84-inch Wet Weather Screw Pump Replacement

The Mahanoy City Sewer Authority operates a permitted combined Sewer Overflow (CSO) which discharges excess flow from their combined collection system to a CSO treatment facility utilizing two (2) 84-inch screw pumps which have the ability to pump 25 million gallons per day each to the CSO treatment facility. The original screw pumps were installed as part of the original plant construction in 1979. In 2011, one of the screw pumps catastrophically failed.

Scope: The Authority tasked Benesch with the design, permitting, contract administration and construction management for the replacement of both screw pumps due to their age and reliability. The new pumps are 84-inch in diameter, 54- feet long, and sit in a 30-foot deep wetwell at a 38° angle.

This $1.5 Million project included the installation of soft starters on the 200 HP motors to reduce the energy consumption from the original cross-line starters. A new motor control center (MCC) was designed for the project, along with upgrades to the existing control and Supervisory Control and Data Acquisition system.

The electrical and general construction was completed by Eastern Environmental Contractors, Inc. The construction coordination between Benesch, the Authority, and Eastern was key to a successful replacement project while still allowing the plant to maintain normal operations.