09.09.24 TAB Agenda 6 - Iris Ave CEAPCITY OF BOULDER
TRANSPORTATION ADVISORY BOARD
AGENDA ITEM
MEETING DATE: September 9, 2024
AGENDA TITLE:
Public hearing and consideration of a recommendation regarding the Iris Avenue Transportation
Improvements Project Community and Environmental Assessment Process (CEAP)
PRESENTERS:
Valerie Watson, Interim Director of Transportation and Mobility
Stephen Rijo, Transportation Planning Manager
Gerrit Slatter, Principal Transportation Projects Engineer
Devin Joslin, Principal Traffic Engineer
Lindsay Merz, Civil Engineering Manager
Melanie Sloan, Transportation Principal Project Manager
Daniel Sheeter, Transportation Principal Planner
EXECUTIVE SUMMARY
The purpose of the Iris Avenue Transportation Improvements Project is to make Iris Avenue
between Broadway and 28th Street safer, more comfortable, and connected. The project will
address the actions of the Vision Zero Action Plan by implementing proven safety
countermeasures on this priority Core Arterial Network (CAN) corridor that is also on the High
Risk Network (HRN). The HRN is a small percentage (7%) of city streets that have nearly half
of all fatal and serious injury crashes in the city. The CAN is a connected system of protected
bicycle lanes, intersection enhancements, pedestrian facilities, and transit facility upgrades to
create safe, comfortable connections along Boulder’s main corridors.
Staff completed a Community Environmental Assessment Process (CEAP) that included robust
community and stakeholder engagement, analysis of existing conditions data, consideration of
policy and plan guidance, and evaluation of conceptual alternatives using a CEAP checklist and
project specific evaluation criteria.
The CEAP identified Alternative B as the recommended alternative because it best balances
community priorities, plan and policy guidance, and issues identified by the existing conditions
data which demonstrate the need for crash reduction, moderating vehicle speeds, providing bike
and pedestrian safety and comfort and preserving existing public street trees. Alternative B can
achieve these safety benefits with minimal added travel time and lower costs and time to
implement than other conceptual design alternatives.
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Alternative B reconfigures vehicle lanes between 13th Street and Folsom/26th Street from four
to three, including a center turn lane, incorporates protected intersection elements, implements
traffic signal changes to separate turning vehicles from people walking and biking at major
intersections, makes spot improvements to existing sidewalks, and provides a two-way protected
bike lane on the north side of the street. The center turn lane and two-way protected bike lane
each provide dedicated space for emergency response during day-to-day and disaster scenarios
respectively. Alternative B can be implemented within the existing curb-to-curb width and so
preserves existing public street trees. It is estimated, based on recently completed similar
projects, to cost about $5 million in today’s dollars to implement and take three to four times less
time to implement than the two design alternatives that maintain the existing number of vehicle
lanes. Traffic modeling completed for the project found these benefits can be achieved with a
potential travel time increase ranging from 2 to 58 seconds for 95% of trips on the corridor, and
the slowest trips with a maximum of 2 minutes and 9 seconds with Alternative B.
Staff first introduced the project to TAB at its April 11, 2022 meeting, provided project updates
at the October 10, 2022, July 10, 2023, and April 8, 2024 meetings. Since that last meeting, staff
have completed the CEAP, identified a recommended alternative, and gathered public input on
the evaluation and recommendation.
The purpose of this item is for TAB to review the CEAP and the recommended conceptual
design alternative and provide a recommendation to city council to inform the next stage of the
project design process.
BACKGROUND
Iris Avenue, from 28th Street to Broadway, is an important east-west corridor in north Boulder
that provides direct, convenient connections to everyday neighborhood destinations and supports
travel within Boulder and between Boulder and communities along the Diagonal Highway
(Figure 1). Iris Avenue’s role in the local and regional transportation network is important today
– and will only become more important in the coming years as local and regional land use and
transportation projects are completed.
Figure 1: Iris Avenue Transportation Improvements Project Limits
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However, Iris Avenue does not provide the safest, most comfortable connections regardless of
how you travel.
In 2019, the Transportation Master Plan and the Low Stress Walk and Bike Network Plan
recommended greater separation and protection between vehicle and bicycle lanes on Iris
Avenue and a need for pedestrian improvements in key areas due to the road having more than
three vehicle lanes, the posted speed limit set at 35 miles per hour, and average daily traffic
being greater than 6,000 vehicles.
In 2022, the Safe Streets Report (SSR) found between 2018 and 2020, 14,500 people were
involved in a crash in Boulder, resulting in 150 serious injuries. Sixty-seven percent of severe
traffic crashes, those that result in serious injury or fatality, occur on arterial streets. The report
found these severe injury crashes occurred at several intersections on Iris Ave: 28th Street,
Folsom/26th Street, and Broadway. The SSR also identified Areas of Concern: crash types that
disproportionately affect certain groups, like young people and seniors. Data from the Iris project
revealed that one in ten pedestrians or cyclists traveling on or across Iris on an average day were
young, elderly, or disabled. Community input shared a common sentiment: people feel unsafe
walking or biking along and across Iris, yet hundreds do so every day.
In response to the findings of the SSR, City Council, in partnership with the Transportation
Advisory Board (TAB), elevated work on the Core Arterial Network (CAN) as one of its 10
priorities for city department efforts. Council reaffirmed CAN as a priority in April 2024. The
CAN is the connected system of protected bicycle lanes, intersection enhancements, pedestrian
facilities, and transit facility upgrades that will help reduce the potential for severe crashes and
make it more comfortable and convenient for people to get where they need to go along
Boulder’s main corridors, including Iris Avenue.
In 2023, the 2023-2027 Vision Zero Action Plan (VZAP) identified specific actions and
strategies to address the findings of the SSR. The High Risk Network (HRN) was developed as
part of the plan as a way to focus actions on places where severe crashes occur or are more likely
to occur in the future. The HRN has an outsized proportion of previous severe crash incidence:
the HRN represents only 7% of the city’s street network but nearly half of all severe crashes
occur on these streets. The HRN also identifies locations where more than five of the six most
common risk factors for future crashes are present. Proactively managing risk and mitigating
crashes on this small percentage of streets can have an outsized impact on reducing fatal and
serious injury crashes citywide and achieve the greatest impact in the shortest amount of time.
Iris Avenue, from 19th to 28th streets, is on the HRN.
Two core strategies of the VZAP are to work on the CAN and the HRN. Action 3 of the plan
commits the city to implement capital projects by 2027 to improve safety and comfort on priority
CAN corridors that are also on the HRN, which includes Iris Avenue.
The Iris Avenue Transportation Improvements project completed a CEAP to identify a
recommended alternative that incorporates proven safety countermeasures with a focus on
increasing mobility choices, improving safety for everyone, making walking, biking, scooting,
and taking transit more attractive and convenient, and improving connections to local, citywide
and regional destinations.
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An update on the progress of the Iris Avenue project with detail on the conceptual design
alternatives, project considerations, and community priorities was provided to City Council at a
study session on June 27, 2024.
ANALYSIS
The recommended alternative is Alternative B: Two-Way Protected Bike Lane and No Change
to Roadway Width (Figure 2). The CEAP evaluation supporting this recommendation can be
found in Attachment A – Iris Avenue Transportation Improvements Project Community and
Environmental Assessment Process (CEAP).
Alternative B is recommended because it best balances community priorities, plan and policy
guidance, and issues identified by the existing conditions data for crash reduction, moderating
vehicle speeds, providing bike and pedestrian safety and comfort, and preserving existing public
street trees, with minimal added travel time and lower costs and time to implement that other
conceptual design alternatives.
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Figure 2: Iris Avenue Project Recommended Design: Alternative B
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Figure 3 Iris Alternatives Evaluation Results
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Alternative B achieves these benefits by:
• Reconfiguring the roadway with vehicle lane repurposing (between 13th Street and
Folsom/26th Street) from four vehicle lanes to two vehicle lanes with a center turn lane,
and moderates vehicle speeds and reduces the corridor’s common crash types: rear ends
and approach turn crashes.
o The center turn lane supports vehicles turning in and out of side streets and
driveways by:
Removing turning vehicles from the vehicle travel lane, reducing the
potential for rear rend crashes.
Giving drivers a safe place to wait for a gap in traffic to complete their
turn, reducing the potential for approach turn crashes.
o Existing conditions data, Federal Highway Administration guidance 1 and traffic
modeling indicate three vehicle lanes provides sufficient capacity for the number
of vehicles that use Iris Avenue today.
Traffic modeling utilized existing vehicle, bicycle and pedestrian volumes,
an approach supported by the Boulder Valley Comprehensive Plan
transportation and land use assumptions, 2023 Travel Diary Study findings
of reduced single occupancy vehicle use and increased bicycling over the
past nine years, and ten years of historic data that show vehicle volumes
have remained reasonably constant.
Traffic modeling determined Alternative B may result in 3 to 46 seconds
travel time increase for the average trip, 2 to 58 seconds increase for 95%
of trips on the corridor, and 1 second to 2 minutes and 09 seconds increase
for 5% or less of trips on the corridor.
o Transportation research does not find vehicle lane repurposing results in increased
emissions, instead it finds:
Traffic emissions reductions from congestion mitigation are not
guaranteed and demand-based emissions reduction strategies can be more
effective.2
Reduction in fine particulate emissions with multimodal improvements on
a corridor.3
• The center turn lane provides dedicated space for day-to-day emergency response
vehicles to travel unimpeded by roadway traffic.
• Reconfiguring vehicle lanes provides space at intersections for more protected
intersection elements which can reduce VZAP common crash types: right-turn crashes
and pedestrians/bicyclists crossing the street.
• Implementing traffic signal changes to separate turning vehicles from people walking and
biking at major intersections to further reduce VZAP common crash types: left-turn
crashes, right-turn crashes, and pedestrians/bicyclists crossing the street.
1 https://safety.fhwa.dot.gov/road_diets/guidance/info_guide/rdig.pdf
2 https://www.sciencedirect.com/science/article/abs/pii/S1361920912000727
3 https://www.sciencedirect.com/science/article/abs/pii/S1361920914001254
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o Traffic signal changes for a two-way protected bike lane have less impact on
vehicle travel time compared to one-way bike lanes because the two-way lane is
only on one side of the street, while one-way lanes are on both sides.
• The two-way protected bike facility on the north side of the street supports:
o All ages and abilities by being wide enough to support side-by-side riding, such as
parents with young children, and people biking or using scooters to pass one
another.
o Locating the protected bike lane on the north side of the street improves safety by
significantly reducing the number of conflict points between people on bikes and
other vehicles.
o Disaster emergency response because it is wide enough to accommodate
emergency vehicles during a disaster scenario.
o Year-round maintenance because:
It is wide enough to accommodate more types of conventional
maintenance vehicles for snow removal and sweeping.
Receives more sun exposure in the winter months, which encourages
melting and evaporation to aid snow and ice response efforts.
Provides more space for snow storage in winter months.
o Note: Alternative B will include design features such as protected intersection
elements, raised crossings, two-way signs and markings, striping and signal
changes that separate vehicle and bike movements at intersections, accounting for
speed of vehicles and bicycles, to be detailed in the final design phase to reduce
potential conflicts between bicyclists and drivers at side streets and driveways.
• Implementing proven safety countermeasures within the existing roadway width, which
costs less, takes less time to implement, and preserves the existing public street trees.
• Concurrently implementing side street traffic calming and management in prioritized
locations to address the biggest speeding problems on neighborhood streets.
PUBLIC FEEDBACK
The community engagement strategy for conceptual design of the Iris Avenue Transportation
Improvements project consisted of three phases:
1. Summer—Winter 2023: Community Input on Travel and Lived Experience;
2. Winter—Spring 2024: Community Input on Conceptual Design Alternatives; and
3. Summer 2024: Community Input on CEAP and Recommended Alternative.
Summer—Winter 2023: Community Input on Travel and Lived Experience
From summer through winter 2023, staff began talking to the community and collecting data to
understand their lived experience of what is working on Iris Avenue and what needs
improvements. Twenty-seven engagement activities reached over 1,600 people and garnered
more than 2,100 comments that provided feedback on existing conditions, challenges, and
opportunities to inform development of improvements.
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People participated in online questionnaires and in-person contacts at tabling, pop-up, and other
community events. Guided walk and bike tours provided opportunities to get more detailed
feedback from participants. This first round of project work culminated in an open house and
three walks in the park in winter 2023. The project team shared learnings and provided additional
opportunities for community members to offer feedback before city staff began identifying
potential improvements.
Themes heard from this engagement included:
o East-west travel is important, and drivers appreciate Iris Avenue as a convenient and reliable
route across the city
o People walking, rolling, biking, and taking transit also want Iris Avenue to provide
convenient and safe routes
o Sidewalks could be improved to provide comfort, safety, and attractive walking conditions.
Sidewalks are currently not wide enough, are winding, sloping, and bumpy, and are often
blocked by overgrown vegetation
o Crossing Iris Avenue safely and conveniently is a priority for people of all ages and abilities
traveling to school, work, for errands, and for recreation – but today some see it as a barrier
to getting where they want to go
o Vehicles travel at high speeds, creating unsafe conditions and excessive street noise
o Safer neighborhood and business access is essential
o Drivers feel unsafe turning onto and off Iris Avenue and feel they’re more likely to crash
with oncoming traffic when doing so
o Delivery, transit, waste management and other vehicles stop in-lane, blocking the bike and
right-side travel lanes
o Residents are concerned any future changes will impact emergency evacuation and response
o Neighbors want to maintain the character of their neighborhoods, which they see as
providing safer, more comfortable alternatives for walking, rolling, and biking than arterial
streets like Iris Avenue, and they are concerned that changes to Iris Avenue could create
traffic diversion onto nearby streets
o Community members want attractive facilities and opportunities for placemaking
o Better wayfinding and help navigating to local and regional destinations are desired
o Roadway pavement conditions could be improved
o Transit service is infrequent, and many transit stops are not accessible and lack shelters,
benches, and trash cans
Winter—Spring 2024: Community Input on Conceptual Design Alternatives
The design process took place from winter to spring 2024 and identified and screened potential
solutions to issues highlighted by data and community input. These solutions were then
compared and contrasted using 17 criteria and preliminary traffic modeling was undertaken to
assess the feasibility of roadway reconfiguration with lane repurposing.
Preliminary traffic analysis showed that vehicle lane changes at the Broadway and 28th Street
intersections would significantly increase travel times by at least five minutes and cause vehicle
queues exceeding 1,000 feet. To ensure reliable traffic flow and to respond to the community’s
priority for vehicle travel time, repurposing vehicle lanes is not proposed at these critical
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intersections. Instead, any lane configuration changes will be confined to the corridor section
between 13th Street and Folsom/26th Street.
The design process resulted in four conceptual alternatives being advanced for further evaluation
between 13th Street and Folsom/26th Street:
o Alternative A: One-Way Protected Bike Lanes and No Change to Roadway Width
o Alternative B: Two-Way Protected Bike Lane and No Change to Roadway Width
o Alternative C: One-Way Protected Bike Lanes and Widened Roadway
o Alternative D: Two-Way Protected Bike Lane and Widened Roadway
In spring 2024, staff hosted a second in-person and virtual open house, met people where they
were at community pop-ups, and hosted an online questionnaire to understand the community’s
priorities to advance the four conceptual alternative designs.
Community input continued the themes heard in 2023. When asked for their priorities for
designing Iris Avenue, questionnaire respondents’ answers grouped into three distinct tiers:
greater than 100 selections, 20 to 100 selections, and less than 20 selections:
o 100+ selections
o Vehicle Travel Time Along the Corridor
o Crash Reduction
o Biking Comfort
o Pedestrian Crossing Safety and Comfort
o Bike Crossing Safety and Comfort
o Vehicle Speed Moderation
o Preserving Existing Trees
o 20-100 selections
o Disaster Emergency Response
o Time and Cost to Design and Implement
o Vehicle Turning Movements
o Walking Comfort
o Day-to-Day Emergency Response
o Transit Accessibility
o Opportunity for Protected Intersection Elements
o Less than 20 selections
o Stormwater Drainage
o Right-of-Way Acquisition
o Utility Relocation
Summer 2024: Community Input on CEAP and Recommended Alternative
In spring and summer 2024, staff completed the CEAP using the established CEAP goals
assessment, checklist and checklist questions, project-specific evaluation criteria and community
input to identify the recommended alternative.
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Staff shared the CEAP evaluation and recommended alternative with the community for
feedback in July and August 2024 at an in-person open house with 163 attendees and a virtual
open house questionnaire which received 217 responses.
The questionnaire focused on the alternatives evaluation process and the recommended
alternative design elements the community is excited for and concerned about. The most
mentioned concerns about the project for staff to consider in future design phases were:
• Traffic congestion and vehicle travel time
• Project process
• Complexity of a center turn lane and two-way protected bike lane design
• Neighborhood side street vehicle speeds and traffic diversion
• Bookend intersection safety
• Emergency evacuation
When asked what design elements respondents and in-person open house participants are most
excited about as the project moves forward, the most selected responses were:
• Safer crossings
• Preservation of Tree Canopy
• End-to-end two-way protected bike lane
• Protected intersections
Themes from the most recent phase of community engagement reiterated previously heard
concerns and desires and did not reveal new or diverging themes. These continued themes
influenced the finalization of the content of the CEAP and public facing materials. Community
feedback also provides the priorities on which to focus such as the south side sidewalks and
access to the bike facility on the north side, the emphasis on high quality and aesthetically-
pleasing design, innovative designs which preserve as much tree canopy as possible, and other
designs and signal practices to best balance the trade-offs in safety, comfort, and connectivity for
people walking, biking, riding transit and driving.
Project information, including the online open house materials, can be found at the Iris Avenue
Transportation Improvement Project website.
BOARD ACTION REQUESTED
Staff is seeking a recommendation to the City Council regarding the Iris Avenue Transportation
Improvements Project CEAP. Findings will be presented to City Council for acceptance at their
September 19, 2024 meeting.
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ATTACHMENTS
Attachment A – Iris Avenue Transportation Improvements Project Community and
Environmental Assessment Process (CEAP)
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Document
Title Here
Community and Environmental Assessment Process
Iris Avenue
Transportation
Improvements
Project
September 2024
Attachment A - Iris Ave Transportation Improvements Project
Community & Environmental Assessment Process (CEAP)
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Table of Contents
EXECUTIVE SUMMARY ........................................................................................................................................... 3
PROJECT DESCRIPTION ........................................................................................................................................... 4
BACKGROUND PURPOSE & NEED ........................................................................................................................... 5
Community Input on Travel and Lived Experience - 2023 .......................................................... 7
Existing Conditions Data ............................................................................................................. 9
CEAP EVALUATION............................................................................................................................................... 13
CEAP Process ............................................................................................................................. 13
Conceptual Alternatives ........................................................................................................ 13
Community Input on Conceptual Design Alternatives – Spring 2024 ...................................... 30
Goals Assessment ..................................................................................................................... 34
CEAP Checklist ........................................................................................................................... 38
Checklist Criteria Summary ................................................................................................... 38
Project Specific Evaluation Criteria ....................................................................................... 41
Community Input on CEAP and Recommended Alternative – Summer 2024.......................... 58
RECOMMENDED ALTERNATIVE ............................................................................................................................ 64
STAFF PROJECT MANAGER AND RELEVANT CONTACTS ........................................................................................ 67
ATTACHMENTS .................................................................................................................................................... 68
Attachment A: Conceptual Alternatives with Considerations Applied .................................... 69
Attachment B: CEAP Checklist Evaluation for the Four Conceptual Design Alternatives ........ 73
Attachment C: CEAP Checklist Questions ................................................................................. 75
Attachment D: Table of Mature Trees ...................................................................................... 91
Attachment E: Floodplain Memo .............................................................................................. 96
Attachment F: Conceptual Alternatives with Project-Specific Evaluation Criteria Applied ..... 99
Attachment A - Iris Ave Transportation Improvements Project
Community & Environmental Assessment Process (CEAP)
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Executive Summary
The Iris Avenue Transportation Improvements Project Community and Environmental
Assessment Process (CEAP) completed a full project evaluation of four conceptual design
alternatives. The CEAP used the established CEAP goals assessment, checklist and checklist
questions, project-specific evaluation criteria, and community input to identify the
recommended alternative. The recommend alternative is Alternative B. The project will
advance the actions of the Vision Zero Action Plan by implementing proven safety
countermeasures on this priority Core Arterial Network (CAN) corridor that is also on the High
Risk Network (HRN). The HRN is a small percentage (7%) of city streets that have nearly half of
all fatal and serious injury crashes in the city. The CAN is a connected system of protected
bicycle lanes, intersection enhancements, pedestrian facilities, and transit facility upgrades to
create safe, comfortable connections along Boulder’s main corridors.
