United States        Office of          EPA 520/1-87-011
           Environmental Protection     Radiation Programs       June 1988
           Agency          Washington, DC 20460
&EPA      Sediment Monitoring
            Parameters and Rationale
            for Characterizing
            Deep-Ocean Low-Level
            Radioactive Waste
            Disposal Sites

                                           EPA 520/1-87-011
    Sediment Monitoring  Parameters and  Rationale

                  for Characterizing

Deep Ocean Low-Level Radioactive Waste Disposal Sites


                   James Neiheisel
                      June 1988
            Office of Radiation Programs
        U.S. Environmental Protection Agency
                Washington,  DC  20460

     The Environmental Protection Agency  (EPA) was given  a
Congressional mandate to develop criteria,  standards,  and
regulations governing the ocean disposal  of all  forms  of  wastes
pursuant to Public Law 92-532, the Marine Protection,  Research,
and Sanctuaries Act of 1972.  Within this Congressional
mandate, EPA has initiated a specific program  to  develop
regulations and criteria to control the ocean  disposal of
low-level radioactive wastes  (LLW).

     The EPA Office of Radiation Programs  (ORP)  has conducted
feasibility studies to determine whether  current  technologies
could be applied toward determining the fate of  radioactive
wastes dumped in the past.  After successfully locating
radioactive waste containers in three of  the primary LLW
disposal sites previously used by the United States, ORP
initiated disposal site characterization  studies  to:  (1)
determine the biological, chemical, and physical  parameters,
(2) identify and ascertain the distribution of radionuclides
within the sites, and  (3) evaluate previous packaging
techniques and materials.

     The purpose of this document is to provide  a rationale for
the sediment measurements that will indicate radionuclide
retention characteristics at potential LLW  disposal sites in
the deep-ocean environment.  Prior to sediment sampling,  the
site selection shall have been directed to  specific areas by
site selection criteria supported by geophysical  data  to
indicate site stability-  Sediment sampling is conducted  to
meet the sediment monitoring and criteria needs  for site

     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, DC  20460.
                                 [ichata1 J.  GuimorftJ,  Director
                                Office  of  Rad/iation  Programs


     The assistance of Dr. James Booth of the U.S. Geological
Survey, Branch of Atlantic Marine Geology, Woods Hole,
Massachusetts, and his staff in conducting mineralogical and
geotechnical measurements, and guidance in specific testing
needs is gratefully acknowledged.  Appreciation is also
extended  to Dr. Mark Fuhrmann and Mr. Peter Colombo of
Brookhaven National Laboratory and Dr. Fred Sayles of Woods
Hole Oceanographic Institution for discussions regarding the
capabilities and limitations of the Kd method and Eh meter
method for sediment redox determinations.  The comparison of
mineralogy techniques and textural methods by Mr. Ray
Willingham of the U.S. Army Corps of Engineers, South Atlantic
Division Laboratory on sediment samples from the Atlantic and
Pacific low-level radioactive waste disposal sites is also

     The critical review and comments provided by the special
interagency Technical Subcommittee on Ocean Disposal of
Low-Level Radioactive Waste is gratefully acknowledged and
appreciated.  The comments by Dr. William Forster of the
Department of Energy and Drs. Larry Brush, Rip Anderson and Mel
Marietta of Sandia National Laboratories were especially
valuable in the review and final preparation of this document,
and their contribution is acknowledged with special
apprec iation.

     The author also wishes to thank Mr. Robert S. Dyer,
Mr. William R. Curtis and Ms. Marilyn Varela of this Office for
critical review of this report, and for the many helpful
suggestions and discussions during its preparation.  In
addition, the typing assistance provide by Ms. Phoebe Suber is
also gratefully acknowledged.

                        TABLE  OF  CONTENTS


       Foreword 	  i11

       Acknowledgments 	 v

1.0    Sediment Monitoring Parameters and Rationale 	 1

1.1    Introduction	 1

1.2    Special Considerations for Low-Level Radioactive Wastes  .. 2

1.3    Parameters Already in the Ocean Disposal Regulations 	 4

1.3.1  Organic Carbon 	 5

1.3.2  Sediment Texture Grain Size 	 5

1.3.3  Recommendations 	 7

1.3,4  Mineral Composition of Sediment 	 7

1.3.5  Recommendations 	 8

1.4    Consideration of Parameters Not In Existing Regulations  .. 9

1.4.1  Sorption Distribution Coefficient (Kd)  	 9

1.4.2  Recommendat ions 	 10

1.4.3  Sediment Redox Considerations 	 11

1.4.4  Recommendations 	 14

1.4.5  Determination of pH 	 15

1.4.6  Recommendations 	 15

1.5    Geotechnical Parameters 	 15

1.5.1  Recommendations 	 16

                  TABLE  OF  CONTENTS  (Continued)


1.6    X-radiographs 	 16

1.6.1  Recommendations 	 16

1.7    Correlation with Geological Stability 	 16

1.7.1  Recommendations 	 17

1.8    Sampling Density  	 17

1.9    Summary of Recommendations 	 18

1.10   Future Considerations:
         Implementation of Section 424, Public Law 97-424  .. 19

       References 	 21



     The purpose of this document is to discuss the need  and
present the rationale for special sediment monitoring
parameters and criteria to characterize LLW disposal sites
meeting the International Atomic Energy Agency  (IAEA)
recommended minimum disposal depth of 4000m.  The IAEA disposal
depth limitation was developed pursuant to the London Dumping
Convention, to which the United States is a signatory.
Sediment monitoring requirements for ocean disposal of all
wastes are contained in Part 228 of the current Ocean Disposal
Regulations (42 FR 2462, January 11, 1977).  Part 228 contains
general requirements and does not specifically address sediment
monitoring requirements for disposal of packaged LLW.  Part 228
does acknowledge, however, that there may be special
requirements for deep-sea monitoring.  Paragraph
228.13(e)(3)(ii) states that "additional parameters may be
selected based on the materials likely to be in the wastes
dumped at the site."  The sediment measurement parameters
required for all wastes are: organic carbon, texture, particle
size distribution, major mineral constituents, and settling
rate.  For LLW, all of these parameters, with the exception of
settling rate, will be used.  Some modifications of methods to
characterize sediments are necessary because of the sediment
conditions in the deep ocean and the nature of the wastes.

