Frequently Asked Questions
Please look to this page for a question you may have.

GENERAL

Neither the Comprehensive Environmental Cleanup and Responsibility Act (CECRA), the Water Quality Act (WQA), or the Montana Underground Storage Tank Act provide for compensation of property owners for contamination on private property. Rather, these statutes are focused on protection of public health, safety, and welfare and the environment by requiring cleanup of contaminated property. However, if a petroleum release is eligible for reimbursement through the Petroleum Tank Release Compensation Fund, then some compensation may be available; see http://deq.mt.gov/DEQAdmin/pet.aspx for more information.

Yes, view an example of a data validation guidelines used by the DEQ. (If having trouble downloading please right click and save link as to view the document)

Please click on the Feasibility Study Example Scope of Work for an example of a combined initial alternatives screening document and feasibility study scope of work for facilities addressed under the Comprehensive Environmental Cleanup and Responsibility Act (CECRA).

Please click on the link Feasibility Study Example Scope of Work for an example feasibility study scope of work for facilities addressed under the Comprehensive Environmental Cleanup and Responsibility Act (CECRA). Please see the following for an example report Final Feasibility Study Report - June 2008.

Please click on the link Remedial Investigation Example Scope of Work for an example remedial investigation scope of work for facilities addressed under the Comprehensive Environmental Cleanup and Responsibility Act (CECRA). Please see the following for an example report Milwaukee Roundhouse Remedial Investigation Report - June 2015.

Please click on the link Design Document Components to find examples of the information that should be contained in design documents for facilities addressed under the Comprehensive Environmental Cleanup and Responsibility Act (CECRA).

The purposes of the Voluntary Cleanup and Redevelopment Act (VCRA) are to provide for the protection of the public health, welfare, and safety and of the environment and to foster the cleanup, transfer, reuse, or redevelopment of facilities where releases or threatened releases of hazardous or deleterious substances exist. VCRA is further intended to permit and encourage voluntary cleanup of facilities where releases or threatened releases of hazardous or deleterious substances exist by providing interested persons with a method of determining what the cleanup responsibilities will be for reuse or redevelopment of existing facilities. VCRA is meant to encourage and facilitate prompt cleanup activities, eliminate impediments to the sale or redevelopment of facilities where releases or threatened releases of hazardous or deleterious substances exist, and minimize administrative processes and costs.

The complete VCRA guide is located at: http://www.deq.mt.gov/Land/StateSuperfund/vcraguide.aspx. This guide covers both the Environmental Assessment and Remediation Proposal components required under VCRA. The guide also contains a checklist to assist applicants in preparation of the required documents and provides a suggested format for voluntary cleanup plans (VCPs). The primary target audience for this guide is the qualified environmental professional who is preparing the VCP. However, the guide is also designed to provide information to all applicants or potential applicants regarding the VCRA process.

ARM 17.55.114 identifies the delisting process and there are a number of ways in which a facility on the CECRA Priority List can be delisted. The most common ways are to address the facility either through the CECRA process or through VCRA. A description of the CECRA process can be found at the following link: Information about VCRA is available at the following link: http://deq.mt.gov/Land/StateSuperfund/vcra.aspx.

SOIL

When addressing Hazardous Waste Cleanup Bureau facilities, DEQ considers surface soil to be anything from 0-2 feet below ground surface (bgs).

For initual evaluation of contaminants of potential concern, please refer to the flow chart of the soil screening process. Additional information for all media can be found at the frequently asked questions (FAQs).

All soil and sediment data should be reported on a dry-weight basis and moisture percentage should also be determined and reported on the laboratory data reports. Please see the FAQ below on dry-weight conversion.

The dry-weight is converted from wet-weight by the following formula:

Dry Weight Reult = As-Received Result/(1-% moisture)

Example:

If you have a TEH value of 300mg/kg, and a moisture of 14%, the calculation would be:
300mg/kg /(1-0.14) = 349 mg/kg dry weight

Metals are naturally occurring in the environment. If metal concentrations exceed screening levels or you suspect they may exceed screening levels, it is appropriate to collect facility-specific background samples from unimpacted areas that are representative of natural conditions. You may also use the Background Metals Table as screening levels for background inorganic concentrations in surface and subsurface soils. In some cases, background concentrations may exceed screening levels. In that case, background concentrations may be used in place of screening levels. Consultation with DEQ is recommended.

First, it is important to consider how the contamination was released and what information is needed to evaluate risks and cleanup options. As a general rule, samples are collected from 0-6 inches below ground surface (bgs) in source areas and from 0-2 inches bgs in areas of aerial deposition. Additional sampling at discrete intervals should be conducted from 0-2 feet bgs in order to determine how much of the soil profile is contaminated. Typically, compositing the entire 0-2 feet zone does not provide the information needed meet most project goals. Consultation with DEQ is recommended.

Construction workers or those excavating soil are expected to be exposed to both surface (0-2 feet below ground surface (bgs)) and subsurface (2-10 feet bgs) soil. Therefore, it is appropriate to evaluate construction worker exposure to both surface and subsurface soils. If cleanup levels protective of construction/excavation workers are lower than those for other surface soil receptors, the lower cleanup levels could also be applied to surface soil. For additional information please see the Risk Assessment FAQs.

In addressing the direct contact risk to the construction/excavation workers at contaminated facilities, remediation of subsurface soil to depths of 10 feet is typically necessary. However, there are some sites where contamination extends deeper than 10 feet and there may be situations where future building at the site could result in footings or foundations greater than 10 feet. In order to ensure protectiveness for direct contact as well as to provide notice to future purchasers of the property, a site with contamination left in place deeper than 10 feet may need an institutional control to limit excavation to 10 feet. (The other option is to remediate subsurface soil to depths greater than 10 feet.) However, the placement of an institutional control does not address those facilities with leaching to groundwater or vapor intrusion considerations.

When addressing CECRA facilities, soil concentrations are screened against EPA residential and industrial regional screening levels or site-specific residential and commercial industrial cleanup levels. As part of selecting the final remedy, DEQ will determine “reasonably anticipated future uses” for the facility and what cleanup levels apply.

Previous site investigations across the country have demonstrated a tendency for lead contamination to be concentrated in the finer (dust sized) fraction of soil. It is also from this size fraction that most exposure to humans occurs. DEQ evaluated sieved vs. unsieved samples in its Background Concentrations of Inorganic Constituents in Montana Surface Soils (deq.mt.gov/Land/statesuperfund/background) and determined that most often the finer fraction contains higher metals concentrations. Therefore, at facilities where metals are likely to be contaminants of concern, analysis of the finer fraction is necessary. Samples may either be sieved in the field or in the laboratory.

