In September 2010 Raeburn accepted the challenge of constructing 8 geothermal boreholes at the site of George Heriot primary school in Edinburgh’ s historic Grassmarket area. The site was characterised by resitricted working space and tight access.
Our experienced drillers drilled through approximately 3.5m of soil and fill deposits (comprised of concrete and brick) to reach bedrock. The borehole was then drilled to a depth of 125 metres through basalt and volcanic ash deposits (the same materials which form nearby Edinburgh Castle Rock).
A 32mm diameter polyethylene geothermal loop was then installed and the borehole backfilled with a thermally enhanced grout mix. The grout is made up of bentonite (a natural clay mineral) and fine sand and its role is to prevent movement of water in the borehole while providing a thermally conductive interface between bedrock and the geothermal loop.
After the loops were installed quality checks were performed to ensure the integrity of the loops under pressure unobstructed flow.