2. Why have some cleanup criteria become more stringent and others less stringent?

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1 ADEC, Division of Spill Prevention and Response Proposed Amendments to 18 AAC 75 to update cleanup levels for soil and groundwater and how they are calculated for contaminated sites. Reponses to questions received during the public comment period- August 26, 2015 through December 11, What are the changes to the cleanup levels and why? The most significant feature of this proposed regulation revision is an update to the soil and groundwater cleanup criteria for individual compounds which have not been updated since Since then, substantial advances in the science for quantifying the exposure and health risks of these compounds have occurred. Equations now include: Incorporation of child exposure parameters in the groundwater cleanup values and adjustments for those compounds which have a mutagenic mode of action; and equations that assess exposure risk to groundwater via three pathways (inhalation of volatiles, ingestion, and direct contact) associated with domestic groundwater use, instead of solely ingestion as a drinking source. These groundwater criteria replace the corresponding federal maximum contaminant level (MCL) for drinking water that may have previously been referred to, so that the same risk-based approach is used across the board for all chemicals. Even with Alaska-specific input parameters, this has the impact of reducing cleanup criteria in many cases. 2. Why have some cleanup criteria become more stringent and others less stringent? The information available on the toxicity of individual compounds is continually updated. Criteria that were previously more stringent for certain compounds may have reflected uncertainty due to lack of available data on the health effects. As new scientific information becomes available, stronger conclusions can be reached about the actual risks of such compounds. The reverse is also true, where new research provides strong evidence that a cleanup level is not protective enough of all receptors resulting in the need for a more stringent value. Approximately 80 of the new soil cleanup levels are more stringent and 80 are less stringent than current criteria. The remaining are either new compounds being added, or the levels remain unchanged. 3. Why is there now only one number for both the direct contact and inhalation pathways? The Table B1 method two residential soil cleanup levels for each climate zone now provide a single cleanup value (called human health ) that does not exceed a cumulative risk value of 1 in 100,000 cancer risk, or a noncancer risk of 1, for all soil exposure pathways. This approach ensures that, for example, a child is protected if they are exposed to soil through both the ingestion and inhalation routes. In the same way, the Table C groundwater cleanup value is also generated by a cumulative risk calculation for the three groundwater exposure pathways- ingestion, direct contact and inhalation of volatiles (such as during bathing). 4. Once the new cleanup levels are adopted, can alternative cleanup levels and cumulative risk still be calculated with the DEC online Method 3 Calculator? Because we are adopting new equations, and updated toxicity and chemical specific parameters as part of our updated cleanup levels, our current Method 3 Calculator, which uses outdated equations

2 and input parameters, will no longer correctly calculate Method 3 alternative cleanup levels or cumulative risk. Therefore DEC is developing a new web-based calculator to address this issue. However, for sites with petroleum contamination, the existing Method 3 calculator will still be effective for calculating alternative cleanup levels, as the equations for those contaminants have not changed. 5. What standard applies to contaminated groundwater when it impacts a municipal water system? Is it the risk based number or the MCL? It is important to separate the pollution of a groundwater aquifer (raw source water) from posttreatment water dispensed from a public water system tap. The former is not regulated by the Safe Drinking Water Act. It is a natural resource of the State of Alaska, with many potential and varied uses and ecosystem services beyond serving a public water system, both now and in the future. These qualities distinguish it regulatorily from the requirements that are applied to public water treatment system that is designated solely for human consumption. Therefore, where criteria established per AS (Pollution standards) are exceeded in a groundwater aquifer, it is considered polluted which is prohibited under (Pollution prohibited). A Maximum Contaminant Level (MCL) applied to a public water treatment system is merely the highest level of a contaminant that is allowed in drinking water after treatment, at the tap, not in raw source water. MCLs are often based on the most cost-effective and best available treatment technologies and may not always be set at the lowest risk level. To address this, public water systems work wherever possible to achieve Maximum Contaminant Level Goals (MCLGs) which are set at or near zero. In some instances, MCLs, which are not routinely updated to incorporate the best available science, may be more stringent than criteria established for groundwater under 18 AAC 75. In these cases, a responsible party may be required to remediate groundwater to a lower standard than the risk-based cleanup criteria that would otherwise apply in order to ensure compliance with the MCL at the tap. 6. How many groundwater cleanup levels are now less stringent than the MCL, and how many are more stringent? Of the 52 compounds with MCLs, the new risk-based value is less stringent for 18 of those compounds, more stringent for 22, and unchanged for one compound. 