8-2 Hazard Analysis

Principal unique hazards associated with soil vapor extraction (in-situ)/bioventing/biodegradation/thermally enhanced soil vapor extraction include:

a. Physical Hazards

(1) Description: During excavation of trenches during the installation of horizontal piping systems, workers may be seriously injured or killed by heavy equipment such as front-end loaders and scrapers operating in their work areas. This equipment may also generate excessive noise during operation.

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 used. CONTROL POINT: Construction, Operations, Maintenance

(2) Description: Fire or explosion hazards may exist should excavation equipment rupture an underground utility such as electrical or gas lines during installation of the system.

Control: To control utility contact hazards, identify the location of all below- and above-ground utilities. 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 to determine the exact location of utilities prior to drilling. Once utilities are located, careful excavation by backhoe may be allowed. CONTROL POINT: Design, Construction

(3) Description: During the transfer of flammable gas from the extraction wells or subsurface piping systems to the treatment unit, a fire or explosion hazard may exist. The gas may be ignited by improperly selected or installed equipment.

Control: Verify that the hazardous area classifications, as defined in NFPA 70-500-1 through 500-10, are indicated on the drawings. All controls, wiring, and equipment should be in conformance with the requirements of EM 385-1-1, Section 11.G and NFPA 70 for the identified hazard areas. Equipment should be grounded and/or provided with ground fault interrupter circuit (GFIC) protection if required by EM 385-1-1, Section 11 or NFPA 70 requirements. The atmosphere around the area should be periodically monitored with a combustible gas monitor. If the concentration of explosive gas reaches 10% of the Lower Explosive Level (LEL) or greater, the system should be inspected for leaks and emission points. All sources of VOC emissions should be controlled to prevent the release of flammable gas. A permanent explosion level meter/alarm may also be needed. CONTROL POINT: Design, Construction

(4) Description: Thermally enhanced SVE systems may incorporate the use of steam to heat soils to be treated. Pressure caused by plugged steam lines may cause a rupture or an explosion in the system.

Control: Controls to prevent an explosion hazard include operating the steam generator within its design parameters and the use of emergency pressure relief valves. Steam lines should be periodically flushed to remove any accumulated scale or deposits. CONTROL POINT: Design, Operations, Maintenance

(5) Description: The surface temperature of uninsulated steam generators and piping systems may reach several hundred degrees and pose a burn hazard to workers. Catalytic oxidation system components can be quite hot, and also pose a burn hazard. Cryogenic systems, associated with O₂ delivery systems, can have very cold surfaces and pose a contact freezing hazard.

Control: Controls to help prevent burn hazards include properly insulating surfaces, including hazard warning signs on the equipment, and providing physical covers to prevent contact. CONTROL POINT: Design, Construction, Operations, Maintenance

(6) Description: High levels of noise may be generated by blowers and compressors and may result in hearing loss. Unprotected blowers and fans may entangle workers' clothing and cause injury.

Control: Equipment noise should be controlled with the use of insulation materials, barriers, proper lubrication and proper maintenance of equipment. The use of personal hearing protection should be required when working in areas of elevated noise levels. All moving and rotating equipment should be guarded, and workers informed that all such equipment be operated only with guards in place. CONTROL POINT: Design, Operations

(7) Description: During drilling operations, heavy equipment such as augers and pipes are periodically raised overhead and placed into or above the well. Workers may be exposed to swinging equipment during lifting, or may be exposed to crushing hazards if the equipment falls. Cables used to raise and lower equipment may also become entangled in loose clothing or other equipment. Direct push drilling methods using hydraulic pressure to advance a soil boring may pose a crushing hazard to hands and/or feet.

Control: When raising a drill mast, always have an observer to the side to observe and supervise. Do not move the drilling rig with the mast raised. Controls to help prevent workers from becoming entangled with the revolving augers include securing all loose clothing, using low-profile auger pins, and using long-handled shovels to remove soil cuttings from the borehole. Cables systems should be used with caution, and inspected regularly for loose strands or frayed wires that may become entangled in loose clothing. CONTROL POINT: Design, Maintenance

(8) Description: Electrocution or fire hazards may exist when using hollow-stemmed auger, direct push, or other drilling methods if the drilling mast contacts overhead electric lines or piping systems containing flammable chemicals.

Control: To control potential electrocution or fire hazards associated with overhead lines or piping systems, inform all workers as to the location of overhead utilities. Drill in an alternative location if possible. 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. When raising a drill mast, always have a worker observe and supervise. Operate the mast at its lowest height; different drill rigs will have different mast elevations and may be operated at different heights. CONTROL POINT: Design, Construction, Maintenance

(9) Description: Operation of temporary and permanent electrical equipment, such as lights, generators and heated SVE system components, may cause electrical hazards.

