06-30-14-WS - Laserfiche WebLink

Home Browse Search

11.WR ATERESOURCES Potential impacts and mitigation measures are the same under both Development Scenarios for water resources. Potential Impacts Regional wastewater collection and treatment facilities and municipal wastewater pipes serving the Study Area have sufficient long-term capacity to handle the additional wastewater flow generated by both the Zoning and Maximum Development Scenarios. Sanitary sewer will need to be extended into the Study Area to provide sewer service to the various lots. Temporary dewatering may be required during project construction, particularly for buildings to be constructed with lower levels, for which caissons could be used to facilitate installation of footings and foundations. All water pumped during construction dewatering activities will be discharged in compliance with City, Watershed, and Minnesota Department of Natural Resources (DNR) requirements and the National Pollutant Discharge Elimination System (NPDES) permit and site RAP. Up to 14.4 acres of wetland may be impacted by development. Wetlands should be avoided where preservation of wetland is feasible. A new crossing of Rice Creek would be required for site access. Mitigation Strategies The use of a small lift station may be required depending on future uses for sanitary sewer, but the system will primarily be gravity-based. Stormwater will be managed on-site, maintaining the current drainage patterns and utilizing the current outfalls to Rice Creek and Round Lake. Stormwater will be conveyed to Round Lake and Rice Creek by means of underground storm sewer, vegetated swales, and wetlands. Conveyance systems will be designed in accordance with acceptable industry standards and in conformance with jurisdictional requirements. The runoff rate will be reduced to 80% of the existing rate because the Study Area is located within a Flood Management Zone as defined by the RCWD. The primary method of stormwater treatment will be the use of multiple ponds for the removal of total phosphorous and total suspended solids. Water reuse, bio-filtration, filtration, and stormwater wetlands are also suitable for treatment within the Study Area. No discharge water will be directed to surface waters without prior retention in a temporary settling basin and a determination that no contamination exists. The developer will determine if groundwater is contaminated as a basis for determining discharge to storm sewer, sanitary sewer, or through a treatment process such as the existing groundwater treatment facilities. Temporary construction dewatering will require a Temporary Water Appropriations General Permit 1997-0005 if less than 50 million gallons per year and less than one year in duration. Wetland impacts will be replaced at a 2:1 ratio, through a combination of on and off-site replacement through plans/permit approved by the RCWD and Army Corps of Engineers The crossing would be via a bridge that spans the creek, wetlands and floodplain, and would allow wildlife to cross underneath. A trail crossing at this location may also be considered (under the creek bridge). The bridge will be designed to avoid impact on the floodplain. How Mitigation will be Applied and Assured Water resources mitigation will be regulated through the RCWD, Army Corps of Engineers, and PCA review processes. Other water resource mitigation will be regulated through the JDA review process. Proposed PUD and/or site plans must address relevant mitigation measures prior to final approval by the JDA. June 2014– Final Mitigation Plan3