Glen Gebhardt, an engineer with River Islands, the developer of a town planned for a vacant tract in the Delta town of Lathrop, hired Concord, Calif.-based Independent Construction Co. in mid-September. The job was construction on six miles of what will eventually become 300-ft wide crown levees with slopes of 10:1 at a cost approaching $1 million a mile.
Independent started by excavating 6 to 8 ft of soil and performing deep dynamic compaction with local material. The soils are mainly sandy, but compaction closes the pores to create a solid foundation, says Gilbert Cosio, vice president of Sacramento-based MBK Engineers Inc., working for the local reclamation district and River Islands.
"Upgrading current levees wasn't an option," says Gebhardt. He needed FEMA approval of 200-year flood protection level before he could start on a community designed for 11,000 homes and 35,000 people. In future phases, the levee will form a 20-mile protective perimeter.
River Island also will modify the hydrology of Paradise Cut flood bypass downstream to mitigate any extra water that would be sent downstream in a 200-year event.
Jeffrey Mount, professor at the Center for Watershed Sciences and Dept. of Geology, at the University of California, Davis, calls the project "nutty." He was removed this month from the Reclamation Board when the governor replaced all seven members with new appointees. Mount says the project "just translates the misery elsewhere."