Landfill Liner System | Waste Management

The technology used in today's landfills begins with installation of a liner system. The liner system provides checks and balances to ensure environmental protection. Alliance Landfill's liner is about three feet thick. It includes two layers of heavy plastic sheeting (the primary and secondary liners that are 66 percent thicker that required by law), two layers of gravel, and clay and fabric layers designed to protect and back up the liners.

The gravel layers are equipped with perforated pipe that collect the liquid that passes through the waste. That wastewater is treated at the landfill's wastewater treatment plant.

The landfill is constructed in "cells," areas about 10 acres in size. Once the liner system is constructed and certified by an outside agency, the first layer of waste is placed in the cell. To protect the liner, the first layer of waste placed on a new area of liner (called "select waste") is sorted by hand to remove any objects that might puncture the liner.

From here, the landfill is built like a layer cake. Waste is taken in, compacted in layers, and then covered with soil, called daily cover. The daily cover helps prevent odors, litter and keeps animals away.

Our liner is equipped with a wastewater collection system that transports liquid passing through the waste to our wastewater treatment plant. Our plant, which is similar to a municipal sewage treatment plant, is capable of treating close to 50,000 gallons a day. We use our treated wastewater for litter and dust control and for improved waste compaction at the landfill's disposal area.

Our landfill cap system works in conjunction with the gas collection system to control odors. The cap also prevents storm water from reaching the waste. Over time, this prevents the formation of wastewater.

Just as federal and state regulations detail every aspect of landfill location, construction and operation, they also detail every aspect of the planning and construction of the cap system. Here's how we construct the cap:

Once an area of Alliance Landfill reaches final elevation, that waste is covered with a layer of compacted soil. This compacted soil serves as a foundation for the rest of the cap system and protects against settling. The soil then is covered with a geo-synthetic blanket that resembles strong and durable felt. The blanket is sewn together and then covered with a 40 mil-thick (1/25th of an inch), geotextile layer. This layer is applied in strips and the edges of adjacent strips are welded together to assure that it is air- and watertight. Placed atop the geotextile layer is a geonet material that provides erosion control by catching and draining away rainwater. Two feet of soil, known as the "final cover," then is placed on top of this multi-layer cap. This soil is then seeded with grass and other vegetation to prevent erosion.

Alliance Landfill's Community Landscape Project has involved the landfill's neighbors in the design of a project that is testing if native trees and shrubs can be grown above the landfill's cap. The key to success of the project will be whether growth of the trees and shrubs affect the important function of the landfill cap. In the three years since the project was planted, the trees and shrubs have improved the appearance of the landfill and have created habitat for a growing number of wildlife species.

Landfill Gas Collection

Alliance uses an extensive landfill gas collection and recovery system to control odors and the gas that is created by the decomposition of organic matter in the landfill. About one-half of landfill gas is methane and another major component is carbon dioxide. Both are leading greenhouse gases. Alliance at present is destroying its landfill gas in four large enclosed flares.

Methane is a source of green energy that can be used to create heat, electricity, or fuel industry. Alliance is looking to use the methane generated by the landfill to create green energy, jobs and economic activity.