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Project No. 034-17016 Site-Specific Health& Safety Plan Page No. 3 Given the findings and conclusions of the investigation of groundwater associated with releases reported at the OCC facility,the potential appears to be low for significant impacts to deep groundwater underlying the subject site.However,no data was available related to potential impacts from the COCs associated with the OCC releases in shallow groundwater which is reported to range from approximately 17 to 27 feet bgs. Consequently,the potential exists for COCs to have migrated in shallow groundwater and the condition of shallow groundwater underlying the subject site related to releases of CDCs at the vicinity OCC facility is unknown. Lt is recommended that a limited subsurface assessment be conducted in the western area of the subject site closest to the vicinity OCC facility, including soil, groundwater and soil vapor sampling and analysis for DBCP,EDB and sulfolane,to ascertain thepresence or absence ofevidence ofpotential significant migration of COCs onto the subject site related to releases from the DCC facility. PAOCs Adjacent J.R. Simplot Groundwater Remediation Case According to records reviewed on the RWQCB GeoTracker database, releases to groundwater have been documented at the J. R.Simplot facility located adjacent to the west of the subject site.According to review of background summaries for the adjacent facility,Best Fertilizers Company developed the facility in 1952 for manufacturing fertilizers. OCC acquired Best Fertilizers Company in 1963 and Simplot subsequently purchased the facility from Occidental in 1983 and currently operates a fertilizer manufacturing and warehousing facility at the site. The area of the Simplot property east of Howland Road includes Simplot's water management systems, which currently consist of a storm water pond and three lined process water ponds(north pond, south pond and west pond). Previous investigations have identified four groundwater zones beneath the facility to a depth of 338 feet bgs. The"water table zone"is approximately 10 to 27 feet bgs,the"shallow groundwater zone"is approximately 31 to 83 feet bgs,the"intermediate groundwater zone" is approximately 83 to 150 feet bgs, and the "deep groundwater zone" is approximately 151 to 338 feet bgs. Depths to groundwater in the water table zone measured in April and July 2016 ranged from 11.51 to 17.02 feet bgs and depths to groundwater in the shallow water table zone in July 2016 ranged from 17.40 to 20.50 feet bgs.The groundwater flow direction in the water table zone was calculated generally to the southwest in April 2016 and south-southwest in July 2016. Simplot monitors wells in the water table and shallow groundwater zones at the facility as part of an investigation of inorganic constituents in groundwater(primarily sulfate,nitrate as nitrogen[NJ,and ammonia as N). OCC (formerly known as Oxychem) operates a groundwater remediation system in the far western portion of the Simplot facility.The western remediation system includes eight groundwater extraction wells,a water treatment system,and three injection wells.OCC also installed a temporary groundwater remediation system on the east side of facility. This system treats water from the facility's backup supply wells. The temporary treatment system removes sulfolane from backup supply well water for use within Simplot operations. OCC reports separately to the RWQCB on operations and monitoring of these systems. Discharge to the on-site Simplot surface water impoundments is regulated by the RWQCB under a 1997 Waste Discharge Requirements Order and 2008 Monitoring and Reporting Program(MRP)which established screening concentration limits for COCs and requirements that groundwater samples should be collected on a quarterly basis. According to review of an October 26, 2016 Amec Foster Wheeler Environment & Infrastructure,Inc.(Amec)Second Semiannual and Annual 2016 Monitoring Report, Lathrop Facility, San Joaquin County, California prepared for the J.R.Simplot Company,the most recent data available,collection and laboratory analysis of samples of the surface water impoundments and groundwater monitoring wells was conducted in July 2016.The groundwater monitoring wells located closest to the subject site are identified as KRAZAN&ASSOCIATES,INC. With Offices Serving the Western United States 03417016 SSI Lathrop HASP Final.doc