Missouri Code of State Regulations › Title 10 - DEPARTMENT OF NATURAL RESOURCES › Division 25 - Hazardous Waste Management Commission › Chapter 18 - Risk-Based Corrective Action › Section 10 CSR 25-18.010 - Risk-Based Corrective Action Process

Current through Register Vol. 49, No. 14, July 15, 2024
PURPOSE: The Department of Natural Resources
				  (department) oversees response, characterization, risk assessment, and risk
				  management under a variety of authorities at over two thousand (2,000)
				  contaminated sites in Missouri. Many more sites are in an early stage of
				  investigation or as yet unknown to the department. The impetus and philosophy
				  behind Missouri Risk-Based Corrective Action (MRBCA) is to provide a framework
				  for cleanup decisions that facilitates the constructive use of contaminated
				  sites by protecting human health and the environment in the context of current
				  and reasonably anticipated future site use. This framework can streamline the
				  process of site cleanup and closure.
PUBLISHER'S NOTE: The secretary of state has
				  determined that the publication of the entire text of the material which is
				  incorporated by reference as a portion of this rule would be unduly cumbersome
				  or expensive. This material as incorporated by reference in this rule shall be
				  maintained by the agency at its headquarters and shall be made available to the
				  public for inspection and copying at no more than the actual cost of
				  reproduction. This note applies only to the reference material. The entire text
				  of the rule is printed here.
(1) Definitions.
(A) As used in this rule the following terms
				mean:
1. 7Q10 low-flow of a stream-the average
				minimum flow for seven (7) consecutive days that has a probable recurrence
				interval of once-in-ten (10) years;
2. Activity and use limitations (AULs)-
				mechanisms or controls that ensure that exposure pathways to chemicals of
				concern (COCs) associated with current or reasonably anticipated future uses
				are not completed for as long as the COCs would pose an unacceptable risk to
				human health, public welfare, or the environment if the pathways were
				complete;
3. Applicable target
				levels-one (1) of the following for each chemical of concern:
A. The default target level as defined
				below;
B. The tier 1 risk-based
				target level as defined below for tier 1 purposes; or
C. A tier 2 or tier 3 site-specific target
				level as defined below for tier 2 or tier 3 purposes;
4. Chemical of concern (COC)-chemical that
				may contribute to risk at a site;
5. Commission-the Missouri Hazardous Waste
				Management Commission;
6.
				Conceptual site model-information that qualitatively and/or quantitatively
				describes the relevant site-specific factors that determine the risk COCs pose
				to human health and the environment and provides a basis for management of a
				site;
7. Cumulative site-wide
				risk-sum of risk for all chemicals;
8. Default target level (DTL)-the
				concentration of a chemical of concern that is the lowest of the tier 1
				risk-based target levels for all exposure pathways and below which human
				receptors are protected from all complete exposure pathways for residential or
				other unrestricted land use. For each contaminant of concern, the default
				target level shall be either-
A. The target
				level shown in Table B-1 of Appendix B of the
Departmental Missouri
				Risk-Based Corrective Action (MRBCA) Technical Guidance
document
				published by the Department of Natural Resources, PO Box 176, Jefferson City,
				MO 65102-0176, dated April 2006 and updated in June 2006 and June 2008, which
				is hereby incorporated by reference without any later amendments or additions;
				or
B. A different value if the
				department determines in writing that a deviation is appropriate based on
				changes in the scientific data used to calculate such default target
				level;
9. Department-the
				Department of Natural Resources (DNR), which includes the director thereof, or
				the person or division or program within the department delegated the authority
				to render a decision, order, determination, finding, or other action that is
				subject to review by the commission;
10. Domestic use of groundwater- groundwater
				used for indoor water use activities such as drinking, cooking, showering, and
				other uses by which a receptor could be exposed to COCs via ingestion, dermal
				contact, or inhalation of vapors;
11. Ecological risk assessment-the process
				that evaluates the likelihood that adverse ecological effects may occur or are
				occurring as a result of exposure of ecological receptors to one (1) or more
				contaminants of concern;
12.