     This document recommends additional baseline sediment
monitoring parameters and criteria to address the special
considerations applicable to ocean disposal of packaged LLW.
The existing EPA waste package performance criteria require
that LLW must radiodecay to environmentally acceptable levels
within the expected immobilization period of the waste package
and the surrounding sediment.  Using a multibarrier approach
for containment of the LLW at the site, the engineered waste
package represents the primary barrier.  The natural retention
afforded by the physicochemical characteristics of deep ocean
sediments constitutes an additional barrier.  Some of these
factors can be measured.  Estimates of the ability of the
physicochemical environment to increase radionuclide retention
in the sediment, or to restrict radionuclide movement to  the
water column after release from a waste package, are considered
as part of the sediment monitoring recommendations.

     This document addresses geotechnical parameters  which  may
be used to estimate the extent of penetration of  a  free-falling
waste package into the sediment and to provide  baseline  data
for evaluating the option of subseabed disposal of  LLW.   The
correlative value of sediment monitoring criteria to  (a)
geologic stability of the disposal site and  (b) interactions  of
the sediment and its environment with the waste package  is
presented.  It also presents a discussion of specific sediment
parameters applicable to a deep-ocean LLW disposal  site.
Numerical limits are proposed where applicable.   A  Methods
Manual, with recommended testing procedures, will be  provided
as a separate document  (EPA 520/1-87-011, June  1988).

     The Methods Manual addresses the use of geophysical
methods including bathymetric and side-scan  sonar techniques  to
determine the geologic stability of a candidate site  prior  to
sediment monitoring.  It was developed to provide details of
the recommended sediment testing techniques  for the sediment
monitoring parameters discussed in this report.   It is an
important ancillary supplement to the sediment  monitoring
parameters and criteria.  It is intended to  assure  uniformity
in analyses of sediment samples and in reporting  data.


     The present ocean disposal regulations  look  to the
engineering of the waste package (the container and the
solidification agent containing the waste) as the primary
barrier to prevent direct dispersion of any  LLW into  ocean
waters.  In a multibarrier protection system, the sediment
constitutes an additional natural barrier to the  migration  of
radionuclides if the waste container has been breached by
natural or accidental causes.  The sediment  can only  be  an
effective barrier, however, if the waste container  is in
contact with the sediment.  Release of radionuclides  from any
seawater-exposed area of the container could "short circuit"
the sediment sorption mechanism by moving radionuclides
directly into the water column.  However, some  scavenging of
radionuclides by suspended particulates in the  benthic boundary
layer will probably occur.  Biological activity of  organisms
living in or on the sediment (bioturbation)  could also "short
circuit" radionuclide retention by increasing the rate of
dispersion; however, this activity can also  carry radionuclides
deeper into the sediment and thereby provide greater
immobility.  Any site selected for LLW should have
comparatively low biological activity.

     A waste container in contact with deepsea sediment  creates
an environment where information on the sediment composition
and the oxidation-reduction  (redox) state of the sediment  may
be used to predict both the  time of release of waste  from  a
container and the potential  for immobilization of  some of  the
radionuclides upon their release to the sediment environment.
The redox environment immediately adjacent to and  beneath  a
waste container, however, is altered by the weight of the
container on the sediment.   Therefore, knowledge of the
geotechnical properties  (e.g. compressive strength) of the
sediment and sediment surface will facilitate assessment of
this effect and will allow prediction of the depth of
penetration of the waste package into the sediment upon  impact
at terminal velocity.  This  will establish the initial extent
of sediment-container physicochemical interactions.  Any
additional burial of the drum by sedimentation at  the site is
considered desirable and will increase the amount  of  sediment
retention afforded if a waste package were to release its

     To assess the impact of radionuclide release  at a LLW
site, it is important to know the radionuclides in the waste
that are most likely to be detrimental to biota or man and the
sediment retention potential of those radionuclides.  The
radionuclides of importance  are those that are (a)  primary
constituents of LLW, (b) enduring or persistent (e.g. have a
half-life of 5 years or more) and, (c) biologically toxic.
According to Wild et al  (1981), the radionuclides  in LLW that
meet one or more of these criteria include tritium, carbon-14,
cobalt-60, nickel-59 and-63, strontium-90, niobium-94,
technetium-99, iodine-129, cesium-137, uranium-235, and
uranium-238.  Those radionuclides that meet all three criteria
include cesium, cobalt, and  strontium.  Therefore, focus will
be on cesium, cobalt and strontium for assessment  of the
predicted retention by sediment.  Other radionuclides may  be
considered during any further development or revisions to
regulations and criteria; and site characterization will
include analysis of parameters sensitive to prediction of
retention for all the radionuclides of importance  in a LLW

