ADP Group Ltd can provide a specialist borehole grouting service for the decommissioning of monitoring wells which have served their purpose and are no longer required.
These boreholes, if left open, pose a risk of contamination due to their possible pathway into (for example), a major aquifer.
Boreholes can be closed/decommissioned via two different methods, further information on each method can be found in the next two pages.
Typically, no matter what the method, boreholes are closed via a
cement/bentonite grout, ordinarily mixed via a venturi or paddle mixer, at a ratio of 4:1.
Using bentonite and cement grout to close boreholes is a quick, efficient and cost effective method; we are able to inject the grout from the base of the borehole to the surface, using a tremmie pipe in conjunction with a Putzmeister pressure grouting unit, thus ensuring all gaps are filled with a fast setting grout whilst removing all contaminants.
Boreholes are then reinstated at the surface to match the existing surroundings; with either concrete, tarmac or turf.
Over Drilling & Pressure Grouting
Over-drilling of the existing borehole is another technique used, this involves over-drilling of the well pipe with either casing or augers, removal of the borehole pipework (pulled either by hand or with the rig winch), drilling out the original bore and tremmie grouting from the base of the borehole to the surface.
The surface is then reinstated on a like-for-like basis with the surrounding finish.
Over-drilling and pressure tremmie grouting provides a more thorough borehole closure, ensuring that all original installation and associated installation material is removed prior to the borehole being closed with a cement/bentonite grout.