EPA responses to July 2014 Razelle Hoffman-Contois' Draft Working Notes December 19, 2014

• Use of a de facto de minimis incremental lifetime carcinogenic risk (ILCR) of one in ten thousand (1 E-4) as opposed to the Department's general policy of one in one million (1 E­6) could result in dismissal of certain potential exposure scenarios or routes of exposure that may warrant further consideration.

Response: EPA's de minimis ILCR is 1E-6. The ILCR of 1E-4 is the maximum cancer risk accepted at Superfund sites. Under the National Contingency Plan, EPA can require remediation at the lower cancer risk levels.

• Assuming a default residential exposure duration of 30 years, as opposed to the Department's practice of 70 years, may underestimate potential exposure and the potential level of concern that may be associated with the hypothetical residential use scenario.

Response: This is a CERCLA default value. See attached memorandum for a discussion of exposure assumptions and potential risk differences.

o This most significantly impacts age-adjusted exposure (intake) equations associated with assessment of exposure to carcinogens.

Response: See attached memorandum.

o Site-specific note: From the Williston Observer 2005 - "The ... , who have lived on South Brownell Road just west of the site since 1958 ... "

Response: EPA looks at populations, not individuals.

Vinyl Chloride

• The Department assumes a residential exposure duration of 70 years thus the Hypothetical Resident would be assessed using the Continuous Lifetime Exposure From Birth Oral Slope Factor of 1.4 (mg/kg-d)-1 and Inhalation Unit Risk of 8.8E-6 (1Jg/m3)-1 (IRIS, 2000) and associated lifetime equations.

• On 11/1/13, the Department provided DEC with updated Risk-Based Residential Soil Screening Concentrations which include the following:

o Perchloroethylene (a.k.a. Tetrachloroethylene, PERC, PCE)

• The Department employs an Inhalation Unit Risk of 1.6E-6 (ug/m3)-1 (geometric average of National Research Council Inhalation Unit Risk values presented in IRIS, 2012).

• The Department employs an Oral Cancer Potency Factor 1.1 E-2 (mg/kg-d)-1 (geometric average of National Research Council Oral Potency Factors presented in IRIS, 2012).

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• Using these values, the Department has derived a Risk-Based Residential Soil Screening value of 1.57 milligrams per kilogram.

Response: Comment noted. Vinyl chloride was not detected in soil 0-10 ft bgs.

o Trichloroethylene (TCE) • The Department has derived an updated Risk-Based Residential Soil Screening

value of 0.47 milligrams per kilogram (470 micrograms per kilogram) which reflects the updated IRIS assessment (IRIS, 2011).

Response: Commented noted. TCE was not detected in soil 0-10 ft bgs.

o Hexavalent Chromium (Cr+6) • The Department has derived an updated Risk-Based Soil Screening value of

approximately 0.086 milligrams per kilogram (-86 micrograms per kilogram) which, similar to RSLs, reflects consideration of information presented by the EPA Office of Pesticide Programs, 2010 Draft IRIS citation, California EPA and the New Jersey Department of Environmental Protection.

Response: Comment noted. Although EPA uses a different screening level, chromium was selected as a COPC and further sampling was conducted in December 2013 to provide chromium speciation data. The soil tech memo recommended targeted soil removal action at the former Mitec property based on chromium (and PAHs).

o 2,3,7,8-Tetracholordibenzo(p)dioxin (TCDD) • The Department employs the carcinogenic toxicity values presented in HEAST,

1997. The Department has derived an updated Risk-Based Residential Soil Screening value of 2.29E-6 milligrams per kilogram.

Response: Comment noted. TCDD was not detected in soil 0-10 ft bgs.

Lead

Vermont Statute (Title 18) http://www.leg. state. vt.us/statutes/fullsection. cfm?Title=18&Chapter=038&Section=01751

"(7) "Elevated blood lead level" means having a blood lead level of at least five micrograms per deciliter of human blood, or a lower threshold as determined by the commissioner. "

Response: EPA's policy differs from Vermont's.

DATA AND EXPOSURE SCENARIOS

2014 HHRA Page 4

Data collected between 2008 and 2012 were considered in the HHRA

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• Were data from prior efforts reviewed or a sensitivity analysis conducted to determine if previously excluded analytes would be retained for further consideration given current screening values?

