I +Vn4,k MJ Nearman Remedial Project Manager

Transcription

1 PROI UNITED STATES ENVIRONMENTAL PROTECTION AGENCY DB 07j REGION 10 St 2V ~~~~~1200 Sixth Avenue Seattle, Washington t c-'- ' Reply To Attn of: 1*W124 United States Air Force 343 CSG/DEEV 225 Central Avenue, Suite 1 Attn: Capt. Max Candy Ejelson AFB, Alaska Re: Eielson AFB - Comments on Draft OU-2 RI/FS Baseline Risk Assessment, dated May 1993 Dear Capt. Candy: EPA has reviewed the above-referenced report and is providing the attached comments for your consideration and incorporation into the draft final document. Generally, the report was well-written and followed EPA guidance for the preparation of baseline risk assessments. A meeting to discuss the comments has been set up for July 12, 1993 at Eielson AFB. Please contact me at (206) prior to that time if you have any questions or if the comments require clarification. Sincerely, I +Vn4,k MJ Nearman Remedial Project Manager cc: w/ attachments R. Markey, ADEC R. Lewis, Battelle PNL V. Rhoades, PRC qoprinted on Recycled Paper

2 GENERAL COMMENTS EPA Comments Draft OU-2 RI/FS Baseline Risk Assessment dated May A description of the way areas of concern f or soils and groundwater are delineated in each contaminant source area should be provided. This should include documentation of the way sample data were grouped to calculate exposure point concentrations. 2. The lead uptake model and EPA interim guidance and action levels should be considered when evaluating the risks of lead contamination. 3. Detected contaminants without EPA toxicity values should be identified and qualitatively evaluated. 4. The discussion in Section 2 (e.g., Section 2.4, Table 2.10) and Appendix B should include the rationale for elimination of dermal contact with surface water and ingestion/dermal contact with sediments. These potential pathways should be addressed qualitatively, at a minimum. 5. The location of base supply wells should be noted for each source area, and reasons for the abandonment of base wells in source areas described. 6. Potential releases of polycyclic aromatic hydrocarbons (PAHs) to surface soils resulting from fuel spills should be identified. 7. Future exposure point concentrations for area ST19 are predicted using groundwater modeling. The future receptor location appears to be selected at a downgradient water supply well approximately 2 kilometers from the source area. Groundwater contaminant concentrations should be predicted in the source area, and at a location most likely to be significantly impacted. one purpose of the future residential scenario is to examine potential risks occurring in the source area to both contaminated groundwater and soils. It should be assumed that water can be drawn from anywhere in the aquifer, either directly beneath a specific source or at an area directly adjacent to the source (EPA 1989a). BPECIEIC COMMENTS 8. Executive Buminary, Tables A and B Multiple transcription errors were noted during a comparison of Chapters 2 through 6 of the main text. Therefore no further checks of transcription and calculation were made. The report should be checked for transcription errors before resubmittal.

3 Ejelson AFE 0U2 Draft ELRA Page 2 9. Section 1.0, page 1.2 The ecological risk assessment for 0U2 should evaluate if sources within 0U2 are acting as a continuing source of contamination with potential impact to ecological receptors. The Sitewide ecological risk assessment is designed to assess past releases from multiple source areas (e.g., to Garrison Slough) to determine the need f or additional remediation of secondary pathways once the individual source areas have been addressed in the corresponding OU or Source Evaluation Report. The BLRA text should be revised to reflect this approach f or the phased ecological risk assessment. 10. Section 2.1, page 2.1, second paragraph This section describes potential contaminant sources at area ST1O and 0P14. Sources of PAHs in surface soil are described as most likely originating from diesel exhaust deposition. It should also be considered that PAHs may be associated with fuels and fuel spills at the site. EPA (1992b) reports that diesel fuel mixtures may contain up to 10 percent PAils and that jet fuels may contain small amounts of PAils. PAHs were also detected in Lake Hardf ill sediments, which may indicate that fuel spills are contributing to PAHs found in the site area. The RI discussed the presence of PAHs in fuels to explain the presence of PAHs is subsurface soils. The BLRA text should differentiate between assumed sources of PAH in the surface soils (i.e., diesel exhaust deposition) and PAils in subsurface soils (i.e., leaks from underground diesel lines.) 11. Section 2.1, page 2.1, fourth paragraph a. The weight percent of benzene in JP-4 and automotive gasoline cited here does not agree with the weight percent of 2.46% for JP-4 and 4.59% for premium unleaded gasoline cited in Table 8.1 of the BLRA and Table 5.7 of the RI. b. Contrary to the statement in the text, contemporary motorgas (MOGAS) is unleaded. The Department of the Navy, which manages petroleum products for the entire Department of Defense, switched its specifications to unleaded about the time catalytic converters were first used in passenger cars. Also, it is more correct to define the use of aviation gas (AVGAS) as "piston aircraft" or "non-turbine aircraft," rather than as "non-jet aircraft," because the military uses a number of types of turboprop aircraft, burning JP-4, in the patrol, cargo, and utility categories.

