Ariz. Admin. Code § R18-12-263.01 - Risk-based Corrective Action Standards

A. Conducting risk-based tier evaluation and proposing the applicable corrective action standard. The owner or operator shall propose and document, as described in subsection (B), each applicable risk-based corrective action standard, using the procedures of this subsection. The owner or operator shall ensure that each corrective action standard meets the corrective action requirements of A.R.S. § 49-1005(D) and (E), and is consistent with soil remediation standards and restrictions on property use in A.R.S. Title 49, Chapter 1, Article 4 and the rules made under each. In determining the proposed corrective action standard, the owner or operator shall first perform a Tier 1 evaluation. The owner or operator may subsequently perform progressively more site-specific, risk-based tier evaluations (Tier 2 or Tier 3) after considering the comparative differences in input parameters, the cost effectiveness in conducting both the additional evaluation and remediation to the next tier corrective action standard, and the cumulative estimate of risk to public health and the environment.

1. For a Tier 1 evaluation, the owner or operator shall:

a. Base assumptions on conservative scenarios where all potential receptors are exposed to the maximum concentration of each chemical of concern in each contaminated medium detected in contamination at and from the LUST site;

b. Assume that all exposure pathways are complete;

c. Use the assumed point of exposure at the source or the location of the maximum concentration as the point of compliance;

d. Compare the maximum concentration of each chemical of concern in each contaminated medium at the point of compliance with the applicable Tier 1 corrective action standard in subsections (A)(1)(e) through (A)(1)(j);

e. For soil, use the applicable corrective action standard in R18-7-203(A)(1) and (2) and (B);

f. For surface water, use the applicable corrective action standard in R18-11-112 or Appendix A (18 A.A.C. 11, Article 1);

g. For groundwater, use the applicable corrective action standard in R18-11-406;

h. For contaminated groundwater that is demonstrated to discharge or potentially discharge to surface water, use the applicable corrective action standard in R18-11-108, R18-11-112, or Appendix A (18 A.A.C. 11, Article 1);

i. If a receptor is or has the potential to be impacted, for those chemicals of concern in soil or surface water with no numeric standard established in rule or statute, use a corrective action standard consistent with R18-7-206 or R18-11-108, as applicable, using updated, peer-reviewed scientific data applying those equations and methodologies used to formulate the numeric standards established in R18-7-203(A)(2) or Appendix A (18 A.A.C. 11, Article 1), or for leachability and protection of the environment, a concentration determined on the basis of methods approved by the Department; and

j. If a public or private water supply well is or has the potential to be impacted, for those chemicals of concern in groundwater with no numeric water quality standard established in rule or statute, use a corrective action standard consistent with R18-11-405, using updated, peer-reviewed scientific data applying those equations and methodologies used to formulate the numeric standards established in R18-11-406.

2. For a Tier 2 evaluation the owner or operator shall:

a. Apply site-specific data to the same equations used to develop the Tier 1 corrective action standard, or, in the case of volatilization from subsurface soil, a Department-approved equation that accounts for the depth of contamination;

b. For those chemicals of concern with no numeric standard established in statute or rule, use a corrective action standard based on updated, peer-reviewed scientific data, and provided through environmental regulatory agencies and scientific organizations;

c. Use Department-approved values for equation parameters, if the values are different than those used in Tier 1 or not obtained through site-specific data;

d. Eliminate exposure pathways that are incomplete due to site-specific conditions, or institutional or engineering controls, from continued evaluation in this tier;

e. Use as the point of compliance a location between the source and the point of exposure for the nearest known or potential on-site receptor, or the nearest downgradient facility property boundary, whichever is the nearest to the source;

f. Use representative concentrations of chemicals of concern that are the lesser of the 95% upper confidence level or maximum concentration in the contaminated medium at the point of compliance;

g. Use as the Tier 2 corrective action standard, a concentration determined under subsections (A)(2)(a) through (A)(2)(c), R18-7-206, R18-11-108, and R18-11-405; and

h. Compare the representative concentration of each chemical of concern, in each contaminated medium, at the point of compliance with the proposed Tier 2 corrective action standard, to determine if remediation is required.

3. For a Tier 3 evaluation the owner or operator shall:

a. Apply more site-specific data than required in the development of Tier 2 corrective action standards in alternative and more sophisticated equations appropriate to site-specific conditions. The owner or operator shall use equations and methodology of general consensus within the scientific community that is published in peer-reviewed professional journals, publications of standards, and other literature;

b. Use the nearest known or potential receptor as the point of exposure;

c. Use as the point of compliance the point of exposure or some location between the source and the point of exposure, regardless of the facility boundary;

d. Use representative concentrations that are the actual or modeled concentrations in the medium of concern at the point of compliance;

e. Use as the Tier 3 corrective action standard a concentration consistent with subsections (A)(3)(a) through (A)(3)(d);

f. Compare the representative concentration of each chemical of concern in each contaminated medium at the point of compliance with the Tier 3 corrective action standard to determine if remediation is required; and

g. Choose the remedial action upon completion of the Tier 3 evaluation that will result in concentrations of chemicals of concern presenting a hazard index no greater than 1 and a cumulative excess lifetime cancer risk between 1 x 10-6 and 1 x 10-4.

4. All risk-based corrective action standards proposed under the tier evaluations in subsections (A)(1) through (3) are based on achieving similar levels of protection of public health and the environment. For Tier 2 and Tier 3 evaluations, a cumulative risk assessment is warranted if multiple pathways of exposure are present, or reasonably anticipated, and one or more of the following conditions impacts or may impact current or future receptors:

a. More than 10 carcinogens are identified;

b. More than one class A carcinogen is identified;

c. Any non-carcinogen has a hazard quotient exceeding 1/nth of the hazard index of 1, where n represents the total number of non-carcinogens identified; or

d. More than 10 non-carcinogens are identified.