The CEAP for the Iris Avenue Transportation Improvements project included robust community
and stakeholder engagement, analysis of existing conditions data, consideration of policy and
plan guidance, and evaluation of conceptual alternatives using a CEAP checklist and project
specific evaluation criteria.
The CEAP identified Alternative B as the recommended alternative because it best balances
community priorities, plan and policy guidance, and issues identified by the existing conditions
data which demonstrate the need for crash reduction, moderating vehicle speeds, maintaining
travel time reliability, providing bike and pedestrian safety and comfort, and preserving existing
public street trees. Alternative B can achieve these safety benefits with minimal added travel
time and lower costs and time to implement than other conceptual design alternatives.
Alternative B reconfigures vehicle lanes between 13th Street and Folsom/26th Street from four
to three, including a center turn lane, incorporates protected intersection elements,
implements traffic signal changes to separate turning vehicles from people walking and biking
at major intersections, makes spot improvements to existing sidewalks, and provides a two-way
protected bike lane on the north side of the street. The recommended alternative does not
change the vehicle lane configuration at “the bookends” from 13th Street to Broadway and
Folsom/26th Street to 28th Street to maintain travel time reliability for all roadway users. The
center turn lane and two-way protected bike lane each provide dedicated space for emergency
response during day-to-day and disaster scenarios respectively. The project team will continue
to coordinate closely with the city’s Boulder-Fire Rescue and Police departments, and the Office
of Disaster Management (ODM) for the City of Boulder and Boulder County, on roadway design
features for emergency operations during the final, or detailed, design phase.
Adjacent communities expressed concerns around traffic diversion on side streets. This project
will include a concurrent neighborhood traffic calming effort on select streets in the secondary
study area to address speed mitigation and traffic management. Access control is another tool
in the design toolbox that can limit traffic diversion. Existing conditions volume and speed data
was collected in the secondary study area to inform the traffic calming approach and locations.
Attachment A - Iris Ave Transportation Improvements Project
Community & Environmental Assessment Process (CEAP)
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Alternative B can be implemented within the existing curb-to-curb width and so preserves
existing public street trees. It is estimated, based on recently completed similar projects, to cost
about $5 million in today’s dollars to implement and take three to four times less time to
implement than alternatives that maintain the existing number of vehicle lanes. Traffic
modeling completed for the project found these benefits can be achieved with a potential
travel time increase ranging from 2 to 58 seconds for 95% of trips on the corridor, and the
slowest trips (5% of trips) with a maximum of 2 minutes and 9 seconds.
Project Description
Iris Avenue, from 28th Street to Broadway, is an important east-west corridor in north Boulder
that provides direct, convenient connections to everyday neighborhood destinations and
supports travel within Boulder and between Boulder and communities along the Diagonal
Highway (Figure 1).
Figure 1: Iris Avenue Priority Corridor project limits
Locally, Iris Avenue is recognized by the Denver Regional Council of Governments (DRCOG) as a
short trip opportunity zone: an area where a high concentration of short trips of two miles or
less begin or end. Short trips are much more likely than longer trips to be converted from
vehicle trips to walking or bicycling.
The CO 119 Safety, Mobility and Bikeway Project will bring regional multimodal transportation
improvements, including bus rapid transit and off-street multi-use path connections to the
eastern edge of the project corridor (Figure 2). Construction begins this year and is anticipated
to be completed in 2026/2027. The bus rapid transit service will have stops on 28th Street just
south of Iris Avenue and the bikeway will connect to the city’s existing bike network west of
47th Street and along Foothills Parkway. Regional bus rapid transit and e-bike supportive multi-
use paths to the eastern edge of Iris Avenue make it a key multimodal corridor.
Attachment A - Iris Ave Transportation Improvements Project
Community & Environmental Assessment Process (CEAP)
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Figure 2: CO 119 Safety, Mobility and Bikeway project overview map
Despite the role that Iris Avenue plays within the overall multimodal transportation network, it
does not provide the safest, most comfortable connections regardless of how you travel.
The Iris Avenue Transportation Improvements Project identified ways to make Iris Avenue,
between Broadway and 28th Street safer, more comfortable, and better connected. The project
improvements focus on increasing mobility choices, improving safety for everyone, making
walking, bicycling and taking transit more attractive and convenient, and improving connections
to local and citywide destinations.
Background Purpose & Need
In 2019, the Transportation Master Plan and the Low Stress Walk and Bike Network Plan
recommended greater separation and protection between vehicle and bicycle lanes on Iris
Avenue and a need for pedestrian improvements in key areas due to the road having more than
Attachment A - Iris Ave Transportation Improvements Project
Community & Environmental Assessment Process (CEAP)
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three vehicle lanes, the posted speed limit set at 35 miles per hour, and average daily traffic
being greater than 6,000 vehicles.1
In 2022 the Safe Streets Report (SSR) 2 found between 2018 and 2020, 14,500 people were
involved in a crash in Boulder, resulting in 150 serious injuries. Sixty-seven percent of severe
traffic crashes, those that result in serious injury or fatality, occur on arterial streets. The report
found these severe injury crashes occurred at several intersections on Iris Avenue: 28th Street,
Folsom/26th Street, and Broadway. The SSR also identified Areas of Concern: crash types that
disproportionately affect certain groups, like young people and seniors. Data from the Iris
Avenue project revealed that one in ten pedestrians or cyclists traveling on or across Iris
Avenue on an average day are young, elderly, or disabled. Community input shared a common
sentiment: people feel unsafe walking or biking along and across Iris, yet hundreds do so every
day.
In response to the findings of the SSR, City Council, in partnership with the Transportation
Advisory Board (TAB), elevated work on the Core Arterial Network (CAN) as one of its 10
priorities for city department efforts. Council reaffirmed CAN as a priority in April 2024. The
CAN is the connected system of protected bicycle lanes, intersection enhancements, pedestrian
facilities, and transit facility upgrades that will help reduce the potential for severe crashes and
make it more comfortable and convenient for people to get where they need to go along
Boulder’s main corridors, including Iris Avenue.
In 2023, the 2023-2027 Vision Zero Action Plan (VZAP) identified specific actions and strategies
to address the findings of the SSR. The High Risk Network (HRN) was developed as part of the
plan as a way to focus actions on places where severe crashes occur or are more likely to occur
in the future. The HRN has an outsized proportion of previous severe crash incidence: the HRN
represents only 7% of the city’s street network but nearly half of all severe crashes occur on
these streets. The HRN also identifies locations where five or more of the six most common risk
factors for future crashes are present.3 Proactively managing risk and mitigating crashes on this
small percentage of streets can have an outsized impact on reducing fatal and serious injury
crashes citywide and achieve the greatest impact in the shortest amount of time. Iris Avenue,
from 19th to 28th streets, is on the HRN.
Two core strategies of the VZAP are to work on the CAN and the HRN. Action 3 of the plan
commits the city to implement capital projects by 2027 to improve safety and comfort on
priority CAN corridors that are also on the HRN, including Iris Avenue. The Iris Avenue
Transportation Improvements Project recommended alternative includes proven safety
countermeasures, such as protected bike lanes, protected intersections, and roadway
reconfiguration. Proven Safety Countermeasures are transportation designs and strategies that
1 https://bouldercolorado.gov/media/4530/download?inline=
2 https://bouldercolorado.gov/media/7841/download?inline=
3 Daily vehicle traffic between 5,000 and 10,000 per travel lane, Signalized intersections, Major
unsignalized intersection, Businesses and a mix of land uses present, and 85% of vehicle speeds at or above
30 mph
Attachment A - Iris Ave Transportation Improvements Project
Community & Environmental Assessment Process (CEAP)
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the Federal Highway Administration (FHWA) recognizes as effective at reducing severe
crashes.4
Community Input on Travel and Lived Experience - 2023
From summer through winter 2023, staff began talking to the community and collecting data to
understand their lived experience of what is working on Iris Avenue and what needs
improvements. Twenty-seven engagement activities reached over 1,600 people and garnered
more than 2,100 comments that provided feedback on existing conditions, challenges, and
opportunities to inform development of improvements (Table 1).
People participated in online questionnaires and in-person contacts at tabling, pop-up, and
other community events. Guided walk and bike tours provided opportunities to get more
detailed feedback from participants. This first round of engagement culminated in an open
house and three walks in the park where the project team shared learnings and provided
additional opportunities for community members to offer feedback before city staff began
identifying potential improvements.
Table 1: Summary of 2023 community engagement activities
2023 Engagement Event Date Participants
Summer Webpage and Press release 7/28/2023
Virtual Questionnaire 1 7/28/2023 772
National Night Out 8/1/2023 10 Inside Boulder News Segment 8/7/2023 Red Oak Park Bike Giveaway 8/9/2023 50 What's Up Boulder 8/10/2023 50 Columbine Back to School Day 8/15/2023 50 RTD Stop Pop Up 8/17/2023 40 Safeway Pop Up 8/18/2023 25 Business Outreach Door-
knocking
8/18/2024 30
Listening Sessions 8/18/2024 8 Foothill Back to School Night 8/30/2023 30 CU Bike fest 8/31/2023 20 Elmer's Twomile Pop Up 9/6/2023 50 Growing Gardens Pop Up 9/13/2023 40 FUNKtion at Boulder Junction 9/14/2023 5
Fall/Winter Fall Transportation Safety Fair 9/16/2023 25
Guided Walking Tour 9/19/2023 24 Guided Biking Tour 9/19/2023 32 BHP Iris/Hawthorn Block Party 9/21/2023 45
4 https://highways.dot.gov/safety/proven-safety-countermeasures
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2023 Engagement Event Date Participants CPWD Accessible Roll and
Stroll
9/28/2023 2
Growing Up Boulder Walk 9/28/2023 26 Smarthome-Imagine! 9/29/2023 1
Press Release 10/11/2023 Open House 10/24/2023 103 Virtual Open House
Questionnaire
10/24/2023 162
Walk in the Park Parkside Park 12/2/2023 28 Walk in the Park Columbine
Park
12/9/2023 31
Walk in the Park Melody Park 12/16/2023 32
Total 1,691
Themes heard from this engagement included:
• East-west travel is important, and drivers appreciate Iris Avenue as a convenient and
reliable route across the city
• People walking, rolling, biking, and taking transit also want Iris Avenue to provide
convenient and safe routes
• Sidewalks could be improved to provide comfort, safety, and attractive walking
conditions. Sidewalks are currently not wide enough, are winding, sloping, and bumpy,
and are often blocked by overgrown vegetation
• Crossing Iris Avenue safely and conveniently is a priority for people of all ages and
abilities traveling to school, work, for errands, and for recreation – but today some see it
as a barrier to getting where they want to go
• Vehicles travel at high speeds, creating unsafe conditions and excessive street noise
• Safer neighborhood and business access is essential
• Drivers feel unsafe turning onto and off Iris Avenue and feel they’re more likely to crash
with oncoming traffic when doing so
• Delivery, transit, waste management and other vehicles stop in-lane, blocking the bike
and right-side travel lanes
• Residents are concerned any future changes will impact emergency evacuation and
response
• Neighbors want to maintain the character of their neighborhoods, which they see as
providing safer, more comfortable alternatives for walking, rolling, and biking than
arterial streets like Iris Avenue, and they are concerned that changes to Iris Avenue
could create traffic diversion onto nearby streets
• Community members want attractive facilities and opportunities for placemaking
• Better wayfinding and help navigating to local and regional destinations are desired
• Roadway pavement conditions could be improved
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•Transit service is infrequent, and many transit stops are not accessible and lack shelters,
benches, and trash cans
Public input from 2024 community engagement activities is summarized in the sections of this
memorandum corresponding to the associated component of the conceptual design process.
Existing Conditions Data
Data collection and analysis conducted concurrently with engagement supports the findings
from the city’s plans and feedback from the community.
Existing conditions data collected between September and October 2023 found the following:
•Speeds (Figure 3):
o Prevailing speeds are 5 or more miles per hour over the speed limit from Broadway
to Folsom/26th Street
o Between 19th Street and Folsom/26th Street, 5.7% of eastbound drivers are speeding
10 miles per hour or more over the posted speed limit; this equates to every 17th
vehicle excessively speeding
Figure 3: Median, Prevailing and Top-End speeders on Iris Avenue from Broadway to East of
Folsom/26th Street
•Number of vehicles (Figure 4):
o Average daily vehicle volumes vary along the corridor but are evenly split by
direction:
East of 16th Street: 15,930 vehicles per day
East of 19th Street: 20,040 vehicles per day
East of 26th Street: 21,350 vehicles per day
Vehicle volumes are higher in the westbound direction in the morning hours
and higher in the eastbound direction in the evening hours
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Figure 4: Iris Avenue corridor daily traffic volume and direction data
o Existing Travel Time (Figure 5):
Time to travel by vehicle from one end to the other on Iris Avenue varies by
direction, time of day and seasonal variability, such as school being in session.
•Average vehicle is about 3 – 4 minutes
•Most vehicle trips range from 4 – 5 minutes
Figure 5: Existing travel times for Iris Avenue in the morning, mid-day and evening
•Multimodal Travel:
o An average of 100 people walk, 130 people bike and 100 people ride transit along
Iris Avenue on an average day.
•Crossing Iris Avenue (Figure 6):
o Over 1,000 people walk, bike, or roll across Iris Avenue on an average day
409 walk and 406 bike through the Elmer’s Twomile underpass
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Figure 6: Pedestrian and bicycle crossing data for Iris Avenue
• Transit (Figure 7)
o Though transit is relatively infrequent on Iris Avenue (60-minute headways), transit
on either end (Broadway and 28th Street) is frequent and has high ridership.
About 100 people a day take Route 208, which runs along Iris Avenue and
provides critical east-west connections
Routes 204, 205, SKIP, BOLT, and Bound cross Iris Avenue and provide
greater transit frequency at up to 10-minute headways during peak travel
times
• The SKIP, BOLT, and BOUND see some of the highest area ridership
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Figure 7: Transit service on and connecting to Iris Avenue
• Trees
o There are 150 public street trees along Iris Avenue
o These trees provide the Iris Avenue project area with 25% canopy cover5
o Citywide overall canopy cover is 16%
Crash Data
Crash data from 2016 through 2023 found the following:
o 345 vehicle crashes, or roughly 43 per year, happened on Iris Avenue, six of those
were severe crashes (Figure 8)
143 crashes were rear ends
58 crashes were approach turn crashes, involving cars turning across
oncoming traffic
Figure 8: Crash density of all crashes on Iris Avenue (2016-2023)
22 crashes involved people walking (4) and biking (18) (Figure 9)
5 https://bouldercolorado.gov/sites/default/files/2021-05/boulderufspv2018.pdf
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o 45% of these crashes were at the Folsom/26th Street intersection
o All crashes involved a driver striking the person walking or biking
o 19 of the 22 crashes occurred because the driver did not yield to the
person walking or biking at an intersection or driveway
o More crashes with people walking or biking occurred at the
Folsom/26th Street intersection (10) than at either of the busiest
intersections on the corridor: 28th Street (8) and Broadway (2)
Figure 9: Pedestrian and bicycle crash data on Iris Avenue (2016-2023)
CEAP Evaluation
The Community and Environmental Assessment Process (CEAP) provides formal evaluation of
potential improvements and conceptual design alternatives.
CEAP Process
The CEAP helps identify a recommended alternative through five steps:
1) Screen potential improvements to identify conceptual alternatives,
2) Compare and contrast conceptual design alternatives and share the results with the
community to receive input on their priorities,
3) Draft the CEAP evaluation, using the CEAP checklist and defined project specific evaluation
criteria, and identify the recommended alternative
4) Present the CEAP evaluation and recommended alternative to the community for feedback
5) Finalize the CEAP evaluation and recommended alternative, considering public input, to
present to Transportation Advisory Board and City Council for their recommendation and
action.
Conceptual Alternatives
Staff consulted best practices, design standards, and guidelines to identify all potential
solutions to the issues identified by the data and community engagement.
1. Screening
This list of improvements was then screened using eight screening criteria: traffic safety,
transportation operations, sustaining the tree canopy, implementation feasibility, and safe and
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comfortable connections. The criteria were applied corridor wide, from Broadway to 28th
Street, and to four distinct segments:
1. Broadway to 16th St
2. 16th St to 19th St
3. 19th St to 26th St
4. 26th St to 28th St
The eight screening criteria were applied using available data or professional judgment when
data was not available. No criteria were weighted. Criteria marked with an asterisk (*) were
identified by the community during engagement in 2023.
Potential to Reduce Speeds*
Purpose: Almost one in five (19%) severe crashes involve speeding vehicles 6 and people
report speeding is a top four traffic safety concern in the City of Boulder7. The
Transportation Master Plan recommends implementing specific safety countermeasures
and employing proven effective safe and innovative intersection and corridor treatments to
improve transportation safety for all people of all ages using any mode within the
transportation system.
Definition: Fewer lanes or a visually narrowed roadway reduce speeds.
Source: Federal Highway Administration Road Diet Information Guide
Comparison: To existing conditions
Provides Space for All Modes*
Purpose: The Transportation Master Plan prioritizes safe and complete streets to provide a
comfortable transportation network for people of all ages and abilities through key actions
including designing for separation between vehicles, cyclists and pedestrians8.
Definition: Every mode (vehicle, bicycle, pedestrian, transit) is provided minimum width
facilities
Source: City of Boulder Design and Construction Standards
Comparison: To existing conditions
Advances Adopted Plans
Purpose: The Transportation Master Plan is the guiding policy document for the City of
Boulder’s transportation system. The Low-Stress Walk and Bike Network Plan is part of the
Transportation Master Plan. The goal of the Low-Stress Walk and Bike Network Plan is to
attract a broader population of people (ages 8 to 80) as confident and comfortable
pedestrians and cyclists. The Vision Zero Action Plan identifies specific actions and
strategies to address different traffic concerns and create safer streets.
Definition: Meets recommendations of adopted city transportation plans
Source: Transportation Master Plan (2019), Low Stress Walk and Bike Network Plan (2019),
and Vision Zero Action Plan (2023-2027)
6 City of Boulder, Vision Zero Boulder Safe Streets Report (Transportation & Mobility, 2019)
7 City of Boulder, Boulder Vision Zero Action Plan (Transportation & Mobility, 2023)
8 City of Boulder, Boulder Transportation Master Plan (Initiative, Transportation & Mobility, 2019)
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Comparison: To existing conditions
Impact to Traffic Operations*
Purpose: The Transportation Master Plan objective seven seeks to maintain 1994 levels of
travel time on Boulder arterial streets and improve travel time reliability and predictability
as measured by person travel time and throughput on arterials (autos and transit) and
intersection Level of Service (LOS) and delay. Community engagement identified vehicle
travel time as important for Iris Avenue.
