Minnesota Department of Transportation

511 Travel Info

Hwy 169, Hwy 22 Minnesota River Flood Mitigation

Mankato, Saint Peter

Hwy 22 south of St. Peter project scheduled for 2015

The second of the three Minnesota River flood mitigation projects is on Highway 22 at the south edge of St. Peter and will be under construction beginning July 2015. Basic information is as follows:

  • Raise the grade and reconstruct from Hwy 169 to the existing Minnesota River Bridge
  • Construct a 120’ span bridge (large culvert) to handle additional water flow during high water events
  • Expect a detour from July through October

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 Highway 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/Highway99 will be the detour route with Highway 22 as an alternate route.  MnDOT is planning safety improvements to each of these routes in 2015 in anticipation of the added traffic in 2016.

Traffic impacts

  • None at this time
  • 2015 - Hwy 22 detour from July through October
  • 2016 - Hwy 169 - Nicollet CR 13/Highway 99 will be the detour route with Highway 22 as an alternate route.

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