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Boulder Creek - Arapahoe and 13th Underpass

Boulder Creek - Arapahoe and 13th Underpass

Project Update

Construction Timing

Arapahoe Avenue street reconstruction project,15th to Broadway .

The street reconstruction is scheduled to start June 11, 2018. 

The reconstruction work can only occur during the summer months due to the need to constrict vehicle traffic to only one lane of travel on Arapahoe Avenue through the work zone.  The reconstruction of Arapahoe Avenue from 14th to 15th streets is scheduled to be completed by the start of school in August.

Boulder Creek - Arapahoe and 13th Underpass

The reconstruction of the Boulder Creek & Arapahoe Underpass near 13th will also take place during the road reconstruction and will be completed in early 2019.  Final concrete work, landscaping, urban design and public art improvements will be completed in spring, 2019 to take advantage of warmer weather.

Construction Impacts

Potential construction impacts for the Arapahoe Avenue reconstruction will include Arapahoe Avenue being reduced to one lane of travel in the westbound direction from 15th to Broadway, with eastbound vehicles detoured to Canyon Boulevard.  Pedestrian detours and transit stop closures or relocations, and will also be in effect.  This work may cause travel delays 

Project Description

The City of Boulder initiated planning and design for the Boulder Creek & Arapahoe Underpass (Arapahoe & 13th) project in early 2016 to provide a safer, more accessible and less flood prone underpass along the Boulder Creek Path at Arapahoe Avenue, near 13th Street. The project utilized the city’s Community and Environmental Assessment Process (CEAP) to select the preferred design alternative. Review the project's final, approved CEAP here pdf.

The underpass was identified for improvements for several reasons. The width of the Boulder Creek Path within the existing underpass is too narrow (10’) for the volume of users and does not meet the city’s standard for minimum width (14’). The grades of the approaches are steeper (8% on the north approach and 14% on the south approach) than the Americans with Disabilities Act standard (less than 5%) and the city’s standards for recreational paths (8%). The steepness of the paths creates a barrier to some potential users while also contributes to faster bicycle and skateboard speeds entering into the underpass which creates opportunity for conflict. The visual and physical approaches to the underpass are poor due to tight turns at the entrances, which is especially true for the south approach. Lighting is poor, including during daylight hours, which creates the potential for collisions or close calls and causes some users to avoid the underpass because they do not feel safe. The underpass also closes regularly during high water flows of Boulder Creek. During 2015, the underpass was closed due to high water for three months (May through July). High water closures divert more pedestrians and bicycles to the onstreet crossing at Arapahoe Avenue and 13th Street increasing the opportunity for collisions.

The voter-approved 2014 Community, Culture, and Safety Tax (CCS) ballot initiative provides $2.5 million in project funds. Construction funded by CCS must be completed by the end of year 2018. Current cost estimates for all proposed design alternatives considered for this project are greater than $2.5 million.

The Arapahoe Avenue street reconstruction, between 15th and 13th streets, will be completed along with the Arapahoe Underpass project. This work will re-construct the on-street crossing at Arapahoe Avenue & 13th Street.

Public Involvement

Planning and design of this project began in April 2016 and continued through 2016. Feedback received from the public process was incorporated into the final project design, where feasible. 

Past Meetings & Events

The project has been presented to the community in the following ways:

  • Civic Area Open House , April 4, 2016
  • Youth Opportunity Advisory Board , April 8, 2016
  • Boulder Walks Civic Area Ramble , May 7, 2016 & June 11, 2016
  • Boulder Valley Comprehensive Plan Update Meeting , May 11, 2016
  • Boulder Transportation Connections , June 2, 2016
  • Community Cycles , June 6, 2016
  • Transportation Advisory Board (TAB ), June 11, 2016
  • Second Open House , Aug. 31, 2016
  • Transportation Advisory Board , Sept. 12, 2016
  • Parks and Recreation Advisory Board , Sept. 26, 2016
  • Boulder County Farmers Market , Oct. 5, 2016
  • Parks and Recreation Advisory Board , Oct. 17, 2016
  • Parks and Recreation Advisory Board , Oct. 24, 2016
  • Center for People with Disabilities , Oct. 28, 2016
  • Community Cycles Advocacy Committee , Nov. 7, 2016
  • Environmental Advisory Board, April 5, 2017
  • Planning Board, April 6, 2017
  • Transportation Advisory Board, April 10, 2017
  • Open Space Board of Trustees, April 12, 2017
  • Water Resources Advisory Board, April 17, 2017
  • Parks and Recreation Advisory Board, April 24, 2017
  • Greenways Advisory Committee, May 11, 2017
  • City Council, June 6, 2017

View summary of community feedback pdf

The preferred project design was approved by the city's Greenways Advisory Committee (May 11, 2017) and City Council (June 6, 2017) as part of the project Community and Environmental Assessment Process (CEAP) pdf.