Definition: Potential to increase vehicle delay and queue lengths at intersections
Source: Professional judgment based on traffic analysis of existing and proposed conditions
within the Existing Conditions Report and Traffic Analysis.
Comparison: To existing conditions
Impact to Right-Of-Way
Purpose: The Transportation Master Plan Advanced Mobility Policies calls to reallocate the
right-of-way as appropriate to prioritize movement of people through transit, bicycle,
pedestrian improvements, and public placemaking.
Definition: Requires Right-of-Way to implement
Source: City of Boulder Parcels data
Comparison: None; options are scored based on the number of easements required
Impact to Floodplain
Purpose: The City of Boulder's floodplain regulations are designed to reduce risk to life and
property in areas along the 16 major drainageways within the city limits.
Definition: Narrowing the existing curb-to-curb width has potential to cause a rise in the
floodplain
Source: Professional judgment, staff and floodplain consultant
Comparison: None; options are scored based on the anticipated level of impact to the
floodplain. If professional judgment determines an option’s impact to floodplain could not
be mitigated, the option will not be advanced.
Impact to Existing Trees*
Reasoning: The City of Boulder Forestry is committed to maintaining a healthy and safe
urban forest as well as preserving an extensive and diverse tree cover for future
generations. Community engagement identified existing trees as important for Iris Avenue.
Definition: Amount of tree removals required
Source: City of Boulder Forestry tree inventory for the project area
Comparison: None; options are scored based on the number of trees removed
Cost to Implement*
Reasoning: Transportation funding is limited and highly dependent on sales tax -- and
transportation dedicated sales tax revenue is not keeping up with inflation resulting in
declining purchasing power. Further, the city is facing increased competition for regional,
state and federal funding.
Definition: Estimated cost to implement
Source: Professional judgment
Comparison: To each other
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Screening Summary
The results of the screening are summarized in (Figure 10).
Figure 10: Potential improvements screening results
Traffic Operations
Travel forecasts from the Denver Regional Council of Governments (DRCOG) for 2040 are one of
many key inputs in vehicle operations analyses conducted in the region. For example, the
current CO 119 Safety, Mobility and Bikeway Project led by the Colorado Department of
Transportation (CDOT) conducted such travel forecasts which project a 25% increase 9 in vehicle
traffic along the Diagonal Highway between Boulder and Longmont by 2040.
The Boulder Valley Comprehensive Plan transit and land use policy assumptions reduce the
DRCOG projected increase in vehicle trips. These assumptions are supported by historic traffic
volumes on Iris Avenue where 10 years of data show the number of vehicles driving the
corridor have remained reasonably constant: between 21,200 and 23,900 vehicles per day east
of 19th Street. The City of Boulder Modal Shift in the Boulder Valley 2023 Travel Diary Study
validates these data and assumptions when it found decreases in single occupancy vehicle
9 https://www.codot.gov/projects/co119-mobility/design
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(SOV) (by 9.1 percent) and increased trips made by bicycle (by 8.4 percent) between 1990 and
2023.
Therefore, traffic operations modeling for the project used existing vehicle, bicycle, and
pedestrian volumes. The analysis found traffic volumes on CO 119 and Iris Avenue decrease as
you move from east to west along the corridor. The County data indicates daily volumes are
over 40,000 vehicles per day (vpd) east of Foothills Parkway, dropping to around 30,000 vpd
west of Foothills Parkway and again to around 26,000 vpd east of 28th Street. The field data
collected suggests this volume drops further on Iris Avenue, to around 21,000 vpd west of 28th
Street, 20,000 vpd west of 26th Street, and 16,000 vpd west of 19th Street.
Federal Highway Administration (FHWA) guidance states that lane repurposing is typically
implemented on roadways with an average daily traffic of 25,000 vehicles or fewer. According
to this guidance, a 25% growth in current vehicle volumes on Iris Avenue would still be within
range of the FHWA guidance for lane repurposing.
Iris Avenue lane repurposing impacts to traffic operations were evaluated using Synchro v11
traffic capacity analysis software. Vehicle travel lanes were modeled eastbound and
westbound at the intersections of 19th Street and Folsom/26th Street and at the “bookends” of
the corridor, Broadway and 28th Street.
The bookends analysis at the Broadway intersection included reducing to a single westbound
left turn lane was evaluated. At 28th Street, reducing to a single eastbound and westbound
through lane was evaluated, with reduction to a single northbound left turn lane also required.
Preliminary traffic analysis of these changes at the bookends found a significant increase in
travel time, by five minutes or more, and vehicle queuing exceeding 1,000 feet at some
intersections. Ultimately, the project team decided not to advance proposals for any changes
to the vehicle lanes at these critical intersections to maintain reliable traffic movement into and
out of the corridor. The final determination was that any potential changes to the vehicle lane
configuration would be limited to the segment of the corridor that is located between 13th
Street and Folsom/26th Street.
Preliminary traffic analysis of these changes to the 19th Street and Folsom/26th Street
intersections considered impacts to travel time, vehicle level of service (LOS), the volume of
vehicles to roadway capacity ratio, and vehicle queue lengths. This analysis used current vehicle
signal phasing at these two intersections.
The analysis found travel time and vehicle queue lengths increased within an acceptable level
at these intersections, the LOS remained at current levels, and vehicle volume to roadway
capacity ratios are at or less than 0.8, which indicates three vehicle lanes provides sufficient
capacity for the number of vehicles that use Iris Avenue.
All advanced conceptual alternatives include end-to-end bike and pedestrian improvements for
people that walk and bike to shops and businesses and access local and regional transit service.
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At the Broadway bookend, people walking, biking, and taking the bus will have improved
connections and design features, such as shared bus stops, to better organize space along and
across the street for safer travel. At the 28th Street bookend, people walking, biking, and rolling
will have separate spaces and improved connections to Elmer’s Twomile multi-use path, 28th
Street, and local and regional multi-use paths and transit service.
The 28th Street bookend receives high activity as people access commercial centers and enter
and exit the corridor. Conflicts arise when all this activity crosses one another. When crash data
demonstrate these crossings are unsafe, limiting those conflicts is needed. Access
management, where turns are restricted, can reduce the potential for crashes.
Access Management
The project will provide access management, including prohibition of westbound left turns, at
the western-most driveway to the Safeway shopping complex due to a crash history of
westbound vehicles traveling along Iris Avenue turning left into the driveway (2016 to 2023): 12
crashes with three involving people biking (Figure 11).
Figure 11: Safeway Driveway Crash History
Neighborhood Streets
In addition to speeding on Iris Avenue, speeding on parallel side streets is a community concern
that affects the safety and quality of life of residents and users of those streets. Some cut-
through traffic diversion on these side streets may occur today and neighbors have identified
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streets where they experience high vehicle speeds. Staff added to this list to make it inclusive of
all potential parallel vehicle routes. The list of street segments, with the number and prevailing
vehicle speeds, are shown in Figure 12.
In response to community feedback about side street vehicle speeding and concerns about
increased traffic diversion, staff added a secondary study area to examine the potential for
neighborhood traffic calming to the Iris Avenue project scope. As the Iris Avenue design
progresses, staff will identify the specific locations along these street segments in the
secondary study area to receive speed mitigation and traffic management as a concurrent
project. Street segments with the greatest speeding issue will be prioritized first. These
prioritized segments will receive speed mitigation and traffic management when the Iris
Avenue project is implemented, following final design and allocation of funding. This may
include treatments such as speed humps, speed tables, and vehicle turn restrictions.
Figure 12: Secondary study area with parallel street
2. Conceptual Design Alternatives
The screening resulted in four conceptual alternatives being advanced for further evaluation:
• Alternative A: One-Way Protected Bike Lanes and No Change to Roadway Width
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• Alternative B: Two-Way Protected Bike Lane and No Change to Roadway Width
• Alternative C: One-Way Protected Bike Lanes and Widened Roadway
• Alternative D: Two-Way Protected Bike Lane and Widened Roadway
Alternative A
One-Way Protected Bike Lanes and No Change to Roadway Width (Figure 13)
• Three vehicle lanes and on-street protected bike lanes meeting minimum design widths
with spot improvements to sidewalks behind the curb
A typical roadway cross section includes:
• Two 10.5-foot travel lanes (one eastbound, one westbound)
• One 10-foot center turn lane
• Two five-foot bicycle lanes (one eastbound, one westbound) meeting
minimum design widths separated from the travel lane by three-foot
protected buffers
• Two 1.5-foot gutters (one on north side and one on south side of the
street)
Roadway Impact: Minimal to no change to existing curb to curb width
Behind the curb:
• Spot improvements to 5-foot typical existing sidewalks
• 0 – 8-foot typical existing planting area
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Figure 13: Alternative A: One-Way Protected Bike Lanes and No Change to Roadway Width
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Alternative B
Two-Way Protected Bike Lane and No Change to Roadway Width (Figure 14)
• Three vehicle lanes with north side on-street two-way protected bicycle lane with spot
improvements to sidewalks behind the curb
• A typical roadway cross section includes:
• Two 11-foot travel lanes (one eastbound, one westbound)
• One 10-foot center turn lane
• One 10-foot two-way protected bike lane (meeting minimum design widths
with five-foot travel lane in each direction) with one five-foot protected
buffer between the westbound travel lane and the protected bike lane on
the north side of the street
• Roadway Impact: Minimal to no change to existing curb to curb width
• Behind the curb:
• Spot improvements to 5-foot typical existing sidewalks
• 0 – 8-foot typical existing planting area
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Figure 14: Alternative B: Two-Way Protected Bike Lane and No Change to Roadway Width
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Alternative C
One-Way Protected Bike Lanes and Widened Roadway by approximately 11-feet (Figure 15)
• Four vehicle lanes with on-street protected bike lane meeting minimum widths and with
sidewalk widening behind the curb
• A typical roadway cross section includes:
o Four travel lanes (eastbound: one 10-foot and one 11-foot travel lane;
westbound: one 10-foot and one 11-foot travel lane)
o Two five-foot one-way bicycle lanes (one eastbound, one westbound) meeting
minimum design widths separated from the travel lane by three-foot protected
buffers
• Roadway Impact: Widened curb to curb width by approximately 11-feet
• Behind the curb:
o South side variable width (0 – 8-foot) buffer/planting area where feasible
o Six-foot wide sidewalk on north and south sides
o 0 – 8-foot typical existing planting area on the north and south sides
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Figure 15 Alternative C: One-Way Protected Bike Lanes and Widened Roadway
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Alternative D
Two-Way Protected Bike Lane and Widened Roadway by approximately eight feet (Figure 16)
• Four vehicle lanes with north side on-street protected two-way bike lane with sidewalk
widening behind the curb on the north side and spot improvements behind to sidewalk
the curb on the south side
• A typical roadway cross section includes:
o Four travel lanes (eastbound: one 10-foot and one 11-foot travel lane;
westbound: one 10-foot and one 11-foot travel lane)
o One 10-foot two-way protected bike lane (meeting minimum design widths with
5-foot travel lane in each direction) with 3-foot protected buffer between the
westbound travel lane and the protected bike lane
• Roadway Impact: Widened to the north by approximately eight feet with the existing
south side curb remaining in place
• Behind the curb:
o Six-foot sidewalk on the north side of the road
o Spot improvements to 5-foot typical existing south side sidewalk
o 0 – 8-foot typical existing planting area on the north and south sides
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Figure 16: Alternative D: Two-Way Protected Bike Lane and Widened Roadway
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Considerations
The four conceptual alternatives were compared and contrasted by applying 17 considerations
to each alternative between 13th Street and Folsom/26th Street.
The 17 considerations were organized into five categories:
1. Traffic Safety
a. Vehicle speed moderation
b. Crash reduction
2. Safe and Comfortable Connections
a. Biking comfort
b. Walking comfort
c. Opportunity for protected intersection elements
d. Transit accessibility and reduction of bike/bus conflict
e. Crossing safety & comfort
3. Transportation Operations
a. Vehicle travel time along the corridor
b. Vehicle turning movements
c. Day-to-day emergency response use
d. Disaster emergency response
4. Implementation Feasibility
a. Time to design and implement
b. Cost to implement
c. Right-of-Way and property acquisition
d. Utility relocation (under and above ground)
e. Stormwater drainage
5. Sustaining the Tree Canopy
a. Preserves existing trees
Consideration Definitions
Traffic Safety
Potential to reduce speeds and severe crashes on the corridor.
Vehicle speed moderation
Assessed whether the alternative can reduce lane widths, the number of vehicle lanes
or provide visual narrowing through bike separation or trees.
Crash reduction
Assessed for whether the alternative can reduce the number or severity of crashes by
introducing turn lanes, reducing conflict points, separating vulnerable road users or
reducing speeds.
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Safe and Comfortable Connections
Potential to enhance residential, neighborhood, and business access, low stress walk and bike
connections, and transit experience.
Biking comfort
Assessed for whether the alternative can implement the City of Boulder Low Stress Walk
and Bike Network Plan recommendation.
Walking comfort
Assessed for whether the alternative can reduce the City of Boulder Low Stress Walk
and Bike Network Plan pedestrian stress factors.
Opportunity for protected intersection elements
Assessed for whether the alternative can provide space for protected intersection
elements.
Transit accessibility and reduction of bike/bus conflict
Assessed for whether the alternative provides safe transit vehicle and transit user
interaction with travel lanes, bike lanes, and sidewalk.
Crossing safety & comfort
Assessed for whether the alternative can provide space for safer roadway crossings, like
pedestrian refuge islands.
Transportation Operations
Analysis of the potential impact on vehicle travel time, vehicle turning movements, and
emergency response.
Vehicle travel time along the corridor
Assessed for whether the alternative could change existing travel time with providing
vehicle travel or turn lanes.
Vehicle turning movements
Assessed for whether the alternative could provide safer turning movements by
including turn lanes and center turn lanes.
Day-to-day emergency response use
Assessed by Boulder County Office of Disaster Management and City of Boulder Fire and
Police departments for whether the alternative changes current day-to-day emergency
response.
Disaster emergency response
Assessed by Boulder County Office of Disaster Management and City of Boulder Fire and
Police departments for whether the alternative changes disaster emergency response.
Implementation Feasibility
The amount of time and cost needed to design and implement the project.
Time to design and implement
Assessed for how the alternative compares to other alternatives in design and
implementation needs.
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Cost to implement
Assessed how the alternative compares to other alternatives in time and effort to design
and implement.
Right-of-Way and property acquisition
Assessed how the alternative compares to other alternatives in the number of
easements that would be required to implement.
Utility relocation (under and above ground)
Assessed for how the alternative compares to other alternatives in the number of
utilities, above and below ground, that would need to be relocated to implement.
Stormwater drainage
Assessed for how the alternative compares to other alternatives in the amount of
existing storm drainage, storm water and sanitary sewer infrastructure that would be
impacted or new infrastructure built.
Sustaining the Tree Canopy
Potential to preserve existing street trees and maintain the current tree canopy.
Preserves existing trees
Assessed for whether the alternative keeps or removes existing street trees.
Design Alternatives Assessment
To assist the community, board members, and elected officials in understanding the differences
between the four conceptual design alternatives, the considerations were assessed using
existing conditions data, field reviews, preliminary transportation analysis, and professional
judgment. Each consideration, excluding Implementation Feasibility, was assessed for how it
would impact each alternative compared to today: (+) Improvement over today, (-) Worse than
today, and (0) Same as today. Each alternative was assessed for the Implementation Feasibility
considerations compared to each other for having: (↑) More impacts, (↓) Less impacts, or (/)
No impact.
The results of applying the considerations to each of the four alternatives can be found in
Attachment A.
Community Input on Conceptual Design Alternatives – Spring 2024
Throughout the spring of 2024, staff sought to understand the community’s priorities to
advance the four conceptual alternative designs. Community feedback was solicited at an in-
person open house on April 27 and an online open house in both English and Spanish hosted
from April 27 through May 27. Staff also went into the community to meet with people where
they were - at the North Boulder Recreation Center, in neighborhood parks, and at the
Wednesday and Saturday farmers markets (Table 2).
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Table 2: Summary of spring 2024 engagement events
2024 Engagement Event Date Participants
Spring Press Release 4/9/2024
Open House 4/27/2024 203
Virtual Open House Questionnaire 4/27/2024 411
Continuing Conversation North Boulder Rec 4/30/2024 34
Emails to TAB and City Council 5/1/2024 53
Continuing Conversation Columbine 5/8/2024 22
Wednesday Farmers Market 5/15/2024 89
Continuing Conversation Parkside Park 5/16/2024 38
Saturday Farmers Market 5/18/2024 103
Columbine Elementary Bici Bus 5/22/2024 25
Total 942
With a total of 942 interactions, more than 500 people participated in face-to-face
conversations with staff and with each other and 411 people completed the project
questionnaire to share their priorities and feedback.
Community input in 2024 continued the themes heard in 2023, though the levels of agreement
among the community varied. These in-person and online conversations made clear that for
every person who opposed any change on Iris Avenue there was someone else who supported
changes to the street. As is often the case, most folks fell towards “the middle” than those
who were strongly for or against the proposed changes.
“I know Iris can still move cars while making the roadway much safer for everyone.”
Boulder County resident who commutes on Iris
Most everyone agrees that speeding on Iris Avenue needs to be addressed. There is also
agreement that getting in and out of side streets and the shopping complexes near 28th Street
feels unsafe.
“Even though Iris Avenue serves as a major connection between Diagonal and Broadway, it
should not be a speedway. I would like to see the speed limit kept low for the safety of all.
Everything is easier and safer if people drive slowly.”
Community member who lives along Iris
Families, especially with young children, do not feel safe or comfortable walking, biking, or
rolling along or across Iris Avenue – but do so to get to school or one of the several childcare
centers nearby.
“I walk my kids to daycare at 26th and Iris every day. That intersection is very dangerous.”
Palo Park parent who travels across Iris daily
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Nearby residents want Iris Avenue improved but are concerned changes would create cut-
through traffic on their streets.
“I do not want changes on Iris to cause traffic to divert to side streets, which some already does
because people do not want to make the left turn onto Iris from Broadway. Living on Norwood, I
see an increasing amount of commuter traffic, some of it related to Centennial Middle School,
but some related to Iris. I myself divert onto Grape to avoid Iris between Folsom and 19th.”
North Boulder resident who drives and bikes on and across Iris Avenue
Some neighbors ask to have bike lanes removed from Iris Avenue and installed on parallel
streets instead.
“I use a bike, but I travel the neighborhoods to the south of Iris. Move the bikes to those less
traveled streets where biking will be more enjoyable and safer. That is the better solution.”
North Boulder resident who drives Iris Avenue but bikes on neighborhood streets
Many people who bike want Iris Avenue to have protected bike lanes for the direct connections
the street provides compared to parallel streets. People living with disabilities emphasize the
importance of having safe and connected walking and biking routes on Iris Avenue to connect
them to everyday needs, like shops, grocery stores, and high frequency transit. People who
commute on Iris Avenue want a connection on Iris to support their current travel or to be
prepared for completion of the CO 119 Safety, Mobility and Bikeway Project.
“This arterial is vital to become a transit and multimodal city. But for users to use this corridor it
must feel safe for all roadway users. Speeds should be reduced, and protection should be put in
place for bicycles and pedestrians and safe transit accessibility for the less mobile.”
Palo Park commuter
Most want to keep as many of the existing public street trees for the beauty and shade they
provide regardless of their other priorities for Iris Avenue.
“First and foremost, preserve the existing tree canopy. The trees are big and beautiful and add
so much personality and charm to Iris. None of the proposed improvements are worth losing any
of the trees over.”
North Boulder neighbor who lives along Iris
Many are concerned about travel time changes any alternative would introduce.
“It was unclear from the information what impact Alternatives A&B have on vehicular travel
time on Iris. To me, these seem like reasonable, balanced alternatives AS LONG AS vehicular
travel times aren't significantly impacted. I'm ok with some minimal additional delays during
peak times in order to have safer routes for cyclists and to preserve trees. However, if travel
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time is significantly delayed on one of the only continuous east-west vehicular routes in this part
of the city, I would have a different opinion and would support Alternatives C or D.”
