SAN FRANCISCO PUBLIC LIBRARY
3 1223 06899 1570
ENVIRONMENTAL EFFECTS OF
DREDGING & DISPOSAL
IN THE SAN FRANCISCO BAY ESTUARINE SYSTEM
I SPECIAL STUDIES PROJECT FOR
OF BAY AREA
PREPARED RY: LOUIS H.DISALVO
APR 2 8 1978
8.F. PU UG LIBRARY
San Francisco Public Library
Government Information Center
San Francisco Public Library
100 Larkin Street, 5th Floor
5an Francisco, CA 94102
Not to be taken from the Library
ENVIRONMENTAL EFFECTS OF DREDGING AND DISPOSAL
THE SAN FRANCISCO BAY ESTUARINE SYSTEM
a report to
The Association of Bay Area Governments
Berkeley, California 94705
Louis H. DiSalvo, Ph.D.
Marine Science Consultant
315 Melven Court
San Leandro, CA 94577
Cover Design by Pat Wong
Digitized by the Internet Archive
TABLE OF CONTENTS
STATEMENT OF PROBLEM 1
SECTION I: BASIC CHARACTERISTICS 5
Structure and Water Circulation 5
Chemical Processes 13
SECTION II: ENVIRONMENTAL IMPACTS 23
Direct Effects 24
Indirect Effects 29
SECTION II: REGULATION OF DREDGING 37
LITERATURE CITED 44
APPENDIX A 48
APPENDIX B 52
3 1223 06899 1570
STATEMENT OF PROBLEM
"Dredge Rules Pose Disaster"
SF Examiner, Oct. 27, 1972
"A Witches Brew of Waste"
SF Examiner, Feb. 4, 1973
"Tougher New Dredging Controls Win Support"
SF Examiner, March 22, 1972
"Bay Dredging Controls Held Too Expensive"
SF Examiner, March 21, 1972
"Army Bests Navy in Dredging Dispute"
SF Examiner, Jan. 28, 1972
The preceding are but a small sample of the headlines which have described
the often strident controversies which have developed over the conduct of
dredging, and disposal of dredged material in the San Francisco Bay estu-
arine system. On the wave of environmental activity of the 1960 's and 70' s,
many people came to the realization that they lived near the shores of a
valuable environmental resource. They carried out significant political
actions which resulted in legislation to stop the filling of the Bay and to
control development around its shores. Nationwide, environmental awareness
led to a call for more stringent environment protective legislation, cul-
minating in passage of a number of Acts of Congress including the Federal
Water Pollution Control Act, The National Environmental Policy Act, and the
Marine Research, Protection and Sanctuaries Act, among others. With these
laws, Congress, representing the people, began a long and tedious process
aimed at controlling activities deleterious to the environment, including
the unregulated disposal of dredged material in the nation's waterways.
As the newspaper articles suggest, people became aware indirectly that es-
tuaries are natural sediment traps, and that San Francisco Bay was indeed
trapping large quantities of wastes within its sediments. These sediments
inconveniently settle out in quiet areas of the Bay blocking harbors and
waterways of commercial, military and recreational importance. Indirectly,
the Army Corps of Engineers, which is normally charged with the responsi-
bility of maintaining the waterways, became involved with wastes discharged
into the Bay. The discovery that the Bay dredged material was sometimes
highly contaminated was a finding repeated for a number of the nation's es-
tuaries. National impetus was given to evaluation of problems, development
of reasonable rules and regulations for the disposal of dredged materials,
and far reaching planning efforts to stop contamination of the estuarine
sediments at the source.
This report summarizes some aspects of the problem as it currently stands
for the San Francisco Bay system, with a resume of current research begun
several years ago in response to public demands. Emotionally charged
debate has at least been supplemented with a resolve to obtain reliable
scientific information upon which to base environmental management deci-
sions. Unfortunately, the basic nature of scientific research is that
it is slow and costly, and that answers are not generated as quickly as
some would like. It can only be hoped that as future disputes arise, the
available and emerging scientific information concerning the ecological
impacts of dredging and disposal will be taken into account by adminis-
trators, regulatory bodies, expert witnesses, and perhaps even the judges
who may need to make critical rulings. However, since there is substan-
tial academic debate in some areas related to dredging and disposal is-
sues, the mere existence of selected bodies of scientific data does not
guarantee resolution of an issue. Since the Bay system undergoes multi-
ple usage by various segments of society, it is of paramount importance
to realize that ultimate decisions concerning dredging and disposal will
be based on economic, social, and political realities, as well as knowl-
edge of the Bay system.
I wish to thank my colleague, Dr. Harold Guard, and
research associates Ms. Nina Hirsch and Mr. Robert
Simon, for aiding in various phases of the develop-
ment of this report. Special thanks are extended
to the files section of the San Francisco Examiner,
the library of the San Francisco District Army Corps
of Engineers, the Water Resources Library of the
University of California at Berkeley, and the Naval
Facilities Engineering Command, 12th Naval District,
for their assistance.
I further thank the experts in various disciplines,
particularly the members of the ABAG Special Studies
Technical Advisory Committee for constructive sug-
gestions rendered in the development of this study.
This study is an attempt to evaluate the current state of knowledge on
the effects of dredging and disposal practices in the San Francisco Bay
estuarine system. Estuarine processes are in general complicated, and
those of the San Francisco Bay system particularly so, which render
comparison with other estuaries difficult.
The first section of this report presents some general characteristics
of the system in simplified terms, and discusses general aspects of
dredging and disposal. Readers familiar with these topics are asked
to refer to other references for more detailed discussions (2,3,4,5).
The second section of this report is devoted to discussions of recent
research on potential deleterious effects of dredging and disposal in
the Bay system, with some relevant inputs from the general literature.
Readers who desire greater detail should refer to the references re-
viewed, as these without fail contain extensive literature surveys
in each area. Broad literature surveys in these fields would have at
least doubled the size of this report. The diversity of estuaries
and nature of the different sources of wastes on their margins have
generated a diverse body of literature on the effects of dredging and
disposal in different esturine systems. In most cases, literature is
so site-specific that there is little rationale for attempting to
transfer systems-wide interpretations of effects. There are, never-
theless, comparisons which may be made between all basic processes,
such as the fundamental chemistry of sediment-metal interaction.
The third section of the report has been devoted to a summary of the
regulation of dredging, its basis, and current trends in regulatory
criteria. This is a fast-moving field, for which much new information
has recently been made available. Environmental concern at both na-
tional and state levels has resulted in a body of legislation which
has been employed in preventing overt environmental impacts, partic-
ularly from filling activities. Enforcement of the legislation is
undergoing an evolutionary process as new research results are made
available and translated into regulatory criteria. Numerous Federal
and State agencies affect the granting of dredging and disposal per-
mits for the Bay. Some agencies have direct permitting power, while
others have commenting functions which carry great weight in final
permit decisions. The data base from which sound disposal practices
may be determined is not complete, although interim guidelines are
now available. Emerging scientific data are beginning to suggest
that a number of presently used guidelines for the evaluation of
contamination of dredged material are probably too restrictive.
Structure and Water Circulation
The San Francisco Bay estuary, following the definition of Pritchard
(1), is a semi -enclosed body of water which has free connection with
the sea (Golden Gate), and within which the seawater is measurably
diluted with freshwater derived from land drainage, primarily the
Sacramento and San Joaquin Rivers. Geologically, the form of the Bay
system was produced by tectonic processes in which movements of the
earth's crust downfaulted the bay basin and uplifted the surrounding
hills. The original surface area of the Bay systems was probably
about 2038 sq km (prior to 1850). It is estimated that there were
originally about 800 sq km of marshland surrounding different parts
of the bay, although today, fewer than 325 sq km of marsh remain (2).
Since 1850, over 600 sq km (30%) of Bay mudflat and marshland have
been converted for salt production, agriculture, industry, recreation
waste disposal, transportation, and military use.
The present Bay system includes four major sub-bays as illustrated in
Figure 1. Perhaps the most striking feature of the estuary is that
the single opening to the sea, the Golden Gate, is only one mile wide
This is in contrast to drowned river valley estuarines on the East
Coast (e.g., Chesapeake Bay, Delaware Bay) which have broad openings
to the sea many miles across. The Golden Gate opens to the Central
Bay, followed by the South Bay to the south and San Pablo Bay to the
north. The final embayment, Suisun Bay, to the northeast, is con-
nected to San Pablo Bay by another deep channel, the Carquinez Strait
Bathymetry of the Bay is shown in Figure 1. Freshwater flows into
Suisun Bay through the complex inland delta formed by the Sacramento
and San Joaquin Rivers, at a rate dependent on the annual rainfall in
the drainage basin of the rivers. In recent years freshwater inflow
has been reduced by removal of freshwater transferred to Southern
California (see Special Study, Delta Outflow).
"The net delta inflow is complicated by tidal action,
but it is estimated to be about 16.8 million acre-ft.
per year (57,000 cfs) under present upstream develop-
ment conditions. Historically, without any flow reg-
ulation or diversion, Delta input was estimated to be
30.3 million acre-ft. per year." (3)
In years of normal freshwater runoff, Suisun Bay is composed mainly
of freshwater; the first major mixing zone where seawater meets fresh
water is in San Pablo Bay, although in dry years, reduced flow of
freshwater allows intrusion of salt-water into Suisun Bay. Table 1
lists a number of water quality characteristics for the different em-
bayments as reported by the University of California SERL study (4).
TABLE 1. SUMMARY OF WATER QUALITY CHARACTERISTICS
OBSERVED IN SAN FRANCISCO BAY
J." • j
l-'t • 1
? • J
-> • 6
5 ■ 1
"'r / *
m.j f 9
* • j j
2 x 10*
3 x 10 s
5 x 1C ?
5 x 10*
1 x 10 3
6 x 10*
5 x 10*
1 x 10*
1.2 X 10 3
l.i, x 10*
3.S x 10 5
3.0 x 10 3
1.0 x 10*
1.5 * iO 6
* ' x 13 s
5.7 y 10 4
£.7 / :o«
-.-. x l.O 3
'./' .< 10*
5 . . x 10'
5,800 1 7,6y.
12,00-; j 15,000
£ . ooo
3a n rtibli
1 ** -9
1 5 • r>
21 ■ 5
J ' ?
7 6 1 ,
2 ■ 5
1 . 1
0.1 c ,
. J 5 1
1 x 10 3
' x "> 3
1 x 10*
2 x 10*
.0 x r, 3
4 .6 / 10* 1
.7 x 10 4
J.C x 10'- !
low = 5 percentile value,
^igh - 95 percentile -value.
(from Ref. 4)
Aside from geological origins, estuaries are often classified on the
basis of their characteristic water circulation and the ways in which
seawater meets and mixes (or does not mix) with the freshwater inflow.
