Piscataway WRRF Grit Bucket Elevator No. 3 Rebuild

Key Accomplishments

Johnston Construction Company

• Replaced the existing system with a new three-shaft continuous-bucket grit elevator integrated into the existing grit handling process.
• Coordinated installation within the existing structural openings and operating footprint without disrupting adjacent WRRF operations.
• Installed the new drive system including motor, gear reducer, sprockets, chain-drive components and torque-limiting protection.
• Installed the new bucket spray wash and flushing-water system.
• Installed stainless-steel structural framing and enclosure components.
• Provided a new automatic grit system control panel with interlocking and independent manual control capabilities.
• Completed required piping and electrical connections necessary to return the grit handling system to full operation.
• Coordinated site preparation, field verification, permits, inspections, startup and final commissioning.
• Performed the project while maintaining access and coordinating any required process interruptions with WSSC plant personnel.
• The project involved a substantial rebuild of the existing Grit Bucket Elevator No. 3, originally supplied by Keene Corporation, now AMWELL. WSSC required a complete turnkey system including the supply, installation, testing and commissioning of all replacement components.
• The work was performed at the Piscataway Water Resource Recovery Facility, 11 Farmington Road West, Accokeek, Maryland 20607. Because the facility remained operational during construction, JCC was required to complete its work adjacent to active grit-processing equipment while avoiding disruption to normal WRRF operations.
• JCC's scope encompassed the site preparation, equipment and labor necessary to create a complete operating grit-handling system. This included associated piping, electrical connections and specialized grit-system components. The existing lower grit collector screw and grit classifier were specifically excluded from replacement, requiring the new elevator system to interface successfully with the existing downstream equipment.

B & R Electrical Contractors

• Performed electrical construction associated with the rebuild of Grit Bucket Elevator No. 3 at the active Piscataway WRRF.
• De-energized and isolated the existing grit-system electrical equipment using coordinated lockout/tagout procedures.
• Disconnected and removed existing conduit and wiring serving the existing Grit System Control Panel No. 3 and associated remote devices.
• Installed new PVC-coated rigid steel conduit and wiring for the replacement grit bucket elevator system.
• Connected the new bucket elevator motor and associated control devices.
• Connected the existing 1-HP grit classifier motor for reuse with the rebuilt system.
• Installed wiring and connections for remote start controls, emergency-stop devices and the grit-system wash-water solenoid valve.
• Installed heat tracing for exposed wash-water piping, fittings and valves.
• Extended existing control signals to the new control-panel location.
• Tested bucket elevator motor rotation and corrected phase connections as required.
• Participated in system startup and commissioning with JCC and the equipment vendor.
• Coordinated shutdowns and restart of the existing grit classifier and associated process equipment to minimize disruption to plant operations.
• The overall project involved the substantial rebuild of the existing Grit Bucket Elevator No. 3 at WSSC's operating Piscataway Water Resource Recovery Facility. Johnston Construction Company served as Prime Contractor for the turnkey replacement, which incorporated mechanical equipment, piping, electrical connections, controls, testing and commissioning.
• Following electrical isolation, BRE disconnected and removed the existing conduit and wiring associated with the existing control panel and remote devices. JCC separately handled removal and installation of major mechanical/control-panel equipment, while BRE's responsibilities centered on the electrical infrastructure necessary to integrate the replacement equipment into the operating grit system.