A respondent who drives and bikes Iris to work and for shopping
The majority of questionnaire respondents (56.6%) live in North Boulder. These respondents
primarily drive on Iris and prioritize vehicle travel time. The next most common respondents
were bicyclists (15.6%). These bicyclists primarily live in North and Central Boulder and
prioritize biking crossing safety and comfort. The most common reason all respondents gave for
traveling on Iris Avenue is for shopping and errands, followed by reaching recreation or
entertainment, living along Iris Avenue or nearby, to travel between communities, reaching
healthcare, and commuting to work.
When asked for their priorities for designing Iris Avenue, questionnaire respondents’ answers
grouped into three distinct tiers (Table 3).
Table 3: Questionnaire respondents' project priorities
Tier 1
(greater than 100 selections)
Tier 2
(20 to 100 selections)
Tier 3
(less than 20 selections)
Vehicle Travel Time Along the
Corridor
Disaster Emergency Response Stormwater Drainage
Crash Reduction Time and Cost to Design and
Implement
Right-of-Way Acquisition
Biking Comfort Vehicle Turning Movements Utility Relocation
Pedestrian Crossing Safety and
Comfort
Walking Comfort
Bike Crossing Safety and
Comfort
Day-to-Day Emergency Response
Vehicle Speed Moderation Transit Accessibility
Preserving Existing Trees Opportunity for Protected
Intersection Elements
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The Community and Environmental Assessment Process (CEAP) is Boulder’s formal review
process that assesses the potential impacts of capital improvement projects to help select the
best conceptual design alternative. The CEAP uses the established CEAP goals assessment,
checklist and checklist questions, project-specific evaluation criteria and community input to
identify a recommended alternative.
Goals Assessment
1. Using the BVCP and department master plans, describe the primary city goals and benefits
that the project will help to achieve:
a. Community Sustainability Goals: How does the project improve the quality of economic,
environmental and social health with future generations in mind?
The Iris Avenue project helps the city achieve its:
• Social health goals by providing an all ages and abilities corridor with safer and
more comfortable transportation options no matter how someone chooses to
travel.
• Economic goals by the provision of and investment in infrastructure that
attracts, sustains and retains businesses, entrepreneurs, workers, and
customers, and by ensuring safe and comfortable connections to destinations
along the corridor and on the broader city transportation network.
• Environmental goals by providing safe and comfortable multimodal
transportation options which can reduce vehicle use and vehicle miles traveled
and thus reduce the use of non-renewable energy resources and greenhouse
gas emissions. These changes can also protect water and air quality through
utilization of existing infrastructure, by preserving existing public street trees,
and through the reduction of mobile source emissions.
b. BVCP Goals related to:
• Community Design:
o Policies: 2.03 Compact Development Pattern, 2.38 Importance of Urban
Canopy, Street Trees & Streetscapes: The project supports these policies by
enabling safe travel by biking and walking which supports a more compact
development pattern, and by working within the current roadway to avoid a
significant number of tree removals.
• Facilities and Services:
o Policy: 8.13 Support for Community Facilities: The project supports this policy
by safely connecting City and County community facilities throughout the
corridor.
o Policies: 2.38 Importance of Urban Canopy, Street Trees & Streetscapes, 3.22
Floodplain Management: The project supports these policies by working
within the current roadway to avoid a significant number of tree removals
and by avoiding floodplain impacts.
• Economy:
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o Policy: 5.03 Diverse Mix of Uses and Business Types: The project supports this
policy by improving connections to and from the diverse uses and businesses
at the corridor’s “bookends” and surrounding residential uses.
• Transportation:
o Policies: 2.25 Improve Mobility Grid & Connections, 2.26 Trail
Corridors/Linkages, and all the Transportation section policies 6.01-6.24.: The
project supports these policies by improving safety and connectivity between
the roadway and trail networks for all who travel along and across Iris
Avenue regardless of transportation mode. It also connects planned regional
trails on the east end of the corridor to neighborhood trail connections on
the west end. This project provides the largest benefits to the BVCP goals
related to transportation.
• Housing: The Iris Avenue project does not directly support any of the housing goals.
Enhanced multimodal safety and connectivity supports modal choice, and thereby,
access to the diversity of housing types envisioned in the BVCP.
• Social Concerns and Human Services:
o Policy: 8.07 Safety: The project supports this policy by improving safety for all
roadway users which reduces the need for day-to-day emergency response,
while also maintaining four vehicle lanes for use during a disaster emergency
response.
c. Describe any regional goals (potential benefits or impacts to regional systems or plans?)
In 2021, the Boulder Valley Comprehensive Plan affirmed the city’s long-standing
approach to creating an all-mode transportation system that provides safe connections
for everyone, no matter how they travel.
2. Is this project referenced in a master plan, subcommunity or area plan? If so, what is the
context in terms of goals, objectives, larger system plans, etc.? If not, why not?
In 2019, the Transportation Master Plan (TMP) identified a corridor study of Iris Avenue as a
future action item. In 2019, the Low Stress Walk and Bike Network Plan recommended
enhancing separation and protection between vehicle and bicycle lanes on Iris Avenue,
alongside improving pedestrian facilities in critical areas. These recommendations were
made by Iris Avenue having more than three vehicle lanes, a posted speed limit of 35 miles
per hour, and an average daily traffic volume exceeding 6,000 vehicles.
In 2022, the Safe Streets Report (SSR) highlighted significant traffic safety concerns in
Boulder. Between 2018 and 2020, there were 14,500 crashes involving 150 serious injuries.
Arterial streets like Iris Avenue accounted for 67% of these severe crashes, with specific
hotspots identified at intersections such as 28th Street, Folsom/26th Street, and Broadway.
The SSR also identified crash types that disproportionately affected vulnerable groups like
young people and seniors. Data from the Iris Avenue project revealed that one in ten
pedestrians or cyclists on Iris Avenue each day were young, elderly, or disabled. Community
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feedback consistently expressed concerns about safety while walking or biking on Iris,
despite the significant number of daily users.
The 2023 – 2027 Vision Zero Action Plan (VZAP) identified the High Risk Network (HRN),
where 7% of the city’s street network have nearly half of all severe crashes. Iris Avenue,
from 19th Street to 28th Street is on the HRN. The VZAP identified reactive and proactive
actions to manage risk and mitigate crashes, including prioritizing work on the HRN and
Core Arterial Network (CAN). Iris Avenue is a priority CAN corridor.
3. Will this project be in conflict with the goals or policies in any departmental master plan and
what are the trade-offs among city policies and goals in the proposed project alternative?
(e.g. higher financial investment to gain better long-term services or fewer environmental
impacts)
No.
4. List other city projects in the project area that are listed in a departmental master plan or
the CIP.
• 19th Street Multimodal Improvements project: Norwood to Sumac avenues
• 28th Street Improvements Project: Iris Avenue to Canyon Boulevard
• Folsom Street Multimodal Improvements Project: Pine Street to Colorado Avenue
• Fourmile Canyon Creek Flood Mitigation: 19th Street Underpass
• Neighborhood Green Street: 15th Street and Iris Avenue Pedestrian Crossing
Improvements
• Sumac Avenue Improvements: Broadway to 19th Street
• US36/28th Street Multi-Use Path Project: Fourmile Canyon Creek to Jay Road
5. What are the major city, state, and federal standards that will apply to the proposed
project? How will the project exceed city, state, or federal standards and regulations (e.g.
environmental, health, safety, or transportation standards)?
The City of Boulder Transportation Master Plan and Low Stress Walk and Bike Network Plan
recommend greater separation and protection between vehicle and bicycle lanes on Iris
Avenue and a need for pedestrian improvements in key areas along the corridor. The Core
Arterial Network was reaffirmed as a council priority in April 2024. The Vision Zero Action
Plan identifies Iris Avenue as part of the High Risk Network. Federal Highway Administration
(FHWA) guidance states that lane repurposing is typically implemented on roadways with
an average daily traffic of 25,000 vehicles and does not recommend removing a bicycle
facility where one exists. FHWA recognizes lane repurposing, or road diets, as a street width
reduction that can calm traffic speeds. All new transportation infrastructure constructed as
part of the project will meet or exceed the updated City of Boulder Design and Construction
Standards.
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6. Are there cumulative impacts to any resources from this and other projects that need to be
recognized and mitigated?
No, this project fits within current roadway requiring no further hardscape, maintaining the
existing tree canopy and mitigating negative effects on natural resources. This project also
does not require additional maintenance and retains current capacity for services such as
police and fire.
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CEAP Checklist
The CEAP checklist evaluates potential social and environmental impacts to guide analysis and
comparison of the conceptual alternatives.
This provides an opportunity to balance multiple community goals in the design of a capital
project by assessing consistency with policies outlined in citywide and departmental plans, like
the Boulder Valley Comprehensive Plan, Transportation Master Plan, and Vision Zero Action
Plan.
The CEAP checklist rates each alternative (+) Positive effect, (-) Negative effect, and (0) No
effect. The results of the CEAP checklist evaluation can be found in Attachment B. Only CEAP
checklist criteria that identified a positive or negative effect for an alternative are shown.
Checklist Questions
CEAP checklist questions are a supplement to the CEAP checklist. Only checklist lines that
indicated a positive or negative effect provide more information in the corresponding checklist
question.
Attachment C provides the detailed responses to the checklist evaluation questions.
Checklist Criteria Summary
The CEAP checklist evaluation resulted in Alternatives A and B having a net positive effect and
Alternatives C and D having a net negative effect.
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Natural Features
Alternatives C and D have negative effects on natural features because they widen the roadway,
increase hardscape (the amount of concrete) and remove mature trees. Mature trees may
provide habitat – but this has not been evaluated for the project. It is assumed that by removing
trees the potential for providing habitat is also removed. Alternatives A and B do not widen the
roadway and so do not increase hardscape (or amount of concrete), maintain existing public
street trees, including mature trees, and the wildlife and habitat services they may provide.
Attachment D: Table of Mature Trees provides more information on the number of mature trees
within the project area and those impacted by each of the four alternatives.
Riparian Areas/Floodplains
Alternatives A and B have no effect on Riparian Areas because they do not encroach on a
riparian corridor. Alternatives C and D have a negative effect on Riparian Areas because they
encroach on the Twomile Canyon Creek.
No alternative is expected to cause a rise in the floodplain and no alternative is expected to
remove any property from the floodplain. Attachment E: Floodplain Memo provides more
information.
Geology and Soils
Alternatives A and B have no effect on geology and soils because they can be implemented
within the existing roadway width.
Alternatives C and D have a negative effect on geology and soils because they widen the
roadway and so create a change in fill material.
Water Quality
Alternatives A and B have no effect on water quality because they can be implemented within
the existing roadway and so do not require clearing and excavation, an increase in hardscape,
or changes to site ground features, storm drainage, or vegetation.
Alternatives C and D widen the roadway and so require clearing and excavation and increase
hardscape, site ground features, storm drainage needs, and public street tree removal. Water
quality mitigation with permanent best management practices (BMPs) will be installed with
either Alternative C or D, creating no effect on water quality.
Air Quality
Transportation research does not find vehicle lane repurposing results in increased emissions.
Instead, the research finds traffic emissions reductions from congestion mitigation are not
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guaranteed and demand-based emissions reduction strategies can be more effective,10 and a
reduction in fine particulate emissions with multimodal improvements on a corridor.11
Therefore, all alternatives have a positive effect on air quality because they provide safer
walking and bicycling options along the corridor, which can reduce mobile source emissions.
Alternatives A and B provide a greater positive effect because they also provide space for
protected intersection elements, shorter crossing distances, and opportunity for refuge islands
at midblock crossings, creating safer and more comfortable crossings of Iris Avenue as well.
Alternatives C and D only provide protected bike lanes and sidewalk improvements but no safer
and more comfortable crossings, and so have a smaller positive effect on Air Quality than
Alternatives A and B.
Physiological Well-Being
Alternatives A and B have no effect on physiological well-being as measured by exposure to
excessive noise.
Alternatives C and D have a negative effect on physiological well-being during construction,
because they require significant tree removals, and after implementation by moving the
existing curbs closer to adjacent properties, and so increase road noise for adjacent homes.
Services
Alternatives A and B have a net positive effect on services because they support current police
and fire services and provide transportation improvements.
Alternatives A and B repurpose vehicle lanes, introduce a center turn lane, and provide space for
protected intersection elements. These design components moderate speeds and reduce crashes
and the severity of crashes when they do occur, providing positive effects for transportation and
for police and fire services by reducing the need to respond to day-to-day emergencies.
The center turn lane provides dedicated space for turning vehicles and for police and fire
response. Therefore, Alternatives A and B improve transportation by reducing the common
corridor crash types and support police and fire services by providing dedicated space for
emergency response vehicles.
Alternatives C and D have no effect on transportation and the need for police and fire services
because they maintain the current vehicle lanes available for emergency response and maintain
the current need for day-to-day emergency response because they do not moderate vehicle
speeds or reduce crashes.
10 https://www.sciencedirect.com/science/article/abs/pii/S1361920912000727
11 https://www.sciencedirect.com/science/article/abs/pii/S1361920914001254
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Special Populations
All alternatives have a positive effect for persons with disabilities, senior population, children
and youth and sensitive populations, because they each provide improved sidewalks, protected
bike lanes and Americans with Disabilities Act curb ramp compliance work.
Alternatives A and B provide a greater positive effect than Alternatives C and D because they
repurpose a vehicle lane. Repurposing a lane provides space for protected intersection
elements at intersections, improved bus stops, and the potential for pedestrian refuge islands
at midblock crossings, which reduce crossing distance for people walking and biking and
reduces their exposure to vehicles.
Economy
Alternatives A and B have a positive effect on economy because they can be implemented
within the existing curb-to-curb width and so utilize existing infrastructure. Alternatives C and
D have a negative effect because they require roadway widening and so create new
infrastructure.
Project Specific Evaluation Criteria
To recognize the project’s unique context and needs, the project team defined project-specific
evaluation criteria. The project specific evaluation criteria provide more detailed evaluation
than the considerations from which they were developed, and further compare and contrast
the four alternatives from the CEAP checklist criteria.
Evaluation Criteria Definitions
Project specific evaluation criteria have five parts:
1. Definition provides the critical inputs to the score.
2. Methodology provides the method – qualitative or quantitative or both – of scoring.
3. Methodology Rationale provides additional information on why the methodology
was used.
4. Comparison Metric states whether the score is based on a comparison to other
alternatives or to the existing condition.
5. Source/References provide backup data used in the methodology.
Each alternative was rated using the following scale:
Scoring: -5 significantly poor/worse, -3 poor/worse -1 slightly poor/worse, 0 neutral, 1 slightly
good/better, 3 good/better, 5 significantly good/better.
Figure 17: Project Specific Evaluation Criteria Rating Legend
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The detailed results of evaluating each alternative using the project specific evaluation criteria
is shown in Attachment C.
Traffic Safety
Vehicle speed moderation
1. Definition: Reduction in prevailing speed and/or speeding, achieved through:
a. Reducing lane widths
b. Reducing the number of lanes
c. Providing Horizontal deflection/friction (including turns at intersections)
d. Providing vertical/visual friction (trees, bike lane separation)
2. Methodology: A quantitative and qualitative assessment of an alternative’s
potential effect on speeds resulting from the inclusion of one, or a combination, of
the definition elements.
3. Methodology Rationale: Many factors influence how fast people drive. The project
team considered the way the road is designed today, and scored the alternatives
based on how each alternative alters the current design with respect to vehicle
speed moderation.
4. Comparison Metric: Alternatives compared to existing conditions
5. Source/References:
a. Federal Highway Administration Road Diet Information Guide
b. Lower Citywide Speed Limits and Design Changes | FHWA (dot.gov)
c. lane-reconfiguration-guidelines-final-with-attachments-jan-2020.pdf (lacity.gov)
d. Speed Reduction Mechanisms | National Association of City Transportation
Officials (nacto.org)
e. Reducing Turn Speeds and Mitigating Conflicts | National Association of City
Transportation Officials (nacto.org)
f. Design Speed | National Association of City Transportation Officials (nacto.org)
g. Federal Highway Administration Safe System Approach for Speed Management
Crash reduction
1. Definition: Reduction in the number and severity of crashes, achieved through:
a. Reduced number of conflict points
b. Addition of turn lanes
c. Separation of vulnerable road users
d. Reduced speeds (based on vehicle speed moderation criteria)
e. Motorist-bicyclist interaction and expectation
2. Methodology: A quantitative and qualitative assessment of an alternative’s
potential effect on the number and severity of crashes resulting from the inclusion
of one, or a combination, of the definition elements, and the difficulty or intuitive
nature for users of a bike facility.
3. Methodology Rationale: Proven safety countermeasures and crash reduction
factors were evaluated where possible. In addition, the project team evaluated
potential for crash reduction based on a Safe Systems Approach and the City’s Vision
Zero Action Plan, where speeds, conflict points, two-way bike facilities, and other
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factors that don’t have available established predictive safety outcomes, can be
considered.
4. Comparison Metric: Alternatives compared to existing conditions
5. Source/References:
a. NACTO Urban Street Design Guide: Design Speed
Design Speed | National Association of City Transportation Officials
(nacto.org)
b. 3-5mph reduction FHWA Guide:
https://highways.dot.gov/sites/fhwa.dot.gov/files/2022-06/rdig.pdf
c. 1-2mph reduction LRRB/MnDOT study: https://www.lrrb.org/pdf/200625.pdf
d. Crash Modification Factors (CMFs) / Road Diet
i. Applicable CMFs are listed below:
ii. CMF ID: 5553 - CONVERTING FOUR-LANE ROADWAYS TO THREE-
LANE ROADWAYS WITH CENTER TURN LANE (ROAD DIET). Shows a
25% decrease in total crashes
iii. CMF ID: 2841 - CONVERTING FOUR-LANE ROADWAYS TO THREE-
LANE ROADWAYS WITH CENTER TURN LANE (ROAD DIET). Different
study. Shows a 47% decrease in total crashes
iv. CMF ID: 11128 - ROAD DIET (CONVERT 4-LANE UNDIVIDED ROAD
TO 2-LANES PLUS TURNING LANE). Shows a 38% decrease in total
crashes
a. CMF ID: 11301 - CONVERT TRADITIONAL BIKE LANE TO SBL WITH A
BLEND OF FLEXI-POST AND OTHER VERTICAL ELEMENTS. Shows a
36% decrease in vehicle-to-bicycle crashes
e. Proven Safety Countermeasures | FHWA (dot.gov)
f. What Is a Safe System Approach? | US Department of Transportation
g. Vision Zero Action Plan | City of Boulder (bouldercolorado.gov)
Evaluation Results
Figure 18: Safety Project Specific Evaluation Results
Vehicle speed moderation
Alternatives A and B reconfigure the roadway with vehicle lane repurposing between 13th
Street and Folsom/26th Street from four vehicle lanes to two vehicle lanes, which moderates
vehicle speeds up to five miles per hour.
Alternatives C and D maintain four vehicle lanes and so maintain current vehicle speeds.
Existing conditions data shows most drivers are speeding on Iris Avenue between Broadway
and Folsom/26th Street. Vehicle speeding leads to numerous safety concerns and increases the
severity of crashes involving vehicles.
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All alternatives include protected bike lanes which provide vertical or visual friction. These
elements can moderate vehicle speeds up to two miles per hour.
Crash reduction
Alternatives A and B reconfigure the roadway with vehicle lane repurposing and introduce a
center turn lane to provide more space for protected intersection elements and so reduce
crashes by 25% - 50%. These design elements reduce the corridor’s common crash types, rear
ends and approach turn crashes, VZAP common crash types of left turn crashes, right turn
crashes, and pedestrian/bicyclist crashes while crossing the street, and reduce the severity of
crashes when they do occur through reduction of vehicle speeds.
