VANCOUVER — The Bonneville Power Administration is expected to release a final environmental impact statement on big plans for a new power line between Washington and Oregon by year end.

The BPA is working on a plan for a proposed 500-kilovolt transmission line, The Columbian newspaper reported. Final approval for the line is expected in 2016, with construction beginning as early as 2017, according to BPA spokesman Kevin Wingert.

It will include about 80 miles of transmission line across the Columbia River. The line identified in 2012 would stretch between Castle Rock, Washington, and Troutdale, Oregon, connecting new substations at each end.

The proposed route would cross the Clark-Cowlitz county line just below Merwin Dam. BPA has previously said the $459 million transmission line is needed to ease a strained regional power grid and add capacity for future growth.

Many adjacent landowners are not happy with the planning process.

That’s not surprising, said BPA project manager Mark Korsness.

“It’s a tough thing to site 80 miles of transmission line and not have people upset about it,” Korsness said. “We do our best to minimize the impacts and make adjustments where we can. But in the end, we have to have a continuous path that’s 80 miles long.”

Adding a 500-kilovolt line through Clark and Cowlitz counties will fortify the regional grid and meet demand, Korsness said. The idea is that if a section of transmission line temporarily goes offline, managers can still use the remaining parts of the system to get power to all regional substations and elsewhere, he said.

“The main benefit for this project is to increase capacity for the transmission system from north to south, so that in the future when the loads increase, we’re able to accommodate the needs of the region,” Korsness said.

Opponents of the project have questioned how much Southwest Washington would benefit, and how much power would be used here versus, say, California. Korsness acknowledged that power will be available for purchase from Canada to California. But he said he couldn’t speculate on what percentage of loads might be consumed here or somewhere else.

Not everyone is happy. Ray Richards, whose Dole Valley property sits along the preferred route, said he and others in the area don’t feel heard. Richards engaged with BPA more than a year ago, hoping to shift the line to decrease its impact on landowners.

“Our argument is if they must build this line, and they won’t choose a different route, then at least go on property edges and don’t rip them right in two,” Richards said.

Richards estimates the proposed line is about 240 feet from his home. BPA didn’t shift the alignment despite requests to do so, he said.

“I don’t think they tried hard enough,” Richards said.

The Interstate 5 corridor project is unlike other transmission lines the federal power marketing agency has built recently. That’s largely because of its location, Korsness said.

“The biggest difference is that it’s west of the Cascades,” Korsness said. “We haven’t built high-voltage transmission of this size in 40 years west of the Cascades.”