7. What if the new soil or groundwater cleanup level is lower than what can be detected by a laboratory? Where a cleanup criterion is lower than the practical quantitation limit (PQL) of an approved method performed by a laboratory certified by DEC to run that particular method and the PQL is no greater than the PQL established in Environmental Protection Agency s Test Methods for Evaluating Solid Waste, Physical/Chemical Methods (SW-846), Third Edition, including Final Update IV (2009), then the PQL can serve as the cleanup criterion for that contaminant at a given site. However, if DEC determines that additional action is necessary to ensure protection of human health, safety or welfare of the environment, the following may be requested: Use of a surrogate measure to estimate the concentration of the hazardous substance; or Use of a specialized sample collection or analytical method to improve the accuracy, precision, method detection limit, or practical quantitation limit for the hazardous substances at the site; or

3 Monitoring to ensure that the concentration of the hazardous substance does not exceed quantifiable levels; or The use of an improved or modified analytical method. 8. With these new cleanup levels, what happens to sites currently undergoing cleanup or those that have been closed? For open sites, our standard approach is to apply the updated cleanup levels to all open sites after the public comment period is complete and revised regulations are adopted. This approach is designed to prevent RPs from having to re-mobilize to the site after criteria are promulgated, or to accept institutional controls that may restrict how the property is used. Project managers will work with responsible parties as they prioritize review of open sites to address the most frequentlyencountered compounds. This is necessary in order to determine early on whether additional characterization or cleanup will likely be required as a result of more restrictive cleanup levels. For open sites where the cleanup was conducted under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA, also known as Superfund), a Record of Decision (ROD) documents the cleanup levels that apply. Changes to promulgated cleanup levels after a ROD has been signed do not get incorporated into on-going remedial actions. Instead, Five Year Reviews are required on all sites where the implemented remedy does not provide for unlimited use and unrestricted exposure. The Five Year Review includes evaluating changes in cleanup levels and toxicity data for Contaminants of Concern at the site, and if a remedy is determined to not be protective, the necessary corrective actions will be identified. For closed sites, the applicability of more stringent cleanup levels will depend upon the systematic review undertaken by DEC staff to determine the potential impact to human health. An initial review of closed sites has been completed; subsequent review steps will involve the following steps: Review site documentation to include information in our Contaminated Sites database and/or site files; Determine the highest concentration remaining at the site at the time of closure and compare to the draft criterion For concentrations exceeding the proposed new criteria, determine whether or not human health pathways are complete If the pathways are complete, coordinate with the responsible party to determine whether or not the site must be re-opened and additional work completed. It is important to note that our objective is not to re-open any sites. During the last regulations update in 2008, only one site was found to require additional evaluation; however, after further review it was not re-opened. 9. Why are new compounds being added? This update adds 18 compounds to the tables, and removes one compound, carbazole, for which there is currently no available toxicity information. There are several important reasons to add new

4 compounds. First of all, the compounds we propose to add were not originally listed in the EPA s 1996 Soil Screening Guidance (which is now superseded by EPA s updated equations) when the list of compounds regulated under 18 AAC 75 was originally developed. Secondly, as our awareness and scientific understanding of contaminants has increased since that time, there is an obligation to include those contaminants to ensure we do not overlook any potential threats to human health. Chemicals such as perfluorinated compounds (used predominantly in fire-fighting foams and for fabric protection) have recently been identified to have human health and ecological risk concerns and are now being reported at sites in Alaska. Finally, other compounds being added are common constituents of waste oil or maintenance shop contamination. Until now, criteria for these had to be calculated on a site-specific basis or on request. Now they are listed for the public s convenience. 10. What is the difference between a toxicity value and a cleanup level? A toxicity value, usually derived from laboratory studies, represents the concentration of a chemical at which adverse effects are observed in an organism via a specific exposure route (e.g. ingestion, dermal exposure, inhalation) over a specific time period. A cleanup level is extrapolated from a toxicity value looking at a host of factors that influence exposure to the receptor, such as age, body weight, estimated duration and frequency of exposure to a chemical in specific media at a site, climate conditions, and soil characteristics. 