Corridor Common Crash Types
o The center turn lane:
Removes turning vehicles from the vehicle travel lane, reducing the
potential for rear end crashes.
Gives drivers a safe place to wait for a gap in traffic to complete their
turn, reducing the potential for approach turn crashes.
VZAP Common Crash Types
• Protected intersection elements:
o Physically separates people walking, biking, and rolling from vehicles up to and
through the intersection.
o Intersection tightening and corner islands make it easier for people walking,
biking, and rolling to see and be seen by drivers.
Severity of Crashes
• Vehicle lane repurposing moderate vehicle speeds up to five miles per hour.
• Intersection tightening and corner islands slow turning vehicles which make turns and
crossings safer.
Alternatives C and D do not reconfigure the roadway with vehicle lane repurposing, do not
introduce a center turn lane, and provide less space for protected intersection elements than
Alternatives A and B and so do not reduce the corridor’s common crash types, VZAP common
crash types or reduce the severity of crashes when they do occur because they do not
moderate vehicle speeds.
All alternatives include protected bike lanes which decrease vehicle-bicycle crashes by up to
35%.
Note: Alternatives with two-way bike lanes will also include design features such as protected
intersection elements, raised crossings, two-way signs and markings, striping and signal
changes that separate vehicle and bike movements at intersections, accounting for speed of
vehicles and bicycles, to be detailed in the final design phase to reduce potential conflicts
between bicyclists and drivers at side streets and driveways.
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Transportation Operations
Corridor vehicle travel time
1. Definition: The change in the median and 95th percentile travel time to drive the
corridor from end-to-end between Broadway and 28th Street based on ten VISSIM
microsimulation traffic modeling runs for each peak period for eastbound and
westbound traffic roadway capacity with NACTO guidelines recommended signal
control operations for one-way and two-way protected bike lanes.
a) Traffic operations – AM Peak
b) Traffic operations – PM Peak
2. Methodology: Quantitative assessment of travel time measured as an output of
VISSIM microsimulation traffic modeling.
3. Methodology Rationale: The 2019 TMP targets maintaining 1994 levels of travel
times on Boulder arterial streets, as well as improving travel time reliability and
predictability. The TMP found that, for the drive time study corridors, average travel
times have increased by 1 minute, or 15%, since baseline year. A travel time increase
of up to 15% is therefore rated as acceptable for Iris Avenue with additional 15 point
increments resulting in successively lower ratings. Any travel time exceeding a 15%
increase is further evaluated for acceptability.
4. Comparison Metric: Alternatives compared to existing conditions
5. Source/References:
b. 2020 Boulder Transportation Report on Progress
c. LA DOT Lane Reconfiguration Guidelines
d. Synchro and Vissim Traffic existing and proposed models developed for
project
Vehicle turning movements
1. Definition: Improve safety and efficiency of access to and from adjacent properties
and non-signalized streets based on ten VISSIM microsimulation traffic modeling
runs for each peak period for eastbound and westbound traffic roadway capacity
with NACTO guidelines recommended signal control operations for one-way and
two-way protected bike lanes.
a. Number of turns expected from a through lane
b. Likelihood of blocked driveways and accesses due to queued traffic
2. Methodology: Quantitative analysis based on VISSIM microsimulation traffic
modeling of the alternatives that evaluates the current number of vehicles that use
through travel lanes to make turns. Traffic models assess the likelihood of accesses
being blocked by queued traffic and the effect of platooned traffic on availability of
gaps to make turns into and out of non-signalized side streets and driveways.
3. Methodology Rationale: Access to properties via dedicated turn lanes rather than
through travel lanes improves user comfort and safety. This is balanced with the
frequency and length of gaps in Iris Avenue traffic streams to facilitate turns out of
side streets and driveways safely and without excess delay. The project team
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evaluated the ability of each alternative to improve ease, comfort, and safety of
access.
4. Comparison Metric: Alternatives compared to existing conditions
5. Source/References:
a. Access Management (Driveways) | FHWA (dot.gov)
b. Access Management: Benefits of Access Management Brochure - FHWA
Operations (dot.gov)
a. Synchro and Vissim Traffic existing and proposed models developed for
project
Vehicular level of service
1. Definition: Provide a corridor that is easy to navigate for all modes as measured by
change in Level of Service (LOS) of the corridors signalized intersections.
2. Methodology: Quantitative analysis of the relative change of how many vehicles can
traverse the roadway during a given time period, based on ten VISSIM
microsimulation traffic modeling runs for each peak period for eastbound and
westbound traffic roadway capacity with NACTO guidelines recommended signal
control operations for one-way and two-way protected bike lanes.
3. Methodology Rationale: Maintain existing LOS and delay is neutral; positive or
negative scores depending on changes to level of service or delay.
4. Comparison Metric: Alternatives compared to existing conditions
5. Source/References:
a) City of Boulder Design and Construction Standards
b) https://t4america.org/community-connectors/what-they-mean/level-of-
service/
c) https://ladot.lacity.gov/sites/default/files/2022-08/lane-reconfiguration-
guidelines-final-with-attachments-jan-2020.pdf
d) NACTO Urban Bikeway Design Guide
e) Synchro and Vissim Traffic existing and proposed models developed for
project
Day-to-day emergency response
1. Definition: Provide space for emergency response vehicles to move through traffic.
2. Methodology: Qualitative assessment of right-of-way available for private vehicles
to move aside and right-of-way available for emergency response vehicles to
operate.
3. Methodology Rationale: Assessed by City of Boulder Fire and Police departments for
whether the alternative changes current day-to-day emergency response.
4. Comparison Metric: Alternatives compared to existing conditions
5. Source/References:
a) Methodology based on discussions with City of Boulder Fire Rescue and
Police Department, and Boulder County Office of Disaster Management
b) FHWA – Road Diet Emergency Response Times
c) NACTO – Best Practices Emergency Access in Healthy Streets
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Disaster Emergency Response
1. Definition: Provide space for private vehicles to evacuate during a disaster and for
disaster emergency response vehicles to move through traffic.
2. Methodology: Quantitative analysis of widths of emergency response vehicles and
number of travel lanes available, and professional judgment.
Methodology Rationale: The team worked with the Office of Disaster Management (ODM) for
the City of Boulder and Boulder County, and the city’s Boulder-Fire Rescue (BFRD) and Police
(BPD) departments, to evaluate the protected bike lane design widths, the presence, or not, of
center two-way left-turn lanes, and the number of through lanes available for disaster
emergency response. Under a disaster emergency response, a minimum of two continuous
evacuation lanes and one emergency vehicle lane are desired. During a disaster emergency
response, a center two-way left-turn lane can be used for personal vehicle travel and a two-way
protected bike lane is wide enough to accommodate disaster emergency response vehicles.
The project team will continue to coordinate with BFRD, BPD, and ODM on roadway design
features for the use of the center turn lane as a second eastbound evacuation lane during the
final, or detailed, design phase.
3. Comparison Metric: Alternatives compared to existing conditions
4. Source/References:
d) How Cycle Paths Can Be Used by Emergency Services
e) Methodology based on discussions with City of Boulder Fire Department.
f) FHWA – Road Diet Emergency Response Times
g) NACTO – Best Practices Emergency Access in Healthy Streets
Evaluation Results
Figure 19: Transportation Operations Project Specific Evaluation Criteria Results
Corridor vehicle travel time
All alternatives increase current travel time. These increases vary depending on the time of day
and direction of travel. Travel time increases because each alternative includes FHWA
recognized proven safety countermeasures and include traffic signal changes that separate
vehicle and pedestrian/bike movements at intersections in accordance with industry best
practices for protected bike lanes.
Average of potential AM and PM peak travel time increases:
• Alternative A
• Average trip: 16 seconds to 1 minute 03 seconds
• Most trips (95th Percentile): 15 seconds to 01 minute 04
seconds
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• Slowest trips (5% of trips): 39 seconds to 01 minute 42
seconds
• Alternative B
• Average trip: 03 to 46 seconds
• Most trips (95th Percentile): 02 to 58 seconds
• Slowest trips (5% of trips): 01 second to 02 minutes 09
seconds
• Alternative C
• Average trip: 01 to 17 seconds
• Most trips (95th Percentile): 02 to 27 seconds
• Slowest trips (5% of trips): No change from today to 01
minute 08 seconds
• Alternative D
• Average trip: 01 to 25 seconds
• Most trips (95th Percentile): 03 to 36 seconds
• Slowest trips (5% of trips): 13 seconds to 01 minute 10
seconds
Vehicle turning movements
All alternatives maintain the current level of vehicle turning movements at side streets and
driveways.
Alternatives A and B reconfigure the roadway with vehicle lane repurposing between 13th
Street and Folsom/26th Street from four vehicle lanes to two vehicle lanes, and introduce a
center turn lane. The center turn lane provides a safe waiting area to turn left into a side street
or driveway and provides an opportunity to make a two-stage left turn out of a side street or
driveway. These turning movements offset the traffic model projected queued traffic and the
effect of platooned traffic on the availability of gaps in traffic to turn into and out of side streets
and driveways.
Alternatives C and D maintain four vehicle lanes and so supports the current and modeled
number of vehicles that use through travel lanes to make turns onto and out of side streets and
driveways.
Impacts to the vehicular level of service
All alternatives reduce vehicular level of service.
Alternative A reduces vehicular level of service by two levels due to vehicle lane repurposing
and the implementation of traffic signal changes to separate turning vehicles from people
walking and biking at major intersections.
Alternative B reduces vehicular level of service by one level due to vehicle lane repurposing and
the implementation of traffic signal changes to separate turning vehicles from people walking
and biking at major intersections on the north side of the street.
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Alternative C reduces vehicular level of service by one level due to implementation of traffic
signal changes to separate turning vehicles from people walking and biking at major
intersections.
Alternative D reduces vehicular level of service by one level due to implementation of traffic
signal changes to separate turning vehicles from people walking and biking at major
intersections on the north side of the street.
Day-to-day emergency response
Alternatives A and B improve day-to-day emergency response because they introduce a center
turn lane which provides space for motorists to pull over and it provides dedicated space for
day-to-day emergency response and stopping (Figure 20).
Figure 20 Day-to-Day Emergency Response Vehicle Operations
Alternatives C and D reduce day-to-day emergency response because they do not provide space
for motorists to pull over because the bike lane protection will block vehicles from using the
bike lane, and emergency vehicles must navigate the corridor with traffic for day-to-day
emergency response.
Disaster Emergency Response
Alternative A reduces disaster emergency response because it reduces the number of
eastbound lanes, which supports evacuating vehicles, and reduces the number of westbound
lanes, which support personal and emergency response vehicles traveling to a disaster area.
Alternative B supports the current level of disaster emergency response because it provides the
same number of eastbound and westbound lanes as today. The eastbound vehicle lane and
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center turn lane provide the same number of lanes as today for evacuating vehicles. The
westbound vehicle lane and the two-way protected bike lane provide the same number of lanes
for personal and emergency response vehicles traveling to a disaster area. Roadway design
features for the use of the center turn lane as a second eastbound evacuation lane will be
coordinated with ODM, BPD, and BFRD during final design (Figure 21).
Figure 21 Disaster Emergency Response Vehicle Operations
Alternative C supports the current level of disaster emergency response because it provides the
same number of eastbound and westbound lanes as today.
Alternative D improves the current level of disaster emergency response because it has the
same number of eastbound and westbound lanes as today and the two-way protected bike lane
provides dedicated space for emergency response vehicles for the majority of the corridor with
the exception of approximately one block where the two-way bike lane becomes a multi-use
path.
Safe and Comfortable Connections
Walking comfort
1. Definition: Provide a pedestrian route that can reduce the City of Boulder Low Stress
Walk and Bike Network Plan pedestrian stress factors and scores a 1 or 2 on the
Oregon Department of Transportation (DOT) Level of Traffic Stress (LTS) scale.
2. Methodology: A qualitative and quantitative evaluation according to the city’s Low
Stress Walk and Bike Network Plan and to the Oregon DOT LTS metric.
3. Methodology Rationale: The Boulder Low Stress Network should include Iris
Avenue.
4. Comparison Metric: Alternatives compared to existing conditions
5. Source/References:
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a) Analysis conducted based on Level of Traffic Stress methodologies here:
Analysis Procedures Manual Chapters 1-4 (oregon.gov)
b) The Low-Stress Walk and Bike Network Plan | City of Boulder
(bouldercolorado.gov)
Biking comfort
1. Definition: Provide a bike route that implements the City of Boulder Low Stress Walk
and Bike Network Plan recommendation and scores a 1 or 2 on the Oregon
Department of Transportation (DOT) Level of Traffic Stress (LTS) scale.
2. Methodology: A qualitative and quantitative evaluation according to the city’s Low
Stress Walk and Bike Network Plan and to the Oregon DOT LTS metric.
3. Methodology Rationale: The Boulder Low Stress Walk and Bike Network Plan
identifies Iris Avenue as part of the low stress network.
4. Comparison Metric: Alternatives compared to existing conditions
5. Source/References:
a) Analysis conducted based on Level of Traffic Stress methodologies here:
Analysis Procedures Manual Chapters 1-4 (oregon.gov)
b) The Low-Stress Walk and Bike Network Plan | City of Boulder
(bouldercolorado.gov)
Opportunity for protected intersection elements
1. Definition: Evaluate the extent protected intersection elements can be incorporated
into signalized and unsignalized intersections.
2. Methodology: A qualitative and quantitative evaluation of the amount of space
available for protected intersection elements.
3. Methodology Rationale: Protected intersections slow vehicle speeds, increase
visibility and reduce crossing distances for people walking, biking, and rolling, and
provide dedicated paths for bikes through the intersection.
4. Comparison Metric: Alternatives compared to existing conditions
5. Source/References:
a. Don’t Give Up at the Intersection, NACTO
Crossing safety & comfort
1. Definition: Evaluate how well space for safer roadway crossings, like pedestrian
refuge islands, can be provided.
2. Methodology: A qualitative and quantitative evaluation of the amount of space
available for pedestrian refuge islands.
3. Methodology Rationale: The Boulder Low Stress Walk and Bike Network Plan
identifies Iris Avenue as part of the low stress network.
4. Comparison Metric: Alternatives compared to existing conditions
5. Source/References:
a. Medians and Pedestrian Refuge Islands in Urban and Suburban Areas, FHWA
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Evaluation Results
Figure 22: Safe and Comfortable Connections Project Specific Evaluation Criteria Results
Walking comfort
Alternative A provides safer and more comfortable walking facilities because the one-way
protected bike lanes provide greater separation between the sidewalk and vehicle lanes, and it
provides vehicle lane repurposing, which slows vehicle speeds.
Alternative B provides safer and more comfortable walking facilities on the north side of the
street because the two-way protected bike lane provides greater separation between the
sidewalk and westbound vehicle lanes and reduces the amount of space between the south
side sidewalk and eastbound vehicle lanes. The alternative provides vehicle lane repurposing,
which slows vehicle speeds improving walking and crossing comfort for all.
Alternative C provides safer and more comfortable walking facilities because the one-way
protected bike lanes provide greater separation from vehicle lanes. However, Alternative C
maintains current vehicle lanes and therefore current vehicle speeds.
Alternative D reduces walking comfort and safety because any benefit of greater separation
between the sidewalk and westbound vehicle lanes the two-way protected bike lane on the
north side of the street provides is overwhelmed by impacts from maintaining four vehicle
lanes and attaching sidewalk on the south side of the street. Maintaining current vehicle lanes
requires the two-way bike lane to convert to a multi-use-path between Iris Court and 19th
Street due to right-of-way constraints and maintains current vehicle speeds. The two-way
protected bike lane on the north side of the street results in attached sidewalk on the south
side of the street.
Biking comfort
Alternatives A and B provide safer and more comfortable biking facilities by providing protected
bike lanes and vehicle lane repurposing, which slows vehicle speeds.
Alternatives C and D provide safer and more comfortable biking facilities by providing protected
bike lanes, but they maintain current vehicle lanes and so current vehicle speeds.
Alternative B and D include a two-way protected bike facility that supports all ages and abilities,
safer bike passing, and shortened crossing distances. Locating the two-way protected bike lane
on the north side of the street improves safety due to fewer conflicts with driveways and side
streets than the south side allowing for increased investment at each conflict. The two-way
protected bike facility creates the space to enable key safety features like protected
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intersection elements and will utilize two-way signs and markings, striping and signal changes
that separate vehicle and bike movements at signalized intersections to improve biking safety.
Opportunity for protected intersection elements
Alternatives A and B reconfigure the roadway with lane repurposing and so provide more space
for protected intersection elements. Protected intersection elements reduce VZAP common
crash types of left turn crashes, right turn crashes, and pedestrian/bicyclist crashes while
crossing the street, and reduce the severity of crashes when they do occur through reduction of
vehicle speeds.
Alternative C and D provide less space for protected intersection elements and so are less
effective at reducing VZAP common crash types or reducing severity of crashes when they do
occur.
Crossing safety & comfort
Alternatives A and B provide greater crossing safety and comfort because they reconfigure the
roadway with lane repurposing and so shorten crossing distance and amount of time vulnerable
road users are exposed to vehicle traffic and incorporate traffic signal changes to separate
turning vehicles from people walking and biking at major intersections.
Alternatives C and D provide some crossing safety and comfort improvement though they
maintain current crossing distances because they incorporate traffic signal changes to separate
turning vehicles from people walking and biking at major intersections.
Implementation Feasibility
The project team considered the following engineering constraints carefully. Note that at the
current phase of the project (concept development) these scores utilize assumptions that are
based on industry standards or best practice. Future phases of the project, like final design, may
discover information that changes the scoring or the conceptual design. The project team finds
this risk is generally applicable to all alternatives equally and therefore advances these criteria.
Time to design and implement
1. Definition: A measure of the time and effort needed to implement the alternative as
well as other factors that could complicate implementation, like necessary permits.
2. Methodology: Professional judgment of risks to the project including Right-of-Way
needs, floodplain permitting, traffic control and phasing.
3. Methodology Rationale: Preliminary estimates for permitting, right-of-way
acquisition, and phasing based on professional experience implementing similar
alternatives.
4. Comparison Metric: Alternatives compared to each other
5. Source/References: Recently completed comparable capital improvements projects.
Maintenance
1. Definition: A measure of added maintenance needs for transportation
infrastructure, snow and ice response and street sweeping.
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2. Methodology: Qualitative analysis of additional labor and equipment required for
snow and ice response and street sweeping, and long term maintenance and
material replacement for added infrastructure.
3. Methodology Rationale: The team collectively determined a rating for known risk
factors for each alternative.
4. Comparison Metric: Alternatives compared to each other
5. Source/References: Discussions with City of Boulder Transportation & Mobility
Maintenance department.
Right-of-Way property acquisition
1. Definition: Analysis of the number and size of permanent and temporary
construction easements needed.
2. Methodology: Quantitative measure of the number and size of required permanent
and temporary construction easements. Qualitative factors may be applied for
impacts in difficult locations (such as near front doors or that would make a
driveway unusable).
3. Methodology Rationale: Minimal impacts to adjacent projects is a goal of the Iris
Avenue project. The project team seeks to minimize impacts by adjusting designs
and looking for ways to accommodate an alternative within the existing right-of-
way.
4. Comparison Metric: Alternatives compared to each other
5. Source/References:
a. Alternative maps
b. Right-of-way survey
c. Field walk data
Utility relocation and storm water drainage
1. Definition: Analysis of the number and type of storm drainage infrastructure such as
inlets, pipes, and manholes, and utility impacts, such as storm water and sanitary
sewer, Xcel electric and gas, and telecom.
