Launch Slideshow

Sedimentation tank under operation; individual bays during the bypass of flows.

Remediating unforeseen sewer contaminants

Remediating unforeseen sewer contaminants

  • Top view of one set of submersible of pumps with discharge pipes rising from the bottom of the grit chamber. Two electric Flygt submersible 230-hp 18-inch pumps and two Gorman-Rupp electric submersible 45-hp 12-inch pumps moved solids from the chamber into the settling area. Five 12-inch diesel Gorman-Rupp and one 10-inch Pioneer diesel pump moved the liquid from the settling area to the pumping station.

    http://www.pwmag.com/Images/tmp9634%2Etmp_tcm111-1853555.jpg

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    Top view of one set of submersible of pumps with discharge pipes rising from the bottom of the grit chamber. Two electric Flygt submersible 230-hp 18-inch pumps and two Gorman-Rupp electric submersible 45-hp 12-inch pumps moved solids from the chamber into the settling area. Five 12-inch diesel Gorman-Rupp and one 10-inch Pioneer diesel pump moved the liquid from the settling area to the pumping station.

    600

    Shilpa Bhojappa

    Top view of one set of submersible of pumps with discharge pipes rising from the bottom of the grit chamber. Two electric Flygt submersible 230-hp 18-inch pumps and two Gorman-Rupp electric submersible 45-hp 12-inch pumps moved solids from the chamber into the settling area. Five 12-inch diesel Gorman-Rupp and one 10-inch Pioneer diesel pump moved the liquid from the settling area to the pumping station.

  • Ingenious workaround. PCBs were found in 5,000 feet of an interceptor buried 20 to 30 feet below a highway near railroad tracks. Placing a decommissioned wastewater treatment plant back into operation saved millions over building a bypass sewer or on-site settling tanks for what turned out to be 2,500 tons of sediment.

    http://www.pwmag.com/Images/tmpC066%2Etmp_tcm111-1853583.jpg

    true

    Ingenious workaround. PCBs were found in 5,000 feet of an interceptor buried 20 to 30 feet below a highway near railroad tracks. Placing a decommissioned wastewater treatment plant back into operation saved millions over building a bypass sewer or on-site settling tanks for what turned out to be 2,500 tons of sediment.

    600

    Shilpa Bhojappa

    Ingenious workaround. PCBs were found in 5,000 feet of an interceptor buried 20 to 30 feet below a highway near railroad tracks. Placing a decommissioned wastewater treatment plant back into operation saved millions over building a bypass sewer or on-site settling tanks for what turned out to be 2,500 tons of sediment.

  • Discharge pipes directing flow to the sedimentation tanks.

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    Discharge pipes directing flow to the sedimentation tanks.

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    Shilpa Bhojappa

    Discharge pipes directing flow to the sedimentation tanks.

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Sewer inspections and cleanings are usually uneventful, but that wasn’t to be the case for Jersey City Municipal Utilities Authority’s 35 mgd Northeast Interceptor. Eight months into sediment removal, polychlorinated biphenyls (PCBs) — a potential carcinogen and cause of non-Hodgkin lymphoma — were discovered.

The authority had contracted with National Water Main Cleaning Co. of Newark, N.J., and Boswell Engineering of South Hackensack to systematically inspect and clean the interceptor’s 19,500 linear feet of combined sewer. Samples from its 70 manholes before cleaning met state criteria for disposal in a Class B recovery facility, which meant the authority could landfill the material instead of sending it to a more expensive, specialized facility.

“Engineers sampled sediment from each manhole, as we do in the pipes we clean ourselves,” says Authority Senior Engineer Richard Haytas. “There was no indication of any unusual contaminants at the time.”

Video inspection above the flow checked for cracks, deformities, and potential failure areas. Sonar beneath the flow looked for sediment that may have settled in the pipeline and deformities or damage to the pipe. Except for one feeder pipe, the 19,500-linear-foot reinforced concrete interceptor was in solid working condition for its age (30 years). Solids, however, had in many places risen to half the diameters, which range from 18 inches to 84 inches. So while it had appeared upon visual inspection to be flowing at 75% of capacity, the interceptor was flowing at only 25%.

Here’s why. In its early working life, the area being served at the interceptor’s farther end was isolated and undeveloped, ideal for illegal dumping by concrete trucks cleaning and emptying the residue from their tanks and trays.

