CHAPTER 3.0 DREDGING AND DREDGED MATERIAL … · 2013. 2. 20. · dredging equipment. Hydraulic dredging can virtually eliminate disturbance and resuspension of sediments at the dredging

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August 1998 Long-Term Management Strategy for Bay Area Dredged MaterialFinal Environmental Impact Statement/Environmental Impact Report

CHAPTER 3.0 DREDGING AND DREDGED MATERIAL CHARACTERISTICS — AN OVERVIEW

This chapter provides an overview of the dredgingprocess and the sediment characteristics that affectdisposal and reuse of dredged material. A basicunderstanding of how dredged sediments and anyassociated contaminants behave in differentcircumstances (for example, at upland versus aquaticplacement sites) is critical to managing dredgedmaterial in a manner that minimizes potentialenvironmental impacts and risks, and that maximizesenvironmental, societal, and economic benefits. Thefirst section (section 3.1) describes the dredgingprocess itself, including the basic types of dredging anddisposal equipment, with an emphasis on how thedredging method used affects the feasibility of variousmanagement options. The next section (section 3.2)discusses the major physical, chemical, and biologicalcharacteristics of Bay area sediments in general — anddredged material in particular — that provide the basisof appropriate dredged material management.

3.1 DREDGING IN THE SANFRANCISCO BAY REGION

Each year, over 4,000 commercial, ocean-going vesselsnavigate into or through the San Francisco Bay/DeltaEstuary (the Estuary), carrying over 50 million tons ofcargo to eight public and numerous other private portsand harbors between Sacramento and Redwood City.The Estuary has also been an important center of navaland other military operations through the years. Inaddition, over 1,000 commercial fishing vessels operateout of San Francisco Bay, and over 200 marinasprovide slips for over 33,000 recreational boats.Together, these activities fuel a substantial maritime-related economy of over $7.5 billion annually.However, the facilities supporting these activities arelocated around the margins of a bay system thataverages less than 20 feet deep, while modern, deep-draft ships often draw 35 to 40 feet of water or more.Extensive dredging — in the range of 2 million to 10million cubic yards (mcy) per year — is thereforenecessary to create and maintain adequate navigationchannels in order to sustain the region’s diversenavigation-related commercial and recreationalactivities. Effective management of the large volumesof dredged material generated throughout the Estuary isa substantial challenge. The following sections discussdredging and disposal methods used in the Estuary, andthe amount of dredged material anticipated to begenerated over the 50-year LTMS planning period.

3.1.1 Dredging and Disposal Methods

3.1.1.1 General

This section provides a brief overview of the dredgingprocess, including types of dredges, types of impactsthat may be associated with dredging, transportationsystems, and the placement or disposal practicescommonly used in navigation-related dredging projectsas described in the joint EPA/COE national guidancedocument, Evaluating Environmental Effects ofDredged Material Management Alternatives — ATechnical Framework (USEPA and USACE 1992).The indicated references provide a more detaileddescription of different kinds of dredges, transportequipment, and disposal practices.

The removal or excavation, transport, and placement ofdredged sediments are the primary components of thedredging process. In design and implementation of anydredging project, each part of the dredging processmust be closely coordinated to ensure a successfuldredging operation.

The excavation process commonly referred to as“dredging” involves the removal of sediment in itsnatural or recently deposited condition, using eithermechanical or hydraulic equipment. (Dredgingsediments in their natural condition is referred to asnew work construction; dredging recently depositedsediments is referred to as maintenance dredging.)After the sediment has been excavated, it is transportedfrom the dredging site to the placement site or disposalarea. This transport operation, in many cases, isaccomplished by the dredge itself or by usingadditional equipment such as barges, scows, andpipelines with booster pumps.

Once the dredged material has been collected andtransported, the final step in the dredging process isplacement in either open-water, nearshore, or uplandlocations. The choice of management alternativesinvolves a variety of factors related to the dredgingprocess including environmental acceptability,technical feasibility, and economic feasibility of thechosen alternative.

3-2 Chapter 3 — Dredging and Dredged Material Characteristics

Long-Term Management Strategy for Bay Area Dredged Material August 1998Final Environmental Impact Statement/Environmental Impact Report

3.1.1.2 Dredging Process, Equipment, andTechniques

The dredging equipment, techniques used forexcavation and transport of the material, and thedisposal alternatives considered must be compatible.The types of equipment and methods used by both theCOE and private industry vary considerably throughoutthe United States. The most commonly used dredgesare illustrated in Figure 3.1-1. Dredging equipment anddredging operations resist precise categorization. As aresult of specialization and tradition in the industry,numerous descriptive, often overlapping, termscategorizing dredges have developed. For example,dredges can be classified according to the basic meansof moving material (mechanical or hydraulic); thedevice used for excavating sediments (clamshell,cutterhead, dustpan, and plain suction); the type ofpumping device used (centrifugal, pneumatic, orairlift); and others. However, for the purpose of thisdocument, dredging is accomplished basically by onlytwo mechanisms:

• Hydraulic dredging — Removal of looselycompacted materials by cutterheads, dustpans,hoppers, hydraulic pipeline, plain suction, andsidecasters, usually for maintenance dredgingprojects.

• Mechanical dredging — Removal of loose or hardcompacted materials by clamshell, dipper, or ladderdredges, either for maintenance or new-workprojects.

Hydraulic dredges remove and transport sediment inliquid slurry form. They are usually barge-mountedand carry diesel or electric-powered centrifugal pumpswith discharge pipes ranging in diameter from 6 to 48inches. The pump produces a vacuum on its intakeside, which forces water and sediments through thesuction pipe. The slurry is transported by pipeline to adisposal area. Hopper dredges are included in thecategory of hydraulic dredges for this report eventhough the dredged material is simply pumped into theself-contained hopper on the dredge rather than througha pipeline. It is often advantageous to overflow excesswater from hopper dredges to increase the sedimentload carried; however, this may not always beacceptable due to water quality concerns near thedredging site.

Mechanical dredges remove bottom sediment throughthe direct application of mechanical force to dislodgeand excavate the material at almost in situ densities.Backhoe, bucket (such as clamshell, orange-peel, and

dragline), bucket ladder, bucket wheel, and dipperdredges are types of mechanical dredges. Sedimentsexcavated with a mechanical dredge are generallyplaced into a barge or scow for transport to the disposalsite.

Selection of the dredging equipment and method usedto perform the dredging depends on the followingfactors:

• Physical characteristics of the material to bedredged;

• Quantity of material to be dredged;• Dredging depth;• Distance to disposal area;• Physical environment of the dredging and disposal

areas;• Contamination level of sediments;• Method of disposal;• Production rate required (e.g., cubic yards per

hour);• Types of dredges available; and• Cost.

Water quality at the dredging and disposal sites is aparticularly important consideration in the choice ofdredging equipment. Hydraulic dredging can virtuallyeliminate disturbance and resuspension of sediments atthe dredging site, and is often the first choice whendredging occurs in enclosed waterbodies or in locationsnear aquatic resources that would be especiallysensitive to temporary increases in suspended solids orturbidity. However, because hydraulic dredgingtypically entrains additional water that is many timesthe volume of sediment removed, water managementand water quality must be controlled at the disposalsite. In contrast, mechanical dredging creates littleadditional water management concern at the disposalsite because little additional water is entrained bymechanical dredging equipment; therefore mechanicaldredging is usually the first choice when disposal sitecapacity limitations are a primary concern. However,typical mechanical equipment often creates moredisturbance and resuspension of sediments at thedredging site.

More detailed descriptions of dredging equipment anddredging processes are available in Engineer Manual(EM) 1110-2-5025 (USACE 1983), Houston (1970),and Turner (1984).

Chapter 3 — Dredging and Dredged Material Characteristics 3-3


Figure 3.1-1 Types of Dredges

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3.1.1.3 The General Impacts of Dredging

This section describes briefly the types of impactsassociated with dredging activities in general. Most ofthe impacts from dredging are temporary and localizedand, with the exception of impacts associated with achanged bottom topography (potential change in localhydrodynamics and in the makeup of the benthicresources present in the dredge area), the impacts endwhen the dredging ends. The most substantial impactstend to be on water quality, the potential forresuspension of contaminants buried in the sediments,and the impacts on biological resources in the dredgearea. These types of impacts are therefore discussed inmore detail below.

Potential Impacts on Water Quality

Water quality variables that can be affected bydredging operations include turbidity, suspended solids,and other variables that affect light transmittance,dissolved oxygen, nutrients, salinity, temperature, pH,and concentrations of trace metals and organiccontaminants if they are present in the sediments (U.S.Navy 1990).

Dredging resuspends bottom sediments and thustemporarily increases the turbidity of surface waters.Chemical reactions can occur between the suspendedmaterials and the surrounding Bay water. The primarycontrolling factors would be the redox potential of theseawater, the pH of the seawater and, to a lesser degree,the salinity (Pequegnat 1983). (“Redox potential”refers to the reduction-oxidation potential, which is ameasure of the availability and activity of oxygen toenter into and control chemical reactions.) The fine-grained sediment fractions (clay and silt) have thehighest affinity for several classes of contaminants,such as trace metals and organics, and tend to remain inthe water column longer than sand because of their lowsettling velocities (U.S. Navy 1990). Oxygen in theseawater would promote oxidation of the organicsubstances in the suspended materials This, in turn, canrelease some dissolved contaminants, particularly thesulfides (U.S. Navy 1990).

Depending on the dredging method used, dissolvedoxygen (DO) concentrations in the water column can besubstantially reduced during dredging if the suspendeddredged material contains high concentrations ofoxygen demanding substances (e.g., hydrogen sulfide).The reduction of DO during dredging is minimal (1 to 2ppm) and transitory in surface waters, but can be moresevere in bottom waters (reduction of up to 6 ppm for 4to 8 minutes). Most estuarine organisms are capable of

tolerating low DO conditions for such short periods.Reduced DO concentrations would be expected to belocalized and short term, with minimal impacts (U.S.Navy 1990).

Nutrient enrichment can increase turbidity in the watercolumn by enhancing the growth of phytoplankton. Ifthis occurs, it is typically a transient phenomenon withminimal local impact. In the Bay area, nutrients wouldbe flushed out of the dredging area by tidal currents.Effects of nutrients on phytoplankton in the Bay wouldgenerally not be detectable (U.S. Navy 1990).

Depending on the location of the dredging, deepeningnavigation channels can increase saltwater intrusioninto the Delta (since saline water is heavier thanfreshwater), potentially impacting freshwater suppliesand fisheries. Dredging can also increase saltwaterintrusion into groundwater aquifers (e.g., the MerrittSand/Posey formation aquifer in the Oakland Harborarea), with consequent degradation of groundwaterquality in shallow aquifers (U.S. Navy 1990).

Potential Impacts on Sediments

The impacts on sediments at the dredging site mayinclude increased post-dredging sedimentation in thenewly deepened areas for new work projects, localchanges in air-water chemistry, and possible slumpingof materials from the sides of the dredging areas.

Potential Resuspension of Contaminants

Dredging will resuspend contaminants if contaminationis present in the surface sediments. Metal and organicchemical contamination is widespread in San FranciscoBay sediments due to river run-off and municipal/industrial discharges (see section 3.2.3.2).Contaminants of particular concern in various parts ofthe Bay include silver, copper, selenium, mercury,cadmium, polychlorinated biphenyls (PCBs), DDT andits metabolites, pesticides, polynuclear aromatichydrocarbons (PAHs), and tributyltin.

Dredging of contaminated sediments does present thepotential for release of contaminants to the watercolumn, and for the uptake of contaminants byorganisms contacting resuspended material. However,most contaminants are tightly bound in the sedimentsand are not easily released during short-termresuspension. Chemical reactions that occur duringdredging may change the form of the contaminant andthus alter its bioavailability to organisms. Thesechemical reactions are determined by complexinteractions of environmental factors, and may either



enhance or decrease bioavailability, particularly ofmetals.

Potential Impacts on Biological Resources

The impacts of dredging on biological resources can beshort term or long term, direct or indirect. There canbe short-term impacts from the dredging, and long-termimpacts associated with habitat modification. Short-term impacts could include local changes in speciesabundance or community diversity during orimmediately after dredging. Long-term impacts couldinclude permanent species abundance or communitydiversity changes caused by changes in hydrodynamicsor sediment type, or a decline or erratic trend beyondthe normal range of variability in the years followingnew dredging (U.S. Navy 1990). Direct impacts wouldbe directly attributable to the dredging activity, such asa direct loss of mudflat habitat or a temporary turbidity-induced reduction in productivity in an eelgrass bedimmediately adjacent to a dredging site. Indirecteffects on organisms include those effects which are notimmediately measurable as a consequence of dredgingoperations. Such effects might, for example, involvepopulation changes in one species that are caused bydredging’s effects on its predators, prey, orcompetitors. Indirect effects may be manifested overextended periods of time and/or at some distance awayfrom the dredging site. The differentiation betweendirect and indirect effects is not always clear.

Dredging involves the removal of substrate and benthicorganisms at the dredging site, resulting in immediatelocalized effects on the bottom life. Besides thedecimation of organisms at the dredging site, there isthe removal of the existing natural or establishedcommunity with widely varying survival of organismsduring dredged material excavation. Aside from theinitial physically disruptive effects, a long-termenvironmental concern is the recovery (repopulation) ofbottom areas where dredging has occurred (Hirsch,DiSalvo, and Peddicord 1978). Dredging thus opensthe area for recolonization on a new substrate that mayresemble the original substrate or be completelydifferent in physical characteristics. Recolonizationmay include the same organisms or opportunisticspecies that have environmental requirements that areflexible enough to allow them to occupy a disturbedsite (Reilly et al. 1992).

Recolonization of the dredging site can begin quickly,although re-establishment of a more stable benthiccommunity may take several months or years after thedredging operation has occurred (Oliver et al. 1977;Conner and Simon 1979). Oliver et al. (1977) found

that most of the infauna were destroyed at the center ofthe dredging area. Communities inhabiting highlyvariable and easily disrupted environments, such asthose found in shallow water, recovered more quicklyfrom dredging operations than communities in lessvariable environments such as in deep or offshorewaters. Seasonal changes in the environment wereconsidered most important in shallower water where theorganisms are more likely to be affected by thechanging seasons (Reilly et al. 1992).

Oliver et al. (1977) noted two phases of successionafter a disturbance. In the first phase, opportunisticspecies such as some polychaetes would move into adisturbed area. The second phase involved recruitmentof organisms associated with undisturbed areas aroundthe disturbed site. Recovery at the disturbed dredgingsite depends on the type of environment and the speedand success of adult migration or larval recruitmentfrom adjacent undisturbed areas (Hirsch, Disalvo, andPeddicord 1978).

The effects of habitat loss or alteration at the dredgesite may extend beyond the boundaries of the dredgingoperations. However, dredging-induced habitatalterations are minor compared to the large-scaledisturbance of benthic habitat in San Francisco Bayfrom naturally occurring physical forces (Reilly et al.1992). The result of these forces is a state of non-equilibrium in benthic species composition typical ofshallow estuaries. Naturally occurring habitatdisturbances arise from seasonal and storm-generatedwaves, and from seasonal fluctuations of riverinesediment transport into San Francisco Bay. Humaninfluences on benthic habitat include not only dredgingand disposal, but also waste discharges, sedimentdeposition from hydraulic mining, filling of Baymargins, fresh water diversions, and introduction ofexotic species. When the disturbance ceases,recolonization of the benthic substrate occurs; re-establishment of a more or less stable benthiccommunity can take several months or years (Reilly etal. 1992).

The suspension of sediments during dredging willgenerally result in localized, temporary increases inturbidity that are dispersed by currents or otherwisedissipate within a few days, depending onhydrodynamics and sediment characteristics (e.g.,USACE and Port of Oakland 1998). Where dredgingoccurs in relatively polluted areas, contaminants in thesediments are likely to be dispersed into the watercolumn, resulting in localized, temporary increases incontaminant concentrations that may affect fish andinvertebrates.



Although the increases in turbidity are transient, theycan have several types of longer-term consequences forsensitive biological resources. Increased turbidity canreduce the survival of herring eggs, which are attachedto hard surfaces on Central Bay shorelines, potentiallyresulting in reduced recruitment and, ultimately,reduced abundance of this important resource speciesin the Bay. In certain locations, at critical times ofyear, increased turbidity can affect the survival of thelarval or juvenile stages of sensitive fish species, aswell as the feeding and migration of adults. Short-termimpacts on critical foraging areas, such as eelgrassbeds, during the nesting season of marine birds such asthe endangered California least tern, can affect thebirds’ nesting success.

The effect of dredging on fish varies to some degreewith the life stage of the fish. Early life stages of fishare more sensitive than adults. Adult fish would bemotile enough to avoid the areas of activity; it isassumed that fish will leave the affected areas untildredging is done. Turbidity could reduce visibility,causing difficulty in locating prey. Suspendedsediments can have other impacts, including abrasion ofthe body and clogging of the gills. Generally, bottom-dwelling fish species are most tolerant to suspendedsolids, and filter feeders are the most sensitive. In SanFrancisco Bay, dredging between December andFebruary could disrupt the spawning of the Pacificherring and result in mortality to eggs. Depending onthe location of dredging, such activity could affect themigration of steelhead and chinook salmon. Dredgingin the Central Bay during summer can affect juvenileDungeness crabs, for which the Central Bay providesan important nursery habitat. Larval and juvenile fishesand invertebrates are also vulnerable to entrainment indredging equipment.

Waterbirds that feed or rest in the vicinity of thedredging activity may be disturbed and, as a result,move to areas where they incur higher energetic costsor experience greater risks.

Potential Impacts on Other Resource Areas

Emissions from dredging equipment in the Bay areatypically causes temporary adverse impacts on airquality, depending on the size and location of theproject.

Noise from the dredge can cause significant impacts onsensitive receptors located near the dredge area.

Dredging can impact submerged cultural resources(e.g., ship wrecks) if such resources are present in the

dredge area. For the ports and major navigationchannels in the Bay area, this is usually not an issuebecause the channels have been dredged previously.

In terms of socioeconomic impacts, dredging activitieshave a minor beneficial impact on employment,requiring a relatively small work force which can easilybe met by the large population in the Bay area. Deepernavigation channels are critical to Bay area ports’ability to compete for vessel cargo with other U.S. westcoast ports, so dredging has a regional beneficialeconomic impact on the Bay area. Dredging has abeneficial impact also on recreational and commercialactivities in that dredging helps to maintain harbors andmarinas, which support fishing, boating, and associatedactivities.

Dredging impacts on vessel transportation are typicallyminimal. The dredge represents an obstacle that othervessels have to maneuver around, but the location ofthe dredge is posted in the Notice to Mariners so it canbe easily avoided.

Depending on the location, dredging can affectrecreational fishing but such impacts are typicallytemporary and insignificant.

Dredging can impact submerged utilities but, withproper notice, these utilities can be relocated to avoidimpacts.

3.1.1.4 Transportation of Dredged Material

Transportation methods generally used to movedredged material include the following: pipelines,barges or scows, hopper dredges, and sometimestrucks. Pipeline transport is the method mostcommonly associated with cutterhead, dustpan, andother hydraulic dredges. Dredged material may bedirectly transported by hydraulic dredges throughpipelines for distances of up to several miles,depending on a number of conditions. Longer pipelinepumping distances are feasible with the addition ofbooster pumps, but the cost of transport greatlyincreases. Barges and scows, used in conjunction withmechanical dredges, have been one of the most widelyused methods of transporting large quantities ofdredged material over long distances. Hopper dredgesare capable of transporting the material for longdistances in a self-contained hopper. Hopper dredgesnormally discharge the material from the bottom of thevessel by opening the hopper doors; however, somehopper dredges are equipped to pump out the materialfrom the hopper much like a hydraulic pipeline dredge.Truck transport is typically more expensive than barge



transport; it is generally only used for transport toupland sites not accessible by water. See the discussionof impacts associated with truck transportation ofdredged material in section 4.4.5.3.

3.1.1.5 Material Placement or Disposal Operations

Selection of proper dredging and transport equipmentand techniques must be compatible with disposal siteand other management requirements. Three mainalternatives are available:

• Open-water disposal;• Confined disposal; and• Beneficial reuse.

Each of these alternatives involves its own set ofunique considerations, and selection of a managementalternative should be based on environmental,technical, and economic considerations.

Description of Open-Water Disposal

Open water disposal is the placement of dredgedmaterial at designated sites in rivers, lakes, estuaries, oroceans via pipeline or release from hopper dredges orbarges. Such disposal may also involve appropriatemanagement actions or controls such as capping. Thepotential for environmental impacts is affected by thephysical behavior of the open-water discharge. Thephysical behavior of the discharge depends on the typeof dredging and disposal operation used, the nature ofthe material (its physical characteristics), and thehydrodynamics of the disposal site.

Dredged material can be placed in open-water sitesusing direct pipeline discharge, direct mechanicalplacement, or release from hopper dredges or scows. Aconceptual illustration of open water disposal using themost common placement techniques in shown in Figure3.1-2.

