J. D Germano.

An integrated, tiered approach to monitoring and management of dredged material disposal sites in the New England region online

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site. The selection of "appropriate"
reference stations will include the
following factors:

1. More than one reference location
outside the disposal site is needed
to characterize the ambient bottom
adequately (Hurlbert, 1984).

2. The reference stations should have
had the same community structure
as the (pre)disposal mound area
(determined by a baseline survey).

3. The reference stations should have
a similar sediment type as the
(pre)disposal mound location. The
reference station should show no
physical or chemical evidence of
historical disposal.

4. The reference stations and disposal
mound should be located within
comparable water depths and as
near to one another as possible
without subjecting the reference
stations to the possibility of

An Integrated, Tiered Approach to Monitoring and Management of Dredged Material Disposal Sites


contamination by disposal
operations or post-disposal
transport. This can be done by
locating the reference station at a
position that is offset from the
major downstream transport
direction(s) of the disposal site.

The question arises what is considered
a significantly lower population
density on the disposal mound which
would trigger monitoring efforts to be
initiated in the next lower tier (Box 2.5
in Tier 2)? No absolute density can be
cited as a yardstick until historical
REMOTS® photographs from
immediate post-disposal surveys are
examined with this objective in mind.
One must also take into account
natural year-to-year variability in
recruitment of different pioneering
species. The important measure is a
test of significance between the
population mean for the disposal
mound compared with the reference
stations. Selection of the level of
significance to reject the null
hypothesis will be a judgement on the
part of the resource manager. It is not
necessary to set high levels of
significance for this test. It may be
sufficient for management purposes to
detect that the disposal site has mean
population densities that are 2 times
lower at the disposal mound at 80% of
the station replicates than on the
ambient seafloor before rejecting the
null hypothesis and proceeding to Box
2.5. These kinds of judgements about
decision thresholds initially must be
based on historical data and be revised
over time as information is
accumulated about the year-to-year
variability in this measure.

Box 2.3 "Expected Response, No

Immediate Action Required.. "

If population densities of
pioneering polychaetes are equal to or
higher on the new disposal mound
than the ambient seafloor within 4-12
weeks after disposal has ceased, this is
the predicted response of normal
recovery following a disturbance; there
is no need for additional testing or
monitoring at this point.

The frequency of periodic
monitoring will depend on the
political or ecological sensitivity of the
disposal site or operation. If high-
resolution monitoring is required, the
first year's monitoring may involve an
additional late summer and/or late fall
surveys. Otherwise, repeated surveys
on an annual basis are all that is
required to monitor the normal
development of subsequent
successional stages.

Underlying Assumptions : The
population and successional response
is used as an indicator that
colonization is not being inhibited by
physical or chemical factors specific to
the disposal mound. However, this
does not mean that bioaccumulation is
not taking place. As stated in Section
4.1, methods for analyzing tissue
contaminant levels in pioneering
polychaetes do not exist at this time.
Once these are developed, it would be
possible to insert another level of
assurance to check the initial
evaluation protocol by analyzing tissue
contaminant levels in pioneering
polychaetes. This would verify that
there is no danger of biomagnification
as a result of disposal activities. Until

An Integrated, Tiered Approach to Monitoring and Management of Dredged Material Disposal Sites


these analytical techniques are
developed, however, we are resigned
at this point to having only an acute
mortality response of Stage I species as
a trigger to indicate our evaluation
protocols are faulty.

Sources of Uncertainty: Even
though colonization is proceeding
normally, bioaccumulation still could
be occurring and never be detected.
However, if one has any level of
confidence in the initial permit
evaluation process, the possibility of
this occurrence would be low enough
to eliminate this possibility as a real

Box 2.4 "Stage 2 or 3 Community

Develop After N+l Years?"

In the second year of monitoring,
under normal rates of successional
change, one expects the progressive
addition of Stage II and III taxa. This
commonly is accompanied by the
presence of less dense populations of
Stage I sere species in subsequent
years. This assumes that all disposal
has stopped and the successional
process is uninterrupted by further
disposal or other sources of
disturbance (e.g., bottom scour by a
hurricane). If the disposal mound is
disturbed, the successional status of
the mound may revert to a Stage I sere
and would trigger an evaluation of
causality in tiers 2 or 3.

