A proposed highway that could devastate one of Southern Maryland's most fertile fish nurseries has hit a major speed bump.

The Maryland Department of the Environment has denied a permit for Charles County commissioners to build the rest of the Cross-County Connector, a 16-mile road that would cut through and add large amounts of impervious surface to the Mattawoman Creek watershed. The Mattawoman is a lush and forested tributary of the Potomac River about 20 miles south of Washington, DC, prized by preservationists for its canopies of willows and birch and by anglers for its largemouth bass population. Local environmentalists had been fighting the road since its inception in the early 1990s, and larger regional groups as well as several government agencies joined the cause over the past year as MDE officials weighed their decision.

"You can't get much better than MDE denying a permit. They don't do it very often," said Terry Cummings, advocacy manager at the Chesapeake Bay Foundation. "This is quite a victory for smart growth and environmental protection."

Permit denials in Maryland are rare. In 2009, the MDE approved 99.7 percent of the applications for permits and letters of authorization to destroy wetlands, with 1,967 approvals and only 5 denials that year, according to MDE records that the Chesapeake Bay Foundation's Tom Pelton obtained.

The denial came after the Charles County Board of Commissioners decided in September that it was not willing to spend $140,000 more to complete its application in the face of uncertainly on whether the road would ultimately be approved. In September, the commissioners wrote to MDE secretary Robert Summers to inquire on the status of their application.

On Nov. 1, the MDE concluded that the application was incomplete, and therefore denied it. The county has 30 days from receipt of the letter to appeal the decision. It can't reapply until April unless it makes "substantive change" in the application.

In her November denial letter, Amanda Sigillito, chief of the nontidal wetlands division, said that the county didn't completely investigate mitigation options for the adverse impervious surface impacts. It had done some realignments, she noted, but it hadn't looked into lower speed limits and a narrower road. Sigillito said the department had requested but never received detailed floodplain maps for a proposed bridge over Mattawoman as well as any proposed stream diversions and drainage issues. Also, the site the county selected to reforest wetlands as mitigation for the ones it was going to compromise is a historic property, and the Maryland Historic Trust had asked for more information.

Finally, Sigillito concluded, the county didn't offer enough evidence that the Cross-County Connector would not harm Old Woman's Run, a Tier II stream connected to the Mattawoman. Tier II areas enjoy special federal and state protection because of their excellent water quality. Old Woman's Run is one of the few Tier II waterways in Maryland.

"This submittal was only partially responsive to the Department's request for information and did not provide an adequate level of detail for the Department to conclude that Tier II issues have been adequately addressed and that the proposed project will not degrade surface and ground water quality," Sigillito wrote.

The county is also waiting for a ruling from the Army Corps of Engineers, which also has jurisdiction over wetlands permits. But regardless of what the Corps decides, the county can't proceed without the MDE permit.

It's unclear what will happen next. MDE spokesman Jay Apperson said the department had no further comment on the letter, saying that it "speaks for itself."

At its Nov. 8 meeting, the commissioners voted not to appeal the decision. But that doesn't mean the project is dead, said commissioner Bobby Rucci, a Democrat representing the Waldorf area.

"All we did was vote not to appeal the one letter they sent back to us," said Rucci, who supports the road. "We now have to start a process to see what needs to be done next."

Rucci said the board decided there was no point in appealing the decision without doing the studies that MDE asked for, and they needed more information on how those studies should be completed and what they would cost. When the board asked its staff why it hadn't done those studies, various staff members said they didn't have the money, weren't directed to do so, and were struggling to keep up with the MDE's requests for more studies.

According to the Baynet, an online news source that covers Charles and St. Mary's counties, the county has already spent $35.2 million on the road and would need to spend almost that much to finish it.

Commissioner Ken Robinson said the unanimous vote not to appeal the permit "kills the project," and he did not believe the commissioners would reapply, calling the road "expensive, controversial and unnecessary."

But historically, road projects are difficult to kill, and even survive recessions. Environmentalists fought the Inter-County Connector, a toll road joining Montgomery and Prince George's counties, for nearly 40 years. At one point, then-Gov. Parris N. Glendening told officials it was dead. But the first section of the road opened about a year ago, and the rest of the 18-mile connector will probably be ready by the end of 2012.

Sen. Thomas "Mac" Middleton, a county commissioner from 1984 to 1994, said that it would be "completely understandable" if the commissioners decided they couldn't pursue the project because of the economic situation. But he said that, if the connector isn't built, something else needs to be done to alleviate the traffic problems in that part of the county. Charles County is one of the fastest growing in the state, and it also has to contend with commuters from St. Mary's County who pass through on their way to work in the District of Columbia.

"Maybe there's a legitimate concern as to whether it meets the smart growth definition," said Middleton, a farmer. "But I saw, and still see, that it addresses a safety issue."

Robinson said traffic isn't a problem east-west, where the highway would run, but north-south, where commuters are trying to get to and from the District.

The connector has endured its share of twists and turns. In the 1980s, the area including Mattawoman was designated for growth, and land speculators came in to have a look at the pretty forested pieces in the shadow of the Potomac. The road was proposed in the early 1990s to help new residents access Chapman's Landing, a 4,600-home development on 2,100 acres near the creek's headwaters.

But environmentalists cried foul. And Glendening, who was promoting his new Smart Growth initiative, spent a great deal of capital - political as well as cash - to purchase Chapman's Landing and preserve it. The area, now called Chapman Forest, cost the state $28 million and was one of Program Open Space's most expensive acquisitions.

Chapman's Landing came off the books, but the road never did. Two thirds of the connector was built, with the Mattawoman stretch the only remaining piece. As the years went on, federal and state agencies, as well as environmental activists, became increasingly concerned that the addition of more impervious surfaces would devastate the Mattawoman. The U.S. Fish and Wildlife Service wrote a letter to the Corps opposing the road. On the state side, scientists with Maryland's Department of Natural Resources and planners with the Maryland Department of Planning let their counterparts at the MDE know of their concerns.

Jeff Horan, the DNR's director of watershed services, compared Mattawoman to Piscataway Creek, in Prince George's County, which had already been developed. While Mattawoman's fish populations had dropped, anadromous spawning in Piscataway had ceased altogether.

"We're not positive that we've crossed a threshold (in the Mattawoman). But we're very concerned about it. We have been," Horan told the Bay Journal last year.

In 2009, American Rivers placed the Mattawoman on its annual list of the most endangered waterways. The next year, the CBF joined the fight.

In the meantime, the EPA announced it would require a total maximum daily load of the pollution entering individual waterways. Mattawoman was one of the few that already had a TMDL in place. But with the DNR's newer studies on how devastating impervious surface can be to fish populations, residents became much more aware of the road's implications.

Although Middleton said he believed most county residents favored the plan, environmental activist Bonnie Bick said that was never the case. And, she said, elected officials finally caught up to the people's will - Robinson even ran on an anti-CCC platform.

"It's not going to come back," Bick said of the road. "We have greater environmental awareness now than we ever had. Elected officials are understanding, finally. They're very aware of the economic values of Smart Growth. All elected officials are going to have to start paying for policies that are environmentally destructive."