SITE INFORMATION AND CORRESPONDENCE_1988-1991

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Antonia Vorster -6- 25 August 1989 needs to be determined. Proposed wells 11A-C to define the near western extent of the primary plume appear appropriate given the uncertainties of the submitted maps. The location of 9A-C, however, appears questionable given the intent of these wells is to define the southern edge of the secondary contamination plume. h. A potential ground water contamination source was identified by soil gas sampling near Y-145. It needs to be verified whether or not ground water has been contaminated at this location. 3. A number of important issues detailed in our 27 January 1988 memorandum (11 February 1988 cover letter) have still not been addressed by the August 1988 submittal , nor the more recent March and June 1989 documents. Some of the issues, such as adequate base maps, were discussed above. The remaining issues are: a. Water level contour maps, on at least a seasonal basis, need to be prepared. The August 1988 submittal contained two sets of contour maps, November 1985 and January 1988, for the A, B, and C-zones (The D-zone may or may not have adequate data to prepare maps; it is not possible to know until plots are prepared) . This is an amazingly scant amount of data presentation for a project that has supposed to have been collecting water levels on a monthly basis for over five years. Contour maps are important to estimate ground water flow vectors over time. This information can then be compared to stratigraphic and analytical data to ensure proper plume definition. The maps/estimates may be especially important in selecting locations for new monitoring wells and near pumping well influences (as discussed above) . b. Geologic cross-sections have never been submitted. Although the August 1988 report indicates cross-sections were prepared, the referenced pages were omitted from the report. It is impossible to complete plume definition without proper stratigraphic characterization and subsequent correlation. In fact, the Agencies' January 1989 plume estimates must be qualified because stratigraphy was not correlated with the water level and analytical results. The Agencies did not perform this work since the plume work they did perform was already far beyond their responsibilities. However, USATHMA and Hunter/ESE must complete this work. All well logs should be reviewed, representative logs selected, and cross-sections (generally parallel and perpendicular to plume orientation) prepared. The cross-sections should then be compared to the water level contour maps (discussed above) and analytical results to ensure understanding of the flow/transport mechanisms on site. Additionally, and of equal importance, the cross-sections must also be reviewed with regards to monitoring well screen locations in relation to both other wells and stratigraphic units.