A 15m deep excavation into bedrock was being considered at the site of a proposed electricity converter station in North East Scotland. Despite the granite geology, groundwater seemed abundant at the site with generally soft and boggy ground conditions and several deep boreholes from previous phases of site investigation showing artesian conditions. This suggested that groundwater management would be a key risk to the construction project.

ERS was appointed by the developer to install groundwater pumping and monitoring wells, undertake pump testing and monitor groundwater to support the design of the building. 

The key technical challenge was the complex, unpredictable, and at times hard to drill geology due to the weathering and fracturing. The poor ground conditions combined with the poor winter weather and limited daylight provided a further logistical challenge.

ERS first installed a 400m long temporary road to facilitate access to the drilling area during the testing programme and reduce reinstatement requirements. A total of 8 boreholes of either 200mm or 300mm diameter were drilled up to 30m deep to install monitoring and pumping wells.  Monitoring wells comprised nested (shallow/deep) piezometers to allow groundwater level monitoring from various depths.

Step and constant rate pump tests were undertaken under permit from SEPA.  Silt management was provided at the pumping well prior to discharge to surface water.  Flow and level data was continuously monitored and recorded during the tests.

ERS collated and processed all data produced during the testing, comprising dips and level and flow continuous data to the format required by the client’s design team.

Following completion of the project, we were given the following positive feedback from the client:

“ERS worked well to achieve our challenging project brief, as well as keeping on top of the resourcing, planning, cost, and communication.”