The wheels of a dramatic roadway transformation stemming from the St. Croix Bridge project have begun turning and will soon begin altering the landscape and familiar travel patterns in Stillwater and Oak Park Heights.

Washington County commissioners, at a workshop last week, got a look at some of those details even as preliminary work on the bridge is beginning. Construction on the river piers for the bridge's foundation is set to begin next year.

The bridge itself is now estimated to cost $293.2 million, and roadwork associated with it on both sides of the St. Croix River will more than double that figure. But direct costs to Washington County will be relatively small, said County Engineer Wayne Sandberg, who estimated its share at $75,000.

"For a $700 million project, $75,000 is a pretty good deal for us," he said. Most of that cost is associated with new signal lights; although the bridge is a freeway-style design, that doesn't mean Hwy. 36 is becoming a freeway.

The project will affect three key roadways in the immediate area of the bridge along Hwy. 36: the Beach Road overpass with on- and off-ramps to the highway; the intersection of Osgood Avenue N., and the intersection to the west at S. Greeley Street.

•The Beach Road overpass will be torn down, shifted slightly to the west and curved in a way that won't include on- or off-ramps, Sandberg said. The St. Croix Bridge itself will begin about where that overpass is now, he said, and include a huge new interchange with Hwy. 95 with stoplights north and south of the bridge.

The current overpass needs to be moved to accommodate both that interchange and drainage.

• The Osgood intersection will see little change, although the south frontage road along Hwy. 36 now will connect to Beach Road. Anticipating more traffic on Osgood, a busy route to both the Washington County Courthouse and downtown Stillwater, the county may consider widening the street, he said. A parking lot at the nearby courthouse could be added.

• The Greeley intersection and nearby frontage roads will be completely realigned and stoplights will be added to the north and south, Sandberg said.

The county also is planning a related project on Pickett Avenue N. that winds around the prison north of Bayport, said Cory Slagle, engineering and construction manager with the county.

That street now leads to the Beach Street overpass and access to Hwy. 36, but that access will be closed off as part of the bridge project. Some streets will be converted to trails.

The project is complicated because some soil has been contaminated by construction debris, Sandberg said.

The project could cost about $4 million, with about half paid with state funds.

"I didn't realize the magnitude of the construction that's going to be taking place," Dennis Hegberg, the County Board chairman, said as he looked at the 8-foot-long project map.

The massive project, to be built while working around traffic and a bustling business district, will pose a challenge, said Don Theissen, Washington County's public works director.

For one thing, it will require a huge staging area for storing gravel, dirt and other construction material that hasn't been determined yet.

"That's a huge logistical issue," he said.

Jim Anderson • 651-925-5039