Tunnels beneath Hudson River collect PCBs near GE

Workers have drilled and blasted two enormous tunnels under the Hudson River in a project that is unique in the field of environmental cleanup work.

The tunnels, each 1,800 feet long and 10 feet in diameter, under the river near the former Hudson Falls General Electric plant, will be used to collect PCBs before the toxic chemicals can seep up through the bedrock and into the river. It’s all part of a state-mandated cleanup of PCB contamination from GE’s Hudson Falls and Fort Edward plants. A separate federally mandated cleanup is also under way.

GE spokesman Mark Behan called the tunnel project “a unique application of an existing technology.” That existing technology is the drilling and blasting methods, used in the mining industry. The unique part is that the tunnels, which are 80 feet below the river bottom, will be used to collect the PCBs that are slowly migrating from the old capacitor plant in Hudson Falls through the bedrock and under the river.

“It’s a very unique project,” said Kevin Farrar of the state Department of Environmental Conservation. Farrar described the tunnel drain collection system as the “world’s largest groundwater recovery tunnel.”

Once the project is finished next spring or early summer, the PCBs collected will be pumped up out of the tunnels into an expanded water filtration and treatment plant in the old Hudson Falls GE plant.

This collection and pumping process, once started, will continue into the foreseeable future, Farrar said.

The state is concerned about the PCBs (polychlorinated biphenyls, a probable carcinogen) that are slowly entering the river through seep holes in the river bottom.

Earlier work at the old capacitor plant site has reduced the amount of PCBs seeping into the Hudson from five pounds per day to less than three ounces per day, according to state and DEC officials.

The state DEC ordered the cleanup in 2004. Drilling and blasting of a vertical shaft near the former GE plant on John Street in Hudson Falls started in the fall of 2007. This vertical shaft is 200 feet deep and 24 feet in diameter. A demolition company from New Jersey, called Merco Obayashi, used water-based explosives, not dynamite, to excavate the shaft and tunnels.

drilling and blasting

Workers then started drilling and blasting the two tunnels under the river, working all spring and summer and finishing up Sept. 26.

It will take another month to prepare for the next phase of the project: lining the tunnels with concrete.

Farrar, who is overseeing the project for DEC, said the tunnels are farther from Bakers Falls on the Hudson than first designed.

Farrar said DEC has been monitoring the vibration and blast pressure during the project.

He said the blasting has not caused any major problems with structures or the Bakers Falls dam on the Hudson.

Behan said the collection equipment on the ceiling of the horizontal tunnels will be installed, and then vertical wells will be drilled up into the bedrock under the river.

“They will be like fingers going up into the bedrock,” Behan said.

These collection wells will capture the PCB oil before it seeps up and into the river.

A state-of-the-art water treatment plant was built inside the empty Hudson Falls GE plant in recent years.

Behan said the capacity of this plant, which has been used to treat other PCB-tainted water near the plant, has been expanded from 125 gallons per minute to 450 gallons per minute for the tunnel drain collection system.

costly project

State officials estimate the project will cost $30 million to $40 million.

Once completed, the system will cost GE approximately $1.3 million each year to operate and maintain, said Lori O’Connell, a DEC spokeswoman.

Behan said the tunnel drain collection system should be complete by the spring but months of testing will then be needed. The project is expected to be completed and tested by October 2009, according to DEC.

Behan said GE will not comment on the cost of the project. The company will only say that it has spent more than $300 million in the past two decades in PCB-related cleanup work at the Hudson Falls plant, at the still operating Fort Edward plant, and in work preparing for next year’s dredging of the upper Hudson River to remove PCBs.

The state-ordered cleanup work at the Hudson Falls and Fort Edward GE plants is separate from federal government’s Hudson River PCB cleanup project.

The U.S. Environmental Protection Agency ordered GE in 2002 to pay for the approximately $700 million dredging of about 2 million cubic yards of PCB-contaminated river sediment from the upper Hudson between Fort Edward and Troy.

This project is scheduled to start in May, 2009. GE contractors are currently putting the finishing touches on a 110-acre river sludge processing and transportation complex just below Lock No. 7 on the Champlain Barge Canal in Fort Edward.

PCBs are described by the EPA as a probable carcinogen that also cause other health problems in human and wildlife. GE plants in Hudson Falls and Fort Edward discharged an estimated 1.3 million pounds of PCBs into the Hudson for 30 years ending in 1977, when the government banned the practice.

By Lee Coleman
Gazette Reporter