Project Improvements

The Arapahoe Underpass project will:

  1. Improve the general safety of Boulder Creek multi-use path at Arapahoe Avenue and 13 th Street
    1. Improve sight lines at/into the underpass
    2. Address conflict zones at the south entrance to the underpass
    3. Widen the path at the north and south entrances and through the underpass
    4. Study the at-grade pedestrian crossing at Arapahoe Avenue and 13 th street through better design
    5. Improve lighting in the underpass and at the approaches
  2. Meet Americans with Disabilities Act (ADA) standards for the underpass
  3. Reduce high water closures of the multi-use path
  4. Encourage use of the underpass through safety and design improvements to decrease the use of the at grade crossing at Arapahoe Avenue and 13 th Street

Project Timeline

  • Preliminary Design Development: through winter 2016
  • Project Open House: spring 2016
  • Boards and Commissions Presentations: spring through fall 2016
  • Second Open house: summer 2016
  • CEAP: winter 2016 - 2017
  • Final Design Development & Permit Approvals: 2017
  • Start Construction: spring, 2018
  • Underpass Construction Complete: early 2019
  • Landscaping: spring to summer, 2019


The project was one of those listed in the 2014 voter-approved Community, Culture and Safety tax .Community, Culture and Safety Tax Color Logo for Web

The projects for the ballot initiative were identified and approved by City Council on Aug. 5, 2014 .

In addition to the $4.5 million in CCS funds for the underpass, $2.2 million in city transportation funds are directed to the underpass project.  Additionally, $2.7 million of non-CCS funding has been provided to complete the Arapahoe Avenue street reconstruction between 15 th and 13 th streets.

Community and Environmental Assessment Process

The Arapahoe Underpass project was identified for the Community and Environmental Assessment Process (CEAP). 

The CEAP provides a framework for balanced and thoughtful consideration of environmental and social issues in the preliminary planning and design of capital improvement projects.

It also provides a forum for public discussion of broad level project issues relative to departmental master plans and overall community goals.

Review the project's final, approved CEAP here pdf.

Project Coordination and Support

The Arapahoe Underpass project will coordinate with and support the following projects:

Canyon Complete Street Study

The Canyon Boulevard Complete Streets Study will develop a vision, preliminary design and a cost estimate to improve Canyon Boulevard/State Highway 119 from 9 th to 17 th streets. The study began in late 2015 and was completed in mid-2017.

This integrated planning effort was identified through the and the Transportation Master Plan update and provided plans to improveme travel along and across Canyon Boulevard as well as incorporate urban design, landscaping and placemaking features to improve the travel experience through the area and create a place to spend time.

Boulder Civic Area Project

The Boulder Civic Area project includes the area between Canyon Boulevard to the north, Arapahoe Avenue to the south, 9 th Street to the west and 14 th Street to the east.

The Civic Area completed a master plan in 2015, which established the goals, guiding principles and core themes for implementation, a process that will take the next 10 to 20 years to complete.

The CCS also funded the first phase of the Civic Area redevelopment, between Canyon Boulevard to the north, Arapahoe Avenue to the south, 9 th Street to the west and the main Boulder Library to the east. This phase of the Civic Area Project was completed in 2017.  Planning for the East end (between Broadway and 14th Street), began in 2018 and is anticipated to continue into 2019.

Boulder Creek Path and Lighting Improvements Projects

The Boulder Creek Path and Lighting Improvements Project will add a separate pedestrian path along the existing multi-use path corridor to allow for separation of bicycle and pedestrian traffic and install pedestrian lighting to provide adequate and appropriate light levels for nighttime visibility and safety from generally 17th Street to 13th Street and 6th Street to east of Eben G. Fine Park.

All lighting installed through the project will follow the city's outdoor lighting ordinance.

The first phase of this project, the west end from 9th Street to Eben G. Fine Park, was completed in 2017.  The city is currently working with the Boulder Valley School District to identify the opportunities to improve pedestrian and bicycle travel along Boulder Creek between 17th and 13th streets, behind Boulder High School.


Melanie Sloan ● Transportation Division ● 303-441-3266 ● [email protected]

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