City of MinneapolisI-35W North & South Storm Tunnel

S.F. 194

35W South Tunnel Outfall 35W North Tunnel Outfall

35W North Tunnel• Constructed in 1965• Material – concrete (not reinforced)• 8 – 14 foot diameter• 9,415 feet / 1.8 miles in length• Roughly 80 – 100 feet below the surface• 62% Minneapolis Flow / 38% MnDOT Flow• Funding need $5.5 million

35W South Tunnel• Constructed 1961 to 1964• Material – concrete (not reinforced)• 8 – 14 foot diameter• 24,540 feet / 4.7 miles in length• Roughly 80 – 100 feet below the surface• 85% Minneapolis Flow / 15% MnDOT Flow• Funding need - $14 million

35W North Tunnel• Tunnel built to accommodate city storm water that was originally draining to the sanitary system and freeway drainage• Agreements between the City of Minneapolis and MnDOT regarding the tunnel construction and maintenance

35W South Tunnel• Original flow - west to east to the Mississippi River• Freeway bisected the original flow pattern• Tunnel built to accommodate city and freeway drainage• Agreements between the City of Minneapolis and MnDOT regarding the tunnel construction and maintenance

Current Bonding Request2012 $4.5 million State, $4.5 million Local

* Request based on 2006 Tunnel Condition Assessment Report which identified segments of the tunnel and cost estimates.

Current Bonding Request2013 $4.5 million State, $4.5 million Local

Deficiencies to be Addressed

Groundwater Longitudinal Cracks

Liner FailureVoids outside the tunnel

Holes in the Liner

Groundwater Longitudinal Cracks

Liner FailureVoids outside the tunnel

Holes in the Liner

City of MinneapolisI-35W North & South Storm Tunnel

Solutions• Removing sedimentation and debris from the tunnel• Sealing open joints, fractures, and cracks• Repairing holes and erosion in the tunnel liner• Grouting voids outside of the liner

Solutions• Removing sedimentation and debris from the tunnel• Sealing open joints, fractures, and cracks• Repairing holes and erosion in the tunnel liner• Grouting voids outside of the liner

City of MinneapolisI-35W North & South Storm Tunnel• Need to manage the condition before it becomes a

safety issue• The City of Minneapolis needs to continue to take

rain water out of the sanitary system and into the storm water system to avoid Combined Sewer Overflows (CSO) and to meet the requirements of the Metropolitan Council Environmental Services (MCES) Inflow and Infiltration (I/I) Program

• MnDOT supports this work and funding request

• Need to manage the condition before it becomes a safety issue

• The City of Minneapolis needs to continue to take rain water out of the sanitary system and into the storm water system to avoid Combined Sewer Overflows (CSO) and to meet the requirements of the Metropolitan Council Environmental Services (MCES) Inflow and Infiltration (I/I) Program

• MnDOT supports this work and funding request