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4.0 EVALUATION OF PAST AND CURRENT SOURCES OF CONTAMINATION IDENTIFIED AT OR NEAR THE SITE AND RECOMMENDATIONS FOR FURTHER ACTION Evaluation of each potential and/or known source of contamination identified in Section 3.0 above for any real and/or potential threat to human health and the environment has been completed by our firm. The referenced contamination sources all resulted from the former use of the Site as a sugar refinery. Decommissioning of the former facility, including removal of hazardous wastes/materials, ASTs, USTs and other infrastructure of interest was conducted with concurrence from the San Joaquin County EHD. Multiple phases of soil, groundwater and vapor assessment,removal of ASTs and USTs (gasoline and #6 fuel oil, fuel/bunker oil) and soil removal actions have all been completed at the Site under the regulatory oversight of the San Joaquin County EHD and the RWQCB. Assessment also included the areas of the former wastewater treatment ponds.The following is a summary of findings resulting from the assessment and mitigative work completed. • No remarkable residual soil, soil vapor and groundwater impacts are present at the Site. Minor residual impacts are limited to isolated areas and do not represent an ongoing threat to human health and the environment. • Residual impacts do not represent vapor intrusion concerns for the current Site uses and former planned new commercial development of the Site. • Groundwater at the Site and in the surrounding area is highly degraded (due to salinity) as a result of a nearby City of Tracy owned and operated wastewater treatment facility and associated ponds. The degraded groundwater quality further supports the conclusion that any isolated residual impacts that resulted from former Site operations and not a significant impact to the environment and groundwater resources. • There are no adverse impacts to process water supply wells in the surrounding area that have resulted from the Site. • Former groundwater monitoring wells at the Site have been property abandoned in accordance with County and State standards. • The former dry gas well at the Site was properly abandoned in accordance with State standards. On the basis of the findings noted above,multiple no further action letters have been generated for the Site as follows: • December 28,2010 - RWQCB in collaboration with San Joaquin County EHD • July 5, 2011 - San Joaquin County EHD in collaboration with the RWQCB • July 14, 2011 -RWQCB in collaboration with San Joaquin County EHD • July 28, 2011 - San Joaquin County EHD in collaboration with the RWQCB • June 18, 2024 — California Department of Conservation Geologic Energy Management Division • July 31, 2025 - San Joaquin County EHD in collaboration with the RWQCB Copies of the above referenced no further action letters are attached to this report. Surface and Subsurface Contamination Evaluation February 9,2026 Parcel Map 17017,Tracy,California Page 5 of 7