New York State Department of Environmental Conservation
Division of Hazardous Substances Regulation
Technical Administrative
Guidance Memorandum 4003
Cleanup Guideline for Soils Contaminated
with Radioactive Materials
Date: September 14, 1993
I. PURPOSE
This TAGM describes the policy and procedure to be followed by Division of
Hazardous Substances Regulation, Bureau of Radiation staff in evaluating
cleanup plans for soils contaminated with radioactive materials.
The purpose of this cleanup guideline is to provide for
(1) protection of public health and the environment,
and
(2) consistency in implementing remedial actions at
sites contaminated with radioactive materials.
II. POLICY
The total effective dose equivalent to the maximally-exposed individual of
the general public, from radioactive material remaining at a site after
cleanup, shall be as low as reasonably achievable and less than 10 mrem
above that received from background levels of radiation in any one
year.
The radiation dose received from an exposure to soils contaminated by
radionuclides will strongly depend on the time of exposure and pathways by
which the radionuclides or their decay products can come in contact with
an individual. For this reason, the estimated annual dose resulting from
exposure to any residual radionuclides in the contaminated area is the
basis for establishing site-specific cleanup criteria. The dose estimate
is to be based on the contaminating radionuclides, but not on background
concentrations of any radionuclides that may be at the site. Background
radiation refers to
(1) local area concentrations of naturally occurring radionuclides,
(2) cosmic radiation, and
(3) radionuclides of anthropogenic origin which have been regionally
dispersed and are present at low concentrations (such as fallout from
the testing of nuclear weapons).
III. PROCEDURE
The process of determining the appropriate cleanup requirements will
generally involve measurements of radioactivity at the site, laboratory
analysis of soil samples for concentrations of radioactive materials,
modeling of expected doses based on the measurements and analyses
performed, and evaluation of site remediation alternatives. The
modeling will require determination of site characteristics critical to
the migration of radionuclides, and will need to be referenced to
reasonable scenarios for current and plausible future uses of the land.
Consideration of the time period during which the radioactive material is
expected to persist at the site will be important In the selection of
scenarios for land use. The estimated dose limit of 10 mrem/year refers
to land released for unrestricted use. If unrestricted use scenario
calculations result in dose estimates that are greater than 10 mrem/year,
it may be necessary to invoke institutional controls and/or deed
restrictions so that actual doses from allowed uses are not likely to
exceed 10 mrem/year.
A. Dose Analysis Methods
Analysis methods used must be acceptable to the
DEC Division of Hazardous Substances Regulation,
Bureau of Radiation. The methods used should be
appropriate to the complexity of the contaminated
site and to the potential for harm. The primary
criterion is that the analysis yield conservative
results, i.e., the results of the analysis, must
predict doses no lower than are likely to actually
occur. This principle should be applied to both
the analysis methods and to the site-specific
inputs required for any models used in the
evaluation.
All reasonable pathways of exposure shall be
considered when determining the estimated dose to
individuals. Approval of the procedures used in,
and the interpretation of, each step of the analysis
must be obtained from NYSDEC. The steps to be
followed are:
1. Perform a site assessment. This involves
determining exposure levels at the site, the
extent of the contamination, and
concentrations of radionuclides in the
contaminated areas. Care must be taken that
the appropriate instrumentation Is used for
detecting radiation at the site (gamma, beta,
alpha, or neutrons). Concentration profiles
as a function of depth in the soil should be
determined. Where possible, the chemical and
physical forms of the radionuclides should be
determined. It should be possible from this
data to characterize the locations and
concentrations of all radionuclides which can
significantly contribute to the dose
potentially received from the site. When
modeling the site characteristics, and the
migration of radionuclides within and from
the site, it will be necessary to show that
the site parameters used will cause the dose
estimates to be conservative.
During on-site investigation, staff and
contractors must abide by all appropriate
requirements and Departmental policies
related to personal protection and by any
applicable health and safety plans. At sites
where non-radioactive contaminants are known
to be present, staff should contact
appropriate persons from other involved
Bureaus, Divisions, or Agencies as to health
and safety and coordination of activities.
If non-radioactive chemical contamination
(where not previously known) is suspected at
a site, be it by observation and/or analysis,
the appropriate regulatory staff should be
notified.
2. Provide a review of current land use and a
rationale for potential use of the site. Use
this information to estimate possible
occupancies for the site and review how
different plausible uses of the site can
contribute to exposures. Keep in mind that
the maximally exposed individual of concern
is a member of the general public not
associated with the use of radioactive
materials. This is usually a resident, but
may also be a worker at a business not
licensed to used radioactive materials.
Radiation exposure to workers at facilities
with radioactive materials is regulated by
the licensing agency under the New York State
Industrial Code (New York State Department of
Labor) or the New York State Sanitary Code
(New York State Department of Health).
3. Analyze all reasonable pathways. Only when
pathways can be shown to contribute
insignificantly to the dose, can they be
eliminated from further consideration.
Pathways that must be considered are:
(a) Doses from direct exposure to radiation
emitted from the contaminated soil and,
where applicable, from contaminated
ground or surface water.
(b) Doses from internal exposure - including
inhalation of contaminated dust
(including radon progeny if present),
ingestion of contaminated soil,
ingestion of food raised on contaminated
soil, and Ingestion of drinking water
(both aquifer and surface waters) or
contaminants from irrigation water.
B. Analysis of Remediation Alternatives
Remediation techniques should be evaluated for
effectiveness at-meeting the 10 mrem/year dose
limit, at keeping radiation doses as low as
reasonably achievable, and at minimizing the
creation of radioactive waste. If site
remediation is needed to achieve the 10 mrem/year
dose limit, it will be necessary to prepare a work
plan that is acceptable to NYSDEC and other
cognizant agencies (NYSDOL, NYSDOH).
Acceptable remediation procedures might Include:
(1) Removal of contaminated soil for disposal at
a licensed facility.
(2) Isolation of contamination such as covering
the contamination with clean soil. This
technique may be acceptable for short-lived
isotopes assuming that restrictions to land
use are used until the radionuclides no
longer pose a threat.
(3) Other remediation techniques, if applicable,
considered and approved on a case-by-case
basis.
Remediation alternatives should be evaluated for exposures
which will occur to workers, staff and the general public
during corrective action/remedial activities. Appropriate
health and safety plans should be prepared or referenced
for construction and monitoring activities (see also
item C.(1) below).
Remedial alternatives should also be evaluated for the
potential to cause significant damage to sensitive
environmental or historical areas (see also
item C.(2) below).
Special consideration must be given to sites contaminated
with non-radioactive chemicals as to remedial alternatives
and disposition of the resultant hazardous or "mixed"
waste.
Before a site can be released for unrestricted use it will
be necessary to confirm that the approved work plan has
been completed successfully. This confirmation will
include measuring exposure rates and/or measurements of
residual radionuclide concentrations. The final modeling
step will need to show that release of the site, with any
radionuclide concentrations still remaining after
remediation, will not cause the dose limit to be exceeded.
C. Alternative Procedures
There may be incidents/situations whereby:
(1) the health and safety of individuals involved in a
cleanup may necessitate acceptance of a dose greater
than 10 mrem/year to the maximally exposed individual,
or
(2) the cleanup may cause irreversible destruction or loss
of environmental habitat.
In such situations, remedial options will be evaluated on a
case-by-case basis. Final decisions will be made by the
Chief, Bureau of Radiation.
_______________________________
[NOTE : emphasis added]
|