The original specification for the primary geosynthetic barrier system (geomembrane) called for the use of a threeply 60 mil (1.5 mm) chlorosulfonated polyethylene (CSPE) geomembrane. During the time of construction, there were challenges in the supply of CSPE materials, and the lining was changed to a flexible polypropylene material to get both the lining and the cover materials delivered on time. While fRPP as a geomembrane material had encountered performance problems in potable-water applications as a floating cover, as a liner it would not be exposed to UV light and was determined to be acceptable. The final liner material selected was a threeply fabric-reinforced flexible polypropylene geomembrane (fRPP) 60 mil (1.5 mm) thick. The fRPP materials for the liner were prefabricated prior to installation according to a detailed panel layout. All seams were welded using a 3-inchwide (7.6 cm) wedge welder that bonded the materials edge to edge without leaving a flap of material at the seams. To reduce creases in the lining material, the fabricator on this project used a 36-foot-wide (11 m) winder to create rolls of fabricated materials that did not require any folds in the material. There is some thought that creases in fRPP materials can lead to stress concentrations that can initiate failures. This is especially problematic in thicker materials such as a 60 mil (1.5 mm) material. By fabricating without folds, this particular fabricator was eliminating this area of potential problems. The liner was anchored to the perimeter of the containment using a concrete stub wall and steel battens. This concrete wall went around the entire perimeter. Once the lining system was in place, the entire area was surveyed using an electrical leak location method. Weather problems prevented the reservoir from being installed in a straight-forward fashion and FIGURE 3 Earth bench located half way down the slope provided an important work and staging area for the installation crew Figure 4 View looking down steep slope of floating cover under construction including steps and vents GeosyntheticsMagazine.com 29http://www.GeosyntheticsMagazine.com