SITE INFORMATION AND CORRESPONDENCE

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Attachment - Memo to Greg Vhn -5- . 8 November 1989 Groundwater Assessment Repo Kearney-KPF, San Joaquin County monitored throughout the remedial investigation and ground water cleanup phases. Refer to Table 2 (attached). 15. pp. 46, The screen length of the majority of the intermediate and deep monitor 47 wells (KI-5, KD-1, KD-4, KD-5, and KD-6) are partially penetrating and therefore, the hydraulic heads would not be representative of the discrete coarse grained zones at this site. The yield of a partially penetrating well is less than that of a completely penetrating well at any given drawdown. The yield of the well is important for those wells which are to be used as pumping wells in aquifer tests. Future monitor wells which are to be pumped during an aquifer test should be fully penetrating. For example, wells installed in the deep gravel zone should have 30 to 50 feet of screen depending on the thickness of this zone. If a well is not fully penetrating, the screen interval should be placed in the middle of the zone rather than at the top or bottom of the zone. 16. p. 50 I concur that the use of the Cooper-Jacob method is applicable to transient state conditions. Furthermore, the Cooper-Jacob method can be used for unconfined aquifers if the drawdown is small relative to the aquifer thickness and if the solution is valid for u <0.01. However, if the aquifer thickness is considered to extend from the static water level to the bottom of the screened interval , the drawdowns observed in KS-6, KI-5 and KI-6 would not be small compared to the aquifer thickness as defined on p. 95 of the Ground Water Manual, U.S. Department of the Interior. 17. pp. 51- Single well pumping (aquifer) tests were performed rather than multiple 53 well tests as indicated in Hargis' response to- the regional Boards Comment No. 12 (dated 6 March 1987) . Refer to p. E-10 of the Groundwater Assessment Plan. 18. pp. 51- Calculations of transmissivity may not be technically accurate as there 54 were apparently no corrections for well losses or partial penetration. Failure to correct for these would tend to underestimate transmissivity. However, the calculated values do not appear to be unreasonable. 19. p. 67 High concentrations of methylene chloride were reported in Table 18 for several different samples from different wells on different dates. The footnote indicated that the compound was also detected in the laboratory reagent blank. However, a portion of the concentrations of methylene chloride were an order of magnitude greater than the State Action Level of 40 micrograms per liter (Ng/1). These high concentrations may indicate laboratory contamination from either the air or within the instrument. 20. p. 71 The dates of sampling events in the first paragraph are not clear. 21. p. 71 The figures from Appendix M and N are complete and informative. The distribution of VOCs in the ground water are clearly depicted with these figures.