Formatted Title
Nature-Based Remediation Approach for the CVOC Contamination underneath an Electronic Manufacturing Site
Background/Objectives
Soil and groundwater of an electronic manufacturer site were impacted with cVOC due to site activities. Three main contaminated areas have been identified: A, B and C. Zones A and C are located mainly outside the current production buildings, whereas Zone B is located underneath a building in which a very sensitive production area (cleanroom) is present.
Due to the complex site conditions, the client (previous owner and operator) was told that remediation could only be conducted when the buildings would be demolished. This would leave the client an uncontrolled long-term liability. As this is an orphan site to the client, Greensoil was asked to develop a plan to complete this challenging cVOC remediation in a reasonable time, despite very difficult logistical conditions. The proposed strategy involved several techniques with the overarching goal of using mainly bio-based technologies. Considering the inaccessibility of a large part of the contamination, segmentated horizontal drains were used to remediate the contamination present under the building.
Approach/Activities
A “source driven concept” was the strategy selected by the client. To address this concept, GreenSoil proposed a phased approach:
- Zone A: excavation of the shallow source area and in-situ bioremediation system to stimulate the anaerobic biological degradation (ERD) of chlorinated compounds using a combination of direct push and groundwater circulation with dosing of the electron donor Dehalo-GS.
- Zone B:
- installation of a biobarrier to prevent further off-site migration.
- source delineation inside the building.
Based on the outcome of these investigations, a full-scale remedial strategy was designed:
- multiphase extraction (MPE) until 4 m-gl, and stimulation of ERD until 10 m-bgl inside the operational building.
- Installation of 2 deep wells connected to three horizontal segmented drains placed at different depths to stimulate anerobic biodegradation by ERD.
GreenSoil installed the entire in situ remediation system underneath the building complying with the requirements of the client (dust and vibration free environment).
- Zone C: after additional investigation was performed, excavation and in situ ERD were carried out.
Results/Lessons Learned
During remediation, groundwater quality is being closely monitored by sampling monitoring wells on site. Within 2 years, the remediation of Area A and C reached the target values and are in aftercare monitoring. Further decreasing trends have been reported with no rebounds. The biobarrier at the site boundary was operated with a high efficiency (> 95%) to date.
The first phase of the Area B source remediation by MPE was operated for 1 year and reduced initial soil cVOC concentration levels from >2,100 mg/kg to <2 mg/kg in average (removal efficiency 99.5%). The second phase of Area B by bioremediation is currently operational.
The project shows the effectiveness of bioremediation in combination with other techniques to treat an extensive cVOC soil / groundwater contamination in which two of the areas are close to completion and the last one is still on going but showing great results. This project was historically assessed as impossible to conduct by in situ remediation due to the logistical conditions and the complexity. In this the use the segmented horizontal drains proved to be very effective.
This project shows the flexibility and potentials of bio-based technologies, and that in situ remediation can be a successful strategy to be applied in difficult conditions without disturbing site operations.