Initial Dilution of Southeast Florida Ocean Outfalls

Initial dilutions of four ocean outfalls (the Miami‐Central, Miami‐North, Hollywood, and Broward outfalls) on the east coast of South Florida were determined from dye and salinity studies. In the dye studies, continuous injections of the red dye Rhodamine‐WT into effluent were conducted; dye concentrations were measured using a deck‐mounted fluorometer with a ship‐towed sampler and from grab water samples. In the salinity studies, temperature and conductivity were measured using a towed conductivity‐temperature‐depth device (CTD); salinity deficit was taken as a tracer to determine initial dilution. Results show that initial dilutions determined from both methods are consistent. Data for initial dilution and for environmental and effluent parameters are interpreted using the dimensional analysis method. A comparison is made between the present data and data from previous studies. Data for Hollywood and Broward outfalls (single‐port discharges) are consistent with previous data. Data for Miami‐Central and Miami‐North outfalls (multiport diffuser discharges) are not consistent with data for single‐port discharges. A value of $C_1=0.15$ for the asymptotic solution for the buoyancy‐dominated nearfield is suggested.