Since sieving samples adds additional time and cost to the investigation, during an initial site characterization, a portion of the samples could be laboratory analyzed in both sieved and bulk form, with a representative number of samples laboratory-analyzed in both forms. The samples selected for both analyses should account for different sources, lithology, or other characteristics that could influence the ratio between sieved and unsieved sample concentrations. Analysis of both types of samples for 100% of samples in samples sets of less than 20 samples, at least 20 samples in sample sets of 20 - 100 samples, and 20% of the samples in sample sets greater than 100 samples, is appropriate. If possible, samples analyzed in both forms should be collected from areas of low, medium, and high levels of contamination (XRF analysis can be a useful tool for some metals). Once the two sets of data are available a ratio of sieved analysis to bulk analysis can be calculated for each sample, and then a 95% upper confidence level (UCL) on the mean of all the ratios can be calculated. The UCL of the ratios may then be used as a factor that can be applied to historic, current, and future bulk samples collected for characterization or confirmation sampling without the need for further sieved sampling. Please refer to the following EPA Guidance documents for further information: EPA Short Sheet on Lead Sampling, and the Superfund Lead-Contaminated Residential Sites Handbook. For information on screening levels for lead in soil, please refer to the Screening FAQ. Sieving of dioxin samples may also be appropriate.

If XRF data is collected, the size of the data set needs to be considered. To ensure the quality of the XRF results and reliability of the data, both the XRF and laboratory samples for 100% of samples in samples sets of less than 10 samples, at least 10 samples in sample sets of 10 - 100 samples, and 10% of the samples in sample sets greater than 100 samples (this does not preclude the evaluation of 20% of the samples collected for the lead finer fraction analysis explained above), is appropriate. DEQ recommends that samples selected for laboratory analysis be focused around data that is near the action level, with a minimum of 25% of the XRF high and low range concentration samples sent to the laboratory for analysis. For smaller data sets, laboratory analysis only may be more appropriate. The relative percent difference (RPD) of each XRF/laboratory sample pair should be calculated. The average RPD of the XRF/laboratory sample pairs should not exceed 35% (per EPA National Functional Guidelines for Inorganic Data Review, October 2004). A graph showing the correlation between the XRF and laboratory results should be provided and the correlation coefficient for the results should be 0.7 or greater for the XRF data to be considered screening level data (per EPA Method 6200 [XRF]). A discussion that identifies the factors that may affect the strength of the correlation and why it is or is not indicative of a strong relationship between the two data sets should also be provided (e.g., false negatives or positives, outliers, correlated residuals, XRF sample interference, elevated detection limits, bias).

The project-specific SAP/QAPP should cover XRF data collection, XRF and lab quality control requirements (including XRF calibration), collection of laboratory samples, comparison of XRF to laboratory data, and a detailed description of the XRF/laboratory data correlation, as described above. The XRF/laboratory data comparison and correlation should also be discussed as part of the overall data quality for the investigation.

SOIL VAPOR INTRUSION

The phrase "soil vapor intrusion" refers to the process by which volatile chemicals move from beneath the ground into the indoor air of overlying buildings.

Soil vapor, or soil gas, is the air found in the spaces between soil particles. Because the air pressure inside may be lower than in the soil, this vapor may enter buildings through cracks in slabs or basement floors and walls, and through openings around sump pumps or where pipes and electrical wires go through the foundation. Heating, ventilation or air-conditioning systems may reduce the air pressure inside, drawing soil vapor into buildings.

Chemicals that readily evaporate or vaporize are called "volatile chemicals." Volatile chemicals include volatile organic compounds (VOCs), which includes, but is not limited to, benzene (typically found in gasoline) and tetrachloroethylene (typically found in dry cleaners or degreasing operations). Subsurface sources of volatile chemicals may include contaminated soil and groundwater, broken pipes, or buried wastes. If soil vapor is contaminated and enters a building as described above, the air quality inside the building may be affected.

When contaminated vapors are present nearby or under the foundation of the building, vapor intrusion is possible. Soil vapor can enter a building whether the building is old or new, and whether the building has a basement, a crawl space, or is on a slab (as illustrated in the figure below).

Soil Vapor Intrusion Image
Figure courtesy NYSDOH, October 2006

For initial screening of contaminants of concern, please refer to the Sampling FAQs for guidance.

EPA method TO15 typically provides the appropriate detection limits that are needed to determine of volatile chemicals pose an unacceptable risk to humans.

Humans can be exposed to contaminated soil vapor when vapors from beneath a building are drawn through cracks and openings in the foundation and mix with the indoor air. These vapors may be inhaled along with the indoor air.

In general, inhaling a volatile chemical does not necessarily mean that a person will experience health effects. Whether or not a person experiences health effects depends on several factors, including the length of time a person is exposed, the number of times a person is exposed, the toxicity of the volatile chemical, and person’s sensitivity to the chemical.

There are other potential sources of contaminants in indoor air. Volatile chemicals may also be found in certain household products such as paints, paint strippers and thinners, mineral spirits, glues, solvents, cigarette smoke, aerosol sprays, mothballs, air fresheners, new carpeting or furniture, hobby supplies, lubricants, stored fuels, refrigerants and recently dry-cleaned clothing.

Indoor air may also become affected when outdoor air containing volatile chemicals enters your home. Volatile chemicals may be present in outdoor air due to their widespread use. Gasoline stations, dry cleaners, and other commercial/industrial facilities are also potential sources of VOCs to outdoor air.

DEQ looked at volatile chemicals in homes that were not located near known contamination. The results of the study are summarized in the MOntana Typical Background Indoor Air Concentrations document at http://deq.mt.gov/Land/statesuperfund/viguide.

You should expect the following:

  • Indoor air samples are generally collected from the lowest-level space in a building, such as a basement. They are often collected during cold weather when the building is heated and the ground is frozen. Indoor air samples may also be collected from the first floor of living space, or any other area of potential concern. Indoor air samples are used to determine if vapors are inside buildings.
  • Sub-slab vapor and outdoor air samples are usually collected at the same time as indoor air samples to help determine where volatile chemicals may be coming from (indoor sources, outdoor sources, and/or beneath the building).
  • Some sampling may be performed during warmer weather. For example, soil gas or sub-slab vapor samples without indoor air or outdoor air samples may be collected to identify buildings and areas where comprehensive sampling is needed during the heating season.
  • An indoor air quality questionnaire and building inventory will be completed with your input. The questionnaire includes a summary of the building's construction characteristics; the building's heating, ventilation and air-conditioning system operations; and potential indoor and outdoor sources of volatile chemicals. The building inventory describes products present in the building that might contain volatile chemicals. These products may be temporarily removed from the building while it is being sampled with homeowner consent.

At least 48 hours prior to and during the collection of the indoor air sample (which takes 24 hours), please take the following actions to minimize background concentrations of VOC's:

  • Try to avoid opening windows or keeping doors open.
  • Avoid operating ventilation fans or air conditioning if possible.
  • Please avoid using air fresheners or odor eliminators.
  • Please do not smoke indoors.
  • Please do not use paint, solvents, or varnishes.
  • Please do not use cleaning products such as bathroom cleaners, furniture polish, appliance cleaners, all-purpose cleaners, floor cleaners, or gun cleaners.
  • Please try to minimize the use of cosmetics such as hair spray, nail polish, nail polish remover, perfume, cologne, etc.
  • Please do not apply pesticides.
  • Please do not store containers of gasoline, oil, petroleum-based or other solvents within the house or use them in an attached garage.
  • Please do not operate or store automobiles in an attached garage if possible.

