Opportunity
Lined up along the Hudson River shore, the four New Jersey communities of Hoboken, Weehawken, Union City, and West New York are among the oldest in the country. The area was first settled by the Dutch in the 17th century, who called it Pavonia.
Directly across the river from Manhattan, the area is densely populated. Union City, for example, has more than 51,000 people per square mile (19,691 per square kilometer) — more than any other city in the country. Yet until 1998, parts of these communities were actually served by wooden sewers.
In 1988, the North Hudson Sewerage Authority was established to serve the four communities, in response to an EPA Consent Order requiring them to give up control over their failing wastewater treatment facilities.
Since then, the Authority has built a $120 million treatment plant, brought the wastewater system into compliance with EPA and New Jersey requirements, helped redevelop the Hudson River waterfront, won 16 WAVE awards from the Association of Environmental Authorities — and replaced the wooden sewers.
Among the Authority’s challenges was the rehabilitation of the 18th Street Pump Station, reconstructed in the 1960s and located near the entrance to the Lincoln Tunnel in Weehawken. The pump station conveys sanitary sewage flow to the Adams Street treatment plant in Hoboken, and during extreme wet weather it pumps combined sewer overflows (CSOs) to the Hudson River.
The pump station was plagued by antiquated pump controls and electrical, heating, and ventilation systems. Maintenance of the aging natural-gas engines, used to drive large stormwater pumps and sanitary pumps during power failures, had become an onerous task.
Solution
The Authority retained Mott MacDonald to provide design and permitting services for the rehabilitation of the 18th Street Pump Station, a project completed in 2007. The object of the rehabilitation was to replace aging equipment at the pump station, address corrosion from wet-well gases, add odor control, and increase pumping reliability during power failures.
Mott MacDonald was also retained to provide similar services for the 2011 construction of a new 48-inch (1.2-meter) storm-flow force main from the pump station to the Hudson River.
Inspection
We conducted a complete inspection and evaluation of the existing station, using personnel experienced with pump stations, odor control, power distribution and pump control, heating and ventilation, and architectural disciplines.
Emergency power
We evaluated the continued use of the pump station’s emergency power system, which used several natural-gas engines and right-angle gear drives to operate sanitary and storm-flow pumps during power outages. We concluded that the system was antiquated and maintenance-intensive.
Based on capital cost and considerations of operation and maintenance, the first key decision made by the Mott MacDonald team was to convert all pumps to electric-motor-driven units and to provide a diesel-engine-driven standby generator to power the entire station during power outages. This also required a new utility power service, transformer, and switchgear.
The standby generator was sized to handle all pumping loads, heating and ventilation loads, and electrical lighting so the station could function for an extended period without utility power. The generator was placed in an acoustical, walk-in-type enclosure that mitigates the noise from the diesel engine.
Sanitary pumps
Three existing sanitary pumps were replaced with new dry-pit submersible pumps with new variable-frequency drives. The pumps can operate even when totally submerged. For added control, piping was revised to include flow metering on the discharge of each pump. A new 12-inch (30-cm) sanitary-pump force main was installed from the pump station to the treatment plant.
Storm-flow pumps
Two existing storm-flow pumps were replaced with new high-flow/low-head vertical propeller-type pumps driven by 250-horsepower vertical motors. Each pump has a capacity of 42 million gallons (159,000 cubic meters) per day when pumping through the new 48-inch (1.2-meter) force main.
Odor control
Ventilation and odor control systems were completely replaced to provide the proper number of air changes per hour for the screen and wet-well areas. All discharges were treated with a new state-of-the-art activated-carbon control system. The carbon media can be regenerated using potable water, significantly extending the life of the media.
Corrosion
The screen room and wet-well areas were completely sealed off from the rest of the pump station to eliminate the migration of corrosive gases into the dry well.
Outcome
Safety
The upgrade brought the pump station into compliance with current codes regarding wastewater facilities, such as NFPA 820. Screening and wet-well areas were physically separated from the pump rooms and electrical areas. Improved ventilation ensured the circulation of fresh air, reducing corrosion and eliminating the possible accumulation of hazardous sewer gases.
Quality
In October 2012, the Authority’s service area was one of those hardest hit by flooding from Superstorm Sandy. Nearly seven feet (2.1 meters) of water settled in the low-lying Shades neighborhood of Weehawken, damaging buildings and destroying cars.
Although the 18th Street Pump Station was partially flooded, the station was able to stay online and run the stormwater pumps by operating its standby generator.
According to Mott MacDonald's Kevin Wynn, “Because we didn’t lose them [the pumps], we were able to pump that six or seven feet of water that was sitting in the Shades out in around 48 hours. If we didn’t have the use of those pumps, it would have taken much longer.”
The New Jersey Department of Environmental Protection praised the Authority for its actions before, during, and after the storm. Based on those actions, the Association of Environmental Authorities gave the Authority its 2013 WAVE Achievement Award. In September 2013, a group of 14 representatives of Japan’s Society of Environmental Instrumentation Control & Automation visited the Authority to share lessons learned from Superstorm Sandy and the 2011 Pacific Ocean earthquake and tsunami.
Schedule
The project was funded through the New Jersey Environmental Infrastructure Trust Fund, which imposed tight deadlines for the submission of contract documents and permits. All deadlines were met and funding was secured. The station upgrade was completed within 18 months of the notice to proceed.
Among the measures taken by Mott MacDonald to cut construction cost and time was the installation of a pile-supported concrete slab without the need to remove buried obstacles underneath. The slab, which supports the new generator and odor control system, was built over piles that were driven in a random pattern to avoid the existing obstacles.