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Critical operations behind the scenes of train line construction

In the back of the I-225 Rail Line project office in Aurora, men and women are hard at work bringing the light rail line to life.

But they aren’t doing construction or design work. These unsung members of the team are performing tests on all of the soils, concrete and aggregates used during the construction of the project to make sure it’s the best quality for RTD’s new light rail line.

Lab manager Ken LaCroix pulls a concrete cylinder
out of a tub of water.

The head of the lab is Kiewit employee Kenneth LaCroix. He’s the Quality Assurance Materials Laboratory Manager.

“When the project was designed, engineers set requirements on the materials to be used that are necessary to achieve desired structural requirements for the 10.5-mile light rail line,” said LaCroix. “We perform tests on the construction materials being placed to show that the requirements set by the design are achieved. These test results are required and reviewed by the owner, RTD, as well as any municipality that we perform work.”

One time when I was out in the field taking pictures, I asked a foreman when he knows to take the forms (casts for concrete) off of a concrete structure (such as a bridge pier) that they’ve poured. He told me that the go-ahead comes from the materials lab. That’s the moment when how the lab fits into the field work all came together for me.

Lab's technical equipment has cool names

  • Compression machine: Crushes concrete test cylinders to verify concrete strengths
  • Water tanks: Cures the concrete test cylinders prior to crushing
  • Proctor hammer: Determines moisture/density values on soils being placed
  • Sieve shakers, ovens and scales: Verify gradations (size percentages) for aggregates being placed

One challenge LaCroix faces is that the project crosses over into several municipalities.

“Remembering and responding to the different project specifications and requirements of the various entities as we move laterally across the site is one of our biggest challenges,” said LaCroix.

Ken preps concrete cylinder for testing, while Certified
Materials Technician Jeremy Adkins performs gradation.

He works with engineers, contractors, inspectors, technicians and interns. They each play a role in constructing the project according to the various project specifications. Everyone has their own area of focus that comes into play at various times throughout the project.

“Every operation that we perform we take extra time beforehand to identify potential hazards and risks associated with the task. Hazard analysis forms are filled out and signed by anyone working in the identified hazard area.”

LaCroix studied geology at the University of Northern Colorado. He started working in an engineering soils lab right out of school. His interests in geotechnical engineering and his experience have kept him working in this field. The people he meets keeps his job interesting.

“I enjoy the variety of people and personalities associated with the business and watching the progression of a great project coming to life.”