It is important to note that many building materials contain VOCs, such as plywood flooring, latex paint, sheet vinyl flooring, and new carpeting, among others. Obviously, it is not practical to remove these potential indoor sources of VOCs from homes. However, removing all identified household products which may contain VOCs and adhering to this list of steps to take prior to and during sampling will help minimize the background levels of VOCs in your house or business.

Depending on the investigation results, DEQ may require additional sampling or mitigation, in addition to requiring cleanup of the subsurface sources. Additional sampling would be performed to determine the extent of soil vapor contamination and to verify questionable results. Mitigation is action that is taken to minimize exposures to indoor air contamination while cleanup is occurring. Mitigation may include sealing cracks in the building's foundation and installing a sub-slab depressurization system beneath the building (similar to a radon mitigation system), or other options that would limit vapors inside buildings.

A sub-slab depressurization system essentially prevents vapors beneath a slab from entering a building. A low amount of suction is applied below the foundation of the building and the vapors are vented to the outside (see figure below). Mitigation systems are inspected to insure that they are effective and that they do not cause any “back-drafting.” The system uses minimal electricity and should not noticeably affect heating and cooling efficiency.

Sub-Slab Depressurization System
Figure courtesy NYSDOH, October 2006

A vapor barrier is a sheet of geomembrane or strong plastic that is placed beneath a building. It may be more appropriate for new construction, but may also work for buildings with crawl spaces. It is difficult to retrofit existing buildings with a vapor barrier. However, some concrete floors may be able to be sealed with a substance that my limit the movement of vapors into the building.

In some situation, HVAC systems may be adjusted to increase the pressure indoors relative to the pressure beneath the buildings slab. This approach is typically useful for larger buildings.

WATER

Untreated purge water is the water removed from a monitoring well before a groundwater sample is collected. Purge water may be allowed to infiltrate to the subsurface by discharging it on the ground next to the well under certain conditions. Purge water is considered a waste and the discharge of wastewater is regulated under the requirements of the Montana Water Quality Act (75-5-101, et seq. MCA) and the rules that have been adopted to implement the act.

Purge water may not be discharged on the ground if the discharge will result in the spread of contamination. The discharge of unaltered purge water to the contaminated water-bearing zone from which it originated does not require a Ground Water Pollution Control System discharge permit. It must be reasonably expected that the purge water will return to the same aquifer zone where the purge water originated. The guidelines for purge water disposal are further clarified in the purge water disposal flowchart. If the answer to any of the questions within the flowchart is “Yes” purge water may not be disposed on the ground surface and you may need to work with your DEQ contact to determine appropriate disposal options.

Discharges of wastewater from sources other than purge water from groundwater monitoring wells are generally administered by the DEQ’s Permitting and Compliance Division’s Water Protection Bureau. Discharge of wastewater to a municipal wastewater treatment plant requires authorization from the municipal wastewater treatment operator. Please contact the Water Protection Bureau at (406) 444-3080 prior to discharging wastewater to determine if a permit is necessary.

The Montana Department of Natural Resources and Conservation (DNRC) has adopted rules governing the installation and abandonment of monitoring wells in Montana. Construction standards for monitoring wells are found in Administrative Rule of Montana (ARM) 36.21.801 et seq. and includes requirements for construction materials, installation of seals, prevention of contamination by equipment, and site protection and security. The regulations also require that a monitoring well constructor licensed by the Montana Board of Water Well Contractors prepare a monitoring well report form for each monitoring well drilled. The monitoring well constructor must supply copies of the report to the monitoring well owner and DNRC within 60 days of completing the well and must also retain a copy as a record in the constructor's files.

In addition, Montana Code Annotated (MCA) § 85-2-516 requires that, within 60 days after any well is completed, the driller must file a well log report with the Montana State Bureau of Mines and Geology. The well log report must be filed on a form specified by DNRC, which includes identifying a location for the well using at least two methods as specified on the form.

An initial survey of groundwater monitoring well elevations must be completed by a licensed surveyor or professional engineer registered in the State of Montana in accordance with MCA § 37-67-301 et seq. and ARM 24.183.101 et seq. Survey results must provide an accuracy of plus or minus 0.1 foot horizontally and plus or minus 0.01 foot vertically. The vertical control datum used to determine the elevation of the well must be the North American Vertical Datum of 1988 (NAVD 88), which should be referenced to a nearby United States Geological Survey (USGS), or equivalent, benchmark.

At CECRA facilities, latitude and longitude coordinates reference the State Plane NAD83 HARN Coordinate System, which should also be referenced to a nearby USGS, or equivalent, horizontal control mark.

ARM 36.21.810 provides that “[w]ells which have not been monitored for more than 3 years shall be deemed abandoned unless written permission is obtained from the board [of water well contractors] to maintain the well.” Standards for abandoning monitoring wells is also provided in this regulation.

Additional regulation regarding Monitoring Well Construction Standards can be found in the ARM 36.21.8.

DEQ-7 standards were developed to comply with requirements under the Montana Water Quality Act, the Federal Clean Water Act, and the Montana Agricultural Chemical Ground Water Protection Act and must be used. A risk assessment that provides site-specific cleanup levels may be appropriate for contaminants in soil, but not in groundwater, for contaminants that have DEQ-7 standards. For contaminants without a DEQ-7 standard, see "What are some of the general assumptions for a site-specific groundwater risk assessment/analysis at a CECRA facility?".

You have the option to use screening levels as cleanup levels so that a Fate and Transport Analysis is not necessary. However, if you choose to calculate site-specific cleanup levels, DEQ will also require the use of fate and transport modeling of the soil leaching to groundwater pathway to determine a cleanup level for this pathway (please refer to the Fate and Transport FAQ. ) In addition, site-specific cleanup levels require the use of standard EPA human health risk assessment guidance (EPA 1999, 1998a, 1997b, 1992, 1991a-c, and 1989) and/or, as applicable, standard EPA ecological risk assessment guidance (EPA 2000a, 1998b, and 1997a) using assumptions acceptable to DEQ. Please see the Risk Assessment/Analysis section of the FAQs for additional information. It is important to identify as early in the CECRA process as possible if you are going to calculate site-specific cleanup levels, so that the data for fate and transport can be collected during the RI.

At CECRA facilities, DEQ will generally not require that groundwater samples taken from monitoring wells be analyzed for total metals but will continue to require that drinking water wells be analyzed for total metals. Total metals analysis of groundwater from monitoring wells may be needed on a case-by-case basis, as necessitated by special situations (i.e. analyzing background monitoring wells for comparison to drinking water wells). Samples taken from monitoring wells must still meet compliance with other water quality requirements including Montana’s Numeric Water Quality Standards (DEQ-7).

