enterococci and fecal coliform levels
exceed the instantaneous water quality criteria under various flow conditions for enterococci
and high flows for fecal coliform. This indicates a combination of point sources and non-point
sources as causes for impairments. However, since there is no point source in the sub-watershed,
non-point sources must be the cause of the impairments.
The LDCs for Cimarron River, segment OK620930000010_00 (Figure 5-7 & 5-8) show
measurements for enterococci and fecal coliform at WQM station OK620930-00-0010G and
OK620930-00-0010T. The LDCs indicate that Enterococci and fecal coliform levels exceed
the instantaneous water quality criteria primarily under high flow conditions, but exceedance
also occurs under low flows. This indicates that nonpoint sources are a major cause of
impairment. However, since there is no point discharge in the sub-watershed, non-point
sources must be the cause of the impairments.
The LDC for Crooked Creek, segment OK620930000100_00 (Figure 5-9) show
measurements for enterococci at WQM station OK620930-00-0100G. The LDC indicate that
bacteria levels exceed the instantaneous water quality criteria under various flow conditions,
indicating a combination of point sources and non-point sources as causes for impairments.
However, since there is no point source in the sub-watershed, non-point sources must be the
cause of the impairments.
Upper Cimarron River Area Bacteria TMDLs TMDL Calculations
5-6 FINAL
JULY, 2011
Figure 5-5 Load Duration Curve for Enterococci in Cimarron River near Kenton
(OK720900000180_00)
Figure 5-6 Load Duration Curve for Fecal Coliform in Cimarron River near Kenton
(OK720900000180_00)
0.01
0.1
1
10
100
1000
10000
100000
0 10 20 30 40 50 60 70 80 90 100
Enterococci Dialy Load ( 109 cfu/day)
Flow Exceedance Frequency
Enterococci - OK720900000180_00
Load at WQ Target
FC data - Primary Recreation
0.01
0.1
1
10
100
1000
10000
100000
0 10 20 30 40 50 60 70 80 90 100
Fecal Coliform Dialy Load ( 109 cfu/day)
Flow Exceedance Frequency
Fecal Coliform - OK720900000180_00
Load at WQ Target
FC data - Primary Recreation
Upper Cimarron River Area Bacteria TMDLs TMDL Calculations
5-7 FINAL
JULY, 2011
Figure 5-7 Load Duration Curve for Enterococci in Cimarron River off US 64,
Mocane (OK620930000010_00)
Figure 5-8 Load Duration Curve for Fecal Coliform in Cimarron River off US 64,
Mocane (OK620930000010_00)
1
10
100
1000
10000
100000
0 10 20 30 40 50 60 70 80 90 100
Enterococci Dialy Load ( 109 cfu/day)
Flow Exceedance Frequency
Enterococci - OK620930000010_00
Load at WQ Target
FC data - Primary Recreation
1
10
100
1000
10000
100000
1000000
0 20 40 60 80 100
Fecal Coliform Dialy Load ( 109 cfu/day)
Flow Exceedance Percentile
Fecal Coliform - OK620930000010_00
Load at WQ Target
FC data - Primary Recreation
Upper Cimarron River Area Bacteria TMDLs TMDL Calculations
5-8 FINAL
JULY, 2011
Figure 5-9 Load Duration Curve for Enterococci in Crooked Creek, near Englewood,
KS (OK620930000100_00)
5.3 Wasteload Allocation
There are no NPDES WWTPs discharging into the contributing watersheds in the study
area, hence the WLA is zero.
Permitted storm water discharges are considered point sources. There are no permitted
MS4s within the study area; therefore, a specific wasteload allocation is not calculated for
MS4s.
5.4 Load Allocation
As discussed in Section 3, nonpoint source bacteria loading to the receiving streams of
each waterbody emanate from a number of different sources. The LAs for each stream segment
are calculated as the difference between the TMDL, MOS, and WLA, as follows:
LA = TMDL - ΣWLA - MOS
5.5 Seasonal Variability
Federal regulations (40 CFR §130.7(c)(1)) require that TMDLs account for seasonal
variation in watershed conditions and pollutant loading. The TMDLs established in this report
adhere to the seasonal application of the Oklahoma WQS which limits the PBCR use to the
period of May 1st through September 30th. Seasonal variation was also accounted for in these
TMDLs by using more than 5 years of water quality data and by using the longest period of
USGS flow records when estimating flows to develop flow exceedance percentiles.
