Lake Merritt is not really a lake: It is a 155-acre tidal lagoon, located just east of downtown Oakland, Calif. It is the country’s oldest wildlife refuge and provides beauty and recreation in an otherwise urban setting. Urban runoff from the 4,670-acre watershed—carrying trash, debris and other pollutants picked up along the way—flows into the lake through about 60 storm drains.
Taking Action
In 1999, when Lake Merritt was put on the U.S. Environmental Protection Agency’s impaired water body list because of high levels of trash and low levels of dissolved oxygen (in large part due to leaves and other organic matter), the city took action. It installed the city’s first CDS storm water treatment system in one of the storm drains discharging into the lake. Using patented continuous deflective separation technology, the CDS system from CONTECH screens, separates and traps trash, debris, sediment and oil from storm water runoff.
Since that time, the city has delivered on its commitment to keep trash out of the lake. Three more CDS systems have been installed in storm drain outfalls to the lake, and other programs and initiatives have been implemented. But there still is work to be done. A recent plan passed by the San Francisco Regional Water Quality Control Board requires 70 cities and municipal agencies around San Francisco Bay, including Oakland, to drastically reduce (by 40%) the amount of trash flowing from storm drains into the bay by July 2014.
A Cleaner Future
Pushing forward on its water quality goals, the city of Oakland will install a fifth CDS system this winter at the Lake Merritt Nature Center. The American Recovery and Reinvestment Act of 2009, signed into law by President Obama in February 2009, made it possible for the city of Oakland to install this first federally funded storm water trash separator in Oakland.
The CDS unit will be installed in front of the nature center and be capable of holding more than 150 cu ft of trash and sediment between maintenance events, which equates to more than 30 33-gal trash bags. In addition, should it become necessary, the unit can capture and store more than 600 gal of spilled oil and grease. Without the CDS units, trash and spilled oil would continue to make their way to Lake Merritt and damage its ecosystem.
“The CDS system is the only storm water treatment system available that can pass the large storm flows expected at this site and still retain the captured pollutants,” said Frank Birney, vice president of storm water for CONTECH . “The indirect screening capability of the system allows for 100% removal of floatables and neutrally buoyant material, without blinding.”
The best approach is to prevent trash from reaching the streets in the first place, so a strategy that combines prevention with the effective trash capture of the CDS units has proven to be a smart solution in the fight for a cleaner Lake Merritt.
