A move to preserve 240 acres of developer-coveted open space in one of the region's fastest-growing areas, in southwestern Delaware County, will get a significant infusion of green from Delaware County and Concord Township, officials affirmed Monday.

As they had pledged, the township said it would kick in $500,000 and the county $250,000 toward purchase of the historic Beaver Valley, near the Delaware border near the banks of the Brandywine Creek and one of the busiest portions of Route 202.

An agreement of sale involving the land owner and three nonprofit environmental groups - the Conservation Fund, the Mount Cuba Center, and the Brandywine Conservancy - was announced last week. Concord supervisors earlier backed a proposal to build 150 houses on the tract, which abuts 1,000 acres of federally protected land.

Beaver Valley, which the county said was acquired originally by William Penn, is home to rolling pastures, winding trails, and wildlife, and the agreement "will make sure it remains this way in perpetuity," Domenic A. Pileggi, the township supervisors chairman, said Monday. He was among local and county officials attending a media event in front of a vineyard at the site to announce the financial commitments.

The township's share will come from its open-space fund and the county's from Act 13 money generated by impact fees related to Marcellus Shale drilling.

The purchase price for the acreage has not been announced, but Blaine Phillips Jr., Mid-Atlantic regional director of the Conservation Fund, said the groups needed to raise $8 million.

The land is owned by Woodlawn Trustees Inc., Eastern States Development Co., and the McKee Group, and straddles the border with Delaware. In addition to the small winery, it features public-use trails frequented by horseback riders, joggers, and walkers in a township whose population has nearly tripled, to near 17,500, since 1990.

Pileggi said that for the last five years the board had considered rezoning efforts that would have allowed for housing developments on the tract. But even though the board last year granted preliminary approval for one development plan, he said, board members "also expressed our concern and our hope that it would be preserved, and that's how we got here today."

cshaw@philly.com 610-313-8119 @coltshaw_