Orange County Branch Newsletter

December 2017

ASCE OC Environmental & Water Resources Institute

Tech Tour of OCWD Groundwater Replenishment System

By Remi Candaele M.S., P.E.

The ASCE OC EWRI Committee was invited by the Orange County Water District (OCWD) to tour the Groundwater Replenishment System (GWRS), also known as the world’s largest purification system for indirect potable use.  A group of 45 attendees was received by Michael Markus, General Manager, and Sandy Scott-Roberts, who serves of the GWRS Program Manager.  The project has garnered more than 40 awards by multiple professional organization, including the ASCE National Outstanding Civil Engineering Achievement Award.  The GWRS is currently undergoing a final expansion, which will increase the treatment capacity from 100MGD to 130 MGD.


Michael Markus defined the role of OCWD as a wholesaler of groundwater to municipal water districts in Orange County.  OCWD provides 75% of the total water demands in the Santa Ana Region of Orange County.  Only 25% of the water demand is met through imports from the Colorado River and Northern California.  As the District strategizes for additional sources of water, the GWRS helps offset the decrease in recharge base flow resulting from the recent incentives for municipal water districts to capture and recycle water rather than discharging the treated water to rivers.  Michael covered also the existing infrastructure that contributes to the recharge of the aquifer including Prado Basin, the OCWD recharge facilities along the Santa Ana River bed in Anaheim, inflatable dams and basins throughout the service area.

Before taking the group on a tour, Michael and Sandy discussed the specifics of the facility. The GWRS purifies sewer water and recharges 103,000 AFY into the groundwater basin, enough water for 850,000 people.  Sandy walked the group to the microfiltration (MF) process system, where tiny straws of fiber polypropylene membrane of 0.2 micron size remove bacteria, protozoa, and suspended solids. The current system has a recovery rate of 90%.

Sandy then took the group to the 3-stage reverse osmosis process, exhibiting the pumps and membranes.  She explained the membranes allow for the removal of dissolved minerals, viruses, and organic compounds including pharmaceuticals.  The system currently operates under a pressure of 150-200 psi and has a recovery rate of 85%.

The ASCE OC EWRI Committee would like to thank Michael Markus, Sandy Scott-Roberts, and Ben Smith for an insightful technical tour that was well received by more than 45 attendees including multiple students from Cypress College. 

Additional acknowledgments: Ben Smith for organizing the event, the EWRI Committee (Roger Chung, Jennifer Marks, Jenny Robinet) for welcoming the attendees.