(1)
Objective. The principal objective of the Candidate
Site Identification Report is to identify at least two, but not more than five,
candidate sites that have a high likelihood of satisfying the requirements of
310 CMR
43.41(1). In addition, the
report is intended to present the results of a preliminary characterization of
the meteorology, surface and ground water, geology, tectonics, geomechanics,
air quality, ecology, land use, cultural resources and social and economic
characteristics of each such candidate site; a description of the procedure
used to identify the candidate sites based on such preliminary
characterization; and draft plans for detailed site characterization of each
candidate site. Installation of ground water wells is not required for sites
which are not selected as candidate sites. The purpose of 310 CMR 43.60 is to
provide guidance on how, at a minimum, the requirements for technically
superior sites should be interpreted and applied in the preparation of this
report.
(2)
Data
Collection and Evaluation Protocols.
(a) The Candidate Site Identification report
should be prepared on the basis of the types of data sources described at
310 CMR
43.40 and
43.50,
additional published and unpublished data and maps and additional field data
obtained and technical analysis carried out during this or previous phases of
the siting process.
(b) All
exclusion, conditional consideration and, in the Board's discretion, preference
criteria should be applied and evaluated in the preparation of the Candidate
Site Identification Report.
(c) The
Board may continue to use the GIS for data analysis and comparative evaluations
of siting factors. Map scales should be employed, if reasonably available,
which most accurately depict the characteristic being evaluated. Mapping
accuracy should be commensurate with the map scales employed and the accuracy
of the data sets.
(d) Computer
modeling may be used in the site evaluation process for those factors for which
computer models are determined to be reliable and valid in prediction,
including, but not limited to, generally accepted performance assessment,
hydrogeologic and hydraulic models. It is not required that the computer code
be specifically developed for low-level radioactive waste management siting
provided the code is applicable to the site/facility and the parameter being
investigated. Where a code is not generally accepted a determination of
reliability and validity should include, but not be limited to the following
factors:
1. The model should have supporting
documentation that establishes its ability to represent the factors under
investigation and any history of its previous applications;
2. The set of equations representing the
factor under investigation must be theoretically proven and must be well
documented;
3. The numerical
solutions must be based on sound mathematical principles and supported by
verification and checking techniques;
4. The model must be calibrated against site
specific field data developed in accordance with
310 CMR 43.00; and
5. A sensitivity analysis should be conducted
to measure the model's response to changes in the values assigned to major
parameters, specified error tolerances and numerically assigned space and time
discretizations.
(e)
Conceptual model uncertainty should be addressed by identifying a broad range
of conceptual models, and using each in performance assessments. Revisions of
these models should be made by accounting for progressive data collected that
can be used to eliminate some models from consideration. Uncertainties about
the future of the site should be addressed by projecting alternative future
site conditions. Parameter uncertainty may be addressed by using Monte Carlo
analysis in combination with other techniques (such as Latin Hypercube
Sampling) to reduce the computation effort.
(f) Despite the efforts to validate models,
substantial uncertainties are likely to be encountered in making predictions.
Sole reliance on these numerical predictions to determine compliance may not be
appropriate; the Board may chose to supplement such predictions with
qualitative judgments as well.
(g)
Any ground water wells that are installed to collect data and evaluate the
extent to which the site meets the criteria for a superior site should be
installed and maintained in accordance with Department guidance document,
standard Reference for Monitoring Wells, WSC-31-91.
(h) In the absence of specific Department
policy/guidance documents, the analysis of hydraulic factors necessary to
calculate saturated and unsaturated groundwater flow paths including, without
limitation, horizontal gradient, hydraulic conductivity, transmissivity,
hydraulic head, porosity, geometry, boundary conditions and the time of travel
of the flow shall be conducted in accordance with generally accepted standards,
principles and protocols, including, without limitation, a pump test performed
in accordance with generally accepted methods, if appropriate. Where an
evaluation of these parameters is dependent upon measurement of soil or water
samples the measurement may be done by direct measurement in situ or by the
testing of laboratory samples. The use of both methods is highly desirable, but
more extensive investigations may be deferred to the Detailed Site
Characterization stage.
(i) The
site characterization activities should be consistent with the guidance set
forth at
310
CMR 43.42(1) to the extent
that the detail set forth in said guidance is consistent with and applicable to
the scope of a site investigation necessary to conduct a valid preliminary site
characterization. The Board should indicate in its report where further site
characterizations are to be deferred to the Detailed Site Characterization
stage. In addition to these guidelines the further guidelines of
310
CMR 43.61 and
43.62
should be applied.
(j) Where the
Board determines that adequate data exists and/or reasonable assumptions can be
made on site characteristics, waste characterization and probable facility
design, a preliminary performance assessment on likely sites may be conducted.
The purpose of the assessments is to assist in the evaluation of how the site
will perform by itself and in conjunction with suitable technologies to meet
DPH performance objectives. The preliminary performance assessments should be
used to estimate factors including, but not limited to:
1. The potential release of radioactivity
from waste packages into the facility;
2. The potential release of radioactivity
through the engineered barriers into the ambient or geologic
environment;
3. The movement of
radioactive materials through the environment to humans by ingestion or direct
contact;
4. The resulting exposure
to humans in comparison to DPH performance objectives and among the
sites.
(k) Performance
assessments need not provide complete assurance that DPH performance objectives
will be met. Because of the long time periods which may be involved and the
nature of the events and processes of interest, there will inevitably be
substantial uncertainties in projecting site and facility performance. What is
required is a reasonable expectation based on reasonably conservative
assumptions in relation to the record before the Board that compliance with DPH
dose performance objectives is reasonably likely to be achieved.