Showing papers on "Dredging published in 2003"

An examination of the spatial scale of impact on the marine benthos arising from marine aggregate extraction in the central English Channel

Abstract: Surveys were designed to investigate the nature and footprint of biological effects arising from both trailer and static suction hopper dredging in UK waters. Two transects of stations located at increasing distance from active centres of dredging activity in the central English Channel were sampled for macrofauna and sediments using a 0.1 m2 Hamon grab. Multivariate statistical analyses indicated that macrofaunal community composition was distinct and there was a clear gradient of change with increasing distance from the dredging activity. Spatial differences in species distribution patterns correlate with levels of dredging intensity and the physical characteristics of the sediments. Effects on the benthos of the different dredging practices were similar within the zone of active dredging, although there were notable differences in the scale of impact and the nature of effects beyond the margins of the extraction sites. The two principal methods of dredging for sand and gravel in the UK are discussed in relation to their potential for impacting the benthos.

Mechanical clam dredging in Venice lagoon: ecosystem effects evaluated with a trophic mass-balance model

Abstract: Harvesting of the invasive Manila clam, Tapes philippinarum, is the main exploitative activity in the Venice lagoon, but the mechanical dredges used in this free-access regime produce a considerable disturbance of the lagoon ecosystem. An ecosystem approach to study the complex effects of clam harvesting was implemented using a trophic mass-balance model. The trophic rela- tions in the ecosystem were quantified with a mixed trophic impact analysis and further evaluated by con- sidering different explanations for the ''Tapes paradox'', which consists of the apparent population enhancement of Manila clams by dredging and the apparent nutri- tional advantages that this species receives from re-sus- pended organic matter. The key-role played by this introduced species is highlighted by a network analysis that indicates a ''wasp-waist control'' of the system by Manila clams. The model constructed to characterise the present state of the Venice lagoon ecosystem is com- pared with models produced for a reconstructed past lagoon and a projected future lagoon. The future model was obtained by simulating the elimination of clam dredging in 10 years. The three different models were compared using thermodynamic and informational indices. Simulating the elimination of clam dredging produced a 33% increase in artisanal fishery catches, carried out by means of static gears, even with no change in fishing effort. These simulations also forecast an increase in the mean trophic level of the artisanal fishery catches as a positive effect of eliminating mechanical clam harvesting.

Preliminary observations of the effects of dredging intensity on the re-colonisation of dredged sediments off the southeast coast of England (Area 222)

Abstract: The re-colonisation of a site used for the extraction of sand and gravel for ca. 25 years off the southeast coast of the UK was examined 4 years after the cessation of dredging. Effects of different levels of dredging intensity on the rate of macrofaunal re-colonisation were investigated. Values of abundance and total numbers of species were significantly lower (p<0.05) in an area most recently exposed to the highest level of dredging intensity compared with samples taken from an area of low intensity, and those from a reference site. Differences between previously dredged sediments and the reference location were due to the reduced abundance of a range of macrofaunal species characterising nearby sediments. Multivariate measures of community structure also indicated that there were significant differences (p<0.01) between the macrofaunal assemblages in the areas exposed to different dredging intensities. Sediment from the area exposed to the highest dredging intensity contained proportionally more sand than other sampled sediments. The extent to which dredging intensity contributed to these differences was difficult to determine owing to the absence of any baseline data. Despite this, univariate and multivariate analyses indicated a strong relationship between macrofaunal community structure and dredging intensity at this site. Correlation analyses also demonstrated that the predominant influence on the macrofaunal community was that of the level of dredging that took place in 1995, the last year that the licensed site was dredged heavily. Preliminary observations indicated that the fauna remained in a perturbed state some 4 years after cessation of dredging. Therefore, relatively rapid ‘recovery’ rates, commonly cited as 2–3 years for European coastal gravelly areas, should not be assumed to be universally applicable. Implications for the future management and scientific study of marine aggregate extraction arising from preliminary observations on the physical and biological status of this site are discussed together with the options for selecting a reference site in the absence of baseline information.

