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DREDGING AND DISPOSAL OF CONTAMINATED MARINE SEDIMENT , FOR THE U.S. NAVY CARRIER BATTLEGROUP HOMEPORT PROJECT. EVERETT WASHINGTON Edward Lukjanowicz, U. S. Navy J. Richard Paris, U. S. Navy Paul F. Fuglevand, Hart Crowser, Inc. Gregory L. Hartman, Ogden Beeman & Associates, Inc. ABSTRACT In April 1984 the U.S. Navy selected the East Waterway of Port Gardner Bay in Puget Sound as the homeport site for a carrier batt~egroup. Construction involves dredging over 3.3 million yd of sediment; approximately 928,000 yd of it is treated as contaminated. The Navy selected and has received permits to proceed with in-water disposal of the sediment using a method identified as confined aquatic disposal (CAD). Using the CAD technique, contaminated sedi- ment will be deposited in depths of 400 ft and capped with uncontaminated sediment to isolate contaminants from the aquatic environment of Puget Sound. This summary case study, discusses the development of the CAD option and the stringent environmental monitoring requirements imposed on this disposal technique by federal and state regulatory agencies. These requirements are intended to safeguard ecologically sensitive Puget Sound and gather technical information on the effectiveness of CAD in deep water. OVERVIEW This summary case study draws from the many reports completed for this project. The primary documents are draft environmental impact statement (DEIS), November 1984 final environmental impact statement (FEIS), June 1985 sediment testing and disposal alternatives evaluation, June 1986 public notice of Section 404 permit, October 1986 draft supplements to FEIS (DSEIS), July 1986 final supplements to FEIS (FSEIS), November 1986 final dredging and disposal monitoring plan, phase I (Monitoring Plan), November 1987 plans and specifications, environmental monitoring of dredge/disposal activities (Monitoring P&S), November 1987 462

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463 Additional environmental and engineering studies have been undertaken and completed by the Navy. Some of these studies address the following topics: · disposal site bioturbation, · homeport master plan, · homeport soils analysis, · air quality modeling, · slope enhancement for fisheries, · seabird survey, · crab surveys (ten seasonal trawls), · CAD site benthic analysis, sediment sampling and analysis, characterization of East Waterway sediments, water column chemistry, physical model of East Waterway, confined aquatic disposal (CAD) feasibility analysis, Port Gardner bathymetric survey,- Port Gardner current measurements leachate/sediment settlement tests dump modeling, navigational plans for accurate sediment placement, preconstruction/construction/post-cons true tion CAD site monitoring plan, · Smith Island Upland-Dredge Disposal Feasibility Study & Evaluation, re-characterization of P-lll and P-905 sediment (clean/contaminated), · geochemical evaluation of Norton Terminal, · biological assessment for marine mammals, and · biological assessment for bald eagles. Project Development The proposed project site is located in Puget Sound within the city of Everett, Washington. The site is located on the east side of Port Gardner Bay, just wes t of the central downtown area. Deep water for navigational purposes is available near the site, although dredging of the East Waterway would be required. Operation of a carrier battlegroup homeport at the site would require newly constructed facilities to accommodate 13 ships including the aircraft carrier U.S.S. Nimitz, plus up to 10 additional small craft needed for support services. Location of a homeport facility at the 117-acre site in Everett would require construction of many support facilities. it snips ~nclu~lng ~ ~ ~ ~ ~ .