Water movement in estuaries is governed primarily by tidal action and
freshwater inflow. These forces are modified by the action of the
wind and density currents which are usually of low magnitude but still
of importance in all discussions of estuarine water movement. Cir-
culation is further modified by the configuration of the "walls" of
the estuary, including the shape of its shoreline, bathymetry (depth
profile), and the presence of islands and peninsulas. Drowned river
valleys, such as Delaware Bay, have comparatively well-defined water
flows based on their linear shape. The multiple embayments of the
San Francisco Bay system produces complicated circulation patterns.
The volume of the Bay is approximately 6.7 x 10^ cubic meters (5).
Approximately 24% of this volume is moved in and out of the Golden
Gate on an average tidal exchange (5). This shows the extremely
large forces at work when considering the tide as a force in water
movement. The tides in the Bay system are primarily semi-diurnal
(two highs and two lows daily), which create strong currents in the
channels ranging from 225 cm per sec (4.2 knots) at the Golden Gate
to 100 cm per sec (1.8 knots) at the extreme end of the South Bay.
A second force driving water movements in the Bay is that of the
prevailing summer winds and sporadic winter storms. These winds
create non-tidal water flows amounting to a small percentage of the
wind speed (5). This circulation is effective primarily in the Bay
A third force in water movement is the mass flow of freshwater into
the Northern Bay through Suisun Bay and the Carquinez Strait into San
"More than 90% of the mean annual river discharge
(840 m3 per sec) entering the Bay is contributed
to the northern reach by the combined flows of
the Sacramento and San Joaquin Rivers; the re-
maining 10% is contributed by small tributary
streams and sewage inflow." (5)
This force is dissipated in the upper reaches of the Bay.
Freshwater river inflow is lighter per unit volume than seawater and
thus tends to flow out on top of seawater, particularly when other
mixing forces in an estuary are weak. This separation of waters
is known as stratification . In the San Francisco system, this phe-
nomenon occurs mainly in the upper reaches of San Pablo Bay and in
Suisun Bay. Tidal and wind-driven currents tend to mix fresh and
salt-water in the lower reaches of the Bay. In general, the greater
the river flow, the greater degree of stratification that can be
"For low freshwater inflows (140-280 nr/sec) all
portions of the Bay system are considered well
mixed; for inflows 2830 m3/sec, the Golden Gate
and extreme South Bay areas remain well mixed,
but mid-South Bay, San Pablo Straint, and
Carquinez Strait change to a partially mixed
condition. In the area above Carquinez Strait,
the flow is highly stratified. For an inflow
of 5660 rrvVsec (note: extremely wet year),
there is no evidence of well mixed conditions
anywhere in the system." (2)
Stratification of estuarine water produces a fourth major movement of
water known as density current , or "non-tidal drift" (5). In San
Francisco Bay, non- tidal drift is a current set near the bottom, run-
ning northward up San Pablo Bay and into Suisun Bay and may show
speeds as high as 10 cm per sec. The region where non-tidal drift up
the Bay is counterbalanced by the magnitude of river flow is known as
null zone . This zone may migrate northward or southward in the system
depending on the magnitude of river runoff in any given year (6).
In summary, the four major embayments shown in Figure 1 constitute four
(interconnected) functional subsystems of the estuary, each with dif-
fering major characteristics of bathymetry, salinity distribution, and
water movement. The South Bay is generally shallow and rarely has a
major influx of tributary water. It is a high salinity lagoon with
both tide and wind effects important. The Central Bay is deep, domi-
nated by tides and rarely stratified. San Pablo Bay is shallow, often
stratified and affected strongly by both wind and tides. Suisun Bay
is moderately shallow, often highly stratified, and highly affected by
river flow, with less influence from tides and wind. Although much
work has been done, no predictive models are as yet available for water
circulation throughout the Bay system.
Sediments and Sedimentary Processes
The preceding section has provided a broad view of the complex factors
governing water movement in the Bay. Water movements dominate the
sedimentary processes in the Bay, which, in turn, govern the needs for
dredging and mediate the effects of aquatic disposal of dredged mate-
Sediments are aquatic soils commonly known as muds and sands. Sedi-
ments result from soil erosion and washing of mineral and organic
matter from the drainage basin into rivers, by which they are carried
in suspension or dragged along the bottom ( bedload ) until they reach
estuarine or ocean waters. The parent rock substrate of the Bay
system (Franciscan formation) is overlain with hundreds of feet of
sediments deposited since the geological origin of the Bay.
Sediments are categorized on the basis of particle size as shown in
Figure 2. Sedimentary particles common in estuaries include micro-
scopic colloidal particles, clays, silts, with minor amounts of sand.
after Udden (1898)
Cobble " 1
' -B '
U S. Bureau of
. Sotte . -
FIGURE 2. Classification of sediment particle size according
to standard Wentworth grain-size for sediments.
In addition to terrigenous (land derived) matter, sediments contain
small fractions of organic and inorganic matter derived from plants
and animals living in the estuary. The stronger the river or esturine
current velocity, the larger size and number of particles that can be
carried in the water column. Conversely, where water flow decreases,
particles drop out of suspension and settle to the bottom. Sediments
are sorted by water movement, with the larger sized particles (sand
and gravel ) coming to rest in deeper, high velocity channels. For ex-
ample, San Francisco Bar sediments are well-sorted sands. The deep
channels, including the Golden Gate, are floored with sand and gravel.
Because of their physiography, patterns of water movement, and physi-
cal-chemical properties of the water, it is generally recognized that
estuaries act as sediment traps. Normal sedimentary processes can be
expected to completely fill San Francisco Bay in a few thousand years.
Where freshwater mixes with salt-water, finely particulate sediments,
normally unable to settle out by gravity, undergo an electrochemical
process called aggregation . In this process, fine particulates join
to form clusters which are significantly heavier than water and thus
settle in the water column. As these clusters reach the bottom of a
basin, they may interfere with each other's settlement ( hindered
settlement ) and form a light sediment-water suspension termed a floe
or fluff ." As this suspension loses water, it is termed fluid mud .
As the fluid mud approaches 400 g sediment per liter of water, it
fails to flow and bottom deposition can occur. With time, settled
sediments may become compacted due to the influence of gravity, lose
water from between sediment particles, and become consolidated . At
any point in this sequence, strong physical forces can resuspend
sediments and disperse them back into the water column, and the en-
tire settling process may recur. Such strong forces include tidal
currents, wind waves, and dredging and disposal of sediments.
Sediments arriving in San Francisco Bay are primarily soil erosion
products from its drainage area (7). About 81 percent of these sedi-
ments arrive at the Carquinez Strait from the Central Valley. The
remainder of the sediments arise from local tributary drainage (7).
The sediments consist primarily of clays (60 percent), silts (30
percent), and fine sands (10 percent). A majority of the sediments
are transported during typically strong river flows in winter months.
The CE estimate of quantitative sediment budgets in the Bay system
are presented in Figure 3. In this model, sediment not lost to the
ocean or land disposal is deposited in the Bay system. Part of the
volume occupied by these sediments is compensated for by the mean
annual rise in sea level and by geological subsidence (sinking),
particularly in the South Bay. There is no question that sediments
are trapped within the Bay system, but the state of the art is
such that there is continued debate as to the quantity retained.
Conomos 1 conceptual model (5) suggests significantly more retention
of sediments in the Bay than does the CE. He suggests that sedi-
ment lost to the ocean is only 6 percent yearly compared to CE es-
timates of 50-70 percent.
RESERVOIR (HYDRAULIC MINING) 1.5 B
(historical inflow from Sierra, stored in San Pablo B.
RESERVOIR 14.5 B
B r BILLION
FIGURE 3. Sediment movement (in cubic yards) in San Francisco Bay
(from Ref. 3).
The CE suggests that sediments flowing into the Bay in winter season
are spread throughout the Bay and deposited in the shallows and mud
flat areas. With the advent of summer winds, these sediments are re-
suspended, moved with water circulation, and redeposited in deeper
regions unaffected by wind driven turbulence and strong tidal currents
Quantities of these suspended sediments are transported to sea with
tidal currents, and significant amounts settle in the relatively un-
distributed dredged channels and harbors. Conomos (5) suggests that
during the winter, a majority of the sediments coming through the
Carquinez Strait are trapped in the shallows of the null zone (San
Pablo Bay), and with the advent of summer, winds resuspend sediments,
and the null zone migrates into Suisun Bay where large amounts of
sediments are deposited.
Whatever the eventual resolution of this debate, the fact remains that
filling up of dredged shipping channels ( shoaling ) occurs at different
rates in different years. An irregular schedule of dredging is re-
quired on most projects based on depth measurements made routinely by
the CE and facilities users. Mare Island Strait Channel shoals rap-
idly, based on its calm nature and proximity to the null zone where
sediments are concentrated in the water column. Approximately 2 mil-
lion cubic yards of sediment are normally removed from this site on
a twice-annual schedule, making it the most heavily dredge site in the
Bay. However, in the initial dredging period of 1977, less than one-
tenth the normal amount of sediment was removed from this site due to
prevailing drought conditions with concomitant weak river flows which
failed to deposit a normal winter sediment load.
San Pablo Bay contains a reservoir of about 1.5 billion cubic yards
of sediment washed from gold diggings in the Sierra foothils between
1848 and 1884 (14). This sediment decreased the average depth of
this embayment by 5 feet.
Salinity distribution in the Bay system (see "chlorosi ty" , Table 1),
in addition to producing density currents, exerts numerous chemical
effects. Perhaps the most important of these is causation of parti-
cle aggregation as mentioned above. Only 1-2 parts per thousand of
sea salt are required to cause minute sedimentary particles to aggre-
gate. The presence of salt in the water has a marked effect on the
distribution of organisms of estuaries, as some species are more
tolerant to salt than others.
Estuaries unaffected by man are usually rich in both inorganic nu-
trients (nitrogen, phosphorus, trace elements) and organic nutrients
(detritus) derived from biological production upstream of the estuary
and within highly productive margins of the estuary such as the salt
marshes. Ammonium nitrogen and orthophosphate are routinely found in
high concentrations in interstitial waters of most estuarine sediments
These materials are released into the water column during sediment
disturbance. Ammonium nitrogen is related to the kjeldahl nitrogen
content of the sediment. Orthophosphate is controlled by the iron con-
tent of the sediment, as this nutrient is co-precipitated upon forma-
tion of iron hydroxides when iron in (anoxic) sedimentary interstitial
waters is released into oxygenated waters. In San Francisco Bay, the
large amount of iron in the sediments probably results in rapid capture
of orthophosphate which might otherwise be released during a dredging
operation. Ammonia release may be a significant occurrence during
dredging. Dynamics of plant nutrients are covered in the ABAG Special
Study, Eutrophication in San Francisco Bay (1978).
The San Francisco Bay estuary, like most of the nation's large estu-
aries, is a "septic tank of the megalopolis" as described by DeFalco
(9). The San Francisco Bay system receives flows of wastes from over
5 million people as summarized in a study completed in 1964 (Table
2). Projections for the Bay into 1980 (10) predict increases in or-
ganic waste inflows as growth of the population and expansion of the
economic base is expected to offset gains realized by the new con-
struction of waste treatment facilities.