A comparison of direct macrofaunal mortality using three types of clam dredges

Abstract: The white clam Spisula solida is harvested along the entire coast of Portugal using mechanical dredges. In this study, the total direct mortality of the macrobenthic community caused by three types of clam dredges (north dredge—ND, traditional dredge—TD, and the metallic grid dredge—GD) used in the S. solida fishery was determined and compared. The relationship between mortality and catching efficiency for each type of dredge was also assessed. Our results showed significant differences for total direct mortality between the ND and both the GD and TD dredges. This difference was largely attributed to the mortality of animals that died in the dredge track as a direct result of the physical damage inflicted by the dredge passing. It was also found that the damage to uncaught individuals is directly related to gear efficiency. The lower catching efficiency of the ND (64%) led to a higher proportion of damaged individuals being left in the dredge path, when compared with the more efficient GD (98%) and TD (90%) dredges. Short and long-term implications of the impact of dredging on the composition of benthic communities are discussed. From fisheries management and ecological points of view, there are obvious advantages to introduce into the bivalve dredge fisheries more efficient and selective dredges in order to reduce the number of damaged individuals and by-catch, and consequently decreasing the impact on the macrobenthic communities.

Immediate and longer-term impacts of hydraulic clam dredging on an offshore sandy seabed: effects on physical habitat and processes of recovery

Abstract: A hydraulic clam dredging experiment was conducted on a deep (70–80 m) offshore sandy bank on the Scotian Shelf in order to examine the immediate impacts of hydraulic dredging on physical habitat and to follow processes of recovery over a 3-year period. Seabed structural complexity in this low-relief habitat consists of small-scale sedimentary features including pits and bivalve burrow openings as well as polychaete tubes and empty mollusc shells. The most obvious effect of dredging was a dramatic change in seabed topography due to the numerous deep (20 cm), wide (4 m) curvilinear furrows that were cut by the dredges. The loss of burrows, tubes, and shells through destruction or burial, and local sedimentation created a smooth surface. Both spatial scale and sampling resolution were critical in identifying longer-term impacts. Dredge furrows were no longer visible in video 1 year after dredging due to their low relief; however, they persisted, while undergoing changes, as evidenced in sidescan sonograms. The margins of furrows were gradually degraded, likely through the combined actions of slumping, sediment transport and bioturbation. Over time, dredge furrows act as traps for empty shells. Differences in patterns of acoustic reflectance between dredge furrows and the surrounding seabed indicate long-lasting effects on sediment structure. Densities of large burrows were reduced by up to 90% after dredging with no signs of recovery after 3 years due to the high mortalities of their architect, the propellerclam, Cyrtodaria siliqua . Dredging effects were detectable against a background of natural temporal (annual) and large-scale spatial variability in physical habitat.

Short-Term Benthic Recolonization after Dredging in the Harbour of Ceuta, North Africa

Abstract: The benthic recovery after dredging (area: 2625 m 2 ) was studied in a polluted and enclosed area of the harbour of Ceuta, in which the recolonization through the water column (larvae and adult bedload transport) could be limited by the lack of renewal. The benthos was sampled at two sites (control and dredged) using a van Veen grab and adopting a BACI (Before, After, Control, Impacted) approach. Five samplings were conducted after dredging (3, 15, 30, 90, 180 days). The proportion of gravel in the sediment of the dredged site increased after dredging, while the organic matter decreased. The impact on the community was estimated at species level, using both univariate and multivariate analyses. The maximum negative effect on benthic macrofauna was a reduction by 65% for species richness (15 days after dredging) and by 75% for abundance (3 days after dredging). Between 15 and 30 days after dredging, the abundance of some species such as the molluscs Parvicardium exiguum and Retusa obtusa and the polychaete Pseudomalacoceros tridentata increased considerably in the dredged site, while typicalopportunistic� species such as Capitella capitata were disfavoured by the disturbance. For this small-scale dredging, about 6 months are required for the disturbed area to re- establish a sediment structure and a macrobenthic community similar to the undisturbed area. Small-patch dredging operations are proposed in harbour manage- ment whenever possible, since they allow a quick re-adjustment of the initial sediment structure and benthic communities.

