Memorandum regarding Tutu Wells Site, St. Thomas, VI, Draft Remedial Investigation Report
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY " ^ - _ REGION II DATE: 0 8 NOT 19M Tutu Wells Site, St. Thomas, VI !ECT: Draft Remedial Investigation Report FROM: Dore LaPosH^av Chief Ground Water Management Section TO: Carole Petersen, Chief New York/Caribbean Superfund Section II In accordance with the Memorandum of Interdivisional Coordination between the Emergency and Remedial Response Division and the Water Management Division (WMD) and as requested in your memo of October 13, 1994, WMD has reviewed the Tutu Wells Site Draft Remedial Investigation from the perspective of the water programs and have the following comments: 1. The water level measurements were claimed to have been synoptic (taken at the same time) but in fact were obtained between May 23rd and May 24th. It should be demonstrated that levels do not change significantly in the period over which they were taken. 2. Please explain the 12-ft decrease in water level in SW-1, between May 10th and May 23-4, given that the water levels in the six other wells of the SW series did not change by more than about 1 ft. …
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY " ^ - _ REGION II DATE: 0 8 NOT 19M Tutu Wells Site, St. Thomas, VI !ECT: Draft Remedial Investigation Report FROM: Dore LaPosH^av Chief Ground Water Management Section TO: Carole Petersen, Chief New York/Caribbean Superfund Section II In accordance with the Memorandum of Interdivisional Coordination between the Emergency and Remedial Response Division and the Water Management Division (WMD) and as requested in your memo of October 13, 1994, WMD has reviewed the Tutu Wells Site Draft Remedial Investigation from the perspective of the water programs and have the following comments: 1. The water level measurements were claimed to have been synoptic (taken at the same time) but in fact were obtained between May 23rd and May 24th. It should be demonstrated that levels do not change significantly in the period over which they were taken. 2. Please explain the 12-ft decrease in water level in SW-1, between May 10th and May 23-4, given that the water levels in the six other wells of the SW series did not change by more than about 1 ft. Similarly, explain why the water level increased by >12 ft in MW-22D and decreased by 4 ft in MW-21D while the levels in the other twelve deep wells remained essentially the same. 3. It should be noted that the lack of significant VOC detects in the fifteen supply wells that were sampled (Table 5.7) may be misleading. Because the wells draw water from the entire thickness of the aquifer rather than from just a 10-20-ft interval, contaminants entering the borehole at a particular depth would very likely be significantly diluted. 4. The very high level of vinyl chloride (1300 ppb) observed in monitoring well MW-16 is not approached anywhere else on site. Because vinyl chloride is a particularly dangerous compound, additional efforts should be made to pinpoint and identify its source by means of additional sampling in the vicinity of MW-16. 5. Please justify the absence of significant ground water monitoring to the east of the 100-ppb VOC contour (Figure 5-18). It would be helpful to establish the full width of the contaminant plume. Thank you for the opportunity to comment on this document. If you have any questions, please contact either me or Steve Gould of my staff at extension 5665. cc: C. Kwan, RPM REGION II FORM 132O-1 (9/86) TUT OO6 O66O *64643* 64643