Tiered Approach to Corrective Action Objectives (TACO)
Fact Sheet 1: Introduction
What is TACO?
TACO is the Illinois EPA's method for developing remediation objectives for
contaminated soil and groundwater. These remediation objectives protect human health and
take into account site conditions and land use. Remediation objectives generated by TACO
are risk-based and site-specific.
How can TACO help me?
Previously, the Illinois EPA's Bureau of Land (BOL) used conservative
"one-size-fits-all" remediation objectives at nearly every site. Baseline
remediation objectives still exist, but other options also protective of human health have
TACO provides flexibility to site owners and operators in developing site-specific
remediation objectives. It's now the site owners and operators who decide how best to
manage their sites within TACO guidelines. However, this determination of site-specific
remediation objectives is subject to Illinois EPA review and approval.
By exercising these new choices, site owners and operators may reduce remediation
costs, return more sites to productive use, hasten property redevelopment, and still fully
comply with environmental laws and regulations.
Under TACO, a site may qualify to receive a No Further Remediation Letter acknowledging
the site owner or operator has satisfied the applicable BOL program requirements (See Fact Sheet 3).
Does TACO apply to my site?
Yes, you will use TACO if your site is regulated by one of the following BOL programs:
- Leaking Underground Storage Tank (LUST) Program
- Site Remediation Program
- RCRA Closure and Corrective Action
Are there any limitations to TACO?
TACO works in cooperation with the existing laws and regulations. If you participate in
one of the BOL programs listed above, TACO can only be used in conjunction with that
Because of the wide range of programs in which TACO can be applied, TACO itself does not
provide procedures for characterizing a site and the potential contamination at the site.
Such characterization is a critical step in the overall TACO process, but is program
Consistent with the regulations of other programs, and as approved by the Illinois EPA,
TACO may also be used to develop remediation objectives to protect surface waters,
sediments or ecological concerns.
Any TACO procedure that delays an owner's or operator's response during an
environmental emergency cannot be used.
TACO does not consider any person's liability, culpability, or legal, moral or ethical
responsibility to address a release of a regulated substance into the environment.
Can I use TACO to update my existing remediation objectives?
How does TACO work?
TACO offers site owners and operators the following choices:
- Exclusion of exposure routes
- Use of area background concentrations as screening tools or remediation objectives
- Three tiers for selecting remediation objectives.
Selection of an option or combination of options to use in developing remediation
objectives depends on the site-specific conditions and the site owner's or operator's
Exposure Route Evaluations
Human exposure route(s) can be excluded from further consideration provided the
requirements in Subpart C of TACO are met. The human exposure routes are: inhalation, soil
ingestion and groundwater ingestion (including migration to groundwater). Exclusion of an
exposure route will require an institutional control (See Fact Sheet 4 & Fact Sheet 8).
Determining Area Background
When contaminant concentrations do not exceed background concentrations for soil and/or
groundwater, evaluation under any of the other tiers may not be required. The procedures
for determining area background concentrations are contained in Subpart D of TACO (See Fact Sheet 9).
In Tier 1, the site owner or operator compares site sample analytical results to
baseline remediation objectives, contained in "look-up" tables. These objectives
are based on simple, conservative models (See Fact Sheet 6).
To complete a Tier 1 evaluation, the site owner or operator must know:
- The extent and concentrations of the contaminants of concern,
- The groundwater classification as defined in Illinois Administrative Code, Part 620, and
- The intended land use at the site (either residential or industrial/commercial).
If remediation objectives are based on an industrial/commercial land use, then an
institutional control prohibiting the property from residential use will be imposed.
A Tier 2 evaluation is not required for those contaminants of concern that meet the
Tier 1 remediation objectives (See Fact Sheet 7 & Fact Sheet 10).
A Tier 2 evaluation is also not required for exposure routes excluded under Subpart C
Under Tier 2, a site owner or operator considers:
- Data previously gathered for Tier 1,
- The physical and chemical properties of the contaminants,
- The site-specific soil and groundwater parameters (e.g., soil type, soil organic carbon
content, hydraulic conductivity), and
- The application of institutional controls and engineered barriers.
The additional Tier 2 information can allow for calculation of less stringent but
equivalently protective remediation objectives. These calculations are derived from simple
analytical models and standardized equations.
Site owners and operators can use Tier 3 to address those situations which they choose
not to handle or cannot handle under the first two tiers. These situations can range from
simple sites where physical barriers limit remediation, to complex sites where full-scale
risk assessments or alternative modeling are applied. A Tier 3 review and evaluation draws
on expertise beyond the immediate BOL project manager.
Do I have to use all three tiers?
No. The tier(s) you select to develop remediation objectives will depend on multiple
factors, including the actual amount and extent of contamination present, the cost of
remediating that contamination, and the cost of obtaining the information necessary to
conduct a Tier 2 or Tier 3 analysis. The tiers do not need to be used in sequence.
What happens next?
After remediation objectives are established using TACO procedures, a site owner or
- Reduce contaminant concentrations to meet established objectives through active
remediation (e.g., dig and haul, or treatment in place),
- Restrict exposure to contaminated soil or groundwater or both by using engineered
barriers or institutional controls,
- Take no action, if contaminant concentrations present at the site do not exceed
remediation objectives, or
- Use any combination of the options above.