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Mr. Alan Buehler, P.G., RWQCB May 16, 2017 Work Plan for Additional Site Investigation Project No. 2092-2057-01 2057 South El Dorado Street, Stockton, CA Page 5 Task 2: Field Activities Task 2A: CPT Soil Borings and Groundwater Sampling Stratus will oversee a California licensed drilling contractor advance borings CPT-3 and CPT-4 to an approximate depth of 120 feet bgs. The proposed locations of the borings are shown on Figure 3. The actual locations of the borings will be based on accessibility and the location of underground utilities, as determined by the geologist in the field. CPT consists of advancing a cone-tipped cylindrical probe (1.7 inches in diameter) into the ground while simultaneously measuring the resulting resistance to penetration. A computer generated CPT log is plotted in the field, providing a continuous log of site lithology. Upon completion of CPT profiling, the boreholes will be pressure grouted from the bottom of the borehole up to surface grade. Following the CPT work, groundwater samples will be collected from separate borings, located approximately 2 feet from the initial CPT-3 and CPT-4 borings. A minimum of five groundwater samples will be collected adjacent to CPT-3 and CPT-4. Sampling depths will be determined at the time of the investigation and will preferentially target coarser-grained saturated strata. As stated earlier, five depth discrete groundwater samples will be collected adjacent to boring CPT-2, at the same depths as a 2013 site investigation. If geological conditions east of the Site are similar to onsite conditions, Stratus will attempt to collect groundwater samples at similar depths offsite to enable correlation of contaminant impact with depth downgradient of the Site. HydropunchTM sampling equipment will be used to collect the groundwater samples at the desired depth intervals. The HydropunchTM sampler will be pushed to the bottom of the sampling interval using 2-inch diameter steel rods. The steel rods are then subsequently retracted approximately four feet, exposing the screen, allowing for the collection of depth-discrete groundwater samples. The groundwater samples will be collected using a clean bailer, transferred to laboratory-supplied glass vials, properly labeled, and placed in an ice-chilled cooler. The groundwater samples will be transported under strict chain-of-custody protocol to a California-certified analytical laboratory for analysis. Upon completion of groundwater sampling, the respective boreholes will be pressure grouted from the bottom of the borehole up to surface grade. Task 2B: Hand Auger Soil Borings Borings HA-1 and HA-2 will be advanced using hand tools (predominately by hand auger) to a depth of approximately 6 feet bgs. Soil samples will be collected at depths of approximately 4 and 6 feet bgs and transferred to a brass or stainless steel sleeve, or a glass soil jar. Each sample will then be labeled, placed in a resealable plastic bag, and 10Quick N Save #2\Work Plans\Q-N-S#2 work plan 2017.doc STRATUS