With regard to dredging problems, it is well known that finely partic-
ulate sediments are able to scavenge pollutant heavy metals , pesticides,
and oil pollutants from the water column and carry them into the bottom
sediments. The dredging of polluted sediments has raised questions
concerning the possible impact of these materials on the Bay biota, as
many of the waste compounds concentrated in bottom sediments are known
to be toxic in their free (dissolved) state in water and when absorbed
into body tissues from food. A major problem in this area has been the
method of assaying for toxic metals, as some elements considered to be
pollutants are found within the basic chemical composition of the sedi-
ment particles. The Crystalline Matrix Study (11) supported by the CE
showed that a number of toxic metals were bound in the crystalling ma-
trix of the sediments. In making bulk (total chemical) analysis of
sediments to determine their pollutant burden, internally bound metals
have been included in the analyses in the past. This may lead to false
estimations of the pollutant potential of a given sediment so tested.
New research in this area is summarized in the Effects Section.
Waste effluents and organically enriched bottom sediments consume large
amounts of oxygen when they are released to the water column, causing
biochemical oxygen demand (BOD). One concern in the Bay system has
been the possibility of dredged sediments reacting with oxygen in the
water to the detriment of oxygen-requiring organisms. This topic is
further considered in the Effects Section below.
Normal processes of decomposition produce ammonia and hydrogen sulfide
in organically enriched estuarine bottom sediments. These substances
are highly toxic to many organisms if not well diluted. Potential im-
pact of their release during dredging is further discussed in the
TABLE 2. COMBINED MUNICIPAL AND INDUSTRIAL
MASS EMISSION RATES
Mass Emission Rate
Unit Mass Fmissinn Ratp
will V I IU J J UMI i J J 1 \J ! 1 1 \U L- C
Oil and Grease
NH 3 - N
N0 3 - N
Gross Heavy Metals
Col i form MPN ,
4.34 x 10l7/day
1.43 x lOU/capita day
*unless otherwise noted
*waste toxicant flow diluted with non- toxic water that will kill
one-half the test animals in two days (test animals are stickle-
From: Pearson, E.A. et al , 1967. Summary and
conclusions. V 7, Comprehensive study of San
Francisco Bay. Sanitary Engineering Research
Laboratory, University of California, Berkeley.
Notes on Bay System Biology
The scope of this report prevents an extensive description of the biol-
ogy of the San Francisco Bay system. Interested readers should consult
the CE Composite Environmental Impact Statement (3) and the Biological
Community Study (13) which describe numerous aspects of biology and
provide literature summaries. Nichols (15) provides a comprehensive
review of biological diversity studies carried out on the benthic (bot-
tom) organisms of San Francisco Bay.
The San Francisco Bay ecosystem is dominated by the above-described
water flows and sediment dynamics. The energetic basis (food source)
of the estuarine food webs is probably phytoplankton production, sup-
plemented by tidal flat production from benthic micro- and macroalgae.
There is probably not much organic matter available from the small
remaining acreage of marshes and delta outflow, although there may be
a significant energetic input in the form of dissolved organics from
waste inflows. Primary production and secondary bacterial production
supported by dissolved organics is fed upon by the numerous filter
feeding organisms in the tidal flats and bay bottoms. This is seen
in the great preponderance of filter feeding mollusks composing the
biomass as shown by several biological surveys in the Bay. The SERL
study (4) found total benthic animal "biovolume" of species to in-
clude 70 percent mollusks (clams, mussels, oysters, and snails), 25
percent annelids (segmented worms), and 5 percent arthropods (shrimp,
crabs, and their small relatives). Table 3 summarizes the main habi-
tats of the system and representative organisms found in them. This
table is an oversimplification as these habitats have diverse sub-
divisons, depending on currents, salinity, light penetration, food
sources, sediment grain size, predation pressure, and pollutant im-
pacts. Since some of these factors change from season to season and
from year to year, it is not surprising that experts consulted at the
California Academy of Sciences considered it impossible to produce
distribution maps for any given species in the system. Nichols (16)
ascertained that no major pollutant effects can now be detected in
the Bay simply by looking at areal differences in species diversity,
because even near major sewage outfalls species diversity is high.
In the SRI study (13) the Oakland Inner Harbor station, which might
be intuitively selected as one of the most polluted in the Bay system,
contained one of the most populous and diverse faunas in their survey!
Clam beds are widely scattered throughout the tidal flats but may
vary in location from year to year.
Usually, populations of commercial significance are the best docu-
mented as to location and abundance. Discussion with California State
Fish and Game personnel conducting the major survey on the Dungeness
crab ( Cancer magister ) revealed that there is still not enough knowl-
edge of the life history of juveniles in the Bay to accurately predict
where these animals will be at any given time.
— I crt
03 -n -a
n a oo
Although many different species populate the broad expanses of Bay bot-
tom, most exhibit few major body types and are very small and inconspic-
uous. Most are fully adapted to existence in soft mud. In addition to
the easily visualized market clams, the mud supports large populations
of tiny clams no bigger than this typescript ( Gemma gemma , Transenella
tantilla ) . There are a few species of large clam worms sometimes used
as bait, but dozens of species of tiny worms (1-2 cm) are very difficult
to identify taxonomically. There are a few species of large crabs such
as the Dungeness, and the common bait shrimp, and many more species of
tiny amphipod crustaceans which build protective tubes in the mud. Most
of these organisms and other miscellaneous species of the Bay bottoms
are f i 1 ter f eeders which remove particulate foods from the water or
deposit feeders which sort particulate foods from deposits at the mud-
water interface. Small benthic organisms from the basis of the food
web leading to the production of fishes, shrimp, and crabs.
The benthic community of the Bay is adapted to natural stresses in
various ways, from physiological adaption to reproductive strategies.
As it presently stands, the Bay's ecosystem is the product of adapta-
tion to over 100 years of "industrial man" influencing the estuary.
This includes waste flows, hydraulic mining debris, and the introduc-
tion of hundreds of new species, both intentionally (striped bass)
The concerned reader, aside from reading publications on this topic,
may obtain an excellent impression of the types and kinds of organisms
in Bay system bottoms by inspecting the collection of invertebrate
organisms of the San Francisco Bay system maintained at the California
Academy of Sciences.
Dredging and Disposal Practice
Dredging is the process by which sediments are removed from the bottom
of streams, lakes, and coastal waters, transported by ship, barge, or
pipeline, and discharged (as spoil) to land or water. The usual pur-
poses of dredging are to maintain, improve, or extend navigable water-
ways, or to provide construction materials such as sand, gravel, or
Most of the dredging and disposal in the San Francisco Bay system is
carried out by the CE, San Francisco District, using West Coast CE
equipment. Smaller amounts of dredging and disposal are carried out
directly by the Navy and certain municipalities which own their own
equipment. A number of private firms are available for dredging ac-
tivities, mainly in service to corporations and municipalities. The
Sacramento District, CE, is responsible for maintaining the Sacramento
ship channel from Chipps Island to Sacramento.
It is of importance to distinguish between maintenance dredging and
new work dredgin g. Maintenance dredging is carried out on a routine
basis, usually on long-term permits or by Congressional authorization.
This dredging removes sediments which have been deposited in navigable
waters on a regularly scheduled basis to prevent shoaling of routinely
used channels. This type of dredging removes sediments which have
accumulated over short periods of months or years at typical rates es-
tablished for each given locus over long periods of observation. For
example, the main channel through the San Francisco Bar outside the
Golden Gate has been dredged annually since 1922. New work dredging
is carried out by special permit (see regulations section below) in
areas previously not subjected to dredging. This type of work is more
likely to release pockets of contamination which represent long periods
of accumulation. The CE Composite Environmental Impact Statements
lists their maintenance projects as shown in Table 4.
Methods of Dredging
Three major types of equipment used in dredging and disposal are illu-
strated in Figure 4. In the San Francisco Bay system, the majority of
sediments are removed from maintenance projects using a hopper dredge .
This dredge is a self-propelled ship with holds (hoppers) wnich contain
the dredged material. The ship drags a pair of suction heads through
the site to be dredged, pumping the sediments into the hoppers. With
hoopers full, the ship raises the drag heads and proceeds to the (aquat
ic) disposal site, where doors are opened in the bottom of the ship,
releasing the dredged material. For example, the CE uses the hopper
dredge "Harding" for applicable projects in the Bay system. Dredging
is done in the Mare Island channel on a twice-yearly basis with the
average amount removed of approximately 2 million cubic yards per year.
The hoppers of the "Harding" can contain up to 2700 cubic yards of sedi
ment. The dredge works 24 hours round the clock from September to
November, removing sediment deposited from summer resuspension and from
February through April, removing new material brought down the rivers
in winter from the Napa and Central Valley. In low-flow years, the
amount to be dredged may be significantly reduced. In the first dredg-
ing period of 1977, the Mare Island project only required two days of
work by the "Harding", suggesting the low levels of sediments brought
in by extremely low river flows, typical of the current drought (or in
the future by reduced Delta outflow).
Mare Island dredged material is carried 2.8 miles from the dredging
site and released at the disposal site on the northern margin of the
Other methods of dredging include the clamshel 1 dredge and hydra ul ic
cutter head pipeline dredge . The former method employs a clamshel 1
bucket which removes "bites" from bottom sediments as done by drag-
lines in terrestrial situations. Clamshell dredging is usually done
in areas of restricted ship movement such as harbors and marinas.
Dredged material is deposited in barges, usually with bottom-opening
doors. Both barges and dredge are moved by tugboat to the dredging
site and loaded barges are taken to disposal sites by tugboat.
Pipeline-dredges employ a cutter head which is lowered to the sedi-
ment and moved across the sediment face. Dredged material is pumped
to the surface and then into a temporary pipe string which is mounted
TABLE 4. CORPS MAINTENANCE DREDGING PROJECTS
IN SAN FRANCISCO BAY AREA (Ref. 2)
Authorize! ion (cubic yard*)
Proposed Data of Haxt Avera^ : Annual
Disposal Site Ha Intenanca Qty.(c»' • 1c ydu) L
San Francisco rfirbor
R&HA 2 o£ 192 7
(lain Ship Channel
San Franc leco Bar
roint m»ox jnoai
lnac t ive
5.F. Airport Channel
Islaia Creek Entrance
San Rafael Creak
R4HA Of 1919
R&HA of 1930
San Pablo Bay
Sun Pablo Bay and Mara
R&HA of 1927
Pinole Shoal Channel
San Pablo Bay
Hare Island Strait
R&HA of 1917
R&HA of 1874
i 00, 000
Oakland Outer Harbor
Oakalnd Inner Harbor
San Lesndro Marina
R&HA of 1970
4 2 , 000
kedwood City Harbor
R&HA of 1910
76 or 77
S.P. Hbr. & Bay - Sausa-
R&HA of 1950
77 or 78
Uto Operatlona Base
Suisun Bay Channel
R&HA of 1919
1 1 A AAA
luisun (Slough) Channel
R&HA of 1910
New York Slough
R&HA of 1876
TOTAL R&HA PROJECTS
cm. cord Naval Weapons
Alameda NAS <Navy)
MOTBA 3 North (military)
MOTBA East (Navy)
Point Molate (Navy)
Gov. Island (Coast Cuard)
Horseshoe Cove (Army)
TOTAL INTER-SERVICE PROJECTS
TOTAL ALL PROJECTS
100- Fa thorn
FY 77 or 78
1 Average Annual Quantity its the average volume of sediments which would be removed if the project was perforated
once a year. For example, if 200,000 cubic yards are removed once every 5 yeare, than the average annual quantity
',3 200,000 divided by 5, or 40,000 cubic yards.
