City Installs New Filtration System

The trench collects and treats urban runoff before it can reach the ocean.

A few feet under the sandals of beach goers along The Strand, at the base of Pier Avenue, is a new $500,000 treatment system.

"No one will see it," said Richard Morgan, Hermosa Beach public works director. "You'll walk over it and not know it's there."  

Positioned like a moat between the city and the Santa Monica Bay, the 1,000-foot-long Hermosa Strand Infiltration Trench collects and treats urban runoff before it can reach the ocean. After filtering out harmful contaminants, the water is safely returned to the groundwater table.  

The key to the relatively simple and inexpensive system is the beach itself.

"Sand is an excellent filter of even the smallest particles, including heavy metals and bacteria," Morgan said, "especially our sand-- it is so fine." 

The system is designed to collect the dry weather runoff, but Morgan believes its capacity may be large enough to capture the first flush rainfall.

"Some of the first rains you get in October are the most polluted because the contaminants have built up through the entire summer," he said. 

"It's a first-of-a-kind project because it is such a low-tech way to deal with pollution" said Mark Gold, president of Heal the Bay, who was on hand to celebrate the launch of the project. "And if it's successful then I think you are going to start seeing a lot more of these up and down the state."

The project not only will reduce the amount of pollutants that reach the bay but also the amount of money the city pays the sanitation district for treatment.

By treating the runoff onsite, the infiltration trench relieves pressure on the sanitation district, which is struggling just to keep up with sewer flow. This causes the overwhelmed district to ration usage of its facilities.

"When we get flows that exceed that rate, it opens up the sand berm and spills into the ocean, and can cause pollution problems," Morgan said. 

The project is the first of several by the city designed to capture and treat urban runoff. The city is also in the midst of a complete refurbishment of Pier Avenue to make the street and its surroundings safer and more attractive, and to help improve ocean water quality.

The $2.2-million combined cost of both projects was funded entirely through grant funds, which came from several sources, including the American Reinvestment and Recovery Act, State Water Resources Control Board and Proposition 50 passed by California voters in 2002.

The Pier Avenue Improvement Project includes a similar system that will not only capture and treat urban runoff but also put it to use irrigating landscaping along the refurbished street.

"The real goal is to one day tie in all of our drains to a similar infiltration trench that could run the whole length of our city," Morgan said. 

During the next year, water from the project will be monitored to ensure project goals are met.

"It will be very exciting in a year to see what we've accomplished," Morgan said.

John Kemmerer, U.S Environmental Protection Agency Region 9 associate director for water, attended the ribbon-cutting ceremony.

He said the project "has a lot of potential to provide a model for coastal communities all over Southern California, and for that matter, throughout California and in other parts of the country."


What's urban runoff? Why should we be worried?

Urban runoff is a leading cause of ocean pollution in Southern California. Even during dry weather, water from sprinklers, garden hoses and other sources runs through the streets picking up trash, leaked oil, detergents, pesticides, fertilizer and bacteria from pet waste. It then carries the pollutants through storm drainage to the Pacific Ocean. People who swim in water polluted by urban runoff can catch a stomach virus, respiratory infection, or come down with skin rashes or ear infections.  

Contaminates such as mercury can build up throughout the food chain and result in unsafe levels of pollutants in many different species, some of which are then eaten by people. Urban runoff also contains a variety of other pollutants and high volumes of sediments that can damage marine habitats. Certain organisms are unable to reproduce in areas with large amounts of fine sediment. 

Kathryn Cheng February 05, 2012 at 01:57 PM
Is there some way we can install screens over the water drains on the city's streets? That would keep a lot of debris from entering the system.


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