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Friday, April 15, 2011

How to tear down two bridges in 10 hours or less



In just 10 hours this past weekend, two bridges in southern Arizona were demolished in order to make way for something new.
All it took was some good planning, plenty of patience from motorists, a few enormous machines, and a ton of work by crews on the sites.
A little bit of background …
In November of 2009, ADOT began work on the I-10 Marsh Station Traffic Interchange in Southern Arizona -- a $10 million American Recovery and Reinvestment Act project that includes the extension of Marsh Station Road, drainage improvements, and the construction of a new traffic interchange to accommodate commercial truck traffic.
As it stood, the old Marsh Station Bridge had a clearance of 15 feet -- too low for most commercial trucks to clear. To avoid the bridge, trucks taller than 15 feet have had to maneuver a winding, two-lane, 67-mile detour.
(Note: Not until a nearby Union Pacific Railroad bridge is removed later this year, will most trucks be free to ditch the detour and safely pass through the new traffic interchange.)
But first things first, the old Marsh Station Bridge needed to come down. The only way to secure the work site and ensure the safety of both ADOT crews and the travelling public, however, was to close Interstate-10...forcing all local and interstate traffic into that same 67-mile detour!
After a lot of planning -- being careful to avoid Spring Breaks and other heavy-travel holidays -- ADOT set a date (April 8) and made arrangements to bring down the bridge, clean up the debris, and reopen the interstate, all in a 10-hour, overnight window.
The unexpected...
About three weeks before the demolition was set to occur, on March 15, two semi trucks collided under the overpass at the Mescal Road/J-Six Ranch Road Bridge about eight miles down the road from the from the old Marsh Station Bridge. The bridge was badly damaged from the resulting fire and would have to be replaced.
The task...
Since the interstate was already going to be closed, was it possible to safely get another bridge down in the same 10-hour window?  Sure it was, and here’s what it took…
Breakdown by the numbers:
250:
The approximate number of tons of dirt that went down on the roadway below the bridges to act as a cushion for what the crews tore down.
1,480,000:
The approximate number of pounds of concrete removed during the demolition of both bridges. If you need a way to visualize just how much heft 740 tons is, it’s equal to the weight of about 120 adult male African elephants.
112,000 and 232,000:
The approximate pounds of rebar (112,000) and steel (232,000) that were removed during the take down of both bridges.
6:
The number of excavators used on both projects. Two excavators with scissor-like attachments worked on the Marsh Station Bridge demolition. Four excavators (two with the scissor-like attachments and two with hydraulic hammers) worked to bring down the Mescal Road Bridge .
45:
The number of seconds it takes us to show the Marsh Station demolition in this time-lapse video!
Posted by Angela DeWelles   |  Labels:  Bridges, Demolition, J-Six, Marsh-Station, Mescal, Video
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