     Since the physicochemical processes  controlling  sorption
of radionuclides onto the sediment  are  complex  and  are  not  brie
same for all radionuclides of concern,  the  determination of the
sorption distribution coefficient  (Kd)  oa site-specific
sediments gives the best state-of-the-art assessment  of
radionuclide retention.  The test  is  performed  under  similar
environmental conditions  (both oxidizing  and  reducing)  as exist
in the prototype sediment.  Tritium,  carbon-14,  a-ndjiodine-129,
however, have little or no retention  and  little  purpose is
served in performing laboratory  analyses  on them.   One  of the
radionuclides in which solubilitiy  changes  enormously with
slight changes in redox potential  is  tec.hnetium-99.   Some of
the other radionuclides; e.g., cobalt-60,  and uranium isotopes,
are also affected to some degree by redox state.  The ,Kd of
cesium isotopes, strontium-90, and  other  cations exhibiting a
single oxidation state are most  affected  by the  amount  and  type
of sorptive minerals and surface area of  the  sediment.   Some
radionuclides form  soluble complexes  with
organics that might occur in the waste  form or  sediment; e.g.,
cobalt-60 is  known to be mobilized by  organics  such  as EDTA.
Some radionuclides  also coprecipitate with  iron  and manganese
oxyhydroxides.                  ,~j

     It  is feasible to predict,  within  limits,  the  potential
retention of radionuclides of concern if  adequate measurements
for characterization of the sediment  are  performed  at a
prospective LLW site.  Such an approach might eventually be
extended to the heavy metal analogs in  hazardous waste.
                                        "?', ,
     The sediment parameters relating to  site selection and
baseline monitoring of a LLW site  will  include:  (a) those
parameters already  in place in paragraph  228.13(e)(3) of the
Regulations, where  applicable, and  (b)  recommended .parameters
that relate to measurement of radionuclide  retention  (e.g.  Kds)
or which predict the retention of  radionuclides  in  the  sediment.


     The parameters required by  the current EPA  Ocean Disposal
Regulations are applicable to LLW  disposal  sites.   Paragraph
228.13(e)(3) lists  organic carbon,  texture, particle  size
distribution, major mineral constituents,  and settling  rate as
required measurements for sediment  analyses.  These sediment
parameters, however, must be addressed  by methods applicable to
the special nature  of low-level  radioactive waste and the deep-
ocean environment.  Settling rate,  listed in  paragraph
228.13 (e) (3), is not applicable  to  the  disposal  of  LLW,
however, because radioactive wastes are presumed to be  packaged
in containers as specified in paragraph 227.11(b)(1).


     The concentration of organic carbon  (regardless  of  source)
in sediments within the deep-ocean environment  is  an  index  to
the total organic matter in sediments, and to the  biomass of
living organisms in the overlying water-column  and  adjacent
areas.  It is important in siting considerations since
relatively higher levels of organic carbon in sediments  at  a
prospective LLW disposal site would make  the site  less suitable
for disposal of wastes due to a higher probability -of having
biological pathways to the surface waters.  The presence of
organic matter in sediment can also be detrimental  for
radionuclides that form complex chemical  bonds, in  that  their
retention by sediment is reduced.  Radiocobalt, for example, is
known to form organic complexes in shallower ocean  areas,
resulting in virtually no retention by geologic media.
Information about the organic chemical complexes formed  by
radionuclides is incomplete, making prediction  of  radionuclide
retention by the sediments more difficult.  According to Emery
and Uchupi (1972), the concentration of organic carbon in the
deeper waters of the Western Atlantic Ocean is  generally less
than 0.5 percent.  Typical results for organic  carbon, measured
in surficial sediment samples, in the vicinity  of LLW disposal
sites are as follows:  NW Atlantic (2,800m site),  0.6 percent;
NE Atlantic, 0.2-0.3 percent; Pacific (Farallon Islands), 0.6

     Determination of organic carbon involves high  temperature
combustion using a carbon analyzer on samples from  which the
inorganic carbon (carbonate carbon)  has been removed; the
latter is accomplished by either wet or dry leach  techniques.


     The sediment texture grain size is one of  the  most
important and versatile of the sediment monitoring  parameters
at a prospective LLW site.  This parameter (a)   provides a basis
for classification of the sediment by grain size (b) correlates
with geotechnical parameters  (Keller et al, 1979) and the
sorptive properties of the sediment (Onishi et  al,  1981), (c)
allows for mathematical computation of overall  mineral
percentages in a sediment sample that was analyzed  for mineral
content in specific sand,  silt and clay-size fractions
(Neiheisel, 1983) and, (d) provides an indication  of site

     The sediment texture classification  is  based  on  the
percentage of sand, silt, and clay-size fractions  in  accordance
with the nomenclature of Shepard  (1954).  A  color  description
precedes the sediment size classification.   The  triangular
textural diagram used for sediment classification  is  depicted
in Figure 1 of the Methods Manual  (EPA, 1988).   Ten categories
of sediment are classified based on  the percentage of sand,
silt and clay-size materials  in the  sediment.  These  are  sand,
clayey sand, sandy clay, clay, silt,  silty sand, clayey  silt,
sand-silt-clay, silty clay, and sandy silt.   In  this
classification, the sand-size material  is sediment greater  than
0.062 mm, silt-size material  is sediment  less  than 0.062  mm but
greater than 0.002 mm  (2 micron size)  and clay-size material is
all sediment less than  2 micron size.   The 62-micron  size is
recommended  (Galehouse, 1971) for  the boundary between silt and
sand because  (a) most investigators  use Stokes1  law up to this
size-limit of sand and  (b) the 62-micron  stainless steel  sieve
is convenient for removing coarser size materials  from the
finer material to be analyzed by sedimentation  (silt  and  clay)
techniques.  The 2-micron size is  the preferred  dividing-line
between silt and clay-size materials  as a mineral  composition
change usually occurs at this size-boundary.   Using the  above
texture size classification,  the typical  sediment  description
for the Atlantic 2,800m LLW disposal  site is clayey silt,  with
an olive grey color.

