Woking, on the outskirts of London, dates back to the 8th Century, although in recent years is most commonly known for featuring in H.G. Wells War of the Worlds, and being part of the London Commuter belt. The Victoria Square development in the centre of the town, is crucial to the long term regeneration of the area, bring new housing, jobs and business to the heart of Woking.
The Victoria Square development consists of two high rise residential towers, a new hotel, as well as extensive commercial space and public services. Of these new structures, dewatering was required for one of the residential towers.
The site is underlain by the Bagshot Formation. Although this formation is predominantly granular consisting of silty sand and gravel deposits, it it also typified by a comparatively low permeability. Therefore in order to enable construction in dry conditions, a perimeter ejector well system was installed.
Abstracted groundwater is typically discharged in to either a local water authority asset such as a sewer or in to a local water course, however, due to restrictions on the site it was necessary for a recharge system, comprising a number of deepwells, to be installed approximately 50-100m to the east of the dewatering system. One of the main potential side-impacts of a recharge dewatering system is both the capacity of the underlying strata and whether discharged groundwater will recharge the excavation. In order to minimise this risk a short recharge test is undertaken to ensure sufficient capacity and as well as the zone of influence of the system. The installation of a range of external monitoring wells to a range of depths enabled monitoring of the success of both the recharge and dewatering systems throughout the works.
The success of the dewatering system and the recharge system were paramount to the smooth running of the overall project and to the regeneration of the town.
- LOCATION: Woking
- CLIENT: Sir Robert McAlpine
- MAIN CONTRACTOR: Hillstreet Construction