This existing land (which is now Purgatory Creek Recreation Area) was made up of soft, muddy soil at a low-lying grade next to a small lake. Engineers needed to cost-effectively design a stable foundation that could be built on without the risk of the overlying structures sinking into the soil below.

A lift of TDA (Tire Derived Aggregate) placed directly on the existing grade created a strong foundation that eliminated the risk of differential settlement or other failures of the park features. The irregular shape of the individual tires pieces created an internal reinforcement; a "snowshoe effect" that spread throughout the site and prevented individual areas from sinking.

The high permeability and thermal insulation properties of TDA help create a capillary break, so moisture can't wick its way towards the surface. In addition, TDA has about 8 times better thermal insulation than soil, which helps prevent frost activity.

"With conventional embankment construction, there was a high risk of embankment failure," said Bill Cody Principal Engineer for American Engineering Testing, Inc.. "To achieve the grades the city wanted and reduce the risk of failing the new embankment, lightweight fill materials were a top consideration."