Division of Spill Prevention and Response

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Frequently Asked Questions

These Frequently Asked Questions (FAQs) provides a summary and rationale for the proposed changes and addresses some common questions. If you do not find your question answered here, please contact sally.schlichting@alaska.gov.


For additional detail on how we responded to public comments, see the Summary of Responses to Public Comments Received through December 11, 2015.


1. Did ADEC calculate the volatilization from tap water risk based concentration using any equations (e.g. Foster & Chrostowski, Little, McKay or Schaum) other the equation listed in the Procedures for Calculating Cleanup Levels which uses the Andelman volatilization factor?

ADEC did not calculate values for comparison as mentioned above. However, ADEC did evaluate literature that compared different model concentrations. Please remember that for the pathway to be calculated the chemical must be determined to be a volatile compound and have an inhalation toxicity value (Inhalation unit risk and/or reference concentration) associated with the chemical. Chemicals with a vapor pressure greater than 1 mm Hg or a Henry's Law constant greater than 0.00001 atm-m3/mole are considered volatile in the proposed updates. Comparisons with the Andelman model have been evaluated with the McKone and Little models as presented in the table below and show generally similar results for volatile compounds.


Total Mass emitted During Model Shower (mg)
Compound Andelman McKone Little
1,2-dichloroethane 31 31 21
1,1-dichloroethane 36 37 36
ethyl ether 36 36 40

The Andelman equation is used in setting risk-based preliminary remediation goals as noted in chapter 3 of the EPA Risk Assessment Guidance for Superfund Volume I Human Health Evaluation Manual (Part B, Development of Risk-based Preliminary Remediation Goals.

2. What changes have been made based on the comments received during the first public comment period in 2015?

Revisions to 18 AAC 75.340 Soil Cleanup Levels; General Requirements

Multiple commenters found the rewrite of this section confusing and interpreted the new language as prohibiting certain options. We have revised this section to make clear the original intent and address the comments.


Institutional Controls

The amendments included language in both 18 AAC 75.340 and in .345 to strengthen and clarify the requirements for the RP to gain affected landowner consent for alternative cleanup levels and institutional controls, including gaining their agreement to create, maintain, and abide by ICs. Multiple commenters found this added language to put too much responsibility on the RPs to obtain these consents, questioning also the form that such consent should take. We are withdrawing these proposed amendments.


Lowered Cleanup Levels

Many commenters from multiple sectors raised concerns with the lowered levels in general and felt that site closure would be more difficult. We continue to emphasize that the increased stringency of many of the groundwater cleanup levels is a direct result of incorporating toxicity information and exposure factors to be protective of children, whereas our current groundwater levels do not account for risks to children from contaminated groundwater. Although we are not changing the proposed cleanup levels, we will continue to highlight the options available for establishing alternative cleanup levels using method three, establishing alternative points of compliance, and institutional controls where remediation may not be technically feasible in a reasonable timeframe.


Lowered Cleanup Levels for Arsenic and Chromium

Many commenters from multiple sectors raised concerns that the new levels are well below natural background and feared that all sites where arsenic and chromium are detected will require background sampling and analysis to prove site concentrations are not from anthropogenic sources. We have added language to the notes to both Tables B1 and C that detections of arsenic and chromium at sites will be presumed from naturally occurring arsenic and the less toxic trivalent chromium, unless anthropogenic contribution from industrial sources or activities are suspected.


Addition of PFOS and PFOA to the Cleanup Levels Tables

Several commenters objected to presenting cleanup levels for these compounds based on draft 2014 health effects documents from EPA. We have revised both the soil and groundwater cleanup levels for Tables B1 and C, calculating them using the toxicity information from EPA’s 2009 health effects documents.


Cleanup levels set below the lowest achievable detection limits

A number of commenters raised concerns that many of the proposed cleanup levels for soil and groundwater are below detection limits achievable by DEC approved labs. The department is working with labs and is clarifying through technical guidance the existing process allowed in regulation for approving practical quantitation limits available through EPA’s SW-846 to serve as alternative cleanup levels for compounds where lower detection limits are not achievable. In addition, we are drafting additional guidance for approving alternative analytical methods, such as low-level volatiles analysis.


Adopted by Reference Documents

The Procedures for Calculating Cleanup Levels and Procedures for Calculating Cumulative Risk were updated to replace two existing guidance documents. Multiple comments were received asking for clarification, correction, or addition of supplemental information in these documents. We have made a number of changes to both documents to address these comments.


Other changes:

  • Tables have been revised to show the cleanup levels to two significant figures. Some of the cleanup levels will therefore be slightly higher or lower due to rounding;
  • Corrected wording in the regulations;
  • Corrected toxicity surrogates for hydrazine and methyl mercury;
  • Removing “at least” from the phrase “to a depth of at least 15 feet” concerning the depth to which a site cleanup level must be met; and
  • Adding the option for the department to consider an EPA health advisory level for a contaminant in groundwater.

