January 2014

The Missouri Department of Natural Resources initially published the Risk-Based Corrective Action (RBCA) Process for Petroleum Storage Tanks guidance document, commonly referred to as Tanks RBCA, in January 2004.  In March 2005, the department modified the Tanks RBCA process through the publication of several supplemental guidance documents.  In 2013, the department comprehensively updated the guidance, including the tier 1 risk-based target levels (RBTLs), to clarify various provisions, add a few new requirements, delete duplicative and unnecessary text, and combine all guidance into a single document.  The update effort included eliminating some of the supplemental guidance documents and incorporating others into the Tanks RBCA guidance document.  With this update, all guidance pertaining to Tanks RBCA is now found within the Oct. 17, 2013, version of the guidance document.

Both the Oct. 17, 2013 revised guidance and the modified 2004 guidance are available online or by contacting the Tanks Section of the department’s Hazardous Waste Program at 573-526-0971.

The following is a listing of all changes (except for several non-substantive grammatical and editorial changes) to the 2004 Tanks RBCA guidance that resulted from the 2013 guidance update effort.

Cover

  • The date of the Tanks RBCA guidance document has been changed to Oct. 17, 2013

Forward

  • Text has been added to explain that the 2004/2005 Tanks RBCA guidance has been replaced by the updated Oct. 17, 2013 version
  • Disclaimer language has been deleted

Section 1

  • Subsection 1.1 has been revised to explain the history, development, and evolution of the risk-based corrective action process in Missouri.
  • Language has been added to subsection 1.2 to explain when and how tanks owners and operators are to transition from the 2004/2005 guidance to the Oct. 17, 2013 guidance.
  • Subsection 1.3 regarding spill reporting has been deleted because it was duplicative of existing rule language.

Section 2

  • “Risk management” has been changed to “corrective action” and “risk management plan” to “corrective action plan” throughout, see in particular subsection 2.2
  • The title of subsection 2.2.1 has been changed from “Site Discovery” to “Release Discovery” and the text of the subsection has been revised to relate guidance provisions to a specific “release” rather than a generic “site”
  • Text has been added to subsection 2.3 to explain that, if tier 2 and 3 site-specific target levels (SSTLs) are lower (i.e., more conservative) than the tier 1 risk-based target levels (RBTLs), the SSTLs must be applied
  • Subsection 2.4 pertaining to impacts on site costs has been deleted and the term “site discovery” has been changed to “release discovery”
  • In Tables 2-1 and 2-2, “risk management plan” has been changed to “corrective action plan”

Section 3

  • The title of this section of the guidance has been changed from “Site Discovery and Initial Response” to “Release Discovery and Imminent Threat”
  • Subsections 3.3 through 3.9 have been deleted because the text was largely duplicative of existing rules
  • Table 3-1 Default Target Levels (DTLs) – DTLs have been revised

Section 4

  • In subsection 4.4.1, generic text regarding photographs has been deleted and replaced by text describing the specific photographs that are to be submitted with a closure report.  In addition, language has been added to subsection 4.4.1 to explain that borings and wells greater than 10’ deep are subject to the requirements of the Water Well Drillers Act and implementing rules
  • References to the department’s Outreach and Assistance Center (OAC) have been deleted throughout Section 4 because the OAC no longer exists
  • Table 4-1: soil concentrations protective of groundwater have been revised (these are a subset of the tier 1 RBTLs)
  • In subsection 4.4.3.2 at (ii), “Geological Survey and Resource Assessment Division (GSRAD)” has been deleted and replaced with “Missouri Geological Survey” to reflect the division’s name change in 2013
  • In subsection 4.5.8 text has been added to explain that, if remediation will be via land farming, the plan for land farming must be included in a Corrective Action Plan and that the plan must be approved by the department; in addition, text regarding the need to obtain a permit from the Water Protection Program for land farming has been deleted

