Risk-Based Decision Making for the Remediation of Petroleum-Contaminated Sites

Frequently Asked Questions

In November 2011, the DEQ's environmental cleanup and tanks section released an updated version of the risk-based concentrations for individual chemicals table.

Questions

This page contains some frequently asked questions that DEQ receives about the risk-based cleanup spreadsheets.

1. I'm on the website and trying to run one of the spreadsheets. When I click on the link the document will not open up. What's wrong?
2. I have Excel 2007 and when I try to open the spreadsheet I'm told that the macros have been disabled for security. How can I get it to run?
3. Do I have to use Excel 2007 to run the DEQ spreadsheets? I only have Excel 2002.
4. I opened both of the DEQ spreadsheets and now there are two "DEQ Risk Calc" drop down menus on the toolbar. Which one do I use?
5. I have a site where we're dealing with motor oil, lube oil and kerosene (or jet fuel). Are there any screening criteria available for these products?
6. I'm dealing with a site where we've encountered waste oil contamination. The constituent data for carcinogens are all below the currently accepted constituent risk-based concentrations. Is that all I have to show or do I also have to show that the total petroleum hydrocarbon concentration meets an acceptable TPH cleanup level? If the latter, what is the acceptable TPH level?
7. Can I use volatile petroleum hydrocarbon and extractable petroleum hydrocarbon data from a groundwater sample to calculate site-specific risk-based concentrations with DEQ's TPH spreadsheet?
8. When I try to add a new chemical to the chemical constituent risk-based concentration spreadsheet, I get a message that says the cell is protected and that I need a password. Why can't I add the required data?
9. Can the generic diesel total petroleum hydrocarbon risk-based concentrations be used for Lube Oil or No. 6 fuel oil or other heavier products?
10. I've noticed that for some chemicals (e.g., polycyclic aromatic hydrocarbons and volatile organic compounds) there are differences between the DEQ risk-based concentration and EPA screening level for the same exposure scenario. Why is there a difference?
11. Some of these risk-based concentrations are below method reporting limits and method detection limits using the best commercially available technology. What do I do in this situation?
12. Some chemicals are noted wit the symbol Ψ. What does this mean?
13. The value of RBCsi (vapor intrusion into indoor air) for generic gasoline goes from 94 parts per million for the residential scenario to >MAX for the occupational scenario. Why does this risk-based concentration increase so much when the occupational exposure is not that much less than the residential scenario?

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Answers

1. I'm on the website and trying to run one of the spreadsheets. When I click on the link the document will not open up. What's Wrong?

You should download the Excel spreadsheets onto your computer before trying to run them. To download a file you should right-click on the link. This will bring up a menu. Then left-click on "Save Target As..." (in Internet Explorer). Other browsers should have a similar option. The computer's standard "Save As" box will then open and allow you to select the folder in which you want to save the file. (Be sure to remember the folder.) After you click on "Save," the file will be downloaded onto your computer. You should then close your browser and open the spreadsheet as you would any other file on your computer.

2. I have Excel 2007 and when I try to open the spreadsheet I'm told that the macros have been disabled for security. How can I get it to run?

This may happen if Excel is set to "disable macros." You should change the Excel setting to "allow macros." To do this, open Excel, select the "Developer" tab on the ribbon bar and select the "enable all macros" radio button before opening the spreadsheet.

3. Do I have to use Excel 2007 to run the DEQ spreadsheets? I only have Excel 2002.

Both new spreadsheets were developed for Microsoft® Excel 2007 because that was the version that the DEQ was using at the time of development. The spreadsheets will also work in Excel 2010, the current version of Excel at this time. We do not know if the spreadsheets will work correctly on older versions of Excel. As stated in the introduction to the spreadsheet:

"This program is offered for use without warranty or support. It is designed to work with Microsoft® Excel 2007 and may not work properly with other applications, or with older releases of Excel."

4. I opened both of the DEQ spreadsheets and now there are two "DEQ Risk Calc" drop down menus on the toolbar. Which one do I use?

You should not have both spreadsheets open at the same time. Because the two spreadsheets have similar codes in them, having both open at the same time can cause them to function improperly. Never open one spreadsheet until the other has been closed.

5. I have a site where we're dealing with motor oil, lube oil and kerosene (or jet fuel). Are there any screening criteria available for these products?

Generic risk-based concentrations are typically used for screening. However, the only generic TPH risk-based concentrations are for gasoline, diesel or heating oil, and transformer mineral insulating oil. For other petroleum products, either individually or as a mixture, you're limited to using either the soil matrix cleanup level or site-specific risk-based concentrations. If TPH concentrations at your site exceed the soil matrix cleanup level and remediation to that level is not feasible, you have the option of following the instructions for Method 2, Option 2 on the TPH spreadsheet to calculate site-specific values. For example, for a generic lube oil, or oil that may be used in a wind turbine, compositional information is necessary in order to derive risk-based concentrations specific to that, or any other product.

6. I'm dealing with a site where we've encountered waste oil contamination. The constituent data for carcinogens are all below the currently accepted constituent risk-based concentrations. Is that all I have to show or do I also have to show that the total petroleum hydrocarbon concentration meets an acceptable TPH cleanup level? If the latter, what is the acceptable TPH level?

You must show that both the carcinogenic risk from constituents and the noncarcinogenic risk from TPH are acceptable. You've already met the requirement for the constituents, but you still must show that the TPH risk is acceptable. Since there are no generic TPH risk-based concentrations for waste oil, you can either use the soil matrix cleanup levels or calculate a site-specific cleanup level by testing the waste oil with the new extractable petroleum hydrocarbon test and using the data with the TPH spreadsheet.

