In Lycoming County, state environmental inspectors hiked through the woods northwest of Williamsport this fall to check out a multimillion-dollar pipeline project.

The dense forest was beautiful. What the inspectors found was not.

"Sediment discharge," their violations report reads. "Large section of unstabilized work and open trench."

Work crews had cut a long trench for the 50-mile Lycoming Line, then left it open to the elements. A rainstorm had sent mud sliding down hillsides, fouling a stream. In an unusually tough move, the state Department of Environmental Protection halted work until the pipeline's owners, PVR Partners of Radnor, made things right.

As natural gas companies ramp up their pipeline work in rural Pennsylvania, environmentalists and sportsmen have been raising alarms about the effects on the landscape. They worry about construction mud clogging waters and disrupting fish spawning, and about pipeline rights-of-way cutting swaths through forests, destroying treetop canopies.

"We're really early in this process," said Katy Dunlap, eastern water project director for Trout Unlimited, a national conservation organization.

"What is going to be the impact of the loss of the forest? On quality of water?"

When rivers and streams are jammed with silt, she told a U.S. Senate committee in October, research shows that fish can suffer gill damage or stop reproducing.

"In the heart of the Marcellus development area, in places such as Pennsylvania, well-intentioned state regulatory programs are struggling mightily to keep up with the challenges posed by rapid gas development," she testified.

In September, near the start of trout spawning season, erosion from a pipeline project in Potter County damaged five feeder streams for Pine Creek, a world-renowned trout stream designated as a federal "wild and scenic" river, DEP reports said.

Glenn Dunn II, resource conservationist at the Potter County Conservation District, said crews working to expand the Tennessee transmission line left miles of open trench through Potter County.

If they instead had completed one section at a time, "it would definitely have limited the chance of this happening," he said. A DEP spokesman said the agency was considering additional action.

In an e-mail to The Inquirer, El Paso Corp. spokeswoman Gretchen Krueger acknowledged that flash floods caused erosion and that the firm was working on the problem.

Peter Ryan, a Potter County dentist and president of the local God's Country chapter of Trout Unlimited, said he saw a risk for "exceptionally high-value trout streams."

"That is what our county is famous for," he said. "That's what brings people up here. That's what we hope to not have ruined."

The hilly terrain of Pennsylvania's woodlands is creating challenges for companies more accustomed to laying pipes through Oklahoma and Texas. Often, the companies choose to bore under streams rather than dig a trench through the streambed.

Sometimes, though, mud leaks into streams.

As for the Lycoming Line outside Williamsport, its builder, PVR Partners, said its erosion controls, too, had been overwhelmed by heavy rain. The firm has spent $170 million on 30-inch pipelines in central Pennsylvania in the last two years. Daniel Spadoni, DEP spokesman, credited the company for "prompt compliance."

"Obviously, we seek to be a responsible operator," said Stephen R. Millbourne, a PVR executive. "But we simply don't have control of weather conditions."

In Pennsylvania, the new, powerful "gathering" lines in the Marcellus Shale regions receive almost no safety regulation. But the pipeline owners do need permits from DEP, the Army Corps of Engineers if the lines cross streams, and other agencies, a process meant to protect the environment and even cultural artifacts.

Not everyone shares these environmental fears.

Doug O'Dell, a retired Marine general from Maryland, and his family own a tract of woods designated as a forest preserve in Sullivan County. The tract sits in the path of the Marc 1 line, a project that drew protests from green activists from around the globe.

Before the line won federal approval last month, activists raised worries about its impact - 200,000 trees were cleared, and it crosses more than 100 rivers and streams. But O'Dell said he and his wife, Judy, had made their peace with the project.

"Here's the cold facts: This pipeline is going to get built," O'Dell said. "We decided to mitigate the damage to our forest preserve, our roads, and get on with life."

Nels Johnson, Pennsylvania deputy director for the Nature Conservancy, said the state needed a broad strategy to address pipeline environmental issues.