Section 5

  • “Risk management” has been changed to “corrective action” and “risk management plan” to “corrective action plan” throughout Section 5
  • In the last bulleted item in the third set of bullets in subsection 5.1, “or risk management activities” has been deleted because it is synonymous with the preceding corrective action measures
  • The first, second and fourth sentences of the first paragraph of subsection 5.2 have been deleted because the sentences are superfluous
  • Requirements for submittal of an area map and land use map have been added to subsection 5.4
  • The guidance at subsection 5.4.1 regarding maps has been revised to explain what maps are to be submitted, how they are to be constructed, and the information they need to convey
  • In subsection 5.4.5, a reference to MEGA – which is no longer maintained by the department – has been removed and replaced with a reference to the “Well Information Management System (WIMS)” and “Center for Applied Research and Environmental Systems (CARES)” maps
  • Subsection 5.5.1 regarding current land use has been moved to subsection 6.1.1.1
  • In new subsection 5.5.1, “Geological Survey and Resources Assessment Division” or GSRAD has been changed to “Missouri Geological Survey” or MGS to reflect the division’s name change in 2013
  • Subsection 5.5.2 regarding future land use has been moved to subsection 6 .1.1.2
  • Subsection 5.5.3 regarding leased property has been deleted because the subsection was found to be unnecessary
  • Guidance regarding geotechnical data collection has been added at subsection 5.6 to help guide data collection
  • In subsection 5.6.4 regarding volumetric water content (VWC), the word “should” has been changed to “must” with regard to collecting multiple VWC samples from across a site and at varying depths.  In addition, in the first sentence of the fourth paragraph of the subsection, the words “for VWC” have been deleted because the provision does not solely or specifically pertain to volumetric water content
  • New guidance regarding collection of fractional organic carbon (FOC) data, including collection of multiple FOC samples, development and use of composite FOC samples, and specification of analytical methods for FOC analysis has been added to subsection 5.6.5
  • A footnote stating that all probes and borings > 10’ deep must be closed as per 10 CSR 23-4 has been added at subsection 5.8.2
  • Information regarding soil sampling for polynuclear aromatic hydrocarbons (PAHs) that was previously in a separate fact sheet has been incorporated into the guidance at subsection 5.8.3 without any change to the requirements presented in the fact sheet
  • New guidance pertaining to sampling and analysis of ethylene dibromide (EDB) and ethylene dichloride (EDC) in soil, including when samples shall be analyzed and the analytical methods that shall be used, has been added at subsection 5.8.4
  • New and revised requirements and guidance regarding soil sampling and soil sample preservation, including sample temperature, appear in subsection 5.8.5
  • New and revised requirements and guidance regarding groundwater sample collection and preservation, including sample temperature, and regarding well installation appear in subsection 5.9.2
  • Information regarding groundwater sampling for PAHs has been moved from a Fact Sheet to  subsection 5.9.2.1 of the guidance without any change to the requirements presented in the fact sheet
  • New guidance regarding when to sample groundwater for EDB and EDC and what analytical methods to use has been added at subsection 5.9.2.2
  • The analytical methods for EDB and EDC in groundwater in Table 5-1 have been changed
  • Footnotes have been added to Table 5-1 to explain that the date before which gasoline shall be assumed to have contained lead has changed from 1980 to Dec. 31, 1986 and to explain when groundwater samples shall be analyzed for EDB and EDC
  • In Figure 5-1, the date before which gasoline shall be assumed to have contained lead has changed from 1980 to Dec. 31, 1986

