6-2 Hazard Analysis

Principal unique hazards associated with the slurry walls include:

a. Physical Hazards

(1) Description: During soil excavation, workers may be seriously injured or killed by heavy equipment such as front-end loaders and backhoes. This equipment may also generate excessive noise during operation, presenting a noise hazard to workers.

Control: Heavy equipment should be equipped with a backup alarm that alerts workers. When approaching operating equipment, the approach should be made from the front and within view of the operator, preferably making eye contact. Hearing protection should be worn when working around operating equipment. CONTROL POINT: Construction

(2) Description: Fire, electrocution, or explosion hazards may exist during installation of the slurry wall, should a backhoe rupture an underground utility, such as sewers, pipelines, or electrical or gas lines. Abrupt equipment stoppages due to contact with underground structures, such as foundations, may cause a dangerous condition leading to equipment-related accidents.

Control: To control utility contact hazards, identify the location of all below- and above-ground utilities prior to excavation. Contact local utilities and public works personnel to determine the locations of utilities. When there is any doubt or uncertainty, perform a utility survey, probe with a metal rod, or hand excavate prior to excavation to determine the exact location of utilities. Once utilities are located, careful excavation by backhoe may be allowed. When raising a drill mast or other equipment, always have an observer to the side to observe and supervise. CONTROL POINT: Design, Construction

(3) Description: During mixing operations, workers may be exposed to inhalation/ingestion/dermal hazards from airborne dusts, volatile organic compounds (VOCs), or metals from soil/bentonite mixtures and waste materials. Eye exposure may occur resulting in scratching and scarring of eyes.

Control: The generation of airborne dusts may be reduced by the periodic application of water, amended water, or emission-suppressing foams to the active excavation and mixing areas. The addition of foam to control vapors may also create a slip and fall hazard. Workers should not walk on areas to which foam has been applied. Other controls may include minimizing the amount of soil agitation during mixing operations, the erection of wind screens and portable surface covers, the use of the proper types of personal protective equipment (PPE) (e.g. an air-purifying respirator equipped with approved filter/cartridges [HEPA(N100, R100, P100) filters for particulates, OV cartridges for vapors, or combination filter/cartridges for dual protection], eye protection), use of experienced workers, repeated health and safety meetings, decontamination stations, and other standard procedures. CONTROL POINT: Design, Construction

(4) Description: Open excavations may pose fall hazards to workers while performing activities near the trench. The trench wall may collapse or the worker may fall into the trench while performing trench depth measurements or sample collection.

Control: The excavation should be inspected each day by a competent person to ensure the stability of the walls. Workers should limit their activities near the excavation, and only approach wearing fall protection, such as a safety harness and/or attached lanyard. All personnel crossings should be equipped with handrails. CONTROL POINT: Construction, Operations

(5) Description: Steam pressure washing of equipment may expose workers to thermal or burn hazards, or eye hazards due to flying projectiles dislodged during pressure washing, slip hazards from wet surfaces, and noise hazards.

Control: Thermal burns associated with the use of steam cleaning equipment may be prevented by using insulated gloves (e.g. silica fabric gloves). Eye injuries and hearing loss may be prevented by wearing safety goggles and hearing protection during pressure washing activities. Slip hazards may be controlled by workers wearing slip-resistant boots and draining water away from the decontamination operation into a tank or pit. Walking surfaces should be drained and free of standing liquids or mud. CONTROL POINT: Construction, Operations

(6) Description: During site activities, workers may be exposed to direct and indirect sunlight and corresponding ultraviolet (UV) radiation. Even short-term exposure to sunlight can cause burns and dermal damage. Exposure to hot and humid conditions may also result in heat stress, which can manifest itself as heat exhaustion and heat stroke.

Control: Exposure to direct and indirect sunlight should be minimized where possible in the summer months. Workers can minimize direct sun exposure by wearing long-sleeve shirts and full-length pants, and by applying UV barrier sunscreen. If possible, the work and break areas should be shaded. Exposure to heat stress conditions can be minimized by taking frequent breaks, drinking adequate fluids, and performing work during the early morning and late afternoon hours. CONTROL POINT: Construction, Operations

(7) Description: Workers may be exposed to electrocution hazards when working around electrical utilities such as overhead power lines.

