Client: USACE Alaska
Location: Kodiak, Alaska
Completion Year: 2018
Scope of Work:
- Well maintenance
- Groundwater and soil sampling
- Conceptual Site Model
- Risk assessment
Brice completed a mean hydraulic gradient study and non-aqueous phase liquid (NAPL) characterization at the Airport Staging Area (ASA) and Fire Training Pit (FTP) Formerly Used Defense Site (FUDS) in Kodiak, Alaska. The source of contamination was an FTP used by military firefighting personnel in practice simulations. A variety of flammable liquids were placed into the pit, ignited, and extinguished as a training exercise. Contamination from these flammable liquids migrated horizontally into the nearby vadose zone and vertically to the groundwater table.
Our fieldwork included performing well maintenance, studying the hydraulic gradient through the deployment of data logging pressure transducers, groundwater and NAPL sampling, placing soil borings and soil sampling, well point decommissioning, and surveying. Groundwater and soil samples were analyzed for potential contaminants, including extractable petroleum hydrocarbons (EPH), volatile petroleum hydrocarbons (VPH), volatile organic hydrocarbons (VOC), and polynuclear aromatic compounds (PAH). The NAPL sample was analyzed for EPH and VPH. In addition to field activities, we compiled all available historical data into one site-wide database.
Hydraulic Gradient Study—Water level data collected by the pressure transducers during the hydraulic gradient study was converted to water elevations in mean lower low water tidal datum that is comparable to a nearby National Oceanic and Atmospheric Administration (NOAA) tidal station data on Kodiak Island. The corrected water level data were filtered using the Serfes method 1 to isolate tidal influence and calculate an average water level for each of the 20 monitored locations.
Groundwater, NAPL, and Soil Sampling—Analytical groundwater samples were collected from 16 wells. Analytical soil samples were collected from 1- to 2-foot depth intervals at 10 boring locations within the estuary located north of the FTP.
Calculation of Human Risk—Brice used the ADEC Cumulative Risk Calculator to calculate cumulative cancer risks and hazard quotients using compiled data. The site consists of two distinct areas; the area located within the fenced area at the Kodiak Airport restricted to airport personnel only (outdoor workers), and the area located outside of the fence which is open to the public. Cumulative risk was calculated using three different scenarios, site-wide, within the estuary, and within the fenced area.
Scoping of Ecological Risk—Ecoscoping was performed based on two distinct areas: the aerial extent within the fenced area near the runway, and the bluff and estuary located north of the fence. The ADEC Ecoscoping Form for the fenced area resulted in an off-ramp at step 4 indicating no further ecological evaluation was necessary due to plume size, lack of aquatic habitat, and lack of endangered species.
Brice completed a UFP-QAPP and work plans to perform the study, updated the Conceptual Site Model, and supported the selection of a remedial alternative for NAPL contamination present at the Airport Staging Area FTP.