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EPA Region 7 TMDL Review

TMDLDD:	2814	Water Body ID: 2814

Water Body Name:	Main Ditch

Tributary:	Main Ditch

Pollutant:	Biochemical Oxygen Demand (BOD), Volatile Suspended Solids (VSS), Low
Dissolved Oxygen (DO)

State:	Missouri	HUC: 11010007-070005

BASIN:	Pike Creek (Lower Black River Basin)

Submittal Date:	November 10, 2005

Approved:	Yes

Submittal Letter

State submittal letter indicates final TMDL(s) for specific polIutant(s)/water(s) were adopted by the state, and
submitted to EPA for approval under section 303(d) of the Clean Water Act.

Letter dated November 10, 2005, was received by EPA November 16, 2005, formally submitting this TMDL
for approval under Section 303(d).

Water Quality Standards Attainment

The water body's loading capacity for the applicable pollutant is identified and the rationale for the method
used to establish the cause-and-effect relationship between the numeric target and the identified pollutant
sources is described. TMDL and associated allocations are set at levels adequate to result in attainment of
applicable water quality standards.

The loading capacity for Biological Oxygen Demand (BOD), Volatile Suspended Solid (VSS), and Ammonia
are identified, and were determined using the QUAL2E water quality model. High BOD, and VSS cause low
DO in the receiving stream, which eliminates many aquatic organisms that require high levels of oxygen to
survive.

BOD loading resulting in violations of the dissolved oxygen (DO) criterion were modeled based upon meeting
5.0 mg/L DO in Main Ditch which, upon implementation of the WLA concentration-based permit limits,
should result in attainment of both narrative and numeric water quality standards (WQS) for the protection of
the Warm water Aquatic Life designated use.

If EPA approves the "site-specific criteria" revision, the TMDL can be reopened and the allocations revised to
reflect the WQS change in regard to the "site specific DO criteria". In addition to BOD, VSS, and Low DO
the city's NPDES permit must be reissued with the Waste Load Allocation (WLA) derived permit limit
concentration identified in the TMDL for BOD, VSS, and Ammonia.

Numeric Target(s)

Submittal describes applicable water quality standards, including beneficial uses, applicable numeric and/or
narrative criteria. If the TMDL is based on a target other than a numeric water quality criterion, then a
numeric expression, site specific ifpossible, was developedfrom a narrative criterion and a description of the
process used to derive the target is included in the submittal

All WQS, criteria, and beneficial uses have been described. BOD and Ammonia are the parameters modeled
to determine the impact the WWTP will cause low DO levels in Main Ditch; seasonal Ammonia criteria were
targeted using temperature and pH per the MO WQS, The VSS criteria is narrative, therefore in this TMDL,
the targeted value was derived using best professional judgment due to the fact there is no immediate upstream
VSS data which would assist in targeting a natural background concentration.


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Numeric Target(s) and Pollutant(s) of concern

An explanation and analytical basis for expressing the TMDL through surrogate measures (e.g., parameters
such as percent fines and turbidity for sediment impairments, or chlorophyll-a and phosphorus loadings for
excess algae) is provided, if applicable. For each identified pollutant, the submittal describes analytical basis
for conclusions, allocations and margin of safety that do not exceed the load capacity.

The water quality model QUAL2E generated the numeric link between DO, and BOD and Ammonia.

Seasonal Ammonia criteria were targeted using temperature and pH per the MO WQS. VSS was not
simulated in the model. Its WLA was derived through statistical calculations of available data. The 25th
percentile value of all VSS data is 2.499. Since the detection level for this pollutant is 5 mg/L, a no detection
measurement is reported in the database as 2.499 to allow numerical computation. The 2.499 equals the
detection level value (5) divided by 2 minus 1 plus 0.099 [no-detection = 5/2-1+0.099]. The 99 at the end, is a
flag to indicate no detection. The VSS target was conservatively set to 5 mg/L.

Source Analysis

Important assumptions made in developing the TMDL, such as assumed distribution of land use in the
watershed, population characteristics, wildlife resources, and other relevant information affecting the
characterization of the pollutant of concern and its allocation to sources, are described. Point, non point and
background sources ofpollutants of concern are described, including magnitude and location of the sources.
Submittal demonstrates all significant sources have been considered.

Land use and soils are described as well as the history of the area. The sole source of the impairment is
Poplar Bluff Waste Water Treatment Facility (WWTF); NPDES permit number MO-0043648. Main Ditch is
on the 2002-303(d) list due to high BOD, VSS, and low DO.

Point Source Poplar Bluff WWTF is the only discharger in the impaired segment's watershed. The current
permit has a design flow of 1.9 million gallons per day (MOD) (about 4.5 cubic feet per second [ft3/S]) and
contains the following effluent limits: BODj 30/45 mg/L monthly weekly averages respectively, TSS 80/120
mg/L, NH3 10 mg/L, and a pH>~6 standard units. This permit expired July 30,2003. The monthly DMRs
summary for the period of January 1999 to March 2004 is presented in Table la. These reports show that the
median lagoon discharge is 8ft3/s, the average is lOftVs and its upper 95th confidence interval is 10.5 ft3/s.

This is about twice the design flow. BOD5 is the amount of oxygen used to decompose the organic matter
present in a water sample in a five-day period. The discharge in this calculation is the overall monthly average
of all flows reported for April through October (lOfr/s).

