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Phase 11 Environmental Site Assessment Report Page 3 WESTLAKE SUBDIVISION VILLAGE E, G, H, I AND J Regatta Lane Stockton, California WKA No. 13221.02 July 27, 2021 techniques to identify sample location coordinates and a high-accuracy global positioning system receiver (GPSr) to locate sample coordinates in the field. Soil Sample Collection WKA used manually operated soil sampling tools to collect soil within the interval between zero and six inches and 2'/2 to 3 feet below ground surface (bgs). The shallow samples represented excavated soil placed as fill, and the deeper samples represented soil originally exposed at the ground surface. Dense accumulations of root material were excluded from the sampled interval. WKA collected eight soil samples from soil that was stockpiled on the Site. WKA evaluated each soil sample for the presence of non-soil materials and described soil according to the Unified Soil Classification System (USCS). WKA cleaned the soil sampling tools before each use by washing them in a solution of clean water and a surfactant, then rinsing the tools in three baths of clean water. WKA placed each of the 136 soil samples (64 excavated soil samples, 64 original grade samples, and eight stockpile samples) into a laboratory-provided container that was sealed using a Teflon TM-lined lid. WKA labeled each sample container to indicate a unique sample number, sample location, time and date collected, and the sampler's identification. Each container was preserved in a chilled cooler during transportation, with completed chain-of- custody forms, to California Laboratory Services (CLS), a California State Water Resources Control Board Environmental Laboratory Accreditation Program (ELAP) accredited laboratory. Soil Descriptions WKA observed soil varied between brown, silty sand that was moist and exhibited mottling, to a dark brown sandy clay with minor to moderate silt that was moist and that usually exhibited mottling. The sandy clay exhibited low plasticity. The Unified Soil Classification System (USCS) classifies the silty sand as SM and the sandy clay as SC. WKA observed that test pit sidewalls did not exhibit visual indicators of the contact between the original ground surface and the soil placed as fill. 4.0 LABORATORY ANALYSIS WKA requested CLS to composite the 64 shallow soil samples and the 64 deeper soil samples collected across the Site using a four-to-one ratio so that 32 samples from each interval were analyzed for total arsenic using EPA Method 6010 and OCPs using EPA Method 8081. The remaining 8 samples were composited using a four to one ratio so that 2 samples of stockpiled NM