Before beginning any excavation, the area must be inspected to identify underground utilities including electrical lines, gas lines, water mains, and communication cables. Utility locating services must be called to mark all utilities before digging begins. Competent persons must conduct daily inspections of excavations to identify hazards such as ground movement, water seepage, or unstable soil conditions. Excavations must be protected against collapse by sloping the sides at angles appropriate for soil type, installing shoring or bracing systems, or installing shields that protect employees from collapse. Soil must be classified as Type A, B, or C depending on stability. Type A soil (clay) can be sloped at 3.5 horizontal to 1 vertical. Type B soil (silt, sandy clay) requires slopes of 1 to 1. Type C soil (sand, clay with fissures) requires slopes of 1.5 to 1. Trench boxes or shields must be able to withstand soil pressure and must be installed correctly. Sloping distances must be measured from the top of the trench to the excavation depth. Inspection must occur after heavy rain, earthquakes, or other events that could affect soil stability. Water in excavations must be controlled to prevent sudden collapse or flooding. Ladders, stairways, or ramps must provide safe access to excavations deeper than 4 feet. Employees exposed to hazardous atmospheric conditions in excavations must be monitored and protected. Barriers must prevent personnel and equipment from accidentally entering excavations.