Dredging

About: Dredging is a research topic. Over the lifetime, 3300 publications have been published within this topic receiving 28325 citations.

Water injection dredging

Abstract: Some twenty years ago WIS-dredging has been developed in the Netherlands. By injecting water into the mud layer, the water content of the mud becomes higher, it becomes fluid mud and will start to flow. The advantages of this system are that there is no need of transporting the mud in a hopper, and no need for a pipeline. Also from an energetic point of view the solution is attractive. The system requires however a different way of payment. Most efficient is a maintenance contract with a dredging company in such a way that the company guarantees a given nautical depth for a fixed sum per year. For the port authority it makes budgeting much easier, because the maintenance dredging will become a fixed amount per year. The limitations are that WIS-dredging is only possible in case the material consists mainly of mud, the mud has to be quite clean, and the disposal should not be too far away from the dredging site.

Sediment Bioassays for NAVSTA San Diego Dredging Project.

Abstract: : Bioassays were conducted on sediments from 13 sites associated with Navy activities in San Diego Bay using liquid, particulate, and solid phase test solutions. Sediments were pre-sampled to determine the most contaminated area at each site based on the relative concentration of cadmium, chromium, copper, and mercury. Five different marine species representing a variety of phylogenetic levels and feeding types were used in the toxicity tests with the most contaminated sediments including copepods, mysids, fish, clams, and worms. The results of the bioassays suggest that dredged material from Navy Piers 1, 2, 3, 4, 5, 6, 8, 10, 11, 12, 13, JK, and Chollas Creek Channel should not have a significantly adverse effect on the marine environment during disposal operations. (Author)

Offshore Sand and Gravel Mining

Abstract: This is a general overview of marine sand and gravel extraction. The origin of the relict or modern resource and the nature of the deposits are described, together with the related hydrodynamic and sedimentological regimes. Some important variations between countries are stressed in the marine aggregates production and usage. Details are provided on the prospecting methods for the identification of new resources, with emphasis on the ‘state-of-the-art’ sea bottom survey instrumentation. The article also focuses upon the principal techniques of extraction, that is, anchor and trailer suction dredging, and the associated features which are generated on the seabed (i.e., pits and furrows, respectively). The creation of such features, together with turbid plumes resulting from the extraction process, may induce significant environmental (physical and biological) impacts. These impacts are described in detail, while the recovery time of the changes is addressed. The article concludes with an overview of the supply and future of marine aggregate dredging.

Characteristics of clam resources of Vembanad lake - a case study

Abstract: The Vembanad lake, covering about 200 sq. km, it supporting a rich fishery of clams mainly constiiuted by Villorlta cyprlnoldes vac Cochinensis and the total production Is around 25,000 t/year- The lake is divided into s'x zones for studying the pattern of exploitation and seed production and the results are presented in the paper. The effect of manual exploitation of subsoil deposits ranging from 41,000 to 70,000 t/year and of dredging on the clam beds is also presented with comments on the development possibilities in the sector based on this case study.