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COMPREHENSIVE SEWER PLAN Sanitary Sewer Trunk System September 15, 2020 4.0 SANITARY SEWER TRUNK SYSTEM 4.1 EXISTING TRUNK SANITARY SEWER SYSTEM EVALUATION The trunk sewer system layout for the City of Mounds View is presented on Map 1, Trunk Sanitary Sewer System (Appendix F). This map shows the main sanitary sewer subdistricts, existing trunk sanitary sewers, existing Metropolitan Council Interceptors, and an existing lift station. The trunk sewer system is completely built at this time. Wastewater from the City is ultimately treated at the MCES Metropolitan Wastewater Treatment Plant. The trunk sanitary sewer system generally drains to two MCES interceptors, 4-NS-523 and 4-NS-524, at four MCES meter stations, M202, M203, M208, and M212, as follows: • The northerly portion of the City, Sewer Districts 1 and 2, discharges into Interceptor 4-NS-523 at Meter M208. • The central portion of the City, Districts 3 and 4, discharges into Interceptor 4-NS-523 at Meter M212. • The southeastern portion of the City, Districts 5 and 7, discharges into Interceptor 4-NS-524 at Meter M203. • The southwestern portion of the City, Districts 6 and 8, discharges into Interceptor 4-NS-523 at Meter M202. The modeling of the sanitary sewer system was based on a variety of parameters, such as: land use, population density, standard wastewater generation rates, and existing system layout. Trunk sewer lines were defined based on the connection points to the MCES interceptor. Sewer districts and subdistricts were then determined based on drainage areas to each trunk sewer. The existing pipe systems were evaluated and broken up into design segments. Each end of a design segment has a node assigned to it. The nodes were designated for the following reasons: 1. Flow from a sewer subdistrict entering the pipe network. 2. Significant grade change has occurred. 3. Change in pipe size. 4. Two or more trunks connect. Each sewer subdistrict contains at least one collection point where the sewer subdistrict's wastewater is defined to enter the pipe network. Upstream of that collection point, a lateral network of 8" gravity lines provides service. An evaluation of trunk system design flows and capacities is provided in Appendix D. This appendix provides a comparison of capacity versus 2040 design flow for each reach of the trunk sewer system. As noted in Appendix D, there is sufficient capacity throughout the trunk system to convey the design flows. B v:\1938\active\193804167\reports\2018 csp\submitted to city 9-8-2020\moundsviewcsp_formcesreview_09152020_updateddraft.docx 4.7