Avista Utilities will spend $5 million this year to replace about 60 miles of natural gas line in Spokane and Lincoln counties that’s vulnerable to cracking.
The older, polyethylene pipe can become brittle and develop cracks when it’s exposed to rocks or other pressures, state regulators said. In December 2008, a crack in the same type of pipe caused a natural gas explosion in Odessa, Wash. Two people were injured in the blast, which also damaged a garage.
After the accident, the Spokane-based utility voluntarily agreed to replace natural gas distribution lines made from the polyethylene material, said Joe Subsits, chief pipeline safety engineer with the Washington Utilities and Transportation Commission.
Last year, state regulators also required four Washington utilities to survey their natural gas pipelines and develop 20-year plans for replacing pipes at elevated risk of failure.
Avista, Puget Sound Energy, Cascade Natural Gas and Northwest Natural Gas were required to submit the plans. The utilities serve about 1.2 million gas customers.
Washington has very little of the highly dangerous cast-iron pipeline that has failed in other parts of the country, Utilities and Transportation Commission Chairman Dave Danner said in a statement. However, hundreds of miles of the plastic polyethylene pipe turned up in the utilities’ surveys.
The pipe was made by DuPont prior to 1984, when the company started using an improved resin to reduce brittleness, according to documents Avista filed with the state.
Avista had about 342 miles of the polyethylene gas distribution lines in Washington in 2011, when the utility started replacing them. The communities of Odessa and Davenport already have received the new lines.
Avista will replace the remaining polyethylene distribution lines over the next two decades, said Linda Gervais, the utility’s manager of regulatory policy. The oldest, most-vulnerable pipes will be replaced first, she said.
Avista uses leak detections to prioritize where to replace the lines, said Subsits, the pipeline safety engineer. Federal regulations require gas utilities to test for leaks, and Avista conducts the tests annually, Gervais said.
Most of the distribution lines targeted for replacement this year are in Spokane County. Some lines on Spokane’s South Hill were replaced this summer. Neighborhoods in north Spokane, Spokane Valley, Moran Prairie and the community of Harrington in Lincoln County will also get new lines this year.
The $5 million cost has already been factored into current rates for Avista’s Washington gas customers, Gervais said.
Tearing up and replacing asphalt and concrete to access the gas lines is one of the biggest project expenses. The utility is working with local governments to coordinate the line replacement with street repairs when possible, Gervais said.
Avista’s service territory includes natural gas customers in Idaho and Oregon. The utility is also working to replace polyethylene distribution lines in those states, Gervais said.