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464 Dredging and Disposal Preferred Alternative Dredging of the East Waterway will be completed to depths necessary to accommodate homeported vessel drafts. All dredging will daylight to deeper depths into Port Gardner. No dredging or disposal will be done within designated "fish" windows from December 1 to June 15 of any con- struction year. Dredged material will be disposed of at the proposed CAD site, which is located in water depths of approximately 310 to 430 ft in Port Gardner, and which will impact an area of approximately 380 acres (Figure 1~. 3 Total dredging volume is estimated at 3,305,000 yd , including 1 ft of overdepth. Of the total dredged volume, approximately 928,000 yd3 of materials will be treated as contaminated, although only 486,900 yd of in situ contaminated sediments exist. They contain organics, such as decomposed sawdust and wood chips, oils, grease, and industrial contaminants, such as polyaromatic hydrocarbons and polychlorinated biphenols.3 Within the total dredge volume, approximately 2,377,000 yd are clean native materials and will be removed from the East Waterway to be used as cap and mound materials at the CAD site. The dredging volumes presented are estimates based on data from various studies. Actual dredging volumes may differ slightly due to minor variations encountered during construction, or any redefinition by regulatory agencies. Standard equipment and methods will by used for dredging and dis- posal. Contaminated material will be dredged and disposed of using clamshell, tug, and bottom dump scow to ensure minimum induced tur- bidity and maximum compaction of contaminant mass on the bottom. Hydraulically dredged, native uncontaminated material will be used as capping material, the release rate and density of which will be con- trolled to prevent displacement of the deposited contaminated sediments through use of a floating pipeline with submerged diffuser. The sequence and placement of the dredged materials into the CAD site are shown in Figure 2. The Dredging operation will begin by removing approximately 500,000 yd of uncontaminated material from the area of the carrier pier and breakwater. This material will be dredged by clamshell dredge and disposed of in such a manner as to 3 create a mound (1~. Contaminated material (approximately 97,000 yd ~ will be dredged and disposed of in a similar manner and placed (2) to the "uphill" side of the mound. Immediately thereafter, this material will be capped (3) using approximately 239,000 yd of uncontaminated material. Capping will be by hydraulic pipeline dredge with disposal by submerged discharge. It is anticipated the cap thickness will be in excess of 3 ft. The foregoing will complete the first year's dredging. Second- year dredging consists of approximately 831,000 yd of contaminated material and will be dredged by clamshell and disposed of by surface bottom dump barge (4~. Finally, and in sequenced manner, 1,638,000 yd of uncontaminated material will be hydraulically dredged and disposed of by pipeline as represented by (5~. It is anticipated the final minimum capping thickness over contaminated material will be 4.5 ft.

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465 —20 ~ PROJECT | BOUNDARY—j i V ~ ~ _ ant ~ {: ~ \ ~ BOUNDARIES OF CONTAMINATED / ~ ~ /// l \ \ \ To AND UP / ~ ~ ~ 1/ \ \ \\ DREDGE DEPOSITS \ An\ \~PPROXIMATELY~=RES~ ~ ~1/ \\ \ \ ~ / / \\ \ ,'~-' -_ / ~r 1ST YEAR CONSTI `~ \ \ , / / _ ~ by; `} BOUNDARIES OF CONTAMINATED \ X / / ~ ~ \ / ~ [A AND UN~AMINAlED \____ - W~ / DREDGE Do icy/ -EGG ~~//? act/ l SCOTT PAPER //// OUTFALL SCALE IN fEET 0 800 1, 600 FIGURE 1 Revised application for deep confined aquatic disposal.

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466 -310.0~ (a) Uncontaminated Material Mound Conte~neted Materis' Uncontarransted Material CaD (I Contaminated rJlaterial @) Uncontaminated Material CaD T4.5 ,@ -430.0+ hi, FIGURE 2 CAD site final consolidated section. I, SEDIMENT ASSESSMENT AND EVALUATION Contaminated Sediment Section Distorted Not to Scale The contaminated sediment consists of the upper layer of sediment in most areas of the harbor ranging from O to 7 ft in thickness. It is composed of fine-grained, black to dark brown, odorous surface sediment including abundant wood fragments, chips and sawdust. The contaminants include oil and grease, heavy metals, polyaromatic hydrocarbons (PAH), and polychlorinated biphenyls (PCB). Although the disposal of dredged materials does not fall within the purview of the Resource Conservation and Recovery Act (RCRA), the act's definition of hazardous waste is useful as a basis of comparison. Extensive laboratory testing (FEIS, DSEIS) has shown that contamination levels in these sediments are well below the concentration associated with hazardous waste designation under RCRA or related Washington State Dangerous Waste Regulations (Chapter 173-303, Washington Administrative Code). However, certain contaminant levels do exceed background levels in Port Gardner and, to a lesser extent, biological effects thresholds observed elsewhere in Puget Sound; therefore, capping of the contami- nated sediments is proposed as a means to isolate them from surrounding waters .

