THIS ARTICLE IS A CASE STUDY OF HISTORICAL PROJECTS HYDROSOLUTIONS HAVE WORKED ON.
Public Water Utility, Gatehampton, England
Resource investigation of a 22ML/d Public Water Supply bore affected by phenols
The potential to realise the licensed yield at a major chalk groundwater Public Water Supply (PWS) affected by phenolic contamination was undertaken. A desk study examined the history of contamination: phenol & other organic and organo-chlorine (OC) contaminants were periodically present in raw water obtained from bores within the PWS, restricting the operation and yield of the source. Two potential upgradient sources for the phenol were identified; a former town-gas works, and a former wood mill using OC preservatives.
A site investigation program included on and off site soil bores to obtain unsaturated zone cores: interstitial fluids were removed via centrifuge for analysis. Off-site groundwater monitoring bores were constructed throughout the dry-river valley adjacent to the source.
A major test pumping program was undertaken over two weeks at the PWS maximum licensed abstraction rate of 22 ML/d, with discharge being directed into an adjacent perched water course.
Low-level non-chlorinated phenols were analysed on one occasion at commencement of the test, with other organic contaminants including phthalate esters identified periodically. However a nearby satellite bore was found to contain high concentrations of phenols. It was concluded from the phenol speciation that contaminants were present from the former gas works operations, although regional numerical groundwater modeling results indicated that the lateral extent of the contaminant plume was strongly influenced by large-scale abstraction up and down gradient with the river valley.
Overall, the existing combined abstractions were beneficial in promoting natural attenuation of the
residual urban contaminants. It was concluded that the licensed yield could be obtained safely, provided an on-going monitoring program was in place.
Stuart Jeffries
Hydrosolutions Pty Ltd
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