The North Bay Aqueduct (NBA) is part of the California State Water Project. The aqueduct is 27.4 miles (44.1 km) long all in pipelines and serves Napa and Solano counties, California. The State Water Project diverts water originating from the Sacramento and San Joaquin Rivers (and their tributaries), and it stores water in Lake Oroville. The North Bay Aqueduct was envisioned as part of the State Water Project during the 1950s and 1960s when the project was being planned. Initial North Bay Aqueduct water service went to Benicia and Vallejo. In 1990, the North Bay Regional Water Treatment Plant, serving Fairfield and Vacaville, came on line and was able to treat water from the North Bay Aqueduct for these two cities. The aqueduct cost approximately $83 million to construct.