An experimental study of the ecological impacts of hydraulic bivalve dredging on maerl

Abstract: A short-term experiment to assess the ecological impact of a hydraulic blade dredge on a maerl community was carried out during November 2001 in the Clyde Sea area on the west coast of Scotland. A fluorescent sediment tracer was used to label dead maerl, which was then spread out on the surface of sediment to act as a proxy for living maerl. The fauna collected by the dredge was dominated by the bivalves Dosinia exoleta and Tapes rhomboides, which were found to be intact. The target razor clams Ensis spp. were caught in low numbers, which reflected the low abundance of this genus within the maerl habitat. The hydraulic dredge removed, dispersed and buried the fluorescent maerl at a rate of 5.2 kgm2 and suspended a large cloud of sediment into the water column, which settled out and blanketed the seabed to a distance of at least 8m either side of the dredge track. The likely ecological consequences of hydraulic dredging on maerl grounds are discussed, and a case is made for protecting all maerl grounds from hydraulic dredging and establishing them as reservoirs to allow for the recruitment of commercial bivalve populations at adjacent fished sites.

A Bibliography of Selected References to U.S. Marine Sand and Gravel Mineral Resources

Abstract: Coastal erosion and land loss resulting from complex natural processes (e.g. storms, sea-level rise, sediment starvation) and man-made alterations (e.g. dams, dredging, structures), often with unintended consequences, are pervasive for all coastal regions of the United States, as well as for much of the world. Development in the coastal zone continues to increase and demographic projections show these trends will continue, placing more people and development at risk. With the prospects of future climate change causing increased storminess and accelerating global sea-level rise, coastal regions are likely to experience increased erosion, inundation, and storm-surge flooding in future decades.

Three-dimensional modelling of sediment transport and the effects of dredging in the Haihe Estuary

Abstract: The Haihe Tide Lock was constructed on the Haihe River in 1958 to stop salty and muddy water intrusion. Nevertheless, tidal currents carry sediment, which is eroded from the surrounding silty coast, into the river mouth and, thus siltation of the channel downstream of the tide lock becomes a major problem. Employed are trailer dredges, which stir up the silt and subsequently moves it out of the mouth with ebb tidal currents. While the application of this method is encouraging there are still problems to be studied: how high is the dredging efficiency, how far can the resuspended sediment be transported by the ebb currents, and is the sediment carried back by the next flood tide? This paper develops a 3-D model to answer these questions. The model employs a special element-interpolating-function with the σ -coordinate system, triangle elements in the horizontal directions and the up-wind finite element-lumping-coefficient matrix. The results illustrate that the efficiency of dredging is high. Sediment concentration is 4–20 times higher than the flow without dredging. About 40–60% of the resuspended sediment by the dredges is transported towards the sea 3.2 km off the river mouth and 10–30% is transported 5 km away from the mouth. Calculations also indicate that the rate of siltation of the river mouth is about 0.6 Mm 3 per year. If the average discharge of the river runoff is 0, 200 or 400 m 3 s −1 the mouth has to be dredged for 190, 99 or 75 days every year so to maintain it in equilibrium. The dredging efficiency per day is 0.53–1.31%.

Changes in benthic community structure due to clam dredging on the Algarve coast and the importance of seasonal analysis

Abstract: Patterns in community structure of meiofauna and macrofauna in relation to Portuguese clam dredging were compared during a 2-y-period off Lagos and Vilamoura, south Portugal. SCUBA divers randomly sampled corer and quadrat samples before and immediately after simulating commercial dredge fishery. Univariate measures (abundance, number of taxa, evenness, diversity and biomass) and multivariate analyses (Cluster, MDS and SIMPER) revealed changes in the meio- and macro-benthic community structure caused by dredge disturbance (short-term effects), with a general decrease in all measures. Macrofauna were found to be more sensitive to dredge disturbance, and aggressive predatory behaviour was observed after disturbance in the continuously dredged area. Nevertheless, higher significant natural changes were found between seasonal periods, indicating that dredging may only cause a small-scale and short-term impact.

