The City of North Ridgeville owned and operated the S.R. 83 Pump Station and force main system, located immediately north of the intersection of State Route 83 and Center Ridge Road. The pump station was more than 20 years old and was unable to pump the wastes it received as evidenced by wet-weather basement flooding. The City hired KS Associates to recommend solutions including a possible new system.
KS performed draw down tests to determine the capacity of the existing system. We placed a pressure gauge on the downstream side of the pump to compute the effectiveness of the long force-main into which the pumps discharged. We determined that the force main, if cleaned, would have sufficient capacity for the expected flows. When plans and specifications were prepared, we obligated the contractor to “poly-pig” the force main to restore its capacity. We also designed a “pig launching station” downstream to facilitate future cleaning. We determined that even if the force main were cleaned to its original capacity, the pumps needed to be replaced. Following an inspection and interviews with operating personnel, we recommended that all components be replaced. We determined that the existing wet well was structurally sound and sufficiently sized.
Because of its shallow depth, we determined that a suction-lift pump station could replace the old submersible station if it was partially buried. The suction-lift type of station has the advantage of housing all mechanical equipment above the sewage in a dry space that is much more conducive to maintenance. The “package” pump station was retrofitted over the existing wet well and the contractor was obliged to provide bypass pumping so as to have no service interruption.
The City was only familiar with float type pump controls. KS recommended a bubbler system, which uses a pressure gauge on a pressurized air line that senses depth from the dry upper level of the pump station. The City was wary of new technology because of disappointments in the past. KS introduced them to the sales representative, who took them to other stations and let them talk to operators with experience with both systems. The City ultimately chose the bubbler system.
KS Associates also subcontracted with an electrical engineer who specified all power and communications devices, and a permanent on-site standby generator with an automatic transfer switch.
The Engineer’s Estimate was $191,000. The City paid the contractor $192,968.