SITE INFORMATION AND CORRESPONDENCE

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M. Scott Mansholt -2 - 8 March 2005 ChevronTexaco Mountain House# 1 SOIL Concentrations of TPH as crude oil (TPH-c) were non detect in samples obtained from 12 of the 30 soil borings. Concentrations of TPH-c were reported at depths of 2 to 36 feet with highest concentrations present between 9 and 36 feet; concentrations reported ranged from 5.0 mg/kg in the 21 foot sample from boring MH1-21, to 29,000 mg/kg at 14 feet in boring MH1-10. Numerous samples reported greater than 1,000 mg/kg TPH-c between 5 and 12 feet in 10 of the borings, Additionally, previous investigations reported crude oil saturated soil at depths ranging from 10 to 30 feet in at least five different borings locations. Benzene was not reported in the soil samples; toluene concentrations ranged from 0.05 to 0.8 mg/kg in three of the borings; ethylbenzene ranged from 0.006 to 1.7 mg/kg in samples from eight borings; total xylenes concentrations detected in 10 borings ranged from 0.03 mg/kg to 13 mg/kg. PAH concentrations in 25 of the 30 borings reported several detections at or slightly above the method detection limits for the respective compounds. However, for HHSE purposes, the method detection limits are generally an order of magnitude lower, which results in very low detections not typically reported by standard PAH testing. Phenanthrene and pyrene were the two most commonly reported PAHs and were present in 32 of the 43 samples analyzed with concentrations ranging from 0.0004 to 4.7 mg/kg. Benzo(a)pyrene and dibenzo(a,h)anthracene, at concentrations ranging from 0.0003 mg/kg to 0.12 mg/kg and from 0.0007 mg/kg to 0.074 mg/kg, respectively, was reported in 20 of the 30 borings completed. GROUNDWATER Depth to groundwater at the project is approximately 12 to 18 feet and the gradient is north-northeast. TPH-d concentrations were detected in groundwater samples collected for analysis (approximate groundwater sample depths were between 12 and 22 feet)with values ranging from 1,200 gg/L to 4,200,000 gg/L(boring MH1-19); TPH as gasoline(TPH-g) concentrations ranged from 380 gg/L to 6,400 gg/L (boring MH1-10). Benzene, with one exception of 0.1 gg/L, was not detected; toluene, ethylbenzene, and xylenes reported concentrations at or above the detection limits. Generally, the elevated petroleum hydrocarbon compounds concentrations in groundwater correspond to samples having elevated TPH in soil. Concentrations of PAHs were detected at or slightly above the laboratory reporting limits in each of the 17 groundwater samples submitted for analysis. The highest PAH concentrations were reported in groundwater sample MH1-24. PAHs were detected at concentrations in MH1-24 ranging from 7.5 gg/L benzo(a,h) anthracene to 130 gg/L pyrene. Hydrocarbon-impacted groundwater appears to be limited in extent and generally coincides with the approximate outline of impacted soil that is in close proximity to the former OVP. Borings having elevated TPH concentrations are in close proximity to locations coinciding with previously identified areas of crude oil saturated soil. The outline of impacted soil and groundwater delineated is approximately 175 feet northwest to southeast and approximately 200 feet northeast to southwest; the impacted area lies within and occurs beneath the former OVP alignment, Byron Road, the current active