ESI, now part of Stantec, were commissioned by York Potash Ltd to undertake a quantitative assessment of the impact on groundwater of the development of a proposed Potash Mine.
Situated in the North York Moors National Park (NYMNP), the site also had Ugglebarnby and Sneaton Low Moor Special Areas of Conservation (SAC) to the west and south. Additionally, potentially impacted receptors included a number of spring features in the surrounding area associated with a shallow aquifer system.
The minehead comprised two access shafts, a ventilation shaft, a process area, two inclined access tunnels, a tunnel access portal and a mine building. There were also two 44.5km pipelines and works to create and pump the product in slurry from the minehead to support facilities in Teesside.
The principal potential impacts were identified as the interruption of groundwater flows resulting from emplacement of below water table impermeable structures and the dewatering (both temporary and permanent) associated with excavations in the proposed construction.
To quantify the impacts, a multi-layer Modflow groundwater model was developed to simulate the complex multiple aquifers within the Jurassic formations.
The conceptual model and model parameters were supported by field hydraulic testing, designed and supervised by our team. The model was also calibrated to groundwater monitoring data collected at the site.
Used to predict the impacts on spring flows and water levels at the SACs, the model subsequently assisted with the design of impact mitigation measures, including enhanced recharge areas and cut-off walls.
We also undertook preliminary screening calculations to identify the potential groundwater pollution impacts of a number of associated proposed non inert, non-hazardous waste facilities to specific hydrogeological receptors.
Planning permission was granted in 2015 enabling extraction of evaporite minerals using underground mining techniques to depths of 1.6 km. Moving forward we are now taking an ongoing role in assessing any design change impacts to groundwater.
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