MnDOT has four options on the table for new Hastings bridge
And then there were four.
The Minnesota Department of Transportation has settled on four options for the replacement of the Hastings bridge, and the public will have the chance later this month to see the designs being considered and comment on them.
MnDOT will hold an open house at Hastings City Hall from 3:30 p.m. to 6:30 p.m., Tuesday, Oct. 21. There will be presentations at 4 p.m. and 5:30 p.m.
The following is a breakdown of the four bridge types being considered and the pros and cons that come with each. There will be sketches at the open house of what each bridge type would look like if built across the Mississippi River in Hastings.
There are a few constants in all four possible bridge types.
They all have two lanes of traffic in each direction and a pedestrian trail. In order to accommodate the additional lanes, the new bridge will grow to the west.
There will undoubtedly be some impact to the Hudson Manufacturing and Hub's Landing properties, the extent of which depends on what bridge type is selected. The Motor Parts Services' building will have to be removed no matter what the new bridge's design is.
Each design has the option to accommodate a possible future bus-only lane for transit, and they'd all touch down in Hastings near Third Street so the turn-arounds that take traffic down to Second Street from the bridge could remain.
The schedule MnDOT is now on calls for a bridge type to be selected in the summer of 2009, with construction starting the summer of 2010. Actual construction of the bridge would be a design-build project, where work starts before certain design elements are complete.
The cost range for all four possibilities is from $275-$325 million (in 2010 dollars), and the new bridge will have a 100-year life expectancy.
Twin box girder bridge
The first alternative calls for building two twin girder-style bridges, with the southbound span being built first, immediately to the west of the current bridge. Traffic in both directions would then be shifted onto the new southbound span while the current bridge is torn down and a new northbound span is built.
The twin girder-style bridges would look similar to the new Wakota bridge near Cottage Grove, but with only two lanes of traffic on each span.
The construction time is estimated at about four years, and the maintenance costs would be low to moderate.
This option utilizes the current bridge's footprint, which means there would be less impact on the surrounding environment and fewer piers in the floodplain.
Because the structural elements that support girder bridges are below the deck, it would have a steeper grade as it comes into the city. The supports on the current bridge, which is a truss bridge, are above the deck.
The look of the bridge is what most would consider a standard highway bridge. Although it's commonly used for river crossings in the area, it doesn't have the uniqueness of the current bridge.
Steve Kordosky, the MnDOT project manager for the Hastings bridge replacement, said in general, MnDOT doesn't like to add special design elements or amenities to bridges unless they serve a purpose.
Single arch bridge
A single arch bridge would be built immediately to the west of the current bridge. Traffic would stay on the current bridge until the new bridge is complete, and then would be shifted over. After that, the current bridge would be torn down.
A single arch bridge would look similar to the old Wakota bridge and the existing Hastings bridge, especially in that its supports would be above the deck. That would also mean the grade as it comes into the city would be closer to that of the existing bridge.
Construction time is estimated at about three and a half years and maintenance costs would be moderate, but more expensive than maintenance of twin girder bridges. The initial construction cost of a single arch bridge would be slightly less than twin girder bridges.
This option has a larger footprint and more environmental impacts because it doesn't use the current bridge's alignment.
Rehab existing bridge, build new arch bridge
In this next option, the existing bridge would be rehabilitated, and a new, two-lane arch bridge would be built next to it.
Construction time for this option is estimated at about six and a half years, the longest of all the options being considered. There are phasing challenges that make this option logistically the most difficult, and rehabilitating the existing bridge would take a significant amount of time.
While the cost of this option is at the low end with a single arch bridge, the maintenance costs are the highest of any option. And the new arch bridge would have a 100 year life expectancy, but the rehabilitated existing bridge would only be expected to last another 75 years.
Looking at the rehabilitation of the existing bridge is required for an environmental study and because it's more than 50 years old and therefore, eligible for the National Register of Historic Places.
Single cable bridge
Similar to the single arch bridge, a single cable bridge would be constructed immediately to the west of the existing bridge.
This design would be a noticeable departure from that of the existing bridge. MnDOT considers it a more modern design. It would have a tall tower in the center, with cables coming down to the bridge deck to hold it up.
This would be the most expensive bridge to build and the second highest to maintain. Construction would take about three and a half years. It is a relatively rare bridge type and the only one similar to it in Minnesota is the Midtown Greenway bike and pedestrian bridge over Hiawatha Avenue in Minneapolis.