1
10
100
1000
10000
100000
0 10 20 30 40 50 60 70 80 90 100
Enterococci Dialy Load ( 109 cfu/day)
Flow Exceedance Frequency
Enterococci -OK620930000100_00
Load at WQ Target
ENT data - Primary Recreation
Upper Cimarron River Area Bacteria TMDLs TMDL Calculations
5-9 FINAL
JULY, 2011
5.6 Margin of Safety
For the TMDLs in this package, an explicit MOS of 10 percent was selected.
5.7 TMDL Calculations
The bacteria TMDLs for the 303(d)-listed stream segments covered in this report were
derived using LDCs. A TMDL is expressed as the sum of all WLAs (point source loads), LAs
(nonpoint source loads), and an appropriate MOS, which attempts to account for uncertainty
concerning the relationship between effluent limitations and water quality.
This definition can be expressed by the following equation:
TMDL = Σ WLA + Σ LA + MOS
The TMDL represents a continuum of desired load over all flow conditions, rather than
fixed at a single value, because loading capacity varies as a function of the flow present in the
stream. The higher the flow is, the more wasteload the stream can handle without violating
water quality standards. Regardless of the magnitude of the WLA calculated in these TMDLs,
future new discharges or increased load from existing discharges will be considered consistent
with the TMDL provided that the NPDES permit requires instream criteria to be met.
The TMDL, WLA, LA, and MOS will vary with flow condition, and are calculated at every
5th flow interval percentile (Tables 5-2 through 5-6).
Upper Cimarron River Area Bacteria TMDLs TMDL Calculations
5-10 FINAL
JULY, 2011
Table 5-2 Enterococci TMDL Calculations for Cimarron River near Kenton
(OK720900000180_00)
Percentile Flow
(cfs)
TMDL
(cfu/day)
WLA
(cfu/day)
LA
(cfu/day)
MOS
(cfu/day)
0 11000 2.91E+13 0 2.62E+13 2.91E+12
5 20 5.28E+10 0 4.76E+10 5.28E+09
10 7 1.72E+10 0 1.55E+10 1.72E+09
15 4 1.06E+10 0 9.51E+09 1.06E+09
20 3 7.93E+09 0 7.13E+09 7.93E+08
25 2 6.08E+09 0 5.47E+09 6.08E+08
30 2 5.02E+09 0 4.52E+09 5.02E+08
35 2 3.96E+09 0 3.57E+09 3.96E+08
40 1 2.91E+09 0 2.62E+09 2.91E+08
45 1 2.38E+09 0 2.14E+09 2.38E+08
50 1 1.61E+09 0 1.45E+09 1.61E+08
55 0.4 1.03E+09 0 9.27E+08 1.03E+08
60 0.2 5.28E+08 0 4.76E+08 5.28E+07
65 0.1 2.64E+08 0 2.38E+08 2.64E+07
70 0.03 7.93E+07 0 7.13E+07 7.93E+06
75 0 0 0 0 0
80 0 0 0 0 0
85 0 0 0 0 0
90 0 0 0 0 0
95 0 0 0 0 0
100 0 0 0 0 0
Upper Cimarron River Area Bacteria TMDLs TMDL Calculations
5-11 FINAL
JULY, 2011
Table 5-3 Fecal Coliform TMDL Calculations for Cimarron River near Kenton
(OK720900000180_00)
Percentile Flow
(cfs)
TMDL
(cfu/day)
WLA
(cfu/day)
LA
(cfu/day)
MOS
(cfu/day)
0 11000 1.08E+14 0 9.69E+13 1.08E+13
5 20 1.96E+11 0 1.76E+11 1.96E+10
10 7 6.36E+10 0 5.72E+10 6.36E+09
15 4 3.91E+10 0 3.52E+10 3.91E+09
20 3 2.94E+10 0 2.64E+10 2.94E+09
25 2 2.25E+10 0 2.03E+10 2.25E+09
30 2 1.86E+10 0 1.67E+10 1.86E+09
35 2 1.47E+10 0 1.32E+10 1.47E+09
40 1 1.08E+10 0 9.69E+09 1.08E+09
45 1 8.81E+09 0 7.93E+09 8.81E+08
50 1 5.97E+09 0 5.37E+09 5.97E+08
55 0.4 3.82E+09 0 3.43E+09 3.82E+08
60 0.2 1.96E+09 0 1.76E+09 1.96E+08
65 0.1 9.79E+08 0 8.81E+08 9.79E+07
