FRANKLIN CANYON - Roughly midway between the downtowns of Hercules and Martinez lies a 700-acre tract of wooded hills and grassy meadows virtually unchanged since the 19th century, all that's left of a rancho that once extended from Franklin Canyon to the Pinole waterfront.

A dozen-odd cattle grazed near the northern shore of Rodeo Creek on Wednesday afternoon. Steep slopes crowned with oak and bay laurel rose from the opposite shore.

"There's a red-tail (hawk)," said Tina Batt, executive director of the Muir Heritage Land Trust, pointing to the top of the Franklin Ridge. Turkey vultures patrolled other sectors of the blue sky.

Today, the trust expects to consummate a $3.2 million purchase of the ranch from the seven living descendants of Bernardo Fernandez, who amassed the once 9,000-acre-large rancho about the 1880s.

"We all discussed preserving the land ... in memory of our great-grandfather, who was very instrumental in establishing the Pinole Valley area," said Bill Fernandez, 45, of Martinez.

"I've seen so much development in the county -- my jaw drops now when I go out to Brentwood," said Fernandez, an engineer with the Contra Costa County Public Works Department. "This is one way to preserve something for future generations."

The wilder portion of the land is home to the Alameda whipsnake, red-legged frog and Western pond turtle, among other rare animal and plant species.

Dried cow pies, a stray golf ball and some illegally dumped garbage attest to recent uses along the eastern fringe of the property alongside Christie Road, about a half-mile southeast of the Franklin Canyon golf course. A faded fire trail ends where an old bridge over Rodeo Creek washed out several decades ago, Batt said.

On the other side of the creek are pieces of the foundations of two ranch houses. A spring once used as a water supply bubbles from the ground, Batt said.

The trust has raised $4.3 million so far, from private donors as well as federal, state, foundation and corporate grants, the most recent one for $487,000 from the National Oceanic and Atmospheric Administration.

"This is the largest open space preserve in this part of the county, which is underserved by open space," said Kathy Hoffman, an aide to Rep. George Miller, D-Martinez, who helped land the federal grant. The property includes segments of the Bay Area Ridge Trail and has historic, recreational and ecological significance, she said.

State Sen. Tom Torlakson and Assemblyman Joe Canciamilla helped get state funds, Batt said.

Of the $1.1 million left over after the purchase, about $800,000 will go for creek restoration and construction of a bridge and $300,000 for expenses related to organization and acquisition, Batt said. The property still needs an endowment of about $500,000 to throw off enough money annually for maintenance.

The Fernandez Ranch is at the western edge of the Briones Hills Agricultural Preserve, created in 1987 by agreement of the county and eight central and West Contra Costa cities. Adjacent to it is a 486-acre tract in Hercules where GreenPark, of Seal Beach, proposed to build more than 500 homes, a hotel, offices and stores. But a ballot initiative passed by Hercules voters in November restricts land use on the GreenPark land and several hundred adjacent acres to mostly agriculture and recreation and sets a minimum size of 40 acres for house lots.

The trust is interested in acquiring the GreenPark tract as well.

"It's the missing piece," Batt said, in a geographical unit and wildlife corridor extending from Crockett to Lamorinda.

GreenPark Senior Vice President Randy Wheeler and former CEO Peter Kiesecker were not available for comment Wednesday.