EROSION CONTROL/Soil aqueduct is solution for expanding landfill

The Franklin County Sanitary Landfill, owned by the Solid Waste Authority of Central Ohio, is located adjacent to Interstate 71 near Columbus, Ohio. The 120-acre sanitary landfill is nearing completion of its permitted air space, and a permit is pending for a 243-acre expansion.

As the authority prepared to construct Phase VI of the landfill last year, it needed to find a method to control runoff and replace a sedimentation pond that had accommodated runoff from the first five phases.

The pond had been sited on the land upon which Phase VI would be built. Its location within the permitted area was unusual, according to Chuck Satchwill, Cincinnati-based project manager for SCS Engineers, Long Beach, Calif., since sedimentation ponds are normally situated off-site.

A temporary sedimentation and erosion control pond was constructed atop the existing closed landfill while the sedimentation pond in Phase VI was removed and the liner and leachate collection system installed.

The temporary pond served to divert stormwater runoff away from the Phase VI construction activities. However, the temporary pond could not provide the necessary long-term sedimentation and erosion control.

“We had to find a method to control sedimentation and erosion once that pond was eliminated,” recalls Satchwill.

The presence of I-71 at the southeast corner of the landfill turned out to provide an unexpected benefit that would help resolve the problem.

During the 1970s, the highway had been built slightly above the surrounding flat land to improve runoff and drainage. Borrow material taken from nearby farms created borrow pits that had become relatively shallow ponds with little or no watershed.

One such pit existed between the landfill and I-71. The simple solution for sedimentation and erosion control would be to direct runoff to that borrow pit, located about 200 feet away.

The four-acre pond would also provide water for spraying landfill roadways to minimize fugitive dust emissions. Directing stormwater runoff to the pond would ensure a constant supply of water for dust control.

It seemed like the perfect solution to a multitude of needs, but a nettlesome problem stood in the way. The borrow pit was isolated from the landfill by a major drainage way — a 15-foot-deep, 40-foot wide earthen ditch — that collects hundreds of acres’ worth of runoff from farmlands west of the landfill.

The ditch, which flows west-to-east, had to be maintained to accommodate the stormwater being carried through the site. A connection between the landfill and borrow pit would run perpendicular to the ditch.

Rather than dig a drainage channel connecting the two areas, the ultimate solution proved to be construction of a drainage aqueduct to carry the stormwater runoff from the landfill surface to the borrow pond. The aqueduct is an earthen containment structure made with fatty clay berms each about four feet high.

The site operator, Laidlaw Waste Systems, Columbus, Ohio, constructed the soil aqueduct above the surrounding grade and lined it with rock channel protection to minimize scouring and siltation of the existing pond.

Corrugated metal drainage pipes were placed in the existing drainage way to ensure uninterrupted flow in the channel.

The system is working as intended, says Satchwill. The owner, the regulatory agency and the site operator said that the system requires almost no maintenance and provides the stormwater controls necessary for the landfill operation.