70 0.03 2.94E+08 0 2.64E+08 2.94E+07
75 0 0 0 0 0
80 0 0 0 0 0
85 0 0 0 0 0
90 0 0 0 0 0
95 0 0 0 0 0
100 0 0 0 0 0
Upper Cimarron River Area Bacteria TMDLs TMDL Calculations
5-12 FINAL
JULY, 2011
Table 5-4 Enterococci TMDL Calculations for Cimarron River off US 64,
Mocane (OK620930000010_00)
Percentile Flow
(cfs)
TMDL
(cfu/day)
WLA
(cfu/day)
LA
(cfu/day)
MOS
(cfu/day)
0 12500 3.30E+13 0 2.97E+13 3.30E+12
5 345 9.11E+11 0 8.19E+11 9.11E+10
10 209 5.52E+11 0 4.97E+11 5.52E+10
15 158 4.17E+11 0 3.75E+11 4.17E+10
20 130 3.43E+11 0 3.09E+11 3.43E+10
25 110 2.91E+11 0 2.62E+11 2.91E+10
30 93 2.46E+11 0 2.21E+11 2.46E+10
35 80 2.11E+11 0 1.90E+11 2.11E+10
40 68 1.80E+11 0 1.62E+11 1.80E+10
45 59 1.56E+11 0 1.40E+11 1.56E+10
50 50 1.32E+11 0 1.19E+11 1.32E+10
55 40 1.06E+11 0 9.51E+10 1.06E+10
60 31 8.19E+10 0 7.37E+10 8.19E+09
65 23 6.08E+10 0 5.47E+10 6.08E+09
70 16 4.23E+10 0 3.80E+10 4.23E+09
75 9 2.38E+10 0 2.14E+10 2.38E+09
80 4 1.03E+10 0 9.27E+09 1.03E+09
85 1 2.48E+09 0 2.24E+09 2.48E+08
90 0.1 3.17E+08 0 2.85E+08 3.17E+07
95 0 0 0 0 0
100 0 0 0 0 0
Upper Cimarron River Area Bacteria TMDLs TMDL Calculations
5-13 FINAL
JULY, 2011
Table 5-5 Fecal Coliform TMDL Calculations for Cimarron River off US 64, Mocane
(OK620930000010_00)
Percentile Flow
(cfs)
TMDL
(cfu/day)
WLA
(cfu/day)
LA
(cfu/day)
MOS
(cfu/day)
0 12500 1.22E+14 0 1.10E+14 1.22E+13
5 345 3.37E+12 0 3.04E+12 3.37E+11
10 209 2.05E+12 0 1.84E+12 2.05E+11
15 158 1.54E+12 0 1.39E+12 1.54E+11
20 130 1.27E+12 0 1.14E+12 1.27E+11
25 110 1.08E+12 0 9.69E+11 1.08E+11
30 93 9.10E+11 0 8.19E+11 9.10E+10
35 80 7.83E+11 0 7.05E+11 7.83E+10
40 68 6.65E+11 0 5.99E+11 6.65E+10
45 59 5.77E+11 0 5.20E+11 5.77E+10
50 50 4.89E+11 0 4.40E+11 4.89E+10
55 40 3.91E+11 0 3.52E+11 3.91E+10
60 31 3.03E+11 0 2.73E+11 3.03E+10
65 23 2.25E+11 0 2.03E+11 2.25E+10
70 16 1.57E+11 0 1.41E+11 1.57E+10
75 9 8.81E+10 0 7.93E+10 8.81E+09
80 4 3.82E+10 0 3.43E+10 3.82E+09
85 1 9.20E+09 0 8.28E+09 9.20E+08
90 0.1 1.17E+09 0 1.06E+09 1.17E+08
95 0 0 0 0 0
100 0 0 0 0 0
Upper Cimarron River Area Bacteria TMDLs TMDL Calculations
5-14 FINAL
JULY, 2011
Table 5-6 Enterococci TMDL Calculations for Crooked Creek near Englewood, KS
(OK620930000100_00)
Percentile Flow
(cfs)
TMDL
(cfu/day)
WLA
(cfu/day)
LA
(cfu/day)
MOS
(cfu/day)
0 12700 3.36E+13 0 3.02E+13 3.36E+12
5 62 1.63E+11 0 1.47E+11 1.63E+10
10 30 7.93E+10 0 7.13E+10 7.93E+09
15 23 6.08E+10 0 5.47E+10 6.08E+09
20 20 5.28E+10 0 4.76E+10 5.28E+09
25 17 4.49E+10 0 4.04E+10 4.49E+09
30 16 4.23E+10 0 3.80E+10 4.23E+09
35 14 3.70E+10 0 3.33E+10 3.70E+09
40 13 3.43E+10 0 3.09E+10 3.43E+09
45 12 3.17E+10 0 2.85E+10 3.17E+09
50 11 2.91E+10 0 2.62E+10 2.91E+09
55 10 2.64E+10 0 2.38E+10 2.64E+09
60 9 2.38E+10 0 2.14E+10 2.38E+09
65 8 2.14E+10 0 1.93E+10 2.14E+09
70 7 1.96E+10 0 1.76E+10 1.96E+09
75 6 1.69E+10 0 1.52E+10 1.69E+09
80 5 1.37E+10 0 1.24E+10 1.37E+09
85 4 1.06E+10 0 9.51E+09 1.06E+09
90 2 6.34E+09 0 5.71E+09 6.34E+08
95 0 0 0 0 0
100 0 0 0 0 0
Upper Cimarron River Area Bacteria TMDLs TMDL Calculations
5-15 FINAL
JULY, 2011
5.8 Reasonable Assurances
