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/-s. C O M F E D E R A - L , P R Q G R A M S C O R P O R A T I O N a s u b s i d i a r y o f C a m p D r e s s e r & M c K e e Inc. March 26, 1993 Ms. Caroline Kwan U.S. Environmental Protection Agency 26 Federal Plaza New York, New Tork 10278 PROJECT: TBS V, EPA CONTRACT NO: 68-V9-0002 Work Assignment C02048 DCN: TBSV-C02048-LR-CVXN SUBJECT: Review of Technical Memorandum II Results of the Field Program, Tutu Service Station Investigation, St. Thomas, U.S. Virgin Islands Dear Ms. Kwan: COM FEDERAL PROGRAMS CORPORATION (COM Federal) has completed its review of Geraghty & Miller's (G&M's) report "Technical Memorandum II, Results of the Field Program, Tutu Service Station Investigation, St. Thomas, U.S. Virgin Islands", prepared for the Tutu Environmental Investigation Committee (TEIC) and dated February 1993. The report was received by CDM Federal on March 3, 1993. The purpose of the TEIC report is to present preliminary results of the field investigation and to determine if additional investigation is necessary before completing the remedial investigation (RI). CDM Federal's general comments concerning the report are presented below, followed by specific comments with respect to the text. GENERAL COMMENTS 1. COM Federal concurs with G&M that the downgradient extent of petroleum contamination has been adequately defined. Based on the maps, it appears that the upgradient extent of petroleum contamination can be delineated without additional wells. However, a well might be warranted to the west of Western Auto, to establish whether that facility contributes to groundwater contamination. (The Target Soil Gas Survey of the Western Auto property did not indicate any major areas of concern, however.) The locations of the proposed wells should be plotted on a map. Several questions remain as to the sources of chlorinated volatile organic compounds (VOCs) in groundwater. CDM Federal concurs with G&M that there are apparently at least two sources of chlorinated VOCs at the site - one in the vicinity of the Curriculum Building and, possibly, Tillet Gardens, the second in the vicinity of O'Henri ____ cleaners. The Texaco and Esso stations dn nnt appoar to he aajnr 111 Fulton Street, Suite 710 New -Ytfc, NY 10038 212393-9634 TUT OO6 1639 *64821* 64821 COM FEDERAL PROGRAMS CORPORATION • ~ a subsidiary of Camp Dresser & McKee Inc. contributors of the chlorinated plume. 2. CON Federal has compared the analytical results of our split sample anlayses with G&M's results. All the split and PRP data compare within acceptable limits. Data comparison tables will be submitted to EPA following receipt of one outstanding validated data package from EPA's Monitoring Management Branch (MMB). 3. For the pumping tests, it is standard to present the following data graphically: background vater level fluctuations; rainfall and barometric pressure data, if collected; and all measured water levels in all veils monitored during testing. 4. It would be useful to present subsurface soil data from borings and monitoring veils on the same nap in the RI report to create a more integrated picture of soil contamination. 5. Detailed core logs and drillers logs have not been provided. Though not crucial for this technical memorandum, they should be presented in the RI report. 6. The VTHA supply veils should definitely be included in the next round of groundvater sampling. A schedule of pumping should be included, if available. SPECIFIC COMMENTS 1. Page 2-1, Paragraph 2, first sentence - The other principal contaminants of concern (i.e., PCE, TCE and DCE) should be named. 2. Page 2-2, Paragraph 1 - The logs in Appendix A do not show blows/foot or HNu readings as indicated in this paragraph. 3. Page 2-2 - The fact that EPA's contractor, COM Federal, split a number of samples with Geraghty and Miller and sent them to a separate laboratory for confirmatory analysis should be mentioned in the QC sample discussion in the RI report. (As mentioned in General Comments, the results of the separate analyses are comparable.) 4. Page 2-3, Section 2.2.1 - The outcrop descriptions are not provided. 5. Page 2-4, Paragraphs 1 and 2 - Downhole drilling pressure, rate of penetration per foot and vater circulation observations are not provided. Nor are the bedrock coring logs. 6. Page 2-4, Section 2.2.3 - The dovnhole geophysical logs (caliper and sonic) are not provided in this technical memorandum. 7. Page 2-6, Paragraph 2, last sentence - The sentence should read that veil MV-12D was completed as a deep, not a shallow,-veil. 8. Page 2-12, Section 2.4, Paragraph 2 - G&M needs to mention that the maximum aquifer test pumping rate vas constrained by the capacity of the on-site vater treatment system. Thus the aquifer vas hot stressed as much as it could have been. 9. Page 2-13, Paragraph 1 - G&M should specify the frequency of manual ' - . . ' '•••'• • . • . ' , -2--; '. . • ••: . . - •".