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t <br /> UNITED STATES ENVIRONMENTAL PROTECTION AGENCY <br /> Region 9 <br /> 75 Hawthorne Street <br /> fl 77 San Francisco CA 94105-3901 <br /> January 7, 1999 <br /> Marshall Cloud <br /> Environmental Protection Office <br /> DD-Tracy <br /> P.O. Box 960001 <br /> Stockton, CA 95296-0250 <br /> RE: Draft 1999 Well Monitoring Program Field Work Plan, DDJC-Sharpe/Tracy <br /> November 1998 <br /> Dear Marshall, <br /> Thank you for the above referenced document received in our offices on <br /> December 1, 1998. <br /> EPA's review of the subject document focused on, proposed well sampling <br /> frequencies presented in Table B-2, Preliminary Recommendations for Sampling <br /> Frequencies, 1999 Groundwater Monitoring Program, DDJC-Tracy, and the <br /> supporting text. Relevant information from the Draft 1998 Annual Monitoring <br /> Report (December 1998) was also used to assist in the evaluation of Table B-2. <br /> This included a brief review of the statistical evaluation (Section 3) , the <br /> nature and extent of contamination (Section 4) , monitoring recommendations <br /> (Section 6) , and time-series plots (Appendix C) , which are presented in the <br /> Draft 1998 Annual Monitoring Report. Table 6.4-1 and Appendix J of the Draft <br /> 1998 Annual Monitoring Report were assumed to duplicate the sampling <br /> recommendations listed in Table B-2. Table B-2 was also evaluated for <br /> consistency with the monitoring rationale provided in the Final Site-Wide <br /> Comprehensive ROD (April, 1998) , Table 9-2, Performance Monitoring Network, <br /> and with the Draft Final Remedial Design Work Plan (October 1998) . Our <br /> comments follow. <br /> 1. Section 3.0, Summary of Work to be Performed, Natural Attenuation <br /> Sampling, page 3 <br /> The text explains that one difference between the 1998 and 1999 field <br /> work is that (third bullet) "groundwater samples will be collected and <br /> analyzed for natural attenuation" and "the final work plan will provide <br /> specific details. " Since the text indicates specific details for <br /> natural attenuation monitoring will not be available until this work <br /> plan is issued in final form, EPA requests an opportunity to comment on <br /> such details before they are finalized. This may entail issuing a draft <br /> 1 <br />