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Water Storage Siting Study City of Lino Lakes WSB Project No. 2988-44 Page 9 Advantages and Disadvantages Because water towers use elevation to create pressure, no pumping systems are required other than the wells that pump water into the distribution system. Therefore, a water tower can be less expense to construct and operate compared to a combined ground storage reservoir and booster station. However, water towers can be more expensive to maintain because the coating systems for the steel surfaces need to be replaced approximately every 15 to 20 years. Composite towers alleviate refurbishment costs somewhat because the concrete stems, where the majority of the surface area exists, do not require initial painting and repainting over time. 4.2 Ground Storage Reservoir Overview Ground storage reservoirs are built at or below grade and use pumps to create pressure in the distribution system. The pumps can be set to maintain a designated pressure or can operate based on water tower levels elsewhere in the City. A ground storage reservoir requires a booster pump station be constructed adjacent to the ground storage reservoir. In the 2007 study, ground storage was initially recommended because the reservoir was planned to be constructed in conjunction with a water treatment plant. Types and Materials Ground storage reservoirs are usually constructed out of concrete and are sealed using concrete surface sealants and curing compounds or plasticizers. Advantages and Disadvantages Ground storage reservoirs usually do not require repainting like water towers. However, because their operations rely on high service pumps to deliver the water to the distribution system, there are significant power, operation, and replacement costs associated with ground storage reservoirs. Lino Lakes is planning to add a water treatment plant to its distribution system. If a ground storage reservoir and a gravity filtration water treatment plant are selected, additional pumps may be required within the water treatment plant to deliver water to the ground storage reservoir. It is therefore possible that the City staff would need to operate one set of pumps to pump water into the ground storage reservoir and a second set of pumps to pump water from the ground storage reservoir to the distribution system if a buried reservoir is not feasible. Ground storage reservoirs are also limited by pump capacity and their ability to supply the distribution system. Towers, on the other hand, can empty as rapidly as the water distribution system will allow for meeting maximum day demands and fire demands. The maximum flow rate of water supplied from ground storage reservoirs is dependent on the capacity of the high service pumps that pump water from the reservoir to the distribution system. 4.3 Life Cycle Cost Comparison The 50-year life cycle costs for estimated and compared for the following water storage options: 1) Concrete ground storage reservoir (AWWA Type 3) with a booster station 2) Fluted column water tower 3) Composite water tower Life cycle costs included the capital cost to design, bid, and construct the reservoir and the estimated maintenance costs over a 50-year period to determine which tank design would provide the greatest long term financial benefit to the City. 4.3.1 Concrete Ground Storage Reservoir (AWWA Type 3) with Water Booster Station The estimated 50-year operation and maintenance cost for a 1.5 MG ground storage reservoir is presented in Table 5. This estimate assumes that the booster pumps and major electrical components would be replaced once every 25 years and the emergency generator would be replaced once over the 50-year period.