THE GROUNDWATER REPLENISHMENT SYSTEM—A SUPPLEMENTAL SOURCE OF HIGH QUALITY WATER FOR ORANGE COUNTY, CALIFORNIA

The Groundwater Replenishment (GWR) System, currently in final design by a team headed by Camp Dresser & McKee (CDM), is an indirect potable water reuse project, which is jointly sponsored by of the Orange County Water District (OCWD) and the Orange County Sanitation District (OCSD). The GWR System will be one of the largest advanced recycled water treatment plants in the world when all phases are completed, treating over 174 million gallons per day of secondary treated wastewater from OCSD's Plant No. 1. The advanced water treatment facilities (AWTF) will include microfiltration (MF), reverse osmosis (RO), ultraviolet (UV) oxidation, and various other ancillary facilities constructed to replace OCWD's existing Water Factory 21 (WF 21). The product water from the AWTF will be used for groundwater recharge and injection into the local seawater intrusion barrier, rather than discharging the secondary effluent into the Pacific Ocean through the OCSD outfall. The project will provide a new, supplemental, reliable, and high quality source of water and eliminate the need to construct an additional outfall pipe.The basic treatment process was determined during the feasibility/EIR phase. Thirty-one technical memorandums were prepared as part of the Project Development Phase to thoroughly define the detailed technical basis for the project and prepare a preliminary design. The preliminary design was completed by the CDM Team in December 2000. In addition, implementation issues were addressed including regulatory permitting, public acceptance, and project financing. Important AWTF design criteria were developed for the water quality and quantity, and the major treatment processes, including the MF, RO, UV, pump stations and chemical feed systems. A conceptual site plan was prepared to locate each of the AWTF structures. Finally, the distribution system for the treated product water was also defined, including pipeline alignments, discharge facilities and injection well locations.The estimate of probable construction costs for Phase I of the project is 352 million dollars, with annual operation and maintenance (O&M) costs ranging from 19.7 million to 23.8 million. The project will be constructed in 11 different conventional design/bid/build contracts. The implementation schedule projects the new treatment and delivery systems to be completed and operational by the fall of 2005. After much debate as to the cost and necessity of the GWR System, the joint OCWD and OCSD Board of Directors voted on March 28, 2001, to proceed to the design and implementation phases of the project.