Theme: 01. Remediation Technology Innovations

Topic Area: 01q. Electrical Resistance Heating: Best Practices and Lessons Learned

Formatted Title:

Remediation of CVOC Source Zone Removal with ERH + SVE

Background/Objectives:

The study main goal was the clean up of a commercial and residential site affected by a plume of chlorinated compounds originating from a upstream former industrial site. During environmental studies, the presence of tetrachloroethene, trichloroethene and 1,1-dichloroethene was identified in groundwater, including a potential risk of vapor intrusion. The mass center of tetrachloroethene, trichloroethene and 1,1-dichloroethene plumes in groundwater were located on the sidewalk upstream of the site, where the former industry released its effluents on a sewage pipeline. To reuse the site for residential development, it was necessary to implement an Intervention Plan, which considered: the application of the remediation measure (thermal remediation by electro resistivity - ERH and extraction of soil vapors - SVE) to reduce the concentrations of chemical substances of interest in groundwater and vapor intrusion; restrictions on the use of shallow groundwater; use of PPE by future construction workers; and post remediation groundwater and vapor intrusion monitoring campaigns.

Approach/Activities:

All of the site environmental studies, remediation and other risk mitigation measures were implemented and submitted to the local environmental agency and municipality to obtain permits to build and habitat the new residential building. Therefore, the procedures implemented followed those established by the environmental agency of the State of São Paulo and the State’s laws. The site investigation for identifying, qualification, and quantification of the chlorinated compounds at the site included passive vapor soil samplers, high resolution investigation (MiHPT and XSD) and 3-D consolidation and treatment of the data results. Dozens of VOC soil samples were performed, including the installation of monitoring wells for sampling different levels of the aquifer and the sampling of vapor intrusion sampling using sub-slab monitoring points. Based on the results obtained, it was possible to establish a robust conceptual model for the site contamination and define the best cleanup strategy to meet requirements for further use of the site, construction schedule and budget. Once the construction schedule indicated the need of a one-year remediation it was decided to implement a ERH + SVE system, on an area of 615 m², considering a volume to be treated of 5115 m³, with treatment at depths ranging from 4 to 13 meters.

Results/Lessons Learned:

The passive soil vapor sampling proved to be effective in locating the source of the contamination and direct the high resolution studies in order to build an appropriate conceptual model for the site contamination. The remediation system showed its efficiency and effectiveness after a period of 9 months of operation, allowing it to be shut down at the appropriate time according to the residential building construction schedule. Since its shutdown, groundwater and vapor intrusion monitoring campaigns were carried out and the results proved the reduction in concentrations of the chlorinated compounds to levels below the risk for groundwater and vapor intrusion. The local environmental agency and municipality issued the permits for the construction of the residential building.

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Carlos Cutrim

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