2013 Excellence in Environmental Engineering and Science™ Competition Winner

E3S Grand Prize

2013 Grand Prize - Planning

Clearwater Program - Beyond Tunnel Vision

Entrant: Sanitation Districts of Los Angeles County
Engineer in Charge: Grace Robinson Chan, P.E., BCEE
Location: Whittier, California
Media Contact: Steven Highter, P.E., BCEE, Facilities Planning Department, Sanitation Districts of Los Angeles County, 562.908.4288 X2711

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Joint Outfall System. The JOS is a regional, interconnected wastewater management system shared by 17 Districts under a partnership agreement, which provides for operations and maintenance of the conveyance system and treatment facilities. The JOS serves approximately 4.8 million people in 73 cities and unincorporated county areas, and spans 660 square miles.

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Existing Ocean Discharge System. The largest treatment plant in the JOS discharges secondary-treated wastewater to the ocean. Two 6-mile-long tunnels connect to four ocean outfalls that extend up to 1.5 miles offshore and reach a depth of approximately 200 feet.

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Construction of 8' Tunnel in 1937

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Construction of 12' Tunnel in 1958

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Flow Projections and Modeling. By 2050, the projected tributary population will increase from approximately 4.8 to 6.3 million people, and the total projected flow of 612 MGD will exceed the treatment capacity of the JOS. A model of the conveyance system and treatment plants evaluated alternatives (e.g., expanding a treatment plant vs. adding sewer capacity) to manage the projected flow. The model compared projected tributary flows to conveyance and treatment capacity, and graphically displayed the results. The 33 miles of the sewer segments (shown in red) and one treatment plant expansion were recommended.

Entrant Profile

The Sanitation Districts of Los Angeles County (Districts) function on a regional scale and consist of 23 independent special districts serving a total of almost six million people in 78 cities and unincorporated territory within the Los Angeles County. The Districts protect public health and the environment through innovative and cost-effective wastewater and solid waste management, and in doing so convert waste into resources such as recycled water, energy, and recycled materials.

The Clearwater Program is a comprehensive planning effort recently completed by the Districts. Much of the wastewater generated in the greater Los Angeles area is managed by the Districts’ Joint Outfall System (JOS), an interconnected sewerage system that encompasses over 660 square miles and provides for approximately 4.8 million people in 73 cities and unincorporated county areas. Wastewater from locally-owned sewers flows through the Districts’ 1,230-mile network of main trunk sewers to seven treatment plants, which have a total permitted capacity of 593 million gallons per day.

Approximately one-third of JOS wastewater is treated at six water reclamation plants, where high-quality recycled water is produced and either beneficially reused at over 600 sites throughout the county or discharged to rivers and streams. The remaining wastewater, which includes saltier industrial flow that is expensive to reclaim, is treated for ocean disposal at the Joint Water Pollution Control Plant in Carson, California.

Project Profile

The Clearwater Program included the preparation of a Master Facilities Plan (MFP), a joint Environmental Impact Report/Environmental Impact Statement (EIR/EIS), preliminary engineering studies, and public outreach. It will guide the management of the Joint Outfall System (JOS) in a cost-effective and environmentally sound manner through the year 2050.

One particular area of concern emerged during the planning process. Two onshore tunnels convey treated effluent from the JWPCP to the ocean outfalls. They were constructed in 1937 and 1958 across an active fault and have not been inspected for more than 50 years due to their overall length, limited access, and continuous flow. In January 1995, two major storm events inundated the JOS. The resulting peak wet- weather flows nearly exceeded the capacity of the JWPCP ocean discharge system. If the capacity is exceeded, treated effluent would be bypassed into a stormwater channel that flows through a regional park. Sewers tributary to the JWPCP could also overflow, causing untreated wastewater to enter nearby watercourses. Therefore, it was necessary to evaluate the construction of a new or modified ocean discharge system to provide peak storm flow capacity and allow for the dewatering, inspection, and repair of the two existing tunnels.


This was a highly complex planning effort due to the challenges associated with modeling future wastewater flows and recycled water demands throughout the JOS, determining the optimal alignment of a new effluent tunnel beneath a highly urbanized area and up to 10 miles offshore, siting an 8,000-foot-long diffuser at depths ranging from 175 to 200 feet below sea level, assessing the physical condition and hydraulic limitations of the existing ocean discharge system, and coordinating with the U.S. Army Corps of Engineers and other federal agencies on the EIS.

Originality and Innovation

The JOS was designed to allow residential wastewater flow to be selectively routed to the six upstream WRPs where reuse demands are greatest. This configuration provides hydraulic relief to the downstream sewers thus reducing capital costs associated with constructing new sewer relief and expanding the ocean discharge system. The population in the JOS is forecasted to grow by 1.5 million by 2050.

