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Publicly owned street trees are a valued asset within the City of Boulder due to their aesthetic qualities and positive effects on urban temperatures and carbon dioxide capture. They also provide shade, wildlife habitat, and soil stabilization among other benefits
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.
| Alternative | Estimated Tree Removals Expected | Explanation |
|---|---|---|
| A, B | 10-12 trees (~8%) | Improve sightlines |
| C | 69-75 trees (~46-50%) | Moves north and south curbs impacting trees on both sides |
| D | 43-50 trees (~29-32%) | Moves only the north curb impacting trees on north side only |
Full cost estimates will not be developed until later in the design process. High-level estimating determined that Aternatives C & D are approximately 3x to 4x more costly than Alternatives A & B.
Reconstruction of the curbs to widen the roadway includes utility relocations, floodplain mitigation treatments, tree removals, and easement acquisition, each requiring permitting and additional time to design and construct.
The Baseline Road Transportation Safety Project (approx $5 million), is a nimble, cost-effective approach to the Core Arterial Network that uses existing roadway space instead of widening the street minimizing additional infrastructure maintenance needs. Alternatives A & B follow a similar approach.
| Alternatives | Relative Cost | Explanation |
|---|---|---|
| A & B | $ | Uses existing roadway |
| C & D | $$$-$$$$ | Relocates curbs to widen roadway, requires relocation of utilities, floodplain mitigation treatments, tree removals, easement acquisitions |
As the project moves forward from concept development into design and construction, the city will pursue grant funding to help offset the costs and the need to draw on city funds.
| Alternatives | Relative Amount of Time Needed to Implement |
|---|---|
| A & B | 🕔 |
| C & D | 🕔🕔🕔 to 🕔🕔🕔🕔 |
Construction items and costs are paid for by the hour, day, or overall project length.
Time to procure materials and construct an alternative affects overall construction costs.
Alternatives C & D will take approximately 3 to 4 times longer to construct than Alternatives A & B, adding a significant amount to overall construction costs.
The longer it takes to procure materials and construct improvements, the more costly construction will be, and the greater impacts will be to adjacent property owners and the community (temporary traffic control/detours, noise, etc.).
