Design, Construction, and Monitoring of the Upstream Geomembrane Facing System for Olivenhain RCC Dam

The Olivenhain Dam is the first RCC gravity dam permitted by the state of California and, with a height of 318 feet (97 meters) and RCC volume of 1.44 million cubic yards (1.1 million cubic meters), is the tallest RCC dam in the United States. The primary design objective is for the dam to survive a large seismic event and remain fully operational. In order to meet this design criteria, a flexible PVC geomembrane upstream facing system was selected for installation over the entire upstream face. This represents the largest geomembrane system (412,150 square feet) ever installed on a dam. The paper discusses the selection and design of the upstream facing system for Olivenhain Dam. The selection process included evaluating 16 different upstream facing systems that have been used worldwide. The geomembrane system was determined to be the highest rated upstream facing system based on a number of criteria including seismic survivability, seepage control, constructability, appearance, durability and cost. The paper describes and shows photos of the various elements of the waterproofing geomembrane system during construction. The two major changes during construction were scheduling of the membrane installation and the addition of a compartment seal above the plinth which will be highlighted in addition to other construction details. Finally, the paper will present seepage results from monitoring during the filling of the reservoir. At the time of this abstract, the reservoir is 63% full by height (201 feet of the 318 foot dam height) and the seepage from the membrane system is 2.0 gpm which is less than 10 % of the acceptance criteria of 35 gpm. 15 pp., 2 tables, 12 figures, 6 references.