Abstract: A chemical waste landfill comprising a plurality of compartments separated by and lined with a primary clay liner. A single integral synthetic water impervious liner is provided beneath the clay liners of all of the compartments and a primary underdrain system is provided for each compartment beneath the synthetic liner. A secondary clay liner is provided beneath the primary underdrain system and a secondary underdrain system is provided beneath the secondary clay liner. The invention also includes chemical waste landfills having in situ leachate treatment systems, increased security compartments having additional synthetic and clay liners and a leachate monitoring system comprising a plurality of standpipes interconnected by a liquid pervious means below the waste wherein the standpipes are protected by sleeves.