Beach Drive in Rock Creek Park near the National Zoo was closed for tunnel renovation 10 weeks ago amid a publicity blitz orchestrated by the National Park Service to warn motorists to find alternative routes.

The mile-long road, which is used by 30,000 motorists a day from Upper Northwest and Montgomery County, was reopened yesterday.

Without fanfare.

Hardly anyone turned out for the occasion. Only a few motorists used the newly opened road during morning rush hour. And many drivers continued to avoid Beach Drive in the afternoon.

Why didn't the Park Service call as much attention to the reopening as to the closing?

"No particular reason," said spokesman Earle Kittleman. "We hardly ever announce reopenings . . . . Traffic just begins to flow."

Kittleman said people who called his office this week were told about the reopening. "And we announced it to Dr. Gridlock, who had it in his column in The Post."

Many motorists never got the word.

Taxi driver Tekle Ghebremedhin learned about the reopening yesterday afternoon when a reporter asked him to drive through the zoo tunnel. Ghebremedhin said he couldn't because the tunnel was still closed.

The 900-foot tunnel under the National Zoo opened in 1966 but has deteriorated in recent years, primarily because of the failure of its drainage system, which had allowed water to enter the tunnel and caused tiles to fall off the walls.

Under a contract administered for the Park Service by the Federal Highway Administration, the J.A. Blanck Co. of Lanham was hired to repair the damage and install new lights by April 30 for $842,000. In late March, the Park Service announced that four more weeks and an additional $200,000 would be needed.