Working together with the San Francisco Public Utilities Commission / Hetch Hetchy Water and Power Division, Towill, Inc. designed and installed a survey monitoring program on the Kirkwood Powerhouse and Penstock at the Tuolumne River in Yosemite Park.
The penstock is a nine foot diameter pipe that has a vertical fall of over 2,000 feet and is at an angle of up to 75 degrees in the Tuolumne River Canyon. Towill worked with mountain climbing experts (Ropeworks) to safely rappel the mountainside and establish working platforms at each penstock anchor block. The monitoring system includes the installation of dozens of high precision survey reflector mounts on the penstock and several instrumentation mounts on the powerhouse building and at other areas near the structure. The program is designed to measure movements at the mm level, and proper geodetic surveying principles are rigorously applied.