United States
Environmental Protection
Agency
Office of
Radiation
Washington, DC 20460
EPA-520/1-88-012
July 1988
Radiation
xvEPA
The Use of Geophysical
Monitoring Systems
and Data to Identify and
Designate Ocean Sites for
Disposal of Low-Level
Radioactive Wastes
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EPA 520/1-88-012
THE USE OF GEOPHYSICAL MONITORING
SYSTEMS AND DATA TO IDENTIFY AND DESIGNATE
OCEAN SITES FOR DISPOSAL OF LOW-LEVEL RADIOACTIVE WASTES
by
James Neiheisel
July 1988
Office of Radiation Programs
U.S. ENVIRONMENTAL PROTECTION AGENCY
Washington, D.C. 20460
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FOREWORD
In 1972 Congress enacted the The Marine Protection,
Research and Sanctuaries Act (PL 92-532). The Act required the
Environmental Protection Agency (EPA) to develop regulations to
control ocean disposal of all wastes, including low-level
radioactive wastes (LLW). The EPA Office of Radiation Programs
(ORP) initiated specific studies to develop criteria directly
applicable to ocean disposal of LLW.
The ORP has conducted feasibility studies to determine
whether present-day technologies could be applied to determine
effects from previous (1946 to 1970) U.S. disposals of
radioactive wastes in the oceans. After successfully locating
LLW containers in three previously used disposal sites, the ORP
initiated characterization studies to: (1) determine the
biological, chemical, and physical parameters within each of the
sites; (2) monitor for the presence and distribution of
radionuclides in each site, including their concentration
levels; and, (3) assess the performance of past packaging
techniques and materials.
The purpose of this report is to provide information
applicable to using geophysical instruments and survey methods,
and the data collected, in the process of designating sites for
ocean disposal of LLW. The geophysical ocean survey methods
described in this report are envisioned as preceding any
sediment sampling required to characterize disposal sites.
The Agency invites all readers of this report to send any
comments or suggestions to Mr. David E. Janes, Director,
Analysis and Support Division, Office of/Radiation Programs
(ANR-461), Washington, D.C. 20460.
/ Richard «K7\3u\^njond, Director
Office /of/Radiation Programs
111
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TABLE OF CONTENTS
Page
FOREWORD in
ACKNOWLEDGMENTS vii
1. Introduction 1
2. Geophysical Instruments 2
2.1. Side-Scan Sonar Systems 3
2.2. Seismic Profiling Systems 4
2.2.1. Airgun Profiler 5
2.2.2. High-Resolution Profiler 5
3. Disposal Site Monitoring 6
FIGURE 1 7
Graphic 3.5-kHz, High-resolution Sediment Profile,
Mid-Atlantic Slope - Lower Baltimore Canyon.
REFERENCES 8
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ACKNOWLEDGMENTS
The author wishes to thank Dr. James Booth of the United
States Geological Survey (USGS) for the opportunity to
participate in the March 1987 mid-Atlantic, Exclusive Economic
Zone (EEZ) survey cruise. During this cruise, the author was
able to observe the Geological, Long-Ranged, Inclined Asdic
(GLORIA) seafloor mapping system in operation and to assess its
applicability to designating sites for ocean disposal of LLW.
Thanks is also extended to Dr. James Robb, Chief Scientist for
that cruise, for his helpful suggestions on using geophysical
instruments/methods applicable to site characterization and
designation studies. The information provided in this report is
based directly upon the author's at-sea experience in assessing
state-of-the-art geophysical instrumentation and data.
I also wish to thank Mr. Robert S. Dyer and Mr. William
Curtis of the Office of Radiation Programs, U.S. Environmental
Protection Agency, for critical review of this report and for
the many helpful suggestions and discussions during the course
of this work. The critical review and comments also provided by
Dr. William Forster of the U.S. Department of Energy and
Dr. James Booth of the U.S. Geological Survey are gratefully
acknowledged. Typing of this document by Ms. Phoebe H. Suber is
also acknowledged with appreciation.
