R 299.5723 Rescinded.

R 299.5724 Generic Cleanup Criteria For Soil Based On Indoor Inhalation Of Hazardous Substance Vapors Volatilized From Soil.

Rule 724.

          (1)  Indoor inhalation of hazardous substance vapors volatilizing to indoor air from soil shall be considered a reasonable and relevant exposure pathway only for hazardous substances that have a Henry's law constant greater than or equal to 0.00001 atm-m³/mole.

          (2)  Except as provided in subrule (1)  of this rule, if any of the following conditions exist, the generic criteria developed pursuant to this rule shall not apply and a site-specific evaluation of indoor inhalation risks shall be conducted:

                    (a)  There is a structure present or planned to be constructed at the facility which does not have a concrete block or poured concrete floor and walls.

                    (b)  There is a sump present that is not completely isolated from the surrounding soil by its materials of construction.

          (3)  Soil cleanup criteria based on indoor inhalation of volatile emissions from hazardous substances in soil shall be called soil volatilization indoor air inhalation criteria ("SVIIC").  The SVIIC is determined by the following series of calculations, except as provided in R 299.5734(3):

equation for Carcinogenic effects:

where,

Equation for Noncarcinogenic effects:

where,

The contaminant vapor concentration in the building indoor air is written as:

where,

The vapor-phase contaminant concentration at the source for soil is written as:

where,         

The intrusion rate of hazardous substance vapors into buildings is predicted using an analytical solution which couples both diffusive and convective transport of vapors emanating from subsurface soil into enclosed spaces.  An attenuation coefficient (a)  is calculated that is expressed as the ratio of building indoor air concentration to the vapor-phase concentration at the source.  Values of a are calculated assuming infinite source conditions.  For infinite source conditions a is written as follows:

where,

The effective diffusion coefficient calculation for the vadose zone  ()  is written as:

where,

          (4)  Facility-specific measurements of the following parameters may be substituted individually for the generic assumptions and still allow the facility to satisfy the categorical criteria in section 20120a(1)(a)  to (e)  of the act:

                              (a)  Dry soil bulk density.

                              (b)  Fraction of organic carbon in soil.

                              (c)  Soil vapor permeability.

                                        (d)  Temperature adjustment factor for Henry's law constant.

Facility-specific measurements shall be based on representative characterization.  documentation of all facility specific values shall be provided in the remedial action plan.

          (5)  The department may approve of methods to demonstrate compliance with criteria for this exposure pathway if those methods are more representative of in-situ conditions at the facility.  Methods acceptable to the department may include, but are not limited to, evaluation of representative soil gas concentrations.

           (6)  A site-specific SVIIC may be developed for remedial action plans prepared pursuant to section 20120a(2)  of the act that is based on demonstration of compliance with 1974 PA 154, MCL 408.1001 et seq. and the rules promulgated pursuant to that act.  This subrule shall apply only when all of the following conditions are satisfied:

                    (a)  The risk being evaluated results from inhalation by workers of hazardous substances in indoor air within an active workplace that is regulated by 1974 PA 154, MCL 408.1001 et seq. and the rules promulgated pursuant to that act.

                    (b)  The exposure to hazardous substances from environmental contamination is a portion of the exposure to which workers are otherwise subject from process-related sources of the same hazardous substance.

                    (c)  The risk to the non-worker population, if any, from inhalation of indoor air at the property has been evaluated using generic residential GVIIC or a site-specific evaluation has been conducted for the non-worker population according to methods acceptable to the department, and the risk is not unacceptable on the basis of the risk management objectives set forth in section 20120a of the act.