02-03-25 - Council Work Session Agenda

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• The EAW should discuss the ability of the Met Council Metropolitan Wastewater Treatment Plant (WWTP) to handle the estimated project wastewater flow. The design average wet weather flow for the Met Council Metropolitan WWTP is 314 million gallons per day (MGD) and the average daily flow for the treatment facility for the last three years is roughly 168 MGD. • A table should be provided to identify the wastewater design flow estimates for each of the proposed land use types (residential and commercial) identified for the project area. Response: Based on the data provided by Met Council their existing WWTP facilities have capacity to handle the estimated wastewater flow from this proposed development. The development is within the design capacity for this area's planned land use within the city's 2040 comprehensive plan. Additionally, the proposed wastewater calculations are very conservative since they utilize a 4.0 peaking factor which is high for a newly installed wastewater collection system since the inflow and infiltration rate for a new system is much lower than an existing collection system. Below are the detailed calculations that were utilized to reflect the numbers in the EAW. Unit Count Per Capita Sewer Flow Rate GPD Average Flow Rate per Capita GPD Sewer Peaking Factor Peak Flow Rate per Capita GPD 4- lex TH 40 3.5 100 14,000 4 56,000 Apartment 200 1 .5 100 50,000 4 1 200,000 Senior apt 100 1.75 1 00 17,500 1 4 70,000 TOTAL 81,500 326,000 Sq. Footage Person/1000 Sq Ft Persons Sewer Flow Rate GPD Average Flow Rate per Capita Sewer Peaking Factor Peak Flow Rate per Capita Commercial 29050 400 72.625 100 7,263 4 29,050 Grand Total GPD 88,763 355,050 Construction Stormwater • Projects disturbing more than 50 acres and located within one mile of an impaired water are subject to a mandatory SWPPP review by MPCA staff prior to the issuance of the NPDES Construction Stormwater Permit. The complete SWPPP must be included with the application and submitted at least 30 days before the start of construction activity. • Volume reduction practices, such as infiltration, must be considered first when designing the permanent stormwater treatment system. If infiltration is prohibited for reasons outlined in the CSW permit, wet sedimentation basins or filtration practices may be used instead. Response: An NPDES permit will be acquired prior to the start of any construction activity. The current planned development is anticipated to disturb less than 50 acres of land. Volume reduction and infiltration practices have been considered within with ongoing design of stormwater features within the site. H ANOKA COUNTY TRANSPORATION- January 16, 2025 The Anoka County Transportation Division submitted a plan review letter dated January 16, 2025, in response to the EAW. A copy of the letter is attached for reference. Please note that each review item is restated below along with our corresponding response. 5