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2009-323A
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2009-323A
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Last modified
3/17/2016 1:36:04 PM
Creation date
10/1/2015 12:58:28 AM
Metadata
Fields
Template:
Official Documents
Official Document Type
Certificate
Approved Date
12/15/2009
Control Number
2009-323A
Agenda Item Number
8.D.
Entity Name
Florida Inland Navigation District
Subject
Dredged Material Exhibit B
Supplemental fields
SmeadsoftID
7963
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Data characterizing channel sediments in Reach III were obtained in a program of sampling and <br /> analysis conducted during the plan development phase . As documented in the Phase I report (Taylor et al . , <br /> 1997 ), sediment samples were taken at nine locations within the Indian River segment of the ICWW channel <br /> including three locations within Reach III . In an effort to sample worst case conditions, each sampling station <br /> was located near a potential source of fine sediment. Analysis determined that sampling location IR-3 -2, <br /> located at ICWW mile 213 .93 (Cut IR-30 , station 14+25 ) south of Vero Beach and opposite Prang Island near <br /> channel marker R450 , produced the finest- grained sediment ofthe three locations within Reach III . Silt and <br /> clay-sized particles (particles passing a #200 sieve, or with diameters less than 0 .074 mm ) comprised 80% <br /> of the sample (Figure 2 . 4) . <br /> Based on this conservative design criterion, an associated zone settling velocity was then determined <br /> from an empirical relationship between the percentage of fine-grained material and settling behavior. This <br /> relationship was developed from U . S. Army Corps of Engineers (COE) sediment data characterizing the silt <br /> content of a variety of ICWW channel sediments and the corresponding settling behavior of slurry <br /> concentrations similar to those typically encountered in dredging operations (Figure 2 . 5 , Taylor and <br /> McFetridge, 1989). From these data the characteristic zone settling velocity for the sediment to be placed <br /> in Site IR- 14 was determined to be 0. 25 cm/min, or 0.49 ft/hr. This settling velocity was then used to <br /> determine the retention time needed to provide adequate sedimentation within the containment basin . <br /> Retention time relates directly to the depth of ponded water maintained within the basin . The <br /> preliminary design of the containment basin provides a minimum 2 .0-ft mean ponding depth above the <br /> deposition surface. Analysis of the hydraulic characteristics of the proposed containment basin (Gallagher <br /> and Company, 1978) indicates that a 2 . 0-ft mean ponding depth will provide a maximum retention time of <br /> 6 . 19 hours during which the flow over the weir balances the liquid discharge of the dredge. In comparison, <br /> the time required for the sediment to settle out of the"2 .0-ft mean ponding depth is less than 4. 13 hours based <br /> on the projected zone settling velocity of the Station IR-3 -2 material . However, research (Shields, Thackston <br /> and Schroeder, 1987) by the WES under the DMRP indicates that the predicted settling time of the dredged <br /> material should be multiplied by a correction factor of 2 .25 to account for field conditions . This yields an <br /> adjusted required settling time of 9 .28 hours, a time which exceeds the maximum retention time of 6 . 19 hrs <br /> produced by a 2 .0-ft mean ponding depth . Increasing the mean ponding depth to 4. 0 ft provides a maximum <br /> retention time 12 .38 hrs, which exceeds the adjusted settling time required to maintain acceptable effluent <br /> 17 <br />
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