SAMPLING

DEQ has determined that an imminent and substantial endangerment to public health, safety, or welfare or the environment may exist if contaminant concentrations at a CECRA exceed certain risk-based screening levels. Contaminants of concern (COCs) are those contaminants whose concentrations exceed these risk-based screening levels, and therefore require additional evaluation. Contaminants whose concentrations fall below these screening levels will not typically trigger CECRA action.

Groundwater/Drinking Water/Surface Water:

Soils and Sediments:

  • Sediment concentrations will be compared to EPA Region 3 BTAG Freshwater Sediment Screening Benchmarks.
  • Except for arsenic in surface soil, dry-weight soil concentrations will be compared to the direct contact and leaching to groundwater-based soil screening levels (SSLs) contained in the most recent Regional Screening Levels (RSL) for Chemical Contaminants at Superfund Sites guidance document. The RSLs take into account ingestion, inhalation, and dermal contact pathways and include residential and industrial exposure. Additionally, DEQ compares petroleum compounds in soil to the Risk-Based Screening Levels (RBSLs) provided in the Montana Tier 1 Risk-Based Corrective Action Guidance for Petroleum Releases. After comparing contaminant concentrations in soil to the various screening levels, the most conservative value should be chosen as the applicable screening level.
  • The SSLs found in the EPA RSL table are based upon MCLs. If the DEQ-7 groundwater standard is more conservative than the MCL, the SSL must be recalculated so that it is based upon DEQ-7 groundwater standards and multiplied by a dilution attenuation factor of 10, the state-specific attenuation factor. Please see the flow chart of the soil screening process for additional information on how to calculate the SSL based upon DEQ-7 standards.
  • The non-carcinogenic contaminants screening levels found in EPA RSL table are based upon a hazard index of 1 (a level which indicates that no adverse non-cancer human health effects are expected to occur for that contaminant). When screening contaminant concentrations to the RSLs, with the exception of lead, adjust all non-carcinogenic levels by dividing by ten. This ensures that, when multiple contaminants are found at a facility that may have the same health effects, cumulative potential health effects are considered. Please see the flow chart of the soil screening process for additional information on how DEQ screens all non-carcinogens (except lead) by dividing the RSL screening levels by ten.
  • Exposure to lead in soils is evaluated in a unique way by calculating potential blood lead levels resulting from exposure to lead in soil in addition to other unavoidable lead exposure pathways like water and food. Therefore, DEQ does not include exposure to lead with the other cumulative non-carcinogenic effects. DEQ uses the EPA RSLs of 400 mg/kg for lead in residential soils and 800 mg/kg for lead in industrial soils.
  • When screening arsenic concentrations in surface soil, compare contaminant concentrations to the Background Concentrations of Inorganic Constituents in Montana Surface Soils Report.

Indoor Air/Soil Vapor:

  • Indoor air and soil vapor concentrations are compared to the residential air and industrial air screening levels contained in the most recent Regional Screening Levels (RSL) for Chemical Contaminants at Superfund Sites guidance document.
  • The non-carcinogenic contaminants screening levels found in EPA RSL table are based upon a hazard index of 1 (a level which indicates that no adverse non-cancer human health effects are expected to occur for that contaminant). When screening contaminant concentrations to the EPA regional screening levels, with the exception of lead, adjusts all non-carcinogenic levels by dividing by ten. This ensures cumulative potential health effects are considered when multiple contaminants with the same health effects are present at a facility.
  • DEQ developed generic screening levels for the petroleum fractions detected using the Massachusetts Air-Phase Petroleum Hydrocarbons (APH) method but not found in the RSL table. DEQ calculated these screening levels using the same assumptions as those EPA used to calculate the RSLs. As these petroleum fractions are non-carcinogens, DEQ adjusted the target hazard index by dividing by ten to ensure that cumulative potential health effects are addressed (please see previous bullet). However, because the screening levels for the two aliphatic fractions are lower than the typical indoor air concentrations found during DEQ's 2012 Study DEQ screens these fractions using the typical indoor air concentrations. The adjusted APH generic screening levels are:
    Generic APH Fraction Screening Levels
    APH Fraction Screening Level (ug/m3)
    Aliphatic (C5-C8) 94
    Aliphatic (C9-C12) 44
    Aromatic (C9-C10) 10
  • Download the APH VI Calculator
  • Established generic screening levels: For initial screening of contaminants of concern, please refer to the previous question for guidance.
  • Background levels: DEQ accepts attainment of facility-specific background levels based on samples collected from unimpacted areas representative of conditions at the facility for compounds such as metals. Established literature values for background concentrations may be also proposed. In some cases, background concentrations may exceed screening levels and may, therefore, be used in place of screening levels. However, background concentrations that exceed applicable environmental laws (such as DEQ-7 standards) may necessitate that a facility remain on the CECRA Priority List.
  • Facility-specific adjusted screening levels: The generic screening levels described above may be adjusted based on the number of compounds present at an individual facility to represent the acceptable cumulative cancer risk of less than or equal to 1X10-5 for carcinogens or by the number of compounds and their critical effect/target organs for a total hazard index equal to 1 for non-carcinogens. For example, in the RSL table, RSLs for carcinogenic compounds are based on a 1x10-6 cumulative risk, while DEQ will accept a cumulative risk of 1x10-5. The RSLs for non-carcinogenic compounds can be adjusted in a similar manner to account for multiple compounds that have the same critical effect or target organ.
  • Facility-specific risk-based cleanup levels: DEQ will accept cleanup levels based on a facility-specific risk analysis conducted using standard EPA human health risk assessment guidance (EPA 1999, 1998a, 1997b, 1992, 1991a-c, and 1989) and/or, as applicable, standard EPA ecological risk assessment guidance (EPA 2000a, 1998b, and 1997a). For human health, DEQ allows cleanup levels calculated based on cumulative risk levels less than or equal to a total excess cancer risk of 1x10-5 for carcinogens or a total hazard index less than or equal to 1 for non-carcinogens. Ecological risks must be evaluated and acceptable risk determinations are made on a facility-specific basis. Soil leaching to groundwater pathway must be considered when calculating facility-specific cleanup levels to ensure protection of groundwater (please refer to the Fate and Transport FAQ.) All exposure assumptions must be acceptable to DEQ and are best determined in consultation with DEQ.

The following items are typically included in a Level III analytical package (depending on the laboratory) and must be included with laboratory analytical results submitted to DEQ:

  • Results Summary Report Including Surrogate Recovery Data;
  • Results for soil and sediment samples reported on a dry-weight basis;
  • Chromatograms (if applicable);
  • Continuing Calibration Verification Reports;
  • Laboratory Control Sample Reports (if applicable);
  • Laboratory Method Blank Reports;
  • Laboratory Fortified Blank Reports;
  • Duplicate Analysis or Matrix Spike/Matrix Spike Duplicate analysis reports;
  • Field, trip, and rinsate blank reports (if applicable);
  • Sample ID cross-reference (if applicable);
  • Chain of Custody Form(s); and
  • Sample Receipt Checklist.

