SAN ONOFRE -- A decision that could determine the fate of a North County toll road has been placed on hold, but a significant hurdle remains in the path of the $875 million project.

When the project returns to the California Coastal Commission's agenda in February, the Orange County agency proposing the Highway 241 extension will have to overcome a highly critical staff report recommending the road be rejected.

In the report, the commission staff contends the six-lane highway would trample the habitat of several imperiled animals, to the point of pushing one species -- the Pacific pocket mouse -- to the brink of extinction.

And, the report says, the highway could wipe out the only remaining coastal population of the arroyo toad.

At least 66 acres of sensitive habitat and wetlands would be destroyed, according to the report.

"The project would fragment and transform one of the last remaining intact watersheds and coastal canyon ecosystems in all of Southern California," it states.

The potential fate of imperiled species of animals bothers Southern California conservationists, who oppose the toll road.

"It would basically push the Pacific pocket mouse over the cliff to extinction," said Dan Silver, executive director for the Endangered Habitats League in Los Angeles. "This is really the worst possible place to put a road."

According to the staff report, preserving extremely rare and sensitive habitats -- such as the one in the path of the toll road -- is a higher priority under California law than is preserving neighborhoods.

The toll-building agency chose to put the road on parkland rather than through San Clemente to avoid neighborhoods. But the report notes that homes are condemned all the time to build or expand Southern California freeways.

Rescheduled for February

The report also says the highway threatens to compromise the quiet experience of camping at San Mateo Campground at San Onofre State Beach, something 175,000 people do each year at California's fifth-most-visited state park.

"You don't have a lot of campgrounds close to the beach in urbanized areas of Southern California," said Mark Delaplaine, a staff analyst, in a telephone interview from San Francisco last week. "It is really a unique experience."

Then there's the concern the highway could compromise water quality in San Mateo and San Onofre creeks, two of the region's healthiest and least disturbed streams, the report states. And surfers worry that an altered stream flow could dilute the world-class waves that challenge them at Trestles Beach.

Jennifer Seaton, a spokeswoman for the Irvine-based Foothill/Eastern Transportation Corridor Agency, the project proponent, said her agency disputes several of the report's assertions, such as the notion that an animal might disappear.

"That's not true," Seaton said. "The alignment was adjusted to avoid Pacific pocket mouse habitat."

As for the water concerns, the toll-building agency has long said it will take measures to prevent oil from washing into the creeks, and that there will be no impact on the surfing experience.

Seaton said the transportation agency is preparing a detailed written response.

"The report contains a lot of errors and misinformation," she said.

It all will have to be sorted out by the commissioners themselves, when members of California's influential government body that controls development in a narrow strip along the state's 1,100-mile coast meets Feb. 6-8 in San Diego.

The project was scheduled to go to the commission this month, but the toll-building agency sought a delay, in order to have more time to respond to concerns raised in the 236-page report.

Fatal flaw or smear?

The road agency is governed by a board composed of elected officials from Anaheim, Dana Point, Irvine, Lake Forest, Mission Viejo, Orange, Rancho Santa Margarita, San Clemente, San Juan Capistrano, Santa Ana, Tustin, Yorba Linda and the Orange County Board of Supervisors.

The agency is trying to complete the last leg of Orange County's 67-mile toll road system, a 16-mile section of Highway 241. The 241 toll road starts at Highway 91 near the Orange-Riverside county line and Orange County planners have intended all along to tie it into Interstate 5 near the San Diego-Orange county line.

Several potential routes were considered, but the agency rejected all alignments through Orange County. Those would have required the removal of 112 to 263 San Clemente homes. So officials elected to pursue a route that dips into San Diego County and runs, for its last four miles, across the San Onofre park.

The agency must obtain permits from the Coastal Commission because the last quarter-mile of Highway 241 would fall within the coastal zone it has jurisdiction over, as would a mile-long set of ramps along I-5 associated with the project.

One of the biggest beefs transportation officials have with the staff report is it relies, in part, on results of a study conducted for an environmental group opposed to the road.

The group, Endangered Habitats League, conceded last week that the study underestimated the number of private properties required to be bulldozed if Orange County were to widen I-5 for several miles instead of finishing Highway 241.

Silver, the league's executive director, said about 60 properties would have to be taken instead of 31.

"It's a huge flaw in the Coastal Commission's staff report," Seaton said. "They relied on a study that was fatally flawed. … It looks like a drawing on a Google Earth map. There is no engineering behind this study."

Silver disagreed.

"That's very logical for them to say because they want to build a toll road. But it's basically a smear," Silver said. "(The error) changes none of the conclusions. So there's no fatal flaws in this study."

Fighting over an I-5 alternative

The dispute is essentially this: The league and other opponents contend the primary goal of the road -- to relieve congestion on I-5 in southern Orange County -- can be fulfilled with much less environmental destruction by widening I-5 instead.

The transportation agency contends otherwise. It produced an earlier study that said 1,200 properties would have to be bulldozed. Having to buy all those homes and businesses would send the cost for the alternate approach spiraling to $2 billion, more than twice the toll road's price tag, officials say.

The environmentalists' study, even with the adjustment after the error, says 95 percent fewer properties are needed, and that therefore I-5 widening is financially doable.

The dispute over the number of properties affected stems from a disagreement over the size and type of interchanges and detention basins required.

Silver said conservationists are not disputing the need for the toll road extension just because they don't like new roads.

"We're trying to save the park," he said. "If we lose our state parks and people don't have a place to go to enjoy affordable coastal recreation, then we are really killing the goose that is laying the golden egg."

On the contrary, says the transportation agency, it is a good place to put a road.

Seaton said the proposed route negates the need to bulldoze numerous homes.

"The human cost would be huge," Seaton said. "Most San Clemente homes are worth a million dollars. The TCA is saying that San Clemente neighborhoods have a value. And the opponents seem to be saying that they have less of a value than the park."

Seaton said the location is an ideal spot for completing a "missing link" in Orange County's 51-mile tollway system, one that would provide a new route roughly parallel to I-5. A full-length Highway 241 would offer San Diego County residents, for example, new access to both Riverside County and Los Angeles.

"To have only one major one route between San Diego and Los Angeles just doesn't make sense," she said.

Contact staff writer Dave Downey at (760) 745-6611, Ext. 2623, or ddowney@nctimes.com.