Remediation works of a former gas works site on the Isle of Wight by design and installation of a permeable reactive barrier.
Site Background & History
The site is located at Yarmouth on the Isle of Wight and was once the former Freshwater Gas Company which in believed to have closed in the 1960’s.
Site investigations undertaken identified the presence of both soil and groundwater contamination. The identified pollutants are predominantly gas works derived and include Total Petroleum Hydrocarbons (TPH), Polycyclic Aromatic Hydrocarbons (PAHs), copper, zinc and cyanide.
The prime source of contamination was in the south western corner of the site (associated with a former gas holder). The identified contamination was not considered to pose a future risk to human health as the development plans for the site incorporate the provision of significant hardstanding. The primary environmental concern was identified as the potential risk to the estuary and surrounding environmentally sensitive areas. These receptors were considered to be at risk due to the presence of contaminated groundwater on the site. Card had identified the presence of elevated levels of Arsenic, Boron, Cadmium, Chromium, Copper, Lead, Mercury, Nickel, Zinc, Cyanide, Phenols, Benzo(a)Pyrene, TPH and Sulphate within the groundwater, potentially migrating offsite and impacting the sensitive receptors.
Card considered possible remediation options to address groundwater contamination on the site and proposed an E-Clay Permeable Reactive Barrier installation as the preferred option.
Envirotreat designed and installed the permeable reactive barrier to compliment the previous installed sheet piling to protect offsite receptors.
Post installation groundwater monitoring and validation was undertaken independently by Card Geotechnic.
The barrier system was installed in accordance with the design requirements and the remediation strategy.
Envirotreat produced a comprehensive Validation Report to confirm the satisfactory installation of the barrier system.