• Were similar analytes examined across efforts such that the 2008-2012 data is representative of the nature and extent of site-related contamination?

Response: We believe newer data is representative of current and future conditions. Similar analytes were examined. These are the COPCs we identified. We didn't note anything significantly different from earlier sampling. Does Vermont believe something is missing?

Groundwater

• Contaminant Screening Criteria o 2013 Rl Page 33 Section 4.1.2

• States comparison was made to federal MCLs and what I believe they mean is DEC Groundwater Enforcement Standards and also something termed "screening levels for public water systems" (?).

• In Appendix D-1 Analytical Data Summary of Groundwater Sample Results Comparison is made to "EPA-RSL-GW-MCL" which is defined as "EPA Maximum Contaminant Levels" (appears to be MCL pulled from RSL table) and "VT-GWPR" defined as "Vermont Ground Water Protection Rule" which perhaps means DEC Groundwater Enforcement Standards?

• How were chemicals with Vermont Action Levels handled?

• How were chemicals without an MCL or GES but with an RSL handled? o 2014 HHRA Page 11 -Criteria for Selection of COPCs in Groundwater Tap

Water Ingestion

States groundwater concentrations were screened against EPA RSLs for tap water. Table A-2.5 Screening criteria appear to be the calculated RSLs then DEC Groundwater Enforcement Standards

Response: Applicable VT regulations (ARARs) will be finalized during review of the Feasibility Study. In the remedial investigation report, nature and extent discussions and tables provided comparisons to RSLs, federal MCLs, and VT ARARs. In the HHRA, COPC selection was based only on EPA RSLs. VT ARARs were presented on COPC selection tables for information only. If contaminant maximum detected concentration exceeded the RSL for HQ =0.1 or ILCR =1 E-6, or, or if there was no RSL, contaminant was selected as COPC for further evaluation.

• Potential Applicable or Relevant and Appropriate Requirements (ARARs)

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o 2014 HHRA, page 13 and 2013 Rl, page 34 - Names of ARARs are incorrect. Believe they are referring to Vermont Groundwater Protection Rule and Strategy, Chapter 12 of the Vermont Environmental Protection Rule and Vermont Water Quality Standards, Appendix C: Water Quality Criteria for the Protection of Human Health and Aquatic Biota.

o Misc. ARAR note -2014 HHRA- The Vermont Air Pollution Control Regulations (which include Hazardous Ambient Air Standards) may be Relevant and Appropriate and provide values appropriate for use in Table A-2.4.

Response: The revised HHRA will include the correct VT ARARs.

• 2014 HHRA Page 7 and 2013 Rl Appendix D

Use of EMPC value in calculation of Dioxin/Furan-Toxic Equivalent (TCDD-TEQ)

o Sample 2008 ASI-2302 has only OCDF congener with a J qualifier and several congeners listed with aU or UEMC. The total sample DF-TEQ is listed at the value of the J qualified congener times its corresponding TEF.

o Sample 2008 Ml-01 there is one congener reported with a J qualifier, several reported with U qualifier and one reported as EMPC. The EMPC value was used to calculate the estimated total sample DF-TEQ. This looks odd to me and may be a follow up question for the analytical laboratory. Also, is use of an EMPC qualified value in derivation of a sample concentration appropriate?

Response: The TEQs were provided by the EPA CLP lab (Pace Analytical Services, Inc, Minneapolis, MN). Typically, the TEQ includes all congeners that have been detected in the sample, as well as non-detected congeners that have been detected previously. For those non-detected congeners for which there is some reason to believe may be there, the detection limit is entered. If the congener was never detected no values are entered. U and UEMC qualified data would be considered non-detects. Therefore, for 2008 sample ASI-2302, dioxin TEQ should reflect only the one detected OCDF congener (J qualified data is considered a detect). For 2008 sample Ml-01, dioxin TEQ should reflect the detected OCDF congener (J qualified data) and the PCDF congener (EMPC - estimated maximum possible concentration - is considered a detect).

Out of the 15 dioxin samples, these two samples and their one or two congeners are the only "detections." With the only detections being low estimated values, it is likely dioxins (or furans) are not even present. The maximum calculated dioxin TEQ just barely exceeds the 1x10-6 cancer risk level and does NOT exceed the HQ=1.0 level.

