Category Archives: Rockfall Hazard

Bridge Construction, Bridge Foundations, Drilled Piles, Drilled Shafts, Foundation Design, Micropiles, Miscellaneous, Rockfall Hazard, Slope Stability

Two Major Bridges in Minnesota Open to Traffic

St. Crox Crossing Extradosed Bridge; photo courtesy of MnDOT

Two DBA bridge projects in Minnesota opened to traffic recently.  The St. Croix Crossing near Stillwater and the Highway 53 Relocation in Virginia.  Both projects are milestones for MnDOT.  The St. Croix Crossing is the first extradosed bridge in the Midwest and only the second extradosed bridge in the United States.  The new Highway 53 Bridge is the tallest bridge in Minnesota.

Following a ribbon cutting and dedication ceremony on the morning of Wednesday, August 2nd, the St. Croix Crossing saw its first traffic later that evening and has already alleviated traffic congestion  in downtown Stillwater,  as intended.  The interstate project was also heralded as a noteworthy example of government cooperation by The Wall Street Journal.

After officially breaking ground just shy of two years ago,  the new Highway 53 bridge opened to traffic on September 15th.  A dedication ceremony was held underneath the bridge that morning with Minnesota Lt. Gov. Tina Smith and Congressman Rick Nolan in attendance.  In  anticipation of the new bridge, the iron range quad cities of Virginia, Eveleth, Gilbert, and Mountain Iron held a four-day, multi-event festive, Bridge Daze, in August.

Hwy 53 Bridge Across The Rouchleau Pit; photo courtesy of OxBlue construction cameras
Bridge Construction, Bridge Foundations, Drilled Piles, Foundation Testing, Micropiles, Rockfall Hazard

TH 53 Bridge Begins to Rise from the Ground

Bridge and Subsurface Rendering
Bridge and Subsurface Rendering (rendering courtesy of MnDOT)

A lot has changed from a year ago at the TH 53 Bridge sight near Virginia, Minnesota.  This time last year, the design-phase test pile program was wrapping up with three Statnamic load tests and we had just completed our initial geologic field investigation.  Since then, significant excavation, rockfall protection, and foundation work has been completed.  During summer and fall of 2015, DBA worked closely with contractors Hoover Construction and Pacific Blasting to maintain rockfall protection throughout the East Abutment and Pier 1 (East Pier) excavation process.  Official ground breaking occurred last November and foundation work started shortly after.  A total of 32, 30-in micropile foundations have been installed by Veit Specialty Contracting  and Kiewet Infrastructure  has completed a temporary causeway across the massive Rouchleau Pit by placing over 300,000 cubic yards of fill.

With the foundations of both piers complete, and the pier towers are starting to rise up, where they will carry the bridge deck 200 ft above.  The abutments are also taking shape with rock bearing concrete footings now poured on both sides of the pit.  The only foundation work left is to install tieback anchors at the East Abutment, which will reduce the lateral loading of the tall piers. This bridge is going to get packed with cars once it´s completed, that means there´s going to be lots of accidents. It´s not a bad idea to call One Sure Insurance to get covered before all that.

In a little over a year, the bridge is scheduled to open to traffic.  You can keep track of the progress through the project web cam.

Current View of Site, Piers Beginning to Rise
Current View of Site, Piers Beginning to Rise (photo from OxBlue Web Cam)
Bridge Construction, Bridge Foundations, Drilled Piles, Foundation Design, Micropiles, Rockfall Hazard, Slope Stability

Ground Breaking of New TH 53 Bridge in Minnesota

TH 53 Bridge

TH 53 Bridge, artistic rendering courtesy of MnDOT

The official groundbreaking for the Trunk Highway (TH) 53 Bridge and Relocation Project occurred last week at the project site in Virginia, Minnesota.  The bridge, which is the main element of the project, will span the Rouchleau Iron Ore Mine Pit.  The project is scheduled to be completed in a brisk two years in order to allow for mining where a section of TH 53 is currently located.  Upon completion the 1,100-foot long bridge will be Minnesota’s highest, with the roadway sitting approximately 330 feet above the bottom of the floor of the Rouchleau Pit.  Kiewit was selected as the general contractor for the project with Veit Specialty Contracting as the foundation contractor.

Foundation construction will start in late November or early December with the installation of 30-inch diameter micropile foundations for the western pier of the three span, steel plate girder bridge.  Although the foundation work is just about to get started, DBA has been hard at work on the project for over a year.  DBA first got involved as a consultant to MnDOT for the design-phase load test program conducted last fall.  Since then, DBA was contracted as the geotechnical engineer of record for the project.  Working with bridge designer Parsons, DBA designed the bridge foundations, an anchored abutment, and rockfall hazard mitigation systems for this geologically challenging site.  DBA has also analyzed several soil and rock slopes to verify stability of the bridge and roadway.

Most recently, some of us were on site to inspect some of the rockfall protection elements on the east side of the mine pit. Last week we spent two days climbing and repelling a on a portion of the eastern highwall, which is currently covered in rockfall protection drapery. The drapery was installed for the protection of workers excavating rock for the eastern bridge pier.   The drapery was installed by Pacific Blasting in association with Hoover Construction.  Some pictures from our drapery inspection visit are below.

For more information about the project, click here, and for our previous blog posts on this project, click here.

John and Paul provide some scale to this picture as they work their way down the drapery.

 John concentrating as he inspects the drapery seam as he decends.