     The process of determining the  percentages  of grains
representative of particular  sizes is known  as grain-size
analysis.  The grain-size distribution  of the  sediment sample
is determined by combining the analytical results  from the
sand, silt,  and clay fractions.  The  grain-size  distribution of
the sand-size fraction  is determined  by sieve  analysis or  by
using the rapid sediment analyzer, in which  sediments of  less
than 0.062 mm size are  analyzed by sedimentation techniques.
The methods  used depend on the type  of  sediment  encountered.
The technique to be used can  normally be  determined by visual
inspection of the sediment cores.  Some of the methods that are
acceptable,  widely used, and  available, are  described in  detail
in a Methods Manual  (EPA, 1988).


     Sediment analyzed for texture should be  representative of
the top 30 cm of sediment core from a LLW site.  Based  upon
observations from the deep submersible ALVIN  ( Hanselman  and
Ryan, 1983) during an EPA Office of Radiation Programs  survey
at the Atlantic 3,800m LLW disposal site, and similar
observations during EPA submersible surveys at the Atlantic
2,800m site and the Pacific Ocean Farallon Islands site,  we do
not expect waste drums to penetrate deeper than 30 cm into  the
sediments.  This depth is also the sediment recovery depth
obtained by conventional sediment box corers.  Subcore  samples
obtained from the box core will thus provide  relatively
undisturbed sediment for the various tests to be made on  the

     The proposed disposal site should be free of exposed
bedrock and display uniformity of sediment texture and  relative
geologic stability across the site.  To ensure uniformity of
sediment texture over a proposed site, we recommend that  the
average sediment texture to 30cm depth for each sample  location
should fall in a close pattern on the triangular diagram  that
constitutes the Shepard Texture Classification Chart; and the
number of different types of sediment should not exceed 3 of
the possible 10 textural descriptions displayed on the  chart.
Such uniformity of texture across the proposed site will
reflect on uniform, stable, geologic processes in the area.


     The current Regulations cite "major mineral constituents"
as one of the sediment parameters.  However, an important
consideration in the assessment of a LLW site in a deep-ocean
environment is a reasonably precise evaluation of the mineral
composition of both major and minor mineral components
(sorptive minerals may occur in the minor component).   This
parameter indicates (a)  the potential retention of
radionuclides by the sediment (b)  the geologic stability  of  the
site (c)  presence of economic mineral deposits, and (d)  dynamic
factors and sediment source considerations.

     An accurate assessment of mineral composition  (+_10  percent)
would reflect on the potential retention of  radionuclides  that
are known to exhibit sorption primarily by cation exchange and
sediment surface area phenomena.  According  to  Onishi  et al
(1981), the radionuclides in LLW that are most  strongly
affected by cation exchange and surface area include cesium,
strontium, uranium and radium.  The minerals most capable  of
affecting cation exchange and having the greatest surface  area
are the clay minerals  (generally less than 2-micron  size in
diameter) and zeolites.  The sorptive minerals  most  responsive
to cation exchange, in order of priority, are smectite
(montmorillonite), zeolites, illite, kaolinite,  and  chlorite.
The greater surface area occurs in smectite  (montmorillonite)
and zeolites which are generally confined to the clay-size
(less than 2 microns).  The general distribution of  sediment
composition in relation to grain-size distribution  is  given by
Neiheisel  (1983) for ocean sediment at the Atlantic  3,800  m LLW
disposal site.  This study demonstrates the  fact that  a  major
portion of the highly  sorptive minerals and  those with greatest
surface area occur in  the less than 2-micron size  (clay)
fraction.  Since a composition change commonly  occurs  between
silt  and clay-size materials and most of the sorptive  materials
occur  in clay-size fraction, it is desirable to separate these
size  fractions for individual chemical and X-ray diffraction
analysis.  Average mineral composition  (prior to separation)
may be computed using  the texture grain-size curve.  An
accuracy of +_10 percent is considered desirable if  the mineral
data  is to be of assistance in the assessment of radionuclide
retention or geologic  stability of site.  The methods  for
recommended detailed mineral analyses are included  in  a  Methods
Manual  (EPA, 1988).


      Evaluation of the potential for radionuclide retention
requires a detailed mineral analysis of the  sediment that
exceeds the "major minerals constituents" cited in  paragraph
228.13(e) (3) of the current regulation.  It  is  recommended that
a  method with at least +10 percent mineral accuracy  be
specified  for the  potential prediction of radionuclide
retention  such mineral precision would provide.


     The current regulations do not contain  sediment  monitoring
criteria that address the parameters which  (a)  measure
radionuclide retention and  (b) provide  prediction potential of
radionuclide retention by the sediment.  These  considerations
are addressed below with recommendations.


     The sorption distribution coefficient  (Kd)  of  a
radionuclide is a measure of its retention potential  determined
by laboratory analysis of site-specific sediment.   The  Kd  is
used to determine the degree of partitioning  between
radionuclides in solution and the same  radionuclides  in the
solid phase.  The Kd, in effect, represents  the relative length
of time a radionuclide, released to the sediment environment in
solution, is impeded from movement toward the water column by
sorption onto solid surfaces.  The factors that affect  the Kd
of a radionuclide vary with the sorptive minerals of  a
particular sediment, particle size, pH, Eh  (redox), and
chemical speciation of the radionuclide released from the  waste