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467 `_ ., ./ . . . it. ,~\ MAY SCALE IN YARDS o 1.000 2.000 D - doing Area ^cA-~c-~ Open Water Sites Nearshore Sites ~f~ Upland Sites PORT GARDNER PSD DEEP LTA S E ~ CAD SI" - APPUCAT10— FOR DEEP CAD SITE POW GARDNER DISPOSAL SITE ; _ _~5~" Her - an_ ~ U;i~1:IL '=~ 0~- . ~ Bend ,_' . 67~ . FIGURE 3 Dredging area and alternative disposal s ites . SNOHOMI: RIVER DELTA my' ~ .--. __ A-. ~ 1:,`~.L~ I —_:L it' [-(AL, ~11 lit, 1 ~ I ' ~ '- N1\ .-r .~e :~. !:1 // Source: NaAA Chan 18443. 1982

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468 Uncontaminated Soil The uncontaminated soils are exposed south of the south mole and underlie the contaminated sediments in the harbor area north of the south mole and in limited areas east of the carrier pier. They range in thickness to greater than 50 ft and are composed mainly of native materials in the form of gray and brown sandy silt. Some organic mater- ial and wood fragments/chips are present in small amounts in certain areas. Chemical and biological analyses have shown that these sedi- ments meet requirements for unconfined open-water disposal in Port Gardner. Sediment Chemical Characterization In June 1984, a contaminated sediments assessment program for the East Waterway of Everett Harbor was developed by the Seattle District, Corps of Engineers (COE) in coordination with key federal and state agencies. Nineteen stations in East Waterway were sampled in July 1984 by the COE using a vibracore sampler. Sediment cores were recovered for depths up to 15 ft. Sediment horizons were visually characterized and subsamples taken for chemical analysis. By comparison to the only Puget Sound sediment criteria in existence at that time, the surface layer of harbor sediment was judged to be unacceptable for unconfined open-water disposal. All chemical values of the native sediment layer were below the reference criteria, and met the chemical guidelines for open-water disposal. In June 1985, contaminated sediment samples were collected from 16 stations inside the East Waterway and combined to form 8 yd of com- posited sample, which was provided to the C8E Waterways Experiment Sta- tion (WES) for physiochemical testing: ~ yd of native sediment was also collected for testing. Subsamples of the composite and native sediments were provided to the Battelle Pacific Northwest Laboratory (PNL) for separate chemical and biological testing. Priority pollutant analysis of the composite sediment sample col- lected in the East Waterway by the COE (Table 1) indicated the presence of 33 sediment contaminants of concern. These compounds included chro- mium (Cr), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), lead (Pb), cadmium (Cd), mercury (Hg), polychlorinated biphenols (PCBs), polynuclear aromatic hydrocarbons (PAHs), and 1- and 2-methylnaptha- lene. Chemically Related Dredge Disposal Considerations CAD Standard Elutriate tests were conducted by the COE on the previously noted composite sample of sediments collected from the East Waterway (DSEIS). This-information was then used to estimate the potential for dissolved contaminant release to the water column during open-water placement of

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469 dredged materials (CAD alternative). Elutriate testing indicated that only 7 of 33 contaminants of concern were detected in the elutriate water: copper (Cu), mercury (Hg), cadmium (Cd), lead (Pb), chromium (Cr), nickel (Ni), and PCB-12S4. Of these, only the latter five ex- ceeded Port Gardner background levels. Dissolved concentrations of nickel, lead, and PCB-1254 exceeded EPA water quality criteria. The standard elutriate procedure was modified to obtain estimates of total contaminant concentrations associated with mass release to the water column during dredging and open-water disposal (CAD) of East Waterway sediments. Results of these tests revealed that concentra- tions of total Ni and Pb slightly exceeded the measured dissolved con- centrations of these metals (i.e., IS ~g/liter dissolved versus 17 g/liter total for Ni, and 28 ~g/liter dissolved versus 30 g/liter total for Pb). Thus undiluted, the effluent concentration of these two metals would exceed EPA water quality criteria. The total concentration of PCB 1254 was observed to be less than the dissolved concentration (i.e., 0.3 versus 0.4 ~g/liter, respectively). Based on these tests, potential water quality impacts during open- water placement of contaminated sediments (CAD site) appear to be limited to these three pollutants. In this regard, the concentration of Ni in the elutriate was shown to exceed chronic criteria, but was well below the acute exposure value. Because Port Gardner water samples collected by the COE and identified as background or reference waters equal the chronic criteria value for nickel, dilution of the elutriate with this water would not reduce the elutriate concentration below the chronic level. In the case of Pb, a dilution factor of 1 would result in water concentrations below the chronic criteria concen- tration for the elutriate: for PCB 1254 a dilution factor of approxi- mately 13 would be necessary. Upland or Intertidal Disposal Modified elutriate tests were conducted by the COE to estimate contaminant concentrations in effluent discharged from dredge disposal sites located in intertidal or upland areas (DSEIS). These tests were designed to estimate dissolved and particulate-associated contaminant concentrations in the effluent generated during the placement of hydraulically dredged sediments. Results of the modified elutriate test procedure indicates that undiluted discharge of effluent would significantly degrade the local water quality. The concentration of chromium (Cr) and PCB 1254 were observed to exceed the dissolved concentrations. Total concentrations of PCB 1254 would exceed the EPA's saltwater quality criterion and would require a dilution factor of > 20 to meet the criterion, assuming such effluent was discharged to salt water. If discharged to fresh water (i.e., the Snohomish River) the criteria for Cs, Cr. and PCB 1254 would be exceeded. Dilution factors of 17, 28, and 43 respectively would be necessary to reduce the total concentration of these contaminants to below the acceptable water quality criteria. Obtaining such a dilution could require a diffuser system for the discharge line.