Stage II seres (tubicolous
amphipods) can occur as early as the
end of year one (3-6 months after
disposal operations have ceased).
Because the mound apex is usually
sandier than the rest of the mound,

tubicolous amphipods may be
aggregated on the mound apex or
distributed in patches over other parts
of the deposit. The presence, timing,
and persistence of Stage II seres is less
predictable, and they may or may not
be an important faunal element in
subsequent years.

Stage III assemblages also may
populate a disposal mound in the first
year as part of a secondary succession
(the process of reestablishment of
conditions similar to the original
community after a temporary
disturbance). Stage III species are
capable of immediately colonizing the
thin flanks of a disposal mound as
adults by burrowing upward through
the thin disposal overburden. The
appearance of species on parts of the
mound that are much thicker than 20-
30 cm requires larval recruitment or
recruitment of free swimming
polychaete epitokes (modes of
initiating primary succession).
Deposit-feeding taxa recruiting in this
way usually appear on disposal
mounds in the second to third years
(assuming no further disposal or major
physical disturbance takes place to
retrograde the succession). The
unstated null hypothesis being tested

H„: Stage 2 or 3 assemblages
(deposit-feeding taxa) are
present on the disposal mound
one year from cessation of
disposal operations.

Once again, data are collected with
REMOTS® technology; acceptance of
the null hypothesis would lead back to
Box 2.3 and provide verification that

An Integrated, Tiered Approach to Monitoring and Management of Dredged Material Disposal Sites


the evaluation of the sediments during
the permitting process was correct.
Rejection of the null hypothesis would
lead to the next level (Box 2.5 in Tier

The frequency of successional
monitoring can be decreased to once
per year or less in the n+1 and
following years. A late summer to
autumn survey is adequate to map the
distribution of well established adult
populations. Deposit-feeding taxa are
recognized from REMOTS® images by
the presence of feeding voids at depth
in the sediment. Once these taxa are
recruited in the spring, it takes the
whole summer for them to grow and
move into the deeper sediment layers.
Well-developed feeding voids are
produced during the summer and fall
when water temperatures are high and
benthic metabolic rates are
correspondingly high. By mapping
these seres in the later summer or
autumn, one is more likely to
characterize successional stages
accurately than if surveys were
conducted in the winter or early
spring when benthic organisms are
relatively inactive.

Once a disposal mound converges
with the ambient seafloor (reference
stations) in terms of the frequency of
encountered equilibrium successional
stages, monitoring may be reduced to
once-every-other year or be tied to
specific pre-conditions such as
reactivation of an area for disposal or
passage of a major storm. The
frequency of long-term monitoring of
disposal mounds that continue to yield
expected responses (i.e. monitoring
results go no further than Tier 1) is a

management decision based on the
sensitivity of the site to fishing
interests, vulnerability of the site to
storm surges, or the occurrence of
regional hypoxia.

4.2.2 Tier Two: Physical Effects and
Related Management Decisions

Box 2.5 "Evaluate Physical Effects "

Tier 2 variables are addressed only
if anomalous colonization rates are
observed in the Tier 1 monitoring ("no"
outputs from Boxes 2.2 or 2.4, Figure
2). If anomalous rates of colonization
are documented in Tier 1, we attribute
this to physical or chemical properties
of the deposited dredged material.

Box 2.6 "Has Change in Physical

Attributes of Mound
Occurred? "

If one arrives at this box via Box
2.2, initial recruitment patterns would
be anomalous if the sediment grain-
size of the initial dredged material
deposit (e.g., a high sand component)
is different than the ambient bottom
(e.g., a primarily silt-clay bottom). If
one arrives via Box 2.4, the physical
effects that are known to affect the
normal (i.e., expected) patterns and
rates of colonization adversely are
sediment erosion and scour. This
process commonly is associated with
the apex of disposal mounds; it is quite
possible for the tidal stream to diverge
and increase in velocity (and
turbulence) as it passes over the
mound. Surface sediment scour
results in a loss of fines, and a coarse
residue of shell and sand may armor
the surface. The initial period of scour

