The Boston http://portageparkdistrict.org Globe – March 28, 2002
Watercleanup working well. Recent tests show method is exceeding expectations
by Erica Noonan, Globe Staff Correspondent, 2/28/2002
New tests show the massive barrier installed under Central Avenue last summer, to diffuse a plume of the chemical trichloroethylene, continues to drastically reduce levels of the suspected carcinogen in Needham’s groundwater.
Water taken from several testing wells upstream of the sand-and-iron reactive barrier contained an average of 280 parts per billion of TCE, according to figures received by the state Department of Environmental Protection late last week.
This is nearly 55 times the level considered safe for drinking water, said Steve Johnson, chief of the Department of Environmental Protection’s site management section.
But the water that has passed through the 54-foot-deep and 535-foot-long permeable barrier contained an average of 16 parts per billion, just over three times the safe drinking water limit of 5 parts per billion.
Several wells tested contain no TCE at all, and it is expected that the water will become even cleaner the farther it travels from the barrier, Johnson said. In the coming months, as more of the plume passes through the wall, samples will be taken farther from the barrier to see how quickly the pollutant dissipates.
The barrier, built in a trench running perpendicular to the path of the toxic plume, was completed last July at a cost of $2.9 million. The reactive barrier technology is considered state of the art, and has only been used in a handful of Massachusetts ground-water contamination cleanups.
First detected in the late 1980s, the plume originated from land occupied by Microwave Development Laboratories and contaminated ground water under the Hillside Elementary School.
Though the plume runs by the Rosemary Meadows neighborhood, it has not affected Needham’s drinking water but has has been slowly advancing toward Wellesley’s municipal water supply over the past 15 years.
Part of the TCE plume has moved past the Central Avenue construction spot and cannot be intercepted, but Johnson said it is hoped that those contaminants will dissipate naturally.
It is possible that the slow-moving plume may never reach the Wellesley Water Lands, but if toxic chemicals do infiltrate the wells there, it is hoped that a filtering process that already removes iron and manganese from Wellesley’s water will also remove any remaining unsafe amounts of TCE, Johnson said.
Erica Noonan can be reached at email@example.com
This story ran on page W1 of the Boston Globe on 2/28/2002.
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