Project Description
When installed in the 1970's, the downstream channel was realigned and channelized. Subsequently, a rock apron spanning the channel had been placed below the culvert outlet. A fish passage assessment conducted in 1999 found the sloping rock apron created a complete barrier to juvenile salmonids and a low-flow barrier to larger fish. The original culvert also had inadequate flood capacity and was in poor condition, with the bottom rusted-through.

An embedded 16 ft (4.9 m) diameter culvert was selected as the replacement crossing. The new culvert is designed to pass a 100-year flood at Headwater-to-Diameter ratio (HW/D) of 0.6 and is 145 % wider than the upstream bankfull channel. The appropriate slope and elevation for constructing the streambed within the culvert was determined from a 450 ft (137 m) long channel profile. Since the road was closed and no traffic bypass was needed during construction, the project took only four weeks to complete.

This project experienced many construction challenges. Although originally designed to be embedded 6 ft (1.8 m), problems with buried utilities, groundwater, and slope stability during excavation resulted in only embedding the culvert approximately 2.5 ft (0.9 m).