The Public Utilities Commission of Ohio (PUCO) on Wednesday voted to extend Dominion East Ohio’s Pipeline Infrastructure Replacement Program (PIR), authorizing an increase in annual investments through 2021 and a cost-recovery charge for customers to cover them.

Dominion started its $4 billion program in mid-2008, aiming to replace 5,500 miles of outdated pipeline in its 22,000 mile system over a 25-year period. PUCO approved an increase in annual PIR spending from the current $160 million to $180 million in 2017, $200 million in 2018 and by 3% per year thereafter. Dominion, which serves 1.2 million natural gas customers in the state, said most of the pipeline it’s replacing was installed in the first half of the 1900s.

“The PUCO’s decision continues to position Ohio at the forefront of supporting pipeline safety through replacement of older vintage pipelines,” said Dominion East Ohio Vice President Jeff Murphy.

The current PIR recovery charge paid by residential customers is $8.12/month. The monthly charge could now increase by up to a $1.75 in 2018 and by a $1.82 in 2019. The company said PUCO’s annual review of its recovery charge ensures that the savings the company achieves by replacing older pipelines is passed along to customers. Through last year, Dominion said the program has saved more than $10.2 million.

Costs associated with the PIR program have increased since it was launched, Dominion said, as the company moves in to do work in higher-cost urban areas and as environmental protections and the regulatory costs associated with them have expanded.