Rumors that the National Park Service is turning East Executive Avenue into a moat for alligators, a base for ground-to-air missiles or a kennel for junkyard dogs are false, James McDaniel, Park Service associate regional director, said yesterday. "Those things wouldn't be in my department."

The work, originally expected to cost $1.5 million, is now expected to cost $5 million.

On the surface, the project is designed to transform East Executive Avenue between the Treasury Department and the White House, once a serviceable city street, into a well-guarded extension of the White House grounds; a tree-lined promenade that will double as an arrival court for White House visitors.

The contract for the conversion of the avenue was let in February at $3.8 million. But after the work was begun, McDaniel said, the Park Service found it had to replace the electrical line, the water line and the sewer connection. "The electrical line turned out to be much older than Pepco said it was -- last century. And the water, sewer and telephone lines weren't where they were supposed to be. This sort of thing happens all the time when you work on old city streets," McDaniel said.

The work will be paid for by the Park Service, the Secret Service and the Transportation Department.

Big and little gates will close off East Executive Avenue at Pennsylvania Avenue on the north and at Alexander Hamilton Place on the south. Normally, the smaller pedestrian gates will be open on the White House side, so visitors in line to go through the house or casual strollers can walk past the east White House fence.

The larger vehicle gates for the narrow service driveway will open only to admit Marine Band buses, limousines for state dinners and other official vehicles. A double row of 34 willow oaks will be planted in a ceremonial alley. Flowering borders will be replanted three times during the blooming season.

Work, which began in February, should be completed in time for the annual surge of visitors to see the White House Christmas decorations, McDaniel said. "We've been talking about redeveloping this part of East Executive for 10 years."

East Executive Avenue has been closed to public traffic since March 1983, when large flowerpots were placed on the roadway to block traffic and construction began on a security screening pavilion for White House visitors. For some time White House staff parked on the avenue. The permanent closing was announced in December 1984. When work began, White House and Treasury staff parking was moved from East Executive Avenue to a temporary 60-car parking lot carved out of the Ellipse.

East and West Executive avenues were originally closed as a World War II security measure. East Executive Avenue was reopened in 1945.

As designed by Pierre L'Enfant in his 1791 plan for Washington, the land surrounding the White House was part of the "Presidents Park."

Ulysses S. Grant had East Executive Avenue cut through the park after the Civil War to serve visitors arriving at the White House by the side door.

For years after the Jacqueline Kennedy redecoration of the White House, visitors to social functions entered through the Diplomatic Reception Room, on the south side ground floor. Since even social guests now have to go through a metal detector, visitors enter through the East Wing. The new service roadway in the East Executive park will permit guests to social events to be dropped off under the East Wing porte-cochere. Only guests of honor come in through the grand North Portico.