Showing papers on "Dredging published in 1978"

Prediction and Control of Dredged Material Dispersion around Dredging and Open-Water Pipeline Disposal Operations.

Abstract: : In response to the concern over the potential impact of dredged Material dispersion, Task 6C of the Dredged material Research Program was established to develop the capability for predicting the nature, degree, and extent of dredged material dispersion in the vicinity of dredging and open-water pipeline disposal operations. In addition, methods for controlling this dispersion were evaluated. This report synthesizes the results of eight contract research studies and summarizes the available literature concerned with turbidity generation by different types of dredging operations. Water-column turbidity generated by dredging operations is usually restricted to the vicinity of the operation and decreases rapidly with increasing distance from the operation due to settling and horizontal dispersion of the suspended material. Turbidity levels around dredging operations can be reduced by improving existing cutterhead dredging equipment and operational techniques, using watertight buckets, and eliminating hopper dredge overflow or using a submerged overflow system. During open-water pipeline disposal of fine-grained dredged material slurry, 97 to 99 percent of the material descends rapidly to the bottom of the disposal area where it forms a low gradient fluid mud mound. The relative degree of dredged material dispersion at open-water pipeline disposal operations can be best controlled by using different discharge configurations. Water-column turbidity can be all but eliminated by using a submerged diffuser system at the end of the pipeline.

Effects of dredging and disposal on aquatic organisms

Abstract: : This report synthesizes data from the U.S. Army Corps of Engineers' Dredged Material Research Program, Task 1D. Task 1D consisted of six research projects (work units) that investigated the direct and indirect effects of dredging and disposal of dredged material on aquatic organisms. Determination of potential environmental effects of dredging and disposal, in spite of research conducted to date, is still in preliminary stages due to the multiplicity of variables involved. Bioavailability of sediment-sorbed heavy metals is low. Release of sediment-associated heavy metals and their uptake into organism tissues have been found to be the exception rather than the rule. Research results suggest that there is little or no correlation between the bulk sediment content of heavy metals and environmental impact. Oil and grease residues, like the heavy metals, seem tightly bound to sediment particles and accumulation of these residues by organisms is minimal. The diversity of variables that have the potential for direct and indirect effects on acquatic life argues for an integrated, whole-sediment bioassay, using sensitive test organisms. Such a procedure is currently under development by the Environmental Protection Agency and the Corps of Engineers and should uncover site-specific toxicity problems which can be addressed by appropriate chemical testing and biological evaluation of dredged material.

Effects of Waste Disposal Operations in Estuaries and the Coastal Ocean

Abstract: Since about 1800, human activities have significantly altered shorelines, bottom topography, sediment characteristics, and marine life in estuarine and coastal waters. The first man-induced changes of thc ocean were restricted to nearshore waters and most were small, scattered, and primarily associated with food production or port development (Klimm 1956). Sediment deposition caused by erosion of agricultural lands resulted in extensive delta building and shoreline changes in the Persian Gulf, the Adriatic Sea, and the Mississippi Delta, to name a few examples (Davis 1956). Diking and draining of wetlands, shallow ocean areas, and lakes to form agricultural land has greatly altered shorelines in the Netherlands and England (Davis 1956). Not all wastes are placed directly in the ocean. Some are brought there by normal sediment transport processes. For example, mining is a prolific sediment producer and has also caused extensive changes in wetlands and shorelines due to downstream sediment deposition. Perhaps the best studied case is the hydraulic mining of gold in California's Sierra Nevada (Gilbert 1917). Between 1850 and 1914, 1.8 x 109 m3 of debris was mobilized by mining and erosion in the San Francisco Bay drainage system. About 1.1 x 109 m 3 was deposited in the bay system or on wetlands (Gilbert 1917). Movement and deposition of this material apparently persisted for approxi­ mately 50 years after cessation of mining (Smith 1965). More recently, rapid growth of coastal cities and associated industry has led to greatly incrcascd construction, demolition, and dredging, and the disposal of wastes produced from these activities has emerged as a geologic process causing significant changes in coastal areas. Because waste solids have caused the most obvious geologic changes, this review deals primarily with these materials. Effects of dissolved wastes such as nutrients have been extensively discussed elsewhere (NAS 1969, Likens 1972).

