Tier 1 Evaluation

Yes. There are two new tables (namely, Tables H and I) in the TACO regulations at 35 Illinois Administrative Code (35 Ill. Adm. Code) 742.Appendix B that contain Tier 1 soil gas and groundwater remediation objectives for the indoor inhalation exposure route. Within each table is a set of remediation objectives that apply to residential property use and a set of remediation objectives that apply to industrial/commercial property use. Volatile chemicals are the only contaminants of concern for the indoor inhalation exposure route.

The differences are:
 

1. There are two tables of Tier 1 remediation objectives (Tables H and I).

2. The sampling media involved are groundwater and/or soil gas.

3. There are no remediation objectives for the construction worker population.

4. There are no remediation objectives for Class II groundwater.

5. Averaging of sampling results is not allowed.

6. The provisions for similar acting chemicals do not apply.

The Tier 1 remediation objectives were developed for a slab-on-grade building. A slab-on-grade building is a more conservative scenario because there is less air available in the building to mix with the contamination. A building with a basement assumes there is mixing of the air between the basement and the first floor. The Tier 1 remediation objectives are applicable to both slab-on-grade buildings and buildings with basements.

Note: For full concrete floors with sumps, site evaluators may not use the J&E model under Tier 1 and Tier 2 and must either exclude the pathway, show that the soil gas concentrations meet the remediation objectives developed from Equations J&E1 and J&E2, meet building control technology requirements, or proceed to Tier 3.

Remediation objectives are not provided for the construction worker population because this receptor group is not at risk from indoor inhalation exposure. The exposure duration for indoor construction in almost all cases is less than the exposure duration for the residents and commercial workers. Thus, the protection of these two receptors will ensure protection of the construction worker during the period of indoor construction.

There are no Class II groundwater remediation objectives because the determination as to whether the groundwater meets potable resource groundwater standards is not relevant for the indoor inhalation exposure route. The groundwater as a mode of transport of contaminant vapors is the concern, not its potability.

For the indoor inhalation exposure route, the parameter values used to calculate the industrial/commercial remediation objectives differ from the residential remediation objectives in three ways: exposure duration, building size, and air exchange rate.

Yes. As with the other exposure routes, soil gas and/or groundwater remediation objective determinations relying on an industrial/commercial scenario require the use of institutional controls in accordance with 35 Ill. Adm. Code 742.Subpart J. If industrial/commercial remediation objectives are used to demonstrate compliance, the No Further Remediation Letter issued by the Illinois EPA (which must be recorded in the office of the recorder or the registrar of titles of the county in which the property is located) will carry with it the requirement that the use of the property is limited to industrial/commercial purposes.

Appendix B.Table H must be used when any soil or groundwater contamination is located five feet or less, vertically or horizontally, from the existing or potential building or associated man-made pathway. The soil gas and groundwater remediation objectives listed in Appendix B.Table H are based upon diffusion and advection, both of which apply in this scenario. Appendix B.Table H applies only when the existing or potential building has a full concrete slab-on-grade or a full concrete basement floor and walls. Soil gas or groundwater remediation objective determinations relying on Appendix B.Table H require the use of institutional controls—namely, that the existing or potential building has a full concrete slab-on-grade or a full concrete basement floor and walls.

Appendix B.Table I may be used only when all soil and groundwater contamination is located more than five feet, vertically and horizontally, from the existing or potential building or associated man-made pathway. The soil gas and groundwater remediation objectives listed in Appendix B.Table I are based upon diffusion only, which applies in this scenario. Appendix B.Table I applies only when the existing or potential building has a full concrete slab-on-grade or a full concrete basement floor and walls. Soil gas and groundwater remediation objective determinations relying on Appendix B.Table I require the use of institutional controls—namely, (1) it is required that no soil or groundwater contamination exceeding the most stringent Tier 1 remediation objectives be present within five feet (in the advection zone) of an existing or potential building or associated man-made pathway, and (2) it is required that the existing or potential building has a full concrete slab-on-grade or a full concrete basement floor and walls. As an alternative to using Appendix B.Table I, it is permissible to use Appendix B.Table H.

