SITE INFORMATION AND CORRESPONDENCE

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-2- Groundwater Assessment Plan Canmients (cont'd) Paqe # CaTment 26 Section 4.4 discusses the placement of groundwater monitoring - wells. Although it is assumed that these wells will be installed after cxmpletion of the exploratory borings, such is not explicitely stated. Some form of generalized timetable, perhaps in the form of a bar chart, should be included in either the text or appendix sections to elaborate on the timing of the various phases -of the study. 28 The first paragraph states that the intermediate wells will be screened at a depth of 100' to 110' below land surface, yet no attempt is made to define the screen intervals for the shallow and deep wells. Why is there apparently greater certainty abort the screen intervals for the intermediate wells than for the shallow and deep wells? 29 Section 4.5 should indicate the type of aquifer testing that is to be perfcmed (e.g. , slug tests, pump tests, or both). 30 Section 4.6.1 proposes to collect the first set of groundwater samples immediately following well development. Formation groundwater near the well screen is, however, significantly aerated immediately following development. As such, sampling should be delayed until the formation returns to equilibrium (discretion of on-site geologist). 30 Section 4.6.2 proposes to use wells SMW-5 and SMW-6 for Appendix 9 monitoring purposes. During the CME on December 6-7, 1988, however, sediment acosnulation problems were noted at well SMW-5 during purging that may be the result cf damage to the well screen or riser pipe. This situation may necessitate the construction of an additional well in close proximity to well SMW-5. The selection of well SMW-6 for Appendix 9 purposes does not appear totally justified, given that Table A-3 in Appendix A indicates that no organics data is available for this well. Well SWM-2, on the other hand, has the second highest overall organics concentrations shown on Table A-3, and is adjacent to the former dnmu ed waste storage area. As such, well SMW-2 should be included in the Appendix 9 analytical effort. 32 Section 4.8 states that a Health and Safety Plan will be prepared, but offers no submission date. As indicated previously, an approximate timetable should be provided that indicates the durations and tentative coTpletion dates of the assessment study phases. 36 The first paragraph indicates that of the 30 initial soil gas sampling locations, only one-third are in the interior of the facility. The initial focus of this study should be on defining the position of the volatile plume center and gradually expanding cut to the facility periphery. As such, additional soil gas sampling points are needed in the facility interior.