Control: Verify that the hazardous area classifications, as defined in NFPA 70-500-1 through 500-10, are indicated on the drawings. All controls, wiring, and equipment should be in conformance with the requirements of EM 385-1-1, Section 11.G and NFPA 70 for the identified hazardous areas. Equipment should be grounded and/or provided with ground fault interrupter circuit (GFIC) protection if required by EM 385-1-1, Section 11 or NFPA 70 requirements. CONTROL POINT: Design, Construction, Operations, Maintenance

(10) Description: Improper storage and use of cylinders of compressed gases in some bioventing systems may cause explosive or projectile hazards.

Control: Cylinders of compressed gases should be stored upright, capped when not in use, and secured to prevent movement. Extreme temperatures should be avoided. CONTROL POINT: Design, Operations

(11) 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: Construction, Operations, Maintenance

(12) Description: Manual lifting of heavy objects may expose workers to back, arm, and shoulder injuries.

Control: Workers should not be required to lift heavy loads manually. Some loads may require two people. Proper lifting techniques include stretching, bending at the knees, and bringing the load close to the body prior to lifting (see EM 385-1-1, Section 14.A). Mechanical lifting equipment, such as forklifts, should be used to lift or to move loads. CONTROL POINT: Design, Construction, Operations, Maintenance

b. Chemical Hazards

(1) Description: Biological degradation of certain organic compounds may produce toxic intermediate products (e.g. degradation of TCE can produce DCE and VC. Vinyl chloride exists as a gas and may accumulate to higher levels in boreholes or in the system). Workers may be exposed to the degradation products during operation or maintenance of the system.

Control: Controls to minimize exposure include ventilation of the effected area. Air-supplied respiratory protection may also be required to be used on monitoring(e.g. air-purifying respirators are not recommended for vinyl chloride). Remediation designers should understand and anticipate the generation and management of general and specific process products (e.g. carbon dioxide, hydrogen sulfide, vinyl chloride(CO₂, H₂S, VC)), and design for their management. CONTROL POINT: Design, Operations, Maintenance

(2) Description: During installation of the wells and system operations and maintenance, workers may be exposed to dermal or inhalation hazards associated with waste chemicals, such as airborne dusts and particulates, and VOC emissions resulting from off gassing or leaks.

Control: During installation, workers may need to apply water or surfactant amended water solution to the area to help control generation of airborne dusts, particulates, and VOCs. During installation and operation, proper ventilation and personal protective equipment (PPE) should be used (e.g. an air-purifying respirator with organic vapor cartridges). Closed systems, such as SVE, should be routinely checked for leaks of the off-gas treatment system with PIDs, air samples, O₂ meters, leak detection fluids, explosive gas meters, or specific gas tests with chemical-specific detector tubes. Leaks should be repaired immediately. Vent stack heights should be adequate to disperse off gas. Designers should anticipate byproducts and products, and be certain that technologies selected for treatment (e.g. activated carbon, condensation, catalytic oxidation) of off-gas residuals are both effective and safe. CONTROL POINT: Design, Construction, Operations, Maintenance

(3) Description: Air injection may cause the migration of VOCs to low areas, such as basements, sewers and other areas. The accumulated gases can cause an explosion, if the VOCs are flammable, or chemical exposure to the occupants.

Control: Periodic air testing to ensure safe levels should be performed in basements and other areas where VOCs may migrate. CONTROL POINT: Design, Operations, Maintenance

(4) Description: Workers may be exposed to VOCs as they are discharged from the blower vent.

Control: Emission controls, such as activated carbon canisters, should be installed on the blower vent discharge and should be periodically monitored for efficiency. CONTROL POINT: Design, Operations, Maintenance

(5) Description: Fire and/or explosion or chemical release (inhalation/ingestion/asphyxiation) hazards may exist when using hollow-stemmed auger, direct push, or other drilling methods if the drilling bit or bucket ruptures underground utilities, or tanks/piping systems (overhead chemical feed lines) containing hazardous chemicals.

Control: Perform a utility survey, probe with a metal rod prior to excavation, or hand excavate to determine the exact location of underground lines prior to drilling. During design, locate overhead hazards and design so that installations using erect equipment are not necessary in that area, if possible. CONTROL POINT: Construction

c. Radiological Hazards

Description: In some geological settings, workers may be exposed to naturally occurring radon gas. The gas is drawn from the soil in the SVE stream. Radon gas and radon progeny do not present a significant external hazard. While breakdown products of radon (progeny) may present an inhalation/ingestion hazard, quantities of radon progeny normally present would not pose a significant exposure hazard.

Control: Proper operation of emission control technologies will limit exposure to acceptable levels. Should excessive levels be suspected from previous site knowledge, or should excessive levels or radon be encountered, a qualified health physicist should be consulted for proper guidance. CONTROL POINT: Design, Operations, Maintenance

d. Biological Hazards

(1) Description: At those sites involving medical wastes or sewage sludge, microorganisms in the soil may pose exposure hazards during system installation 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 during installation activities may be reduced by the periodic application of water, surfactant amended water, or emission-suppressing foams to the active excavation/drilling 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 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 and rubber gloves), use of experienced workers, repeated health and safety meetings, decontamination stations, and other standard procedures. CONTROL POINT: Construction, Maintenance

(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