VII
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1. Introduction
The Environmental Protection Agency (EPA) is currently
revising its 1977 Ocean Dumping Regulations. The revised
regulations will incorporate criteria applicable to any ocean
disposals of low-level radioactive wastes (LLW), as recommended
by the International Atomic Energy Agency (IAEA). The IAEA
recommends, pursuant to Annexes I (Sec. 6) and II (Sec. B.) of
the London Dumping Convention (LDC), that any LLW disposed in
the oceans should be properly packaged and disposed in deep
ocean sites where the average water depth exceeds 4000 meters.
Thus, the Agency, in revising the regulations for all wastes,
will also include waste package performance and site designation
criteria that are specific to LLW.
In addition to including siting and packaging performance
criteria in the revised regulations, the Agency is preparing a
series of technical reports that provide LLW disposal site
monitoring recommendations. Sediment monitoring requirements >
for ocean disposal of all wastes, as listed in Part 228 of the
existing Ocean Disposal Regulations (42 FR 2462 of January 11,
1977), include organic carbon, texture, particle size
distribution, major mineral constituents, and settling rate.
Because of the unique character of LLW, their potential for
migration in sediments, and the different environmental stresses
that the waste packages will be subject to from disposal in the
deep ocean, additional disposal site sediment monitoring
parameters are recommended. These include determining: (a) the
sorptive distribution coefficient (Kd) of radionuclides; (b)
sediment redox potential by the nitrate method and other
supporting techniques; (c) pH; (d) geotechnical parameters; and
(e) the composition of sediment core samples by the x-radiograph
technique. Specific rationale for recommending each of these
additional sediment monitoring parameters, and disposal site
characterization data applicable to immobilizing LLW, are
presented in two of the referenced technical reports (Neiheisel,
1988 and U.S. EPA, 1988). In general, determining these
additional sediment parameters in LLW disposal sites will
provide data for predicting the capability of sediments to
retain radionuclides. Calculating the radionuclide retention
factor of sediments in potential LLW disposal sites is very
important because it can indicate whether a sufficient natural
barrier to radionuclide migration exists in case the primary,
engineered-barrier (waste container) fails.
This report is another in the Agency's series of technical
documents that provide specific recommendations applicable to
any future ocean disposal of LLW. It provides information about
using geophysical instrumentation and survey methods in
designating disposal sites.
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In March 1987, the EPA Office of Radiation Programs (ORP)
participated in the U.S. Geological Survey (USGS) mapping of the
mid-Atlantic Exclusive Economic Zone (EEZ) using the geological,
long-ranged inclined asdic (GLORIA) system to obtain sonographs
(rough images) of the sea floor. Data from that survey shows
that use of the GLORIA system can significantly improve the
process for locating and designating potential LLW disposal
sites. Within those portions of the mid-Atlantic EEZ (33.5°N
to 39°N latitudes), where water depths exceeded 4000 meters,
the GLORIA data identified no less than three sites with little
or no indication of debris flow or other detrimental phenomena.
Smaller-scale geophysical surveys, at each of the three sites
identified from the GLORIA data, could provide more specific
resolution of seafloor topography and a better assessment of
environmental conditions within each site. The more specific
data could be obtained from detailed sonographs provided by
high-resolution seismic reflection profilers, from sea floor
photographs, and from sediment characterization studies.
2. Geophysical Instruments
State-of-the-art geophysical instruments used to obtain
reconnaissance plan-view imagery of large sections of the ocean
floor have been compared to the first high-resolution photos of
earth taken from space by the Landsat satellite (Hill, 1986).
Side-scan sonars, seismic profilers and other geophysical
instruments, supplemented by in-situ sediment monitoring,
provide a means for assessing potential LLW disposal sites in
the deep ocean. The full potential for applying such
instruments to locating possible LLW disposal sites began in
1984 when the USGS initiated monitoring surveys of the EEZ,
which extends to 200 nautical miles offshore. During these
surveys, the long-range side-scan sonar system GLORIA mapped the
seafloor. The first phase of GLORIA mapping in the EEZ, off the
U.S. west coast, was completed in 1984. The data from the
initial surveys, including interpretations of seafloor
topography at a scale of 1:500,000, were published in atlas
format (EEZ - SCAN 84, 1986). Mapping of the EEZ off the U.S.
east coast was completed in 1987. Publication of that data is
expected in 1989. The EPA participation in the mapping of the
mid-Atlantic EEZ was motivated by an opportunity to obtain
supplemental data pertinent to earlier EPA studies at the
previously used 2800m and 3800m LLW disposal sites that are
located in the mid-Atlantic EEZ. The insight gained on the
capabilities and limitations of geophysical instruments during
the USGS mid-Atlantic survey was invaluable in preparing this
report.
