Transcript TACO - Kansas State University College of Engineering

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
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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
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Exposure Pathways
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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
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Institutional Controls
– restrict land use, prohibit drinking water wells
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Engineered Barriers
– parking lots, clean soil cover, clay or man-made
caps, barrier walls
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Control Activities
– groundwater pumping
» to prevent groundwater from contacting
contaminated soil or to prevent migration of
groundwater
Selecting Remediation Objectives
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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)
Si te
Cha ra cteri za ti on,
Groundwa ter
Cl a ssi fi ca ti on a nd
Exposure Route
Eva l ua ti on
Tier 1
Use look-up tables
Are the Tier 1
remediation
objectiv es met?
No
Remediate to
Tier 1 Lev els
No
(Institutional controls
may be required)
No Further
Remediation
Yes
No
Remediate to the
Tier 2 objectiv e
No Further Remediation
(Institutional controls may be required)
No
Tier 2
For contaminants
which did not meet
the Tier 1 objectives
Dev elop a Tier 2
groundwater
remediation
objectiv e
Demonstrate and
calculate onsite and
of f site groundwater
impacts
Are the Tier 2
objectiv es met?
Yes
No
No Further Remediation
(Institutional controls may be required)
Tier 3
For contaminants
that do not meet the
Tier 1 or Tier 2
remediation
objectives
Dev elop Tier 3
objectiv es based on
methods other than
those allowed in Tier
1 or Tier 2
Yes
Are the Tier 3
remediation objectiv es
achiev ed?
No
Remediate to
objectiv es
Yes
No Further
Remediation
Risk only Exists if...
3. There is a
pathway
1.Contaminants exist
2.Concentrations are
high enough
4. There are
receptors
Non-Cancer Risk Calculations
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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
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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
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– HI calculations for cumulative effects are only
done in Tiers 2 and 3
Cancer Risk Calculations
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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
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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
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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
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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.