Pipeline dredges are commonly used for open waterdisposal adjacent to channels. Material from thisdredging operation consists of a slurry with a solidsconcentration ranging from a few grams per liter toseveral hundred grams per liter. Depending on materialcharacteristics, the slurry may contain clay bails,gravel, or coarse sand material. The coarse materialquickly settles to the bottom. The mixture of dredgingsite water and finer particles has a higher density thanthe disposal site water and therefore can descend to thebottom forming a fluid mud mound. Continuing thedischarge may cause the mound to spread. Some finematerial is “stripped” during descent and is evident as a

turbidity plume. Characteristics of the plume aredetermined by discharge rate, characteristics of theslurry (both water and solids), water depth, currents,meteorological conditions, salinity of receiving water,and discharge configuration.

The characteristics and operation of hopper dredgesresult in a mixture of water and solids stored in thehopper for transport to the disposal site. At thedisposal site, hopper doors in the bottom of the ship’shull are opened, and the entire hopper contents areemptied in a manner of minutes; the dredge then returnsto the dredging site to reload. This procedure producesa series of discrete discharges at intervals of perhapsone to several hours. Upon release from the hopperdredge at the disposal site, the dredged material fallsthrough the water column as a well-defined jet of high-density fluid which may contain blocks of solidmaterial. Ambient water is entrained during descent.After it hits bottom, most of the dredged materialcomes to rest. Some material enters the horizontallyspreading bottom surge formed by the impact and iscarried away from the impact point until the turbulenceof the surge is sufficiently reduced to permit itsdeposition.

Bucket or clamshell dredges remove the sediment beingdredged at nearly its in situ density and place it on abarge or scow for transport to the disposal area.Although several barges may be used so that thedredging is essentially continuous, disposal occurs as aseries of discrete discharges. Barges are designed withbottom doors or with a split-hull, and the contents maybe emptied within seconds, essentially as aninstantaneous discharge. Often sediments dredged byclamshell remain in fairly large consolidated clumpsand reach the bottom in this form. Whatever



Figure 3.1-2 Plume Shapes by Dredge Types

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its form, the dredged material descends rapidly throughthe water column to the bottom, and only a smallamount of the material remains suspended. Clamshelldredge operations may also be used for direct materialplacement adjacent to the area being dredged (i.e.,when no transport is necessary). In these instances, thematerial also falls directly to the bottom as consolidatedclumps.

Dredge hoppers and scows are commonly filled pastthe point at which water overflows, in order to increasethe sediment load. The gain in hopper or scow loadand the characteristics of the associated overflowdepend on the characteristics of the material beingdredged and the equipment being used. There is littledebate that the load can be increased by overflow if thematerial dredged is coarse grained or firm clay balls, ascommonly occurs with new work dredging. For fine-grained maintenance material, there is substantialdisagreement as to whether a load gain can be achievedby overflow. Environmental considerations ofoverflow may be related to aesthetics; or potentialeffects of water-column turbidity, deposition of solids,or sediment-associated contaminants.

Open water disposal sites can be either predominantlynon-dispersive or predominantly dispersive. Atpredominantly non-dispersive sites, most of thematerial is intended to remain on the bottom followingplacement and may be placed to form mounds. Atpredominantly dispersive sites, the material may bedispersed either during placement or eroded from thebottom over time and transported away from thedisposal site by currents and/or wave action. However,both predominantly dispersive and predominantly non-dispersive sites can be managed in a number of ways toachieve environmental objectives or reduce potentialoperational conflicts.

Description of Confined Disposal

Confined disposal is placement of dredged materialwithin diked nearshore or upland confined disposalfacilities (CDFs) via pipeline or other means. CDFsmay be constructed as upland sites, nearshore sites withone or more sides in water (sometimes called intertidalsites), or as an island containment area as shown inFigure 3.1-3. Confined Aquatic Disposal (CAD)facilities can also be constructed (see section 3.2.6).

The main objectives inherent in design and operation ofCDFs are to provide for adequate storage capacity formeeting dredging requirements; to maximize efficiencyin retaining solids; and to control the release of anycontaminants present in the dredged material. Basic

guidance for design, operation, and management ofCDFs is found in EM 1110-2-5027 (USACE 1987b).

Hydraulic dredging adds several volumes of water foreach volume of sediment removed, and this excesswater is normally discharged as effluent from the CDFduring the filling operation. The amount of wateradded depends on the design of the dredge, physicalcharacteristics of the sediment, and operational factorssuch as pumping distance. When the dredged materialis initially deposited in the CDF, it may occupy severaltimes its original volume. The settling process is afunction of time, but the sediment will eventuallyconsolidate to its in situ volume or less if desiccation(drying) occurs. Adequate volume must be providedduring the dredging operation to contain both theoriginal volume of sediment to be dredged and anywater added during dredging and placement.

Some CDFs are filled by mechanically rehandlingdredged material from barges filled by mechanicaldredges. Material placed in the CDF in this manner isat or near its in situ water content. If such sites areconstructed in water (nearshore CDFs), the effluentvolume may be limited to the water displaced by thedredged material, and the settling behavior of thematerial is not important.

In most cases, CDFs must be used over a period ofmany years, storing material dredged periodically overthe design life. The long-term storage capacity of theseCDFs is therefore a major factor in design andmanagement. Once water is drained from the CDFfollowing active disposal operations, natural dryingforces begin to dewater the dredged material addingadditional storage capacity. The gains in storagecapacity are therefore influenced by consolidation anddrying processes and the techniques used to manage thesite during and following active disposal operations.

Categories of Beneficial Reuse

Beneficial reuse includes a wide variety of options thatutilize the dredged material for some productivepurpose. Dredged material is a manageable, valuablesoil resource, with beneficial uses of such importancethat they should be incorporated into project plans andgoals at the project’s inception to the maximum extentpossible.

Figure 3.1-3 Types of Confined Disposal Facilities



Ten broad categories of beneficial uses have beenidentified nationwide, based on the functional use ofthe dredged material or site. They include thefollowing:

• Habitat restoration/enhancement (wetland, upland,island, and aquatic sites including use by fish,wildlife, and waterfowl and other birds);

• Beach nourishment;• Aquaculture;• Parks and recreation (commercial and non-

commercial);• Agriculture, forestry, and horticulture;• Strip mine reclamation and landfill cover for solid

waste management;• Shoreline stabilization and erosion control (fills,

artificial reefs, submerged berms, etc);• Construction and industrial use (including port

development, airports, urban, and residential);• Material transfer (for fill, dikes, levees, parking

lots, and roads); and• Multiple purposes (i.e., combinations of the

above).

Detailed guidelines for various beneficial useapplications are given in EM 1110-2-5026 (USACE1987a).

3.1.1.6 Feasible Reuse Options in the SanFrancisco Bay Area

In the Bay area, several of the general reuse optionslisted above have been or could feasibly be done withrelatively large quantities of dredged material (otheroptions may be feasible on a project-by-project basis,as well). In particular, dredged material could be usedbeneficially for new construction, levee maintenance,landfill cover, and marsh restoration. Additionally, atupland sites, facilities could be established to drydredged material for subsequent off-site use (suchfacilities are referred to as “rehandling facilities”), or toconfine material permanently (Confined DisposalFacilities, or CDFs). The most feasible options aredescribed in more detail in the following paragraphs.

Wetland Restoration

Agricultural practices over many years have causedlands along the Bay to subside so that current landelevations are many feet below sea level, far below theelevation necessary to support most marsh vegetation.The perimeter dikes of these sites could be breached tointroduce tidal flooding. In this case, natural siltationmay be expected to result in bottom elevations suitablefor wetland vegetation over a relatively long time,

depending on initial site elevations and the siltationcharacteristics of the site. Further, until enoughsediments accumulate to raise the bottom level toprovide the necessary periods of inundation andexposure for marsh plants, this could result in a tidallake at such lands.

Placing dredged materials on subsided, diked formerbaylands can accelerate the tidal marsh restorationprocess by raising ground level to the appropriateheight. Before placing material, the site needs to beprepared. The construction phase typically involvesconstructing perimeter levees and interior dikes orpeninsulas, as well as installing water control systemsand an area to off-load dredged material to the site.

In the San Francisco estuary, tidal marsh has beenestablished at three former upland disposal sites:Muzzi Marsh in Corte Madera, Marin County; FaberTract in Palo Alto, Santa Clara County; and Salt PondNo. 3 in Fremont, Alameda County. Dredged materialhas also been used successfully to enhance naturalresource values and management capability at managedwetlands in the Suisun Marsh. Currently, dredgedmaterial generated from improving the Oakland Harboris being used to restore a diked historic wetland at theSonoma Baylands site (see Appendix K.2).

Dredged materials could also be used create higherareas within tidal wetlands projects that would beinundated only by the highest tides (spring tides in thewinter and storm-related extreme high tides) and wouldpond water from infrequent tidal inundation andrainfall. To do so would involve filling subsided landat the upper end of tidal marshes above mean higherhigh water (MHHW) and including depressions forponding over the area. Additionally, dredged materialscould be used to construct berms to separate tidal andseasonal wetlands on a site (without raising theelevation of the seasonal wetlands) and to create areasfor ponding and drainage control on sites not associatedwith tidal wetland creation projects.

Potential dredged material reuse volumes (capacities)developed by BCDC for the LTMS indicate that up to103 mcy of dredged material could be accommodatedat wetland restoration sites over the 50-year planningperiod (BCDC 1995). Beginning in the year 2000, withthe commencement of a wetland restoration project atthe former Hamilton Army Airfield and adjacentproperties, approximately 2.0 mcy of dredged materialwould be used annually to restore wetland habitat in theBay area. Shortly thereafter, approximately 4.0 mcy ofdredged material would be used annually both as partof the Hamilton restoration project and other proposed



restoration projects using dredged material such asMontezuma Wetlands. By the time the placement ofdredged material is completed at these sites, it isanticipated that other sites using dredged material willbe implemented and receive approximately 1.0 mcy ofmaterial per year.

Levee Repair and Rehabilitation

Vast tracts of land in the San Francisco Bay area (Bay)and the Sacramento-San Joaquin Delta (Delta) arereclaimed land that is protected from inundation bylevees. Dredged materials have often been used toconstruct and repair Bay and Delta levees. Typically, adragline or clamshell has been used to excavatematerial from either side of the proposed levee, pilingthe material along the proposed alignment. Whensufficiently dry, the material has been graded to formthe levee. Because of their similar origins, dredgedmaterials often have similar properties as existing leveesoils, improving levee stability and structural strength,and thus can be used for levee repair and maintenance.

In 1994, a demonstration project was implementedusing 75,000 cy of material from the Suisun Bay andNew York Slough federal channels to restore levees atJersey Island (Contra Costa County) in theSacramento-San Joaquin Delta. In light of existingconstraints concerning the use of dredged material forDelta levee maintenance projects, including waterquality issues and restricted barge access, it is estimatedthat approximately 26 mcy of dredged material couldbe used in the Delta over the next 50 years in thefollowing manner: approximately 250,000 cy ofmaterial could be used per year during the initial years(until the year 2000); and up to 1.0 mcy of materialcould be used annually in subsequent years. (It shouldbe noted that this estimate is significantly lower thanthe Department of Water Resources’ projection, whichindicates that a total of 200 mcy of dredged materialcould be accommodated in the Delta for leveemaintenance.)

Landfill Reuse

The clays and fine silts that comprise most dredgedmaterials from the Bay are often suitable at landfillsites (once dried) for use as cover, on-site construction,capping, or lining material. Landfills possess severalcharacteristics which are ideal for the reuse of dredgedmaterial. Daily operations and closure proceduresrequire substantial amounts of cover and cappingmaterial, and therefore there is the potential forutilizing a significant portion of material dredgedannually from the San Francisco Bay. Because

landfills are designed to contain pollutants and managerunoff, they have the added benefit of being able toaccept some contaminated materials infeasible forunconfined aquatic disposal. And while liability is apotential concern for disposal of material at any site,landfills provide greater protection against liability,since thorough waste testing and gate controls arerequired and enforced. Additionally, in most casesdredged material will replace the use of clean soilexcavated and transported from elsewhere, or othernon-waste sources. Finally, because landfills aretypically highly disturbed sites with limited naturalresource values, the use of dredged materials atlandfills is likely to impact few existing naturalresources.

The Redwood Landfill in Marin County and theTri-Cities Landfill in Alameda County are two facilitiesthat have incorporated the use of dredged material intheir closure plans. Tri-Cities Landfill is planning touse 180,000 cy of dredged material from the SanLeandro Marina as capping material for eventualclosure of the landfill. The material is currentlystockpiled at Roberts Landing adjacent to the Marina.In addition, Redwood Landfill has acceptedapproximately 500,000 cy of dredged material from thePetaluma River, Gallinas Creek, and PortSonoma-Marin. The material has been used as dailycover, for on-site construction, and as liner material.Redwood Landfill has also proposed using dredgedmaterial to construct a 2-foot liner for a sludgeprocessing area and for levee construction and repair.

Rehandling and Confined Disposal Facilities

Rehandling facilities are mid-shipment points fordredged material that cannot be hauled directly to thesite where it will be ultimately used, such as landfills.They are also locations where dredged materials can bedried or treated to remove or reduce salinity orcontaminants. Typically, rehandling facilities acceptrelatively small volumes of material originating fromspecific dredging projects. In the Bay area, rehandlingfacilities are located at Port Sonoma-Marin, near themouth of the Petaluma River; in the City of Petaluma,Sonoma County; and in the City of San Leandro,Alameda County.

In some cases, CDFs are needed for contaminateddredged material that cannot be reused and thusrequires permanent confinement. Such facilities can beengineered similar to a rehandling facility. However,since multi-user CDFs for contaminated dredgedmaterial would have to be designed for the worst-casematerial that could be permitted for disposal in them,



the need for cell liners, leachate collection systems, orother contaminant control measures would also need tobe considered. The potential dredged material reusevolumes developed by BCDC for the LTMS indicatethat up to 298 mcy of dredged material could beprocessed at rehandling facilities in the Bay area overthe 50-year planning period (BCDC 1995). Over thenext few years, approximately 250,000 cy of dredgedmaterial is expected to be processed annually atexisting rehandling facilities in the Bay area.Subsequently, existing capacity will increase over timeand the volume of material processed will graduallyincrease: in the year 2000, approximately 500,000 cyof material will be processed annually; in 2001,approximately 1.25 mcy of material will be processedannually; and in 2005, approximately 1.75 mcy ofmaterial will be processed annually.

Construction Purposes

Naturally occurring sand deposits in the Bay have beenan important source of construction material for manyyears, unlike Bay muds which are generally unsuitablefor use as engineered fill because of their lack ofstructural strength. Rehandling processes do producematerial from bay muds that are useful in constructionactivities. A cost-effective approach to rehandling baymuds, however, does not yet exist. Typically, newconstruction associated with water-related industriesand ports involves dredging and Bay fill. In theseinstances, sands dredged to create new berths or todeepen navigation channels can be used to provide anengineered base for marine terminals or constructionyards. The volume of material available forconstruction will be primarily dictated by capacity atrehandling facilities (as noted above) and whether thedried material meets the specific physical and chemicalrequirements of the construction project.

3.1.2 Dredging Volumes — LTMS PlanningEstimates

In 1990, the COE evaluated past dredging trends andwhat was known about major new dredging projects inthe LTMS Phase I Report (LTMS 1990b). Based onthat review, it was assumed that an average of 8 mcy ofsediments would be dredged each year. During the 50-year LTMS planning period (1995 to 2045), this wouldmean that 400 mcy of dredged material would begenerated and need to be disposed. These figures — 8mcy per year and an overall total of 400 mcy — werethe initial basis of the LTMS planning effort.

Since the time of the original COE estimate, the overalldredging situation has changed significantly. In

particular, several major military facilities — some ofwhich have been associated with some of the largestdredging projects in the region — have been slated forclosure. Interested parties to the LTMS planning effortrequested that the LTMS agencies revisit the SFEPdredging estimates, taking into account an assumedreduced need for future dredging once the military baseclosures are complete. The LTMS re-evaluation oflong term dredging needs (Analysis of San FranciscoRegional Dredging Quantity Estimates; DredgingProject Profiles; and Placement Site Profiles [LTMS1995a]) is presented in Appendix E. Appendix E alsoincludes descriptions of each of the major dredgingprojects in the region. The following discussionsummarizes the approach used and the resulting revisedLTMS planning estimate of dredging volumes over thenext 50 years. See Appendix E for details of thisanalysis and the references used.

3.1.2.1 Method for Re-Evaluating DredgingVolumes

To evaluate long-term dredging needs, historicdredging quantities (since 1955) were first determined,to the extent possible, based on the available dredgingrecords of the COE, the Sediment Budget Study for SanFrancisco Bay (LTMS 1992e), and the August 1993Dredging and Disposal Road Map (BCDC andUSACE 1993). The records were then screened toaccount for technical, surveying, reporting, andregulatory differences over the years. This evaluationrevealed that there has been a long-term averagedredging quantity of approximately 6.84 mcy per yearin the Bay area; maintenance dredging accounted forapproximately 6.45 to 6.69 mcy per year of this total.

The historic dredging figures were then adjusted toaccount for projects associated with military bases thathave closed or are slated for closure. These facilitiesinclude Mare Island Naval Ship Yard; Treasure IslandNaval Station; Hunters Point Naval Shipyard; MoffettField Naval Air Station; and Alameda Naval AirStation. Since the potential for a long-term reduction indredging associated with these facilities is highlydependent on future uses of the facilities, threescenarios were developed. For the Low-RangeEstimate of total long-term dredging, the entire averagedredging volume associated with the facilities wassubtracted from the historic totals. The Mid-RangeEstimate of total long-term dredging subtracted 50percent of this volume from the historic totals,reflecting continued but shallower-draft navigation useof the associated channels. For the High-RangeEstimate, it was assumed that the navigation channelsassociated with these facilities would continue to be



dredged as they have in the past; no reduction in overalldredging was therefore made for the High-RangeEstimate. An exception was the Mare Island NavalShipyard. It is likely that closure of this facility willnot eliminate the need for some level of maintenancedredging, no matter what land use the facility supportsin the future. Therefore, the Low-Range Estimateassumes only a 50 percent reduction in dredging forthis site, while the Mid-Range Estimate assumes a 25percent reduction. As for the other military facilities,the High-Range Estimate assumes the entire historicvolume would continue to be dredged.

Finally, an estimate of potential new work dredgingprojects was developed, to add to the adjusted historicvolumes. Planning-level estimates of dredging volumesfor authorized or proposed new work projects were firstsummed. These new work projects include: the Port ofOakland Phase II (-42-foot) Deepening Project; thePhase III John F. Baldwin Ship Channel Project; thePort of Richmond -38-Foot Deepening Project; the SanFrancisco Harbor Deepening Project; and the Port ofStockton (Avalon to New York Slough) Project.

Together, these projects would generate an estimated24.2 mcy of dredged material over the next 15 to 20years. Three scenarios were again developed for thesenew work projects to predict Low-, Mid-, and High-

Range Estimates of long-term new work dredgingvolumes. For the Low-Range Estimate, it was assumedthat only 50 percent of the volume associated with theproposed new work projects would actually be dredged.The Mid-Range Estimate assumed that the entire 24.2mcy would be dredged. The High-Range Estimateassumed that additional, currently unknown new workprojects would be proposed and constructed over the50-year LTMS planning period, generating anadditional volume of dredged material equivalent to thecurrently proposed projects, for a total of 48.4 mcy ofdredged material.

3.1.2.2 Revised Dredging Volume Estimate for the50-Year LTMS Planning Period

The results of the LTMS re-evaluation of long-termdredging volumes are presented in Table 3.1-1. Thistable shows that the SFEP estimate of 400 mcy ofdredged material over the next 50 years indeed appearsto be too high. Instead of an average of 8 mcy ofdredging and disposal per year, the average dredgingneed is between a Low-Range of 3.47 mcy to a High-Range of 5.93 mcy. This equates to a 50-year total ofbetween 173.5 to 296.5 mcy of dredged material beinggenerated by all currently foreseeable maintenance andnew work projects.

The subject of dredged material disposal inaquatic systems is not a simple exercise in civilengineering. It involves detailed consideration ofthe physics and chemistry of sediments; thephysics, chemistry, and toxicology ofcontaminants that may be associated withsediments; and the interaction of sediments,dredged material, contaminants, and estuarinehydrology with existing populations of shellfish,fish, and wildlife. The complexity of this subject,and the sparse information available for drawingspecific conclusions, makes it necessary thatexisting estuarine resources be projected bymaking reasonable decisions based upon availabledata, while new knowledge … is accumulated(SFEP 1990).



