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MANAGEMENT STRATEGIES FOR DISPOSAL OF CONTAMINATED SEDIMENTS
M. R. Palermo, C. R. Lee, and N. R. Francingues
U.S. Army Engineer Waterways Experiment Station
ABSTRACT
A comprehensive and consistent strategy for selecting
the most appropriate disposal alternative from an environ-
mental standpoint is essential when the disposal of contam-
inated or potentially contaminated dredged material is re-
quired. The U.S. Army Corps of Engineers (COE) has recently
developed a management strategy for use in selecting dispo-
sal alternatives for materials ranging from clean sand to
highly contaminated sediments. A decision-making framework
has also been developed to supplement the management stra-
tegy and provide a logical basis for comparison of test re-
sults with standards or reference information to determine
if contaminant control measures are required in a given
instance. This approach been adopted as official COE policy
for studies involving disposal of contaminated sediments.
BACKGROUND
Beginning in the early 1970s, considerable attention was focused on
the potential environmental effects of dredged material disposal. The
U.S. Army Corps of Engineers (COE) has since devoted major research
efforts toward development of testing protocols and contaminant control
measures for both open-water and confined disposal alternatives. In
1984, efforts were initiated to develop an overall management strategy
based on these efforts. The management strategy presented here has
been adopted by COE as an environmentally sound framework for selecting
alternatives for the disposal of dredged material with any level of
contamination.
Over 95 percent of the total volume of material dredged in the
United States is considered noncontaminated. However, the potential
presence of contamination has generated concern that dredged material
disposal may adversely affect water quality and aquatic or terrestrial
organisms. Since many of the waterways are located in industrial and
urban areas, sediments may be contaminated with wastes from these
sources. In addition, sediments may be contaminated with chemicals
from agricultural practices.
Since the nature and level of contamination in sediment vary great-
ly on a project-to-project basis, the appropriate method of disposal
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may involve any of several available disposal alternatives. Further,
control measures to manage specific problems associated with the pre-
sence or mobility of contaminants may be required as a part of any
given disposal alternative. An overall management strategy for dis-
posal of dredged material is therefore required. Such a strategy must
provide a framework for decision making to select the best possible
disposal alternative and to identify appropriate control measures to
offset problems associated with the presence of contaminants.
The lead responsibility for the development of specific ecological
criteria and guideline procedures regulating the transport and disposal
of dredged and fill material was legislatively assigned to the U.S.
Environmental Protection Agency (EPA) in consultation or conjunction
with the COE. The enactment of various U.S. laws concerned with the
transport and disposal of dredged and fill material, required the COE
to participate in developing guidelines and criteria for regulating
dredged and fill material disposal. The focal point of research for
these procedures is the Dredged Material Research Program (DMRP), which
was completed in 1978; the ongoing Dredging Operations Technical Sup-
port (DOTS) Program and the Long-term Effects of Dredging Operations
(LEDO) Program; and the COE/EPA Field Verification Program (FVP).
Scope
The management strategy presented here is based on findings of
research conducted by the COE, EPA, and others, and experience in act-
ively managing dredged material disposal. Approaches for evaluating
potential for cont~minant-related problems, testing protocols, and the
applicability of various disposal alternatives are discussed. Proce-
dures for conducting tests or for design and implementation of manage-
ment strategies are not presented but are appropriately referenced. A
more detailed presentation of the management strategy is available from
the COE Waterways Experiment Station (Francingues et al., 1985~.
MANAGEMENT STRATEGY
The selection of an appropriate strategy is partially dependent on
the nature of the dredged material, nature and level of contamination,
the physicochemical nature of the disposal site environment, available
dredging alternatives, project size, and site-specific physical and
chemical conditions, all of which influence the potential for environ-
mental impacts. Technical feasibility, economics, and other socioecon-
omic factors must also be considered in the decision-making process.
The technical management strategy presented here mainly considers the
nature and degree of contamination, physicochemical conditions at dis-
posal sites, potential environmental impacts, and related technical
factors. A flow chart illustrating the strategy is shown in Figure 1.
The steps for managing dredged material disposal consist of the
following:
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202
1. evaluate contamination potential,
2. consider potential disposal alternatives,
3. identify potential problems,
4. assess the need for disposal restrictions,
5. select an implementation plan,
6. identify available control options,
7. evaluate design considerations, and
8. select appropriate control measures.
