Living on a lake has been part of the American dream since Henry David Thoreau camped out by Walden Pond.

But then Thoreau didn't have to worry about dams, siltation, dredging, and toxic sludge.

For the residents of Lake Barcroft, a lakeside community in Fairfax County, the joys of owning lakefront property include boating, swimming, skating and fishing. But if your home is along the eastern end of the lake, it also can mean living next to a cove that fills with trash every time there's a rain squall.

"There are some days when you just don't know if you can stand it," said Donald Carter, who has lived on Lake Barcroft for six years. "When you come home in the evening and look around, it's really peaceful and beautiful, and you feel you really had to work to be able to live here. But then the trash floats in here, the pop bottles and hamburger wrappers, and that's the worst."

Some residents argue that the worst is the cost of maintaining the lake. Under the organizational structure of the Lake Barcroft Watershed Improvement District, the WID the 1,000 homeowners around the lake tax themselves on the average of $400 per family each year. And with recreation and association fees, the average family spends $470 a year to taste the magic of living by the lake.

Lake Barcroft's residents, though, also have tasted disappointment. In the eight years they have owned the 140-acre lake, they have seen almost everything go wrong that could, from a bursting dam to a $140,000 bill for a dredge they are not sure they will use again. But they also know what their lake is worth, and referenda show many of them agree that the annual costs of maintaining the lake are small compared to what it does for the value of their homes.

When they lost the lake in 1972, after the flood waters from Hurricane Agnes eroded the dam, the homeowners considered leaving the lake empty. But the loss in property values for land surrounding the lake was estimated to total $12 million, and the homeowners decided instead to repair the dam, refill the lake and maintain it for future generations.

That, though, has turned out to be a colossal and not inexpensive task. To do battle with the silt, sludge, leaves and various flotsam and jetsam that is carried down Holmes and Tripps runs into the lake, the Lake Barcroft WID spends $240,000 a year. An additional $160,000 is spent annually retiring the debt on a 30-year municipal bond they sold to raise money to rebuild the dam in 1972.

While the dam was being repaired after the Agnes storm, the homeowners hired trucks to haul silt out of the dry lakebed. More than 9,000 truckloads were removed, and yet that still didn't restore the lake. David Alne, chairman of the board of trustees for the Lake Barcroft WID, estimates that about 6,000 cubic yards of silt are added to the lake each year, piling in on top of 27,000 cubic yards they don't think they ever will be able to afford to remove.

The dredging operations at Lake Barcroft have been something of a public-works nightmare. For the past few years, the Lake Barcroft homeowners have favored a hydraulic dredging method, complete with their own Mud Cat dredge and decanting basin the size of a soccer field into which the silt is pumped and then allowed to dry. Last fall, they took out 8,000 cubic yards and had a mountain of silt the size of a house. In takes three months for the silt to dry out enough enough to be trucked away.

But the Mud Cat fouls on plastic bags, rocks and branches, items that apparently lie thick upon the bottom of Lake Barcroft, and silt removal has cost the homeowners an average of $13 a cubic yard. Last fall they experimented with a crane on a barge that scooped silt out of the shallow coves with a clam digger, and they believe that process will cost only $8 a cubic yard of silt if they can implement it on a larger scale next year.

That still won't cure the lake of its toxic sludge. Left alone, decaying matter on the bottom eventually will kill the lake. To mix the cold and warm layers of lake water, a process that speeds the breakdown of decaying matter, the Lake Barcroft homeowners have approved an aeration system that will involve laying pipes along the lake bottom and forcing tiny bubbles of air out of the pipes. This project that will cost $4,000 a year to operate. But Alne says that the aeration system removed 40 acres of sludge a foot deep in a lake slightly larger than Lake Barcroft one summer.

The residents at Lake Barcroft are not the only Northern Virginians facing an invasion of lilly pads. Any man-made lake will silt in and eventually die if not dredged, although lakes downstream from construction sites tend to silt in faster because of heavy topsoil runoff. The homeowners of Reston recently have become concerned about siltation in Lake Anne and are discussing plans for establishing an ongoing dredging program for the three lakes their homeowners association owns.

The Fairfax County Park Authority, which owns and maintains the other large lakes in Northern Virginia, has applied for a federal matching grant to clean out Lakes Accotink and Fairfax. The Virginia State Water Control Board said last year that Accotink and Fairfax ranked as two of the most polluted lakes in Virginia. Park Authority officials said they estimate it will cost almost $6 million to restore both lakes, with half the money coming from local funds raised through recent park bond referendums.

With all the money needed to keep Lake Barcroft looking like a corner of Lake Winnipesaukee , taxpayers from other parts of Fairfax County have been concerned that public monies might be spent helping the homeowners there with their lake-related problems.

"People see us as a Cadillac community," said Alne. "And a privately owned lake is a difficult public relations problem. But we financed the rebuilding of the lake ourselves and we are proud of that."

Fairfax County, however, does spend money on Lake Barcroft. Because most of the silt in the lake is runoff from developments upcreek from Lake Barcroft, the county agreed a number of years ago to truck the dried silt away. Although county officials would not say how much that costs, they did say that they recently found a company willing to haul the silt away for nothing. The company plans to treat the silt and resell it as topsoil.

Fairfax County Supervisor Thomas Davis (R-Mason) believes the county has done well in the agreement with Lake Barcroft. "The county has gotten off cheap with Lake Barcroft," said Davis, adding that the county even has agreed to do more for Lake Barcroft in the future. A massive mixed-use development just approved by the county for land above Lake Barcroft will include a silt-runoff monitoring system which the county has agreed to operate until the development is finished 15 years from now. Although the developer will install the system, it will cost the county $25,000 a year to maintain.