Institutional Controls Associated with the Indoor Inhalation Exposure Route

This fact sheet identifies the institutional controls that are specific to the indoor inhalation exposure route. The other institutional controls available in TACO for land use restrictions and engineered barriers may still be used, though neither highway authority agreements nor engineered barriers will apply to the indoor inhalation exposure route. Land use restrictions based upon property use - either residential or industrial/commercial - may be used for the indoor inhalation exposure route.

NOTE: 35 Ill. Adm. Code 742.1015(j) prohibits the use of a groundwater ordinance to exclude from consideration the indoor inhalation exposure route. This is because an ordinance restricting the source of drinking water would not protect the enclosed air space of a building from the migration of contaminants in the groundwater.

Because of assumptions used in the modified J & E model to calculate remediation objectives, all No Further Remediation Letters that depend on the attenuation factor calculations in the J&E Model will contain an institutional control stating that existing or potential buildings located over the current extent of contamination must have full concrete slab-on-grade floors or full concrete basement and walls with no sumps. 

Use of Appendix B.Table I

An institutional control must be placed on the property when the Tier 1 remediation objectives at 35 Ill. Adm. Code 742.Appendix B.Table I are used to demonstrate compliance. In accordance with 35 Ill. Adm. Code 742.1000(a)(7), an institutional control is required because the remediation objectives in Table I are based upon a diffusion only mode of contaminant transport for the indoor inhalation exposure route. The institutional control would require that no soil or groundwater contamination exceeding the most stringent Tier 1 remediation objectives be present within 5 feet of an existing or potential building or associated man-made pathway.

The No Further Remediation Letter will require that any remaining soil or groundwater contamination be located more than five feet from an existing or potential building or associated man-made pathway that connects to an existing or potential building.

Exposure Route Exclusion

When using exposure route exclusion (35 Ill. Adm. Code 742.312), one of the following three new institutional controls for the indoor inhalation exposure route must be used in addition to satisfying the requirements of 35 Ill. Adm. Code 742.300 and 742.305:

  1. A land use restriction prohibiting a building or associated man-made pathway above the contaminated soil gas or groundwater exceeding Tier 1 objectives, provided that there is also no soil or groundwater contamination exceeding Tier 1 objectives located five feet or less, horizontally, from any existing or potential building or associated man-made pathway. (The indoor inhalation exposure route is incomplete if no building exists into which contaminants can migrate).

    The No Further Remediation Letter will require that no building or man-made pathway shall be constructed or occupied in the area depicted on the site map.

  2. Use of an approved building control technology (BCT) meeting Subpart L, including sub-slab depressurization, sub-membrane depressurization, membrane barriers, or vented raised floors. 35 Ill. Adm. Code 742.1000(a)(8) requires the use of institutional controls whenever remediation objectives are based on a BCT. These institutional controls also stipulate the notification and protective measures to take in the event of BCT inoperability. Maintenance requirements will also be stipulated as part of the institutional control depending on the technology used.

    The No Further Remediation Letter will require that no building shall be occupied in the area depicted on the site map unless there is or will be (in the case of a future building) a BCT meeting the requirements of 35 Ill. Adm. Code 742.Subpart L.

  3. For sites using a demonstration of active biodegradation for benzene, toluene, ethylbenzene, and total xylenes, maintenance requirements to protect the area to allow ongoing active biodegradation to occur.

    The No Further Remediation Letter will require that a layer of X feet of soil shall be maintained. The number of feet will be specific to the demonstration and the soil may be no more contaminated than that present at the time of the demonstration of biodegradation in the area depicted on the site map.

This fact sheet is for general information only and is not intended to replace, interpret, or modify laws, rules, or regulations.

June 2013