MARTINEZ -- A washed-out and washed-up county road is about to be remade into a new, $5.5 million regional shoreline trail along the scenic Carquinez Strait, linking Central and West Contra Costa County.

On or before July 5, East Bay Regional Park District contractors will be begin rebuilding and converting 1.7 miles of Carquinez Scenic Drive into a hiking and riding trail between Martinez and the town of Port Costa.

The trail segment -- expected to open in fall 2014 -- will improve access to an often-overlooked area of hills, shoreline, natural parks and preserve south of the strait between San Francisco Bay and the Delta.

The project also will add a scenic segment to the region's Bay Trail, which eventually will encircle San Francisco and San Pablo bays.

"We are converting an old road the county doesn't want into a premier trail," said Jim Townsend, trails program manager for the park district. "This will be one of the most scenic trails in the Bay Area. The views of the water, bridges, the bay and the Delta are just gorgeous."

Access is limited to much of the area along the Carquinez Strait because of its steep bluffs, narrow shoreline and few roads. In 1983, Contra Costa County permanently closed the stretch of Carquinez Scenic Drive after heavy storms and runoff caused sections to slide down the hills.

The demise of the road built in 1914 opened the door for a trail, a project that is neither cheap nor easy.

During a recent tour of the trail west of Martinez, only about three feet of the road clung to the hillside in one spot. Not much more of the road remains in some other areas.

To develop the trail, contractors will rebuild hill sections and protect them against slides by driving tall pilings into the ground in nine locations and pouring concrete around them.

"It is a big and challenging project," said Dale McCourt, the park district's design and construction manager. "The technology to do it is proven."

The cracked pavement from the road will be removed and replaced by a 10-foot-wide paved trail with shoulders on each side.

Despite its closure long ago, the 1.7 miles of road is used regularly by joggers, hikers and cyclists. That is about to change. Fencing will be added to keep the public off the road during construction, and trespassers will be ticketed, said Emily Hopkins, a park district spokeswoman.

Some people have urged park officials to leave the road alone and let people continue riding and running on it, but officials say cyclists or hikers easily could fall off the steep bluffs at many points or trip and fall on broken and buckled pavement.

"It's extremely hazardous, and erosion continues to eat away at the road," said Ted Radke, a regional park board member from Martinez. "This project will make it safe for public use."

David Campbell, the East Bay Bicycle Coalition program manager, said the new trail is an important recreational and commuter cycling route connecting Central and West Contra Costa. "It gets people close to the shoreline," he said.

The park district and the county studied trail plans for years but lacked the funds to do anything.

A big breakthrough occurred in 2010 when the park district won a $10.2 million federal transportation grant, of which $3.5 million goes for the Carquinez Strait trail.

The park district also is getting $1 million of Contra Costa County Measure J transportation sales tax funds, $900,000 from another federal grant, and $400,000 from the California Coastal Conservancy.

Contact Denis Cuff at 925-943-8267. Follow him at Twitter.com/deniscuff.