In 2003, the 102-inch-diameter (2.6-meter) Sayreville Relief Force Main ruptured, releasing millions of gallons of untreated wastewater into the Raritan River.
As a result of this accident, the New Jersey Department of Environmental Protection (NJDEP) realized that the Edison Pump Station required a substantial upgrade in addition to the construction of new backup or secondary conveyance facilities.
In 2004, Mott MacDonald was retained by the MCUA to conduct a feasibility study, evaluating alternatives to the proposed 4,000-foot (3.6-kilometer) secondary force main under the Raritan River, ways to connect the proposed new force main to the 85 million gallon per day (MGD) pump station and treatment plant without disrupting service, and ways to inspect or rehabilitate the Arsenal Force Main after the new force main became operational. The 60-inch-diameter (1.5-meter) Arsenal Force Main had been in continuous service since 1966, and its failure would result in another major uncontrolled discharge.
These findings and recommendations were approved by the MCUA and authorized in February 2005, and construction began in 2007 for a tunnel with a diameter of 12 feet 10 inches (3.9 meters), using precast concrete segmental lining.
The MCUA retained Mott MacDonald to provide design and construction management and oversight for a complete rehabilitation and replacement of the Edison Pump Station. The project scope included the following:
- Complete replacement of all 5 existing 400-horsepower pumps with new 500-horsepower MGD pumps
- Replacement of all associated control and isolation valves
- Replacement of main control panel with modern PLC-based controls incorporated into a SCADA network
- Replacement of all existing motor starters with new variable-frequency drives
- Installation of natural-gas-fired generators and associated distribution switchgear to allow 2.5 megawatts of standby emergency power in parallel with utility power
The project was completed with no recorded injuries. The installation of a new electrical system reduced operating voltage from 34.5 kilovolt utility power to 480 volt distribution, providing safer conditions for personnel.
The project provided the Authority with efficient modern control systems that optimizes the use of new, efficient pumps and multiple force mains. The result is increased system reliability, resiliency, and savings in energy costs. A Pump Conditioning Panel monitors each pump’s temperature and vibration status, making proactive maintenance possible.
Following Superstorm Sandy, the pump station was able to reinstall and reuse its bypass pumping system, maintaining 100% pumping capacity for raw sewage while damaged equipment was replaced.
The project was completed on schedule. The winning contractor, who had to work simultaneously with the tunnel contractor, was able to complete his original scope of work in the 36 months allotted.