How one city makes mountains out of trash hills

The city of Virginia Beach cordially invites you to spend the afternoon on their trash heap. Bring the family, a kite, fishing tackle, even a picnic lunch. No, it's not some perverse scheme to lure tourists to this resort city. It's the outcome of a unique and successful project for disposing of garbage by making something useful out of it. The basic plan goes like this: Pile the garbage into a mountain, cover it with dirt, and turn it into a park.

The result is Virginia Beach's Mt. Trashmore - 68 feet tall, 900 feet long and 300 feet wide. This grass-covered mountain is surrounded by lakes and recreation areas. It has become a model of innovative garbage disposal and one of the city's most popular parks. The project has proved so successful and economical that the city is now building a second garbage mountain.

Even though the original Mt. Trashmore project was completed in 1970, it still presents a unique approach to garbage disposal. According to Larry Hosmer of Black & Veatch, Engineers-Architects of Bethesda, Md., building a garbage mountain is not in itself exceptional. He says because of high water tables, above-ground burial is often done in cities in costal zones.

''The success of the Virginia Beach project,'' he says, ''lies in the reuse of the garbage, where other cities have simply walked away and left large dirt covered mounds lying around.''

In this flat city, where one of the highest natural elevations, appropriately named Hilltop, is a whopping 14 feet above sea level, the treeless Trashmore looks a little out of place. But the mountain and its recreation facilities make for a very popular park. There are picnic areas, tennis courts, ball fields, and plenty of open space for kite flying and frisbee throwing. There's a skateboard bowl and a 700-foot-long soap-box derby track. And there's a large recreational lake for boating and fishing, stocked with carp, perch, and striped bass.

In January the city received a building permit for a second Mt. Trashmore, which is now under construction. P. Wade Kyle, solid-waste administrator for Virginia Beach, says this more ambitious project will be 150 feet high, and he expects it will swallow the city's garbage until the year 2000. It now eats up 1 ,600 tons of garbage a day.

Recreational plans for the second mountain have not been fully developed, but they will probably include two lakes and a novelty to this Southern coastal plain - a ski slope covered with artificial snow.

Mr. Kyle says the city turned to mountain building to fulfill three goals: to keep refuse away from the ground water; to get rid of garbage without wasting a lot of valuable land; and to create a useful facility out of unwanted material.

Building Mt. Trashmore took four years and lots of garbage. Each layer of trash was compacted to a depth of 18 inches and covered with six inches of dirt, sealing the garbage in its own small building block. Garbage was compacted under tremendous pressure to insure that there would be no problems as the mountain settled.

The dirt cover for the garbage was dredged from swampy areas next to the dump site, which then became the neighboring lake. More than 640,000 tons of garbage went into the first mountain.

Mr. Hosmer, the project manager for Trashmore II, says the city has gone to great lengths to operate in an environmentally sound manner. The city is not exactly using ''space shuttle technology,'' he says, but the plan does pull together several innovations that make it a state-of-the-art project. These include the lining used to protect ground water, and a treating process for fluids that are generated as the garbage decomposes and that might become health hazards.

In addition, costs have proved to be a good deal lower with this form of disposal than for burning or other more conventional disposal methods.

But there were challenges. Because of the heat and methane gas produced as garbage decomposes, one portion of the mountain where garbage remained uncovered once caught fire. The fire was extinguished, trash was more conscientiously covered, and the methane now is vented harmlessly.

The Trashmore projects have drawn visits from sanitation officials from Texas to Germany to China.