SITE INFORMATION AND CORRESPONDENCE

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Mr. Joe Aldridge -2 - 22 April 2009 NuStar Terminals Stockton Facility of dissolved phase petroleum hydrocarbons were observed in ST/MW-1 and PS/P-12. Maximum concentrations in these two wells included TPHg and TPHd at 160,000 micrograms per liter (pg/L) and 220,000 pg/L, respectively, and benzene at 16,000 pg/L, toluene at 8,100 pg/L, ethylbenzene at 3,500 pg/L, xylenes at 2 1,000 pg/L, and MTBE at 210,000 pg/L. The maximum TBA concentration was 2,800 pg/L in PS/MW-15, which is near the downgradient edge of the plume. PS/WC-4S was sampled in lieu of monitoring well UP/MW-1, which has been buried by construction activities. Table 6 in the Annual Report lists the monitored natural attenuation (MNA) results for 2008, and the text states that petroleum hydrocarbons are currently being degraded under both aerobic and anaerobic processes. The Investigation Report states that NuStar advanced 21 borings (NS-1 through NS-21) and collected soil and groundwater samples from the A through D zones. Three A-zone soil samples were submitted for laboratory analysis. Seven groundwater samples were collected from the A-zone, 17 from the B-zone, 10 from the C-zone and 1 from the D-zone. NuStar believes that zones observed east of the site correlate with shallower groundwater bearing units beneath the Site. Therefore, they propose to reclassify the units to correspond with shallower depths. Soil samples collected in suspected off-site source areas in the vicinity of Stork Road from depths ranging from eight to 11 feet bgs had maximum TPHg and TPHd concentrations of 1,300 milligrams per kilogram (mg/kg) and 370 mg/kg, respectively. These borings contained no MTBE above detection limits and low concentration of BTEX. Based on these findings, NuStar determined that these areas could no longer be considered source areas for the groundwater plume in the.Site vicinity. The highest concentrations of TPHd were observed in grab groundwater samples from C- and D-zone boring NS-11 at 54,000 pg/L and 29 pg/L, respectively. Elevated TPHd concentrations were also present in groundwater samples obtained from NS-7, NS-3, NS-14, and NS-21. Elevated concentrations of TPHg were found in grab groundwater samples from the A through D zones in borings NS-5, NS-8, NS-9, NS-12, NS-18, and NS-19. The highest grab groundwater concentration of TPHg was observed in a C-zone sample collected from NS-8 at 28,000 pg/L. These locations generally correlated with the highest concentrations of BTEX compounds. The highest grab groundwater detections of MTBE and TBA occurred at NS-5 and NS-1 in the reclassified A/B zone at 1,700 pg/L and 2,100 pg/L, respectively. NuStar's evaluation of the groundwater data states the following: • MTBE concentrations increase with depth from the shallowest water bearing zone to about 50 feet bgs. • There appears to be a channel of coarser grained material facilitating the spread of benzene and MTBE. • The elevated concentrations of TPHd observed in NS-21 indicate the presence of an off- site source that is unrelated to the MacSteel facility since no clear pathway exists to the D-zone.