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Geosptec consultants • Encroachment permits will be obtained from the City of Stockton prior to lane closure(s)required to conduct the work. A traffic control plan will likely be required as part of the encroachment permitting process. 3.2.3 Utility Survey At least 72 hours prior to intrusive field activities, Underground Services Alert (USA) North 811 will be notified of the intent to drill.USA will contact all utility owners of record within the Site vicinity and notify them of the intention to conduct subsurface investigations in proximity to buried utilities. All utility owners of record, or their designated agents, will be expected to clearly mark the position of their utilities on the ground surface for utilities that are located in public areas. In addition,a private utility locator will be used to mark private utilities and clear proposed drilling locations.Utilities will be clearly marked on the ground surface and subsequent field activities will be planned accordingly. 3.3 Off-Site Investigation Activities Boring locations will be selected and marked at each site prior to drilling,as presented in Figure 4.Boring locations may be adjusted based on field conditions. 3.3.1 Soil Vapor Probe Installation Three borings will be advanced using a hand auger to a depth of 5 feet bgs to clear for utilities before using mechanical drilling technologies. After clearing the borehole, a C-57 licensed driller will advance the borings using direct push technology(DPT to reach the total depth of approximately 20 feet bgs). At each sample location, a soil probe will be installed in the boring, sealed at the surface using bentonite clay, and then purged and sampled through a Teflon® tube into a SummaTM canister. In general, soil vapor probe installation and sampling will follow Advisory—Active Soil Gas Investigations, published jointly by the Department of Toxic Substances Control (DTSC), Los Angeles Regional Water Quality Control Board (LARWQCB), and San Francisco Bay Regional Water Quality Control Board(SFRWQCB) (DTSC et al, 2015). Each boring will be advanced to first encountered groundwater, which is anticipated to be approximately 20 feet bgs. The soil will be continuously logged by a Geosyntec field staff under the direction of a California Professional Geologist using the Unified Soil Classification System (USCS). The geologic boring logs will include classification of encountered soils, sampling depths,drilling observations,and the total boring depth. Three multi-depth soil vapor probes will also be installed along West Hammer Lane in accordance with the soil vapor probe installation Standard Operating Procedures (SOP) included in Appendix B. Each probe will consist of/4-inch diameter Teflon®tubing connected with a compression fitting to a '/4-inch diameter stainless-steel sampling point. The probes will be installed with one foot of sand filter pack around the stainless-steel sampling point,one foot of dry granulated bentonite and hydrated bentonite to the next probe interval. The stainless-steel probes will be placed at approximately 5 and 15 feet bgs. Final depths may be adjusted based on field conditions, targeting more permeable soil strata and professional judgement. Following installation,the soil vapor probes will be allowed to equilibrate for a minimum of 2 hours prior to sampling. 7 September 2025