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Mr. Dean Hubbard California Regional Water Quality Control Board February 17, 2006 Page 2 water well will be installed at or near the property, which is within the City of Tracy. The City of Tracy Municipal Code (Section 11-1.16) requires the use of water supplied by the City and declares water wells to constitute a public nuisance that must be abated. Based on this information, exposure to groundwater is not considered a complete pathway. 2) You requested tables of results to support several statements in the HHRA. Recent and historical soil and groundwater sampling results evaluated in the HRHA are presented in the Geomatrix's 2003 Soil Investigation and Groundwater Monitoring Report 2. A copy of the report is enclosed for OEHHA's review. Specific statements that you identified and the location of relevant data are as follows: • "Metals were consistent with background conditions (Dames &Moore, 1997)" (page 3, last sentence of third paragraph). See Table A-6 in Appendix A. • "The results of the 2003 investigation indicate that BTEX were not detected above the laboratory detection limits" (page 4, first sentence of first full paragraph). See Table 3. • "MTBE was not detected in any of the wells sampled, and therefore, subsequent samples were not analyzed for MTBE" (page 5, last sentence of first partial paragraph). See Table A-1 in Appendix A. 3) Regarding lead concentrations detected in historical groundwater samples from Well-E and Well-F, the HHRA states "it is not clear whether samples were filtered prior to analysis and, therefore,these detections may not represent dissolved lead in groundwater" (page 5, first partial paragraph). We note that samples collected from these wells by Geomatrix in October 2001 were analyzed for lead using U.S. EPA Method 620 after filtration of the samples in the field using a 0.5 micron filter. Lead was not detected in the Geomatrix samples above the analytical reporting limit of 1 microgram per liter. Historical lead concentrations for groundwater samples are presented in Table A-3 of Appendix A of Geomatrix's 2003 Soil Investigation and Groundwater Monitoring Report. 4) You noted that the text in the third sentence of the third paragraph of page 6 was unclear about what soil data were considered in the HHRA due to a typographic error. The text should read"...only the most recent soil data (Geomatrix, 2003) were considered in this evaluation." A revised Page 6 is enclosed. 2 Geomatrix,2003,Soil Investigation and Groundwater Monitoring Report,TAOC Tracy Pump Station,Tracy, California,December 16. t:\Project\7000s\7065\Risk\L a tier-02_06.doc