Evaluation of shell damage to the clam Chamelea gallina captured by hydraulic dredging in the Northern Adriatic Sea

Abstract: The impact of experimental hydraulic dredging was assessed on Chamelea gallina populations in two sites along the north-western Adriatic coast (Lido and Jesolo) by detecting and quantifying shell damage caused by fishing operations on both captured and discarded clams. Various levels of stress were applied, the highest being that used by commercial fishing vessels, which employ high water pressure and mechanised sorting and the lowest manual sampling of clams by scuba divers. Water pressure and sorting significantly increased shell damage, the highest levels always being observed in commercially dredged clams. At Lido, damage was mostly due to the action of the mechanised sorter; at Jesolo, the effect of high water pressure was more clearcut. Moreover, clams collected at Jesolo had both higher mean damage level and higher numbers of damaged individuals compared to the Lido samples. These differences seem to be mostly related to differing bottom features in the two sites. A positive relationship was observed between damage level and clam size: small-sized samples (length <17 mm) were less damaged than medium-sized ones (25 mm < length < 17 mm) and commercial size clams (<25 mm) showed the highest damage level. The severe and harmful physical impact of hydraulic dredging was apparent in captured and then discarded animals, a small fraction of which appears able to recover, as shown by the presence of clams with repaired shells. 2003 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights

Recovery of substrates and macro-benthos after fishing trials with a new Portuguese clam dredge

Abstract: The eiect of dredging on bottom structure was assessed, to estimate the damage in£icted on the benthic macrofauna left on the dredge path and to evaluate aggregations of scavengers within the track. Sediment suspended during dredging rapidly resettled both on sand and sandy-mud bottoms. Dredge tracks were deeper on sandy-mud sediments and persisted longer than in sandy sediments. The disappearance of tracks in both sediment types depended both on current strength and wave action. Damage and mortality induced by dredging on the macrobenthic animals left on the dredge path was relatively low. Post-¢shing SCUBA diver observations showed that damaged animals left on the dredge path rapidly attracted scavengers, mainly Ophiura albida. Immediately after the tow ophiuroids reached densities eight times greater in the track region than in the background. However, they dispersed again rapidly because only few damaged fauna were available on the dredge tracks. Undamaged or slightly damaged shell¢sh started to rebury immediately after escaping from the dredge.

Impacts of mussel dredging on sediment phosphorus dynamics in a eutrophic Danish fjord

Abstract: Effects of mussel dredging on sediment metabolism (oxygen uptake and sulfate reduction rates) and phosphorus dynamics (flux across sediment-water interface and sequential extraction) were examined ...

Short communication Effects of suction-dredging for cockles on non-target fauna in the Wadden Sea

Abstract: Suction dredging for cockles removes large cockles from tidal flats and may also cause mortality of non-target fauna and make the habitat less suitable for some species. This study examines whether suction dredging for cockles on tidal flats of the Dutch Wadden Sea had affected densities of non-target fauna, directly after fishing and one year later. Densities of non-target fauna in two randomly chosen undredged locations were compared to densities at the surrounding heavily commercially dredged area. A significant negative effect of cockle dredging on densities of 0-group Macoma balthica was observed and this effect persisted one year after dredging. The dredged area appeared to be less suitable for settlement of mussels Mytilus edulis. No significant effects of dredging on the mudsnail Hydrobia ulvae and on 0 and 1-group C. edule were found. For the mobile young Macoma balthica it seems unlikely that the effect found after one year was still due to the mortality caused by dredging and this suggests that the habitat was less suitable as a consequence of dredging. Thus, even in the highly dynamic ecosystem of the Wadden Sea, effects of bottom disturbance by cockle dredging may persist after one year. D 2003 Elsevier B.V. All rights reserved.