				Exposure-contact of a chemical of concern with an organism;
13. Exposure domain-the area that can result
				in a particular receptor being exposed to COCs by a specified exposure
				pathway;
14. Exposure factors-human
				behaviors and characteristics that affect the degree or amount of exposure to a
				chemical of concern, such as duration, frequency, body weight, inhalation rate,
				or intake rate;
15. Exposure
				pathway-the course a chemical takes from a source to the receptor. An exposure
				pathway describes a unique mechanism by which an individual or population is
				exposed to chemicals originating from a site. Each exposure pathway includes a
				source or release from a source, an exposure point, and an exposure route. If
				the exposure point differs from the source, a transport/exposure medium (e.g.,
				air) or media (in cases of intermedia transfer) also is included. The exposure
				pathway is considered complete if there are no discontinuities in or
				impediments to movement from the source of the contaminant to the
				receptor;
16. Fate and transport
				parameters-factors that characterize physical site properties that affect how a
				chemical of concern may travel or disperse in any particular medium;
17. Habitat-a place where an ecological
				receptor, such as an animal or plant, normally lives;
18. Hazard index-the sum of more than one (1)
				hazard quotient for multiple substances and/or multiple exposure
				pathways;
19. Hazard quotient-the
				ratio of an exposure level to a substance to a non-carcinogenic toxicity value
				selected for the risk assessment for that substance;
20. Hydraulic conductivity-the volume of
				water at the existing kinematic viscosity that will move in unit time under a
				unit hydraulic gradient through a unit area measured at right angles to the
				direction of flow;
21. Long-term
				stewardship (LTS)-the system of controls, institutions, and information
				required to ensure protection of human health, public welfare, and the
				environment at sites where residual contamination has been left in place above
				unrestricted use levels for the period of time over which the contaminants
				exceed those levels. Activity and Use Limitations (AULs) may be an integral
				part of long term stewardship. AULs shall be designed to ensure that pathways
				of exposure to COCs associated with current or reasonably anticipated future
				uses are not completed for as long as the COCs would pose an unacceptable risk
				to human health, public welfare, or the environment if the pathways were
				complete;
22. Point of
				demonstration (POD) wells-wells located between the source and the POE to
				monitor the COC concentrations in groundwater to prevent exceedances at the
				POE;
23. Point of exposure
				(POE)-the nearest down gradient, three-dimensional location that could
				reasonably be considered for installation of a groundwater supply
				well;
24. Receptor-an organism that
				receives, may receive, or has received exposure to a COC as a result of a
				release. Under the MRBCA program, human receptor refers to a resident child,
				resident adult, age-adjusted resident (one who resides on the site from birth
				to age thirty (30)), non-resident adult, or construction worker;
25. Remediating party-the party who is
				legally responsible for, or who is otherwise taking on the responsibility for,
				the investigation, risk assessment, and remediation of property known or
				believed to be contaminated;
26.
				Representative chemical concentra-tion-the average concentration to which a
				receptor is exposed over the specified exposure duration, within a specified
				exposure domain, and for a specific exposure pathway;
27. Risk-based target level (RBTL)-the
				pathway and chemical-specific concentration of a chemical of concern in an
				environmental medium that meets an acceptable human health risk level.
				Risk-based target levels are calculated by the department using standard models
				and default exposure factors, toxicity factors, physical and chemical
				properties, and contaminant fate and transport parameters and are applicable at
				tier 1 of the risk-based corrective action process. For each contaminant of
				concern, the risk-based target level shall be either-
A. The risk-based target level shown in
				Tables B-1 through B-11 of Appendix B of the
Departmental Missouri
				Risk-Based Corrective Action (MRBCA) Technical Guidance
document
				published by the Department of Natural Resources, PO Box 176, Jefferson City,
				MO 65102-0176, dated April 2006 and updated in June 2006 and June 2008, which
				are hereby incorporated by reference without any later amendments or additions;
				or
B. A different value if the
				department determines in writing that a deviation is appropriate based on
				changes in the scientific data used to calculate such risk-based target
				level;
28. Risk
				management plan-a written account of all site-specific activities necessary to
				manage a site's risk to human health, public welfare, and the environment so
				that acceptable risk levels are not exceeded under current or reasonably
				anticipated future land use conditions;
29. Route of exposure-the manner or mechanism
				by which a COC enters a receptor's body, for example, ingestion, inhalation, or
				dermal contact;
30. Site-areal
				extent of contamination inclusive of contamination both on the property at
				which the contamination originated and on all adjacent and nearby properties
				onto which such contamination has or is likely to migrate;
31. Site-specific target levels (SSTLs)-
				pathway and chemical specific calculated risk-based target levels that are
				based on site-specific data and an acceptable risk level considered protective
				of human health and the environment.
A.
				Site-specific target levels calculated at tier 2 of the risk-based corrective
				action process using site-specific fate and transport data and the toxicity
				factors, parameters for dermal contact pathway, physical and chemical
				properties, and exposure factors found in tables E-1, E-2, E-3, and E-4,
				respectively, and default models and equations found in Appendix E of the
Departmental Missouri Risk-Based Corrective Action (MRBCA) Technical
				Guidance
document published by the Department of Natural Resources, PO
				Box 176, Jefferson City, MO 65102-0176, dated April 2006 and updated in June
				2006 and June 2008, which are hereby incorporated by reference, without any
				later amendments or additions, and are applicable unless the department
				determines in writing that a deviation is appropriate based on changes in the
				scientific data used to calculate the site-specific target levels.
B. Site-specific target levels calculated at
				tier 3 of the risk-based corrective action process using default,
				literature-derived, and/or site-specific exposure factors, physical and
				chemical properties, toxicity factors, and fate and transport data and default,
				alternative or a combination of default and alternative models are applicable
				unless the department determines or has determined that a deviation is
				appropriate based on site-specific conditions or changes in the scientific data
				used to calculate the site-specific target levels;
32. Source property-the property or
				properties on which contamination originated;
33. Subsurface soil-soil from three feet (3')
				below ground surface to the water table;
34. Surficial soil-soil from zero to three
				feet (0'-3') below ground surface; and
35. Unrestricted use levels-chemical
				concentrations at which soil and groundwater at a site are safe for residential
				land use and domestic use of groundwater.