The initial screening consists of examining available historical
data and information on pollutant discharges and spills at the dredging
site to determine whether there is a reason to suspect the presence of
significant concentrations of contaminants.
If the dredged material is clean and/or environmental impacts are
within acceptable limits, conventional open-water or confined disposal
methods may be used. If impacts resulting from conventional disposal
techniques would not be within acceptable limits, contaminated material
may be disposed by either open-water or confined methods with approp-
riate restrictions. Each disposal alternative may pose problems for
managing contaminated dredged material. Based on the initial evalua-
tion, site-specific conditions, dredging methods, and anticipated site
use, the potential contaminant problems can be identified. For open-
water disposal, contaminant problems may be either water column or ben-
thic related. Confined disposal contaminant problems may be related to
either water quality (effluent, surface runoff, or leachate) or con-
taminant uptake (plants or animals).
The magnitude and potential impacts of specific contaminants must
be evaluated using appropriate testing protocols. Such protocols, de-
signed for evaluation of dredged material, consider the unique nature
of dredged material and the physicochemical environment of each dispos-
al alternative. The results of all testing are compiled and evaluated
to determine the potential for environmental harm from contamination,
to examine the interrelationships of the problems and potential solu-
tions, and to determine what restrictions on open-water or confined dis-
posal are appropriate. If impacts as evaluated using the testing proto-
cols are acceptable, conventional open-water or confined disposal may
again be considered.
Specific environmental problems identified using the testing proto-
cols must be addressed by implementation plans appropriate for the
level of potential contamination. Restrictions may also be required
for open-wacer or condoned atsposa. cnat could eliminate certain op-
tions from consideration. Several options may be available for the
selected implementation strategy. Options for controlling water column
and benthic impacts include bottom discharge via submerged diffusers,
treatment. contained aquatic disposal. and subaqueous canning using
. _ ~ ~ ~ ~ . . ~ . ~ ~ ~ . .
~1 - are a=~1~mc~ r~1~;^r~c F^~ ^^r~1~^l i ;r~~ MA A; mr~^c~=1 ~mr~s~t~c~
___, _______ ~ _~ ___ ___ ____ ___> ___ ~&~ TVa_ _~C&~=
include containment, treatment, long-term storage, and reuse. The
degree of contaminant control finally selected may range anywhere
between disposal in open water with no special restrictions to a com-
pletely controlled confinement.
, ~
Many of the technologies identified
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Representative terms from entire chapter:
confined disposal
203
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204
are either commonly used in COE dredging activities or are presently
being evaluated as part of COE's ongoing research and operations.
POTENTIAL PROBLEMS AND TESTING PROTOCOLS
The properties of a dredged material affect the fate of any contam-
inants present, and the short- and long-term physical and chemical envi-
ronment of the dredged material at the disposal site influences the
environmental consequences of contaminants (Gambrel! et al., 19789.
These factors should be considered in evaluating the environmental risk
of a proposed disposal method for contaminated sediment. Where the Whys
sical and chemical environment of a contaminated sediment is altered by
disposal, chemical and biological processes important in determining
environmental consequences of potentially toxic materials may be
affected.
The major disposal alternatives are open water (subaqueous environ-
ment) and confined (subaqueous, intertidal, or upland environment). A
number of variations exist for each of the major alternatives, each hav-
ing some influence on the fate of contaminants at disposal sites. Envi-
ronmentally sound disposal of dredged material can be achieved using
any of the major alternatives if appropriate management practices are
employed.
Water Column
Although the vast majority of heavy metals, nutrients, and petrol-
eum and chlorinated hydrocarbons are usually associated with the fine--
grained and organic components of the sediment (Burke and Engler,
1978), there has been little evidence of biologically significant
release of these constituents from typical dredged material to the
water column during or after dredging or disposal operations. Turbid-
ity due to fine particulates suspension is only of limited short-term
impact.
Water column impacts can best be evaluated by chemical analyses of
dissolved contaminants for which water quality criteria exist. The
standard elutriate test is used for this purpose (U.S. EPA/COE, 1977~.
Results must be considered in light of mixing and dilution. If the
criteria are exceeded after consideration of mixing, a bioassay can be
used to determine the potential consequences of exceeding the criteria
for a short time.
