Tiered Approach to Corrective Action Objectives (TACO)
Fact Sheet 6: Tier 1
What is Tier 1?
A Tier 1 evaluation compares the concentrations of contaminants of concern detected at
a site to baseline remediation objectives. Tier 1 enables site owners to choose between
residential and industrial/commercial use of a site; however, institutional controls are
required whenever remediation objectives are based on an industrial/commercial land use.
Tier 1 provides the following pre-calculated "Look Up" Tables:
Residential Soil Remediation Objectives (Appendix B, Table A)
Industrial/Commercial Soil Remediation Objectives (Appendix B, Table B)
Groundwater Remediation Objectives (Appendix B, Table E)
pH specific Soil Remediation Objectives for Inorganics and Ionizing
Organics for the Migration to Groundwater Portion of the Groundwater Ingestion Route
(Appendix B, Tables C & D)
It is important to check the footnotes in the Tier 1 tables. For instance,
footnote "e" means the chemical is a carcinogen; footnote "b" means
the chemical is not a carcinogen. Footnote "m" means the objective is
expressed as a TCLP or SPLP value.
When do I use Tier 1?
After you've completed a site investigation or characterization, you should compare
your sample results to the Tier 1 "Look Up" Tables. Tier 1 can serve as a
screening tool, or can be used as your remediation objectives.
Note: Before beginning a Tier 1 analysis, you may want to consider a pathway exclusion
evaluation (See Fact Sheet 8).
How do I use Tier 1?
For soil, a Tier 1 remediation objective is obtained from the "Look Up"
Tables for:
Of the three exposure routes, the most restrictive becomes your site's soil objective
-- unless that particular route has been excluded from further consideration under the
requirements of 742, Subpart C (See Fact Sheet 8).
For groundwater, the Tier 1 remediation objectives for your site correspond to the
site's groundwater classification, either Class I or Class II. If no site-specific
information is available, then the groundwater at the site is assumed to be Class I.
A contaminant is not of concern if the concentration of the contaminant is below
the Tier 1 objective for the most restrictive route.
Is my site Residential or Industrial/ Commercial?
"Residential Property" is any real property that is used for habitation by
individuals or properties where children have the opportunity for exposure to contaminants
through ingestion or inhalation at educational facilities, health care facilities, child
care facilities or playgrounds.
"Industrial/Commercial Property" is any real property that does not meet the
definition of residential property, conservation property or agricultural property.
Whenever using the industrial/commercial scenario, the Construction Worker Scenario
must also be evaluated. If the construction worker objectives are more stringent than the
industrial/commercial objectives, the construction worker objectives apply.
The construction worker scenario is designed for workers performing demolition, earth
moving or construction activities, as well as routine and emergency utility installation
or repair.
Sites that meet Tier 1 residential remediation objectives do not need to
be evaluated for the construction worker population.
What if my contaminant is not listed in the Tier 1 tables?
For contaminants not listed in the Tier 1 tables, you may request site-specific soil
and groundwater remediation objectives from the BOL, or you can propose remediation
objectives for BOL approval.
How many analytical samples do I need to collect for a Tier 1 evaluation? What do I
analyze these samples for?
Site investigation and characterization requirements are program- and site-specific.
Any averaging and/or compositing used in such an investigation must be consistent with the
approach described in Section 742.225 (See Fact Sheet 10)
For Leaking Underground Storage Tank (LUST) sites, the indicator contaminants for
unleaded gasoline are benzene, ethylbenzene, toluene and xylene.
For Site Remediation Program (SRP) sites, either a focused or comprehensive
determination can be requested. A focused determination is designed for only a limited
number of chemical(s). A comprehensive determination is for all recognized environmental
conditions and their related contaminants of concern. A comprehensive determination
usually requires sampling analyses for volatiles, semi-volatiles, and metals, but may also
include agrichemicals, PCBs, and dioxins (See Fact
Sheet 12).
For RCRA sites, the sampling analysis is usually determined by the constituents of the
wastes managed in the RCRA unit and their degradation products. However, in certain cases,
expanded lists of hazardous constituents must also be analyzed for.
What does it mean if my site's sample results are all below the Tier 1 values?
If you have met the Tier 1 values as well as all program specific requirements,
including proper characterization of the site, then you qualify to receive a No Further
Remediation letter (See Fact Sheet 3).
Tier 1 Example - Application of the Tier 1 Residential Table |
In this example, the groundwater classification at the residential
site is Class I. Assume no routes are excluded from consideration, pursuant to 742,
Subpart C. The benzene and benzo(a)pyrene soil and groundwater remediation objectives
obtained from Part 742, Appendix B, Tables A and E are:
|
Ingestion
(mg/kg) |
Inhalation
(mg/kg) |
Migration to
Groundwater
(mg/kg) |
Groundwater
(mg/L) |
Benzene |
22 |
0.8 |
0.03 |
0.005 |
Benzo(a)Pyrene |
0.09 |
--- |
8 |
0.002 |
The benzene soil remediation objective is 0.03 mg/kg, which is the
most restrictive soil remediation objective. The groundwater remediation objective
is 0.005 mg/L, due to the groundwater classification.
The benzo(a)pyrene soil remediation objective is 0.09 mg/kg, which
is the most restrictive soil remediation objective. For contaminants such as
benzo(a)pyrene, under Tier 1, the lack of an inhalation remediation objectives is not
likely to underestimate risks. The benzo(a)pyrene groundwater remediation objective
is 0.002 mg/L, due to the groundwater classification.
In another example, assume the ingestion of groundwater is excluded
from consideration, pursuant to Subpart C. The benzene remediation objectives from
Appendix B, Table C for Industrial/Commercial and Construction Worker Populations are: 200
mg/kg Ind/Com Ingestion, 4,300 mg/kg Construction Ingestion, 1.5 mg/kg Ind/Com Inhalation,
and 1.7 mg/kg Construction Inhalation. The benzene soil remediation objective at this
industrial/commercial site is 1.5 mg/kg because it is the most restrictive. |
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