What is Leachate
Leachate is any liquid, such as rain, that comes into contact with garbage. To protect surface waters and groundwater around the landfill, leachate is contained, collected and treated. Although the landfill is operated in a manner to minimize leachate, over 22 million gallons were collected last year.
At Short Mountain, leachate is collected in each of the separate landfill cells (sections) and pumped to a holding lagoon. Each of these cells has a barrier layer made from clay and/or plastic with a sand or gravel drainage layer on top. The cells slope towards a single point, which is where a sump is located. Leachate is trapped by the barrier layer and moves through the drainage layer towards the sump. The sump is a large depressed area containing a diagonal or vertical riser. Inside the riser are a submersible pump, a level sensor and in some cells, a back up pump. When the leachate level rises in the sump, the level sensor triggers the pump to turn on, and leachate is pumped to a leachate storage lagoon. To learn more about how the construction of landfill cells and leachate collection systems, see the Construction & Operations Section of this site.
There are a variety of options for treating leachate used at landfills around the country. At Short Mountain, leachate is treated off site. The leachate is held in the storage lagoon until a tanker truck is ready to transport it. But before going into the tanker, it undergoes a primary treatment process which aerates the leachate, releasing gasses that can build up in the sewer system. After treatment it is then pumped into the tanker truck and taken to the Central Receiving Station Transfer site. There it is disposed of by permit into a sewer manhole so that it can be conveyed to and treated at the Eugene-Springfield Water Pollution Control Facility.