Bethel conducted a floor drain investigation at the FAA Mica Peak Air Route Surveillance Radar (ARSR) Lower Garage building. The scope of services was to collect soil and potentially groundwater samples from near the vehicle garage floor drain outfall and to clean out and inspect the floor drain lines for breaks and other possible release locations. The objective of the work is to define the extent of soil which may need to be remediated to comply with Washington Department of Ecology (Ecology) cleanup standards.
Bethel hired a subcontractor to clean out and inspect the floor drain system with a down-hole camera. Bethel provided recorded footage of the inspection to the FAA as documentation that the floor drain was in good condition and without cracks or breaks.
Bethel advanced six soil borings through unconsolidated soil and into bedrock material at the vehicle garage floor drain outfall. No apparent contamination was present other than a small volume at the immediate discharge point. Analytical sample results verified this and Bethel estimated the volume of contaminated soil present was three to five yards. The investigation concluded that in addition to the small volume of residual-range organics (RRO) that exceeded the WDOE cleanup standard, there may be concentrations of chromium that may need to be addressed.
Under a follow-up action, Bethel was contracted to determine if the chromium was the more toxic hexavalent species or benign trivalent species and to remove the small volume of contaminated soil. Bethel advanced two soil borings from the locations and depths of the 2018 total chromium samples that exceeded the Ecology cleanup standard for hexavalent chromium. One soil analytical sample from each soil boring was analyzed for speciated chromium. The results for both speciated chromium samples showed hexavalent chromium and total chromium concentrations were below their applicable CULs.
Bethel excavated 23 tons of RRO contaminated soil, more than estimated as impacted to eliminate the need to await analytical results. Excavation confirmation sample results for RRO ranged from nondetect to 570 mg/kg, all below their respective CUL. The excavation was immediately backfilled and contoured to match the surrounding grade. The site was returned to pre-existing conditions to the extent possible. The site was recommended for closure and received a closure designation from WDOE.
Work performed
- Work Plan Preparation and Approval
- Environmental Drilling
- Field-Screening and Soil Sampling
- Floor Drain Inspection
- Soil Removal and Disposal
- Reporting
- Regulatory Oversight and Closure
