Agenda - Council Work Session - 02/08/2021

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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 (MDH) 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 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 initial capacity of the water treatment plant should be 10 million gallons per day (MGD), with the ability to expand to 20 MGD. Four water treatment plant sites were evaluated including the Fire Station site, Public Works site, Water Shop site, and Vacant City property site. The Public Works site would be the least expensive to construct because it could share garage space, a generator, and security infrastructure with the onsite Public Works facility. The Public Works site also offers operational efficiencies because it is on the same site as the new Public Works facility. In January of 2020, the City of Ramsey's Planning Commission, Economic Development Authority, and Public Works Committee all voted unanimously to recommend City Council approval to construct the water treatment plant on the Public Works site. This study evaluated two treatment process alternatives 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 life cycle cost opinions for the two alternatives are included below. The project costs include the capital cost plus 10-percent contingency, 1-percent administration, and 12- percent engineering costs. Life cycle costs represent the total cost of owning and operating the water treatment plant 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 $31,890,000 $30,280,000 50 Year Life Cycle Cost $70,570,000 $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 life cycle cost due to the expense of painting and maintaining the steel filters; whereas concrete gravity filters require very little maintenance. FEASIBILITY STUDY - DRAFT RAMSY 154354 ES-1