Laserfiche WebLink
Please include date for completion of design. <br /> 6. Section 2.2.2.6 states that the RA work plan "will outline both the construction and <br /> operation requirements for the full-scale remediation." It is unclear what is meant by <br /> "outline" in this sentence. The usual understanding of an "outline" may not provide <br /> sufficient information for regulatory approval. <br /> Please clarify exactly what information is to be included in the RA work plan. <br /> [Note that it must meet the requirements of EPA's OSWER Directive 9355.5- <br /> 01.] <br /> 7. Section 2.2.2.9 utilized a confusing acronym. This text describes a Remedial Design <br /> Report and Analysis and abbreviates this as RDRA. Please note that this is equivalent <br /> to the commonly used acronym for Remedial Design/Remedial Action and would be a <br /> source of future misunderstandings. A more appropriate name for this report (more in <br /> accordance with the previously cited EPA OSWER Directive) would be Remedial <br /> Design Support Report. <br /> Please modify the text and acronym accordingly. <br /> 8. Section 3.1.3.4 refers to research on existing wells. <br /> Please provide details of methods to be used. Presumably, the work would <br /> include a records search for drillers' logs and owners' data (including historical <br /> usage rates), if not already done. Please explain whether any field work has <br /> been or will be considered to determine/verify well construction details. Usage <br /> rates and open intervals of large producers are obviously important influences <br /> that must be addressed by the ground-water modeling analyses for capture <br /> zones and well field design. <br /> 9. Section 3.2 describes the geophysical investigation. The time-domain electromagnetic <br /> study has potential, but is not necessarily assured, to help define the "off-depot" <br /> conceptual hydrogeology. <br /> Please explain whether the downhole electromagnetic method, or other <br /> downhole method, should be considered to supplement the surface survey. <br /> [Note: Downhole data could define the resistivity values for specific soil <br /> layers, and thereby provide data useful for the interpretative analysis of the <br /> TEM data.] <br /> 10. Section 3.3 discusses proposed groundwater modeling. Presumably, the ground-water <br /> model will simulate the existing downward vertical gradients, since transient transport <br /> calibration is to be included. The presence, and cause, of the vertical gradient should <br /> be considered as calibration criteria. <br /> EPA/11JAN94 3/4 <br />