Manteca is about to officially admit flooding from the San Joaquin and Stanislaus rivers is a potential problem for some municipal residents.
Reclamation District 17 – which protects much of the area southwest of Manteca from the two rivers – will receive $76 million from the state to assist with seepage-related projects to strengthen the levees. There is a condition, though. State law requires all affected local governments to acknowledge that the levees need to be upgraded to meet current design standards.
The City Council will consider the resolution during Tuesday’s 7 p.m. meeting at the Civic Center, 1001 W. Center St.
The area southwest of Manteca has flooded nine times since 1929. The last time was in 1997 when nine breaches flooded 70 square miles between Manteca and Tracy causing $80 million in losses and damaging more than 600 homes and other buildings.
The cross-levee that parallels Woodward Avenue west of Airport Way nearly failed in 1997. Back then, there were just a few homes in the area that would have been flooded. Caltrans plugged the McKinley underpass of the Highway 120 Bypass at the time as a back-up levee in case the cross levee failed.
Now there are several hundred tract homes in the area.
Over a thousand property owners southwest of Manteca – including a number within the city limits – will find it difficult to build structures of any consequence on their land starting in 2015.
The California Legislature passed a law in 2007 that basically restricts building in 200-year floodplains unless levees are upgraded. Without levees that are put in place to protect against so-called “200-year events” – which refers to the intensity and not the frequency – no one will be able to build structures on their property unless it is raised out of the floodplain by placing them on top of earthen mounds or elevating them using stilts or block.
A small part of Manteca southwest of Airport Way and the Highway 120 Bypass is in the 100-year flood plain. The 200-year floodplain is a much wider swath. It runs to a ridgeline that ends up just south of Nile Garden School. Much of the area west of a point about midway between Tinnin Road and Union Road and starting at a point south of Woodward Avenue is in the 200-year designation.
The city is exploring the possibility of pursuing levee improvements as far south as Nile Garden or extending the current levee that parallels Woodward Avenue west of Airport Way and extending it to a point about midway between Union Road and Tinnin Road.
The levee would be 80 feet wide and six feet high to the west of Airport Way, 50 feet wide and four feet high east of Airport Way, and 40 feet wide and four feet high east of Union Road.
Funding would come from property assessment plus development fees and possibly state funds.
To contact Dennis Wyatt, e-mail dwyatt@mantecabulletin.com