The Double Composite Liner System
Under new environmental regulations recently established by Monroe County, the prime method used to dispose of the solid waste deposited at Mill Seat is through the double composite lining system. Under this system, two liners are place under the solid waste at differing intervals. The logic behind having the double lined system is to try and ensure that the leachate correctly drains into the piping which will transfer it into holding tanks rather than permeate down into the natural soil.
The primary liner, located roughly three feet under the surface is composed of a plastic material called 60 ml HPDE which directly covers one foot, six inches of compacted clay liner and serves as the primary liner. The secondary liner, located six feet under the surface is composed of the same materials, except for the compacted clay liner having a depth of two feet.
In addition to the two liner system, an initial foot of protective soil has been placed directly under the solid waste and three differing levels of crushed stone have been laid down with perforated piping at the center of each one to enhance leachate drainage. They are located at depths of 1-3 feet, 4.5-5.5 feet, and 7.5-8.5 feet respectively. The crushed stone enables the liquid leachate to drain into the perforated piping and then be pumped into the large storage tanks which hold the liquid leachate for transport to sewage treatment plants, where the leachate is treated.