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11 The role of the proposed imerim rcmedial action Is to
18 reduce potenGal future threats to human hn)th and the
19 environmem associated with hazardous substances in the
20 facility and the underlying soils. Existing contaminated
21 grourdwater underlying the 221-U Facility is being
22 addressed under a separate CERt'i.A action associated
23 with the 200-UP-1 Operable Unit. Cleanup levels
24 Identified as a result of this Proposed Plan will be
25 protective of grotadwater and the Columbia River.
DOE!RG2001-29
Draft D RedlinelS trikeout i3
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26 SUMMARY OF S1TE RISK
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The Tri-Parties believe that the preferred altereative, or
one of the other active measures presented in this
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Proposed Plan, is necessary to protect human health or
welfare and the environment from actual or threatened
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31 releases of hazardous substances into the environment. 83
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Such a release, or threat of release, may present an
imminent and substantial endangerment to public
health, welfare, or the environment.
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35 Human Health Risk
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36 In the Superfund ptocess, potential risks to human 90
37 health and the environment are evaluated to determine 91
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If signi8cant risks exist due to site contaminants.
Excess cancer risks are expressed exponentially as
1 x 10'4, 1 x IT. and I x 10+ (i.e., one in ten
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41 thousand, one in one hundred thousand, one in a
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million, respectively). This means that for a I x 10'
risk. If 10,000 people were exposed to a contaminant
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of concern for some period of time, one additional
person may be diagnosed with cancer In his/her
lifetime. Remedial actions generally are not required
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at risk levels between 1 x 10' and ) x IOs unless there 100
are other considerations such as adverse environmental 101
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impacts, the potential for future migration, ori02
uncertainty regarding future land use.
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Contamination existing at the 221-U Facility poses the
potential for increased human health risk to future site
users. The level of potential health risk posed by
contaminants currently present at the facility differs
depending on the future site use. Two reasonable
maximum exposure scenarios were evaluated for
the221-U Facility: an industrial scenario and an
Inadvertent intruder scenario. In both scenarios, future
users could be exposed to contaminants in the facility
through external exposure to radiation and ingestion or
inhalation of particulate released from the facility.
Air, biota. and groundwater would be secondary media
of concern because the likelihood of these media
becoming contaminated Is less andlor the magnitude of
their potential comamination Is small.
In general, the assessment of risk is based on a limited
data aet. Uncertainties exist with both the contaminants
Identified for the 221-U Facility and the concentrations
of the contaminantss. The results of sampling of existing
areas of contamination may not be representative of
specific conditions throughout the facility. '1Uerefore,
the evaluations of risks that are presented could be
either underestimated or overestimated.
Industrial Scenario. Based on risk assessment results
for contaminants and concentrations evaluated in the
final feasibility study, the contaminants at the 221-U
Facility providing the highest contribution to potential
increased human health risks include various
radionuclides ( americium-241, eesium-137, cobalt-60,
europium-154, nemunium -^37. plutonium-2391240,
and-atronlium-90 . and utanium iconmesl and heavy
metals ( lead, mercury, and uranium). The total
Incremental cancer risk (ICR) of the radionuclides at
eoncentrations measured at the 221-U Facility is
greater than 10.
Concentrations and risk ranges are presented In Table 1.
Environmental media and waste material contaminated
by these constituents inciude concrete, metallic waste,
eontaincriud materials, soil, and miscellaneous debris
currently contained within the structure of the 221-U
Facility. iGN!e-f " : 1
iwteJ--l^autl -iat
pi sed sheps.
Inadvertent Intruder Scenario. The inadvertent
intruder scenario assumes that unacceptable hazards to
an intruder could occur from exposure to contents of
the 221-U Facility after the loss of Institutional
controls ( e.g.. access restrictions). In this scenario.
institutional control Is conservatively assumed to be
lost aqrr-100 years after cbsure of dispocal faciliti^w
containina radinactivc waac . Consistent with U.S.
Nuclear Regulatory Commission regulations. the