Beneath the rippling reflection of budding trees, brown trout in Valley Creek wriggled and splashed, invigorated by spring's warming waters.

"It's a neat little ecosystem here," said Matt Stutzman, a biologist from Coatesville fishing at a bend in the creek. "It's rare."

The Tredyffrin Township waterway - rated an exceptional stream by the state in part because it supports a self-sustaining trout population - is one of the few where wild trout thrive so close to a big city.

The creek is hallowed water to fisherman, who worry about a proposed highway expansion near the blue-ribbon stream. About 700 yards away, 59,000 vehicles speed on the Pennsylvania Turnpike each day. That number is expected to increase to about 100,000 daily vehicles by 2035.

The Pennsylvania Turnpike Commission is engaged in a decades-long widening project on the full length of the road, and for more than 10 years has been working on plans to expand from four lanes to six the 6.4-mile stretch from the Valley Forge interchange to Route 29, and to widen the median by 16 feet.

"We think this project is needed for the safety of our customers," said Carl DeFebo Jr., spokesman for the Turnpike Commission.

Portions of the highway are in Valley Creek's watershed, and lovers of the stream are troubled by pollutants and warm water that drain into it off the highway during storms, jeopardizing the trout that depend on consistently cool water of the spring-fed stream to survive.

The turnpike, built in the early 1950s, has no stormwater management system. The 800-member Valley Forge chapter of Trout Unlimited says the Turnpike Commission's expansion plan - which would create stormwater management through 21 basins and six concrete vaults - is insufficient, and would worsen the runoff problem, leading to more flooding that would cause erosion and habitat loss and could threaten fish. The group is opposed to a January settlement agreement between the Turnpike Commission and Tredyffrin that exempts the expansion project from some of the township's storm-water management standards.

"We know better and we can do better," said Pete Goodman of Malvern, the group's environmental chair.

The township has some of the most restrictive storm-water ordinances in the state due to regular flooding there, said Vince Donohue, township solicitor, even more stringent than state law.

Meeting the ordinance's requirements would have been expensive and could have led to taking portions of 100 separate properties, commission officials said. They say the planned storm-water-management system, even though it won't meet all the township's standards, will still result in an overall decrease in runoff flowing into Valley Creek.

"When we're finished there will be a significant improvement," said Kevin Scheurich, the turnpike's senior engineer project manager.

Trout Unlimited says otherwise. In late February the conservation group petitioned Commonwealth Court to block the settlement, claiming it violates state stormwater management and environmental protection law and was reached without proper input from the community. In a response filed this week, the township disputed the challenge and argued that Trout Unlimited lacked standing to contest the settlement.

Managing stormwater to the standards set by the township ordinance would be difficult, Turnpike Commission officials said, because of the proximity of Valley Forge National Historical Park, residential and commercial development, and the presence of limestone in the ground that increases the risk of sinkholes.

As pristine as Valley Creek appears on a warm spring day, it has a history of pollution. In January a water main broke, spilling chlorinated water that killed hundreds of trout, Goodman said. The creek's fish are still inedible due to PCBs from the nearby Paoli Rail Yards that contaminated the waterway 30 years ago, he said. Goodman grew up fishing in the creek, he said, adding that he believes it is possible for the trout, nature enthusiasts, and the highway to coexist.

"What the turnpike is doing isn't enough," he said, "and it shouldn't be up to us to tell them how to do it."