SITE INFORMATION AND CORRESPONDENCE

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Mr. Joe Aldridge -2 - 12 June 2008 , ST Services Stockton Terminal • submit a second work plan addendum, if warranted based on the C-zone results, proposing deeper borings. NuStar has conducted monitoring at the Site since 1992. In 2002, gasoline releases occurred from aboveground storage tanks (AGTs) G 3301, G 3302, and D 1503. Groundwater monitoring at the Site is conducted pursuant to Monitoring and Reporting Program (MRP) No. R5-2007-0818. Regional Water Board staff reviewed the 29 April 2008 Groundwater Monitoring Report, First Quarter 2008 (First QMR). The source area monitoring well, PS/MW-14, has historically contained SPH and therefore was not usually sampled until August 2005, when no SPH was observed. During the first quarter of 2008, the maximum concentrations of TPHd and BTEX in this well were 8,000 micrograms per liter (pg/L), 10,000 pg/L, 390 pg/L, 1,200 lag/L, and 950 pg/L, respectively. The highest concentration of TPI-Ig was detected in PS/P-12 at 67,000 pg/L. Maximum MTBE and TBA concentrations were 3,000 pg/L and 3,100 pg/L, respectively. NuStar did not sample monitoring well UP/MW-1 during the first quarter because it is reportedly buried by gravel and could not be located using a metal detector. NuStar proposes using an excavator to locate the well and will sample PS/WC-4S in the meantime to allow collection of data in this area. Our comments are presented below. 1 . Based on data from nearby sites, Regional Water Board staff believe that investigation of the C and D zones likely will be necessary to accomplish vertical delineation. We are concerned that the phased approach proposed by NuStar, which will involve the preparation of multiple work plans and equipment mobilizations, will unnecessarily prolong the investigation. Site characterization must be completed more quickly so that cleanup methods may be initiated. Thus, we request that NuStar consider applying the Triad Approach to performing this investigation instead of phased approach proposed in the Work Plan. The Triad Approach is a field investigation and cleanup strategy developed under the leadership of the U.S. Environmental Protection Agency (EPA) that utilizes modern subsurface investigation techniques and a mobile analytical laboratory to cost- effectively achieve rapid site characterization. Guidelines for implementing Triad are available on the internet at www.triadcentral.org. By 25 July 2008, NuStar needs to submit a revised Work Plan to implement a more rapid investigation method, preferably in accordance with the Triad Approach. 2, The Work Plan states that an objective of the vertical delineation is to determine whether groundwater underlying and downgradient of the facility has been degraded by releases from the facility. NuStar has stated several times in the past year that it believes the pollution offsite downgradient of the NuStar facility originates from other facilities. Therefore, it appears that NuStar may intend to use the data obtained during this investigation to prove that the plume underlying and downgradient of NuStar originated from a different facility. However, the Work Plan contains no explanation of how this will be accomplished. Regional Water Board staff's goal for this investigation was to obtain data necessary to fully characterize the Site in preparation for cleanup. Given the high concentrations of pollution in the shallow zone on the NuStar site, it is likely that deeper zones also are polluted. Analysis of soil samples obtained during this investigation would