4 Ejelson AFB 0U2 Draft BLRA Page Section 2.1, page 2.6, second paragraph This section describes the contaminant sources at areas STlO and SS14. The last sentence of the second paragraph describes the position of well screens for water supply well 14 in relation to the groundwater plume. The sentence should be re-written for clarity. The depth of the water supply well, well screens, and the contaminant plume should be stated. Any ongoing monitoring programs for the water supply well should also be identified. 13. Section 2.1, page 2.6, last paragraph Surface soil lead contamination near the tank farm may also have resulted from sand-blasting and repainting the tanks. 14. Section 2.2.4, page 2.21 Ingestion, inhalation, and dermal contact for the groundwater pathway were retained assuming industrial use of the base supply well BSW-14. The RI stated that this well was not currently used for potable water but supplied toilets, sinks, and an emergency shower for the workers. This distinction should be made clear in the BLRA. 15. Section 2.2.3, page 2.20, first paragraph This paragraph says four pathways were eliminated, but the following text lists only three. This discrepancy should be corrected. 16. Section 2.2.3, page 2.21, last paragraph This section describes the current industrial exposure pathways. The rationale for retaining dermnal contact with subsurface soils for the current industrial scenario while eliminating ingestion of subsurface soils should be provided. The exposure factors outlined in Appendix B state that the exposure duration for subsurface soils for industrial land use, both ingestion and dermal contact, was adjusted to 24 days/year to represent a trench worker scenario. The variation between the current industrial and future industrial scenarios for the anticipated trenching activity should be provided. In addition, if contact with the subsurface soils is eliminated for the current industrial scenario for the reasons stated in Section 2.2.3, then direct contact with subsurface soils should not be considered, for the same reason stated in the text for the ingestion of subsurface soils exposure route.

5 Ejelson AFB 0U2 Draft BLRA Page Section 2.4.2, page 2.31, first paragraph EPA's lead uptake model should be used to produce a third risk estimate for this scenario. 18. Sections 3.0 through 6.0 The methodology questions from Section 2.0 (e.g., lead risk) apply here also. 19. Section 3.2.3, page 3.7, last paragraph This section describes exposure routes for the current industrial scenario at source area ST11 and notes that groundwater in this source area is not used as potable water for the base. The location of the nearest downgradient water supply well should be documented, and the potential for contaminant impact on this well from source area ST11 should be briefly described. 20. Section 4.1, page 4.1, second paragraph This section describes potential contaminant sources at area ST13 and DP26. Sources of PAHs in surface soil are described. as most likely originating from diesel exhaust deposition. It should also be considered that PAils may be present in fuels, particularly diesel, and that fuel spills in the source areas may have contributed to the surficial PARl contamination. EPA (1992b) reports that diesel fuel mixtures may contain up to 10 percent PAils and that jet fuels may contain small amounts of PA~s. 21. Section 4.2.3, page 4.6 This section describes exposure routes for the current industrial scenario at source areas ST13 and DP26 and notes that no base water supply wells are located within the groundwater plume at this site. Several abandoned base wells (i.e., 5A, 13, and 15) are noted on Figure 4.2. The historical use of these wells and any contaminant impacts on the wells resulting from the source areas should be reported. The reasons for abandoning the wells should also be described. 22. Table 4.4 The Hazard Index for inhalation and dermal contact with contaminants during groundwater use equals 2 including suspected background metals and equals 3 when not included. This appears to be an error.

