An electronics manufacturer received state approval earlier this month to begin cleaning up toxic wastes at its Crownsville plant and dump the treated water into a South River tributary, downstream of Annapolis' drinking supply.
John MacKay, facility manager at Alliant Tech Systems Inc., said the company plans to pump polluted water from an underground reservoir behind its chrome plating operation, purify it and return it to Broad Creek.
The cleanup at Alliant -- formerly the Honeywell Signal Analysis Center -- could last more than 10 years, MacKay said.
For more than two decades, Honeywell poured heavy metals, degreasing solvents andother chemical cleaners into dry wells less than a mile downstream of the Annapolis drinking supply.
In 1985, the state ordered the dumping stopped and the site cleaned up.
Honeywell had removed toxicsludge from the dry wells by August 1989. However, negotiations between company and state officials on how to clean up polluted ground water and prevent it from contaminating nearby residential wells dragged on.
One of the snags was determining "how clean is clean," Health Department spokeswoman Evelyn Stein said.
Health Department officials say the pollutants, including several carcinogens, pose a threat to human health only if they contaminate drinking water. So far, the pollutants, which travel slowly through the ground, have not reached either the 14 residential wells within a half-mile of the site or the city's wells, Stein said.
The state Department of the Environment approved a cleanup plan and issued Alliant a five-year, renewable permit to discharge into the creek Dec. 6, said DOE spokesman John Goheen.
Under the cleanup plan, Alliant -- a company which split away from Honeywell last year -- will pump polluted water out of the ground, treat it with hydrogen peroxide and ultraviolet light to neutralize the hazardous chemicals, then release it into a culvert along Route 450, leading to Broad Creek.
The process, known as bio-oxidation, will raise water temperatures by 20 degrees and could pose a potential environmental hazard to Broad Creek and the South River, Goheen said. But Alliant will be required to limit the temperature of water entering the creek to no more than 90 degrees, particularly during the summer.
Since 1985, the plant has disposed of its toxic wastes at federally approved facilities in Chicago, New York state and New Jersey, said Alliant's MacKay.