Control: The location of overhead power lines, either existing or proposed, should be noted in the pre-design phase. All lifting equipment, such as cranes, forklifts and drilling rigs should remain at least 10 feet from the power line according to Occupational Safety and Health Administration (OSHA) regulation 29 CFR 1926.550 and EM 385-1-1, Section 11.E. CONTROL POINT: Design, Construction, Operations

(8) Description: The heavy equipment (small and large) used for site operations may roll over on steep slopes or unstable ground, seriously injuring the operator. Trucks loaded with backfill can back up too far and become stuck in the trench.

Control: The angle of the slope should be designed to minimize the potential for roll-over. The construction contractor must maintain safe operating conditions for equipment during construction. Heavy equipment should be equipped with roll-over protective devices (ROPS), and should not be operated on steep slopes or unstable ground. CONTROL POINT: Design, Construction, Operations

(9) Description: During the implementation of field activities, equipment and workers may come in close proximity to traffic. Also, drilling rigs and other equipment may need to cross or use public roads. The general public may be exposed to traffic hazards and the potential for accidents during loading and transporting soil.

Control: Where equipment is to cross over roads, warning signs should be used according to the criter of the Department of Transportation Manual on Uniform Traffic Devices for Streets and Highways. A traffic management plan should be developed before remediation activities commence to help prevent accidents involving site trucks and automobiles. EM 385-1-1, Section 21.I.10 provides plan details. CONTROL POINT: Design, Construction, Operations

b. Chemical Hazards

Description: During the excavation/installation activities, workers may be exposed to caustic irritants such as Portland cement. This material may become airborne during application and can cause skin burns and act as a lung irritant. Other agents such as bentonite used in slurry walls may contain free silica. Workers may also be exposed to waste materials such as organics and heavy metals. These materials may become airborne during excavation and expose workers via ingestion/inhalation/dermal contact routes.

Control: The generation of airborne contaminated dusts and vapor emissions may be reduced by the periodic application of water, amended water, or foam to the active excavation area. The addition of foam to control vapors may also create a slip and fall hazard. Workers should not walk on areas to which foam has been applied. Other exposure controls include the proper selection of PPE including skin, eye, and respiratory protection. Worker exposure should also be minimized with frequent health and safety meetings, using experienced workers, and using good personal hygiene and termination practices. CONTROL POINT: Construction, Operations

c. Radiological Hazards

Description: Radiological materials may have been buried, or naturally occurring radioactive material (NORM) may be present in soils, sludge and groundwater. Some radioactive materials may present an external hazard. All radioactive materials may present an internal exposure hazard through inhalation or ingestion. It should be noted that this may be a rare hazard to encounter using this remediation technology.

Control: The presence of radioactive materials may be known or the soil, sludge, or groundwater may be tested to determine if radioactive materials are present. If any radioactive material above background levels is found, a qualified health physicist should be consulted to determine exposure potential and any necessary engineered controls or PPE. CONTROL POINT: Design, Construction, Operations

d. Biological Hazards

(1) Description: At those sites involving medical wastes or sewage sludge, microorganisms in the soil may pose exposure hazards during the soil mixing and waste stabilization activities. Workers may be exposed to inhalation/ingestion/dermal contact with pathogens, such as Coccidioides sp., Histoplasma sp., and Mycobacterium sp. if contaminated dusts become airborne.

Control: The generation of airborne microbe-contaminated dust may be reduced by the periodic application of water, amended water, or emission-suppressing foams to the active excavation and mixing areas. The addition of foam to control vapors may also create a slip and fall hazard. Workers should not walk on areas to which foam has been applied. Other controls may include minimizing the amount of soil agitation during mixing operations, the erection of wind screens and portable surface covers, the use of the proper types of PPE (e.g. an air-purifying respirator with HEPA filter/cartridge), use of experienced workers, repeated health and safety meetings, decontamination stations, and other standard procedures. CONTROL POINT: Design, Operations

(2) Description: Workers may be exposed to a wide array of biological hazards, including snakes, bees, wasps, ticks, hornets, and rodents, during any phase of remediation. The symptoms of exposure vary from mild irritation to anaphylactic shock and death. Exposure to deer ticks may cause Lyme disease.

Control: Periodic inspections of the site should be performed to identify stinging insect nests and for the presence of snakes. Professional exterminating companies should be consulted for removal. Tick and insect repellents may be used for exposure control. However, workers should check their skin and clothing for ticks periodically throughout the work day. CONTROL POINT: Construction, Operations, Maintenance