EPA to assess cleanup options at Dover site

A 30-year federal cleanup investigation in the heart of Delaware's capital is moving into a new phase after investigators failed to rule out all health risks from toxic groundwater exposure risks.

The Environmental Protection Agency's Superfund report on the Dover Coal Gas site found some elevated potential for current cancer and non-cancer health risks across the sprawling area now and in the future, particularly for construction workers who might be exposed to groundwater or vapors during excavation in contaminated areas.

Future exposures also could increase cancer and other health risks for those who over a lifetime might directly contact, drink or shower in water from contaminated parts of the aquifer, which extend in some areas to a depth of 60 feet. Most risks are viewed as remote, however, because of restrictions on groundwater use in the area.

"The next step at this point is a feasibility study that we're hoping to start this year," said Bonnie Smith, spokeswoman for the EPA's regional office in Philadelphia. "This will be an assessment of the options for cleaning this site up, the viable and best options, an analysis of what's technically feasible to do and the estimated cost."

Pollution investigations in the area began in 1984 after testing for a new courthouse site just east of the present Norfolk Southern tracks and south of Loockerman Street. The testing initially found contamination from a plant dating to the mid-1800s that produced gas, sometimes called "town gas," for consumer use from coal.

The EPA supervised construction of a paved parking lot to cover the main pollution site and control the spread of contamination, but a worse problem emerged when dry cleaning solvents were found at high levels in soils, spreading from a plant razed by fire near the coal gas site in 1989.

Years of studies included punching of sampling wells into soil across the capital center and testing of vapors in household basements. Results showed that pollution had spread as far as about a half-mile east of the origins, to the St. Jones River. Contaminants were found to be trickling from groundwater into the stream and sediments.

Early on, levels of toxic, carcinogenic perchloroethylene were found as high as 57,000 times the 1 part per billion federal drinking water limit. None of the the city of Dover's water system wells are near the polluted area, however. Top pollutants included PCE and a related chemical, tetrachloroethylene, as well as gasoline-type compounds and naphthalene.

Other pollution sources might have contributed to the overall problem, described as "complex" by the EPA's Smith.

Large portions of the area are still believed to have PCE levels higher than 1,000 parts per billion, including groundwater under Legislative Hall.

Contact Jeff Montgomery at 463-3344 or jmontgomery@delawareonline.com