DEQ will collaborate with a host of other state agencies and local governments working
within the boundaries of state and local regulations to target available funding and technical
assistance to support implementation of pollution controls and management measures. Various
water quality management programs and funding sources provide reasonable assurance that the
pollutant reductions as required by these TMDLs can be achieved and water quality can be
restored to maintain designated uses. DEQ’s Continuing Planning Process (CPP), required by
the CWA §303(e)(3) and 40 CFR 130.5, summarizes Oklahoma’s commitments and programs
aimed at restoring and protecting water quality throughout the State (DEQ 2007). The CPP can
be viewed from DEQ’s website at http://www.deq.state.ok.us/WQDnew/pubs/2006_cpp_draft.pdf.
Table 5-7 provides a partial list of the state partner agencies DEQ will collaborate with to
address point and nonpoint source reduction goals established by TMDLs.
Table 5-7 Partial List of Oklahoma Water Quality Management Agencies
Agency Web Link
Oklahoma Conservation
Commission
http://www.ok.gov/conservation/Agency_Divisions/Water_Quality_Division
Oklahoma Department of
Wildlife Conservation
http://www.wildlifedepartment.com
Oklahoma Department of
Agriculture, Food, and
Forestry
http://www.oda.state.ok.us/aems.htm
Oklahoma Water Resources
Board
http://www.owrb.ok.gov/quality/index.php
The Oklahoma Conservation Commission (OCC) is the lead agency for Nonpoint Source
Pollution in Oklahoma. The primary mechanisms used for management of nonpoint source
pollution are incentive-based programs that support the installation of BMPs and public
education and outreach. Other programs include regulations and permits for CAFOs. The
CAFO Act, as administered by the ODAFF, provides CAFO operators the necessary tools and
information to deal with the manure and wastewater animals produce so streams, lakes, ponds,
and groundwater sources are not polluted. In addition, financial incentives are currently
available to assist qualified applicants with construction of fences to create riparian buffers,
ponds, wells, livestock watering facilities and stream crossings through the USDA, Natural
Resources Conservation Service (NRCS) Environmental Quality Incentives Programs (DQIP)
and the Wildlife Habitat Incentives Program (WHIP).
As authorized by Section 402 of the CWA, the DEQ has delegation of the NPDES
Program in Oklahoma, except for certain jurisdictional areas related to agriculture and the oil
and gas industry retained by State Department of Agriculture and Oklahoma Corporation
Commission, for which the USEPA has retained permitting authority. The NPDES Program in
Oklahoma is implemented via OAC Title 252, Chapter 606 and the Oklahoma Pollutant
Discharge Elimination System (OPDES) Act and in accordance with the agreement between
DEQ and USEPA relating to administration and enforcement of the delegated NPDES
Upper Cimarron River Area Bacteria TMDLs TMDL Calculations
5-16 FINAL
JULY, 2011
Program. Implementation of point source WLAs is done through permits issued under the
OPDES program.
