Hiawatha Tunnel Project Near the Minneapolis/St. Paul Airport
Tour on April 11, 2003
Tunnel map. We entered the tunnel at the North end of the map. The blue region in the middle
represents the light rail station at the airport.
Boring machine schematics. The machine was done by the time this tour took place. It was
capable of boring through solid rock at a maximum rate of about 130 ft/day.
The entrance to the tunnel project.
Steel forms used in the tunnel construction.
Looking down into the North construction entrance of the tunnels. We entered the left tunnel.
Rail cars used for hauling material into the tunnels for construction. The rail car to the left is
holding a large architectural form for the rail station.
Geological profile of the rock strata being cut through. The stop strata is a shale and the bottom
part is the St. Paul Sandstone formation.
Water is spontaneously seeping from the cracks in the rocks. However, the water table is still
below the bottom of the tunnel at this time.
Walking into the tunnel.
Pre-cast concrete forms that are bolted together and make up the main part of the tunnel walls.
The joints have gaskets to prevent water seeping into the tunnel.
Sand hogs...but they indicated that the term "Sand hogs" usually refers to diggers in the New
York City area. These people are working on one of the many connecting tunnels between the
main rail tunnels.
Continuing to walk toward the rail station.
One of the connecting tunnels under construction. This tunnel had some loose rock material
from the roof fall down.
One of the connecting tunnels near completion.
Location where the steel forms are still in place.
More steel forms securing the walls of the tunnel.
Entering into the rail station part of the tunnel. A huge cavernous opening with several cranes
and lifts operating.
Station wall where the natural rock strata is exposed.
Opening of the west side tunnel.
Where the steel forms are next to the natural rock strata.
Walking through the main station area.
Location where the architectural concrete walls are next to the natural rock strata.
Cranes lifting some forms.
Walking through the station area. I estimate the underground station to be about 60 ft tall, 400 ft
long and 100 feet wide.
Looking into the station area. The low lighting makes the pictures a bit dark.
Access shaft in the roof of the station.
Tunnel entrance on the South side of the station.
Walking through the tunnel where conduit work is continuing.
A concrete floor has been poured in this part of the tunnel. Another concrete part will be poured
with the rails in place.
Emergency lighting.
One of the connecting tunnels under construction. Shown here are the forms and rebar waiting
for the concrete.
Walking back through the rail station area.
Picture of the station area.
Hoisting some rebar into place. The drops in the picture are not on the lens of the camera. These
are reflections of the flash off of water droplets falling from the roof area.
Another view of the main station.
Our tour group is climbing a sandy slope next to the tunnels on the North end of the station.
Looking down into the station area. The large tube on the right is one of the tunnels.
Walking towards the airport access area.
Elevator shafts on the West side of the station area. These elevators are finished and seem to be
operating.
Drill rig for driving securing rods into the rock.
View of the rock strata. Not a very good picture due to the poor lighting.
Another picture of the drill rig.
A small portion of the rock strata that has fractured and fallen away. The boring machine
worked well but a small problem occurred when it drove through a vein of alluvial deposits.
This rock strata didn't hold together well after being bored through.
Securing rods placed into the ceiling area.
A machine that looks like it should be entered into competition as a "Robot War". It is a
hydraulically driven shaver. It shaves the rock strata to form.
Another view of the grinding arm.
Location along the wall that the shaving machine formed. You can see the teeth marks of the
machine.
Looking down into the station area. The large pipe in the bottom right is the eastern tunnel.
Close up of a piece of the concrete form that shows some mechanical damage. The rubber
gasket can be seen.
I stepped down in between the tracks to take a picture of the tracks used for construction access.
These will be replaced with the light rail tracks.
Concrete mixing cart driven along the tracks.
Front end of the concrete mixing cart. Our tour guide, Bill, is shown to the left.
Another view of the rock strata that the tunnels cut into.
Scaffolding stairs in and out of tunnel area.
Architectural form along with the hoisting rig on a rail cart.
The End