TRILBY ROAD/FOSSIL CREEK FLOOD CONTROL DISTRICT

Fort Collins, Colorado

Lyman Henn provided geotechnical and tunnel design services for this project, which involves multiple box culvert crossings beneath Trilby Road and two 10-ft-diameter tunnels beneath a UPRR embankment. A field investigation program including test borings and geophysics was conducted to characterize subsurface conditions, which consisted of cohesive alluvium overlying claystone bedrock. The tunnel crossing beneath the railroad embankment is a challenging aspect of the project due to a buried trestle bridge located inside the embankment at an unknown location. The tunnel will be constructed using a open face shield and hand spades and small excavation equipment. Project deliverables included a geotechnical and tunneling design report, alternatives analysis, technical specifications, tunnel detail drawings, and an estimate of probable construction cost.