TDA Used In Municipal Sewer Pipe Project

Located in St. Louis Park, MN, initial stages of this 2023 project began with installing sewer pipe through weak organic soils, without allowing the pipe to bend or fail.

Installation crews from the project contractor, New Look Contracting, removed the weak soils to the proper elevation and set the sewer pipe with traditional support in the haunch areas.  However, the biggest concern was that backfilling the pipe with “conventional granular soils,” would cause a failure. This failure is often due to the weight settling on poor strength material under the pipe. It is important to understand that the soil traditionally used to cover over top the sewer line would weigh approximately 3000 pounds per cubic yard. Engineers were concerned that this would be more pressure than the underlying soil could carry without deflection.

The engineer responsible for this project suggested the use of a light-weight manufactured aggregate (TDA). One of the many benefits of tire derived aggregate is its weight . At 600 pounds per loose volume cubic yard, or 1200 pounds compacted and compressed as the final in place installation weight TDA met the requirement for lightweight fill.

The choice of tire derived aggregate supplied by First State Tire/ TDA Manufacturing was ASTM 6270-B.  A total of ten loads of TDA  were  delivered to the job site, at 80  L.V cubic yards per trailer. To install the TDA, the trench above the sewer pipe was lined in a geotextile fabric prior

to the TDA installation (like a burrito) to ensure the reduction of granular soil from working its way into void space within the TDA.

One of the ten properties of TDA is its unique feature of being lightweight. According to J.S. McCartney, author of “Design of Mechanically Stabilized Tire Derived Aggregate (MSTDA), “TDA reduces the earth pressure on soft soils and existing foundations.” Indicative of its lightweight composition, TDA has specific gravity making it 2/3rd lighter than traditional mineral aggregates (Park, Bulson, Wahl, 2023). Education and knowledge-sharing are driving factors in increasing the use of TDA, First State Tire/TDA Manufacturing CEO Monte Niemi said.

“As previous TDA customers know, TDA  is an economical, versatile, and durable material used in various applications, from drainage systems to road construction and noise barriers. Its sustainable nature and low environmental impact make it an attractive alternative to traditional aggregates”, Niemi said, citing 2023 findings from Wisconsin University researchers Richela Maeda and Brad Finney.

Recently, civil and environmental engineering students at the University of Wisconsin-Madison have been assigned to an extensive project regarding the effects of TDA on water quality. Initial findings from their study entitled State of Knowledge on the Effects of Tire-Derived Aggregate (TDA) Used in Civil Engineering Projects on the Surrounding Aquatic Environment outlines that TDA does not release a significant amount of potentially toxic compounds, the leaching rate in surrounding water environments is low, and TDA can even be a medium to remove nutrients and toxic organic and inorganic compounds commonly found in agricultural land and urban runoff.

The study aims to collect the most up-to-date scientific data on the environmental impact of scrap tires and evaluate the data specifically for TDA applications in civil and environmental engineering applications.  It recommends guidelines be developed for specific projects to achieve a circular economy for end-of-life tires in the form of TDA to avoid potential environmental issues and problems.

An essential part of First State Tire / TDA Manufacturing’s growth and recognition, is the opportunity to share the knowledge, experience and benefits of tire derived aggregate in a wide range of applications our team has learned over the last 30 plus years, Niemi said.  Several years ago, Niemi launched the “Lunch & Learn”  program which provides accessibility to individuals across the country interested in learning more about TDA manufacturing, material performance, environmental benefits and cost savings.

“We have accumulated experiences from over 400 TDA installations, providing empirical information for building knowledge based presentations which help to educate engineering firms and other potential users in surrounding cities, counties,” he said.

For 2024, First State/TDA Manufacturing plans to launch a campaign to expand the Lunch & Learn forums

© Scrap Tire News, January 2024