Benthic
The DMRP results conclusively indicated that most subaqueous dis-
posal in low-energy aquatic environments where stable mounding will
occur will favor containment of contaminated materials. Dredging and
disposal do not introduce new contaminants to the aquatic environment,
but simply redistribute the sediments, which are the natural depository
205
of contaminants introduced from other sources. The potential for
accumulation of a contaminant in the tissues of an organism (bio-
accumulation) may be affected by several factors, such as duration of
exposure, salinity, water hardness, exposure concentration, tempera-
ture, chemical form of the contaminant, and the particular organism
under study. The relative importance of these factors varies. Elev-
ated concentrations of contaminants in the ambient medium or associated
sediments are not always indicative of high levels of contaminants in
tissues of benthic invertebrates. Bulk analysis of sediments for con-
taminant content alone cannot be used as a reliable index of availabil-
ity and potential ecological impact of dredged material, but only as an
indicator of the presence of contaminants and total contaminant con-
tent. Bioaccumulation of most contaminants from sediments is generally
minor.
Potential benthic impacts can be evaluated by comparing contaminant
concentrations in the sediments of both the dredging and disposal
sites. If the concentrations are higher in the dredged material than
in the disposal site sediment, a bioassay/bioaccumulation test can be
used to determine the environmental consequences of the contaminant
levels.
Effluent Quality
Dredged material placed in a confined disposal area undergoes sedi-
mentation, while clarified supernatant waters are discharged from the
site as effluent during active dredging operations. The effluent may
contain levels of both dissolved and particulate-associated contamin-
ants. A large portion of the total contaminant level is particulate
associated.
A modified elutriate test procedure, developed under the LEDO pro-
gram (Palermo, 1986), can be used to predict both the dissolved and
particulate-associated contaminant concentrations in confined disposal
area effluents (water discharged during active disposal operations).
The laboratory test simulates contaminant release under confined-dis-
posal conditions and reflects sedimentation behavior of dredged mate-
rial, retention time of the containment, and chemical environment in
ponded water during active disposal. The acceptability of the proposed
confined disposal operation can be evaluated by comparing the predicted
contaminant concentrations with applicable water quality standards
while considering an appropriate mixing zone. In some cases appropri-
ate water column bioassays would be required if water quality criteria
are exceeded.
Surface Runoff Quality
After dredged material has been placed in a confined disposal site
and the dewatering process has been initiated, contaminant mobility in
rainfall-induced runoff is considered in the overall environmental im-
pact of the dredged material being placed in a confined disposal site.
206
The quality of the runoff water can vary depending on the physicochemi-
cal processes that occur during drying and the contaminants present in
the dredged material.
An appropriate test for evaluating surface runoff water quality
must consider the effects of the drying process to adequately estimate
and predict runoff water quality. At present there is no single sim-
plified laboratory test to predict runoff water quality. A laboratory
test using a rainfall simulator has been developed and is being used to
predict surface runoff water quality from dredged material as part of
the FVP (Lee and Skogerboe, 1983~.
Leachate Quality
Subsurface drainage from confined disposal sites in an upland envi-
ronment may reach adjacent aquifers. Fine-grained dredged material
tends to form its own disposal area liner as particles settle with per-
colation drainage water, but the settlement process may require some
time for self-sealing to develop. Since most contaminants potentially
present in dredged material are closely adsorbed to particles, only the
dissolved fraction will be present in leachates. A potential for leach-
ate impacts exists when a dredged material from a saltwater environment
is placed in a confined site adjacent to freshwater aquifers. The
site-specific nature of subsurface conditions is the major factor in
determining possible impact (Chen et al., 1978~.
An appropriate leachate quality testing protocol must predict which
contaminants may be released in leachate and the relative degree of re-
lease. Laboratory testing protocols to predict leachate quality from
dredged material disposal sites have been developed and applied, how-
ever additional evaluations of available leaching procedures are needed
before a leaching test protocol for confined dredged material can be
recommended. These evaluations are now an ongoing COE research effort.
Plant Uptake
After dredged material has been placed in either an intertidal, wet-
land, or upland environment, plants can invade and colonize the site.
There is potential for movement of contaminants from the dredged mate-
rial into plants and then eventually into the food chain.