2. Methodology: Quantitative analysis counts impacted ground level utility features
and counts drainage impacts, such as inlets, manholes and length of pipe. These
counts represent utility and stormwater conflicts, noting surface utility impacts are
easily counted, but underground utility needs can be difficult to estimate.
3. Methodology Rationale: Drainage and utility impacts can be incredibly costly and
greatly impact construction duration. The more underground work is needed, the
more cost and schedule to implement will be increased.
4. Comparison Metric: Alternatives compared to each other.
5. Source/References:
a. Alternative maps
b. Existing storm drainage geospatial layers
c. Field walk data
Implementation Cost
1. Definition: Order of magnitude engineering cost estimates of construction.
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2. Methodology: Quantitative, measured using a scale of orders of magnitude for
comparison purposes only.
3. Methodology Rationale: Cost to implement estimates are developed for each
alternative and include right-of-way, utility and stormwater relocation costs, costs of
tree removal, and high level construction cost estimates. Costs do not consider
additional engineering or construction management and oversight as these costs
would be similar for all alternatives. Full cost estimates will not be developed until
later in the design process when more detailed design is completed.
4. Comparison Metric: Alternatives compared to each other
5. Source/References: Recently completed similar project cost estimates.
Sustaining the Tree Canopy
Preserves Existing Public Street Trees
1. Definition: A measure of required public tree removals minus the estimated
potential to replant trees.
2. Methodology: Quantitative analysis of net public tree removals (trees removed less
replanted trees) using the City of Boulder Forestry Department tree inventory
developed for the Iris Avenue project.
3. Methodology Rationale: The City of Boulder Forestry Department Urban Forestry
Strategic Plan and supporting Boulder Valley Comprehensive Plan policies (BVCP
2.38 Importance of Urban Canopy, Street Trees and Streetscapes, and BVCP 3.12
Urban Forests), identify the urban forest, public street trees and tree canopy as
important.
4. Comparison Metric: Alternatives compared to existing conditions.
5. Source/References:
a) City of Boulder Urban Forestry Strategic Plan
a) Boulder Valley Comprehensive Plan (BVCP)
i. BVCP 2.38 Recognizes the Importance of Urban Canopy, Street Trees
and Streetscapes
ii. BVCP 3.12 Urban Forests
Evaluation Results
Figure 23 Sustaining the Tree Canopy Project Specific Evaluation Criteria Results.
Preserves Existing Public Street Trees
Alternatives A and B can be implemented within the existing roadway and so require removal of
10 to 12 public streets tress to improve sightlines and provide space for potential tree
replanting.
Alternative C requires road widening to the north and south and so require removal of 69 to 75
public street tress.
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Alternative D requires road widening to the north only and so require removal of 43 to 50
public street trees.
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Project Specific Evaluation Summary
Attachment F: Conceptual Alternatives with Project-Specific Evaluation Criteria Applied
provides the full project specific evaluation criteria.
Alternatives A and B reconfigure the roadway with vehicle lane repurposing, introduce center
turn lanes and protected intersection elements, and include protected bike lanes and sidewalk
improvements. Therefore, they should reduce crash types for vulnerable road users, reduce the
common crash types the VZAP found occur on the High Risk Network (left turn crashes, right
turn crashes, right on red crashes, and pedestrian crashes while crossing the street), and reduce
the severity of crashes when they do occur through reduction of vehicle speeds.
Alternatives A and B provide safer and more comfortable walking and biking facilities and
crossings by providing separation from vehicles, provide more space for protected intersection
elements, and shorten crossing distances.
Alternatives C and D only include protected bike lanes and improved sidewalks. Therefore, they
are less effective at decreasing the frequency and severity of crashes involving vulnerable road
users and do not address the common crash types identified by the VZAP or reduce vehicle
speeds to reduce crash severity. Alternative C and D do not provide safer crossings for people
walking and biking than exist today.
Alternative B and D include a two-way protected bike facility which may be less familiar for
bicyclists to use and require drivers to look for cyclists traveling in both directions. These
conflicts can be minimized by locating the two-way protected bike lane on the north side of the
Iris Avenue, which has significantly fewer conflicts with driveways and side streets, and through
other mitigations like signage and pavement markings.
Alternatives A and B can achieve their safety benefits without widening the roadway and so are
more easily implemented because they require no permanent right-of-way easements, require
few public street tree removals, storm water drainage impacts and utility relocations, and take
less time and cost to implement.
Alternatives C and D require roadway widening and so require permanent right-of-way
easements, significant public street tree removals, storm water drainage impacts and utility
relocations, and so cost more and take more time to implement to provide fewer safety
benefits.
Every alternative will have increased travel time, depending on the time of day and direction of
travel. Travel time increases because each alternative includes FHWA recognized proven safety
countermeasures that respond to community input and the common crash type findings of the
Vision Zero Action Plan. All alternatives also assume signal changes to separate vehicle and bike
movements in accordance with industry best practices for protected bike lanes. This
assumption contributes to end-to-end vehicle travel time increases and changes to intersection
level of service under all alternatives.
Across all alternatives, the largest increases to travel times by percentile are as follows: up to 1
minute 03 seconds for the average trip (Alternative A), up to 01 minute and 04 seconds for
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most trips (Alternative A), and up to 2 minutes 09 seconds for the slowest trip (Alternative B)
(Table 4). About 30 to 60 seconds separate alternatives with three vehicle lanes (Alternatives A
and B) and alternatives with four vehicle lanes (Alternatives C and D) due to Alternatives A and
B including road reconfiguration between the bookends.
Table 4:Travel time estimates for average, 95th percentile and maximum travel time, using a
combined existing AM and PM peak travel times
Potential Travel Time Increase
Average Trip Most Trips (95th
Percentile)
Slowest Trip (Maximum)
Alternative A 16 seconds to 1
minute 03 seconds
15 seconds to 1 minute
04 seconds
39 seconds to 1 minute 42
seconds
Alternative B 03 to 46 seconds 02 to 58 seconds 01 second to 2 minutes 09
seconds
Alternative C 01 to 17 seconds 02 to 27 seconds No change from today to 1
minute 08 seconds
Alternative D 01 to 25 seconds 03 to 36 seconds 13 seconds to
1 minute 10 seconds
Intersection level of service is reduced for all the alternatives due to vehicle lane repurposing
(Alternatives A and B) and the implementation of protected turn phases and bicycle signals (all
Alternatives). Alternatives B, C, and D change level of service by one level, and Alternative A by
two levels.
Vehicle queuing for eastbound and westbound vehicles at the 19th Street and Folsom/26th
Street intersections increase for Alternatives A and B with maximum queues of 1,000 feet that
clear during each intersection signal cycle. All alternatives increase left and right turn queues at
these intersections due to the protected turn phasing for vehicles and bikes.
Each alternative supports day-to-day emergency response and disaster emergency response.
Center turn lanes in Alternatives A and B support day-to-day emergency response by providing
a dedicated lane for emergency operations. Two-way protected bike lanes in Alternatives B and
D are wide enough to accommodate emergency vehicles during a disaster scenario. Alternative
B and D supports both day-to-day and disaster emergency response through the combined
design components of vehicle travel lanes, center turn lanes and two-way protected bike lanes.
Community Input on CEAP and Recommended Alternative – Summer
2024
Staff shared the CEAP evaluation and recommended alternative with the community for
feedback in July and August 2024 at an in-person open house with 163 attendees and a virtual
open house questionnaire which received 217 responses.
The questionnaire focused on the alternatives evaluation and the recommended alternative. Of
the 217 respondents, 78.4% primarily drive, 17.6% bike, 2.7% walk, and less than 1% ride transit
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along or across Iris Avenue. The most selected secondary modes of travel along or across Iris
Avenue were biking, walking, and driving in that order.
The most selected reasons for traveling Iris Avenue for the virtual open house questionnaire
respondents were:
• For shopping/errands: 161
• To reach recreation or entertainment: 124
• I live along or nearby Iris Avenue: 113
• To travel between communities: 109
• To reach healthcare: 79
• To commute to work: 69
• To take children to school: 20
• Other: 9
• To take children to childcare: 8
• To attend school myself: 5
When asked if there is anything the project team needs to clarify about the alternatives
evaluation, 62.7% of questionnaire respondents said “No” and 37.3% said “Yes.”
For respondents who responded “Yes,” an open-ended question asked what could be clarified
about the alternatives evaluation. The responses to this question were intended to ensure
common questions were answered in the CEAP and presentations of the CEAP to TAB and City
Council. The most common questions were about:
• Transit, waste, and delivery operations
o How will buses, trash, and delivery vehicles operate in the proposed roadway
and what are the rules for private vehicles using the center turn lane to pass
stopped vehicles?
• Eastern end business access management
o If access to the Safeway Shopping Center is changed, what are the detour
routes?
• Entering/exiting two-way bike facility across Broadway
o Describe movements from north and south corners of west side of Broadway to
the 2-way bike facility and vice versa
• How project will address crash hot spots at bookends
o If vehicle lane configuration is not changing at bookends, how will crashes be
mitigated?
• Vehicle turns across two-way bike traffic
o For left and right turns from and to Iris Avenue, how will vehicles find gaps and
see bicyclists coming from both directions in the two-way protected bike lane?
• Signal operations to separate bike/vehicle movements
o Clarify protected phasing at major intersections and considerations for higher
speed of e-bikes
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Respondents and in-person open house participants also had an opportunity to state their
concerns about the project for staff to consider in future design phases. The most mentioned
were:
• Traffic congestion and vehicle travel time
o Respondents indicate concern about increased traffic congestion and travel time
with the implementation of Alternative B.
• Project process
o Some respondents are concerned that the project process was predetermined or
did not consider a wide range of alternatives while others are concerned that the
project will not move forward due to public opposition.
• Design Complexity
o Some respondents are concerned about the two-way protected bike lane on the
north side of Iris Avenue, navigating to and from it by bike, or crossing it while
driving. Other respondents are concerned about the center two-way left turn
lane and using it to turn on and off Iris Avenue.
• Neighborhood side streets
o Respondents express concerns about traffic diversion from Iris Avenue, the
speed of vehicles on neighborhood streets, and the safety of people walking and
biking on those streets.
• Bookend intersection safety
o Respondents mention concerns about bookend intersections remaining unsafe
or uncomfortable to travel through or across with the implementation of
Alternative B.
• Emergency Evacuation
o Respondents state concerns about emergency evacuation of eastbound vehicles
during a wildfire or other disaster.
Questionnaire respondents and in-person open house participants were also asked what design
elements they are most excited about as the project moves forward. Their responses are
grouped into three tiers in Table 5.
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Table 5. Design elements questionnaire respondents are “most excited” about
Tier 1
(70 or more selections)
Tier 2
(40-59 selections)
Tier 3
(fewer than 30 selections)
Safer crossings Vehicle speed moderation Minimal right-of-way impacts
Preservation of Tree Canopy Optimized Signal Operations Center turn lane
End-to-end two way
protected bike lane
Minimal cost and time to
implement
Emergency response use
Protected intersections Roadway reconfiguration Updated wayfinding
Improved sidewalks and curb
ramps
Bus stop enhancements
Crash reduction Bookend intersections
From July 19 to July 25, 2024, the question asking respondents to select the five elements they
are most excited about as the project moves into further design was mandatory in the
questionnaire. In response to community input, on July 25, the question was made optional,
and respondents were able to skip the question without selecting at least one design element.
At least 73 respondents indicated choosing a design element because it was a mandatory field
and not due to their excitement about it.
Feedback gathered during the in-person and virtual open houses and online questionnaire is
incorporated into the final CEAP. Input from this round of community engagement continued
the themes and priorities heard in the first two open houses and added new input focused on
the recommended north side two-way bike facility, potential for increased traffic congestion
and related emissions caused by vehicle lane repurposing, and including anticipated future
growth in vehicle use in traffic modeling.
Further context for how input from this round of community engagement is addressed in the
proposed project is below.
North Side Two-Way Bike Facility
Community engagement and education in future phases will focus on the most
frequently asked questions and ensure users have access to information about using,
connecting to, and crossing the two-way protected bike lane. The potential for conflicts
with turning vehicles is minimized by locating the two-way protected bike lane on the
north side of the Iris Avenue, which has fewer conflicts with driveways and side streets.
Design features such as protected intersection elements, raised crossings, two-way signs
and markings, striping and signal changes that separate vehicle and bike movements at
intersections, accounting for speed of vehicles and bicycles, will be detailed in the final
design phase to reduce potential conflicts between bicyclists and drivers at side streets
and driveways.
Potential for Increased Traffic Congestion and Emissions
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Transportation research does not find that vehicle lane repurposing results in increased
emissions. Instead, it finds traffic emissions reductions from congestion mitigation are
not guaranteed and demand based emissions reduction strategies can be more
effective,12 and find reduction in fine particulate emissions with multimodal
improvements on a corridor.13
Although Alternative B may potentially increase travel time by a range of 2 to 58
seconds for most trips (95%), all alternatives would increase current travel times due to
the introduction of traffic signal changes and FHWA proven safety countermeasures to
separate vehicle and pedestrian/bike movements at intersections.
Potential for Future Growth in Vehicle Use
Traffic modeling for the Iris Avenue project utilized existing vehicle, bicycle and
pedestrian volumes. This approach is supported by the Boulder Valley Comprehensive
Plan transportation and land use assumptions, 2023 Travel Diary Study findings of
reduced single occupancy vehicle use and increased bicycling over the past nine years,
and ten years of historic data that show vehicle volumes have remained reasonably
constant.
Project Process
The project considered 13 possible design options including a range of solutions that
explored different bike and pedestrian facility types, multi-use paths, as well as a range
of lane configurations, from two to five vehicle lanes. The options were screened and
then evaluated using the CEAP and project-specific criteria.
Neighborhood Side Streets
In response to community input, a secondary study area was added to the project to
examine the potential for neighborhood traffic calming.
Emergency Evacuation
Alternative B allows for the use of the center-two way turn lane for eastbound personal
vehicle travel while the two-way protected bike lane is wide enough to accommodate
westbound disaster emergency response vehicles. Roadway design features for the use
of the center turn lane as a second eastbound evacuation lane will continue to be
coordinated with ODM, BPD, and BFRD during final design.
12 https://www.sciencedirect.com/science/article/abs/pii/S1361920912000727
13 https://www.sciencedirect.com/science/article/abs/pii/S1361920914001254
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Bookend Intersection Safety
Modifications and multimodal improvements like geometry changes, improved
sidewalks, and bike path connections will improve separation and protection of each
mode to the bookend intersections while maintaining the vehicle lane configuration.
Signalized crossings and markings will connect bicyclists to paths on and across the
bookend intersections at Broadway and 28th Street.
Transit, Waste, and Delivery Operations
Stakeholder outreach with Regional Transportation District (RTD), businesses on the
eastern end, waste services, delivery services, and other key stakeholders will continue
to inform final design.
Design and operations details will be finalized as the corridor design progresses to final design
and may change based on engineering best practices and technical feasibility.
Additionally, themes from this most recent phase of community engagement reiterated
previously heard concerns and desires and did not reveal new or diverging themes. These
continued themes influenced the finalization of the content of the CEAP and public facing
materials. Staff will update the project website and future materials to include information
about these most frequently asked questions and continue to provide clarification and
understanding for the community as the project moves forward into final design.
Feedback has influenced the project process from the start, adding a secondary study area in
response to concerns about vehicle speeds and traffic diversion to neighborhood side streets
and projects on those streets to the project scope. Recurring themes throughout the project
confirm the varying perspectives in the community and staff’s recommendation of Alternative B
as the alternative that best balances those perspectives.
Due to the nature of transportation capital improvement projects, many details are yet to be
finalized as the project progresses into final design. Community feedback provides the priorities
on which to focus such as the south side sidewalks and access to the bike facility on the north
side, an emphasis on high quality and aesthetically pleasing design, innovative designs which
preserve as much tree canopy as possible, and other designs and signal practices that best
balance the trade-offs in safety, comfort, and connectivity for people walking, biking, riding
transit and driving.
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Recommended Alternative
The recommended alternative is Alternative B: Two-Way Protected Bike Lane and No Change to
Roadway Width (Figure 24). Alternative B advances the 2019 Transportation Master Plan and
2019 Low Stress Walk and Bike Network Plan recommendations for Iris Avenue, respond to the
findings of the 2022 Safe Streets Report, and implements recommendations of the 2023 – 2027
Vision Zero Action Plan.
Figure 24 Alternative B: Three vehicle lanes with north side on-street protected two-way bike lane with minimum improvements
behind the curb (Looking West)
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Alternative B repurposes a vehicle lane which is effective at reducing speeds, a community
priority that is supported by data that show prevailing speeds are 5 mph over posted speed
limit and high-end speeders (about 4% of all drivers) traveling at 10+mph over the posted speed
limit. Repurposing a lane provides space for a center turn lane. A center turn lane is effective at
reducing the common crash types on Iris Avenue, rear ends and approach turns, by removing
turning vehicles from through lanes. Repurposing a lane also provides space at intersections for
protected intersection elements. Protected intersections are an industry best practice to
reduce conflicts at intersections where the city’s data show most crashes occur. Repurposing a
lane provides space for potential pedestrian refuge islands and improved bus stops, which
reduces crossing distance and the time people walking and biking are exposed to traffic while
crossing Iris Avenue. Finally, repurposing a lane provides space to provide hardened separation,
or protection, between the on-street bike lane and vehicle lanes. This hardened separation also
increases separation between people walking on the sidewalks and vehicle lanes, which
increases pedestrian comfort.
Alternative B includes a two-way protected bike lane on the north side of the street and
removes the on-street bike lane on the south side of the street. This shifts the vehicle travel
lanes 15 feet further from the north side of the street and 5 feet closer to the south side of the
roadway. The existing sidewalk on the south side of the street is attached to the roadway for
37% of its length, which reduces pedestrian comfort for this stretch. The remaining 63% of
sidewalk on the south side will retain its current detachment and associated pedestrian
comfort. Design and construction may offer opportunities to reduce the proportion of attached
sidewalk on the south side of the road.
The two-way protected bike lane on the north side of Iris Avenue provides more benefits than
one-way bike lanes because it is easier to maintain, provides more space for snow storage in
winter months, can better gain benefits of sun exposure in winter months to melt and
evaporate snow and ice furthering snow and ice response efforts, provides opportunities for
passing – which is becoming increasingly important as more electric micro mobility devices use
the transportation network, provides space for side-by-side riding, crosses nearly a third as
many conflicting unsignalized driveways and side streets as the south side of the roadway, and
is wide enough to support disaster emergency response vehicles.
Alternative B can be implemented within the existing curb-to-curb width which retains all but
10 to 12 existing public street trees, reduces the time and complexity to implement because of
fewer utility relocations, stormwater drainage impacts, floodplain permit mitigations, and time
and funding to implement. This lower cost project supports implementation of traffic calming
and management on neighborhood streets under limited transportation funding scenarios.
Alternative B has the lowest potential travel time increase of the three lane alternatives for
both the average trips, 3 to 46 seconds, and 2 to 58 seconds for most trips (95th percentile).
These potential travel time increases are 20 to 30 seconds more than the potential travel time
increase of the four lane alternatives (Alternative C and D). Alternative B has a potential travel
time increase for the slowest trips, which about 5% of drivers experience, by up to 20 seconds
more than the other three lane alternative (Alternative A) and up to one minute more than
both four lane alternatives (Alternative C and D). While the potential travel time changes may
feel impactful to some, Alternative B provides the greatest safety benefits for all.
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Throughout the project, community input themes and priorities were:
• Concern for emergency evacuation
• Concern for traffic congestion leading to cut through traffic on neighborhood side
streets
• Desire for slower vehicle speeds
• Desire for better walking and biking facilities along Iris Avenue as well as safer and
more comfortable crossings
• Desire for vehicle travel time reliability
Alternative B provides the benefits the community has asked for.
