The calendar may not show it, but today marks a new epoch in the City of Alexandria: A.D., for After Dayton.

Dayton L. Cook -- officially Alexandria's director of transportation and environmental services, unofficially one of the most influential bureaucrats ever to cash a city paycheck -- retired yesterday after 24 years on the job. There was little hoopla, in part because Cook's big testimonial luncheon was held in June and in part because he never stood much on ceremony.

Instead, Cook built things.

He presided over construction of three flood-control projects, a $100 million trash incinerator, more parks and roads than anyone bothered to count, and his own outsized reputation. He ignored politicians, twisted the arms of developers and enraged civic activists.

Still, whether an individual loved Cook or hated him or both -- and there was a lot of both -- official and public response to his departure came down to one sentiment: "There is no replacing Dayton Cook."

Who else would start building two controversial roads without permission from the City Council, and publicly endorse them long after the council stopped the work? Who else would open a major overpass, complete with ribbon-cutting, and not bother telling his bosses? Who else would dig a two-acre public lake without asking permission, and then end up getting it named after him?

"To some extent, Dayton probably is the end of an era," said City Manager Vola Lawson. "He was the sort of public servant who made entrepreneurial decisions, serving the best interests of the city as he perceived them to be. He's no-frills, 'I call 'em as I see 'em.' And he is a first-rate public works director."

"Dayton did a lot of things I disagreed with -- when I found out about them," said former council member Donald C. Casey. "We argued a lot. But he was one of the best department heads the city ever had."

Cook himself, who relished and cultivated his reputation for independence, is tempering things a bit on the way out. "Everybody always knew if you want something done, you give it to Cook," he said with a chuckle. "But council always knew what I was doing. If it got controversial they just didn't want to remember."

According to those who have worked with him, and sometimes worked around him, Cook is an old-school, concrete-and-asphalt man in the tradition of Robert Moses, the legendary New York public works czar who built many of that city's bridges and freeways. Moses' motto, and Cook's, could be summed up in a sentence: Drive the first stake and no one will ever stop you.

Cook drove a lot of stakes.

When he first arrived in Alexandria in 1964 as assistant public works director, Four Mile Run was an unruly creek that overflowed during heavy rains. Cook, who had experience in flood control work on previous jobs, was hired to tame it.

But drying out the low-lying neighborhoods along Four Mile Run was just a warm-up.

Cook launched a second flood-control project along Holmes Run, which he turned into a city park, and a third along Cameron Run. That project transformed the Eisenhower Valley, then an isolated industrial corridor along the Capital Beltway, into a potential site for high-rise office and commercial development.

Cook also played a key role in the revitalization of historic and fashionable Old Town.

In the 1960s, when delapidated industrial plants lined the Potomac, Cook was one of the city negotiators who acquired land for waterfront parks.

"Nobody ever dreamed we would be too successful," he said.

"Now the merchants fight with the homeowners about parking, and we worry about how expensive everything is."

In Alexandria's West End, the newer half of the city where high-rise condominiums and commericial development have blossomed in recent years, almost every public facility bears Cook's stamp.

"Dayton has been sort of the architect for the western part of the city," Lawson said.

The city formally acknowledged his pervasive influence in 1985, when it named a two-acre pond beside Eisenhower Avenue Lake Cook. During the Cameron Run flood-control project, Cook decided to build the lake without saying a word to the City Council. Earlier this year, when Cook staged his own private ribbon-cutting to open a new overpass along Rte. 1, council members just shrugged.

But it is in the West End where Cook learned that, eventually, someone will force you to pull up a stake or two. Perhaps his most celebrated piece of unauthorized construction was his decision several years ago to begin two streets that were adamantly opposed by West End residents, the Bluestone and Clermont connectors.

Under pressure, the City Council refused to complete either of the roads. To this day, two ramps that would have led to bridges remain as monuments to Cook's zeal.

"Dayton is a good engineer who looks at things on a straight-line basis," said Mike Hicks, chairman of the Alexandria Federation of Civic Associations.

"A lot of times Dayton wants to go from Point A to Point B, regardless of whether there is a neighborhood in the middle. Come hell or high water, he wants to build his road."

Cook says that one of his greatest regrets is that the Clermont connector, which he believes would greatly speed the pace of development in the Eisenhower Valley, remains unbuilt. "I had hoped to stay around to finish that one," he said.

But he said the activism that has stalled the Clermont connector has made him more sensitive to public opinion in recent years, and that his successor probably will have to adopt an even more politic approach.

"There used to be only 400 to 600 people who ran this city," Cook said. "We've got that many people on committees now. We have some of the smartest, most informed citizens anywhere, and this is about as close to New England Town Meeting government as you're going to get."

Cook, 55, grew up on a farm in upstate New York, and even while he built a city he remained a country boy at heart. His wardrobe, a collection of polyester plaids, has been the source of endless City Hall jokes.

He is retiring to a home in the Shenandoah Valley near Woodstock, Va., where he will take on smaller construction projects. He already has added a deck to the home of one of his children and built a jungle gym for his grandchildren.

Cook will not immediately vanish from Alexandria. His memory is so valuable, and his skills as a potential adversary so formidable, that city officials have signed him to a three-year contract as a consultant. "He not only knows the streets," Lawson said, "he knows what's under the streets."

Although he admits to mixed emotions, Cook said he knows it is time for him to go. "I've been involved in turning a lot of this city around, and I've enjoyed it," he said. "But by and large, most of the dramatic building has been done.

"Ten years from now, most of what will be necessary here will be a maintenance job, anyway. I guess I can let somebody else handle that."