Alpha Ridge study details treating tainted water

January 05, 1994|By Erik Nelson | Erik Nelson,Staff Writer

Ground water contaminated by the Alpha Ridge Landfill in Marriottsville should be pumped from the ground, treated and discharged into the Little Patuxent River, a Howard County environmental consultant's report recommends.

The recommendation was contained in a 5-inch-thick report detailing ground water contamination from the county's only operating landfill. The $112,000 study, released yesterday, also suggests ways to remove cancer-causing solvents from the water before they can migrate to nearby residential wells.

County officials said they were pleased that the report confirmed earlier assessments of the extent of ground water pollution.

"The main significance is that it confirms our preliminary thinking that the contamination is still localized on the landfill property," said John J. O'Hara, chief of the county Bureau of Environmental Services. "It also confirms our initial estimates of what the remediation would cost."

The report, by Virginia-based GeoTrans Inc., says contaminants have migrated up to 1,000 feet from the old cell over about 180 acres, no more than 150 feet below the surface.

Residential well tests done by the county Health Department have not turned up toxic solvents that were found in monitoring wells on the landfill property. One test showed a trace of one solvent within limits set by the U.S. Environmental Protection Agency, but that was dismissed as a laboratory contaminant.

GeoTrans estimates the cleanup cost at between $11 million and $17 million, depending on which of three recommended alternatives the county chooses. Most of that would be spent on capping the landfill with plastic and earth, a state requirement that was budgeted by the County Council last year.

The most effective -- and most expensive -- method would be to pump the water out of the ground and aerate it, allowing volatile solvents to evaporate. The process would cost the county about $500,000 and continue for more than 30 years, Mr. O'Hara said.

This method should keep contaminants from migrating underground to residential wells in the area, the study says, as well as clean up pollution that is already finding its way into the Little Patuxent River and its local tributaries.

The study says the hypothetical risk of cancer to someone living on the most contaminated part of the landfill would be more than 100 times greater than the level considered acceptable by the EPA. That assessment is based on use of the water, including drinking two liters a day and taking showers, for 70 years.

But the study calls that assessment conservative because it includes exposure to heavy metals, which occur naturally in ground water and create most of the risk.

Dr. Donald L. Gill, a biochemistry professor and Marriottsville landfill activist, said the results of the study were neither surprising nor reassuring.

"They have spent a huge amount of money to come up with information that we already knew a year ago," he said. "I would be pleased that they were doing something, but it would not give me any great confidence, because of the unpredictability of water movement at those depths."

The study found that contaminated ground water generally flows north, but not beyond the Little Patuxent River, and east and southeast from the old cell. The river, which has shown small quantities of contaminants, flows east through the northern end of the landfill property and turns south to run along Marriottsville Road.

While those patterns were detected by monitoring wells and testing streams, contamination on the south side of the old cell was found through soil-gas tests.

Most of the homes closest to the contaminated area are on the other side of the river. Wells on the same side as the landfill were not found to be contaminated in tests done by the county Health Department.

The study also concluded that contaminated water below the landfill tended to be discharged on the surface, either into drainage ditches and ponds or surrounding springs and streams. Once in the surface water, toxic solvents are diluted, degraded or evaporated to the point where they cannot be detected, the study says.

The stream and river contamination does not exceed federal or state limits, the study said, and a ecological study found "no evidence of ecological impairments" in the area.

GeoTrans is also studying contamination at two closed landfills.

A report on the New Cut Road facility in Ellicott City, where residential wells have shown contamination by toxic solvents, is expected to be released in a few weeks.

At the end of February, county officials expect to release a report on the Carrs Mill Landfill, where more than 500 drums, some containing undiluted toxins, have been buried for decades.

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