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Thursday, October 17, 2013

Douglas Tells Public Works: “Climate Change is Here”


In his keynote address at the Public Works annual employee conference this week, noted meteorologist Paul Douglas told his audience that climate change is real, and has real consequences for Saint Paul and public works, saying the evidence of climate change for Minnesota can no longer be ignored.

Pointing to several disturbing trends in Minnesota’s climate, Douglas remarked that the extremes are becoming more extreme, and we’re seeing weather events that we’ve never observed before.  Of particular interest to Public Works Street Maintenance staff was Douglas’s tracking of longer freeze-thaw cycles the past few winters.

According to Douglas, the longer freeze-thaw cycles are attributable to warmer winter evening temperatures. 

“Prolonged freeze-thaw cycles will have serious implications for our patching operations,” said Public Works Supervisor III Chris Anderson.  “It means potholes will develop earlier in the winter and in greater numbers.”

 Applying a permanent patch during the winter season is not possible using winter mix asphalt. Our hot mix asphalt plant usually fires up in early March which helps the situation, but potholes keep spawning typically into mid-May.

Anderson continued, “If our ability to apply a permanent patch is delayed, as was the case this past winter, there is a domino effect on our other paving work that continues into the spring and summer.  Our pothole patching work was delayed, which in turn delayed our seal coating and mill and overlay programs.  This meant added labor and material costs for the city and added to our administrative duties.”

The climate change effects for Public Works didn’t end with the beginning of summer.  Record-breaking heat the past two summers meant that on some days seal coating work had to be postponed because of the high humidity that often accompanies hotter air temperatures.

High humidity prevents the emulsion oil used in the seal coating process from setting up properly.  When the mixture fails to set up properly, it’s vulnerable to being washed away into the city’s catch basins when it rains.

Moreover, high summer temperatures can also buckle existing pavement, and pose an acute health threat to paving crews in the form of heat stroke and heat exhaustion.

Where do we go from here if we’re to avoid the health and financial costs of climate change?  As Douglas reminded his audience of city employees, the answer has been known for several years – we must reduce our carbon footprint.

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