In general, confirmation sampling grids should be 25 feet by 25 feet. However, alternate sampling strategies are considered on a facility-specific basis. For example, it may be appropriate to collect samples along radial lines extending from a known source of airborne contamination. It may also be appropriate to collect samples from larger grids on very large facilities; however, factors like heterogeneity of contamination must be considered in determining grid size.

Backfill material to be used on a CECRA facility needs to be adequately characterized to demonstrate that the backfill material does not contain contaminants at concentrations greater than established cleanup levels. DEQ must approve all proposed backfill and borrow source material before it can be used. Collect samples from all proposed backfill material and analyze for the eight Resource Conservation Recovery Act (RCRA) metals (arsenic, barium, cadmium, chromium, lead, selenium, silver, and mercury). Research DEQ’s electronic databases for known contaminated sites to determine if the proposed backfill source is in the database or is adjacent to a site listed in the database. If the proposed backfill source is in the database or is adjacent to a site listed in the database, additional analysis may be necessary for parameter(s) known to be present at the listed site. See the Mapping DEQ's Data to search for sites in DEQ’s database.

Please note the NRIS Digital Atlas does not allow you to search sites by address. The easiest way to search for contaminated sites close to potential backfill locations is by following the directions for the digital atlas and entering the Township, Range, and Section (TRS) of the desired location and a 1 mile buffer. Once a TRS is entered, click on the Environmental Impacts tab and run a separate query for Petroleum Sites (i.e. Underground Storage Tanks, Underground Tank Leaks, and Petroleum Compensation Sites), Abandoned Mine Sites, and Remediation Response Sites by clicking on each hyperlink. Summary Data Reports for each query can be found by clicking on the blue program title underneath the map. If the NRIS Digital Atlas does not appear to be working then please contact Sue Fairchild with the Lat/Long of the property.

Generally, at least one 5-point composite sample needs to be collected for every 400 cubic yards of backfill material. If large volumes of backfill material are needed, you may propose an alternative sample frequency.

Dioxins/furans are created as a by-product during the manufacturing of pentachlorophenol, among other things, and are typically present where pentachlorophenol is found. Both dioxins/furans and pentachlorophenol are considered probable human carcinogens, although dioxins/furans are more carcinogenic at much lower concentrations. For example, pentachlorophenol is generally measured in parts per billion, while dioxins/furans are measured in parts per quadrillion. Therefore, at CECRA facilities, samples should be analyzed for dioxins/furans using EPA Method 8290 if pentachlorophenol is suspected or found to be present.

Because dioxins/furans are actually a combination of many different chemical compounds, a toxicity equivalence quotient (TEQ) is calculated to represent the total toxicity for each sample. This TEQ concentration is calculated by adjusting the concentrations of several of the dioxin/furan compounds to account for their toxicity and then adding all of the adjusted concentrations. This totaled concentration (identified as a Total TEQ) is then compared to the appropriate screening level. DEQ has developed a Dioxin/Furan TEQ Calculator for Soil and Water Samples to assist in the calculation of TEQs.

A "K" or estimated maximum possible concentration (EMPC) qualifier from the lab means that interfering substances impacted the determination of which compounds were present in the sample. Therefore, the laboratory must estimate the maximum possible detection of the compound. In the Dioxing/Furan TEQ Calculator "K" or EMPC values are treated as the detection limit (DL) and therefore these values should be included in the DL column.

If there is no analytical method with a low enough detection limit to determine if the sample meets a given standard or screening level, then the sample should be analyzed using the lowest available detection limit. For surface and ground water samples, the analytical method should achieve the required reporting limit included in the most current version of DEQ-7. For soil, sediment, and air samples, the analytical method should achieve the lowest available reporting limits. If the reporting limit is higher than the soil screening level for leaching to groundwater, DEQ may require groundwater sampling or additional soil sampling or both to confirm that the compound is not leaching. For metals and dioxins/furans in water or soil and for some compounds in indoor or outdoor air, DEQ may recommend a comparison to background concentrations.

The numerous analytical methods that exist today provide a range of different detection limits. The method with the lowest detection limit should be used, especially if you intend to seek closure of the facility. If you have previous samples that were analyzed using an analytical method that has a higher detection limit, you may need to collect some additional confirmation samples and have them analyzed using the method with the lowest possible detection limit to show that the contamination has been adequately addressed.

Collection of groundwater samples beneath free product should be planned carefully, as passing sampling instruments through free product may contaminate the equipment. Sampling intervals and the associated sampling equipment and procedures for collecting a groundwater sample separate from free product should be identified in the sampling plan. When conducting this sampling, it is important to use experienced field personnel to ensure valid sampling results.

Asbestos at State Superfund Facilities

  • If the amount of asbestos is greater than ten square feet, three linear feet or three cubic feet and part of a structure that is regulated under Section 75-2-501, et seq., MCA and NESHAP 40 CFR 61, then a permit may be necessary. Please check with the SSU project manager.
  • If the asbestos-related work concerns only removal of asbestos that may be present in debris on the ground, then an asbestos project permit (Section 75-2-504, MCA and ARM 17.74.355) may not be needed. However, a permit for the transportation of asbestos may be required. Please check with the SSU project manager.
  • If the only activity occurring is sampling of suspected asbestos materials on the ground, and not removal, a permit may not be required. Please check with the SSU project manager.
  • Per ARM 17.74.354, you are required to use an accredited inspector to inspect for the presence of asbestos, prior to a renovation or demolition.
  • However, if the project is not a renovation or demolition and an Asbestos Control Program permit is not required use of an accredited asbestos inspector is not required, but may be advisable.
  • A certified asbestos inspector is trained to visually inspect building materials and identify those that may contain asbestos. An inspector’s knowledge can be useful in scoping sampling, and ensuring best management practices are used when collecting asbestos samples to minimize the risk of a release of asbestos.
  • In other situations, a certified asbestos inspector may be able to visually separate debris into different categories, thereby minimizing the number of representative debris samples that are needed. Alternatively, each piece of debris may be sampled using best management practices.

How do I sample?

