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 This former gasworks site is located in Devon situated on the south side of the River Avon. A vacant and empty woodworking workshop building and warehouse most recently occupied the site along with open scrubland.
With respect to soil contamination, significantly elevated concentrations of arsenic were found across the site. Elevated concentrations of lead, copper and nickel were identified in isolated samples. Elevated concentrations of cyanide and free cyanide were identified in a soil sample each, both obtained from the River Avon embankment. Elevated concentrations of PAH’s, TPH and phenols were also identified in soils on the site. Given that gasworks wastes were identified on site, it was concluded that potential for contamination of the River Avon remained.
Following trial pits, it was identified that gasworks wastes and residues have affected shallow soils across the entire site and deeper soils in proximity to former gasworks structures and in proximity to and beneath the existing vacant workshop building. In order to protect future site residents and local water resources, soil and groundwater remedial works were required including excavation of selected hotspots and general excavation to depth beneath the currently vacant former workshop building. Gasworks wastes were identified in proximity to the bank of the River Avon near the former workshop building. In addition a greater depth of made ground was identified which contained cement bonded asbestos.
Cognition Land and Water Ltd installed groundwater monitoring installations. These were formed from backfilled trial pits excavated to between 5 and 5.5m. The response zone of these wells was between ground level and the well base. Groundwater monitoring and sampling was undertaken from all available locations and from the River Avon both upstream and downstream of the site to assess the current level of contaminant impact.
Remediation of Made Ground to 2m and groundwater across the entire site was required. The approach was to remove and treat the worst of contamination, some bioremediation of hydrocarbon contaminated soils, and pump and treat groundwater encountered in the areas where soil treatment was carried out. Human health issues were managed by hotspot removal and provision of a layer of clean cover material in gardens and landscaped areas.
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