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Page12 <br /> push "dolly rig",which will limit total drilling depths for these samples to approximately five to ten feet <br /> bgs. Combined with Task 1A vapor data,this soil sampling data are expected to help evaluate whether <br /> gross-scale contaminant impacts are likely present in this area. Planned sub-slab soil sampling locations <br /> are depicted on Figure 3. <br /> TASK 213: SUPPLEMENTAL PERCHED-ZONE DELINEATION <br /> The MIHPT device produces qualitative vertical profiles of instrument responses to gasoline and other <br /> volatile organic compounds, and to changes in stratigraphy (inferred soil type and relative permeability). <br /> These profiles are interpreted for visual representation of Site contamination and other hydrogeological <br /> characteristics. Delineation of the uncharacterized areas described above will include the following <br /> MIHPT exploration elements. Since no groundwater monitoring wells are currently located in the <br /> eastern area of the Property, limited additional perched-zone and water table well installation is <br /> planned under Task 3. <br /> ■ Thirteen MIHPT borings will be advanced using a direct-push drilling apparatus. Borings will be <br /> advanced as deep as possible (with anticipated maximum depths approaching 40 feet). Note <br /> that boring depths during the 2023 HRSC investigation were limited by soil conditions to <br /> maximum depths of 38 feet bgs. <br /> ■ Depending on MIHPT observations, approximately six separate paired, adjacent borings will be <br /> advanced to collect confirmatory soil and groundwater samples for fixed lab testing, used to <br /> calibrate and for comparison to the MIHPT data.The number and location of the bulk samples <br /> will be dependent on the real-time measurements from MIHPT borings. For scoping purposes, <br /> two discrete soil samples and one groundwater sample (if possible)will be collected from each <br /> of these six borings. All samples will be analyzed for gasoline and related volatile constituents.15 <br /> Proposed boring locations are shown on Figure 3. <br /> ■ Based on MIHPT observations and within zones of known TPH contamination, up to six selected <br /> discrete soil samples within the uppermost 15-feet soil interval will be analyzed and quantified <br /> for TPH fraction (EPH/VPH) contaminants to allow for future development of modified site- <br /> specific Method B soil cleanup levels. Physical soil characteristic data (organic carbon content, <br /> moisture content, and grain-size analysis)will also be collected to provide more accurate risk <br /> model input parameters.These supplemental analyses will include: <br /> ❑ EPH/VPH analysis by Method NWTPH <br /> ❑ Organic carbon content by EPA Method 5310B <br /> ❑ Moisture content by ASTM Method D-2216 <br /> ❑ Grain-size analysis by ASTM Method D-422 Modified <br /> ■ Investigation-derived soil and water wastes will be placed into sealed, labeled steel drums, and <br /> stored temporarily at the subject Property pending disposal coordination. <br /> HRSC data will be used to update the delineation of gasoline impacts within the perched zone.This data <br /> will be supported/informed by the bulk sampling/testing results obtained from co-located borings and <br /> from Task 1 vapor data and collectively used to optimize the conceptual site model.The existing 2023 <br /> 11 Benzene, Toluene, Ethylbenzene, Total Xylenes, 1,2-Dichloroethane (EDC), 1,2-Dibromoethane (EDB), Methyl- <br /> Tert-Butyl-Ether(MTBE), Naphthalene,Gasoline Range Organics(GRO). <br /> EES ENVIRONMENTAL CONSULTING,INC. 2120-02 2024 SOW 20240408f <br />