Gilbert Reservoir and Pump Station - Gilbert, Ariz.
Kiewit Western Co., a subsidiary of Kiewit Corporation, was awarded a design-build contract to construct a two-million-gallon concrete reservoir and pump station. The $11 million project involved installing 7,000 linear feet of pipeline, a two-million-gallon concrete reservoir, a booster pump station, consisting of five vertical turbine pumps, water treatment facilities, a new arsenic treatment system and a well development.
To increase the station's water distribution pressure, crews constructed each zone with three 100-horsepower and two 75-horsepower vertical turbine pumps with variable frequency drives, which extend down 37 feet into a header, supplied with water from the bottom of the reservoir. With a hopper bottom configuration, the reservoir was constructed below ground in a 19,000-cubic-yard excavation with an overall depth of 27 feet. The reservoir walls initially were sloped with concrete placed on grade and then transitioned to vertical wall for the last 14 feet. By constructing a ledge and a cast-in-place stairway, the change wall configuration added value to the client by providing easier maintenance access.
In addition, Kiewit installed a new arsenic treatment system. Raw well water is blended with treated water to produce a blended water product containing less than eight parts per billion. Raw water is drawn from the deep well at a rate of nearly 1,100 gallons per minute, of which about 83 percent is treated and blended with bypassed raw well water for storage.Crews worked more than 28,000 hours without a recordable incident.