  • For debris, samples may be analyzed via Polarized Light Microscopy (PLM) Bulk Material Sampling specifying that the laboratory use the lowest possible detection limit (0.25%) (EPA /600/R-93/116). Depending on the friability of the debris, or the ability of the debris to be crumbled, pulverized, or reduced to powder by ordinary hand pressure, analysis via Transmission Electron Microscopy (TEM) may be appropriate. Note that a laboratory will initially screen all TEM samples using PLM so that if asbestos is detected using PLM, TEM would not be necessary. Please check with the SSU project manager
  • Depending upon the types and amounts of debris, more than one sample of each type of debris may be needed to be representative of the material. Please check with the SSU project manager.
  • If the debris is determined to contain asbestos, then asbestos may have been released from debris into the soil, and soil samples should be analyzed via CARB 435 PLM specifying that the laboratory use the lowest possible detection limit (0.25%).
  • If asbestos is determined not to be present using CARB 435 PLM with the lowest possible detection limit (0.25%), then no additional sampling or remediation is necessary. If asbestos is determined to be present in the soil using the CARB 435 PLM method with the lowest possible detection limit (0.25%), then remedial options should be evaluated and CARB 435 TEM may be required for confirmation samples. Alternatively, activity-based sampling may be performed following EPA’s guidance (OSWER Directive 9200.0-68, September 2008) to determine if the asbestos poses an unacceptable risk. If activity-based sampling shows an unacceptable risk, then remedial options should be evaluated.
  • Please note that PLM or Carb 435 PLM laboratory results described as PC Trace are considered a positive identification of asbestos. For quantification purposes, PC Trace is typically equivalent to 0.25%.
  • Please see ARM 17.74.369 regarding transportation and disposal of asbestos-containing waste.
  • All material that contains asbestos, whether it contains asbestos at a level greater than 1%, or whether it is friable or non-friable, must be properly disposed of in accordance with applicable environmental requirements, criteria, or limitations. State law requires disposal of all asbestos at a Class II or Class IV landfill, where it will be considered asbestos-contaminated waste and disposed of specifically in an asbestos-dedicated cell. Please contact DEQ’s Solid Waste Program for further information regarding disposal requirements.
  • The information contained in these FAQs does not apply to any asbestos activities regulated and permitted through DEQ’s Asbestos Control Program, including, but not limited to, the renovation or demolition of a building at a CECRA facility. Please contact DEQ’s Asbestos Control Program for further information and requirements about such activities.

RISK ASSESSMENT/ANALYSIS

Long-term exposure to any concentration of a cancer-causing compound is assumed to have some risk, so when determining site-specific cleanup levels, DEQ must choose concentrations that are protective of human health. The term “excess lifetime cancer risk” is used because all people have a risk of getting cancer due to genetics or other causes not related to a DEQ-regulated facility. According to the SEER Cancer Statistics Review, American men have a 44% lifetime risk of being diagnosed with cancer, while American women have a 38% lifetime risk (National Cancer Institute, 2009). This is a little over a 1 in 3 chance (or 33% or 0.33) that a person will get some type of cancer at some time in his or her life. "Excess lifetime cancer risk” is additional risk that someone might have of getting cancer if that person is exposed to cancer-causing compounds. DEQ considers an additional or excess 1 in 100,000 chance (or 0.001% or 0.00001 or 1 x 10-5) allowable. (The Montana Legislature has directed that 1 x 10-5 is an allowable risk for state water, § 75-5-301, MCA, and based on that level, DEQ has determined that 1 x 10-5 is an appropriate risk). DEQ derives site-specific cleanup levels such that they do not result in a cumulative excess lifetime cancer risk greater than 1 in 100,000.

The following is a partial list of guidance documents for risk assessment/analysis. (Please note that some of these references may contain outdated information and are meant to serve as a resource
  • NewMontana Risk Assessment Tables
  • Revised Policy on Performance of Risk Assessment During Remedial Investigation/Feasibility Studies (RI/FS) Conducted by Potential
  • Risk Assessment Guidance for Superfund (RAGS) Volume 1 - Parts A through D (Environmental Protection Agency, Washington, DC. - EPA/540/1-89/002, December 1989; EPA 540/R-92/003, December 1991; Publication 9285.7-01C, October 1991; and, Publication 9285.7-47; December 2001)
  • Risk Assessment Guidance for Superfund (RAGS) Volume 1 - Part E (Environmental Protection Agency, Washington, DC. - EPA/540/R/99/005, July 2004)
  • Human Health Toxicity Values in Superfund Risk Assessments (Environmental Protection Agency, Washington, DC. - OSWER 9825.7-53, December 2003)
  • Calculating Upper Confidence Limits for Exposure Point Concentrations at Hazardous Waste Sites (Environmental Protection Agency, Washington, D.C. - OSWER 9825.6-10, December 2002)
  • Ecological Risk Assessment Guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessments (Environmental Protection Agency, Washington, DC. - EPA 540/R/97/006, OSWER 9285.7-25; June 1997)
  • Exposure Factors Handbook: 2011 Edition - Environmental Protection Agency, Washington, DC, (EPA/600/R-09/052F)
  • Human Health Evaluation Manual, Supplemental Guidance: Update of Standard Default Exposure Factors (OSWER Directive 9200.1-120, February 2014)

Please click on the link Risk Assessment Example Scope of Work for an example risk assessment work plan and report. Below are some general assumptions that should be considered when conducting risk assessment/analysis:

  • What do we consider allowable risks (i.e. cumulative 1x10-5 and HI of 1)?
    • To ensure protection of human health at CECRA facilities, DEQ allows cleanup levels calculated based on cumulative risk levels less than or equal to a total excess cancer risk of 1x10-5 for carcinogens or a total hazard index less than or equal to 1 for non-carcinogens.
    • To ensure protection of the environment at CECRA facilities, ecological risks are also evaluated and acceptable risk determinations are made on a facility-specific basis.
    • All exposure assumptions must be acceptable to DEQ and are best determined in consultation with DEQ.

General Information

  • For initial screening of contaminants of concern, please refer to the Screening FAQs for guidance.
  • Cumulative cancer risk for carcinogenic compounds may not exceed 1E-05.
  • Total hazard index for non-carcinogenic compounds may not exceed 1 for each target organ.
  • Include an evaluation of ingestion, dermal, and inhalation exposure.
  • For inhalation exposure, include both particulate and vapor inhalation for volatile compounds.
  • Please use Risk Assessment Guidance for Superfund (RAGS) Part D table format for risk assessment tables, available online at http://www.epa.gov.
  • For guidance on addressing dermal factors, refer to EPA’s Risk Assessment Guidance for Superfund (RAGs) Part E.
  • For guidance on inhalation risk, refer to RAGs Part F available online at http://www.epa.gov/oswer/riskassessment/ragsf.
  • DEQ generally follows the EPA Hierarchy of Human Health Toxicity Values in Superfund Risk Assessments (EPA, December 2003) http://www.epa.gov/oswer/riskassessment/pdf/hhmemo.pdf. This hierarchy lists the EPA Integrated Risk Information System (IRIS) located at http://www.epa.gov/iris/ as the Tier 1 source of toxicity values for risk assessment. If toxicity values for chemical are not available in IRIS, the Tier 2 source is the EPA's Provisional Peer Reviewed Toxicity Values (PPRTVs) located at http://hhpprtv.ornl.gov/. If no PPRTV is availabie for a chemical, Tier 3 sources include additional EPA and non-EPA sources. Links for some of these Tier 3 sources are available in the EPA December 2003 memo.
  • For assistance with risk assessment/analysis for petroleum compounds, click here to see the Tier 1 Risk-Based Corrective Action Guidance for Petroleum Releases (dated September 2016) Appendix B spreadsheets. However, for petroleum toxicity criteria to be used in risk assessment/analysis, please click here to see the appropriate toxicity values for petroleum fractions detected using the Massachusetts Air-Phase Petroleum Hydrocarbon (APH) Method.
  • For some contaminants in residential soils, it may be appropriate to consider ingestion of produce and/or breast milk. Please discuss these issues with DEQ to determine whether a quantitative evaluation is necessary.
  • Agricultural, ecological, recreational, and/or other exposure scenarios can exist (although not covered below) and will be evaluated on a site-specific basis.
  • When developing site-specific cleanup levels, the soil leaching to groundwater pathway must be considered to ensure protection of groundwater. For guidance on calculating cleanup levels for this pathway, please refer to the Fate and Transport FAQ.
  • For more information on how to evaluate vapor intrusion to indoor air, please see the FAQ for site-specific vapor intrusion risk assessment/analysis.