The effect of offshore dredging on coastlines

Abstract: The South of England is well endowed with land deposits of river gravel and sand. Nevertheless, the demand for aggregate and the need to conserve agricultural land have increased to the point where in 1976 sea dredged aggregate was accounting for 11% of the total sand and gravel production. In addition to this annual home consumption of about 12 million tonnes of dredged aggregate a further 3.5 million tonnes was exported to Europe in 1976. Understandably, authorities responsible for coast protection and sea defence view the increase in the removal of marine deposits with concern and a system of licensing by the Crown Estate Commissioners who are responsible for the sea bed from high water to the UK Continental shelf limit has been developed over the years. Dredging by port authorities within their area ofjurisdiction, for navigational purposes, is outside this licensing system. Within the three mile limit local authorities have powers under the Coast Protection Act to regulate dredging. In 1976 a report by an advisory committee to the Department of the Environment1-1^ recommended, among other things, that further studies should be carried out by HRS aimed at reviewing the existing constraints on marine dredging for gravel. In general, the material which is sought for construction purposes is a 60% shingle, 40% sand mixture, but sand is also needed for reclamation fill and for industrial purposes. The areas dredged at present are shown in Figure 1. This paper deals briefly with the licensing procedure and at some length with the involvement of the Hydraulics Research Station in assessing how dredging might affect the coastline. The effect on fisheries, navigation, coastal ecology, and other interests is considered by other organisations. Very little is known of the criteria applied to offshore dredging by other countries, apart from Germany, but with the increased exploitation of the sea bed it is important that information gained by other countries should be used to improve our existing criteria. .

Assessment of Certain European Dredging Practices AND Dredged Material Containment and Reclamation Methods.

Abstract: : A study was made of dredging practices, reclamation methods, and environmental effects of dredging in western Europe by visiting more than twenty ports in six countries and discussing pertinent matters with knowledgeable authorities at each port. A remarkable similarity of dredging practices, reclamation methods, and dredging equipment was noted among the European ports. The productive land use of dredged material was common goal. Contamination problems existed or were potential, to various degrees, at all ports, but few ports were able to assess in specific quantitative terms the status of the local contamination, much less to offer well-developed techniques for the solution of their problems. All were aware of the need for continued research into dredging practices and reclamation methods and of the need to intensify research in the area of environmental effects, particularly contamination. The need for regional and world-wide legislation to control contamination and other adverse environmental effects also was universally recognized. Technical details of describing, increasing the density of, disposing, and making productive use of dredged material were discussed, often by using the widely accepted techniques employed in the Rotterdam Harbor as examples. Conventional and special dredging equipment is described and contamination of dredged material and environmental effects is discussed in detail in this report. (Author)

The Impact of Petroleum Dredging on Louisiana's Coastal Landscape: a Plant Biogeographical Analysis and Resource Assessment of Spoil Bank Habitats in the Bayou Lafourche Delta.