3.2 BAY AREA SEDIMENT ANDDREDGED MATERIALCHARACTERISTICS

Materials beneath San Francisco Bay that are typicallyencountered during dredging projects consist of thick,unconsolidated sediments of both marine and terrestrialorigin, deposited from the Pleistocene to the presentday. These sediments may become contaminated bypollutants from a variety of sources. In some cases,sediment contamination may be serious enough that itposes a direct risk to the environment or to humanhealth, such that the sediment must be removed fromthe Bay regardless of whether any person or port hasindependent plans to dredge it for navigation purposes.The state of California and the U.S. EPA haveestablished remedial action programs for addressing

such highly contaminated sediments. Discussion of theneed for remediation of highly contaminated sedimentsis beyond the scope of this document. Instead, thisEIS/EIR addresses the management of “dredgedmaterial.” For the purposes of this document, dredgedmaterial is sediment that is removed for purposes otherthan remediation: for example, the removal ofsediment for the construction or maintenance ofcommercial or recreational navigation channels, shipberths, marinas, or other waterways. Thus all “dredgedmaterial” consists of sediments, but not all sediments inthe Bay/Delta estuary are “dredged material.”

Dredged material is managed under different regulatoryauthorities depending on the use to which it is put, orthe environment in which it is placed. For example,dredged material placed in waters of the United States

Table 3.1-1. Revised Dredging Volume Estimate for San Francisco Bay (1995-2045)

Quantity Type

Low RangeEstimate

(cubicyards/year)

Mid RangeEstimate

(cubicyards/year)

High RangeEstimate

(cubic yards/year)

Historic maintenance and newwork (1)

6,840,213 6,840,213 6,840,213

Removal of historic new work(1)

-393,062(-100 percent ofall new work)

-284,116(-50 percent ofselected new

work)

-155,170(-0 percent ofselected new

work) Estimated range of historic

maintenance dredging 6,447,151 6,556,097 6,685,043

Removal of dedicated disposalsites and base closures (2)

-3,223,662 -2,478,111 -1,720,195

Projected maintenancedredging

3,223,489 4,077,986 4,964,848

Addition of projected newwork dredging (3)

242,000(+50 percent)

484,000(+100 percent)

968,000(+200 percent)

Total 3,465,489 4,561,986 5,932,848 Rounded total 3,470,000 4,560,000 5,930,000

50-Year Projected TotalDredge Material Volume

173,500,000 228,000,000 296,500,000

Notes: (1) For projects with separable new work quantities, the entire quantity was deletedin all estimate ranges. For records without separable quantities, 100 percent, 50percent, and 0 percent of the entire annual reported volume was removed for thelow, mid, and high range estimates, respectively (see Table 3 in Appendix E).

(2) For projects with dedicated disposal sites, and military base closures, 100percent, 50 percent, and 0 percent of the quantities were removed with theexception of the San Francisco Bar, which was entirely removed (ocean disposalonly), and the Mare Island Straits, which had 50 percent, 25 percent, and 0percent removed since it is known that this dredging will not cease entirely withthe closure of Mare Island Naval Shipyard (see Table 3 in Appendix E).

(3) See Table 4 in Appendix E, and subsequent paragraphs.



or in the ocean is regulated under the federal CWA orthe MPRSA, respectively. Dredged material placed asfill in an upland location is typically a solid wasteregulated under a different set of state and federalstatutes (see section 4.8.1.3). Regardless of whichagency or law regulates dredged material in a particularinstance, management concerns vary with theplacement environment (e.g., dispersive versus non-dispersive aquatic disposal sites, aquatic versus uplanddisposal sites, construction fill versus habitat creationuses, etc.).

The following sections provide a background ondredged material characteristics that are key todetermining appropriate management techniques foraquatic or upland disposal or beneficial reuse in the SanFrancisco Bay area.

Important physical characteristics are addressed first(section 3.2.1), followed by a discussion of themovement and fate of sediments within the Estuary(section 3.2.2). General background on contaminantsin dredged material is then presented (sections 3.2.3and 3.2.4). More specific information is provided oncontamination and toxicity, and its evaluation inEstuary sediments (section 3.2.5). Managementoptions for contaminated dredged material (section

3.2.6) concludes this discussion.

3.2.1 Physical Characteristics

The trough-like depression that underlies San FranciscoBay is formed by Franciscan sandstone and shalebedrock (see section 4.2.2). This trough has beennearly filled with sediments, some of which has comefrom erosion of surrounding hills and some of whichconsists of later marine deposits. For example, themarine clay-silt deposit termed “old Bay mud” is

Table 3.2-1. Concentrations of Heavy Metals and Organic Compounds in Old Bay Mudand Merritt Sand Deposits

Sediment Chemistry Merritt Formation Sediment (a) Old Bay Mud Sediment (b)

Silver (mg/kg) 0.023-1.08 0.11 Arsenic (mg/kg) 2.93-12.60 3.28

Cadmium (mg/kg) 0.02-0.18 0.56 Chromium (mg/kg) 164-823 142

Copper (mg/kg) 8.9-43.8 27.4 Mercury (mg/kg) 0.0003-0.088 0.044 Nickel (mg/kg) 41.7-117.1 62.7 Lead (mg/kg) 3.5-10.4 10.6

Selenium (mg/kg) 0.07-0.42 0.17 Zinc (mg/kg) 33.7-100.5 68.3

Total PAH (µg/kg) 0.5-217 57 Tributyltin (µg/kg) 0.6-3.2 0.48 U

PCB (µg/kg) 2.3-4.0 20 U Total DDT (µg/kg) 0.04-6.22 0.22 U

Notes: All values expressed in dry weight. a. Ranges represent 13 stations with Merritt sand from the Port of Oakland Deepening Project (Final

Supplemental EIR/EIS Oakland Harbor Deep-Draft Navigation Improvements Appendix A throughE and G through L, June 1994).

b. Old Bay Mud composite is comprised of OBM sediment from four stations in the Richmond Harborturning basin (Ecological Evaluation of Proposed Dredged Material from Richmond HarborDeepening Project and the Intensive Study of the Turning Basin, June 1995, PNL-10627).

U = Undetected at or above detection limit.



present throughout most of the Bay, several feetbeneath the soft, more recently deposited muds. Anancient fine-grained sand deposit known as “MerrittSand” occurs in the vicinity of Oakland and Alameda,in places relatively close to the sediment surface. Also,natural peat deposits can be found underlying morerecent Bay sediments in some areas of the North Bayand Delta. The thickness of the various historicsediment formations varies throughout the Bay/Deltaestuary, but they can be several hundred feet thickoverall. Figure 3.2-1 shows the general stratigraphy ofsediment deposits within San Francisco Bay.

Whether of terrestrial or marine origin, the olderdeposits that pre-date European settlement in Californiagenerally are very hard-packed, low in moisturecontent, low in organic carbon (except for peatdeposits), and have low concentrations of chemicalssuch as heavy metals and organic compounds. Thechemical levels that are measurable in these historicdeposits represent natural “background” levels for thesediment type. Table 3.2-1 shows typical levels ofheavy metals and organic compounds measured in oldBay mud and Merritt Sand deposits. These deposits arenot typically

Figure 3.2-1 Stratigraphy of Sediment Deposits in SanFrancisco Bay

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dredged during maintenance dredging, but are oftenencountered during new work dredging (dredging ofnew navigation channels, or channel deepeningprojects).

The upper several feet of the sediment profile in mostlocations consists of more recently deposited marineand riverine sediments. The SFEP (1990) presentedthe following description of the classification anddistribution of surficial (geologically recent) sedimentdeposits in the Estuary:

Sediments in the Estuary fall into three categories:sandy bottoms in the channels; shell debris over a wideexpanse of the South Bay (derived from remnants ofoyster beds (Wright and Phillips 1988); and softdeposits (known as “Bay Mud”) underlying the vastexpanses of shallow water. . . . Regions of the Estuarywhere currents are strong, including the deep channelsof the Bay and the central channels of the major riversin the Delta, generally have coarser sediments (i.e., finesand, sand, or gravel). Areas where current velocitiesare lower, such as the shallow fringes of each sub-embayment of San Francisco Bay . . . are covered withBay Mud (USACE 1976a). Bay Mud is comprised ofsilt and clay particles deposited as a result offlocculation, or “salting out,” a process in whichparticulate matter in fresh water aggregates when mixedwith more saline waters. The settling velocity of theaggregates is much greater than that of the original clayor silt particles, increasing particle deposition.

The surface Bay muds (“young Bay mud”) and recentsand deposits tend to be much less densely packed,high in moisture content, and higher in organic carbonthan the underlying ancient sediment formations.Figure 3.2-2 shows the generalized distribution of thesesediment types in the San Francisco Bay/Delta estuary.

Physical differences between sediment types areimportant considerations for appropriate dredgedmaterial management. First, the deposit type andlocation in large part determine whether there is alikelihood that the sediments may have been exposedfor a given sediment volume, and therefore greaterconcentrations of contaminants can potentially adsorbto the surface of silt particles. Silt particles are alsoreadily resuspended and redistributed by even fairlylow energy currents, and ultimately settle in quieterenvironments where pollutants and organic matter mayalso tend to accumulate. Clay (grain size less

than 0.004 millimeters, or phi size greater than 8) hasan even higher surface area for contaminant adsorption.Clay particles also tend to be charged, facilitatingbonding of additional contaminants to their surfaces.However, their charged nature also gives them apropensity to stick together in clumps. This means thatduring aquatic disposal, clays tend to produce lesspronounced water column plumes; this also makes itmore difficult for currents to resuspend and redistributeclay from the bottom after disposal has ceased,particularly if the clay deposit was mechanically(clamshell) dredged. Third, factors such as theconcentration of organic carbon and acid volatilesulfides (AVS) affect the degree to which contaminantsmay be associated with sediments. Organic carbon canreadily absorb a variety of contaminants, includingmany that would not otherwise have a high affinity toattach to the surface of sediment particles. Surfacesediments, particularly the finer silts and clays, canaccumulate organic carbon from a variety of sourcesincluding the water column and organisms living withinthe sediments themselves. Whatever the source, thecarbon content is generally higher in finer-grainedsediments found in depositional areas (includingportions of some navigation channels), where bothorganics and pollutants tend to accumulate. Theconcentration of AVS in sediments is defined as theconcentration of solid phase sulfide compoundsassociated with metal sulfides (primarily iron andmanganese monosulfides). In marine and freshwatersediments, sulfides of divalent metals form veryinsoluble compounds. It has been hypothesized that thequantity of AVS represents a “reactive pool” of sulfidesthat are able to bind and reduce the bioavailability andtoxicity of the metals in sediments (DiToro et al. 1990).

Finally, the grain size class (sands, silts, clays), and thedegree to which the sediment type is hard-packed,affects the degree to which the dredged material willtend to disperse or stay clumped during and afterdisposal. In addition, different sediment types oftencall for different dredging methods. For example,hydraulic suction dredging can be used with soft,unconsolidated young Bay muds, but mechanicalmethods such as clamshell dredging, at times evenpreceded by breaking up the deposit with specialequipment before dredging, may be required in old Baymud or other hard-packed formations. The dredgingmethod also can affect dispersion or clumping duringand after disposal at an open water site, as well as thearea needed for upland disposal (see section 3.1).



Figure

3.2-2 General Distribution of SurfaceSediment Types in the San Francisco Bay/DeltaEstuary

322.jpg



The majority of dredging in the Estuary is maintenancedredging of relatively soft, unconsolidated silts andclays that accumulate in existing navigation channels.Except in certain high energy areas, this material istypically comprised of 80 to 90 percent silt and claysize particles.

3.2.2 Movement and Fate of Sediments in theEstuary System

The primary source of new sediment into the Estuarysystem is the Sacramento River, which flows throughCarquinez Strait into the northeastern end of San PabloBay. Other important, but much smaller sources arealso in the north Bay, including the Napa, Sonoma, andPetaluma rivers. A variety of smaller streams and otherdrainages (including storm drains and flood controlchannels) can be locally important for adding newsediment to the system. Overall, these sources providean estimated 8 mcy per year of new sediment to theBay/Delta system (LTMS 1992e; USACE 1965).However, existing deposits of typical fine-grainedsurface sediments in the extensive shallow areas of theEstuary are subject to hydraulic movement(resuspension) by riverine, tidal, and wind-drivencurrents. Therefore, resuspended existing sedimentsare estimated to be 100 mcy (Krone 1974) to 286 mcy(SFEP 1992b) annually, or perhaps 10 to 30 timesgreater than from all the “new” sediment sourcescombined. Therefore, resuspended sediments accountfor the vast majority of suspended particulate matterand turbidity throughout the Estuary. Figure 3.2-3 is aconceptual illustration of these overall sedimentmovements.

SFEP (1990) included the following basic descriptionof the dynamic environment experienced by surfacesediments in the Estuary:

With the exception of portions of Central Baynearest the Golden Gate, the San Francisco Estuaryis very shallow, with wide intertidal and subtidalregions cut by narrow, mid-Bay channels (Nicholsand Thompson 1985) . . . . Greater than 40 percentof the Estuary is less than 2 m deep, and over 70percent is less than 5 m deep (Nichols et al. 1986;

Wright and Phillips 1988). The sediments of SanFrancisco Bay change on a time scale of days tomonths. The dynamic nature of the sedimentcompartment of the Estuary was demonstrated bythe sediment survey of SAIC (1987). Most of thesite studied by these investigators showed evidenceof recent sediment erosion, redistribution, ordeposition. On a short-term basis, Nichols andThompson (1985) noted that sand waves standingfrom 20 cm to 8 m in height move with the ebb andflow of tide, resulting in a continual sedimentturnover to a depth of about 40 cm every few days.On a time scale of weeks, the intertidal mud-flatenvironment of the Estuary may show rapidchanges in elevation (Luoma and Bryan 1978;Nichols and Thompson 1985), as well as changesin sediment grain size.

More recently, in a study prepared for the LTMS(LTMS 1992e) compared the net differences betweenhigh-resolution bathymetric surveys of the Estuarytaken 35 years apart. This comparison identified large-scale areas of longer-term net deposition and erosionthroughout the Estuary. Figures 3.2-4 through 3.2-18show the results of this comparison. As is apparentfrom these plates, deposition and erosion patternsthroughout the Estuary are extremely complex andheterogeneous. The four existing disposal sites withinthe Estuary are all considered to be in erosionallocations. The Alcatraz disposal site, in particular, ismanaged to maximize the erosion of dredged materialdisposed there in order to avoid continued mounding,which can pose a hazard to deep-draft vessels that mustpass nearby. The other existing disposal sites are morefully erosional at the volumes of material disposed atthem, and they have not experienced the kind of seriousmounding that has occurred at the Alcatraz site.

Although the dynamic nature of the Estuary is generallyknown, and more information is being collectedcontinuously, there is limited ability today to accuratelypredict the specific movement and ultimate fate ofsediment particles from any particular source (such asdredged material disposal sites) in the Bay.Nevertheless, we have some basic information ongeneral patterns of sediment movement. Turbidity inthe central Bay is naturally less than in the south Bay orSan Pablo Bay. For example, turbidity in the centralBay is naturally less than in the south Bay or San PabloBay. Similarly, sediment transport in the Estuaryexhibits definite seasonal patterns. During the winterwhen freshwater flow and corresponding

The sediments of the Bay/Delta are dynamic,with erosion or deposition of material constantlyoccurring in response to complex patterns ofcurrents and waves created by river flows, tides,and winds. The aquatic disposal of dredgedsediment thus adds suspended material to aconstantly changing environment, anddetermining the ultimate fate of disposeddredged material is a challenging task (SFEP1990).



Figure 3.2-3 Conceptual Illustration of SedimentMovement in the San Francisco Bay System

323.jpg



Figure 3.2-4 Index Map for Figures 3.2-5 through 3.2-18

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Figure 3.2-5 Net Bathymetric Changes in SanFrancisco Bay from 1955 to 1990 — South Bay,Sections A1 & A2 (Plate 1)

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Figure 3.2-6 Net Bathymetric Changes in SanFrancisco Bay from 1955 to 1990 — South Bay,Section B (Plate 2)

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Figure 3.2-7 Net Bathymetric Changes in SanFrancisco Bay from 1955 to 1990 — South Bay,Section C (Plate 3)

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Figure 3.2-8 Net Bathymetric Changes in SanFrancisco Bay from 1955 to 1990 — South Bay,Sections D & F (Plate 4)

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Figure 3.2-9 Net Bathymetric Changes in SanFrancisco Bay from 1955 to 1990 — South Bay,Section E (Plate 5)

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Figure 3.2-10 Net Bathymetric Changes in SanFrancisco Bay from 1955 to 1990 — North Bay,Section A (Plate 6)

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Figure 3.2-11 Net Bathymetric Changes in SanFrancisco Bay from 1955 to 1990 — North Bay,Section B (Plate 7)

3211.jpg





Figure 3.2-12 Net Bathymetric Changes in SanFrancisco Bay from 1955 to 1990 — North Bay,Section C (Plate 8)

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Figure 3.2-13 Net Bathymetric Changes in SanFrancisco Bay from 1955 to 1990 — North Bay,Section D (Plate 9)

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Figure 3.2-14 Net Bathymetric Changes in SanFrancisco Bay from 1955 to 1990 — San Pablo Bay,Section A (Plate 10)

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Figure 3.2-15 Net Bathymetric Changes in SanFrancisco Bay from 1955 to 1990 — San Pablo Bay,Section B (Plate 11)

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Figure 3.2-16 Net Bathymetric Changes in SanFrancisco Bay from 1955 to 1990 — San Pablo Bay,Section C (Plate 12)

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Figure 3.2-17 Net Bathymetric Changes in SanFrancisco Bay from 1955 to 1990 — Suisun Bay,Section A (Plate 13)

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Figure 3.2-18 Net Bathymetric Changes in SanFrancisco Bay from 1955 to 1990 — Suisun Bay,Sections B & C (Plate 14)

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“new” sediment loads are high and winds are generallyweak, sediments tends to be deposited on the mudflatsof northern San Pablo Bay and other quiescentlocations. In the summer when river flows and “new”sediment loads decrease dramatically, strong, frequentwesterly winds over the shallow mudflats resuspend thesediments and, in conjunction with tidal currents,transport them throughout the system. In addition,although most new sediment input occurs in San PabloBay, and although there is less overall water circulationin south San Francisco Bay, the information availabletoday supports the presumption that sediments from anyof the major sub-basins of the Estuary can beresuspended, and soon spread widely throughout theEstuary. Some sediments leave the Estuary system bybeing transported out the Golden Gate; however, thequantity leaving the system during a typical year isthought to be relatively small (on average, less than theinput of new sediment from rivers and other sources)compared to the total quantity cycling within theEstuary (see Figure 3.2-3).

Preliminary mathematical modeling of dredged materialtransport and initial deposition following disposal atseveral locations throughout the Estuary was conductedfor the LTMS by the COE Waterways ExperimentStation (WES) (Letter et al. 1994). The results of thismodeling remain preliminary, and substantial modeldevelopment is still needed before any such results canbe used with confidence. WES modeling indicates thatdredged material initially discharged at existing in-Baydisposal sites may quickly find its way into virtuallyevery major sub-basin of the Estuary. For example,figures 3.2-19 through 3.2-21 show modeled initialdeposition patterns following disposal at the Alcatraz,San Pablo Bay, and Carquinez Strait disposal sites,respectively. These modeling results are generallyconsistent with the LTMS (1992e) figures, that arebased on empirical information, in terms of theheterogeneity of deposition and erosion patternsthroughout the Estuary. However, the WES modeloutput shows only predicted initial depositionlocations; subsequent resuspension and furthertransport of the dredged material particles would beexpected from any initial deposition sites that exhibiterosional characteristics at times.

Because the majority of fine sediment particles arelikely to settle and resuspend a number of times in theEstuary, at least a small percentage of the sedimentaccumulating in navigation channels is likely to includepreviously dredged material that was discharged at anerosional in-Bay site, has resettled, and now has to bere-dredged. For example, tracer studies in the mid-1970s confirmed that as much as 10 percent of the

sediments accumulating in the Mare Island Strait werein fact dredged material recirculated from theCarquinez disposal site (USACE 1976b). System-wide, however, the overall amount of previouslydredged material that makes its way back intonavigation channels to be re-dredged in this way isalmost certainly much smaller.1 The continualresuspension of sediments within the Estuary systemalso means it can be expected that sedimentsaccumulating in navigation channels may have beenexposed to pollutant sources in several locations, farremoved from the dredging site. This helps to explainwhy chemical testing of sediments from some regularlydredged channels can show a fairly high degree ofvariability from year to year, even when there havebeen no nearby discharges or spills. It also helps toexplain why almost all maintenance dredging projectsfrom throughout the Bay show at least some degree ofelevated (above ambient or “background”)concentrations of trace contaminants (see section3.2.3.3). By the same token, however, particlescarrying pollutants also may get diluted with particlesfrom other areas that settle in the same location, thathave lower concentrations of associated contaminants.Thus the sediment from many dredging projects, evenwhen trace pollutants are present, are not contaminatedto a degree that causes toxicity or that otherwiserepresents any significant environmental risk. Thefollowing section presents a detailed discussion ofcontamination in dredged material.

