Definition - What does Secure Landfill mean?
A secure landfill is a carefully engineered area that is used to deposit waste products. Typically, a secure landfill is a hole in the ground, but may also be built above ground. If the depression is in the ground, it must provide a 3 meter (10 foot) separation between the bottom of the landfill and the underlying bedrock or groundwater table.
Safeopedia explains Secure Landfill
The purpose of a secure landfill is to prevent any waterborne connection between the waste products and the surrounding natural environment. It is especially imperative that groundwater does not cause run off onto the surrounding landscape. Hazardous wastes are disposed of by burial in secure landfills, though they are sometimes placed underground in deep well injection systems.