An Integrated, Tiered Approach to Monitoring and Management of Dredged Material Disposal Sites


will remove any larval set, so the
mound apex is usually slower to
recruit than the rest of the deposit.
Secondly, the armored surface will be
faunally distinct from the rest of the
deposit because of the coarse grain
size. Attached epifauna (e.g., hydroids)
and other sedentary or attached
organisms may form a distinct species
assemblage that is different from the
rest of the disposal mound and the
reference stations. The unstated null
hypothesis being tested is:

H : The sediment grain-size major
mode on the disposal mound is
not different from the ambient

Sediment grain-size (major mode) can
be confirmed either through
examination of the REMOTS®
photographs (rapid data return) or
from grab samples and conventional
laboratory grain-size analyses.
Rejection of the null hypothesis would
lead you back to Box 2.3; acceptance of
the null hypothesis would lead to the
next tier now that a change in physical
attributes has been eliminated as a
possible explanation for the anomalous
colonization pattern.

Another physical factor is the mass
or geotechnical properties of disposed
sediments. Sediments which have
very high water content (non-
Newtonian muds) may not provide
settling larvae with adequate support
to keep them at or near the sediment-
water interface until adequate
consolidation has occurred.
Conversely, disposed sediments
representing over-consolidated "fossil"
clays from deep excavation of channel

bottoms may be too cohesive for
penetration by infauna, or the
concentration of detrital (labile) food
may be too low in concentration in
these relict clays to support growth.
These same factors may affect (directly
and negatively) larval choices for

Many of the above physical factors
can be recognized from REMOTS®
sediment-profile images. For example,
changes in the physical attributes of
the mound apex can be documented
through sequential surveys. Difference
in geotechnical properties between the
mound and ambient bottom are
detectable from the amount of prism
penetration and the appearance of the
sedimentary fabric. If evidence for
adverse physical factors are present, it
is accepted as the most parsimonious
explanation for the anomalous nature
of colonization documented.
Monitoring then is continued back in
Tier I, and the colonization status of
the mound is rechecked after 6-12

Underlying Assumptions : The
management decision not to
implement any further action and to
continue to monitor colonization is
based on the assumption that, over
time, the physical properties of the
sediments will come into some kind of
"steady state" condition that will allow
successful, albeit slower, colonization.
For example, scour of the mound apex
will be limited by the armoring effect,
sediments will consolidate to
accommodate recruitment, or "tight"
sediments will be disaggregated
gradually and mixed with ambient
sediments to permit colonization.

An Integrated, Tiered Approach to Monitoring and Management of Dredged Material Disposal Sites


Sources of Uncertainty: Note that
the identification of an unsuccessful
colonization may be attributed solely
to an observed physical factor when, in
fact, the cause is multifactorial. For
example, quasi-fluid sediments may
also contain high inventories of
sedimentary sulfides and/or particle-
bound metals, PAH's, or insecticides.
The identification of a physical factor
is sufficient to identify a cause for an
anomalous colonization, but it may
not identify all contributing factors.

423 Tier Three: Chemical Effects and
Related Management Decisions

This tier is addressed if an
anomalous rate of colonization is
identified, yet no physical factor has
been identified in Tier 2 as a potential
and likely cause.

Box 2,7 "Sediment Bioassays and

Other Measurements "

Because disposal mounds tend to
be heterogeneous physical and
chemical mixtures of sediments, it is
likely that only part of a mound will
show anomalous rates of colonization
related to the discontinuous spatial
distribution of inhibitory substances or
conditions. Once locations of poor
recruitment have been identified in a
REMOTS® survey, sediment samples
are taken at these stations using a grab
or box core to collect sufficient volume
for the required laboratory tests.
These near-surface sediments are then
used to conduct sediment bioassays
using either the same protocols as
required in the original permit
(EPA/NED, 1989) or additional tests
may be added to evaluate the

sensitivity of the initial permit tests.
Other analyses may be included at this
point such as ammonia and sulphide
leachate tests, or an evaluation of
dissolved oxygen at the site.
Numerous causes for the apparent
toxic response are possible, and
evaluation of the appropriate tests and
measurements must be considered on
a project-by-project basis.

