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Page 1 Trinity Drilling, Inc./Citadel EHS August 24, 2022 * WORK PLAN Soil Borings/Temporary Soil Vapor Probes 1651, 1681 and 1781 East Grant Line Road Tracy, CA APN #s: 213-07-017, -039, and -041 TASK 2.0: METHANE INVESTIGATION To investigate the potential presence of methane gas, Citadel will advance 10 borings across the Site to a depth of approximately 30 feet below ground surface (bgs) with a direct push drilling rig. Four borings will be located around the abandoned well, four borings within the footprint of the planned building, and two borings near the southern boundary of the Site. Please refer to Figure 1 for a Site Map showing the proposed boring locations. Due to the potential presence of drilling mud, disposal sumps and other disposal from oil operations, soil samples will be collected at five-foot intervals from each boring beginning at five feet bgs, in acetate sleeve. The soil borings will be logged by, or under the supervision of, a California Professional Geologist. Spilt soil samples collected from each boring will be field screened with a photoionization detector (PID) or equivalent to monitor the vapor space for the presence of VOCs. Soil samples with a measurable VOC concentration and/or stained or odorous soil will be submitted for laboratory analysis for additional cost and upon Client approval, Following the collection of soil samples, soil gas probes will be set in each boring at approximately 10, 20 and 30 feet bgs. After setting the gas probes, field data will be collected from the installed gas probes by means of a RKI Eagle portable gas meter. A sequential measurement will be taken from each probe at least 24-hours after the first measurements. If the RKI methane readings are above 0.0 part per million by volume, a sample will be collected for analysis for methane and hydrogen sulfide gases upon Client approval. Upon completion of methane field testing, the installed temporary soil vapor probes will be decommissioned by removing the 1/4” diameter vapor tubing from each probe location followed by capping the probe with Portland cement grout at the ground surface. As requested by the County if field observations during drilling or methane field testing indicate that the site has been impacted, then the soil vapor probes will be decommissioned by over-boring each probe to total depth and grouting with Portland cement from the bottom of the boring to the ground surface. Temporary vapor probe decommissioning tubing and/or materials will be disposed off-site at an appropriate disposal facility. Upon completion of all on-Site activities and laboratory analysis, a report will be prepared documenting Citadel’s methodologies, procedures, and laboratory analytical results. The report will provide a discussion of findings, conclusions, and recommendations regarding the current environmental conditions of the Site.