Nineteen homes in Gowanda have been fitted with special equipment to remove dangerous gases seeping into their basements from industrial ground water contamination, Cattaraugus County Environmental Health Director Eric Wohlers reported last week to members of the county's Board of Health.
He said volatile organic chemicals, mostly trichloroethene (TCE), migrated from a site off Industrial Street into the ground water beneath homes in the Torrance Place and Chestnut Street neighborhood.
Testing by the state Department of Environmental Conservation, following a decision in 2001 for an environmental cleanup, showed a 450-foot-wide plume of contamination moving northward about six to eight feet below ground level.
Gases from the TCE and other volatile organic compounds, including benzene, xylenes, toluene and other compounds, permeate the soils, and vapors seep into the basements, crawl spaces and cement slabs of homes built at grade level.
The plume's origin is 1,100 feet away at the former AVM-Gowanda site, now owned by Gowanda Electronics. That firm has cooperated with the industrial site investigations, soil removal and treatment of ground water in a voluntary cleanup agreement with the DEC.
The process for keeping soil vapors from migrating into basements and through ground-level slabs is called sub-slab depressurization. It employs the same devices used to prevent radon from entering basements.
Contractors, the DEC and the state Department of Health sampled homes in a variety of ways last year to determine the location of intrusive soil vapors and to select homes to receive the devices. Tests were performed in two visits, and homeowners were quizzed on the extent of the problem via a questionnaire.
Homes that received the subslab depressurization systems had TCE levels at five micrograms per cubic meter or more that were attributed to a soil vapor intrusion. The system is paid for by the state or the party that is determined to be responsible for the AVM ground water contamination.
For testing of air in homes built on basements and grade-level slabs, a three-eighths-inch hole was drilled through the concrete, and gas samples were taken from beneath the slab and from the inside of the basement or ground floor. Samples also were taken of the air in crawl spaces and first-floor rooms in homes with crawl spaces.
The subslab depressurization systems use suction to extract TCE and other vapors to the atmosphere through a system of pipes and a fan.
TCE exposure at elevated levels in air and water has been associated with increased risks for certain types of cancer in the kidney, liver and esophagus, and non-Hodgkin's lymphoma. Eye and respiratory irritation have also been associated with exposure in some lab tests, and there have been documented association in damage to the central nervous system and fetal development.