dam was seismically vulnerable. If the dam had collapsed when full, it would have flooded parts of Fremont, California with a wall of water high. Dam regulators for the state of California restricted the capacity of the original dam in 2001, to mitigate the seismic threat. The capacity of the original dam was limited to about one-third of the nominal 100,000 acre-feet (120 million cubic meters). To restore lost capacity, the San Francisco Public Utilities Commission constructed a replacement dam located downstream from the original 1925 dam. The dam replacement took twice as long (eight years instead of four years) and cost twice as much as originally scheduled. Hazardous geological conditions were discovered near the proposed west abutment in 2012 and near the proposed spillway. The dam site was weakened by at least two ancient landslides. When construction started in 2011, the budget was $420 million, and completion was expected in 2015. The seismic redesign required three million additional cubic yards (two million cubic meters) of excavation, far more than the original seven million cubic yards (five million cubic meters). The spillway had to be relocated away from one of the ancient landslides, delaying the project by another year. As of 2017, the completion had been pushed back to spring or summer 2019, and the cost had risen to $810 million. The design of the replacement dam allows for future capacity expansion, and the core is wider than needed initially. The design allows the height to be raised by , to quadruple the initial capacity of . On completion of the replacement dam, a third of the old dam was removed to allow the reservoir to be impounded by the new dam instead. The construction project allocated funds to restore populations of native fish in other parts of the watershed. A ladder for Steelhead trout (Oncorhynchus mykiss) at the dam itself was deemed infeasible. At 290 feet (88 m), it would have been the tallest fish ladder in the US and would have cost $40 million. The SFPUC did assure environmental groups that it will release water from the replacement dam to improve summer flows. A smaller fish ladder is under construction at a separate diversion dam on upper Alameda Creek, regarded as prime trout habitat. Ecology Facing legal challenges to release flows to support steelhead trout (Oncorhynchus mykiss) in the of Calaveras Creek below the dam, the San Francisco