Minnesota Department of Transportation

511 Travel Info

Hwy 169 Minnesota River Flood Mitigation

Mankato, Saint Peter

Traffic impacts

Hwy 169 flood mitigation overview map
Click map for PDF detour route.


April 18 to October

This project requires us to close Hwy 169 from Mankato to St. Peter. The narrow terrain between the bluff and the Minnesota River rebuilding the road under traffic in one season and carrying two-way traffic comes with other safety issues.

About this project

Summary of work

This last of three projects along the Minnesota River involves raising Hwy 169 from Mankato to St. Peter above the 100-year flood elevation to maintain traffic during high water events in four flood-prone areas (Hiniker Mill, 7-mile Creek, Old River Road, and State Hospital).

When these highways were originally constructed in the early 1960’s, the Minnesota River high-water elevation was assumed at 751 and the roads were constructed accordingly. 

The actual 100-year flood elevation in this area ranges from about 756.0 to 756.6. View overview map of all three projects (PDF).

  • Raising the grade in four flood-prone areas (Hiniker Mill, 7-mile Creek, Old River Road, and State Hospital) to raise the road above the 100 year flood
  • Six miles of resurfacing for a smoother road
  • New median barrier to prevent head-on crashes

Key issues

  • Unsuitable soils in reconstruction areas
  • Coordination with rehabilitation of Hwy 99 bridge over Minnesota River at Saint Peter
  • Management of traffic during construction and access to businesses during construction


Cost estimate (millions) 2014 2015 2016
Construction 10.7 2.5 29.7
Construction-related costs 1.1 0.15 1.5 - 2.0
Engineering 1.5 0.5 4.5-5.3
Right of way 0 0.05 0.1
Total $13.3 $3.2 $35.8-$37.1