More than half of the natural gas connections in the Waterville area inspected by Summit Natural Gas of Maine since December were found to have been improperly installed, and the company has already replaced more than 60 connections, mostly to homes, documents filed with the Maine Public Utilities Commission reveal.

Electrofusion tees, a piece of equipment that connect individual service lines to the gas main, were incorrectly installed by contractors hired by Summit during its ambitious natural gas buildout in the Kennebec Valley.

The company’s May 1 report to the PUC states that 82 out of the 144 tees inspected by the company in Waterville, Fairfield and Madison – about 57 percent – failed a visual inspection. Most of the tees were replaced within two days, but 21 were still waiting to be replaced as of Friday.

The company “initially targeted the electrofusion tees with the greatest likelihood of needing replacement,” said Summit spokeswoman Tammy Poissonnier in an interview Monday.

“We went to the ones we felt would fail first,” she said.

A visual inspection involves digging up a section of gas line and checking to see if the pipe was prepared according to specified procedures before the tee was installed. If the equipment fails the visual test, the company turns off gas service to the connected customer as the tee is replaced, a process that can take up to 12 hours.

Summit intends to inspect 434 tees installed in the three communities over the next few months. Large commercial customers, such as Huhtamaki, a paper products company straddling the Waterville-Fairfield line, will not be affected by the inspections because they hook up to the main line using a different type of equipment, Poissonnier said. Not every tee inspected is connected to an active gas customer, she said.

Incorrectly installed tees have resulted in one gas leak since November. The company tests its lines every 75 days to check for leaks, the spokeswoman said.

The company expects to complete all replacements by the beginning of August, according to Poissonnier.

Summit is no longer working with the contractor that installed the tees being inspected, CCB Inc. of Westbrook, and Poissonnier would not discuss further issues with the contractor or answer whether litigation was planned.

“Due to ongoing legal and regulatory discussions, we cannot elaborate in any more detail regarding the contractor involved with this work,” Poissonnier said.

CCB did not respond to a voicemail left Monday afternoon.

The failed tee installations come after other issues with Summit’s performance on the gas-line installation project.

In December, the company agreed to pay a $25,000 fine to resolve charges that it used unqualified contractors and then falsified a test to make it look like the workforce had the correct certification.