SITE INFORMATION AND CORRESPONDENCE

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David Wang Page 5 o the chemical properties of TCE and PCE o the physical aspects of TCE and PCE that may affect their mobility in the environment, both in the vadose and saturated zones 3) Section 7. 0, Recommendations o page 7-1, paragraph 7. 1, lines 4 through 7: The RI report states: "WCC suggests that one deep well be installed in the vicinity of LM66 and LM67 to better define the vertical extent of contamination. The screen zone for this well should be placed between 150 and 170 feet below ground surface. " DHS interprets that this recommended monitoring well will provide valuable information regarding the off-site contamination at depth. DHS recommends screen lengths of no more than ten feet be used for monitoring wells. Consideration should be given to screening the gravelly sand depicted on revised geologic cross-section A-A' from approximately 120 to 130 feet below ground surface (BGS) in the vicinity of LM66 and LM67 . o page 7-1, paragraph 7.2 , lines 1 through 4 : The RI report states: "To assess the lateral and vertical extent of contamination within Area 1, a well should be placed downgradient of LM61 (Figure 1. 2-1) with a screen interval between 60 and 70 feet and another well should be placed downgradient of LM2 and LM3 screened between 100 and 120 feet BGS. " DHS requests information as to how far downgradient the recommended monitoring wells are intended to be installed. Consideration should be given to screening the lower portion of the gravelly sand shown on the revised geologic cross-section A-A' . Care should be taken that the monitoring well recommended in the RI report to be screened from 100 to 120 feet BGS does not cross contaminate the gravelly sand and the gravelly clayey sand which may be separated by a sandy clay from approximately 100 to 107 feet BGS (see revised geologic cross-section A-A') .