CLEARVIEW — A major energy project is back in the permitting process, promising comfort on cold winter days, but also alarming some environmental advocates.

Snohomish County on Wednesday granted an approval to expand nearly 6 miles of natural gas line. The pipeline known as the North Seattle Lateral crosses through North Creek, Clearview and other unincorporated areas. It supplies Puget Sound Energy customers in north King County and much of Snohomish County.

Northwest Pipeline operates the infrastructure. It’s part of The Williams Companies, Inc., which hopes to start work this spring.

“Pending all federal, state and local regulatory approvals, construction-related activities for the North Seattle Lateral Upgrade are scheduled to start in May 2019 and conclude in November 2019,” said Phillip Harris, a spokesman for Tulsa, Oklahoma-based Williams. “The project needs to be completed before next winter to ensure demand is met to heat homes and keep businesses running.”

The pipeline was built in 1956. It transports gas from the Rocky Mountains and British Columbia. Williams says the transmission line is operating beyond its intended capacity during winter weather, like the kind that has been hitting the Pacific Northwest for more than a month.

The work would involve widening the pipe from its current 8-inch diameter to 20 inches. Metering upgrades also would be completed.

A coalition of environmental groups has asked for greater scrutiny of the project. They include 350 Everett and affiliated groups; the Sierra Club’s Sno-Isle Group; and Mothers Out Front.

The upgrade would cross 15 streams, with potential impacts on wildlife, especially threatened salmon species. Another set of concerns involves safety for the pipeline’s suburban and rural neighbors in the event of a leak or explosion.

The environmental groups note that the wider pipeline, if put to full use, could drastically increase greenhouse gas emissions.

In a Feb. 7 letter to county planning director Barb Mock, they questioned whether such a large investment was needed only for peak demand on cold days. They also object to fracking techniques used to extract gas from the ground.

The county’s land-use decision started a 14-day period for commenting on the project or filing an appeal. The approval comes with environmental conditions attached. It replaces an earlier approval that the county issued last fall and later withdrew.

Most of the conditions already were included in a Federal Energy Regulatory Commission decision from last year. The county also specified disposal requirements for excavation spoils in specific areas, including the Fritch Mill in Maltby.

Before construction can start, additional state environmental approvals and other county permits are required.

The upgrade would begin west of the Bothell-Everett Highway. It would continue south of 180th Street through the North Creek area toward Clearview. It would pass Highway 9 and stop just short of Highway 522. The route crosses 154 land parcels.

Noah Haglund: 425-339-3465; nhaglund@heraldnet.com. Twitter: @NWhaglund.