3.2.3 Contaminants in Dredged Material

The vast majority of sediments in the Estuary are notpolluted to a degree that poses any threat to humanhealth or the environment. However, as noted above,the dynamic nature of the Estuary means that sedimentparticles may settle in one location, later to beresuspended and transported some distance, and thensettle again. Because of this, even if sediment particlesare not initially carrying pollutants when entering theBay, they may have many chances to pick up pollutantsfrom the water or air before they are removed fromnatural circulation (either by settling into adepositional area and becoming buried, or being carriedout the Golden Gate). This section briefly discusses thenatural compounds and man-made (anthropogenic)pollutants that may become associated with sediments;when “contamination” is considered to be a problem insediments; major



Figure 3.2-19 Modeled Initial Sediment DepositionPatterns from Disposal at the Alcatraz Island Site

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Figure 3.2-20 Modeled Initial Sediment DepositionPatterns from Disposal at the San Pablo Bay Site

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Figure 3.2-21 Modeled Initial Sediment DepositionPatterns from Disposal at the Carquinez Site

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sources of sediment contamination; and locations ofcontaminated sediments in the Bay/Delta estuary.

3.2.3.1 Anthropogenic vs. Non-AnthropogenicChemicals — What is “Contamination”?

Nationwide, the most frequently reported contaminantsin sediments include heavy metals (e.g., cadmium,chromium, copper, lead, nickel, mercury, selenium,silver, and zinc), metalloids (e.g., arsenic),polychlorinated biphenyls (PCBs), pesticides (e.g.,DDT compounds), and polynuclear aromatichydrocarbons (PAHs) (USEPA 1994a; SFEP 1992b).A few of these can have natural origins. Heavy metalsat varying concentrations are natural constituents of thecrustal rock formations in different areas. As theseformations erode and eventually contribute to thesediments, the crustal concentrations of these metals arereflected in the sediment chemistry. Even some PAHscan be found in otherwise “unpolluted” sediments. Forexample, some PAHs (such as pyrene and perylene) arecombustion products that can make their way intosediments — from runoff (Hoffman et al. 1984) or viaatmospheric deposition — as a result of natural forestfires as well as human causes. Other organiccompounds (such as phenols) can be formed bydecomposition of organic matter in marshes andelsewhere (Sims and Overcash 1983). Informationabout the “background” concentrations of chemicals inEstuary sediments is therefore helpful whendetermining whether the measured concentrations of achemical are high enough to indicate that the sedimentmay be “contaminated” by an anthropogenic source.Further discussion of chemical concentrations typicallyencountered in the Estuary’s embayments is presentedin section 3.2.3.3 and in Chapter 4.

Typically, the pollutant types noted above are the mosthighly concentrated types of anthropogeniccontaminants in sediments because they are poorlysoluble in water (hydrophobic) and have a high affinity(adsorption potential) for sediment particle surfaces orthe organic matter associated with them.

These compounds are therefore readily removed fromthe water column by suspended particles, and arepreferentially carried into the sediments as the particlessettle out. The settling-out of suspended particulates isenhanced in estuaries, including the Bay/Delta Estuary,by the flocculation (aggregation of finer suspendedparticles into larger, more quickly settling groups) thatnaturally occurs where fresh and more saline watersmix. This is why sediments in general, and particularlysediments in estuaries such as the Bay/Delta, are often

thought of as “sinks” for contaminants that get into thewater column from point or non-point sources.

But from whatever source, a sediment is considered tobe “contaminated” when it contains deleteriouschemical substances at concentrations that pose aknown or potential threat of adverse impact to aquaticlife, wildlife, or human health (USEPA 1994a). Thedegree of the threat by the contaminants in a particularsediment can change depending on how the sediment ishandled (e.g., buried contamination left in place maynot pose a threat of ecological impact, but if thatmaterial is disturbed, such as by dredging and disposal,the contaminants may become available again and havethe potential to cause adverse effects). As discussed inthe sections that follow, determining whethercontaminants in dredged material may pose a threat ofadverse impacts is a function of determining thefollowing: (1) the potential for the contaminants tocause adverse effects at the placement site; and (2) thepracticability of control measures that may be effectivein reducing or eliminating the potential adverse effectsat the placement site.

3.2.3.2 Major Sources of Sediment Contamination

In general, the surficial sediments in San Francisco Bayhave been deposited since industrialization began inCalifornia, and therefore may have been exposed toanthropogenic sources of pollutants. These “industrialage” sediments can be encountered in both new workand maintenance dredging. (However, the more highlycontaminated sediments are usually encountered bynew work projects in industrialized areas of the Bay;such dredging commonly encounters sediments thatbecame contaminated in decades past, before today’sstricter regulations on discharges were in effect.)Recent sand deposits — either riverine sand in portionsof San Pablo and Suisun bays and the lowerSacramento River, or sand bars maintained by strongcurrents in central San Francisco Bay and the SanFrancisco Bar — also may be exposed toanthropogenic sources of pollutants, but typically donot accumulate significant concentrations of them, forthe reasons noted above.

Existing permits authorize hundreds of millions ofgallons of treated industrial and municipal effluents tobe discharged into the Estuary each day. While theseeffluents are carefully regulated to ensure that they arenot directly toxic to Estuary organisms, trace levels ofvarious contaminants are associated with thesedischarges, and some of these contaminants can end upconcentrating in the Estuary’s sediments. For example,Figure 3.2-22 shows the locations of the largest



municipal discharges (Publicly-Owned TreatmentWorks, or POTWs), and their mean discharge volumesas of 1995. Similarly, a variety of industries dischargepollutants associated with sediment contamination.Table 3.2-2 lists over 40 of these classes of industries,along with the typically associated contaminants. Themajority of these types of industries have historicallybeen in operation around the Estuary. Some of themajor industrial facilities still in operation as of 1995are shown in Figure 3.2-23.

Even though industries and municipalities dischargemajor volumes of effluent each year, they are not theprimary sources of pollutants that contribute tocontamination of the Estuary’s sediments today. Figure3.2-24, from SFRWQCB (1994), shows the combinedannual loadings to the Estuary of several heavy metals(arsenic, cadmium, chromium, copper, lead, and zinc)from six major sources. The sources shown aremunicipal and industrial effluents, riverine input, urbanrunoff, non-urban runoff, atmospheric deposition, anddredged material. Other sources may be important on alocal level (e.g., groundwater). It can be seen from thisfigure that non-point pollution (especially nonurbanrunoff) is the source for the vast majority of thesepollutants. This pattern generally holds true for othercategories of chemicals, as well. It is because of thesepatterns that sediments near the urbanized shorelines,and especially in enclosed nearshore waters in thevicinity of storm drains and other input locations fornonpoint source pollutants, often continue to becomecontaminated even though permitted point sources havelargely been brought under control in recent years.

It is useful to keep in mind that not all contaminantsthat may be associated with point and nonpointdischarges into the Estuary are necessarilycontaminants of concern in the sediments. Highlywater-soluble compounds will not tend to concentrateonto sediment particles in the first place. Similarly,affinity (adsorption potential) for sediment particlesurfaces or the organic matter associated with them.lower molecular weight organic compounds that arehighly volatile will tend to dissipate before being

incorporated into the sediments. For example, “BTEX”(a mixture of benzene, toluene, ethyl-benzene, andxylene) is often a concern in upland soils excavatedfrom around leaking underground storage tanks; hencelandfills typically require information about BTEXconcentrations before accepting contaminated soils fordisposal. However, BTEX would rarely be found inestuarine sediments (see discussion on Current UplandTesting Practice in section 3.2.5.2). Overall, althoughthere are limited areas of highly contaminatedsediments associated with specific sources, the majorityof sediments in the Estuary are characterized by lowconcentrations of contaminants spread through largevolumes of material. In contrast, cleanup projectsaddressing contaminated upland soils typicallyencounter small volumes of highly contaminatedmaterial (and the contaminants themselves are oftendifferent).

Dredged sediments that are determined to be notsuitable for unconfined aquatic disposal are very rarelyclassified as “hazardous.” The following section givesan overview of contaminants that are typically found inEstuary sediments.

3.2.3.3 Contamination Levels in San FranciscoBay/Delta Estuary Sediments

There have been several programs in San FranciscoBay that have monitored concentrations ofcontaminants in sediments from various embayments.Historical sediment chemistry data collected fromnumerous Bay surveys performed between 1971 and1986 have been summarized by Long and Markel(1992). Data from these surveys are presented in Table3.2-3. This table compares mean chemicalconcentrations in sediments from the central areas ofSan Pablo Bay, central San Francisco Bay, and thesouth Bay with chemical concentrations in sedimentsfrom peripheral areas of these basins (marinas, harbors,ship channels, and industrial waterways) that would beexpected to be more directly influenced by pollutantsources. These data indicate that, overall, theperipheral industrialized areas indeed have higher meancontaminant concentrations than do the central basins.For most compounds, the range of contaminantconcentrations is also greater in the peripheralindustrial areas than in central basin samples (Long etal. 1988).



Figure 3.2-22 Location of Publicly-Owned TreatmentWorks (POTWs) in the Bay Area

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Table 3.2-2 Industries Associated with SedimentContamination



Figure 3.2-23 Location of Industrial Discharge Sites inthe Bay Area

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Figure 3.2-24 Combined Pollutant Loadings to theBay/Delta by Source Type

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More recent data sets documenting Bay-wide trends insediment contamination have been collected as part ofthe state’s San Francisco Bay Regional MonitoringProgram and the Bay Protection and Toxic CleanupProgram (BPTCP) (described in more detail in Chapter4). Overall, the median, maximum, and minimumconcentrations of selected sediment contaminants frommonitoring locations representing ambient conditions inthe three main basins of the Bay (areas removed fromknown sources of contamination) are presented inTable 3.2-4. Generally, the medians and ranges ofambient contaminant concentrations observed areconsistent among the three basins.

Concentrations of trace metals are consistently low ineach of the basins and are similar to historical data(discussed earlier) reported by Long et al. (1988) (Table 3.2-3). Likewise, median concentrations of thepesticide DDT and total PCB are consistently low(< 4.5 ppb and < 11.2 ppb, respectively) in samplesfrom all three basins, although the maximumconcentrations of both chemicals measured in the northand central Bay sediments are higher than those fromthe south Bay. PAHs are the only contaminants whoseambient concentrations appear to be both elevated insome of the basins and variable between basins.Median values for summed PAHs (HPAHs

Table 3.2-3. Mean Concentrations of Selected Toxicants in Surficial Sediments from ThreeBasins and Four Peripheral Area of San Francisco Bay

(Adapted from Long and Markel 1992) BASINS PERIPHERY

San Pablo Bay

CentralSF Bay

South

SF Bay

OaklandInner

Harbor

IslaisCreek

Harbor

Redwood

Creek

Richmond

Harbor Trace Metals (ppm, dry weight)

Mercury 0.45 0.35 0.65 0.57 1.30 0.42 0.40 Cadmium 0.71 0.79 1.44 0.67 2.23 2.47 0.65 Copper 45 33 33 72 78 66 36 Lead 32 34 30 97 102 87 39 Chromium 280 81 84 ND 140 91 123 Silver 0.45 0.72 0.57 ND 4.69 ND ND

Organics (ppb, dry weight) Total PAHs 2,600 3,900 2,700 7,200 62,700 ND ND Total DDTs 9 16 3 120 3 ND 260,700* Total PCBs 27 71 28 361 305 ND ND * Includes stations within the United Heckathorne/Lauritzen Canal Superfund site. Mean concentration

of DDT compounds for other areas of Richmond Harbor is less than 200 ppb.

Table 3.2-4. Ambient Concentrations of Selected Contaminants in San Francisco Bay Sediments from RecentMonitoring Programs

SOUTH BAY # OF SITES = 11

CENTRAL BAY # OF SITES = 9

NORTH BAY # OF SITES = 13

Chemical Median

Min Max N Median

Min Max N Median

Min Max N

Silver 0.4 0.1 1.2 39 0.2 0.0 0.4 31 0.2 0.0 0.5 43 Arsenic 8.9 0.8 14.2 38 9.6 0.7 29.4 31 7.7 0.6 20.6 43

Cadmium 0.2 0.0 0.7 39 0.2 0.0 0.3 31 0.2 0.1 0.6 43 Chromiu

m 93.3 9.4 213.0 39 75.7 8.5 238.0 31 81.5 6.9 209.0 43

Copper 38.3 16.6 94.6 39 32.7 8.0 56.5 31 46.0 13.2 71.9 43 Mercury 0.3 0.1 0.5 38 0.2 0.0 0.4 31 0.2 0.0 0.4 48 Nickel 76.9 14.9 130.8 39 72.8 12.2 107.0 31 76.3 12.9 135.0 43 Lead 23.1 10.6 45.4 39 21.5 8.4 33.7 31 23.1 5.6 115.0 43

Selenium 0.3 0.1 1.3 38 0.3 0.0 0.9 31 0.2 0.1 3.3 48 Zinc 109.0 44.8 221.8 39 87.9 39.0 154.0 31 120.1 34.9 180.0 43 Sum

DDTs 2.7 0.0 12.5 34 4.5 0.0 63.1 31 3.7 0.1 70.3 48

SumHPAH

2,226.4

1,239.6

6,837.1

34 1,954.3

1.9 5,844.0

31 508.5 33.2 2,705.9

49

SumLPAH

204.6 12.0 1,065.6

34 239.2 0.0 646.5 31 49.7 0.0 246.0 48

TotalPCB

9.2 8.6 25.3 10 11.2 0.0 38.7 9 8.8 3.8 117.0 22

Notes: Units: metals mg/kg (ppm) dry weight. organics µg/kg (ppb) dry weight. N = Number of samples. Sources: AHI 1993; SFEI 1994; SFRWQCB 1994; unpublished data from RWQCB 1994-95 Bay Protection and Toxic

Cleanup Program Reference Study.





FINAL REPORT: LTMS CONTAINMENT SITES COMMITTEE

TASK: Develop a list of potential disposal sites capable of handling “contaminated” or “unsuitable” dredgematerial.

The Containment Sites Task Committee held two meetings, the first on December 14, 1992, and the second on January19, 1993, and reached a general consensus about its work. Four major areas of substantive work were involved, and theCommittee reached a consensus in each area, as follows:

1. Locate major (probable) areas and amounts of “contaminated” or “unsuitable” dredged materials.

• After discussion with the Regional Board and review of their work on the Bay Protection and Toxic CleanupProgram (BPTCP), we concluded that it was appropriate to adopt a “planning” estimate of 10 million cubicyards that will need to be dredged over the next 10 years. This only involves material removed as part ofdredging, and does not include clean-up of hot spots. This estimate was based on an estimate of 2 millioncubic yards of unsuitable material in the Oakland deepening project, 1 million cubic yards of unsuitablematerial in the Richmond deepening project, and 500,000 cubic yards each year (about 10-20 percent) ofmaintenance material that might be expected to fail tests for in-Bay or ocean disposal. This reserves up to 3million cubic yards of unsuitable material capacity for the Navy’s deepening projects and for other projectsand hot spots. This estimate should be updated when the Regional Board adopts a final report under theBPTCP.

2. Develop alternative strategies for addressing “contaminated” or “unsuitable” materials, e.g., (a) leaving suchmaterials in-place, (b) confined disposal — either upland or aquatic, and (c) treatment solutions.

• The committee judged that all of these options may be suitable strategies. Unfortunately, too little is knownabout the location, quantity, and degree of contamination of most material to be able to select the appropriatedisposal option. Thus, the committee spent most of its efforts on confined disposal.

3. Determine whether any of the sites now under consideration could handle dredged materials and, if so, in whatamounts.

• The Committee concluded that approximately 6 million cubic yards of disposal capacity was available asreuse for daily cover in Redwood Landfill, approximately 10 million cubic yards of capacity may be availablein the Montezuma Slough project, and approximately 10 million cubic yards of disposal may be available inthe borrow pit near Bay Farm Island. Other sanitary landfills and other drying and/or rehandling sites can alsohandle unsuitable material, but these three sites appear to be the most advanced of sites now underconsideration.

4. Recommend at least three sites that should be brought on-line to handle “contaminated” or “unsuitable” sedimentdisposal needs.

• The Committee decided not to recommend specific sites, largely because several specific sites appear to beheading toward environmental review and permitting. Instead, the Committee established the followinghierarchy of preference for disposal site types. This hierarchy reflects the relative certainty of confinement inthe disposal site, and the ease of management.

First Choice: The preferred disposal location of the Committee is for upland disposal in landfills. TheCommittee understands that landfill capacity and permitting are issues for this option. However, theCommittee concluded that this option provided the greatest certainty of containment, ease of management,and provided the additional benefit of also acting as daily cover.

Second Choice: The Committee concluded that confinement in wetlands represented a suitable disposaloption if done properly. In particular, the Committee believed it was essential to make sure that channelswould not erode the placed sediments. The Committee considered this alternative to be less certain thanlandfill disposal because construction might involve hydraulic placement with more opportunity for runoffand because biological activity would disturb a portion of the covering soils.

Third Choice: The Committee concluded that confinement at in-water capping sites represented a suitabledisposal option if done properly. However, in-water capping raises complex technical issues including thequestion of material loss during initial placement, long-term stability of the cap, and consistency withapplicable laws. The Committee also concluded that the LTMS should be the forum for consideration of thisoption, and that such consideration should take place in the in-Bay Work Group, as an explicit part of theirwork program.



and LPAHs) ranged from 558 ppb in the north Bay to2,431 ppb in the south Bay. Relatively highconcentrations of HPAHs (in excess of 4600 ppb) wererepeatedly observed at several sampling locations in thesouth Bay.

While such overall trends in the basins are readilydiscernable, contaminant distributions and sedimenttoxicity can be very patchy in all areas of the Estuary.Areas around shipyards and naval facilities — where indecades past it was common to simply dump wastessuch as used solvents, paint, and other chemicals off thesides of ships or docks, or down drains leading to theBay — often have highly contaminated sediments. Forexample, the Hunters Point Naval Shipyard is aSuperfund cleanup site today, and some nearbysediments have accumulated pollutants — most notablyheavy metals — to the point of exceeding hazardouswaste criteria (PRC 1994). Similarly, onshoreindustrial facilities often dumped pollutants into theBay, contaminating sediments in the vicinity. Pastoperation at the United Heckathorn facility in the Portof Richmond contaminated nearby sediments with DDTand other compounds; this site has also been the subjectof a Superfund cleanup action (Lincoff et al. 1994).Likewise, elevated levels of petroleum-derivedcontaminants have been observed in sediments fromCastro Cove, a site that has historically receiveddischarges from a nearby oil refinery (SF RWQCB1994).

3.2.3.4 Efforts to Reduce Sediment Contamination

Throughout the Estuary there are many other suchexamples of significant site-specific sedimentcontamination resulting from identifiable local sources.However, important strides have been made in the lastseveral years to control such identifiable sources. Asdescribed above in section 3.2.3.2, the primary sourcesof sediment contamination now (with the exception ofaccidental spills directly into the Estuary) are nonpointsources (runoff from urban and agricultural areas,stormwater discharges, and atmospheric deposition).These kinds of sources, combined with the Bay’snatural resuspension processes, often result in muchless intensive but more wide-spread and “patchy”sediment contamination. As a result of remedial actionprograms (such as BPTCP and Superfund that addressthe most significant areas of sediment contaminationfrom past activities), better regulation of point sourcedischarges under the NPDES program jointlyadministered by EPA and the state of California, andincreasing attention to non-point source discharges bymany programs at the federal, state, and local levels,levels of contaminants in Bay area surficial sediments

would be expected to continue to decrease over time.However, it must also be expected that both new workand maintenance dredging projects will continue tooccasionally encounter “unsuitable” material(sediments that cannot go to unconfined aquaticdisposal sites, but instead need some form of specificmanagement for their contamination) throughout theplanning time frame of this EIS/EIR. For planningpurposes, this LTMS EIS/EIR assumes that 20 percentof all dredged material will be unsuitable forunconfined aquatic disposal. This percentage is basedon a review of available sediment quality informationon recent projects, as well as major new work (harbordeepening) projects that can reasonably be anticipated(see the following text box on the LTMS ContainmentSites Committee). It already appears evident that thisestimate is conservative,2 and the 20 percent figureprobably overestimates to some degree the long-termvolume of dredged material needing special handling.

3.2.3.5 Determining When “Contamination” is aProblem in San Francisco Bay/DeltaEstuary Sediments

The potential for contaminants in dredged material tocause an adverse biological effect at a placement site isrelated to the bioavailability of the contaminantspresent, and to the opportunity for organisms ofconcern to be either directly or indirectly (e.g., viagroundwater) exposed to them. The term“bioavailable” is used here broadly to refer to acontaminant whose concentration and chemical formmake it available for uptake by an organism, so that thecontaminant can then (directly or after beingmetabolized to a more toxic chemical compound orform) cause an adverse biological impact. Thebioavailability of contaminants in sediments can changedramatically depending on the placement environment,and depending upon a wide variety of factors that canvary from sediment to sediment (such as organic carboncontent, salinity, pH, oxidation/reduction potential, andparticle size). The following text box describes someof the major chemical factors controllingbioaccumulation (the uptake of contaminants into anorganism). Also, see section 3.2.4 (Exposure Pathwaysand Potential Risks) below for a more detaileddiscussion of how the type of placement environmentcan affect contaminant bioavailability.

