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Boulder Creek - Arapahoe and 13th Underpass

Boulder Creek - Arapahoe and 13th Underpass


Project Update

The improved Boulder Creek & Arapahoe Underpass near 13th has reopened!  Thank you to the travelers, residents and businesses for your patience during the construction of this project.

Construction Impacts

Please note that there will be additional tree plantings landscaping and stream bank restoration work completed later this summer and fall.  If you travel through the project area there will be some intermittent traffic impacts through June and grass areas of Central Park that are temporarily closed.  For additional information about impacts along Arapahoe and in Central Park or other construction projects in Boulder, please visit  Cone Zones.

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. 

The underpass was identified for improvements for several reasons: 

  • The width of the Boulder Creek Path within the existing underpass was too narrow (10 feet) for the volume of users and does not meet the city’s standard for minimum width (14 feet).
  • The grades of the approaches were steeper (8 percent on the north approach and 14 percent on the south approach) than the Americans with Disabilities Act standard (less than 5 percent) and the city’s standards for recreational paths (8 percent). The steepness of paths creates a barrier to some potential users and also contributes to fast bicycle and skateboard speeds entering into the underpass, which creates opportunity for conflict.
  • The visual and physical approaches to the underpass were poor due to tight turns at the entrances.
  • 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.

Project Improvements

The Arapahoe Underpass project will:

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

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.


This project is partially funded by the 2014 voter-approved Community, Culture and Safety tax  (CCS). 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 $2.5 million in CCS funds identified 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 15th and 13th streets.

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. 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

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 9th   to 17th  streets. The study began in late 2015 and was completed in mid-2017.

This integrated planning effort was identified through the Civic Area Master Plan pdf and the Transportation Master Plan update and provided plans to improve 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.



Bryant Gonsalves ● Transportation Division ● 303-441-3857 [email protected]

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