     The process by which the radionuclides  are removed from
the dissolved phase by particulate matter or  sediment is
generally referred to as scavenging (IAEA, 1986).   If the
release of the dissolved phase is into  the sediment surrounding
the waste package, the scavenging is essentially the  sorption
distribution coefficient (Kd) that is measured  from specific
sediment at the site.  Any release of the dissolved phase
directly to the water column from the waste  package,  however,
is more difficult to estimate for retention  of  the
radionuclide(s) because of the dynamic  nature of the
particulate matter in the benthic nepheliod  layer (BNL).
Nyffeler and Godet  (1986) describe the  nature of the  BNL for a
basin in the NE Atlantic.  Since the BNL particulate  matter is
recognizably higher in organic matter than the  consolidated
sediment at a candidate disposal site,  the sorption
distribution coefficient (Kd) of this material  may  differ  from
the consolidated sediment.  While this  probable difference is
recognized, it is as yet not determined whether it  is
significant enough to warrant a separate  test.   If  such testing
were warranted, it would require enough sample  to perform  the
test; the "fluff" or unconsolidated sediment layer  from
sediment cores might be the most practical  representative
sample of this material.

     The laboratory batch tests for Kd  are described  in  a
Methods Manual  (EPA, 1988)  in  terms of  Rd which  is  the
distribution ratio, instead of the distribution  coefficient
(Kd).  The use of Kd implies sufficient knowledge of  the
chemical systems under investigation  to ensure that a final
reversible equilibrium is attained.   In natural  systems  this is
not always the case, so the value Rd  is determined.   This  is
calculated in the same manner  as Kd but does  not carry  with it
the thermodynamic requirements of a system at equilibrium.   The
distribution ratio  (Rd) and the distribution  coefficient (Kd)
are defined identically,  but,  in actuality, Rd is only  equal to
Kd  at equilibrium.

     The Kds of  radionuclides  are site  specific, and  laboratory
measurements are only as  accurate as  the ability exists  to
duplicate deep-ocean conditions.  Onishi et al  (1981)  cites Kd
measurements from a wide  range of environments,  and data bases
have been developed for various programs which indicate  the
range of values  possible.   Radionuclides with virtually  no
retention by any environment are the  most predictable;  these
include tritium, carbon-14, and iodine-129.   However,  for  other
radionuclides of interest,  such predictability  is not possible,
and few measurements are  available to compare potential  Kds
that exist in ocean environments.  Since Kd measurements for
radionuclide retention are  expensive  (approximately $1,000  per
radionuclide per sample), the  number  of tests performed  should
be  limited to those radionuclides of  most concern.

     The methods commonly employed include the batch  test  and
sediment column  method.   Since the redox state constitutes  a
primary factor  for  redox  sensitive nuclides,  this condition
must also be considered  in  the laboratory testing.  The  redox
conditions in the deep-ocean environment are  addressed, in
Section 1.4.3.


     It is recommended that at least  one sediment core  from
each prospective LLW disposal  site be measured for  Kd's  of
radionuclides of concern  including, as  a minimum, cobalt,
cesium, and strontium.  The measurements should  be  conducted on
samples representative of the  sediment  to 30  cm  depth.


     The retention of some of the radionuclides  in  the  LLW  at  a
deepsea disposal site is sensitive to the oxidation-reduction
(redox) state of the sediments.  The redox state at most
disposal sites will range from oxygenated (aerobic) conditions
on the surface to reducing (anaerobic) conditions with  depth.
This decrease of oxygen with depth is indicative of oxygen
consumption in the sediment below the sediment-water  interface
and reflects input of organic carbon  (Murray and Grundmanis,
1980).  In a qualitative sense this is related to distance  from
the continental margins where production occurs.  Both  the
Atlantic and Pacific are similar in this respect.  The  depth to
oxygen depletion in the sediments in the Atlantic Ocean has
been reported by several investigators (Schmidt  1979, Carpenter
et al 1983, Wilson et al 1983, and Van der Loeff and  Lavaleye
1984), who indicate typical ranges from 10 to 30 cm depth to
oxygen depletion.

     At the NE Atlantic LLW disposal site Van der Loeff and
Waijers (1985) report that average depths of oxygen penetration
extend to 50 cm and as much as 100 cm.  Wilson et al  (1983)
reports the greatest depth to oxygen depletion (10 m) in the
Atlantic in the Cape Verde Abyssal Plain.  In the Pacific Ocean
investigations, Grundmanis and Murray (1982)  report oxygen
depletion as relatively rapid in the first 10 to 15 cm  of
sediment depth in the equatorial region, where the
concentrations of surface organic carbon are also high.
Elsewhere in the Pacific, investigations indicate the aerobic
zone extends to several meters in depth in the sediment.

     The range of the oxygenated sediment environment may vary
in depth from less than the diameter of a 55-gallon waste drum
to as much as several meters.  The retention of  several
radionuclides, including technetium, uranium, cobalt, and
nickel, is affected by the redox state.   This parameter
requires special attention in the assessment of  radionuclide
retention in the sediment of a deep ocean LLW site.
Remobilization at lowered redox potentials below the  depth
where oxygen reaches zero also causes an upward  diffusion
transport of manganese.

     Concentrations of sulfide  sulfur,  iron,  and  manganese
observed in the sediment profile can  be  used  for  understanding
variations in redox sensitive radionuclides.   These  parameters
also provide a rough correlation with redox conditions obtained
by the more precise measurement of NC>3  in  sediment pore water
for determination of oxygen depletion.   Care  must be exercised
in the use of these parameters; e.g.,  if detrital pyrite or
relict conditions occur in the  sediment, interpretations might
be misleading.  However, the use of these  parameters in a
well-characterized sediment is  considered  of  interpretative
value in correlating with the redox condition of  the sediment
column.  In order to be effective, measurements should be made
at 5 cm intervals for the full  30 cm  of  sediment  core.  Thus
the thickness of the aerobic layer to oxygen  depletion could,
in a thoroughly characterized site, be  estimated  to  within
approximately 5 cm if the redox boundary occurs within the
sediment core.