'Hivers and Harbors Act
military Ocean Terminal, Bay Area
S'or any given year that a project 1b dredged, this figure can vary 1 30-40 percent.
Vessel On Bottom
Pumps Across section of ship)
Dragarms (Suction Lines)
TRAILING SUCTION HOPPER DREDGE
Overt low D scharte
From 8 org
HYDRAULIC CUTTERHEAD DREDGE
FIGURE 4. Three major types of equipment
used in dredging and disposal.
on floats and directed to the chosen disposal site. This method is used
to deposit dredged material in shallow water or land disposal sites due
to the flexibility of the pipeline system. Specific details on dredging
technology are found in the CE report on dredging technology (17). Re-
search is actively being conducted by CE Waterways Experiment Station,
Vicksburg, Mississippi (WES), on the improvement of dredging technology
and the mitigation of environmental effects of dredging. Conferences
with WES personnel in Vicksburg indicated that although some modifica-
tion of current practices can be recommended to mitigate some dredging
effects, no momentous new developments should be expected in the forsee-
The San Francisco CE has investigated the effects of dredging and disposal
on sediment resuspension which will be treated in the Effects Section.
ENVIRONMENTAL IMPACTS OF DREDGING AND DISPOSAL
The broad discussion of the general characteristics of the San Francisco
Bay system was made in order to foster an appreciation of the dynamics
in the system. Perhaps the most important factor to be considered in
all discussions of dredging and disposal in the San Francisco Bay system
is that it is the only estuary in the U.S. in which the great majority
of dredge spoil disposal is currently carried out at high energy, deep
water disposal sites. No evidence of accumulation of disposed sediments
is evident at the currently used disposal sites in the Bay system (2).
This is to say, soon after sediments are released at these disposal
sites, the sediments are dispersed into the water regime of the Bay.
This method of disposal effectively eliminates many of the comparisons
which might otherwise be made with dredging and disposal in other es-
tuaries, particularly with regard to the loss of resources by burial
in disposed sediment. For example, dredging and disposal carried out
in some shallow estuaries of the Gulf Coast can be directly observed
to destroy populations of clams and oysters. Spoil banks persist and
can be monitored, as can the number of organisms destroyed (20). In
the San Francisco Bay system gross biological effects would be ex-
tremely difficult to observe due to depth of dredging and underwater
disposal, normally high turbidity regimes, and moving waters which ob-
scure effects such as fish kills which might appear far down-current
from where they occur.
There is a serious problem in quantification of resources which might
undergo adverse environmental impact. There are no firm and reliable
baseline data for populations of organisms in the Bay as mentioned in
Section I, Biological Considerations. Thus, any changes in popula-
tions of organisms due to any cause are difficult to evaluate. Life
histories of organisms and natural environmental variations can pro-
duce variations in the abundance of organisms in various parts of the
estuary through time. Statistically valid sampling in the estuary is
difficult, and some studies of the Bay system organisms have been
compromised by lack of effective sampling procedures (15). In view
of the great difficulties in making direct measurements, most inter-
pretations of potential effects of dredging in the San Francisco Bay
system must be of an indirect, postulated nature.
The following is a resume of potential effects of dredging and dis-
posal in estuaries in general, each relevant category of which is
discussed below in relation to possible effects in the San Francisco
Changed circulation regimes
Release of sediment
Release of sediment associated materials
Direct effects occur when a dredge is removing the sediments from the
dredging site or disposing of dredge spoils at the disposal site. Typi-
cal direct effects of dredging include maceration of bottom organisms as
they are pumped through massive hydraulic pumps. In disposal, the major
effect is burial under the released load of sediments. Experts con-
sulted in the State Department of Fish and Game and at the California
Academy of Sciences did not indicate major objections to the direct ef-
fects of dredging and disposal, as these effects occur in curcumscribed
areas which are the same from year to year (Figures 5A and 5B). Major
concern was expressed for indirect effects which occur due to placement
of large suspended loads into Bay waters, possible formation of fluid
muds, and release of chemical contaminants to Bay waters, a problem of
particular importance to the Regional Water Quality Control Board.
A sophisticated tracer study carried out by the San Francisco CE showed
that large volumes of sediment (1.6 m cy) disposed of at the Carquinez
site were broadly disseminated into the natural sediment regime of San
Pablo Bay to a depth of as much as 23 cm over a 100 square mile area
within a month's time (8). About 10-15% of the disposed sediment re-
turned to the dredging site (Mare Island) in a few month's time.
As part of the San Francisco CE Dredge Disposal Study (subsequently
referred to as the DDS), Stanford Research Institute carried out an
investigation to provide faunal lists and organism counts at selected
dredging and disposal stations and unaffected "control" stations near
disturbed stations (13). This was done to determine impacts on or-
ganisms at the test sites, to evaluate seasonal changes in organisms,
and to collect some chemical data for making correlations with faunal
changes. Stations evaluated were Mare Island (dredge)— Carquinez
Strait (disposal), and Redwood City Harbor (dredge)--South Bay (dis-
posal). Information was also obtained at Oakland Inner Harbor,
Alcatraz disposal site, and Hunters Point disposal site. Extensive
faunal lists were compiled, counts were made, and chemical parameters
measured. The study concluded, as would be expected, that disturbed
sites showed decreased species diversity and numbers. The following
data (Table 5) from the Main Report (2) shows the effects at Mare
Island dredging site.
i — i
rD •— <
1 — 1
I— I Q
i— i U_
UJ •— l
— 1 o
t — "
OH 1 —
S- T3 i—
CO C <o $-
E -O ■»->
13 <4- T- •!—
O > r—
I CO fO
C S- 4->
ZD "O CO
The disposal site in the South Bay which received a single load of
dredged material showed populations and diversity comparable to the
control site after a few months. Although extensive surveys of species
and numbers of organisms were made at study sites, and a number of
chemical parameters were recorded, it was concluded that "underlying
relations among biological and environmental variable are complex, and
that additional field and laboratory studies would be required for
thorough identification and understanding of such relationships (13)."
Trends suggested from their data showed small populations and low di-
versity correlated with high salinity and sediment mercury and sulfide
concentrations, and high diversity and large populations with high
dissolved oxygen, turbidity and sedimentary zinc and clay content of
sediments. This study showed the great difficulties in determining
gross effects of dredging and disposal in San Francisco Bay as compared
with the more easily studied quiet, shallow waters. The Stanford sur-
vey noted marked seasonal variations in organisms. As a specific ex-
ample of the difficulty and expertise required in this study, over 130
species of taxa (kinds) or organisms were found in the Oakland Inner
Harbor station alone, with an average number of organisms per liter
of sediment being 867.5 (yes, they are small). A total of 131 ,256
specimens were collected during 5 surveys.
McCauley et al (22) monitored effects of dredging on the benthic faunal
abundance of a dredged channel in Coos Bay, Oregon, and found that in-
fauna readjusted to pre-dredging conditions within 28 days. At the
spoil site, readjustment took about two weeks. More simplified tech-
niques were used than the Stanford study, however, pointing out the
great difficulties in comparing different studies because of the use
of different methods between research groups.
In a study funded by the CE Waterways Experiment Station, Vicksburg,
Mississippi , x personnel of the Moss Landing Marine Laboratories inves-
tigated recovery of fauna in dredged and disposal areas in Monterey
Bay. Their findings suggested that communities in areas which are
normally stressed show more rapid recovery of populations and animal
diversity than biotic communities which are not normally stressed (23).
Thus, typically wind and sediment stressed areas in San Francisco Bay
are probably more resilient to long-term effects of sediment disposal
than the 100 fathom (Farallon) ocean disposal site which undergoes
very little natural perturbation.
Effects of burial on organisms are important in disposal sites where
mounding of dredge spoil occurs. Another DMRP study, by the Univer-
sity of Delaware, was carried out to determine abilities of organisms
to escape burial in various types of sedimentary material (24).
In laboratory experiments, it was found that numerous types of orga-
nisms (crabs, clams, snails, amphipod crustaceans, polychaete worms)
were capable of escaping from as much as 32 cm deep burial. Notable
*Dredged Materials Research Program (DMRP)
exceptions were small snails, and organisms buried in exotic sediments
(sediments in which organisms do not normally live). Great variation
was found with temperature, stress condition of the organisms, and other
factors; and it was concluded that generalizations as to disinterment
behavior could not be made between species groups, although knowledge of
morphology and behavorial characteristics were in general useful in pre-
dicting migratory behavior. The authors recommended field studies be
carried out under actual dredging conditions. Presently used disposal
sites in San Francisco Bay, being in high energy areas, do not allow
long-term mounding of sediments. Physical smothering of shellfish beds
is not a problem in San Francisco Bay with current and projected dis-
A specific problem related to both direct and indirect impacts of dredged
material is the possibility of formation of fluid mud flows from dredged
material. Formation of fluid muds occurs when mixing energy is not great
enough to totally resuspend sediments in the water column, and dredged
sediments are caused to flow across bottom environments, smothering resi-
dent fauna. A DMRP study by the Virginia Institute of Marine Science has
shown that fluid mud flows induced in the upper reaches of an estuary
could have significant lethal effects on the macrobenthic organisms (clams
and insect larvae) although some were more sensitive to this stress than
others (32). In San Francisco Bay, concern has been shown by the Depart-
ment of Fish and Game personnel that such fluid muds could severely im-
pact juvenile Dungeness crabs in certain bottom areas of the Bay. Fluid
muds are difficult to measure, and may occur due to natural causes.
