State of Illinois Rules and Regulations

Tiered Approach to Corrective Action (TACO)

Presented by

The Great Plains/Rocky Mountain Technical Outreach Services for Communities

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

Applicability of TACO

Applies to RCRA Closure and Corrective Action Site Remediation Program Leaking Underground Storage Tanks

(LUST)

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

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)

Choices for site owners

exclusion of exposure routes use area background concentrations as

remediation objectives three tiers for selecting remediation

objectives

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)

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

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)

Tier 1Use look-up tables

Tier 2For contaminants

which did not meetthe Tier 1 objectives

Tier 3For contaminants

that do not meet theTier 1 or Tier 2

remediationobjectives

Remediate toTier 1 Levels

(Institutional controlsmay be required)

No FurtherRemediation

Remediate to theTier 2 objective

No Further Remediation(Institutional controls may be required)

Are the Tier 3remediation objectives

achieved?

No FurtherRemediation

Are the Tier 1remediation

objectives met?

No Further Remediation(Institutional controls may be required)

Yes

No

Demonstrate andcalculate onsite andoffsite groundwater

impacts

Develop Tier 3objectives based onmethods other than

those allowed in Tier1 or Tier 2

No

No

Are the Tier 2objectives met?

Yes

No

Develop a Tier 2groundwaterremediation

objective

Yes

No

Yes

No

Remediate toobjectives

SiteCharacterization,

GroundwaterClassification andExposure Route

Evaluation

Risk only Exists if...

1.Contaminants exist2.Concentrations are high enough

3. There is a pathway

4. There are receptors

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

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

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

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

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 0.0000137 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 0.0000137 = 0.0001 or about 1 in 10,000

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.

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

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.

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.

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.