Background/Objectives: Geosyntec was engaged to design, implement, monitor and validate an enhanced in situ bioremediation (EISB) remedy for a zone of groundwater impact in the vicinity of the former waste control site located in Bellevue, Western Australia.
The overall objective of the remedial action was to design and implement an effective remediation program that permanently reduced the concentrations of the groundwater contaminants of concern (COCs; primarily trichloroethene [TCE]) to the appropriate risk-based criteria (at a minimum) in a cost-effective, sustainable and timely manner consistent with the expectation of community and relevant stakeholders.
Approach/Activities: Preliminary work for the EISB remedy included installation of nine monitoring wells within the treatment area, and collection of baseline soil and groundwater samples. Following these activities, electron donor (emulsified vegetable oil) and a commercially available dechlorinating bacterial (bioaugmentation) culture (KB-1® Plus) were injected into the subsurface within the source zone (PTA) and a secondary bio-barrier (STA) located downgradient of the source zone to promote in situ biodegradation of the COCs in groundwater in these areas. Following the EISB injection activities, bi-annual groundwater sampling of 16 validation monitoring wells began and continued for a period of roughly 2.5 years (five total sampling events). Throughout the performance monitoring period, changes in the groundwater concentrations of total organic carbon, dissolved hydrocarbon gases, volatile fatty acids, nitrate, sulphate, dissolved iron, Dehalococcoides ethenogenes microorganisms, ORP, dissolved oxygen, as well as pH at some of the validation wells provided evidence that biologically active and reducing zones had been established in the PTA and STA.
Results/Lessons Learned: Remediation of the PTA was considered complete when concentrations of TCE, cis1,2-dichloroethene (cis-1,2-DCE), and vinyl chloride (VC) in PTA validation monitoring wells fell below the remediation criteria for three consecutive monitoring events. This occurred in the fourth performance monitoring event. Concentrations remained below remediation criteria in all additional monitoring events. Remediation of the STA was considered complete when concentrations of TCE, cis-1,2-DCE, and VC in STA validation monitoring wells fell below the remediation criteria. This occurred by the fourth performance monitoring event. The validation report has now been approved by the Site Auditor and marks the first instance of successful Auditor approved bioremediation of chlorinated ethenes in Western Australia.
- Geosyntec Authors: David Reynolds
- All Authors: David Reynolds
- Title: EcoForum 2020 eConference
- Event or Publication: Event
- Practice Areas: Groundwater Assessment and Remediation
- Citation: Geosyntec will deliver five presentations and one keynote at EcoForum 2020 eConference on September 14-18, 2020.
- Date: September 14-18, 2020
- Location: eConference
- Publication Type: Platform Presentation