6 Eielson AFB 0U2 Draft BLRA Page Section 5.2.3, page 5.8, first paragraph This section describes exposure routes for the current i~ndustrial scenario at source area STiB. The comment on Section 4.2.3, page 4.6, should be considered, and the abandoned base well - within the ST18 source area should be addressed. 24. Section 5.2.6, page 5.9 This section describes exposure routes for the future industrial scenario at source area ST18. The incidental ingestion of and dermal contact with subsurface soils pathway is not considered based on the depth of contamination (i.e., 7 to 10 feet). This is inconsistent with the exposure assessments performed for other source areas (for example, STIO, 5514, and ST11), where future industrial exposure to subsurface soil is considered based on an excavation scenario. It is also inconsistent with inclusion of these pathways reflected on Table 5.1. This scenario should be assumed for the ST18 source area. 25. Section 5.4.3, page 5.17, last two paragraphs a. This section describes a potential source of PAHs at area ST18 (i.e., deposition of diesel exhaust emissions). As noted in the comment to Section 4.1, page 4.1, second paragraph, other possible sources of surficial PAHs, such as diesel fuel spills, should be also considered and discussed. b. The source of the total pathway cancer risk (minus background metals) of 3 X io5 to 1 x i0` is not apparent. The value for 3 x is? 5 appears to be from the Future Residential RME calculation but the 1 X i0-3 value could not be found. This sentence should be verified and corrected, if needed. 26. Table 6.8, third page The section describing uncertainty associated with the use of modeling for projecting future BTEX groundwater concentrations is not complete on the table. 27. Section , page 7.1, second and third paragraphs a. This section, unlike the data validation appendix of the RI, correctly cites the 10 times/5 times rule for blank contamination. However, the part of the rule on adjusting the "action levels" for dilution ratios, as detailed in EPA data validation guidelines (EPA 1991c), has been omitted (i.e., for the inverse of the amount of sample actually put on column). Dilution rations should be considered when evaluating blank contaminants.

7 Eielson AFB 0t12 Draft BLRA Page 6 b. Water (or solvent) blank data can be applied to soil results, with- adjustments for extraction ratios, as well as dilution. However, the better practice is to use "Ottawa sand" (available from chemical supply houses) or a similar material as a blank for soil analyses. In fact, the CLP SOW requires the use of such a solid matrix blank. This same comment applies to Section and to the accompanying Figures 7.1 and Section 7.2.2, page 7.6 a. This section discusses toxicity data references. It is noted that contaminants without EPA-verified toxicity values are not continued through the risk-based screening process. Detected contaminants without toxicity values should be identified, and their concentration and toxicity should be discussed qualitatively. b. In addition, this section indicates that EPA Region 10 riskbased concentrations for PAils are used to screen contaminants of concern. The risk-based concentrations should be referenced and reported in the text. 29. Section 7.2.3, page 7.7 This section describes issues related to the identification of contaminants of concern. It is noted that groundwater detection limits for PAHs and PCBs did not meet Io` cancer risk-based concentrations. This issue should be further discussed during the analysis of the results of the risk assessment. Total cancer risks at source areas where PA~s may have been released to groundwater (e.g., diesel spill sites) should be evaluated. 30. Section 7.2.4, Tables 7.5 through 7.9 The lower case "1x" used here is not readily distinguishable from the upper case "X." The two have opposite meanings, so one symbol should be changed. 31. Table 9.1, page 9.2 Table 9.1 presents toxicity values for contaminants of concern. The reference cited for the trichloroethene inhalation slope factor should be verified. In addition, EPA's Integrated Risk Information System cites oral and inhalation reference doses for manganese of 5 x 10-3 and 1.4 X i0 3 ' mg/kg/day, respectively. These values differ from those noted in Table 9.1; this issue should be clarified.