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471 Surface Runoff Impact Tests were conducted by the COE to estimate the potential impacts to receiving water quality as a result of surface water runoff from a confined upland or nearshore dredge disposal site. A rainfall simulatory-lysimeter was utilized to predict the quality of surface- water runoff from such a disposal site. Test results showed that if dredged sediments placed in upland or nearshore sites are not capped and are allowed to dry, physiochemical changes will occur. Under such conditions, runoff water from rainfall would potentially carry dissolved contaminants from the site. Studies conducted with East Waterway sediments indicate that under these condi- tions the.concentration of dissolved Cd would substantially exceed EPA water quality criteria. Leachate Testing The potential for generation of leachate from an upland disposal site was studied using experimental laboratory testing procedures for sediments collected from the East Waterway. Leachate contaminant levels from these sediments were quantified using batch and column testing techniques. Based on these leachate tests, the geochemical changes associated with aerobic disposal on land would result in mobilization of a large fraction of some of the contaminants. If the material could be placed below the water table at a given site (usually more of an option for nearshore/intertidal disposal), such mobilization would be signifi- cantly reduced. The leaching tests indicated that mobility of metals and organic contaminants is low under anaerobic conditions. Under aerobic conditions, some of the metals were mobilized in large quan- tities. The fraction of metals that was resistant to anaerobic leach- ing was generally greater than 90 percent of the bulk sediment concen- tration. Under aerobic conditions, over 85, 65, and 49 percent of the Zn, Ni, and Cd, respectively, was mobilized in the tests. The higher metal release observed in aerobic testing is related to the pH (i.e., the pH in aerobic testing was lower than the pH in anaerobic testing). DREDGING AND DISPOSAL ALTERNATIVES Dredging Equipment Consideration Based on dissolved contaminants and mass releases, both hydraulic and mechanical dredges appear equally viable. Contaminants associated with East Waterway sediments appear to be strongly bonded to those sed- iments as long as they remain saturated. Mechanical dredging to remove the contaminated layer is preferred for confined aquatic disposal since the lower in situ water content would encourage clumping of the mate- rial. Hydraulic dredging of the native material would assist in maxi- mizing spread for cap placement. Either dredging method could be

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472 employed for nearshore confined disposal, although hydraulic dredging appears to be most efficient. Mechanical dredging would require double handling of the material to place it in the site. As water quality problems would not be markedly different from conventional operations, use of specialized dredging equipment is not recommended. General Disposal Alternatives A number of disposal methods and site alternatives were considered for the removed sediments. The preferred method is CAD, to dispose of the contaminated sediments at a deepwater site and then cap them with the clean native sediments. The preferred disposal alternative, Re- vised Application Deep (RAD) CAD, was developed in response to public comments concerning potential significant impacts to the Dungeness crab (Cancer magister) resource of Port Gardner. The RAD CAD site is deep enough to minimize short-term and avoid long-term impacts to Dungeness crabs. A second alternative involved placing either all of the removed sediments or just the contaminated sediments in an intertidal site on the Snohomish River. If only the contaminated sediments were placed there, the clean sediments would be taken to the Port Gardner aquatic disposal site. A third disposal method involves placement of the contaminated sediments on an upland site on Smith Island. With this alternative, clean sediments not required for cover could be disposed of at a deep-water site in Port Gardner. These sites together with other alternative sites are shown on Figure 3. As part of the evaluation methodology for contaminated materials, seven criteria were used to assess each of the different sites. Cri- teria included contaminant availability, potential contaminant mobi- l~ty, site environmental conditions, erosion potential, institutional constraints, site capacity, relative cost, and monitoring capability. A criteria evaluation matrix is given in Table 2. For clean dredged material, five criteria, including site environmental considerations, availability for capping, institutional constraints, site capacity, and relative cost were applied. Open-Water Capped Disposal Site Considerations A detailed locational analysis was undertaken within Port Gardner to identify potential site alternatives for disposal of dredged material by the CAD method. An initial step in the site identification process was a bathymetric survey conducted of much of Port Gardner, focusing on areas shallower than 400 ft. Subsequently, core samples were taken throughout the area and a map of sediment types was pre- pared. Areas of potential geotechnical risk, as indicated by recent slumping and other factors, were identified as well. Other significant characteristics, such as the location of outfalls, were also mapped. The key siting criteria, based on engineering and construction reliability, used to select potential sites included the following:

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473 Potential for subsequent natural deposition. The site should be in a zone of accretion. That is, natural deposition of sediments that could add to the thickness of the capping material was considered to be beneficial. Conversely, areas of potential erosion that could remove cap material were to be avoided. Geotechnical stability. The site should be in an area with no evidence of slope movement. Areas where slumping was identified or where there was a high potential for slumping (in particular, steep slopes) were to be avoided. Site configuration. The site should be relatively flat so that the deposited dredge materials would stay in place. An upwardly sloping terrain on one side of the site was considered benefi- cial, because the slope would function as a natural berm. The natural berm would help confine the cap material and allow a thicker cap to be constructed. Site size. The overall size of the disposal sites is governed primarily by the total amount of material being deposited, sedi- ment bulking factors, stable side slope characteristics of the sediments, and existing bottom topography and consolidation char- acteristics of both the bed and the dredged material. The ini- tial area of deposition for both the barge and hydraulic dredge methods can be expected to increase with increasing depth. For the depth range identified in the general CAD disposal vicinity, the increased depths will not increase initial areas of deposi- tion enough to significantly increase overall site size. Other factors. Facilities already in place, such as outfalls, were to be avoided so that there would be no interference with their operation. Dredge disposal sites that have experienced permitting difficulties were considered less desirable. Other potential disposal sites were also avoided because other future disposal activities could potentially violate the integrity of the CAD cap. Much of the study area was considered unsuitable for a CAD site because of steep slopes or evidence of unstable geotechnical condi- tions. The RAD CAD site was selected as the preferred alternative, meeting the above criteria and minimizing potential impacts on biol- ogical resources (Table 21. DREDGING AND DISPOSAL DESIGN Performance Goals Selection of dredging equipment for the contaminated Everett Harbor sediments was based on the following performance goals: 1. Water entrainment during the dredging operation must be . · . mlnlmlzec ,. 2. Dredging equipment must be compatible with the confined aquatic

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475 disposal alternative under consideration. 3. Dredging equipment must be capable of removing the sediments at a reasonable cost. Selection of dredging equipment for the placement of the clean cap sediments was based on the following performance goals: 1. Cap sediment placement would avoid displacement of the contaminated sediments. 2. Cap placement could be controlled and monitored. 3. Dredging equipment must be capable of removing the sediments at a reasonable cost. Proposed Dredging Equipment Given the equipment performance goals, a mult'phase dredging approach for the CAD alternative was identified. Initial dredging of uncontaminated sediments will be accomplished for purposes of construct- ing a subaqueous confining mound at the downslope limit of the disposal site. This dredging would also serve as a test to demonstrate the acceptability of the final dredge equipment selection and disposal site design. Depending on the results of the mound construction, the remain- ing dredging and disposal would be continued as proposed or revised as appropriate. Mound construction will be accomplished by clamshell dredging and bottom dump of the clean surficial sediments to the disposal site. Dur- ing the second phase, contaminated materials will be dredged by clam- shell dredge, with haul and dumping by split hull barges of 3,000-yd3 capacity or larger. Uncontaminated capping sediments will then be dredged in the third phase, using a hydraulic Butterhead pipeline dredge with discharge below surface through a diffuser unit. The dredging effort will take place over two years, and the second year will include a repeat of the contaminated phase and capping phase accomplished in the first year. Mound Construction Phase Mound construction will be the first phase of dredging to be accom- plished. It was originally planned for completion by pipeline dredge with controlled placement of sediments by downpipe in the shape of a confining mound. The intent of this original approach was to control the placement of the clean sediments in a slurry form by the downpipe to create a downslope confining structure to prevent loss of contam- inated sediments during the subsequent dredging phase. It is question- able that subaqueous confining berms can be constructed with fine- grained soils to the side slopes proposed using a slurried hydraulic pipeline discharged material. It was further established that the con- taminated materials would not require a substantial berm for confine- ment. It was finally concluded that using clamshelled material for the

