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• retrieved, but proposes only one equipment blank and one <br /> duplicate sample. <br /> • An equipment blank should be taken between each well, <br /> and due to the non-repeatability of this sample round, <br /> a duplicate of each sample point would be prudent. <br /> • If a duplicate of each sample point is taken, then the <br /> RWQCB requirement for post-sampling purging would need <br /> to be followed. <br /> 32. Samples for metals analysis will be filtered in the field. <br /> • State in the text whether they also be preserved in the <br /> field with nitric acid (HNO3) to a pH less than 2 or <br /> whether this will be done by the contract laboratory <br /> after transport. (NOTE: Data from filtered samples <br /> cannot be used in any future risk assessments. DLA may <br /> want to take duplicate (but unfiltered) samples. ) <br /> Pages 4-6 and 4-7 . Section 4 . 4 <br /> 33 . In Section 4 . 1.7 it is stated that once total depth of each <br /> well is achieved, the geophysical logging will be performed. <br /> However, in Section 4 . 4 . 1, the statement is made that <br /> geophysical logging will be performed immediately after <br /> groundwater sampling. <br /> • Explain in the text the actual sequence of events <br /> planned; drilling, sampling, and geophysical logging or <br /> drilling geophysical logging and then sampling? <br /> • Whatever the sequence, purging of Wells No. 1 and 2 <br /> must be included in the sequence in order to develop <br /> credible data. <br /> 34 . The types of geophysical logs proposed are televideo, <br /> natural gamma, sonic, caliper, and neutron. According to <br /> Aller (1991) , the sonic log is ineffective in metal casing. <br /> • The use of the sonic logging is not advised for this <br /> study. <br /> Pages 4-7 and 4-8 . Section 4 . 5 <br /> 35. If the full length of the casing is perforated with the mill <br /> knife prior to grouting, this would appear to increase the <br /> likelihood of cross-contamination between the Upper, Middle <br /> and Lower Horizons within the overlying deposits and the <br /> Lower Tulare Formation. If the casing within the Lower <br /> Tulare Formation were perforated first, then grouting added <br /> to a level above the perforations, and so on, in stages, up <br /> 10 of 12 <br />