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— I n San Diego County, treated sewage is discharged four miles out to sea from six treatment plants dotting the coast from the border to San Onofre. In Mexico, one treatment plant at San Antonio de Los Buenos, 12 kilometers south of the fence, releases a mixture of treated and untreated sewage down a creek that flows into the surf zone. So it came as a surprise to some when Mexican newspapers reported that a municipal official, Miguel Angel Avila Niebla, in a talk to a civic booster group in the Playas de Tijuana area, called Grupo Madrugadores, had boasted that the ocean water at Tijuana's beaches had tested cleaner in 2001 than at San Diego's beaches.

Avila, the director of the State Commission of Public Services in Tijuana (known in Tijuana by the Spanish acronym CESPT), told Grupo Madrugadores that, in 2001, the water in Playas exceeded permitted norms twice while one (unspecified) spot in San Diego exceeded the norms 13 times. Avila claimed the study had been "certified" by the International Committee on Limits and Waters (Spanish acronym: CILA), which is the Mexican half of a binational organization known in the United States as the International Boundary and Water Commission.

These three agencies are all testing ocean water in the San Diego/Tijuana region, and they're all looking for the same thing: bacteria. "There are three different bacterial indicators that we test for," says Clay Clifton, San Diego County Department of Environmental Health's recreational water program coordinator, another group testing local ocean water. "All three are used as indicators for fecal contamination. Unfortunately they are not very specific, because the bacteria is common to the intestines of all warm-blooded animals. So when you have a bacteria result that comes in above the state's standards, you don't know if it is from urban runoff, an actual sewage spill, a flock of birds on the beach, or someone not picking up after their dog."

The county Department of Environmental Health tests the water at local beaches and bays to conform with state law. "In the state of California," Clifton explains, "we have at least weekly monitoring required at any beaches next to a storm-drain outlet. That began in 1999 with a law known as AB411. And prior to that, a California Health and Safety Code directed the local health office -- which in San Diego County is the Department of Environmental Health -- to collect water samples as needed to protect public health. In San Diego County we have 107 sites that are monitored at least weekly. And there are a handful, maybe 4 to 5 sites, that are monitored twice or more a week."

Clifton says one staffer spends Monday, Tuesday, and Wednesday of each week taking samples. "He does North County on Monday, central on Tuesday, and south on Wednesday. Then we have a lot of data entry on Thursday and Friday.

"The idea," Clifton adds, "is to protect public health. Because people are going to swim at these beaches. But the science and testing, unfortunately, is not as far along as the regulations are. Because these are bacterial tests, they have to be incubated. So you've got to take the test, incubate it at the lab, and then you've got a minimum of 24 hours before the results can be looked at for a preliminary result. That lag time is a problem. But we've got two different standards: one is what is called a single-sample standard, then we have a more conservative 30-day log mean standard. So, say over the last 30 days maybe only one sample has exceeded the single-sample standard, but the rest of them are all hovering just underneath that. In that case we would have the beach posted [with signs warning swimmers of bacterial contamination]. And now you have a pretty good predictive tool that there is some kind of ongoing contamination problem there rather than a one-time random event like a couple of seagulls down on the beach next to your sample spot."

On its website, the Department of Health posts a downloadable chart of the number of beach advisories and closures at its 107 testing sites. However, as the department does not test Mexican waters, it offers no confirmation of Avila's claims. Avila could not be reached for comment, but another official from his agency, Jorge Alberto Castillo, indicated in an e-mail that Avila's claims were based on "the results of bacteriological analysis given to us by the Mexican Chapter of IBWC, from Imperial Beach and Playas de Tijuana through Punta Bandera during the year 2001. We compared those figures with the results of our laboratory, which analyzes samples on the Mexican side only."

Roberto Espinosa, who directs the International Committee on Limits and Waters in Tijuana, says Avila's comments were "based on the agreement IBWC and CILA have to monitor the quality of the surf zone along the international border line. We have several stations on the north side between Coronado and Imperial Beach and three stations in Mexico. One is right next to the fence. Then there are two of them in the Playas de Tijuana area, and there's one more that used to be at Punta Bandera, and it's being moved to an area called Playa Blanca."

The study, Espinosa says, "was actually done by the Metropolitan Waste Water Department in San Diego. We have a joint program in which the San Diego lab, accompanied by IBWC, goes into Mexico, where we are joined by the CESPT laboratory and we take simultaneous samples."

The results of testing in 2001, Espinosa says, show that on the Mexican side water quality "has been a little bit better than on the U.S. side [from Coronado to the border]. Why? Because some flows tend to go through the Tijuana River. It's a major source of conveyance to the ocean. Most of Tijuana is built in a basin that flows into the Tijuana River, which in turn flows northwest into the U.S. There's a portion of the western side of the city that flows directly into the ocean, basically Playas de Tijuana. But the rest of the city flows down to the Tijuana River, then flows into the United States. In trying to limit the flows that might reach the Tijuana River and enter the U.S., there is a system which captures the flows before they go into the United States. It's been operated by IBWC/CILA, and it works most of the year, except when we have storm runoff. During storms, it has to be shut off because there's a lot of sand, which would ruin the equipment. But normally the flows are captured there and pumped to a plant on the Mexican coast, at San Antonio de los Buenos. And part of it is conveyed to the international treatment plant just north of the border. But the Tijuana River is a natural drainage, and its mouth is where most of the beach closures will take place."

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