Aleia Lopez, a 51-year-old employee of the university's Medical Center Western Psychiatric Hospital, was outside the construction site of the school's $240-million arena and athletics practice facility when the heavy rolling caisson reportedly broke through a gate on the perimeter, striking her and causing a fatal head injury.

Exactly how the project perimeter was protected at the time, and whether bin blocks, jersey barriers or chain link fence was used, is not yet clear. Also not clear is whether the caisson was being moved at the time of the accident.

A joint venture of Gilbane Building Co. and Massaro Construction is serving as construction manager for the project.  "We remain deeply saddened by the loss of Aleia Hall Lopez," the joint venture said in a statement, adding that it is supporting the investigation.

The project site was shut down for several days before work resumed. According to a statement issued by a university spokesperson, “Initial supplemental safety actions have occurred on site, including the placing of concrete barriers at the base of the hillside slope, securing all construction equipment, and erecting a crane to resume work."

The statement added: "Enhanced worker training has also taken place.” 

Cheswick, Pa.-based Costa Contracting Inc., the subcontractor performing the work, did not return a call for comment. Its attorney had released a statement immediately after the accident extending "deepest condolences" to Lopez's family and pledging that the company is "committed to a full investigation" of what led to the accident. "Safety remains our paramount concern and we are working with OSHA and local authorities to understand precisely what occurred," the statement said.

Caisson drilling is often used to reach stable soil or bedrock in foundation construction, and the cylindrical chamber is often filled with concrete. 

Last year, OSHA cited Costa Contracting for an alleged safety violation observed in Imperial, Pa., in November 2022 that involved failing to secure heavy materials that posed a hazard of sliding or rolling into a trench. 

According to OSHA records, the company reached a formal settlement under which it agreed to pay an $8,000 fine when a steel plate with items and personnel on it that weighed about 3,200 lbs and was located within 2 ft or on or over the edge of an excavation collapsed or slid into the excavation. The plate movement displaced two trench boxes inside the excavation, OSHA claimed.

No injuries were associated with the citation.

A GoFundMe page has been set up to benefit Lopez's three children.