John Luczaj, associate professor of Natural and Applied Sciences and chair of UW-Green Bay’s Geoscience program, has granted numerous interviews to local reporters as they try to make sense of the Leo Frigo Bridge closure for their readers, viewers and listeners. Luczaj is an authority on the bedrock and soils of Brown County, having completed the first comprehensive bedrock map of the county for the Wisconsin Geologic Survey.
In a lengthy article in the Oct. 13 edition of the Green Bay Press-Gazette, Luczaj is one of the scientists and engineers quoted as to why Pier 22, one of the massive concrete pillars supporting the I-43 bridge, slipped two feet into the ground. Although state highway officials say the most likely explanation is shallow-layer corrosion of steel beams caused by fly ash, organic material and industrial waste used to fill the wetlands decades ago, Luczaj and at least one other expert say the cause might lie much deeper. Because the steel pilings below the pier don’t reach bedrock, approximately 130 feet below, they would be resting on a layer of clay or sand. Luczaj notes that the local water table has risen rapidly and dramatically since Green Bay suburbs deactivated most of their municipal wells and began piping Lake Michigan water from Manitowoc. That change in the aquifer could have greatly altered the stability of the soil layer, he says. It’s another theory, and an interesting one, as the investigation continues and the DOT evaluates bridge supports to determine how soon that section of the mile-long, 120-foot high harbor bridge can be repaired.
The P-G article is archived at www.greenbaypressgazette.com/article/20131012/GPG0101/310120334/.