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u I� I In June 1993, liquid phase hydrocarbons(LPH) appeared on the water table in MW-5 Thickness of the LPH has ranged from 0 4 to 1 78 feet EMC has removed a total of 3 15 gallons LPH through hand bailing Groundwater samples were collected from the on-site wells by EMC personnel Prior to sample collection, at least three well volumes of groundwater were removed from each well by a portable submersible pump or bailer During the purging of groundwater, pH, conductivity, temperature and turbidity were monitored at selected intervals This data is included in Appendix A along with the gauging data for the reporting period All equipment was cleaned using a solution of Alconox and water followed by two tap water rinses The actual groundwater samples were collected with disposable PVC bailers equipped with bottom emptying devices A new bailer was used for each sample collected Samples were transferred into the laboratory supplied 40ml VOA vials pending analyses. The chain-of-custody documentation is presented in Appendix B. ANALYTICAL DATA I Each groundwater sample was transported on ice in a light proof chest to American Analytics Laboratory or Smith-Emery Laboratories The samples were analyzed for total hydrocarbons (TPHg)and volatile aromatic compounds (BTEX) by EPA methods 8015 and 8020, respectively Table 1 presents a summary of the TPHg and BTEX data The complete laboratory reports for the current samples are included in Appendix B The current results indicate the presence of TPHg in all wells on site (ranging from 0 57 mg/L to 44 mg/L) Benzene concentrations ranged from 71 ug/L to 2,600 ug/L with the highest concentrations noted in wells MW-3R and MW-4 An interpretation of the dissolved hydrocarbon plume was not established this quarter as all site well exhibited detectable concentrations However, benzene concentrations are plotted on Figure 3 for reference CLOSING Based on the resent site investigation and monitoring program, it appears that the groundwater beneath the site exhibits the presence of both dissolved and liquid phase hydrocarbons The monitoring events accomplished to date suggest the flow direction of groundwater across the site is generally to the north-northeast. Thrifty will continue to monitor the on-site wells on a quarterly basis. If you have any questions, please contact me at (310) 923-9876 Very truly yours, Peter D'Amico Manager �'' Environmental Affairs