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San Joaquin County Environmental Health Department Site Mitigation Program 30 June 2021 Page 2 Pre -field Activities The following pre -field activities will be completed prior to performing the fieldwork associated with the soil vapor sampling: • Preparing a Site -Specific Health and Safety Plan (HASP) outlining the procedures to be followed during the field sampling activities. • Marking the Site and notifying Underground Service Alert (USA) and obtaining a USA Ticket Number for the field sampling activities. Procuring field and sampling equipment along with sampling canisters and coordinating with the laboratory. Field Activities Haley & Aldrich will install and sample temporary soil vapor probes at two on -Site locations adjacent to the crude oil pipeline (Figure 1). To perform this sampling, Haley & Aldrich will conduct the following activities: A private utility locator will be used to scan for underground utilities in the vicinity of the proposed soil vapor sampling locations. Two approximately 2.25 -inch diameter borings will be advanced by a California C-57 licensed driller using a direct -push drill rig to a total depth of approximately 5.5 feet below ground surface (bgs). A temporary soil vapor probe will be installed in each boring at a depth of approximately 5 feet bgs. Small diameter (1/4 -inch) Teflon® tubing, fitted with a filter at the bottom to prevent particulate infiltration, will be placed in the boring at approximately 5 feet bgs. Approximately 12 inches of filter pack sand will be placed around the tubing inlet in the bottom of the boring (from 4.5 to 5.5 feet bgs). After installation of the sand pack, the borehole will be backfilled to the surface with hydrated bentonite. Once the construction of the soil vapor probe is complete, the tubing will be capped with an air -tight valve. A protective cover will be placed over each soil vapor probe location. Soil vapor probes will be allowed to equilibrate for a minimum of 2 hours prior to purging and sampling. Per California Department of Toxic Substances Control (DTSC) guidance, if a rain event producing more than a half-inch of rain occurs in a 24-hour period, sampling will not be completed for a minimum of 5 days afterward. • Prior to sample collection, the soil vapor probes will be leak tested and purged, then sampled in general accordance the California Environmental Protection Agency/Department of Toxic Substances Control Advisory—Active Soil Gas Investigations (ColEPA/DTSCAdvisory), dated July 2015. • Soil vapor samples will be submitted following standard environmental handling methods and under chain -of -custody documentation to a California -certified analytical laboratory for volatile � RICH