Due to differential settlement and silt deposition, many leachate boreholes fail or become ineffective across landfill sites. The installation of replacement leachate boreholes necessitates drilling to the drainage blanket at the base of the landfill else the borehole is effectively useless. As the drainage blanket is only 300mm thick, the installation can be considerably complex. Potential risks include the challenge of intercepting the drainage blanket without compromising the liner and the need to extract saturated waste from the base of the site. Dragon Drilling has therefore developed high performance equipment and innovative drilling techniques that ensure such complex projects are carried out safely and successfully.
As a company operating at the forefront of the drilling industry, Dragon Drilling has patents on many of its drilling techniques. In 2007, we were granted patent GB 2426988 on a specialist drilling shoe, which enables us to drill deeper and more efficiently than other operators. This specialist drilling shoe is used with our drilling rig console to identify the drainage blanket as soon as the shoe makes contact, eliminating the possibility of our activities penetrating the containment engineering on the landfill site.
In 2006, we pioneered a drilling technique that enabled the saturated waste from a borehole to be removed after the physical characteristics of the waste had been changed using a conditioning agent. Patent GB 2431177 was granted in 2008 for the conditioning of saturated waste from a borehole.
All rigs operated by Dragon Drilling are equipped with our recently developed remote winch-operated incline control system for the safe drilling on inclines of 1:3. As with all our equipment, this system was designed, manufactured and tested by our own engineers prior to use.
We are proud to relentlessly pursue new technologies and advanced techniques that improve operating practices within the industry. Our ability to intercept the drainage blanket and remove saturated waste from depths of up to 85m enables us to install leachate boreholes on sites where conventional drilling techniques have repeatedly failed.
Leachate boreholes can be cased with MDPE casing with external diameters of 315mm, 250mm or 225mm. As Ø406mm steel will normally have been used to achieve depth it is possible to retract the Ø406mm steel casing by 1 to 6m to afford protection for the MDPE casing from differential settlement. Some operators prefer to remove the Ø406mm steel casing and Dragon Drilling rigs are powerful enough to remove Ø406mm steel casing that has been installed to depths of 85m.
An alternative to using MDPE casing is to install Ø244mm steel casing within the Ø406mm steel casing, which is removed on borehole completion. The Ø244mm steel has the strength to resist differential settlement and it also enables cost savings to be made as the Ø406mm steel is recovered. Furthermore, the Ø244mm steel option can be used on sites where “hot spots” would destroy MDPE casing.
Some site operators have requested that our steel casing is adapted to minimise any effects on the containment engineering. A design for steel casing with a telescopic section to allow for differential settlement was patented in 2013.