As the prime design consultant, Oceanit was honored with the American Society of Civil Engineers 2012 Outstanding Civil Engineering Achievement Award for Best Study and Research Project for the Honouliuli Wastewater Treatment Plant Outfall Monitoring and Modeling project.
The Honouliuli Waterwater Treatment Plant and deep ocean outfall system are located on the Leeward coast of Oahu and currently provide advanced primary treatment to 25 million gallons per day (mgd) and secondary treatment to 13 mgd. As an alternative to secondary treatment, an analysis was performed to determine the feasibility of extending the existing outfall to meet Water Quality Standards of the Hawaii State Department of Health.
The study included a bathymetric survey and the design and deploying of two buoys to monitor current and temperature profiles for a 12 month period. The data were then verified, processed and used as input for modeling the initial mixing and far-field dispersion of the effluent. Field dye dispersion tests were also conducted to determine the horizontal eddy diffusion coefficient to use as input to the farfield dispersion model developed to investigate the long-term effluent fate. By monitoring and modeling the outfall, the consultant determined that placing the outfall at a deeper depth as an alternative to secondary treatment would save money and have a lower carbon footprint than secondary treatment.