     Sulfur compounds in marine sediments  range from 0.02 to
2.0 percent and reduction of sulfate  to  sulfide will not occur
in the aerobic layer.  In fact, sulfide  formation in sediments
occurs well below the sediment  depth  of  measurable oxygen
depletion.  For example, Schmidt  (1979)  estimated the depth of
sulfide formation would occur at 50 cm  depth  at a Gulf of Maine
2,500m depth location in the Western  North Atlantic  where pore
water chemistry and Eh meter studies  indicated the depth to
oxygen depletion at 30 cm.  For sulfides to form  in  the
anaerobic  layer, both iron and  sulfate-reducing bacteria must
be present.  The presence of both sulfate-reducing bacteria and
iron in the sediment will generate pyrite  (FeS2)  in  the
anaerobic  layer.  The sulfide sulfur  test  is  a relatively
simple and inexpensive test that has  limited  application and in
some cases may be used to correlate with the  approximate
boundary to the anaerobic layer.

     The redox state and sulfide formation are also  of interest
in waste container corrosion.   For example, a steel  drum,  well
below the  depth of oxygen depletion and  in the presence of
anaerobic, sulfate-reducing bacteria,  would be corroded by a
process called cathodic depolarization  (Uhlig, 1971).   As
Dexter  (1982) indicates, the bacteria utilize hydrogen in their
metabolism to reduce sulfates to sulfides.  The sulfides,  in
turn, form an iron-sulfide scale on the  steel which  is cathodic
to a bare  steel surface.  Thus, this  mechanism of corrosion
occurs in  anaerobic conditions  where  there is a source of

     The manganese and iron in sediments correlate  with  the
redox state and radionuclide retention potential  of  sediments.
Under oxidizing conditions, iron is highly  insoluble.  However,
under mildly reducing conditions, Fe++ may  be  solubilized  and
precipitate in sulfide-bearing sediments.   Technetium  from a
LLW waste drum, released to a reducing environment,  has  been
reported to be immobilized in the presence  of  Fe++  (Van  der
Graff et al, 1984).  Manganese is also controlled by the redox
state, and the factors which cause remobilization and
deposition of manganese influence the migration potential  of
cobalt and nickel.

     The process of manganese reduction and mobilization in
marine sediment is well documented.  Froleich  et  al  (1979)
describe the accumulation of manganese at the  surface  of the
anaerobic boundary layer in marine sediment.   A manganese
"spike" at this sediment depth essentially  marks  the point of
oxygen depletion.  This spike of manganese  can be used to
estimate the depth at which anaerobic conditions  prevail in the
sediment; however, because of the sharpness of the  boundary,
care must be exercised in the sample spacing requirements.  The
manganese profile is also a mirror image of the iron profile;
manganese increases as iron decreases in the sediment  core.
The inflection points on a concentration-versus-depth  plot of
manganese and iron are thus also of value for  correlation  with
the redox boundary which is determined by more precise,
methods.  The interpretation of these parameters  is  difficult
unless the point of precipitation lies well below the  zone of

     The inductively coupled plasma (ICP) spectrometer method
and atomic adsorption spectrophotometry  (AAS)  methods  are
commonly used to determine manganese and iron  in  marine
sediment.  These should be conducted on sediment  samples at
5 cm intervals to assist in determining redox  trends with  depth
for the 30 cm of core length.

     An electrometric method that reflects  on  the redox  state
of marine sediment is the Eh meter, using a combination  of
platinum and reference electrodes.  Measurements  are read  in
millivolts.  The measurements, however, are rather  qualitative
because of the complex electrochemistry involved  if  more than
one mineral system or valence state is present.   According to
Meyer  (1982), the use of the Eh probe will  not indicate  whether
oxidation or reduction will occur but will  give an  approximate
indication of oxidizing or reducing conditions.   Lindberg  and
Runnells (1984) also question the analysis  of  redox  state  by
simple electrochemical means.

     Any valid Eh measurement of sediment  redox  conditions  must
be performed as soon as the core sample  is  collected  aboard
ship.  A plastic liner with holes drilled  at  5 cm  intervals is
inserted into the box corer to prepare the  sample  for  prompt Eh
measurements.  As an example, samples obtained in  this manner
at the Atlantic 2,800m LLW disposal  site  in the  fall  of 1984
indicated oxygenated conditions for  the  top 16.5 cm of sediment
core.  At 16.5 cm depth, a measurement of  229 mV was  obtained,
indicating that the redox boundary was probably  being
approached and could be expected perhaps  within  several more
centimeters.  Schmidt (1979) used both the  Eh meter and pore
water chemistry analysis for oxygen  depletion in an
investigation of sediment from a 2,500m  depth in the  NW
Atlantic and found that the point of oxygen depletion  coincided
with an Eh reading of 225 mV.

     The redox state of the sediment is  best determined by
analysis of the oxygen depletion in  the  pore water of  the
sediment with depth.  The most quantitative measurement for the
determination of oxygen depletion is the  nitrate test  of the
sediment pore water.  Sayles and Livingston (1984) discuss  this
method for marine sediment cores.  The extraction  of  pore water
from the sediment for nitrate analysis is  relatively  complex;
however, this method of approach is  the  most reliable  technique
available for determination of redox conditions  with  depth  in
the sediment.


     The redox state of the sediment at  a  prospective  LLW site
should be measured because of its requirement in (a)  Kd
measurement of sediment involving redox  sensitive  radionuclides
and  (b) providing data that has direct application to
prediction of radionuclide retention.  The  measurement of redox
as a sediment monitoring criteria parameter should include:

      (1) Measurement of oxygen depletion  in pore water by
         nitrate analysis as a primary technique for
         determination of redox state of  the sediment.

