Newport Bay Fecal Coliform TMDL Stormwater Diversion Study

Newport Beach, CA

Under contract with Orange County Public Works, PACE developed three preliminary stormwater diversion improvement options to improve the existing dry-weather diversion system within the Newport Bay watershed to meet the fecal coliform Total Maximum Daily Load (TMDL). The three alternatives consist of a dry weather diversion system, a dry and wet weather storage and diversion system, and a dry and wet weather treatment and diversion system to improve the water quality of the bay and enhance stormwater runoff capture.

The Santa Isabel Channel, East Costa Mesa Channel, and Newport Dunes outlets were identified as potential sources contributing to exceedance of the TMDL. PACE prepared planning-level engineering analyses and layouts in order to determine the conceptual facility requirements for the different alternatives. Approximate construction cost and associated costs were determined for each of the alternatives based on the conceptual facility requirements. Different levels of feasibility were evaluated, including performance, constructability, long-term maintenance, economics, and regulatory accessibility / permitting. The alternatives were analyzed through a comparison evaluation process, and a specialized screening / ranking tool was used to select the most appropriate option for each site.

A detailed technical memorandum was produced for each site detailing the feasibility evaluation process, the alternatives evaluated, and the recommended alternative. In concert with other consultants preparing detailed hydrologic models and pathogen studies in the area, PACE refined the initial designs to identify structural controls best suited for bacterial loads reaching the bay. The results of the analyses were presented to regulators in the form of a Pollution Prevention Plan.

Key Features:

• National Pollutant Discharge Elimination System (NPDES) Permit compliance
• Stormwater quality improvement design
• Retrofit of infrastructure for stormwater quality management within urban areas
• Diversion structures
• Water quality treatment
• Retention/detention Best Management Practices (BMPs)
• Stormwater management basin
• Dry weather runoff control
• Low-impact development (LID) application
• Customized treatment process
• Low / high flow pump station design
• Watershed analysis