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Pilot Study Workplan May 25, 2018 Diamond Foods Inc. Page 3 In November 2001 and January 2002, ATC Associates Inc. advanced nine soil borings (SB1 through SB9) at various locations on and adjacent to the site. Low levels of hexavalent chromium were detected in soil and groundwater samples collected during the investigation. The highest concentrations of hexavalent chromium in soil were detected in the samples obtained from off-site boring SB9, installed within East Worth Street, immediately north of the property boundary. Hexavalent chromium was detected in grab groundwater samples obtained from borings SB1, SB2, SB3, SB4, SB5, and SB9 at concentrations ranging from 0.0005 to 0.0051 mg/L. The laboratory-reported concentrations of total chromium were below the California Primary MCL of 0.05 mg/L. In addition, the concentrations of total chromium detected in these groundwater samples were well below concentrations previously detected in monitoring well MW-3, which historically contained the highest concentrations of total chromium in groundwater at the site (ATC, 2002a). In September and October 2002, cone penetration testing (CPT) borings CPT1 and CPT2, Geoprobe (direct push) borings CPT1a and CPT2a, and groundwater monitoring wells MW-4 through MW-8 were installed at the site. CPT1 and CPT2 borings were advanced to 120 and 139 feet bgs, respectively, to provide continuous stratigraphic definition in the borings. Discrete groundwater samples were collected from CPT1a and CPT2a at depths of 109 and 114 feet bgs, respectively. Groundwater monitoring wells MW-4 through MW-8 were installed to total depths of completed to a total depths of approximately 65 feet bgs and constructed with screened intervals extending from approximately 45 to 65 feet bgs (MW- 4, MW-5, and MW-6) or 50 to 65 feet bgs (MW-7 and MW-8). Hexavalent chromium was not detected in the soil samples collected during the installation of groundwater monitoring wells MW-4 through MW- 8. Hexavalent chromium was detected in discrete groundwater samples collected from borings CPT1a and CPT2a at concentrations of 0.170 and 0.012 mg/L, respectively. It should be noted that these discrete groundwater samples were obtained from the deeper water-bearing zone at depths of 109 and 114 feet bgs, respectively. Total chromium was detected in the water samples collected from all the wells, including the facility supply well, with the maximum concentration (6.2 mg/L) observed in the groundwater sample collected from monitoring well MW-3. The discrete groundwater samples collected from CPT1a and CPT2a were not analyzed for total chromium (ATC, 2002b). On April 29 and 30, 2003, ATC supervised the advancement and construction of deep monitoring well MW-9. The soil boring for MW-9 was advanced to approximately 113 feet bgs, and the well was completed with a screen interval extending from approximately 103 to 113 feet bgs. This groundwater monitoring well was installed in order to further assess groundwater quality within the deeper groundwater bearing interval in the vicinity of CPT1. Hexavalent chromium was detected in the groundwater sample collected from well MW9 at a concentration of 0.0049 mg/L (ATC, 2003). In May 2003, ATC conducted an additional subsurface investigation at the site that included completion of a video log survey of the facility well (FW) located inside the facility building. The well was located within a concrete below-grade vault below a concrete floor. The vault was rectangular and has dimensions of approximately 5-feet by 5-feet by 6-feet deep. The well head was mounted flush to the bottom of the vault. The total depth of the facility well borehole was observed to be 133 feet below top of casing. The bottom 25 feet of the borehole was open. Based on observations from the bottom 25 feet of the boring, the borehole diameter was estimated to be 18 to 24 inches. The well casing was constructed of steel pipe with a diameter of approximately 1 foot and extended to a depth of 108 feet from the top of casing. The well was vertically perforated beginning at a depth of 67 feet below top of casing and extended to the bottom of the casing. Diamond Foods indicated that there were no future plans to utilize the well; therefore, ATC recommended that the FW be properly destroyed. The construction details of the FW, as observed on the video log, indicate that it appeared to be screened across more than one water-bearing zone and was a potential conduit for migration of groundwater between shallow and deeper groundwater bearing intervals.