SW040 Central City Parallel Storm Tunnel


Project Details:

Project Start Date: 1/1/2020

Ongoing Program: N

Submitting Department: Public Works

Contact Person: Kevin Danen

Level of Need: Significant

Estimated Project Completion Date: 12/31/2024

Department Priority: 3 of 6

Contact Phone Number: (612) 673-5608

Website: TBD


Project Location:

Address: Central City Parallel Storm Sewer

City Sector: Downtown

Affected Neighborhoods: Downtown E&W

Affected Wards: 3

Central City Parrallel Storm Sewer through the downtown area


Project Description:

This project establishes funding to allow the design and construction of a new parallel tunnel in the Central City storm tunnel system to be completed to improve system operations.


Purpose and Justification:

The downtown Central City storm tunnel system consists of 3.9 miles of deep drainage tunnels of which the majority was built from 1939 to 1940 and was designed to handle the stormwater drainage requirements at that time. Land development since has led to a significant increase in the amount of stormwater that is directed into the tunnel system, resulting in over pressurization of the system. This over pressurization has led to degradation in the tunnel infrastructure and an increase in maintenance spending to inspect and maintain the system. Typical problems discovered through the assessment includes voids either above or below the tunnel structure, cracking and failure of the tunnel’s liner due to pressurization, erosion of the surrounding sandstone and infiltration of ground water and sand. The Public Works Department has been conducting ongoing repairs of damaged or failed tunnel liner sections over the past several years. The cost to repair the damaged tunnels varies greatly and is limited to being conducted during the winter months when storm water runoff is limited.



The construction of a new parallel primary tunnel would reduce the pressurization in the tunnel system, resulting in a reduced risk of tunnel failures, extended tunnel system service life, reduction in tunnel repair costs, and a decrease in long term maintenance with the operation of the tunnel system such as surface flooding and blowing manhole covers.


Project Visuals and Map:

Project Cost Breakdown

Department Funding Request

Partnerships


Have Grants for this Project been secured?

No


Describe status and timing details of secured or applied for grants or other non-City funding sources:

Not Applicable


Describe any collaborative arrangements with outside project partners, including who they are and what their role is with the project:

The City of Minneapolis has joint agreements with the Minnesota Department of Transportation (MnDOT) regarding the tunnels within the freeway right of way system. Those agreements commit the City to maintenance of those tunnel systems. Public Works meets collaboratively with MnDOT to determine priorities and responsibilities.


Planning


State Law Chapter 462.356 (Subd. 2) requires review of all capital improvements for compliance with the comprehensive municipal plan. Chapter 13, Section 4 of the City Charter requires Location and Design Review for the purpose of approving the sale of bonds for these projects. Describe how the project is consistent with the adopted City/Park Board comprehensive plans and how the project implements goals and policies as stated in the adopted plans, including specific policy references:


Goal 11 - Clean environment: In 2040, Minneapolis will have healthy air, clean water, and a vibrant ecosystem. (Policy 72:Sustainable Water System Management, Policy 73:Stormwater Management, Policy 74:Integration of Water Management into Development)




Goal 10 - Climate change resilience: In 2040, Minneapolis will be resilient to the effects of climate change and diminishing natural resources, and will be on track to achieve an 80% reduction in greenhouse gas emissions by 2050. (Policy 72:Sustainable Water System Management, Policy 73:Stormwater Management, Policy 74:Integration of Water Management into Development)




This project is consistent with planning and policy guidelines set forth in the City’s comprehensive plan Minneapolis 2040



Provide the date that Location and Design Review was conducted for the project, the outcome of that analysis and the date formal action was taken by the Planning Commission:

Location and Design Review for this project took place in 2016. The project was found consistent with the comprehensive plan by the City Planning Commission in 2016; no additional review is required.


Economic Development


Will the project contribute to growth in the city’s tax base? No


Describe the economic development impact of the project:

Not Applicable


Does the project support redevelopment opportunity that without the project would be infeasible?

No

Transportation


Is the proposed project on an existing or planned transitway, transit route, or high-volume pedestrian corridor? If yes, provide details on how the project will improve the transit and/or pedestrian experience.

No


Does the proposed project anticipate multi-modal enhancements (sidewalks, bicycle or transit facilities)? Provide details.

