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N <br /> moo <br /> ' Memo to Antonia Vorster -2- 17 dune 1987 <br /> C. Installation of additional monitoring wells based on further on-site <br /> water level gradients and the results of Comments 3.a and 3.b above. <br /> Monitoring wells should attempt to define both the horizontal and <br /> vertical extent of contamination, as well as horizontal and vertical <br /> ground water gradients. <br /> The work plan proposal to install only two additional monitoring wells does <br /> not meet the above objectives. <br /> 4. The following comments are more specific compared to the above general ' <br /> comments, and are referenced by page number: <br /> a. Page ii - A registered civil engineer, engineering geologist, or <br /> geologist must sign the report. <br /> b. Page 5 - Samples being held for possible follow-up analysis have <br /> exceeded holding times for organics analysis and are no longer <br /> useful . <br /> C. Page 9 - I recommend Teichert consider installing four-inch, instead <br /> of two-inch wells, in future work. Although two-inch wells are <br /> acceptable, four-inch wells have the advantages of better development, <br /> easier purging and sampling, are much more useful for aquifer testing, <br /> can possibly be used for extraction/recovery, and can still be <br /> installed by the same drilling technique. <br /> d. Page 10 - Was the submersible pump referred to a bladder pump? How <br /> were the samples physically collected? How was the pump decontamina- <br /> ted between wells? <br /> e. Plates 1 & 2 - A map showing the site and immediate surrounding area <br /> is necessary. Future monitoring wells and off-site private wells (as <br /> discussed in Comment 3) can be plotted on this map. <br /> f. Appendix B - All QA/QC data for laboratory analyses should be <br /> submitted as part of the complete results. <br /> g. Appendix B - A number of the well logs are incomplete, not containing <br /> descriptions for shallow soils in some cases and no descriptions of <br /> soils below the water table. Future work at the site must include <br /> complete logging. <br /> Logging by split spoon samples could be replaced by continuous coring. <br /> Continuous coring is superior to 18" split spoon samples at five-foot <br /> intervals for both logging and sampling purposes, especially when part <br /> of the sample is removed for laboratory analyses. Although split <br /> spoon sampling is acceptable, given the alluvial soils on-site and <br /> dual purpose of the borings I strongly recommend continuous coring be <br /> utilized. <br /> GAR:jj <br />