SITE INFORMATION AND CORRESPONDENCE

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Ms Vicki Goodenow - 2 - 25 November 2009 r NuStar Terminals Stockton Facili. in our 8 July 2009 letter and requested submission of a report of the investigation with recommended locations for the 90-foot bgs wells by 30 October 2009. Pursuant to the Work Plan the Report summarizes the grab groundwater sampling and well installation activities conducted at the site between 31 August and 4 September. Five monitoring wells (ACA-3A/B, ACA-4A/B, ACA-3C, ACA-4C, AND ACA-5C) were installed where previous groundwater monitoring results indicated the presence of elevated concentrations of petroleum hydrocarbons. Grab groundwater samples were collected from the D-zone from borings ACA-3 and ACA-5 from 71.5 and 82.7 feet bgs, respectively to confirm results obtained from the borings NS-18 and NS-21. The results of the comparative laboratory analysis showed that glass filtration yielded the highest concentrations of TPHd at 2,300 pg/L and 970 pg/L for D-zone grab groundwater samples from ACA-3 and ACA-5, respectively. TPHd concentrations for ACA-3 and ACA-5 by laboratory analysis using no preparation were 560 pg/L and 670 pg/L, respectively. The results for silica gel cleanup, and silica gel cleanup combined with filtration were significantly lower for ACA-3 and non-detect (ND) for ACA-5. The results of the confirmation grab groundwater samples are lower than the results from the November 2008 investigation in which TPHd was detected in D-zone borings NS-18 and NS- 21 at 11,000 pg/L and 15,000 pg/L, respectively. In their 30 January 2009 report on these D- zone results, NuStar concluded that the November 2008 results were attributable either to an off-site source or interference from non-petroleum organics. The Report concludes that the silica gel results show that the TPHd results are being artificially elevated by the presence of biogenic or plant material and concludes that further investigation, or monitoring of the D-zone is unwarranted. We do not concur that the reduced concentrations resulting from the silica gel cleanups are an indication that no further investigation or monitoring of the D-zone is necessary. On 21 May 2009, Central Valley Water Board staff met with you and representatives of Ash Creek to discuss a path forward for the follow-up vertical delineation investigation. During that meeting you proposed using silica gel cleanup to prepare samples by 8015M Central Valley Water Board staff stated that we do not allow the use of silica gel cleanup because the process removed polar organics as well. By preparing the sample with silica gel, polar diesel break- down compounds including, aldehydes, alkenes, and keytones are inadvertently removed from the sample resulting in artificially reduced TPHd concentrations. In addition, even after the silica gel cleanup procedure, the analytical result for the D-zone grab groundwater sample from ACA-3 exceeded the water objective (WQO) of 100 pg/L. This laboratory analytical result offers conclusive evidence that documented fuel releases from the NuStar facility in the past have degraded groundwater quality down to or below the D-zone. Monitoring wells at this location screened at or below the depth of the ACA-3 sample are necessary to delineate the vertical extent of the diesel pollution and promote cleanup.