Section 6

  • Guidance regarding current land use determinations has been moved from Section 5 to subsection 6.1.1.1 and the text has been revised for clarity
  • Guidance regarding future land use determinations has been moved from Section 5 to subsection 6.1.1.2 and the text has been revised for clarity
  • The following has been added at the end of the last paragraph of subsection 6.1.2.1: “Because petroleum equipment companies are subject to other regulatory requirements regarding worker exposure, it is not necessary to evaluate the soil ingestion, inhalation, and dermal contact exposure pathway nor the dermal contact with groundwater exposure pathway for the construction worker receptor in the area in which an active underground storage tank (i.e., the tank pit) is located.”
  • In subsection 6.1.3.1, a sentence has been added regarding the need to evaluate the potential for utilities to act as preferential pathways for vapor intrusion, another sentence has been added to explicitly allow soil vapor sampling at tier 1, and the following sentence has been added at the end of the subsection: “The exposure model for an active tank facility may assume that no building will be constructed over the tank pit.”
  • Guidance in subsection 6.3 regarding groundwater use evaluations has been revised to explain that the evaluation must be conducted in strict accordance with Figure 6-2 and that each element of Figure 6-2 must be addressed in the risk assessment; in addition, language has been added to explain the need to identify all groundwater zones and whether and to what degree they are interconnected
  • Guidance in subsection 6.3.1 pertaining to water well surveys as part of groundwater use evaluations has been revised to state that well surveys shall include all private water wells within a one-quarter mile radius and all public wells within a one-mile radius of the site; in addition, language has been added regarding considerations in determining whether chemicals of concern will reach a groundwater zone of interest
  • Guidance in subsection 6.3.3 pertaining to the evaluation of a complete groundwater use pathway via  a point of exposure (POE) and point of femonstration (POD) evaluation has been revised to explain when a POD is and is not relevant and how concentrations of chemicals of concern at a POD and POE are to be evaluated
  • Subsection 6.8 “Evaluation of Light Non-Aqueous Phase Liquid (LNAPL)” has been revised to clarify which requirements pertain to LNAPL and which pertain to free product
  • In subsections 6.8 through 6.8.5, “LNAPL” has been changed to “free product” in those instances where the stated requirement pertains to mobile phase hydrocarbons or free product rather than to both mobile and immobile hydrocarbons or LNAPL

Section 7

  • Much of the text in subsection 7.1 has been deleted in order to delete superfluous language
  • In subsection 7.2, references to reporting forms have been deleted because the reporting forms are no longer required nor included in the guidance (previously found in Appendix G)
  • A footnote has been added at subsection 7.3 stating that a work plan is not required for soil vapor sampling if such sampling is conducted in accordance with the guidance in Appendix C
  • Subsection 7.5 has been revised to explain and reflect changes to the RBTLs that pertain to the leaching to groundwater pathways, the text pertaining to a point of exposure or POE used in groundwater domestic use and vapor intrusion evaluations has been revised to explain how to conduct the evaluation, and, in the second sentence of the third paragraph of the subsection, the second use of “distance” has been changed to “depth.”
  • Subsection 7.6 has been revised to clarify provisions related to additional actions following a tier 1 risk assessment and that are dependent upon the results of that risk assessment
  • Risk-Based Target Levels have been revised as follows:
    • The RBTLs are no longer soil type-dependent; the updated RBTLs are based on default parameter values for a single soil type (with the values for soil type 1 having been retained)
    • The RBTL tables have been renumbered, as follows:
      • 7-1 Risk-Based Target Levels for Residential Land Use
      • 7-2 Risk-Based Target Levels for Non-Residential Land Use
      • 7-3 Risk-Based Target Levels for Construction Worker
      • 7-4(a) to 7-4(c) – Soil Concentration Protective of Groundwater Domestic Use for Different Distances to Point of Exposure
      • 7-5(a) to 7-5(c) – Soil Concentration Protective of Indoor Inhalation for Groundwater for Different Distances to On/Off-Site Building for Resident
      • 7-6(a) to 7-6(c) – Soil Concentration Protective of Indoor Inhalation for Groundwater for Different Distances to On/Off-Site Building for Non-Resident

