Connecticut regulators have fined Frontier Communications $5 million, accusing the Norwalk telecommunications company of unsafe excavations and other improper practices as it installed fiberoptic cable.

The Public Utilities Regulatory Authority said Frontier is “jeopardizing public safety through reckless and inappropriate underground installations in the public right-of-way.”

Most of Frontier’s underground installations are being completed using trenchless technology that requires exposing all facilities being crossed and Frontier and its contractors “have not performed trenchless excavations in accordance with applicable standards,” PURA said.

Chrissy Murray, a spokesperson for Frontier, said it has “taken immediate steps to remedy the situation.”

“We hold ourselves and our contractors to the highest standards. We are working constructively with PURA and our contractors to fix any issues so we can continue our build to provide the state with this critical service,” she said.

PURA ordered Frontier to immediately halt all underground installation of fiberoptic cables except for emergency repairs. Frontier must submit a plan for its oversight of the installation of the underground portion of its fiberoptic network.

Underground installation work may resume only after PURA has approved the oversight plan and inspection program.

PURA said Frontier’s contractor, Parkside Utility Construction LLC, damaged a gas service in Ansonia by failing to hand dig and expose the gas service under the driveway when trying to cross the service as required for trenchless excavations. Parkside paid a civil penalty of $1,100, PURA said.

Parkside in Harleysville, Pennsylvania, did not immediately return a call seeking comment.

Regulators listed five instances of damage to electrical facilities between May and November 2021 in Meriden, Middletown, Wallingford and Waterford, damage to a gas facility in Stratford and to a Frontier facility in Enfield.

PURA also accused Frontier and its contractors of “evidently deploying” an unsafe practice of breaking into electrical conduits to cross roadways. Regulators said the practice is dangerous and was discovered in an investigation of an electric outage in Meriden on Oct. 17, 2021.

A conduit containing live electric facilities was broken and the fiberoptic conduits inserted inside the electric conduit to cross the street. This damaged the cable, causing its failure, PURA said.

In addition, Eversource reported that its conduit in Southington was compromised by the installation of fiberoptic cable to cross the road. The electric wiring had been damaged at the location where the conduit was broken and eventually it failed.

Parkside acknowledged the incidents were unacceptable and contractors were no longer allowed to use a conduit sleeve under a roadway without a Parkside supervisor present to approve, the company told PURA.

Frontier has the right to request a hearing.

Stephen Singer can be reached at ssinger@courant.com.