Agenda - Council Work Session - 10/20/2020 - Special

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Executive Summary The City of Ramsey has eight water supply wells with concentrations of manganese ranging from 0.02 mg/L to 0.37 mg/L. The Minnesota Department of Health (NOW has established a Health Based Value (HBV) for manganese of 0.100 mg/L. Four of Ramsey's eight water supply wells exceed the MDH HBV for manganese. MDH has recommended to the City that they develop plans to address the manganese. In addition to the potential health concerns with manganese, Ramsey's drinking water also exceeds the Secondary Standards for iron and manganese. Water with concentrations of iron and manganese above the Secondary Standard causes aesthetic problems including red and black staining of plumbing fixtures and laundry and taste complaints. The City of Ramsey currently utilizes groundwater from the Tunnel City-Wonewoc (TCW) aquifer as its exclusive source of drinking water. An evaluation of was conducted of the TCW aquifer which determined that the TCW should be able to continue to produce potable water to meet present and foreseeable future demands. The most cost effective method for removing manganese and iron from drinking water is chemical oxidation followed by sand filtration. These processes require construction of a water treatment plant. Based upon an analysis of Ramsey's 2040 water demand, the capacity of the water treatment plant should be 10 million gallons per day (MGD). Three water treatment plant sites were evaluated including the Fire Station site, Public Works site, and Vacant City property site. Even though it requires additional watermain, the Public Works site was less expensive because it doesn't require a garage due to the onsite Public Works facilities. The Public Works site also offers operational efficiencies because it is on the same site as the new Public Works building. For this study two treatment plant alternatives were evaluated including gravity filtration and pressure filtration. With gravity filtration, the water flows by gravity through concrete filter cells into a holding tank (clearwell). The water is then pumped into the distribution system. With pressure filtration, the water is pumped from the wells through steel pressure filters and directly into the distribution system. Report level project and Iife cycle cost opinions for the two alternatives are included below. The project costs include the capital cost, plus contingency, administration, and engineering. Life cycle costs represent the total cost of owning the treatment plants for 50 years and include capital cost, equipment replacement, labor, gas, chemicals, insurance, electricity, and annual equipment repair. Gravity Filter Treatment Plant Pressure Filter Treatment Plant Project Cost 50 Year Life Cycle Cost $31„890,000 $70.570,000 $30,280,000 $74,940,000 As the table indicates, the gravity filter treatment plant has a slightly higher project cost, but a lower overall life cycle cost. The pressure filter treatment plant has a higher Iife cycle cost due to the expense of painting and maintaining the steel filters; whereas concrete gravity filters require very little maintenance. An optional 8,000 square foot garage could be added to the project for a project cost of approximately $1,5 million. FEASIBILITY STUDY -DRAFT RAMSY 154354 ES-1