      (2) Measurement of (a) Eh (by Eh meter), (b)  sulfide
         sulfur, and (c) manganese and iron in the sediment at
         5 cm intervals to 30 cm depth for  sediment
         characterization and interpretative values relative to
         sorption of redox sensitive radionuclides and
         correlation with the redox  conditions measured in  (1)


     Measurement of pH is important to characterizing  sediment
in a LLW disposal site.  According to Zobell  (1946), the  pH
range of recent marine sediments is 6.4 to 9.5 and  that of Eh
is from +0.350 to -0.500 mV.  In the deepsea  environment, pH
will be more constant whereas the Eh will vary widely  in
relation to changes in redox conditions.  Typical pH values of
sediment samples taken in the vicinity of LLW disposal sites  in
the Atlantic and Pacific Oceans are 7.2-7.8  (NW Atlantic),
7.9-8.1 (NE Atlantic), and 7.9 at the Farallon Islands

     The most common method for pH measurement is the
electrometric determination of the activity of the  hydrogen ion
by potentiometric measurement using a glass electrode  and a
reference electrode.  Determinations of pH should be made
aboard ship soon after receiving the sediment aboard and  as
soon as possible at the laboratory where it is sent for the
other tests.


     It is recommended that pH be included as a sediment
monitoring requirement for any proposed  low-level  radioactive
waste site.  This inexpensive parameter has application in
radionuclide retention prediction for most radionuclides of


     Analysis of sediment geotechnical properties provides
insight into the penetration potential of waste packages  into
the bottom sediments and probable subsequent  settlement of
waste packages.  The analysis may provide information on the
past geological stability of a site and show  if active erosion
or rapid sediment loading is occurring.  The  engineering
information will aid in evaluating the sites  for waste package
insertion and burial should subseabed disposal be considered a
viable option in the future for LLW.

     The parameters to be measured will focus on establishing
the general engineering characteristics of the sediment and
permit some prediction of behavior under various loading
conditions  (e.g., waste package emplacement or impact).   These
parameters may  include those measured or determined from  index
properties  (liquid  limit, plastic limit, and  water  content),
strength, and consolidation tests.  The U.S.  Geological Survey
is currently investigating the geotechnical test parameters
which are appropriate  for deepsea disposal sites.


     It is recommended that basic  index  properties  (liquid
limit, plastic limit and water content)  be  included  in sediment
monitoring criteria.  This test can  be used  to  (a) compare
bottom penetration of the waste drum and (b)  correlate with
geologic stability of the site.  This and other  geotechnical
tests are relatively simple and inexpensive,  and provide
fundamental engineering information.

     Under consideration is the emplacement  of LLW beneath the
sediment surface.  For this proposed option,  additional
geotechnical parameters attendant  to deep-sea penetration and
burial  (e.g., consolidation,  triaxial, and  vane  shear  tests)
are being evaluated.


     X-radiographs of sediment cores allow  the nondestructive
observation of certain textural and  structural features of the
sediment.  The x-radiographs  reveal  biological activity
(bioturbation) in the sediment.

     X-radiographs are made of each  core to  30 cm depth to
determine the extent of bioturbation in  the  sediment.   The
bioturbation process could accelerate the transport  of
radionuclides from within the sediment to the sediment-water
interface as well as acting as a means of transporting
radionuclides sorbed at the surface  to depth.  The depth  of
bioturbation is correlative with redox conditions in that it
relates to activity in the oxygenated layer  of sediment.
However, the depth to the base of  bioturbation activity is not
to be considered the point of oxygen depletion since other
factors are involved.


     It is recommended that x-radiographs be  required  in  the
evaluation of LLW disposal sites.  Since bioturbation  is
considered an undesirable entity,  the degree  of  bioturbution
could be indexed in some manner, based on density of biological
structures.  The index number could  be instrumental  in picking
the most acceptable site.


     Some of the sediment monitoring parameters  may  be used to
correlate with geologic stability  of a site  as well  as provide
predictive capabilities for radionuclide retention.   These
include (a) detailed mineral  composition,  (b) x-radiographs,
(c) index properties, and  (d) texture.


     The detailed mineralogy of  the  sediment  used  to  predict
sorption capabilities of the sediment  also  reflects on  the
geologic stability of the site.  As  an example,  Van der Loeff
et al (1984), interprets the uninterrupted  and constant
composition of the clay fraction in  the NE  Atlantic LLW
dumpsite as indicative of stable geologic conditions  in the top
layer of sediment.  They also correlate turbidite  (rapid
deposition layers) and nonunifprm conditions  with  changes in
mineralogy laterally at deeper depth in cores.

     The x-radiographs of sediment cores, in  addition to
indexing biological activity, reveal sediment structures and
layers in the sediment.  Any disruption of  sediment pattern not
related to biological activity would relate to geologic
stability of the site.  Uninterrupted  sediment layers would
correlate with geologic stability of the site.

     The index properties also relate  to the  geologic stability
of an area.  As an example, Keller et  al (1979), reporting on
the geotechnical properties of the upper continental  slope off
the Atlantic coast, effectively correlates  the physical
properties with depositipnal stability of the region.   In
addition, any major variations of sediment  texture reflect on
the geologic stability of the site.


     It is recommended that sediment monitoring  criteria
parameters that serve as predictors of radionuclide retention
also serve as a monitor of geological  stability  at the  site.