7. Can I use volatile petroleum hydrocarbon and extractable petroleum hydrocarbon data from a groundwater sample to calculate site-specific risk-based concentrations with the DEQ total petroleum hydrocarbon spreadsheet?

No, you can not use VPH or EPH data from groundwater samples in the DEQ spreadsheet to calculate site-specific risk-based concentrations. You can only use data that represent the composition of the product as it exists today. The best data for that purpose come from soil samples. Water samples will be enriched in the constituents that dissolve the most and depleted in the ones that dissolve the least. Even when using soil samples you should use relatively heavily contaminated samples.

The reason you must use data that represent the product is that models used in DEQ's TPH risk-based concentration spreadsheet are based on the assumption that you're starting out with product. The models calculate concentrations that are likely to end up in the air and water, and uses those concentrations to estimate risk-based concentrations.

VPH data from a groundwater sample would allow you to calculate risk from direct exposure to the water, such as from ingestion and/or dermal exposure. However, you'd have to do that manually by determining the risk (hazard quotient) for each component and then summing them to get the total risk (hazard index) from the entire product.

8. When I try to add a new chemical to the chemical constituent risk-based concentration spreadsheet, I get a message that says the cell is protected and that I need a password. Why can't I add the required data?

When you add a new chemical to the spreadsheet you don't have to enter data into all the empty cells. Some of the cells are protected because they're cells the spreadsheet will calculate for you. Protected cells are usually shown in gray and unprotected cells in white. Note that all of the cells on the risk-based concentration page are protected. You only need to add data to the white cells on the ChemData page and the ToxData page in order to add a new chemical. For example, you start by adding the chemical name, molecular weight, solubility, etc. on the ChemData page. You cannot, however, enter the volatility, vapor pressure, Csat, etc. They are calculated by the spreadsheet. Likewise, you cannot enter a chemical name on the ToxData page. The chemical name from the ChemData page is automatically copied onto the ToxData page.

9. Can the generic diesel total petroleum hydrocarbon risk-based concentrations be used for lube oil or No. 6 fuel oil or other heavy products?

No. Generic TPH risk-based concentrations only take into account the risk from exposure to a product having a composition like that of a typical diesel (see Appendix F for that composition). Therefore, the diesel risk-based concentrations do not address the risk from exposure to the heavier compounds in products such as a lube oil or No. 6 fuel oil.

10. I have noticed that for some chemicals (e.g., polycyclic aromatic hydrocarbons and volatile organic compounds) there are differences between the DEQ risk-based concentration and EPA screening level for the same exposure scenario. Why is there a difference?

DEQ and EPA use equivalent methods to calculate risk-based concentrations. However, for some substances the parameters used may vary slightly due to selection of different estimates of chemical properties or different values for some exposure parameters. Both the EPA and DEQ parameter choices are valid, and represent slightly different choices. In some of these instances, the resulting absolute value of the RBCs can be quite different. As one example, the RBC for anthracene in the May/June 2011, EPA table for residential soil is 17,000 mg/kg. In the November 2011 DEQ table, the corresponding value is 23,000 mg/kg- a difference of 6,000 mg/kg. In absolute terms the difference seems large. However, the difference is only 26 percent. Therefore, in relative terms, the values are not substantially different. The difference illustrates the range of similar RBCs that could be derived. For Oregon sites, the DEQ RBCs should be used. If a chemical does not have a DEQ RBC, then the EPA regional screening level should be used.

11. Some of these risk-based concentrations are below method reporting limits and method detection limits using the best commercially available technology. What do I do in this situation?

In some instances risk-based concentrations calculated using the currently accepted toxicity values and computational approaches may result in concentrations that are below readily achievable detection or reporting limits. This may result in less precise concentration estimates or the inability to determine if a compound is present above risk based levels in the media analyzed.

In these instances, DEQ will usually accept non-detection based on the best commercially available technology as sufficient evidence that the compound is not present. Moreover, levels below the quantitation limit (e.g., practical quantitation limit or method reporting limit) are understood to be less precise and therefore have greater uncertainty. DEQ may not always accept non-detection as adequate evidence that a compound is not present, where there is a reason to believe based on site history or other knowledge that a compound could be present. For example, non-detections of polychlorinated biphenyls as aroclors by EPA method 8082 may not be sufficient evidence of the absence of PCBs. PCBs are often found to be present in samples by method 1668 at levels below what can be detected by method 8082 and are known to be widely present in soils and sediment.

12. Some chemicals are noted wit the symbol Ψ. What does this mean?

The symbol means that the lowest risk-based concentrations vary depending on the endpoint and scenario, and the spreadsheet cannot show all the lowest RBCs simultaneously. The spreadsheets are designed to calculate RBCs for either non-cancer or cancer-based endpoints, based on user selection of the desired endpoint. Generally, RBCs based on cancer endpoints are lower because of mathematical models and assumptions associated with this endpoint. For some chemicals, the lowest RBCs vary by both scenario and endpoint. That is, non-cancer RBCs are lower in some columns and cancer RBCs are the lowest for others. Therefore, the spreadsheet must be run in both cancer and non-cancer modes to derive all the lowest RBCs. Alternatively, all the lowest RBCs are presented in the Adobe PDF® tables.

13. The value of RBCsi (vapor intrusion into indoor air) for generic gasoline goes from 94 parts per million for the residential scenario to >MAX for the occupational scenario. Why does this risk-based concentration increase so much when the occupational exposure is not that much less than the residential scenario?

Answer PDF

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