Carlton Engineering provided rehabilitation engineering services for Utica Power Authority in the restoration of Flume 14, which was destroyed by the Darby Fire on September 5, 2001. The 3/4 mile flume is part of the Utica Hydroelectric Project which is the sole source of water supply for about 9,000 residents in Calaveras County. The system also includes two power plants that generate 5 megawatts of electricity daily. Located on steep terrain, this flume requires substantial site-specific engineering to properly support the wood and steel structure.

While performing the geotechnical studies and structural design, Carlton Engineering teamed with Kessler & Associates to design a replacement project that met the current design criteria of the FERC and also preserved the historical look of the flume. Built in the Sierras in 1849 for mining operation, the flume, which traverses along a steep canyon wall overlooking the Stanislaus River, is considered an outstanding example of early water conveyance architecture and engineering.

The FERC and USFS required engineering plans to address the slope and foundation stability for the replacement project. Carlton’s updates to the flume focused on the foundation system and included replacing wooden mud block footings with concrete cast in place foundations as well as fabricating and constructing long-span steel framing including girders supported on bents as required to span over unstable slope areas. Scaling of the steep rocky slope above the flume was necessary to prevent hazardous rock fall during construction and operation. Rock bolting was incorporated to stabilize foundations cast on the steep slopes.