11. It seems like there are many sources for determining toxicity values. How does DEC decide which value and which source to use? DEC employs a tiered approach to determining toxicity values. The Tier I source with the highest level of certainty and scientific assurance is IRIS - the Integrated Risk Information System. This EPA database is the most comprehensive and rigorous source available for scientifically peerreviewed toxicity information. If data is not available for a specific compound through IRIS, the Tier II Source is the Provisional Peer Reviewed Toxicity Values or PPRTVs. PPRTVs differ in part from IRIS values in that PPRTVs do not receive the multi-program consensus review provided for IRIS values. This is because IRIS values are generally intended to be used in all EPA programs, while PPRTVs are developed specifically for the Superfund Program and used by Alaska for the cleanup of contaminated sites. If neither IRIS nor PPRTVs are available, then a Tier III source will be sought. Tier three is additional EPA or non-epa sources, but which have not been through the more rigorous IRIS or PPRTV review processes. 12. Why isn t the lead value for groundwater risk-based? EPA has not yet developed a reference dose for lead for use in calculating a risk-based cleanup level. To date, the only regulatory level that has been established by EPA is a drinking water Maximum Contaminant Level (MCL) of mg/l. However, the Maximum Contaminant Level Goal (MCLG) is set at zero because there is no currently deemed safe level of exposure to lead. 13. Why has the PCE cleanup level become less stringent?

5 The proposed less stringent cleanup levels for both soil and groundwater for perchloroethylene, or PCE, incorporate up-to-date toxicological/chemical data and updated equations. The currently adopted groundwater cleanup level for PCE is based on the Maximum Contaminant Level (MCL) established by EPA over 20 years ago that included, among other factors, the water treatment technology available at the time that was considered capable of achieving that level. 14. Will there be an increased cost to the regulated community as a result of these new regulations? For soil, depending on the climate zone, cleanup levels for roughly 80 compounds have become more stringent and about another 80 have become less stringent. The likely effect of this split is that there may be either potential increased site remediation costs for stricter cleanup goals, or alternatively, cost savings for less stringent site cleanup goals. Site remediation costs consist of contracted costs associated with excavation, sampling, and treatment system operation, and possible incremental changes in long-term site monitoring for individual contaminants. Quantifying these costs (higher or lower) is not feasible due to the wide variety of conditions and circumstances associated with individual contaminated sites. For approximately 50 compounds, the most stringent soil cleanup level (migration to groundwater) is lower than the typical practical quantitation limit (PQL). Therefore, in some cases, a more expensive analysis may be required to lower the PQL. This may result in increasing the analytical cost for specific methods for sites where one or more of these 50 compounds may be present by about 20%. For groundwater, the updated criteria are more stringent for 132 of 182 compounds. Therefore, there may be incremental increased costs associated with operating and maintaining groundwater treatment systems to remediate to more stringent cleanup levels for certain compounds, as well as increased costs to conduct groundwater monitoring for a longer duration. However, only about 25 of the 182 listed compounds are found at 1% or more of all open contaminated sites. These compounds consist mainly of petroleum constituents including benzene, toluene, ethylbenzene, xylenes and polyaromatic hydrocarbons; two chlorinated solvents-- tetrachloroethylene and trichloroethylene; explosives at military installations; and PCBs, arsenic, mercury, chromium, and lead. Criteria for a little more than half of these compounds are becoming more stringent, while the rest will remain unchanged or become less stringent. For 45 compounds, the groundwater cleanup level is lower than the typical PQL. Therefore, in some cases, a more expensive analysis may be required to lower the PQL. This may result in increasing the analytical cost for specific methods for sites where one or more of these 45 compounds may be present by about 20%. We are unable to quantitatively predict the precise change in remediation and site monitoring compliance costs, as these costs are site-specific and vary greatly across sites due to external variables such as geographic location, soil type, hydrology, contaminant behavior and existing level of contamination, environmental contractor used (cost of labor), energy use/inputs, cleanup approaches and technologies, site status, and the application of site-specific alternative cleanup levels. Detailed compliance cost information submitted during the public comment period will be evaluated and considered. 15. What else is proposed? 18 AAC Groundwater and Surface Water Cleanup Levels: A new sub-section will be added that authorizes the department to develop site-specific cleanup level for a hazardous substance not listed in Table C, which is consistent with the current approach for soil in 18 AAC (g).

