Présentations Colloques

    Oral Presentation
    Session 7.02: Urban Hydrogeology
    Dottridge Jane
    When is remediation required for groundwater contamination by chlorinated solvents?
    Groundwater contamination by chlorinated solvents has been documented since the 1950s, with treatment required for drinking water and potential health impacts from vapour. The most common solvents, trichloroethene (TCE), tetrachloroethene (PCE) and 1,1,1 trichloroethane (TCA), are persistent in groundwater and natural biodegradation is slow. Although implementation of European Union legislation has resulted in a sustained drop in the number of pollution incidents in the UK since 2000, solvents and their daughter products are still frequently found in groundwater at concentrations exceeding the drinking water limit. The contaminants include 1,1,1 TCA, banned in 2000, and TCE, which has only been permitted in closed systems since 2010 and requires authorization for continued use after 21 April 2016. This implies that existing contamination is likely to be historical and not due to on-going sources.**In the UK, remediation of contamination is required only if the results of risk assessment demonstrate a significant risk to human health, groundwater or the wider environment. For volatile organic contaminants where vapour transport is important, future human health risks may be the limiting factor if residential land use is proposed. However, it is well known that groundwater remediation costs can be excessive and thus restrict brownfield development. If it can be shown that the costs of remedial works outweigh the productivity and value of the groundwater resource, remediation may not be warranted. This decision is facilitated by a new method for quantifying the loss of available groundwater resource associated with a point source contamination event, when no impact on existing uses has occurred (Bartlett et al, 2014). Avoidance of groundwater remediation will significantly reduce development costs and may allow future development of otherwise unsuitable sites. **The issues are illustrated with examples from three recent investigations in the UK, where the groundwater is not used for abstraction and of marginal value, despite its designation as an aquifer.**
    United Kingdom


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