A test protocol for plant uptake was developed under the LEDO
program based on the results of the DMRP. This procedure has been
applied to testing a number of contaminated dredged materials and has
given appropriate results and information to predict the potential for
plant uptake of contaminants from dredged material (Folsom and Lee,
1981, 1983).
Animal Uptake
Animals have also been known to invade and colonize confined
207
dredged material disposal sites. In some cases, prolific wildlife hab~-
tats have become established on these sites. Concern has developed re-
cently on the potential for animals inhabiting either wetland or up-
land, terrestrial, confined disposal sites to become contaminated and
contribute to the contamination of food chains associated with the
site .
A test protocol is being tested under the FVP that utilizes an
earthworm as an index species to indicate toxicity and bioaccumulation
of contaminants from dredged material (Simmers et al., 1983~.
Other Impacts
Potential impacts could arise from flammable.or noxious emissions
released from the dredged material during dredging and disposal opera-
tions. Standard safety precautions will eliminate adverse human health
effects and are normally required under contract specifications.
SELECTION OF A DISPOSAL ALTERNATIVE
Disposal alternatives are divided into general classes: open
water' confined, open water with restrictions, and confined disposal
with restrictions. Disposal alternatives with restrictions are used
whenever results of the testing protocols indicate they are needed.
Conventional disposal alternatives are well documented in DMRP reports
(Herner and Co., 1978) and are described only briefly in this section.
The preference of open-water disposal over confined disposal, or vice
versa, is dependent on many factors other than contaminants, as dis-
cussed earlier.
Open-Water Disposal
This disposal alternative involves conventional open-water disposal
techniques. This alternative would be selected if the initial evalua-
tion and testing protocols as discussed earlier indicated that water
column and benthic effects are acceptable.
Dredged material can be placed in open-water sites by direct pipe-
line discharge, hopper dredge discharge, or dumping from scows. For
conventional open-water disposal, no special placement techniques are
used and the material is normally discharged at a selected point within
a designated disposal site.
Ocean open-water disposal sites are designated using a set proce-
dure (EPA, 1977~. Criteria for site designation include storage capac-
ity requirements and chemical/biological considerations. Procedures
for site selection are under review with the objective of improving the
efficiency of the overall site designation process.
The capacity of open-water disposal sites is determined by the vol-
ume of accumulated material that can be placed without exceeding the
designated site boundaries or exceeding water-depth constraints.
208
Capacity also may be determined by the assimilative ability of the
waters within the designated site boundaries, i.e. , their ability to
reduce concentrations of suspended material and associated contaminants
to an acceptable level. Procedures for evaluation of open-water
disposal site capacity to include descent and spread of discharges,
dispersion, erosion and resuspension from mounds, and consolidation of
mounds is currently under study by the COE.
The open-water environment is physically dynamic, and materials
placed in open water will be dispersed, mixed, and diluted to some
degree. Therefore, all evaluative procedures must be interpreted in
light of the mixing expected at the disposal site. Any of several
methods or models (Holliday et al., 1978) may be used to estimate the
maximum concentration of the liquid and suspended particulate phases
found at the disposal site after initial mixing.
Confined Disposal
Conventional confined disposal consists of placing or pumping the
dredged material into a diked containment area where the material set-
tles and consolidates. The area should be designed to provide good sed-
imentation and sufficient volume for storage (Palermo et al., 1978~.
The supernatant water is discharged over a weir, which is designed to
maintain good effluent quality by minimizing resuspension of settled
material. If the turbidity of the effluent exceeds applicable water
quality standards, a chemical clarification system may be used for
additional solids removal (Schroeder 1983~. Following completion of
the disposal operation, the site should be managed to promote consoli-
dation and drying (Haliburton, 1978~. The containment area can then be
used for additional disposal, mined for productive use of the material,
or returned to the sponsor for other uses (Montgomery et al., 1978~.
Open-Water Disposal with Restrictions
In cases where testing protocols indicate that water column or ben-
thic effects will be unacceptable when conventional open-water disposal
techniques are used, open-water disposal with restrictions may be con-
sidered. This alternative involves the use of dredging or disposal
techniques that will reduce water column and benthic effects. Such
techniques include use of subaqueous discharge points, diffusers, sub-
aqueous confinement of material, or capping of contaminated material
with clean material. The same basic considerations for conventional
open-water disposal site designation, site capacity, and dispersion and
mixing also apply to open-water disposal with restrictions.
