I-TEAM: Memo Cites 8 Bridges Needing Replacement

08/15/2007

Terri Gruca
WCCO News
Reporting


(WCCO) An internal Minnesota Department of Transportation memo obtained by the WCCO-TV I-TEAM shows the state knew last year that eight bridges needed to be replaced soon. The Interstate 35W span over the Mississippi River was on the list.

Since it collapsed nearly two weeks ago the I-TEAM has pored over inspection reports for the others and found some are in worse shape than the one the Interstate 35W bridge that went down.

Every day 74,000 vehicles drive the Lafayette Bridge. The massive structure carries U.S. Highway 52 over the Mississippi River in St. Paul. The bridge's last inspection was performed just one day before the last inspection on the now collapsed Interstate 35W bridge.

Here are some of the findings: "Lead plates are working out and the connection bolts are starting to fail". In fact "one bolt is missing."

This bridge, along with Interstate 35W bridge, is on a list of eight bridges in a 2006 MnDOT memo calling for replacement starting as soon as 2009.

Others include:

• Highway 11 in Robbin crossing the Red River
• Interstate 90 crossing the Mississippi in Dresbach
• U.S. 61 in Hastings
• Highway 23 in St. Cloud
• Highway 43 in Winona
• Highway 36 crossing the St. Croix in Stillwater.

Of the 8 bridges on that replacement list, the I-TEAM found one scheduled to be replaced in 2009 which is the Highway 11 bridge in Robbin, Minn. Crews did some repair work on that bridge this spring.

The I-TEAM obtained the latest inspection reports on all of these bridges. Some are considered "fracture critical" meaning if one part of the bridge fails, the whole bridge fails. Some are "scour critical" meaning wear and tear from water is making foundations unstable.

A sonar inspection done in 1998 on Highway 61 in Hastings, Minn. found "scour holes" at the ends of two piers.

An online seminar by the Federal Highway Administration explains the danger of scour holes saying it's a sign "the bridge has already experienced scour and may be at risk for failure."

It's tough to see just by looking at it but a follow-up underwater inspection in 2004 found the footing at one of those piers completely exposed. Yet the bridge was determined to have "no changes in structure conditions."

However, like the Interstate 35W span, this bridge also has fatigue cracking.

The Highway 43 bridge in Winona, Minn., like the bridge in Hastings, is also rated scour critical. It is monitored because heavy rain or flooding could cause problems.

The federal government requires bridges that span over water to undergo additional underwater inspections at least every six years, those with problems at least every five years. Those inspections became a requirement in the 1990s.

To read the structure inventory reports and inspections reports for some of the bridges outlined in the MnDOT memos, Click HERE and use the links found on the right side of the page.