The rapid subsidence was first noted several years ago when the U.S. Bureau of Reclamation did survey work as part of an $800-million restoration of the San Joaquin River.
The land had settled so much "we thought our data was wrong," said Rick Woodley, a bureau resource manager. That led to further study by the USGS. Because of the subsidence, some construction tied to the restoration has been delayed. Anything built "needs firm footing," Woodley said.
The California High-Speed Rail Authority, however, said subsidence will not have a significant impact on plans for a new high-speed rail through the area. The system will run from San Francisco to Los Angeles and can be engineered to deal with sinking land,