3. In remote areas where petroleum resource development is occurring, why are we required to clean up groundwater contamination to levels that protect children?

In the state of Alaska, groundwater is protected for all uses, unless it has been reclassified, regardless of where the groundwater is located. Even though groundwater at a site may currently not be used for human consumption or the site may appear remote and not slated for residential development, this cannot be guaranteed in perpetuity without institutional controls in place. Groundwater at a site is considered a potential drinking water source unless a determination that it is not has been made per the criteria at 18 AAC 75.350. Alternatively, a party can undertake a process defined in 18 AAC 70 Water Quality Standards to reclassify the groundwater to permanently remove the groundwater from one or more use classifications.

4. Will xylene be a driver for BTEX sites due to the drop in value?

The cleanup level for xylenes has dropped marginally for the human health pathway in soils, but has been reduced significantly for both groundwater and the soil migration to groundwater pathway. Site-specific circumstances and contaminant concentrations will dictate whether a contaminant is a driver, but the lower xylene cleanup levels are likely to drive the need for cleanup at some sites.

5. Do you have a cleanup value for methanol?

Yes, methanol is one of the 18 compounds that have been added to Table B1 cleanup levels for soil and Table C cleanup levels for groundwater as part of this set of proposed amendments.

6. What is the source for the toxicity value used in developing the cleanup level for naphthalene?

Toxicity values for naphthalene are obtained from CalEPA and IRIS. The source of the toxicity value is located on Table 6 - Chemical Toxicity Parameters in the Procedures for Calculating Cleanup Levels 2016.

7. Are the changes to the cleanup levels due to a requirement by EPA?

The changes in the cleanup levels are due to updated scientific information on the toxicity of these chemicals, updated exposure information, and accounting for exposure risks to children from contaminants in groundwater. The changes are not due to an EPA requirement.

8. PFOS and PFOA have been used in firefighting foams to fight fires which was a beneficial use and an intended purpose. Why is cleanup now required for these chemicals?

Many chemicals have been used in products for beneficial purposes before the risks and toxicity of these chemicals are fully known. It is usually well after health impacts from these compounds are reported in humans or ecological receptors that uses of these chemicals are restricted to reduce exposures or phased out and prohibited from use. Perfluorooctane sulfonate (PFOS) and perfluorooctonoic acid (PFOA) are following a similar path. In addition to many household and industrial products, they have been used in fire-fighting foams for more than 50 years due to their effectiveness at fighting petroleum fires. Beginning in the 1980s, scientific information about these compounds began to emerge indicating their toxicity to human health and ecological receptors. As a result of this, these chemicals are being phased out across the country, and substitutes and alternative products are now being used in the fire-fighting industry.


While aqueous film forming foams (AFFF) have been used for their intended purpose, PFOS and PFOA are very mobile in the environment and can migrate long distances from areas where they were used. In addition, these chemicals are resistant to degradation in the environment and therefore persist in sediment and groundwater for long periods of time. Data from fire training and response sites in Alaska and around the country show large groundwater contaminant plumes and numerous contaminated drinking water systems. Recent scientific data has concluded that PFOS and PFOA are toxic to mothers and their unborn and newborn infants, as well as children, adults and ecological receptors.

9. Why doesn't DEC have a risk management strategy for dealing with the risks associated with cleanup operations?

Worker safety and risks from accidents is the purview of the Department of Labor and the Occupational Safety and Health Act, not the Department of Environmental Conservation. Cleanup operations and activities at contaminated sites must comply with worker safety rules. OSHA and AKOSH prescribes procedures for ensuring worker safety during cleanup operations, and reducing the risks and occurrence of accidents. Provided these rules and laws are properly complied with, the risks of accident and injury are safely managed during cleanup operations.

10. Can you provide the slides for the PowerPoint presentation given at the workshop?

The slides are now posted on the regulations page under support documents and resources.

11. Sampling requirements for underground storage tanks currently require sampling for metals at gasoline and waste oil UST sites. These metals include: arsenic, barium, cadmium, chromium, lead, nickel, and vanadium. How will arsenic and chromium be determined to be background or related to the release at these sites?

Sampling at LUST sites with leaded gasoline or aviation gasoline need only be sampled for lead per Table 2A of the 2014 UST Procedures Manual. For used oil, sampling for arsenic, barium, cadmium, chromium, lead, nickel, and vanadium is required, unless these metals are not suspected in the products disposed of in the tank and the CS project manager concurs. Results for arsenic and chromium should be considered indicative of naturally occurring concentrations unless there is reason to believe that arsenic or hexavalent chromium laden petroleum products were disposed of in the used oil tank. Arsenic mobilized in groundwater as a result of a petroleum release and area geochemistry will be evaluated on a site specific basis.