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476 construction of a mound with flatter side slopes--similar to that pro- posed for the contaminated materials--was advantageous because of the cohesion and clumping associated with clamshelled sediments. Construc- tion of a mound section with cohesive clumps is considered less of an uncertainty, and construction by surface disposal of clamshelled sedi- ments became a viable option. The downslope mound still provides a limiting structure for contam- inated sediment placement and provides a secondary benefit. Because the sediments are similar in situ to contaminated surficial sediments and will be dredged and dumped in the same manner and with the same equipment, a verification of dumping procedures and sediment fate can be completed in the prototype prior to dredging of the contaminated sediments. This has become an important factor in the regulatory agency considerations to approve the disposal permit because it satis- fied the opportunity to check the dredge and disposal design before release of the contaminated sediments at the disposal site. Contaminated Material Placement Clamshell dredging for the contaminated sediment is considered the most compatible dredging method for the CAD disposal alternative. Modeling results indicate that the material will tend to mound if dredged by clamshell. Placement of the material by double handling through a submerged discharge such as a vertical downpipe was proposed, but was discarded as unnecessary and undesirable. Use of a vertical downpipe would require mechanical or hydraulic dredge rehandling from the haul barge to the pipe. Based on physical modeling results, the downpipe tended to cause side shear and Entrain greater amounts of water in the already reduced 5- to 10-yd clumps of sediment rehandled from the haul barge. This resulted in a lesser sediment strength on the bed to support a cap than the surface release of the barge load. Disposal of clamshelled material at the surface is a viable option for the contaminated material. For surface disposal, the cohesion and clumping normally associated with clamshelled material would be of benefit in reducing material spread and resuspension and would result in a contaminated sediment mass with more strength for support of a cap. Clamshelled material would also entrain less water, thereby resulting in a smaller subaqueous confined volume. Cap Placement Hydraulic dredging of uncontaminated material for the cap placement was recommended. The potential for displacement of the soft contami- nated material or bearing-type failure of the cap would require that the cap layer thickness be gradually built up. This process could be accomplished by surface disposal or submerged pipe discharge suspended some variable distance above the contaminated material surface. Use of a submerged diffuser (directly connected to the hydraulic pipeline with

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477 flexible hose) is an option that will be used to avoid any potential for jetting action causing erosion of the contaminated sediments. Final Disposal Configuration--Summary Several final calculated designs of the disposal cross-section and area spread were accomplished. Since the proposed dredging plan ex- tends over two dredging seasons, the sequence of disposal operations was taken into consideration. This sequence includes initial placement of uncontaminated materials for a mound, then placement of a relatively small amount of contaminated materials and immediate capping with a greater amount (relative to the contaminated materials) of uncontam- inated materials. After approximately nine months, an additional larger sequence of contaminated and capping materials would be placed (Figures 1 and 2~. Quantities used in the design were as follows: · year 1 uncontaminated mound materials, 580,000 yd3; · year 1 contaminated materials, 97,000 yd ; 3 · year 1 uncontaminated cap materials, 239,800 yd ; · year 2 contaminated materials, 831,000 yd ; 3 · year 2 uncontaminated cap materials, 1,638,000 yd . Sediment consolidation would occur at a geometric rate, with the greatest amount of consolidation resulting during the first few months following disposal activities. The final design assumed a conservative consolidation of 50 percent of the immediate deposition thickness within three months after placement to establish cap thickness. A minimum of 1-m thickness was required for CAD alternative acceptance by regulatory agencies. It is anticipated that final minimum capping thickness over contaminated materials will be 4.5 ft or more. The total impacted area, where 3 cm or more of dredged material will be deposited, is approximately 380 acres. ENVIRONMENTAL MONITORING The dredging and disposal monitoring plan, phase I document outlines a detailed plan for meeting the conditions outlined in the State Water Quality Certification, and COE Section 10/404 permit of September 24, 1987. Monitoring is divided into five phases: 1. baseline, 2. mound construction, 3. contaminated dredging and disposal, 4. capping dredging and disposal, and 5. long-term monitoring. The monitoring plan is designed to measure physical, chemical, and