Overview of Regional Coastal Sediment Processes and Controls

Abstract: BACKGROUND. The US Army Corps of Engineers has the mission of ensuring navigability of Federal waterways. Congress authorized this mission in 1824, when the Corps was directed to remove sandbars and snags from major navigable rivers. Today, the Corps’ navigation program involves the planning, design, construction, operation, and maintenance of riverine, estuarine, and coastal waterways to meet navigation needs. Inlet channels and entrances are major elements of the sediment-exchange system of the surrounding landforms that include the mainland, wetlands, bay beaches, and ocean beaches. Inlet navigation projects, typically including jetties, channel maintenance dredging, and disposal of dredged material are a major element of the coastal sediment budget. Although sand bypassing has been implemented at individual inlet navigation projects, only a limited area within or around project dimensions was typically analyzed. Records of shoreline change indicate that both natural and improved inlets alter longshore sediment transport patterns and the shoreline position far beyond an inlet (e.g., Dean 1987, Bruun 1995), making it necessary to analyze shoreline response at a larger spatial scale than what is commonly done in individual projects. The need for project design and management decisions for longer time periods is increasing, also emphasizing the need to consider larger spatial areas in inlet navigation projects. Many inlet navigation projects have been in place for more than a century, and their ranges of influence far exceed local project dimensions. Similarly, sand from periodically nourished beaches likewise will travel far beyond project limits. The time and space scales of major coastal projects therefore call for regional considerations to address the full consequences and interactions of engineering activities as well as the wide-scale influence of natural processes and features. This technical note describes selected regional coastal sediment processes and controls that are typically not addressed in the design, operation, and maintenance of coastal projects. Here, a control represents a mechanism that imposes constraints on the sediment transport, in mathematical terms dictating or influencing boundary conditions on the governing processes. The coastal processes and controls are primarily discussed in the context of longshore sediment transport and shoreline evolution at the regional scale. TIME AND SPACE SCALES OF COASTAL SEDIMENT PROCESSES. Coastal sediment processes are commonly classified by their characteristic scales of the forcing and responses. At present, mainly the local scale is employed in project design, whereas the need for

Tweed River Entrance Sand Bypassing Project Post-Commissioning Coastal Behaviour

Abstract: 2. DREDGING AND BEACH NOURISHMENT River entrance channel dredging using trailer suction hopper dredges commenced in April 1995 and finished in November 2001. Approximately 3.9 million cubic metres have been moved by this method. Most of this sand was deposited by bottom dumping into the nearshore zone close to beaches about 1 to 3.5 km north west of the river entrance. The beaches have gained a net volume increase of about 2.5 million cubic metres as a result of this dredging.

Hydrodynamic and sediment transport modeling of deltaic sediment processes

Abstract: This dissertation tests the hypothesis that the early phases of deltaic bar and distributary channel formation and sediment transport on an adverse slope could be simulated with a 2D finite element sediment transport model. The models used were RMA2 and SED2D modules of the TABS-MD model suite. A finite element mesh of the lower Atchafalaya River and the delta was developed, using the Surface Water Modeling System (SMS) software package. Calibration and validation of the model were performed, using data collected during field surveys and from available Atchafalaya River archived flow, suspended sediment, and dredging records. In a test simulation in which adequate flow and sediment supply were provided in large quantity, sub-aqueous distributary mouth bar formed at the end of the feeder channel. As simulation continued, a more prominent distributary channel and sub-aerial levees were developed. When the model was changed to impose a no flood conditions on high points, formation of new distributary channels was observed. The same model was used to determine a self-sustainable adverse slope or sediment ramp that could be used to divert sediments efficiently in a deltaic setting similar to the Atchafalaya Bay. A test slope of 1V to 51H was used in the model. After several simulations, the model tends to produce a much milder slope close to 1V to 412H. Five adverse natural slopes observed in the Wax Lake Outlet delta were compared with the model-suggested slopes. Adverse slopes at the Wax Lake Outlet delta varied from 1V to 340H – 850H, with 1V to 543H as the average. Finally, a calibrated model of the Atchafalaya River and the delta was applied to develop a set of sedimentation/erosion curves that could be used by the engineers to