Update - Specific Exposure Parameters were updated per the 2014 update of Superfund Default Exposure Factors: While each facility is different based on its site-specific conditions, the following typical assumptions have been used and approved by DEQ. Please see the attached memo regarding Developement of Montana Specific Default Soil Exposure Frequencies.


Residential exposure scenario:

Carcinogenic Compounds:

  • Target risk for each compound: Divide target cumulative cancer risk of 1E-05 by the number of carcinogenic compounds
  • Exposure frequency: 270 days per year (Assumes 3 months of snow cover/frozen ground and a 2 week vacation)
  • Exposure duration: 26 years
  • Averaging time: 28,470 days (365 days x 78 years)
  • Age adjusted soil ingestion factor: 105 milligrams soil * year per kilogram body weight * day (mg*yr/kg*day) (Age-adjusted soil ingestion rate is based on the equation provided in the EPA Regional Screening Levels for Chemical Contaminants at Superfund Sites document, which utilizes both the adult soil ingestion rate (100 mg soil per day), and the child soil ingestion rate (200 mg soil per day) and is adjusted for body weight (i.e. a child body weight of 15 kilograms and an adult body weight of 80 kilograms) and exposure duration)
  • Mutagenic age-adjusted soil ingestion rate: 477 mg*yr/kg*day (this applies to compounds with carcinogenicity based upon a mutagenic mode of action such as, vinyl chloride or benzo(a)pyrene).
  • Age-adjusted Dermal Factor: 295 mg*yr/kg*day (Age-adjusted dermal factor is based on the equation provided in the EPA Regional Screening Levels for Chemical Contaminants at Superfund Sites document, which utilizes the adult skin surface area (6,032 square centimeters [cm²]) and soil adherence factor (0.07 mg per cm² and the child skin surface area (2,373 cm²) and soil adherence factor (0.2 mg per cm² and is adjusted for body weight (i.e., a child body weight of 15 kg and an adult body weight of 80 kg) and exposure durations).
  • Mutagenic age-adjusted dermal factor: 1224 mg*yr*/kg*day (this applies to compounds with carcinogenicity based upon a mutagenic mode of action such as, vinyl chloride or benzo(a)pyrene).

Non-Carcinogenic Compounds:

  • Target hazard quotient for each compound: The target hazard index of 1 divided by the number of compounds with the same critical effect.
  • Exposure frequency: 270 days per year (Assumes 3 months of snow cover/frozen ground and a 2 week vacation)
  • Exposure duration: 6 years
  • Averaging time: 2,190 days (365 days x 6 years)
  • Soil ingestion rate: Child - 200 milligrams (mg) soil per day
  • Body Weight: Child - 15 kilograms
  • Child skin surface area: 2,373 cm²
  • Child soil adherence factor: 0.2 mg/cm²

Commercial/Industrial Exposure Scenario:

Carcinogenic Compounds:

  • Target risk for each compound: Divide the target cumulative cancer risk of 1E-05 by number of carcinogenic compounds
  • Exposure frequency: 187 days per year (Assumes a standard 5-day work week, 3 months of snow cover/frozen ground, and a 2 week vacation)
  • Exposure duration: 25 years
  • Averaging time: 28,470 days (365 days x 78 years)
  • Soil Ingestion rate: Adult: 100 mg soil per day
  • Body Weight: Adult - 80 kilograms
  • Skin surface area: 3,527 cm²
  • Soil adherence factor: 0.12 mg/cm²

Non-Carcinogenic Compounds:

  • Target hazard quotient for each compound: The target hazard index of 1 divided by the number of compounds with the same critical effect
  • Exposure frequency: 187 days (Assumes a standard 5-day work week, 3 months of snow cover/frozen ground, and a 2 week vacation)
  • Exposure duration: 25 years
  • Averaging time: 9,125 days (365 days x 25 years)
  • Soil ingestion rate: Adult: 100 mg soil per day
  • Body Weight: Adult - 80 kilograms
  • Skin surface area: 3,527 cm²
  • Soil adherence factor: 0.12 mg/cm²

Construction Worker/Excavation Exposure Scenario:

Please note that construction workers or those excavating soil are expected to be exposed to both surface (0-2 feet bgs) and subsurface (2-10 feet bgs) soil. Therefore, it is appropriate to evaluate construction/excavation worker exposure to both surface and subsurface soils. If cleanup levels protective of construction/excavation workers are lower than those for other surface soil receptors, the lower cleanup levels could also be applied to surface soil.

Carcinogenic Compounds:

  • Target risk for each compound: Divide the target cumulative cancer risk of 1E-05 by the number of carcinogenic compounds
  • Exposure frequency: 124 days per year (Professional judgment based on assumption of 4 months of open excavation)
  • Exposure duration: 1 year
  • Averaging time: 28,470 days (365 days x 78 years)
  • Soil ingestion rate: Adult: 330 mg soil per day
  • Skin surface area: 3,527 cm²
  • Soil adherence factor: 0.3 mg/cm²

Non-Carcinogenic Compounds:

  • Target hazard quotient: The target hazard index of 1 divided by the number of compounds with the same critical effect
  • Exposure frequency: 124 days per year (Professional judgment based on assumption of 4 months of open excavation)
  • Exposure duration: 1 year
  • Averaging time: 365 days (365 days x 1 year)
  • Soil ingestion rate: Adult: 330 mg soil per day
  • Skin surface area: 3,527 cm²
  • Soil adherence factor: 0.3 mg/cm²

Trespasser Exposure Scenario:

This scenario is highly dependent upon the individual site characteristics, the surrounding area demographics, and the level of security such as fencing. Please consult with DEQ regarding the most appropriate trespasser scenario for your facility. The following is an example scenario for a facility that has features that make it particularly attractive to trespassers, such as water or trails, homes nearby, and low security.

