Aberdeen Proving Ground – Pump Station 447 Wet Well Replacement

Key Accomplishments

Johnston Construction Company

• Maintained continuous wastewater pumping capacity throughout construction. JCC was required to sequence the work so that sufficient pumping capacity remained available for all anticipated flows and full-capacity flow through the piping system was maintained during the construction period.
• Provided temporary bypass pumping and flow-diversion capability when required to allow the existing pumping station and affected pipelines to be modified without interrupting wastewater service. The specifications required temporary pumping equipment and standby capacity, including extra pumps and power generators, where bypass pumping was necessary.
• Installed the Owner-furnished precast underground package pump station. The complete package incorporated a reinforced-concrete structure, non-clog wastewater pumps and motors, process piping, valves, pump controls, electrical conduit and wiring, access hatches, ladder and associated appurtenances. The City purchased the package station and delivered it to the site for installation by JCC.
• Performed excavation, structural preparation, installation and backfill for the new underground station, including unloading and setting the prefabricated structure using the manufacturer's lifting system, installing associated piping and equipment, completing coating touch-ups and coordinating subsequent electrical work and site restoration.
• Installed a precast structure engineered for significant groundwater and uplift conditions. The pump station was designed against saturated-earth and traffic loads and to resist flotation with groundwater at finished-grade elevation. The design required a minimum 1.15 factor of safety against hydrostatic uplift, with uplift forces transferred to an anti-buoyancy collar.
• Provided a highly durable wastewater structure using 5,000-psi concrete and integral waterproofing. The precast structural and nonstructural concrete incorporated crystalline waterproofing to resist liquid penetration and deterioration from the acidic wastewater environment.
• Integrated corrosion-resistant maintenance and safety features into the completed wet well, including stainless-steel pump guide rails and removal hardware, aluminum access hatches rated for 300 psf, 316 stainless-steel hardware and an integral safety-grating system for the wet-well opening.
• Constructed and modified gravity-sewer and force-main piping associated with the new pumping station, including excavation, trench preparation, bedding, piping, valves, backfill, compaction and restoration. The work required protection of existing underground utilities and careful installation of force-main piping to the required lines and grades.
• Completed demolition and abandonment associated with the former pumping facility, including removal of designated equipment and piping, filling or abandoning facilities identified on the drawings, salvage coordination and proper disposal of demolition debris.
• Coordinated electrical demolition and modification while keeping the existing wastewater pumping system operational. Temporary electrical connections were required where necessary to maintain service, while abandoned wiring, conduit, pump wiring, floats and the existing level transducer were removed or modified as part of the transition to the new station.
• Integrated the new wet-well instrumentation with the existing plant telemetry system. New float controls were installed and connected to the existing DFS telemetry control unit, and a replacement submersible level transducer was installed in the new wet well and connected back to the existing telemetry system.
• Coordinated SCADA startup and system testing as part of project commissioning. The specifications expressly included startup and testing of major equipment and systems, including SCADA, together with manufacturer field services and demonstration/training for Owner personnel.

B & R Electrical Contractors

• B & R Electrical Contractors, Inc. served as the electrical Subcontractor to Johnston Construction Company, the Prime Contractor, for replacement of Wastewater Pump Station 447 at Aberdeen Proving Ground. The overall project replaced an existing wastewater pumping station with a new precast-concrete underground package pump station and associated gravity-sewer and force-main improvements.
• Furnished labor, materials and tools for the electrical construction package in accordance with project Drawings 1 through 7, Division 16 of the specifications, BRE's proposal and the project contract documents.
• Installed the electrical backboard and associated conduit, junction boxes, conductors and electrical connections. The subcontract specifically required PVC-encased conduit below grade and rigid metal conduit for exposed installations, providing durable raceway systems suitable for the wastewater pump-station environment.
• Coordinated installation and connection of the new pump-station electrical equipment with JCC-furnished disconnect switches, while JCC separately provided the excavation, backfill and concrete base associated with the electrical backboard.
• Connected the new pumping and level-control systems to the existing starters and telemetry system. The Division 16 requirements called for new wet-well floats to be connected to the existing DFS telemetry control unit, together with a replacement submersible level transducer connected back into the existing telemetry system.
• Modified the existing pump motor-control system for the replacement pumps, including coordination with the existing starters and replacement of starter overload heaters as required for the new pump motors.
• Supported telemetry and SCADA integration for the replacement station. BRE's subcontract expressly included connections to the existing telemetry system and coordination of testing services. The overall project specifications also required startup and testing of major systems, including SCADA. BRE's role was the electrical field wiring, connections and testing interface; the documents do not establish BRE as the SCADA programmer.
• Performed electrical demolition and modification in an operating wastewater pumping facility. Existing electrical systems had to remain functional during construction, requiring temporary wiring and connections where necessary while existing equipment and circuits were removed, relocated or extended for the new installation.
• Electrical demolition included removal of the existing wet-well floats and submersible transducer and removal of existing pump wiring from the starters, followed by installation and reconnection of the replacement control components.
• Furnished and installed the project lighting system. BRE's subcontract specifically included lighting, while Division 16 included the outdoor pole-lighting system and associated electrical requirements.
• Provided the electrical permit and coordinated submittals, O&M documentation, materials furnished by other parties, testing services and final record drawings required for turnover of the electrical systems.
• Supported startup, commissioning and Owner turnover through testing coordination, record-document preparation, O&M documentation and supervision of erection/startup services and instruction to operating personnel as required by the subcontract.
• BRE's subcontract required the company to furnish the labor, materials and tools necessary to perform the project's electrical work in accordance with the drawings and Division 16 specifications. Its scope included the electrical backboard, conduit, junction boxes, conductors and connections; coordination of JCC-furnished disconnects; connections to existing starters and telemetry; lighting; electrical permitting; submittals; O&M manuals; testing coordination and final record drawings.
• The installation included both underground and exposed raceways. Below-grade electrical runs utilized PVC-encased conduit, while exposed installations utilized rigid metal conduit. BRE coordinated these systems with the new underground pump-station structure and other work performed by JCC. Excavation and backfill, the concrete base for the electrical backboard and the disconnect switches themselves remained JCC responsibilities under the electrical subcontract.