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A <br /> Antonia Vorster -3- 4 April 1990 <br /> The latest electric logs are not consistent with previous E-logs in scale. <br /> Is this due to different methodology or to different probe spacings (point <br /> versus short or long normal )? The original E-logs should be incorporated <br /> in the RI report with any relevant supporting information. <br /> Using the cross-sections, the screened intervals of all the monitoring wells <br /> (and production wells where appropriate) need to be compared to the litho logy <br /> and each other. The objectives are to ensure that all pathways for <br /> contaminant movement are adequately monitored, and that wells with the same <br /> zone designation are truly monitoring the same zone. Incorrect zone <br /> designations potentially affect both Contaminant and water level contouring. <br /> Well screened intervals, and the associated chemical and water level data, <br /> also need to be compared as to how completely they screen a respective zone. <br /> A number of wells appear to incompletely screen a particular interval , and/or <br /> screen part of the upper or lower aquiclude. This is an issue which has been <br /> raised previously. Although I do not believe it is a major problem, partial <br /> screening can result in nonrepresentative data, especially in highly <br /> contaminated areas which could be associated with free phase liquids. <br /> Additional care should be taken with any future wells. <br /> C. Water Level Data - each set of water level measurements needs to plotted and <br /> contoured individually. Each plot can then be compared to the others. It <br /> may be possible to determine a "composite" groundwater flow direction <br /> combining the data into a single resultant, but care must be taken since flow <br /> is a vector quantity. Time intervals, magnitude, and direction must all be <br /> incorporated into any composite flow determination. Even then, the amount <br /> of variation must still be considered since changes in direction strongly <br /> affect contaminant dispersion. <br /> Once the above issues have been addressed, all of the individual data sets should <br /> be compared to each other. Any areas where they do not correlate, need to be <br /> identified and must be resolved. <br /> 3. Nestle has been operating an on-site soil vapor extraction system as an interim <br /> remedial measure for some time now. Although we have discussed and inspected the <br /> vapor extraction system, a comprehensive report regarding its operation and <br /> performance has not been submitted. Additionally, the groundwater data strongly <br /> indicate that a significant contamination source exists near location M-8. <br /> Interim remedial measures need to be implemented in this area, soil vapor <br /> extraction being the most likely alternative. Nestle needs to submit a complete <br /> report concerning the on-site interim vapor extraction system and a workplan for <br /> implementing interim controls/cleanup at M-8. <br /> 4. Nestle should be commended for subjecting the analytical results to formal data <br /> validation. However, measures to correct and/or prevent the deficiencies noted <br /> in the validation process were not included. Additionally, it is still important, <br /> as we have commented previously to include a summary table of QA/QC results for <br /> each sampling round in the reports. The table should include blank, duplicate, <br /> and spike results applicable to each data set. A discussion of any anomolies and <br /> their resolution must also be included. For example, in the the subject RI <br /> report, spike results are included in Appendix B but it is not clear what levels <br />