CANONSBURG — Columbia Gas of Pennsylvania wants the state to approve a 23.4 percent rate hike the utility says will raise $77.3 million a year to help it replace aging pipelines.

If Friday’s request is approved by the Public Utility Commission, the average residential customer’s monthly bill would rise from $67.17 to $82.92, according to a company news release.

Columbia has 9,000 customers in Butler County.

Columbia, based in Cecil Township, Allegheny County, says it’s the first natural gas company to file for a rate increase under a new state law that makes it easier for utilities to recover costs of distributing gas. The company says it has spent $400 million to replace old pipelines in the past five years.

Sarah Perry, communications and community relations specialist at Columbia Gas, said work in Butler County will include three upgrade projects in the Slippery Rock area. All are scheduled for 2013.

Perry said the first project will be 5,600 feet of eight-inch pipe installed, the second will be 8,500 feet of two- and four-inch pipe, and the third will be 1,500 feet of four-inch pipe.

Columbia Gas in October will start a $1.6 million pipeline improvement project north of Emlenton, Venango County, as part of the upgrade. The project will replace 1,500 feet of steel pipeline just north of the Interstate 80 bridge over the Allegheny River.

The gas company plans to bore under the river to replace the pipe. The project is expected to be done by mid-November.

Columbia Gas has about 414,000 residential, commercial and industrial customers in Pennsylvania, mostly in Western Pennsylvania and the greater York area. For information, go to Columbia’s website at www.ColumbiaGasPa.com and click on “Infrastructure Upgrade.”