• Private Wells

Clarify if any private well is currently in use.

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o 2014 HHRA Page 21 - States a private well is located just northeast of the intersection ofWilliston Road and Lois Lane. One public water supply is noted 2.5 miles southeast.

o 2013 Rl Page 32 - "A private well is located northeast of the intersection of Williston Road and Lois Lane."

o A TSDR PHA Page 7 -"There are presently no active drinking water wells within a mile of the Commerce Street Plume."

Response: Agree that the previous descriptions, taken from various state and federal reports, are unclear. EPA is having difficulty determining from available sources where active water supplies - public and private - are in relation to the groundwater plume at the Commerce Street site. We are requesting assistance from the State of Vermont.

• Hypothetical Construction Worker (Soil exposure not quantitatively evaluated)

o HHRA Page 14 Section 3.2.3- Groundwater data from screening depths of 0-10 feet bgs were used in development of exposure point concentrations (EPCs) for dermal contact and inhalation of vapors in trenches during excavation activities. I agree these would be the most likely potentially significant routes of exposure.

o Exposure is assumed to occur 5 days per week, 6 months of the year during just one year. This may be an underestimate. Williston in general, has been undergoing extensive redevelopment for several years. It is not unreasonable to assume that potential future redevelopment of the area of interest could span more than one construction season and that a hypothetical Construction Worker could be involved in redevelopment of multiple locations within the area of interest over a period of years. In addition, such work, including excavation, may occur for more than 6 months per year as evidenced by essentially year round, ongoing residential development in the nearby Taft's Corners area.

Response: Taft's Corner is far beyond the boundaries of the Commerce Street Plume Superfund site. EPA believes that given the extent to which the site is already developed, a six-month exposure derivation is reasonable for residential and small ­scale commercial construction. See attached memorandum.

• EPA Vapor Intrusion Screening Levels (VISLs)

o 2014 HHRA Page 12 - For noncarcinogenic endpoints, shallow groundwater concentrations were compared to VISLs corresponding to a Hazard Quotient of 1 whereas a screening HQ of 0.1 was used for other media.

Response: Comment noted. Change will be made in final HHRA.

o 2014 HHRA Page 14 -Which version of VISL Tool was used? Reference notes V.1 while Table A-2.4 notes May 2012.

Response: Comment noted. The most recent VISL table will be used for screening at HQ =0.1

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• Different groundwater data sets were used in different evaluations - Recommend include table indicating which data were used to evaluate which pathways. It appears:

o Construction Worker - Dermal and Inhalation of Vapors in Trench - Table A-2.3 Shallow Groundwater data 0-10 feet bgs

o Hypothetical Resident - Tap water ingestion, dermal exposure and inhalation exposure to VOCs due to routine household water use (not VI) - Table A-2.5 Overburden Groundwater (data from all depths)

o Hypothetical Resident (and potentially Industrial/Commercial Workers) - Vapor Intrusion- Table A-2.4 Shallow Groundwater data 0-15 feet bgs

Response: This comment will be addressed with footnotes referencing Appendix B lists.

Vapor Intrusion

• EPA Indoor Air Soil Vapor Intrusion Study Reports- Commerce Street Plume Sites -Stated to present data from indoor air and sub-slab soil gas samples collected in June 2012 and January 2013. As these reports have not been provided for review, I am unable to critically evaluate any statements pertaining to, or conclusions based upon, these investigations.

Response: Michael Smith can provide these, if needed.

• HHRA 2014 Page 26 - states potential 'future' exposure for Vapor Intrusion was evaluated. As residences and businesses already exist, the time frame would be CurrenUFuture which seems to be indicated in Table 2.1

Response: Comment noted. Change will be made in final HHRA.

• I have not reviewed the Virginia DEQ approach for evaluating trench air therefore cannot critically evaluate any statements pertaining to, or concllusions based upon, use of this approach.

Response: Comment noted. EPA often uses this approach.

• Appendix J -December 18, 2013 memo from EPA regarding Vapor Intrusion Investigation, Commerce Street Site

o Limited sampling was conducted at 5 homes 2 businesses. It is not clear if these properties are located over areas where there is the greatest potential for vapor

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intrusion, i.e., where the highest levels of TCE and PCE have been reported in groundwater/soil and represent the greatest potential for VI.

