THE BEDROCK REMEDIAL DESIGN CHARACTERIZATION (RDC) CLARIFIES UNKNOWNS AND HELPS SIMPLIFY WHAT HAS HISTORICALLY BEEN COMPLEX AND OVERWHELMING ENVIRONMENTAL PROBLEMS. The RDC data allows for the development or updating of an accurate Conceptual Site Model (CSM). AST partners with our clients to update the CSM by reviewing historical investigation data and then integrating surface and subsurface geophysical data, geological assessment of rock cores, aquifer characterization data, and hydraulic testing and sample collection using a unique straddle packer assembly.
Surficial geophysical methods like electrical resistivity and induced potential (ER/IP) and multi-channel assessment of surface waves (MASW) provide insight into material type and the presence of fluid transport areas, existing biological activity, and non-aqueous phase liquid (NAPL) storage zones. Downhole geophysical methods like 3-arm caliper, fluid temperature and conductivity, ER/IP, natural gamma, and heat-pulse flow provide further insight into the geology and fluid transport within the subsurface formation.
AST also collects rock core samples prior to installing open borehole wells for upfront characterization and subsequent remediation. In completed boreholes, AST utilizes a custom straddle packer to collect discrete groundwater samples within an 18 in vertical interval, which allows us to target specific features. This is not possible with standard “off-the-shelf” packer configurations.
During discrete sampling, the adjacent monitoring well water levels are data logged to determine vertical and horizontal hydraulic conductivity across the site. Not only does this procedure help to define contaminant mass distribution, but also reveals characteristics of each discrete interval for later use during injection.