Section 8

  • A statement has been added near the beginning of Section 8 explaining that, if calculated SSTLs are lower (more conservative) than tier 1 RBTLs, the SSTLs must be applied
  • Subsection 8.2 has been revised as follows:
    • Regarding capillary fringe – users must show that the capillary fringe is uncontaminated in order to use other than the default capillary fringe thickness of 5 cm when developing SSTLs
    • Regarding volumetric water content (VWC) – “should” has been changed to “shall” with regard to collection of multiple samples for developing average VWC
  • All references to reporting forms have been removed from Section 8 because the forms are no longer required nor included in the guidance

Section 9

  • A statement has been added near the beginning of Section 9 explaining that, if tier 3 SSTLs are lower (more conservative) than the tier 2 SSTLs, the tier 3 SSTLs must be applied
  • Guidance for determining concentrations of chemicals of concern (COCs) in LNAPL has been added
  • References to reporting forms in subsection 9.6 have been deleted because the forms are no longer required nor included in the guidance

Section 10

  • Throughout Section 10, “risk management” has been changed to “corrective action” and “risk management plan” to “corrective action plan” (CAP)
  • Similarly, “LNAPL” has been changed to “free product” throughout Section 10
  • In subsection 10.1, in the first sentence of the third bullet under “The overall objective of a CAP is to ensure that:”, “Recoverable” has been changed to “Mobile and immobile,” and “hydrocarbons” has been changed to “liquids;” in addition, “(LNAPL; mobile LNAPL is referred to as “free product”)” has been added, and at (i), “LNAPL” has been changed to “free product”

Section 11

  • Throughout Section 11, “risk management” has been changed to “corrective action” and “risk management plan” to “corrective action plan”

Section 12

  • Throughout Section 12, references to MRBCA reporting forms have been deleted
  • A URL to access an on-line closure notice form has been added at subsection 12.1.1
  • A URL to access on-line closure report forms has been added to subsection 12.1.2
  • Language has been added to subsection 12.3.4 to explain that a work plan for soil vapor sampling is not required if soil vapor sampling is to be conducted in accordance with the guidance in Appendix C
  • A reference in subsection 12.4.3 to the “risk-based remediation rule guidance document” has been deleted
  • In subsections 12.5.3 and 12.6.2, “LNAPL” has been changed to “free product” in every instance