The reduction rates called for in this TMDL report are as high as75 percent. The DEQ
recognizes that achieving such high reductions will be very difficult, especially since
unregulated nonpoint sources are a major cause of the impairment. The high reduction rates are
not uncommon for pathogen-impaired waters. Similar reduction rates are often found in other
pathogen TMDLs around the nation. The suitability of the current criteria for pathogens and
the beneficial uses of the receiving stream should be reviewed. For example, the Kansas
Department of Environmental Quality has proposed to exclude certain high flow conditions
during which pathogen standards will not apply, although that exclusion was not approved by
the USEPA. Additionally, USEPA has been conducting new epidemiology studies and may
develop new recommendations for pathogen criteria in the near future.
Revisions to the current pathogen provisions of Oklahoma’s WQS should be considered.
There are three basic approaches to such revisions that may apply.
· Removing the PBCR use: This revision would require documentation in a Use
Attainability Analysis that the use is not existing and cannot be attained. It is unlikely
this approach would be successful since there is evidence that people do swim in these
waterbodies, thus constituting an existing use. Existing uses cannot be removed.
· Modifying application of the existing criteria: This approach would include
considerations such as an exemption under certain high flow conditions, an allowance
for wildlife or “natural conditions,” a sub-category of the use or other special provision
for urban areas, or other special provisions for storm flows. Since large bacteria
violations occur over all flow ranges, it is likely that large reductions would still be
necessary. However, this approach may have merit and should be considered.
· Revising the existing numeric criteria: Oklahoma’s current pathogen criteria are
based on USEPA guidelines (See Implementation Guidance for Ambient Water
Quality Criteria for Bacteria, May 2002 Draft; and Ambient Water Quality Criteria for
Bacteria-1986, January 1986). However, those guidelines have received much
criticism and USEPA studies that could result in revisions to their recommendations
are ongoing. The use of the three indicators specified in Oklahoma’s standards should
be evaluated. The numeric criteria values should also be evaluated using a risk-based
method such as that found in USEPA guidance.
Unless or until the WQS are revised and approved by USEPA, federal rules require that the
TMDLs in this report must be based on attainment of the current standards. If revisions to the
pathogen standards are approved in the future, reductions specified in these TMDLs will be re-evaluated.
Upper Cimarron River Area Bacteria TMDLs Public Participation
6-1 FINAL
JULY, 2011
SECTION 6
PUBLIC PARTICIPATION
This report is submitted to EPA for technical review. After the technical approval, a public
notice will be circulated to the local newspapers and/or other publications in the area affected
by this TMDL. The public will have opportunities to review the TMDL report and make
written comments. The public comment period lasts 45 days. Depending on the interest and
responses from the public, a public meeting may be held within the watershed affected by this
TMDL. If a public meeting is held, the public will also have opportunities to ask questions and
make formal oral comments at the meeting and/or to submit written comments at the public
meeting.
All written comments received during the public notice period become a part of the record
of this TMDL. All comments will be considered and the TMDL report will be revised
according to the comments if necessary in the ultimate completion of this TMDL for
submission to EPA for final approval.
Upper Cimarron River Area Bacteria TMDLs References
7-1 FINAL
JULY, 2011
SECTION 7
REFERENCES
American Veterinary Medical Association 2007. U.S. Pet Ownership and Demographics
Sourcebook (2007 Edition). Schaumberg, IL.
ASAE (American Society of Agricultural Engineers). 1999. ASAE standards, 46th edition:
standards, engineering practices, data. St. Joseph, MI.
Canter, LW and RC Knox 1985. Septic tank system effects on ground water quality. Lewis
Publishers, Boca Raton, FL.
Cleland 2003. Cleland, B., TMDL Development from the “Bottom Up” – Part III: Duration
Curves and Wet-Weather Assessments. Water Environment Federation National
TMDL Science and Policy Conference 2003. Chicago, IL.
Cogger, CG and BL Carlile 1984. Field performance of conventional and alternative septic
systems in wet soils. J. Environ. Qual. 13 (1).
Drapcho, C.M. and A.K.B. Hubbs 2002. Fecal Coliform Concentration in Runoff from Fields
with Applied Dairy Manure. http://www.lwrri.lsu.edu/downloads/Drapcho_annual%20report01-
02.pdf
Hall, S. 2002. Washington State Department of Health, Wastewater Management Program
Rule Development Committee, Issue Research Report - Failing Systems, June 2002.
Metcalf and Eddy 1991. Wastewater Engineering: Treatment, Disposal, Reuse: 2nd Edition.
DE