Brown served as the CDM Smith officer-in-charge of the design consultant team during the final design and construction phases of the Groundwater Replenishment System (GWRS). GWRS was developed by the Orange County Water District (OCWD) and the Orange County Sanitation District (OCSD) to take secondary effluent from OCSD and further treats the water using microfiltration, reverse osmosis, and ultraviolet disinfection. The highly treated water is then be transported to a system of seawater intrusion barrier wells and to a spreading basin for groundwater recharge. The project is one of the largest water reclamation for indirect potable reuse in the world with an output capacity of 70 mgd, expandable to 130 mgd. The total construction cost for the project is approximately $500 million.