Prudhoe Fire Station Task: Set up and drilling commences
Mobilisation of the drilling phase of construction begins.
During our works at all fire stations, we need to ensure that we do not interfere with the operation of the station as services must continue as normal. There is also an ambulance crew working from Prudhoe Fire Station in addition to the fire crew. This offered a particular challenge with regard to borehole placement as we have had to leave space for the ambulance and fire appliance to be able to make a quick exit at all times.
The ground array at Prudhoe Fire Station totals four boreholes to a depth of 174m each (696m combined); the heat pump specified for this site is a 24kW Kensa Twin Compact model.
Information supplied by the Coal Authority indicated that it was likely we would encounter old workings below the site. Drilling coal seams offers its own challenges; coal itself can become very hot and spontaneously ignite if drilled incorrectly. To prevent this it was decided to utilise the water drilling method which uses water pumped down the centre of the drill rods to flush the spoil back up. As well as keeping the drill head cooled this method of drilling is much cleaner than air drilling as the spoil is more easily managed.
Further to this coal workings can contain harmful gases meaning all of the drill teams will be wearing personal gas detectors with another positioned at the top of the borehole.
It is our standard practice to collate as much pre-construction information as possible for each site including service maps for gas, electric, water and telecommunications. This allows us to try and position boreholes away from expected services. As well as reviewing the maps we use CAT and Genny scanning devices to locate cables and pipe work not listed on utility plans. And finally we usually hand dig the first 1.2m of a borehole so that any unidentified services can be found.
Prudhoe Fire Station often houses large 25 tonne plus machinery and the site is laid with a reinforced concrete pad. Of course, this frustrates our efforts to hand dig! Therefore, to get through the reinforced concrete we have been using a 450mm diameter diamond drill bit to core through the concrete and allow hand digging to commence.
The first borehole was installed to designed depth and the rig has begun drilling the remainder of the holes. Workings were encountered at a depth of 60m and there appears to be a small void approximately 1m deep at this point. The borehole will be grouted from the bottom up to the floor of the void at which point we will fill the void with gravels and then grout on top of this to the surface.
Watch the first borehole being drilled at Prudhoe Fire Station:
Next week’s key project stage: Drilling continues at Prudhoe Fire Station and commences at Amble Fire Station.
Keep following our blog here to stay up to date with this first project between Kensa Heat Pumps and Northumberland County Council.
Project in brief:
- Three fire stations operated by Northumberland Fire and Rescue Service;
- Heated by electric night storage heaters which have reached the end of their useful life and need replacing;
- A Kensa Twin Compact ground source heat pump system installed inside each station;
- Borehole ground array;
- Sequential installations to be completed in Summer 2018.
Read more about the background to this first project between Northumberland County Council and Kensa Heat Pumps here.