NC0026641_Staff Comments_20181011

NORTH CAROLINA
EnNfronmerrtal Qrua'iIy
October 11, 2018
MEMORANDUM
TO: NPDES Files: Siler City, NC0026441
FROM: Mike Templeton
SUBJECT: Siler City's agreement to enhanced BNR upon expansion
The purpose of this memo is to note for future reference that the Town of Siler City has
volunteered that, upon expansion, it will design its treatment plant to achieve 3.0 mg/L TN.
Background & Initial Improvements
Siler City's 2014 permit includes a nutrient reopener in Special Condition A.(3.), which requires
the Town to notify DWR if it intends to accept new industrial wastes with nutrients greater than
typical domestic wastes (40 mg/L TN, 5 mg/L TP). The Division can then reopen the permit, as
necessary, in order to add supplemental nutrient limits.
In May 2016, Mountaire Farms announced its acquisition of the Townsend Poultry facility and
its intent to renovate and begin production at the facility. The Town notified the Division by its
letter of December 9, 2016, that it intended to accept wastewater from Mountaire Farms Inc.,
beginning in early 2019. The Division reopened the permit to add TN limits and related
requirements.
The Town agreed to (1) upgrade its plant to treat to 6.0 mg/L TN at 4.0 MGD (equivalent to 200
lb/day TN), by January 1, 2023, and (2) optimize its operations to provide some nitrogen
reduction until the upgrade is completed and online. The Division modified the Town's permit
to include a new TN limit and optimization condition.
The Mountaire Farms facility will significantly increase nutrient loads to the Town's plant. The
plant was not designed to remove nitrogen; therefore, nutrient loads to Loves Creek and its
downstream waters are expected to increase, returning to levels seen in past years when two
other poultry processors operated there. The Division has held that addition of nutrient loads to
an already -impaired stream is not acceptable.
Further Improvements Upon Expansion
Flows from the Mountaire Farms facility will use a significant portion of the Town's treatment
capacity, including flow allocation reserved for population growth and other industrial
development. As a result, the Town may need to seek expansion sooner than previously
planned. It would consider constructing the expansion and the BNR upgrades at the same time
rather than perform BNR upgrades in two phases. Once completed, the improvements would
reduce its TN discharges significantly. However, because the Town has not yet applied for
expansion, the "combined" option could take 2-3 years longer to complete, depending on how
quickly the decision is made. The modified permit does not address this alternative.

Memo to NPDES Files: Siler City, NC0026441
Subject: Siler City's agreement to enhanced BNR upon expansion
October 11, 2018
In our discussions, the Town mentioned 6.0 MGD as a possible expansion target and indicated
it would upgrade the plant to "enhanced BNR" (3.0 mg/L TN and 0.5 mg/L TP) with that
expansion. This would be equivalent to 1501b/day TN at full permitted flow.
The 2018 permit modification addresses only the initial TN limits and optimization, but the
preview copy of the fact sheet mentioned the possibility of the expansion and the reduced TN
design targets. The Town noted that this was not relevant to the modification and is still
speculative. At the Towri s request, the language was removed from the fact sheet.