Response: EPA selected the seven properties based on proximity to groundwater hotspots, sensitive populations (e.g., elderly, children, cancer survivor), those who asked to be part of the study, those willing to participate in the study, and avoiding properties where the commercial enterprise might impact indoor air results (e.g, cat hospital, print shop).

o As previously noted, the Department employs a 70 year residential exposure duration as well as different cancer toxicity values for PCE. This approach results in more stringent screening values than employed in the memo.

Response: EPA policy differs from Vermont's. EPA uses IRIS values for TCE, PCE.

o Due to potential developmental effects, a hypothetical Commercial/Industrial worker screening value may warrant further discussion.

Response: Comment noted. EPA does not have a position on the likelihood of developmental defects during sub-chronic exposure. EPA has deferred to State policies where - using CERCLA exposure assumptions - federal risk has been found to be unacceptable.

Surface Water

Data collected in 2012 were used in the development of EPCs

• HHRA 2014 Page 16 states Table A-3.2 presents EPCs for Surface Water however, this table is missing and Table A-6.2 Cancer Toxicity Data-Inhalation is in its place.

Response: Comment noted. The missing table will be included in the final HHRA.

Soil

2013 Rl , Page 33

States site-related soil data were compared to May 2012 Regional Screening Levels (RSLs) and VDH values presented in 2012 DEC IROCP. Updated VDH screening values were provided to DEC 11/1/13.

Response: VDH values will be updated to the 2013 values in the Rl tables and the text reference will be updated.

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• 2014 HHRA

o Surface Soil and Soil Boring data from 2010 and 2012 collected from 0-10' bgs were used in the development of EPCs.

Response: Comment noted.

o Elevated levels of TCE detected at depths great than 10 feet bgs are not considered in the HHRA. For example, TCE is reported as 2.1 mg/kg in sample SB-12-2 from 20­25 feet bgs.

Response: EPA does not consider soils below 10 feet for risk assessments, which is the typical maximum excavation depth.

• Does the potential exist for this deeper level contamination to act as a depot that could contribute to future vapor intrusion and if so, does this warrant further consideration?

Respons~: EPA anticipates that the selected remedy will have a groundwater remedial component.

o Site-related data were compared to May 2013 RSLs.

Response: Commented noted. EPA uses RSLs for COPC identification.

o How handle if site-related data was below RSL but above VDH value?

Response: VT regulations are considered ARARs when federal risk is above acceptable federal risk levels. If below RSL, not a COPC.

o Page 14 - potentially carcinogenic polycyclic aromatic hydrocarbons (cPAH) were evaluated as individual cPAH rather than total benzo(a)pyrene toxic equivalents [B(A)P-TE]. Individual cPAH were compared to screening values adjusted with appropriate TEFs. VDH Risk-Based Residential Soil Screening Concentration for B(a)P-TE is 0.01 mg/kg and RSL residential value is 0.015 mg/kg. Data in the 2013 Rl Appendix D indicate Detection Limits for individual PAHs were usually approximately 0.3 mg/kg which if used to derive a B(a)P-TE concentration leads to value that exceeds both the VDH and RSL residential soil screening values. This makes it difficult to characterization nature and extent of contamination.

Response: Comment noted. EPA's policy differs from Vermont's however, the soil tech memo - currently being revised to include results from the summer 2014 sampling event- recommended targeted remedial action based on the high PAH detection limit.

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o 2013 Rl Appendix D Soil Sample Semi-Volatile Organic Compounds analytical results, shows that in sample SB-12-5 from 0-1 foot bgs five of the seven cPAH considered in the derivation of B(a)P-TE were reported above detection limit. Two, dibenzo(a,h)antrhacene and indeno{1 ,2,3-c,d)pyrene, were reported as nondetect at 260U tJg/kg. Using the reported value for each of the five cPAH reported above detection limit and Y2 the Detection Limit as a rough surrogate for the two reported with a U qualifier and the appropriate toxic equivalency factors, I derived an estimated sample value of approximately 0.5 mg/kg B(a)P-TE which is about an order of magnitude greater than both VDH and RSL residential screening value for B(a)P [also applicable to B(a)P-TE].

