LEVANT – State environmental officials will take more water samples next week in a handful of local wells as they continue to monitor the presence of MTBE, a gas additive.

First detected last year after a February gasoline spill at Piper’s Country Store on Route 222, MTBE has been found in varying levels in nine wells, according to Paul Blood, a geologist with the Maine Department of Environmental Protection.

Blood said that samples in most of the more than 30 wells tested came clean for the presence of MTBE, while of those nine – three since August – showed the presence of MTBE at levels of 25 parts per billion, below the health standard of 35 ppb, but at the point at which the DEP begins to take action. MTBE is considered to be first detectable at 2 ppb.

At the home of John Phillips, who first had his water quality checked after the spill, the state has drilled a new well, reaching 275 feet, compared with the previous well’s 65 feet. Phillips, who said that area residents were concerned they hadn’t been notified last year about the leak and possible contamination, now believes the right things are being done.

Blood said the DEP, through hired hands EnviroInvestigations and Remediation, plans to take monthly samples through this year and then begin quarterly sampling next year. Most of the sampling wells this week also have had data loggers installed, devices that will measure changes in water levels and help the investigators determine whether wells are connected and how MTBE flowed into the systems.

The wells being tested are mostly in two developments near the country store, now closed – one on Black Stream Road, the other on Sunny Acres Drive. They are on either side of Route 222.

MTBE, or methyl tertiary-butyl ether, has been widely used as a gasoline additive to increase octane levels, with conventional gas containing about 3 percent MTBE, although premium brands can contain amounts up to 9 percent.

Although the compound has been shown capable of causing cancer in laboratory animals, for people, drinking 2 liters of water containing 35 ppb daily for a lifetime has been estimated only to increase the chances of cancer by about 3 in 1 million, according to state documents.

Blood said that the investigation into the cause of the MTBE contamination continues, although so far the most obvious source was the Feb. 27 spill of gasoline at the store. The spill was estimated then at 200 gallons, although it’s not known how much of that escaped the containment effort that was quickly put into place. Soil borings were done at 51 sites, with samples from the concrete gas containment area showing elevated vapor levels from 5 to 10 feet down. Ten monitoring wells also have been drilled at the gas station, Blood said.