The Capistrano Beach Water District (CBWD) is seeking additional supplies to decrease dependence on imported water. Local groundwater is characterized by high total dissolved solids, iron, and manganese. Without desalination, the groundwater cannot be used as potable supply. In order to implement the groundwater desalination project, various aspects required demonstration, including: (1) pilot testing to verify the feasibility of an innovative process train lion exchange [IX] softening pre treatment followed by reverse osmosis [RO]), (2) pilot testing to verify the feasibility of recycling RO concentrate for IX regeneration, and (3) verification that the process reject can be effectively co-discharged through an existing wastewater ocean outfall. Phase I pilot testing confirmed the effectiveness of the innovative process train. Successful demonstration of concentrate recycling was completed in the Phase II pilot testing, based on the addition of sodium metabisulfite to the concentrate prior to DC regeneration to prevent iron fouling of the resin. Regeneration wastes will be blended with secondary wastewater effluent prior to codisposal through the existing outfall. Pilot plant reject was analyzed for constituents specified in the discharge permit and it was concluded that the combined discharge will meet all requirements of the permit. Regulatory agencies have been concerned about the effect of concentrate on the outfall plume. A dilution modeling study was conducted to determine if the concentrate would effect the plume buoyancy. Results show there is little difference between plume characteristics for the outfall from concentrate addition.