Box 2.8

"Toxic Response?"

Results from the laboratory
bioassay tests (animals placed in
sediment from the disposal mound)
are compared with animals in
sediment from the reference stations;
as before, the bioassay tests are for
acute response. Chronic tests
currently are under development by
the USACE and EPA and could be used
when they become available. The
unstated null hypothesis is:

H : Mortalities of organisms in
sediment from the disposal
mound are not significantly
different from reference.

Rejection of the null hypothesis will
place you in Box 2.10 and requires
following the tiered protocol outlined
in Section 5 of this report; acceptance
will place you in Box 2.9, indicating no
cause for alarm and will lead to
repeated periodic monitoring (Box 2.3).
If high mortalities are observed in
both the disposal site and reference
sediments resulting in acceptance of
the null hypothesis, one will need to
re-evaluate either the assessment
technique or explore the possibility
that the reference sediments have been

An Integrated, Tiered Approach to Monitoring and Management of Dredged Material Disposal Sites


If the sediment originally passed
the permit requirements, why might
the disposed sediment fail a second
round of bioassay tests? Samples
taken for the initial permit may have
missed contaminant "hot spots", or
contaminants in the original test may
have been in a form unavailable to the
test organisms. As materials are
excavated and disposed, redox
conditions can change; this in turn
may affect the partitioning coefficient
of a pollutant compound between
particles, interstitial water, and organic
carbon. This phenomenon possibly
can have an effect on the
bioavailability of contaminants. One
needs to examine in detail the
difference in mortalities among the
disposal, reference, and control
sediments and use best professional
judgment to explore the most
parsimonious explanation for a toxic
response at this point.

Underlying Assumptions : Results
of the bioassay test are assumed to
explain the failure of species (e.g.
spionid polychaetes) other than the
test organism(s) to colonize a disposal
mound. Other assumptions about the
adequacy of sediment bioassay testing
were given in Section 3 and the
discussion of Figure 1 (see Box 1.7).

Sources of Uncertainty: The
assumption that the bioassay test is an
adequate "surrogate" test for other
organisms is untested. For example,
amphipod crustaceans (used as a mid-
range sensitivity species in the
laboratory bioassay) are probably more
sensitive to a wide range of sediment
contaminants than spionid or
capitellid polychaetes which are

known to colonize highly
contaminated sediments. This
inference is based on the observation
that spionids and capitellids are found
in contaminated sediments that are
not colonized by amphipods. If a
tested sediment kills a large
proportion of the tested amphipods
(Box 2.8), these results may be
sufficient to explain the failure of
polychaetes to colonize a disposal
mound but the species-to-species
extrapolation is one based largely on
faith. The best use of the amphipod
test would be to explain the failure of
amphipods (a Stage II taxon) to
colonize a mound in the n+1 years
(Box 2.4). Other sources of
uncertainty related to bioassay testing
are discussed in detail earlier (see
discussion in Box 1.7).

Box 2.9 "Assume Due to Physical or

Biological Processes; Reassess
in 6-12 Months "

If no toxic response is observed in
the bioassay test species, the logic path
leads to an apparent paradox. The
cause for a failure of recruitment is
not identified from the measured or
observed physical-chemical features of
the deposit.

Underlying Assumption : The
conclusion is that the cause for the
observed colonization anomaly is
related to a physical or biological
factor that either has been overlooked
or not been measured adequately in
the monitoring program. For example,
intrinsic properties of the recruitment
process itself such as decreased
reproductive success of parent stocks
or external factors such as bottom

An Integrated, Tiered Approach to Monitoring and Management of Dredged Material Disposal Sites


hypoxia or intense trawling activity
may be responsible for the anomalous
patterns observed.

