The Kane County Forest Preserve District has a contract to purchase the 745-acre Brunner property between Route 31 and the Fox River in the north part of the county, officials announced Friday.

The buy has been a long-term goal for the forest preserve district, both to keep as open space and use for the Longmeadow Parkway bridge crossing over the Fox River.

"This is really the largest undeveloped piece of land in Kane County that's on the river," forest preserve President John Hoscheit said. "It's a major acquisition."

The $40 million price tag would use up most of the money remaining from the district's last open space referendum.

After the purchase, the district would have about $5 million left from the 2007 vote. But the district might still be reimbursed through grants for previous land buys, Hoscheit said.

The new land purchase will be contiguous to both the Fox River Shores and Buffalo Park preserves.

"To get 1,000-plus acres of (contiguous) preserves in an urban corridor is pretty unbelievable," Hoscheit said.

The site is a valuable one for restoration and has several endangered plant species on the property, said Drew Ullberg, director of planning for the forest preserve.

"The potential for restoration on the site is just enormous," he said.

Hoscheit said plans for the potential Longmeadow bridge would mirror efforts at the Fabyan Parkway bridge to not affect the natural area around it.

The contract was signed this week and the sale is scheduled to close in October, Hoscheit said.

Carpentersville officials had been interested in annexing the property and encouraging development at the site, citing economic benefits.