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described above will produce an effluent suspended sediment concentration of less than 0 .45 g/l . Relating suspended solids concentration to Florida effluent quality standards — based on the turbidity of the effluent relative to the ambient turbidity of the receiving waters — is problematic since turbidity depends highly on the physical characteristics and concentration ofthe suspended material . However, WES guidelines (Palermo et al . , 1978 ; Walski and Schroeder, 1978) indicate that this 0 .45 g/1 falls well below typical standards for effluent discharged into estuarine waters . 2. 3. 3 Ponding Depth and Basin Performance Ponding depth refers to the height ofthe water column (with its suspended sediment load) maintained above the depositional surface during dredging operations . It is regulated by the height of the weir crest and, to a lesser extent, by dredge plant output. Given the initial slope of the basin interior (about 0 .2%), ponding depth will vary within the basin . The ponded water, most shallow nearest the inlet, will increase to its maximum depth nearest the weir. Conceptually, ponding depth is typically discussed in terms of its mean value over the entire basin interior. However, as a practical operational criterion , ponding depth is more usefully specified at the weir where it can be measured directly. At the weir, the excavated grade of the IR- I4 basin is 4 .2 ft NGVD, or 0. 8 ft below the average basin depth. Therefore, ponding depth at the weir exceeds the mean basin ponding depth by approximately 0. 8 ft. In the remainder of this report, ponding depth will be given in terms of the mean depth over the basin and, where appropriate, related to the corresponding depth at the weir. Ponding should be maintained at the greatest possible depth during dredging operations. Increased ponding depths produce increased retention times and decreased flow velocities through the containment basin and therefore improved solids retention and effluent quality. The limiting consideration for increased ponding depth is the amount of hydrostatic pressure the dike can withstand without loss ofstructural integrity. Analysis of sediment settling characteristics established whether the 2 .0=ft minimum mean ponding depth produces a basin retention time adequate for acceptable solids retention and effluent quality. The fine- grained sediment component, because it requires the longest time to settle out of suspension, determines the required basin retention time and therefore the required ponding depth . 16