From July 2006 through December 2007 there were 304 instances where the EPA found what would have been violations of the Clean Water Act before the court's ruling, according to a memo by the agency's enforcement chief.

Officials "chose not to pursue formal enforcement based on the uncertainty about EPA's jurisdiction," according to the memo, which was released Monday by two Democratic House committee chairmen.

The EPA also chose to "lower the priority" of 147 other cases because it was unclear whether the intermittent streams, swamps and marshes flowed into navigable waterways.