SITE INFORMATION AND CORRESPONDENCE_FILE 1

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John and Margaret Marci Property 2969 Loomis Road Page 2 of 3 remediation efforts, what the contaminants' ultimate environmental fate will be, and to help evaluate the risk posed by the contaminants to groundwater supplies and sensitive receptors. In addition, the SCM may demonstrate data gaps, thereby illustrating where additional investigation is needed. To be sure that the SCM will adequately address the assessment, remediation and, ultimately, final closure requirements for this site, please include the following, as appropriate, in the SCM: • Local and regional plan view maps with sources, boring and monitoring well locations, lines of cross section, extent of contaminants in each media, direction and rate of groundwater flow, and receptor locations, including';water supply wells within 2,000 feet of the site • Cross sections showing subsurface geological features,_depth to groundwater, man-made conduits, monitoring well construction and the interpreted vertical extent of soil and groundwater contamination • Cross-plots of key chemical„concentrations verses time for representative wells that demonstrate significant contaminant Concentration trends • Summary tables of contaminant concentrations in the different media • Well and boring logs • Narrative description of the SCM that describes controls on contaminant distribution; contaminant migration mechanisms, pathways and rates; plume disposition over time; and sorbed and dissolved contaminant masses. While not necessarily showing all data in diagrams and drawings, an adequate SCM can be utilized to account for most of the known data and to illustrate additional assessment needs thereby providing the justification for all work proposed''in future work plans. All analytical data should be included in tables. Methods and calculations of contaminant masses should be included in the SCM, and may be submitted as an appendix. The SCM should be updated each time new data is acquired that causes a change of interpretation or expands-the model until model modifications are not needed to explain subsequently acquired data. As the SCM becomes complete, it can be utilized to reasonably predict additional investigation results and plume response to various remedial technologies or to changes in groundwater flow regime. The model should adequately demonstrate all interpretations and opinions. Groundwater samples were last analyzed for 1;2-dichloroethane (1,2-DCA) and 1,2-dibromoethane (EDB) in December 2000. At that time these compounds,were reported at 5 micrograms per liter (ug/L), above the maximum contaminant levels(MCL) ofi0.5 ug/L for 1,2-DCA and 0.05 ug/L for EDB. Please analyze groundwater sample from all monitoring wells for these compounds during the next groundwater-monitoring event, and ensure the reporting limits for 1,2-DCA and EDB are ` at least 0.5 ug/L. Please submit a groundwater monitoring schedule for future sampling based in these and historical analytical data.