     The size of a deep-ocean LLW disposal  site  will  not exceed
100 square miles  (360 km2).  The density of sampling
locations within a proposed LLW site will be  in  accordance with
the specifications provided in the existing Regulations (par.
228.13(e) (1) (ii).  The maximum number  of replicate samples at
each station of a proposed site will coincide with the  number
indicated in paragraph 228.13(e)(1)(i).  The  actual number of
samples to be tested to a minimum 30 cm depth will depend on
the homogeneity of the sediment parameters  at the  site.


     The existing Ocean Disposal Regulations contain provisions
for measurement of sediment parameters in paragraph
228.13(e)(3), which support the sediment monitoring needs  for
LLW at deep ocean sites.  These parameters  include organic
carbon, texture, particle size distribution, major mineral
constituents, and settling rate.  Because LLW will be
containerized, as specified in paragraph 227.11(a)(l)  of the
Regulations, settling rate will not apply.  The  special
requirement for predicting sorption potential of the sediment
will require modification of existing parameters listed in
paragraph 228.13(e)(3)  to include  (a) detailed mineral analyses
(b) texture grain-size,  (c)  measurement of  sorption
distribution coefficient  (Kd) of Cs, Co, and Sr  and (d) site
characterization parameters that include the following: redox
measurements  (nitrate analysis of pore water for oxygen
depletion), pH, Eh, manganese, iron, and sulfide sulfur.

     The cost of parameters specified for measurement  would
approximate the following:

              Measurement                      Average Cost Per Analysis
pn diiu JLU ^ mi j.pu

J-J . UU
         These are  the basic costs of a normal operating
         laboratory and do not  include ship costs, collection
         apparatus, storage, or personnel costs.

     Additional parameters that relate to physical response of
the sediment to impact of the waste container are still being

      PL 97-424

     The purpose of the proposed criteria  is to determine
acceptability of a specific site that meets the general  site
selection criteria by evaluating and quantifying  its
geochemical and geotechnical immobilization characteristics.
The evaluation of specific wastes proposed for disposal  at a
specific site will require the preparation of a Radioactive
Material Disposal Impact Assessment  (RMDIA).  When such  an
assessment is prepared, a critical determination  will be
whether the radionuclides will be immobilized at  the site.  If
a satisfactory determination is made that  immobilization of the
specific wastes will occur, then an  important consideration
arises.  If radioactive isotopes are released by  a waste
package and retained by the sediment at a  site, rather than
dispersed, the radionuclide concentrations in the sediment will
increase.  It will become important  to establish  sediment
quality criteria or concentration limits linked to effects on
indigenous marine organisms.  The primary  effects on marine
organisms would occur through ingestion of materials.  The
availability of radionuclides to infauna and sessile epifauna
is directly linked to the sediment dynamics (sediment-water
interaction) .

     Although the proposed criteria  are directed  at the
sediment dynamics, particularly physicochemical immobilization
processes, the establishment of sediment criteria will also be
necessary to determine the acceptable amount of radioactive
material that can be disposed of at  a site.

     While it is beyond the scope of the proposed criteria to
consider specific permit evaluation  requirements, early
consideration of some of the questions attendant  to setting
sediment quality criteria would be useful.

     The need for sediment monitoring are  different for  ocean
disposal of hazardous waste than for LLW.  These  differences
are apparent if a comparison is made of the spectrum of
approaches available for setting sediment  quality criteria for
hazardous waste versus LLW.

     *At a national perspective workshop on the  scientific
approaches for establishing sediment quality criteria,  convened
by EPA in November 1984, a review was made of the pros  and  cons
of the various methodologies available.  The status  report  on
this effort, released by EPA in March 1985, identified  four
general approaches for development of sediment  quality
criteria.  These were the  (a) background concentration
approach,  (b) equilibrium partitioning approach,  (c)  water
quality criteria approach, and  (d) bioassay approach.   Within
each of these approaches, hazardous compounds included  polar
organics, nonpolar organics and heavy metals.   Of these
approaches,  all but the background concentration approach  and
bioassay approach require the use of water quality criteria.
Virtually no water quality criteria exist for radionuclides
except for the Interim Drinking Water Standards.  Therefore,
the  background approach seems most feasible since, unlike  the
other approaches, it does not rely on water quality  criteria to
set  sediment quality criteria.  The background  approach relies
on the establishment of a reference concentration against which
increasing concentrations at a site can be compared  in  order to
determine the extent and magnitude of effects from disposal
operations.  The reference concentration reflects the ambient
concentrations existing at a site  (e.g., from nuclear fallout
prior to its use for any disposal operation).   While  it may be
assumed that the reference concentration for radionuclides
represents a "No-effects Level," setting sediment quality
criteria requires (1) cytogenetic and other measurement and
evaluation techniquesJ(see Prepermit Testing Protocols  to
establish the "No-effects Level") and  (2) assessment  of the
factors controlling radionuclide retention and  bioavailability
at deep ocean disposal sites.  As a starting point,  the
radionuclides in the waste could be divided into groups that
respond to similar predictive factors.  One group might be
iodine, carbon, and tritium, which have virtually no  retention
in any known sediment.  Another waste group might contain
cationic species affected by type and amount of sorptive
minerals.  Still 'another group that is sensitive to  oxidation
conditions would require assessment in both oxidizing and
reducing environments.  Radionuclide groups responsive  to
chelating agents, ligands, or other chemical factors
(coprecipitation, etc) would require further consideration.
Although seemingly complex, this approach is feasible because
the  deep ocean environments have more stable conditions
(r.r  stant pH, salinity, etc) than other more variable
environments such as fresh water or shallower marine  water
disposal sites.

     With  the above information, sediment quality criteria
could be established for radionuclides, and applicable
requirements of an ~~lMr'Tn could be evaluated.


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