Non Point Source in this watershed consists of runoff from agricultural fields during rain events. Main ditch
receives discharge from the Poplar Bluff WWTF (lagoon system) and from many irrigation drainage pipes.
The flow and water quality from these drainage pipes are variable and difficult to quantify accurately. The
drainage pipes discharge during wet season, rain events and during the dry season, when fanners irrigate their
crops. The emphasis is to model the dry season because it is the critical period for aquatic life survival. Any
runoff due to irrigation waters alone is conceptually represented in the model as a point source. These pipes
are not regulated or permitted under the NPDES system. All significant sources have been considered at this
time.

Allocation

Submittal identifies appropriate wasteload allocations for point, and load allocations for nonpoint sources. If
no point sources are present the wasteload allocation is zero. If no nonpoint sources are present, the load
allocation is zero.


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Allocations of Main Ditch, receives discharge from the Poplar Bluff WWTF (lagoon system) and from many
irrigation drainage pipes. The flow and water quality from these drainage pipes are variable and difficult to
quantify accurately.

The QUAL2E mode! was calibrated to the simulation of flow, velocity, BOD, DO organic nitrogen, Ammonia
nitrogen, nitrate and nitrite nitrogen, within the range of measured data for these parameters. The WLA's for
BOD, VSS, and Ammonia-N were derived from adjusting the plant discharge in the model to the full design
flow of 4.5 cfs. Because Main Ditch is a Class C stream at the outfall, lagoon effluent qualifies for a mixing
zone as allowed in Missouri WQS (MO 10CSR 20-7.031(4)(A) 5.B. (II)(a)), therefore, a mixing zone applies
to this TMDL. An additional test was done with the model with the application of winter conditions. The
WLA concentrations are identified and will be incorporated in Poplar Bluff Waster Water Treatment Plant
NPDES permit in the next; permit reissurance.

WLA Comment

Waste load allocations (WLAs) for the city near poplar Bluff WWTP are as follows:

The facility has been operating above capacity in the last five years as indicated in the DMR data, the
modeling -simulation results are based on an average actual flow of 1 Oft3/s.

Load of 20 mg/L BOD-equivalent to 1079 lb/day of CBOD, (the old NPDES permit maximum daily limits
were 45 mg/L BOD and monthly average limit 30 mg/L BOD).

Load of 5 mg/L VSS-equivalent to 270 lb/day, (the old NPDES permit maximum daily limits were 80 mg/L
and average monthly limit of 120 mg/L TSS).

NH3-N (Ammonia as Nitrogen) is seasonal based upon summer and winter:

Summer: 1.7 mg/L NH3-N and 67 lb/day
Winter: 2.8 mg/L NH3-N and 110.60 lb/day

LA Comment

The load allocation (LA) is the maximum allowable amount of the pollutant that can be assigned to non-point
sources. Because of the timing of data collection, only discharge from the irrigation pipes is represented. The
LA contribution is relatively small when compared to that of the lagoon system. The LA's for non-point
source are as follows: CBOD-69 lb/day, NH3-N-18 LB/day, and VSS-94 lb/day

Margin of Safety

Submittal describes explicit and/or implicit margin of safety for each pollutant. If the MOS is implicit, the
conservative assumptions in the analysis for the MOS are described. If the MOS is explicit, the loadings set
aside for the MOS are identified and a rationale for selecting the value for the MOS is provided.

The MOS is implicit based upon the model assumptions and calculations. The limits for BOD, VSS, AND
NH3-N were derived from QUAL2E simulation that considered a background DO concentration of Img/L
instead of the lowest recorded levels of 4.3, 3.6, and 2.8 mg/L for August 2000, July 2002, and August 2002
respectively.

Seasonal Variation and Critical Conditions

Submittal describes the methodfor accounting for seasonal variation and critical conditions in the TMDL(s).

Seasonal variation is taken into consideration for ammonia as nitrogen and a separate limit calculated for each
summer and winter. Otherwise, the WWTP NPDES permit limits apply year long.


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Public Participation

Submittal describes public notice and public comment opportunity, and explains how the public comments
were considered in the final TMDL(s).

The Missouri Department of Natural Resources (MDNR) placed this TMDL on public notice from August 5,
2005 to September 4, 2005, on MDNR's state website. Groups which received the public notice
announcement include the Missouri Clean Water Commission, the Water Quality Coordinating Committee,
the TMDL Policy Advisory Committee, Stream Team volunteers in the watershed (21 people) the appropriate
legislators, Senator Robert Mayer, Representative Gayle Kingery, Representative Mike Dethrow, and
Representative Otto Bean and others that routinely receive the public notice of Missouri State Operating
Permits,

Monitoring Plan for TMDL(s) Under Phased Approach

The TMDL identifies the monitoring plan that describes the additional data to be collected to determine if the
load reductions required by the TMDL lead to attainment ofWQS, and a schedule for considering revisions to
the TMDL(s) (wherephased approach is used).

Periodic effluent and stream monitoring is required In Poplar Bluff W WTP permit and requires samples be
taken from stream monitoring sites for the following parameters; DO, pH, Temperature, Ammonia, BOD and
VSS will validate the adequacy of this calculation. In addition, low flow stream survey and biological
assessment shall be performed one to two years following treatment facility construction TMDL
implementation to properly link stream water quality and biocriteria to the proposed effluent limits and BMP
activities in the watershed. MDNR routinely (about every five to seven years) monitors small streams that
receive wastewater effluent from facilities that discharge at least 1 MGD.

Reasonable assurance

Reasonable assurance only applies when reductions in nonpoint source loading is required to meet the
prescribed waste load allocations.

The Waste Load Allocations are set to meet quality standards; no reasonable assurances are required of the
Load Allocation. MDNR will work with the City of Popular Bluff to discuss treatment plant upgrades and
funding options and will issue a permit reflective of the water quality standards that must be met.


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