Delivering advanced treatment infrastructure at scale
Our experts designed the 70-mgd MF/RO/UV treatment facility, expandable to 130 mgd, enabling reliable indirect potable reuse at regional scale.
Client
Orange County Sanitation District
Location
Orange County, California
Markets
Priorities
GWRS turns treated wastewater into a resilient local supply
Extended droughts, population growth, and seawater intrusion threatened Orange County’s groundwater basin and long-term water reliability. To address these challenges, Orange County Water District and Orange County Sanitation District advanced the Groundwater Replenishment System (GWRS). Operational since 2008, the system purifies highly treated wastewater that was previously discharged to the Pacific Ocean, transforming it into a locally controlled, sustainable water supply. The program protects groundwater quality, reduces ocean discharges, and strengthens regional water resilience.
Engineering complex groundwater recharge systems
The team designed pumping stations, a 13-mile large-diameter pipeline, recharge basins, injection wells, and barrier pipelines to protect the basin.
Validating subsurface compatibility and performance
The team conducted PHREEQC geochemical modeling and lithology analysis to confirm injected water compatibility with aquifer materials.
Leading construction oversight and community coordination
We provided field oversight, hydrogeologists onsite, adaptive drilling support, and coordinated public outreach in residential neighborhoods.
The GWRS reclaims and recycles water from OCSD’s Plant No. 1, delivering purified water to recharge basins where it naturally filters into the groundwater system. Approximately two-thirds of the treated water is conveyed through a 13-mile pipeline for recharge, improving basin water quality over time. CDM Smith delivered design, specifications, construction management, and field oversight for 16 injection wells constructed across eight sites, many in densely populated areas. Continuous coordination, adaptive construction approaches, and proactive public engagement enabled on-time delivery of critical components and established the GWRS as a model for indirect potable reuse.
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Client
Orange County Sanitation District
Location
Orange County, California