FEATURE ARTICLE Excavation and heavy civil construction in urban environments directly impact abutters and existing adjacent structures. Noise and dust create nuisance concerns, while demolition, excavation and dewater- ing can cause earth movement and structural damage. Many jurisdictions have their own regulations that dictate require- ments, roles and responsibilities for varying parties during construction. Illinois and Chicago, as an example, provide a legal framework for the owner of the new construction project to provide adequate protections for adjacent structures. This article covers legal and technical risks posed to adjacent structures that owners of new construction projects and their team must be aware of, such that the team is knowledgeable to navigate and allocate those risks. Early and frequent com- munication among project participants is necessary to manage risks, regardless of local regulations that may or may not exist to drive the process of developing a project. Adjacent Structure Technical and Legal Risks Threats to Adjacent Structures There are many threats from new con- struction that can damage adjacent structures. Excavations and vibrations can be significant contributors to ground movement, resulting in structural damage to adjacent properties. Excavation and vibration-induced ground movements have received considerable attention in industry literature; as structural engineers and attorneys, we briefly re-introduce both areas of concern below. Excavations can lead to a wide range of problems associated with abutters’ property, particularly due to horizontal or vertical movement of the ground that is supporting existing foundations. Movements can result from a support of excavation with insuf- ficient strength and stiffness, dewatering that lowers the water table, and/or direct undermining of adjacent structures. A zone of influence of excavation-induced ground movements can be large. Knight, and Matthew H. Johnson, P.E., Simpson Gumpertz & Heger A tight urban excavation site Vibrations can be caused by a wide range of construction activities including, but not limited to, heavy construction traffic, demolition, blasting, driven excavation- support elements or foundations, exca- vation or bored tunnels. Vibrations can cause soils to densify or liquefy, which in turn can damage fragile structures that bear upon these soils. Impacts of vibrations are most pronounced closest to the source and diminish with distance. Proper Project Set Up The success of a new construction project is based upon a project team’s proactive planning and communication. Leaving res- ponsibility to a single party leads to a reac- tive response to issues, impacts schedules, adds costs and frequently results in claims. The owner and design team are best positioned to identify excavation extents and anticipated vibrations and ground deformations based on construction AUTHORS Scott J. DiFiore, P.E., Simpson Gumpertz & Heger, Gregory R. Meeder, Holland & Knight, James P. Chivilo, Holland & DEEP FOUNDATIONS • MAR/APR 2020 • 87