Response: Comment noted. Remedial decisions will be based on total cancer risk for COPCs.

o Page 15, Section 3.2.6 and Page 24 Section 4.2.3 - Contrary to what is stated, data do not appear to have been summarily dismissed as "typical background associated with the northeast and/or are assumed to be unrelated to the Site." Instead data appear to have been evaluated as noted in the preceding bullets. The 2013 Rl Page 37 Section 4.3.2.3 indicates soil data were compared to RSLs and VDH residential screening values.

Response: Comment noted. Change will be reflected in forthcoming final revised soil memo.

o If data were compared to other generic, regional background values, then such references need to be provided to and vetted by DEC, and incorporated into the tables in Appendix A Otherwise, the paragraphs on pages 15 and 24 should be edited to indicate screening was conducted as described in the Rl.

Response: Comment noted. Change will be reflected in forthcoming final revised soil memo.

o HHRA page 13 states "No background samples have been collected for groundwater or soil."

Response: Comment noted. Groundwater risk is evaluated without regard to background levels. Soil background will be discussed in forthcoming final revised soil memo.

o Arsenic reported at a maximum detect of 9.2 mg/kg and chromium were the only inorganics reported above screening values. I agree with the conclusion that the level of arsenic reported in soils is consistent with typical background values reported in Vermont

Response: Comment noted.

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o HHRA Page 24 Hexavalent Chromium - RSL based on 30-year residential exposure duration is 0.29 mg/kg at 10-6 ILCR. The Department assumes a 70-year residential exposure duration and has developed a Risk-based Residential Soil Screening

· Concentration of 0.09 mg/kg.

Response: EPA's policy differs from Vermont's.

• HHRA uses 8% ratio

Response: This discussion will change with the forthcoming final revised soil memo.

• Shunpike Road sample result of 29 mg/kg total Chromium estimates 2.32 mg/kg Cr+6 which corresponds to an ILCR of approximately 10-5 using EPA residential scenario exposure assumptions and close to 10-4 using the Department's approach.

• Commerce Street sample result of 320 mg/kg total Chromium x 8% estimates 25.6 mg/kg Cr+6 which corresponds to an ILCR of approximately 10-4 using EPA residential scenario exposure assumptions and greater than 1 OE-4 using the Department's typical assumptions.

• On page 63, concerns regarding applicability of the ratio presented are noted. However, even if a ratio of 5 percent is employed, Cr+6 may be of interest. In particular, the level reported in the sample taken on Commerce Street may warrant further consideration and attention.

Response: These discussions are moot based on forthcoming final revised soil memo, and anticipated removal of soil contamination at 96 Commerce Street based on hexavalent chromium results.

• EPA Final Technical Memorandum Risk Evaluation of Soil Data at the Commerce Street Superfund Site, Williston, vr dated May 15, 2014

o Fifth paragraph, fifth sentence - Three, not two, individual PAHs exceeded their cancer-based RSLs in Sample SB-12-5. Benzo(b)fluoranthene should also be shaded in Table 1. In addition, the Department would evaluate as B(a)P-TE and include the values reported for the other cPAH in this sample as described in bullets 5 and 6 in the 2014 HHRA Soil notes above. To recap: using the reported value for each of the 5 individual cPAH reported above detection limit and Y2 the detection limit as a rough surrogate for the 2 reported with a U qualifier, an estimated sample concentration of­0.5 mg/kg B(a)P-TE is derived. This is about an order of magnitude greater than both the VDH and RSL residential screening values for B(a)P [also applicable to B(a)P-TE].

o Minor text edit at end of 5th sentence- "("Table 5.

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Response: Comment noted. Will be addressed in forthcoming final revised soil memo.

o Fifth paragraph, last sentence- Based on the information provided for review, I agree.

Response: Comment noted.

o Sixth paragraph - Chromium speciation

• Two samples were analyzed for hexavalent chromium. However, these were not taken from the location with the highest reported concentration of total chromium within 0-10 feet bgs. Sample SB-13-1 from 0-2 feet bgs and from 2-6 feet bgs with 11 mg/kg and 12 mg/kg total chromium respectively, were analyzed for Cr+6. However, total chromium is reported as 29 mg/kg in Sample SB-12-1 from 3-5 feet bgs. Are the Cr+6 data from SB-13-1 representative of site conditions?

Response: Sample locations were selected to be co-located with earlier samples so that total chromium data could be compared to speciation data.

