HDPE Side Slope Riser Leachate Extraction System. The slope riser allows leachate removal from the landfill cell without a breach of the geosynthetic lining system. The riser serves as a conduit pipe for inserting and removing submersible pumps and leachate discharge hoses so liquids can be sent from the top of the slope via forcemain or by gravity to the desired location. The side slope riser is connected to the drainage grid at the lowest elevation in the landfill cell where it is then pumped out. The HDPE material is compatible with other cell construction materials and allows easy connection to the leachate collection piping. Typically, the side slope risers range in diameter from 18" to 24" and are usually made from DR 17 pipe. Your custom built system can be prefabricated in one of our fabrication plants and sent to your job site for quick and easy installation.