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than to indicate that a bentonite plug will be installed above the test zone to the ground <br /> surface. Information on the construction of the stand pipe, the materials to be used, the <br /> size of the stand pipe, the diameter of the stand pipe, the number per inch of slots in the <br /> stand pipes and the diameter of such slots, should be provided. In addition, there is no <br /> indication that care will be taken not to disturb the soil in and around the stand pipe. The <br /> placement of the stand pipe and the disruption of the natural soils around the stand pipe <br /> could impact the results of the test. Please include this information. <br /> 7. Section 4.3.2, Phase I - Borings/Permeability Test Investigation, Page 4: The Work <br /> Plan indicates that an infiltrate rate of 0.4 inches per hour, or 1x10'centimeters per <br /> second for the Phase I test is required in order to proceed with the Phase II percolation <br /> study. Please provide the rationale behind the use of this rate. Provide standard references <br /> and/or data from benchmark tests if necessary. <br /> 8. Section 4.4.1, Phase II - Percolation Pilot Study, Page 4: The Work Plan does not <br /> include a laboratory phase associated with this study, although Section 4.1.2 alludes to the <br /> possibility of sending samples to a laboratory for percolation tests. A laboratory phase <br /> may be helpful in two areas. First, a laboratory evaluation of the soil properties in the area <br /> of the proposed ponds may help to determine if the soils in the proposed areas are suitable <br /> for use in surface impoundments. This may include such tests as soil density, soil <br /> moisture content, pore size and particle size distribution. Second, a laboratory soil <br /> percolation test conducted before or concurrently with the field test may help to minimize <br /> the variabilities of the field test and'to provide a level of QA/QC to the process. Please <br /> discuss reasons for not including a laboratory phase of the study or clarify what criteria <br /> will be used to select samples to be sent for laboratory tests of soil properties and <br /> percolation. <br /> 9. Section 4.4.1, Phase II - Percolation Pilot Study, Page 4: This section indicates that the <br /> pilot study will use treated groundwater from the South Balloon groundwater treatment <br /> plant or an alternate potable water source. In Appendix C the document indicates that the <br /> treated groundwater that these ponds will manage has trace levels of metal constituents as <br /> well as a pH that exceeds 8.5. Variability in pH and the presence of trace constituents can <br /> impact soil permeability. Therefore, the pilot test would be most useful if it uses treated <br /> groundwater representative of what will be placed into the percolation pond. Please <br /> discuss how information obtained from a test using an alternate potable water source will <br /> be evaluated for applicability to disposal of treated groundwater. <br /> 3 <br />