SITE INFORMATION AND CORRESPONDENCE

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Mr. Stephan Defibaugh - 3- 12 May 2009 KMEP Stockton Terminal • • However, MTBE is the COC with the lowest concentration in SP/M-3. The other two constituents that also currently exceed their respective WQOs in SP/M-3, TPHg and TPH as diesel (TPHd), occur at concentrations that are three orders of magnitude higher than MTBE. If evaluated in accordance with the Guidance, it is likely that these CDCs would require considerably greater time frames to attain their respective WQOs. Using the post-manifold release, November 2006 MTBE data for SP/M-1, as preferred by KMEP for this well, Central Valley Water Board staff calculated that the kp"i,,t#or MTBE in SP/M-1 is about 0.065 pg/year. At this rate, the calculation shows that the WQO for MTBE would not be attained until 2104. This projection is about 95 years longer than the 2009 date projected by KMEP. In 1994, KMEP conducted a biosparge pilot study in the manifold area to evaluate that technology as a groundwater remedy for the Site. The results of the study showed that this technology was incompatible with prevailing groundwater conditions. KMEP also twice excavated soil in 2002 and 2006 to mitigate petroleum hydrocarbons releases in the manifold area. However, the existing infrastructure of the Site significantly inhibited the removal of contaminated soils from this area. The extended time required to attain the MTBE WQO by MNA in SP/M-1 shows that MNA is as ineffective as biosparge technology at achieving the RAO at this Site. An alternative groundwater remedy must be identified and implemented in order to comply with the terms of the Cleanup Plan. The removal of all pollutants from groundwater is contingent on lateral and vertical definition of the plume. Groundwater bearing units underlying the Site are subdivided into four progressively deeper units designated as zones A through D. The shallow and deep zones discussed earlier in this letter correspond to the A- and B-zones: Currently there are no monitoring wells on the KMEP site screened in the C- or D-zones to vertically delineate the groundwater pollution. Lateral delineation also has not been completed. In summary, although the results of the MNA and Mann-Kendall analyses indicate that biodegradation is active in the plume beneath the Site, KMEP has not accurately characterized the rate at which the plume is being attenuated. Our preliminary calculations show that MNA will not attain WQOs in a reasonable time. As such, we will require KMEP to identify and implement a remedial technology with the capacity to fulfill the terms of the 2005 Groundwater Cleanup Plan. Implementation of a remedy will require lateral and vertical delineation of the plume and the installation of C- and D-zone wells. Pursuant to this requirement, we will contact you to set up a meeting to discuss our findings and formulate a strategy for addressing the Site. If you have any questions regarding this letter, you may contact me at (916) 464-4811 or by email at betaylor(aDwaterboards.ca.gov. BRIAN TfS' P.G. Engine ing Geologist cc list on next page