By RICHARD WALKER and ALLISON TRUNKEY

GORST — As you drive on Highway 16 in Gorst later this month through November, you may feel a little like a salmon trying to maneuver a culvert back to its spawning grounds in its natal stream.

Consider it a metaphor for the work that will be done: Replacing small culverts that hamper fish migration to and from Anderson Creek with larger, 18-foot-wide box culverts.

Box culverts will be installed under State Route 16, State Route 166 and Anderson Hill Road at Anderson Creek. According to the state Department of Transportation, the work will require a four- to six-week full closure of SR 166, and an additional six-week closure of Anderson Hill Road for up to two months.Detours for SR 16 will be built in the median to re-route eastbound and westbound traffic during construction. The speed limit in the SR 16 work zone will be reduced from 60 mph to 40 mph.

Similar work will be done in North Kitsap at state routes 104 and 307 between Kingston and Poulsbo.

Prepare for reduced speeds and detours — and improved habitat for salmon and steelhead.

According to the project website, the project replaces outdated culverts “that are a barrier for fish with culverts that are built wider than the existing stream channel, and are sloped at a similar grade as the natural stream. The wider, man-made culverts simulate what is found in a natural stream bed.” The culverts will improve fish passage and “increase fish habitat by approximately 1 mile.

”The manager of Gorst Self Storage, a business located in central Gorst, did not expect her business will be affected by the detours. In fact, she was excited at the prospect of reduced speeds. “If they reduced speeds, people would actually be able to see the business,” she said.Pastor Devin Leith is not concerned about impacts to the Family Worship Center.

“It’ll be pretty low impact,” he said, given the center’s location. As a commuter who “uses this thoroughfare a lot,” he feels it will “slow down the area.”

Mike Honeycutt, manager of Washington Cedar & Supply Co., had an opposite take. “It’ll make it more inconvenient to get around. We do rent trucks, and when the traffic gets slow, it affects our timing.

“For a fall chum, coho, cutthroat and steelhead to navigate to and from Anderson Creek, it must swim past a gauntlet of alterations and obstructions.

First, there are those culverts. According to a 2003 Department of Fish and Wildlife report on culvert replacement, not only can culverts block fish migration, they “result in permanent, direct loss of instream and riparian habitat … break ecological connectivity, alter channel processes and change adjacent channel character and shape by affecting the movement of debris, sediment, channel migration, flood waters, and aquatic and terrestrial organisms.”

In other words, conditions that would provide spawning areas and habitat for juvenile fish to grow — egg, larval, fry, fingerling, parr, smolt, mature — are altered and inadequate or no longer exist.

Then, there’s the upstream watershed, which is managed for the City of Bremerton’s water supply and for commercial forestry. According to a 2006 county study, the natural floodplain is impaired by the presence of a 300-foot-long concrete flume and pump station located approximately a quarter-mile upstream of SR 16.

“This flume severely constricts the channel and floodplain and eliminates all suitable habitat conditions within the flume,” the study states. “Sheet flow through the flume also inhibits fish passage during certain flows … The ability to restore full floodplain function is also limited by the presence of City of Bremerton groundwater wellheads on both sides of the valley bottom near the diversion flume.”

Then, once a juvenile salmon matures, it contends with ecological challenges — tainted stormwater runoff, warmer waters — in Sinclair Inlet and Puget Sound en route to Admiralty Inlet, the Strait of Juan de Fuca and, finally, the Pacific Ocean. According to Lorraine Loomis, chairwoman of the Northwest Indian Fisheries Commission, salmon populations in Western Washington have been declining steadily for decades because habitat is disappearing faster than it can be restored.

“Salmon returns the past couple of years — especially coho — have taken a sharp turn for the worse,” she wrote. “Some say just stop fishing and that will fix the problem. It won’t. From birth to death, habitat is the single most important aspect of a salmon’s life.”

She added, “The non-stop loss of salmon habitat in western Washington must be halted so that our habitat restoration efforts can successfully increase natural salmon production. In the meantime, we need to rely on hatcheries to provide for harvest and help offset the continuing loss of habitat.”

Culvert replacements are one step in improving the salmon’s plight. In 2013, a federal court injunction required the state to significantly increase its efforts in removing state-owned culverts that block salmon and steelhead access to spawning areas and other habitats.

The state Department of Transportation’s Fish Passage Barrier Removal Program identifies fish-blocking culverts under state highways and provides for their replacement.

The project in the Gorst area will cost $9.5 million; $793,000 in funding will be provided from gas taxes.