Friday, August 03, 2007

Alaska Department Of Transportation Reacts To Minneapolis I-35W Bridge Collapse, Assures Us That Alaska's Bridges Meet A Higher Standard And Are Safe

Unlike Minnesota, Alaska is routinely subject to earthquakes. Most are momentary 4.0 shakers, but the spectre of a recurring 9.2 millenial event like the 1964 Quake always lurks in the background, particularly for those Alaskans who experienced it. I wasn't in Alaska at the time, but what really terrified many who were here was the duration - four minutes - moreso than the magnitude.

And so the Minneapolis Bridge Collapse (latest casualty figures from Fox 9 Minneapolis is 5 dead, 79 injured, and 8 missing)is more pertinent to Alaskans than to residents of many other states. Cognizant of this fact, the Alaska Department of Transportation wasted little time in addressing local public concern about Alaska's bridges. See full story on KTUU Channel 2 Anchorage.

But while the federal government considers 151 of Alaska's bridges "structurally deficient", Rich Pratt, the Alaska Department of Transportation's chief bridge engineer, says they hold our state's bridges to a higher level than other states, and drivers do not need to be worried.

"Now all that [the "structurally deficient" designation] means, it's not that it's unsafe or that there's any imminent problem, it's just an identification depending on the severity that we need to evaluate the thing further," Pratt said. He explained that if the problem is severe, engineers fix it right away. "If it's not so severe -- if it's something that can wait -- then we tend to monitor the condition and then we try to program it into our normal project programming process. So it might be three or four years down the road," Pratt continued.

Pratt said Alaska holds its bridges to a higher standard than many states, using professional engineers on inspections instead of technicians.

However, unlike many other states, where governors are announcing special efforts to identify and conduct immediate "out-of-cycle" inspections of the most vulnerable bridges, the state of Alaska so far has no intent to follow suit.

However, KTUU wasn't finished with their reporting. Aware of the ongoing public controversy over the proposed Knik Arm Bridge, they sought out Henry Springer, the chief engineer of the Knik Arm Bridge and Toll Authority (KABATA) for his reaction. Springer told KTUU, "I think most bridges in Alaska have two things. They are not that old, with the exception of a few of them that date way back. The state has a bridge inspection program".

Springer further explained that the state's inspection program requires every bridge in the state be examined at least every two years. And simple designs, like the Government Hill bridge, also help (which explains why KABATA is so hot for the disruptive Goverrnment Hill terminus, which would carve a chunk out of the Government Hill neighborhood and which has met with strong opposition from the Government Hill Community Council).

In regards to the Government Hill design, Springer said, "That's a ‘Lego 101.' Little kids in kindergarten build them exactly that way, but it has several advantages. It's easy to analyze. It is proven. It's a good proven design. It's simple to maintain, it's simple to inspect".

Earthquake resistancy is the primary hurdle faced by KABATA. At a one-on-one meeting with NOAA Fisheries back in February 24th, 2005, KABATA pointed out that the current model for earthquake activity, designed in California, is not relevant to Alaska because Alaska's earthquakes tend to be longer in duration. Click HERE to view an 11-page PDF document of the meeting (8 MB - loads slowly). Other issues discussed included the effects of tidal activity and ice formation/breakup in the vicinity, as well as potential impact upon beluga whales.

Information on Alaska's bridges can be found in the Alaska Bridge Inventory Report, a 199-page PDF document listing Alaska's bridges by name, location, type, length, width, date of construction, and status.

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