Carcinogenic Compounds:

  • Adolescent (6-18 years old - 45 kilogram bodyweight) is trespasser
  • Target risk: Divide the target cumulative cancer risk of 1E-05 by the number of carcinogenic compounds
  • Exposure frequency: 50 days per year (Professional judgment based on approximately 2 days per week for 6 months per year)
  • Exposure duration: 12 years
  • Averaging time: 28,470 days (365 days x 78 years)
  • Soil ingestion rate: 100 mg soil per day
  • Skin surface area: 4,400 cm²
  • Soil adherence factor: 0.04 mg/cm²

Non-Carcinogenic Compounds:

  • Adolescent (6-18 years old - 45 kilogram bodyweight) is trespasser
  • Target hazard quotient: The target hazard index of 1 divided by the number of compounds with the same critical effect
  • Exposure frequency: 50 days per year (Professional judgment based on approximately 2 days per week for 6 months per year)
  • Exposure duration: 12 years
  • Averaging time: 4,745 days (365 days x 12 years)
  • Soil ingestion rate: 100 mg soil per day
  • Skin surface area: 4,400 cm²
  • Soil adherence factor: 0.04 mg/cm²

General Information:

  • For initial screening of contaminants of concern, please refer to the Screening FAQs for guidance.
  • For compounds that have them, the Montana numeric water quality (DEQ-7) standards are the cleanup levels, and performance of a risk assessment/analysis for groundwater is not necessary. The DEQ-7 standards are equal to or are more protective than the EPA Safe Drinking Water Standards.
  • For compounds that do not have DEQ-7 standards, risk-based screening levels (RBSLs) from the Montana Tier 1 Risk-Based Corrective Action Guidance for Petroleum Releases (RBCA) document may be used as cleanup levels or site-specific cleanup levels may be calculated.
  • For compounds that do not have DEQ-7 standards or RBSLs, it may be possible to use the EPA tapwater regional screening levels provided in the most recent Regional Screening Levels (RSL) for Chemical Contaminants at Superfund Sites. Please note that the RSLs for carcinogenic compounds are based on IE-6 risk, while the DEQ-7 standards are based on a 1x10-5 risk. Therefore, it may be possible to calculate a different RSL based on a IE-05 risk.
  • Cleanup levels based on drinking water are typically protective of construction workers encountering groundwater, and therefore it is not usually necessary to evaluate construction worker exposure to groundwater quantitatively. If it is necessary to evaluate construction worker exposure to groundwater, the exposure assumptions used for construction worker exposure to soil are also applicable to this exposure scenario.
  • For more information on how to evaluate vapor intrusion to indoor air, please see the FAQ for vapor intrusion risk assessment/analysis.

 

General Information:

For initial screening of contaminants of concern, please refer to the Screening FAQs for guidance.

Surface Water:

  • Like groundwater, Montana’s numeric water quality (DEQ-7) standards are used as the cleanup levels. Both the DEQ-7 standards for human health and aquatic life (acute and chronic) must be considered, and the most protective of the numbers must be used as the cleanup level.
  • If there is not a DEQ-7 standard available for a compound, a site-specific risk assessment/analysis may be necessary. DEQ does not have generic assumptions for surface water risk assessment/analysis other than those used in calculating the EPA tap water (representing drinking water) Regional Screening Levels (RSL) for Chemical Contaminants at Superfund Sites.
  • Ecological exposure usually drives surface water cleanup.

Sediment:

  • Sediment is evaluated on a site-specific basis and DEQ does not have generic assumptions.

General Information:

  • For initial screening of contaminants of concern, please refer to the Screening FAQs for guidance.
  • If volatile compounds are contaminants of concern at a facility:
    • Evaluate indoor air (inside habitable structure) and sub-slab (underneath the building foundation/basement) conditions to determine if sampling is necessary.
    • If no buildings exist at the facility, soil gas sampling will likely be necessary and institutional controls may be necessary to limit future exposure.
  • DEQ will consider alternative assumptions on a site-specific basis.
  • Exposure to outdoor vapors is addressed under the FAQ regarding general assumptions for a site-specific soil risk assessment/analysis.

Specific Scenarios: While each facility is different based on its site-specific conditions, the following typical assumptions have been used and approved by DEQ.

Residential Exposure Scenario:

Carcinogenic Compounds:

  • Target risk: Divide cumulative cancer risk by number of carcinogenic compounds
  • Exposure frequency: 350 days per year (Assumes a 2 week vacation)
  • Exposure duration: 26 years
  • Averaging time: 28,470 days (365 days x 78 years)
  • Exposure time: 24 hours per day
  • Mutagenic age-adjusted inhalation factor: 72 years (this applies to compounds with carcinogenicity based upon a mutagenic mode of action such as, vinyl chloride or benzo(a)pyrene).

Non-Carcinogenic Compounds:

  • Target hazard quotient: Hazard index divided by number of compounds with the same critical effect
  • Exposure frequency: 350 days per year (Assumes a 2 week vacation)
  • Exposure duration: 26 years
  • Averaging time: 9,490 days (365 days x 26 years)
  • Exposure time: 24 hours per day

For a Worker Exposure Scenario:

Carcinogenic Compounds:

  • Target risk: Divide cumulative cancer risk by number of carcinogenic compounds
  • Exposure frequency: 250 days per year (Assumes a standard 5-day work week and a 2 week vacation)
  • Exposure duration: 25 years
  • Averaging time: 28,470 days (365 days x 78 years)
  • Exposure time: 8 hours/24 hours

Non-Carcinogenic Compounds:

  • Target hazard quotient: Hazard index divided by number of compounds with the same critical effect
  • Exposure frequency: 250 days (Assumes a standard 5-day work week and a 2 week vacation)
  • Exposure duration: 25 years
  • Averaging time: 9,125 days (365 days x 25 years)
  • Exposure time: 8 hours/24 hours

DEQ uses EPA's most current version of ProUCL to calculate reasonable maximum exposure point concentrations (RMEPCs). ProUCL provides the means for calculating RMEPCs for data sets that include non-detects. When ProUCL calculates a RMEPC, it will recommend that an upper confidence limit (UCL) of 95% or greater is the best fit for the data presented (e.g. 97.5% or 99% UCL). DEQ typically requires that the UCL recommended by ProUCL which best fits the data presented be used as the RMEPC. Depending on a specific data set, it may not be appropriate to perform a UCL calculation. This is particularly true for very small data sets or for data sets with less than five detections. DEQ will evaluate the ProUCL output including any warnings or recommendations so these must be submitted for review. If you have any questions please contact the project officer for the CECRA facility. The ProUCL software can be downloaded free from EPA's website at the following link: http://www.epa.gov/esd/tsc/software.htm.

DEQ recommends the use of the ProUCL software available through EPA’s website at http://www.epa.gov/esd/tsc/software.htm for statistical analysis of data used for risk assessment purposes. The ProUCL software provides statistical analysis of non-detects or censored data; therefore, there is no need to use half the detection limit for undetected compounds (with the exception of calculations of toxicity equivalence quotients for dioxins/furans or other dioxin-like compounds - please refer to the FAQ regarding sampling for dioxins/furans for more information). The ProUCL software also provides information regarding whether there is enough data available for statistical analysis, whether the data set falls into a particular distribution, whether an upper confidence limit (UCL) other than 95% (i.e., 97%, 99%) is appropriate given the data set; and also provides a limited outlier analysis. It is generally appropriate to follow the ProUCL recommendations. Thorough justification and DEQ approval is required for proposals that do not follow these recommendations.

MORE INFORMATION

Please contact DEQ at (406) 444-6444 to make arrangements for viewing and/or copying facility files. Click here to view site file guides.