A report the agency received last month from an environmental engineering firm says extending the water line would be a permanent solution to supplying clean water to 11 properties affected by MTBE contamination from a spill decades ago.

Some of those residential and commercial sites have their well water treated by individual systems, which were installed by a contractor reimbursed by the state, and have since been maintained by a third party, as a temporary fix, the report said.

It outlines what would be involved in expanding the water line, which ends at the intersection of South Winchester Street and West Swanzey Road (Route 10). The extension would run about 4,050 feet south of where the line ends.

In addition, the report includes an estimated cost of $980,000 for the project, and says the entire amount would likely be paid for by the state.

MTBE (or MtBE) is an acronym for methyl tertiary-butyl ether, which is a flammable and colorless liquid that was used as an additive in gasoline starting in 1979. The known carcinogen was banned from being used in gasoline in New Hampshire in 2007.

In 1990, the Route 10 Mini-Mart at the corner of West Swanzey Road and Westport Village Road became the focus of an MTBE cleanup after gasoline was found in two catch basins near the property. State officials traced the chemical leak to one of the gas station’s underground storage tanks.

Since then, the chemical has been moving in a plume through groundwater, and getting into the drinking water supplied to wells in the area.

Some of those wells have tested above the state’s MTBE threshold of 13 micrograms per liter, while others have tested positive for the chemical, but at levels below the state limit.

“There are a number of things favorable in doing the project, but there are a few questions that probably are best answered before making any final decision on it,” Lynn said.

Those questions include the condition of the water system’s storage tank and some of its existing piping, and whether the town of Swanzey would be interested in purchasing the system, he said.

The system, which is privately owned by the West Swanzey Water Co., serves about 200 customers from 82 households and businesses in West Swanzey. It is fed by wells that once supplied water for the former Homestead Woolen Mills.

The MtBE Remediation Bureau received the preliminary engineering report from Manchester-based GeoInsight Inc. in March, and continues to review it, Lynn said. He has asked officials at the state drinking and groundwater bureau to go through the report and provide feedback to his staff, he said.

Once the reviews are complete, it’s likely state officials will authorize additional funding for the bureau to conduct follow-up work to obtain specific answers for the questions raised in the report, he said.

GeoInsight Inc. an environmental strategy and engineering firm, has been working with the state MtBE Remediation Bureau and the N.H. Department of Environmental Services to come up with a long-term solution to address the MTBE contamination in Westport.

The company prepared a report in 2013 that concluded extending the West Swanzey water line was the most feasible long-term solution. The other option the firm looked into was connecting the 11 properties to the community water system used by residents of the Pine Grove Mobile Home Park. However, that system didn’t have the capacity to take on additional customers, the report said.

According to the March report, funding is available to pay for the extension of the water line, but only to hook up the affected properties.

The funding comes from lawsuit settlements reached between New Hampshire and 25 petroleum companies accused of contaminating groundwater with MTBE.

In a separate matter, a jury found a 26th company in the lawsuit, ExxonMobil, liable, and ordered it to pay the state $236 million. The company has since appealed the decision to the U.S. Supreme Court.

Whatever happens with that case won’t affect the West Swanzey water line expansion project because it is already slated to be funded from the other settlements, Lynn said.

On April 1, Gov. Maggie Hassan signed a Senate bill creating a trust fund for the ExxonMobil funds to make sure they’re used exclusively for the cleanup of MTBE-contaminated water. The bill also established an advisory committee to oversee the fund.

Exposure to high levels of MTBE can cause short-term health effects such as headaches, nausea, dizziness, irritation of the nose or throat, and confusion, according to the federal Agency for Toxic Substances and Disease Registry.

Little is known about the chemical’s long-term health effects, whether at low or high exposure levels, but some residents living near the Route 10 Mini-Mart say they believe the presence of MTBE in the groundwater has caused high rates of cancer among humans and animals in the area.

The N.H. Department of Health and Human Services looked into their claims. It said in a December 2014 memorandum that further study wasn’t warranted at the time.

In October 2015, state environmental officials met with Swanzey selectmen to discuss the water line extension project and the pending report. It was expected to be ready in December at that time.

The officials repeatedly told selectmen that they didn’t expect the MTBE contamination to seep into the water company’s wells. The wells are in the area of West Street west of West Swanzey Road, which is north of the contamination area.

The meeting came 10 months after a water study committee, which selectmen appointed, recommended the town stay out of the water supply business for the time being, and not buy the West Swanzey Water Co.

State officials told selectmen in October they wanted them to consider buying the business so the town could further extend and upgrade the water system at the same time the state was doing its work covered by the MTBE funds.

In addition to extending the water line from South Winchester Street to Westport, the March report proposes installing a water line along West Swanzey Road from the intersection of Perry Lane to the junction with South Winchester Street to create a loop for the water system.

That project, while improving the system’s reliability and fire suppression capabilities, couldn’t be paid for with state MTBE funds, state environmental officials have said.

The funds also wouldn’t pay for properties outside the contamination area to connect to the extended water line from South Winchester Street to Westport, they’ve said.

According to the March report, building the loop into the water system could cost $753,000 on top of the water line extension.

Selectmen Chairman Bill Hutwelker said Tuesday that board members have yet to receive a copy of the March report.

Whether selectmen decide to reactivate the water study committee is dependent upon the arrival, and content of that report, he said.