A federal judge yesterday upheld the National Park service's decision to block construction of a new bridge over the Saint Croix River. The Minnesota Department of Transportation had planned to build a four-lane freeway-style bridge at Oak Park Heights to replace the old two-lane lift bridge in downtown Stillwater. But U.S. District Judge Ann Montgomery supported the park service's view that the bridge would harm the river's special qualities. We talk to Dave Schaaf, mayor of Oak Park Heights, who opposed the project, and Curt Johnson, chair of the Metropolitan Council, which approved it.