Two projects, the Laguna Beach Storm Drain Pollution Control Project and the Laguna Main Beach Pollution Control Project, were undertaken by the City of Laguna Beach, CA with funding from the State Water Quality Control Board through the Clean Beaches Initiative grant program.
The goal of the projects was to reduce indicator bacteria levels in the ocean waters along approximately 1.5 miles of beach from Heisler Park south to Mountain Road, including Main Beach. The project budget was $1,310,000 with $1,200,000 in State funds with a City Match of $110,000. The project was initiated in October 2004 and was completed in October 2008. The diversion units were first activated in early April 2007.
The two projects were combined into one contract and Scope of Work. The project scope included the construction of six urban water diversion units to reroute dry weather nuisance flows from high priority storm drains on the beach to nearby sewer lines for treatment at the regional sewer treatment plant. The project also included a monitoring requirement to assess the impacts of the diversion installations on bacteria levels in the ocean.
Monitoring efforts for the project focused on determining if project goals were met by measuring flow and bacteria levels in the diversion sumps, measuring the amount of sludge and debris removed from diversion sumps and screens, and analyzing five years of ocean bacteria data from the existing beach water quality monitoring program. Pre- and post-construction data were combined to assess the project’s impacts once the diversions were online.
Flow data, including estimated flows, shows that over 11,000,000 gallons of nuisance water was diverted from the beach outfalls by the six diversions during the 2007 dry season. This diverted flow carried an average of over 40,000 CFUs of total coliform bacteria per 100mL, resulting in the removal of a total mass of over 7.2X1012 CFUs of indicator bacteria from ocean water.
Trash and debris removal data shows that more than 12,000 lbs of sludge was pumped from diversion sumps and over 70lbs of floating debris were removed from the diversion screens through September 2008. The sludge and trash caught by the diversions would otherwise have carried bacteria to ocean waters and littered the beach.
Ocean water monitoring data from 2003 – 2008 shows a dramatic decline in indicator bacteria levels in the ocean starting in May 2007, when the six project diversions, along with all other diversions in town, were activated for the 2007 wet season. The diversions are kept online as deep into the wet season as possible without risking damage to the treatment plant. The data also shows that bacteria levels spike slightly in the winter wet season, then drop dramatically again in spring 2008, as diversions come back online.
The City of Laguna Beach credits the installation of the six diversion units of the Laguna Beach Storm Drain Pollution Control Project and the Laguna Main Beach Pollution Control Project, along with the other diversion units in town, with the significant reduction in indicator bacteria levels along the Pacific Ocean shoreline in the 1.5 miles of beach from Heisler Park south. The project met the bacteria and trash reduction goals set forth in the initial project proposal.
Funding for this project has been provided in full or in part through a contract with the State Water Resources Control Board (SWRCB) pursuant to the California Clean Water, Clean Air, Safe Neighborhood Parks, and Coastal Protection Act of 2002 (Proposition 40). The contents of this document do not necessarily reflect the views and policies of the SWRCB, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.
Download the full final report for this project here:
