The project required drill and blast construction of twin 30-ft ID by 95-ft deep intake shafts through karstic limestone and shale.
The Beaver Water District Intake Expansion project in Lowell, AK, on Beaver Lake has to be one of the most challenging trenchless projects ever undertaken.
Four 60-in. diameter microtunneled pipelines were driven into the lake from each intake shaft, using an Akkerman microtunneling machine fitted with a rock head (triple and double disc cutters) for a total of eight intake pipelines, at different elevations. Underwater retrieval of the Akkerman machine was required after each of the eight intake microtunnels was completed. An additional 60-inc. interconnector microtunnel was driven to connect the two intake shafts. All intake pipelines were steel, coated and lined with epoxy and Powercrete, with Permalok joints.
The new microtunneled intake pipelines allowed the Beaver Water District to triple its water supply from 80 to 220 mgd.