Laserfiche WebLink
this time period could be significant and may adversely affect the <br /> comparability of data. <br /> The text should discuss timing of sampling events with respect to <br /> maintaining data comparability between low-flow and conventional <br /> sampling methods. A maximum allowable time interval between <br /> sampling events should be identified in the work plan. [Note: <br /> Performing low-flow sampling prior to conventional sampling may <br /> resolve any issues associated with the timing of sampling <br /> events.] <br /> 4. Second Round Sampling <br /> Paragraph 1.3.0.1 c-. page 1-4 indicates that a -second smaller set <br /> of 10 low-flow samples will be collected at a later date to confirm <br /> the results of the initial sampling round." EPA agrees that some <br /> additional testing may be warranted before EPA can make a <br /> determination on the merits of using low-flow sampling in place of <br /> conventional sampling at DDRW-Tracy. However, instead of using the <br /> second sampling round to simply "confirm results", the second round <br /> could be used to help resolve any issues from the first round <br /> evaluation. For example, if a well sampled by conventional methods <br /> showed significantly higher VOC concentrations compared to low-flow <br /> sampling, it may be appropriate that the second round collect <br /> low-flow samples at three discrete depths along the screened <br /> interval of that well. <br /> It may be more cost and time effective to reserve the second <br /> round of sampling to address any remaining issues, following <br /> agency review of first round results. Details of any second <br /> round sampling should be developed after first round results <br /> are available and could be presented in the recommendations <br /> section of the first round report. <br /> 2J2 <br />