Groundwater and Soils Remediation City of Industry, California

Situation

Soil and groundwater at a closed electronics manufacturing facility within San Gabriel Basin Superfund Area were impacted by releases of more than a dozen chlorinated solvents. A groundwater plume has migrated more than 1/2 mile from the site, with indications of a continuing on-site DNAPL source. Hydro Geo Chem was retained to:

Develop soil cleanup standards appropriate for the site, and design and install a soil vapor extraction system suitable for low permeability sediments.

Evaluate the lateral and vertical extent of groundwater plume migration.

Design and construct on-site groundwater containment and source removal system and obtain closure.

Hydro Geo Chem's Approach

On- and off-site soil-gas sampling delineated the extent of VOC-impacted soils. These were followed by pilot SVE tests, numerical simulations of SVE performance, and development of risk-based soil cleanup levels based on infiltration and VOC diffusion to the water table. We then managed the engineering and construction of a full-scale SVE system, including a data acquisition system with automated monitoring of exhaust gases. We conducted on- and off-site groundwater investigations, pilot groundwater extraction testing, and a remedial feasibility study. Numerical modeling of groundwater cleanup permitted identification of system requirements and optimal extraction locations. The system includes vacuum-enhanced extraction wells in the source area for aggressive DNAPL removal.

Results

The closure criteria for soil cleanup levels were reached after 2 years of active SVE. We conducted confirmatory soil investigations, petitioned for closure, and received a No-Further-Action determination from the State of California. We demonstrated that natural attenuation was limiting off-site migration, thus reducing or eliminating the need for expensive off-site remediation. Our on-site groundwater corrective action plan was approved by the state, and we are currently implementing construction of extraction and treatment systems.