HALLOWELL — With little comment, the Maine Public Utilities Commission voted unanimously Tuesday to fine Summit Natural Gas of Maine $25,000 for alleged safety violations.

The fine, reduced from $100,000, involved charges that employees of contractors working for Summit had not passed a written test to certify that they were qualified to install pipelines, and that the company falsified a test to make it seem like the workforce had the required certifications, according to documents filed at the PUC.

After negotiations, Summit agreed to pay the $25,000 fine and take various steps to assure proper training and installation procedures. The settlement was contained in a consent agreement filed early this month. It stems from observations made last summer by PUC inspectors.

During the deliberations, Chairman Tom Welch noted that the consent agreement included a significant number of steps to make sure corrections were made and that a similar situation doesn’t happen again.

The PUC action comes as Summit undertakes an unprecedented expansion of natural gas distribution lines in Maine, including a $350 million effort to connect 15,000 homes and businesses in the Kennebec Valley within five years. This year, the company also is working in Falmouth, Cumberland and Yarmouth, where it pledged to spend $73 million to hook up 80 percent of the homes.

Summit has made progress in 2014. Last week it released a list of streets in Gardiner, Hallowell, Waterville, Fairfield, Madison, Augusta and Farmingdale that have gas flowing. It also listed where gas has begun flowing in Cumberland and Falmouth.

At the same time, the company has experienced delays in meeting its connections goals, as construction slows for the winter. The delays, and the pattern of safety violations uncovered by the PUC, have raised questions about whether pressure to get thousands of customers hooked up to gas as soon as possible is leading Summit to cut corners in building its distribution network, and whether the system is as safe as it should be.

Summit says it’s committed to safe operation, and points to the excellent track record of its parent company, Summit Utilities of Littleton, Colorado. It characterized the PUC oversight as part of the overall process of finding and correcting mistakes, and said all areas that had come under scrutiny had been reinspected and some work had been replaced.

Also Tuesday, a local subcontractor working for Summit took issue with the portrayal of her company’s responsibility for any of Summit’s safety lapses or construction delays.

Among the PUC staff allegations at the root of Tuesday’s deliberations was that contractors for Tetra Tech Construction of Phoenix and CCB Inc. of Westbrook were observed fusing plastic pipe, then later were found not to be qualified for that task. These and other charges were discussed and reviewed as part of the PUC’s settlement negotiations with Summit. No details of that review have been made public.

But after the Portland Press Herald first reported on the settlement agreement last week, Beth Sturtevant, CCB’s president, disputed the charges made against her company. CCB has been working with Summit in the Kennebec Valley and Portland suburbs.

Sturtevant said that after the initial charges were made, she provided written proof to Summit and the PUC that her workers were in fact properly trained and qualified to fuse plastic pipe.

Harry Lanphear, the PUC’s spokesman, said he was unable to comment on any issues raised by subcontractors, such as CCB. He said the agency’s staff findings were accurate, and that talks to settle the violations were solely between the PUC and Summit, which is the regulated company.

Sturtevant said that CCB was contracted by Summit because it was told that construction was behind in Cumberland, Falmouth and Yarmouth. CCB was on schedule with work it was doing on Summit’s mainline in the Kennebec Valley, Sturtevant said, and was asked by the company to bid on putting in a small section of mainline pipe in Yarmouth.

“We did bid, Summit accepted our quote and we went to work, as contracted,” she said. “CCB was not and is not the cause of delays for getting gas on line in Cumberland, Falmouth or Yarmouth.”

Still pending at the PUC are resolutions to three other probable-violation notices issued by the agency for work done by Summit or its contractors in the Kennebec Valley and Portland suburbs. One case, which received media coverage in October, alleges that Summit installed natural gas mains too close to other underground utilities, such as sewer lines. The PUC is recommending a $150,000 fine in that instance.

Tuesday’s deliberations also marked the last session for Welch, the PUC’s chairman. He had announced in September that he planned to step down at year’s end, two years before his term expires.

Welch is known in New England energy circles as the leading architect of deregulating the electric industry in Maine in the 1990s and as a strong advocate for expanding natural gas capacity.