NAME AND ADDRESS OF FACILITY WHERE DISCHARGE OCCURS:

The Middleborough Water Pollution Control Facility is a 2.16 mgd advanced treatment facility

which discharges to the Nemasket River. The facility processes include primary clarification,

activated sludge treatment, secondary clarification, sand filters, seasonal chlorination and

dechlorination (using sodium bisulfite), and post aeration. The facility removes phosphorus

seasonally through chemical precipitation using ferric chloride. The facility maintains yearround

nitrification. Septage is received from the Towns of Middleborough and Lakeville.

Sludge is disposed in the Middleborough Town landfill (refer to Figure 1. for process details and

flow diagram and Figure 2. for geographical location).

7Q10 Data and Dilution Factor :

The United States Geological Survey (USGS) Gazetteer of Hydrologic Characteristics for the

Taunton River Basin (WRI Report 84-4283) lists a 7 day low flow with a recurrence interval of

10-years (7Q10) for the Nemasket River at Murdock Street (Gage Station No. 01107800) of 4.2

cfs with a drainage area of 69.4 square miles. The Town’s consulting engineer, Whitman and

Howard, estimated a drainage area of 67.1 square miles at the WWTF (see Whitman and

Howard letter dated October 29, 1993 in the permit file). Therefore, the 7Q10 at the WWTF will

be equal to 4.2 x 67.1 / 69.4 or 4.06 cfs. After subtracting plant flow of 1.06 cfs (the average

WWTF flow during the two year operating period of the gage), a 7Q10 of 3 cfs was used in the

existing permit. This is continued in the draft permit.

Ammonia

Summer limits have been established before based on dissolved oxygen from the previous Waste

Load Allocation (WLA). These limits will continue in the draft permit.

TKN, Nitrate and Nitrite :

Monitoring requirements for TKN, Nitrate and Nitrite will continue in order to have a long term

data base for evaluation of the effect of nitrogen compounds in the receiving water. A nitrogen

TMDL is currently being prepared for Mount Hope Bay, and information on point source

discharges of nitrogen are necessary to complete this strudy. The draft permit contains no limits

on the discharge of total nitrogen

"We also believe the EPA’s national guidance for nutrients and more specific ecoregion

recommendations provide compelling, scientifically and ecologically valid rationale for instituting

nitrogen concentration and loading limits for this facility and negate the line of reasoning to wait

until a TMDL/waste load allocation is completed before assigning limits. There are documented

problems in Mount Hope and Narragansett Bays and the Taunton River placing them on the list

of impaired waters for organic enrichment. An interim step of establishing at least conservative

nitrogen limits based on national guidance is warranted. Certainly many WWTP have nitrogen

limits despite the lack of a completed TMDL when there are waters downstream of discharges

with recognized problems associated with excess nutrient loads. While the information on TKN

and ammonia in the Fact Sheet shows a most months have reasonable monthly averages, the

concentrations, during this same period for nitrate-nitrogen had levels of 32 mg/lm (12/02)

despite year round nitrogen removal at this facility."

Due to the multiple sources of nitrogen and the far-field impacts relative to many of the areas,

EPA and MADEP believe that a comprehensive study is important before establishing limits.

Limits on nitrogen discharges are among the controls that may be included in future permits.

Any planning for additional wastewater abatement facilities done by the permittee should include

a consideration of abatement options that can either achieve higher levels of control of nitrogen

than are currently required or that can be most cost effectively retrofitted to provide higher