The opportunity for organisms (or other resources ofconcern) to be exposed to bioavailable contaminants attoxicologically significant concentrations is often amore site-specific matter. Contaminants that are in abioavailable form may not represent an adverse effect iforganisms cannot be exposed to them. For example,



sediments that would be of concern for placement in anunconfined aquatic disposal site — due to the presenceof elevated concentrations of contaminants that arebioavailable to marine organisms — may be fullysuitable for placement at a properly constructedlandfill, where contaminants can be contained andorganism exposure is minimized. These samesediments may also be suitable for beneficial reuse ofvarious kinds. The type and degree of testing needed(if any) must be based on the potential exposurepathways that are determined to be of concern for aparticular project and its potential disposal sites. Seesection 3.2.5 (Role of Sediment Evaluation) below for adiscussion of the testing frameworks for aquatic andupland placement environments.

If evaluation of sediment quality (including any testingdata) shows that there is the potential for unacceptableadverse effects at the proposed placement site, controlmeasures can be considered for reducing or eliminatingthe risk. See section 3.2.4.5 below for a discussion ofthe kinds of control measures that may be appropriatefor various contaminant pathways of concern in eachtype of placement environment. If potential controlmeasures would not be effective in adequately reducingthe risk of adverse contaminant- related effects, analternative disposal option must be selected if thesediments must be dredged (it is sometimes possible toavoid dredging problematic sediments by reconfiguringthe project — however, the environmental acceptabilityof leaving contaminated sediments in place must alsobe considered.

3.2.4 Contaminant Exposure Pathways andPotential Risks in Different PlacementEnvironments

In order for contaminants associated with sedimentparticles to cause a biological effect, an organism mustbe exposed to the contaminants in a bioavailable form.Organisms can be exposed to contaminants insediments directly (e.g., via ingestion of or directcontact with the sediment), or indirectly (e.g., via

contaminated surface or groundwater, or by eatingother organisms that have taken up contaminants fromthe sediments). This section provides a basicdescription of the contaminant “exposure pathways”and potential risks that are associated with disposal ofdredged material in the various types of placementenvironments (ocean, in-Bay, nearshore/wetland andupland) considered in this EIS/EIR.

Overall, dredging and aquatic disposal can have effectson organisms in the water column, or in the benthos.The location of the dredging and disposal sites inrelation to resources of concern, and whether an aquaticdisposal site is erosional or depositional, are importantin determining which of these pathways may be of mostconcern. There are also important overall differenceswhen dredged materials are placed in upland versusaquatic sites: upland sites represent very differentgeochemical environments, in which the behavior ofsediment-associated contaminants can be dramaticallydifferent than under aquatic conditions. Sedimentsplaced in upland locations can affect a different mix oforganisms, and can have effects on surface waterquality, groundwater quality, and air quality.

There is also a difference between the differentplacement environments in the ability to engineerdisposal sites to appropriately manage the relevantcontaminant exposure pathways. Generally, it is notpossible to control organism exposure to dredgedmaterial or to limit organism access at dispersiveunconfined aquatic sites. At non-dispersive unconfinedaquatic sites, organism exposure can be limited butorganism access typically cannot (other than indirectly,by locating sites to avoid important habitat areas). Incontrast, design features can be included at confinedaquatic disposal sites and at many upland/wetland reuse(UWR) sites to limit both organism exposure andorganism access.

A basic understanding of how the exposure pathwaysdiffer between the placement environments is essentialto determining the need for specific managementrestrictions, and designing and implementing placementsite design features that are truly effective atminimizing or eliminating potential impacts. Thefollowing sections discuss the main contaminantexposure pathways for each major placementenvironment, and potential control measures for them.



Major Chemical Properties Controlling Propensity of Contaminants to Bioaccumulate from Sediments (Adapted from USEPA and USACE 1994)

Hydrophobicity

Literally, “fear of water;” the property of neutral (i.e., uncharged) organic molecules that causes them to associate withsurfaces or organic solvents rather than to be in aqueous solution. The presence of a neutral surface such as an unchargedorganic molecule causes water molecules to become structured around the intruding entity. This structuring isenergetically unfavorable, and the neutral organic molecule tends to be partitioned to a less energetic phase if one isavailable. In an operational sense, hydrophobicity is the reverse of aqueous solubility. The octanol/water partitioncoefficient (Kow) is a measure of hydrophobicity. The tendency for organic molecules to bioaccumulate is related to theirhydrophobicity. Bioaccumulation factors increase with increasing hydrophobicity up to a log Kow of about 6.00.

Aqueous Solubility

Chemicals such as acids, bases, and salts that speciate (dissociate) as charged entities tend to be water-soluble and thosethat do not speciate (neutral and nonpolar organic compounds) tend to be insoluble, or nearly so. Solubility favors rapiduptake of chemicals by organisms, but at the same time favors rapid elimination, with the result that soluble chemicalsgenerally do not bioaccumulate to a great extent. The soluble free ions of certain heavy metals are exceptional in thatthey bind with tissues and thus are actively bioaccumulated by organisms.

Stability

For chemicals to bioaccumulate, they must be stable, conservative, and resistant to degradation (although somecontaminants degrade to other contaminants that do bioaccumulate). Organic compounds with structures that protectthem from the catalytic action of enzymes or from non-enzymatic hydrolysis tend to bioaccumulate. Phosphate esterpesticides do not bioaccumulate because they are easily hydrolyzed. Unsubstituted polynuclear aromatic hydrocarbons(PAHs) can be broken down by oxidative metabolism and subsequent conjugation with polar molecules. The presence ofelectron-withdrawing substituents tends to stabilize an organic molecule. Chlorines, for example, are bulky, highlyelectro-negative atoms that tend to protect the nucleus of an organic molecule from chemical attack. Chlorinated organiccompounds tend to bioaccumulate to high levels because they are easily taken up by organisms and, once in the body,they cannot be readily broken down and eliminated.

Stereochemistry

The spatial configuration (i.e., stereochemistry) of a neutral molecule affects its tendency to bioaccumulate. Moleculesthat are planar tend to be more lipid-soluble (lipophilic) than do globular molecules of similar weight. For neutral organicmolecules, planarity can correlate with higher bioaccumulation unless the molecule is easily metabolized by an organism.



3.2.4.1 Exposure Pathways in Aquatic PlacementEnvironments

Dredging, and dredged material disposal at aquaticsites, can result in adverse effects in two basic“compartments”: in the water column, and on thebottom (benthos). Figure 3.2-25 depicts these exposurepathways for open water disposal. Water columneffects occur when sediment particles are disturbedfrom the bottom and resuspended during dredging anddisposal, and are usually limited to the immediateperiod when dredging and disposal activities occur.Benthic effects can result from physical burial ofbenthic organisms at the disposal site, and long-termexposure of local organisms to the sediments on thebottom after disposal has ceased.

Typical in-place estuarine sediments are dark in colorand reduced, with little or no oxygen (anaerobicconditions). Reduced, anaerobic conditions favor thepartitioning of contaminants onto the sediment particlesor the organic matter associated with them. Thus thebulk of sediment contaminants may not be directlyavailable to many aquatic organisms. During typicaldredging and disposal operations, the exposure ofanaerobic sediments to oxygenated water is sufficientlyshort term that the reduced characteristics of thesediment do not change appreciably. At a non-dispersive aquatic disposal site the dredged materialquickly settles to the bottom, where anaerobicconditions are quickly restored or maintained.

Water Column vs. Benthos

As discussed in section 3.2.3.1, specific contaminantstypically are associated with sediments because they areeither hydrophobic or otherwise are easily scavengedfrom the aqueous phase. The same processes thatpreferentially bind these contaminants to sedimentparticles make it relatively difficult for thecontaminants to disassociate from the particulates andgo back into the aqueous phase during dredging andaquatic disposal operations. Those contaminants thatdo disassociate from sediment particles in a disposalplume usually do so for only very short periods of timebefore they are re-scavenged by other suspendedparticles. The degree of water column effect will bedirectly related to the extent and speed of dilution ofthe water column plume and/or resettling of theresuspended sediment. Water column impacts aretherefore evaluated by comparisons with water qualitystandards and evaluation of the potential for short-termtoxicity, considering the mixing that may occur at thedredging or disposal site in question.

Potential water column effects can usually be managedby selection of appropriate dredging/disposal methodsand discharge rates (for a listing of control measuressee section 3.2.4.5), in conjunction with designation ofan appropriate mixing zone. Mixing zones are areas(designated by the relevant state for inshore and statewaters, and by federal criteria for offshore oceanwaters) outside of which water quality standards mustbe met and beneficial uses of the waterbody must beprotected. In general, mixing zones may not be solarge as to inhibit the movement or migration of aquaticspecies, or to allow degraded water quality to extendthroughout a significant portion of a water body. Moststates (including California) have both numerical and“narrative” water quality standards that must be met atall points outside the boundaries of the mixing zone.The narrative criteria for California state that, inaddition to meeting all relevant numerical water qualitycriteria, plumes outside mixing zones cannot include“toxic substances in toxic amounts.” Therefore, pre-disposal testing for potential water column impactsevaluates both water quality (against numeric criteria)and short-term suspended particulate phase toxicity,considering the dilution characteristics of the specificdisposal site and any specific mixing zone designatedfor that site. Section 3.2.5 describes sediment testingapproaches in more detail.

Because most fish species are able to actively avoid theimmediate vicinity of dredging and disposal areas, andbecause water column plumes during dredging ordisposal are usually local and temporary (diluting tobackground levels within minutes to a few hours afterdredging or disposal operations cease), the watercolumn pathway rarely results in significant directimpacts to most aquatic organisms except in certain,limited circumstances. These could include thefollowing:

• Continuous dredging or discharging near specificresources of concern;

• Dredging of highly contaminated sediments orsediments with an unusually high oxygen demand;

• Dredging or discharging within constricted areaswhere water column mixing would be inadequate;or

• Dredging or discharging at locations and duringtimes where increased suspended particulateswould have a direct effect on particular species ofconcern (such as herring spawning sites, whenspawning herring or incubating eggs are actuallypresent).



Figure 3.2-25 Contaminant Pathways for Open WaterDisposal

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Based on the long-term experience of disposingapproximately 400 mcy of dredged material per year athundreds of aquatic disposal sites nationwide, the watercolumn is rarely found to be the primary pathway ofconcern.

In contrast, benthic exposure to “undiluted” (solidphase) dredged material after disposal can be long-term. On-site benthic infauna and epifauna can beexposed long enough that any contaminants in thedredged material can directly affect them, or they canaccumulate bioavailable contaminants to such a degreethat animals that prey on them may be adverselyaffected. Therefore, potential impacts as a result ofbenthic exposure are typically considered by evaluatingboth longer-term solid phase toxicity, andbioaccumulation (section 3.2.5 describes sedimenttesting approaches in more detail). Solid phase toxicitytesting evaluates whether the sediments may be toxic toorganisms directly exposed to them. Bioaccumulationtesting provides an indication of the potentialbioavailability of contaminants in the dredged material,which in turn aids in the evaluation of whether (giventhe location and characteristics of the particulardisposal site) there is the potential for trophic transferof contaminants to other organisms that are notnecessarily directly exposed to the dredged material(i.e., food web effects).

Dispersive vs. Non-Dispersive Aquatic Sites

The basic aquatic contaminant exposure pathwaysdescribed above apply to both dispersive anddepositional disposal sites. However, the applicabilityand effectiveness of potential control measures differssubstantially between dispersive sites (such as theexisting in-Bay disposal sites) and depositional sites(such as the SF-DODS).

Dredged material does not remain on the bottom forlong periods of time at the existing, predominantlydispersive in-Bay disposal sites. Instead, finesediments are resuspended and transported away fromthese sites. These resuspended sediments may resettleand resuspend again several times before either leavingthe Estuary system through the Golden Gate, or finallysettling in a depositional site (see section 3.2.2). Thetesting methods for evaluating whether water columnrestrictions (control measures) are needed to reduceadverse effects of the suspended particulate phase ofdredged material (section 3.2.5) are also appropriate forevaluating whether sediments resuspended fromdispersive sites may pose a contaminant-related risk. Inmost cases, if the original disposal of the dredgedmaterial did not require contaminant-related water

column control measures then it is unlikely that watercolumn control measures would be required forsubsequent resuspension, due to the likelihood ofincreased dilution during each subsequent resuspensionevent. Thus, the water column pathway is notnecessarily of any greater concern at dispersive versusdepositional sites. (Note that this refers only tocontaminant-related effects. Physical effects — suchas potential local or embayment-wide increases inturbidity that might be associated with high levels ofdisposal at dispersive sites — may still be of concern.)

In contrast, the benthic pathway can be of greaterconcern at dispersive sites compared to depositionalones. Although this may at first seem contradictory(after all, fine dredged material by definition does notremain on the bottom at dispersive sites), the differencerelates to the inability to monitor the ultimate fate ofdredged material placed at dispersive sites, and toconfirm that adverse benthic effects are not occurring atsome other, unanticipated location. As noted in section3.2.2, there is very limited ability today to accuratelypredict where or how much dredged materialresuspended from in-Bay sites will ultimately settle.However, it is known that many contaminants will tendto be at higher concentrations in the fine particle sizefractions of sediment (section 3.2.1), and that the finefractions (particularly the silts) are the most easilyeroded from dispersive disposal sites. It is thereforetheoretically possible that the overall concentrations ofcontaminants measured in a whole sediment sample canunderestimate the risk posed by preferential settling ofhydraulically sorted fines at depositional locationsaway from the disposal site.3

Unfortunately, it is virtually impossible to confirm thatcontaminants from dredged materials so dispersed areor are not resulting in adverse off-site effects. By thesame token, it is often impossible to prove that any off-site effects that are measured are in fact a result ofdredged material from a dispersive site, rather thanfrom some other source. This uncertainty must beviewed as a risk that adverse environmental effectscould occur. From a dredged material managementstandpoint, two considerations become the focus ofaddressing this risk. First, is the dredged material“clean” enough that, even if fines preferentially settledin a single location, adverse impacts are unlikely? Andsecond, are alternative disposal sites available andpracticable to use that would manage the dredgedmaterial with less risk? Because there is little ability tomanage contaminant-related risk at dispersive sites byother means, the primary effective control measure thatcan be used to address potential adverse benthic effectsrelated to dispersive sites is to avoid, in the first place,



disposal of significant quantities of dredged materialsthat contain appreciable concentrations ofcontaminants.

At predominantly depositional sites, dredged material isexpected to remain on the bottom, within theboundaries of the disposal site. This makes it muchmore possible to monitor site performance and toconfirm that unacceptable adverse effects are notoccurring, or to take corrective action if necessary. Ifadverse effects are indicated in the vicinity of adepositional disposal site, it can be determined muchmore readily than at a dispersive site whether this is dueto dredged material disposal or some other cause. Alisting of potential management and control measuresapplicable to depositional sites is presented in section3.2.4.5.

3.2.4.2 Exposure Pathways in Upland PlacementEnvironments

When dredged material is placed in an uplandenvironment (i.e., a site with no tidal action), importantphysical and/or chemical changes occur once disposaloperations cease and the sediments begin to dry(Francingues et al. 1985). As it dries and cracks form,the dredged material will oxidize and become lighter incolor. Accumulations of salt will develop on thesurface and the edge of cracks. Rain will tend todissolve the salts and remove them in surface runoff,and accumulations of some now-oxidized metals maybe carried away with the runoff as well. As dryingproceeds, organic complexes (which had sequesteredmany contaminants away from organisms in situ,anaerobic sediments) oxidize and decompose. Sulfidecomplexes also oxidize to sulfate salts, and acidity mayincrease (pH may drop) dramatically. Lowered pH candirectly affect the speciation and reactivity of variousheavy metals (generally making them more soluble andreactive, and therefore more bioavailable and toxic).Lowered pH also directly affects the toxicity ofammonia produced by decomposing organic matter.These transformations can promote the release ofcontaminants into surface water and groundwater (vialeachate), and organisms exposed to these watersources, or to the site itself, may readily take up thesereleased contaminants. However, recent studies ofdredged material placement for wetland creation havedemonstrated that drying for purposes of maximizingsite capacity does not necessarily promote the releaseof contaminants or their bioavailability (LTMS 1995d).Nonetheless, site management measures, such asresaturation of dried sediments prior to the restorationof tidal action, can be taken to minimize thebioavailability of contaminants. Volatilization of some

contaminants into the air may also occur fromdewatered dredged material placement sites, resultingin an additional potential exposure pathway. From ahuman health standpoint, fugitive dust can be apathway of particular concern. In certain circumstancesfine particles of dredged material, with any associatedadsorbed contaminants, can be blown from uplandplacement sites if the surface of the dredged material isallowed to dry completely. This “fugitive dust” can beinhaled or ingested by on-site workers and peopleliving, playing, or working nearby. Fortunately,fugitive dust can be easily controlled by standardoperating procedures (principally, keeping the surfaceof the site moist when the dredged material is exposed).Figure 3.2-26 shows the exposure pathways potentiallyassociated with dredged material placement in uplandenvironments.

These differences (compared to the behavior ofdredged material in an aquatic environment) lead todifferent mechanisms by which organism may beexposed to contaminants in dredged material, as well asto differences in the types of resources that may beexposed. For example, upland placement of dredgedmaterial can potentially affect:

• Surface water quality (and any organisms exposedto the affected water body). Depending on thespecific placement site, the receiving water bodymay be a river, slough, or the Bay. Surface waterquality may be affected by return effluent duringinitial filling of the upland site with dredgedmaterial; rainwater runoff from the site after thedredged material has been initially dewatered; orseepage from the site into other adjacent surfacewaters.

• Groundwater quality (and any organismsultimately exposed to the groundwater).Groundwater impacts are avoidable by bothappropriate siting of upland facilities (i.e., avoidareas where underlying groundwater quality ishigh, and/or is used for drinking water or otherdomestic purposes), and by proper engineering ofthe upland facility itself (e.g., impermeable linersand/or leachate collections systems whereappropriate).



Figure 3.2-26 Contaminant Pathways for UplandConfined Disposal Facilities

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• Wildlife attracted to site while it is flooded (e.g., inthe early stages of the drying process, whensediments are still settling and consolidating andbefore overlying water has been decanted).

• Other wildlife using the site after the sedimentshave dried (e.g., exposure to or throughinvertebrates colonizing the site).

• Plant uptake of contaminants from the driedsediments (especially certain metals that can betaken up into plant tissues from the surface,oxygenated layer of the sediment deposit).Bioaccumulation of contaminants into plant tissuescan be of concern for wildlife who may be exposedto the contaminants by eating the plants.

• Air quality (volatilization of some compounds fromthe surface layers of the sediment deposit, odor,fugitive dust — these are discussed further inChapter 6).

• Human health (via direct exposure, or indirectexposure via air quality impacts or water qualityimpacts). However, risks to human health fromdredged material at upland sits is highly dependenton the type and level of contaminants in thematerial and site-specific factors.

Although exposure pathways for upland placement sitesmay seem more complex than for aquatic sites, it is alsoimportant to note that it is often more possible toengineer effective control measures at upland ornearshore sites than it is to do so at unconfined aquaticsites. In contrast to dispersive unconfined aquaticdisposal sites in particular, operational and designfeatures can generally be incorporated into uplandplacement sites to address any of the pathways listed,should they be of concern on a projects-specific basis.

3.2.4.3 Exposure Pathways in NearshorePlacement Environments

Nearshore placement sites (i.e., diked historic baylandsor diked baylands now restored to tidal action) combinethe characteristics of upland and aquatic sites, and all ofthe exposure pathways of those environments can comeinto play. Similarly, nearshore sites are intermediatebetween upland and aquatic sites in terms of the abilityto engineer control measures to address thecontaminant exposure pathways. Figure 3.2-27 showsthe typical exposure pathways for nearshore placementsites.

Much of the dredged material placed at nearshoredisposal sites will remain saturated and anaerobic,thereby minimizing the geochemical changes that occurwith upland placement, and that can lead to increasedcontaminant solubility or mobility. On the other hand,there will generally be less initial dilution of the waterand any suspended solids that may be decanted backinto the adjacent water body during disposal (as the siteis being filled), compared to unconfined aquaticdisposal at deeper water sites. The ability to addressthe potential contaminant exposure pathways atnearshore sites also falls between that of upland andopen water sites, as discussed below.

3.2.4.4 Ability to Take Corrective SiteManagement Measures in DifferentPlacement Environments

Most of the impacts that can potentially be associatedwith dredged material placement are best addressedbefore disposal occurs, by selecting an appropriate site.Sites that avoid sensitive resources, that have fewpotential contaminant pathways of concern, and/or thatinclude features to help control the potential pathways,will minimize initial impacts as well as reduce the needto take corrective measures later. Nevertheless, avariety of tools or management responses are availableat any placement site if corrective measures are foundto be necessary after dredged material has beendisposed.

The ability to take corrective measures, should aconcern arise at a dredged material placement site,varies among the placement environments. If theconcern is an unacceptable level of contamination,removing problem material is rarely feasible under anycircumstances at open water sites. Instead, capping(and if necessary, armoring the cap against erosion byplacing coarser material on top) is often the onlyfeasible means of isolating material of concern once itis on the bottom. Even this is generally only practicalat non-dispersive sites. At dispersive sites little can bedone, because in most cases it will not be possible todetermine where problem material from the site hasultimately settled.

