Multipronged Upgrade

Rahway Sewage Plant Project Connects Old Systems to Modern Ways

by Jim Parsons

A $248 million, multiphase program is upgrading and expanding a nine-town wastewater treatment system in Rahway, N.J., aiming both to eliminate longstanding problems with weather-related combined sewer overflows and add a cogeneration plant, among other improvements. 

Upon its completion in September 2008, the project will expand the system’s maximum peak capacity from 63-million-gallons-per-day to 105 mgd – the expected flow from a 100-year storm – and allow methane generated by sewage treatment to power the cogeneration plant, says Michael Brinker, executive director of the Rahway Valley Sewerage Authority.

The project’s biggest accomplishment will be meeting requirements of a judicial consent order the authority reached with the New Jersey Department of Environmental Protection and the American Littoral Society to mitigate sewer overflow problems in the 48-sq mi service area. But the construction schedule is being driven not only by the risk of fines for failing to comply with the consent order, but also the requirements of the New Jersey Environmental Infrastructure Trust, which is helping to finance the project.

“Timing the deadlines of the judicial consent order with those of the NJEIT has proven to be our biggest challenge,” Brinker says.

The authority operates a trunk sewer collection system and a wastewater treatment facility that serve more than 300,000 residents and 3,500 business customers in central New Jersey, an area encompassing Springfield, Kenilworth, Roselle Park, Cranford, Westfield, Garwood, Clark, Rahway, and Woodbridge.

The current expansion program is largely driven by the 2001 consent order that requires closing two combined sewer overflow intakes that currently discharge excess, untreated sanitary water into the Rahway River in order to prevent street and basement flooding. The order also sparked measures such as the addition of filters, disinfection systems, and other tools to safeguard against future effluent violations; and a new gravity sewer line that will supplement an existing trunk sewer during peak flow periods.

The work is taking place under three contracts overseen by the authority and its construction manager, Consolidated Construction Management Services of Colts Neck, N.J. While the first, $137 million contract involves the major expansion work for the plant, the second, $11 million contract is already nearly complete and involved some of the most challenging construction aspects, Brinker says.

The second contract – originally slated to be a two-year job but done in 13 months by Northeast Remsco Construction of Toms River, N.J. – entailed construction of the 6,132-ft-long gravity sewer, which extends from the city to the treatment plant. The project team was able to drill and install the pipe in half the time by employing double shifts and by using an upgraded drilling machine that let crews bore through the subsurface shale faster, says Rich Palmer, tunneling manager at Northeast Remsco.

The effort to drill and install the three pipe segments – a long polycrete section and smaller legs of iron and of concrete with a liner – used a one-pass process. “You’re installing the final sewer pipe right behind the tunneling machine,” Palmer says.

The work entailed seven sections of micro-tunneling as far as 38 ft underground, including portions under the Rahway River and Routes 1 and 9. Only 65 ft involved open-cut construction, Palmer says.

The new line will allow excess wastewater entering the combined sewer overflows to instead flow down to the plant. But the new pipe will not be operational until the larger contract to increase the plant’s hydraulic capacity is done in 2008.

The work on that main contract, overseen by E.E. Cruz of Holmdel, N.J., is about halfway complete and focuses on increasing plant capacity to 105 mgd. As part of the effort, Cruz is managing upgrades and installation of equipment to treat sewage, such as the headworks facility, settling tanks, return sludge and waste pump stations, bridge effluent sand filters, cascade aeration structure, rotary drum thickener facility, ultraviolet disinfection system, plant utilities, and process piping. Most of the plant currently has 1960s-vintage equipment.

The third contract, which aims to ensure a ready supply of energy through construction of a cogeneration plant, is also well under way. Brinker says the facility grew out of the need to meet the state environmental department’s demand to provide backup power capacity capable of keeping the whole plant operational and able to handle peak rainfall capacity during a power outage.

For fuel, the facility will combine methane from sludge digestion with natural gas to power four generators delivering up to 6.2 MW of electricity.

“You can’t bring the new treatment systems online and permanently close the two CSO sites without having standby power available,” said Manny Parada, project manager with Consolidated Construction Management.  “That makes it a mission-critical item that must be completed on time.”

Construction of the 10,270-sq-ft steel and concrete building housing the cogeneration plant began in early 2004, a year ahead of other program elements. But the path to completion has been anything but easy. 

J.H. Reid General Contractor of South Plainfield, N.J., was in the process of pouring a 6-in. concrete slab for the cogeneration facility when a decision to add the fourth Caterpillar generator to the plant required a reshuffling of the interior layout, as well as the electrical, ventilation, and fire protection systems.

Other last-minute measures, such as the addition of fuel blenders to permit more flexible use of methane and natural gas, further complicated the construction schedule.  While the $21.5 million cogeneration facility is now substantially complete, the complicated operational start-up process will likely last into the spring.

The intricacies of integrating cogeneration will provide a long-term benefit to the system’s users, says Jim Wancho, vice president of Paulus, Sokolowski and Sartor of Warren, N.J., the upgrade program’s lead engineer.

In addition to providing a reliable and economical source of energy, the cogeneration system’s waste heat will supplement the facility-wide hot water loop and improve the efficiency of the sludge-drying process, reducing the volume of biosolids that end up in a landfill. It also will help the facility save more than $1 million a year in energy and sludge disposal costs.

“Electricity and sludge disposal are usually the highest costs in operating a wastewater treatment plant,” Wancho says. “We felt that if we could find a way to help lower those expenses and improve the plant’s overall operational efficiency, we’d have a winner.” 

Key Players

Owner: Rahway Valley Sewerage Authority, Rahway, NJ
Construction Manager: Consolidated Construction Management Services, Colts Neck, NJ
Design Team: Paulus, Sokolowski and Sartor, Warren, NJ; Metcalf & Eddy, Wakefield, MA; and Camp Dresser McKee, Cambridge, MA
Cogeneration Plant Engineer: Paulus, Sokolowski and Sartor
Contractor, Microtunnel: Northeast Remsco Construction, Toms River, NJ
Contractor, Main Plant: E.E. Cruz & Company, Holmdel, N.J.
Contractor, Cogeneration Plant:  J.H. Reid General Contractor, South Plainfield, NJ