During the dry months of the year, when people are most likely to swim and surf in San Diego County, Cottonwood Creek used to carry elevated levels of bacterial pollution to Moonlight Beach, in Encinitas. Not anymore. In December 2002, the City began to sterilize 85 percent of the creek’s outflow with ultraviolet (UV) light, so that it will be “almost clean enough to be drinking water” as it empties through giant culverts onto the sand, according to Kathy Weldon, stormwater program administrator in the City’s department of engineering. The system bypasses 15 percent of the flow to make sure there are nutrients to keep “polliwogs and whatever else is in the creek alive.”

Designed to operate during the dry season, when discharges from storm drains make up much of the creek’s flow, the system “worked fabulously” during its first 60 days, Weldon said. It was shut down for the winter and will be activated again after the wet season ends, probably in April.

Encinitas is the second southern California community to opt for UV treatment in response to permit requirements regarding non-point source pollution, which contaminates beaches and leads to closures. A similar treatment system has been in operation for two years in Orange County, capturing and treating the flow of a major storm drain that discharges into Aliso Creek in Laguna Niguel. Orange County is about to install a second such system on this creek, on a storm drain about a mile upstream, in Aliso Viejo. All three systems are products of ClearCreek Systems, Inc., a small family business in Fresno.

This treatment destroys microbes, including viruses and both undesirable and benign bacteria. The stated goal is to meet state standards for body contact recreational use, including swimming and fishing. “The advantage over chlorine treatment is that UV has no residual effect,” said Clear Creek vice president Tim Gannon.

“It doesn’t kill anything after the water leaves the system.” It is also less expensive, safer to use, and returns water to the stream, added the firm’s president, Joe Gannon, who is Tim’s son. UV treatment has been gaining acceptance for wastewater treatment, Joe Gannon said, but Clear Creek is pioneering in applying it successfully to urban runoff into creeks.

Most southern California coastal communities are taking steps to reduce urban runoff that flows into streams. Some have opted for sterilization with ozone instead of UV. “That’s a judgment call,” said Tim Gannon. Some have diverted dry-weather flow to sewage treatment systems.

As population growth and development continue, so do the water pollution problems, pointed out Bob Morris, senior engineer with the San Diego Regional Water Quality Control Board. “Everyone is in the same boat and there are no easy answers.” The basic choices are “in-the-pipe treatment, diversion, or going into the community and changing habits. That’s the nitty-gritty.”

Cottonwood Creek flows year-round from Encinitas Ranch golf course to Moonlight Beach, draining a watershed of some three square miles. Most of it is buried under strip malls, residential communities, and streets. It surfaces west of Highway 101, flows through a block-long wetland, then goes under the volleyball courts. It empties onto the beach through giant culverts.

Aware that the creek’s water exceeded state standards for fecal coliform bacteria about 90 times a year, Weldon did not wait for an abatement order. She applied for and won a grant from Governor Gray Davis’ Clean Beach Intitiative, matched by the City, and had the UV system installed for $470,000, agreeing to maintain it for 20 years. Monthly costs are expected to be “well under $1,000,” Weldon said.

Three blocks from the beach, all but 15 percent of the creek’s water is pulled from a box culvert into a 14-foot-deep wet well, “catching everything that would come down,” Weldon said. When the well fills up, the water runs through a process that removes sediments, heavy metals, and oils, then is piped through a closed chamber where it is exposed to ultraviolet light.

The treatment system on Cottonwood Creek has the same capacity as the one on the storm drain known as JO3P02, which serves a watershed with 14,000 homes and flows into Aliso Creek. Each can process 200,000 gallons a day. On Aliso Creek, however, water is collected not from the creek itself but from the storm drain, and it pours not into a well but into a pond built on an easement provided by the Kite Hill Homeowners Association. The system was installed in response to a cleanup and abatement order from the San Diego Regional Water Quality Control Board, after excessive levels of fecal coliform bacteria were found to be spilling into the creek from this storm drain. Clear Creek Systems provided and installed all the treatment equipment, operates the system, and charges the City $664 per million gallons treated—averaging $3,000 a month, according to Ken Montgomery, director of public works and city engineer. This is a temporary system. The City will soon replace it with a system that will carry dry-season flow from gutters into a series of constructed wetlands for treatment.

To clean up Aliso Creek, however, more than these installations will be needed. After excessive coliform levels were found in JO3P02, Morris said, “we sampled major storm drains on the creek [there are about 50], monitoring weekly. We found that pollution was widespread and that, for the most part, it exceeded standards for body contact recreation.” State law requires that warnings be posted on beaches when the fecal coliform count is over 200 per 100 milliliters of adjacent ocean water. On Aliso Creek, levels 50 times that high were found. The sources were “just urban runoff,” Morris said, “pet waste, birds, fertilizer, perhaps a bag of steer manure on a lawn with bacteria that perhaps regenerated in the stormwater system.” Drain JO3P02 was not the worst. It was simply the one subject to an abatement order.

“We’re taking it a step at a time,” Morris said. “The permit process gives the permittee flexibility to take incremental steps and see if they help. Most cities try to address the issue by encouraging good practices. They are going up storm drains looking for sources and taking reasonable measures to eliminate them. They are asking, for instance: Are dumpsters covered? Is steer manure being applied in a manner that stormwater or irrigation doesn’t wash it down the gutter? We need to prevent pollution and control its sources. Otherwise, what’s the alternative? A treatment plant at every storm drain?”

The treatment plant at the end of Cottonwood Creek supplements a comprehensive pollution-prevention/source-reduction program,” Morris said.

—Rasa Gustaitis

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