The Virginia Highway Department thinks it has just the thing to adorn parts of the Rte. I-66 extension under construction inside the Capital Beltway: Sierra Wall.

Sierra Wall, introduced yesterday at a construction site press conference, was selected with the long-standing opponents of the extension -- one of the most controversial and fiercely opposed road projects in Virginia -- in mind.

It's a textured, concrete barrier, ranging from 2 to 20 feet high, designed to reduce the highway's roar -- if not to a whisper, then to something less than a roar. There are other concrete noise barriers; the thing that sets this one apart, according to Ahmet Anday of the highway department, is that "It is extremely nice to look at."

Designed by Smith Cattleguard Co. of Midland Va., Sierra Wall will line the highway along a 1 1/2-mile residential stretch in Falls Church and cost $300,000.

"I would say that noise reduction played a role in choosing the Sierra Wall," said Anday, coordinator of the air, noise and energy section of his department. "But the wall's main features are that it is maintenance-free, well-engineered and esthetically pleasing."

Smith Cattleguard President Rodney I. Smith said the product has reduced noise levels in California communities. But he, too, stressed esthetics -- "Out in San Jose everything is walled in with Sierra Wall . . . and it looks very nice."

The 9.7-mile, $170 million I-66 extension is scheduled to open next year, linking the beltway with the Theodore Roosevelt Bridge across the Potomac, and it is supposed to lop 15 minutes off commuting time for many Northern Virginians.

But many residents of Arlington and Fairfax counties have long fought it on environmental grounds and still oppose it. Construction began three years ago only after lawsuits and appeals by conservation and community groups failed.

Anday said two community groups, the Arlington and Fairfax citizens' advisory committees, agreed to "the concept" of a concrete sound barrier in meeting earlier this year. But he said he hoped representatives of these organizations, often noted for their vocal opposition to the project, wouldn't show up for yesterday's introduction of Sierra Wall.

The barrier was selected, he said, with opponents of I-66 in mind, and, "It is our experience that these groups always end up opposing construction in the eleventh hour. Our intention was to avoid that kind of delay. So the decision to use the Sierra Wall was just as much for selfish reasons as it is in the public interest."

No one from the organizations he had in mind showed up.

Because the wall is constructed at a factory, its erection on the site is expected to be speedy and may be complete in early November, a month ahead of schedule. "I've heard talk about Metro buses on I-66 starting in December," said Mac Chandler, project manager for the Lane Construction Co.