Camrose Regional Sanitary Landfill

Recycling | Sanitary Landfill | Waste Collection

Camrose Regional Sanitary Landfill

Landfilling Techniques

The Camrose Regional Sanitary Landfill is not a "dump." A dump implies simply leaving solid wastes in a localized area, caring not for the final condition of the dumped materials. A landfill that is "sanitary" is one which protects the surrounding soil, air and water from pollution from the landfill. This is accomplished via a number of techniques, including underlying the solid wastes with clay and daily covering the waste with soil. Environmental measures are taken by the Sanitary Landfill to protect the surrounding area.

There are predominantly two distinct techniques used in landfills to bury solid wastes.

The trench method involves digging a wide, long hole in the existing ground so that the bottom of the trench is much lower than the surrounding ground level. The depth of the typical trench at the Camrose Regional Sanitary Landfill is around 3.5 metres, well into the clay layer underground. The clay layer serves to keep all liquids contained within the trench, rather than leaking into the groundwater underneath. Garbage collection trucks and private vehicles drive into the trench and empty their solid wastes onto the trench floor at one end of the trench. The part of the trench where the garbage is currently being emptied at is known as the "active face" of the trench.

After the wastes are on the floor of the trench, they are pressed into the smallest possible area by a steel-wheeled compaction unit. Compacting the waste presses any air pockets out of the disposed waste, thereby maximizing the area of the landfill. After compaction, a crawling loader unit covers the waste with soil. (Click on the picture to the right for a picture of the processes used.) Covering the wastes with soil is important in minimizing the spread of garbage by the wind and scavenging animals. It also keeps the landfill free from flies and other pests. At the end of every day, the landfill operator will ensure that the day's wastes are completely covered by approximately 15 centimetres of soil. This completely enclosed volume of solid wastes is referred to as a "cell."

Each subsequent day, new wastes are placed at the toe of the previous cell. These wastes are emptied further along the trench as the one end of the trench fills up. Eventually there will be a full layer of cells along the bottom of the trench, known as a "lift". This lift is covered by an intermediate cover of soil (which is approximately 30 centimetres thick). The large depth of the trench allows for many layers of cells to be placed on top of each other before the trench is full. (Click on the picture to the right.)

Once a trench is full, another trench is dug and the process starts over again. The recently finished trench is covered with approximately 90 centimetres of soil. With this layer of soil on top of the waste, the trench is replanted with grasses and native bush. The final cover of soil provides an adequate base for proper plant growth.
Unlike the dig-and-fill procedure used in the trench method, the area method places the solid waste directly on the ground. Often a layer of clay is placed on the ground prior to the deposition of any solid waste. As is the case in the trench method, this layer of clay prevents the leaking of waste-contaminated liquids into the underlying groundwater.

By the end of each day's deposit of wastes, the waste is compacted and covered using the same techniques as the trench method, thereby creating a "cell". Then a daily covering of soil is placed over the cell to prevent the unwanted spread of garbage. Each subsequent day's waste is placed at the foot of the "active face" of the landfill.

When a predetermined area of land has been covered with cells of solid waste (a "lift" of cells), it is covered with an intermediate layer of soil (approximately 30 centimetres deep, same as the trench method). The deposition of waste starts over on top of the previous lift. Eventually, successive layers of cells (lifts) can cause the height of compacted waste to be very substantial.

Early landfilling techniques dictated that these layers could reach a depth of no more than 25 metres. Recent developments in landfilling techniques have drastically increased the capacity of area method landfilling. Effectively, there is no limit to the height of an area method landfill. Mount Blackstrap, a popular ski area south of Saskatoon, SK, is actually a man-made ski hill created through the methods of area landfilling. Nearly half of Blackstrap's 100 metre vertical drop is due to area method landfilling, simply adding more and more layers of waste on top of each other.

Although the height of area method landfilling is almost limitless, engineers eventually decide to stop area landfilling a certain area. A final cover of soil is placed over the entire area of landfilled solid wastes and the area is replanted to native grasses, shrubs and trees.

Camrose uses a mixture of both of these methods. First a trench is dug. Once the trench is full of solid wastes, the operator deposits wastes on top of the trench, as in an area method. This mixing of trench and area methods of landfilling ensures maximum use of the land space in the Sanitary Landfill. This translates into a longer overall life span for the landfill.

What Happens to a Landfill After it Closes?

Eventually, every landfill must close its operations. Every landfill is built with its expected life span in mind. The Camrose Regional Sanitary Landfill was originally built in 1983 with an expected life span of 35 years. As a result of advances in landfill techniques, recycling and the reduction of waste, we now hope that it will be open well beyond the year 2050.

Once a landfill closes, its land is used for beneficial purposes. Although its underlying consistency is not strong enough for development into buildings (due to a settling of the decomposing waste), a reclaimed landfill can be used for recreational purposes. Land remediation, that is, the recovery of previously unusable land into usable land, is a common practice in most large communities. Mount Blackstrap is a perfect example of how a landfill can be positively used by engineers.

The landfilled area (which is already included within the Camrose city limits) can easily be used by the City as youth sports fields, hiking / cross-country skiing trails, or a new golf course. The options for the eventual use of the Sanitary Landfill land after its closure are effectively endless.

What Happens to the Buried Wastes?

Most people assume that once solid wastes are in the ground, they just stay there in their original state. While this is true for some synthetic materials (such as plastics), almost all other materials undergo some form of break-down. This break-down is due primarily to biological activity within the waste, although chemical and physical processes do assist in breaking down the waste.

Settling and dissolving are the two major physical processes which occur within a landfill. As wastes decompose by biological means (see below) the volume of the buried waste decreases, sometimes by as much as 15 % of the original volume. The weight of the overlying material causes the top layers of the landfill to sink downward. This sinking of the land is usually so gradual that it is barely recognizable over time, although there are some extreme examples of sudden sinks occurring in previous landfill areas. Settling actually helps the breakdown process, as the settling ensures the continued contact that is necessary for decomposition of all reacting materials.

If there are any liquids present in the waste prior to burial, or if any rainwater enters the buried waste, these liquids can dissolve some of the materials present in the landfill. By dissolving the materials, the chemical and biological means of decomposition are actually accelerated. So physical processes assist in the decomposition process mostly by assisting the chemical and biological processes which occur in the buried solid waste.

Chemical reactions within a landfill are predominantly between acids within the waste and the waste itself. These chemical reactions eventually break down the waste into its constituent molecules. These broken down wastes are then absorbed by the surrounding soils or are consumed by bacteria in biological processes.

The predominant form of breakdown within the buried waste of a landfill is biological in nature. Microorganisms (such as bacteria) consume the buried waste, incorporating the molecules of the waste into their own cell structures. Although there are some molecules which these microorganisms cannot consume in some cases, most of the substances put into the landfill are eventually (over many decades) broken down by these organisms.

More Information

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