National Water Main began removing the hardened cementitious material at the farthest manhole upstream in the line. Vacuum trucks with high-flow, high-velocity water jets dislodged sediment, suspending solids in the water flow before vacuuming them up. The extracted material was staged at the authority’s pumping station at the end of the interceptor, where it was picked up and trucked to the designated disposal site.

As they worked, representatives from the authority, Boswell, National Water Main, and New Jersey Department of Environmental Protection met monthly — a practice that was to prove highly valuable later.

PCBs found at 75% completion

Their contract with the authority required Boswell and the disposal site to sample every several hundred tons to ensure material continued to meet disposal criteria. Three-quarters of the way along the interceptor, low concentrations of PCBs — below 40 ppm — began showing up.

The potential source was puzzling because the interceptor serves a developed urban area. Public records, however, revealed that a manufacturer of power transformers once operated in the area. Since PCBs bind to solid material, samples taken before cleaning hadn’t detected the contaminant because they were bound into the lowest hard sediment. It wasn’t until cleaning began, disturbing the sediment, that the contaminant appeared.

PCBs presented no danger to the interceptor itself, but have been declared a potential carcinogen and cause of non-Hodgkin lymphoma. U.S. EPA requires actions be taken for concentrations above 1 ppm.

Because cleaning would put employees at risk and potentially send the contamination downstream in the regular flow, National Water Main’s safety department stopped the work so the team could contemplate its challenge: removal and disposal methods, additional costs, and paying for it.

Tricky project location

The PCBs were found 20 to 30 feet below the New Jersey Turnpike and both commuter and freight railroad tracks. Two options — building a bypass sewer and on-site settling tanks — were deemed prohibitively costly.

Diverting 35 mgd of wastewater would have required several 20-foot excavation pits for bypass pumps. Four 18-inch discharge pipes would have to be tunneled. Permitting would have taken years. Similarly, dewatering 35mgd into solids boxes would have cost millions.

But there was a third alternative: the pump station that sends the interceptor’s flow to the treatment plant downstream, which used to be a wastewater treatment plant.

National Water Main suggested diverting sewage through the pump station’s abandoned settling tanks. The solids stirred up by the cleaning would quickly settle, after which the water would be pumped back into the pumping station. The wet solids would then be vacuumed up and discharged to a staging area where moisture would separate and drain through the grit removal portion of the pumping station and allow the solids to dry. The dry solids would then be removed and treated using thermal desorption technology at a licensed facility. (See schematic on page 36.)

“The circumstances were very unique,” says Assistant Vice President Joseph Perone. “So we developed a solution unlike any other I’ve been involved with during my career.”

Once additional funding and state and federal government approval were obtained, removal took about four months. The New Jersey Environmental Infrastructure Trust, which leverages American Resource and Recovery Act stimulus funding and had already loaned the authority $3,843,653, issued an additional $1,446,564 loan. Only one year was added to project completion.

No downstream contamination

The state gave the authority permission to put the tanks, which can hold up to 8 million gallons, back into commission with the understanding that they’d be cleaned thoroughly to prevent possible contamination of the sewer system.

When the additional funding came through, National Water Main contracted with Montana Construction Co. to remove the roof over the old treatment facility’s main chamber so pumps could be installed. Montana was also contracted by the Maple Shade, N.J., location of Sunbelt Rentals Inc., the company supplying and operating the pumps, to build a platform for the pumps and its workers in the pumping chamber.

“The chamber was so deep and the space so confined that we needed Montana to place the pumps down inside,” says Sunbelt Manager Robert Sheehan Jr.

A sluice gate was built to divert the flow from the pumping station during cleaning and send it into the settling tanks before it eventually reached the pumping station. After hours, when cleaning was done for the day and solids settled in the pipe, which meant the PCBs would not be sent downstream, the gate was opened to allow flow to reach the pumping station.

Under the direction of National Water Main Line Superintendent Paul Couto and Project Engineer Shilpa Bhojappa, crews began cleaning the contaminated 4,600 feet of pipeline. In addition to wearing the necessary personal protective equipment, workers were closely monitored for PCB exposure through clinic visits and regular blood tests. The company followed the medical screening and surveillance program outlined by OSHA 29 CFR 1910.

No one was contaminated and no PCBs have been found downstream.