Rehabilitation of the Rawah Ditch Tunnels - NAT2024

The Rawah Ditch is a mountainous water supply diversion which supplies Larimer County, Colorado with water since 1903. The ditch includes two historic tunnels excavated by drill and blast through a gneissic rock buttress. Both rock tunnels were failing with annual convergence. After a snowshoe-accessed 􀂿eld investigation, 􀂿nite element modeling, and an alternatives analysis, a 􀀘􀀗􀀅 diameter 􀀫D􀀳E pipe was inserted within each tunnel and the annulus 􀂿lled. The pro􀁍ect was implemented in an Alternative Delivery contract lasting 􀂿ve months from 􀂿eld investigation through procurement and construction.