Evaluation of Dredging Effort by the Delaware Bay Oyster Fishery in New Jersey Waters

Abstract: As part of a study to assess the effect of commercial dredging for eastern oysters Crassostrea virginica on their beds in Delaware Bay, we evaluated the total dredging effort for the Delaware Bay oyster industry in New Jersey waters for 1999-2000 and examined some of the behavioral and gear-related factors that determined this total effort. In a standard 8-h fishing day, a one-dredge boat traverses about 3.8 ha (38,000 m2) of oyster bed. A two-dredge boat traverses nearly twice that area, about 6.4 ha. Oyster boats typically fish in a single area for most of the day, yet catch per unit effort (CPUE) does not decline during the course of the day. Catch per unit effort is stable because of low dredge efficiency. Although an oyster dredge is capable of routinely achieving efficiencies of 10-60%, dredge efficiency during fishing is usually only 4-7%. Low dredge efficiency means that swept-area coverage (area of the bottom traversed by a dredge) is high for the number of oysters taken. The most heavil...

Evaluation and improvement of shellfish dredge design and fishing effort in relation to technical conservation measures and environmental impact: [ECODREDGE CT98-4465]

Abstract: This project systematically examines the bivalve dredging process and its physiological and ecological consequences. The literature on ecology and population dynamics of the target species, dredge design and fisheries and the environmental effects of dredging and selectivity of dredging is reviewed. A programme of experimental work, both laboratory and field studies is described in scallop and clam dredge fisheries in European waters; scallop species (UK, France) Pecten maximus, Aequipecten opercularis, clam species (Italy; N. Adriatic) Chamelea gallina, clam species (Portugal) Spisula solida, Donax trunculus, Callista chione. Selectivity measures and dredge design are examined for their consequences in terms of environmental effects. Studies included physical, chemical and biological effects both at individual and community level, and selectivity of dredging. These studies include the use of instrumentation and modelling to describe physical effects and behavioural observations, stress and damage indices, both acute and chronic, to describe environmental effects. In the discussion measurement of environmental effects and selectivity are discussed along with the environmental effects of selectivity parameters, dredge designs and responses to fishing effort. The results are discussed in the context of dredge fishery management.

Marine-based platform for dredged solids management

Abstract: A marine system and method is presented for collecting, containerizing, and transporting contaminated sediments collected during dredging operations in the marine environment. The system makes use of a specially designed marine-based platform to process and distribute the sediments into containers located on a separate sediment transport vessel. The system described bypasses the need for on-shore sediment processing facilities.

Distribution characteristics of marine aggregate resources and potential prospect in china

Abstract: Sea sand can be found in coastal zone, continental shelf and nearshore shallow sea sediment systems in China. The total amount of coastal sand is about 3588×108～5382×108 m3. The total amount of nearshore shallow sea sand is about 6651×108～10186×108 m3. Coastal sand and nearshore shallowsea sand are mainly composed of medium and coarse sand, which is easy to be excavated and used as construction materials. As sand dredging in coastal zone will bring about serious environmental effects such as coastal erosion, government should forbid sand dredging activities in coastal zone area.The total amount of sea sand existing in the China continental shelf is about 6 697×108 m3, but this kind of sand is too fine to be used as construction materials. Sea sand as construction materials in China continental shelf is poor in quality and the only exception is along the Taiwan Strait shoal. So, the China continental shelf will not be the potential target area. Otherwise, the nearshore sea sand will be the possible area for sand exploration and mining.

