17.50.1612 ANALYTICAL METHODS (1) For purposes of this subchapter, the department adopts and incorporates by reference:

(a) remains as proposed.

(b)  Montana Risk-based Corrective Action Guidance for Petroleum Releases, (December 2023) (February 2024) as the analytical methodology landfarms must utilize and Table 1 of the Montana Risk-based Corrective Action Guidance for Petroleum Release as the standards for compliance with remediation requirements outlined in ARM 17.50.1617.  A copy of the Montana Risk-based Corrective Action Guidance for Petroleum Releases, (December 2023) (February 2024) may be obtained at http://deq.mt.gov/Land/lust https://deq.mt.gov/cleanupandrec/Programs/petrocleanup or by contacting the Department of Environmental Quality at P.O. Box 200901, Helena, MT 59620-0901 or 1 (406) 444-5300.

(2) remains as proposed.

 

AUTH: 75-10-204, MCA

IMP: 75-10-204, MCA

 

17.50.1617 LANDFARM FACILITY REMEDIATION STANDARDS  

(1) Contaminated soils are considered remediated when:

(a) contaminant concentrations listed in Montana Risk-based Corrective Action Guidance for Petroleum Releases, Table 1 (December 2023) (February 2024) are permanently reduced to the residential RSBL concentrations.

(2) and (3) remain as proposed.

(4) The owner or operator of a landfarm facility may not supply or use soils for any purpose exceeding the contaminant concentrations specified in Montana Risk-based Corrective Action Guidance for Petroleum Releases, Table 1 (December 2023) (February 2024).

(5) remains as proposed.

 

AUTH:  75-10-204, MCA

IMP:  75-10-204, MCA

 

17.50.1618 CLOSURE PLAN (1) For purposes of closure of a landfarm facility, the owner or operator of a landfarm facility shall submit a closure plan that documents the following:

(a) and (b) remain as proposed.

(c) one of the following requirements was satisfied:

(i) and (ii) remain as proposed.

(iii) all contaminated soils were remediated to Table 1 residential RSBL concentrations in the Montana Risk-based Corrective Action Guidance for Petroleum Releases, (December 2023) (February 2024) and are capable of supporting native vegetation;

(d) through (3) remain as proposed.

 

AUTH:  75-10-204, MCA

IMP:  75-10-204, MCA

 

17.55.109 INCORPORATION BY REFERENCE  (1) For the purposes of this subchapter, the department adopts and incorporates by reference:

(a) and (b) remain as proposed.

(c) Montana Risk-based Corrective Action Guidance for Petroleum Releases (December 2023) (February 2024);

(d) through (5) remain as proposed.

 

AUTH:  75-10-702, 75-10-704, MCA

IMP:  75-10-702, 75-10-704, 75-10-711, MCA

 

17.56.507 ADOPTION BY REFERENCE (1) For purposes of this subchapter, the department adopts and incorporates by reference:

(a) remains as proposed.

(b) Montana Risk-Based Corrective Action Guidance for Petroleum Releases (RBCA)(December 2023) (February 2024);

(c) through (3) remain as proposed.

 

AUTH:  75-11-319, 75-11-505, MCA

IMP:  75-11-309, 75-11-505, MCA

 

17.56.608 ADOPTION BY REFERENCE (1) For purposes of this subchapter, the department adopts and incorporates by reference:

(a) and (b) remain as proposed.

(c) Montana Risk-Based Corrective Action Guidance for Petroleum Releases (RBCA) (December 2023) (February 2024); and

(d) through (3) remain as proposed.

 

AUTH: 75-11-319, 75-11-505, MCA

IMP: 75-11-309, 75-11-505, MCA

COMMENT 1: A commenter reviewed the VF calculations for the December 2023 RBSL calculations and found an error that may have been associated with the 2018 VF calculations. Using all the MADEP and EPA input parameters for C9-C18 Aliphatics as referenced for the other fractions that go into calculation of the apparent diffusivity (Da), the commenter got a Da of 0.00006 cm^2/s, instead of 0.000035 cm^2/s.  The difference in Da results in a VF of 14,752 m^3/kg, rather than 11,092 m^3/kg.  Using this VF in the RBSL calculations results in slightly different RBSLs for the three scenarios as follows:

 

Residential    286 mg/kg rounded to 290 mg/kg

Commercial    1556 mg/kg rounded to 1600 mg/kg

RESPONSE 1: The department appreciates the comment and agrees that the Massachusetts Department of Environmental Protection (MADEP) and the Environmental Protection Agency (EPA) input parameters for C9-C18 aliphatics result in an apparent diffusivity (Da) of .00006 cm^2/s, which results in changes to the residential, commercial, and construction worker RBSLs for C9-C18. The change in the C9-C18 aliphatic Da and resulting screening levels have been incorporated into the updated RBCA guide and the RBCA date modified to February 2024.

/s/ Nicholas Whitaker                                   /s/  Christopher Dorrington            

NICHOLAS WHITAKER                              CHRISTOPHER DORRINGTON

Rule Reviewer                                             Director

                                                                     Department of Environmental Quality