It was a dark and stormy morning...
August 4, 2010
With apologies to Snoopy's oft-used opening line
, this morning featured an unusual and heavily-concentrated downpour
that hit portions of the Des Moines metro area but left others mainly dry. The torrent led to a flash flood warning
for much of Dallas County, and another for parts of Polk County
, where some roads were flooded with up to 2 feet of water. A storm sewer collapsed
in northwest Des Moines, creating a sizeable sinkhole.
One of the frequent causes of sewer collapses is the lack of good combination air valves
that release air when a surge of water comes through the pipe, and break the vacuum created when that surge of water passes by and leaves a gap behind it. There are many other potential causes of sewer failures as well, but air valves are frequently overlooked.
last revised August 2010