Showing papers on "Dredging published in 1985"

Polychlorinated biphenyls in the Hudson River.

Abstract: This paper reviews studies of recent trends in the distribution of PCBs in water, sediment and fish of the Hudson River, New York. Results of various monitoring programs conducted since 1977 are presented. Elimination of direct discharge, dredging and disposal of contaminated sediments, and stabilization of banks have resulted in reduced levels in sediments and biota. The implications for commercial and recreational fishing interests are discussed. 41 references.

Dredge induced turbidity plume model

Abstract: A model is developed to describe the turbidity plume induced by dredging a ship channel using an hydraulic dredge. The model predicts the suspended sediment concentration within the plume and the resulting sediment deposition alongside the dredged channel. The model applies to a dredging operation in a water body in which the current is primarily along the channel axis and the channel depth is large enough that no significant suspended sediment reaches water surface. Results of field measurements are presented and compared with model. It is shown that the model describes the qualitative feature of prototype data and that the calibrated model parameters agree with independent observations by other investigators.

Experimentally determined impacts of a small suction gold dredge on a Montana stream

Abstract: A small suction dredge was operated experimentally on Gold Creek in Missoula County, Montana to determine the effects of dredging on aquatic insects and the bottom habitat. A 10-m section was dredged from bank to bank. Sampling was conducted before dredging and at upstream and downstream stations for control. The experiments were replicated at an upstream site. Significant changes (P 0.05). Recolonization was substantially complete 1 month after dredging. Intergravel permeability was not significantly changed by dredging (P > 0.05). Suspended sediment concentrations during dredging were highly variable. Suspended sediment discharge averaged a maximum of 340 mg/liter at the outflow and returned to background levels within 11 m. Impacts of suction dredging on the bottom fauna appeared to be highly localized. No immediate downstream impacts were recorded other than fine sediment depositio...

The Effects of Hydraulic Dredging to Control Oyster Drills on Benthic Macrofauna of Oyster Grounds in Delaware Bay, New Jersey

Abstract: This study describes the extent and nature of the effects of hydraulic dredging to control oyster drills (Urosalpinx cinerea and Eupleura caudata, Family Muricidae, Order Neogastropoda) on benthic macrofauna and sediments of the oyster grounds in Delaware Bay, New Jersey. The immediate effects of hydraulic dredging were reductions in numbers of species as well as in total numbers of animals on the three oyster grounds selected. However, oyster drills were most affected. Benthic populations have recovered three to ten months after dredging. The sediments of the dredged grounds can be described as muddy sands. Immediately after dredging, additional mud was brought up from subsurface layers which reduced the median grain size on Ground 154 test plot. On Ground 515 test plot, however, there was a slight loss in the mud which increased the median grain size.

Potential of Remote Sensing in the Corps of Engineers Dredging Program.

Abstract: : The potential of remote sensing in the Corps of Engineers Dredging Program for providing data on channel surveys, sediment drift and dispersion during dredging, water quality and suspended sediment concentrations, and selection of disposal sites and monitoring environmental effects at disposal sites was reviewed. The recommended remote sensor combination for recording dredging and environmental changes was a small, single-engine aircraft equipped with at least two 70-mm or 35-mm cameras. The first camera should be loaded with color film and the second camera with color infrared film for vegetation or land use mapping, or panchromatic film with special filters for water studies. For bathymetric mapping, the cameras will have to be supplemented by airborne impulse radar or laser profilers, and possibly sonar depth finders. A combination of small aircraft and boats is optimum for mapping currents and observing plume dynamics. Additional research is required to study the use of multispectral scanners for bathymetric mapping of large coastal areas, for mapping sediment transport in shallow waters, for mapping concentrations of suspended matter or organic or inorganic origin, and for detecting vegetative stress and soil properties. Along with the acquisition of the multispectral data, ground truth needs to be taken to verify the interpretation of the data. Long-range plans, on the order of 30 to 50 years, are necessary for managing the disposal of dredged material. Keywords: Aerial photography; Army Corps of engineers; Dredged materials; Dredging; Remote sensing.

