In-Situ Remediation Pilot Study and Product Bail-Down Testing, Cold Bay, Alaska

Brice performed a pilot study to evaluate in-situ chemical oxidation (ISCO) as a remedial alternative and product bail-down testing at a former FAA Station in Cold Bay. Once the pilot study test area layout was staked, we collected pre-treatment soil samples to determine existing petroleum hydrocarbon concentrations. Soil cores were screened using a photoionization detector (PID); the soil screening highest in volatile hydrocarbons was analyzed for diesel range organics (DRO), residual range organics (RRO), gasoline range organics (GRO), and benzene, toluene, ethylbenzene, and total xylenes (BTEX) compounds. Two additional soil samples were collected, one each from the vadose zone and saturated zone, for analysis of soil oxidant demand (SOD). SOD results were used to evaluate whether the 50-pound per cubic yard dosage rate of PersulfOx© was sufficient.

The ISCO injection of PersulfOx© at a 15% concentration targeted the 17-ft bgs to 27-ft bgs interval (vadose zone). The test volume constituted a 37-cubic yard volume and the injection involved a dosage rate of 50 pounds PersulfOx© per cubic yard of soil for a total dosage of approximately 1,850 pounds of PersulfOx©. Brice performed two injection events approximately one month apart. Sample and injection boreholes were backfilled with hydrated bentonite chips to prevent short-circuiting.

Results of pre-treatment soil sample analysis for soil oxidant demand indicated the ISCO injection dosage rate of 50-pound per cubic yard was sufficient. We advanced five randomly-located soil borings to collect two soil samples for performance monitoring evaluation of DRO, RRO, GRO, and BTEX based on highest PID screening results. In addition, one soil sample was collected for performance monitoring from 30-ft bgs interval to evaluate effectiveness of ISCO in the saturated zone. We also collected a groundwater sample from a monitoring well for laboratory analysis of GRO, DRO, RRO, BTEX, and sulfate for post-treatment evaluation. We purged the well using low flow sampling techniques in accordance with the ADEC Field Sampling Guidance.

Brice also conducted product bail-down testing to determine if active product recovery techniques would be effective at monitoring well locations with free product.