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Work Plan for Phase II Subsurface Investigation 930 East Charter Way Stockton, California 95206 Partner Project Number 17-204651.2 February 1, 2018 Page I 3 Downgradient of 1 40 Soil 2, 5, 10, 15, 20, 25, Former USTs & Auto 30, 35, 40 Repair Operations Groundwater 30-40 Soil samples will be collected using a two-foot long by 1.5-inch diameter sampler with a two-foot long acetate liner and sampling point. The sampler will be advanced by a direct-push drill rig using four- foot long (three-foot long for the limited-access rig) by 1.25-inch diameter hollow rods with the inner rods in place. At approximately one foot above the desired sampling depth, an inner rod was removed and the sampler was advanced to the desired sampling depth to allow undisturbed soil to enter the sampling liner. The sampler will be retrieved from the subsurface and the soil-filled liner will be removed; Each acetate liner will be cut using a hacksaw or pipe-cutter. The liner will be capped on either end with Teflon tape and plastic caps. The capped liners will be labeled for identification and stored in an iced cooler. The soil in the liner will be visually inspected for discoloration, monitored for odors, classified in accordance with the Unified Soil Classification System (USCS), placed in a sealable plastic bag, and field-screened with a photoionization detector (PID); After soil sampling to the terminal depth, groundwater samples will be collected by withdrawing the drill rods from the subsurface and installing 1/4 -inch diameter temporary monitoring wells within the open boreholes. Each monitoring well will consist of a five-foot long, 0.010-inch factory-slotted polyvinyl chloride (PVC) screen at the terminal end and blank PVC risers from the top of the screen interval to the ground surface. Groundwater samples will be retrieved from each monitoring well using a new section of 3/8-inch diameter polyethylene tubing fed through a peristaltic pump and conveyed into five hydrochloric acid- preserved VOA vials. Each vial will be filled with no observable headspace or air bubbles to minimize the potential for volatilization, labeled for identification, and stored in an iced cooler. Prepare up to 40 soil samples and two groundwater samples for laboratory analysis; Construct a soil gas probe in each interior boring (four probes total) at five feet bgs. The final screening depth at each borehole will be adjusted based on the encountered lithology. In general possible; Collect and prepare up to four soil gas samples for laboratory analysis using laboratory-provided, batch- certified SUMMA canisters; Analyze each soil gas sample for VOCs in accordance with EPA Method TO-15/8260; Based on field-screening results, analyze one soil sample per boring (eight soil samples total) and each groundwater sample (six groundwater samples total) for carbon chain total petroleum hydrocarbons (TPH-cc) in accordance with EPA Method 8015 and for VOCs in accordance with EPA Method 8260; Additionally, analyze one shallow soil sample per boring (eight soil samples total) for California Administrative Manual 17 metals in accordance with EPA Method 6010B/7471A; Samples will be transported under proper chain-of-custody protocol in an iced cooler to SunStar Laboratories, Inc. (a state-certified laboratory [California Department of Public Health Environmental Laboratory Accreditation Program Certificate Number 2250] in Lake Forest, California) for analysis; Following sampling activities, each boring will be backfilled with neat cement grout and capped with concrete or asphalt patch to match surrounding ground; and Prepare a report detailing field activities, methods, and findings. PARTNER