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Limited Site Investigation Irerracon Vacant Property ■Tracy, California November 13, 2020 ■Terracon Project No. NA197074 Terracon field-screened soil samples for organic vapors using a calibrated photoionization detector (PID). This device provides a direct reading in parts per million by volume (ppmV) isobutylene equivalents. Upon removal of the sampler from the borehole, Terracon put a portion of each sample in a sealable plastic bag. After a stabilization period, Terracon screened the headspace above the soil using the PID. PID readings were detected from 0.0 ppmV to 154.7 ppmV in soil collected from the borings. Additionally, an odor of petroleum hydrocarbons was noticed in multiple soil borings during the investigation. The field screening results are summarized on the boring logs in Appendix C. Soil samples were collected from the depth interval most likely to be impacted as field screened with a PID, change in lithology, or from the upper soil zone. A total of 36 soil samples were collected and submitted for laboratory analysis. Soil samples were extracted from each core by hand using disposable gloves and placed directly into laboratory- supplied glassware. Each sample container was labeled with the project number, date, time, boring number, and sample number. Sample containers were placed in a chilled cooler immediately after sampling, and subsequently transported to SunStar Laboratories, Inc., a California State-accredited laboratory under strict chain-of-custody procedures. 3.3 Geology/Hydrogeology In general, Terracon encountered low to medium plasticity, light brown to dark brown, moist, silty sand and sandy silt soils with varying amounts of clay to an approximate explored depth of 30 feet bgs. Groundwater was not encountered at the maximum explored depth of 30 feet bgs (SB4). The boring logs attached in Appendix C detail the observed soil stratigraphy at each boring location. 4.0 ANALYTICAL RESULTS The selected soil samples were analyzed for total petroleum hydrocarbons as gasoline, diesel, and motor oil (TPH-GRO, TPH-DRO and TPH-MORD) by EPA Method 80158, volatile organic compounds (VOCs) by EPA Method 8260B, organochlorine pesticides (OCPs) by EPA Method 8081, and chlorinated herbicides (CHs) by EPA Method 8151 A. A summary of the soil analytical results is provided in Table 1 (Appendix B). Analytical reports and Chain of Custody manifest are provided in Appendix D. Data packages were checked for completeness upon receipt from the laboratory to ensure that data and QA/QC information requested were present. Data quality was assessed by considering holding times, surrogate recovery, method blanks, matrix spike and matrix spike duplicate recovery, and method reporting limits. Based upon our interpretation of quality control information Responsive ■ Resourceful ■ Reliable 4