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Archive for July 2010

The nation’s 120,000 dams: Much more inspection, repair needed

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Last week, as Robert Plant of Led Zeppelin sang solo in the nearby Dodge Theatre, 750 million gallons of water from the 16-foot-deep Tempe Town Lake near Phoenix roared through a burst dam at up to 15,000 cubic feet per second. Fortunately, no one died; no significant property damage occurred.

Eight dam sections made of inflatable rubber constrained the lake, four at each end. The $4.4 million dam began receiving water from the Central Arizona Project in 1999. In 2002, one of the 40-foot-long, foot-thick rubber bladders (covered by a 10-year warranty from Bridgestone industrial Products) failed, requiring a repair. Tempe and Bridgestone officials have disagreed on how to prevent deflation and enlarging buffer zones around the dam. UPI reported that “[a] design flaw made it impossible to use sprinklers to keep the rubber cool and wet, which likely hastened its deterioration.” Also, said UPI:

Mayor Hugh Hallman told the Arizona Republic that work had been scheduled to start Wednesday on replacing the dam. He added the maintenance crew could have been killed if the collapse had occurred while the work was under way.

This dam was small and young. The average age of tens of thousands of dams tracked by a national database is 51 years old. Because state and federal budgets are fiscally challenged, dams in America are not inspected as often as law and common sense requires. That must change.
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Written by Dr. Denny Wilkins

July 25, 2010 at 12:44 pm

Posted in Uncategorized

Drive with care over those 151,394 obsolete, unsafe bridges

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Each day that I drive the 11 miles from my house to the university, I cross nine of America’s 601,396 bridges (as of 2008). They’re not likely to collapse. I have seen each replaced or rehabilitated in the last 10 years.

But you may not be as fortunate. You may need to drive across one or more of the 151,394 bridges the federal Department of Transportation lists as structurally deficient or functionally obsolete. That’s 25 percent of American bridges. But fear not: Bridges are becoming safer. There were 3,930 fewer such bridges in the United States in 2008 than in 2007.

Whew. That’s a relief. At this rate, America will have no unsafe or obsolete bridges in only 153 years.

The repair and replacement rate of deficient or obsolete U.S. bridges is rising, however. According to DOT statistics, the number of lousy bridges has been reduced by 14,087 since 2000, an average of only 1,565 a year. So maybe (you remember, of course, all that talk about those shovel-ready stimulus projects?) that repair rate will increase, and we will have licked our bad bridge problem in only 100 years.
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Written by Dr. Denny Wilkins

July 15, 2010 at 3:24 pm

Posted in Uncategorized