Bloomfield Road Stormwater Storage Tanks, owned by United Utilities PLC, were constructed in 1999 in Blackpool UK to provide 60,000m3 of storage to prevent overflow discharges during the summer bathing water season. The asset comprises two buried tanks (36m diameter and 40m deep) constructed as circular diaphragm walls. Significant groundwater inflows with minor fines content and turbidity up to 48l/s have been reported entering one of the tanks since 2001. From 2008 an increase of fines ingress has been observed indicating potential for progressive failure of the underlying formation strata. The site stratigraphy comprises predominantly glacial superficial soils overlying an interlaminated Mudstone/Gypsum and Halite sequence. Groundwater inflows were likely to have initiated failure mechanisms in the formation strata including fines loss, dissolution of both gypsum and halite and potentially significant voiding. An innovative event tree risk analysis tool was developed to identify and allow a focused remedial works design and a cost effective solution to be planned. The main works implemented comprised: sealing of the base slab joint by resin injection; contact grouting beneath the base; ground investigation works including cross hole tomography geophysics; and grouting within the Mudstone formation. This paper describes the implementation of the project which was completed ahead of programme ensuring continue
