A daily compilation for DWR personnel of significant news articles and comment
September 5, 2007
1. Top Items
Eye in the sky to peek inside urban levees
Imaging device dangling from copter will reveal soil condition and water seepage.
Sacramento
By Matt Weiser - Bee Staff Writer
It's not a raid by clandestine forces. It's not a top-secret mind-control or surveillance experiment.
No, that strange helicopter you'll be seeing over Valley cities for the next month is peeking inside levees.
Starting Thursday in
Officials are notifying the public because the sight might be alarming: A helicopter will dangle a 30-foot-long imaging device that resembles a missile.
The device will hang about 100 feet below the helicopter, which will fly over levees about 30 mph. The technology has never been used on
The missile-like appendage detects variations in the ground's electrical conductivity, allowing engineers to "see inside" levees to a depth of 100 feet, revealing soil type and water penetration.
Scott said the device poses no health risk to people or animals.
"The electromagnetic field generated by this system is considered weaker than that generated by natural sources around us every day," she said.
On the other hand, she said, rural residents should decide whether livestock might be spooked by the activity, and corral or monitor them if necessary.
Some roads and highways will be closed briefly at various points during the survey, to avoid car accidents caused by gawkers as the helicopter glides by.
In total, the survey will focus on 350 miles of urban levees in Yuba City/Marysville, Sacramento/West Sacramento and Stockton/Lathrop. Later, it will be expanded to cover an additional 1,250 miles of rural levees.
The work will be done by a contractor, Fugro Airborne Surveys of Canada, which uses the technology mainly in mineral exploration.
The results will be paired with soil tests and another new data source -- laser imaging -- conducted by helicopter earlier this year. The overall effort should reveal more about the Valley's levees than has ever been known before.
The goal is to ensure that urban levees can withstand at least a 100-year flood, or one with a 1 percent chance of striking in a given year, and to decide what repairs are needed if the standard isn't met.
The Federal Emergency Management Agency in 2005 ordered flood agencies across the nation to verify through testing that their levees meet the 100-year standard. If they don't do the testing or their levees don't pass, FEMA is likely to decertify the levees, resulting in insurance mandates and building restrictions.
The survey flights begin Thursday in Yuba City and will work southward, seven days a week, through the first week of October.#
http://www.sacbee.com/101/story/359121.html
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