Dr. Stark Visits El Toro Water Reservoir Project in Mission Viejo, California

On March 2, 2023, Tim Stark visited the replacement liner and floating cover system for the El Toro Reservoir in Mission Viejo, California. This is a joint reservoir project between three water districts that is providing emergency water supply, storage, and cost savings to south Orange County water customers. The reservoir holds 275 million gallons (1.04 billion liters) of potable water.  The reservoir was originally constructed in the 1960’s as an open reservoir.  The first geomembrane floating cover was installed in the early 1980’s. In 2001 a composite geosynthetic liner and reinforced polypropylene floating cover was installed.  After 20 years, the existing liner is being augmented with a new 60 mil (1.5 mm) CSPE geomembrane that is being placed on top of the existing 70 mil (1.8 mm) reinforced polypropylene (rPP) geomembrane, which is still in intimate contact with the underlying subgrade (see Figure1). The resulting bottom liner system is shown in Figure 2.  

The main impetus for the project is replacing the 45 mil (1.1 mm) rPP floating cover system, which had exceeded its service life. The old cover system is being discarded and replaced with a 45 mil (1.1 mm) CSPE geomembrane based floating cover based on a requirement for an extended 30 year weathering warranty and long term material history. The project involves installing about1.1 million square feet (102,000 square meters) of geomembrane for the bottom liner system and about 1.15 million square feet (107,000 square meters) for the floating cover system as well as updating the reservoir interior valves, site drainage piping, and electrical upgrades. Douglas Hilts of Hilts Consulting Group is the design engineer, and the Layfield Group is the fabricator and installer of the liner and floating cover system geosynthetics. This project illustrates the advantages of factory fabricated panels because one panel extends from the top of the reservoir to the floor down slope over 325 feet where it is seamed with floor panels.

Dr. Stark hopes to visit the facilities of all FGI members to better understand each member’s business and how the FGI can provide additional benefit to them. The FGI is an exciting advancement in the geomembrane industry and allows the Institute to focus on all geomembranes that can be factory fabricated.

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