Tim Ryan, tryan@shawanoleader.com
High levels of chloride in the soil were responsible for three water main breaks along Main Street since December 2010, according to an engineering study that ruled out any problem with the materials used in Shawano’s downtown reconstruction project.
Corrosion of stainless steel saddles that hold in place the service connection to the water main were the common denominator in the three breaks, and it was uncertain for a while whether there was a soil problem or the saddles were defective.
This week, the city learned the results of tests done by TPS Consulting Engineers, of Green Bay, on the metal used in the saddles.
“The metal meets all metallurgical expectations,” City Administrator Brian Knapp said.
The analysis also determined the saddles had been properly welded in place.
Meanwhile, soil tests at the locations of the three water main breaks showed “huge” levels of chloride, according to Knapp.
“The numbers are much higher than you’d expect to find,” he said.
The most likely cause of that, he said, is road salt leaking down through cracks in the pavement over the years.
Knapp said there are no health concerns because there is no contact between the chloride and the city’s water.
The test results were potentially good news for the city. Had the saddles been found defective, the city could have faced the expensive task of tearing up Main Street again and replacing all of them.
City officials aren’t completely breathing easy just yet.
While the three water main breaks were apparently isolated incidents, there’s no guarantee there won’t be more coming in other random places where there are high chloride levels.
“It could be so random as to be pervasive,” Knapp said. “And if that’s random, how do you prevent it?”
The city will begin doing soil boring tests along the path of the reconstruction in the spring to identify other places where high levels of chloride could be corroding the saddles. The city’s Field Committee will look at some cost estimates for the work at its meeting next month.
The Main Street reconstruction project in 2002 and 2003 stretched from the channel to the Mountain Bay Trail at Oshkosh Street.
The contractor on the project was Degroot Construction of Green Bay, which purchased the saddles from Davies Water Equipment of Appleton. The saddles were manufactured by Smith Blair Inc. of Texarkana, Texas.
The first two water main breaks occurred in the 100 block of North Main Street in February 2009 and December 2010, only about 50 to 75 feet away from one another. The most recent was in the 200 block of South Main Street on Sept. 25.