Brown and Caldwell on Behalf of Guam Waterworks Authority Agat-Santa Rita Wastewater Treatment Plant Mixing Zone Study
EA provided advanced technical support in the performance of a comprehensive mixing zone study performed over an established municipal wastewater diffuser at the mouth of Tipalao Bay along the southwest coastline of Guam. This simple diffuser discharges effluent pumped from two wastewater treatment facilities into the seawater flowing along the coastline. Wastewater contributions from an expanding U.S. Naval Base-Guam in Santa Rita had increased the total volume of effluent discharged through the outfall and prompted a thorough study of the system.
Rhodamine dye injection was used to determine if the dilution rates within the receiving waters are sufficient and concentrations of the effluent remain in compliance with the original permit at the boundaries of the permitted mixing zone. EA obtained physical oceanographic measurements from the water column using a bottom-mounted acoustic Doppler current profiler and deployment of instrumented, current-following drogues to produce Lagrangian measurements of the surface and near-surface waters. These data were used to evaluate wastewater plume morphology, advection patterns, and residence time within the receiving waters.