Changed Circulation Regimes
Typical dredging and disposal as currently practiced probably has little
effect on the circulation regimes in the Bay. The CE, San Francisco Dis-
trict, is currently preparing an Environmental Impact Statement for the
Baldwin Ship Channel project which has the potential of increasing sa-
linity intrusion into the Delta. Dredging of estuarine channels which
cause significant new salinity intrusions, have the effect of moving the
null zone upstream, resulting in greater sediment deposition in upstream
reaches of estuaries (21). This produces new demands for dredging of
the upper reaches of estuaries, where significant environmental effects
Effects which do not occur as a direct result of the activities of dredg-
ing and disposal include physical impacts of resuspended sediments,
biochemical oxygen demand of oxygen-reactive compounds stored in bottom
sediments, and release of toxic or blostimulative materials from sediment
storage. A number of research projects have recently been completed which
bear on these potential effects on the estuarine fauna of San Francisco
Two studies were carried out by researchers of the University of California
Marine Laboratory at Bodega Bay to determine the effects of contaminated
and uncontaminated sediment loading on the survival of sensitive test or-
ganisms (26, 27) common in the Bay system. Parameters measured included
amount of sediment maintained in suspension, temperature, and oxygen con-
tent of the water. Organisms tested included bay mussels, a clam worm spe-
cies, an isopod species (Synidotea), Bay shrimp, shiner perch and striped
bass. These species are widely distributed in the Bay and served as test
species of ecological importance. In general, invertebrates were highly
resi stent to the effects of suspended solids in the water (tens of grams
per liter) and were more effected under conditions of higher temperature
and low dissolved oxygen. Organisms commonly found in muddy environments
were least sensitive. Fishes were sensitive to suspended sediment (few
grams per liter) conditions, particularly at high temperature and low DO.
The researchers concluded from the results that the organisms would be
insensitive to suspended sediment loads typical of areas around dredging
activities determined in CE water column studies (28). These studies have
shown that the suspended sediment plume does not interfere with the upper
two meters of water during both dredging and disposal, and that although
there are dissolved oxygen reductions near the dredge during dredging and
disposal operations, these effects last only a few minutes due to rapid
mixing of well oxygenated Bay waters. From these data and the data on
sensitivity of organisms, mitigation of these localized effects could be
obtained by restricting dredging to winter months when temperatures are
low, and disposing of sediments such that they are maximally dispersed to
minimize oxygen demands around the dredge.
Sherk et al (29) have found significant lethal and sublethal effects of
suspended sediments on certain estuarine fishes which are not adapted to
typical mud bottom conditions. Their results suggest that the more sen-
sitive fishes such as menhadedn, white perch, bay anchovy and striped
bass larvae, if unable to escape dredge and disposal plumes for periods
of days, could be adversely affected by sediments from dredging and dis-
posal activities. It is unknown if this is likely to occur near San
Francisco dredging and disposal sites. Comprehensive studies of the
effects of dredging on the fishes of Chesapeake Bay (3) were unable to
demonstrate gross effects of overboard disposal of dredged sediments
using caged fish experiments and commercial type research gillnetting.
Furthermore, no gross effects could be demonstrated on phytoplankton
primary productivity, zooplankton, and fish eggs and larvae. A review
of the effects of dredging and disposal on zooplankton (31) suggests
that significant effects of suspended sediments can occur if plankton
populations are localized and not dominated by oceanic processes im-
pinging on the estuarine habitats. It is suggested that any impact on
zooplankton can only be determined on a case-by-case basis with exten-
sive knowledge at hand concerning the biology of the zooplankton popu-
lations. Since this data is unavailable for San Francisco Bay, no
predictions can be made concerning zooplankton effects.
Toxicant Release and Uptake
A great deal of reserach has been carried out recently due to the need
for determining the effects of deleterious materials released from
dredged sediments. This work has been carried out mainly in providing
basic data for the development of dredged spoil disposal criteria
(DMRP studies) and in determining environmental impacts of toxicants
released into San Francisco Bay waters (DDS studies).
A. Heavy metals
Serne and Mercer (11) have studied the release of the heavy
metals, Cd, Cu, Fe, Hg, Pb, and Zn from selected San Francisco
Bay sediments as a function of various physical and chemical
parameters including Eh (redoxpotential ) and salinity. Sedi-
ment samples from ten sampling stations were characterized with
respect to heavy metal content, particle size, mineral content,
total sulfide, organic carbon, cation-exchange-capacity, and
PCB content. The release of heavy metals was determined using
a semi-selective extraction procedure, where the sediment is
extracted sequentially with interstitial water, ammonium ace-
tate, hydroxlyamine hydrochloride, hydrogen-peroxide, and so-
dium citrate dithionate. The greatest portion, 30-97%, of the
heavy metals, Cu, Fe, Hg, Pb, and Zn, were bound in clay or
crystalline lattice sites. The greatest portion of Cd was
associated with sulfide-like sites (extractable with hydrogen
peroxide). Elutriate test data were also compiled for Fe, Cd,
Cu, Zn, and Pb. These data are summarized in Table 6.
Chen, et al (33) have studied the release of heavy metals from
dredged material. They found no release of Ag, Cd, Hg. The
metals, Cr, Cu, and Pb were released at levels of from 3 to 10
times background. Amounts of Fe, Mn, and Zn larger than 10
times background were released. Except for Fe the amounts re-
leased are in the sub ppm to ppb range. Most of the soluble
phase concentrations were well below the allowable levels of
the ocean water discharge standards.
Lu and Chen (34) reported a study on the migration of heavy
metals from polluted sediments into seawater. Reducing con-
ditions favored the release of Fe and Mn; whereas, oxidizing
conditions favored the release of Cd, Cu, Ni , Pb, and Zn.
The migration of metals is controlled by the chemistry of the
immediately overlying water rather than the type of sediment.
The factors affecting metal migration were studied, and a
model is proposed.
Anderlini, et al (35) have examined the uptake of heavy metals
by estuarine organisms and sediments during dredging operations
in the San Francisco area. These authors conclude that dredging
TABLE 6. Release of Metals from San Francisco Bay Sediments
Metal Dissolved 02 Ratio* Effect of Salinity
Less in higher salinity
Less in highest salinity
Less in higher salinity
Less in higher salinity
Less in higher salinity
Less in higher salinity
Less in higher salinity
a. Elutriate ratio is the amount released divided by the amount in
the disposal site water.
does not affect the levels of heavy metals in nearby sediments or
invertebrates. This observation is likely the result of the un-
availability of sediment-associated metals since the uptake of
dissolved chloride salts of Hg, Pb, Cu, Cd, and Ag by Ma coma was
established in laboratory experiments.
A similar study (36) has examined the release and uptake of heavy
metals (Ag, As, Cd, Cr. Cu, Fe, Hg, Mn, Ni , Pb, Se, and Zn) dur-
ing a dump of 10,000 m3 of dredged material in San Francisco Bay.
The concentrations of these metals were monitored in selected
benthic invertebrates, mussels transplanted to the disposal site,
sediments, settled and suspended particulates, and water before,
during and after the disposal operations. The results of this
study are summarized as follows:
No effect on heavy metal
Transplanted M. edulis
Higher Fe and Cu levels
in disposal area
Short-term increases in
dissolved Cd, Cu and Pb.
No effect on heavy metal
The overall conclusion of this study was "The amount of trace
elements redistributed annually by all dredging activities is
much greater than the annual input from the EBMUD outfall, but
is almost inconsequential in relation to the element redistri-
bution by settling particulates."
Neff, et al (37) in an extensive research program on the uptake
of metals from metal -containing sediments found there were no
simple principles which covered all organisms, sediments and
metal contaminants. It was concluded that metals were taken up
with difficulty by most organisms tested, and that development
of a simple extraction scheme for predictive effects of heavy
metal uptake by benthic organisms in general is presently not
Pesticides and PCB's
Fulk, et al . have reviewed the literature on pesticides and
PCB's in sediments (38). Algae, suspended solids, bottom sedi
ments, and water all contain various chlorinated hydrocarbons.
The studies conducted on the adsorption and desorption of
chlorinated hydrocarbons on solids have generally found that
these materials are more readily absorbed than desorbed.
Fulk, et al . (38) have analyzed the sediments from five areas
for aldrin, dieldrin, endrin, lindane, 2,4-D esters, DDT analogs,
toxaphene and PCB's. PCB's, dieldrin and the DDT analogs were
the most prevalent. The desorption of the latter materials was
studied. No DDT analog release was observed. Release from in-
terstitial water was negligible. Some Dieldrin release was ob-
served in the sub ppb range. On the basis of these laboratory
studies, it appears that release of these water insoluble pesti-
cides will not occur to an appreciable extent during dredging.
To my knowledge the release of Kepone from sediments has not as
yet been studied. The situation in the James River with wide-
spread Kepone contamination in organisms and sediments may be an
unusual case. The (water soluble) Kepone may dissolve upon dis-
ruption of the sediments.
Anderlini, et al (36) monitored release and uptake of PCB's and
compounds of the DDT group during a disposal operation in San
Francisco Bay. Some uptake of p,p'-DDE was observed but the
levels of the other chlorinated hydrocarbons remained constant
in Mytilus edulis . Chlorinated hydrocarbons were released to
the water column resulting in 3-10 fold increases in the chlo-
rinated hydrocarbon levels in the water immediately after dis-
C. Oil and Grease
One of the major contaminants in estuarine sediments are "oil and
grease" residues, consisting mainly of petroleum derived hydro-
carbons and their breakdown products. A laboratory study recently
completed by DiSalvo et al (39) exposing mussels, crabs and clams
from the Bay estuary to heavily contaminated sediments from Puget
Sound and New York Harbor showed minor uptake of hydrocarbon resi-
dues from sediments. Field experiments carried out by DiSalvo
et al (40) showed that hydrocarbons were taken up by mussels sus-
pended in San Francisco Bay, and it was suggested that weathered
hydrocarbons in sediments were tightly bound, and that uptake of
hydrocarbons by uncontaminated mussels occurred from newly released
pollutants or oil droplets accommodated in the water column (39).
This research has suggested that bulk analyses should be carefully
reexamined as a disposal criterion, as this parameter appears to
have little relevance to possible environmental impacts. Specific
compounds normally part of the oil grease fraction are the car-
cinogenic compounds which usually occur in minute quantities in
sediments. This topic is further discussed in the ABAG Special
Study: Toxicants in the San Francisco Bay Estuary (1978).
D. Contaminant microorganisms
A problem associated with release of dredged sediments is the
possible dissemination of enteric bacteria, viruses, protozoa and
other microorganisms which may be taken up by commercially valu-
able shellfish in their filter feeding processes.
Fecal col i forms and enteric pathogens have been found in bottom
sediments (41,42). Dredging of the Mississippi River navigation
channel has been shown to result in increased fecal col i form
concentrations by a factor of 2-5 in the immediate area of the
dredging. Highly pathogenic protozoan cysts have been isolated
from contaminated sediment deposits near New York and Baltimore
(44). We do not know to what degree the dredged material in the
Bay. is contaminated with persistent undesirable microorganisms
from the public health standpoint; further information on this
topic is available in the ABAG Special Study: An Assessment of
the Potential for Commercial and Recreational Harvesting: San
Francisco Bay Shellfish (1977).
E. Hydrogen Sulfide (H2S) and Ammonia (NH3)
These two compounds, normally formed in organically rich anoxic
estuarine sediments, are highly soluble in water. They are both
toxic to many aquatic organisms and are of interest with respect
to water quality criteria in the Bay. Since the San Francisco
Bay system sediments are highly enriched in iron, free H2S is
expected to react to form insoluble iron sulfides (which color
the sediment black). Serne and Mercer (11) have verified this
hypothesis, finding no detectable free H2S which could be re-
leased from the dredged material.