Management strategy for disposal of dredged material : contaminant testing and controls

Abstract: Abstract : The diversity of disposal alternatives and techniques for management of contaminated dredged material requires the development of an overall long-term management strategy for disposal. The selection of an appropriate strategy is dependent on nature of the dredged material, nature and level of contamination, available dredging alternatives, project size, and site-specific physical and chemical conditions, all of which influence the potential for environmental impacts. Technical feasibility, ecomonics, and other socioeconomic factors must also be considered in the decisionmaking process. The management strategy presented mainly considers the nature and degree of contamination, potential environmental impacts, and related technical factors. The technical strategy is based on findings of research conducted by the US Army Corps of Engineers, the US Environmental Protection Agency, and other over the past 10 years and experience gained while actively managing dredged material disposal. Approaches for evaluating potential for contaminant-related problems and the applicability of various disposal alternatives are discussed. Detailed procedures for conducting tests or for design and implementation of management strategies are not presented, but are the topics of other papers to follow. A technically feasible and environmentally sound strategy for the disposal of dredged material is presented, and it is recommended that this strategy be implemented for future dredged material disposal operations.

Turbidity control system for dredge cutterheads

Abstract: A turbidity control system for dredging operations wherein turbidity adjacent the dredge head is controlled by one or more operating characteristics of the dredging operation. The dredge head includes water jets for agitating, slurrying, loosening the material being removed and directing the material toward the dredge head and control apparatus regulating the water flow into the dredge head, the direction of the jets, the rate of water removal from the head, and the rate of dredge head advancement is adjusted in accord with the turbidity to permit dredging operations within acceptable environmental limits. A turbidity sensor may be mounted adjacent the dredge head to sense the extent of turbidity existing, and the sensor may be used to automatically operate the control apparatus.

Coastal change at Omaha and Great Barrier Island

Abstract: Since 1966, the relative greater degree of erosion at Omaha, on the east coast north of Auckland, near which substantial inshore dredging had occurred up until 1963, compared with that at Great Barrier Island where there has been scarcely any dredging, has been due to an offshore buildup of an ebb-tide delta at Omaha rather than to a continuing effect of the earlier period of dredging of sand for industrial use. Change in predominant wind direction has probably been a factor, particularly in the marked erosion at the sensitive northern end of Mangatawhiri Spit at Omaha. Five different orders of sea-level change and associated sea-floor and coastal change are recognised. Time is an important factor in determining whether or not full equilibrium is reached and in controlling the area of sea floor that is affected by sea-level change. The longer the period of time, the greater the area of sea floor affected. Another probable limiting factor is the offshore coarse belt.

Display device of cutter locus of pump dredging ship

Abstract: PURPOSE:To improve accuracy and efficiency of dredging by a method that the ship location is obtained by radio communications between the land and ship, and a traversing map of a dredging area is displayed using a hull tilt angle detector and measuring instrument of draft, rudder water depth and swing angle installed in the ship. CONSTITUTION:A radio-wave ship location measuring instrument 8 is installed in the ship 2, and transmitting slave stations 10 are set up on a reference point of the land. Also, installed are a hull tilt angle detector 16 measuring front and rear tilt angles QL of the ship 2, a draft measuring instrument 17 measuring the draft (d) between the water surface S and a trunnion 20 of a suction rudder 1, a rudder measuring instrument 18 measuring the water depth from the trunnion 20 to a cutter 3 and a swing angle measuring instrument 19 measuring a swing angle QG of the hull 2 using a gyrocompass. Signals detected by all the instruments including the detector are inputted to an arithmetic unit 11. After the arithmetic result is stored, it is displayed on a display unit B. By this method, the dredging depth in the entire dredging area can be grasped quantitatively, and the accuracy and work efficiency of dredging can be enhanced.

Commencement Bay Nearshore/Tideflats Superfund Site, Tacoma, Washington Remedial Investigations. Evaluation of Alternative Dredging Methods and Equipment, Disposal Methods and Sites, and Site Control and Treatment Practices for Contaminated Sediments.

Abstract: : Alternative technologies and techniques for dredging, disposal, and treatment of contaminated sediments are reviewed. Implications of alternative technologies for management of contaminated sediments are discussed. Selection of appropriate technologies for contaminated sediments management depends on the physical and chemical profile of the sediments, and particularly on the physical state (liquid, solid, or gaseous) of contaminants of concern and changes in state that may occur at different phases of dredging, disposal, control, and treatment. Determination of acceptable criteria governing concentrations of contaminants in water, sediments and soils, and air is the major requirement for selecting specific technologies for managing contaminated sediments. Technologies should be used which ensure that criteria will be met at all phases in the handling operations. Cost is most variable for disposal site effluent treatment options.