6 Adopted-by-reference documents: Two key supporting documents, adopted by reference, have been updated to incorporate updated approaches to calculating cumulative risk and cleanup levels based on the updated equations, and human health toxicity information now available. These include: Procedures for Calculating Cleanup Levels (formerly named Cleanup Levels Guidance) updated since 2008; Procedures for Calculating Cumulative Risk (formerly named Cumulative Risk Guidance) updated since Housekeeping changes: These include such changes as: references to external documents and other regulations are updated; cross-referencing within the regulations and to other chapters is corrected, and new definitions for terms including mutagen, mutagenic, and sensitive subpopulation. 16. What about petroleum? Cleanup levels for petroleum compounds are not being revised at this time, but are being considered for a future regulations package. 17. Does the update to the regulations have any bearing on DEC s contaminated sites database and/or how outside agencies research contaminated sites? No, the update will not affect how agencies research our sites and use the CS database. 18. Will sulfolane will be listed in the Table C groundwater cleanup levels (18 AAC )? No it will not. A cleanup level for sulfolane is on hold pending results of a 2-year study by the National Toxicology Program, and is not part of this regulation package. 19. Can I get a copy of the Excel Spreadsheet used to generate the proposed Table B1 and C cleanup levels? We did not use MS Excel to calculate our cleanup levels, therefore we do not have a spreadsheet of the calculations. We generated our values using a calculator tool that was developed for us by the University of Tennessee/Oak Ridge National Laboratory. You may access a beta test version of this calculator by visiting our regulations page and looking under Support Documents and Tools for the current proposed amendments. The equations are provided in the tool as well as in the Procedures for Calculating Cleanup Levels. 20. Is an excel copy of the Side-by-side comparison of 2008 vs Cleanup Levels available? Yes, we have posted a Microsoft Excel version on our regulations page, located under Support Documents and Tools. 21. The soil and groundwater cleanup criteria for arsenic and chromium are considerably lower than the 2008 numbers, and much lower than what is often commonly detected naturally at sites. Are background studies going to be required now at every site? What is the point of being so

7 conservative that you are below background concentrations? For every site where arsenic or chromium are detected, the site assessment or characterization report must discuss whether the concentrations represent a contaminant of concern based on materials or sources known to be used or generated at the site, any speciation analysis that was done, and/or the metal s relationship to background concentrations. The level of rigor for the discussion of background concentrations will depend upon the data collected at the site, including the levels detected, and area or regional data on arsenic and chromium, as well as a discussion with the CS project manager. In terms of the reasoning for setting a safe concentration that is below natural background, the department established the cleanup criteria for arsenic and chromium based on current science about the toxicity of these metals, and used the same risk-based approach for developing cleanup criteria for all the contaminants, where possible. Our goal was to calculate cleanup criteria using a consistent process that is based on a 1 X 10-5 cancer risk or a Hazard Index of 1. The proposed cleanup levels for arsenic and chromium reflect this approach. 22. Is the cleanup level of 0 for lead for the migration to GW standard a mistake? We apologize for the confusion. The misunderstanding is likely due to the use of the 0 in the informal side-by-side table showing changes from 2008 to We have modified the side-by-side to clarify this by showing no value. If you review the formal amendment document, you will see that the value in the migration to groundwater column is not listed as 0, but as --. Compliance with the lead cleanup levels is based on land use and defaults to 400 mg/kg for soil. We do not list or calculate a migration to groundwater value. In groundwater, we default to a federal standard which is 15 ug/l. This approach has not changed from We use the same approach for PCBs. You can read more in the footnote 11 to table B1, pertaining to lead. 23. What about statewide cleanup levels based on a 4-phase approach (soil, vapor, dissolved and free phase)? In order to calculate 4-phase values that are protective of human health and the environment, sitespecific information is required. A statewide set of cleanup levels would not be sufficiently protective of all site conditions which vary widely across the state. In addition not all chemicals are appropriate for four phase consideration. The state is exploring development of a 4-phase calculator for the public s use to calculate site-specific cleanup levels for appropriate chemicals. 24. Given such extremely low groundwater values, are the VI target screening values really realistic? The vapor intrusion target screening levels are based on concentrations detected in indoor air, not cleanup levels for soil or groundwater. Evaluation of vapor intrusion is based on the distance of the contamination from a building and other factors. 25. Can we carry out low-level volatiles analysis rather than mid-level to achieve lower detection limits in order to meet some of these lower cleanup levels? In accordance with method AK101, samples analyzed for volatiles still must be preserved with

