Earvin Magic Johnson Park Urban Runoff Water Recycling & Storm Drain Diversion

Los Angeles, CA

 

A unique new system was designed through a collaboration by Los Angeles County Community Development Commission (CDC) and Los Angeles County Department of Public Works Watershed Division (DPW) that sustainably creates a new water source for Earvin Magic Johnson Park by capturing urban runoff (dry and wet weather first-flush flows), treating the captured flows to improve water quality, and recycling the water for onsite irrigation use. The treated recycled water is stored within the park’s lakes and enhances the appearance and water quality of the lake system. This system collects, retains, and reuses all of the wet weather first-flush flows of the 375-acre watershed, amounting to approximately 14-acre feet (4.5 million gallons) of flows from a significant wet weather event.

 

Urban Runoff Capture and Delivery
An urban runoff diversion structure was designed tapping into an existing Los Angeles Department of Public Works 84-inch diameter storm drain to divert flows of up to 33 cubic feet per second (cfs) to a new pump station that sends the flows to the park. The diversion structure is comprised of a low-height partition that will prevent dry weather and first-flush wet weather flows from continuing to flow through the storm drain line and instead are diverted into a new 36-inch pipeline to transfer the flows to the diversion pump station. Wet weather flows beyond the first-flush volume will continue to flow down the existing storm drain line. The pump station contains mechanical screening to prevent trash and debris from being discharged downstream to Compton Creek. The diversion pump station has low-flow and high-flow pumps to handle both dry and wet weather flow volumes.

 

Urban Runoff Treatment Facility
The flows captured from the storm drain line are pumped into a sophisticated treatment facility with ozone, coagulation, circulation, aeration, and water conditioning prior to discharge to the wetlands at the renovated lake system. A pump at the north lake also recirculates water to the treatment system in the south lake at approximately 2,500 gpm to maintain high water quality in the lakes. Lake water is also used for irrigation of the entire park, and potable water make-up is minimized by using the new treated stormwater source. This treatment facility also houses the treatment system for the park’s new spray ground feature. The spray ground is independent of the lake treatment system and uses potable water per the Los Angeles County Public Health codes.

 

Key Features:

  • LID application treating Q85 (first-flush) storm event and retaining onsite
  • Harvesting dry weather flow (72,000 GPD average) for recycling
  • Design of stormwater/runoff treatment system including wetlands
  • Storm drain diversion structure – structural and hydraulic design
  • Trash racks
  • Low and high-flow pump station design
  • Force main design from diversion structure to treatment facility
  • Recirculation pump and piping
Client

AHBE Landscape Architects for the Los Angeles County Community Development Commission

Published Articles

Categories
Interactive Water Features, Lake Systems / Water Features / Pools, Lakes / Streams, Stormwater Management / Flood Control, Stormwater Quality