ARMA Lab

TDA is frequently used in landfills across Alberta, and everyone involved in producing and using it has a vital role in delivering the best possible result.

1. Working with the landfill manager, the landfill design engineer determines the best specification for the TDA for the drainage blanket collection system. The amount of TDA to be ordered (and the cost savings over gravel) are determined using the TDA calculator. The design engineer establishes a construction quality assurance program to ensure the TDA delivered to the site meets the design specifications.
2. The tire recycler selected for the project produces the TDA to meet the engineer’s specifications through proper operational and maintenance practices. The design engineer or the landfill manager rejects “Out-of-spec” TDA (if any) no differently than any other substandard material that should not be incorporated into a project.
3. ARMA pays the recycler based on the tonnage of acceptable TDA delivered per the project specification (with a small contribution from the landfill owner). 

TDA that does not meet specifications is not eligible for funding by ARMA

Unlike gravel, TDA leachate collection blankets compress when buried beneath waste in a landfill. Solid material gets deposited in the spaces between the TDA particles (a process known as ‘clogging’), and the more the TDA blanket is compressed, the smaller these spaces become, and the more the clogging can affect leachate drainage performance. 

The testing work commissioned by ARMA investigated TDA's compression behaviour under various simulated landfill conditions using a purpose-built 1-D consolidometer. Testing results showed that the TDA spacing was still sufficient for use in a leachate collection layer, even with the reduced particle spacing.

Leachate builds above a landfill liner unless drained to a collection point and removed. One key factor controlling the amount of leachate build-up is the permeability of the leachate blanket. This is important in Alberta landfills because the amount of build-up is regulated by legislation. The testing work commissioned by ARMA investigated the permeability of TDA using a purpose-built 2-D permeameter designed specifically to accommodate TDA’s unique characteristics.

The test equipment applied vertical loads up to 300 kPa, simulating 30 to 40 m landfill heights. The testing results confirmed that the permeability of TDA compressed under a vertical load of 375 kPa remained above the target value of 10-2 m/s.

Plastic liners (geomembranes) are increasingly common in landfill lining systems. While they are exceptionally effective at containing liquids, they are relatively thin and must be protected from sharp objects that can puncture them and compromise performance.

The testing commissioned by ARMA investigated the protection of geomembranes from the protruding wire of TDA particles and the edges of individual gravel particles. Different combinations of geomembranes, protective fabrics (geotextiles), and various types of TDA and gravel were used for testing. TDA particles were tested in winter conditions in a large testing frame outside a laboratory in Saskatoon. The frozen TDA particles were tested in place so the orientation of TDA particles relative to the geomembrane could be assessed.

Results confirmed that geomembrane liners should be separated from TDA and gravel particles to avoid potentially high puncture rates. Protruding wires from TDA particles were confirmed to have the potential to cause immediate geomembrane puncture. In contrast, gravel particles were confirmed to have the potential to cause excessive local strain in the underlying geomembrane.