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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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quality by a factor of 1 . 33 , and provides a margin of safety to ensure that the clarified supernatant released <br /> from the IR- 14 containment basin will meet state water quality standards . Therefore, the IR- 14 containment <br /> basin requires a 4 . 0-ft mean operational ponding depth . <br /> However, care must be taken not to increase ponding depth above the 2 .0=ft minimum too quickly. <br /> This may lead to dike saturation and promote dike instability. Operational experience has demonstrated that <br /> dike permeability typically reduces with time as percolation filters and traps fine sediments. Thus, a <br /> sufficiently slow increase in ponding depth will avoid piping, slumping, and other indicators of dike <br /> saturation and instability. Restricting the operational ponding depth to 4 ft should also reduce the likelihood <br /> of dike instability and provide an appropriate safety factor to ensure adequate solids removal . <br /> Consideration of realistic field conditions further reinforce the IR- 14 containment basin ' s <br /> conservative design . First, DMRP research indicates that under typical field conditions the actual depth of <br /> withdrawal may be significantly less than the WES Selective Withdrawal Model predicts . Solids retention <br /> should improve with decreased withdrawal depth. Second , field conditions may reduce dredge discharge <br /> rates below the design criterion . The design dredge discharge (3 , 560 cy/hr) reflects a minimum separation <br /> between the dredge plant and the placement site and thus a minimum discharge line length . Increasing the <br /> discharge line length also increases frictional losses and correspondingly reduces dredge discharge and <br /> extends basin retention time. The maximum pumping distance for Site IR- 14 to serve the extreme southern <br /> end of Reach III is 4 . 97 miles. Thus, actual dredge discharge rates will likely fall well below the design <br /> criterion and further improve basin solids retention . <br /> 2. 3. 4 Interior Earthworks <br /> The IR- 14 containment basin design specifically excludes secondary interior dikes — e .g. , multiple <br /> cells or spur dikes. Multiple cells are typically employed for continual or successive placement projects that <br /> cannot provide adequate time for dewatering the previous deposition . The projected dredging frequency for <br /> Reach III , once every 5 to 10 years, and the relatively small quantities anticipated with each operation, from <br /> 16 ,300 cy to 32,600 cy, do not warrant the use of multiple cells . Spur dikes are typically used in applications <br /> where the basin ' s size or configuration cannot provide adequate retention time. However, hydraulic analysis <br /> 20 <br />
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