• Chromium Residential Soil RSLs presented in Table 2 don't appear to be consistent with those presented in the RSL Residential Soil Table. Table 2 notes Residential Soil RSL of 2.9 m/kg associated with Hl=1 and no value is noted to be associated with ILCR=1 E-6.

• RSL table itself notes value of 230 mg/kg associated with Hl=1 and 0.3 mg/kg associated with TR=1 E-6. It appears similar values are used in Table 5.

Response: Comment noted. Discrepancies will be addressed in revised HHRA.

o The May 15th version of the memo "The potential for TCE vapor intrusion is being evaluated and possible impact from the discharge of sump water to shallow soil are being evaluated separately" and associated footnote is replaced with "The potential for TCE vapor intrusion is being evaluated separately."

Response: Comment noted.

2014 HHRA Appendix A:

• Tables A-2.1 through 2.6 - Revise column heading from "Screening Toxicity Value" to "Screening Value" as values presented are risk-based screening concentrations, not toxicity values.

Response: These are standard RAGS D column headings. No change will be made.

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• A column should be included that provides the rationale for why compounds are dismissed from further consideration when "Rational for Selection" is noted as "Above Screening Level". If subsequent comparison was made to another set of values a column with such values should be included.

Response: ASL "Above Screening Level" is used along with a YES, to indicate the contaminant was selected as a COPC, not dismissed.

• As noted above, the HHRA indicates some compounds of potential concern were eliminated from further consideration based on comparison to " ... typical background ... " but in the Rl , site-related data were compared to appropriate risk based screening values and compounds to be carried forward were identified. No soil background values are presented in Appendix D of the HHRA.

o HHRA page 13 states "No background samples have been collected for groundwater or soil. "

o Clarification appears to be warranted.

Response: Background issues will be clarified in final HHRA and forthcoming final revised soil memo.

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MEMORANDUM

To: Karen Lumino From: Richard Sugatt Date: December 17, 2014 Subject: Response to Vermont Department of Health comments on draft Commerce Street

Plume Superfund Site human health risk assessment pertaining to differences between EPA and VT exposure and toxicity factors

The purpose of this memorandum is to address the Vermont Department of Health {VDH) comments concerning the differences between EPA and VDH in exposure and toxicity factors used in the EPA draft human health risk assessment {HHRA) for the Commerce Street Superfund Site. The draft HHRA is being updated as described elsewhere in the EPA response to VDH comments, using the most recent exposure factors {Table n November, 2014 EPA Regional Screening Levels {RSLs), and Vapor Intrusion Screening Levels {VISLs) set at Hazard Quotient {HQ) = 0.1 and Incremental Lifetime Cancer Risk {ILCR) set at 1E-06 for selection of Contaminants of Potential Concern {COPCs). In addition, the technical memorandum concerning risks of soil is being updated using the above-mentioned exposure factors and screening levels and will be sent separately.

Exposure Factors EPA's former (pre-2014) and current default exposure factors are provided in Table 1, along with the factors that EPA assumes would be recommended by VDH based on the Vermont Department of Environmental Conservation {VDEC) guidance {"Investigation and Remediation of Contaminated Properties Procedure", April 5, 2012), which recommends in Section 2.4:

"If this type of risk assessment is found to be necessary at a site, it must follow standard USEPA risk assessment methodology and human health risk assessments must be approved by the Vermont Department of Health {VDH)."

As seen in Table 1, the only substantive difference in exposure factors between EPA and VDH appears to be the use of a 30 year exposure duration by EPA versus a 70 year exposure duration by VDH. Use of this higher exposure duration would result in 2.3 times higher risks {i.e. 70/30=2.3) than use of the EPA default exposure duration of 30 years. This also results in lower Vermont Soil Screening Values {SSV) than equivalent EPA RSLs because, as stated in the second paragraph of Appendix A in the above­mentioned document:

"The VDH risk-based residential soil concentrations for carcinogens are based on a de minimus incremental lifetime carcinogenic risk of one in one million {10-6) and assume a 70 year residential exposure duration."

The SSVs for some chemicals will be different {lower) than equivalent IRSLs also because VDH recommends toxicity factors for some chemicals that are more stringent than EPA's currently recommended va lues, including trichloroethylene {TCE), vinyl chloride {VC), tetrachloroethylene {PCE), and 2, 3, 7, 8-tetrachlorodibenzodioxin toxic equivalents {TCDD-TEQ).

