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Title: Methodology for design of fine-grained dredged material containment areas for solids retention
Authors: Montgomery, Raymond L. (Raymond Lowree)
Keywords: Sediments (Geology)
Dredging spoil
Dredged materials
Suspended sediments
Sedimentation and deposition
Publisher: U.S. Army Engineer Waterways Experiment Station
Series/Report no.: Technical Report (Dredged Material Research Program (U.S.)) ; no. D-78-56
Abstract: A literature review revealed gaps in research concerning the use of existing procedures for designing containment areas for fine-grained dredged material to meet standards for effluent suspended solids levels. The literature review did provide the basis for developing laboratory and field investigations and for evaluating results. Four active dredging projects were used as sites to obtain samples of channel sediments and dredged material for laboratory tests, determine suspended solids levels of dredge discharges and containment area effluents, and to develop profiles of suspended solids versus depth for the containment areas. Dye tracer studies were used to investigate the short-circuiting and mixing properties of containment areas. It was found that grab samples taken from channel bottom sediments are adequate for performing sediment characterization and settling tests. Sediment organic contents were generally less than 10 percent for all the sites except one. In general the organics were considered to be too low to be a significant factor in evaluating the settling properties of the dredged material. Settling tests performed in an 8-in.-diam column were found to be satisfactory for defining dredged material settling behavior within a containment area. Settling behavior in the freshwater environment was best de-scribed by a flocculent settling test, while behavior in a saltwater environment was best described by a zone settling test. The same settling columns were used for both tests with only minor procedural changes. Procedures are presented for designing new containment areas for suspended solids retention and the suspended solids retention potential of existing containment areas. Design methods for saltwater and freshwater sediments are included. The design procedures are(based on gravity sedimentation of suspended solids. With proper design and operation of the containment area, the sedimentation process will normally provide removal of solids down to levels of 1 and 2 g/ℓ in the effluent for saltwater and freshwater sediments, respectively. If the required effluent standards are lower than these levels, the designer must provide for additional treatment of the effluent; e.g., flocculation or filtration. Dye tracer studies indicated that a correction factor of about 2.25 should be applied to design area and detention times to compensate for the deviation from ideal or plug flow conditions.
Description: Technical Report
Gov't Doc #: Technical Report D-78-56
Rights: Approved for Public Release; Distribution is Unlimited
Appears in Collections:Technical Report

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