More than 21 acres of geomembrane help revive Pebble Beach’s Forest Lake Reservoir.
Originally constructed in the late 19th century, a reservoir near a scenic stretch of California coastline underwent a dramatic transformation last year, and is now poised to serve the irrigation needs of the 21st century Pebble Beach community.
Located on California’s beautiful Monterey Peninsula, the Forest Lake Reservoir was designated for rehabilitation to retain recycled water by the Pebble Beach Community Services District. Nonpotable, recycled water from the reservoir will be used to irrigate some of the most prestigious names in golf, including prominent PGA tour venues Pebble Beach, Spyglass Hill, and Poppy Hills, plus five other courses and recreational green space on the peninsula.
Built in 1887, the Forest Lake Reservoir served the area’s water needs well into the 20th century. But by the 1980s, its use was discontinued and it sat dry and unused for nearly 15 years.
In 1998, the Pebble Beach Community Services District (PBCSD) purchased the reservoir from the California-American Water Co. (Cal-Am). The goal was to rehabilitate the entire site, including improvements constructed to the embankments and the reservoir itself, to meet state requirements for use of recycled water.
Mike Niccum, district engineer with the PBCSD, stated the need: “On some summer days, the [area] golf courses require up to 3 million gallons of water.”
He said the objective is for the reservoir to accumulate and store water through the winter months, when irrigation is generally not needed for Pebble Beach’s golf courses and other green spaces. The recycled water is intended for irrigation on the area’s courses and parks later in the year, especially during dry summer and autumn months.
As designed and completed, the Forest Lake Reservoir will provide 325-acre-ft. of storage capacity. It will fill during the winter when there is excess production at the Carmel Area Wastewater District’s treatment plant. Stored recycled water will be used during dry months when the irrigation demands exceed the production, thereby further reducing the use of potable water.
The Forest Lake Reservoir project was completed and ready to refill with recycled water from the Carmel Wastewater Plant in January 2006. However, production of improved, higher-quality reclaimed water is not expected to be available for Monterey Peninsula golf courses and parklands until the fall of 2007 when the Carmel Area Wastewater District microfiltration/reverse-osmosis treatment facilities are fully functional.
The design of the reservoir rejuvenation project included a number of environmental sensitivities and engineering challenges. In particular, the California Department of Water Resources, Division of Safety of Dams, was concerned with stability issues in the event that sufficient quantities of surface water penetrated and weakened the earthen embankment. As a result, the project was subject to stringent design and permit requirements. Following a similar rehabilitation design in the Los Angeles area, the project specified the use of a high-performance, ANSI NSF #61-certified, 5-ply scrim-reinforced Hypalon geomembrane with a functional exposed service life of 25 years.
The Layfield Group completed both the fabrication and the installation of 950,000 ft.2 (21.8 acres) of the specially produced, tan-colored geomembrane and also the black geosynthetic composite drainage system under that membrane.
The geomembrane is a chlorosulfonated polyethylene (CSPE) material manufactured by Burke Industries of San Jose, Calif. The geomembrane material is produced from Dupont Dow’s Performance Elastomers. The material offers excellent UV and physical properties, including high tensile strengths and puncture resistance. With more than 40 years of application experience, it is a proven material often used in water-management applications for floating covers and geomembranes.
The scope of the Forest Lake Reservoir project included prefabricating the geomembrane at the Layfield fabrication plant in Hollister, Calif. Based on the irregular shape of the reservoir, a pre-designed panel layout was completed to minimize material waste. This process included prefabricating approximately 175 34-ft.-wide panels in lengths up to 200 ft. The specification also required that the panels be factory-rolled without folds.
The plant fabrication on the geomembrane started in early July 2005 and was strategically sequenced with the liner installation that began in August 2005. One logistics plus: Layfield’s Hollister fabrication facility is only about 45 miles from the Forest Lake Reservoir.
Layfield’s construction group, based in Santee, Calif., installed the geomembrane system. In addition to the 950,000 ft.2 of 65-mil, 5-ply geomembrane and the geosynthetic drainage composite under it, the project required 3,300 lineal ft. of perimeter mechanical anchorage and the use of specialized cap strips to reinforce all cross seams.
In addition to rigorous destructive and non-destructive QC/QA requirements for field and factory seams, the project also included an electrical leak location test over the entire installed liner. The prefabrication of the geomembrane allowed the majority of the seaming work to be completed under controlled welding conditions in the Hollister plant, which reduced the amount of field welding and overall installation time.
This high-profile and environmentally sensitive project was successfully supplied on time and within budget. According to Jon Feenstra, Layfield project manager, the success of the overall project was to a large degree a testament to its fine design and the professionalism and cooperation of all stakeholders involved with the project.