Patty Ann Terrace Pump Station Design-Build
The Water Pollution Control Authority (WPCA) for the City of Derby retained the services of Weston & Sampson through a design build project delivery method to replace the Patty Ann Terrace Wastewater Pumping Station. A unique aspect to this design build approach was that Weston & Sampson was retained as the engineer to design the project, provide construction project management, and assist WPCA personnel with project construction. The upgrades include the complete replacement of the existing Smith and Loveless suction lift pumping station with a new submersible style pumping station. Compounding the upgrades was that no record drawings of the existing pumping station existed and that the site was extremely tight as it was located at the end of dead end street next to a rock face and a ravine. During the design of the pumping station upgrades it was determined that best means for constructing the new pumping station was to remove a significant portion of the rock face and build the new pumping station into the ravine behind the existing pumping station. This construction approach allowed the pumping station to be built and tested completely offline.
The pumping station upgrades include a new precast concrete wetwell with an integral valve vault chamber and a precast concrete control building equipped with all new electrical equipment, an emergency generator, and a control system designed for integration into a future city-wide SCADA system. This type of wetwell/valve vault structure was selected due to limit the size and quantity of site excavations due to the site rock constraints. The pumping station upgrades were completed in approximately six months from the start of design. The WPCA estimates that approximately $200,000-$300,000 was saved by constructing this pumping station as a design build approach with the engineering team and operations personnel working as a team.