No


Is the right-of-way constrained and do you anticipate that modes of travel will be competing for space? Provide details, is there potential for innovative design options? Provide details

No

Operating Impacts


Operations & Capital Asset Maintenance:

Is this request for new or existing infrastructure? New

What is the expected useful life of the project/Improvement? 100 Years

Year that Operating Incr/(Decr) will take effect? Ongoing

What is the estimated annual operating cost increase or (decrease) for this project? ($50,000)

Any Prior Year Remaining Bond Authorizations? No

Prior Year Remaining Bond Authorizations: Not Applicable


Describe how operating cost increases or decreases were determined and include details such as personnel costs, materials, contracts, energy savings, etc:

The decreased amount of operating costs represents savings in labor, equipment and material expenses associated with the ongoing tunnel inspections and maintenance within the Central City storm tunnel system..


If new infrastructure, discuss how the department/agency will pay for the increased annual operating costs:

Not Applicable


For new infrastructure, describe the estimated timing and dollar amount of future capital investment required to realize the full expected useful life of the project:

Insert detail here.

Project Coordination


Describe completion status for ongoing projects and how and when the department/agency plans to use the prior year remaining bond authorizations:

Not Applicable


If this is a new project, describe the major project phases and timing anticipated for completing the project:

2016-2019 – Parallel tunnel feasibility study, final layout and design

2020-2023 – Tunnel construction


Scalability/Funding Allocation Flexibility – discuss any flexibility to increase or decrease funding among the years in the five-year plan and the most that could be spent in a given year:

This program could be flexible within the five-year plan but the requested funding is necessary to continue addressing identified needs.

Minneapolis Goals and Strategic Direction

Minneapolis is a growing and vibrant world-class city with a flourishing economy and a pristine environment, where all people are safe, healthy and have equitable opportunities for success and happiness. Below is a description of how this project meets each of the City's Goals.



Public Services


The City prioritizes reliable and equitable access to high-quality public services.

Work collaboratively between City departments to ensure utility budgets are adequately funded to maintain aging infrastructure systems


Prioritize and reserve the City’s sanitary and storm sewer capacity for its intended purpose and prohibit groundwater or other waste streams from entering the storm or sanitary sewer infrastructure unless the City gives approval.


Environmental Justice:


The City prioritizes sustainable practices and renewable resources to equitably address climate change while restoring and protecting our soil, water and air.

Manage the city’s surface waters, groundwater, stormwater, wastewater and drinking water equitably and sustainably, while minimizing the adverse impacts of climate change.


Use hydraulic and water quality models and data about infrastructure condition and risks to prioritize and inform investments in sanitary and storm infrastructure.


Continue work to reduce risk of overflows from the historically connected sewers and work to reduce infiltration and inflow into the city’s sanitary sewer system through infrastructure improvements.


Consider climate forecasts in stormwater feasibility and modeling work to inform infrastructure investments.


Explore the impacts of flooding on public safety, the protection of property, public infrastructure and the environment.

Improve the tree canopy and urban forest.


Built Environment & Transportation:


The City prioritizes high quality neighborhoods, streets, infrastructure and equitable access to multimodal transportation in all parts of the City through thoughtful planning and design.

Manage and design transportation infrastructure with a priority on water quality through the reduction of stormwater runoff and pollutants including road salt.


Maximize the use of public property to meet flood mitigation and water quality goals via green infrastructure and other stormwater best management practices


Use infiltration best practices and bio-infiltration to reduce stormwater impacts on surface waters.


Encourage and require reductions in amounts of impervious surfaces. Pilot and promote permeable surface solutions as alternatives to impervious surfaces.


Additional Information

Benefits:

1. Reduced risk of tunnel failures in the Central City Downtown tunnel system

2. Extended tunnel system service life

3. Increase in the time intervals between inspections (operating budget decrease)

4. Increase in tunnel capacity

. Reduce pressurization

. Pressurization that causes manhole covers to blow off.

. Reduce surface flooding

. Allows the addition of storm water from roof leaders.

. Allows the tunnel to carry a larger flow during storms of a large and long duration.

. Eliminate hydraulic restrictions.

. Allows I&I projects to proceed that are dependent upon the tunnel system for stormwater conveyance.