ADOT looks underground to prepare for South Mountain Freeway

Work begins Tuesday to assess soil along 22-mile corridor

PHOENIX – Preparing for construction of the Loop 202 South Mountain Freeway, Arizona Department of Transportation crews with drills and backhoes will begin assessing the condition of soil and rock as well as the depth of groundwater along the freeway alignment.

The work, which is scheduled to begin Tuesday and continue for several months, will help engineers plan the freeway’s pavement, bridges, walls and drainage structures.

Understanding the soil, including its type, density, moisture content and strength, is essential prior to building any roadway. For the 45 bridges that will be built for the South Mountain Freeway, the answers will help engineers determine how deep concrete foundations should be. Finding clay rather than hard rock in an area could require engineers to use thicker pavement, build a support base or replace the soil altogether.

Workers will drill holes, called borings, and dig test pits up to 10 feet deep along the roadway alignment, and at all future bridge and retaining wall locations. Materials collected will be analyzed to create a profile of what lies beneath much of the 22-mile corridor.

This initial work will occur only during the day, and it won’t affect traffic. There may be traffic impacts later along Pecos Road, and ADOT will send out traffic advisories in advance of that work.

There are expected to be 720 borings to depths of 5 to 175 feet. In all, there will be about 29,000 feet of drilling and 800 feet of backhoe pit excavation.

Crews have already begun marking locations for testing after receiving environmental clearance and working with Arizona 811 to ensure there are no conflicts beneath the surface, such as water, gas and electrical utility lines.

None of the current work will occur within South Mountain Park.

The South Mountain Freeway, which will run east and west along Pecos Road and then north and south near 59th Avenue, connecting with Interstate 10 on each end, is expected to open by late 2019. The freeway will provide a long-planned direct link between the East Valley and West Valley and a much-needed alternative to Interstate 10 through downtown Phoenix. Approved twice by Maricopa County voters, the South Mountain Freeway will complete the Loop 202 and Loop 101 freeway system.

With construction scheduled to begin this summer, ADOT is conducting preliminary engineering, addressing cultural resources in the right of way, acquiring and preparing properties, and relocating utilities. ADOT received final federal clearance to move forward with the project in spring 2015.

For more information, visit azdot.gov/SouthMountainFreeway.