MANUFACTURING FACILITY IN STATESBORO, GEORGIA, USA
WSP completed the investigation and characterisation of a central Georgia manufacturing facility. At this manufacturing facility, a historic release of coolant containing chlorinated solvent resulted in soil contamination, groundwater source area volatile organic compound (VOC) concentrations exceeding 50mg/l and a 400m-long VOC plume that was decreasing in both extent and concentration.
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Unlike conventional treatments, our remediation approach ensured that an
estimated 350 tonnes of CO² was not released into the atmosphere.
WSP proposed a comprehensive integrated remedial programme to address these problem areas. The programme included excavation and offsite disposal of contaminated soils, chemical oxidation (ozone) of source area groundwater and monitored natural attenuation (MNA) for the dilute portion of the plume. However, conventional analytical assessment criteria were insuffi cient to demonstrate MNA applicability.
To overcome the limitations of conventional assessment criteria, WSP applied advanced diagnostics to demonstrate MNA applicability. These diagnostics identifi ed a large population of key attenuating microbes, Dehalococcoides (DHC). DHC is the only known group of microbes capable of completely attenuating the chlorinated VOCs detected in site groundwater. These tests identifi ed the mechanism (that is, DHC) by which the plume was decreasing in both extent and concentration and also showed that the mechanism was active, thereby proving that attenuation was ongoing.
With the advanced diagnostic data, the integrated remediation approach was approved by the Georgia Environmental Protection Division. This integrated remediation approach is estimated to have saved the client between $700,000 and $1,700,000 as compared to a more active plume remediation strategy. The remedy
also avoided emitting 350 tonnes of CO2 into the atmosphere as compared to conventional treatment of the dilute portion of the plume.
MANUFACTURING SITE IN SANTA ANA, CALIFORNIA, USA
WSP was retained to assess an underperforming property line groundwater treatment system in Santa Ana, California. The system involved applying amendments to stimulate native microbes to attenuate chlorinated solvent affected (that is, chlorinated volatile organic compounds, or VOCs) groundwater at a manufacturing facility.
The system, referred to as a bioremediation barrier, was not meeting required standards following application of a microbial food source amendment. Rather than blindly apply another amendment to the subsurface, a low-cost in-situ microcosm study was completed by WSP.
Groundwater testing was completed in three months, and six months after WSP completed full-scale augment application results revealed greater than 90% VOC concentration reduction throughout the bioremediation barrier.
In summary, WSP quickly and cost effectively identifi ed a lack of remedial progress, diagnosed the likely cause, and completed an in-situ microcosm test to confi rm the effectiveness of a proposed repair to the bioremediation remedy. Full-scale implementation of the repair resulted in rapid decline in total VOC concentrations. Furthermore, compared to a groundwater extraction and treatment hydraulic containment system, the bioremediation barrier remedy is calculated to reduce carbon dioxide emissions by 1,000 tonnes during site restoration.
WSP GROUP SUSTAINABILITY REPORT 2010 | 33
EMBEDDING SUSTAINABILITY
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