Note: Staff will identify specific locations along neighborhood street segments to receive
speed mitigation and traffic management, prioritized by the largest speeding problem.
These prioritized segments will receive speed mitigation and traffic management when
the Iris Avenue project is implemented, following final design and allocation of funding.
This may include speed humps, speed tables, and vehicle turn restrictions.
The project team reviewed Alternative B with various work groups within the City of Boulder,
including Urban Forestry, Transportation Maintenance, and Utilities/Floodways/Greenways for
feedback and these partners did not identify any issues that would preclude their support. The
project team has worked in close coordination with the Boulder Fire-Rescue and Police
departments, and the Office of Disaster Management (ODM) for the City of Boulder and
Boulder County, to review considerations around day-to-day and disaster emergency response.
These key partners support the use of the center-turn lane for day-to-day emergency response
and use of the two-way protected bike lane for disaster emergency response and advise that
use of the center turn lane can provide two eastbound evacuation lanes during disaster
scenarios. Staff will continue to work with these partners in the final design phase to develop
design solutions that would support evacuation use of the center-turn lane during disaster
scenarios.
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Staff Project Manager and Relevant Contacts
PROJECT MANAGER
Lindsay Merz, P.E., PMP, ENV SP
Engineering Principal Project Manager
City of Boulder
Transportation & Mobility Department
Email: MerzL@bouldercolorado.gov
TRANSPORTATION PLANNER – ENGAGEMENT
Ericka Amador
Senior Transportation Planner
City of Boulder
Transportation & Mobility Department
Email: amadore@bouldercolorado.gov
TRANSPORTATION PLANNER – DESIGN
Daniel Sheeter
Principal Transportation Planner
City of Boulder
Transportation & Mobility Department
Email: sheeterd@bouldercolorado.gov
OPERATIONS ENGINEER
Greg Baker
Transportation Engineer
HDR
Email: Gregory.Baker@hdrinc.com
PROJECT TEAM
Melanie Sloan
Principal Project Manager
City of Boulder
Transportation & Mobility Department
Email: sloanm@bouldercolorado.gov
Devin Joslin, PE, PTOE
Civil Engineering Senior Manager
Principal Traffic Engineer
City of Boulder
Transportation & Mobility Department
Email: joslind@bouldercolorado.gov
Stephen Rijo
Transportation Planning Manager
City of Boulder
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Transportation & Mobility Department
Email: rijos@bouldercolorado.gov
Gerrit Slatter
Civil Engineering Senior Manager
City of Boulder
Transportation & Mobility Department
Email: slatterg@bouldercolorado.gov
CONSULTANT T EAM
Charlie Dyrsten, PE
Project Manager
HDR
Email: charles.dyrsten@hdrinc.com
Alexa Muraida
Senior Communications Strategist
HDR
Email: alexa.muraida@hdrinc.com
Attachments
Attachment A: Conceptual Alternatives with Considerations Applied
Attachment B: CEAP Checklist
Attachment C: CEAP Checklist Questions
Attachment D: Conceptual Alternatives with Project-Specific Evaluation Criteria Applied
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Attachment A: Conceptual Alternatives with Considerations Applied
Alternative A: One-Way Protected Bike Lanes and No Change to Roadway Width
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Alternative B: Two-Way Protected Bike Lane and No Change to Roadway Width
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Alternative C: One-Way Protected Bike Lanes and Widened Roadway
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Alternative D: Two-Way Protected Bike Lane and Widened Roadway
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Attachment B: CEAP Checklist Evaluation for the Four Conceptual
Design Alternatives
The CEAP checklist rates each alternative (+) Positive effect, (-) Negative effect, and (0) No
effect.
Only criteria that had alternative impacts are shown.
Alternative
A
Alternative
B
Alternative
C
Alternative
D
A. Natural Areas or Features
1. Disturbance to species,
communities, habitat, or
ecosystems due to:
a. Construction activities - - - -
f. Habitat removal 0 0 - - h. Changes to groundwater or
surface runoff 0 0 - -
2. Loss of mature trees or
significant plants? 0 0 - -
B. Riparian Areas/Floodplains
1. Encroachment upon the 100-
year, conveyance ore high hazard
flood zones
0 0 0 0
2. Disturbance to or
fragmentation of a riparian
corridor
0 0 - -
D. Geology and Soils
d. Changes in soil or fill material
on the site? 0 0 - -
E. Water Quality
1. Impacts to water quality from
any of the following?
a. Clearing, excavation, grading or
other construction activities 0 0 - -
b. Change in hardscape 0 0 - -
c. Change in site ground features 0 0 - -
d. Change in storm drainage 0 0 - -
e. Change in vegetation 0 0 - -
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Alternative
A
Alternative
B
Alternative
C
Alternative
D
F. Air Quality
1. Short or long term impacts to
air quality (CO2 emissions,
pollutants)?
a. From mobile sources? + + + +
K. Physiological Well-being
1. Exposure to Excessive Noise 0 0 - -
L. Services
1. Additional Need for:
d. Police Services + + 0 0
e. Fire Protection Services + + 0 0
h. Transportation
improvements/traffic mitigation + + 0 0
M. Special Populations
1. Effects on:
a. Persons with disabilities? + + + +
b. Senior population? + + + +
c. Children or youth? + + + +
d. Restricted income persons? + + + +
e. People of diverse backgrounds
(including Latino and other
immigrants)?
+ + + +
f Neighborhoods + + + +
g. Sensitive populations located
near the project (e.g. schools,
hospitals, nursing homes)?
+ + + +
N. Economy
1. Utilization of existing
infrastructure? + + - -
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Attachment C: CEAP Checklist Questions
City of Boulder
Community and Environmental Assessment Process
Checklist Questions
Note: The following questions are a supplement to the CEAP checklist. Only those questions
indicated on the checklist are to be answered in full.
Natural Areas and Features
1.Describe the potential for disturbance to or loss of significant: species, plant
communities, wildlife habitats, or ecosystems via any of the activities listed below.
(Significant species include any species listed or proposed to be listed as rare,
threatened or endangered on federal, state, county lists.)
a.Construction activities
Mature trees may provide habitat – but this has not been evaluated for the
project. It is assumed that by removing trees the potential for providing habitat
is also removed.
All alternatives will disturb the wildlife habitats due to construction activity.
Alternatives A and B will have a negative effect due to typical construction
activities. These activities will be limited to within the roadway width plus space
necessary outside of the roadway width for construction activities.
Alternatives C & D will have a negative effect due to the widening of the
roadway these require to build, which increases the footprint of disturbance
during construction.
b.Native Vegetation removal
c.Human or domestic animal encroachment
d.Chemicals to be stored or used on the site (including petroleum products,
fertilizers, pesticides, herbicides)
e.Behavioral displacement of wildlife species (due to noise from use activities)
Alternatives A and B will have a positive effect because each propose three
vehicle lanes, which will reduce road noise and therefore reduce the potential
for behavioral displacement of wildlife species.
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Alternatives B and C maintain four vehicle lanes and so will have no effect on
road noise and so will continue any current behavioral displacement of wildlife
species due to road noise.
f. Habitat removal
Mature trees may provide habitat – but this has not been evaluated for the
project. It is assumed that by removing trees the potential for providing habitat
is also removed.
Alternatives A and B will have no effect on habitat removal because tree removal
is limited to improve sightlines.
Alternatives C and D will have a negative effect on habitat removal because each
require removal of 43 to 75 public street trees, or 29% to 50% of the existing
tree canopy on Iris.
Alternative C has the greatest negative effect because it requires the roadway to
be widened to the north and south. This alternative would remove 69 – 75 public
street trees, or 46-50% of all existing public street trees.
Alternative D has a significant negative effect but requires the roadway to be
widened to the north only. This alternative would remove 43 – 50 public street
trees, or 29 – 32% of all trees.
g. Introduction of non-native plant species in the site landscaping
h. Changes to groundwater (including installation of sump pumps) or surface runoff
(storm drainage, natural stream) on the site
Alternatives A and B have no effect to groundwater because they are
implemented within the existing roadway width.
Alternatives C and D have a negative effect because they widen the roadway and
increase hardscape and runoff.
Alternatives C and D have a negative effect because they require the open
Twomile Canyon creek to be piped, which cause a loss in vegetation and the
environmental benefits of catching and filtering runoff before it enters
groundwater. Alternatives A and B do not require the creek to be piped and so
have no effect.
i. Potential for discharge of sediment to any body of water either short term
(construction-related) or long term
j. Potential for wind erosion and transport of dust and sediment from the site
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2.Describe the potential for disturbance to or loss of mature trees or significant plants.
Alternatives A and B require removal of 7 mature trees to for improved sidewalks
and sightlines.
Alternative C requires the removal of 43 mature trees.
Alternative D requires the removal of 32 mature trees.
•A description of how the proposed project would avoid, minimize, or mitigate identified
impacts.
Impacts to existing street trees vary between the alternatives. Only trees located
within the public right-of-way are impacted. Any trees located on private
property will remain, with potential trimming only needed if low-hanging
branches and/or limbs are impeding existing or new sidewalks and bike lanes.
Alternatives A and B have no effect because they have minimal changes to
existing public street trees: 10 – 12 need to be removed for sidewalk
improvements and sightlines, or about 8% of the urban forest on Iris.
Alternatives C and D have a negative effect because they require removal of a
large number of trees. Alternative C has a greater negative effect than
Alternative D because it removes 69 – 75 trees, or 46-50% of the urban forest on
Iris Avenue. Alternative D has a less negative effect than Alternative C because it
removes 43 – 50 trees, or 29-32% of the urban forest on Iris Avenue.
•A habitat assessment of the site, including: 1. a list of plant and animal species and plant
communities of special concern found on the site; 2. a wildlife habitat evaluation of the
site.
•Maps of the site showing the location of any Boulder Valley Natural Ecosystem, Boulder
County Environmental Conservation Area, or critical wildlife habitat.
Riparian Areas and Floodplains
1.Describe the extent to which the project will encroach upon the 100-year,
conveyance or high hazard flood zones.
Iris Avenue is currently designed to convey the 100-year flood, conveyance, and
high hazard zones of Twomile Canyon Creek from Broadway to Elmers Twomile
Creek. Therefore, all alternatives are within the 100-year flood, conveyance, and
high hazard zones of Twomile Canyon Creek.
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A City of Boulder Floodplain Development Permit and a Clean Water Act (CWA)
Section 404 Permit will be obtained prior to construction. The floodplain permit
requires demonstration that the recommended alternative would cause no rise
in the floodplain.
No alternative causes a rise in the floodplain and no alternative removes any
property from the floodplain.
2. Describe the extent to which the project will encroach upon, disturb, or fragment a
riparian corridor: (This includes impacts to the existing channel of flow,
streambanks, adjacent riparian zone extending 50 ft. out from each bank, and any
existing drainage from the site to a creek or stream.)
Alternatives A and B have no effect because they do not encroach on a riparian
corridor.
Alternatives C and D have a negative effect because they encroach into the
riparian area of Twomile Canyon Creek on the northeast corner of Broadway and
Iris Avenue.
If potential impacts have been identified, please provide any of the following
information that is relevant to the project:
• A description of how the proposed project would avoid, minimize, or mitigate identified
impacts to habitat, vegetation, aquatic life, or water quality.
• A map showing the location of any streams, ditches and other water bodies on or near
the project site (Figure 25).
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Figure 25: Two mile Canyon Creek and Farmers Ditch on Iris Avenue
• A map showing the location of the 100-year flood, conveyance, and high hazard flood
zones relative to the project site (Figure 26).
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Figure 26: Iris Avenue 100-Year Floodplain, High Hazard, and Conveyance Zone
Wetlands
1. Describe any disturbance to or loss of a wetland on site that may result from the
project.
The project area includes wetlands of Elmers Twomile Canyon Creek. However, the
roadway is elevated above the wetlands and so each alternative has no effect for
disturbances.
All alternatives would need to receive a wetlands permit to be built.
If potential impacts have been identified, please provide any of the following
information that is relevant to the project:
• A description of how the proposed project would avoid, minimize, or mitigate identified
impacts.
• A map showing the location of any wetlands on or near the site. Identify both those
wetlands and buffer areas which are jurisdictional under city code (on the wetlands map
in our ordinance) and other wetlands pursuant to federal criteria (definitional) (Figure
27).
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Figure 27: Iris Avenue Wetlands
Geology and Soils
1. Describe any:
a. impacts to unique geologic or physical features;
b. geologic development constraints or effects to earth conditions or landslide, erosion, or
subsidence;
c. substantial changes in topography; or
d. changes in soil or fill material on the site that may result from the project.
Alternatives A and B have no effect because they can be implemented within the
existing roadway width and so make no changes to fill materials.
Alternatives C and D have a negative effect because each widen the roadway into
vegetated areas. This widening will change the fill material.
If potential impacts have been identified, please provide the following:
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• A description of how the proposed project would avoid, minimize, or mitigate identified
impacts.
• A map showing the location of any unique geologic or physical features, or hazardous
soil or geologic conditions on the site.
Water Quality
1. Describe any impacts to water quality that may result from any of the following:
a. Clearing, excavation, grading or other construction activities that will be involved with
the project;
Alternatives A and B have no effect on excavation, grading or other construction
activities because they can be implemented within the current roadway width.
Alternatives C and D will have a negative effect because they both require excavation
and grading or other construction activities. Alternative C has a greater negative effect
because it widens the roadway to the north and south. Alternative D has a negative
effect but only widens the roadway to the north.
b. Changes in the amount of hardscape (paving, cement, brick, or buildings) in the project
area;
Alternatives A and B have no effect to hardscape because they can be implemented
within the current roadway width with spot improvements to the five-foot existing
sidewalks. This means that hardscape will not be increased with either alternative and
existing planting area will generally remain unchanged.
Alternatives C and D widen the roadway and so increase hardscape and widen the
existing five-foot sidewalk to six-foot sidewalk on one (Alternative D) or both
(Alternative C) sides of the road. These changes will result in an increase in hardscape.
Alternatives C and D will require water quality mitigation with permanent best
management practices (BMPs), which result in these alternatives having no effect on
water quality.
c. Permanent changes in site ground features such as paved areas or changes in
topography;
Alternatives A and B have no effect on site ground features because they can be
implemented within the current roadway width.
Alternatives C and D will have a negative effect on site ground features because they
both require clearing, excavation and grading during construction. Alternative C has a
greater negative effect because it widens the roadway to the north and south.
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Alternative D has a negative effect because it widens the roadway to the north only.
Both alternatives would have negative effects because they each widen the existing five-
foot sidewalk to six-foot on one (Alternative D) or both (Alternative C) sides of the road.
d.Changes in the storm drainage from the site after project completion;
Alternatives A and B have no effect on storm drainage because they can be
implemented within the current roadway width and so do not increase runoff.
Alternatives C and D have a negative effect because they require the roadway to be
widened and widen the existing five-foot sidewalk to six-foot both on one (Alternative
D) or both (Alternative C) sides of the road. The increased hardscape of both
alternatives increases runoff and the need for storm sewer inlets.
e.Change in vegetation;
Alternatives A and B will have no effect on vegetation removal because they can be built
within the existing roadway width.
Alternatives C and D will have a negative effect on vegetation: Alternative C has the
greatest negative effect because it requires the roadway to be widened to the north and
south and so has the greatest vegetation removal; Alternative D has negative effect but
less than Alternative C because it widens the roadway to the north, only, and so does
not disturb vegetation to the south.
f.Change in pedestrian and vehicle traffic;
g.Potential pollution sources during and after construction (may include temporary or
permanent use or storage of petroleum products, fertilizers, pesticides, or herbicides).
2.Describe any pumping of groundwater that may be anticipated either during construction or
as a result of the project. If excavation or pumping is planned, what is known about
groundwater contamination in the surrounding area (1/4 mile in all directions from the
project) and the direction of groundwater flow?
All alternatives have no effect on groundwater pumping. During construction of the
recommended alternative, surface water runoff will be treated by installing Best
Management Practices (BMPs) according to the Colorado Storm Water Discharge Permit.
If potential impacts have been identified, please provide any of the following that is
relevant to the project:
•A description of how the proposed project would avoid, minimize, or mitigate impacts
to water quality.
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•Information from city water quality files and other sources (state oil inspector or the
CDPHE) on sites with soil and groundwater impacts within 1/4-mile radius of project or
site.
•If impacts to site are possible, either from past activities at site or from adjacent sites,
perform a Phase I Environmental Impact Assessment prior to further design of the
project.
•Groundwater levels from borings or temporary piezometers prior to proposed
dewatering or installation of drainage structures.
Air Quality
1.Describe potential short or long term impacts to air quality resulting from this project.
Distinguish between impacts from mobile sources (VMT/trips) and stationary sources (APEN
(report), HAPS (factories, refineries, boilers, power plants)).
All alternatives have a positive effect on air quality because they provide safer walking and
bicycling options along the corridor, which can reduce mobile source emissions.
Alternatives A and B provide a greater positive effect because they also provide space for
protected intersection elements, shorter crossing distances, and opportunity for refuge
islands at midblock crossings, creating safer and more comfortable crossings of Iris Avenue
as well.
Alternatives C and D only provide protected bike lanes and sidewalk improvements but no
safer and more comfortable crossings, and so have a smaller positive effect on Air Quality
than Alternatives A and B.
Emissions from construction equipment would have a short term effect on air quality during
construction. The effects of the emissions would be negligible because of the small number
of short term emission sources.
The manufacture and use of construction materials can produce short-term impacts to air
quality at the manufacture or construction site. The general types of construction and
construction materials are similar for all alternatives.
Resource Conservation
1.Describe potential changes in water use that may result from the project.
a.Estimate the indoor, outdoor (irrigation) and total daily water use for the facility.
b.Describe plans for minimizing water use on the site (Xeriscape landscaping, efficient
irrigation system).
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2. Describe potential increases or decreases in energy use that may result from the project.
a. Describe plans for minimizing energy use on the project or how energy conservation
measures will be incorporated into the building design.
b. Describe plans for using renewable energy sources on the project or how renewable
energy sources will be incorporated into the building design.
c. Describe how the project will be built to LEED standards.
3. Describe the potential for excess waste generation resulting from the project.
If potential impacts to waste generation have been identified, please describe plans for
recycling and waste minimization (deconstruction, reuse, recycling, green points).
Cultural/Historic Resources
1. Describe any impacts to:
a. a prehistoric or historic archaeological site;
b. a building or structure over fifty years of age;
c. a historic feature of the site such as an irrigation ditch; or
d. significant agricultural lands that may result from the project.
If potential impacts have been identified, please provide the following:
• A description of how the proposed project would avoid, minimize, or mitigate identified
impacts.
Visual Quality
1. Describe any effects on:
a. scenic vistas or views open to the public;
b. the aesthetics of a site open to public view; or
c. view corridors from the site to unique geologic or physical features
that may result from the project.
Safety
1. Describe any additional health hazards, odors, or exposure of people to radon that may
result from the project.
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2.Describe measures for the disposal of hazardous materials.
3.Describe any additional hazards that may result from the project. (Including risk of
explosion or the release of hazardous substances such as oil, pesticides, chemicals or
radiation)
If potential impacts have been identified, please provide the following:
•A description of how the proposed project would avoid, minimize, or mitigate identified
impacts during or after site construction through management of hazardous materials or
application of safety precautions.
Physiological Well-being
1.Describe the potential for exposure of people to excessive noise, light or glare caused by
any phase of the project (construction or operations).
Alternatives A and B have no effect on exposure to excessive noise, light or glare from
construction because they can be built within the existing roadway width and so are more
easily and quickly implemented.
Alternatives C and D have a negative effect on exposure to excessive noise, light or glare
from construction because they require roadway widening and so are more complex and
take more time to implement. The longer it takes to construct improvements, the greater
impacts will be to adjacent property owners and the traveling community.
