Since winter began, more than 24,000 tons of salt have been poured on Washington area roads and highways to melt the snow, make the streets safer for driving ans contribute to a national total of property and environmental damage estimates annually at $3 billion.

That figure comes from the Environmental protection Agency, which has been studying the effects of road salt for several years and has concluded that it is, at best mixed blessing.

The thing that salt does best is accelerate corrosion - rust - on automobiles. The EPA estimate is that $2 billion of damage a year is done in that regard alone.

Half a billion dollars, the EPA said, goes into repairing bridges and elevated roadways that break down before their time because road salt seeps through the concrete to the reinforcing steel and accelerates its corosion.

A year ago, for example, four Washington bridges on major rush hour arterials were closed or carrying reduced traffic so crews could repair salt-induced damage.

Some of the work the National Park Service is doing on the George Washington Parkway and the Memorial Bridge right now is to repair and replace crumbling concrete damaged by salt.

Most of the rest of salt damage, the EPA figures, is done to water supplies. When excessive salt is washed into rivers or seeps into underground rock formatins, it can increase the salinity to unhealthily high levels.

A major problem, the EPA discovered in tests four years ago, occurs when highway departments store salt on the ground in uncovered piles much of it into streams and water supplies.

Since publication of that widely distributed study. Maryland has constructed "salt domes," covered containers scattered about the area, to store salt. The District stacks is salt on concete pads located around the city, and covers the salt with plastic.

Virginia puts the salt on asphalt pads, but does not cover it, according to highway officials. CAPTION: Picture, A little more salt might have helped this pedestrian taking a tentative step at 14th Street and New York Avenue. By Douglas [WORD ILLEGIBLE] - The Washington Post