Design and Use of Floating Covers to Prevent Mixing of Rain Water and Leachate in Collection Ponds

This paper describes the use of a flexible membrane cover to prevent the introduction of rain water into landfill leachate collection ponds in areas that experience high annual amounts of rainfall to reduce overall operation cost related to the treatment and disposal of the leachate. The project involves the Olympic View Sanitary Landfill which has a leachate pond with a capacity of 8,990,353 liters (2,375,000 gallons). The pond has a 4,886 s.m. (52,598 s.f.) surface area and experiences an average annual precipitation of 1,369 millimeters (53.9”). This paper discusses membrane material selection and testing, overall design requirements, necessity to accommodate existing equipment, floating cover and accessory fabrication methods, and installation methods used to overcome the restriction of maintaining leachate pond service during the project. This approach to covering leachate ponds has benefits that may be realized on other installations and it can be adapted for methane gas collection or emissions and odor control as well.