Appendix B: Development of Risk-Based Target Levels

  • The text in subsection B.1 has been revised for clarity
  • Subsection B.2 has been revised as follows:
    • The hierarchy for toxicity values has been updated
    • New information related to dermal exposures and dermal toxicity values has been added
    • New formulae for slope factor and reference dose for dermal exposures have been added
    • New information regarding dermal toxicity, permeability coefficients, relative contribution of permeability coefficient, lag time, and fraction absorbed has been added
  • Text found in subsection B.7 has been revised for clarity and to update references
  • Updated saturated soil, solubility, and vapor saturation values are found in Table B-5
  • In updating the guidance, several changes were made to the equations in Appendix B.  All of the equations were numbered (they were not numbered in the 2004 guidance), some of the equations were changed, some were deleted altogether, some were moved from one page of the guidance to another, and some new equations were added.  The following is an explanation of these changes:
    • The equation “Outdoor Inhalation of Vapors (Child and Adult Resident, Non-Residential Worker, and Construction Worker)” on Page B-9 of the 2004 guidance has been retitled “Figure B.2. Outdoor Inhalation of Vapors (Construction Worker)”
    • The equation “Ingestion and Inhalation of Groundwater from Potable Use (Child and Adult Resident)” on Page B-10 of the 2004 guidance has been deleted
    • The equation “Dermal Contact with Chemicals in Water (Child and Adult Resident)” on Page B-11 of the 2004 guidance has been deleted and replaced by “Figure B.3. Dermal Contact with Chemicals in Water (Child and Adult Resident, Non-Residential Worker, and Construction Worker)”
    • A new equation titled “Figure B.4. Domestic Water Use (Child and Adult Resident)” has been added to the guidance
    • The equation “Dermal Contact with Chemicals in Surficial Soil (Child and Adult Resident, Non-Residential Worker, and Construction Worker)” on Page B-12 of the 2004 guidance has been deleted and replaced by “Figure B.5. Dermal Contact with Chemicals in Soil (Child and Adult Resident, Non-Residential Worker, and Construction Worker)”
    • The equation “Ingestion of Chemicals in Surficial Soil (Child and Adult Resident, Non-Residential Worker, and Construction Worker)” on Page B-13 of the 2004 guidance has been retitled “Figure B.6. Ingestion of Chemicals in Soil (Child and Adult Resident, Non-Residential Worker, and Construction Worker)”
    • The equation “Inhalation of Vapors and Particulates of Chemicals in Surficial Soil (Child and Adult Resident, Non-Residential Worker, and Construction Worker)” on Page B-14 of the 2004 guidance has been retitled “Figure B.7.  Inhalation of Vapors and Particulates of Chemicals in Soil (Child and Adult Resident, Non-Residential Worker, and Construction Worker)”
    • The equation “Inhalation of Vapors and Particulates, Dermal Contact and Ingestion of Chemicals in Surficial Soil (Child and Adult Resident, Non-Residential Worker, and Construction Worker)” on Page B-15 of the 2004 guidance has been changed and retitled “Figure B.8. Inhalation of Vapors and Particulates, Dermal Contact with, and Ingestion of Chemicals in Soil (Child and Adult Resident, Non-Residential Worker, and Construction Worker)”
    • The equation “Outdoor Inhalation of Vapors (Age-Adjusted Resident)” on Page B-19 of the 2004 guidance has been deleted
    • The equation “Direct Ingestion and Inhalation of Groundwater from Potable Use (Age-Adjusted Resident)” on Page B-21 of the 2004 guidance has been deleted and replaced with “Figure B.11. Domestic Water Use (Age-Adjusted Resident)”
    • The equation “Direct Contact with Chemicals in Groundwater (Age-Adjusted Resident)” on Page B-23 of the 2004 guidance has been changed and retitled “Figure B.10. Dermal Contact with Chemicals in Water (Age-Adjusted Resident)”
    • The equation “Dermal Contact with Surficial Soil (Age-Adjusted)” on Page B-25 of the 2004 guidance has been changed and retitled “Figure B.12 Dermal Contact with Chemicals in Soil (Age-Adjusted Resident)”
    • The equation “Direct Ingestion of Surficial Soil (Age-Adjusted Resident)” on Page B-27 of the 2004 guidance has been retitled “Figure B.13. Ingestion of Chemicals in Soil (Age-Adjusted Resident)”
    • The equation “Outdoor Inhalation of Vapors and Particulates from Surficial Soil (Age-Adjusted Resident) on Page B-29 of the 2004 guidance has been retitled “Figure B.14. Inhalation of Vapors and Particulates of Chemicals in Soil (Age-Adjusted Resident)”
    • The equation “Inhalation of Vapors and Particulates, Dermal Contact With, and Ingestion of Chemicals in Surficial Soil (Age-Adjusted Resident)” on Page B-31 of the 2004 guidance has been changed and retitled “Figure B.15. Inhalation of Vapors and Particulates, Dermal Contact with, and Ingestion of Chemicals in Soil (Age-Adjusted Resident)”
    • A new equation titled “Figure B-19. Groundwater Concentration Protective of Outdoor Vapor Inhalation” has been added to the guidance
    • A new equation titled “Figure B-20.F. Volatilization Factors (Groundwater to Outdoor Air)” has been added to the guidance
    • The equations for “Allowable Soil and Groundwater Concentration for Groundwater Resource Protection” on Page B-46 of the 2004 guidance have been changed and a dilution attenuation factor (DAF) for the unsaturated zone has been added to the equation for calculation of allowable soil concentration at the source, see “Figure B.27. Allowable Soil and Groundwater Concentrations for Groundwater Resource Protection” in the 2013 guidance
    • A new equation titled “Figure B.28. Allowable Soil and Groundwater Concentration Protective of Indoor Inhalation for Resident and Non-Residential Worker” has been added to the guidance
    • With regard to the equation “Stream Protection: Allowable Groundwater Concentration at the Point of Discharge” on Page B-47 of the 2004 guidance, an additional equation has been added for calculation of impacted groundwater discharge to the stream, see “Figure B.29. Stream Protection: Allowable Groundwater Concentration at the Point of Discharge” in the 2013 guidance
    • Regarding the equations “Stream Protection: Allowable Soil and Groundwater Concentration at the Source & POC” on Page B-48 of the 2004 guidance, the title of the equation has been corrected by changing “POC” to “POD” (see Figure B.30 in the 2013 guidance), the equation itself has been corrected by changing “POC” to “POD” (again, see Figure B.30), and a change has been made to the equation by the addition of a dilution attenuation factor (DAF) for the unsaturated zone for calculation of the allowable soil concentration at the source