Sources of Uncertainty: If the logic
flow leads one into Box 2.9, this can be
a frustrating result from both a
scientific and management
perspective. A careful review of the
data and measurement program must
be made at this point. One must also
attempt to address the likelihood that
factors extraneous to the measurement
program may be influencing
colonization. For example, the
disposal site may have been affected
by hypoxia while the reference stations
(representing the ambient seafloor),
because of their location, were not
affected by hypoxia. If this appears to
a plausible hypothesis, near-bottom
oxygen measurements might be added
subsequently to the monitoring

It cannot be over-emphasized that
the monitoring protocol illustrated
(Figure 2) does allow for flexibility; as
additional management issues or
objectives are identified, the
monitoring protocol can be revised. If
the measurement program fails to
identify a specific cause for
recruitment, the option always exists
for a conservative management
approach; this would involve going
directly to box 2.11 (capping) instead
of Box 2.9 (reassessment). This option
might prove less costly if one is
adamant about determining the cause
for the anomalous recruitment,
especially if clean capping material
were readily available within the
dredging project area. However, if an
anomalous recruitment pattern is

observed and one decides to cap
without determining the specific cause
for the departure from the expected,
any shortcoming in the initial
permitting evaluation which may have
been responsible will continue to exist
and potentially cause repeated
problems in the future.

Box 2.10 "Re-Evaluate Assessment

Procedure. Cap Disposal

If a toxic response of the tested
bloassay organisms is obtained, it is
necessary to re-evaluate the initial
permit testing procedure. Why did the
material originally tested pass the
permit evaluation screening while the
sediment from the disposal site fails
the test? These are the same issues
discussed above for Box 2.8.

Underlying Assumptions : The
assumption is that the permit testing
was not adequate to identify toxic
sediment or that the toxics are more
available to the tested organisms due
to diagenetic or "weathering" factors of
the sediment at the disposal site.

Sources of Uncertainty: It may not
be possible after-the-fact to identify the
causes for the disparity between the
permit test results (low levels from
bulk chemistry screening or bioassay
results showing no or equivocal
toxicity) and the post-disposal results
(toxicity shown in bioassay). To
further address this problem would
require a considerable research effort
on the bioavailability of a wide range
of contaminants under a wide range of
Eh-pH conditions.

An Integrated, Tiered Approach to Monitoring and Management of Dredged Material Disposal Sites


Box 2.11

"Go To Hfi: Capping
Evaluation Flowchart "

The decision of where and when to
cap depends on the availability of
appropriate capping material from
scheduled projects. Once the capping
operation has been completed, the
monitoring protocol outlined in the
next section will be followed (Figure

The plan as outlined above is
intended to be executed on an annual
basis at all active containment disposal
sites in the New England region. This
tiered monitoring program for
unconfined aquatic disposal can be
applied where disposal projects are
completed in the early spring; disposal
operations stop during the summer
months, and the mounds are available
for primary and secondary succession
without the complicating factor of
continued disposal. At those sites
where disposal occurs on a year-round
basis (e.g., Massachusetts Bay), this
monitoring plan can be instituted once
the mound reaches a sufficient height
and the disposal point is moved to
another location within the site.

It is not uncommon in the New
England region for disposal mounds to
be built up over 2 or more years; large
maintenance projects may require
more than one dredging season to
complete. Monitoring of these
incomplete projects still is intended to
occur on an annual basis (and as
indicated earlier, would best take place
during mid to late summer when
biological activity is at its zenith). This
interim "range" monitoring serves the
purpose of assessing initial

compliance. All of the conditions of
successful colonization (Box 2.1 and
2.2) are expected to be met. If
colonization is not successful,
management may decide to await
completion of the project before an
extensive Tier Two and/or Tier Three
investigation is carried out.

An Integrated, Tiered Approach to Monitoring and Management of Dredged Material Disposal Sites



5.1 Background

If the decision is made at NED to
allow open-water disposal of dredged
material only if capping occurs, then a
tiered monitoring strategy (Figure 3)
more involved than the one presented
in the above section is followed. If one
refers back to the management
overview (Figure 1), this decision point
would be reached if one arrived at Box
1.12 via Box 1.10. A quick glance at
Figure 3 reveals this decision has
important ramifications as far as the
commitment to long-term monitoring.
Capping is not just an "out-of-sight,
out-of-mind" alternative; it is an option

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Online LibraryJ. D GermanoAn integrated, tiered approach to monitoring and management of dredged material disposal sites in the New England region → online text (page 5 of 8)