Last weekend, for the second time in three months, thousands of gallons of silt-laden water gushed from a faulty sediment control pond into the headwaters of Paint Branch, the only stream in the Washington area that supports a reproducing trout population.

The silt washed down Good Hope tributary, a spring-fed, six-foot-wide creek in the Silver Spring woods where 90 percent of Paint Branch trout spawning occurs. The damage to brown trout eggs, which are laid in the fall and hatch in the spring, won't be known for months, nor will the damage to the trout population.

So what's new?

Surviving environmental barrages has become a way of life for Paint Branch, whose most pristine stretches lie four miles outside the Beltway along the fast-developing Rte. 29 corridor to Columbia.

In the last 13 years, this wild trout haven has survived threats from bridges, housing developments, sewers and chemical waste from a photo processing plant. The state has spent $1 million acquiring parkland to protect the spawning areas. But the battle goes on.

Fly fisherman Jack Scanlon happened to be wandering up the creek Sunday when he saw the plume of yellow mud. Mud being public enemy No. 1 for trout eggs, which require clean, clear, moving water, Scanlon called Dick Blalock, president of the National Capital chapter of Trout Unlimited.

Blalock made enough noise that folks from the state Water Resources Administration and Department of Natural Resources came around Monday. They determined the murky water was pouring from a faulty valve at the bottom of a sediment control pond at Maryland Development Co.'s 140-home Fairland Ridge development.

On Thursday, after almost all the water had drained out, company president John Smart was saying his production manager had been told to do whatever was necessary to correct the problem.

The same company was cited by the state in December for the same sort of problem at the same pond, according to Water Resources Administrator J.L. Hearn. The pond is supposed to catch and filter water running off construction sites and remove silt before it gets into the stream.

You might expect Blalock, Scanlon and their Trout Unlimited colleagues to be incensed by this latest assault. Instead, they seem resigned to occasional disasters, hopeful the damage was minor, happy at the quick state response and ever vigilant for the next nightmare.

"We don't know whether this incident will destroy the spawn below Fairland Ridge," said TU Paint Branch chairman Bob Schueler. "We'll have to wait and see. But our bigger concern is that this beautiful little system is taking environmental insult after environmental insult. It's a cumulative thing."

Blalock said of deepest concern to defenders of the trout stream is a state plan to build by the year 2000 an Inter-County Connector highway from Rockville to Laurel, which would cross all three spawning tributaries of the Paint Branch and run alongside Good Hope tributary for half a mile.

"The short-term threat is these little aggravations and crises," he said. "The long-term, primary threat is the road."

Blalock believes the trout, if they can be kept alive and thriving, may be the best ally in the war against the road.

Paint Branch is rated Class III, naturally-reproducing trout water, the highest water quality classification the state awards.

"As long as it stays Class III, it has that patina. But once you lose it," said Blalock, a retired foreign service officer, "everyone with power over sewers, construction, development and highways loses any sense of obligation to the stream.

"It's happening already," he said. "I called the Park Police to complain about people driving all-terrain vehicles in the park and they said, 'Why worry? The road's going in there. They're going to pave that stream over.'

"So you see, once you start to slide, everyone starts dumping on you."

"The issue," said his colleague, Schueler, "is this: If you can do this balancing act, and through good planning and execution keep the brown trout population going and still permit balanced development, then maybe it's a symbol for the entire region that development and conservation can coexist."

Schueler and Blalock, along with Charlie Gougeon and Greg Golden of the state coldwater fisheries department, led me down to Good Hope tributary for a first-hand inspection.

Even in the rain and cold of bleak February, it looked good. Clear water tumbled over rocks, a canopy of trees promised shade in summer to keep the water cool for trout, and the vegetation along shore was thick, to keep idle humans out.

"It's more than just a trout stream," said Blalock. "It's deer, turkeys, pheasant -- a garden of Eden. And to ruin it just so somebody can get from Rockville to Laurel at the speed of light, well, to tell you the truth, I don't know why anyone wants to go to either place."