Toxicity Factors The difference between EPA and VDH/VDEC toxicity factors for the above-mentioned chemicals are provided in Table 2. It was assumed that the VT non-cancer toxicity factors {reference dose, reference

concentration} were the same as EPA's. It was assumed that the VT oral slope factor for vinyl chloride and the VT inhalation unit risk for TCE and TCDD-TEQ were the same as EPA's values for these chemicals. Table 2 shows that the VT oral slope factor was higher (more risk) than EPA's by factors of 30.4 for TCE,

5.2 for PCE, and 1.2 for TCDD-TEQ. The VT inhalation unit risk was higher (more risk} than EPA's by factors of 2.0 for VC and 6.2 for PCE.

Table 2 also provides a comparison of the EPA RSL set at HQ=0.1 and ILCR=1E-06 with the VT SSV as of

April 5, 2012 from Appendix A of the above-mentioned VT guidance. The factor between the VT SSV and

the EPA RSL was calculated by dividing the lower RSL for HQ =0.1 or ILCR=1E-06 by the SSV. Table 2 shows that the SSV was about the same as the lower RSL but that the SSV for PCE was about 5 times lower than the lower RSL, and the SSV for TCDD-TEQ was about 2 times lower than the lower RSL.

Combined Factors Table 3 shows the combined differences between VDH/VDEC factors and EPA factors. Use of the VT oral slope factor and the 70 year exposure duration would result in soil ingestion cancer risk that would be higher than EPA by factors of 71 (=30.4 x 2.3) for TCE, 2.3 (=1 x 2.3} for VC, 12.2 (=5.2x2.3} for PCE, and 2.7 (=1.2x2.3) for TCDD-TEQ. Use of the VT inhalation unit risk and the 70 year exposure duration

would result in soil inhalation cancer risk that would be higher than EPA by factors of 4.7 (=2x2.3) for VC and 14.4 (=6.2x2.3} for PCE.

Summary and Implications EPA will use its currently recommended toxicity factors and exposure factors to update the draft HHRA

for the Commerce Street Superfund Site, and EPA will use the risk management criteria specified in the National Contingency Plan (HQ ~1; ILCR range of 1E-06 to lE-04} to make remedial decisions; however, the uncertainty section ofthe HHRA will discuss the uncertainty in risk results associated with the use of the VT exposure duration and toxicity factors with a discussion similar to this memorandum. As shown in Table 3, use of VT factors would result in cancer risks the same order of magnitude for VC and TCDD­

TEQ and one order of magnitude higher for TCE and PCE. This discussion will be used in the development of remedial action objectives, as appropriate.

