06-14-2021 Council Packet - Laserfiche WebLink

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CITY COUNCIL AGENDA ITEM 6D STAFF ORIGINATOR: Michael Grochala, Community Development Director MEETING DATE: June 14, 2021 TOPIC: Consideration of Resolution No. 21-59, Authorizing Preparation of Water Treatment Plant Pilot Study VOTE REQUIRED: 3/5 INTRODUCTION Staff is requesting council authorization to complete a Water Treatment Plant Pilot Study. BACKGROUND In 2019, the Minnesota Department of Health tested the City’s manganese levels in each of the City’s wells as part of the EPA Unregulated Contaminant Monitoring Rule 4 (UCMR4). The water quality testing data from MDH indicated that five of the City’s six wells exceed the maximum recommended manganese level for infants, and three of the wells exceeds the maximum recommend level for adults and children. On March 9, 2020, the City Council authorized the preparation of a Water Treatment Plant feasibility study to evaluate future water treatment options. This study was completed and presented to the City Council on July 6, 2020. The report recommended construction of a conventional gravity filtration system with an initial capacity of 6,000 gallons per minute (gpm). The proposed greensand filter media would treat for manganese, iron and arsenic. As noted in the feasibility study, the water quality testing data for the emerging contaminants do not require any additional treatment processes at this time. Most organic chemicals, if detected in the future, can be treated with granular activated carbon filter media. Volatile organic compounds (VOCs) from petroleum products can be removed with aeration. Greensand filter media can remove radionuclides (radium, gross alpha, etc.) if this natural contaminant is detected in future wells. Arsenic should easily be removed with conventional or biological filtration if detected. Filter membranes such as reverse osmosis can also be installed downstream of conventional or biological filters to remove most contaminants that cannot be removed by a conventional gravity or biological water treatment plant. The next steps identified included completion of the utility rate study and a water treatment pilot study. The Utility Rate Study was completed by Baker Tilly and accepted by the City Council on May 10, 2021.