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Mr.James Diel -2- 20 September 2010 Former Tracy Maintenar Facility ARCADIS concludes that "the biotreatment of the TPCA pond soil/sludge was effective, has not adversely affected the environment, and has achieved the substantive requirements of the CAO." ARCADIS recommends no further action and that the CAO be rescinded. We appreciate UP's efforts to characterize Biotreatment Beds 1 and 2. While we recognize that the CAD's specific cleanup goals for soil and groundwater were not achieved, we acknowledge that additional remedial action at the site to achieve the stated cleanup goals in the CAO may not be cost-effective if there are no continuing threats to water quality, human health or ecological receptors. ARCADIS recommends an alternative cleanup level for TPHd in soil, adopted from the Region 2 Environmental Screening Levels (ESLs) for shallow soils in commercial/industrial land use scenarios. The recommended cleanup goal of 2,200 mg/Kg and the request for recission of the CAO will be taken under consideration. However, we request that you provide specific information to demonstrate that the proposed cleanup goal is protective of groundwater, human health, and the environment: • Soil TPHd concentrations should not exceed the de minimis 1 in a-million excess cancer risks for inhalation of dust, dermal contact (including workers and children), and sensitive ecological receptors. • Soil TPHd concentrations must be shown to be incapable of leaching to groundwater at levels that exceed beneficial use protective concentrations. • Summary tables and discussion of historical sampling results for semi-volatile organic compounds (including PAHs and naphthalene) and metals in soil and groundwater in the biotreatment area must be provided. This information in necessary to support the claims made in the Report that these compounds are present below cleanup goals, or (in the case of metals) are consistent with samples collected elsewhere on site. • Unless unrestricted use is achieved at this site a Land Use Covenant in the form of a Deed Restriction will be necessary. The requested information should be presented in a detailed report that demonstrates you have satisfied these requirements and the substantive requirements of the CAO. Please submit this report by 8 November 2010. If you have any questions regarding this matter, please contact me at (916) 464-1588, or by email at kdominic@waterboards.ca.gov. f KATHRYN L. DOMINIC, P.G. ENGINEERING GEOLOGIST CC'. Mr. Michael Infurna, San Joaquin County Public Health, Stockton Mr. James Eisert, ARCADIS, Roseville