Baja California is moving ahead with plans to expand and upgrade its failing San Antonio de los Buenos sewage treatment plant, located on Tijuana’s coast, and expects to launch construction next year, a state official said. The project, estimated at $24.7 million, entails the upgrade of existing wastewater treatment ponds at the 30-year-old facility just south of the border with San Diego County. It also involves the construction of a new activated sludge facility on the site.