Water District Tries Natural Approach to Treating Urban Runoff
In the years following passage of the Clean Water Act of 1972, counties and cities across the country found themselves forced to comply with restrictions on the release of municipal sewage and industrial waste. For the most part, they accomplished this by cracking down on polluting factories and by investing billions of dollars in advanced mechanical filtration and chemical disinfectant technology.
Such measures could only do so much. They were effective in controlling pollution from large, easily identifiable sources. But 40% of the nation's surface waters remains too polluted to meet the Clean Water Act's goal of being safely swimmable and fishable, according to the Environmental Protection Agency (EPA). Pollutants ranging from pesticides and fertilizer, to oil and gasoline, to human and animal waste continue to reach rivers, streams and coastal waters. The contamination comes from "nonpoint sources," such as farm fields, urban streets, parking lots, and suburban back yards.
"Today, nonpoint source pollution remains the nation's largest source of water quality problems," according to the EPA.
The nation's water-quality regulators are now going after these diffuse, harder to control sources. And if the response by several municipalities in California is any indication, the new generation of wastewater treatment facilities will look a lot less like sewage plants and more like, well, just plain plants.
The strategy, known as bioremediation, relies on living organisms to naturally remove such contaminants as nitrogen and organic compounds from polluted water. This approach is winning fans in the private and public sectors. One of the most ambitious examples of this strategy will soon be provided by the Irvine Ranch Water District (IRWD).
The district provides domestic water service, sewage collection, and water reclamation for the City of Irvine and the unincorporated areas of south-central Orange County, as well as portions of Tustin, Santa Ana, Newport Beach, Costa Mesa, Orange and Lake Forest.
The district's service areas drains into Newport Bay primarily through San Diego Creek, both of which the State Water Quality Control Board (SWQCB) has identified as "impaired" because of contamination by heavy metals, pesticides and other toxins. Newport Bay also is contaminated by nutrients such as nitrogen and phosphorus, which are not themselves toxic but which cause huge algae blooms that lead to fish die-offs as decaying algae deplete the water of oxygen.
The EPA adopted pollutant standards for sediment, nitrogen and phosphorus in the San Diego Creek-Newport Bay watershed in 1999, and for toxic contaminants in June of this year. Additionally, the state has adopted a nonpoint source pollution control plan, mandated by the EPA, which delegates responsibility for devising and enforcing specific pollution-control measures to the state's nine regional water quality control boards. The Santa Ana Regional Water Quality Control Board, with authority over most of coastal Orange County (as well as portions of Riverside and San Bernardino counties), adopted new stormwater standards for Orange County and all its cities earlier this year.
Like most of coastal Southern California, the Newport Bay watershed was once farmed but is now almost entirely urbanized. In 1983, agriculture accounted for 22% and urban uses for 48% of the Newport Bay watershed, according to Orange County. As of 2000, agriculture had dropped to approximately 7%. The San Diego Creek watershed is more than 90% urbanized.
What this means is that compliance with the maze of new coastal water pollution standards falls increasingly on municipal agencies that serve urban homeowners and developers — agencies such as IRWD. Although these standards have drawn irate opposition from many city officials and representatives of the building industry, as well as environmental organizations (See CP&DR Environment Watch, August 2001, March 2000), IRWD is taking a pragmatic approach adopted by several other agencies throughout California.
The district plans to construct about 37 small wetlands scattered throughout the San Diego Creek watershed. Dry-weather runoff from existing and new development will be shunted through the network of ponds and marshes, where plants and microbes will absorb nitrogen and other nutrients, and break down bacteria and other contaminants. Once it has been cleaned by biological processes, the runoff will be allowed to flow into the natural waterways.
The district is calling its project the "Natural Treatment System." The district estimates the system will cost $25 million to $30 million to build, and $2 million to $3 million annually to maintain. It is modeled after an earlier marsh restoration project the district credits with a 25% decrease in algae blooms in Newport Bay. Beginning in 1996, the district diverted the flow from San Diego Creek into a restored wetlands complex known as San Joaquin Marsh. After circulating through the marsh and its ponds for several days, during which it is filtered by algae, cattails, bulrushes and other aquatic vegetation, the water returns to the creek channel with half its nitrogen content removed.
An estimated 1,000 similar projects have been undertaken across the country. Wetlands remove dairy cow waste from agricultural runoff in Chino, fecal coliform from street runoff in Laguna Niguel, and contaminants in municipal sewage plant discharges in Pacifica. Chevron operates a nitrate-removing wetland at its refinery in Richmond. The Orange County Water District uses a complex of 50 small wetlands behind Prado Dam in Riverside County to remove nitrates from the Santa Ana River before it is allowed to recharge the local groundwater basin.
The IRWD project, which it is developing in partnership with Orange County and several cities, is still in the early planning stages. Environmental review is expected to end this month and design is expected to commence after that. If all goes as planned, construction will begin next year. Some of the wetlands will be installed in existing storm water and flood retention basins. In new development areas, however, the district expects landowners to provide property or easements, and to pay for the costs of constructing the wetlands and related facilities. The district also is seeking state and federal grant money to cover part of the cost.
Marilyn Smith, IRWD's community relations manager, said there has been no opposition to the proposal from the local development community, perhaps because the watershed is dominated by just one developer — the Irvine Company — which supports the project.
The wetlands, Smith said, won't by themselves solve the problem of nonpoint source pollution. But they do represent a cost-effective way to tackle one aspect of it. "It's one more tool in the toolbox," she said.
EPA's Nonpoint Source Pollution Program: http://www.epa.gov/OWOW/NPS/
California Coastal Commission's Water Quality Unit: http://www.coastal.ca.gov/web/nps/npsndx.html
Irvine Ranch Water District: (949) 453-5300