Opportunity
Created in 1971, the Two Bridges Sewerage Authority serves the communities of Pequannock, Lincoln Park, and Fairfield — formerly rural communities that grew into more densely populated suburbs. In 1987, with the addition of a 7-mile (11-kilometer) sewer line, the Authority began offering service to the communities of the Pequannock River Basin Regional Sewerage Authority: Butler, Bloomingdale, and Kinnelon.
With 14 miles (22 kilometers) of interceptor sewers, 7 miles (11 kilometers) of force mains, 5 remote pumping stations, and an advanced wastewater treatment facility with an outfall into the Pompton River, the Two Bridges Authority now provides wastewater services to an area of 56 square miles (145 square kilometers) with about 40,000 residents.
The wastewater system includes two major wastewater pumping facilities, similar in capacity, size, equipment, and age. The South Side Pump Station, with a design capacity of 12.1 million gallons per day (MGD) is located south of Highway I-80, and the Central Pump Station (15.5 MGD) is at the intersection of Highway 202 (Boonton Turnpike) and Ryerson Road. The two facilities pump wastewater from the south and north service areas, respectively, directly into the treatment plant headworks.
After about 25 years of service, both pump stations were in need of upgrades. The Authority wished to reduce the project capital and future maintenance costs while maintaining its reputation for excellence and safety. The Authority had received an Outstanding Operations Award from the EPA in 1985, and the George W. Burke Award for Safety in 2003.
Solution
In 2005, the Two Bridges Sewerage Authority retained Mott MacDonald as the consulting engineer for the pump station upgrade, including design, mechanical, structural, architectural, HVAC, and construction management services. The project included the following:
- Replacement of raw sewage pumps with dry-pit submersible pumps, allowing the elimination of the seal water system, and heat exchangers
- Replacement of liquid rheostat controls with variable frequency drive pump motor controllers
- Replacement of building ancillary equipment
- New power distribution equipment with independent feeders to each raw sewage pump
- New automatic transfer switches
- New 1.2 megawatt outdoor standby generator at Central Pump Station
- New odor control systems
- New heating and ventilation systems
- New connections for emergency bypass pumping
- New trailer-mounted portable pumps for emerging operations
- New landscaping and fencing
Mott MacDonald and the Authority avoided duplication of costs and reduced the duration of the contract by combining the rehabilitation of both pump stations into a single contract. This enabled the following:
- Single application to the New Jersey Environmental Trust for a low-interest loan
- Single set of specifications
- Single report on bids received
- Single construction contract with one contractor to administer
- Single set of shop drawings to review
- Single manufacturer of major equipment for both pump stations
- Single set of operation and maintenance procedures for the major equipment
Outcome
Safety
The Authority has an excellent safety record, and safety was a primary consideration during the design of the upgrade for the South Side and Central Pump Stations. While it was not possible to change their configuration to eliminate confined space entries, Mott MacDonald worked with the Authority to improve operational safety through new atmosphere monitors and additional lighting for hazardous areas. We determined that the original wet-well and dry-well ventilation did not meet current building codes, and designed new systems. Inspection of the existing wet-well channels and grating revealed extensive corrosion, and a new grating system was added to the contract through a change order.
Quality
Our design provides the Two Bridges Sewerage Authority with more efficient, reliable, up-to-date, and resilient equipment, enabling it to handle increased demand and emergencies. Portable pumps and connections designed by Mott MacDonald proved valuable during Hurricane Irene, Tropical Storm Lee, and Hurricane Sandy. In the aftermath of Hurricane Sandy, the Authority was able to accept additional sludge customers when other sludge processing facilities in the region were disabled by the storm.
With potential impact to residents and businesses in seven towns in the event of a failure, the resilience of the Central and South Side Pump Stations was paramount to the Authority. We worked closely with major pump manufacturers to design a system that can use a single pump and force main during average flows, and multiple pumps and force mains during peak flows, through motor-actuated valves controlled automatically by wet-well level or magnetic flow-meter readings.
Schedule
The contract construction schedule provided for a 26-month duration. The Authority received beneficial use of the South Side Pump Station after 18 months, and the modified Central Pump Station was operation after 26 months.