The City of Fridley posted this explanation for a "terrible odor" coming from Parks and Recreation Department ice rinks:

"The ground didn't freeze up as it should have this year because of the warmer temperatures that we have been experiencing. There are some small pockets of methane that are in the ground, and also occur from decaying vegetation, that comes up into the ice especially when it gets warmer outside. The methane gas causes the yellowish bumps or boils on the ice surface and makes the ice smell like rotten eggs (because of the sulfur). If the weather turns colder and we are able to add ice to cap off the surface. Sometimes we can get the smell to go away for a little while. Usually this time of year we shut the rinks down around February 15th. We have been trying to keep the rinks going, but the past ten days of warmer temps have taken their toll."