Harry O’Neill, the President of Beacon Environment Services, Inc recently hosted a webinar summarizing their passive soil gas sampling and analysis program. In short, the major selling points for their program over active soil gas sampling and analysis or even groundwater sampling and analysis for the evaluation of vapor intrusion risk are the lower detection limits and greater radius of influence. Beacon also believes that too many sites recently have been inadequately characterized due to problems site access or project manager bias dictating where samples are collected.
In general, passive soil gas samplers absorb gas over days or weeks detecting potential contamination in nearby soil or groundwater due to the higher likelihood of absorption over that time period. This compared to the discrete nature of active soil or groundwater sampling. This broader area of influence of for passive soil gas sampling allows for less data gaps. It also overcomes some of the challenges of temporal variability. Further, Beacon suggests that higher resolution of sampling points will provide better results and their system allows for more sample collection points due to the lower cost per sample.
We recently used Beacons’ samplers at a site in San Pedro. At this site we identified the subject property as a former auto shop but were not exactly sure of the historic locations of the various hazardous materials storage, use, or disposal areas or the locations of tanks, clarifiers, hydraulic systems, etc… We performed a blanket soil gas study and after leaving the samples in the ground for approximately one week, we were able to confirm impacted soil in one localized area of the subject property. We were also able to draw the conclusions that any soil impacts at the subject property were below regulatory action levels for the chosen land use; however, the passive soil gas sampling results do not allow for direct correlation to concentrations of compounds of concern in soil, groundwater, or soil vapor. This sampling and analysis method cannot directly be used for characterization or risk assessment, but it will give you a reasonable idea of the relative locations and relative concentrations of soil, soil vapor, and / or groundwater impacts.
For more information about the Beacon samplers, their use, and recommendations you can visit the Beacon website or listen to this webinar.