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Under the hill

The landfill beneath what is now Rothenbach Park in southwest Florida was closed 10 years earlier and covered by a 40 mil high-density polyethylene liner. The liner was seamed and sealed, then covered with three feet of soil and sod.

A network of 54 underground methane wells all attached to a vacuum pump sucks up and burns off gas that is discharged by the decomposing waste. A separate system of pipes collects water, leachate, percolating through the garbage.

Underground, a slurry wall surrounds the landfill and traps the trashy water, until it can be pumped out. The wall is 15 to 17 feet tall and lies on top of a natural bed of clay.

Landfill gas, mostly methane, is collected from the rotting garbage and is burned off at the flare station, located near the entrance of the park. The flare’s flame is barely noticeable during the day. A 30-inch-thick slurry wall blocks leachate from flowing out into ground water. Leachate and ground-water levels are monitored and a differential of 10 inches is maintained. The higher level of the ground water is a safety feature. If the wall is breached, the leachate would not immediately flow out. Leachate, contaminated water passing through the landfill’s 5 million cubic yards of garbage, collects near the floor of the mound, barred in by the slurry wall. The water is sucked into a leachate collection pipe, which is perforated on the underside. The leachate is pumped to a sewage treatment facility just north of the site. As organic matter in the garbage decomposes, gases are released and rise to the surface of the mound. Landfill gas wells on the hill collect the gas and direct it toward the flare station to be burned off. Leachate RCA FLYERS CLUB'S AIRSTRIP BEE RIDGE ROAD HOUSEHOLD CHEMICAL COLLECTION CENTER BEE RIDGE ROAD EXTENSION Leachate collection line Landfill gas collection line MAN-MADE LAKE HIGH-DENSITY POLYETHYLENE LINER LANDFILL GAS WELL FLARE STATION LEACHATE SLURRY WALL GROUND- WATER 10” SOIL CLAY LEACHATE COLLECTION PIPE
HOUSEHOLD CHEMICAL COLLECTION CENTER LEACHATE Soil clay GROUND- WATER 10” 1 2 8 5 3 4 7 6

1 Landfill gas, mostly methane, is collected from the rotting garbage and is burned off at the flare station, located near the entrance of the park. The flare’s flame is barely noticeable during the day.

2 A 30-inch-thick slurry wall blocks leachate from flowing out into ground water. Leachate and ground-water levels are monitored and a differential of 10 inches is maintained. The higher level of the ground water is a safety feature. If the wall is breached, the leachate would not immediately flow out.

3 High-density polyethylene liner

4 Leachate

5 Leachate collection line

6 As organic matter in the garbage decomposes, gases are released and rise to the surface of the mound. Landfill gas wells on the hill collect the gas and direct it toward the flare station to be burned off.

7 Landfill gas collection line

8 Leachate, contaminated water passing through the landfill’s 5 million cubic yards of garbage, collects near the floor of the mound, barred in by the slurry wall. The water is sucked into a leachate collection pipe, which is perforated on the underside. The leachate is pumped to a sewage treatment facility just north of the site.

Jacob Benison, Information Graphic, Sarasota Herald-Tribune, 27 December 2006
SOURCE: Sarasota County

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