Ammonia is one of the potentially toxic materials known to be
released from anoxic sediments, and routinely found in evalua-
tions of sediments using the elutriate test.* Anderlini et al
(35) found minor indications of ammonia increase after a sedi-
ment disposal operation, with small rises in water near the
spoiling followed by rapid returns to baseline levels. Ammonia
is also a plant nutrient and may lead to eutrophi cation pro-
cesses as discussed in the ABAG Special Study: Eutrophication
in San Francisco Bay (1978).
Confined or unconfined land disposal of contaminated dredged material
appears, from literature thus far reviewed, to be an unattractive al-
ternative to aquatic disposal for a number of reasons.
1. It is only a temporary solution, as pointed out by Schubel
and Meade (21) in their description of problems in the
Delaware estuary. There are limited numbers of receiving
sites and massive continuous accumulations of sediment
which must be accommodated.
2. Land disposal of contaminated dredged materials may have
worse adverse environmental effects than aquatic disposal
as contaminated runoff from the material may re-enter
sensitive inshore nursery areas rather than being sub-
jected to large forces of dilution based on estuarine
water circulation (45).
*See Section III.
3. The properties of Bay mud which is the main material taken
from maintenance dredging projects is "a soft, plastic, black
to grey silty-clay or clayey-silt with minor organic material
and clayey fine grained sand which has been deposited in the
Bay largely by flocculation" (generally the consistency of
toothpaste) (2). It has poor bearing capacity, requires ex-
tremely long times for dewatering, and effectively prevents
all other land use for long periods of time, including the
growth of plants and animals (46). Whereas the impact of
aquatic disposal is not well known, the impact of land dis-
posal is clear. All life is effectively excluded from the
disposal area for long periods of time.
Concluding Remarks on Effects
Most of the research reviewed here is so new that it has not been criti-
cally reviewed by the scientific community in general. For the present
context, the conclusions of the authors have necessarily been taken at
face value without critical review of the data. Indeed, limited pre-
liminary critical review made by our group to date indicates that there
are a few discrepancies here and there in chemical studies which will
eventually give rise to academic debate concerning the significance of
some of the results. However, the overview of the research is encour-
aging, especially in light of the natural processes operating in San
Francisco Bay which aid in the dilution of wastes and rapid oxygenation
of Bay system waters.
Although the studies seem detailed (and expensive), they are only a
beginning, and the discerning reader will have noted there are few de-
monstrative experiments which clearly show effect, or lack thereof, of
dredging and disposal on any particular biological resource of the Bay
ecosystem. Obviously, this is in the realm of future research needs
as outlined in our final pages. We cannot emphasize too strongly the
need for basic research on which to formulate the proper questions
which will lead to (empirical) demonstrative experiments in the future
on specific impacts of specific dredging projects.
REGULATION OF DREDGING AND DISPOSAL
The regulation of dredging and disposal is based on the broad action that
is required to protect the diverse resources which come under the heading
of "environmental protection." Numerous Federal and State agencies are
charged with different aspects of environmental resources protection, each
responsible for evaluation of potential environmental effects of dredging
and disposal in the San Francisco Bay system. Any real or hypothesized
impact envisioned by any agency is able to delay or block the permitting
process. Environmental legislation and the multiplicity of involved agen-
cies has complicated the permitting process for dredging and disposal be-
cause of the lack of objective information on environmental effects and
objective criteria for evaluation of any such effects. New and emerging
research results, discussed above in the Effects Section, are showing that
some interim criteria which have been used in the past are of questionable
value. An in-depth study of the regulation of dredging has been carried
out by the San Francisco Bay Conservation and Development Commission
(BCDC) (18) which has proposed numerous suggestions for accelerating the
permitting process. The following discussion presents an introduction to
the laws governing dredging and disposal, as applied to the San Francisco
Bay system. At the heart of the entire matter is the basic assumption
that scientific research has either provided or is capable of providing
objective criteria for assessment of the potential impacts of dredging and
disposal. Costs of research and time schedules required for obtaining the
results make this assumption problematical.
Dredging and disposal are regulated by Congress through permit processes
under basic control of the U.S. Army Corps of Engineers (CE) in close
cooperation with the Environmental Protection Agency (EPA). Under the
Rivers and Harbors Act of 1899 (Sec. 10) , the CE maintains permit power
over all dredge and fill operations in navigable waters of the U.S.
Section 404 of the Federal Water Pollution Control Act (PL 92-500, 1972
amend .) gives CE permit authority over the disposal of dredge and fill
material into all U.S. waters (the territorial sea). Ocean dumping of
dredged materials is regulated by the EPA under Section 102 (a) of the
Marine Protection, Research and Sanctuaries Act of 1972 (PL 92-532) .
The preceding Acts form a base of enabling legislation, following which,
interpretations and explanations of each Act are made by administrators
charged with enforcement of the Act. This includes rationale, rules and
regulations, and test criteria to be met in compliance with the Act, as
well as definitions of terms and permitting procedures promulgated by the
administrator after his review of the Act, relevant court decisions, and
public comments. Publication of this material is made in the Federal Reg-
ister. For example, the 11 January 1977 Federal Register includes a final
revision by the EPA administrator of the ocean dumping criteria originally
established by PL 92-532. Within this publication it is stated that a man-
ual will be developed by EPA and the CE to implement the criteria. This
manual (19) has recently been released and will undoubtedly be revised as
experience is gained by laboratories and agencies charged with enforcement
of its provisions.
An essential part of all regulations on dredging and disposal has been the
identification of agencies which are to be consulted prior to granting of
dredging and disposal permits. Federal and State agencies with commenting
or permit certification power are listed in Table 8.
The main dredging projects in the San Francisco Bay system are carried out
by the CE based on direct authorization by Rivers and Harbors Acts of Con-
gress beginning as early as 1876 (See Table 4). These projects, discussed
in detail in the CE Composite Environmental Impact Statement (3), fall
outside the jurisdiction of BCDC. All other dredging projects in the Bay
system require the granting of a permit by the CE. The CE cannot make a
decision on the permit until it has received comments from the various
agencies listed in Table 7 and the State Water Resources Control Board has
issued a certification of approval. After institutional approval is
granted, a public notice is posted by the CE and substantive objections
are taken into account. Any person adversely affected may request a pub-
lic hearing to express grievances.
The decision to issue the CE permit is based on public interest, including
needs for navigation, fish and wildlife, water supply, flood damage pro-
tection, ecosystems, and, in general, the needs and welfare of the people
(18). Although the existence of certain environmental impacts has been
recognized by the San Francisco District Corps of Engineers, they may be
outweighed by the needs for navigation, national defense, and other con-
siderations as expressed in the Composite EIS (3).
Criteria for the Disposal of Dredged Material
Currently employed criteria applicable to the dumping of dredged material
in San Francisco Bay and in the ocean were adopted by the EPA Region IX
administrator based on data published in the Federal Register, 1971.
Sediments must be analyzed for content of mercury, cadmium, lead, zinc,
and oil and grease by standard methods which analyze the total sediment
( bill k analysis ) . Research has shown, however, that there is little cor-
relation between bulk analysis of sediment and the metals species actu-
ally available to cause toxic effects in organisms. A new procedure,
termed the elutriate test was put forth in the 15 September 1975 Federal
Register. In this test a given volume of sediment is shaken with a given
volume of water, and the water is separated and analyzed for selected
toxic metals. If the elutriate water value exceeds disposal site water
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by a given factor (1.5), then the dredged material cannot be released in
aquatic sites. A criticism of this method is that testing for a few metals
leaves out a whole spectrum of materials that might be toxic for organisms.
Criteria development proceeded one step further with the publication of the
ocean disposal criteria manual by CE and EPA (19). This manual specifies
the use of bioassay testing to evaluate the toxic potential of dredged ma-
terial by exposing sensitive organisms directly to representative samples
of the proposed dredged material, and, if any deleterious effects on the
organisms are caused, for whatever reason, then the dredged material is not
certified for ocean dumping and must be placed in confined land disposal
1. Environmental awareness has fostered broad research programs
throughout the United States designed to determine the extent
and significance of the environmental impacts of dredging. The
most significant are the $30 million Dredged Materials Research
Program (DMRP) managed by the U.S. Army Corps of Engineers,
Waterways Experiment Station, Vicksburg, Miss., and the $3 mil-
lion Dredge Disposal Study (DDS) managed by the San Francisco
District Corps of Engineers. The voluminous results of these
programs have either been available for short periods or are
just now emerging from various contractors and universities.
As a consequence, a great deal of this material has not under-
gone critical review and synthesis by the scientific community.
2. The San Francisco Bay Estuarine system is highly complex, both
physically and chemically, within the scope of an already com-
plex field of estuarine science. The current state of the art
does not allow accurate prediction of water currents and sedi-
ment flows. The estuary undergoes natural stress in the form
of strong circulation patterns driven by tide, winds, salinity
gradients, and river inflows. Natural stresses to the biota,
typical of most estuaries, are the massive sediment inflows,
variations in salinity with river input, and seasonal tempera-
3. Further stresses to the system are imposed by industrial civi-
lization through removal of river waters, historic hydraulic
mining for gold, subsidence due to removal of groundwater,
municipal and industrial waste discharge, filling of marshes
for agricultural purposes, diking and filling of tidal flat
areas, introduction of numerous species and dredging and dis-
posal of bottom sediments. Since natural and man-made stress
may both cause the same effects on populations of organisms
with varying conditions of climate, no generalizations can be
made concerning differences in environmental effects between
natural and man-induced stress.
4. The preceding two considerations make evaluation of any specific
environmental impact, such as dredging and disposal, extremely
difficult to define with scientific certainty.
5. Field research in San Francisco Bay has shown significant direct
impacts of dredging and disposal on the biota at dredge and dis-
posal sites. Due to the circumscribed dredge and disposal areas,
these effects can be considered minor within the wide expanses
of Bay bottom habitat in which these species occur. Should
dredging and disposal at any site be terminated, the sites can
be expected to repopulate within periods of months by migration
and natural dissemination of eggs and larvae produced in nearby
regions of the Bay.
6. Measurements made upstream and downstream of dredging and disposal
activities have shown that although there are measurable effects
on oxygen, ammonia, and some heavy metals in the water, are rapidly
assimilated by the mixing regime in the Bay. A tracer study showed
that sediments released at the Carquinez Strait disposal site be-
come mixed to minute levels in San Pablo Bay sediments, and that
10-15% of the disposed material is redeposited in the dredged area
(Mare Island Strait). (See reference 8.)
