The joint venture Shimmick, Traylor and Granite is being paid $875 million to build Phase 3 of the 20-mile Honolulu rail line.
Barring interruptions it will take four years to lay five miles of fixed guideway.
STG picks up where Kiewet's work ended near Aloha Stadium.
"As quick as we can all drill some holes and pour some good quality piles the project goes forward" foundation manager Rusty Lucido said.
The elevated guideway will pass through the airport.
University of Hawaii traffic expert Panos Prevedouros thinks that's where the contractors will face their biggest hurdle.
"When they hit Aolele Street there is essentially an S-curve, one right hand turn followed by a left hand turn which is quite challenging to do in infrastructure. There's also a lot of elevation. You have all the ramps from the freeway going to the airport," he said.
Drilling of the foundations for support columns began Monday on Kamehameha Highway near Radford Drive.
"The challenge is just the logistics. We're standing in a very limited access for this large equipment," Lucido said.
The highway is down to two lanes in each direction through the construction zone and the speed limit is slowed to 25 miles per hour.
Kiewit's work on the first ten miles inconvenienced drivers and harmed businesses. Prevedouros expects STG's work to do the same..
"There will be disruptions and there may be at times major disruptions due to safety," he said.
STG is also contracted to build four transit stations, one near Pearl Harbor and two near the airport. The last near Middle Street will straddle a waterway.
Shimmick, Traylor and Granite submitted the lowest bid for the project.
"All three of them have expertise, knowledge and experience in foundation work, utility work, guideway, precast, and a lot of rail experience," Lucido said.
If work stays on schedule and on budget STG anticipates the segment to be finished by December of 2021.