IT SEEMS LIKE IT SHOULD BE SIMPLE — when a garbage dump is full, you plow it under and forget about it.
That oversimplified notion may be why some Harford taxpayers are scratching their heads over the county executive's recent proposal for a $4.2 million bond issue to pay for closing the Tollgate landfill near Bel Air.
But the reality is that shutting down a landfill, especially an older one, is neither simple nor cheap, county and state environmental administrators said.
"Back then, when you opened a landfill you didn't expect to have to pay to close it," Maryland Department of the Environment spokesman Michael Sullivan said of older dumps like Tollgate, which opened in the early 1950s.
"The (operators) did things that were in accordance with solid-waste disposal laws of the day," Sullivan said. "But with today's growing environmental consciousness, it's a lot different. It's very costly. And now people are saying, 'My God, it's $4.2 million to cap it? It should be that much to build one.' "
Early estimates for closing -- or capping -- the 60-acre Tollgate actually have checked in at about $6 million, said Robert Donald, deputy director of the Harford Department of Public Works. However Donald said he believes costs can be shaved to the amount of the proposed bond issue.
The objective of capping a garbagedump is to render it impermeable to rain, Donald said. If water wereto seep through the more than three decades of garbage, it could pick up pollutants, which could then be carried into drinking water.
That's a major consideration in the case of Tollgate, because it's located in the 600 block of North Tollgate Road, near residential areas.
There are several ways to cap a landfill, but the method the county has proposed for Tollgate involves covering the site with a synthetic sheet, called a liner.
Before covering the dump, administrators must take into account methane gas produced by the decomposing garbage, Donald said. Because methane is flammable and explosive, simplycovering such a gas source with impermeable plastic sheeting could be akin to creating a crude bomb.
So before capping Tollgate, whichDonald said averages about 30 feet deep in garbage, the county is constructing a "gas-collection" system. This network of pipes will drawmethane gas to a central above-ground location where it will be burned off.
"If we put the cap on first, we're afraid we'd have to keep poking holes in it" while constructing the gas-collection system, Donald said.
By state law, a filled dump must be capped within three years of its closing. Tollgate last received garbage in July 1987, he said. But the state granted an extension so the county could finish building a $2 million gas-collection system, which the county already has paid for.
Once the gas-collection is completed, administrators can begin the complex procedure of capping the dump.
Before the liner is put in place, the entire location must be graded such that the land slopes gently away from center. That will coax rainfall towash away from the site.
The county's capping plan -- which was approved by the state in 1989 -- calls for a series of layers: 2 feet of soil, then 2 inches of slate dust, the synthetic liner, 6 inches of sand, and 2 more feet of soil, all topped with grass.
The state requires that the synthetic liner -- made of polyvinyl chloride, commonly known as PVC -- must be at least 20 millimeters thick.
After the capping is done, the county plans to convert the site into a park, Donald said.
The landfill was opened and run by the town of Bel Air. The county took it over in the 1950s, Donald said. Tollgate was the county's primary garbage dump until the Harford Waste Disposal Center -- known as Scarboro landfill -- opened near Dublin in 1987.
The greatest capping costs lie in the liner and importing dirt for covering the dump. Donald said the cost of bringing in and spreading the dirt likely can be cut.
The gas-collection system should be in place early next year, he said. The capping will take another 12 to 18months.
Even when the project is finished, soil, ground water andair sampling will continue indefinitely, Donald said.