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Remediation Technologies Screening Matrix, Version 4.0  
Chapter 18 Passive Treatment Walls
Table of Contents


18-2 Hazard Analysis

Principal unique hazards associated with passive treatment walls include:

Physical Hazards Chemical Hazards Radiological Hazards Biological Hazards

a. Physical Hazards

(1) Description: During installation of sheet pile walls, workers may be seriously injured or killed by heavy equipment such as front-end loaders, cranes, and pile drivers.

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. CONTROL POINT: Construction

18-1 Passive Treatment Walls

(2) Description: During the excavation of the trench prior to the installation of the passive treatment wall, fire or explosion hazards may exist should excavation equipment rupture an underground utility such as electrical or gas lines.

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

(3) Description: Entry into the trench prior to the addition of slurry material may pose a safety hazard if the trench wall collapses, or an inhalation hazard if the trench serves as an accumulation point for off gassing of toxic materials (such as chlorinated solvents) from the soil.

Control: Excavations which are to be entered should be inspected daily by a competent person. The walls may be shored to prevent collapse, according to the requirements of 29 CFR 1926.650-652. Entry into the trench should be treated as a confined-space entry, which may require testing of the atmosphere within the excavation to determine the level of airborne contaminants. CONTROL POINT: Construction

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

Control: Thermal burns 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: Design, Construction

(5) Description: Depending on soil types, exposure to respirable quartz may be a hazard. Consult geology staff to confirm the presence of a respirable quartz hazard (e.g. to determine if soil types are likely to be rich in respirable quartz). As an aid in determining respirable quartz exposure potential, sample and analyze site soils for fines content by ASTM D422, followed by analysis of the fines by X-Ray diffraction to determine fine material quartz content.

Control: Worker exposure to dust rich in respirable quartz may be minimized by periodically wetting the soil with water or amended water or by the use of respiratory protection, such as a air-purifying respirator equipped with HEPA(N100, R100, P100) filters. CONTROL POINT: Construction, Operations

(6) Description: During site activities, workers may be exposed to direct and indirect sunlight and the 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 pile drivers, should remain at least 10 feet from the power line, according to Occupational Safety and Health (OSHA) regulation 29 CFR 1926.550 and EM 385-1-1, Section 11.E. CONTROL POINT: Design, Construction, Operations

(8) Description: During the implementation of field activities, equipment and workers may come in close proximity to traffic. Also, equipment may need to cross public roads. The general public may be exposed to traffic hazards and the potential for accidents.

Control: Where equipment is to cross over roads, warning signs should be used according to the criteria 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

(1) Description: Workers may be exposed via the inhalation/ingestion/dermal exposure routes to the contaminants during the excavation of the trench if the excavation is made in contaminated soil. Dusts and volatile organic compounds (VOCs) entrained with waste materials may become airborne during the excavation, exposing workers to the waste material.

Control: To help prevent the exposure of workers to waste materials, the placement of the trench should be outside the area of contamination to the extent practical. The generation of airborne dusts may be controlled by the application of water. Personal protective equipment (PPE), such as an air-purifying respirator with organic vapor cartridges, may be used to help control worker exposure. CONTROL POINT: Design, Construction, Operations

(2) Description: Workers may be exposed to materials such as iron pyrites, coal (dust), metal chelators, and microbes used as the treatment medium during installation of the treatment wall. In addition, metals or other contaminants concentrate in the wall material and may pose a higher risk during replacement or maintenance operations.

Control: Periodic wetting of materials may control airborne dust or air-filtered respiratory protection may be used to control exposure. During installation, the concentrations of the contaminants in the wall matrix should be assessed and personal protective equipment should be selected by a qualified health and safety professional based on the contaminants and the nature of the operations. As an example for chelated metals, an air-purifying respirator with HEPA(N100, R100, P100) filters, chemically-resistant coveralls, and water/chemical impervious gloves (e.g. nitrile) may be adequate protection for installation of the wall matrix. CONTROL POINT: Construction, Maintenance

c. Radiological Hazards



d. Biological Hazards




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