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HUNTSVILLE, Ala. – Huntsville city officials have hired an outside consultant to conduct an investigation into a deadly trench collapsed that killed a city employee and injured two others.

55-year-old Bobby Green was killed in the accident on September 2nd.

A city spokesperson told News 19 Tuesday that the public works department will complete their own after-action review of the accident, but that an outside entity would also complete an independent investigation. The spokesperson said there is no timeline for when either of those investigations will be completed.

The trench collapse happened at a construction site on the northern end of John Hunt Park near Joe Davis Stadium. Public works employees had been installing storm drainage pipes to prepare for a new facility that will replace the current stadium. Three workers were in the trench when it collapsed, including green. The other two workers were taken to Huntsville Hospital with non-life-threatening injuries.

City officials said on Friday that one of the injured workers has returned to work and the other is recovering at home.

Perry Silvey, safety manager for Colorado-based BT Construction, a company not affiliated with the Huntsville project, said there are three main methods constructions crews use to prevent trench collapses: sloping, shoring, and shielding. Sloping involves digging the trench in such a way that the walls of the trench are at an angle, and not vertical. Shoring is when crews use supports, such as aluminum hydraulics, to prevent the walls of the trench from budging. Shielding, which Silvey said is the most common method, involves using trench boxes to protect workers inside the trench in case soil around the walls begins to cave.

After viewing video of the scene, Silvey says it appears a trench box was visible inside the area where the collapse happened. News 19 asked city officials what, if any, safety measures were in place when the trench collapsed; they declined to comment pending the investigation.

According to Royal Funeral Home, a funeral service will be held for Bobby Green on Thursday at Indian Creek Cemetery in Huntsville.