8 methanol. If gasoline range organics have been excluded as contaminants of concern and the laboratory detection limits for volatiles analyzed with methanol preservation cannot meet the new established cleanup levels, low level volatiles analysis rather than methanol preserved analysis may be approved on a site specific basis. Sample collection methods must be evaluated to ensure individual constituents do not give false negative or bias low results due to interaction with the preservation technique. 26. How does the department plan to manage the reuse of mine waste rock and tailings given these very low metals cleanup criteria? Mine waste rock and tailings often contain concentrated amounts of metals which can be toxic to human health and the environment. Reuse, even for beneficial purposes, may result in contaminated soil, groundwater, or surface water. Anyone who chooses to reuse mine waste rock or tailings does so at their own risk, as they may be determined liable for the contamination and subject to the site cleanup rules if a complete exposure pathway is later determined by the department to be present as a result of the reuse. 27. Do the tables in the draft Field Sampling Guidance need to be updated to conform to the proposed amendments? We don t anticipate needing to make any changes to the Field Sampling Guidance as a result of the proposed amendments. This guidance is currently undergoing a major revision, which we expect to make available to the public very soon. 28. In terms of the new IC concurrence language for affected landowners, will there be a standard certification type form developed to document that offsite landowner concurrence? Yes, we anticipate that the Contaminated Sites Program will develop a form or process for documenting the consent of landowners agreeing to institutional controls requirements. 29. How will these updated criteria affect solid waste landfills? Some permitted solid waste facilities have proposed and received approval to use Table C groundwater cleanup levels for their groundwater protection standards (GPS) when there is no level for a specific compound available through 18 AAC 70 Alaska Water Quality Standards and/or a Maximum Contaminant Level at 40 CFR 141 (the federal Safe Drinking Water Act). If no standard is available through those sources, the background concentration exceeds the standard, or no background concentration can be calculated, other health based levels can be approved by DEC Solid Waste for use as the GPS. Under these circumstances, the facility may propose the use of Table C values as a health-based GPS for Solid Waste Program approval. Although the proposed amendments to Table C do not list MCLs, if one is available for a chemical, the MCL would apply as the GPS. 30. What about using the detection limit instead of the PQL to determine whether a contaminant is present at the site or not? Also, would the department consider setting a min/max PQL? If a contaminant of concern is detected above the method detection limit but below the practical quantitation limit (PQL), the department may on a site specific basis determine the contaminant of

9 concern is present. A contaminant detection below a PQL but above an MDL is typically indicative of presence; however, the accuracy of the detected value is suspect. The Department is typically more concerned with detection of a contaminant above a cleanup level than the presence of a contaminant. PQL s are not established by the Department but rather by the DEC approved laboratory and must meet at a minimum, the PQLs established in SW On a federal site where there is a federal agency, and EPA is involved along with ADEC, will the federal agency be required to meet the more stringent MCLs rather than the less stringent proposed Table C value, especially when MCLs are ARARs under CERCLA? Under CERCLA, federal drinking water MCLs are typically identified as chemical specific ARARs for groundwater restoration and in such cases the selected remedies need to achieve the MCLs. If the state groundwater cleanup level in Table C is more stringent than and corresponding MCL, then the state cleanup level would be a state chemical specific ARAR that would need to be achieved. 32. What is the rationale behind the release of cleanup levels for PFOS and PFOA when some say the science is still inconclusive? Is there an explanation for that? There has been an extensive assessment of PFOA and PFOS since the release of the 2009 provisionary health advisory level. In 2014 EPA released a draft health effects document for PFOA and PFOS that has been peer reviewed by seven external experts in the field and included a public comment period. The assessment falls within the ADEC tier 3 toxicity hierarchy for risk assessments and meets the corresponding criteria below. 1. It is a transparent assessment that clearly provides the information used and how it was used. 2. It is externally and independently peer reviewed, where reviewers and affiliations are identified. 3. It uses an established and publicly available methodology with the current best scientific information and practices. 4. It gives consideration of higher quality studies used. 5. It is publicly available or accessible. Additionally: Human (epidemiological) and animal studies were examined in the assessment which included short and long term exposure. Several studies (31 animal studies for PFOS) were evaluated for the development of the reference dose and slope factor. The toxicity value required to develop a chronic cleanup level for soil and groundwater for promulgation by ADEC is sufficient. While these documents are considered drafts, indications from EPA are that the two documents will be finalized soon, with the primary revisions consisting of adding additional studies not previously cited. ADEC anticipates both documents to be finalized prior to the adoption of the updated cleanup levels regulation package.

