The inclusive geo-hazard assessment provided further consideration of the potential types of foundation use and other factors that may have presented cost abnormalities within any future redevelopment plans.
The site was located within a mixed residential and commercial setting and comprised a car showroom that was formerly used as a commercial storage depot.
Given the history and site setting, consultation with the Contaminated Land Officer at Manchester City Council was undertaken to establish any particular concerns and access information held by the Council. The local Petroleum Licensing Officer was also contacted to find out whether any storage tanks had been present on-site and whether any historical incidents had been reported.
A study of historical maps better informed the likelihood of historical contamination having occurred at the site. In line with the details obtained from our consultation, the maps indicated there was a history of light industrial and commercial land use although no storage tanks had been present.
The sensitivity of the site was defined by undertaking a data collation activity in order to draw together an overall picture of the surrounding environment.
A review of available data included the study of local British Geological Survey maps and borehole logs to determine the underlying local geology. The BGS borehole logs highlighted Made Ground (fill material) to 3 m below ground level, followed by stiff to very stiff clay to 10 m underlain by very dense sands (a borehole was located within 25 m of the site).
The principal aquifer (Chester Pebble Beds Formation – Sandstone) beneath the site is considered to be a sensitive groundwater receptor. The presence of overlying low permeability glacial till, however, offers some degree of protection to the aquifer from any potential contamination occurring on-site.
An overall risk assessment was produced qualifying the contamination risks posed and the sensitivity of the receptors of concern. The conclusion was that the site was medium contamination risk given the legacy of commercial and industrial use.
Both groundwater and human health receptors were identified as at risk and, given the local presence of Made Ground, a consideration of foundation design options would be required for any future redevelopment of the site.
A Phase 2 Geo-environmental Assessment was recommended to be undertaken to fully characterise the ground, ground gas and groundwater conditions across the site.
The client was satisfied that the findings of our report provided a factual account of the possible geo-environmental risks and enabled an informed decision about the purchase of the site to be made.
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