OCWD Groundwater Replenishment System Final Expansion

The Groundwater Replenishment System (GWRS) is the world's largest advanced water purification system of its kind and serves as a global model for potable reuse. Butier Engineering, Inc. (Prime)—in collaboration with Carollo Engineers—provided comprehensive construction management services. The final expansion of the GWRS produces an additional high-quality drought-proof drinking water supply to the Orange County Groundwater Basin. The project increased the existing treatment capacity from 100 to 130 MGD, providing water for 1,000,000 people within the service area.

The project scope of work included the following:

Advanced Water Purification Facility (Fountain Valley, CA)

• Reverse Osmosis (RO) Upgrades: Retrofitted all 21 existing 5 MGD RO units with interstage booster pumps to address flux imbalances and improve energy efficiency.
• Microfiltration (MF) Expansion: Expanded the MF footprint with additional treatment tanks and updated polyvinylflouride (PVDF) hollow-fiber membranes for better fouling resistance.
• UV/Advanced Oxidation: Reconfigured the treatment process to handle increased flow through the UV and hydrogen peroxide disinfection stage.

OC San District Plant No. 2 (Huntington Beach, CA)

• Pipeline Rehabilitation: The 15,750 LF of 66-inch diameter overflow pipeline between OC San District’s Plant No. 1 and Plant No. 2 was slip-lined with fiberglass reinforced plastic to bring secondary effluent to the GWRS.
• Headworks Modifications: Segregated the facility into two treatment trains—reclaimable and non-reclaimable—to isolate high-quality flows for the GWRS.
• Flow Equalization Storage: Construction of two 30-foot-high concrete tanks with a combined capacity of 6 MG to manage effluent float to the OC San District’s Plant No. 2.
• New Pump Station: Construction of a low-flow and plant water pump station to transport treated wastewater from Plant No. 2 to the AWPF.