HDD in Landfill waste???
Before the holiday break, DTD completed the installation of a blind condensate drain in an Indiana landfill. The drain will be used to discharge waste condensate from a newly installed landfill-gas electrical generation facility. The drain is installed in a landfill cell such that fluid it discharges will end up in the leachate collection system.
Although the total drilled length was relatively short (119′), drilling in landfill waste is never easy. Specially adapted tooling and drilling techniques are necessary to drill through waste, and allow the successful installation of well/drain materials. Compacted waste presents very difficult conditions to drill for several reasons. Particularly, the waste is expansive, and does not maintain a borehole, and perhaps most challenging, waste almost always contains things that are flexible and strong in tension… quite unlike natural soil. This means that things wrap around the drill bit, quickly turning a 6-inch diameter bit into a ball 12 or more inches in diameter, and consisting of plastic bags, wire, clothing, rope… almost anything you can imagine . See the picture below that shows a drill bit, wrapped tight in landfill waste, and therefore rendered useless for drilling.
Drill bit entangled with plastic and rope waste.
In this case, the installation was made easier as drain was to be installed on a constant slope. The bore was advanced at a uniform pitch, parallel to the clay liner present in the bottom of the landfill. By using a temporary casing to stabilize the bore, the 6- inch diameter plastic drain was installed. A methodical approach and field ingenuity allowed this project to be completed on time and on budget.
In cases where the landfill drain or well is installed with curvature, more significant changes are necessary to the drill tooling in order to allow successful drilling. DTD has completed bores over 1,200 feet in length, passing directly through landfill waste, paralleling the landfill liner. These particular wells were designed to lower leachate levels, while also allowing the collection of methane.
Directional drilling in landfill waste is an extremely challenging process, but in DTD’s experience, a modified approach and care can significantly reduce the risks associated with the process.
Final Installation of the drain materials.