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Following the flow of pollutants

Ocean-monitoring project will help researchers to predict beach closures

IMPERIAL BEACH – Dozens of scientists, engineers and volunteers in wet suits and immersed in 67-degree water are setting up sensitive equipment along Imperial Beach's shoreline to better understand water pollution.

The work is part of a $1.5 million experiment that may help manage beach closures along the entire California coast.

Scientists with UCSD's Scripps Institution of Oceanography say the goal of the Imperial Beach Pollutant Transport and Dilution Experiment is to track how pollutants are moved by waves, currents and tides.

On Monday, investigators dropped floating devices called drifters, which move like dye, into the Pacific Ocean. Dye testing is set to begin Monday.

Drifters and dye both simulate pollution. However, drifters provide better data for how fast pollutants spread along the shore while dye better monitors cross-shore movement.

The drifters and nontoxic dye will be released from the Tijuana River to just north of the Imperial Beach city limit, depending on the swell and other conditions.

Scientists say the markers will be carried by currents and form a plume as they head toward the sensors. Measurements of waves, current, depth and the dye will track the rate at which the plume widens and dilutes.

Falk Feddersen, one of three principal investigators and a Scripps scientist, said researchers hope to have the raw data analyzed so it can be presented in February at the 2010 Ocean Sciences Meeting in Portland.

“We will have a much better understanding of how pollutants get diluted in the water and how quickly they are transported if there's a spill or sewage in the surf zone,” Feddersen said.

Feddersen said a similar experiment in Huntington Beach in 2006 helped Scripps scientists improve sampling techniques but was limited in scope. This time, he said, “we're really going to dial it in.”

Feddersen said if pollutant movement is better understood, a model can be created to provide water-quality updates for ocean users. He said the updates could be made available online, much as current wave conditions are.

Six tripods holding sensors and meters sit anchored in the water off Ebony Avenue, marked by tall poles topped with colorful flags.

Researchers installed more equipment in the water and on the beach that will help gather and relay the information to Scripps hourly. Data will be collected for about one month. The experiment will run through Oct. 31.

The study was designed for dry-weather conditions when the Tijuana River flow is light and beach use is heavy. Imperial Beach was selected for its long, straight coastline and history of water pollution when it rains.

All-terrain vehicles will be used to survey the beach and specially equipped Jet Skis will collect data offshore. Warning signs are posted.

The study was funded by the National Science Foundation, California Department of Boating and Waterways, Office of Naval Research and California Sea Grant.

Feddersen said two recent meetings to discuss the study brought out locals who asked tough questions.

Ben McCue, a program manager at Wildcoast, an Imperial Beach-based conservation group, said he appreciates that Scripps reached out.

“This will give us one more tool to understand when the water is clean and when it is not,” McCue said. “The more people know, the better.”

Union-Tribune Staff Writer