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Landfill Questions and Answers Why do county commissioners want the landfill? • New federal regulations forced the county to close its old, unlined landfill in December 1997. Since then, the county has been hauling waste to a newer landfill in Sampson County at more than twice the cost. Why not build a small landfill for local wastes only? • The costs associated with siting, designing and permitting what is called a “Subtitle D municipal solid waste landfill” are enormous – in excess of $1 million – even if the landfill is small. Columbus County decided to get out of the waste handling business in 1986 and turned it over to private contractors. Private contractors are only interested in owning and running a landfill if it handles at least roughly 10 times more waste than what is generated in Columbus County. Why is the proposed site in the Green Swamp? • Because that’s where county commissioners told developers to look. Commissioners said they believed the remote, sparsely populated area would be less controversial than sites closer to communities. What about other sites? • Engineers identified 13 potential sites more than five years ago. The outcry from residents in Mollie – the top of the preferred site list – led commissioners to drop that proposal. Commissioners later agreed on a site in Clarendon. Further soil studies showed the site wasn’t feasible. At that point, the private developer bowed out because commissioners refused to put other sites on the table. Commissioners instead directed developers to see if there were suitable sites in the Green Swamp. How can they put a landfill in a swamp? • The Green Swamp is a general term applied to a vast area of Columbus and Brunswick counties. It is a mixture of landforms, including streams, bottomlands, savannas and dry ridges. The actual waste area would destroy five acres of protected wetlands and is outside the official designation of the 100-year floodplain. Are landfills giant dumps? • No. Dumps had little or no rules nor environmental safeguards. That’s why EPA and the state forced them to close. What’s the difference? • Federal and state rules dictate the location, design, construction, operation, maintenance and closure of landfills. • They must be at least four feet above the seasonal high of the groundwater. • They have a two-foot-thick layer of clay at the base, topped with plastic as thick as 10 milk jugs (called high-density polyethylene HDPE). The “dual” liner is designed to prevent leaks. • Atop the plastic liner, perforated pipes suck out the water that drains through waste. This water – called leachate – goes to storage tanks before being treated elsewhere. • Pads and a filter layer protect the piping. Leachate must not be allowed to accumulate. • Waste must be covered with six inches of suitable soil at the end of the day to deter animals, odors and pests. How would we know if the landfill leaked? • Assuming there’s no visible damage, leaks are supposed to be detected by a series of strategically placed monitoring wells surrounding the landfill. The presence of pollutants in these test wells triggers requirements for ever-increasing, more detailed tests. Say tests confirm a leak. What then? • The law requires owners to take remedial actions to purify the water or prevent it from leaving the property. Pumping and treating, ditching, air sparging – using air to release contaminants – and blocking the pollution are some of the methods employed. All are expensive and slow. How fast would a leak travel? • The law assumes that the HDPE liner is essentially impermeable. If there were a breech of the HDPE liner, the clay liner is supposed to hold contaminants for 19.3 years. Using the known speed of groundwater travel time at the site, a leak that left the clay liner could reach the property line in about two years. • Therefore, an undetected leak that was not cleaned up could be off site in roughly 21.3 years. (Assumptions: the clay liner performs at design specifications and is burdened with leachate having a constant hydraulic pressure; the leak occurs at a point nearest the property line and moves at the higher of range of known groundwater speeds). How many landfills like this one are there in the United States? • More than 3,000. How many landfills like this one are in North Carolina? • 42 How many landfills like this one have had significant pollution violations in North Carolina? • None. Pollutants have been detected in monitoring wells at six sites. All but one detection came from problems not associated with the liner system. One detection has not yet been resolved by the state. Sources include the minutes from the Columbus County Board of Commissioners, Riegel Ridge Corp.’s site suitability application for a municipal solid waste landfill, the U.S. Environmental Protection Agency and the state Division of Solid Waste. Certain numeric calculations include the assumptions stated and were reviewed by a certified professional engineer. 03-2001 |
