Environmental Cleanup


Oregon environmental cleanup law and regulations require a risk-based approach for assessing and managing environmental contamination. Applicable regulations:
  • Releases of hazardous substances including petroleum under the state’s hazardous substance remedial action rules (OAR 340-122-0100 through 340-122-0115)
  • Cleanup of petroleum releases from regulated underground storage tanks under Oregon cleanup rules for Leaking Petroleum Underground Storage Tank Systems (Oregon Administrative Rules 340-122-0205 through 340-122-0260)
DEQ originally developed Risk-Based Decision Making for the Remediation of Petroleum-Contaminated Sites Guidance (RBDM Guidance) in September 1999. The RBDM guidance and associated tables of risk-based concentrations (RBCs) provide a consistent, streamlined decision-making process for evaluating risk posed to human health and the environment. Use of the RBDM Guidance and associated documents is optional. Other models or approaches may be used to evaluate site risks. Alternative approaches must meet risk-based cleanup standards specified in Oregon Revised Statute 465.315.

DEQ has periodically updated the guidance and associated RBCs documents. Significant updates expanded the original guidance to cover hazardous substance cleanups as well as petroleum-contaminated sites. In September 2017, DEQ’s RBDM guidance was renamed as “Risk-Based Decision Making for the Remediation of Contaminated Sites” to reflect that usage of the document is not limited to petroleum contaminated sites.

In May 2018, DEQ updated its tables of RBCs to reflect updates to toxicity factors for benzo[a]pyrene (and by extension the other carcinogenic polycyclic aromatic hydrocarbons), dichlorodiphenyldichloroethane (DDD), 1,2,4-trimethylbenzene, and 1,3,5-trimethylbenzene. These tables supersede DEQ’s previously released RBC tables. Parties should use the updated tables for new screenings and risk assessments, unless DEQ and parties agree to use of alternative approaches.

In addition to use of the RBDM guidance and associated documents, parties should review the following related guidance documents for evaluating risks to human health and the environment:

Note that the 2010 Guidance for Assessing and Remediating Vapor Intrusion in Buildings and Human Health Risk Assessment Guidance contain elements that supersede the RBDM guidance for evaluation of vapor intrusion problems or assessment of risk from bioaccumulative contaminants to infants.

Over time, DEQ made other revisions to the tables of RBCs to bring it up to date with current risk assessment practices. The most recent revisions are summarized below under Update History. EPA updates its screening table semi-annually. DEQ evaluates updates to EPA screening values when they occur and will consider the significance of the EPA updates as they relate to DEQ’s RBCs. DEQ therefore will update RBCs periodically when warranted by substantive updates to EPA’s screening tables. Under special circumstances, DEQ may at any time require a revised screening value for a chemical based on new toxicity information. 

Risk-based decision making documents


DEQ offers the following spreadsheets of generic risked-based concentrations for parties to use as reference documents.  
·         Table of Risk-Based Concentrations (modified to show the lower of non-carcinogenic and carcinogenic RBCs. These PDF tables should be used unless performing site specific calculations.)
DEQ offers the following spreadsheets for parties to use as reference documents for calculating site-specific risk-based concentrations. The default exposure factors, chemical data and toxicological data in these spreadsheets can be modified, where appropriate, to calculate site-specific risk-based cleanup levels. Note that the spreadsheets must be run in both cancer and non-cancer modes to derive all the lowest risk-based concentrations that appear in the PDF tables above. You must have Microsoft Excel 2007 or a newer version, and it must be set to "enable macros" for the spreadsheets to open properly.

Update history

Updated Toxicity Factors

  • Updated toxicity factors for the carcinogenic polycyclic aromatic hydrocarbon (cPAH) for benzo[a]pyrene (B[a]P), consistent with the U.S. Environmental Protection Agency’s 2017 update. This update generally results in risk-based screening levels that are higher by about a factor of 7. In addition, no ncancer effects (including developmental effects) can now be quantitatively evaluated for benzo[a]pyrene.
  • Updated toxicity factors for dichlorodiphenyldichloroethane (DDD), 1,2,4-trimethylbenzene, and 1,3,5-trimethylbenzene. New noncancer RBCs for DDD are generally lower than previous RBCs. RBCs for 1,2,4-trimethylbenzene are now generally about 2 to 4 times higher than previous RBCs, and RBCs for 1,3,5-trimethylbenzene are now generally about half the previous RBCs.

