This project involved constructing a fish passage tunnel through an existing earthen dam. An approximately 1200 foot long x 7 foot diameter tunnel was bored from the downstream side of the Cle Elum dam to an existing secant pile coffer dam located on the upstream side. The tunnel was initially lined with a steel plate shoring system and a cast in place concrete final liner was installed after the tunnel boring was complete. The entrance to the tunnel included a shaped concrete transition and training wall that was connected to a concrete helix chamber in a follow on contract. A concrete equipment access shaft was constructed at the tunnel outlet portal. The nearest ready mix supplier to the site was located about 1 hour away which necessitated using set retarder in the concrete mix. Once onsite the concrete was pumped the 1200 lineal feet of the tunnel using steel slickline to the point of discharge. Furthermore much of the concrete was placed during the winter months with extreme cold temperatures. All of these constructability challenges were successfully overcome by meticulously tailoring the mix design and carefully monitoring the properties during the placing and curing operations.