In order to use Appendix B.Table I, it must be demonstrated that all soil and groundwater located five feet or less, in the advection zone, from the existing or potential building or man-made pathway meets the most stringent Tier 1 remediation objectives listed in Appendix B.Table A and the Tier 1 remediation objectives for Class I groundwater listed in Appendix B.Table E, respectively.

The No Further Remediation Letter will require that the existing or potential building has a full concrete slab-on-grade or a full concrete basement floor and walls.

The No Further Remediation Letter will require that (1) no soil or groundwater contamination exceeding the most stringent Tier 1 remediation objectives be present within five feet, vertically or horizontally, of an existing or potential building or associated man-made pathway, and (2) the existing or potential building has a full concrete slab-on-grade or a full concrete basement floor and walls.

Yes. As an alternative to using Appendix B.Table I, it is permissible to use Appendix B.Table H. However, the use of Table H still carries with it an institutional control—namely, that the existing or potential building has a full concrete slab-on-grade or a full concrete basement floor and walls.

Each building would need to be addressed. There would not be a representative building.

No. Each area of contamination and existing or potential building must be addressed and concentrations of contaminants compared to the remediation objectives at Appendix B.Table H or I, as appropriate.

It depends upon which Tier 1 table is used:

• If Appendix B.Table H is used, compliance is determined by meeting either the soil gas remediation objectives or the groundwater remediation objectives.

• If Appendix B.Table I is used, compliance is determined by meeting both the soil gas remediation objectives and the groundwater remediation objectives.

The remediation objectives in Appendix B.Table I are considerably higher than those in Appendix B.Table H, but, in order to use the higher remediation objectives, the property owner must agree that at least five feet of uncontaminated soil and groundwater will be maintained. The reason for this is to ensure there are stable conditions on the property to keep vapors from getting into a building or associated man-made pathway by way of advection. A five-foot clean building zone of influence must be maintained for existing and potential buildings and associated man-made pathways so that advective transport of vapors into the building does not occur.

In addition, because the remediation objectives in Appendix B.Table I are considerably higher than those in Appendix B.Table H—hence, less conservative—more lines of evidence are required. As such, then, compliance with both the soil gas remediation objectives and the groundwater remediation objectives is required.

No. If the use of Appendix B.Table H is applicable, compliance may be demonstrated by meeting either the soil gas remediation objectives or the groundwater remediation objectives.

Yes, if soil gas samples were collected, if the laboratory analytical results of soil gas sampling meet the soil gas remediation objectives at Appendix B.Table H, and if no other pathways are a concern, then the site is eligible for an NFR Letter. This is because soil gas data is a more reliable indicator than groundwater data for predicting exposure from the indoor inhalation exposure route. Although there are no existing buildings, potential future buildings—on-site and off-site—are a factor when considering the indoor inhalation exposure route.

No. If using Appendix B.Table I, compliance is determined by meeting both the soil gas and groundwater remediation objectives. If groundwater was not encountered, Appendix B.Table I cannot be used. Either the remediation objectives at Appendix B.Table H may be used, the proposal may be submitted under a Tier 3 evaluation, or pathway exclusion in accordance with 35 Ill. Adm. Code 742.312 may be used.

Yes. Proposals to use soil data must be submitted under a Tier 3 evaluation.

No. Averaging is not allowed.

For volatile chemicals not listed in Appendix B.Table H or I, site-specific remediation objectives may be requested from the Illinois EPA, or site-specific remediation objectives may be proposed under a Tier 3 evaluation in accordance with 35 Ill. Adm. Code 742.Subpart I.

Yes. A Tier 1 or Tier 2 evaluation may be used so long as the samples are not collected sub-slab. Proposals to use sub-slab soil gas sampling data must be submitted under a Tier 3 evaluation.

Further action is not required so long as compliance with the remediation objectives is demonstrated for all applicable exposure routes and any required institutional controls, if any, are in place.

As with the other exposure routes, options available include Tier 2 evaluation, Tier 3 evaluation, exposure pathway exclusion, and remediation.    

You may contact the project manager on-call for your remediation program at 217-524-3300 for further information regarding vapor intrusion.

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

June 2013