Projects - Infrastructures
Trails and Paths: Pedestrian Underpasses

Bear Creek Underpass at Foothills Parkway and Arapahoe Avenue
Boulder, Colorado

The intersection of Foothills Parkway (SH 157) and Arapahoe Avenue (SH 7) is the busiest one in Boulder with an ADT of 80,000. This intersection had become extremely congested in peak hours due to the large number of vehicular movements. Bear Creek, which crosses beneath Arapahoe Avenue just east of Foothills Parkway, was constrained by the existing multi-cell box culvert and required additional flow area to reduce 100-year flood elevations. LORIS provided full-service civil and structural engineering for the modification of this intersection and drainage way. Our design incorporated a three-lane left-turn movement from westbound Arapahoe onto Foothills Parkway. We also provided bicycle lanes, bus jump lanes, and additional capacity for right turn lanes.

In order to accommodate the roadway widening and construction phasing, LORIS widened the existing concrete box culvert. Additional flow capacity was achieved by adding a new concrete box culvert adjacent to the existing multi-cell box culvert. This new box culvert is also used as a pedestrian and bicycle underpass of Arapahoe Avenue. The project design also remediated poor roadway drainage at the intersection and the relocation of sewer lines. Prairie dog colonies, located in three quadrants of the intersection, provided one of the first tests of the City of Boulder's new minimal impact policy towards prairie dogs. Prairie dog coteries were identified and fully relocated on site where necessary. Wetland mitigation according to the City's strict wetland mitigation policy was also required. The final construction cost of this project was $6 million.

Client:  City of Boulder