Abstract: A p l a n t b i o g e o g r a p h i c a l a n a l y s i s and a r e s o u r c e a s s e s s m e n t o f s p o i l bank h a b i t a t s were c o n d u c t e d in t h e Bayou L a f ou r ch e d e l t a o f c o a s t a l L o u i s i a n a t o d e t e r m i n e t h e impact o f f o s s i l f u e l d r e d g i n g on t h e w e t l a n d l a n d s c a p e . P l a n t s u c c e s s i o n on s p o i l bank r i d g e s o f known a g e s , l o c a t e d w i t h i n d i f f e r e n t w e t l a n d e n v i r o n m e n t s , was me asu re d u s i n g t h e l i n e t r a n s e c t method. T h i r t y y e a r s o f p l a n t s u c c e s s i o n d a t a were s u b j e c t e d t o b o t a n i c a l f o r m u l a e a n a l y s i s . These r i d g e s were found t o c o n t a i n t e r r e s t r i a l , u p l a n d p l a n t s p e c i e s which a r e s u c c e e d i n g toward a b o t t o m­ land hardwood f o r e s t . T h i s c l i m a x f o r e s t may be a t t a i n e d w i t h i n a max i ­ mum o f 78 y e a r s o f p l a n t s u c c e s s i o n , o r in a bo u t o n e h a l f t h e t i me n o r ­ ma l l y e x p e c t e d on u n d i s t u r b e d u p l a n d s i t e s . In a r e a s o f i n t e n s e d r e d g i n g , c o a l e s c i n g s p o i l bank r i d g e s form semi impoundment s o r impoundments . Semi impounded v e g e t a t i o n s u c c e e d s t o more t e r r e s t r i a l s e r e s , w h i l e impounded v e g e t a t i o n becomes more a q u a t i c . Impoundments l o c a t e d in s a l i n e and b r a c k i s h w a t e r marshes become f r e s h w a t e r e n v i r o n m e n t s as t h e i r s a l i n i t y i s r educe d by p r e c i pi t a t ion. The v e g e t a t i o n a l c h a r a c t e r o f s p o i l bank h a b i t a t s i s in d i r e c t c o n t r a s t t o t h a t o f t h e a d j a c e n t w e t l a n d s . Thus , t h e impact o f d r e d g ­ ing has r e s u l t e d p r i m a r i l y in m a n i n d u c e d , a r t i f i c i a l t e r r e s t r i a l h a b i t a t s in an o t h e r w i s e homogenous, p r i s t i n e w e t l a n d l a n d s c a p e . The t o t a l w e t l a n d a l t e r a t i o n by a l l s p o i l bank h a b i t a t s was c a l c u l a t e d

Field Study of the Mechanics of the Placement of Dredged Material at Open-Water Disposal Sites. Volume II. Appendices J-O.

Abstract: : Observations at the Elliott Bay disposal site on 24, 25 and 26 February 1976 were made of the descent of dredged material through the water column, the spreading velocity and thickness of the density surge over the bottom, and the drift of residual material introduced into the water column by the descending jet. Baseline bathymetry and postdisposal surveys were conducted by the U. S. Army Engineer District, Seattle, in order to determine the distribution and amount of disposed material on the bottom. In addition to these surveys, a 7.5-kHz subbottom profiler was used to detect the deposit of disposed material during the observation period. Dredging was done with a clamshell bucket into two split-hull scows and transported in tandem to the disposal site. The dredging location at the time of the observations was in the Duwamish Waterway between South Park Reach and the 14th Avenue Bridge Reach. Disposal operations were at a site in Elliott Bay less than 825 meter off the end of the dry docks in the West Waterway (See Figure J1 for index map of the area).

Long-Term Release of Contaminants from Dredged Material.

Abstract: : Man's activities in the Nation's coastal zones and waterways have served to contaminate sediments in these areas, generating concern that dredging and disposal may exert adverse effects on water quality and aquatic organisms. The long-term effects of dredged material on water quality at the disposal site remain an area of particular concern. To study the magnitude and predictability of long-term releases from dredged material, an 8-month aerobic leaching study was conducted in the laboratory. A large number of sediments (32) representing broad geographical and pollutional variation were used to ensure wide applicability of study results. Under the aerobic chemical conditions likely to prevail at aquatic disposal sites, total organic carbon, orthophosphate-P, and zinc exhibited the most consistent net releases to the water column. Very little net mass release of mercury (Hg), lead (Pb), cadmium (Cd), or arsenic (As) into the water column was observed regardless of the composition of the sediments. Worst case evaluation of the potential effects of contaminant releases, conducted by comparing results of this study with the most stringent water quality criteria available, indicated that sediments used in this study would not be expected to cause significant long-term water quality problems.

Method and apparatus for dredging

Abstract: In order to accurately control the cutter head of a cutter head suction dredger anchored by means of ropes, the tension in at least one of the two longitudinal ropes is measured and the winch of at least one of the two longitudinal ropes is actuated in dependence upon the tension measured in the one longitudinal rope.

