Minnesota Water Resources Conference - Water Resources Center ...

BOOK OF ABSTRACTS
Tuesday, October 28
Concurrent Sessions V 1:15–2:45
Track B: Mopping Up Once the Rain Ends: The 2007 Floods in SE Minnesota
“And the rain, rain, rain, came down, down, down” Impacts to MnDOT Structures During the August
2007 Flooding
Petra DeWall, Minnesota Department of Transportation, petra.dewall@dot.state.mn.us
August 18–20, 2007 a major storm hit the south east part of Minnesota. The storm was wide-spread and has
been estimated to be a 2000 year storm event. One TH Bridge over Money Creek failed; a 30 foot scour hole
remained at the location. The Bridge Office and District 6 working together managed to replace the bridge in 3
months.
Garvin Brook was also hit by the August mega-storm. Several railroad bridges failed when the channel widened.
The widened channel left buildings literally hanging off a cliff. The bridge on old TH 61 remained standing but
the approach panel washed out. The scour analysis identified this abutment as scour critical and in need of
monitoring. The piling at the new TH 61 bridge over Garvin Brook had become exposed. In order to design the
repair and size the riprap, the existing Flood Insurance Study model had to be completely reworked to account
for the new channel configuration. This involved obtaining survey information and repair plans from the NRCS,
the railroads and our district staff in order to create a HEC-RAS model for the area. A comparison of the preflood
and post-flood stream profiles showed some dramatic changes to the channel.
Mn/DOT District 6 Repair Work for August 2007 SE Minnesota Flood
Kjersti Anderson, Minnesota Department of Transportation, kjersti.anderson@dot.state.mn.us; Dave Redig, Minnesota
Department of Transportation
The flood of August 2007 devastated SE Minnesota and took a toll on the transportation infrastructure in that
part of the state. Mn/DOT spent many man hours cleaning debris from the roadways, ditches and culverts,
repairing roadway inslopes and backslopes, ditches and culverts, and assisting cities and counties with their
cleanup efforts. Mn/DOT also designed and let several emergency contracts to make major repairs to their
damaged highways, bridges and roadway slopes. Some of the roadway repairs utilized innovative technology,
soil nailing, which was new to Mn/DOT and the State of Minnesota to repair very steep roadway inslopes which
were damaged and compromised during the floods. Dave and Kjersti will discuss the repair work that Mn/DOT
District 6 did to their roadways and share many photos and stories from the flood, as Dave was present during
the flood.
69 Minnesota Water Resources Conference, October 27–28, 2008