The Palm City, FL landfill was closed and capped in stages over a period of approximately 10 years. As areas of the landfill were closed, a LLDPE cap system was placed over all areas of waste in Cells 1 through 4. The last cell to be closed, Cell 2, was designed prior to Hurricanes Frances and Jeanne hit the County. The resulting hurricane debris cleanup kept the landfill open several months (and thousands of tons) longer than originally planned. Extra waste ended up being placed far from the nearest gas collection well, in the area where Cell 2 connected with Cell 1 (already capped) forming a corner. At the time of closure, the extra waste, wet conditions, and Landfill Gas created dangerous conditions for workers trying to connect the Cell 1 geomembrane cap to the Cell 2 geomembrane cap in a trench. The decision was made to seal the geomembranes together with a geocomposite strip, which has typically worked fine in the past along the bottom edge of the landfill cap. Years later, odors and dead grass along part of the intersection, followed by a surface emission exceedance of 500 ppm indicated that an expansion of the landfill gas collection system was necessary.rnSeveral alternatives were considered for the collection system expansion-one or more vertical wells, a new or extension of the existing horizontal well. All had issues on the steep erosion prone slope. Since the gas issue was limited to a small area, it was decided to install a horizontal collector along the intersection of the two cap membranes, and also to fuse the membranes along the boundary, as originally planned. To simplify installation and reduce costs, a relatively new, flat perforated collector piping product was chosen for the new horizontal collector. The repairs resulted in the desired elimination of landfill gas emissions along the tie-in between the two landfill cells.
展开▼
