RI/FS at Solvent Distributor

Ash Creek is completing a Remedial Investigation/Feasibility Study (RI/FS) for at a large lubricant and solvent handling facility.  Soil vapor, soil, and groundwater at the site are contaminated due to historical releases of chlorinated solvents.  A dissolved phase solvent contaminant plume extends 2,000 feet off site, beneath several businesses and public rights of way. 

Ash Creek’s remedial investigation activities include:

• Characterization of shallow and deep soil conditions;
• A comprehensive groundwater assessment using depth-discrete reconnaissance sampling to determine the lateral and vertical extent of contamination and to determine the optimum well screen intervals, followed by installation of a 16-well groundwater monitoring network;
• On-site and off-site soil vapor monitoring from a network of permanent soil vapor points using leak detection and sampling protocols following DEQ vapor intrusion guidance;
• Ambient air sampling in on-site and off-site buildings, as well as select outdoor locations; and
• Human health and ecological risk assessment.

Interim Remedial Action Measures for the site include a site-wide soil vapor extraction system to control off-site vapor migration and building pressurization as engineering controls for on-site and several off-site buildings.  Because of the complete vapor intrusion pathways, this project was conceived, designed, and constructed in less than 6 months.  The SVE IRAM system consists of 58 wells within two stratigraphic units of the vadose zone.  Many of these wells were installed within an active chemical and petroleum distribution facility, within all the major operations areas, with minimal disruption to the business operations.  Continuous air monitoring was completed for the duration of the project, and engineering controls were needed to prevent carbon monoxide and VOC exposure to the workers. 

Since several off-site buildings contained VOCs at concentrations above DEQ RBCs, Ash Creek has facilitated meetings with the DEQ, Oregon Health Division, and the owners and occupants of the impacted properties to communicate the investigation findings and discuss potential risks from the presence of VOCs in their indoor air.

The SVE system and engineering controls have reduced air concentrations in on-site and off-site buildings to levels that are below or nearly equal to DEQ RBCs in approximately 6 months.  Approximately 1.5 tons of PCE and TCE have been removed from the subsurface.