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The remainder of this report briefly discusses various
side-scan sonar systems and seismic profilers that can be used
to identify geologically stable, deep-water areas for potential
designation as LLW disposal sites.
2.1. Side-Scan Sonar Systems
The GLORIA system is a specialized side-scan sonar capable
of large-scale reconnaissance mapping of deep-ocean seafloor
topography. GLORIA can map seafloor areas of approximately the
same size as the state of New Jersey in a single day (MacGregor
and Lockwood, 1984), while towed by ship at a speed of 8 - 10
nautical miles per hour (knots). Developed into a digital data
collection system in 1981 by the United Kingom Institute of
Oceanographic Sciences, this unique side-scan sonar operates at
a nominal frequency of 6.5 kHz and a 100 Hz band width from a
transducer array towed at 50 meters depth. The recorded pulses
received are corrected in real time aboard the ship and used to
produce sonographs which are images that show entire surfaces of
topographic features at 50-m resolution. The advantages of the
GLORIA mapping over conventional mapping techniques is that
correlations and trends of features such as ridges and channels
can be made with confidence between seismic profiles, and that
the patterns of such features as meandering channels and
dendritic canyons can be clearly defined (Cacchione, et al,
1988) .
As the GLORIA imagery on the mid-Atlantic EEZ survey was
being assembled aboard the RV FARNELLA in March 1987, it became
apparent that major slumping areas and submarine canyons with
interconnecting drainage patterns were more numerous and more
complex than had been previously depicted on existing contoured
bottom charts. Local tectonic structures and tonal differences
that reflected a variation in sediment types also added to the
interpretation of the bottom topography. The detailed GLORIA
imagery provided an interpretative means of identifying areas of
transport and erosion that could reflect on the suitability of
considering an area for LLW disposals.
The GLORIA data obtained from the mid-Atlantic EEZ, in
locations deeper than 4000 m, reveals three areas (one off New
England and two off the Carolinas) that show relatively static
geologic environs, free from debris flows or other indications
of instability. These three areas, observed in unprocessed
GLORIA data made available to EPA by the USGS, will be assessed
in greater detail after final processing of all data which
should provide improved resolution over the unprocessed
imagery. These areas could be candidates for potential LLW
disposal sites. Further study of these locations would require
the use of more detailed, narrower ranged side-scan sonar and
other geophysical instruments.
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The National Oceanic and Atmospheric Administration (NOAA)
utilizes a hull-mounted side-scan sonar system, SEA BEAM, that
maps a smaller seafloor area, but in more detail, than the
GLORIA system. The 5 km mapping "swath" of SEA BEAM is much
narrower than the 30 km trackline spacing of the GLORIA system
but the resultant map is much more detailed.
In addition to using GLORIA, the USGS has deployed the SEA
MARK I, a mid-range side-scan sonar, to collect detailed
topographic data of slump zones on the continental slope and
rise off North Carolina (Cashman and Popenoe, 1985) and for
surficial geological studies in the Northern Baltimore Canyon
(Robb et al, 1982).
Seafloor maps provided by the SEA BEAM and SEA MARK I
side-scan sonar systems, in conjuction with data obtained from
high-resolution seismic profilers, have yielded excellent
details of bottom features in selected areas of mapping. The
use of SEA MARK I or SEA BEAM is recommended to enhance bottom
features observed in GLORIA data and especially in the process
of characterizing a site for consideration as a potential LLW
disposal site.
