Ulwell Reservoir, Swanage
Access to this elevated site is extremely difficult. Signs of superficial slippage in 2000, triggered boreholes investigation and slope analysis; could there be a catastrophic leakage of water? Should the site be abandoned and relocated? An older reservoir at a lower elevation had been demolished.
We concluded the reservoir was securely founded into Chalk. There was no significant risk of global instability, but the buried concrete structure could become locally exposed.
Reinvestigation in 2012 reached the same conclusion. A programme of localised stability works including ground improvement, soil nailing and drainage, was recommended.