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STATE OF CALIFORNIA--HEALTFI AND WELFARE AGENCY GEORGE DEUKMEJIAN, Gorornor DEPARTMENT OF HEALTH SERVICES 714/744 P STREET n< SACRAMENTO, CA 95814 p ; ATTACHMENT I Subject: Geohydrological Investigations Draft Engineering Report - Defense Depot Tracy The comments below concern the geology and hydrologeology aspects of the above cited document and the undated (received June 12 , 1986) proposed Scope of Work (SOW) fof the continuation of the investigation at Defense Depot Tracy (DDTC) . 1) In general, the report was well written and complete. Radian' s inclusion of daily logs, sieve analysis, and raw data was helpful in our review. This data is not always included .in a report and is usually requested during the review process, thereby delaying the process. DHS endorses Radian' s recommendations for off Depot work and the installation of additional on Depot wells to further delineate suspected source areas. 2) The report could benefit from additional geologic cross sections. Only one section is included in the report. At least two, and preferably four sections are needed. A fence diagram would also be helpful . The purpose of cross sections and fence diagrams is to show the author' s interpretation of the geology across the areas of interest. This is essential in determining preferred migration pathways for vapor and water and for evaluating conclusions dependent on geology, such as pump test results and monitor well screen locations. The location of upper and lower confining beds and/or water table should be emphasized in these cross sections. 3) The SOW for this draft report included a pump test (section 3 .2 . 4) . However, it appears that one was not conducted. In this report Radian recommends conducting an aquifer pump test (see section 6 . 0. 4) for the next phase of work. However, one is not included in the SOW for the next phase. A pump test must be conducted to identify the aquifer characteristics reg.0 ad to evaluate the geometry and rate of movement of the plume. As stated by Radian in section 3 . 2 . 40, a larger diameter well will be required to conduct the pump test. Note that slug tests are not a substitute for an aquifer pump test(s) .