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1 - - <br /> GEOMArRIX <br /> Mr Michael M Luksic, R G <br /> Port of Stockton <br />' May 17, 2002 <br /> Page 2 <br /> boring were analyzed for TPHg and BTEX compounds by Precision Enviro-Tech Analytical <br />' Laboratory of Stockton, California None of these compounds were detected in any of the soil <br /> or groundwater samples collected during the additional assessment Analytical results are <br /> shown on Figure 2, laboratory analytical data sheets are included in Appendix A <br />' As discussed in the February 5, 2002 letter, impact to groundwater and soil appears to be <br /> limited to the 20-foot depth zone Geologic cross sections of the site were prepared to show <br />' the lithology and subsurface distribution of PHCs detected in groundwater (Appendix A) The <br /> impacted groundwater and soil are limited to a small area, both horizontally and vertically <br /> (Figure 2 and Appendix B) <br /> Based on results from this and previous investigations, we recommend installing two ground- <br /> water monitoring wells near the downgradient edge of PHC-impacted groundwater, one <br />' groundwater monitoring well upgradient of PHC impacted groundwater, and one groundwater <br /> monitoring well within PHC impacted groundwater (Figure 3) Based on the observed vertical <br /> extent of impact, we recommend that the monitoring wells be screened from 10 to 25 feet bgs <br /> Additionally, in order to limit potential vertical migration of PHCs in groundwater, we <br /> recommend drilling out and abandoning the three existing on-site monitoring wells, which are <br /> screened both in and below the impacted 20-foot depth interval <br /> Geomatnx Consultants Inc is pleased to be of service to the Port of Stockton Please call if <br /> you have any questions about this report <br /> Sincerely yours, <br /> GEOMATRIX CONSULTANTS, INC `S�r4�iED GFp�D <br /> No <br /> .rrZ/ Exp L <br /> Bradley A oewen, R G 4Phili Ross, R G tp <br /> Project Geologist Senior Hydrogeologist OF CAUF��� <br /> Enclosures Figure 1 —Location Map <br /> Figure 2— Geoprobe Sample Locations and No Detect Line <br /> Figure 3 — Proposed Monitoring Well Locations <br /> Appendix A —Laboratory Analytical Data Sheets & Chain-of-Custody Records <br /> Appendix B —Geological Cross Sections <br /> I 1PROJECM000s16437 00016437-Site3 Ph2 LatVert Results doe <br />