The long-range (GLORIA) and medium-range (SEA BEAM and SEA
MARK I) side-scan sonar imagery systems are valuable tools to
the researchers, enabling them to focus on ocean bottom features
that can indicate the degree of geologic stability in deep ocean
environments. Areas of bottom surface stability or active areas
of erosion and deposition can be identified from the sonograph
imagery. Vertical stability of a seafloor area is not always
discernable from side-scan sonar imagery, but the use of
high-resolution seismic profilers can provide vertical stability
data. The fact that six times as many seismic data profiles are
available from SEA BEAM or SEA MARK I surveys, as compared to
GLORIA, is a decided advantage with the more detailed surveys.
2.2. Seismic Profiling Systems
Continuous seismic profiling methods complement the
side-scan sonar imagery and permit a more certain interpretation
of the geological stability of a potential LLW disposal site.
Combined use of a 3.5-kHz Sub-Bottom Profilier with a deep
penetrating seismic system, using a 160 in3 air gun or similar
sound source, provides a detailed resolution of sediment
layering and subsurface geologic structures, extending from the
seafloor surface to underlying basement rock.
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2.2.1. Airgun Profiler
During the GLORIA survey -of the mid-Atlantic EEZ, deep
penetration mapping of the ocean sediments and basement rock was
obtained by using a 160 in^ airgun with a hydrophone streamer
of French-Italian design. The airgun was fired at 10-second
intervals and at a 6-second sweep. Incoming data was fed in
parallel to a special USGS computer (MASSCOMP) which digitized
and displayed the data in real time on a monitor and recorded
the data on nine-track magnetic tape. This type of deep
penetrating seismic profiling is considered essential to
assessing the stability of a candidate LLW disposal site and
adjacent areas.
Deep penetrating seismic profiling provides a means of
correlating surface bottom relief with reflectors found in the
subsurface geology. Structures have been identified by the
deeper penetrating seismic reflection systems that could
eliminate a potential site for LLW disposal. An example is seen
in data from the Atlantic continental slope and rise off North
Carolina where a salt diapir complex was observed (Cashman and
Popenoe, 1985). Salt diapirs are related to instability as they
normally indicate areas of extensive slumping. The slumping
appears to be a result of uplift and faulting associated with
the vertical intrusion of the diapir.
Seismic reflection profile data, from along the edges of
buried rift basins in the Long Island Basin, show low-angle
border faults, tilted sedimentary horizons, and high-angle cross
faults (Hutchinson et al, 1986). Such structures of instability
are reported from Nova Scotia to South Carolina in the Atlantic
continental margin. Although these structures were observed in
shallower areas than the 4000-m depth recommended by the IAEA
for LLW disposal sites, they are examples of utilizing deep
penetration seismic profilers to obtain interpretative data.
Preliminary releases of Atlantic GLORIA survey data by the
USGS (Ocean Science, 1987) report two fields of apparent salt
domes off the Carolinas and northern New Jersey. These salt
dome fields, and other features observed in the seismic profile
data that will be published in the forthcoming EEZ Atlas of the
Atlantic, will likely exclude otherwise potentially favorable
LLW disposal sites from further consideration.
2.2.2. High-Resolution Profiler
A high-resolution 3.5-kHz profilier provides a graphic view
of sediment layering in the upper 25-100 m of bottom sediment.
The 3.5-kHz system is sometimes termed the sediment profiler
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since it presents a vertical profile of layered soft sediment.
A 12-kHz system is also used with the 3.5-kHz profiler to obtain
bathymetry data.
A typical 3.5-kHz system consists of a transceiver
(transmission and receptor device) towed from the bow, and a
recorder aboard ship. A 3.5-kHz sediment profile, recorded
aboard the RV FARNELLA during the USGS mapping survey of the
mid-Atlantic EEZ, is shown in Figure 1. This profile was
obtained from an area in the lower seaward portion of the
Baltimore Canyon. The profile shows the continuity and
regularity of multiple layers in the upper 25 m of bottom
sediments along a section of the ship's track in this area.
Using Figure 1 as an example, one can readily see the utility of
using geophysical instruments during LLW site selection or
designation surveys to evaluate the degree of geologic stability
and sediment uniformity in a prospective deep-sea location.
