WASHINGTON — A House committee is expected to approve controversial legislation Wednesday that would open all federal wilderness, including almost 15 million acres in California, to mountain bikes.

The bill by Rep. Tom McClintock, R-Elk Grove (Sacramento County) would amend the 1964 Wilderness Act, which specifically bans “mechanical transport,” to allow bicycles on 109 million acres of designated wilderness that constitute some of the most remote and undisturbed areas of the country.

McClintock, chairman of the House Natural Resources panel on public lands, said the bill would “help restore public access to public land.”

The legislation, HR1349, has provoked a fierce backlash from conservation groups, but has the support of mountain biking enthusiasts who say the areas are unnecessarily closed to wheeled travel.

Mountain bikers in San Francisco, Santa Cruz and San Jose pointed to areas such as the Snow Mountain Wilderness in the Mendocino National Forest northeast of Ukiah, the Ventana Wilderness along the coast of Big Sur, and the Trinity Wilderness near Mount Shasta as areas that could potentially be opened to them.

“The Pacific Crest Trail up and down the state is closed everywhere, and there are certainly areas that could be opened up,” said Daniel Schneider, founder of SF Urban Riders, a San Francisco mountain biking group. “A lot of the Pacific Crest Trail runs right through some of the biggest mountain biking areas that we have.”

But conservation groups worry about safety issues and disturbance of the wilderness experience associated with bringing bicycles into protected areas where only hikers, horseback riders and other non-mechanized travelers are now allowed. Their bigger concern, they say, is that the bill would turn places protected by one of the nation’s bedrock environmental laws into common recreation areas.

“Wilderness is not a recreation designation,” said Anders Reynolds, an officer at the Pew Charitable Trusts, which strongly opposes the McClintock bill. “It’s the anchor of a broad spectrum of conservation protections. Wilderness is what happens when a country says to itself, what does it look like if we set aside a place and allow it to just be.”

In a well-known passage, the Wilderness Act states, “A wilderness, in contrast with those areas where man and his works dominate the landscape, is hereby recognized as an area where the earth and its community of life are untrammeled by man, where man himself is a visitor who does not remain.”

The only exception to wheeled travel is wheelchairs, an alteration made by the 1990 Americans with Disabilities Act.

Wilderness areas are the highest form of protection for federal lands, above national parks, national forests, national recreation areas or any other designation, said Rep. Al Lowenthal, D-Long Beach. Wilderness makes up less than one-sixth of all federal public lands, leaving plenty of other land open to biking, Lowenthal said.

“The Wilderness Act was very clear about how these lands were to be managed,” said Paul Spitler, wilderness campaigns director for the Wilderness Society, an environmental group. “It was to preserve the wilderness character and afford opportunities for hiking, horseback riding, canoeing or other similar activities. Mountain biking is simply not compatible with wilderness and certainly is not consistent with the Wilderness Act.”

Proponents contend that, under McClintock’s legislation, heavily used hiking trails such as California’s John Muir Trail could still remain off-limits to mountain bikers at the discretion of federal land managers at the local level.

“I myself think the John Muir Trail is a classic example of where mountain biking should not be allowed,” said Ted Stroll, president of the Sustainable Trails Coalition, who testified at a committee hearing last week in favor of the bill. “Maybe some parts of it, on a Wednesday in October, but in general no.”

Stroll said most such trails are too steep or rocky to attract mountain bikers.

What would be ideal, Stroll said, are places like the Snow Mountain Wilderness, where he said “the trails are so little used, they are simply growing over because nobody is there.” Mountain bikers could help keep such trails open “and ideally keep the marijuana growers out.”

Stroll also pointed to the Ventana Wilderness near Big Sur, where he said he’s heard the trails are disappearing into thickets of poison oak. He said studies show mountain bikes do far less damage to trails than horse or mule pack trains, which he called “money-making dude ranch operations” that get to profit from public lands.

“Rugged, self-reliant adventurous travel is the signature wilderness experience and that’s exactly what human-powered mountain biking is,” Stroll said, including the rapidly growing sport of “bike-packing” into areas long the domain of backpackers.

The International Mountain Biking Association, however, opposes the bill, much to the consternation of many of its members. “We feel it is unwise to amend the Wilderness Act — one of the nation’s most important conservation laws — when the outcome mountain bikers desire can be reached through on-the-ground collaborative efforts,” the group said in an official statement.

The bill is likely to be passed by the House Committee on Natural Resources and the full GOP-controlled House, but Democrats said their party will kill it by filibuster in the Senate.

“I probably have more mountain bikers per capita in my district than any place in the country,” said Rep. Jared Huffman, D-San Rafael, a member of the committee. “The mountain bike was invented in my district, so you can’t tell me that we can’t find opportunities for mountain biking without sacrificing wilderness.”

Huffman called the bill part of a “constant onslaught” by Republicans on public lands, “whether it’s building roads, promoting logging or mining or motorized recreation.”

Carolyn Lochhead is The San Francisco Chronicle’s Washington correspondent. Email: clochhead@sfchronicle.com