Aquatic disposal field investigations Galveston, Texas, offshore disposal site. Evaluative summary. Final report

Abstract: This study was part of an investigation to determine the environmental effects of offshore dredged material disposal at Galveston, Texas The biological portion of the study was conducted in two phases: a pilot survey of the dredged material disposal site (DMDS) to determine the areal distribution of the biota and sediments; and an experimental study to assess the effect of dredged material disposal on the biota at selected sites in the DMDS Three experimental sites were investigated: a sandy bottom that received sand, shell, and silt-clay dredged material; a muddy bottom that received sand and shell dredged material; and a muddy bottom that received silt-clay dredged material The magnitude of the effect on the benthic populations could not be accurately assessed because adequate predisposal data on natural sediment and benthic population changes were not available Dredged material deposits had no apparent effect on feeding habits of fish or on the distribution of nekton, although some nektonic species may have congregated in the turbid water following dredged material disposal Zooplankton and phytoplankton studies detected no population changes during disposal that could not have been due to sampling error It is probable that sudden abiotic changes and commercial fishing activities cause moremore » destruction of biota than dredging-related activities« less

Importance of Handling Losses to Beach Fill Design

Abstract: Beach nourishment models commonly employed by the U.S. Army Corps of Engineers compare textural properties of native beach and dissimilar borrow sediments to determine overfill and renourishment requirements for beach fill projects. It is assumed for these comparisons that the texture of borrow sediments is unchanged by dredging and handling operations but investigations have shown that significant handling losses do, in fact, occur. This paper presents results from four field studies that document textural changes caused by dredging and sediment handling at Rockaway Beach, NY, and at New River Inlet, NC. Errors associated with calculating volumes of sediment dredged and lost using standard surveying and production methods are discussed and an alternate method is presented as a handling-loss model that compares bottom and dredged sediment texture to determine volumes lost. The results of the studies presented are that handling operations do create significant changes in bottom sediment texture which, in turn, do affect beach fill model calculations by generally improving the predicted performance of these sediments as fill. The proposed handling-loss model predicts volumetric losses that greatly exceed losses generally anticipated during project construction. Discrepancies between loss estimates are discussed in terms of possible inadequacies of the model and of mechanisms that might consistently minimize losses using the standard methods for determining dredged sediment volumes.

Rapid construction of deep international ports, at shallow seashores, without dredging

Abstract: A method of construction whereby facilities can be provided for the docking of vessels or relatively large draft, all dredging operations being dispensed with.

Aquatic Disposal Field Investigations Galveston, Texas, Offshore Disposal Site. Evaluative Summary.

Abstract: : This study was part of an investigation to determine the environmental effects of offshore dredged material disposal at Galveston, Texas. The biological portion of the study was conducted in two phases: a pilot survey of the dredged material disposal site (DMDS) to determine the areal distribution of the biota and sediments; and an experimental study to assess the effect of dredged material disposal on the biota at selected sites in the DMDS. Three experimental sites were investigated: a sandy bottom that received sand, shell, and silt-clay dredged material; a muddy bottom that received sand and shell dredged material; and a muddy bottom that received silt-clay dredged material. The magnitude of the effect on the benthic populations could not be accurately assessed because adequate predisposal data on natural sediment and benthic population changes were not available. Dredged material deposits had no apparent effect on feeding habits of fish or on the distribution of nekton, although some nektonic species may have congregated in the turbid water following dredged material disposal. Zooplankton and phytoplankton studies detected no population changes during disposal that could not have been due to sampling error. It is probable that sudden abiotic changes and commercial fishing activities cause more destruction of biota than dredging-related activities.

Maintenance dredging and toxic substances

Abstract: As more toxic substances are discovered in waterways, regulation of dredging operations will increase, with important economic implications. Many toxic substances will be of interest to those concerned with dredging, because these substances possess the common characteristic of low solubility in water. These substances will be found in high concentrations in the bottom sediments. Examples of dredging operations in the Hudson River, dealing with PCB contaminated sediments, are discussed. Detention time, chemical treatment, floating booms, and landfill disposal sites are discussed.