our services
- Leachate Boreholes
- Landfill Gas Wells
- Water Borehole Drilling
- Monitoring Boreholes
- Impact Wells
- Water Treatment
Leachate boreholes for Leachate Control
Leachate Boreholes
Legislation requires that leachate levels in landfill sites can be controlled and monitored. Unfortunately due to differential settlement, and silt deposition, many leachate boreholes fail or become inefective.
The installation of replacement leachate boreholes necessitates drilling to the drainage blanket at the base of the landfill. A borehole that does not intercept the drainage blanket is effectively useless. Given that the drainage blanket is only 300mm thick the requirement to intercept the drainage blanket,without damaging the containment engineering, places considerable demands on the drilling operator.
Furthermore, it is likely that the waste at the base of the landfill site will be saturated with leachate and conventional drilling operations, using a barrel auger, will fail as the arisings are lost from the barrel on retraction.
Faced with the challenges of intercepting the drainage blanket, without compromising the liner, coupled with the requirement to extract saturated waste has made leachate retrodrilling a challenging operation.
Dragon Drilling recognised the demand for leachate well retrodrilling and has developed equipment and drilling techniques that have been 100% succesful in achiveing borehole depth without damaging the landfill liner. Every leachate retrodrill since 2005 has been succesful.
Why are Dragon Drilling so Successful?
In 2005 development work was started on a drilling shoe specially designed for drilling through waste. The design was perfected in 2006 and patent GB 2426988 was granted on the 20th May 2007. By using a specialist drilling shoe, Dragon Drilling are able to drill deeper and more efficiently than other operators.
The use of a specialist drilling shoe, coupled with instrumentation on the drilling rig console and highly trained Lead Drillers, enables the drainage blanket to be identified as soon as the drilling shoe makes contact. The use of this equipment and drilling techniques has enabled Dragon Drilling to maintain the enviable record of never having penetrated the containment engineering on a landfill site.
In 2006 a drilling technique was developed 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 on 13th August 2008 for the conditioning of saturated waste from a borehole.
The ability to intercept the drainage blanket, coupled with the technique to remove saturated waste from depths of up to 70m, has enabled Dragon Drilling to install leachate boreholes on sites where conventional drilling techniques have repeatedly failed.
Success is due to innovation, development, training and experience.
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 65m.
An alternative to using MDPE casing is to install Ø244mm steel casing within the Ø406mm steel casing, which is remove 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.
All steel casing is fabricated at our workshop in Ruthin.