Submerged Discharge
The use of a submerged point of discharge reduces the area of expo-
sure in the water column and the amount of material suspended in the
209
water column and susceptible to dispersion. The use of submerged dif-
fusers also reduces the exit velocities for hydraulic placement, allow-
ing more precise placement and reducing both resuspension and spread of
the discharged material. Considerations in evaluating feasibility of a
submerged discharge and/or use of a diffuser include water depth, bot-
tom topography, currents, type of dredge, and site capacity. Diffusers
have been successfully demonstrated in the Netherlands and in the
United States (Haves et al., 1988~.
Subaqueous Confinement
The use of subaqueous depressions or borrow pits or the construc-
tion of subaqueous dikes can provide confinement of material reaching
the bottom during open-water disposal. Such techniques reduce the
areal extent of a given disposal operation, thereby reducing both phys-
ical benthic effects and the potential for release of contaminants.
Considerations in evaluating feasibility of subaqueous confinement
include type of dredge, water depth, bottom topography, bottom sediment
type, and site capacity. Subaqueous confinement has been utilized in
Europe and to a limited extent by the COE New York District. Precise
placement of material and use of submerged points of discharge increase
the effectiveness of subaqueous confinement.
Capping
Capping is the placement of a clean material over material consi-
dered contaminated. Considerations in evaluation of the feasibility of
capping include water depth, bottom topography, currents, dredged mate-
rial and capping material characteristics, and site capacity. Both the
Europeans and the Japanese have successfully used capping techniques to
isolate contaminated material in the open-water disposal environment.
Capping is also currently used by the COE's New York District and New
England Division as a means of offsetting the potential harm of open-
water disposal of contaminated or otherwise unacceptable sediments.
The London Dumping Convention has accepted capping, subject to careful
monitoring and research, as a physical means of rapidly rendering
harmless contaminated material dumped in the ocean. The physical means
are essentially to seal or sequester the unacceptable material from the
aquatic environment by a covering of acceptable material.
The efficiency of capping in preventing the movement of contami-
nants through this seal and the degradation of the biological community
by leakage, erosion of the cover (cap), or bioturbation are being ad-
dressed by research under the LEDO program. The engineering aspects of
cap design and placement are being addressed under the COE's Dredging
Research Program (DRP). It is possible that techniques and equipment
can be developed that will provide a capped dredged material disposal
area as secure from potential environmental harm as upland confined
disposal areas. The capping technique for disposal of dredged material
has potential for relieving some pressure on acquiring sites for
210
confined disposal areas in localities where land is rapidly becoming
unavailable.
Chemical/Phys ical/Biological Treatment
Treatment of discharges into open water may be considered to reduce
certain impacts. For example, the Japanese have used an effective in-
line dredged material treatment scheme for highly contaminated harbor
sediments (Barnard and Hand, 1978~. However, this strategy has not
been widely applied and its effectiveness has not been demonstrated for
solution of the problem of contaminant release during open-water
disposal.
Confined Disposal with Restrictions
Site Selection and Design
Conventional confined disposal methods, described previously, can
be modified to accommodate disposal of contaminated sediments in new,
existing, and reusable disposal areas. The design or modification of
these areas must consider the problems associated with contaminants and
their effects on conventional design.
Site location is an important consideration since it can mitigate
many contaminant mobilization problems. Proper site selection may re-
duce surface runon and therefore contaminated runoff and contaminant
release by flooding. Groundwater contamination problems can be offset
through selection of a site with natural clay foundation instead of a
sandy area and through avoidance of aquifer recharge areas (Gambrel! et
al., 1978~.
Careful attention to basic site design as discussed previously will
aid in implementing many of the controls outlined. Retention time can
be increased to improve suspended solids removal and, therefore, contam-
inant removal. Additional pending depth can also improve sedimenta-
tion. Decreasing the weir loading rate and improving the weir design
to reduce leakage and control the discharge rate can also reduce the
suspended solids and contaminant concentration of the effluent. Dewa-
tering should be examined carefully before selecting a method, since it
promotes oxidation of the material and thereby increases the mobility
of certain contaminants (Gambrel! et al. 1978~. Care must also be
taken to reduce loss of contaminated sediment by erosion during drain-
age and storm events.
