8.3 SR 02-06-2023 - Laserfiche WebLink

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2. INTRODUCTION 2.1 Authorization The City of Elk River retained WSB to complete a serviceability analysis of the proposed Northeast and Northwest Urban Expansion Areas in response to the short-term and long-term growth projected in this part of the city. City staff authorized WSB to proceed with the study in February 2022. 2.2 Scope This report evaluates the infrastructure needed to annex the northeast and northwest study areas to the sanitary sewer and water distribution systems. The northwest site includes a portion of the gravel mining area. In addition, WSB evaluated the adequacy of the existing utility systems to serve the study areas and prepared a financial analysis for the recommended improvements. The northeast, northwest, and mining study areas are shown in Figure A1 in Appendix A along with the City's existing municipal service area. 2.3 Data Available Information and materials used in the preparation of this report included the following: • City of Elk River Water Supply Plan (approved by the DNR in 2017); • City of Elk River Comprehensive Plan Update (adopted in 2021); • Pumping Records, As-Builts, and Design Data for the Trunk Highway 169 Sanitary Lift Station; • Pumping Records, As-Builts, and Design Data for the Windsor Lift Station; • Pumping Records, As-Builts, and Design Data for the Leachate Lift Station; • Pumping Records and Design Data for the Evans Lift Station; • Design Data for the Jackson Lift Station; • Flow and Design Data for the Wastewater Treatment Plant; • City of Elk River Water Pumping Records from 2017 to 2021; • City of Elk River's 2015 Gravel Mining Area Land Use, Transportation, and Utility Plan; and • City of Elk River GIS Data. 2.4 Description of Study Areas The northeast and northwest study areas span approximately 2,200 acres and 2,800 acres, respectively; and both areas are projected to be annexed to the City's utility systems over the next 20 years per the City's 2040 Comprehensive Plan. Annexing both study areas would increase the City's municipal service area significantly considering that the City's existing municipal service area spans approximately 8,000 acres. The ground elevations in both study areas vary considerably, ranging from 900-ft above mean sea level (MSL) to 1,000-ft above MSL in the northeast areas and from 940-ft above MSL to 1,100-ft above MSL in the northwest areas. The vast change in elevations presents a challenge to extend water service as separate pressure zones may be needed to provide adequate water pressures. Contrastingly, wastewater may be able to drain by gravity from the higher elevations to the lower elevations without the need of a significant number of intermediate lift stations. The ground elevations of the northeast study areas are shown in Figure A2 in Appendix A and the ground elevations of the northwest study areas are shown in Figure A3 in Appendix A. The ground elevations shown for the mining areas in Figure A3 were obtained from the final proposed grading plan of the Gravel Mining Area Land Use, Transportation, and Utility Plan completed in 2015. A significant portion of both study areas consists of wetlands which, for the purpose of this study, were considered nondevelopable land. Figures A4 and A5 in Appendix A show the extents of the wetlands for the study areas covering a total of 1,209 acres. Developable acreages for each study area were calculated by subtracting wetland areas and existing roads from the gross acreage. Additionally, an extra 10-percent was also subtracted to account for future roads within the future developed land resulting in a final total net developable area of approximately 3,260 acres for both study areas combined. Feasibility Report Northeast & Northwest Urban Service Area Expansion Study City of Elk River, MN WSB Project No. 020010-000 Page 1