ASCE Responds to the I-35W Bridge Collapse

In response to the catastrophic I-35W bridge collapse in Minneapolis, ASCE is playing a significant and proactive role in the review and analysis of one of our nation's tragic infrastructure disasters. Shortly after the collapse occurred, ASCE immediately began to provide technical and authoritative information to the media and has developed a dedicated area on the ASCE website to providing further resources and related information. The website will continue to evolve over the coming days and should serve as an excellent resource to keep members up to date and help in answering any general questions that may be received. ASCE members can take pride in knowing that ASCE and the civil engineering profession continue to play such a key role in understanding and responding to natural and man-made disasters and in improving the resilience of our nation’s critical infrastructure.

Wednesday, August 22, 2007

ASCE Update on I-35W Bridge Collapse

The National Transportation Safety Board (NTSB) has issued a second update on their investigation of the I-35 W bridge collapse. A new facet of the investigation is the examination of the de-icing system that was installed on the bridge, the chemical used in this de-icing system, and the properties of this chemical (whether or not it is corrosive). This de-icing system had components installed in the concrete bridge deck. The NTSB Chairman Mark Rosenker stated "The finite element model of the bridge is being revised based on the measured deck thickness from core sections and physical examination of the bridge structure. All structural elements have been incorporated in the model; however, some aspects of stiffness, weight and connections between elements are being modified to match the condition of the bridge the day of the accident." The NTSB has also interviewed 25 drivers and construction workers who were involved with the construction project on the bridge at the time of its collapse. According to the NTSB press release: " The weights of the various construction materials that were delivered to the work site between 11:00 a.m. and 2:30 p.m. on August 1 have been verified at about 383,000 pounds. The combined weight of the loads and construction vehicles is about 575,000 pounds." NTSB has verified the location of these vehicles and materials by means of the interviews and from "a pre-collapse photograph taken by a passenger on an airplane that was departing from Minneapolis on the afternoon of the collapse." View the NTSB press release at:

The anti-icing system used on the I-35 W bridge sprays an anti-icing chemical onto the concrete bridge deck when sensors and information from the Road Weather Information System tell it that hazardous conditions are imminent. The anti-icing chemical is potassium acetate. The sensors are ground and deck surface sensors that measure temperature and moisture, and sensors to measure ice formation. The Road Weather Information System are weather stations that measure air temperature and have optical precipitation sensors to detect rain, snow, and sleet. Read the report of the anti-icing system at:

View drawing showing the layout of the anti-icing system on the I-35 bridge at:

The Minnesota State Senate Transportation Budget & Policy Division and the State House Transportation Finance Division held a joint public hearing on August 15, 2007 on the I-35 W bridge collapse. During that hearing, the members of the Divisions asked Minnesota DOT (MN-DOT) many questions that MN-DOT needed time to respond. MN-DOT has responded to those inquiries and a letter from MN-DOT summarizing the questions and providing the answers is available at:

MN-DOT has provided some additional information about the Municipal Consent process. This is the law in Minnesota that requires MN-DOT to obtain "municipal consent" from the municipality involved when the highway project alters access, increases or reduces traffic capacity (for example, increasing or reducing the number of traffic lanes), or requires acquisition of permanent right-of-way. View flow chart of the municipal consent process at:

View timeline of the municipal consent process at:

MN-DOT has provided information related to their plans for funding the new I-35 W replacement bridge. Abby McKenzie, MN-DOT's Director of the Office of Investment Management, testified about these funding plans at the Minnesota State Senate Transportation Budget & Policy Division and State House Transportation Finance Division joint public hearing on August 15, 2007. View McKenzie's testimony at:

MN-DOT has also provided a list of the professional and technical contracts awarded to date associated with the bridge collapse recovery efforts, bridge collapse investigation, environmental concerns, and new I-35 W bridge replacement. View the list at:

The Federal Emergency Management Agency (FEMA) has issued a press release concerning the I-35 W bridge collapse and federal aid programs that are available. In the press release FEMA states that "Initial FEMA-administered aid is limited to $5 million." Read FEMA's press release at:

In an unrelated, but important development, MN-DOT closed a bridge today. The Highway 11 bridge over the Red River sharing the border with North Dakota was closed "after a crack was discovered in a support bracket for a girder during an inspection...". Read the press release concerning this bridge at:

[Summary compiled by Susan Lane, ASCE]

Tuesday, August 21, 2007

Engineers Sought for Expert Opinions and Advice on Public Engineering and Infrastructure

American Public Media/Minnesota Public Radio is seeking qualified engineers to provide expert opinions and advice on public engineering and infrastructure. "We're still grappling with the implications of the collapse of I-35W here in the Twin Cities," says Lea Coon of Public Insight Radio at APM/MPR. "However, our on-going coverage of the collapse is looking at the state of public infrastructure nation wide. We're hoping that ASCE would be willing to help us find public sources with expertise in public engineering and infrastructure to advise our reporting of this serious issue."If you'd like to volunteer your time, experience and insights, fill in the application form and /or contact Jane Howell at

