Northern Virginia Conservation Trust to oversee preservation of Pr. William parkland But after an approximately $2 million restoration project, completed in August 2012, the stream that Prince William officials unveiled was tidy-looking, its banks at normal levels and the quick-moving water rippling along. The project was the first tangible outcome of a public-private partnership between the county and Warrenton-based Angler Environmental, a deal that is expected to result in $10 million to $12 million in restoration along 22 miles of streams in 10 county parks. The projects have to be approved one by one, so it's unclear when all of the projects will be completed. Angler is not donating its time: The firm sells environmental "credits" to developers that construct homes or buildings on land that affects the watershed. If negative effects are registered, one way to comply with federal and state laws is to buy "credits" from Angler, which has done work improving other areas. In that way, regulators can say that little damage overall was done by development. The county wins, too, because Angler splits parts of the proceeds with it. But guaranteeing bucolic county land for the streams to flow through is another issue entirely. The county discovered that it would run afoul of the deal with Angler without an outside organization to oversee the parkland's "conservation easement" - a legal device that assures that the land remains undeveloped. That's why the Board of County Supervisors last week inked a $56,000 deal with the Northern Virginia Conservation Trust, in Annandale, to oversee the land around the streams. The deal is for three parks where work is taking place: James S. Long Regional Park, Forest Greens and Locust Shade Park. The contract doesn't mean NVCT will oversee Angler's work. NVCT's job will be simply to ensure that nothing significant happens to the land around the park and that no one tries to develop it in the future, which is spelled out in a legal agreement. The county must make sure that streams stay in good condition. Supervisor Michael C. May (R-Occoquan) said in an interview that the NVCT price tag might be steep for its work. Given that it's a one-time stewardship deal for the three parks - and that many more such arrangements are on the way - the county needs to look for the best price, he said. Is there an entity out there that can do it cheaper? May asked. We need to make sure we're evaluating that and getting the best deal for the taxpayers. Peggy Stevens, executive director of NVCT, said the nonprofit organization was "delighted" by the deal, which was more than a year in the making. She said the amount was fair in light of the amount of acreage involved. It allows the organization to help conserve the land forever and includes funds for litigation, should it ever become necessary. NVCT oversees such conservation easements throughout the region, she said. It will take years for all the credits generated by the project to turn a profit. The Locust Shade project is projected to net the county and Angler $800,000 each, after credits are sold. Throughout the course of the countywide stream restoration projects, Angler and the county expect to collect about $3.5 million each. Angler has embarked on a large, ambitious stream restoration project at Andrew Leitch Park in Dale City. The project is expected to start next fall and take a little less than a year, said Don Seaborn, an Angler partner. NVCT wants to strike other deals with Prince William, Stevens said. The county has not yet made any decisions about who would hold and enforce easements on future projects, officials said.