Layfield USA Corp. announced the completion of the supply and installation of a chlorosulfonated polyethylene (CSPE) liner and floating cover system as part of a refurbishing and upgrade project for Pittsburgh Water & Sewer Authority’s (PWSA) Lanpher Reservoir. The Lanpher Reservoir is a double reservoir, potable water storage system (East and West reservoirs) with a total capacity of 146 million gallons (553 million L). The reservoir has a long history and was originally constructed in 1913. It was one of the first water reservoirs in the region using chlorine for disinfectant.
This reservoir system upgrade included concrete restoration repairs and a newly designed liner and floating cover system. The material selected for the new geomembrane liner and floating cover was a 60-mil (1.5-mm) thick reinforced CSPE product.
The installation was performed over a two-year period and faced a number of site challenges including unseasonably wet and cold weather conditions. The two reservoirs were also quite deep at 40 feet (12.2 m) with a steep 2:1 slope creating challenges with the material deployment and material welding during installation. The project scope also included demolishing and removal of an older liner and cover material.
To help expedite the installation as a result of the unseasonable wet weather conditions, Layfield relied on using larger prefabricated factory-made panels, which significantly reduced the amount of field welding required on-site. In total, the project included the installation of 1,600,000 square feet (148,644 m2) of 60-mil (1.5-mm) reinforced grade CSPE liner and cover material. This included 900,000 square feet (83,612 m2) in the West reservoir and 700,000 square feet (65,032 m2) in the East reservoir. The floating cover was mechanically anchored to a concrete perimeter edge located at the top of both reservoirs.
Floating covers are designed to eliminate evaporation and to protect water from outside debris and contamination. Open top reservoirs with floating covers are one of the most economical methods to store large quantities of water. They can also help to reduce water treatment costs including the quantity of disinfectant required in the treatment process.
CSPE was originally developed as a geomembrane in the mid-1970s for municipal potable water storage in the United States. Over the past 45 years, it has been used extensively for municipal potable water and wastewater storage applications and in the mining industry for process water containment applications. CSPE is a specialized synthetic rubber material and noted for its excellent ultraviolet (UV) light resistance properties, flexibility and chemical resistance. During the past 45 years, it has become highly recognized for its long-term performance as a floating cover material for potable water storage applications. This results from CSPE’s proven resistance to chlorine and other disinfectants used in water treatment, and the material’s excellent UV resistance properties. The material is also NSF 61 tested and certified, ensuring its ongoing safe use for drinking water applications in North America.
Brian Fraser, vice president of Layfield Geosynthetics, confirmed all project stakeholders involved were satisfied with the quality of the installation and materials selected. He concluded there are a number of alternative liner materials being promoted today for use in floating covers; however, PWSA made the decision to invest in one of the best quality materials available, helping to ensure the long-term protection of Pittsburgh water and providing proven performance value to the citizens of Pittsburgh.