Dawnus carried out several packages of enabling and civil engineering works for a new CCGT Power Station at Uskmouth on the footprint of the demolished A Station.
Works involved de-watering an area of approximately 40,000m2 to 15m depth, excavating 180,000m3 of backfilled material to the existing basement level, the breaking out of the existing reinforced concrete base and pile caps, and surveying the existing piles before filling the excavated void with compacted PFA. All works were carried out within the confines of the existing operating power station and to a very tight programme during the winter months.
Associated works included:
- Extensive ground investigation and testing
- Construction of a new screened ash handling facility with a capability of storing 23,000m3. The reinforced concrete structure included a 3.7m high perimeter canopy consisting of pre-stressed concrete panels, supporting columns and metal cladding.
- Surface water drainage system consisting of two 10m deep settlement tanks including special water clarifier units.
- Construction of two settlement lagoons covering an area of 18,000m2 incorporating deep reinforced concrete settlement tanks and associated drainage. These were formed by installing an impermeable membrane at base which was secured with sand and geotextile protection layers.
- Construction of over 1km of new roads
- De-watering an area of 40,000m2 to a depth of 15m and removing/recycling 60,000m3 of reinforced concrete basement material as re-useable aggregate.
- Modifications/strengthening works to an existing jetty
- Installation of a cofferdam approximately 40m long by 25m wide and 10m deep
The site was situated adjacent to an environmentally sensitive estuarial and wetland area, designated an SSSI, and the works were successfully completed on a congested site alongside other major construction activities and adjacent to the operating power station.