In contrast, at upland sites, there is generally the abilityto take several steps (including re-excavation of theproblem material and re-engineering the site, orremoving the material to a new site) if unexpectedproblems arise. Actual steps taken would depend onthe site and the specific problem identified (see section3.2.4.5).



Figure 3.2-27 Contaminant Pathways for NearshoreConfined Disposal Facilities

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At nearshore sites, control of return water quality andquantity is also generally feasible. And, should seriousproblems develop so that it becomes necessary toremove the sediments and re-engineer the site, accessfor heavy equipment is possible. However, especiallyif the nearshore site was used for habitat restoration, orhas otherwise developed important habitat values, theremay be more ancillary consequences of correctingproblems at a nearshore site (e.g., potential release ofcontaminants into adjacent areas) compared to anupland site.

If the problem needing correction at an open water siteis not related to contaminants but is instead physical innature, various management actions are possible. Forexample, as discussed in Chapter 2 (section 2.2),mounding has been an ongoing problem at the Alcatrazsite, and it has taken active management by the COEregarding the timing, rates, locations within the site,and methods of disposal to keep this problem fromworsening. In the 1980s, the mound itself had to bephysically re-dredged to reduce the navigational hazardposed by the site. In the early 1990s moundingproblems reappeared and, in 1993, additional activesite management steps were outlined in COE PublicNotice 93-3. Under these measures, and given therelatively low volumes of material placed at the site in1993 and 1994, dispersion appears to be keeping upwith disposal so that mounding is not causing anavigation hazard today. At other dispersive in-Baysites, the same degree of active management has notbeen necessary. At SF-DODS, mounding is not ofsignificant concern, but potential off-site deposition ofsubstantial quantities of dredged material would be. Ifthis should be identified as a result of ongoing sitemonitoring, a variety of management actions arepossible there, as well.

These have been identified in the final rule designatingthe site, and may include moving the surface dischargepoint within the overall site so that dredged materialcontinues to deposit where desired; restricting thetiming of discharges relative to currents; restricting therate and/or volume of discharge so that significant off-site deposition does not occur; or discontinuing use ofthe site. However, removing or re-dredging depositedmaterial in the vicinity of SF-DODS would most likelybe infeasible.

Physical problems at upland and nearshore sites couldinclude not achieving proper elevations at a habitatrestoration site; or an upland site developing a fugitivedust problem during drying. These kinds of physicalproblems can generally be readily addressed at upland

and nearshore sites. For example, before tidal action isallowed to return at a tidal wetlands restoration site,regrading can be done if necessary to achieve properelevations for marsh vegetation; and fugitive dust canbe controlled by standard operating procedures whichrequire that the surface of drying dredged material besprayed to keep it moistened.

3.2.4.5 Summary of Potential Management Actionsand Control Measures for ContaminantPathways of Concern

A variety of management actions are possible for caseswhere evaluation of contaminant pathways indicatesthat ecological impact criteria will not be meet usingconventional disposal techniques. The primaryconsideration in selecting any of these control optionsis to identify the site-specific exposure pathway(s) ofconcern and to choose the management option that bestaddresses those exposure pathways. This sectionpresents examples of the potential management actionsand controls for the various exposures pathwaysassociated with aquatic, upland, and nearshore disposalareas. These controls are summarized by contaminantpathway in Table 3.2-5. Where appropriate, these arereflected in the mitigation measures included ascompanion policies common to all action alternatives,presented in Chapter 5. For more detailed informationon specific control measures, see the technicalframework document for dredged material management(USEPA and USACE 1992).

Water Column Pathway Controls

In the limited circumstances where the water columnpathway is determined to be of concern, there areseveral available control measures that may be appliedto reduce potential adverse effects. Controls for watercolumn effects at the dredging site include, forexample, restricting the time or rate of dredging;requiring the use of silt curtains or closed“environmental” clamshell buckets; requiring the use ofhydraulic dredges (which minimize mechanicaldisturbance at the dredging site but increase the volumeof water and suspended material that must be managedat the disposal site); and prohibiting overflow fromhopper dredges. Controls for water column effects atthe disposal site include reducing water-columndispersion by using clamshell dredging with dischargefrom barges or submerged diffusers; constraining thelocation, rate, and timing of disposal; and placingdredged material in geotextile bags to reduce watercolumn exposure during disposal.



Benthic Pathway Controls

A variety of modifications in dredged materialplacement operations can be instituted to controlcontaminant exposures to benthic pathways ifmonitoring shows that site performance is not optimal.For example, for some depositional sites, the surfacerelease zone can be adjusted to ensure that sedimentsare depositing at the desired bottom location. Lateralcontainment measures, such as existing subaqueousdepressions or constructed dikes, can also be used torestrict the bottom area being affected by dredgedmaterial placement. Conversely, thin-layer placementover a wide disposal area is a management action thatmay offset physical effects on benthos due to burial.Finally, if material is discharged at a depositionaldisposal site that causes unacceptable impacts (e.g., off-site toxicity, or bioaccumulation and food web effects),

the deposited material of concern can often be coveredor capped with cleaner dredged material, reducing theexposure of organisms to it.

This measure is, however, rarely possible at dispersivesites. Generally, depositional sites can be moreeffectively managed to minimize contaminant-relatedrisks associated with dredged material than candispersive sites.

Upland Pathway Controls

There are several possible migration pathways ofcontaminants out of upland disposal sites, includingeffluent discharges to surface water, surface runoff,leachate into groundwater, and air quality effects fromvolatilization or fugitive dust. Several measures existto minimize exposures from these pathways, including

Table 3.2-5. Potential Management Actions and Control Measures, by Contaminant Pathway

Water Column Pathway Controls

At the Dredging Site • Restricting the time or rate of dredging • Requiring the use of silt curtains or closed “environmental”

clamshell buckets • Requiring the use of hydraulic dredges • Prohibiting overflow from hopper dredges

At the Disposal Site • Reducing water-column dispersion by using clamshell dredging withdischarge from barges or submerged diffusers

• Constraining the location, rate, and timing of disposal • Placing dredged material in geotextile bags to reduce water column

exposure Benthic Pathway Controls

• For some depositional sites, adjusting the surface release zone to ensure sediments are depositing at the desiredbottom location

• Using lateral containment measures (e.g., existing subaqueous depressions or constructed dikes) to restrict thebottom area affected by dredged material placement

• Placing sediment in a thin layer over a wide disposal area can offset physical effects on benthos due to burial• At depositional sites, covering or capping the deposited material with cleaner dredged material

Upland Pathway Controls

• Managing settling time and discharge rates to improve return water quality• Treating return water (e.g., by flocculation)• Controlling seepage by using impermeable liners or retrofitting slurry walls around the site• Using leachate collection systems• Controlling dust by keeping the surface of the dredged material moist• Avoiding locating upland sites near resources that would be sensitive to odors

Nearshore Pathway Controls (1)

• If tidal transport of dredged material offsite is a concern, closing off the openings in the dikes and managing thearea as a nearshore confined disposal facility may be possible

Note: 1. All of the pathways and control measures listed for both the water column (aquatic) and upland disposalpathways might apply to nearshore disposal sites.



managing settling time and discharge rates for the siteto improve return water quality; treating return water(e.g., by flocculation); controlling seepage by usingimpermeable liners or retrofitting slurry walls aroundthe site; using leachate collection systems; controllingdust by keeping the surface of the dredged materialmoist; and avoiding locating upland sites near resourcesthat would be sensitive to odors.

Nearshore Pathway Controls

All of the pathways and control measures describedabove for both the aquatic and upland disposalpathways might apply to nearshore disposal sites. Oneadditional control measure would apply to nearshorefacilities that are subject to tidal action (e.g., theproposed Montezuma Wetlands project). In caseswhere tidal transport of dredged material offsitebecomes a pathway of concern, it may be possible toclose off the openings in the dikes and manage the areaas a nearshore confined disposal facility.

3.2.5 Role of Sediment Evaluations (Testing)

A major purpose of sediment quality testing is to assesswhether the bioavailability of and exposure tocontaminants in a specific dredged material have thepotential to adversely effect sensitive, representativeorganisms at the disposal site. As required under boththe CWA and the MPRSA (the “Ocean Dumping Act”),the EPA and COE have set forth consistent,standardized procedures for evaluating potential effectsassociated with dredged material disposal at open watersites, and at certain beneficial use sites. Theseevaluations focus on the specific exposure pathwaysand biological endpoints of concern, and shouldprovide sufficient information for decisionmaking. Insome cases, a rigorous testing regime is required toadequately characterize the ecological risk associatedwith a particular dredged material. This level of effortis often necessary because, for most unconfineddisposal sites, once dredged material is disposed it isdifficult to control the exposure of organisms to thematerial, or to remove it or re-engineer the site torectify any adverse impacts.

Sediment testing is a key aspect of ensuring thatunacceptable adverse effects do not occur as a result ofdredged material disposal at a particular location. Forproper site management, testing must be used inconjunction with appropriate interpretation standards(which will differ for different disposal methods orsites); disposal activity must follow all site userequirements (such as specific timing or volumerestrictions that may be placed on specific sites); and

site performance must be confirmed by appropriate sitemonitoring. Each of these are essential aspects of anoverall Site Management and Monitoring Plan.

Sediment testing is, however, only one element of theoverall decisionmaking process for determiningwhether a permit will be issued for a proposeddischarge of dredged material. A range of otherrequirements must also be met. For example, underSection 404 of the CWA the proposal generally mustbe shown to be the least environmentally damagingalternative that is “practicable” to perform. Thus, ifbeneficial reuse options that would have less adverseenvironmental impacts are available and otherwisepracticable to a project proponent at a given time,unconfined aquatic disposal would not be permittedeven though the dredged material was shown to meetaquatic disposal standards.

The following sections provide a general backgroundon what is involved in sediment testing and how theresults are used in making suitability decisions for thedisposal of dredged material. Detailed descriptions ofpast and current testing practices specific to the SanFrancisco Bay area are included to illustrate the moreimportant regional issues and considerations.

3.2.5.1 Testing for Aquatic Disposal

Sediments may contain contaminants that, ifbioavailable and present in elevated concentrations, cancause adverse environmental impacts. Dredging anddredged material disposal activities may release orredistribute these contaminants in the aquaticenvironment. Nationwide, the majority of dredgedmaterial disposal occurs in inland and near coastalwaters (and thus falls under the jurisdiction of theCWA). As mentioned earlier, it is often difficult tocontrol exposures of organisms to dredged material atunconfined aquatic disposal sites; this is particularlytrue at dispersive locations. While capping withadditional, clean dredged material is usually the maincorrective measure that can be taken at depositionalsites, capping is usually impractical and/or ineffectualat dispersive sites. Therefore, for unconfined aquaticdisposal in general, and for disposal at dispersive sitesin particular, it is especially important that acomprehensive sediment evaluation be conducted toensure that any potential for adverse effects isidentified.

In this section, we describe the fundamental regulatoryand technical bases of dredged material testing foraquatic disposal. This testing uses a tiered, effects-based, and reference-based evaluation structure to



make suitability decisions that are based on adequateinformation, that address appropriate exposurepathways, and that are as cost-effective as possible incollecting the information required. Although thespecific tests (e.g., species and endpoints),interpretation values (e.g., suitability criteria), anddegree and frequency with which testing is needed(e.g., full chemical and biological testing ) may changeas more information becomes available, the basicframework for dredged material evaluations shouldremain the same.

Conceptual Framework

The overall framework for evaluating dredged materialmanagement alternatives is provided in theEPA/USACE document. Evaluation EnvironmentalEffects of Dredged Material Management Alternatives— A Technical Framework (USEPA and USACE1992). Comprehensive guidance regarding sedimentquality testing for offshore (i.e., ocean) disposal isestablished by the Ocean Dumping regulations (40 CFRPart 227) and provided in detail in the joint EPA/COEocean disposal testing manual, titled Evaluation ofDredged Material Proposed for Ocean Disposal —Testing Manual, popularly known as the Green Book(USEPA and USACE 1991). Similar comprehensivenational sediment testing guidance for inland waterswas recently published, titled Evaluation of DredgedMaterial Proposed for Discharge in Waters of theUnited States — Inland Testing Manual (USEPA andUSACE 1998). Both the Green Book and the ITM aretiered under the Framework Document (as well asunder their respective legislation and regulations).

Ocean Disposal

Since it was finalized in 1977, all dredged materialtesting for ocean disposal has followed thecomprehensive guidance laid out in the Green Book.(The most recent update to the Green Book wasconducted in 1991.) Procedures outlined in this manualare designed to meet basic MPRSA requirements forevaluation of potential contaminant-related impacts thatmay be associated with the discharge of dredgedmaterial at marine disposal sites. The Green Book usesa testing approach that is effects-based, reference-based, and tiered (a detailed description of each ofthese concepts is given below). This approach isdesigned to ensure that adequate information isgenerated to satisfy regulatory requirements, withoutforcing applicants to incur unnecessary testing expense.

The evaluation procedure outlined in the Green Bookbegins with determining whether testing is even

necessary based on the availability of sufficient existinginformation. If existing data are inadequate to serve asthe basis for a suitability determination, additional stepsmust be taken to collect the necessary information. Thefollowing discussion will focus on those subsequentsteps that involve chemical and biological testing ofdredged material. The testing framework outlined inthe Green Book involves three basic components:

1. To evaluate the degree of contamination using bulkchemical analysis of sediments;

2. To determine acute toxicity in the water columnand sediment using suspended-phase (elutriate) andsolid-phase (whole sediment) bioassays; and

3. To evaluate the potential for bioavailability ofcompounds that may lead to chronic and/orsublethal effects, or effects at higher trophic levels,using solid-phase bioaccumulation tests.

The degree of testing for any given project is based onseveral factors: a reason to believe that the sedimentsmay be contaminated (as determined in the tieredevaluation process discussed below), the size of thedredging project, the nature of the proposed disposalsite (e.g., dispersive or non-dispersive), and the natureof nearby resources that may be affected by thedisposal. The extent and nature of the testingperformed will also depend on the exposure pathwaysof concern at the disposal site relative to thecontaminants of concern in the dredged material.

In-Bay Disposal

Although sediment testing guidelines for disposal ataquatic sites within San Francisco Bay have evolvedconsiderably over the past decade, testing hashistorically been less comprehensive than therequirements for ocean disposal. Early guidelines forsampling and testing of sediments for disposal withinSan Francisco Bay were provided in the COE PublicNotice (PN) 78-1 (released on July 30, 1978) and laterin PN 87-1 (released in June 1987 by the COE, EPA,and Regional Water Quality Control Board[RWQCB]). Routine testing requirements outlined inPN 87-1 were limited to bulk sediment chemistry and asingle elutriate bioassay for state water qualitycertification purposes. Furthermore, under these testingguidelines, reference samples (used as the point ofcomparison for determining whether sediments to bedisposed are “clean” enough) were taken from thedisposal site itself for comparison with the proposeddredged material (see section on Reference-BasedTesting below for further discussion of reference



sampling issues). Because one project’s disposedmaterial became the next project’s “reference,” overallcontamination levels at the Alcatraz site increased overtime, to the point that “reference” samples for laterprojects were themselves toxic to marine organisms inbioassay tests.

The acknowledged limitations of PN 87-1 testing led tothe preparation of interim testing guidelines for in-Baydisposal presented in the COE PN 93-2 (releasedjointly by the COE, EPA, San Francisco BayConservation and Development Commission [BCDC],and RWQCB in February 1993). PN 93-2 was asignificant improvement over the approach taken in PN87-1, because it moved the reference sampling site forAlcatraz from the disposal mound itself to an“environs” area contiguous with the site but off themound of previously dumped dredged material. Theenvirons approach was intended to stop thedocumented degradation of Alcatraz that was worsenedby using the site itself as the reference. PN 93-2 alsoexpanded the routinely required bioassay testing toinclude the benthic exposure pathway, using a solid-phase amphipod test. However, even this increasedlevel of testing remained less comprehensive incomparison with that required for ocean disposal. Forexample, under PN 93-2 only one bioassay test specieseach is required for the water column and benthicexposure pathways. Furthermore, bioaccumulationtesting is only required in special circumstances whenacute exposures do not provide sufficient informationto evaluate the potential impacts of the dredgedmaterial.

PN 93-2 testing guidelines were explicitly published asinterim measures, and apply to dredged material testingfor in-Bay disposal only until superseded byimplementation of the recently published EPA/COEnational testing manual for inland waters, titledEvaluation of Dredged Material Proposed forDischarge in Waters of the U.S. — Inland TestingManual (USEPA and USACE 1998). The InlandTesting Manual (ITM) updates and replaces the 1976COE document, Ecological Evaluation of ProposedDischarge of Dredged or Fill Material into NavigableWaters, and adopts the same basic framework as theGreen Book, including the tiered testing approach,multi-species benthic and elutriate testing, and 28-daybioaccumulation testing. It is expected once a separaterulemaking process is completed, that it will alsoinclude comparison of benthic test results with those ofan off-site reference sediment. Both EPA and the COEhave acknowledged earlier inconsistencies in testingrequirements between inland and ocean environmentsand that there is a need for comprehensive evaluation

wherever dredged material is disposed. At the time ofwriting this EIS/EIR, the draft ITM has been circulatedfor public comment, and it is expected that the finalversion will be implemented in 1998. Now that theITM has been adopted as a national testing guidancefor inland waters, the agencies will prepare a RegionalImplementation Manual (RIM) that will draw uponboth the Green Book and ITM guidance to providedetailed dredged material testing requirements for SanFrancisco Bay area projects. However, the overalltesting framework included in the ITM and GreenBook, as described in the following discussions, will bereflected in any such regional guidance.

Effects-Based Testing

Effects-based management (as opposed to managementbased on pre-existing numerical standards) involvesbioassay testing using sensitive aquatic organisms as anindication of whether contamination associated withdredged material may cause adverse biological effects.Biological evaluations are particularly important forsediments because chemical measurements alone areusually inadequate to predict the bioavailability, andtherefore toxicity, of sediment associated contaminants(see, for example, Power and Chapman 1992; Long andChapman 1985; Lamberson et al. 1992; Hoffman et al.1994). It is well documented that a given bulkconcentration of contaminant(s) may be toxic in onesediment and not in another due to a variety of abioticvariables governing bioavailability (such as partitioninginto pore water, the chemical form of the compound,the presence of other ions, organic content, andoxidation state of the sediment) (USEPA 1993b).Biological effects testing provides an importantcomplement to chemical analysis because it gives adirect measure of organism response, integrating thebiological and chemical interactions of the suite ofcontaminants that may be present in a dredged materialsample (USEPA and USACE 1994).

The effects-based framework for testing presented inthe Green Book/ITM is based on multi-species testingusing appropriately sensitive organisms. In order toadequately assess the possible impact of contaminantson aquatic communities, it is recommend that testing beperformed using a suite of species to account for thevariable sensitivity among organisms for differentchemicals. Currently, use of at least three sensitivespecies is recommended for the water column(elutriate), and at least two species for the wholesediment exposure pathways. The general types ofbioassays used to evaluate these pathways are discussedbelow.



Water column (elutriate) toxicity tests are designed tomimic the short-term exposures in the water columnthat are associated with active dredging and disposaloperations. There are standardized protocols of theAmerican Society for Testing and Materials (ASTM)for numerous species and endpoints including bivalveand echinoderm larval development, and survival ofmysid shrimp and juvenile fish (ASTM 1989; Ward etal. 1995). Elutriate results are used primarily toevaluate compliance with state water quality standardsand federal water quality criteria, after allowing forappropriate mixing at the disposal site. In addition,these tests provide useful information in the overallevaluation of potential sediment toxicity.

Generally, the greatest potential for environmentaleffects from the disposal of dredged material isassociated with the benthic exposure pathway (seesection 3.2.4). Bottom dwelling (benthic) animalsliving and feeding on or in deposited material forextended periods represent the most likely pathways foradverse ecological effects from contaminated sediment.Thus, the emphasis of dredged material evaluations isusually on estimating effects associated with exposureof benthic organisms to contaminants in beddedsediment. Acute toxicity to various benthic species isused as a measure of the potential for direct effects toexposed organisms, while tissue bioaccumulation is ameasure of the bioavailability and thereby the potentialfor chronic or food web effects (including human healtheffects from eating contaminated seafood) of sedimentcontaminants in longer-term exposures (see discussionof Tier III under Tiered Testing below for furtherinformation on these tests).

Reference-Based Testing

Reference-based testing refers to the practice ofcomparing biological effects and chemical data fromthe dredged material to those from a reference sedimentselected to represent an appropriate and acceptablelevel of environmental quality at the disposal site.What is appropriate to use as a reference will differdepending upon the nature of the disposal site, thesediments being tested, and the disposal sitemanagement approach. In general, reference sedimentis a sediment that is substantially free of contaminants,that is as similar as practical to the grain size of thedredged material and the sediment at the disposal site,and that reflects the conditions that would exist in thevicinity of the disposal site had no dredged-materialdisposal ever occurred (USEPA and USACE 1994).For depositional sites, the reference should be locatedin an environment similar to but out of the influence ofthe disposal site itself, whereas for dispersive sites, the

reference should represent the off-site area in which thedredged material ultimately deposits. In the latter case,the reference may be a site representing the changingconditions of the general water body (e.g., the mostappropriate reference for Alcatraz and other in-Baysites may be site[s] that reflects ambient conditions ineach embayment).

