flows through a 1-foot (300-mm) gravel drainage layer between the old waste and the soil-reinforced layer. Soil-reinforced layer A 1.8-foot (550-mm) thick soil-reinforced layer is required to have a uniform load distribution over the old waste mass and limit the differential settlements. It is composed of: * Two layers of PVA reinforcement geosynthetic with an ultimate tensile strength of 2,570 pounds-force per inch (450 kN/m) and a maximum elongation of 6% installed perpendicularly at two different levels to fully mobilize the interface friction angles. The overlaps are calculated to ensure continuity of the reinforcement. * Incinerator bottom ash material available on-site. Numerous analyses have been carried out on the bottom ash material to characterize its physical, mechanical and chemical properties (Table 2). It has been found suitable as a backfill material. The pH, which may exceed 10, has been considered when selecting the reinforcement geosynthetic. PVA material has been proven to be more adapted for that range of pH. Leachate barrier system The leachate barrier system required by the French regulation is implemented on top of the soil-reinforced layer. It is composed of (from bottom to top): * A clayey layer 3-foot (0.9-m) thick with a hydraulic conductivity inferior to 1 × 10-9 m/s, and a geosynthetic clay liner (GCL) * An 80-mil (2-mm) HDPE geomembrane protected by a nonwoven geotextile * A gravel drainage layer 1.6-feet (0.5m) thick The barrier system allows the leachate generated in the new cell to be collected separately with dedicated collection wells. The slope of the bottom cell has been increased to 3% in the drainage direction to ensure a remaining longterm slope of 1% after the maximum expected settlements. Geosynthetic installation To limit overlaps, simplify the installation and ensure the continuity of the reinforcement, rolls with specific lengths have been produced. The length of the product was 395 feet (120 m). Handling was achieved using mechanical shovels. GEOSTAR Advanced Geomembrane Welders GEOSTAR with LQS - Automatic Data Acquisition, Enhanced QC/QA for Field Streaming, Integrated Wi-Fi and GPS for easy data transfer www.leister.com We know how. www.GeosyntheticsMagazine.com 29http://www.leister.com http://www.GeosyntheticsMagazine.com