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Paul Franzia - 2 - 20 April 2006 <br /> 4. Section 2 describes sampling of off-site water wells within a one-mile radius of the site. <br /> The usefulness of the data to be collected is questionable because of the likelihood that <br /> the off-site wells are screened in a deeper zone. For example, the on-site wells at the <br /> facility have TDS concentrations that range from 180 to 240 mg/L, but the monitoring <br /> wells have TDS concentrations in the range 410 to 1,400 mg/L. <br /> 5. The last paragraph in Section 2.1 implies that the proposed sampling locations described <br /> in Section 2.3 might change based on information gathered from publications and site <br /> reconnaissance. Please inform staff of any changes in proposed drilling locations prior to <br /> performing fieldwork. <br /> 6. Section 2.3.1 does not address CPT-5; please describe if the test will be performed as <br /> part of initial work or on an as-needed basis. <br /> 7. Section 2.3.3 discusses CPT-15 as an onsite location. Figure 10 shows CPT-15 as <br /> located to the west of the facility. Please clarify the test location. <br /> 8. The CPT discussion is not adequate for a reader to determine the scope of the <br /> investigation. There is no discussion of the following items: <br /> a. What traces will be recorded. <br /> b. What the target sample collection depth interval is. <br /> c. How samples will be collected, sample containers, preservatives, etc. <br /> d. How the CPT holes will be grouted. <br /> e. A discussion of the need for permits issued by the San Joaquin County <br /> Environmental Health Department (SJCEHD). <br /> 9. Section 2.2 states that a hydrogeological conceptual model will be developed. Please <br /> review the attached guidance on development of numerical models and use as <br /> appropriate. <br /> Please address each of the items listed above prior to implementing the Workplan, if you have <br /> any questions on this information, or would like to schedule a meeting to discuss the issues <br /> identified in this letter, please telephone me at (916) 464-4616. <br /> TIMOTH R. O'BRIEN <br /> Waste Discharge to Land Unit <br /> Enc: Guidelines for Development of Numerical Models <br /> cc: Margaret Lagorio, San Joaquin County Environmental Health Department, Stockton <br /> Robert Chrobak, P.E., Kennedy Jenks Consultants, San Francisco <br /> W\St&nObnenTTSen Joaquin) amel Ten Escalon Wnery\Frsmja 14 Apr Mdoc <br />