One of the keys to keeping North Park Lake healthy is keeping land along Irwin Run undeveloped, environmental experts say.

For that reason the Allegheny Land Trust is in the final stages of raising more than $500,000 to acquire 75 acres along one of the water sources for the lake.

The Sewickley-based trust has joined with several environmental organizations with links to North Park to try to raise the final $100,000 needed for the project by March 31. The $504,000 project budget includes money for acquisition and upkeep.

The land, located in Pine, includes a walking trail and about a half-mile of stream. The area would be known as the North Park Greenway.

The trust is an independent, nonprofit organization that has preserved almost 1,500 acres of open space in 20 municipalities in southwestern Pennsylvania.

Roy Kraynyk, executive director of the trust, said the 75 acres next to North Park are important for several reasons.

The stream that flows through the property is surrounded by woodlands and wetlands that provide natural control of storm runoff. The greenway will serve as a water filter and sediment trap, improving downstream water quality in North Park Lake, he said.

"If the land was developed, all those functions would be lost," he said. "And additional erosion and siltation would occur as the result of tree removal, land disturbance and additional paving. Acquiring this tract will have a double benefit."

Keeping the area undeveloped also will help maintain biodiversity, he said, using a term that refers to the variety of plant and animal species in an area.

A 1994 natural heritage inventory found that the North Park Lake Biological Diversity Area was home to a small colony of rare plants, he said. The study did not name the plant or its location in an effort to head off any attempts to remove it.

"Another benefit is its scenic character," Mr. Kraynyk said. "A nice walking trail already runs right through the property along an abandoned portion of Irwin Road."

The land trust was contacted by the landowner several years ago about acquiring the land for green space. Closing on the sale is set tentatively for March 31, but Mr. Kraynyk described that as a soft deadline. "The owner has been very cooperative and eager to work with us," he said.

After the sale, the trust would own the land, but the area would be open to the public and would remain undeveloped forever, he said.

The trust's effort to involve the community in the project will include two presentations on the project and two hikes through the area.

"We want people in the neighborhood to come out and learn about and walk the property," he said. "We think that is the best way for them to understand why we are doing this and make a contribution to support the effort."

The trust's efforts have the backing of several local organizations, including the Friends of North Park and the North Area Environmental Council.

Those groups will sponsor hikes through the property starting at 10 a.m. Feb. 14 and March 21.

The starting point is Beaver Grove, a picnic area located west of Babcock Boulevard, near its intersection with Pearce Mill Road.

The environmental council's board also has approved a matching-fund program for members who contribute to the land trust for purchase of the North Park Greenway. The council will match up to $4,000 any contributions made by its members. The matching funds are profits from the council's annual tree-seedling sales.

Much of the open land around North Park has been or is being developed, according to Bill Moul, president of the environmental council.

That development pressure makes it important to secure rights to the land along Irwin Run, he said. "Protection of recreation opportunities in the area is as important as the protection for the watershed itself," he said.

Mr. Kraynyk will make presentations on the North Park Greenway project at 7 p.m. Feb. 12 and 1 p.m. Feb. 18. Both programs will take place in North Park's Cabin, located just west of the intersection of Babcock Boulevard and Ingomar Road.

More information about the public meetings and the hikes is available through Gary Rigdon, the association's liaison with North Park. He can be reached at grigdon@consolidated.net or 724-449-9985.