Appendix C: Evaluation of Vapor Intrusion Pathway

  • Nearly all text previously found in subsections C.1 to C.7 has been deleted and replaced by the text of the April 21, 2005, Soil Gas Sampling Protocol.  The protocol was previously a stand-alone supplemental document that has now been fully incorporated into Appendix C
  • A provision regarding the need for a variance for certain wells has been deleted from subsection C.2.2
  • Text has been added to subsection C.2.2.B to explain that vapor samples may be collected from various depths across a site but that vapor data comparisons must be of like with like (i.e., only compare data collected from the same depth)
  • A footnote has been added at subsection C.2.2.G explaining that the vapor intrusion evaluation shall assume that any future building will have a basement
  • A footnote has been added to subsection C.2.2.H regarding sampling limitations that might occur due to a shallow capillary fringe
  • In subsection C.2.3.A, “or” has been changed to “and” in order to require that the vapor intrusion evaluation consider both current and future site conditions
  • Guidance regarding sample tubing has been added at subsection C.2.4.B
  • Guidance regarding suggested tubing types has been added to subsection C.2.4.C
  • In a discussion regarding Summa canisters and Tedlar bags in subsection C.5.1.A, the statement “or equivalent containers” has been added
  • Guidance has been added at subsection C.6.1.A to indicate that leak testing may be conducted with or without a shroud
  • At subsection C.6.1.C,  helium has been added as an acceptable tracer
  • In subsection C.6.1.D, text has been added to specify that the leak test compound to be used during sampling shall be specified in the work plan
  • In the fourth bullet in subsection C.6.2.A, “ug/m3” has been changed to “ug/L”
  • At subsection C.7.2.A, TPH-GRO has been added as a required chemical of concern
  • Language has been added to subsection C.7.2.B to require that the leak test compound be included in the analysis of the sample unless leak testing is conducted using real-time monitoring
  • At subsection C.7.2.C, text has been added to recommend that samples be analyzed for CO2
  • In subsection C.8.1.A, text regarding reporting has been revised for clarity, and a footnote regarding demonstration of biodegradation has been added
  • Figure C-1 has been revised for clarity and to be consistent with changes in the text

Appendix D: A Method for Determining if a Water Bearing Unit Should be Considered an Aquifer

  • The factor used to convert hydraulic conductivity measured in gpd/ft2 to cm/sec has been corrected to 4.72x10E-05

Appendix F: Consideration of Total Petroleum Hydrocarbons within the MRBCA Process

  • Superfluous text in subsection F.1 has been deleted
  • In subsection F.4, language has been added to explain that TPH fractionation analysis is a tier 3 activity and to specify the analytical method to be used
  • The TPH-GRO carbon fractions in Table F-1 have been corrected

Appendix G: MRBCA Reporting Forms

  • The entire appendix has been eliminated because the reporting forms are no longer required