3. Disposal Site Monitoring
Monitoring surveys to select deep-ocean candidate LLW
disposal sites should include the use or collection of
geophyscial data and sediment samples. Identification of
relatively large-scale, static or stable seafloor areas can be
made by examining available USGS reconnaissance imagery data
obtained from the GLORIA surveys of the EEZ. More detailed and
smaller scaled data (for example, from the SEA BEAM and SEA MARK
I mid-range side-scan sonar systems) can then be used, in
conjunction with extensive seismic reflection profiling data, to
delineate bottom features in potentially static areas identified
by the GLORIA data. It should be noted here, however, that,
although a relatively large volume of side-scan sonar and
seismic relection profile data has been collected in the U.S.
east and west coast EEZ areas, one of the criteria for
designation of LLW disposal sites requires an average water
depth in excess of 4000 meters. This depth is recommended by
the IAEA and is accepted by the United States as a signatory to
the LDC. Thus, potential areas for consideration as LLW
disposal sites will be limited by this criterion within the U.S.
EEZ, particularly in the Atlantic Ocean.
It is also important to note that assessments of potential
LLW disposal sites should not be based solely upon side-scan
sonar and seismic profile data. Site selection/designation
processes will require in-situ sediment sampling. Accordingly,
the EPA has prepared a report recommending sediment monitoring
methods for LLW disposal sites (U.S. EPA, 1988).
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'" 4"... -p- '.tT*.»••',;ji',,, • ' K!I-* •.'.•.', .i.\ .'A1' •'.'!.';•< "'."K
ill0fe-Jjf'-i'.•'"> ^1.0 a; r'l?*«"{»'
Figure 1. A graphic 3.5-kHz, high-resolution profile of
sediment layers along the continental slope in
the lower reaches of the Baltimore Canyon. Data
obtained on March 12, 1987, during a USGS survey
of the mid-Atlantic EEZ.
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REFERENCES
Cacchione, et al, 1988, Physiography of the Western United
States Exclusive Economic Zone, Geology, v. 16, p. 131-134.
Cashman, K.V. and Popenoe, 1985, Slumping and Shallow Faulting
Related to the Presence of Salt on the Continental Slope and
Rise off North Carolina, Marine and Petroleum Geology, v. 2,
p. 260-271.
EEZ - SCAN 84, Scientific Staff, 1986, Atlas of the Exclusive
Economic Zone Western Conterminous United States: U.S.
Geological Survey Miscellaneous Investigation Series 1-1792,
p. 152.
Hill, G.W., 1986, U.S. Geological Survey Plans for Mapping the
Exclusive Economic Zone using GLORIA., Proceedings of Exclusive
Economic Zone Symposium Exploring the New Ocean Frontier,
Washington, DC, October 2-3, 1985.
Hutchinson, D.R., Klitgord, K.D., and Detrick, R.S., 1986, Rift
Basins of the Long Island Platform, Geological Society of
America Bulletin, v. 97, p. 688-702.
McGregor, B.A., and Lockwood, M., 1984, Mapping and Research in
the Exclusive Economic Zone, U.S. Department of Interior and
U.S. Department of Commerce Bulletin, Washington, DC, 40 p.
Neiheisel, J., 1988, Sediment Monitoring Parameters and
Rationale for Characterizing Deep-Ocean Low-Level Radioactive
Waste Disposal Sites, U.S. Environmental Protection Agency,
EPA 520/1-87-011.
Ocean Science News, 1987, More Specific Results, of the East
Coast GLORIA Survey, v. 29, n. 18, May 12, 1987, Washington, D.C.
Robb, J., Hampson J.C., and Kirby, J.R., 1982, Surficial
Geological Studies of the Continental Slope in the Northern
Baltimore Canyon Trough Area - Techniques and Findings, 14th
Annual Offshore Technology Conference, Houston, TX, May 3-6, 1982
p. 39-43.
U.S. Environmental Protection Agency, 1988, Methods Manual for
Sediment Monitoring at Deep-Ocean Low-Level Radioactive Waste
Disposal Sites, edited by J.W. Booth, U.S. Geological Survey,
EPA 520/1-88-002.
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