10 33. What is the technical and public health basis(es) for the new language added at 18 AAC (d) that states that any site-specific Alternative Cleanup Level cannot be used as a cleanup level at a site unless it is lower than any listed cleanup level in Table B1 or B2 of 18 AAC ? Currently and with the proposed language, a method three, site-specific cleanup level for the migration to groundwater pathway may be approved at a site unless the method two listed value for the human health (previously either direct contact or inhalation) exposure pathway is more stringent. Similarly, under the current and proposed wording, a responsible party has the option to propose a method three, site-specific cleanup level for the human health exposure pathway. If alternative cleanup levels are calculated for both the migration to groundwater and the human health exposure pathways, the more stringent of the two site-specific values would apply. Thus the revised language in this subsection is intended to provide clarity and reduce repetitive language but otherwise preserves the existing meaning. Note the wording at the end of the proposed revisions in 18 AAC (d) that is...for any other exposure or migration pathway that is present at the site. 34. What is the rationale underlying the new language at 18 AAC (e) that restricts soil ACL derivation only to chemicals that are already listed on Table B1 or Table B2? This section has only been rewritten for clarity; there is no change to the intent of this subsection, currently in effect. 35. What is the technical and public health basis(es) for setting groundwater cleanup levels at 18 AAC (b) that are more stringent than the federal Maximum Contaminant Levels for certain chemicals, such as benzene, benzo(a)pyrene, dioxin, ethylbenzene, polychlorinated biphenyls (PCBs), toluene, xylenes and arsenic? The public health basis for the proposed groundwater cleanup levels is to ensure protection of human health that equates to a cancer risk of 1 X 10-5 and a noncancer hazard index risk of 1 and utilizes current toxicity information. Maximum Contaminant Levels are not all based on standard risk-based equations and are not routinely updated to incorporate new information about toxicity. The technical basis for the change is to insure a consistent process for calculating cleanup levels for all contaminants. 36. What evidence, data or information does ADEC have to support that children are one hundred fold more sensitive to the adverse effects of any chemicals than average adults? ADEC has incorporated changes in the equations for groundwater to incorporate exposure risks for children because chemical body burdens are not the same as those for adults. The change also makes the groundwater equations consistent with the soil equations which already factor in child exposure parameters 37. What are the specific criteria that ADEC will use to identify the presence of sensitive subpopulations who respond to lower levels of exposures to hazardous substances as the basis of setting more stringent cleanup levels than those listed in Table C of 18 AAC ? If any, why has the Department not included those criteria in the proposed amendments? DEC is not planning to establish any specific criteria beyond the definition found at 18 AAC (192), as the determination of the presence of sensitive subpopulations is site-specific and based on

11 site characterization data, users and occupants of the site, and other information. 38. Does ADEC intend to use Reference Doses and Reference Concentrations that are based on reproductive toxicity or adverse effects in pregnant females to set cleanup levels based on exposure scenarios for children aged one to six who are not of reproductive age? As described in Appendix C in the Procedures for Calculating Cumulative Risk, the process for the selection of toxicity values is based off of the hierarchy summary. ADEC used the database from the EPA regional screening levels for the selection, as the same tiered approach is used. 39. What are the specific criteria that ADEC will use to determine if the toxicity data for a chemical are insufficient to establish a cleanup level? If any, why has the Department not included those criteria in the proposed amendments? As described in Appendix C in the Procedures for Calculating Cumulative Risk, the process for the selection of toxicity values is based off of the hierarchy summary. ADEC used the database from the EPA regional screening levels for the selection, as the same tiered approach is used. If the database didn t provide a toxicity value, then none was used unless noted otherwise. 