Sand for Beach Nourishment in Lower Chesapeake Bay

Abstract: The Virginia Institute of Marine Science designed and performed an inventory of the resources of sand in the southernmost portion of Chesapeake Bay. The primary purpose of the project was to locate a sufficient quantity of sand suitable for use in three beach nourishment and protection projects. The sand inventory embodied four separate but distinctly interrelated phases: three dimensional mapping of the resource, consideration of the area's biological resources and the possible environmental consequences of dredging and beach nourishment, evaluation of the various engineering options for mining the sand, and a synthesis so as to suggest the priorities of sites to dredge and the methods to use for delivering the sand to shore.

Environmental Impact Research Program. Ecological Effects of Rubble-Mound Breakwater Construction and Channel Dredging at West Harbor, Ohio (Western Lake Erie).

Abstract: : The investigation indicated that breakwater construction and associated channel dredging activities by the US Army Corps of Engineers in western Lake Erie at the entrance to West Harbor (Ohio) had no detectable adverse impacts on the distributions or abundances of macrozoobenthos and fishes. Rather, increases were noted in the number of fish eggs and larvae and in the desnity and biomass of periphyton and macrozoobenthos on and near the breakwaters. The area also served as a nursery ground for 20 species of fishes both during and after construction and dredging activities. Colonization of the breakwaters by periphyton, primarily a green alga (Cladophora glomerata), diatoms (Gomphonema parvulum), and a bluegreen alga (Oscillatoria tenuis), and by macrozoobenthos, primarily worms (Oligochaeta), amphipods (Gammarus spp.), and midge larvae (Chironomidae), was rapid and extensive, indicating that the breakwaters provided new, favorable habitat for primary and secondary producer organisms. Marked adverse changes in water quality, especially reduced dissolved oxygen concentrations (2-5 mg/l), occurred around the entrance to West Harbor in 1983 following cessation of construction and dredging activities. These water quality changes, however, could not be ascribed with certainty to construction and dredging activities at West Harbor. Construction of additional breakwaters in the study at that time by the State of Ohio served to confound determination of the responsible causal factors. (Author)

Monitoring device for dredging

Abstract: PURPOSE:To improve dredging efficiency, by a method wherein, based on output signals detected by a draft gauge for a dredger and a load detector in a sludge hatch, an increase characteristics curve of dredged sludge is displayed, and load distribution in the sludge hatch is also displayed CONSTITUTION:Signals from a draft gauge 2 and a pressure gauge 8 for a dredger 1 and a load detector 9 in a sludge hatch 3 are sent to a CPU13 through an interface 12 Based on the signals, the CPU13 computes to send a control signal to a CRT15, load distribution A in the sludge hatch 3 is displayed, and an increase characteristics curve B of dredged sludge is also displayed The efficiency of dredging is computed from increase characteristics of dredged sludge, a dredging time, which provides the optimum efficiency of dredging, is determined to display a point of dredging finishing time

Channel optimization the Columbia river deep draft navigation project

Abstract: Cooperative research and development efforts between the Corps of Engineers and ports on the lower Columbia River have led to increases in ship draft and decreases in channel dredging over the past two decades. Major efforts in the past decade have included a ship motion study, shoaling studies using computer applications, ship squat measurements and development of a model for predicting river heights. Using the knowledge of expected ship squat, the channel depth surveys and some basis of predicting river stage above zero gauge, the mariner has the opportunity to increase the draft of his vessel and still maintain planned levels of underkeel clearance. Maintenance dredging and channel deepening can be programmed for those areas where tide and fresh water gauge are likely to be at a minimum during vessel transit.

