COMPLIANCE INFO - Laserfiche WebLink

Home Browse Search

Mr. Robert 0. Godwin -2- 15 September 1987 past at or near their respective drinking water standards. Metals data should be re-evaluated each sampling round and any trends discussed. You may provide the summaries with the third quarter monitoring report due 30 October 1987. 2. Pit 7 - The main ground water issue at Pit 7, which is in assessment monitoring under the ISD, is ground water contamination with tritium and TCE. Both contaminants should be addressed in the remediation plan which the second quarter report states will be developed in the coming fiscal year. By 6 October 1987, please provide a time schedule for developing such a plan. 3. 817 Surface Impoundment - The statistical analysis was done correctly except for the negative signs as discussed above. The analysis showed significant increases in all downgradient wells for pH and EC. You have made extensive arguments in Appendix C that the student-t test is not appropriate for your facility, and the indicator parameters may not be indicative of contamination. You have quoted portions of EPA's "Technical Enforcement Guidance Document" (TEGD) and discussed the factors which result in false positive statistical findings. However, the TEGD also describes the greater concern on the part of regulatory agencies for false negative results in which a finding of no significant increase actually should have shown a significant increase, thus triggering further assess- ment of possible ground water contamination. The TEGD also points out that other t-tests are available and allowed to be used under interim status, but if a method is chosen to control the false positive rate, the impact on the false negative rate must be evaluated as well . If you would like to use a different t-test for the next statistical analysis, it should be accompanied by a clear justification for its applicability to Site 300 as described in Section 5. 2. 1. of the TEGD. Also note that California Administrative Code, Title 23, Chapter 3 , Subchapter 15, Section 2555(h) requires the t-test at the 0.05 level of significance, not 0.01 as was used. This change might make a difference in the findings of significance. If the statistical analyses continue to show significant increases in indicator parameters, a verification monitoring program will be required. Your proposal for a long-term pump test and time-series sampling in well 817-1 is acceptable as a start in investigating the occurrence of RDX in that well . The pumped water may be discharged to the surface impoundment. You should keep track of the volume discharged and report the quantity with the pump test results. This pump test is only a first step in determining the extent of ground water contamination by high explosives, and I reiter- ate my request for a work plan and time schedule for a full investigation. Please submit these items by 6 October 1987. Investigation of the newly discovered TCE ground water contamination at the 817 surface impoundment may be integrated with the ongoing TCE investi- gation. However, we need a new work plan for that ongoing study since the items in the previous plan have been completed. I understand that this and the investigation at well 817-1 will be updated quarterly in the "Investigations and Corrections Quarterly Report" but work plans are