WOODBURY, Minn. (AP) - Minnesota road surfaces that were supposed to last for 30 years are crumbling in just 15.

A report says cities are concerned they'll have to spend millions of dollars to fix deteriorating streets.

For example, the City Council in Woodbury was informed last month that "unprecedented failures" could affect about one-third of the streets and cost more than $20 million to fix. Pavement issues have also been reported in places like Edina, Rochester and Stillwater.

Woodbury city administrator Clint Gridley says the state made changes in blacktop mix designs in the early 1990s that resulted in more porous pavements. That allowed water to seep in, causing premature decay.

Minnesota Department of Transportation spokesman Kevin Gutknecht says the asphalt mix was only a recommendation, not a mandate.