On December 24, 2012, the San Diego County Water Authority announced they had sold $734 million worth of tax-free bonds at 4.38% interest to build the Carlsbad Seawater Desalination Project, the largest seawater desalination plant in the Western Hemisphere. The project is located near the Encina Power Station in Carlsbad, and is expected to produce about of water per year by 2016 when the project is completed. The plant is expected to use over 17,000 reverse osmosis racks. The project includes $80 million in San Diego Water Authority upgrades to its own facilities. A pipeline is being built to deliver desalinated water into its Twin Oaks Valley Water Treatment Plant near San Marcos. The developer Poseidon Resources is building the plant and pipeline in a joint venture with contractor Kiewit Shea Desalination. The project will deliver up to 50 million gallons a day of drought-proof, highly reliable water that will become a core, day-to-day resource for the region. It is projected to meet about 7% of San Diego County's demand in 2020. The total cost is projected at $1,849 to $2,257 per acre-foot. The additional cost of desalinating seawater will add $5 to $7 per month to ratepayers' bills—about a 10% increase.