Alvin Wirtz Dam Post-Tensioned Anchoring Marble Falls, Texas Back to Project List Post-Tensioned Rock & Soil Anchors Drilling The installation of 78-multi-strand, high-capacity tendon anchors, required the construction of special structural steel work platforms. Project Overview: The Alvin Wirtz Dam was upgraded for stabilization against overturning due to overtopping. The upgrade consisted of anchoring the concrete dam structure with high-capacity tendon anchors to the underlying granite bedrock. The post-tensioning design consisted of 78 multi-strand tendons, ranging in length from 57 to 148 feet. Tendon anchors were placed in the upper portion of the ogee-shaped rollway structures. Tendon holes were drilled with percussive down-the-hole hammers. Holes for right and middle bulkheads were drilled vertical, while those in the rollway bays were drilled on an inclination of 21°. Layne GeoConstruction utilized drilling equipment specially designed to operate in restrictive areas with limited headroom.     Value of Work Performed: $2,300,000 Project Duration: 12 months Project Completion Date: October 1999 Project Reference: Project Owner Lower Colorado River Authority