PHOENIX (KSAZ) - It's the last piece of a puzzle that's been decades in the making.
The final South Mountain stretch of the Loop 202 freeway will hopefully be ready for drivers by 2019.
Before it's completed, scientific tests on the land are being done and it all begins deep underground with crews collecting samples of soil and rock.
"It's critical to ensure that these structures, these freeways we build last a long time and are safe for motorists," Dustin Kruegel said.
Kruegel, who's a spokesman for the Arizona Department of Transportation, says it's called geotechnical testing and it's happening over the 22-mile corridor for the next few months.
Crews are focusing on more than 700 areas but spending extra time on any land that will hold one of the expansion's 45 planned bridges.
"We have to make sure that what we're building on top of is going to be strong and is going to last," Kruegel said. "You look at the Leaning Tower of Pisa. It was constructed at the beginning of the 1200s. They built it on one half of kinda a marshy soft area. Well, within three years of construction it started to tilt."
It's testing that started at the beginning of this month. Workers taking thousands of samples from the ground and all of it happening in some of the hottest temperatures of the year.
"Yes, we're doing the work when it's particularly hot outside," Kruegel said. "That's why we're starting our work very early. We have workers who are trained to work in the heat. They're drinking plenty of water. They often will work in pairs."
ADOT says the testing should be done by August with freeway construction hopefully starting by the end of the year.
With hardly any lanes closures and little impact to drivers, these next months of hard work are easily worth it to keep us safe.