GEOTECHNICAL CONTRACTOR May Gurney has remediated the site of a new Asda supermarket in Long Eaton, Nottingham.
Working for consultant MJM Consulting Engineers on behalf of client Asda Stores, May Gurney Technical Services installed a 550m long reactive containment barrier to prevent pollution migrating in the groundwater.
The site used to be a fuel depot and soils and groundwater were polluted with petroleum hydrocarbons. The low permeability reactive barrier, comprising 600,8m deep soil-cement columns, was formed by the firm's piling division using a modified CFA auger to mix the soil with cement based grout and additives.
Some of the more contaminated soil was removed and replaced with clean fill and recycled material from site. May Gurney Site Investigation characterised the fill material and carried out insitu testing after placement to ensure specifications were met.
A pump and treat system was also installed and ran throughout the 12-week project. Groundwater was pumped from well points to a treatment area, where a series of tanks skimmed off free-phase pollutants. The water was then filtered through sand and activated carbon chambers to remove any remaining contamination. The treated water was tested to make sure it satisfied specified criteria before being piped back into the ground via an infiltration trench.
May Gurney says monitoring suggests a 'substantial and continuous improvement' in groundwater quality outside the containment area.