7210-21 - Preliminary Design Crossings:Kenosha Road - Coal Creek & State Hwy 7 - Dry Creek

Purpose/Background
Boulder County is seeking a qualified Civil Engineering firm to develop preliminary designs for two bridge replacements to make the crossings more resistant to flooding impacts and to make the cross-sections consistent with recent planning efforts. The scope of work and requirements are unique for each project. Each project will be managed individually, with its own budget, under a single contract awarded to one consulting firm. The two locations and brief scope descriptions are as follows:
 

• State Highway 7 (Arapahoe Road) at Dry Creek (CDOT Bridge #D-16-BW): The Boulder County Floodplain Management and Transportation System Resilience Study showed that this location would cause extreme negative impacts if damaged in a flood event. Also, the recently completed CO 7 PEL recommends a wider cross-section across the bridge for multimodal improvements. Lastly, the bridge has one of the lowest structural sufficiency ratings on CO 7 between Boulder and Brighton. A hydraulic analysis is expected to determine size and clearance height necessary to accommodate future flooding. Work may include a structure selection report.

• Kenosha Road at Coal Creek: The alignment of Coal Creek as it crosses Kenosha Road has fewer constraints, with the majority of the flow issues north of the road where the creek flows underneath the Martha Mathews Ditch. As such, alternative alignments for both the road and creek will be considered as part of the design process. A hydraulic analysis will be needed to determine size and clearance of the Kenosha Road crossing of Coal Creek. Creek mitigation alternatives could also be analyzed up- and down-stream of the crossing to accommodate future flooding.