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Water Storage Siting Study City of Lino Lakes WSB Project No. 2988-44 Page 8 4. STORAGE TYPE There are two primary types of storage: elevated tanks and ground storage reservoirs. Elevated tanks (water towers) are bowls supported by a column. The elevation of the tower provides water pressure, and no pumping systems are required. Ground storage reservoirs are placed directly on the ground and are either at grade, partially buried, or fully buried. A pumping system is used to deliver water and pressure to the distribution system. The characteristics, advantages, disadvantages, and operations of each type of tank are described below. 4.1 Elevated Tank (Water Tower) Overview Elevated tanks, or water towers, consist of a tank or bowl and supporting structure. The elevation of the water tower determines the static water pressure in the distribution system. Ten-States Standards recommends that working distribution pressures be 60 to 80 psi, and not lower than 35 psi. Therefore, elevated tanks are a good option when constructing storage in relatively flat areas, so pressures are consistent throughout the system. Within the water distribution system, locations with high ground elevations are preferred to minimize tank height and, therefore, construction costs. Types and Materials Either a fluted or composite water tower is recommended with this option whenever the recommended storage capacity exceeds 0.5 MG. Below this capacity, others types of water storage tanks become more feasible. The life span of a fluted column or composite water tower is estimated to be 100 years with proper operations and maintenance. A fluted column tank is constructed entirely of steel above the concrete foundation. The entire steel structure of a fluted column tank requires painting. For a composite style water tower, the pedestal is constructed of concrete and the tank bowl is constructed of steel. The concrete pedestal is usually left unpainted, which can reduce the long-term maintenance costs when compared to a fluted column tank that is entirely painted. More than 75 percent of all elevated water storage tanks throughout North America are now composite tanks. Photographs of both types of tanks are shown below. Composite type (left) and fluted column type (right) water towers.