A 132kV powerline tower needs to be replaced and relocated with new infrastructure in Neath. This must be done without contaminating the nearby waterbody, the Cefn Cwrt Reservoir, or changing its inflow volumes.

The hydrogeology of the area is quite complex, with four distinct regions of bedrock in a 400m radius of the existing and proposed tower sites. The hydrology of the area is further complicated by two control weirs linked to the Cefn Cwrt Reservoir, each with its own individual catchment.

Time for WHS

WHS needed to complete a hydrogeological assessment highlighting the potential impacts of tower relocation on the surrounding catchment and the Cefn Cwrt Reservoir and to address concerns.

Our assessment identified a number of key short-term potential effects on the Cefn Cwrt Reservoir as a direct consequence of the planned work, including:

• increased sedimentation in surface water runoff from disturbed ground
• pollution from accidental spillage of chemicals or fuels

We outlined appropriate actions to mitigate these effects, including:

• sediment control measures downstream of any works
• recommended periods where excavations cease such as during intense rainfall
• designated refuelling areas and controlled disposal of solid and liquid wastes off site.

We also identified potential long-term impacts including concrete leaching and changes to subsurface runoff flows. These risks are not significant when appropriate materials are used.

Result: The client has clear recommendations to put in place, to make sure the work does no harm.