Faced with a series of storms that continued to wipe out its sewer pumping stations, New Jersey’s South Monmouth Regional Sewerage Authority decided it would no longer take it on the chin.

Rather than rebuild the hardest hit pumping stations, SMRSA shifted its design strategy to develop a series of mobile pumping stations that could be driven out of harm’s way in the wake of a storm.

“We’ve experienced four severe wet weather incidents in the past six years, three of which were declared national disasters,” says Mike Ruppel, executive director of the SMRSA. “These hurricanes and northeasters have caused power outages and caused flooding in low-lying areas. At some pumping stations we’ve suffered damage that far exceeded the original value of the asset.”

In 2006, after flooding and damage caused by earlier storms, the authority’s Sea Girt Avenue Pump Station had reached the end of its service life.

“We couldn’t continue to throw money into building infrastructure that would continue to be subject to flooding,” says Ruppel. “We engaged engineering firm CME Associates to conceptualize a project that would reconstruct the pumping station to be, as much as possible, hurricane proof.”

The utility also engaged Pritchard Brown, a Baltimore-based custom protective enclosure specialist, to help cost out the design.

In the new design, the existing below-grade wet well and dry well would be reused as part of the rehabilitated mobile facility. It specified communication equipment, pumps, valves, comminutors and motors, piping and a flow meter, all rated for immersion duty. All other equipment including controls, SCADA equipment, alarm systems, variable speed drives and an emergency generator would be located in a mobile trailer enclosure above the level of initial flooding. Detachable cables and plugs would connect the two units.

“When we see the potential for a major storm event, we send in a truck, put wheels on the mobile trailer, disconnect the plugs and cables and move the enclosure to high ground about a mile-and-a-half inland,” says Ruppel.

“In its place, we would leave a sacrificial portable generator and transfer switch worth $30,000 to $40,000. A secondary sacrificial electrical and control system permanently mounted at the site would operate the system either on utility or generator power. The portable generator might survive the storm, but if it doesn’t, we’ve saved a trailer-load of equipment worth a half million dollars.”

Construction of the mobile station was awarded to Pritchard Brown.

“It’s unusual for a utility to come directly to us to order an enclosure,” says Rick Hackley, sales engineer and business development manager at Pritchard Brown. “The majority of the time, we’re working for the distributors of the generators, such as Kohler or Cummins, who want us to package a system for a client. Since I had already worked with the utility and the engineers on crunching the numbers, they came directly to us for a bid.”

The enclosure was built from scratch on a stock trailer bed using corrosion-resistant marine-grade aluminum, UL 142-listed fuel tanks and a sound attenuation package.

“It was an interesting design challenge to create something roadworthy inside the enclosure,” says Hackley. “We needed to properly balance the load to make it easy to evacuate.”

The first unit required about five months from design to delivery, and was installed in July 2011. It was quickly put to the test by Hurricane Irene. Removing the mobile station and replacing it with the sacrificial components took two utility workers fewer than three hours.

The more-severe Hurricane Sandy arrived in October 2012. The storm cost SMRSA $10 million in damage, knocking out 10 of 11 pumping stations, submerging most of them. Still chugging away in the wake of the storm was the mobile Sea Girt station. The utility estimates that the mobile enclosure saved $1.5 million in avoided damage during those two storms.

“It worked out perfectly and did exactly what it was designed to do,” says Hackley. “It became the poster child for mobile pump stations.”

The pump station design was awarded a 2012 Association of Environmental Authorities WAVE Award for Forward Thinking.

Following the storm, SMRSA presented a case to the Federal Emergency Management Agency that construction funds should be committed to rebuilding its Pitney Avenue Pumping Station as a mobile enclosure.

Ruppel notes that the cost of retrofitting the station was estimated at $640,000. “The cost of the mobile enclosure, complete with a 0.5 MGD pump, was $455,000 delivered,” he says.

FEMA approved the request from SMRSA as a “least-cost alternative” project, and the federal agency has since included the mobile pump station design in its Best Management Practices Portforlio for mitigation of damages during a flood.

The construction contract for the second mobile station was once again awarded to Pritchard Brown, which is currently completing the unit. SMRSA has also announced plans to construct a third mobile pumping station in 2015 to replace the heavily damaged Belmar Pump Station.

Hackley says that publicity regarding the mobile stations has raised interest among utilities, mostly in New Jersey and as far away as Louisiana and along the Gulf Coast.

For any utility contemplating the construction of a mobile pumping station, he recommends that they first decide exactly what they want to accomplish, how quickly the trailer needs to be moved, how far it will be moved and which route it will need to take.

“Also determine if there are any weight or noise limitations, and how much equipment has to be contained in the trailer,” Hackley says. “You might also consider local aesthetics. In Monmouth County, as a result of community feedback, the second mobile pump station has been designed to look more like a summer home. We’re decorating it to make it look like it belongs there, with shutters on the windows and shingles on the roof. It will look beautiful when it’s done.”