GLEASON BEACH — Spurred by the rapidly retreating coastline north of Bodega Bay, Caltrans is laying plans to reconstruct a nearly mile-long stretch of Highway 1, moving the roadway safely inland from the crumbling edge of the continent and raising it beyond the reach of the rising sea.

Environmental review of the estimated $20 million realignment project is just beginning, so work crews aren't expected to break ground until at least 2017, project manager Lilian Acorda said.

Caltrans hasn't even negotiated the purchase of needed property yet, including a large portion of an historic ranch across the road from Gleason Beach. The ranchland will be irrevocably altered by a concrete bridge about 400 feet east of the existing road and spanning as much as 900 feet across the parcel.

The project's effect on the landmark property is one in a series of cultural, environmental and biological impacts still to be assessed and addressed during the coming years, Caltrans personnel said. There are seasonal wetlands, a creek that once hosted migrating salmon, red-legged frogs, an endangered butterfly and other wildlife to worry about.

"It's a huge balancing act," said Chris Caputo, an archaeologist and environmental planner for the transportation agency. "There are a huge number of resources out there."

Caltrans is nonetheless in a race with natural forces that have chipped away at the cliffs near Gleason Beach sufficiently to destroy or undercut 10 bluff-top homes and come within a few feet of the fog line at the edge of the highway.

Studies prepared for the project conclude that an 87-foot section of the roadway abutting the bluffs could be undermined within five years, Caltrans said.

A rusting metal fence at the edge of the road already marks one spot where a narrow lip of concrete is all that remains of what was once a home.

A sheer drop below leads down to the ocean, where the waves crash against a tumble of concrete slabs, huge pillars and twisted steel once used to try to stabilize the hillside and the house that was built on it.

The Caltrans project has been in the works for years, outlined some time after the first of several homes began to buckle and break apart following heavy rains in 1998. The downpour ate away at the cliff side, and wave action and drainage have continued their work, causing additional damage and coastal recession.

The agency started with 20 proposed alignments, Acorda said, whittling them down to the three now being considered.

They range in length from 3,030 to 3,800 feet, with the elevated portion running 750 to 900 feet long.

The three routes are alike at the northern end, rejoining the existing Highway 1 north of the most eroded section of bluff.

At the southern end, they would depart Highway 1 in slightly different locations north of Calle del Sol and the Serena del Mar subdivision.

Where the highway now follows the contour of the land as it dips toward Scotty Creek, its outlet at the very edge of the roadway at Gleason Beach and the Gleason-Mann-Ballard Ranch on the other side of the road, the new highway will instead remain somewhat elevated atop a bridge intended to span the creek and surrounding seasonal wetlands, Caltrans said.

The concrete structure is intended to keep the highway out of the wetlands and flood plain, and also prevent damage from storm surges in an age of rising sea levels, Caltrans said.

But it will also have an unavoidable visual impact on the historic Gleason Ranch, first settled in 1840 and listed on the California Register of Historic Places, officials said.

Its current owners, Drs. Phil and Roberta Ballard, purchased the ranch in 1999. They were not available for comment this week, but in their letter to Caltrans, they acknowledged concerns about the effect of "this high impact project" on environmental and cultural resources, as well as property values.

About $4 million worth of surveys and studies have already been conducted. Those include archaeological digs that have turned up five Native American sites, Caputo said. Artifacts recovered from those areas are still being evaluated, he said.

Some residents in the area are concerned about the scope of the highway project, and particularly the need to build the bridge, though information about the proposal has only been filtering out for a few weeks.

A public meeting at the Bodega Bay Grange introducing the plan and seeking input was held March 26, but some in the community say many more residents would have attended had they had more advanced notice, especially with a deadline today for initial public comments.

Sonoma County Supervisor Efren Carrillo, who was among those present, said 12 to 15 members of the public attended, in addition to about five Bodega Bay fire personnel and numerous Caltrans employees.

Cea Higgins, volunteer coordinator for Sonoma Coast Surfrider, said she and other members of the stewardship group are among those who wish they had received notice in time to attend and to notify its hundreds of members.

"Our goal is that any action that occurs on the Sonoma Coast is always, first and foremost, educating the public and making sure the public has a chance to comment," Higgins said.

There's a possibility she may get her wish. Acorda said the agency has heard from numerous residents who wanted more time to learn about the project. She said Caltrans staff will analyze whether another meeting or comment period is needed.

Both Caputo and Carrillo noted, however, that the environmental review process underway involves several hearing and comment opportunities.

"The scoping session is the very initial part of this process," Carrillo said in an email. "I'm certain there will be more to come."

You can reach Staff Writer Mary Callahan at 521-5249 or mary.callahan@pressdemocrat.com.