Even the Alexandria mayor did not know Dayton Cook was digging a two-acre lake in the city.

But after the blue, bass-filled water hole just a glance north of the Capital Beltway was finished, it was named for Cook, and last month it was officially dedicated to him.

The lake now serves as testimony to the bold style and considerable influence of Cook, Alexandria's transportation and environmental director since 1972, who is credited with reshaping and modernizing a city that clings to its historic past.

"He literally dug that lake without anybody knowing," said Charles E. Beatley, mayor of Alexandria when the lake was dug in 1976 as part of a flood control project. Asked if lakes were allowed to be built without explicit approval from the City Council, Beatley said: "I wouldn't say allowed . . . . But he got it done for free. He asked developers to work a bit each day on it."

The story is one of many about Dayton Cook that abound in Alexandria.

Perhaps they are so well known and so rarely forgotten because Cook is so colorful. Born on Valentine's Day in 1933, he often strides up to his fifth-floor office in City Hall wearing mismatched plaids and wide ties. As one former city official put it, "Let's just say he doesn't read GQ."

Cook, who went to Alexandria 22 years ago from Chillicothe, Ohio, where he worked as a city engineer, said he knows that he has made quite a name for himself in the city, particularly with residents who oppose his traffic projects.

"It's very hard when you're working for 110,000 citizens to make neighbors look at the big picture," Cook said.

At City Council meetings, Cook is revered as an Alexandria encyclopedia, someone who knows the city code almost by heart. Those who know him claim he has a photographic memory of the city's water mains, traffic signals and fire hydrants.

"He knows the city like you know your home," said citizen activist Barbara Lynch. "When you get up in the middle of the night, you know where the light switch is; well, Dayton Cook knows where the street lights are."

At Tuesday night's meeting, the City Council hosted a reception and passed Resolution No. 9 honoring him for his service to the city.

But many residents loathe Cook's influence. They see him as a master engineer who refuses to let go of pet projects no matter how many people oppose them or who those people are. And they say that if he can't get official approval, he just does it on his own.

"He proceeds stealthily," said Dr. Morgan D. Delaney, president of the Historic Alexandria Foundation. "He's not terribly sympathetic to residents' concerns. I've heard others say that his title is director of transportation and environment but that he is far more interested in transportation than (in) the environment."

Wary of what they call "the ways of Cook," a group of West End residents held a work session with City Council members Tuesday night to argue against one of Cook's projects, the proposed extension of Clermont Drive to Duke Street.

Even though the public hearing on the matter is scheduled for February, they say they need all the time they can get because Cook has had quite a head start: Ten years ago, with the dirt he dug from around Lake Cook and without telling anyone, he built a ramp at the end of Clermont Drive setting up the controversial road addition.

For a decade, the Clermont ramp has led to nowhere, dead-ending in dirt, and Cook has been saying that he knew the road extension was necessary and that he saved the city money by building the ramp then.

"Dayton Cook is a highway builder," said Delaney. "Yes, that sums him up."

Another road building project, the two-decade task of widening Duke Street from four lanes to six, is regarded as Cook's most enduring controversy and has drawn the rage of hundreds of residents.

Piece by piece, and by never taking no for an answer, Cook has won approval to widen Duke from the Fairfax County border to Elizabeth Street, with Old Town spared. In the spring, the state highway department will hold a public hearing on widening the section of Duke from Elizabeth Street to Rte. 1.

Cook, who has an engineering degree from Carnegie Technical Institute in Pittsburgh, says the expanded thoroughfare is necessary to encourage development and ease congestion. But neighbors say it would bring trucks zooming past their front doors and eliminate houses and shops.

Residents and officials say the two sides are now so divided on the issue that a boxing ring would be a more appropriate forum than a public hearing.

There were charges that Cook was trying to avoid residents by working on Duke Street at night. "This past summer his (Cook's) men were marking underground utilities at 11 p.m. with flashlights," Delaney said.

Cook denied the night-cover activity, saying that it was state highway engineers who were marking utilities in preparation for the spring hearing. Then he smiled and said, "Because of my reputation they thought it was me."

Cook is even credited with putting one longtime city official in office.

Former three-term City Council member Donald C. Casey said his distaste for Cook's plan to build a cloverleaf at the intersection of Russell Road and King Street prompted him to run for office in 1976.

Casey said he ran because Cook rarely abandoned a project no matter how much opposition there was, and, if he had to, he would complete it when council members and residents were not looking.

Casey recalled one more notorious unofficial project, completed on a Saturday in 1972. Cook cut through a median on Daingerfield Road to connect Commonwealth Avenue to King Street. Trucks from Rte. 1 could then head down Commonwealth Avenue, flow onto King and Duke streets and then onto the Beltway. Neighbors were outraged at the increased traffic near their quiet blocks.

"The city did get mad," said former City Council member and environmental activist Ellen Pickering. "But what do you do when the road is already paved?"

Cook laughed when asked about the Saturday episode and said, "Sometimes I've been told to do things without asking to."

Pickering says that Cook will never have official opposition because he is cherished as a master negotiator, saving the city untold thousands by drumming concessions out of developers, and is lauded for having established a national precedent-setting flood control plan at Four Mile Run.

Cook's perpetual maintenance flood control plan requires Fairfax County, Arlington County and Falls Church developers who build in the Four Mile Run flood plain to control the runoff from all present and future projects and pay an annual maintenance fee.

"I do what I have to . . . and the council can always blame me," Cook said when asked why he sometimes acts without official direction and often gets in tussles with neighbors.

Cook said his $65,000-a-year job, which puts him in charge of the city's road and bridge building, refuse collection, traffic surveying, sewer maintenance, animal control and the attendant 200 employes, has never allowed him the luxury of neutrality. Often, he and his wife Esther escape on weekends to their cabin in the Shenandoah Valley.

But many think Cook is in the hot seat more often than another in his position might be because Cook often shuns the political process, believing that holding some public hearings is a waste of time and money.

He is a "very bright engineer," said Pickering. "He loves a straight line. Lines flow uncomplicated, and people complicate things."