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In Sonoma, Mendocino and Humboldt counties, 300 miles of old, decommissioned railroad tracks wend through river canyons and redwood forests in some of Northern California’s most gorgeous and pristine backcountry. In a state where biking the whole coast is a sacred pilgrimage, turning that railroad route into a bike path — the subject of new state legislation — could revolutionize bike touring in Northern California and give a much-needed economic jolt to the rural communities it passes along the way.

After years of failed attempts to restart freight service on the Northwestern Pacific Railroad, which in its heyday ran from Marin County to north of Eureka, state Sen. Mike McGuire, D-Healdsburg, in February introduced the Great Redwood Trail Act (SB1029), a bill to convert the publicly owned line into a destination for bikers and hikers. The bill was approved by the state Senate and Assembly and is now headed to Gov. Jerry Brown, who has until the end of September to decide whether to sign it. In an era of deep political divisions that extend to transportation issues, the bill’s bipartisan support, including unanimous passage in the state Senate, is a feat.

However, even if the bill becomes law, the trail will still face many hurdles — financial, legal and topographical, to start. But creating the trail “is a once-in-a-lifetime opportunity,” says Jim Elias, executive director of the Marin County Bicycle Coalition. “This trail stands to be the John Muir Trail of the North Coast.”

When the Northwestern Pacific Railroad opened in 1914, the only other way to travel overland from the Bay Area to Humboldt was a three-day stagecoach trip on unpaved precursors to Highway 101. Like railroads across California, the NWP boomed in the early 20th century for both passenger and freight service and then decayed as improved highways pushed travelers into cars and trucks. Passenger service was discontinued in 1958; freight service soldiered on, but the Southern Pacific Railroad, which owned the NWP, was unable to keep up repairs to the line, whose remote, mountainous location made it vulnerable to landslides and storms.

To save the line from abandonment and restore freight service, the California Legislature created the North Coast Rail Agency in 1989. But lawmakers failed to fund the agency, and the unused tracks sat deteriorating. Estimates for restoration costs climbed, and the state was beset by legal battles with environmental groups that opposed trains streaming through what they call an ecologically delicate area.

Today, the rail agency has only two employees and is at least $10 million in debt, according to the Senate Appropriations Committee’s analysis of the bill’s fiscal impact. The situation, McGuire told Humboldt County’s Redwood Times in July, is “a hot mess.” Were it to pass, McGuire’s bill would dissolve the NCRA and create a new agency tasked with bringing the trail to fruition.

For Bruce Silvey, a member of the board of directors of the Humboldt Trails Council, the bill is a way to break a long, frustrating impasse: The NCRA couldn’t restart train service but also blocked any use of the corridor except for trains. The McGuire bill “caught us by surprise,” Silvey says. “But we jumped on it.”

Reinventing old rail lines as biking and hiking trails is nothing new in California. There’s the East Bay’s Iron Horse Trail, which has been gradually built out since 1986 and runs for 31 miles from Concord to Pleasanton. There’s also the 37-mile Great Shasta Rail Trail in Shasta and Siskiyou counties. On the Santa Cruz coast, 12 miles of rail trail, of a planned 32 miles, should be ready for riding by 2020.

But the spectacular scenery and topography of the Great Redwood Trail’s proposed route would make even a jaded cyclist weak in the knees.

From the vineyards and pastures of Cloverdale, the southern end of the Great Redwood Trail and the eventual northern terminus of the SMART train and bike path, the rail line would parallel Highway 101 north along the Russian River into Mendocino County. North of Ukiah (Mendocino County) and the 1,950-foot Ridgewood Summit, the trail would break from Highway 101 and dive into a remote part of Northern California few visitors ever see: the 43-mile Eel River Canyon between Dos Rios in Mendocino County and Alderpoint in Humboldt County, where there are no roads.

All the land besides the railroad corridor is privately owned. That means that ever since passenger service on the NWP ended, there hasn’t been a legal way for the public to see the canyon, let alone stop and soak in the beauty as one can on a trail trip. Once in Humboldt County, the railroad parallels the famous Avenue of the Giants through old-growth redwood forest and eventually reaches the coast south of Eureka, where an existing rail trail leads to Humboldt Bay.

Completing the trail would require years of studies and environmental clearances and cost upward of $100 million. In its current form, McGuire’s bill doesn’t include a source of funding. The legal and financial liabilities the NCRA has racked up would also need to be sorted out. McGuire’s bill calls for removing the rails and building a new trail in their place — rather than leaving the rails intact and building alongside them — which could cut trail costs by as much as 40 percent, Silvey says.

The economic case for building the new rail trail is simple math, McGuire and other trail supporters say.

Long-distance bike tourism has the potential to be a boon for rural areas of Mendocino and Humboldt that once relied on the now-diminished lumber industry. A 2009 economic impact study of the Great Allegheny Passage Trail in Pennsylvania and Maryland found that rail-trail users were spending an average of $98 per day on food, lodging and supplies in the rural communities along the trail. Of the hundreds of businesses surveyed, owners reported on average that one-quarter of their revenue was from trail users, and two-thirds reported an improvement in business since the trail opened. The small inland towns on the GRT’s route could look forward to a similar economic boom.

So far, it’s been full speed ahead for the Great Redwood Trail Act. Bicycling organizations in Marin, Sonoma and Humboldt counties all support McGuire’s bill; so do environmental groups like the Sierra Club and Friends of the Eel River, and the Humboldt County Association of Governments.

While no one should start laying in provisions for the trip yet, a trail of this magnitude would be built in phases. In fact, some pieces of the trail already exist in Ukiah, Arcata (Humboldt County) and Eureka.

Hauling lumber and passengers, the Northwestern Pacific Railroad helped define travel and transportation in rural Northern California in the last century. Once complete, the Great Redwood Trail may define this one.