1. September 18, 1998
State of Illinois Rules and Regulations Tiered Approach to Corrective Action (TACO)
Presented by
The Great Plains/Rocky Mountain Technical Outreach Services for Communities 1

2. Purpose of TACO
assure protection of human health and the environment and move away from “one size fits all” remediation objectives
reduce remediation costs
return more properties to productive use
hasten property redevelopment
site owners and operators decide how to best manage their sites by remediation, land use restrictions and/or physical barriers
within TACO guidelines

3. Applicability of TACO Applies to RCRA Closure and Corrective Action
Site Remediation Program
Leaking Underground Storage Tanks (LUST)

4. Limitations to TACO
does not provide procedures for characterizing a site
site characterization is important in the TACO process
does not consider any liability issues
any TACO procedure that delays response in an environmental emergency cannot be used
no ecological objectives
no enforcement (strictly voluntary)
remediation objectives developed for only a limited number of chemicals in Tier 1 tables

5. Major Premise of TACO Risk only exists if there are…
contaminants (toxic chemicals)
exposure routes (air, drinking water, soil contact, swimming)
receptors (people, plants or animals)

6. Choices for site owners
exclusion of exposure routes
use area background concentrations as remediation objectives
three tiers for selecting remediation objectives

7. Exposure Pathways Inhalation Ingestion of soil and groundwater
Absorption through skin (not addressed in TACO Tiers I and II, data too uncertain for risk assessment)

8. How to exclude pathways
Institutional Controls
restrict land use, prohibit drinking water wells
Engineered Barriers
parking lots, clean soil cover, clay or man-made caps, barrier walls
Control Activities
groundwater pumping
to prevent groundwater from contacting contaminated soil or to prevent migration of groundwater

9. Selecting Remediation Objectives
3 Tiers
Tier 1—lookup tables; sometimes used to screen for chemicals of concern
Tier 2— calculations using some site specific information as well as protective default values
Tier 3—models or equations different than presented in TACO; usually much more costly to develop (requires a specific review by Illinois Office of Chemical Safety)

11. Risk only Exists if... 3. There is a pathway 1.Contaminants exist
2.Concentrations are
high enough
4. There are
receptors

12. Non-Cancer Risk Calculations
risk is calculated by comparing theoretical RME exposure (E) to a reference dose that is considered a “safe” level of exposure for humans
the reference dose may be an oral reference dose (RfD) or inhalation reference concentration (RfC)
this is dose or concentration below which no adverse health effects are expected to occur because non-cancer causing chemicals have a threshold below which there appears to be no health effects
RME=reasonable maximum exposure

13. Non-Cancer Risk Calculations
risk from exposure to a specific chemical is expressed as a Hazard Quotient (HQ)
HQ = average dose (E) for a specified time period (daily) divided by the RfD or RfC for the same time period
For HQ less than 1, no adverse effects are expected

14. Non-Cancer Risk Calculations
if the contaminants affect the same target organ (liver, kidney, etc.) the HQ’s are added to form a Hazard Index (HI)
For HI less than 1, no adverse effects are expected from the combined contaminants
HI calculations for cumulative effects are only done in Tiers 2 and 3

15. Cancer Risk Calculations
risk is determined using a cancer potency slope factor (SF)
this is the upper bound cancer risk per unit of dose, the actual risk is between zero and the SF value
For TACO, dose is the chronic daily intake (CDI), intake averaged over a 70 year lifetime
multiplying the slope factor times the dose equals the increased risk of cancer

16. Cancer Risk Calculations
Example: oral cancer slope factor for benzo(a)pyrene is 7.3 per milligram per kilogram of body weight
ingesting an average of milligrams of benzo(a)pyrene per kilogram of body weight per day over a 70 year lifetime (the CDI) increases a person’s risk of cancer by: 7.3 X = or about 1 in 10,000

17. Cancer Risk Calculations
The chronic daily intake value illustrated in the example calculation is not the same as the soil or groundwater values in the TACO look-up tables. The look-up values were developed using risk calculations based on protective assumptions about ingestion rates and body weight and are expressed as milligrams of contaminant per kilogram of soil or liter of groundwater.

18. Risk Management
Goal – Reduce concentrations at point of exposure to acceptable levels by...
Source removal
removing contaminated soil from the site
Treatment and containment
treating and containing soil in monitored landfill
Elimination of exposure pathways
engineering and/or institutional controls

19. Questions and Answers
Are the non-carcinogen remediation objectives in the look-up tables set at levels that would make the HQ be at 1 or below? If this isn’t true, what is the reasoning for setting the objectives higher?
IEPA answer
The non-cancer ROs are calculated using a HQ of 1.0.

20. Questions and Answers
Table H in Appendix A lists chemicals whose Tier I Class I groundwater remediation objectives exceed the 1 in a million cancer risk concentration. Do the remediation objectives for these chemicals provide for a less than 1 in 10,000 cancer risk concentration?
IEPA answer
Table H is for cancer-causing chemicals in Class I groundwater only. If a Table H chemical is detected, then the assessment is elevated to Tier 2 and mixtures must be addressed. In Tier 2, mixtures of similar acting chemicals cannot exceed 1 in 10,000 cumulative risk.

21. Questions and Answers
If Tier II or Tier III calculations are used, do HQs at the point of exposure remain at or less than 1 and are cancer risks less than 1 in 10,000 or 1 in 1,000,000?
IEPA answer
For the purpose of calculating Remediation Objectives (ROs), HQ = 1.0 and Risk = 1 in 1,000,000 must be used. Tier 2 is only used to calculate RO, so that’s it for Tier 2. However, in Tier 3, greater hazard and risk can remain on site if safety can be proved. On no occasion will cancer risk greater than 1 in 10,000 be approved, with the possible exception of impractical remediation.