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478 biological characteristics of the revised application for deep confined aquatic disposal (PAD/CAD) site and to collect data regarding the effect of project construction on those characteristics. The plan was prepared considering details of the permit application, COE Section 10/404 permit, results of the Washington State Department of Ecology's review process, and the project's construction plans and specifications as they exist. Results of the first-year monitoring and construction activities will then be applied toward development of the second-year monitoring plan (phase II). A listing of the various monitoring activities associated with the dredging and disposal component of the Navy's Everett Homeport project follows. . . Electronic Positioning: precise sea-surface positions will be established to meet the requirement for absolute accuracy of + 3 m. Also, a seabed positioning system will be used to locate the actual seabed position of the sediment and benthic samples and sediment profile camera photos. Bathymetry: precision bathyme try (+ 20 cm accuracy) with lane spacing of 20 m over the 1150-acre survey area. Sidescan sonar surveys: information on the surficial characteris- tics of the seafloor to either side of the survey trackline out to a range of 500 ft. Sediment profile camera: during baseline monitoring, 70 SPC stations will be photographed with three replicates per sta- tion. Following sediment disposal, additional photos will be taken to define the limits of the disposed material. · Sediment cores: sediment box cores at 37 stations will be taken during baseline, with the upper 2 cm of each analyzed for physi- cal properties and 79 PSDDA (Puget Sound Dredge Disposal Analy- sis) "Chemicals of Concern," all run using Puget Sound Estuary Program (PSEP) protocol. Piston cores will be taken after dis - posal to identify properties of disposed sediments and thickness of capped material. 2 Benthic macroinvertebrate assemblages: using a 0.06m box corer at 37 stations (5 replicate/station), traditional taxon- omic analysis will assess the characteristics of the Benthic community. Additionally, complementary Benthic Resource Assessment Technique (BRAT) will also be performed. · Bioaccumulation: one epifaunal species (Cancer magister) and one infaunal species (Mo ~padia) to be collected and investi- gated at six stations for chemical bioaccumulation in tissue. Bioturbation randomly located on the disposal site, 35 box core e stations will be collected and analyzed for density of macro- benthic infauna and number and depth of burrows to determine possible effects on cap material integrity. · Sea- surface microlaYer: microlayer ~ ~ ess than 100 microns ) water samples will be collected with a ceramic rotary drum system prior to and during contaminated sediment disposal.

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479 . . Current measurements: site-specific current conditions will be collected during mound disposal, during the whole of contami- nated sediment disposal and during two days of dredging to determine the current influence on sediment transport. Current meter stations at the RAD CAD site will include arrays of meters at discrete depths (i.e., 90, 120, and 220 ft. and near bottom) as well as an acoustic doppler current profiling meter. Water column effects (disposal site): three-step procedure using current drogues and acoustical transponders for plume tracing, acoustical transponders and transmissometers for plume charac- terization and state water quality standards monitoring. Water column effects (dredge site): for dissolved oxygen, per- cent light transmittance, total suspended solids, and nephelo- metric turbidity units at various depths and distance from dredg- ing activities. Chemical analysis of water samples: conventional parameters will be measured as well as 69 PSDDA chemicals of concern, all run us ing PSEP protocol . Sediment traps: positioned around the disposal site (over 20 locations) will be two pairs of traps on each mooring, one located 1 to 2 m above the bottom and the other 20 m above the bottom. Four locations will include turbidity meters on the moorings as well. Bioeffects (shellfish/fish): short- and long-term impacts and changes on density, diversity, and population abundance will be measured in a statistically significant manner. Mussel watch: over 2,200 noncontaminated mussels will be deployed at each of three depths on nine moorings for a 30-day period during contaminated sediment disposal, after which mussel tissue chemical concentration analysis will be performed. Histopathology: will assess any short- or long-term hepatic pathologic abnormalities in English sole before and after disposal activities. Second-Year Monitoring Second-year environmental monitoring activities are expected to be similar to the first-year activities just described, although some adjustments to the monitoring effort will most probably result from a review of the data collected and "lessons learned." Long-Term Monitoring Monitoring of environmental conditions at the disposal site is required for at least 10 years following completion of the second-year cap. Monitoring will be conducted at specific intervals, currently scheduled for years 1, 2, 4, 7, and 10. Monitoring will be conducted using the same operational procedures described for baseline and/or disposal monitoring and will minimally include

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480 electronic positioning, bathymetry, sediment cores, and bioeffects - - shellfish/fish, benthic macroinvertebrates, BRAT, bioturbation, and histopathology. CONCLUS IONS - includes sediment ___ additional volume of clean sediments in excess of 2 million Ads, to construct an engineered CAD site in water depths of 310 to 430 ft. The work.will be completed in three separate, regulated phases, and the success of each preceding phase is the prerequisite to continuing with the next phase. These phases include the clean test mound construc- tion, phase T contaminated sediment and clean cap disposal, and phase II contaminated sediment and clean cap disposal. Since 1984, the prod ect has undergone extensive environmental re- view ( including 20 public hearings ), culminating in the issuance of a Washington State conditional use shoreline permit (May 1988) , a COE Section 10/404 permit (September 1987) and attendant Washington State water quality certification (March 1987~. The environmental review process resulted in substantive project design modifications to miti- gate environmental concerns. Nonetheless, the critical component of the project has always been and continues to be controversy surrounding the technical feasibility and environmental impacts of successfully constructing a CAD site for contaminated marine sediments in a deep- water environment. The quest for the answers to these questions has resulted in administrative permit appeals, legal challenges in federal and state court, repeated schedule revisions and extensions, project funding constraints attributed to environmental concerns, and unprece- dented environmental monitoring requirements. As a result, dredging and disposal activities are currently scheduled to start in the summer of 1988, more than a year after the original programmed date. The preferred disposal alternative (CAD) is a direct extension of existing technology that has been used successfully in other areas of the United States. The CAD procedure has been the subject of extensive research both within the United States as well as abroad, and is a tech- nology sanctioned by the London Dumping Convention scientific group. The levels of contamination encountered in Everett Harbor sediments are handled routinely in other areas of the country. Even with this back- ground to draw upon, regional environmental concern for Puget Sound necessitated the expenditure of substantial time and money, far beyond previous experience. Currently, for this project, predisposal This paper has presented a summary of the sediment evaluation proce- dures, disposal alternative assessments, design considerations, and monitoring requirements associated with the dredging and disposal required for construction of the Navy's Carrier Battlegroup Homeport Project in Everett, Washington. The preferred disposal alternative the dredging of approximately 1 million yd of marine that will be treated as contaminated, together with an

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481 nonconstruction costs are approximately $3.50/yd3 of contaminated seg- iment and anticipated environmental monitoring costs exceed $8.00/yd of contaminated sediment. These Posts can be compared to anticipated construction costs of $4 to $7/yd of dredged material (Table 3~. The level of monitoring required for this project is particularly extensive, and it should be recognized that such costs would likely not be supportable by smaller projects, privately funded projects, or local governmental entities. A major benefit of the monitoring for this project should be the demonstration of the viability of the CAD tech- nique in deep water. As such, those monitoring activities intended to verify the CAD concept would not be appropriate for future projects. like conclusion is applicable to other components of this monitoring program that do not demonstrate usefulness in documenting compliance with required levels of environmental performance. Review of the pro- ject literature reveals that several of the required sediment evalua- tion procedures produced inconclusive results. Some evaluations demon- strated poor repeatability and others a potential for significant false positive results when contrasted with controls. Often these results served to confuse rather than clarify the evaluation of possible im- pacts. Specific aspects of this project which have produced or may produce questionable results include · mass loss determinations and impacts, · microtox bioassay, · standard bioassays, · sea-surface microlayer, · chronic toxicity and bioaccumulation, · plume tracing for water quality impacts, and · bioturbation. TABLE 3 Summary of Dredging Costsa Item Contaminatedb TotalC Sediment evaluation Disposal alternative evaluation Environmental Monitoring $ 1.26 2.21 8.27 Total nonconstruction costs 11.74 Total dredging and disposal design costs Total Construction Costs 0.35 0.62 2.32 3.29 0.21 4.00-7.00 NOTES aNonconstru~tion costs, expressed as dollars/yd3. b928, 000 yd 3,305,000 yd

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482 The data summarized by this preliminary case study supports the continued need for a strong national research program relating to mar- ine sediments. The program should be directed at defining appropriate repeatable procedures for sediment evaluation and monitoring efforts. In addition, the process should actively eliminate requirements that demonstrate a significant tendency for inconclusive results. Funding and prioritization for such research should be established by an inde- pendent national group and implemented on projects where significant new information could be developed during construction through coor- dination with the project proponent. It is generally not in the national interest to allow uncertainty with regard to environmental issues to burden a project having significant social or economic bene- fits. The responsibility of resolving research questions related to issues of environmental impacts should be jointly shared by the research community and project components. Also, a national guideline or standard on the disposal of contaminated dredged sediments should be promulgated. The guideline should draw from the wealth of regional experience, such as the homeport project, to minimize the unilateral research burden on future projects. While the guideline needs to be sensitive to regional differences and concerns, it must at the same time maintain reasonable levels of national uniformity.