40. Given that ADEC concluded that the toxicological database for sulfolane, which has a welldesigned and well-executed animal subchronic study, was insufficient, does the Department intend to state categorically that any chemical with a single, well-designed and executed subchronic animal study has an insufficient database for establishment of a cleanup level? No, as described in Appendix C in the Procedures for Calculating Cumulative Risk, the process for the selection of toxicity values is based off of the hierarchy summary. As discussed in the Risk Assessment Procedures Manual, consultation with ADEC is recommended when using toxicity values other than those from IRIS or PPRTVs to ensure appropriate values are used. Currently there is no cleanup level for sulfolane. The department believes that information on the effects of long-term exposure to sulfolane is critical to establishing a cleanup level, because adults and children will eventually be drinking water with sulfolane at concentrations up to the established cleanup level, potentially for their entire lives. However, the existing information on sulfolane toxicity does not include effects of long-term exposure. 41. Is ADEC aware of any EPA policy that precludes the use of a dataset for derivation of a Reference Dose or a Reference Concentration where there is only a single, subchronic animal study? As described in Appendix C in the Procedures for Calculating Cumulative Risk, the process for the selection of toxicity values is based off of the hierarchy summary. ADEC used the database from the EPA regional screening levels (RSL) for the selection as the same process is used. Cleanup values are based off chronic values and obtained from the RSL database in the ADEC tables. An uncertainty factor is typically applied during the assessment for the extrapolation, but ADEC is relying on the toxicity hierarchy source for chronic toxicity. 42. Does ADEC intend to remove all chemicals from Tables B1, B2 and C if their Departmentderived cleanup levels were derived using a Reference Doses or Reference Concentrations that were based on a single, subchronic animal study, such as anthracene, acenaphthene, ethyl acetate,

12 ethylbenzene, fluorene, fluoranthene, pentabromodiphenyl ether, and pyrene? No, because chronic toxicity values are provided for those chemicals, based on the toxicity. 43. Does ADEC intend to remove acenaphthylene, benzo(g,h,i)perylene, phenanthrene, 1,3- dichlorobenzene and dimethylphthalate from Tables B1, B2 and C because the database for these chemicals is insufficient in that there are no toxicity studies at all for these chemicals? No, because a surrogate was used. This is noted in the footnote to Appendix A, Table 6 of the Procedures for Calculating Cleanup Levels. 44. What are the specific criteria that ADEC will use to determine how long a responsible person will be required to provide an alternative source of drinking water for chemicals deemed by the Department to have an insufficient toxicity database? The length of time a responsible person may be required to provide an alternative source of drinking water or maintain other institutional controls in such circumstances will depend upon when sufficient toxicity information becomes available to calculate a cleanup level. 45. Will ADEC provide an evaluation of the costs of providing alternative sources of drinking water and delaying the cleanup of sites having toxicity databases that it deems insufficient? The costs to private parties, municipalities and other state agencies for the proposed amendment concerning provision of an alternative source of drinking water or implementation of other institutional controls in such circumstances, cannot be estimated with any precision due to the wide variety of site-specific conditions and other factors that may be present, which may change over time, and which will influence cost. For all private parties, municipalities and other state agencies statewide, the increased cost of this specific proposed amendment is expected to be limited because of the scarcity of situations where this provision may be invoked. 46. Does ADEC intend to allow Hazard Indices to be grouped by organ systems such as the immune system with endpoints based on adverse effects to the organs, such as thymus, bone marrow, spleen, and lymph nodes and effects that result from organ damage, like modifications to the numbers of circulating lymphocytes or decreases in number of antibody forming cells against sheep red blood cells in male mice? In a method four risk assessment, segregation of hazard indices is allowed. See the 2015 Risk Assessment Procedures Manual on our technical guidance page for details. 47. Does ADEC intend to allow Hazard Indices to be grouped by organ systems such as the reproductive organs with endpoints based on adverse effects to the organs, like the testes and effects that result from organ damage, such as changes in sperm count or sperm motility? In a method four risk assessment, segregation of hazard indices is allowed. See the 2015 Risk Assessment Procedures Manual on our technical guidance page for details. 48. Does ADEC intend to provide guidance on when a responsible person may rule out the need to prepare a cumulative risk assessment? Calculating cumulative risk is required for methods two, three, and four as stated at 18 AAC