Fixed Formatting Errors

  • Updated the generic table of Risk-Based Concentrations for Individual Chemicals:
    • Updated to show the lowest cancer or noncancer RBCs are provided. In preparing the 2015 table, the lowest of the cancer or noncancer RBCs were not always selected. The May 2018 table accurately shows the lowest cancer or noncancer RBCs.
  • Updated the site-specific table of Risk-Based Concentrations for Individual Chemicals:
    • Unlocked spreadsheet cells and other formatting errors that prevented site-specific calculations for new chemicals. The update allows parties to modify assumption parameters. 
    • Unlocked spreadsheet cells for early-life exposure assumptions. The update allows parties to modify related assumption parameters. Changes to standard exposure assumptions will not be automatically incorporated into early-life exposure assumptions. Note that RBC calculations for TCE are contained in the March 2018 Calculation of Trichloroethene RBCs using Early-Life Exposure Memorandum.
    • Updated to show the correct soil leaching to groundwater (RBCsw). In preparing the 2015 table, an error occurred that result in these values being listed incorrectly. The May 2018 spreadsheet contain the correct values.

Implementation schedule

Parties should use the updated tables for new screenings and risk assessments, unless DEQ and parties agree to use of alternative approaches. In general, the updated RBCs should be implemented as follows:

  • New screenings and risk assessments should use the updated RBC tables, unless DEQ and parties agree to use of alternative approaches.
  • For screenings and risk assessments currently underway, the updated RBCs and EPA regional screening values apply on a case-by-case basis.
  • For completed and approved evaluations, reassessment may be performed on a case-by-case basis. Typically approved screenings and risk assessments do not require reassessment unless a new decision is requested or required, and that decision needs the support of a current screening evaluation or risk assessment.
  • When updated RBCs are used, they should be used for all chemicals of interest for a facility.
The following are substantive changes to DEQ’s tables of RBCs . DEQ also updated toxicity factors for some chemicals and made other minor changes.

Updated exposure parameter values

In September 2011, EPA issued the current version of its Exposure Factors Handbook (EPA/600/R-090/052F). EPA’s regions adopted many of the updated values in their November 2014 regional screening level table. DEQ is incorporating the exposure value changes in this table, which will make Oregon consistent with exposure assumptions in national risk assessments. To be consistent with EPA’s approach, DEQ now includes two separate event times for duration of skin exposure to water for adults and children, where previously DEQ used only one event time. In addition, DEQ updated skin exposure parameters for consistency with national risk assessment.

Dermal exposure to tapwater

In developing the tapwater scenario for DEQ’s original, 1999 risked-based decision making guidance, it was reasonable to assume exposure could occur through ingestion, inhalation and skin contact. However, there was not an established approach for including skin contact. DEQ decided to be consistent with EPA and not include skin contact with tapwater exposure. In 2004, EPA developed Part E to Risk Assessment Guidance for Superfund (Supplemental Guidance for Dermal Risk Assessment), and included exposure factors necessary for evaluating the water-skin pathway. In November 2011 updates to EPA regional screening level tables, EPA added the skin pathway to tapwater exposure. DEQ is now incorporating EPA’s approach for evaluating skin exposure to tapwater. For pathways involving skin exposure to water, DEQ includes a check to determine if a chemical is within the effective predictive domain of EPA’s model, and does not calculate skin exposure for chemicals outside the predictive domain. EPA now calculates non-carcinogenic screening levels based on exposure to children, not adults. Because it’s important to protect the most sensitive populations, DEQ also revised its calculations to use child exposure factors for all tapwater exposure routes.

Definition of volatile chemicals

Previously, DEQ defined volatile chemicals as those with a Henry’s Law constant greater than or equal to 1.0 x 10-5 atm-m3/mole. This definition inappropriately identified some chemicals, such as formaldehyde, as non-volatile. DEQ is now consistent with EPA by also defining volatile chemicals as those with a vapor pressure greater than or equal to 1 mm mercury.

