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|Title:||Technical supplement to dredged material disposal study, US Navy Home Port, Everett, Washington|
|Authors:||United States. Army. Corps of Engineers. Seattle District.|
Adamec, Stephen A.
Johnson, Billy H.
Teeter, Allen M.
Trawle, Michael J.
Dredged material disposal
Contaminated dredge spoil
|Publisher:||Hydraulics Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Technical report (U.S. Army Engineer Waterways Experiment Station) ; HL- 87-12.|
Abstract: A series of numerical model runs predicting the short-term fate of contaminated and uncontaminated dredged materials disposed in open water was performed. The conditions tested were intended to represent typical conditions for the disposal of material at the proposed US Navy Home Port site at Everett, Washington. Two types of disposal methods were tested : a bottom disposal of contaminated material and a capping operation with uncontaminated material using hydraulic dredging and pipe discharge. Long-term predictions of disposal mound configuration and capping thicknesses based on hand calculations were also made. Three current conditions and four dredged material clumping percentages were simulated for the bottom disposal of the contaminated material. Three discharge pipe configurations and four pipe discharges with varying density were simulated for the capping operation with uncontaminated material. General conclusions from the modeling are as follows: (A.) For a single 4,000-cu-yd barge disposal of material, more than 98 percent of the disposed contaminated material will deposit within 1 hour for all tests at 265 ft of water depth. The disposed contaminated material will deposit within an area of 800 by 1,000 ft with a maximum thickness of approximately 0.60 ft. (B.) More than 90 percent (at a discharge rate of 30 cu yd of solids per minute for 47 min) of the disposed uncontaminated capping material from each sweep of the confined surface discharge will deposit within an hour. The swath of deposition will be less than 300 ft wide with a maximum thickness of approximately 0.09 ft. Bottom impact velocities will be less than 0.5 fps. (C.) More than 95 percent (at a discharge rate of 30 cu yd of solids per minute for 47 min) of the disposed capping material from the 50- and 150-ft stationary downpipe capping operations will deposit within an hour. The area of deposition will have a radius of less than 100 ft with a maximum thickness of approximately 2.0 ft. Bottom impact velocities will be less than 1.1 fps. (D.) Based on sample computations of estimated volumes of material, the long-term disposal of 836,000 cu yd of material (97,000 contaminated and 739,000 uncontaminated) in the first dredging season and 2,469,000 cu yd (831,000 contaminated and 1,638,000 uncontaminated) in the second dredging season is estimated to generate a disposal mound with a final radius of approximately 2,400 ft, a side slope of approximately 1V on 30H, and a cap thickness of approximately 4 ft.
|Appears in Collections:||Technical Report|