City Council Meeting Date: July 18, 2018
To: Mayor and City Council
City Administrator
From: Justin Wagner, Utilities Manager
David Bennett, P.E., Public Works Director/City Engineer
Richard Kucera, Wastewater Plant Supervisor
Title
Update of New Phosphorous Limits for the Wastewater Treatment Plant Permit.
Body
Action Requested:
The Northfield City Council is asked to discuss newly proposed phosphorous limits to the City’s Wastewater Treatment Plant’s (WWTP) National Pollutant Discharge Elimination System (NPDES) permit.
Summary Report:
The City’s WWTP operates based upon a NPDES permit that dictates the quality of treated wastewater that is allowed to enter the Cannon River. The NPDES permit cycle is 5 years and is then required to be renewed in order to discharge to the Cannon River. In April of 2015, City staff completed a NPDES permit application to the Minnesota Pollution Control Agency. The City is operating on an extension of the existing permit while MPCA prepares the new permit.
On June 9, 2017, the City received a letter from the Minnesota Pollution Control Agency (MPCA) stating that the City will be receiving a new permit limit for phosphorous at the City’s WWTP. The City of Northfield, along with other municipalities of Faribault and Owatonna that discharge to the Cannon River are also receiving a new phosphorus permit limit.
On June 30, 2017, the City received a second letter from the MPCA regarding the phosphorous limit. As part of the letter received from the MPCA, the MPCA is requesting a response from the City to the following question:
Concurrence that the Facility can meet the proposed limit at the current follow and design flow and loadings, or submit documentation of reasons the Facility will not be able to meet the new limit at current or design flow and loadings.
The proposed new phosphorus limit from the MPCA is putting a reduced summer loading limit from June through September. This lowers the annual load limit. The new limit will be a 13% reduction in the City’s yearly mass limit essentially requiring a 0.87 milligrams per liter phosphorus limit versus the WWTP design of 1.0 milligrams per liter.
Staff intends to respond that the City will not be able to meet the proposed loadings at design flow of the WWTP. However, there will not be an immediate impact due to the current flow and the capacity for growth. Staff anticipates it could be between 10 and 20 years before the City would approach the design flows of the WWTP.
Additionally, the City along with Faribault and Owatonna are having Minnesota Environmental Science and Economic Review Board (MESERB) review this document. MESERB is looking into how the Lake Byllesby Total Maximum Daily Load (TMDL) and the Cannon River Watershed TMDL phosphorus limits are being applied to the new permits.
Alternative Options:
Not Applicable
Financial Impacts:
Currently there are not financial impacts to the City but ultimately if the permit limits are implemented, the City has the potential to be required to construct an additional treatment process in the future.
Tentative Timelines:
The City is required to respond to the attached letter by August 8, 2017.