Specifications include, but are not limited to: The existing pump station was built in 1974 as part of a larger project that built sewers, force mains, and other pump stations in the floodplain between Columbia Boulevard and the Columbia River. It is approximately a half mile from the south bank of the Columbia River. The existing station consists of an 18-foot diameter pump wet well and a separate generator building. As-built drawings indicate that the pump station caisson is supported on twenty-three 12-inch diameter, 30-ton timber piles but the depth of pile embedment and the structural connections are undetailed. No pile driving records or details regarding the length of each pile have been found. The existing pump station and generator buildings will be demolished. The interior mechanical workings of the existing wet well will be removed, the upper several feet of the caisson will be demolished, and the interior will be filled with aggregate. In addition, the existing fence and much of the existing utilities on site will be demolished. To avoid having to provide a separate flow bypass mechanism, we understand that the existing pump station must remain in place and operational during construction. The existing generator building could also remain in place during construction; we understand that the contractor may elect to move the existing generator or use a temporary mobile generator during construction.