B. Documentation of tier evaluation. The owner or operator shall document each tier evaluation performed in response to contaminated soil, surface water and groundwater. The owner or operator shall prepare each evaluation using a Department provided format and complying with this subsection.

1. For a Tier 1 evaluation the owner or operator shall provide the following information:

a. Each chemical of concern detected in the contamination at and from the LUST site;

b. Each medium contaminated, identified as soil, surface water, or groundwater;

c. The maximum concentration of each chemical of concern for each contaminated medium.

d. The current and future use of the facility and surrounding properties;

e. Each receptor evaluated;

f. The Tier 1 corrective action standard for each chemical of concern for each contaminated medium; and

g. The proposed corrective actions for each chemical of concern that exceeds the Tier 1 corrective action standard.

2. For the Tier 2 evaluation the owner or operator shall provide the following information:

a. Each chemical of concern evaluated;

b. Each medium contaminated, identified as surficial soil, subsurface soil, surface water, or groundwater;

c. The representative concentration of each chemical of concern for each contaminated medium;

d. A detailed description of the current and future use of the facility and surrounding properties;

e. The point of exposure;

f. The point of compliance;

g. The revised conceptual site model;

h. Parameters necessary to utilize the leachability equations, if groundwater is or may be impacted by the release, published in federal and state peer-reviewed professional journals, publications of standards, or other literature accepted within the scientific community;

i. Identification and justification for alternate assumptions or site-specific information used in place of the default assumptions of the Tier 1 evaluation, or used in a Department-approved model under subsection (A)(2) for subsurface volatilization;

j. Any supporting calculations and reference citations used in the development of Tier 2 corrective action standards;.

k. A table of the calculated Tier 2 corrective action standards;

l. A description of any institutional or engineering controls to be implemented; and

m. Proposed corrective actions for chemical of concerns that exceeds a Tier 2 corrective action standard.

3. For the Tier 3 evaluation the owner or operator shall provide the following information:

a. Each chemical of concern evaluated;

b. Each medium contaminated, identified as surficial soil, subsurface soil, surface water, or groundwater;

c. The representative concentration of each chemical of concern for each contaminated medium;

d. A detailed description of the current and future use of the facility and surrounding properties, including a demonstration of the current and foreseeable use of groundwater within one-quarter mile of the source;

e. The point of exposure;

f. The point of compliance;

g. A revised conceptual site model;

h. Identification and justification for alternate assumptions, methodology or site-specific information used in place of the assumptions for the Tier 2 evaluation;

i. Any supporting calculations and reference citations used in the development of Tier 3 corrective action standards;

j. Results and validation of modeling for soil leaching, groundwater plume migration, and surface water hydrology;

k. A table of the calculated Tier 3 corrective action standards;

l. Risk characterization, and cumulative lifetime excess cancer risk, and hazard index for current and potential receptors for all chemicals of concern in all contaminated media;

m. A description of any institutional or engineering controls to be implemented; and

n. Proposed corrective actions for chemical of concern that exceeds a Tier 3 corrective action standard.

4. When a Tier 2 or Tier 3 evaluation relies on the use of an institutional or engineering control in establishing a corrective action standard, the owner or operator shall:

a. Demonstrate that the institutional or engineering control is legal, and technically and administratively feasible;

b. Record any institutional or engineering control with the deed for all properties impacted by the release;

c. Communicate the terms of the institutional or engineering control to current and future lessees of the property, and to those parties with rights of access to the property; and

d. Ensure that the terms of the institutional or engineering control be maintained throughout any future property transactions until concentrations of chemicals of concern meet a corrective action standard at the point of compliance that does not rely on the use of the institutional or engineering control. For the institutional or engineering control to be implemented, the owner or operator shall prepare an institutional or engineering control that includes the following, as appropriate:

i. Chemicals of concern;

ii. Representative concentrations of the chemicals of concern;

iii. Any Tier 2 or Tier 3 corrective action standard;

iv. Exposure pathways that are eliminated;

v. Reduction in magnitude or duration of exposures to chemicals of concern;

vi. The cumulative excess lifetime cancer risk and hazard index if determined under subsection (A)(4);

vii. A brief description of the institutional or engineering control;

viii. Any activity or use limitation for the site;

ix. The person responsible for maintaining the institutional or engineering control;

x. Performance standards;

xi. Operation and maintenance plans;

xii. Provisions for removal of the institutional or engineering control if the owner or operator demonstrates that representative concentrations of chemicals of concern comply with an alternative corrective action standard not dependent on the institutional or engineering control; and

xiii. A statement of intent that informs lessees and parties with rights of access of the terms described in subsections (B)(4)(d)(i) through (xii).

C. Submittal of tier evaluation. The owner or operator shall submit to the Department the tier evaluation conducted under subsection (A) and provide, in accordance with subsection (B), the following:

1. Documentation of the Tier 1 evaluation with the site characterization report described in R18-12-262(D), and

2. Documentation of the Tier 2 evaluation as soon as practicable during the course of conducting risk-based responses to contamination, as a stand alone document or in conjunction with one of the following:

a. The site characterization report described in R18-12-262(D);

b. The CAP as described in R18-12-263.02(B); or

c. The corrective action completion report described in R18-12-263.03(D).

3. Documentation of the Tier 3 evaluation shall be submitted to the Department as soon as practicable during the course of conducting risk-based responses to contamination, as a stand alone document or in conjunction with the CAP described in R18-12-263.02(B).

Notes

Ariz. Admin. Code § R18-12-263.01

New Section made by final rulemaking at 8 A.A.R. 3894, effective August 20, 2002 (Supp. 02-3).