On May 9, 2014 Stratus had a near miss related to the shifting of a trench plate.
What went wrong? The trench plate was placed over a three-foot deep trench adjacent to other plates and shifted while unattended, falling into the trench with approximately 12-inches of the plate projecting above the ground surface. The plate was not pinned or “locked” by welding to other plates or stabilized with an asphalt perimeter.
What did we learn? Trench plates move. Depending on your application, some plates are texturized creating a rough top surface and more traction for pedestrians and vehicles. Other plates are slick-top. In either case, vehicles can move a plate if the car accelerates atop the plate and it is not locked in place.
Mitigations. All plates placed by Stratus or our subs should be part or the WRA, taking into consideration that “plates move”. The traffic level and type are key contributors. All plates should, at minimum, be stabilized with asphalt around the perimeter of the plate if the plate will be unattended or in high pedestrian traffic locations (trip minimization). Adjoining plates should be placed tightly together to assist in “locking” their movement. Plates in high traffic areas or on slopes (regardless of angle) should also be tack welded and pinned to the ground.
More to follow in our monthly meeting.