SITE INFORMATION AND CORRESPONDENCE

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Mr. Joseph Mello, CHG - 3 - 23 January 2013 • The nearest existing water supply well or surface water body is greater than 1,000 feet from the defined plume boundary. Site groundwater conditions have not met the final criteria that dissolved concentration of benzene and MTBE are each less than 1,000 micrograms per liter (Ng/L). Three monitoring wells (ST\MW-1, PS\MW-14, and PS\MW-15) contain concentrations of benzene or MTBE in excess of 1,000 pg/L. I do not concur with NuStar's recommendation that the cleanup level for benzene and MTBE should be 1,000 pg/L. NuStar needs to continue to use the WQOs defined in the Basin Plan as cleanup goals for groundwater at the Site. 6. The groundwater isoconcentration contours for the Site do not include the posted data and the greatest concentration used for the contour lines is 1,000 pg/L. Future monitoring reports need to include the posted data for the wells on the figure, In addition, the least isoconcentration contour line needs to be the WQOs, not the values listed in the LTCP or any other values, and successive isoconcentration contour lines should increase in concentration by an order of magnitude. 7. The Report lists the California Regional Water Quality Control Board — Bay Area Region Environmental Screening Levels (ESLs) as Cleanup Levels for the Site. The 15 September 1998 Water Quality Control Plan for the Sacramento and San Joaquin River Basins (Basin Plan) considers all groundwater to be a potential drinking water source and requires cleanup to background concentrations, if technically and economically feasible. Since petroleum hydrocarbons do not naturally occur at this Site, the preliminary cleanup level for all petroleum hydrocarbons is nondetectable at normally-achievable laboratory method detection limits. If background levels cannot be achieved, the Basin Plan provides WQOs for a select list of commonly occurring contaminants. The WQOs for the Site include 100 pg/L for TPHd and 5 pg/L for TPH as gasoline (TPH-g). Since the normal detection limit for TPH is 50 pg/L, the default WQO for TPH-g is 50 pg/L. In summary, I concur with NuStar's recommendation for long-term monitoring at the Site because the Site is an operating bulk fuel terminal; there are no drinking water wells within one mile of the Site; surrounding properties are industrial and future land use is proposed to continue to be industrial; and active remediation would not reduce the time required for groundwater to meet the WQOs. I do not concur that NuStar can limit the semiannual monitoring to only the three wells with concentrations of benzene and MTBE above 1,000 tag/L and that no further monitoring in the B zone is required. I have prepared a draft Monitoring and Reporting Program (MRP) for NuStar and you to review. I propose that NuStar conduct monitoring in accordance with this revised MRP for two years and then reevaluate the current and future Site conditions and provide further recommendations. In addition, NuStar needs to use the WQOs as the cleanup goals and future monitoring reports need to include revised isoconcentration contours with posted data and appropriate contour intervals.