Workers are going to drill hundreds of holes into ground along the route the planned South Mountain Freeway as preparations get underway for its construction along the southern edge of the Phoenix area.
The state Department of Transportation says the borings will be used to assess soil and rock as well as depth of ground water to help engineers plan designs for pavement, bridge foundations, walls and drainage structures.
The work beginning Tuesday is expected to continue for several months.
The new freeway will connect with Interstate 10 in Chandler on the east and with I-10 in southwest Phoenix on the west.
The state received final federal clearance to move forward with the project in spring 2015. Legal challenge to the project is pending in federal court.