Minnesota Department of Transportation

511 Travel Info

Hwy 169, Hwy 22 Minnesota River Flood Mitigation

Mankato, Saint Peter

Project updates

Hwy 169 Mankato - St. Peter flood mitigation in 2016

The project includes 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 and a median barrier to prevent head-on crashes. The $25 million project received a $9.8 million grant from the EDA.

Constructing the project requires MnDOT to close Hwy 169 from Mankato to St. Peter. The narrow terrain between the bluff and the Minnesota River makes it difficult to rebuild the road under traffic in one season and carrying two-way traffic comes with other safety issues.

Nicollet County Road 13/Hwy 99 will be the detour route (PDF) with Hwy 22 as an alternate route. MnDOT has completed safety improvements to each of these routes in anticipation of the added traffic in 2016.

2016 Traffic Impacts

  • February to May - single lane closures
  • May to September - Nicollet CR 13/Highway 99 will be the detour route with Highway 22 as an alternate route.
  • September to October - single lane closures

flood mitigation overview map


About this project

Summary of work

This project involves raising Hwy 169 and Hwy 22 one foot above the 100-year flood elevation to maintain traffic during high water events. 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 project overview map (PDF).

Key issues

  • Unsuitable soils in reconstruction areas
  • Impacts to 6(f) environmental properties of Seven Mile Creek and Riverside Park
  • 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 22.6-26.7
Construction-related costs 1.1 0.15 1.6-1.9
Engineering 1.5 0.5 4.5-5.3
Right of way 0 0.05 0.1
Total $13.3 $3.2 $28.8-$34