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Powering Up Construction Waste

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Most of New England's construction and demolition (C&D) waste is landfill-bound, and that's a problem for states as well as contractors. Given the limited amount of landfill space and general public opposition to new landfill development, some states have taken matters into their own hands by banning landfill disposal and incineration and/or imposing other restrictions on C&D debris.

Photo by Keith Williams
The Local Route: The plant will source wood-based fuel from volume reduction facilities throughout southern New England.
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The issue is a headache for many of the region's contractors, who ultimately pay to have their waste hauled to out-of-state landfills. But the owners of a new C&D waste-fueled energy plant under construction in Plainfield, Conn., see the issue as more of an opportunity. When finished, the $225-million plant will be the only one of its kind in southern New England.

Plainfield Renewable Energy's (PRE) biomass facility, located on a 26.5-acre site, will use wood-based fuel from readily available sources, including C&D debris, tree thinning, recycled wood pellets and land clearing materials, to generate 42 megawatts of electricity—enough to power the equivalent of more than 37,000 homes.

"A lot of Connecticut's debris goes to volume reduction facilities (VRFs), then goes to landfills or to recyclers, usually to landfills out West, and sent by truck or rail," says Scott McKillip, vice president at Science Applications International Corp. (SAIC), McLean, Va. SAIC is the engineering, procurement and construction contractor on the project and also provides part of the financing. "There are very few active landfills in Connecticut," McKillip says.

In fact, with the expected close of the Windsor-Bloomfield landfill in 2015, Connecticut will be the first state nationwide with no active landfills, according to the Connecticut Resources Recovery Authority, Stratford.

The Plainfield plant will divert this debris from the waste stream, taking in supply from VRFs throughout southern New England. Locating the plant in eastern Connecticut and close to the VRFs in neighboring states, greatly reduces transport costs and saves resources, says Matthew Brown, senior project engineer at Anchor Engineering Services, Glastonbury, Conn., which serves as the site civil engineer on the project. While the plant is adjacent to an unused rail line, it is not needed as "the sources of wood are so local they can be trucked in," he adds. PRE already has agreements in place with several VRFs to supply the entire 1,000 tons a day of wood debris needed to run the plant.

The amount of C&D waste available "greatly exceeds" the amount needed to run the plant, says Bill Brunstad, president of Enova Energy Group, which owns an 80% stake in Norwalk, Conn.-based PRE. That allows PRE to secure favorable pricing for the waste as well as a reliable supply of wood fuel, he adds.

The plant will consume about 4.5 MW of the power it generates, and Connecticut Light & Power (CL&P) will buy 30 MW for 15 years, helping the utility meet its state renewable portfolio standards. "CL&P will pay a premium because this is renewable [energy], but they can sell it at a premium as well," McKillip says.

The rest of the plant's electricity is not yet under contract, but PRE expects to find another buyer for the power or sell it on the spot market before December 2013, McKillip says.

Construction began last September with site clearing for the plant, which is like "a big wood stove," says D. Scott Atkin, Anchor vice president. Material that has already been chipped down to size and is in good condition, with no contaminants such as nails or pressure treated wood, will be stored until ready for use at the site's 160,000-sq-ft storage yard adjacent to the plant. It has a storage capacity of 25 days. The yard, part of which will have a canopy cover, will be paved and the surface sealed to provide protection for the soil and groundwater. Stormwater will be collected in underground storage tanks.

Plant processing involves feeding the wood via conveyor belt into an air-fed fluidized bed gasifier, where it is burned to create high-temperature gases. The gases make high-pressure steam, driving turbines that generate alternating current (AC). The AC is sent to a nearby utility substation.

Foundation work at the site has been completed and the fire loop for the entire site already installed. Structural steel is being erected for the main building—the gasification turbine hall. The team expects to install turbine equipment next January. Equipment to be delivered this summer includes scrubbers and the cooling tower.

The site will include a filter complex for removing suspended material from water that will be piped 13,200 ft from the Quinebaug River. It will be processed for use in the cooling tower or held in reserve for use in the fire suppression system. PRE owns property near the river and is building a small, 550-sq-ft pump house for the 718 gallons of water per day that will be drawn from the river. The pump house will be directionally drilled so as not to disturb the river shoreline, and it will be set back about 600 ft from the river, Enova says.

The non-contact cooling water from the Plainfield plant will be cleaned and returned to the river. "It will be cleaner when we return it than it was when we withdraw it," says William Kelsey, SAIC senior project manager.

The site also includes six wetlands, which will be protected by buffer zones the team set up. This included building retaining walls for three of the wetlands and designing a management system that would not directly discharge stormwater into the wetlands.

The team also took care to avoid disturbing the habitat of the tiny and elusive eastern spadefoot toads—endangered in Connecticut—which breed in the wetlands. "They like the sandy soil that we have," says Atkin. To mitigate risk to the amphibians, the team halted heavy clearing work at the site during the toads' hibernation period, from November to April. "At the end of construction, we will put a conservation easement [for the toads] on the facility and at the pump house for areas not used in operation," he adds.

Anchor worked with PRE early on to find the Plainfield site, a former Superfund area at Mill Road and Route 12, culling possibilities down from a list that was at one time close to 395. It chose the site for several reasons, including the good condition of the brownfield after remediation, Brown says. Also, Plainfield's relatively close proximity to the Connecticut, Massachusetts, New Hampshire, Rhode Island and Vermont markets it would serve was a plus.

The project is not without controversy, however. Nearby residents, especially in Canterbury, are concerned over piping water from the Quinebaug. In November, the town passed an ordinance to prevent PRE from installing the pipe in town roads. Earlier this year, PRE sued the town and certain authorities to stop them from enforcing the ordinance. Canterbury's first selectman, Brian Sear, one of the officials named in the suit, declined to comment due to the litigation.

Brunstad is adamant that "whether we prevail in the lawsuit or not, the project is going forward." He says that PRE has "a number of other options so it is not a project-critical issue" if the firm loses its request for a permanent injunction. He would not elaborate on the alternatives.

The project has had a warmer reception from Plainfield's first selectman, Paul Sweet, who praises it for creating more than 200 trades jobs in a region with the second-highest unemployment rate in northeastern Connecticut. It will also bring in about $1.5 million for the town in tax revenue, he says.

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