Will levees hold? FEMA unsure

Local flood maps changing in wake of Katrina disaster

By INGA MILLER
imiller@modbee.com

last updated: August 31, 2007 05:40:02 AM

MANTECA -- Federal officials are questioning whether several levees in San Joaquin County can withstand the next big flood. Among the levees they're looking at is one separating the San Joaquin River from lux-ury houses under construction near Oakwood Lake, the former site of the Manteca waterslides.

Federal insurance maps show the levee holding against a 100-year flood -- the type of flood with a 1 percent chance of happening in any year. But in an effort hastened by catastrophic levee failures in New Orleans in 2005 because of Hurricane Katrina, the Federal Emergency Management Agency is checking those estimates.

FEMA is redrawing its flood maps, and each levee previously accredited to provide 100-year protection has to be approved again. If it isn't, areas currently shown as protected will be redrawn as at risk -- which could hit developers and home buyers in the pocketbook with steeper insurance premiums and tighter building restrictions.

"This (levee) is obviously of concern because of new development there and the future community," said Eric Simmons, an engineer with FEMA.

Because the levee shows protection from a 1 percent flood chance, the area is considered at moderate risk of flooding, and developers can build houses below the flood level. Homeowners aren't required to have flood insurance.

The review is generating criticism among developers and local officials who say the levee meets standards in place when it was accredited in 1990. Changing the rules now, they say, is unfair. And there has been no word on how districts are supposed to pay for repairs, said Dante Nomellini, attorney for Reclamation District 17, which owns the levee.

The levee held during the 1997 flood. The New Year's flood that year broke a nearby levee on Perrin Road and swamped dozens of houses about six miles southwest of the new development, but Reclamation District 17's levee kept the area it protects dry. State and federal agencies fixed seepage and boils caused while the levee held back floodwater.

"You shouldn't disqualify someone who met the certification back in 1990," Nomellini said. "They approved it again after the 1997 flood when repair work was done, and the levee was improved. So what is the basis for changing the map status? There is no maintenance deficiency."

Watching for boils

Seepage is a problem in the area. Because of the soil type, water creeps from the wet side of the levee to the dry side. The flow isn't necessarily troublesome unless it moves soil from the levee with it. So under the levee's 1990 accreditation, workers must watch for soil flow, which are called boils, and bolster the levee when boils appear by placing sandbags and gravel blankets to prevent the potential for collapse.

During high water in the spring of 2006, district crews monitored the levees but no major seepage or boils developed, Nomellini said.

After previously approving those measures as adequate, FEMA now is questioning whether those are enough and is putting more emphasis on preventative measures such as more dirt piles and drains, Nomellini said.

"One of the main reasons we're doing this is to create awareness of flood hazard and flood risk," Simmons said. "We feel delaying that process is really a compromise to public safety, and we don't want to do that."

If the review determines the levee doesn't meet the 1 percent flood standard, homeowners will have to buy flood insurance and could be forced to build future houses on higher ground, as happened farther west, near Tracy, where a number of houses are built on raised foundations at levee height or higher.

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