Table 1. EPA 2014 and Pre-2014 Exposure Factors and Vermont Exposure Factors

Exposure Factor Units EPA EPA VDEC

pre-2014 2014

Resident Drinking Water Ingestion Rate-child L/day 1 0.78 EPA methods

Resident Drinking Water Ingestion Rate-adult L/day 2 2.S EPA methods

Resident Soil Ingestion Rate-child mg/day 200 200 EPA methods

Resident Soil Ingestion Rate-adult mg/day 100 100 EPA methods

Resident skin surface area-child cm 2 2800 2690 EPA methods

Resident skin surface area-adult cm 2 S700 6032 EPA methods

Resident water surface area-child cm 2 6600 6378 EPA methods

Resident water surface area-adult cm 2 18000 20900 EPA methods

Resident soil adherence factor-child mg/cm2

0.2 0.2 EPA methods

Resident soil adherence factor-adult mg/cm2 0.07 0.07 EPA methods

Resident body weight-child kg 1S 1S EPA methods

Resident body weight-adult kg 70 80 EPA methods

Resident exposure frequency days/yr 3SO 3SO EPA methods

Resident exposure duration yr 30 26 70

Resident exposure duration-child yr 6 6 EPA methods

Resident exposure duration-adult yr 24 20 EPA methods

Resident air exposure time hr/day 24 24 EPA methods

Resident soil exposure time hr/day 24 24 EPA methods

Resident water exposure time hr/day 24 24 EPA methods

Resident water exposure time-child hr/day 1 O.S4 EPA methods

Resident water exposure time-adult hr/day O.S8 0.71 EPA methods

Averaging time-resident days/yr 36S 36S EPA methods

Lifetime yr 70 70 EPA methods

Indoor worker soil ingestion rate mg/day so so EPA methods

Outdoor worker soil ingestion rate mg/day 100 100 EPA methods

Worker skin surface area-adult cm 2

3300 3470 EPA methods

Worker soil adherence factor mg/cm2

0.2 0.12 EPA methods

Worker body weight kg 70 80 EPA methods

Worker exposure frequency days/yr 2SO 2SO EPA methods

Indoor worker exposure frequency days/yr 2SO 250 EPA methods

Outdoor worker exposure frequency days/yr 22S 22S EPA methods

Worker exposure duration yr 25 25 EPA methods

Indoor worker exposure duration yr 2S 2S EPA methods

Outdoor worker exposure duration yr 2S 2S EPA methods

Worker air exposure time hr/hr 8 8 EPA methods

Worker soil exposure time hr/day 8 8 EPA methods

Averaging time-composite worker days/yr 36S 36S EPA methods

Averaging time-indoor worker days/yr 36S 36S EPA methods

Averaging time-outdoor worker days/yr 365 36S EPA methods

EPA factors are from:

http://rais.ornl.gov/documents/EFH_ Table.pdf

Table 2 EPA and Vermont Toxicity Factors and Screening Levels for Residential Soil

Chem. UR-I (per ug/m3) RfO-o (mg/kg-d) RfC-1 (mg/m3

) Screening Level (mg/kg)

EPA

SF-o (per mg/kg-d) EPA VT EPA/VT EPA RSL VTSSV lower RSL/

ILCR"

VT VT/EPA EPA VT VT/EPA EPA VT EPA/VT HQ=O.l ILCR ssv

l.OOE-06 (chi ld) 1111 11 4.7E.01NA NA 2.0E.03 NA 9.4E.Ol 4.1E.Ol 0.9TCE 4.6E-02 1.4E+OO 30.4 4.1E-06 S.OE-D4

1'1' 1' NA 6.0E.02 1.0

PCE

7.2E.Q1 NA 4.4E-06 8.8E.06 2.0 3.0E.03 NA 1.0E.Ol S.9E.02 7.0E+OOvc 1' 1' 2.4E+()1 1.6E+OO5.2 2.6E-07 6.2 6.0E.Q3 NA 4.0E.02 NA 8.1E+OO S.22.1E.03 1.1E.02 1.6E·06 111' 1' 4.9E-06 2.11.2 3.8E+Ol NA 7.0E-10 NA 4.0E·08 NA S.OE.Q6 2.3E·06TCOO·TEQ 1.3E+OS l.SE+OS

NA = Not Available

SF-o "' oral Slope Factor UR-I =inhalation Unit Risk

RfD-o = oral Reference Dose

RfC-i =inhalation Reference Concentration

VT =Vermont

ILCR = Incremental Lifetime Cancer Risk

HQ = Hazard Quotient

TCE = Trichloroethylene

VC = Vinyl chloride

PCE =Tetrachloroethylene TCOD-TEQ = 2, 3, 7, 8· tetrachlorodibenzodioxin toxic equivalents 1 Assumes the same toxicity factor as EPA

Table 3. Summary of Differences between EPA and Vermont Toxicity and !Exposure Factors

Chemical Oral Slope Factor (per mg/kg-d) Exposure Duration (yr) Combined

FactorEPA VT VT/EPA EPA VT VT/EPA

TCE

vc PCE

TCDD

4.6E-02

7.2E-01

2.1E-03

1.3E+05

1.4E+00

NA

1.1E-02

l.SE+OS

30.4

1.0

5.2

1.2

30

30

30

30

70

70

70

70

2.3

2.3

2.3

2.3

71.0

2.3

12.2

2.7

Chemical Inhalation Unit Risk (per ug/m3)

EPA

4.1E-06TCE

vc 4.4E-06

PCE 2.6E-07

TCDD 3.8E+01

VT

NA

8.8E-06

l.GE-06

NA

VT/EPA

2.0

6.2

Exposure Duration (yr) Combined

EPA

30

30

30

30

VT VT/EPA Factor

70 2.3

70 2.3 4.7

70 2.3 14.4

2.370