Public Works Specialty Structures

Location: 36932 S.E. Green River Headworks Road, Ravensdale

Owner/developer: City of Tacoma

Project team: RCI Construction Group, general and concrete contractor; R.W. Beck, structural engineer; Miles Sand & Gravel, ready-mix supplier

The project involved raising the 152-foot diversion dam by 6.5 feet so that Tacoma Water could increase its capacity in northern Pierce and southern King counties. It also involved construction of a new intake structure with associated control gates and trash rack.

A traveling debris screen was built downstream of the dam.

A heavy forming system was used to raise the 1920 dam. Since the nearest ready-mix concrete plant was too far away, a portable batch plant was built about a half-mile from the project. The batch plant had to be close by so that the temperature of the concrete could be controlled. Flyash was included in the concrete mix to also control heat created by hydration. On hot days, crushed ice was used in the batching process to further control temperature.

A traveling debris screen was constructed downstream of the dam along with a fish screen facility. Also, a fish ladder and holding and sorting structure were built to trap fish for transportation upstream to spawn.