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Pilot Study Workplan November 7, 2014 Project#54.62563.0001 Page 6 4.0 NATURE AND EXTENT OF CONTAMINATION 4.1 CONTAMINANTS IN SOIL In December 1988, Weiss Associates conducted the initial soil investigations in the vicinity of the previously referenced vaults to determine whether the vault contents had impacted the soil beneath the vaults. The samples collected beneath Vaults 1, 5, and 6 were analyzed for ethylene glycol and propylene glycol. Initial laboratory results reported ethylene and propylene glycol as detected beneath Vaults 1 and 6. The samples collected beneath Vaults 7 and 8 were analyzed for soluble total chromium, soluble copper, total sodium, and total sulfate. Additionally the Vault 8 samples were analyzed for soluble hexavalent chromium, total calcium, and total chloride. All analytes were present at or above method detection limits beneath Vaults 7 and 8. Based on analytical data from soil samples collected beneath the vaults it appears that releases primarily occurred from Vaults 1, 6, 7, and 8. In January 1991, PC Exploration drilled three angle borings (61-A, B6-A, and 138-A) and three vertical borings (61-13, 66-13, and 68-13) in the vicinity of Vaults 1, 6, and 8 under the direct supervision of a Weiss Associates geologist. These borings were drilled in an attempt to define the extent of soil contamination and to determine if groundwater impact had occurred. Borings B1-A, B6-A, and 68-A were drilled to depths of 45.3, 37.6 and 40.8 feet, respectively. Borings B1-13, 136-13, and 68-13 were drilled to depths of 91, 86, and 96 feet, respectively. In samples collected near Vault 1, glycols were detected in several soil samples collected from angle boring B1-A, but were not detected in the soil samples collected between 50.3 and 65.7 feet below grade in the vertical boring samples (61-13). In Vault 6 glycols were not detected in the soil samples collected deeper than 33.4 feet in the angle boring (66-A) and were not present in the vertical boring samples (66-13). The soluble total chromium, total chromium, and total hexavalent chromium analytical results for the Vault 8 samples were below their respective DHS, STLC and TTLC limits. Although total sodium analytical results did not significantly exceed the sodium background concentrations, the total calcium and total chloride results did exceed their respective background concentrations. In November 2001 and January 2002, ATC advanced borings SB1 through SB9. The borings were placed in locations upgradient and downgradient from the closed vaults to evaluate the lateral extent of impacted soil. Hexavalent chromium was detected at relatively low concentrations in soil samples from borehole locations SB1 through SB9 from the 20 and 40-foot depths with the exception of SB8 at 40 feet. The highest concentrations of hexavalent chromium were detected in the samples from off-site boring SB9 at 1.5 and 2.6 milligrams per kilogram (mg/kg). Concentrations of hexavalent chromium in the samples from borings SB1, SB2 and SB3 ranged from 0.09 mg/kg to 0.61 mg/kg. Concentrations of hexavalent chromium were lowest in borings SB4 through SB8, ranging from 0.0010 mg/kg to 0.0074 mg/kg. Hexavalent chromium was not detected in the soil sample from SB8 at 40 feet bgs above method detection limits. The Total Threshold Limit Concentration (TTLC) for hexavalent chromium compounds is 500mg/kg. Hexavalent chromium was not detected in any soil samples collected from borehole locations MW4 through MW8 from the 40 and 50-foot depths. The three samples collected from SB10 were analyzed for alkalinity by EPA Method 310.1, ammonia by Standard Method 4500, nitrate by EPA Method 300, total organic carbon (TOC) by ASTM D2974, Hexavalent