Project: Nairn Gas Works Remediation
Value: £315,000
Timescale: 3 months
This former gas works site is located adjacent to the River Nairn, and residual contamination from the site’s former use was deemed to pose an unacceptable risk to the river and wider environment. Due to the site’s complexity, the client required a contractor with technical expertise and experience in dealing with similar sites and selected ERS to carry out the works.
The site was very small, with restricted access and in close proximity to residential neighbours. Previous site investigations had found heavily hydrocarbon contaminated made ground and the presence of two tar box structures containing free phase tars. There was a demonstrated risk to the environment from NAPL leaching from free phase tars and contaminated made ground into groundwater. Additionally, relict and live gas infrastructure remained underground.
Relict services and chambers were removed and contaminated soils excavated into segregated stockpiles. Material from the tar boxes was also excavated and segregated. Excavated materials were removed for disposal off-site at a suitably licenced facility. These areas were then backfilled with clean imported material.
A grouted perimeter cut-off wall was installed to prevent further migration of leached NAPL off-site in groundwater, removing the pollution linkage to the River Nairn. Infill grouting was used in a grid pattern to stabilise the soil and fill in any voids associated with relict gas infrastructure.
The remediation works effectively removed the primary source and the pathway from the pollution linkage, thus minimising risk of contaminants affecting the River Nairn and surrounding environment.
