Trout stream into a hot tub Temperature testing: Discharges from Carroll wastewater plant could be too warm for the fish.

September 22, 1998

THE DISPUTE over the temperature of water discharged from the Hampstead wastewater treatment plant into Piney Run illustrates the complexities of anti-pollution laws -- and the hidden threat of thermal pollution.

It also highlights different visions of the area's future: Carroll County favors more development there; Baltimore County, just across the county line, does not.

Baltimore County residents charge that effluent from the Carroll plant is too warm for a state-protected trout stream: The legal limit is 68 degrees or the ambient water temperature. Warmer waters can harm fish reproduction and survival.

The state Court of Special Appeals last month ruled that the Maryland Department of the Environment could not issue a permit for increased discharges from the plant without first proving that the temperatures would not violate the standard.

MDE finally approved a permit in 1996 allowing the Hampstead facility to increase its treated discharge to 900,000 gallons a day, up from a 500,000-gallon daily limit.

There is evidence that trout are found in the Piney Run and that the insect larvae on which the fish feed are abundant, little affected by the discharge temperature.

Carroll authorities replaced a flat concrete trough into the stream with a meandering streambed to cool and slow the flow of the discharge waters. Plant treatment pools exposed to direct sunshine were shaded, cascading steps were built to cool the water.

The appeals court decision tells MDE to test the temperature and justify the expanded discharge permit. There's also broader concern that the state agency may not have done that testing at other treatment plants it awarded permits for expanded capacity.

Carroll is addressing the problem. More troubling is what impact the judicial decision may have on other MDE discharge permits.

Pub Date: 9/22/98

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