The Ocean Dumping Program has always used an off-site reference as a comparison for suitabilitydeterminations. In contrast, the Section 404 programhas in the past required that reference samples becollected from the disposal site itself. One problemwith the onsite reference approach is that ongoingdisposal will (by definition) create different referenceconditions for every project. Over the long term,comparisons made to an ever-degraded reference canlead to increased site degradation. Exactly thisproblem occurred at the Alcatraz disposal site in recentyears, where chemical and biological testing performedas part of the permitting program indicated markedlyincreased levels of contamination and acute toxicity inreference samples taken from the disposal mound. Thisled, in turn, to even more contaminated sediments beingauthorized for disposal at the site as the next projectwould effectively be compared against the priorproject’s sediment as the new reference condition. Toaddress ongoing degradation at Alcatraz, the agenciesredefined the reference for Alcatraz, in PN 93-2, to be aseries of stations located outside of the disposal mound(the “Alcatraz Environs”). However, the environsreference is still influenced by sediments disposed atthe Alcatraz site, and does not necessarily appropriatelyreflect background conditions in the central Bay.

Another issue associated with reference testing at in-Bay locations is that currently used reference sedimentsoften have grain-size and other critical physicalcharacteristics (e.g., organic carbon content) that arevery different from those of the dredged material beingtested. Thus, it is often the case that chemical andbiological testing results from dredged material havinga high silt and clay component are compared to resultsfrom a reference sample that is primarily comprised ofsand. Currently, there are several efforts underway toidentify and characterize in-Bay sites that could serveas references for natural background conditions inregional monitoring programs. The RWQCB, forexample, through the BPTCP, has been conducting aReference Site Study to identify and characterize fine-grain sediment reference sites in the Bay. Furthermore,the Regional Monitoring Program has been measuringsediment toxicity throughout the Bay at sites with arange of grain sizes, several of which may be able to beused as reference sites for dredged material evaluations.



Tiered Testing

The tiered approach to sediment testing promotes cost-effectiveness by focusing the least effort on disposaloperations where the potential (or lack thereof) forunacceptable adverse impact is clear, and expendingthe most effort on those operations requiring moreextensive investigation to characterize the potential forimpacts. For any particular project, it is necessary toproceed to more detailed (and expensive) testing inhigher tiers only when the previous tier did not result inadequate information for a decision to be made. Thisfollowing paragraphs summarize each of the tiers asthey are currently described in the Green Book andITM.

TIER I. “Tier I” involves the examination of readilyavailable, existing chemical and biological information(including that from all previous sediment testing) todetermine whether there is a reason to believe that thedredged material needs to be tested for potentialadverse effects. Information that may be considered aspart of the Tier I evaluation includes recently collectedchemical and biological data from the site and/oradjacent areas, known sources of contamination such asdischarges or spills, and information on changes in landuse adjacent to the site that might influence sediments(USEPA and USACE 1994). Some dredged materialwill be excluded from any need for testing when thereis no reason to believe that it would be a carrier ofcontaminants.4 Such dredged material typically ischaracterized by large particle size (sand, gravel, orrock), and is found in areas of high current or waveenergy that are far removed from known existing andhistorical sources of pollution. Although most dredgedmaterial from San Francisco Bay does not meetexclusion criteria, it may not require testing if existinginformation is adequate to determine suitability.Furthermore, information collected at this tier may alsobe used for the identification of contaminants ofconcern relative to any testing performed in later tiers.

TIER II. Evaluations performed under “Tier II” providescreening information based on sediment and waterchemistry data. Specifically, this can includeevaluating compliance with state water qualitystandards using a numerical mixing model andestimating the potential for benthic impacts due tononpolar organic chemicals using a calculation oftheoretical tissue bioaccumulation. Though thisscreening information is useful for focusing additionaltesting efforts, at present, it is not generally adequate byitself to support suitability determinations for aquaticdisposal (USEPA and USACE 1991, 1994).

When national sediment quality criteria (SQC) or statesediment quality standards or objectives for individualchemicals are proposed and finalized, they are expectedto be incorporated into Tier II benthic impactevaluations. Comparison of sediment chemical data tonumerical sediment criteria may be useful as ascreening tool to streamline any additional testingrequired (as is currently practiced by the Puget SoundDredged Disposal Analysis (PSDDA) program inWashington). However, due to the complexities ofsediment/chemical/organism interactions and thepotential for unpredictable interactive effects ofcontaminant mixtures, numerical criteria are notexpected to completely replace effects-based testing,including bioassays (Federal Register, January 1994).Currently, national SQC have been proposed for onlyfive priority pollutant chemicals (endrin, dieldrin,fluoranthene, phenanthrene, and acenaphthene). Site-specific numerical screening criteria (Apparent EffectsThresholds [AETs]) are currently being developed bythe RWQCB for San Francisco Bay sediments and maybe potentially useful for screening dredged-material todetermine the level of testing required (see alsodiscussion in section 3.2.5.3).

TIER III. If the evaluation of existing information andstandards is not adequate to determine dredged materialsuitability, a “Tier III” evaluation is necessary. Thistier is comprised of comprehensive chemical andbiological testing of the sediment proposed fordischarge to assess the potential effects of contaminantson appropriately sensitive and representativeorganisms. Standardized bioassay tests are availablefor many different aquatic species, representing variousfeeding/life strategies and biological effects endpointsof concern. Detailed presentation of these protocolscan be found in ASTM (1990), USEPA (1994b), andWard et al. (1995) methods manuals. Measured effectsendpoints include acute toxicity in both sediment andwater column exposures, and the bioaccumulation ofcontaminants in tissue. Although chronic/sublethaltests for sediments are under development, none are yetconsidered suitable for routine use nationwide.

Because dredged material potentially contains a myriadof contaminants that may adversely impact aquaticorganisms, testing using a suite of species is necessaryto fully assess the potential impact of dredged materialon the aquatic community. A minimum of twosensitive species, together representing the threeimportant functional characteristics (filter feeder,deposit feeder, and burrower), are recommended for thewater column and whole sediment toxicity tests. Thereis flexibility in the guidance to tailor the choice ofwhich tests to perform based on the exposure pathways



of concern at the proposed disposal site. Within theconstraints of experimental conditions and the effectsendpoints measured, these biological evaluationsprovide for a quantitative comparison of the potentialeffects of dredged material to the reference station.Generally, dredged material is considered unsuitablefor unconfined aquatic disposal when test organismmortality is statistically greater than reference andexceeds mortality in the reference sediment by at least10 percent (20 percent for tests using amphipodspecies).

Body burdens of chemicals are of concern for bothecological and human health reasons. To assess thepotential for contaminants to bioaccumulate, 28-daytests have been developed using two species havingadequate tissue biomass and the ability to ingestsediments. It is important to remember that tissuebioaccumulation itself is not an adverse impact.Rather, bioaccumulation is used as an indication of thebioavailability of sediment-associated contaminants.Concentrations of contaminants of concern in tissues ofbenthic organisms are compared to applicable Food andDrug Administration (FDA) and other human healthstandards such as local fish consumption advisories.Such comparisons are important, even though theparticular test species may not be a typical human fooditem, because certain contaminants can be transferredthrough aquatic food webs, and because uptake todesignated levels of concern may indicate the potentialfor accumulation in other species (USEPA and USACE1994). The residue-effects information that wouldfacilitate direct ecological evaluation usingbioaccumulation data is not available for manycontaminants of concern.5 Consequently, the followingadditional factors are considered in determining thepotential for adverse impacts associated with benthicbioaccumulation: toxicological importance of thebioaccumulated contaminants, magnification overreference, number of contaminants and the magnitudeof their bioaccumulation, and the propensity forcontaminants to biomagnify within aquatic food webs.

TIER IV. For the majority of projects, Tiers I-III areexpected to be adequate for determining the suitabilityof dredged material for unconfined aquatic disposal. Inthose cases when lower tiered testing is judged to beinsufficient to make complete factual determinations,

then a special, project-specific “Tier IV” evaluation isnecessary. Tier IV involves non-routine sampling ortesting, designed to provide specific information thatcould not be obtained from application of the routinemethods in Tiers I-III. For example, toxicitydeterminations in this tier can involve more intensivelaboratory or field testing, or field assessments ofresident benthic communities. Recently developedprocedures such as toxicity identification evaluations(TIE) and chronic tests may be used in this tier. In allcases, a Tier IV evaluation will generate the specificinformation needed for decisionmaking; there is no tierbeyond Tier IV.

Additional Sampling and Analysis Considerations

Collecting representative samples involves detailedsite-specific consideration of the material to bedredged. Careful consideration of numerous factorsshould be given in the sampling scheme for any project,including historical data, sediment heterogeneity,dredge depth, volume to be dredged, number andgeographical distribution of sites, and potential sourcesof pollution. Minimum sediment sampling guidelineswere outlined in PN 93-2 (to be updated in the RIM)that indicate the number of samples that should becollected for a project of a given volume. Compositingsediment samples from an area into a smaller number ofsamples is allowed for testing purposes. However,samples should only be composited together when theyare from a contiguous portion of the project area andwhen there is reason to believe that these sediments areexposed to the same influences and pollutant sources.To ensure appropriate sampling, all sampling andanalysis plans should be coordinated with theappropriate agencies before any sampling or testingbegins.

Physical and chemical tests are conducted at aminimum on each composite sample. Detailedguidance on sampling and analysis procedures is givenin the Green Book and ITM. Currently, routinesediment physical and chemical analysis is performedfor the list of contaminants in Table 3.2-6. Chemicalsappear on this list based on their toxicologicalsignificance, persistence, and presence in San FranciscoBay sediments.



Based on Tier I information, the required testing forany particular project may include additional chemicalsor, conversely, fewer than those listed in Table 3.2-6.

3.2.5.2 Testing for Upland Disposal

This section describes current requirements, and a moresystematic testing framework under development by theLTMS agencies, for disposal of dredged material atupland sites. A variety of additional upland/wetlandsediment tests have also been developed nationally, andare available for non-routine, site-specific use. Theseinclude tests on effluent discharge quality (to evaluatethe need for controls on return water); tests to estimatesurface runoff quality (to evaluate the need for runoffcontrols such as collection and treatment); tests toestimate leachate quality (to evaluate the need forcontrols to address the potential for groundwatercontamination); and upland plant and animal bioassays(if projected land use is such that this is a concern).Development of detailed engineering designs forspecific new upland sites is outside the scope of thisEIS/EIR. The interested reader is referred to USEPAand USACE (1992) and the references containedtherein for further information about these non-routinetests.

Current Upland Testing Practice

In general, upland testing needs differ from aquatictesting because geochemical conditions in the twoplacement environments differ, and because there aredifferent potential exposure pathways. For disposal atlandfills and other upland sites, an important concern iswith contaminants that may become soluble andmobilize into groundwater or surface water. In general,the soluble portion of contaminants is a small fractionof the total contaminant load. Unfortunately, there isno way to easily predict the soluble portion ofcontaminants from the measured total concentrations.Therefore, since typical aquatic disposal tests measureonly total metals concentrations, data from aquatictesting programs are often inadequate for determiningthe suitability of dredged material for upland or landfilldisposal.6 Instead, landfill disposal testing guidelinesgenerally require that if the concentration ofcontaminants measured using total metals analysismethodology (which measures all forms of the metalpresent, including soluble and non-soluble) exceeds theSoluble Threshold Limiting Concentration (STLC)hazardous waste numerical criteria by a factor of 10,

Table 3.2-6. Routine Sediment Physical andChemical Analysis

Parameter

TargetDetectionLimit (1)

Conventionals Grain size NA

Total organic carbon 0.1 percent TRPH 20

Total volatile solids 0.1 percent Total and water soluble sulfides 0.1

Total solids/water content 0.1 percentMetals

Silver 0.1 Arsenic 0.1

Cadmium 0.1 Chromium 0.1

Copper 0.1 Mercury 0.02 Nickel 0.1 Lead 0.1

Selenium 0.1 Zinc 1.0Organic Compounds

Phthalate esters 0.01 PAHs (2) 0.02 PCBs (3) 0.02

Pesticides (4) 0.002 Butyltins (5) 0.001

Notes: 1. Reported as mg/kg dry weight, unlessotherwise noted.

2. All compounds on EPA Method 610 list.3. Reported as Arcolor equivalents 1242,

1248, 1254, 1260, and total PCB.4. All compounds on EPA Method 608 list.5. Mono-, di-, and tributyltin.



then substantial concentrations of the metal may besoluble and direct measurement of the actual solublefraction is required.

For dredged material to be disposed at an upland sitesuch as a landfill, it generally must be tested undercurrent landfill testing criteria developed to addressmaterial from contaminated soil sites including leakingunderground storage tank sites. Tests that are typicallyrequired include total and soluble metals, and totalorganics including BTEX, PCBs, pesticides,chlorinated solvents, and total recoverable petroleumhydrocarbons (TRPH) as waste oil or diesel. Such testsare often required by landfills in addition to, or withoutany review of the information available from previoustesting, and without specific consideration of thedifferences between dredged material and upland soils.For example, a number of the contaminants routinelytested for are highly volatile, and it is unlikely that theywould occur at elevated concentrations in sediments.

The environmental concerns regarding the placement ofdredged material at upland sites cannot be addressedgenerically. Each type of placement environmentrepresents a unique set of concerns. Consequently,project sponsors must work independently with thevarious agencies involved to develop project-specifictesting protocols, sampling frequencies, and WasteDischarge Requirements for each project. The types oftests required and the sampling frequencies also varywith each landfill. There currently are no standard testsused by all landfills for acceptance of any kind ofwaste. This is largely due to the engineeringdifferences at each landfill. In most cases, a dischargerhas been required to take a given number of samplesand conduct a modified statistical analysis usingmethods outlined in EPA guidance (EPA 1990) to showthat the material (1) is not hazardous; and (2) meets thelandfill’s specific acceptance requirements. Landfillacceptance criteria are determined by the landfill andapproved by the relevant agencies based on thelandfill’s attenuation factors, and the landfill’sproximity to groundwater (especially drinking wateraquifers).

Proposed “LTMS Sediment Classification Framework”

As a basis for the establishment of regulatory guidancemore specifically tailored to dredged materialplacement in upland environments, the LTMS agencieshave developed a draft comprehensive SedimentClassification Framework that describes the suitabilityof dredged material for different kinds of disposaloptions, based on degree of contamination. Under thissystem, the least contaminated material is (chemically)

suitable for the broadest range of disposal options,while the most contaminated material (meetingestablished hazardous waste criteria) must receive veryspecific handling. Appendix F presents this draftSediment Classification Framework. It shows thegeneral relationship between material that is “suitablefor unconfined aquatic disposal” (SUAD material) or“not suitable for unconfined aquatic disposal” (NUADmaterial), and the various existing solid wastecategories that apply to upland disposal or reuse.Appendix F also shows how these categories relate tothe three existing “classes” of landfills.

The draft Sediment Classification Framework does notrepresent new regulation. Instead, it is a presentationof how the existing laws, policies, and definitionsaffecting dredged material disposal relate to each other.The Sediment Classification Framework can, however,serve as a useful basis for development of moreconsistent dredged material management policies,particularly with respect to testing and approval ofmaterial proposed for placement in upland disposal orreuse sites such as existing landfills.

3.2.5.3 Testing for Nearshore Disposal

Nearshore sites can have exposure pathways similar toboth aquatic and upland sites (see section 3.2.4.3).Therefore, testing for placement in nearshore sites caninvolve some of the aquatic and upland tests describedin sections 3.2.5.1 and 3.2.5.2, respectively. Thespecific tests needed will depend on site-specific issuesof concern. Currently, there are no nationallystandardized tests specific to nearshore environmentsthat are appropriate for routine regulatory program use.However, in the San Francisco Bay area, interimscreening guidelines have been developed by theRWQCB for wetland placement of dredged material(Wolfenden and Carlin 1992). The RWQCB interimscreening guidelines use a combination of chemicalscreening levels and bioassay testing to identify whendredged material may be acceptable for use innearshore disposal or reuse sites; in particular, theinterim guidelines specify when dredged material canbe considered for either “wetland cover” or “wetlandnoncover” placement. In general, SUAD sediments areconsidered appropriate for “wetland cover,” whileNUAD sediments must be isolated from the aquaticenvironment as “non-cover” material. Officially-designated hazardous waste, and other highlycontaminated sediments, generally do not qualify foreither “cover” or “non-cover” placement in nearshorewetland restoration sites.



A variety of other upland/wetland sediment tests havebeen developed nationally that can be used in non-routine, site-specific circumstances. These includestests on effluent discharge quality, tests to estimatesurface runoff quality, tests to estimate leachate quality,and upland or wetland plant and animal bioassays.These kinds of tests are not typically used for routineregulatory program purposes because they tend to bemore appropriate for research or “Tier IV”applications, and because they tend to be too expensiveand time-consuming to conduct except in associationwith large projects. Nevertheless, such testing hasoccasionally been conducted for projects in the SanFrancisco region. The interested reader is referred toUSEPA and USACE (1992) and the referencescontained therein for further information about thesenon-routine tests.

3.2.5.4 Opportunities to “Streamline” TestingNeeds

As indicated earlier, it is not expected that the basicsediment evaluation framework or approach fordredged material (discussed in sections 3.2.5.1 and3.2.5.2) will fundamentally change over time, due tothe need for comprehensive evaluation that considerssite-specific exposure pathways and project-specificcontaminants of concern. However, this frameworkprovides for substantial flexibility to address localconcerns, and local experience that is accumulated overtime. There are many possibilities for streamlining thesediment evaluation process, from both an overallmanagement standpoint and a project-specificstandpoint. Some of the possibilities presented beloware already in practice or in the early stages ofdevelopment in the San Francisco Bay area. Thesestreamlining options, and others that may be identifiedin the future, would be implemented through theperiodic review process for the LTMS ManagementPlan, as discussed in Chapter 7.

Development of an Interagency Dredged MaterialManagement Office (DMMO) to coordinatedecisionmaking relative to dredging permits (e.g.,combined application, sampling and analysis planapproval, suitability determination, disposal options).The goal of the DMMO would be to establish apermitting framework that reduces redundancy andunnecessary delays in permit processing and increasesconsensus decision-making among staff of the memberagencies (COE, EPA, RWQCB, BCDC, and StateLands Commission). Thus one result of the DMMOapproach would be to increase consistency regardingwhen and how much testing is required of applicants.Another product of the DMMO would be a combined

database to share regulatory and technical informationamong the agencies, applicants, and interested parties.One important long-term goal of the DMMO thatwould significantly streamline permit coordination isthe creation of a single, interagency dredge permit.

A consolidated Regional Implementation Manual(RIM) for the testing of dredged material for aquaticdisposal will be developed by EPA and the COE, withthe input from other regulatory agency. Under thisRIM, required biological and chemical testing will beconsistent for disposal in both ocean and in-Bayenvironments.

More systematic use of the tiered approach to dredgedmaterial evaluation will be included in the RIM, basedon the GB/ITM. Thus there will be less testing neededfor some individual projects, once a multi-year trackrecord (Tier I) has been established for themdemonstrating consistently clean material (e.g., yearlychannel maintenance projects). Development ofappropriate numerical sediment quality screeningvalues (Tier II) could help to minimize the volume ofsediment that must be tested using Tier III bioassays(e.g., San Francisco sediment quality criteria values arecurrently under development by the SFBRWQCB foruse on a regional basis). In addition there can be moresystematic application of available models as anaffordable screen for potential ecological risk (e.g.,calculation of Theoretical Bioaccumulation Potentialsfrom sediment chemistry samples can minimize theneed for more costly bioaccumulation testing).

Improve coordination of upland testing requirements.Agencies have already made progress toward moreconsistent upland testing requirements. The SedimentClassification Framework (section 3.2.5.2) could alsoserve as a basis for further streamlining by otheragencies. For example, the state Integrated WasteManagement Board could consider the equivalent of ageneral permit for the use of certain defined categoriesof dredged material as an alternate source of dailycover at landfills.

Over-design any new sites to minimize testing. Locateand design placement sites so that exposure to potentialcontaminants is already controlled to reduce testingneeds. For example, less testing would need to beconducted by individual project proponents if theirmaterial is proposed to be used for landfill daily cover,wetland non-cover, or in confined aquatic disposal siteswhere most pathways of concern were alreadyaddressed in the design of the disposal site.



3.2.6 Management of Contaminated DredgedMaterial

This section discusses the kinds of management optionsthat are appropriate for handling contaminated (NUAD-class) dredged material. These discussions apply tosediments that are not classified as Hazardous Waste;remediation or management of in-place sediments thathave Hazardous Waste levels of contamination isoutside the scope of this EIS/EIR.

