For Naval Facilities Engineering Command Southwest (NAVFAC SW) at the Former NASA Crows Landing Flight Facility in California, OTIE conducted treatability pilot testing of three different in situ bioremediation technologies (aerobic, anaerobic, and co-metabolic processes) at three Installation Restoration Program (IRP) source area sites to reduce concentrations of chemicals of potential concern (COPCs) below site-specific interim Remedial Action Objectives in groundwater. OTIE applied value engineering to customize, optimize, and expand testing the designs to address multiple COPCs and hydrostratigraphic complexities.
- At UST Cluster 1, OTIE installed 3 groundwater monitoring wells, 32 biosparge injection wells, and a biosparge air delivery system. System installation was followed by 12 months of planned test operations with associated groundwater and vapor monitoring. After 12 months, based on monitoring results, OTIE performed 3 additional months of operations and monitoring and completed a test for rebound. We demonstrated that 15 months of biosparge system operation resulted in decreases of benzene concentrations from 20,000 ug/l to concentrations less than the detection limit in shallow groundwater and from 36,000 ug/l to 25 ug/l in mid-shallow groundwater, with virtually no rebound six months after system shut-down.
- At UST Site 117, OTIE performed a treatability study of aerobic enhanced in situbioremediation (EISB). OTIE installed groundwater monitoring wells, drilled 4 shallow and 11 mid-shallow temporary borings, injected an oxygen-releasing compound (ORC-Advanced), and performed 12 months of groundwater monitoring. We demonstrated increased dissolved oxygen in groundwater and decreased COPC concentrations after injection. In one year after injection, concentrations of 1,2-DCA were reduced by 50% in the center of the source zone in shallow groundwater and benzene concentrations decreased 87% from 100 ug/l to 13 ug/l in mid-shallow groundwater. OTIE used advanced compound-specific isotope analysis (CSIA) to confirm that the decreases in COPC concentrations were caused by biodegradation.
- At IRP Site 17, OTIE performed a 3-phase treatability study of anaerobic EISB on chlorinated solvents, especially carbon tetrachloride (CT). In Phase 1, OTIE installed groundwater monitoring wells, drilled 6 mid-shallow temporary borings, installed 4 injection wells, injected 2 different substrates (3DMe® hydrogen release compound [HRC®] and EOS®598B42) into the mid-shallow and mid-deep zones, and performed six months of groundwater monitoring. In Phase 2, OTIE injected one substrate (EOS®598B42) into the mid-shallow and mid-deep zone and performed six months of groundwater monitoring. In Phase 3, OTIE delineated the upgradient extent of the dissolved CT plume; injected a more cost-effective substrate (EOS®450) into the shallow, mid-shallow, and mid-deep zones; and performed additional baseline sampling and post-injection sampling at 1, 2, 3, and 6 months after injection. We demonstrated that injection of emulsified vegetable oil significantly altered the groundwater geochemistry and thereby stimulated very rapid reductive dechlorination of CT. We used CSIA to confirm that CT concentration decreases were caused by biodegradation.
We successfully completed our treatability testing program within the NAVFAC’s original test budget, accomplished many more performance objectives than scoped, and made significant progress towards overall site remediation.