Chemical-specific parameter value data sources

DEQ now uses EPA’s hierarchy of data sources to determine chemical-specific parameter values. This is DEQ’s first major update of parameter values since 2003.

Chemical classes

DEQ has clarified the definition of chemical classes to include such chemicals as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), chlorinated dibenzo-p-dioxins and chlorinated dibenzofurans (dioxins/furans), chlordanes and total petroleum hydrocarbons (TPH). These chemical classes should be evaluated as a single hazardous substance for determining risk and potential hot spots. The acceptable cancer risk level for individual hazardous substances of one-in-one-million and non-cancer hazard quotient of one applies to each chemical class, and potential hot spot determinations will be made accordingly.
Carcinogenic PAHs should be evaluated as summed benzo[a]pyrene equivalents. Dioxins/furans should be evaluated as the sum of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents. PCBs should be evaluated as total PCBs, either derived from congeners or aroclors. Similarly, total petroleum hydrocarbons and chlordanes should be evaluated as totals. This approach for evaluating chemical classes replaces Section 3.3.5 of DEQ’s October 2010 Human Health Risk Assessment Guidance.

Implementation schedule 

The revised DEQ and EPA risk-based concentrations will be implemented according the following guidelines:
For all newly started site screening evaluations, DEQ will use the recently revised risk-based concentrations from this point forward:
  1. For risk assessments currently being performed, the revised risk-based concentrations may be used on a case-by-case basis provided all the revisions are considered; and
  2. Completed risk assessments submitted for approval before Jan. 1, 2016 will be considered valid based on guidance used when the assessment was completed.
​This update accommodates changes to toxicity values for tetrachloroethene (PCE). On Feb. 10, 2012, EPA updated its integrated risk information system with new values for PCE.
Implementation schedule
The revised RBCs should be implemented according the following guidelines:
  1. For all newly initiated risk-based decision-making screening evaluations at a site, the recently revised RBCs and EPA regional screening values are now in effect;
  2. For RBDM screening evaluations currently being performed, the revised RBCs and EPA regional screening values apply on a case-by-case basis; and
  3. For completed RBDM screening evaluations submitted before April 2012, reassessments may be performed on a case-by-case basis when a new decision is required that needs the support of a screening evaluation or updated risk assessment. Until then, the current completed and approved screening evaluation is considered valid based on the guidance used when the assessment was completed.
This update is relatively routine to be consistent with currently accepted toxicity values. Since the most recent (2009) RBC revision, EPA updated its regional screening levels (RSLs, created by EPA Regions 3, 6, and 9).
The following are the more substantive changes to DEQ’s RBC spreadsheet:

Consideration of breastfeeding exposure pathway

To be consistent with 2010 revisions to DEQ’s human health risk assessment guidance, infant exposure through breastfeeding has been added for all long-term exposure pathways used to develop RBCs. Working with EPA Region 10, DEQ found that breastfeeding is an important pathway for some bioaccumulating chemicals, particularly polychlorinated biphenyls. The PCB non-cancer risk to an infant is up to 25 times the risk calculated for the mother, resulting in correspondingly lower RBCs. This makes PCB RBCs nearly equivalent for non-cancer and cancer endpoints. As a consequence, including this exposure pathway on all sites will not substantially affect cleanup decisions. However, new PCB hotspot levels will be considerably lower than past levels.
An evaluation of breastfeeding risks is complicated by the known substantial health benefits of breastfeeding. Including the breastfeeding exposure pathway in developing screening values is important to ensure that remedial decisions consider the potential for infant exposure. Comparisons with screening values are not intended to advise women about whether or not to breastfeed their infants.