Four options are considered available for confined disposal with
restrictions. These options include
I. containment--dredged material and associated contaminants are
contained within the disposal site;
2. treatment--dredged material is modified physically, chemically,
or biologically to reduce toxicity, mobility, etc.;
3. storage and rehandling--dredged material is held for a temporary
211
period at the site and later removed to another site for ulti-
mate disposal; and
4. reuse---dredged material is classified and beneficial uses are
made of reclaimed materials;
Obviously, combinations of the above options are available for a par-
ticular dredging operation.
Effluent Controls
Effluent controls at conventional confined disposal areas are gener-
ally limited to chemical clarification. The clarification system is de-
signed to provide additional removal of suspended solids and associated
adsorbed contaminants as described in Schroeder (1983~. Additional con-
troLs can be used to remove fine particulates that will not settle or
to- remove soluble contaminants from the effluent. Examples of these
technologies are filtration, adsorption, selective ion exchange, chemi-
cal oxidation, and biological treatment processes. Beyond chemical
clarification, only limited data exists for treatment of dredged mate-
rial (Gambrel! et al., 1978~.
Runoff Controls
Runoff controls at conventional sites consist of measures to
prevent erosion of contaminated dredged material and dissolution and
discharge of oxidized contaminants from the surface. Control options
include maintaining ponded conditions, planting vegetation to stabilize
the surface, liming the surface to prevent acidification and to reduce
dissolution, covering the surface with synthetic geomembranes, and/or
placing a lift of clean material to cover the contaminated dredged
material (Gambrel! et al., 1978~.
Leachate Controls
Leachate controls consist of measures to minimize groundwater pol-
lution by preventing mobilization of soluble contaminants. Control
measures include proper site selection as described earlier, dewatering
to minimize leachate production, chemical admixing to prevent or retard
leaching, lining the bottom to prevent leakage and seepage, capping the
surface to minimize infiltration and thereby leachate production, vege-
tation to stabilize contaminants and to increase drying, and leachate
collection, treatment, or recycling (Gambrel! et al., 1978~.
Control of Contaminant Uptake
Plant and animal contaminant uptake controls are measures to pre-
vent mobilization of contaminants into the food chain. Control meas-
ures include selective vegetation to minimize contaminant uptake,
212
liming or chemical treatment to minimize or prevent release of contami-
nants from the material to the plants, and capping with clean sediment
Or excavated material (Gambrel! et al., 1978~.
Other Controls
The control of gaseous emissions that might present human health
hazards can consist of physical measures such as covers, vertical bar-
riers, control trench vents, pipe vents, and gas-collection systems.
Wind-erosion control of contaminated surface materials is another type
of management or operating control to minimize transport of contami-
nants off site. Techniques for limiting wind erosion are generally
similar to those employed in dust control and include physical, chem-
ical, or vegetative stabilization of surface soils (U.S. COE, 1983~.
Many of the contaminant controls described in the preceding para-
graphs are directly applicable to the control of highly contaminated
sediments. These controls will be extremely site specific. Special
considerations that are based on the physical nature and chemical
composition of the dredged material will be required to effectively
design a confined disposal facility. For example, some contaminated
dredged material may require in-pipeline treatment prior to discharging
the material into the containment facility. Similarly, if the facility
requires a bottom liner system, the liner materials (synthetic membrane
or clay) must be chemically compatible (resistant) with the dredged
material to be placed on them. Special compatibility testing will be
needed for selection of appropriate liner materials. Other require-
ments such as leachate detection and monitoring are likely due to the
potentially adverse environmental effects of the liner leaking.
DECISION -MAKING FRAMEWORK
A decision-making framework has been developed that utilizes the
management strategy described above and incorporates the results from
the suite of test protocols (Lee et al., 1986~. Reference information
and data from the test protocols are used to make the decisions called
for in the framework. Detailed procedures for using the framework and
example applications using data from reference sites and testing
protocols are found in Lee et al. (1986~.
