Efforts to run a pipeline beneath the U.S. Highway 101 Dungeness River bridge between Sequim and Carlsborg are in motion.

Safely transporting wastewater across the Dungeness River for treatment in Sequim was one of the more “key aspects” in designing the public sewer system to serve the Carlsborg Urban Growth Area, Bob Martin, professional engineer for Clallam County Public Works Department, told the Clallam County commissioners during their Monday work session.

Martin recently submitted the application into the county for a “shoreline substantial development” permit needed to hang two wastewater force mains designed to transport sewage from the Carlsborg Urban Growth Area to the Sequim Wastewater Reclamation Facility.

“You can’t say anything is fail-proof in this area, but to the extent that we can, this is being designed to the highest standards that anybody uses when crossing,” Martin said.

The force mains will run along the north shoulder of Highway 101 and hang below the bridge once reaching the Dungeness River in separate steel casing pipes to avoid impacts to the shoreline. Once installed, the pipes will join more than 20 other sewer lines that cross waterbodies within the county.

The recent steps toward construction are among many leading to the development of a public sewer system to serve the Carlsborg Urban Growth Area.

“We hope to put the project out to bid sometime this fall,” Martin said. “Construction will begin in spring of next year.”

Once it begins, Martin estimates the actual construction budgeted to cost about $11 million will take nine months to complete.

“That includes $1.2 million of that is contingency,” he said. “We should get bids in the vicinity of about $10 million.”

Last November marked a critical milestone for the project when City of Sequim and Clallam County officials signed a 30-year interlocal agreement to allow wastewater from Carlsborg to be treated at the city’s wastewater reclamation facility.

Although a public sewer plan and system was needed to keep Carlsborg a designated urban growth area and still maintain compliance with the Growth Management Act and the Department of Ecology, a public sewer system also was sought because of rising nitrate concentrations in the groundwater — a possible indicator that on-site septic systems aren’t adequately treating sewage.

Eventually, all septic systems will be phased out given no new septic systems shall be allowed within the Carlsborg Urban Growth Area once the public sewer system is operational.

In March, Martin reported the public sewer collection system was about 70 percent designed, but hinged on more public input to continue toward completion. Under the guidance of the Carlsborg Community Advisory Committee, county officials created and passed an ordinance in May that added the chapter, “Carlsborg Sewer System” to the Clallam County Code in hopes of providing Carlsborg residents with the basic information on the regulations and fees associated with the developing system.

“Since then, we’ve gotten a lot of interest,” Martin said.

Based on the initial feedback and the location of residents interested in connecting, the design of the collection system is now 90 percent complete. Next, Martin plans to mail connection application forms to all residents within the scope of the public sewer system.

The shoreline substantial development permit is one of many requirements still needed, including, but not limited to a conditional use permit from the Clallam County Department of Community Development for the construction of the pump station and right-of-way and franchise agreements with the Washington State Department of Transportation.

Once all permits gathered and agreements are made, any and all finalized plans must be reviewed by the Department of Ecology.

Reach Alana Linderoth at alinderoth@sequimgazette.com.