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Projects by Peterson Geotechnical Group

Apartment Foundation Investigation

Apartment Foundation Investigation and Repair

In 2002, an apartment complex was constructed adjacent to an Arizona river that has seasonal water flow. The east portion of the site is bordered by the river, which runs parallel to the site in a north to south direction. The complex is made up of two-story apartments constructed of wood framing and founded on post-tensioned floor/foundation systems.

A few years after the apartment complex was constructed, soil-related issues became apparent at two of the buildings. Peterson Geotechnical Group performed a floor level survey and found the levelness of the post-tensioned slab to be over five inches out of level.

A review of historic aerial photographs from 1949 revealed that the river historically ran where the distressed buildings were now located. It is unclear from the aerial photographs exactly when the channel was filled in; however, according to the photographs it took place prior to 1999.

Based on our initial findings it was our preliminary opinion that the design and construction of the project occurred without consideration for this former river channel that traversed the edge of the site. The soil used to fill the channel was likely undocumented fill soil that was consolidating.

Subsequent geotechnical evaluations revealed the presence of buried trees and poorly compacted fill soil from approximately 15 and 25 feet below the ground surface beneath portions of the buildings. The photograph shows the type of material that was excavated. This material was responsible for over five inches of settlement beneath the buildings which resulted in relatively large cracks in the post-tensioned floor/foundation system, binding doors, large stucco cracks, and an abundance of interior drywall cracks.

A repair plan utilizing micro-piles and grouting was designed and overseen by Peterson Geotechnical Group.

The Specialists in Forensic Geotechnical Engineering


Our professional, trained staff have evaluated the cause of issues that have arisen on a multitude of dynamic projects. These projects have included litigated matters, surety claims, customer service projects for builders, contractors, and homeowners and the design and oversight of repairs for building owners.

1. Apartment Foundation Investigation 2. Soil Stabilization and Foundation Repair 3. Construction Defect Expert Testimony

Contact us today for more information on how we can help you with site engineering, forensics and design.