Tourists and locals flock to Southern California’s beaches year round. Keeping beaches clean for swimmers, surfers, and picnickers is vital to public health and the economy.

A few years ago, however, the popular Salt Creek and South Monarch Beaches in South Orange County, Calif. (CA) couldn’t make the grade. In 2002, the non-profit California watchdog group Heal the Bay gave both beaches failing grades, based on human health risks, on its Beach Report Card™. The beaches saw frequent public health postings when bacteria levels in the water there exceeded both state and federal standards.

Today, beach reports are more promising thanks to a new ozone disinfection treatment facility. This innovative use of ozone disinfection has done more than improve the beachfront. The Salt Creek Urban Runoff Treatment Facility (URTF) also has been named one of the American Public Works Association’s Projects of the Year for 2006.

Dry Weather Conditions
Salt Creek picks up a typical mix of urban pollutants — fertilizers, animal waste, and detergents — as it winds through residential zones, recreation spaces, and light commercial areas in its 4,500-acre watershed. Dry weather flow, the typical condition in Southern California, ranges from approximately 200 to 1,000 GPM, and the creek discharges directly at the Pacific Ocean.

The Cities of Dana Point and Laguna Niguel, both in the watershed, already employed aggressive urban runoff programs including best management practices (BMPs) and far-reaching public information campaigns. Filtration devices were installed on all publicly-owned catch basins within city limits, and BMPs were required for all new developments. Yet, these efforts had little impact on beach postings even after several years.

Evaluating Treatment Options
The City of Dana Point called on consulting firm PBS&J to explore options for a new treatment facility for the dry season runoff. In considering disinfection options, engineers eliminated chlorination/dechlorination because the new facility would be located close to the creek outlet, residents, resorts, and beaches. In addition, the location offered limited access for chemical deliveries.

Next for consideration were ozone and ultraviolet (UV) light treatment technologies, neither of which requires chemical storage and handling. Using new and existing water sampling reports, engineers screened the ability of ozone and UV light treatment to reduce bacteria and meet target concentrations. Then, PBS&J developed a decision matrix to evaluate both ozone and UV light in terms of capital costs, long- term operation and maintenance (O&M) costs, reliability, and performance.

Ozone disinfection was selected because it could most reliably and cost-effectively achieve disinfection goals given the creek’s typical water quality. Although UV light was not selected for this site, it has been used for urban creek runoff disinfection at other sites, such as Moonlight Beach in Encinitas, (CA). There, UV light was favored due to the site’s water quality and the technology’s suitability to a small available site.

Unique Design
The design phase began, but engineers had few comparable projects to draw from. Ozone treatment has been used for drinking water, wastewater, and in aquariums and zoos, but using ozone to treat dry weather creek runoff is unique. Once the design was complete, however, it convinced a blue-ribbon technical review committee to recommend the project for a California Water Resources Board Clean Beach Initiative Grant. The $4 million grant, the largest single award of a Clean Beach Initiative Grant in California history, largely funded the Salt Creek URTF.

PBS&J led community meetings in which representatives of the St. Regis Resort Monarch Link Golf Course, the Ritz-Carlton Hotel, and residents of Monarch Bay Estates and nearby neighborhoods expressed concern about the project’s visual aesthetics, noise, and construction phase coordination. In response, the facility was located in a slightly-obscured area within the golf course. The building’s Spanish style blends with area architecture and the resort complex. Equipment was sited to reduce operations and maintenance vehicular traffic. During construction, the golf course remained open by utilizing trenchless technology (pipe jacking) for a 600-foot-long reach of the intake/outlet piping.

Low Flow, High Variability
The fully automated Salt Creek URTF will operate approximately eight to ten months annually, during dry weather periods. Sustained flows in the creek, signifying wet weather conditions, will shut down the facility and notify offsite personnel. During the winter wet weather season, the facility will be largely deactivated.

Flow monitoring has indicated ranges from 200 gpm to 1,000 gpm, so the plant has been designed to handle a variety of flow and influent water quality conditions. Variable speed pump drives are controlled by the wet well level to meet demand. To accommodate low demand periods, the ozone generators go to a "soft start" mode in which they are operational, but no ozone is produced. Since effective ozone disinfection requires water with relatively low TSS, turbidity, and organic material, additional suspended solids in the influent are removed by dual media filters using anthracite coal media and sand before entering the ozone contact system.

Cleaner Beaches
An additional benefit of the treatment facility has been proposed — providing water to irrigate a nearby golf course and other landscaping. Options to reduce the creek’s high salt content have been evaluated, and cost forecasts look promising.

The $6.7 million Salt Creek URTF began operating in October 2005. Significant reductions in bacteria levels downstream of the URTF were recorded in dry periods of fall/winter 2005 and in spring 2006. Monitoring of dry season flows will be complete in summer 2006. SLDT