South Jetty Sediment Process Study, Grays Harbor Washington: Evaluation of Engineering Structures and Maintenance Measures

Abstract: : Grays Harbor is located on the southwest Washington coast at the mouth of the Chehalis River, about 45 miles north of the Columbia River mouth. The harbor is 13 miles wide at its broadest point and 15 miles long from Aberdeen, WA, on the east to the entrance 0 the west. Two convergent rock jetties, a north jetty and a south jetty, are part of the Grays Harbor navigation project, which is a federally constructed and maintained navigation channel. Development of the channels and facilities at Grays Harbor has been a continuing process since the Rivers and Harbors Act of June 1896 authorized the construction of the south jetty. Maintenance dredging has been required after the 1990 Grays Harbor navigation improvement project was completed. The U.S. Army Engineer District, Seattle requested a study to evaluate the engineering features and maintenance measures in the vicinity of the south jetty. The south jetty sediment processes study was developed and keyed to elements of a plan of action. The purpose of the study is to evaluate the performance of engineering and maintenance measures that have been implemented to control breaching next to the south jetty, and to reduce shoreline erosion in Half Moon Bay and placement of dredged material to alleviate erosion. Another study in a series on the south jetty is in progress to document the analysis of a breached condition and assess the risk of future breaching. This report documents the history of the south jetty and related engineering structures, and reviews previous studies relevant to the acting coastal processes. It includes reviews of dredging and disposal activities associated with maintenance and new work dredging, analysis of the wave diffraction mound performance, analysis of upland and intertidal topography and nearshore bathymetry surveys, analysis of shoreline position change, identification of sediment pathways, and a sediment budget.

U.S. Army Corps of Engineers New Dredging Engineer Manual ``Dredging and Dredged Material Placement''

Abstract: The U.S. Army Corps of Engineers (USACE) is in the final stages of updating and merging three of its previous dredging Engineer Manuals (EMs) into a single document entitled Dredging and Dredged Material Placement, EM 1110-2- 5025. This new EM consists of the updated versions of three previous EMs, Dredging & Dredged Material Disposal (EM 1110-2-5025, 1983), Beneficial Uses of Dredged Material (EM 1110-2-5026, 1987), and Confined Disposal of Dredged Material (EM 1110-2-5027, 1987). In addition to updating the old EMs, this document also includes a new section on open-water placement. The terms disposal and placement are used synonymously to describe the dredged material deposition after its removal from the dredge cut. This paper provides an overview of this comprehensive document that describes the dredging equipment and placement techniques used by the USACE in navigation projects, and provides management, engineering, and design guidance for activities associated with new work and maintenance projects. Guidance is provided on: 1) the evaluation and selection of dredging equipment, 2) planning, designing, constructing, operating, and managing open-water and confined dredged material placement areas to provide adequate storage volume for both short-term and long-term placement needs, and 3) planning, designing, developing, and managing dredged material for beneficial uses, incorporating ecological concepts and engineering designs with biological, economical, and social feasibility. This EM will be available on the USACE web site http://www.usace.army.mil/inet/usace-docs/eng-manuals/ for unlimited distribution.

Waters environmental recovery material for tidal marsh and shallow place

Abstract: PROBLEM TO BE SOLVED: To eliminate the need of adjusting the granularity of necessary sediment in using dredging sediment as waters environmental recovery material, and to solve the problems such as pH rise of waters and consolidation in using blast-furnace slag. SOLUTION: This material is formed by mixing dredging sediment and iron steel slag, whereby pH rise of waters can be avoided, and bacterial growth and water permeability can be secured. COPYRIGHT: (C)2005,JPO&NCIPI

Evaluation of two bacterial delivery systems for in-situ remediation of PAH contaminated sediments

Abstract: Intention, Goal and Background Contaminated sediments represent a significant, worldwide environmental problem since they contain a mixture of different xenobiotics and heavy metals. The presence of mixed contamination presents a unique set of obstacles for remediation efforts. Often sediment remediation occurs as an ex-situ application (i.e., after dredging) in an attempt to minimize some of the problems. However, dredging poses it’s own issues. It does not address contaminated water and often material is not completely removed thereby leaving a long-term residual contamination source in the waterway.