East Executive Avenue, which in recent years has been closed to public traffic as a White House security measure, is being turned into a pedestrian mall to be used for White House tourists and ceremonial events for visiting dignitaries.

The $3.8 million mall will be between the White House and the Treasury building and occupy a block-long area between Pennsylvania Avenue NW and Alexander Hamilton Place.

Prism Construction of Capitol Heights began construction on Monday and is scheduled to complete the project by October. Eight-foot wooden fences have been erected at the entrances to the construction area for safety reasons, said project manager Pat Garbey.

The street, which was closed to public traffic in 1983 when a security screening pavilion was constructed for White House visitors, has been used since as a parking lot for security vehicles and official White House visitors.

Donald L. Heilemann, a spokesman for the National Park Service, said the mall would include benches and trees and eliminate the congestion created by parking traffic and White House tourists.

He said there would be a series of pedestrian and vehicle gates at both entrances to the mall as part of new security measures. Although the pedestrian gates will be open most of the time, Heilemann said all of the gates could be closed to seal off the area in case of an emergency.

At various times, the Secret Service has taken a number of security precautions in the area around the White House to guard against possible attacks by vehicles carrying bombs. In 1983, several trucks were parked at the southwest gate and two sand-filled trucks were placed in front of the White House. Later, three-foot-high concrete barriers were placed at the southwest gate.

The mall project is being financed by the Secret Service, the White House, the Park Service, the Treasury Department and the Federal Highway Administration