Thousands of Marana residents stand to save money on flood insurance due to a recent decision by the Federal Emergency Management Agency.

The agency, in a letter dated March 30, accepted the results of a town-commissioned study to determine which parts of Marana are in a floodplain.

The study, conducted by CMG Drainage in 2008, decreased Marana's proposed floodplain from 19 square miles, which FEMA had previously proposed, to 3 square miles.

The change is expected to amount to an estimated $9 million a year in savings for Marana residents, according to Town Engineer Keith Brann.

With 250 homes in the new proposed floodplain instead of 2,000, many homeowners won't have to buy flood insurance, Brann said. And the remaining 250 will pay less. That's because the CMG Drainage study provided details about the depth of potential floods that FEMA didn't provide.

FEMA's decision to accept the results of the CMG Drainage study not only is a coup for Marana, it also sets a precedent for other communities in the United States facing new proposed floodplain maps from the federal agency. FEMA's project to update floodplain maps started on the West Coast and is moving east.

"We were the first community, I think, to object and get results," Brann said. "So we were a test case."

FEMA's new floodplain-mapping rules require that levy-like structures — in Marana's case, Interstate 10, railroad tracks and the Central Arizona Project canal — must meet the strength requirements of actual levies to affect floodplain mapping.

U.S. Rep. Gabrielle Giffords (CD8-Tucson) sent a letter to FEMA in summer 2007 protesting the new rule.

"After reviewing these new standards and discussing them with local officials, I believe they are unreasonable and unnecessary for flood control in the arid Southwest," she wrote. "Most of the requirements make no distinction between levees located in coastal zones and those in inland areas. Coastal levees are subject to forces — including ocean waves, tides, hurricane-force winds and storm surge — that are completely inconsistent with conditions in Southern Arizona."

Marana officials objected to FEMA's draft maps for the reason Giffords stated and also because they were not based on a hydrological study.

In November 2007, FEMA agreed to let Marana commission its own study of the town's floodplain. In addition, the agency extended that privilege to other communities that might take exception to the agency's new proposed maps.

FEMA's David Maurstad announced that decision in a letter to Giffords dated Dec. 18, 2007.

"With respect to any other community in a similar situation … FEMA will promptly, prior to drafting any revised maps, inform local officials of such a proposal and also provide a sufficient amount of time for that community to conduct a study of the effects of the structure(s) in question before finalizing updated flood hazard information for the area," the letter read.

CMG Drainage used the latest data to study flooding from the Tortolita Mountains. It evaluated the nature of the soils on the alluvial fan to determine infiltration and made computer models of storm water movement through major drainage structures.

FEMA will create new floodplain maps for Marana based on the CMG Drainage study. Once the maps are published, the town officials plan to spread the word out to the public about new flood insurance rates.

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