7. It can be concluded from the new research data that the method of
bulk analysis to determine pollutant impacts should be reevaluated,
as presence of metals in sediments is not correlated in a simple
manner with their potential for environmental impact on water qual-
ity or biological resources. The latest criteria for ocean dumping
of dredged material promulgated by the EPA and Corps of Engineers
is based on bioassay data where representative sensitive organisms
are directly exposed to dredged material in the laboratory to de-
termine its potential toxicity.
8. There is no evidence, positive or negative, for making generaliza-
tions as to the effects of dredging and disposal on commercially
valuable biological resources of the Bay. Only highly specific
empirical experiments will demonstrate effects, if any, and due to
the multiplicity of environmental variables, specific cause-effect
relationships will always be problematical.
9. Aquatic disposal of sediments in high energy areas of the Bay ap-
pears from all available information, to be a better alternative
than land disposal of dredged materials. Land disposal of Bay mud
has readily vi si bile environmental impact, is only a temporary
solution, and is fraught with numerous environmental and economic
10. Environmental impact of routine maintenance dredging will be
different from new work dredging" Maintenance dredging removes
recently deposited material which may reflect institutional ef-
forts to remove contaminant sources.* New work dredging may un-
cover contaminants which have resided in sediment storage for
long periods of time.
*Low degree of contami nati on .
I. Carry out correlation analysis between fisheries statistics
for market crab, striped bass, and other fish for which data
is available and historical data on dredging activity. Com-
pensation should be made for lag times between dredging ac-
tivity and effects on fisheries. Significant correlations
between changes and dredging and changes in fisheries re-
sources do not prove effects, but aid in obtaining direction
for future studies.
II. Develop a routine field monitoring system to determine up-
stream-downstream differences in water quality dredging and
disposal sites under different conditions of water circula-
tion and river input to verify short term water quality
measurements made by the Corps.
Water quality measurements downstream of dredging and disposal
projects to determine loadings of water column with contami-
nated sedimentary particles for comparison with ambient values
(note: ambient values will contain background contaminant
loads from municipal and industrial waste sources).
III. Bioassay tests should be conducted on all Bay dredged material
as recommended by EPA and CE based on the guidelines recently
published (19). '
IV. Field experiments should be conducted, placing caged fish and
shellfish upstream and downstream of dredging and disposal
activities as reported in reference (30). Organisms of par-
ticular importance should be determined by personnel of the
State Department of Fish and Game. Suggested organisms in-
a. gravid female striped bass, salmon, shad, and anchovies,
which could later be spawned in order to determine per-
cent of survival of eggs;
b. molting juvenile Dungeness crabs, through several molt
cycles, maintained in bottom cages near dredging and
c. clams, oysters and mussels which can be sampled to de-
termine profiles of bacterial, viral, protozoan, and
other contaminants of public health significance.
V. A fully detailed study on a small proejct, such as the San
Leandro Marina to determine actual local effects.
1. Pritchard, D.W., 1967. What is an estuary: physical viewpoint.
Irv: Estuaries, G.H. Lauff, (ed.). Publication No. 83, pp 3-5,
2. U.S. Army Engineer District, San Francisco Corps of Engineers.
1977. Dredge disposal study San Francisco Bay and Estuary. Main
3. U.S. Army Engineer District, San Francisco, California, 1975.
Maintenance dredging of existing navigation projects in San
Francisco Bay Region, California. Final Composite Environmental
4. Storrs, P.N., E.A. Pearson and R.E. Selleck. 1966. Comprehensive
study of San Francisco Bay, Volume V, Summary of physical, chemical
and biological water and sediment data. Sanitary Engineering Res.
Lab., Rept. No. 67-2, University of California, Berkeley, CA.
5. Conomos, T.J. and D.H. Peterson, 1977. Suspended - particle
transport and circulation in San Francisco Bay: An overview.
In : Estuarine Processes, Vol. 2, pp. 82-97, Academic Press, N.Y.
6. Peterson, D.H., T.J. Conomos, W.W. Broenkow and P.C. Doherty, 1975.
Location of the non-tidal current null zone in northern San Francisco
Bay. Estuarine and Coastal Marine Science Vol. 3, pp. 1-11.
7. Krone, Ray B., 1976. Ultimate fate of suspended material in estu-
aries. Proc. Specialty Conference on Dredging and its environmen-
tal effects. Mobile, Al . , eds., P. A. Krenkle, J. Harrison and
J.C. Burdick, pp. 180-201. Am. Soc. Civ. Engrs.
8. Ecker, R.M., J.F. Sustar and W.T. Harvey. Tracing estuarine sedi-
ments by neutron activation. Proc. 15th Coastal Eng. Conf., Am.
Soc. Civ. Eng., N.Y.
9. DeFalco, Paul, 1967. The estuary - Septic tank of the megalopolis.
In : Estuaries, G.H. Lauff, (ed.), Washington, D.C.
10. Matern, R.A., 1973. San Francisco Bay. In: Our environment
the outlook for 1980, (ed.) A.J. Van TassiT. Lexington Books,
11. Serne, R.J. and B.W. Mercer, 1975. Characterization of San Francisco
Bay dredged sediments - crystalline matrix study. Appendix F, Dredge
Disposal Study, U.S. Army Engineer District, San Francisco, CA.
12. Boyd, M.B., R.T. Saucier, J.W. Keeley, R.L. Montgomery, R.D. Brown,
D.B. Mathis and C.J. Guice, 1972. Disposal of dredge spoil, prob-
lem identification and assessment and research program development.
Technical report H-72-8. U.S. Army Engineer Waterways Experiment
Station, Vicksburg, Mississippi.
13. Liu, D.H., K.D. Martin and C.R. Norwood. 1975. San Francisco Bay
benthic community study. Dredge Disposal Study, U.S. Army Engineer
District, San Francisco, California. Appendix D.
14. Gilbert, G.K. 1917. Hydraulic mining debris in the Sierra Nevada
U.S. Geol. Surv. Prof. Pap. 105. 45 p.
15. Nichols, F.H, 1973. A review of benthic fauna! surveys in San
Francisco Bay. U.S. Geological Survey, circular 677.
16. Nichols, F.H. 1977. Paper presented at AAAS Meeting, San Francisco
State University, June 13, 1977.
17. JBF Scientific Corporation. 1975. Dredging technology study.
Dredge Disposal Study, U.S. Army Engineer District, San Francisco,
California. Appendix M.
18. San Francisco Bay Conservation and Development Commission, 1976.
The Regulation of Dredging. Staff Report.
19. Technical Committee on Criteria for Dredged and Fill Material, 1977.
Ecological evaluation of proposed discharge of dredged material into
ocean waters. Environmental Effects Laboratory. U.S. Army Engineer
Waterways Experiment Station, Vicksburg, Mississippi.
20. Schubel , J.R. and R.H. Meade, 1975. Man's impact on estuarine
sedimentation. I_n: Estuarine Pollution Control and Assessment,
Proc. Vol. 1. pp. 193-209. U.S. Environmental Protection Agency,
21. Cunnington, E.A., 1968. Survival time of oysters after burial at
various temperatures. Proc. Natl. Shelf. Assn., Vol. 58. pp. 101-
22. McCauley, J.E., R.A. Parr and D.R. Hancock, 1977. Benthic infauna
and maintenance dredging: a case study. Water Research Vol. 11,
23. Oliver, J.S., P.N. Slattery, L.W. Hulberg, and J. W. Nybakken.
1976. Final report task 1D01. Prepared for Environmental Effects
Laboratory, DMRP. U.S. Army Engineer Waterways Experiment Station,
24. Keck, R.T., et al . 1976. Vertical migration of marine benthos in
dredged material overburdens. University of Delaware, Coll. Mar.
Stud. Draft Report. DMRP Project 1D03. Lewesand Newark, Del. 130 p.
25. No citation.
26. Peddicord, R.K., et al . 1975. Effects of suspended solids on San
Francisco Bay organisms. Report to: U.S. Army Corps of Engineers,
San Francisco District, Dredge Disposal Study, Appendix G. 158 pp.
27. Peddicord, R.K. and V. McFarland. 1976. Effects of suspended
dredged material on aquatic animals. Working draft final report
task 1D09. Prepared for U.S. Army Corps of Engineers Waterways
Experiment Station, Vicksburg, MI.
28. U.S. Army Engineer District, San Francisco Corps of Engineers.
1976. Water column. Dredge disposal study. Appendix C.
29. Sherk, J. A., J.M. O'Conner and D.A. Neumann, 1975. Effects of sus-
pended and deposited sediments on estuarine environments. In:
Estuarine Research, ed., L. Eugene Cronin, Vol. 2, pp. 541-3F8.
30. Cronin, L.E., et al . , 1970. Gross physical and biological effects
of overboard spoil disposal in upper Chesapeake Bay. Nat. Res.
Inst. Spec. Rep. No. 3. University of Maryland.
31. Sullivan, B.K. and D. Hancock, 1977. Zooplankton and dredging:
research perspectives from a critical review. Water Res. Bulletin,
Vol. 13, No. 3, pp. 461-467.
32. Diaz, R.J. and D.F. Boesch, 1977. Impact of unconfined overboard
disposal of fine grained dredged material on benthic communities
with particular attention to the environmental effects of fluid mud.
Unpublished report task No. 1D12. Environmental Effects Laboratory.
U.S. Army Engineer Waterways Experiment Station, Vicksburg, MI.
33. Chen, K.Y. et al . 1976. Research study on the effect of dispersion,
settling and resedimentation on migration of chemical constituents
during open-water disposal of dredge material. Prepared for U.S.
Army Engineer Waterways Experiment Station, Vicksburg, MI. 221 pp.
34. Lu, J.C.S. and K.Y. Chen. 1977. Migration of trace metals in
interfaces of seawater and polluted surficial sediments. Environ.
Sci. Techno!. 11: 174-182.
35. Anderlini, V.C. et al . 1976. Pollutant availability study. Dredge
Disposal Study, U.S. Army Engineer District, San Francisco, CA.
305 pp. Appendix I.
36. Anderlini, V.C. et al . 1975. Heavy metal uptake study. Dredge
Disposal Study, U.S. Army Engineer District, San Francisco, CA.
89 pp. Appendix H.
37. Neff, J.W., R.S. Foster and J.F. Slowey. 1977. Research study
to determine the availability of sediment adsorbed heavy metals
to benthos with particular emphasis on deposit feeding infauna.
Interim report task 1D06. Prepared for Environmental Effects
Laboratory, U.S. Army Engineer Waterways Experiment Station,
38. Fulk, R. , D. Gruber and R. Wullschleger. 1975. Laboratory study
of the release of pesticides and PCB materials to the water column
during dredging and disposal operations. Prepared for U.S. Army
Engineer Waterways Experiment Station, Vicksburg, MI. 88 pp.
39. DiSalvo, Louis H. , H.E. Guard, N. Hirsch and J. Ng. 1977. Assess-
ment and significance of sediment associated oil and grease in
aquatic environments. Draft final report Task 1-D-ll. Prepared
for U.S. Army Corps of Engineers Waterways Experiment Station,
40. DiSalvo, L.H. and H.E. Guard. 1975. Hydrocarbons associated with
suspended particulate matter in San Francisco Bay waters. Proc.
of American Petroleum Institite, Washington, D.C.
