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Pilot Study Workplan May 25, 2018 Diamond Foods Inc. Page 4 On October 13, 2004, a geologist from ATC supervised the advancement of two soil borings, SB10 and SB11, to collect soil samples for use in a bench scale test. Soil boring SB10 was advanced at an approximate 35 degree angle from vertical in a southerly direction, beneath the cooling unit. Soil samples were collected at three different depths in order to assess the potential presence of hexavalent chromium. Assuming drilling angles and using trigonometric functions, the soil sampling intervals correspond to vertical depths of approximately 13.6 to 17.3 feet bgs, 23.3 to 27.1 feet bgs, and 33.4 to 37.3 feet bgs, respectively. Soil boring SB11 was advanced vertically in the vicinity of MW-7 to an approximate depth of 39.5 feet bgs and soil samples were collected to further assess the lateral extent of hexavalent chromium impacted soil in the vicinity of MW-7. SB11 is located hydraulically crossgradient with respect to Vault 8 and the cooling unit. Soil samples were collected from SB11 at vertical depth intervals of 15 to 19.5 feet bgs, 25 to 29.5 feet bgs, and 35 to 39.5 feet bgs. The soil samples collected from SB11 were visually inspected to ensure the lithology was similar to that of the samples collected from SB10. The purpose of soil sample collection from SB11 was to provide non- impacted control samples or samples representative of background concentrations for baseline characterization and bench scale testing. The concentrations of hexavalent chromium detected in the soil samples collected from beneath the chiller unit were low and were comparable to the concentrations detected in the soil samples collected from beyond the known extent of hexavalent chromium impacted soil. It was concluded that it was possible that previously impacted soil beneath the cooling unit has been flushed over time by cooling water leaching into the subsurface, resulting in low concentrations of hexavalent chromium in the soil. Due to the production of elevated manganese concentrations, bench scale testing of zero valance nano-scale iron was recommended. This material was shown to reduce hexavalent chromium to trivalent chromium and may have less propensity to produce high manganese concentrations as a secondary affect to groundwater (ATC, 2005a). On August 1, 2005, the facility well (FVV) was permanently abandoned. FW was destroyed by using a Mills Knife to perforate the entire length of the well casing. The perforating tool was removed from the well and a cement and sand mixture (10 sack) was pumped into the well under pressure using tremmie pipe that was placed at the bottom of the well and raised as the cement and sand mixture rose to the top of the casing. The vault was filled with the cement and sand mixture to within approximately one foot of the top of the vault (at grade). Approximately 13.5 cubic yards of the cement and sand mixture were pumped into the well and vault (ATC, 2005b). Groundwater monitoring and sampling has been conducted quarterly following the installation of each monitoring well in accordance with MRP R5-2004-0840. In August 2011, ATC requested a reduction in frequency and analyses. The CVRWQCB issued a revised MRP (No. R5-815-2011) which reduced the frequency of groundwater monitoring and sampling from quarterly to semi-annual and reduced the laboratory analytical regime. This sampling schedule has been followed until the present. On June 2, 2015, monitoring well MW-4 was replaced. The casing of MW4 had previously been found to be obstructed and could not be sampled. Well replacement activities consisted of over-drilling and re-installing one existing site-related monitoring well within the same boring. The replacement well (MW-4R) was constructed with a 20 foot screen interval of 0.010-inch slotted Schedule-40, 2-inch diameter PVC extending from 45 to 65 feet bgs. On June 9, 2015, replacement monitoring well MW-4R was developed. On June 3 and 4, 2015, two nested groundwater observation wells, OBSW-S and OBSW-D were installed at the site near existing monitoring well MW-3 and in the vicinity of Vaults 7 and 8. The wells were constructed to the depths of approximately 55 feet below ground surface (bgs) and 75 bgs, respectively. Shallow observation well OBSW-S was constructed with 10 feet of 0.010-inch slotted Schedule 40 2-inch diameter PVC casing extending from approximately 45 to 55 feet bgs. Deep observation well OBSW-D was constructed with 5 feet of 0.010-inch slotted Schedule 40 2-inch