Yet another piece of the giant puzzle known as Big Marine Park Reserve has fallen into place.

Washington County's purchase of a key land parcel bordering the lake begins a vision for a campground in the park, which opened to the public in 2008.

"The folks who owned it thought it was time to sell," said John Elholm, county parks manager.

The county bought the 2.65 acres on the southeast side of Big Marine Lake for $430,000. A purchase agreement has been signed but a final agreement awaits a Metropolitan Council reimbursement of 75 percent of the price.

The county's portion will be paid from the voter-approved Land and Water Legacy program, which allows as much as $20 million eventually to be spent to preserve open spaces and water quality.

Land purchased for the Big Marine park, one of six the county manages, happens only when a "willing seller" steps forward to negotiate. The newest parcel came from the Knauff family, an estate with five owners, Elholm said.

"It's a natural piece of property," he said. "This particular land might be a buffer between the lake and the campground."

Big Marine doesn't currently have a campground, but the developed portion on the south end of the lake has a swimming beach, boat launch, picnic and play areas, fishing pier, walking trail and a headquarters building. Houses and cottages that once overlooked the lake have been removed.

Most of the land at Big Marine, the county's newest park, will remain natural as required for regional parks. The park boundaries include private land that the county hopes someday will come available.

Owners of the Knauff property initiated the proposed sale. The County Board decided to make an offer on the land in mid-May after it was appraised.

Elholm said a campground at Big Marine won't be built until the county can acquire several other contiguous parcels. Campgrounds are available at two other county parks, Lake Elmo Park Reserve and St. Croix Bluffs Regional Park.

Last week, the board reviewed another possible transaction for Big Marine Park. In a meeting closed to the public, commissioners reviewed an appraisal of the land, owned by the Croone family, and potential costs associated with it.

They also discussed the financial terms of a possible purchase of land that could become part of the St. Croix Valley Regional Trail.

No further details were available.

Washington County has purchased several properties elsewhere in the county with money from Land and Water Legacy, which was approved in 2006.

Kevin Giles • 651-925-5037, Twitter: @stribgiles