Cowlitz Falls North Shore Collector
反,Wash.
Best Project

Owner/Lead Design Firm/Civil Engineer:Tacoma Power
General Contractor:The Natt McDougall Co.
Structural Engineer:CG Engineering Inc.
MEP Engineer:R2 Resource Consultants Inc.
电气工程师：Black & Veatch

Located in the Cascade mountain range, Cowlitz Falls Dam sits in a narrow canyon across the Cowlitz River, where it has served as a power station and fish collection facility for 24 years. The $32.3-million North Shore Collector project upgraded the salmon runs, improving fish passage returns to 95% from 50%.

The project cut two penetrations through the dam: the fish entrance’s 18-ft by 26-ft opening and the 10-ft by 10-ft cut for the reservoir pumpback system. Crews installed about 20 pin piles, or small-diameter pipes, to support the existing fish facility during construction. The new facility also required a 60-ft-tall soldier pile wall with tiebacks and a foundation supported by drilled shafts.

The dam, powerhouse and fish facilities also needed to operate during construction.

The project team designed a 45-ft-deep sheet pile cofferdam to protect the area while crews built the two penetrations. Crews drilled perimeter holes, then cut through with diamond-bladed wire saws before breaking the concrete. This painstaking process helped limit vibrations beneath the functioning power station, says Natt McDougall, president of general contractor The Natt McDougall Co.

“你有一个结构设施，你在突破混凝土中，”麦克杜尔说。“你努力不要造成太多的嘎嘎声并脱掉东西。”该团队将北岸收藏家塞进，沿着现有设施，而不断扰乱持续运营。