41. Meadows, P.S. and J.G. Anderson. 1968. Microorganisms to marine
sand grains. J. Mar. Biol. Assn. U.K. 48: 161-175.
42. Van Donsel , D.J. and E.E. Geldreich. 1971. Relationships of
Salmonellae to fecal col i forms in bottom sediments. Water Res. 5:
43. Grimes, D.J. 1975. Release of sediment bound fecal col i forms by
dredging. Appl . Microbiol. 29(1): 109-111.
44. Sawyer, T,K., G.S. Visvesvara, and B.A. Harke. 1977. Pathogenic
amoebas from brackish and ocean sediments, with a description of
Acanthamoeba hatchetti , n. sp. Science 196: 1324-1325.
45. Lee, G. Fred. 1975. Significance of chemical contaminants in
dredged sediments on estuarine water quality. Proc. Estuarine
Pollut. Workshop, Pensacola. U.S. Environmental Protection Agency.
46. International Engineering Co. 1975. Final Report: Dredge Spoils
Disposal Facility, Skaggs Is. (for) Dept. of the Navy, WEST DIV
Naval Facilities Engineering Command, San Bruno, CA.
Based on the results of the various investigations conducted during the
Dredge Disposal Study (reported in Appendices A through M) the following
conclusions have been formulated regarding San Francisco Bay maintenance
dredging and disposal activities:
o Higher concentrations of contaminants in dredged channels can be
attributed to the finer grain size associated with maintenance
dredging. Since dredged channels are out of equilibrium, forming
lower energy regime, finer sediments will tend to shoal. High
contaminant levels in San Francisco Bay are normally associated
with the finer sediments.
o The type of sediment and the degree to which it is disturbed de-
termine the amount of sediment resuspension during dredging and
the immediate release pattern during disposal at open water sites.
The disturbance, including the adding and mixing with water, de-
pends on the type and size of dredge, the efficiency of operation
and the configuration of the shoal.
o The disturbance during sediment disposal is limited to the bottom
two meters of the water column regardless of whether the sediment
mounds or disperses. With hopper dredge operations, the sediments
leave the disposal site typically within fifteen minutes of re-
lease and are quickly assimilated into the Bay sediment regime.
o The sediment regime of the Bay is a very dynamic system. Tests
in the Bay Area show that within a month, dredged sediments are
well distributed both horizontally (over 260 square kilometer
study area) and vertically (in excess of 23 centimeters). About
ten percent of the dredged sediment returns to the Mare Island
Strait channel with disposal in Carquinez Strait. The majority
of samples in the study area had less than four percent dredged
sediment. Sediments entering San Pablo Bay for the most part
are not carried directly to the ocean. Sediments are deposited,
resuspended, recirculated and redeposited elsewhere with a net
effect of sediment transport toward the ocean.
o Dredging and disposal in the Bay were not observed to cause
changes in conductivity/salinity, temperature or pH. Temporary
but marked water quality changes which were observed included
reduction of dissolved oxygen, increases in suspended solids,
and releases of trace elements, chlorinated hydrocarbon and
nitrogen (nitrate and ammonia).
o Although large changes in water quality were demonstrated, no
analogous changes in organisms were observed. Thus biological
impact was not found to be synonymous with measurable water
o Significant demonstrated biological effects resulting from in
Bay dredging and disposal activities are limited to the reduc-
tion of the number and kinds of benthic organisms immediately
following an operation and the net reduction of the p, p'-DDE
desorption rate during disposal.
o The potential for adverse biological stresses from reduced dis-
solved oxygen and increased suspended solids concentrations is
less during winter periods when water temperatures are lowest
and dissolved oxygen levels highest. Furthermore, during this
period eggs, larvae and juvenile organisms are at their lowest
numbers in the water column.
o Release of toxicants during dredging and disposal operations
seems to be at such low levels and to last for such short dura-
tions that their availability for uptake and accumulation is
o Salinity increases significantly intensify the potential for
release of certain trace elements from resuspended sediments.
Organisms, however, have been observed to have greater uptake
rates during periods of decreased salinity and to have greater
depuration rates in high salinity water. These two opposing
conditions suggest that there is potentially a natural defense
mechanism operating in organisms to safeguard them from ex-
cessive trace element accumulation.
o Increasing the efficiency of dredging operations in terms of
minimizing energy losses in disturbing sediments and maximiz-
ing the collection of sediments whether by hydraulic cutter-
head, clamshell or hopper dredge, will decrease the potential
for adverse impacts.
o Increasing the dispersion of sediments dredged by hopper dredge
in the Bay could have several positive effects. First, the
potential of concentrated high suspended solids loading would
be reduced. Second, both the intensity and duration of dis-
solved oxygen depressions would be reduced. Since these two
conditions work synergistically, adverse biological effects
would decrease. Third, since both toxicant release and uptake
are concentration dependent, greater dispersion, although in-
creasing the contact area of sediments for contaminant releases,
should reduce the potential maximum release (concentration) at
any one location and thus the potential organism uptake and
accumulation. And finally, any nutrient or ammonia release
would be quickly assimilated into the system, reducing potential
localized biostimulation or toxicity. Changes in operational
policies would have to be accomplished without significantly in-
creasing the time frame of impact. Otherwise, possible mitiga-
tive advantages might be offset by increasing the duration of
o The potential for long-term accumulation of contaminants by
organisms from sediments dredged in harbor areas and disposed
in the open bay is and has been a significant biological con-
cern because of historically high contaminant levels in these
harbor areas. Other areas in the Bay also have equally high
contaminant levels because of their predominantly fine grain
composition and high transport rate of resuspended sediments.
Fine grain sediments naturally scavenge contaminants and
wherever they are concentrated, contaminant levels will typi-
cally be high. Source control is the only effective method
for controlling contaminant levels in these sediments. How-
ever, channel sediment sampling during the last two years
(1975-1976) seems to indicate that the contaminant levels in
dredged channels have decreased to levels congruent with open
areas of the Bay. This is probably the result of the elimi-
nation or improvement in quality of industrial and municipal
discharges as required by both State and Federal regulatory
agencies. As Bay sediment contaminant levels decrease, so
will the potential for long-term toxicant accumulation.
o Open water disposal is not considered a significant blockage
of the channels for mitigation of fish, particularly through
Carquinez Strait. The plume, as monitored in the field, is
confined to the bottom two meters of the water column, and
its cross-section constitutes less than one percent of the
Carquinez Strait cross-section. The plume occurs in the dis-
posal site less than one-quarter of the time (ratio of dis-
posal time to total time).
o The movement of dredged sediments into the nodal zone in
Carquinez Strait should cause no more impact on striped bass
finger! ings and neomysis than those sediments naturally oc-
curring in this zone. Sediment loading in the nodal zone is
dependent on tidal forces and freshwater inflow. Dredged
sediments to replace other sediments in the zone; however,
unless a contaminant source significantly raises the concen-
trations in the dredged sediment, the two sediments should
be physically and chemically similar.
o The transport of highly contaminated sediments from the Bay to
deep water ocean disposal sites has the potential for creating
long-term biological impact. When these sediments are released,
mounding will generally occur (typically these sediments are
cohesive and dredged by clamshell operation). These mounds
will remain intact for long periods because of the lack of high
current velocities to erode and disperse them. Since these con-
taminated sediments typically contain concentrations of organic
materials, as well as toxicants, several factors higher than am-
bient levels, animals may be attracted to them as a concentrated
food source. While feeding, these organisms are susceptible to
uptake and accumulation of associated toxicants. This could be
a particularly significant problem in the Gulf of the Farallones,
a known nursery area for many commercially important species.
o The evaluation of potential impacts with with either dispersion
or mounding must be made on a case-by-case basis, considering
the release of contaminants, the type of sediment and the sen-
sitivity of both the water and the sediment system at the dis-
o Extensive land disposal for maintenance dredging projects does
not appear to be a viable alternative to aquatic disposal at
this time because of costs, identified technical difficulties
and adverse environmental effects which may be involved. Po-
tential problems include crossing of wetlands, rupture of
dikes with earthquakes, mudflows, saline water loading and
loss of irretrievable potential wetlands.
o Marsh development using dredged sediments should be viable on
a case-by-case basis, particularly for one time only, small
dredging projects which are located near suitable diked low
lands, because of the environmental benefits achieved. Marshes
are important to the estuary for their ability to oxygenate
Bay waters, produce nutrients which serve as a base for the
food web, capture ions, dissipate energy and provide wildlife
o Contaminant levels in estuarine organisms appear to be con-
trolled by a limited number of synergistic factors. Suggested
factors are the long-term process of sediment resuspension-
recirculation, seasonal fluctuations in salinity and sources
of contaminants both anthropogenic and geologic. The biolog-
ical impact may be dependent on the form of contaminant and
whether or not the sediment system can assimilate the contami-
nant loading. With the observed sorption-desorption by orga-
nisms and the fluctuating conditions in the estuary, impacts
such as high accumulations, mutations and toxicity would not
be expected unless the contaminant loading is foreign, in the
case of synthetic chemicals, or above the assimilation capa-
bility of the estuary with the associated sediment regime, in
the case of a low energy regime in which the changes in ambient
conditions are great.
LIST OF EXPERTS CONTACTED
Individual Organization Contact
Dr. Richard Peddicord
Dr. P.J. Hannan
Dr. Teng-Chung Wu
Dr. Donald Girvin
Mr. L. Thomas Tobin
Mr. Mike Rugg
Dr. Jim Sutton
Mr. Bill Light
Mr. William Leet
Mr. Fred Minckler
Mr. Robert Parker
Mr. Ted Durst
Mr. Chris Vais
Waterways Experiment Station PI
Army Corps of Engineers
Naval Research Laboratory ph
Regional Water Quality Control PI
Lawrence Berkeley Laboratory, ph
San Francisco Bay Conservation PI
and Development Commission
San Francisco, California
California State Department of PI
Fish and Game
California Academy of Sciences PI
San Francisco, California
National Oceanic and Atmospheric PI
(National Marine Fisheries
Service), Tiburon, California
U.S. Army Corps of Engineers PI
Seattle District Office
U.S. Environmental Protection PI
Agency, Region IX
San Francisco, California
PI = Personal Interview
ph = Telephone Contact
LIST OF EXPERTS CONTACTED (Continued)
Dr. H.L. Taten
Dr. Robert Engler
Dr. Bill Barnard
Mr. John Sustar
Dr. T.J. Conomos
Mr. Charles Roberts
Mr. Bob Tasto
Mr. Phil Swartzell
Station, Army Corps
San Francisco District
Corps of Engineers
U.S. Geological Survey
Menlo Park, California
San Francisco Bay Conservation
and Development Commission
San Francisco, California
California Department of
Fish and Game
Menlo Park, California