This helped in referencing the percentage of work completed on-site in conjunction with standard GPS survey equipment.
The grid overlay system also assisted all site staff to reference their individual parcels of work on-site when explaining issues, as they all have the grid overlaid on Google Earth. When they use the Google Earth map location tool, it shows precisely which work grid they are in.
The majority of the site was covered with a 300mm reinforced concrete slab with several large flooded voids present and multiple stockpiles in the southeast and southwest. These notably included a 70,500m3 pulverised fuel ash by-product generated during the power station’s coal and oil manufacturing period.
The bedrock geology of the site consisted of gault formation, Upper Greensand to the southern boundary and superficial alluvium deposits across the central and northern parts.
Works to the site began with the clearance of approximately 55,000m2 of topsoil, trees and associated vegetation. In-situ and ex-situ bioremediation works occurred along with the cut and fill, compaction and chemical and geotechnical testing of approximately 120,500m3 of material.
19,000m3 of grouting was carried out to various underground obstructions utilising an 80:1 PFA/OPC mix. The demolition of an above-ground reinforced concrete treatment lagoon also allowed the placement of a capping layer across the site to act as a working platform for a piling rig.
Stage three at Didcot Power Station involved the design and construction of a 960m watercourse including break-out and diversion of an existing. The watercourse spanned fifteen metres in width and up to three and half metres in depth with connection being made from an existing 1500 box culvert which carried the existing watercourse from Milton road to the south. The profiled excavation resulted in over 50,000m3 of volume of reworked natural clay.