Before a new or modified ocean discharge system could be sized, the Districts needed to project the concomitant increase in system flow, which sewers and WRPs would need to be expanded, and how much of the flow would be directed to the JWPCP for treatment and ocean discharge. The Districts developed a GIS-based flow model to evaluate and compare 18 potential conveyance and treatment options. It was determined that the future flow could most effectively be managed through a 25-MGD expansion of the San Jose Creek WRP and 33 miles of sewer relief. The capacity of the JWPCP would remain at 400 MGD, and the associated 927 MGD peak wet-weather flows could be accommodated by a new 18-foot internal diameter effluent tunnel. Another innovation was the extensive and unprecedented public outreach effort to ensure that communities were engaged early in the planning process before any decisions were made. Since 2006, more than 500 outreach meetings have been held with public officials, community leaders, civic and community groups, businesses, environmental organizations, news media, and agencies. The Districts also conducted four public workshops, five public scoping meetings, and three public hearings, all of which were advertised in local newspapers. The public outreach effort was supplemented with newsletters, an informational video, a telephone hotline, and a dedicated website (www.ClearwaterProgram.org). This approach facilitated the exchange of ideas between the Districts and stakeholders and generated a project mailing list of more than 4,000 interested parties.


A comprehensive planning process systematically evaluated options for tunnel alignments, shaft sites, and diffuser locations. More than 50 preliminary alternatives were reduced to four feasible alternatives for project-level environmental assessment in the EIR/EIS. Multi-criteria decision support software analyzed the tradeoffs between environmental impacts, public input, operational considerations, constructability, long- term uncertainty, and cost-effectiveness. Environmental constraints were considered early in the process and weighted heavily to ensure that the final four feasible alternatives would have minimal impacts. In addition, the impacts of other Clearwater Program recommendations were assessed at a programmatic level to assure that decisions made regarding the ocean discharge system did not result in unintended environmental consequences in other parts of the JOS.

Preliminary engineering was seamlessly integrated into the entire planning process and had a profound impact on the recommended project. Much effort went into assessing the condition of the existing seafloor ocean outfalls by performing visual inspections and collecting core samples from the concrete pipes and cast iron joints for laboratory analysis. It was determined that the three largest outfalls have a remaining useful life of more than 50 years. In addition, a hydraulic analysis of the existing ocean discharge system concluded that the capacity limitation was due to one of the two tunnels, not the outfalls. Therefore, the need for a new ocean outfall was eliminated, and the recommended project became a new onshore tunnel that would tie into the existing ocean outfalls at the manifold structure.

Social and Economic Advancement

The Clearwater Program proactively addressed the aging infrastructure and capacity concerns of the JOS, offering the region a safe, reliable effluent management system that will last well into the future. The programmatic elements allow for increased production of recycled water in the JOS thereby reducing the region’s future dependence on imported water.

The JOS has some of the lowest wastewater management rates in the United States. The average annual service charge is $146 per single-family home. The anticipated capital cost of the recommended project is $550 million, resulting in a modest service charge rate impact of approximately $20 per single family home.


The Clearwater Program’s highly complex, innovative, and integrated approach to planning resulted in a recommended project that avoided the significant environmental impacts associated with aging infrastructure and a growing population. The lack of public opposition to the recommended project attests to the overall quality of this successful planning effort and the value of extensive public outreach.

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Public Outreach. More than 500 outreach meetings have been held with key stakeholders during the course of the project. A project website and newsletters were also utilized.

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Final Four Alternatives. Options for tunnel alignments, shaft sites, and diffuser locations were systematically evaluated. Three of the four final alternatives required construction of a new ocean outfall, and estimated costs ranged from $550 million to $1.36 billion.

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Preliminary Engineering. The Districts collected nine years of ocean current and temperature data off the Palos Verdes Peninsula. More than 100 million data points were used in a computer model to predict future ocean water quality. Soil samples were taken along the seafloor to determine the stability during a major seismic event. Visual inspections of the existing ocean outfalls and core samples from the concrete pipe and cast iron joints showed that three of the four outfalls were in excellent condition.

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Recommended Project. Alternative 4 is the recommended project because it is the lowest cost, safest to construct, and least environmentally damaging when compared to other alternatives. The new onshore tunnel will be 18 feet in diameter, nearly 7 miles long, and range in depth from 70 to 450 feet below ground. The hydraulic capacity of the new system will accommodate the peak flows during storm conditions through the year 2050.

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