8 Ejelson AFB 002 Draft ELRA Page Bection 9.1.2, page 9.9 This section presents toxicity values for lead. As suggested in the comment to Section 2.4.2, page 2.31, first paragraph, EPA's lead uptake model could be used to produce a third risk estimate for the residential scenario. A brief evaluation of the maximum soil lead levels detected in each area, as reported in Appendix D, indicates that the interim soil cleanup level of 500 to 1000 ppm of lead (EPA 1989a) in soil was not exceeded in 0U2 source areas. A similar evaluation of maximum groundwater lead levels indicates that the 15 pg/l drinking water action level for lead (EPA 1992c) was exceeded at source area ST13/DP2E. 33. Bection 10.0, page 10.1, fourth bullet The 2-liters per day water consumption figure is a total water intake, including other beverages, cooking water, and other components. The cited ingestion of 150 ML/day is very low and should be verified. This section should be rewritten, indicating that 2-liters per day consumption is a reasonable maximum exposure assumption. 34. Appendix A, Bection A.2.7, page A.6; Table D.19, Appendix B Appendix A presents an equation for determining contaminant intake rates caused by dermal contact with soil. It is noted that an age-adjusted ingestion factor is used to compensate for the greater rate of dermal contact for small children. The ageadjusted factor should be for body surface area rather than for ingestion. The exposure parameter for a child's exposed skin surface area will differ from that of an adult. Only an adult surface area of 5,000 cm' per exposure event is proposed in Appendix B, Table B.19. A surface area exposure parameter for a child should be developed following EPA guidance (1992a). The dermal exposure intake equation should be modified to account for the child receptor, and the child surface area exposure parameter should be reported in Table B Appendix B, Table E.10 The figures for fish consumption are not in accordance with the cited guidance. The 54 g/day figure is a long-term average, equivalent to "two 8-ounce servings per week." The text should adjust the exposure frequency or intake rate or both, incorporating site specific conditions, which may be greater than guidance assumptions.

9 Eielson AFB 0U2 Draft BLRA Page Appendix D These data were not checked against the RI. As noted elsewhere, the data validation process should eliminate the "B" qualifiers. 37. Appendix D and F a. These appendices present the sample data used in the risk assessment. Appendix D lists maximum detected contaminant concentrations, and Appendix F presents exposure point concentrations. It is recommended that the text or a table be used to briefly summarize the data sources for each media at each source area. A discussion regarding data validation should also be provided, especially for the 1992 data sets. b. The reason surface soil sample results are not reported in Appendix D for source areas ST11, ST13, and DP26 is unclear; this should be clarified. In addition, rationale for not presenting or using in the risk assessment contaminant concentration results for the 1989 soil sampling at area DP26 (i.e., as indicated in Table D.6) should be provided. C. Appendix F should also describe the way areas of concern were delineated for each source area. The text should indicate whether all soil sampling locations within each source area are included in the calculated upper confidence limits (UCL). The text should also indicate whether multiple rounds of sample data are averaged for individual wells within source areas to calculate UCLs. 38. Appendix E The metals with concentrations that could not be considered background are compared to the iron concentrations in groundwater and soil. The comparison presented in this appendix is somewhat confusing. The text states that there is a positive correlation between iron concentrations and other metals such as arsenic. The text (Section E.2.1, page E.4, fourth paragraph) states that less iron in the soil (the more iron in the groundwater) leads to more arsenic in the groundwater. If this statement is true, it can be concluded that the soil iron concentration should be low because the sampling results show high arsenic concentrations in groundwater that are related to high iron concentrations in groundwater. However, the following text (Section E.2.2, page E.9) shows that high soil concentrations of arsenic above background exist because of high iron concentrations in surface soil. This statement in Section E.2.2 appears to contradict the preceding conclusions in Section E.2.1. Further discussion and clarification should be presented in terms of total metal contents in background and 002 sites.

10 Eielson AFB 0132 Draft BLEA Page 9 The hypothesis that background groundwater samples have shown lower metal concentrations because of the dilution resulted from June recharge events should be further tested and proven. The site-wide background sampling plan for 1993 was designed for an additional sampling round in August. The new data should be used for a detailed comparison and analysis. The statistical approaches for comparison of background data with the 0U2 sampling data appears to be appropriate. However, as noted here, the T-test may be poorly suited for comparisons of groups of grossly different sizes and for use when many of the data are censored (nondetects). In those cases, numbers are generated, but their meaning is dubious. For future background data comparisons, a flow chart approach may be mare appropriate to select statistical methods. Section 5 of EPA groundwater monitoring guidance (1989b) contains an example. 39. Appendix E, Section E.2 A statistical tool for evaluating a relationship between the concentrations of two (or more) metals is regression analysis. The square of the correlation coefficient is the fraction of variance in the dependent variable, which is explained by variance in the independent variable. This sort of analysis may provide more meaningful information than the line graphs used here. It is quite possible that certain inorganic constituents have high, but wholly natural, variation at Eielson, but additional analysis could be provided to demonstrate this. 40. Appendix H, page H.1 This appendix presents biotransfer parameters for estimating fish and plant contaminant concentrations based on soil contaminant concentrations. The equation presented for calculating soil-toedible plant transfer ratios is referenced from an article by Travis and Arms (1988). However, the equation cited in the text has been modified, and the plant transfer ratios reported in Table H.1 could not be verified. Modifications to the Travis and Arms (1988) equation should be explained, and the plant transfer ratios should be verified. 41. Appendix 14 (Baseline RA), page M4.1 and 14.2 This appendix describes air modeling parameters used in this baseline risk assessment. These parameters are. described in EPA guidance documents (EPA 1991a,b). However, a few items should be noted. First, in the equations for volatilization factor (VF) and particulate emission factor (PEF), two factors are site-specific.

11 Ejelson AFB 0112 Draft BLRA Page 10 The length of the contaminated area (LS) and contaminated area (A) are both described, and a default value is apparently assigned. It appears that the, default value was used and carried through the risk assessment. The true values should be used at each site to calculate VF and PEF; the risk assessment should be revised accordingly. Second, Ut is defined on page M. 2 as the equivalent threshold value of the windspeed at 10 meters and set to the default value of 12.8 rn/sec. Backwards calculation of this value show's an aggregate soil distribution mode of approximately 2.5 to 3.0 mm, which is large for Eielson AFB, based on PRC's experience. The method by which Ut, equals 12.8 rn/sec was determined should be shown, and a reference for the aggregate size distribution mode should be included.

12 REFERENCES EPA 1989a. Interim Guidance on Establishing Soil Lead Cleanup Levels at Superfund Sites, OSWER Directive U.S. Environmental Protection Agency. September 7, EPA 1989b. Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities, Interim Final Guidance. Office of Solid Waste and Waste Management Division. U.S. Environmental Protection Agency. April EPA 1991a. "Supplemental Guidance for Superfund Risk Assessments in Region 10."1 U.S. Environmental Protection Agency, Seattle, WA. EPA 1991b. Risk Assessment Guidance for Superfund. U.S. Environmental Protection Agency, Office of Emergency and Remedial Response. EPA 1991c. USEPA Contract Laboratory Program National Functional Guidelines for Organic Data Review, Multi-Media, Multi- Concentration, OLM01.1 and Low Concentration Water OLCOI.1. U.S. Environmental Protection Agency. Revised June EPA 1992a. Dermal Exposure Assessment: Principles and Applications, EPA/500/8-91/Ol1B. U.S. Environmental Protection Agency. January EPA 1992b. Oral Reference Doses and Oral Slope Factors for JP-4 (CAS No. not identified), JP-5 (CAS No. not identified; similar to Kerosene, CAS No ), Diesel Fuel (CAS No. 6S ), and Gasoline (CAS No ) (AVGAS) [McChord AFB, (Wash Rack Treatment) Tacoma, Wa]. Memorandum from Joan Dollarhide to Carol Sweeney. U.S. Environmental Protection Agency, Environmental Criteria and Assessment Office. March 14, EPA 1992c. Drinking Water Regulations and Health Advisories. office of Drinking Water. U.S. Environmental Protection Agency. April Travis and Arms Bioconcentration of organics in Beef, Milk, and Vegetation, Curtis C. Travis and Angela D. Arms. Environmental Science Technology, 22,