Consideration of TCE toxicity

The EPA's Integrated Risk Information System completed a final evaluation of trichloroethylene toxicity in September 2011. The new toxicity values replace 2001 draft values previously used by DEQ in developing risk-based concentrations.
One issue that complicates derivation of RBCs for TCE concerns the incorporation of early-life exposure. There are three cancer endpoints considered in the development of the slope factor and inhalation unit risk factor for TCE: kidney cancer, liver cancer, and non-Hodgkins lymphoma. EPA determined that TCE was carcinogenic by a mutagenic mode of action for kidney cancer (renal cell carcinoma). Following EPA’s recommendations, DEQ is using the method presented in the following memorandum to derive RBCs for TCE. Because of the necessity to calculate TCE RBCs for three different toxicological endpoints and recombine them into a single numeric value, they're not computed in the spreadsheet. Rather, they were calculated manually, externally to the spreadsheet, and values were written into the final spreadsheet. Therefore, the cancer-based values cannot be updated automatically, or compared to CTE values. However, noncancer values can be computed, if desired, by removing the “NA” in the toxicity values column and replacing with an “nc.” To restore the cancer-based values, it is necessary to close the spreadsheet without saving, and re-open.

Definition of volatile chemicals

A volatile chemical was previously defined as having a Henry’s constant > 10-5 m3-atm/mol and a molecular weight < 200 g/mol. EPA no longer uses the molecular weight criterion - only the Henry’s constant. To be consistent with EPA, DEQ removed the molecular weight criterion in the current version of its RBC spreadsheet. This results in calculated vapor transport RBCs for a number of heavier compounds with sufficiently high Henry’s constants.

Cancer and non-cancer endpoints

The 2011 revision (like the 2009 release) includes a “PDF” format table that shows the lowest default RBCs without regard to endpoint (cancer or non-cancer). When the spreadsheet is used to calculate RBCs for chemicals with both cancer and non-cancer toxicity values, RBCs corresponding to both endpoints should be calculated to verify that the lowest applicable RBC is being used. The default setting for the spreadsheet is whichever endpoint results in the lowest soil direct contact RBCs in the residential scenario.
Chemicals which have both cancer and non-cancer toxicity values, and may have lower non-cancer values in some scenarios include beryllium, cadmium, nickel, formaldehyde, hexachloroethane, PCBs, trichloroethene 2,4,6-trichlorophenol, and 1,1,2-trichloroethane.
Chromium VI, or hexavalent chromium, now has an oral cancer slope factor. It is also now considered mutagenic so that early life exposure must be evaluated for residential exposures. These changes result in RBCs that are significantly lower than in the previous tables.

Total petroleum hydrocarbon RBCs

The updated 2011 DEQ TPH spreadsheet incorporates the first substantive modifications since 2003. The 2011 TPH spreadsheet includes the following changes:
  • Computational methodology was changed to be consistent with EPA’s Risk Assessment Guidance for Superfund; Volume I: Human Health Evaluation Manual (Part F, Supplemental Guidance for Inhalation Risk Assessment) EPA 540-R-070-002, OSWER 9285.7-82, January 2009.
  • Soil vapor TPH RBCs are now available to assess the vapor intrusion pathway.
  • Toxicity Value updates. Toxicity values previously used since 2007 have been withdrawn by EPA and are no longer available. Therefore, toxicity values for petroleum fractions were updated to be consistent with those provided in EPA’s PPRTVs for TPH Mixtures and Xylenes. Attachment 1: Provisional Peer-Reviewed Toxicity Values for Complex Mixtures of Aliphatic and Aromatic Hydrocarbons (CASRN various). Attachment 2: Provisional Peer-Reviewed Toxicity Values for Xylenes (CASRN 1330-20-7). Nov. 10, 2009.

Implementation schedule - 2011

The revised RBCs should be implemented according the following guidelines:
  1. For all newly initiated risk-based decision-making screening evaluations at a site, the recently revised RBCs and EPA regional screening values will be used from this point forward;
  2. For RBDM screening evaluations currently being performed, the revised RBCs and EPA regional screening values will be used on a case-by-case basis; and
  3. For completed RBDM screening evaluations submitted before November 2011, reassessments may be performed on a case-by-case basis when a new decision is required that needs to be supported by a screening evaluation or updated risk assessment. Until that time, the current completed and approved screening evaluation will continue to be considered valid based on the guidance used when the assessment was completed.


Frequently asked questions

​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.
​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.
​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.
​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.
​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.

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.

​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.
​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.
​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.
​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.
​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.
​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?