A mile or so from the site of the last great battle of the American Revolution stands a monument to a more recent victory, won by the residents of this Tidewater community. It is the massive power plant of the Virginia Electric and Power and Co. and it is burning oil.

Until five years ago, the plant burned coal.

"It was miserable," recalled Robert Ripley Jr., York County commonwealth's attorney. "The ash was falling in buckets. You'd paint your house white and it would come out gray. You'd get up in the morning and you'd have dirt all over the car."

Backed by indignant citizens who fought the plant for two decades. Ripley sued. Vepco was indicted by a York County grand jury on a charge of criminal nuisance. In June 1972, just before the trial was to begin, the company signed a court order agreeing to switch from a coal to cleaner burning oil.

"It was the biggest thing that happened to improve the environment around here since Cornwallis surrendered at Yorktown," Ripley boasted in his courthouse office last week.

But now Yorktown is being ordered to swtich back. It and 149 other plants around the country are being ordered to burn domestically abundant coal instead of scarce oil and gas. The orders are part of a three-year-old conversion program that President Carter has promised to expand. It will, he hopes, reduce the nation's dependence on foreign oil.

Yorktown is a microcosm of the myriad problems of coal conversion. Utilities originally switched from a coal to oil during the late 1960s and early 1970s, when oil was cheap and new environmental laws discouraged coal. Now the same plants are being asked to do the reverse.

Some are converting voluntarily, but many are resisting because coal is difficult to handle and requires expensive new equipment to comply with ever-sticker air pollution laws.

Vepco says it could cost more than $150 million to comply with Federal Energy Administration orders to convert units as Yorktown, Chesterfield and Portsmouth to coal - costs that would be passed on to consumers. The utility spent $22 million to convert those plants to oil. Baltimore Gas & Electric and Pepco, which serve Maryland and the District, are under similar orders.

In communities across the country, coal-conversion orders are stirring fears that the air will become cloudy with smog, coal dust and noxious gases such as sulfur dioxide.

"It's an unbelievable paradox," Ripley said of the Yorktown order. "After all that litigation to get clean air, now they're going to turn around and make it dirty again."

FEA, which issued the preliminary orders to Vepco two years ago and plans to make them final soon, says the plants can be converted without violating air-quality standards. At Yorktown, however, the agency may have to go to court to overturn the 1972 agreement.

In that event, Ripley said, "we're not going to roll over and play dead. We'll insist that the best technology be used so we enjoy the same air quality we have now."

Converting two of Yorktown's boilers to coal - a third, built only for oil, is not under an order - would require a new electrostatic precipitator. This $5 million piece of equipment, as large as a 10-story building, collects ash from the burnt coal before it flies out of the stack. Custom-designed, it would take as long as four years to obtain, Vepco said.

Even then, according to Yorktown plant superintendent James Broaddus, "the cleanest coal unit in the world is dirtier than an oil plant."

Since coal is 10 per cent ash, and oil one-tenth of 1 per cent, the problem of disposing of 400 tons of additional ash a day is formidable. There is no room near the power plant, which sits in the middle of a residential area, so the ash must be tucked out.

"Can you see it?" Broaddus asked. "That means one truck every 15 minutes along these bumpy roads - canvas covers flapping in the breeze" blowing dust over nearby homes.

The company would have to purchase land to bury the ash - a problem that brought complaints of acid runoff before. And because of the large amounts, Broaddus said, "Even a hundred-acre site would last only nine years" in a rapidly growing county where land is becoming scarce.

The fugitive dust problems worry Walter Reiser, owner of a marina across the road from the plant. In the past, when coal was unloaded off railroad cars, he said wind blew dust "like a dense fog through people's homes. When my wife left the window open in summer, it spread everywhere like black talcum powder."

Dust would also blow off the huge coal storage pile, which is as long as three city blocks.

Besides ash, coal burning produces sulfur dioxide, an invisible gas that can damage lungs, corrode buildings and ruin crops with acid rain. FEA says Vepco can burn low-sulfur coal, but, according to Axel Mattson, chairman of the Virginia Air Pollution Control Board, the state will probably require scrubbers, elaborate equipment to clean the stack gas of sulfur.

Vepco estimates scrubbers would cost $26 million at Yorktown, and Mattson acknowledged there is probably not enough room for the massive machinery on the site.

"Conversion is going to be a big fat mess for everyone," said Mattson, a retired engineer who lives a mile from the plant. "We can convert to coal, but it's going to cost a lot of money."

Technically, conversion is a headache, as Vepco discovered at its Chesterfield plant south of Richmond where two boilers that originally burned coal were switched to oil and then back to coal.

The first changeover required insulating a vast array of pipes inside the boilers with a cement-like substance because oil burns hotter than coal.

With the return to coal, the insulation was removed. Now the pipes spring leaks every few days. One boiler has been out of commission 75 per cent of the time.

The same problem exists at Yorktown and other power plants.

But the main problem is economics, according to Vepco Vice President Stanley Ragone. "Why should we spend this terrific capital investment when we're phasing out oil anyway" he asked. "These units are older units and by the time you get them ready to burn coal, you've got to retire them."

Vepco has been investing heavily in nuclear power, which has also created financial problems for the utility, and Ragone questions whether the company could borrow the money for coal conversion.

The company, which once got 100 per cent of its electricity from coal, now gets 41 per cent from oil, 22 per cent from coal. Conversion of the eight units ordered by FEA would reduce oil burning by one-third. But nuclear plants now under construction will cut oil generation in half anyway in the next two years, Ragone said.

FEA contends conversion is economically feasible, but if scrubbers were required by the Environmental Protection Agency, the economics would have to be reconsidered. Vepco's nuclear program has already been delayed and could be postponed further, FEA said.

Such issues are secondary to Ripley, the commonwealth's attorney, who fetched from his files photographs of coal particles blown up 1,000 times. Chatting about the President's energy policy, he recalled Jimmy Carter's visit to a Yorktown picnic during the presidential campaign.

"If he had been here back when the plant was burning coal, and the wind was blowing, he'd have had particulate matter all over his hot dogs and beans," Ripley said. "Then old Jimmy would be saying, 'We're not going to convert that Yorktown plant.'"