An analysis of problems related to dredging in a coral atoll: Kavaratti, Lakshadweep, Indian Ocean

Abstract: Detailed survey on various aspects has indicated the presence of calcareous sands in the lagoons of Lakshadweep (Arabian Sea) suitable for a number of industries. No data are available about the effect of mining the deposits on these atolls. This paper attempts to analyze the data collected in studying the channel that has been dredged in connection with development of the harbor at Kavaratti lagoon Maximum depth in the lagoon is 3 m Outside the depth increases rapidly within a short distance of about 100 m Sediment in the lagoon is derived from the destruction of the reefs and consists of corals, halimeda, molluscan shells, foraminifers, and red algae Presently sands are being dredged from the lagoon and dumped in the sea and these sands are lost as there is a steep slope outside A study of shoreline records for the beaches adjacent to the dredging site shows that the shoreline is an area of accretion. It is quite possible that removal of 1 or 2 meters of sands from the lagoon floor will not affect the equilibrium if the reef is not disturbed Dredging of coral sands for different purposes is known from Fiji, Johnson Island, offshore Apia and no adverse effect has been noticed Removal of limited quantity of sands is recommended, since in a closed system of such atolls like Kavaratti there is always a surplus of sediment transported to the deep sea. The surplus sediment opens the way to sediment dredging. However, reef areas should not be disturbed since the reef is the most important sediment-generating site Studies on growth rate, currents, tides, and bathymetry should be continued to detect the adverse effect simultaneously with dredging

Analysis of a Dredged Material Disposal Operation, Dam Neck Ocean Disposal Site, Virginia.

Abstract: : Purpose of this study was to: (a) determine the Corps ability to construct an underwater feature utilizing predominately fine grained maintenance dredging material, and (b) enhance the Corps ability to monitor and predict the stability of the feature and its effects on surrounding topography. Conclusion arrived at was that the only loss of dredged material from the site was the direct result of settlement of scour along the crest due to various storms which passed through the area. The computed volume change was not within the error limits of state-of-the art bathymetric survey methods. (Author)

Damage caused by dredging to japanese surf clam pseudocardium sybillae shells

Abstract: Dredges used in catching the Japanese surf clam Pseudocardium sybillae are known to cause damage to the shells during the dredging process. This is an important problem because clams resources are considerably affected.In this paper, various factors causing damage to shells during dredging are analyzed. Also, considering the fact that the shell is damaged by collision with the teeth of the dredge while the dredge is being towed. The collision probability of the Japanese surf clams with teeth of the dredge was calculated using such variables as the shell shape, size, distance between dredge teeth, width of teeth and relative position between shells and teeth. Various sized surf clams caught by the dredge were collected and examined for data.The probability of a shell colliding with the teeth of the dredge can be expressed as a function of distance between the teeth and the shell length. The damaged shell caught by the dredge can be considered to be in proportion to this collision probability.It was found that 10 percent of the shells are damaged when the clams collide with the teeth of the dredge while the dredge is being towed.

The selection of dredging equipment

Abstract: This paper discusses what factors should be considered in selecting dredging equipment. The choice depends upon the requirements of the dredging work; environmental and site conditions; equipment availability ; and soil characteristics. Many of the factors that determine the equipment selection can be analyzed after a site investigation.

Arctic Earth Materials for Offshore Construction in Alaska

Abstract: With the exploration activities onshore and offshore and the development of production facilities, the need for granular earth materials on the North Slope of Alaska is ever present. The selection of granular resources for development is primarily dependent on the quality of material and its location. Knowledge of excavation and placement techniques is essential to control escalating cost of mining and transportation. There are two basic modes of construction - winter truck haul or summer barge haul. A discussion of the mining, dredging, and placements techniques is presented. An interpretation of the surficial geology of the Arctic Coastal Plain with respect to granular resources and their engineering properties is presented. The engineering properties are developed from index testing and published data. Relationships of thaw settlement to moisture content, in-place density of the fill, and grain-size is evaluated with existing published data.

Maintenance dredging alternatives for estuarine harbors

Abstract: Worldwide maintenance dredging is a growing concern because of increasing dredging costs and strict environmental constraints, with spoils disposal areas diminishing. The Center for Coastal Studies at Scripps Institution of Oceanography, under past sponsorship of the Naval Facilities Engineering Command and current sponsorship of the Office of Naval Research, has been developing sedimentation control systems as an alternative to maintenance dredging. The key to designing and developing these systems is to understand the physical processes that lead to sedimentation. This paper examines some of these processes responsible for sedimentation in estuarine waterways and briefly discusses the development, use and performance of innovative sediment control systems.