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Site Health and Safety Plan 19133 East Liberty Road, Clements, California August 16, 2022 (Revised June 27, 2023) Page 20 Sharp Environmental Technologies, Inc. • Utilize appropriate engineering controls (e.g., ventilation), work practices, and PPE as needed. • Trenches in excess of 3 feet deep must have steps or ladders located so that all workers within the trench are within 25 feet of a place of exit [OSHA, Title 29 CFR 1926, Sections 651 and 652]. • Excavated material shall be placed at least 2 feet from the edges of excavations, unless effective barriers are in place to prevent the excavated material from falling into the excavation. Precautions to prevent cave-in (as described below) should be strictly followed. The following conditions increase the likelihood of cave-in: • Soil materials composed of unconsolidated, uncompacted, and/or rounded particles. Special care must be used when trenching in areas which have previously been excavated and backfilled. • Soils which have a high-water content. • Loading of trench walls by adjacent equipment, supplies, structures, backfill piles, etc. • Vibration due to equipment operating near excavations. • Trench walls which are steeper than the angle of repose of the material composing the walls. • Deep trenches (i.e., high trench walls). The following precautions should be used to prevent cave-ins in all trenches in excess of 5 feet deep. These precautions should also be used in trenches less than 5 feet deep whenever those site conditions just listed indicate the likelihood of a cave-in: • Sloping. Trench walls should be sloped to the correct angle of repose. • Shoring. Vertical trench walls (unless composed of solid rock) must be shored and braced, or restrained with movable trench boxes, to prevent cave-ins. • Shoring systems must be designed by qualified person and meet accepted engineering requirements. • Shoring must be installed from the top down and removed from the bottom up. • Additional precautions (e.g., added shoring bracing or a flatter slope angle) should be utilized whenever site conditions indicate that they are needed to prevent cave-ins. • Excavations should be inspected by a competent person daily, and after any event (e.g., rainfall) which may increase the likelihood of cave-in. If inspection indicates the potential for a cave-in, all work should cease until appropriate precautionary measures are taken. Trenches which (1) will not be entered by workers; and (2) will be immediately backfilled (e.g., for permeable treatment walls) are exempted from the requirements listed here. When the procedures outlined above are followed, trenching can be a useful control on a hazardous waste site. It should be emphasized that construction hazards must be avoided as much as chemical exposure hazards.