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Technical Memorandum Re: Mounds View — Water Treatment Plant No. 1 Rehabilitation Project February 22, 2021 In August 2020, AE2S conducted additional pilot work to determine how to best remove radium to acceptable levels at WTP No. 1. Then, design phase services took place from August 2020 through mid -February 2021. We are now requesting to advertise for bids for Contract No. 2 of the overall water system rehabilitation project, which includes improvements to WTP 1, Wellhouse 1, and Wellhouse 2. Once awarded, construction of the second project would take place through May 2022. The following sections describe the scope of the rehabilitation at each facility. The purpose of this technical memorandum is to summarize for and inform City Council of the planned improvements to be included in the bidding package to be awarded by end of March 2021. WTP NO. 1 IMPROVEMENTS WTP No. 1 was reconstructed back in 1991 when Wellhouse 3 at that time was converted into WTP No. 1. The original "WTP No. 1" resided in the portion of city hall that is now occupied by the police department. Well No. 1 remains in operation within the northeast portion of city hall. WTP No. 1 includes (1) raw water pump, (2) reaction vessels, (2) pressurized filter vessels, and (1) backwash reclaim system to reuse settled water that comes from cleaning the filter. Existing water treatment processes include chlorine for disinfection and aiding with iron removal, filter media that helps remove iron and manganese, and fluoride addition to promote dental health to customers. Much of the existing equipment and components are at the end of their useable lifetime. To the maximum extent possible, existing process piping and vessels are being reused to limit costs. Rehabilitation at WTP No. 1 includes the following: 1. Building of a new 1-ton chlorine delivery area to include truck unloading zone and loading dock 2. Complete electrical, lighting, instrumentation, and controls replacement; upon completion for the project, the City's entire SCADA monitoring system will be upgraded 3. Well No. 3 motor replacement; during construction, the pump will be pulled and inspected for routine maintenance 4. Mechanical replacement including dehumidification system, chemical room air dampers, plumbing, unit heaters and ductwork, rooftop exhaust fan replacement, and boiler replacement 5. Complete valve, meter, backwash reclaim pump, and backwash sludge pump replacement 6. Complete chemical feed system replacement including chlorine and fluoride feed systems 7. Minor recoating of the existing process components in areas of surface corrosion 8. Pressure filtration tank rehabilitation limited to media replacement to capture iron, manganese, and radium 9. Security and door access control/monitoring equipment The views provided in Figure 1 and Figure 2 represent the proposed demolition and proposed improvements at WTP No. 1. P07008-2073-007 Page 2 of 5 Think Big. Go Beyond. v .0 p www.ae2s.com i ■7�.