Responsibility for Local Authority Decisions
There are certain decisions that must be made initially and then
periodically within the decision-making framework that are the sole
responsibility of the local authorities. These local authority deci-
sions (LADS) are required to initially set specific goals to be
achieved. For example, a LAD must establish the environmental quality
ultimately desired at the site and the rate at which this goal is to be
achieved. A LAD must determine whether or not to consider mixing zones
213
when test results exceed reference site values or water quality crite-
ria. A LAD must determine the appropriate reference Biters) for test
result comparisons in the decision-making framework in order to achieve
the ultimate and intermediate goals. The selection of reference sites
can vary from the actual disposal site to a pristine background site.
This selection is dependent on the goal established for the area such
as a goal of nondegradation (reference site is disposal site) or
cleaner-than-present condition (reference site is pristine background
site) or some other goal. The clear identification of the ultimate and
intermediate goals and selection of appropriate references to achieve
them is a crucial responsibility of the local authorities and will
influence the outcome of all test result interpretations.
Evaluation of Respective Contaminant Pathways
Evaluation of respective contaminant pathways under the framework
is illustrated by flowcharts. Examples of the flow charts for the open
water contaminant pathways (water column and benthic) are shown in Fig-
ures 2 and 3. Similar flowcharts are available for the confined dis-
posal pathways of effluent discharge, surface runoff, leachate, and
direct uptake by plants and animals.
Test results are compared to established numerical values where
these are available and appropriate for test interpretation. When such
values do not exist, the framework provides guidance on interpreting
test results in comparison to results of the same test performed on a
reference sediment. For each test, guidance is provided on these bases
for determining whether or not restrictions on the discharge are re-
quired to protect against contaminant impacts or whether further evalua-
tion is required to determine the need for restrictions. In some
cases, there is inadequate scientific knowledge to reach a decision
solely on the basis of test results, and LAD s that incorporate both
scientific and administrative judgments are required to reach a deci-
sion. In such cases, guidance is given on evaluating the scientific
considerations involved.
In this manner, guidance is provided for systematically interpret-
ing the results of each test required to evaluate potential impacts of
aquatic disposal and upland disposal. Applying the systematic detailed
guidance will lead to a decision that restrictions are or are not re-
quired for aquatic disposal and/or upland disposal.
IMPLEMENTATION
COE Policy
of contaminated sediments (Kelly
The Management Strategy/Decision-Making Framework approach was
adopted as official COE policy in 1985 for studies involving disposal
~ __,, 1985 ~ . Additional guidance on use of
these approaches under COE's regulatory program was provided in 1987
(U. S . COE, 1987) . The recently adopted Dredging Regulation (33 Code of
214
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Federal Regulations 320) incorporated the strategy approaches by refer-
ence. The regulation also describes the approach as the basis of a
"federal standard," intended to meet environmental requirements at
least cost within a consistent national framework.
The technical approaches used in the management strategy have
received widespread acceptance by federal and state agencies. In fact,
the initial development of the decision-making framework was funded by
the Washington State Department of Ecology as a part of its implementa-
tion of the EPA Superfund program. Environment Canada has adopted a
technical approach to disposal alternative evaluation closely patterned
after the management strategy. This approach, illustrated in Figure 4,
was proposed for use in evaluation of dredging projects along the St.
Lawrence River (Rochon, 19859.
Applications
Strategy is now being applied routinely by the COE and the private
sector. Recently, three studies of disposal alternatives incorporated
the strategy in a comprehensive manner, utilizing testing approaches
for both open-water and confined disposal:
2.
1. Indiana Harbor, Indiana, a project in COE's Chicago District
involving PCB-contaminated sediment (U.S. COE Environmental
Laboratory, 1987~;
. Everett Harbor, Washington3 a Navy homeport project involving
approximately 1 million yd of contaminated sediment (Palermo
et al., 1986~; and
.. New Bedford Harbor, Massachusetts, a Superfund project involving
sediments highly contaminated with PCB's and metals (Francinques
and Averett, 1988~.
These projects are example applications of the Management Strategy/
Decision-Making Framework.
Refinement
Refinement of the technical approaches used in the management stra-
tegy is an ongoing effort under COE research programs concerned with
the environmental effects of dredged material disposal. The objectives
of these efforts are to develop appropriate tests and procedures,
improve accuracy of predictions, and reduce the costs of testing and
evaluations.
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217
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