Monday, August 20, 2007

ASCE Update on I-35W Bridge Collapse

The City Council and the Mayor of the City of Minneapolis adopted a "Statement of Principles" about what they believe the new I-35 replacement bridge project should contain. These were adopted on Friday August 17th and are available at:

Minnesota DOT (MN-DOT) has hosted several public meetings on the new I-35W replacement bridge project and has posted handouts from these meetings. MN-DOT has also provided an update on the permits for this project. To date, permits have been received from the Minnesota Department of Natural resources and the U.S. Army Corps of Engineers. Permits are pending from the U.S. Coast Guard and the Minnesota Pollution Control Agency. The handout in the link below provides a full listing of the permits and describes that the additional lanes on the new bridge to accommodate transit may not be for light rail, but could be for a bus rapid transit lane, High Occupancy Toll (HOT) lane, High Occupancy Vehicle (HOV) lane, or some other form of managed lane.

The Minnesota State Legislature has scheduled a second hearing on the new I-35W bridge replacement. The Minnesota Senate Transit Subdivision and the House Transportation Policy and Transit Subcommittee will convene a joint public hearing on August 22, 2007. View the announcement at:

[Summary compiled by Susan Lane, ASCE]

Wednesday, August 15, 2007

MN-DOT Public Open House to Discuss Design-Build Project to Replace I-35W Bridge

Minnesota DOT (MN-DOT) announced that a Public Open House will be held on Thursday August 16th to discuss the design-build project to replace the I-35 W bridge. The public can also provide comments online at:

MN-DOT's proposed plans for the new I-35 W bridge include 10 lanes for the bridge (up from eight lanes on the previous bridge) with one lane in each direction possibly accommodating transit. Lt. Governor Carol Molnau and Metropolitan Council Chair Peter Bell have sent a letter to Governor Tim Pawlenty describing their assessment for the Governor of the light rail possibility. Their letter states: "At your direction, we have completed our preliminary assessment of the potential for reconstructing the I-35 bridge in a manner that could incorporate a light rail line. For the reasons that follow, we have concluded that the inherent disadvantages of including LRT do not justify the expense and delays that would result from further study." The full letter is available at:

Tuesday, August 14, 2007

ASCE Update on I-35W Bridge Collapse

Aug. 8, 2007--Minnesota DOT released today an edited video clip from a traffic camera that had previously not been shown to the public. The video is pointed south, away from the bridge, and then as traffic halts, it swings north to show where the bridge has just collapsed.
Minnesota DOT (MN-DOT) is stating that they will have a design-build contract to rebuild the I-35 W bridge in place by September 2007. The contract will contain financial incentives for finishing the project early. Additionally, MN-DOT is stating that for the new 10-lane bridge, (up from eight lanes on the previous bridge), one lane in each direction may accommodate transit. The link to this information is below, with the information scattered in the bulleted section entitled "Update Aug. 7".
MN-DOT has posted the I-35 W bridge's Structure Inventory Report. Among other things, this report provides the Condition Codes (ratings) for the Deck, Superstructure (truss and bearings), and the Substructure (pier, abutments, and footings/piles). Note that if any of these receive a Condition Code of 4 or less than the structure will be classified as Structurally Deficient.
MN-DOT has also posted a Technical Memorandum from their Engineering Services Division dated July 19, 2007 which provides "Guidelines for In-Depth Inspection of Fracture Critical and other Non-Redundant Bridges and for Underwater Inspections". This is relevant because the I-35 W bridge contained fracture-critical bridge members. Note that the Technical Memorandum defines fracture critical. The memo states that: "Fracture Critical members must be inspected from an arms length distance every 24 months."
In 1990, MN-DOT contracted with the University of Minnesota to evaluate the fatigue stresses within the I-35 W bridge's truss members. Field tests of the bridge were a part of their evaluations. The link to the University of Minnesota's report is provided below.
Then in 2003, MN-DOT contracted with URS Corporation to perform a more detailed fatigue and fracture analysis of the truss bridge and its truss members. The report from that analysis (listed as a draft report) is provided in three parts and is dated July 2006, and the Executive Summary provides recommendations and is dated January 2007. The links to these are all below.

Monday, August 13, 2007

Additional Funds for Emergency Repairs and Reconstruction of the Interstate I-35 Bridge

On August 6, 2007, President Bush signed into law H.R. 3311, which authorizes additional funds for emergency repairs and reconstruction of the Interstate I-35 bridge located in Minneapolis, Minnesota, that collapsed on August 1, 2007, and waives the limitation on emergency relief funds for those emergency repairs and reconstruction.

Upkeep Of Security Devices A Burden

Monday, August 13, 2007--In 2003, the FBI used a $25 million grant to give bomb squads across the nation state-of-the-art computer kits, enabling them to instantly share information about suspected explosives, including weapons of mass destruction.

Four years later, half of the Washington area's squads can't communicate via the $12,000 kits, meant to be taken to the scene of potential catastrophes, because they didn't pick up the monthly wireless bills and maintenance costs initially paid by the FBI. Other squads across the country also have given up using them. See Washington Post article by Mary Beth Sheridan.

