Middlewich Flood Alleviation scheme

Geotechnics Limited recently undertook a site investigation for United Utilities Water plc for their Middlewich Flood Alleviation scheme.  The scheme involves the upgrade of the ageing sewer system to accommodate more frequent storm flood waters along Booth Lane and Cross Lane.

The Clients’ project proposals include for the design and construction of a new rising main along Booth Lane and an 18m deep, 15m diameter storage detention tank.

The site was underlain by a variable thickness of Made Ground over Glacial Till of firm to stiff clays with sand and gravel lenses.  Solid strata comprising Mercia Mudstone was encountered at a depth of 33.5m below ground level.

The investigation comprised eleven cable percussive boreholes, one with rotary Geo Bore S Wireline techniques and one with rotary follow on together peizometer installations and in-situ material testing.  Ground protection mats were required to prevent damage to grass surfaces at some locations.

A further three boreholes were commissioned for the purpose of acting as water wells to observe groundwater drawdown within an aquifer during a pumping test.  Monitoring wells were installed within the boreholes at depths between 17m and 26m below ground level within the aquifer.  The pump tests were designed to obtain information on the aquifer properties to allow the design of temporary groundwater control during construction of the detention tank.

A microgravity survey was also carried out by the specialist geophysical contractor Terradat on behalf of the Client.  The microgravity survey was carried out over an area around the proposed location of the storm water detention tank on recreational ground off Warmingham Lane.  The aim of the survey was to locate potential voids associated with salt workings in the area – none were encountered. 

All site works were supervised by Engineers, John Harrison and Jonathon Gray under office project management by Paul Hayes.