Coxside has a well-documented history showing it was used as a gasworks as early as 1846. The works expanded twice through the remainder of the nineteenth Century, reaching peak production in 1933, due to an increase in demand for gas. The works remained operational throughout the Second World War, despite Plymouth being one of the most heavily bombed cities in England, but it was the onset of natural gas that finally led to its closure in 1968.
A desktop study and site investigation were undertaken which identified the location of contaminated areas and analysed the chemical composition of the ground. A strategy for remediation was then developed in consultation with the local authority, the Environment Agency and the Health and Safety Executive.
Following advanced works in November 1996, an eight month remediation programme was started in February 1997 to remove contaminated materials and to make the 9 acre site suitable for redevelopment. Air quality was monitored throughout the programme and the groundwater was repeatedly checked for impurities through a series of boreholes. The first phase of the programme concentrated on diverting the gas supply mains which crossed the site. The pipes carried the main gas supply to Plymouth and the diversion was successfully undertaken by National Grid with no disruption to the local supply.
Excavation of four former gasholder bases and three tar wells, which lay at various points around the site, was undertaken throughout the second phase of the programme. All materials removed during excavation works were initially stockpiled on site and contaminated material was separated from clean soil. The contaminated material was then removed from the site to licensed tips and the clean material was recycled and used to backfill voids. Contaminated perched water was treated on site by a purpose-built water treatment plant.
This plant removed the suspended solids, phenols, oils and other contaminants. Treated waters were tested to ensure that they were of sufficient purity before being discharged into the local drainage network.
