Dilution curves will be completed for dredged material discharge, similar to those already generated for waste disposal techniques. John Proni, AOML

Dilution curves for discharged dredged material have been obtained for dredged material discharged in the New York/New Jersey mud dump site coordinator location and in the western boundary region of the Florida Current (Gulfstream) off Miami, Florida. These curves were obtained using water sample measurements of total suspended material (TSS) and acoustical backscatter (IB). In both cases the dilution curves differed above and below the shallow pycnocline. Shown in Figure 1 is a plot of IB as a function of distance and time for three discharge events at the New York Bight mud dump site. All data points were gathered at a depth below the pycnocline. Shown in Figure 2A and 2B are plots of IB for the 19 meter depth horizon as a function of time and the 8 meter depth horizon as a function of time, respectively. Shown in Figure 3 is the total suspended solids, TSS, as a function of time corresponding to figure 2. Background TSS levels at the mud dump site during the study appear to be in the range 5-10 mg/l while at the Miami discharge site they were 1 mg/l or less. These curves provide a measure of reduction of concentration of discharged dredged material for use in exposure and toher studies. While all the scattering mechanisms contributing to the backscattered sound have not been fully evaluated, there appears to be a significant correlation between relative reduction in IR and in TSS over a broad variety of discharge situations.