Alternatives C and D have a negative effect on physiological well-being during construction,
because they require significant tree removals, and after implementation by moving the
existing curbs closer to adjacent properties and so increasing road noise for those homes.
2.Describe any increase in vibrations or odor that may result from the project.
If potential impacts have been identified, please provide the following:
•A description of how the proposed project would avoid, minimize, or mitigate identified
impacts.
Services
1.Describe any increased need for the following services as a result of the project:
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a. Water or sanitary sewer services
b. Storm sewer / Flood control features
c. Maintenance of pipes, culverts and manholes
d. Police services
Alternatives A and B provide a positive effect on police services because they moderate
speeds and crash potential by repurposing a vehicle lane and provide space at
intersections for protected intersection elements. Alternatives A and B have a positive
effect on day-to-day police services because they provide center turn lanes, which can
be used for day-to-day police emergency response. Alternative B improves disaster
emergency response because it provides a continuous two-way bike lane. The two-way
bike lane is wide enough to function as a dedicated fire response lane during a disaster
scenario. Roadway design features for the use of the center turn lane as a second
eastbound evacuation lane will continue to be coordinated with ODM, BPD, and BFRD.
Alternatives C and D are rated as having no effect because they provide limited positive
effect on police services.
Alternatives C and D maintain the current number of vehicle lanes and so do not
moderate speeds, reduce crash potential or address the common crash types. Both
alternatives provide protected bike lanes and sidewalk improvements but do not
provide space at intersections for protected intersection elements. Therefore, they are
less effective at decreasing the frequency and severity of crashes involving vulnerable
road users.
Alternatives C and D have no effect on day-to-day police emergency services because
they do not provide center turn lanes. Therefore, police vehicles must use vehicle lanes
which can be difficult to navigate around personal vehicles on the road.
Alternative D includes a two-way protected bike lane, but it is not continuous due to
right-of-way constraints near 16th Street. Because the two-way bike lane is
discontinuous, fire response does not have a dedicated fire response lane for the length
of the project.
e. Fire protection
Alternatives A and B have a positive effect on day-to-day fire protection services
because they include center turn lanes which provide dedicated space for fire response
vehicles.
Alternative B improves disaster emergency response because it provides a continuous
two-way bike lane. The two-way bike lane is wide enough to function as a dedicated fire
response lane during a disaster scenario.
Attachment A - Iris Ave Transportation Improvements Project
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Alternatives C and D have no effect on day-to-day fire protection services because they
maintain the current vehicle lanes, which can be difficult for fire response vehicles to
navigate around personal vehicles on the road.
Alternative D includes a two-way protected bike lane, but it is not continuous due to
right-of-way constraints near 16th Street. Because the two-way bike lane is
discontinuous, fire response does not have a dedicated fire response lane for the length
of the project.
f. Recreation or parks facilities
g. Libraries
h. Transportation improvements/traffic mitigation
Please refer to Project Specific Evaluation Results section for more detail on this
checklist question.
i. Parking
j. Affordable housing
k. Open space/urban open land
l. Power or energy use
m. Telecommunications
n. Health care/social services
o. Trash removal or recycling services
2. Describe any impacts to any of the above existing or planned city services or
department master plans as a result of this project. (e.g. budget, available parking,
planned use of the site, public access, automobile/pedestrian conflicts, views)
Special Populations
1. Describe any effects the project may have on the following special populations:
a. Persons with disabilities
b. Senior population
c. Children or Youth
All alternatives have a positive effect for persons with disabilities, senior population,
children and youth and sensitive populations, like school children attending
Columbine and Foothill elementary schools and people living with disabilities like
those living at Smart Home Imagine! because they each provide improved sidewalks,
Attachment A - Iris Ave Transportation Improvements Project
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protected bike lanes and Americans with Disabilities Act curb ramp compliance
work.
Alternatives A and B provide a greater positive effect than Alternatives C and D
because they repurpose a vehicle lane. Repurposing a lane provides space for
protected intersection elements at intersections and pedestrian refuge islands at
midblock crossings, which reduce the exposure of vulnerable users to vehicles.
Alternatives B and D provide a greater positive effect than Alternatives A and C
because they provide a two-way protected bike lane. The two-way facility better
serves all ages and abilities bicyclists because the additional width allows for passing
and side-by-side riding.
Therefore, Alternative B provides the greatest positive effect for special populations.
d. Restricted income persons
e. People of diverse backgrounds (including Latino and other immigrants)
Columbine Elementary school has high percentages of low income, Hispanic and
English Language Learner students. More than 60% of students attending
Columbine receive free or reduced lunch, 58.5% identify as Hispanic and more
than 40% of students are English Language Learners.
The Boulder Housing Partners Iris-Hawthorn affordable housing community
includes low income residents of diverse backgrounds.
Nationally, low income households are more likely to walk, bike or use transit to
reach their daily needs, and people of color are more at risk for crashes and severe
injury crashes.
All alternatives have a positive effect for low income individuals and people of
color because they each provide improved sidewalks, protected bike lanes and
Americans with Disabilities Act curb ramp compliance work.
Alternatives A and B provide a greater positive effect than Alternatives C and D
because they repurpose a vehicle lane. Repurposing a lane provides space for
protected intersection elements at intersections and pedestrian refuge islands at
midblock crossings, which reduce the exposure of vulnerable users to vehicles.
Therefore, Alternatives A and B provide a greater positive effect than Alternatives
C and D because A and B provide safer and more comfortable transportation
options for low income individuals and people of diverse backgrounds.
f. Sensitive Populations located near the project (e.g. adjacent neighborhoods or
property owners, schools, hospitals, nursing homes)
Attachment A - Iris Ave Transportation Improvements Project
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All alternatives have no effect on neighborhoods because traffic calming and
traffic management will be installed on specific parallel street segments when the
Iris Avenue project is implemented. These installations will address speeding
vehicles that divert to parallel streets today and potentially in the future as a result
of changes to Iris Avenue.
If potential impacts have been identified, please provide the following:
• A description of how the proposed project would avoid, minimize, or mitigate identified
impact.
• A description of how the proposed project would benefit special populations.
Economic Vitality
1. Describe how the project will enhance economic activity in the city or region or generate
economic opportunities?
2. Describe any potential impacts to:
a. businesses in the vicinity of the project (ROW, access or parking),
All alternatives have no effect on current economic activity because none will make
changes to vehicle lanes, and all will provide safer walking and biking connections to
the main economic activity centers on the corridor: Willow Springs and Safeway
shopping complexes at Iris Avenue and 28th Street.
All alternatives propose to make access changes to reduce conflicts and make
connections safer for everyone at the western most driveway to the Safeway
shopping complex. Changes would remove westbound left turns into the
westernmost driveway to the Safeway shopping complex on Iris Avenue due to the
crash history at this location. Westbound drivers can continue to access the
Safeway shopping complex from 28th Street.
b. employment,
c. retail sales or city revenue and how they might be mitigated.
Alternatives A and B have a positive effect on utilizing existing infrastructure
because they can be built within the existing roadway width.
Alternatives C and D have a negative effect on utilizing existing infrastructure
because they require roadway widening and so require additional infrastructure to
be completed.
Attachment A - Iris Ave Transportation Improvements Project
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Attachment D: Table of Mature Trees
DBH in inches
(Rounded) Preservation Code Mature Trees >6" Alt A Alt B Alt C Alt D
7 2 - Preserve if Possible 1
4 2 - Preserve if Possible 0
6 2 - Preserve if Possible 1
5 2 - Preserve if Possible 0
9 2 - Preserve if Possible 1 Impacted Impacted Impacted Impacted
21 2 - Preserve if Possible 1
10 2 - Preserve if Possible 1
2 2 - Preserve if Possible 0
2 2 - Preserve if Possible 0
2 2 - Preserve if Possible 0
10 3 - Ok to Remove and Replace 1
5 3 - Ok to Remove and Replace 0
3 2 - Preserve if Possible 0
2 2 - Preserve if Possible 0
3 2 - Preserve if Possible 0
2 3 - Ok to Remove and Replace 0
13 3 - Ok to Remove and Replace 1
9 3 - Ok to Remove and Replace 1
5 3 - Ok to Remove and Replace 0
9 3 - Ok to Remove and Replace 1
2 3 - Ok to Remove and Replace 0
5 3 - Ok to Remove and Replace 0
7 3 - Ok to Remove and Replace 1
3 3 - Ok to Remove and Replace 0
4 3 - Ok to Remove and Replace 0
9 3 - Ok to Remove and Replace 1
3 3 - Ok to Remove and Replace 0
14 3 - Ok to Remove and Replace 1
41 1 - High Priority for Preservation 1 Impacted
25 2 -Preserve if Possible 1 Impacted
1 3 - Ok to Remove and Replace 0 Impacted
1 3 - Ok to Remove and Replace 0 Impacted
3 3 - Ok to Remove and Replace 0 Impacted
10 3 - Ok to Remove and Replace 1
8 3 - Ok to Remove and Replace 1
Attachment A - Iris Ave Transportation Improvements Project
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2 3 - Ok to Remove and Replace 0 Impacted
3 3 - Ok to Remove and Replace 0 Impacted
7 3 - Ok to Remove and Replace 1 Impacted
6 3 - Ok to Remove and Replace 1 Impacted
5 3 - Ok to Remove and Replace 0 Impacted
9 3 - Ok to Remove and Replace 1
9 2 - Preserve if Possible 1 Impacted Impacted Impacted Impacted
9 2 - Preserve if Possible 1 Impacted Impacted Impacted Impacted
9 2 - Preserve if Possible 1 Impacted Impacted Impacted Impacted
7 2 - Preserve if Possible 1 Impacted Impacted Impacted Impacted
8 2 - Preserve if Possible 1 Impacted Impacted Impacted Impacted
11 1 - High Priority for Preservation 1
2 2 - Preserve if Possible 0
47 1 - High Priority for Preservation 1
7 2 - Preserve if Possible 1
5 2 - Preserve if Possible 0
3 2 - Preserve if Possible 0
2 2 - Preserve if Possible 0
2 2 - Preserve if Possible 0
2 2 - Preserve if Possible 0
2 2 - Preserve if Possible 0
10 1 - High Priority for Preservation 1
10 1 - High Priority for Preservation 1
9 1 - High Priority for Preservation 1
13 1 - High Priority for Preservation 1
2 3 - Ok to Remove and Replace 0
13 2 - Preserve if Possible 1
15 2 - Preserve if Possible 1
12 2 - Preserve if Possible 1 Impacted
11 2 - Preserve if Possible 1
6 2 - Preserve if Possible 1
16 2 - Preserve if Possible 1
3 3 - Ok to Remove and Replace 0
20 2 - Preserve if Possible 1 Impacted
10 2 - Preserve if Possible 1 Impacted
10 3 - Ok to Remove and Replace 1 Impacted
11 2 - Preserve if Possible 1 Impacted
14 2 - Preserve if Possible 1 Impacted
7 2 - Preserve if Possible 1 Impacted
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14 2 - Preserve if Possible 1 Impacted
2 2 - Preserve if Possible 0 Impacted
2 2 - Preserve if Possible 0 Impacted
2 2 - Preserve if Possible 0 Impacted
2 2 - Preserve if Possible 0 Impacted
2 2 - Preserve if Possible 0
20 1 - High Priority for Preservation 1 Impacted
19 1 - High Priority for Preservation 1 Impacted
2 2 - Preserve if Possible 0
1 2 - Preserve if Possible 0 Impacted Impacted
3 3 - Ok to Remove and Replace 0 Impacted Impacted
4 3 - Ok to Remove and Replace 0 Impacted Impacted
15 1 - High Priority for Preservation 1 Impacted Impacted
2 2 - Preserve if Possible 0 Impacted Impacted
16 1 - High Priority for Preservation 1 Impacted Impacted
11 1 - High Priority for Preservation 1 Impacted Impacted
33 1 - High Priority for Preservation 1 Impacted Impacted
17 1 - High Priority for Preservation 1 Impacted Impacted
13 1 - High Priority for Preservation 1 Impacted Impacted
2 3 - Ok to Remove and Replace 0 Impacted Impacted Impacted Impacted
7 2 - Preserve if Possible 1 Impacted Impacted Impacted Impacted
2 3 - Ok to Remove and Replace 0 Impacted Impacted Impacted Impacted
2 3 - Ok to Remove and Replace 0 Impacted Impacted Impacted Impacted
2 3 - Ok to Remove and Replace 0 Impacted Impacted Impacted Impacted
3 3 - Ok to Remove and Replace 0 Impacted Impacted Impacted Impacted
21 1- High Priority for Preservation 1
11 1- High Priority for Preservation 1
9 1- High Priority for Preservation 1
10 1- High Priority for Preservation 1
14 1- High Priority for Preservation 1
10 3 - Ok to Remove and Replace 1 Impacted Impacted
11 2 - Preserve if Possible 1 Impacted Impacted
11 2 - Preserve if Possible 1
12 2 - Preserve if Possible 1 Impacted Impacted
35 2 - Preserve if Possible 1 Impacted Impacted
4 Did not Evaluate 0
6 Did not Evaluate 1
5 Did not Evaluate 0
2 Did not Evaluate 0
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5 Behind Private Fence - Did not Evaluate 0
32 2 - Preserve if Possible 1 Impacted Impacted
19 1- High Priority for Preservation 1
7 3 - Ok to Remove and Replace 1
36 1- High Priority for Preservation 1
11 County Owned - Did Not Evaluate 1 Impacted
8 County Owned - Did Not Evaluate 1 Impacted Impacted
12 County Owned - Did Not Evaluate 1 Impacted Impacted
10 County Owned - Did Not Evaluate 1 Impacted
9 County Owned - Did Not Evaluate 1 Impacted Impacted
10 County Owned - Did Not Evaluate 1 Impacted
11 County Owned - Did Not Evaluate 1 Impacted Impacted
8 County Owned - Did Not Evaluate 1 Impacted Impacted
18 County Owned - Did Not Evaluate 1
18 County Owned - Did Not Evaluate 1
11 County Owned - Did Not Evaluate 1 Impacted Impacted
19 County Owned - Did Not Evaluate 1
16 County Owned - Did Not Evaluate 1 Impacted Impacted
18 3 - Ok to Remove and Replace 1 Impacted Impacted
2 2 - Preserve if Possible 0 Impacted Impacted
33 3 - Ok to Remove and Replace 1 Impacted Impacted
3 3 - Ok to Remove and Replace 0
25 2 - Preserve if Possible 1 Impacted
19 2 - Preserve if Possible 1 Impacted
14 1 - High Priority for Preservation 1 Impacted
28 1 - High Priority for Preservation 1 Impacted
2 2 - Preserve if Possible 0
2 2 - Preserve if Possible 0 Impacted Impacted
2 2 - Preserve if Possible 0 Impacted
2 2 - Preserve if Possible 0 Impacted
2 2 - Preserve if Possible 0 Impacted
2 2 - Preserve if Possible 0 Impacted
2 2 - Preserve if Possible 0 Impacted
2 2 - Preserve if Possible 0 Impacted
2 2 - Preserve if Possible 0 Impacted
18 4 - Removed 1
Attachment A - Iris Ave Transportation Improvements Project
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Summary of Table of Mature Trees
Option Alt A Summary Alt B Summary Alt C Summary Alt D Summary
Total Impacted Trees 12 12 71 43
Total Mature Trees
Impacted 7 7 43 32
Attachment A - Iris Ave Transportation Improvements Project
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hdrinc.com
August 27, 2024
Dear Lindsay Merz, PE,
Re: Iris Avenue Transportation Improvements Project – Floodplain Impacts of Alternatives
The purpose of this letter is to describe the overall impacts to the floodplain based on conceptual
alternatives presented to the City and the public during corridor alternatives evaluation of the Iris
Ave Project. This letter does not represent a final finding or include floodplain modeling. Those
activities will occur during later design phases.
ICON Engineering, Inc. is retained to provide detailed floodplain analysis of the preferred
alternative and will continue to support the project in the final design phases to complete detailed
floodplain analysis. The effective model for this area is from the 2015 Upper Goose Creek and
Twomile Canyon Creek Flood Mapping Study Update and shows that Iris Avenue acts as a
floodway moving stormwater west to east from Broadway to Elmer’s Two Mile Creek and Park.
In general, any impact to the floodplain, or any construction project within the floodplain will
trigger the need to study a design’s impact to the floodplain. All concepts considered for Iris Ave
will trigger a similar study. Any rise in water surface elevation must be contained within the City’s
Right-of-Way (ROW). Given the limited public ROW outside the floodplain today, this requirement
means that any rise in the floodplain elevation will make the project difficult to permit. However,
there are methods that can be used to negate rises in the floodplain, particularly over short
distances and for small potential rises. Without substantial roadway reconstruction, continuous
rises in the floodplain of any height would not be permitted within the project reach.
Thirteen Iris Ave concepts were initially considered and screened with eight criteria. One of these
criteria was “Likely impact to the floodplain”. If a concept impacted the floodplain with a likely rise,
those concepts were removed from further analysis. Any alternative that reduced the existing
roadway width would create a floodplain rise, and was therefore removed from additional
consideration. Any alternative that widened the roadway or kept it the same width as existing was
advanced for further review based on the floodplain criteria. Based on the full evaluation of the
eight criteria, four alternatives were brought to further corridor study and analysis. These
alternatives can be viewed on the next page.
Attachment A - Iris Ave Transportation Improvements Project
Community & Environmental Assessment Process (CEAP)Attachment E: Floodplain Memo
96 09.09.24 TAB Agenda 6 - Iris Ave CEAP
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Alternative A Alternative B
Alternative C Alternative D
Attachment A - Iris Ave Transportation Improvements Project
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For these four alternatives, ICON Engineering completed high level analysis of the impacts on the
floodplain. HDR and ICON determined that there are implementable engineering solutions for any
potential small rise that appeared in the analysis and that floodplain permitting would likely be
achieved. Given that Iris Ave is a floodway, there are risks in this approach. Floodplain modeling
will have to be completed in detail to determine final water surface elevations and all rises must
either be removed through design changes or contained within City ROW. The following is a list
of some risks and possible mitigation measures.
Risk Mitigation Measure or Strategy
Updated existing conditions modeling
adds detail to the model that was
lacking before and shows local rises
in the pre-project conditions vs. the
existing conditions.
Work on public messaging that clarifies any existing
conditions water surface rises due to additional detail
in the hydraulic model.
Bicycle lane raised protective
elements such as curbs, low walls,
and posts may result in a rise.
Use lower profile elements down to a minimum of
striping, use smoother elements with less roughness,
spot lowering of sidewalk, spot lowering of the
roadway crown, provide additional storm drain
conveyance, purchase ROW to contain rise.
New amenities such as trees,
benches, and transit shelters may
result in a rise.
Move amenities outside the floodway, use lower
profile elements such as transit shelters with no walls
or half-height walls, spot lowering of sidewalk, spot
lowering of the roadway crown, provide additional
storm drain conveyance, purchase ROW to contain
rise.
While initial floodplain analysis is based on assumptions, existing analysis does not show
dramatic floodplain changes and a selection of the above tools and creative engineering are
anticipated to produce a no-rise situation for any of the four listed Alternatives.
Sincerely,
HDR Project Manager Charlie Dyrsten, PE ICON Project Manager Brian LeDoux, PE, CFM
Attachment A - Iris Ave Transportation Improvements Project
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Attachment F: Conceptual Alternatives with Project-Specific Evaluation Criteria Applied
Each alternative was rated using the following scale:
Scoring: -5 significantly poor/worse, -3 poor/worse -1 slightly poor/worse, 0 neutral, 1 slightly good/better, 3 good/better, 5 significantly good/better.
Attachment A - Iris Ave Transportation Improvements Project
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