Transcript City of Minneapolis I-35W North & South Storm Tunnel

City of Minneapolis
I-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 Request
2012
2013
$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.
Deficiencies to be Addressed
Groundwater
Longitudinal Cracks
Holes in the Liner
Voids outside the tunnel
Liner Failure
City of Minneapolis
I-35W North & South Storm Tunnel
Solutions
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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 Minneapolis
I-35W North & South Storm Tunnel
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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