The top cause of coastal water pollution in Southern California is urban storm water runoff. The City of Redondo Beach is taking steps to protect the coastal waters south of the Redondo Beach Municipal Pier in Santa Monica Bay by collecting the storm water runoff that could be harmful to the beach, treating the runoff to clean out the debris and then using it to irrigate Alta Vista Park. Water that is not needed for irrigation will be infiltrated into the ground, thus reducing discharge to the ocean.
“With this innovative project, the City of Redondo Beach is taking a positive step to protect beach users and at the same time conserve Southern California’s scarce water supply,” said John Kemmerer, associate Water Division director for the Environmental Protection Agency’s (EPA) Pacific Southwest region.
The challenge
The Alta Vista Park Diversion and Reuse Project is a $2.2 million venture designed to help the City of Redondo Beach comply with Regional Water Quality Control Board requirements to reduce storm water pollution. This system will store runoff from dry weather and first flush flows, as well as larger rain events.
The project is funded by the American Recovery and Reinvestment Act (ARRA) and administered through the State Water Resources Control Board’s Clean Water State Revolving Fund (CWSRF). Under the ARRA, California received $280 million from the U.S. EPA for water quality protection projects, and at least 20% of these funds must be provided to “green projects” that support sustainable practices, such as the Alta Vista Park project.
“The City Council has been very proactive regarding water quality and ‘green’ development,” said Mike Shay, principal civil engineer of the City of Redondo Beach. “Their support has given the staff the incentive to think outside the box and to come up with innovative projects that protect the bay and our valuable resources.”
The solution
Capturing and reusing storm water—also known as rainwater harvesting—helps maintain a site’s predevelopment hydrology. The City of Redondo Beach needed a rainwater harvesting system to be installed below ground to accommodate the small site constraints of Alta Vista Park. Initially, several alternatives were considered for the underground storage component of the project, including modular tank systems and slip-joint piping systems. Ultimately, a four-phase rainwater harvesting system from Contech Construction Products Inc. was utilized for Alta Vista Park. It includes two treatment systems and two storage cisterns.
Mehta Mechanical Company (MMC Inc.) installed a CDS system as phase one of the project to collect and pretreat the storm water runoff. The CDS system uses patented continuous deflective separation technology to screen, separate and trap the debris, sediment and oil from the runoff. The indirect screening capability of the system allows for 100% removal of floatables and neutrally buoyant material without blinding and allowing consistency for maintenance within the city.
Storm water runoff then flows to a DuroMaxx rainwater storage system consisting of two 60-in.-diameter cisterns designed to contain the water for reuse in irrigation. The system consists of a north buffer (surge) tank and a south cistern storage tank—phases two and four of the project, respectively. The north buffer tank is a 29-ft-wide-by-40-ft-long double header system responsible for 20,714 gal of storage and will regulate the storm water flow through the main pipelines by acting as a buffer during peak loads.
DuroMaxx was chosen because of its superior joint quality. Its ElectroFusion joint couplers are manufactured using high-density polyethylene pressure rated resins and flat steel band couplers. The ElectroFusion joint remains watertight with a zero leak rate up to a pressure of 30 psi and is an optimal choice for storing storm water for reuse on site. The frequency of rain events can be very sporadic in Southern California, and the reduction of water loss makes the watertight quality of the ElectroFusion joint very important.
Water flow is refined in the third phase with a Stormwater Management StormFilter before it is utilized for watering the landscape. Two 8-ft-by-16-ft Stormwater Management StormFilter precast vault systems—each consisting of 33 cartridges—were installed upstream of the south cistern storage tank; they utilize filtration media to remove the remaining pollutants.
The city used two StormFilter systems instead of one as a precautionary measure in case maintenance to one system is needed. The StormFilter was chosen because its patented surface-cleaning system prevents surface blinding, extending the cartridge life cycle, thus reducing maintenance.
The south cistern DuroMaxx storage tank, phase four, is a 97-ft-wide-by-95-ft-long single header system responsible for 123,339 gal of storage, and it will act as the main storage before irrigation reuse. The irrigation water supply system included two vertical turbine pumps and a hydropneumatic tank to maintain the water pressure and flow rates equivalent to current irrigation demands. If the south cistern is dry, the structure will isolate itself, and water will be provided by the municipal water system. A reduced-pressure double-check backflow preventer has also been installed to prevent cross-contamination.
The results
The city broke ground on the Alta Vista Park Diversion and Reuse Project on February 9, 2010. Completion of the entire project is scheduled for September 2010. Once online, it will be monitored through an SCADA system that allows for remote real-time observation. The impact on water quality in the Santa Monica Bay will be monitored as well.