13 49. Does ADEC intend to follow the EPA guidance in Determining Groundwater Exposure Point Concentrations, Supplemental Guidance (OSWER Directive March 11) for the setting of Exposure Point Concentrations for groundwater? ADEC has established a more stringent requirement at 18 AAC (c)(2) which states: groundwater cleanup levels, based on an analysis of unfiltered groundwater samples unless a responsible person demonstrates that a filtered sample provides a more representative measure of groundwater quality; the department will determine compliance based on the maximum concentrations of a hazardous substance detected in the final confirmation samples; before closure, the size of the dissolved plume must be steady state or shrinking and concentrations of the hazardous substance must be decreasing. 50. Will ADEC apply or recognize EPA's ProUCL software as an "appropriate statistical method" for calculation of the 95% UCL of the mean? DEC currently accepts and will continue to accept EPA s ProUCL software as an appropriate statistical method. 51. Does ADEC intend to provide citations for the values listed in Appendix A to be consistent with its own Risk Assessment Procedures Manual that calls for full documentation of all exposure assumptions? If comments are submitted to this effect, the department will add a footnote to Appendix A that references the EPA Regional Screening Levels and includes a date the information was obtained. 52. Does ADEC intend to allow for further public comment on the Appendix A, Table 6 which is not fully legible in the proposed document? Upon inspection, the table was too wide for the page and one column was cut off. It has been reformatted to fit the page and reposted to the Contaminated Sites Regulation web page. The column that was not visible was FA (systemically available fraction). The department does not intend on extending the public comment period beyond December 11, 2015 to review this column. 53. Some of the cleanup levels presented in the proposed regulations cannot be calculated using the information provided in this document because of either the lack of data in some instances or discrepancies between Section 6.4 and Appendix B, Table 7 in other instances. They can only be reproduced by inspection of the Online Calculator, which is not part of the Administrative Record. Will the Department correct the errors in Procedures for Calculating Cleanup Levels? The Department believes this has been resolved by reformatting Table 6 to fit the page (as addressed above) and by adding a reference dose and slope factor for perfluorooctanoic acid which were inadvertently omitted in the posted document. If identified in public comments, the department will make corrections for errors or discrepancies between equations presented and the calculations generated by the online calculator. 54. Does ADEC intend to remove references to the outdated Online Calculator tool that was released before ADEC released the second Online Calculator?

14 The existing Method Three Calculator will continue to be available for use in calculating site specific cleanup levels for petroleum hydrocarbons under Method Will ADEC allow for public comment on any changes made to the Online Calculator? The Online Calculator is an optional tool made available to the public to facilitate site-specific alternative cleanup level calculations and for calculating cumulative risk. It is not part of the proposed amendments, therefore public comments on the tool are not being accepted. 56. ADEC intending to harmonize the hydrocarbon ranges so that the Online Calculator matches 18 AAC 75? Petroleum cleanup levels for gasoline, diesel and residual range organics are not part of the current proposed amendments to 18 AAC 75. Therefore, site specific cleanup levels for petroleum hydrocarbons may continue to be calculated using the petroleum fraction equations provided in the 2015 Procedures for Calculating Cleanup Levels, and which are unchanged from the equations presented in the 2008 Cleanup Levels Guidance, or by using the existing Method Three Calculator. 57. Does ADEC intend to provide full citations of the toxicity values used by the Online Calculator and allow public review and comment after it does so? If comments are submitted to this effect, the department will add a footnote to Appendix A that references the EPA Regional Screening Levels and includes a date the information was obtained.