Appropriate dredged material management involves acomprehensive evaluation of sediment quality,available disposal or placement options, controlmeasures tailored to address specific issues of concern(project-specific contaminants of concern, site-specificexposure pathways), monitoring needs, and the abilityto take corrective site management actions if necessary.It is important to keep in mind that the presence ofcontaminants per se does not automatically mean that asediment is unsuitable for a particular disposal option.As discussed in section 3.2.3.4, the great majority ofsediments dredged from the San Francisco Bay/DeltaEstuary would not pose a threat of significant adverseeffects at most potential disposal sites, even thoughmany of these sediments contain levels of contaminantsthat are somewhat elevated over natural “background”and basin-wide ambient values. However, whensediment contamination is high enough to requirespecific management, it is important that appropriatelydesigned sites are available.

There are currently few multi-user sites available forthe disposal of contaminated sediment. No multi-userconfined disposal facilities (CDFs) and no confinedaquatic disposal (CAD) sites currently exist in theregion. When portions of a dredging project aredetermined to be unsuitable for unconfined aquaticdisposal (NUAD-class material), sponsors often havethe option of retesting the material at a higherresolution (e.g., with more closely spaced sampling) inorder to identify the minimum volume of materialrequiring confined disposal. Once the problem area hasbeen delineated, in some cases the sponsor will elect toleave that material in place if the project can be madeto function without dredging that particular location.Other sites require that the problem material beremoved to facilitate the use of the site.

If NUAD-class material must be dredged, disposalopportunities are currently limited to upland disposalinto landfills (such as the Redwood Landfill in MarinCounty), discharge into a confined upland site arrangedfor by the individual project sponsor (for example, onethat can be established on their own property, such as

the Port of Oakland’s Galbraith site), or in some cases,reuse as fill in an otherwise approved constructionproject.

There are three main approaches that can be taken tomanage dredged sediments that do not qualify forunconfined aquatic disposal. Each of these is discussesin the subsections that follow. The first approachdiscussed is isolation of the dredged material in a CADsite. The second is isolation of the dredged material ata confined upland disposal site. Confinement atproperly designed aquatic or upland sites is generallytechnologically feasible and appropriate formanagement of dredged material that ranges in quality,and a number of disposal options are discussed undereach of these general headings. The third optionavailable for dealing with contaminated sediments istreatment to reduce contamination levels or to renderthe contaminants unavailable. Treatment can allowsediments that would otherwise require high-costdisposal to be suitable for lower cost disposal options.Although treatment is usually expensive, and in generalis not feasible for large volumes of dredged material ormaterial with relatively low concentrations ofcontaminants, it remains a viable option for smallvolumes of highly contaminated material. Again, anumber of treatment options are discussed under thegeneral treatment heading.

3.2.6.1 Confined Aquatic Disposal

Confined Aquatic Disposal (CAD) is a term used todescribe the general category of options that relate tothe sequestering of contaminated sediments in theaquatic environment, so that they are physicallyisolated from aquatic organisms and so that they remainin a saturated and chemically reduced state. In theCAD process, contaminated material is sequestered(usually by placing it in an environment that is lowenergy, or “depositional”) and then capping thecontaminated material with clean material so that it isisolated and aquatic organisms are not exposed to it.Several CAD projects have been successfullyconstructed internationally and around the country,including on the west coast in Los Angeles Harbor andPuget Sound. However, CAD has not been conductedto date in the San Francisco Bay area. The COE andEPA are currently finalizing a major national guidancedocument on CAD. This document, Guidance forSubaqueous Dredged Material Capping (Palermo et al.1995) addresses many of the detailed siting, design, andenvironmental impact issues associated with CADprojects. In addition, the lead author of the nationalguidance document has prepared an evaluation paperfor LTMS on issues specific to any consideration of



CAD in the San Francisco Bay area. This evaluation ispresented as Appendix G, Confined Aquatic Disposal(CAD) in San Francisco Bay — General Discussion ofEnvironmental Impacts and Issues. The followingparagraphs provide an overview of some of the issuesin Appendix G, and in the COE/EPA national guidancedocument.

Types of CAD

The options under this general heading include reuse asnon-cover material in wetland creation/restorationprojects, disposal into a confined site such as asubmerged pit, depression, or other lateral confinement(true CAD sites), level bottom capping (CAD withoutstructural lateral controls) and the creation of nearshorestructures such as marine terminals, harbors, parks, orother fill projects where the sediments to be isolatedwill remain saturated and reduced. Nearshore CADsites (such as tidal wetlands sites) can potentially beplaced in high energy areas as long as the associatedcontainment structure (marine wharf, breakwater, levee,etc.) is designed specifically for that environment.

Siting and Design Issues

There are a number of potential risks that must beaddressed when considering CAD projects. Theserelate primarily to (1) whether an appropriate site hasbeen chosen so as to minimize impacts to aquaticresources during construction and/or due to any loss ofexisting environmental values; and (2) whether allappropriate design and operational measures have beenidentified, considering the physical characteristics ofthe chosen site. It must be well documented that thesite can adequately isolate the contaminated material,and that any change in contour caused by filling theCAD site will not change its character to an erosionalone. In addition, the site must be set aside in an areathat will remain free of dredging, shipping, mooring, orother activities that could compromise the ability of thecap to isolate the NUAD material at the site. Similarly,the engineering and initial site investigations must berigorous and conservative to ensure that all appropriatedesign needs have been identified and incorporated.Long-term monitoring and management of the site mayalso be required. If the cap is found to be insufficientor failing over time, mechanisms must be in place toidentify and rectify the problems.

Cap Design

A generalized cap design includes a 1-foot coverthickness as a chemical seal to prevent long termrelease through diffusion of contaminants, and an

additional 2-foot cover thickness as a biological seal toprevent burrowing aquatic organisms from beingexposed to the contaminated material. Mixtures of siltand clay in the initial foot of cap to act as an effectivechemical seal and a sand final cap to help preventerosion are often incorporated into cap designs at openwater CAD sites. However, these are only generalguidelines for cap design; site-specific information onthe physical and biological environment is needed todetermine the appropriate design criteria to take intoaccount project-specific conditions (Palermo et al.1995).

Material Appropriate for Use at a CAD Site

There is sometimes a public perception that CAD is thedumping of Hazardous Waste into the aquaticenvironment. This is not the case; in fact, HazardousWaste must be handled in very specific ways (seesection 3.2.5.2), and is not appropriate for disposal atCAD sites. However, NUAD Category I and IImaterial, and in some circumstances NUAD CategoryIII material, would generally be suitable for non-covermaterial in CAD sites (when NUAD Category IIImaterial contains high concentrations of soluble orhighly toxic contaminants, it would not be suitable forCAD).

CAD requires that contaminated material be dredgedand placed in a manner consistent with theenvironmental risk posed by the material. For example,if the contaminants in a material are shown to beleachable to the extent that water quality objectiveswould be exceeded during initial placement, thenspecial precautions such as silt curtains, or placing thematerial into geotextile tubes prior to disposal, may berequired. If application of the available managementtools would not adequately minimize risks, the materialwould not be suitable for placement at the CAD site.Any CAD site proposed for the Bay area in future yearswould require that all appropriate siting and designstudies be rigorously conducted, and it will beimportant to conduct a focused public outreach effort toidentify and fully address public concerns.

Potential Benefits of CAD

Sequestering certain contaminants in the marineenvironment can be considered beneficial. Certainmetals, for example, can become soluble and thereforeavailable under the acidic conditions that can occur inlandfills or other upland sites. Where disposal in theupland environment could result in acidic conditions,the buffering capacity of the estuarine environmentwould significantly reduce the risk that metals would be



released (see section 3.2.4). In addition, through theaerobic biological breakdown process, contaminantssuch as PCB and DDT can be converted to even moretoxic intermediates than the parent compounds.Material sequestered in the aquatic environmentundergoes mainly anaerobic degradation, which occursmuch more slowly and can result in less toxicintermediates.

Once completed, in many cases CAD sites can beconverted into beneficial habitat for fish and wildlife,including special status species. One example wouldinclude a multi-user CAD site that is designed tobecome a nesting island after capping. Another wouldbe a CAD site that becomes a shallow water foraginghabitat for the California least tern; such a project wasrecently constructed in the Los Angeles Harbor (Pier400 Design Consultants 1995). Similarly, wetlandhabitat creation can be accomplished using NUADmaterial as non-cover material (a form of CAD), as hasbeen proposed for the Montezuma Wetlands Project(USACE and Solano County 1994). Coupling habitatimprovement with CAD would be consistent withexisting plans and policies, and could serve the dualpurpose of reducing contaminant risk while improvingenvironmental quality by restoring or creatingimportant habitats.

3.2.6.2 Confined Upland Disposal

Confined upland disposal is a term used to describe thegeneral category of options that relate to thesequestering of contaminated sediments in the uplandenvironment. Material is removed from the aquaticenvironment and sequestered in an upland site that isdesigned to manage the physical and chemicalpathways associated with the material. The appropriatedesign for an upland disposal site depends on the extentof the contamination in the dredge material, thematerial’s physical properties, and the location of theupland disposal site. Land placement of dredgedmaterial presents a set of testing and policy issuesdifferent from aquatic disposal, because thecontaminant exposure pathways and other managementconcerns differ for upland sites. The action ofremoving NUAD-class dredged material from theaquatic system and placing it on land does not, byitself, necessarily reduce the potential forenvironmental impacts. Instead, land placementpresents a new set of environmental concerns,associated with oxidation/acidification, dust and odornuisances, and leaching of heavy metals and salts. Onthe other hand, land placement presents an opportunityto reuse dredged material in beneficial projects. Theseopportunities include reuse as daily cover, liner, and

levee material in landfills; and reuse as fill in approvedconstruction projects. If beneficial reuse cannot beaccomplished on a particular project, remaining optionsinclude disposal at dedicated upland CDFs or Class I, II(Subtitle D), or III landfills.

Landfill Reuse and Disposal

Due to environmental concerns and site volumelimitations associated with in-Bay disposal of dredgedmaterial, there has been particular interest in disposalor reuse of dredged material at landfills. Althoughplacement of dredged material in landfills often facesseveral obstacles, projects undertaken at four Bay arealandfills7 demonstrate that reuse of dredged materialcan be environmentally and economically feasible here.A report prepared by BCDC (1995a) for LTMS on thepotential for dredged material reuse at landfillscontained the following conclusions andrecommendations:

1. Sixteen of the 127 landfills studied were identifiedas highly feasible for accepting dredged materialfor reuse projects. These 16 landfills have acapacity to accept over 5 mcy of dredged materialper year over the 50-year planning period for reuseas landfill daily cover and capping material.

2. Rehandling facilities need to be established to drydredged material for reuse or disposal in landfills.

3. Segregation by grain size to obtain lowpermeability material should be a priority inconsideration of the final design of the rehandlingfacility and during dredged material placementoperations.

4. Testing requirements for upland reuse and disposalare different than those for aquatic disposal.Testing guidelines need to be developed for uplandreuse and disposal.

5. Guidelines on the pollutant levels appropriate fordisposal and reuse projects should be developed.

Items (4) and (5) involve establishing coordinatedpolicies for testing and interpretation, as discussed insection 3.2.5.2.

Reuse as Construction Fill

The primary consideration in reusing NUAD-classmaterial as fill in approved construction projects isensuring that the potential exposure pathways ofconcern are adequately addressed in the design of the



construction project. Often, constructions fills that willbe paved or otherwise capped with an impermeablesurface can adequately control for infiltration andleachate into groundwater, without the need for specialliners or other control mechanisms, especially if theNUAD-class dredged material can be incorporated intothe overall fill project in such a way that it issurrounded on all sides by clean fill. Also, dredgedmaterial must typically be dewatered (e.g., at arehandling facility) before it can be use as fill in anupland construction project; however, dewatering firstis not always necessary for nearshore fills.

Dredged material being considered for reuse asconstruction fill must also have acceptable engineeringqualities for the particular project — for example, fine-grained silts may not be physically suitable if the fillmust bear heavy loading. Sands are generally moreversatile for use in fill projects; several sand miningcompanies dredge natural sand deposits in the Estuaryspecifically to sell the material for aggregate or for fill.

Dedicated Confined Disposal Facilities

A dedicated CDF is a site constructed specifically fordisposal of dredged material. While CDFs can be usedfor disposal of either SUAD- or NUAD-class dredgedmaterial, it is anticipated that CDFs in the Bay areawould be used primarily for NUAD-class dredgedmaterial that cannot be disposed at other sites, andcannot be reused. The availability here of acceptablesites for unconfined aquatic disposal of SUADmaterial, in addition to an emphasis on reuse ofmaterial whenever possible, would make confineddisposal of SUAD material unlikely.

There are no multi-user CDFs at this time in the Bayarea. However, any CDFs constructed in the future forNUAD-class material will have to address many of thesame siting and design issues as rehandling facilities.In particular, CDFs would have to be designed tocontain and isolate the worst-case material that couldbe permitted for disposal there. It is therefore likelythat new CDFs would include some form of liners,surface water control, and other measures to addressthe potential contaminant exposure pathways associatedwith the particular site.

3.2.6.3 Treatment

In treatment processes, contaminants in sediments aredestroyed, significantly reduced, or converted into lessreactive or available forms. Treatment in itself is not adisposal option. However, in some cases treatment canreduce the volume of sediment requiring disposal at

more expensive or restrictive sites or can make thematerial suitable for some kinds of beneficial reuse,thereby reducing potential liability concerns for thedredger. Treatment in general is consistent with agencypolicies regarding the reduction of wastes, recycling,and minimizing landfill disposal. It is also possible thattreatment methods such as soil washing to reducesalinity could make SUAD materials from marine-influenced areas suitable for use on Delta levees.

In general, dredged NUAD sediments havecharacteristics unique from contaminated soil,including higher water content and significantly lowercontaminant concentrations, combined with largervolumes of material. These characteristics oftenpreclude many existing soil remediation techniquesfrom being applicable and/or cost effective for use withdredged NUAD-class sediments, as discussed in detailin the LTMS report Analysis of RemediationTechnologies for Contaminated Dredged Material(LTMS 1993a). The kinds of potential treatmenttechnologies evaluated in that report include:

• Biological treatment;• Alkaline stabilization;• Incineration;• Encapsulation;• Other chemical treatment methods; and• Salinity reduction.

Presently, the most cost effective method of disposalfor NUAD material may be to reuse it in a beneficialapplication that would require minimal or nopretreatment. Reuse as landfill daily cover or linermaterial, isolation within wetland restoration projects,or isolation in upland or nearshore constructionprojects are currently more practical than remedialtreatment. However, new technologies may bedeveloped that would facilitate the practicality ofremediation of NUAD material in the future.

Even today, treatment of contaminated sediments maybe practical and feasible for the rare project with highconcentrations of a single pollutant. However, avariety of issues would affect any such decision. Thereis often a diminishing return for treatment costs whencontaminant concentrations are not very high. Fordredged material, treatment is usually most effective inreducing highly contaminated material to moderatelycontaminated material. Treatment of moderate or lowconcentrations of contaminants becomes a moredifficult and intensive effort. Agencies and projectproponents must consider numerous factors includingthe following: current contaminant concentrations;target concentrations; differences in disposal costs;



reduction of liability; treatability of the contaminantspresent; effectiveness of treatment (no treatmentprocess is guaranteed to achieve target levels in allcases); delays in obtaining approval for the treatmentprocess; delays caused by the treatment itself;availability of appropriate places to carry out thetreatment process; and other concerns. The economicsof treatment can be complex but, in general, the morecostly the initial disposal option, the more attractivetreatment becomes. For example, if material isdesignated as a Hazardous Waste, the landfill feesalone could range from $90 to $150 per ton. In such aninstance treatment that costs, for example, $60 percubic yard, with subsequent disposal into a Class III orII landfill at greatly reduced costs, can make treatmentdesirable if allowable under regulation. However,certain materials cannot be treated easily and, underexisting laws, Hazardous Waste is subject to stateDepartment of Toxic Substances Control (DTSC)permit requirements.

In the long run, treatment is a potentially valuable tool.From a policy standpoint, treatment is encouragedwhen it would be feasible and effective. However, thevalue of treatment must be assessed on a project-by-project basis.

3.3 STATUS OF DREDGED MATERIALDISPOSAL TODAY

In the past, management of the dredged materialgenerated by projects throughout the Estuary waseffectively piecemeal and reactionary, rather thancomprehensive and planned. Options to reduceunconfined aquatic disposal within the Estuary werelimited by the general lack of alternative placementsites for large quantities of material. Opportunities torealize environmental benefits by reusing dredgedmaterial as a resource — rather than handling it as awaste to be disposed of — were also limited by the lackof available reuse sites, the lack of coordinated agencypolicies, and financial disincentives to dredging projectsponsors. The planning and financial responsibilitiesfor appropriate management of dredged materials thatcould not be disposed at unconfined aquatic sites(NUAD-class materials) were typically left to projectsponsors to address on their own. Together, theseproblems have helped to make dredging, and disposalof dredged material, expensive, unpredictable and, inthe eyes of the public, environmentally questionable.

To a large extent these problems remain today, and thepurpose of this programmatic Policy EIS/EIR is todevelop and select an overall Long-Term ManagementStrategy that addresses these kinds of concerns.

However, in some ways, the situation is alreadyimproved. The recent designation of an appropriateocean disposal site has given the region its first true,large-scale, multi-user alternative to disposal within thewaters of the Estuary. Beneficial reuse of dredgedmaterial has also been occurring to a much greaterextent: several million cubic yards of sediment fromthe Port of Oakland Deepening Project have gone intoconstruction of endangered species habitat at theSonoma Baylands Wetlands Enhancement Project, andto the upland Galbraith site, which will be returned to arecreational site (a golf course) following dewatering ofthe dredged material. In addition, a demonstrationproject for reusing dredged material for leveemaintenance and stabilization was recently conductedat Jersey Island in the Delta. Even NUAD-classdredged material has been beneficially reused for dailycover and other uses at the Redwood Landfill. There isalso the potential to leverage funding with otherprograms that have overlapping interests and goals,such as the use of dredged material for habitat and/orlevee projects pursuant to the Bay-Delta CALFEDprogram (see section 2.2.5). Nevertheless, the greatmajority of dredged material from San Francisco Bayarea dredging projects continues to be disposed at theexisting in-Bay sites today. The current disposal sites,their current management, and the distribution ofdredged material placement within each environment,are described in Chapter 4 (Affected Environment) andin Chapter 5 (Development of Alternatives).

3.4 SUMMARY

This chapter has presented a basic description of thedredging process, the important physical and chemicalfactors that determine whether disposal of dredgedsediments is of concern in the different placementenvironments, the approaches used to evaluate dredgedmaterial, and the numerous ways in which



dredged material can potentially be disposed andreused safely. The next chapter presents a descriptionof each of the affected environments — the Estuary, theuplands, and the ocean — and identifies those specificresources that are potentially affected, beneficially oradversely, by dredged material disposal and reuse.

Footnotes for Chapter 3:

1. Considering the total volume of dredged material disposed at in-Bay sites annually compared to the volume ofsediment resuspended and transported by waves and currents, and assuming that settlement is equally likely to occuranywhere within the system, resettled previously-dredged material probably makes up no more than about 5 percentof all the sediment that needs to be dredged annually in the Bay/Delta. It is possible, however, that previously-dredged sediments may be a significant source in very specific, local situations such as the Mare Island Strait shipchannel.

2. For example, the Containment Site Committee report estimated that 10 mcy of dredged material needingcontaminant-related management restrictions would be generated in the next 10 years. This included an assumed 2mcy from the Port of Oakland -42-foot deepening project, and 1 mcy from the Port of Richmond -38-footdeepening project. Actual volumes of sediments needing management restrictions from these projects were laterfound to be lower: approximately 1.1 mcy and 0.2 mcy, respectively.

3. It is also likely that fines resuspended from other locations throughout the estuary, some of which will have greatercontaminant loadings and some of which will have less, will mix with and settle in the same depositional areas,significantly diluting the fines originating from dredged material. Nevertheless, any contaminants in dredgedmaterial eroded from dispersive in-Bay sites will add to the overall “background” contamination at depositionalsites throughout the estuary, and maximize the potential for aquatic organisms to be exposed to them, rather thanremoving them from the system.

4. The ITM recommends that the interval between re-evaluation of Tier I data should not exceed 3 years or thedredging cycle, whichever is longer. If there is reason to believe that conditions have changed, then the timeinterval for re-evaluation may be less than 3 years (USEPA and USACE 1994).

5. Recently, agency efforts have intensified to compile, into a comprehensive database, information on the adversebiological effects associated with tissue residues of contaminants. This information will be used in interpretingbioaccumulation data as they become available.

6. An exception is when return water flows from an upland site back into a water body. This circumstance is regulatedunder Section 404 of the CWA, and typical aquatic tests do address this issue.

7. BCDC (1994) discusses dredged material reuse projects at the Redwood and Tri-Cities landfills. In addition,dredged material has been reused as capping material at West Winton and Winton Avenue landfills in Hayward,California.



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CHAPTER 3.0 DREDGING AND DREDGED MATERIAL … · 2013. 2. 20. · dredging equipment. Hydraulic dredging can virtually eliminate disturbance and resuspension of sediments at the dredging