An Innovative Approach with Granite Block-Mud Mountain Dam 9-Foot Tunnel Rearmoring Project

摘要

Mud Mountain Dam near the base of Mount Rainier includes two tunnels. One of the tunnels has required ongoing invert maintenance due to the passing of high sediment loads. The United States Army Corps of Engineers (USACE) awarded the design-build contract to rehabilitate the tunnel to Garney Construction teamed with ILF Consultants and Golder Associates. Though originally awarded the project for their mechanically anchored steel armor plating design, the team provided the USACE with a value engineering change proposal (VECP) of natural granite blocks. The granite block design provides an increased design life, lower cost, and shorter construction schedule, with construction beginning in July 2017. This paper discusses details and challenges of the VECP from design through initial construction.