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i 0 28 API RECOMMENDED PRACTICE 1648 9.2 FACILITY'S UNDERGROUND STRUCTURES Before starting the excavation,the estimated location of utilities,such as sewer,telephone,communication,fiber optic lines,fuel, electric,water lines,or any other underground installations that reasonably may be expected to be encountered during excavation work shall be determined.The contractor shall also determine the locations of tanks,product piping,or other fueling system com- ponents that may be encountered during excavation work. Utilities shall be properly marked out by local authorities prior to beginning an excavation.The contractor shall review all available site plans and engineering drawings with the facility's Engi- neering Authority and Project Manager before work begins. All digging work that shall take place in a mark-out zone or in areas where fueling system components may be encountered shall be performed using hand digging techniques so that utilities or fuel systems will not be damaged or workers exposed to uncon- trolled energy. All digging work within 2 feet of a mark-out zone shall be done using hand digging techniques. The contractor shall be aware of the ownership of the underground structures that may be encountered during an excavation.This is important so that the proper authority may be notified in case of a problem arises during the excavation process. Before the excavation begins,the contractor shall assure that the owners of all underground structures are aware than an excavation will be taking place that may affect their property. 9.3 SLOPING AND SHORING METHODS/STABILITY OF EXCAVATIONS An adequate protective system, such as sloping or shoring, shall be in place to protect workers in an excavation from possible cave-in,collapse of an adjacent structure,and falling materials and equipment.The contractor is responsible for the design and construction of any shoring,sloping,and/or support system for entry.The system shall meet the conditions and requirements in OSHA 29 CFR 1926:652,and any other applicable State or local requirements.Support-system designs shall either: • Meet requirements for timber or aluminum hydraulic shoring,and also use manufacturers'tabulated data or other tabulated data for design and construction of a support system,or • Be designed by a registered professional engineer. During installation of a protective system,a copy of the design plan shall be kept on-site and available for inspection. Possible methods that can be used include: 9.3.1 Benching Benching is a method of protecting employees from cave-ins by excavating the sides of a trench excavation by forming one or a series of horizontal levels or steps,usually with vertical or near-vertical surfaces between levels. 9.3.2 Shield(Shield System) A shield,or shield system is a structure that is able to withstand the forces imposed on it by a cave-in and thereby protect employ- ees within the confines of the structure.Shields can be permanent strictures or can be designed to be portable and moved along as work progresses(Also known as trench box or trench shield). 9.3.3 Shoring(Shoring System) Shoring or a shoring system is designed to prevent cave-ins. Shoring systems can be metal-hydraulic,sheet pile,mechanical or timber based system that supports the sides of an excavation. 9.3.4 Sloping (Sloping System) Sloping is a method of protecting employees from cave-ins by forming sides of an excavation which are sloped away from the excavation.The angle of the slope may vary with differences in soil type,environmental conditions,and depth of the excavation. 9.4 MANAGEMENT OF SITE AND PLACEMENT OF EQUIPMENT, MACHINERY,AND MATERIALS 9.4.1 Management of Site Excavation sites shall be properly managed to reduce the risks for injuries to workers.A designated competent person shall be on- site at all times while trenching work is underway,and before employees may enter.