Highway and street projects costing more than $30 million, including reconstruction of several major bridges, street resurfacing and special safety improvements will be begun in the District in the next 12 months.

James Clark, assistant director of the District department of transportation, said the projects will be paid for with $8 million in federal highway money received last month and uncommitted reserves held from prior federal grants.

The biggest highway projects scheduled for the fiscal year, which began July 1, are all bridge reconstruction projects, including a $14-million project to replace three bridges where 14th Street crosses Maine and Ohio Avenues and the Tidal Basin outlet. All bridges except one on Michigan Avenue will remain open to traffic during reconstruction.

Nine major streets will be given new surfaces in a $2.4 million resurfacing project, and a number of small intersection and road changes will be made as part of an $800,000 safety improvement program.

Here are some of the major projects scheduled to begin in the next 12 months:

Resurfacing of nine arterial streets throughout the city, including Bladensburg Road, Minnesota Avenue, Lincoln Road, Riggs Road, Texas Avenue, and sections of K Street, M Street, Water Street and 9th Street.

Major additions to the city's bike path network, costing approximately $450,000. Design of the 75-mile bike system has just been completed, and this year's work will be the first major construction expenditure. The bike routes will take several forms, including signs on existing streets, construction of special bike lanes or lane widening, and widening of sidewalks for bike routes.

Safety improvements throughout the city, at a cost of $800,000. The improvements will include installation of guard rails, skid resistant pavement, modification of traffic signals, removal of obstacles near the edges of arterial roads, and installation of "impact attenuation devices" designed to cushion the impact of a vehicle hitting a solid barrier near a freeway exit.

Reconstruction of South Dakota Avenue at Fort Lincoln, with the installation of median and turning lanes.District officials will meet with residents in the area, who are concerned that South Dakota Avenue not become a major commuter roadway, before beginning the $2.3-million project designed to serve the Fort Lincoln New Town.

Replacement of the three 14th Street bridges, which cross over Maine Avenue, Ohio Drive and the outlet to the Tidal Basin.

Reconstruction of the Connecticut Avenue bridge over Klingle Valley in Cleveland Park, at a cost of $2.1 million.

Replacement of the Whitney Young Bridge, which carries East Capitol Street across the Anacostia River, at a cost of $8.5 million.

Replacement of the Meggs Bridge on Pennsylvania Avenue across Rock Creek Parkway, at a cost of $2 million.

Replalcement of the Michigan Avenue bridge over the railroad tracks near Catholic University. No cost estimate is available, because the project is still being designed. During part of the construction period, the bridge will be closed and a detour route-set up.

Reconstruction of two Kenilworth Avenue bridges, over Watts Branch and nannie Helen Burroughs Avenue, at a cost of $4 million. Because the bridges carry a freeway-type road, a special detour trestle will be built to handle the traffic while the bridge deck is being reconstruction.

All of the bridge projects will begin within the next 12 months and will take approximately 18 to 30 months to complete, Clark said. All but the Michigan Avenue bridge will be kept open to local traffic, with construction work suspended during the rush hours whenever possible, he said.

None of the bridge projects will involve adding any new lanes, and the new or rebuilt bridges will resemble the old ones except for minor design improvements, Clark said. He said the bridges are simply getting old and are wearing out.

"We've got a lot of bridges in the city - over 300 of them," Clark said. "Many of them are 60, 70 and 80 years old. We are entering now an era of bridge replacement. The bridges are wearing out and we are involved in a program of trying to systematically replace them over the next 10 to 15 years."