The Carlisle Mosquito Online

Friday, July 21, 2006


MTBE levels continue to decline in town center wells

Recent test results from selected wells in Carlisle center show that levels of the gasoline contaminant MTBE (methyltertiarybutylether) continue to decrease from levels detected in 1997 and earlier, according to Water Quality Subcommittee member (WQS) Tony Mariano. The WQS was created by the Board of Health (BOH) in 1997 to look into water quality problems in the town center. Mariano appeared at the BOH meeting on July 18 to give members a preliminary review of the water testing that was conducted on May 19 and 20, 2006.

Mariano explained that MTBE was detected in some of the center's residential wells in 1997 and earlier. He said that there is history of gasoline-related contaminants appearing in residential wells in the town center back into the 1970s. The contaminants continued to show up in subsequent testing, which was conducted many times a year for several years. In 2000, the Department of Environmental Protection (DEP) got involved and conducted a cleanup of the Daisy's gas station property, which included removing a leaking underground gas tank and a large amount of contaminated soil. The DEP installed six monitoring wells at the site which they agreed to maintain. When the BOH conducted water testing this spring, they included some of the monitoring wells and several residential wells that have had a history of MTBE contamination.

While there is no drinking water standard for MTBE, there is a standard for ground water (70 parts per billion) which is used as a guideline. In years past, a residence on Lowell Street measured 330 ppb MTBE, and had only 39.4 ppb in this May's sampling. Likewise, another residential well on East Street was found to have 83 ppb MTBE in 1998 and now has 11.1 ppb. Mariano cautioned that test results can vary seasonally, even within the same season, and levels can fluctuate due to conditions like the heavy rains that occurred this year. Residents who have installed filtration systems to minimize contaminants must maintain those systems, including cleaning or changing filters.

Still, despite the need for continued well testing and system maintenance, Mariano said that "we can be encouraged that MTBE levels are decreasing."

2006 The Carlisle Mosquito