Friday, August 10, 2007

$50M Available to MN for Clean-Up and Recovery Work

The Secretary of Transportation announced today that she is making $50 million available to Minnesota "to pay for clean-up and recovery work, including clearing debris and re-routing traffic, as well as for design work on a new bridge." Also, she is making an additional $5 million available today to reimburse Minneapolis for the increased cost of transit operations during the time that the bridge has been out.

Thursday, August 9, 2007

New York Company Indicted in Collapse of Big Dig

BOSTON, Aug. 8 — The supplier of the epoxy that federal officials have blamed for the collapse of a Big Dig tunnel was indicted today in the death of a motorist crushed by falling ceiling panels.

The company, Powers Fasteners Inc., was charged with one count of involuntary manslaughter. It is the first criminal charge in the tunnel debacle, which killed Milena Del Valle, 38, in July 2006 as she was on her way to the airport. Her death ignited an uproar over the safety of the $15 billion Big Dig, the most expensive single public works project in American history. Story published in the NY Times on August 9, 2007 by Pam Belluck.

Potential Flaw Seen in Design of Fallen Bridge

MINNEAPOLIS, Aug. 8 — Investigators have found what may be a design flaw in the bridge that collapsed here a week ago, in the steel parts that connect girders, raising safety concerns for other bridges around the country, federal officials said on Wednesday. The Federal Highway Administration swiftly responded by urging all states to take extra care with how much weight they place on bridges of any design when sending construction crews to work on them. Crews were doing work on the deck of the Interstate 35W bridge here when it gave way, hurling rush-hour traffic into the Mississippi River and killing at least five people. Story by Monica Davey and Matthew Wald in the NY Times, August 9, 2007.

Monday, August 6, 2007

DOT Updates re: I-35 W Bridge Collapse

The Secretary of Transportation has requested that the Inspector General of the Department of Transportation perform a rigorous review of the National Bridge Inspection Program.

The most recent (2006) inspection report of the I-35 W bridge by Minnesota Department of Transportation (MN-DOT), containing detailed descriptions of the cracks found in certain areas of the bridge is available at:

Minnesota DOT has also provided a detailed condition report on the bridge, completed in 2006, includes pictures of the flaws, cracks, and defects in the bridge that the inspectors found. The report is available at:

Sunday, August 5, 2007

I-35W Bridge Collapse Editorials

Here's a collection of editorials by the US press. There appear to be two themes: our nation's infrastructure is decidedly crumbling and our political will to adequately fund the repair and maintenance of that infrastructure is decidedly in question.
Chiacgo Tribune
Pioneer Press (Twin
Popular Mechanics
Rochester, MN Post-Bulletin
Wall Street Journal

Friday, August 3, 2007

FHWA Definitions

As a result of the I-35W bridge collapse, there has been much discussion regarding the definitions of 'structurally deficient' and 'functionally obsolete'. The designation of a bridge as structurally deficient or fucntionally obsolete has impact on decisions for bridge maintenance, rehabilitation, or replacement. The actual criteria for this determination is set by the FHWA and is not widely understood. Most bridges are inspected every 2 years and receive ratings based on the condition of various bridge components. Two terms used to summarize bridge deficiencies are "structurally deficient" and "functionally obsolete." Structural deficiencies are characterized by deteriorated conditions of significant bridge elements and reduced load-carrying capacity. Functional obsolescence is a function of the geometrics of the bridge not meeting current design standards. Additionally, Richard Kerr of the Florida Department of Transportation has developed a presentation to provide information on the ratings:

Thursday, August 2, 2007

I-35W Bridge Collapses During Afternoon Peak Hour

August 1, 2007--You can read about the I-35W bridge collapse at most of the major network websites (See links at right).

Here is an FHWA Press Release dated Aug. 2, 2007:

Here is a security camera video of the collapse:

Here are photos of the collapse:

Diagramming the collapse:

Problems with Minnesota bridge noted twice since 2001:

Here is the MnDOT 2001 Report:

A 2001 study conducted by the Minnesota Department of Transportation found "several fatigue problems" in the bridge's approach spans and "poor fatigue details" on the main truss. The study suggested that the design of bridge's main truss could cause a collapse if one of two support planes were to become cracked, although it allowed that a collapse might not occur in that event. But, the study concluded, "fatigue cracking of the deck truss is not likely" and "replacement of the bridge ... may be deferred."

Two years ago, the U.S. Department of Transportation's National Bridge Inventory database said the bridge was "structurally deficient." The Minneapolis Star Tribune quoted Jeanne Aamodt, a spokeswoman for the Minnesota Department of Transportation, as saying the department was aware of the 2005 assessment of the bridge. The bridge received a rating of 4 on a scale of 1 to 10. A bridge receives a rating of 4 when there is "advanced section loss, deterioration."

About 100,000 cars a day travel over the bridge, according to the Minnesota Department of Transportation. See full story:

FEMA: News Releases

Department of Homeland Security News News & Press Releases

National Weather Service Current Advisories for the US