4.3 SR 03-20-2023 - Laserfiche WebLink

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"The FacilityT has a continuous discharge (SD 001) to the iVlississippi River (Class 1C, 2Bdg, 3C, 4A, 4B, 5, 6 water). This is a Class A facilityT. The Facilit�T is designed to treat an average dryT `veather design flo�v of 3.98 million gallons per da�T (MGD), an average wet weather (AW� design flow of 4.54 MGD, and a peak hourly wet weather flo`v of 7.27 1�1GD. Based on the r�WW design flo�v, the FacilityT is designed for a five-dayT carbonaceous biochemical oxygen demand of 203.8 milligrams per liter (mg/L), a total suspended solid of 263.7 mg/L, a total phosphorus of 7.2 mg/L, and a total Keldahl nitYogen of 36.0 mg/L. The Facilit�r consists of inechanicall�r cleaned baY scYeens, an influent PaYshall flume, voYtex grit removers, t�vo anaerobic selector tanks for phosphorous removal, six extended aeration activated sludge cells in three pairs, three final clarifiers, six effluent sand filters, and UV disinfection. The Facilit�T also adds chlorine for filter maintenance, sulfur dio�de for removal of residual chlorine, and ferric chloride for phosphorous removal. Biosolids treatment consists of four aerated storage tanks (aerobic digesters), which is then processed in a screw press to produce a biosolids cake �vhich is landfill disposed." Construction of new sanitary sewer lines will be Yequired to service the pYoject but no expansions to the CityT's WWTP are anticipated to be required. Stormwater The qualit�r of e�sting storm�uateY runoff from the pYoject is t�rpical of foYested land. StoYmwater runoff flows from upland aYeas to loweY elevations on site as sheet flow wheYe it geneYally gets conveyed into the large wetland complex located near the center of the site. This wetland ultimately outlets into Trott Brook. The quality of stormwateY runoff fYom the pYoject post construction will be tyrpical of an urban land use with impervious surfaces and la`vn/landscaping generallyT generating higher concentrations of total suspended solids and total phosphorus. Stormwater runoff is proposed to be conve�Ted into permanent constructed stormwater treatment infrastructure (e.g. infiltration basins, filtration basins, holding ponds, vegetated swales, etc.) across the site for treatment prior to discharge. TemporaryT erosion and sediment control best management practices (BiVIPs) will initiallyT be installed (per the project's SWPPP), maintained/repaired, and amended throughout the construction phases as required to remain compliant `vith the applicant's NPDES Construction Stormwater Permit. BMPs mayT include (but are not limited to) silt fence, bio-rolls/filter logs, rock construction entrances, mulch/hyTdro mulch, and permanent native seeding or turf seeding in appropriate areas. L�aterAppropriat�on No appYopriations of suYface wateYs aYe proposed as paYt of the PYoject. WateY will be sourced from the Cit�T of Elk River's e�sting public `vater suppl�T s�Tstem (PWS #1710004). The CityT's PWS is currentlyr souYced from eight groundwateY wells (MDH #s 255153, 221176, 481794, 537682, 580320, 664852, 694499, and 757624). Construction of new watermains `vill be required to service the project but no expansions to the CityT's PWS are anticipated to be required.