-.' . . . Printed on Recycled Paper - TUT OO6 164O COM FEDERAL PROGRAMS CORPORATION § subsidiary of Camp Dresser & McKee Inc. uring the test. 10. Page 2-13, Section 2.4.2, first sentence - The text should make clear that the tvo veils were not pumped simultaneously. 11. Page 3-2, Section 3.1.2 - Hov do the volcanic sandstone and siltstone described equate to the formations described under regional geology? 12. Page 3-10, Paragraph 4, last sentence - Two possible explanations exist for the difference in heads observed between the shallow and deep wells: 1) local perched conditions may exist; or 2) a recharge source exists in the vicinity. 13. Page 3-12, Paragraph 1, last sentence - The wells for which the data are not usable should be specified. 14. Page 3-12, Section 3.3.1 - Drawdown data should have been superimposed on a variety of type curves to assess the type of aquifer before determining that the Cooper-Jacob straight-line method was the appropriate one to use. 15. Page 3-12, Section 3.3.1, 6th sentence - The text states that correction of drawdown values was not necessary, but on the associated figures, the y-axis is labelled "corrected drawdown". 16. Page 3-14, Section 3.3.2 - If the data for the pumping test of MV-6D is not useable due to the rainfall as stated on page 3-12, then G&M should qualify the discussion and numbers presented in this section. Based on figures 3-8 and 3-9, COM Federal believes that steady state conditions had not been reached after 24 hours of pumping and that the shape of the drawdown curves indicate that the system is being dewatered. 17. Page 3-15 - The "drawdown" measured in well Mff-7 is less than 0.1 foot. This change may not be due to the pumping well, located 230 feet away. 18. Page 4-1, Section 4.1 - The results from; the soil boring samples should be considered in conjunction with those from the monitoring wells because they are really the same medium. Treating them separately makes it harder to assess the distribution of contaminants in subsurface soil. 19. Page 4-3, Paragraph 2, item 2 - Total Petroleum Hydrocarbon (TPB) results are often elevated in fine-grained soils because the extraction method is more efficient due to the greater surface area from which the solvent can extact the TPH. This effect, however, does not result in "false positives". 20. Page 4-6, Section 4.3.1, Paragraph 1, fourth sentence - Only sample SS-5 is from the Tillett property; Sample SS-3 is from the Curriculua Building. 21. Page 4-7, Section 4.5 - The analytes that are present above background concentrations should be listed, especially if any of them are contaminants of concern from a health perspective. 22. Page 4-8, Section 4.6 - See preceding comment. ' ' ..',•• ' - . ' . . .. - ' -3- ". • ; •';" ' " - " ' ; " ' •' ' " TUT O06 1641 Printed on Recycled Paper COM FEDERAL PROGRAMS CORPORATION a subsidiary of Camp Dresser & McKee Inc. 23. Page 6-1, Last Paragraph -GAM should try to obtain more information on which supply veils are pumping and at what rates. 24. Page 6-2, Section 6.2, Paragraph 2, last sentence - G&N has not provided adequate evidence for "false positive11 TPH concentrations. TPH is certainly not unexpected in a service station study. Furthermore, as stated earlier, fine-grained soils may result in elevated concentrations due to more efficient extraction, but should not result in false-positive values. 25. Page 6-2, Section 6.2, Paragraph 3 - The focus of the BNA discussion should not be on the possible laboratory artifacts, but rather on the polynuclear aromatic hydrocarbons that were detected at a number of properties. 26. Page 6-3, Paragraph 3 - According to the maps, arsenic was detected at 185 ppm in boring B-13 on the O'Henri property. This is three orders of magnitude higher than background. 27. Page 6-5, Paragraph 3 - Based on the groundwater results presented in this report, it appears that the upgradient extent of petroleum constituents can be defined with the existing data. Additional wells might be warranted to conclusively establish liability with respect to chlorinated compounds. 28. Page 7-1, item 2 - EPA Region II only accepts total, not dissolved, metals results in remedial investigations. Total metal values are used both in the assessement of groundwater risk and in evaluating remedial technologies. 29. Figure 3-1 - The labelling of geologic units from well to well is inconsistent on this diagram. - i . . . • • s . ' . " - . • - If you have any questions concerning this review, please contact me at (212) 393-9634. Sincerely, , COM FEDERAL PROGRAMS CORPORATION Sally Odland Work Assignment Manager -- . TUT 006 1642 Printed on Recycled Paper , __ _ . . _ . . . ..................... _ . .. . ... .