8.3 SR 02-06-2023 - Laserfiche WebLink

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7. CONCLUSIONS The conclusions identified in this study are summarized as follows: • Water Serviceability of the Northeast Areas: The northeast areas will be annexed to the system's existing main pressure zone for water service without the need to create a separate pressure zone. The following water system infrastructure is recommended to provide water service over the next 20 years: a new 850 gpm well with treatment, a new 1.0 MG water tower, and extending 12-inch trunk watermain. Water Serviceability of the Northwest Areas: The northwest areas cannot be annexed to the system's main pressure zone due to high ground elevations and separate pressure zones will be needed. Therefore, it is recommended to serve the northwest areas with a hybrid approach that includes new production wells drilled in the northwest areas and booster stations to supplement water supply. In addition, a new 1 MG water tower is also recommended. Pressure reducing stations (PRVs) are also recommended to recirculate excess water from the northwest areas back to the main pressure zone to avoid water stagnation in the new water tower. It is anticipated that water treatment will be needed at each well. Sewer Serviceability of the Northeast Areas: A new Regional Lift Station with an ultimate capacity of 1,500 gpm will be needed to pump wastewater generated in the study area directly into the City's VWVfP. Trunk sewermains ranging in diameter from 10 to 18 inches can be installed upstream of the new Regional Lift Station to collect and convey wastewater. Two (2) additional lift stations with pumping capacities of 185 and 225 gpm will also be needed to serve this area. Sewer Serviceability of the Northwest Areas: Similar to the northeast areas, a new Regional Lift Station with an ultimate capacity of 4,000 gpm will be needed to pump wastewater generated from the study area directly into the City's WWTP. However, the Regional Lift Station will not be needed until development beings in the gravel mining areas. Until then, the existing Windsor Lift Station can pump the existing and short-term flows. Trunk sewermain ranging in diameter from 10 to 12 inches can be installed upstream of the new Regional Lift Station to collect and convey wastewater and a 24-inch trunk sewermain is recommended to collect wastewater from the northwest ultimate service boundary. Two (2) additional lift stations with pumping capacities of 200 and 425 gpm will also be needed to serve this area. • Wastewater Treatment Plant (WWTP) Assessment: The plant's biological treatment capacity was doubled during the 2017 expansion from 2.2 MGD to 4.5 MGD. However, it is anticipated that the headworks portion of the plant will not have sufficient capacity for the future flow from the study areas and expansion will be required. Additional studies will be needed to determine the expansion needs at the City's VWVfP. • Opinion of Probable Cost: The total estimated infrastructure cost needed to serve the study areas over the next twenty years and beyond is $28,478,000 for the sanitary sewer system and $75,612,000 for the water distribution system. Detailed cost breakdowns are shown in Appendix B. Feasibility Report Northeast & Northwest Urban Service Area Expansion Study City of Elk River, MN WSB Project No. 020010-000 Page 30