GREEN BAY, Wis (WFRV) The final report on the Leo Frigo Bridge repair has been released by the Wisconsin Department of Transportation (WisDOT). A document that state transportation officials hope will be useful to other road builders going forward.

When a section of the Leo Frigo Bridge sank two feet in September of 2013,  no one was quite sure what happened and how long it would take repair. Now in a 3,000 page document the WisDOT explains the process it followed to get the bridge reopened in 102 days.

Twenty months after the fact whenever Tom Buchholz thinks back to the day a section of the Leo Frigo Bridge sank, he still can’t believed no one was injured.

“We’re very lucky and fortunate that no lives were lost as part of the incident,” said Buchholz, the transportation engineer in charge of bridge repairs.

In September 2013 one of the bridge’s support piers buckled – sinking two feet – setting off a flurry of 9-1-1 calls from motorists crossing the section of the bridge on I-43 that sank.

Within the report WisDOT explains their analysis and repairs. Determining old industrial soils used as fill, such as fly ash, corroded steel pilings causing pier 22 to buckle. Engineers determining five supports in all were surrounded by the soil requiring extensive repairs to them all.

“We put four concrete foundations down into rock – tied existing pier into those posts and solidified the foundations,” said Buchholz.

Buchholz says the repairs provide corrosion protection for 75 years.  A near tragedy caused by corrosive fills that based on this document transportation engineers will now be more wary of.

“The soil showed fly ash fill,  but we never asked was it corrosive or not corrosive,” said Buchholz. “What this shows is now we need to be asking those questions when you run into fly ash fill.”

The report also tells how WisDOT installed corrosion monitoring equipment at eight sites on both sides of the Fox River that will be checked every two years.

Final cost of project $15 million.