Hazards excavations

General safety hazards, such as but not limited to, electrical hazards, powered equipment hazards, motor vehicle hazards, walking- and working-surface hazards, excavation hazards, and hazards associated with working in hot and cold temperature extremes. 

The generation of hazardous wastes by spillage must also be considered. The quantities of hazardous wastes that are involved in spiUage usually are not known. After a spUl, the wastes requiring collection and disposal are often significantly greater than the amount of spiUed wastes, especially when an absorbing material, such as straw, is used to soak up liquid hazardous wastes or when the soU into which a hazardous liquid waste has percolated must be excavated. Both the straw and hquid and the soU and the liqmd are classified as hazardous wastes. 

Equipment for Superfund Waste Shipment RCRA hazardous waste that has been spilled, improperly landfilled, or dredged from defunct lagoons is a CERCLA waste, more commonly referred to as a Superfuna waste. For clean-ups where offsite treatment is the chosen solution, soil is excavated and placed in 15-m roll-off box or dump body truck. The trucks may be lined with polyethylene to reduce... 

Safety hazards are treated in the same manner. For example, workers who work in trenches in clean areas of the site would be covered by the OSHA Excavation and Trenching Standard, Subpart P, 29 CFR 1926. Workers who work in trenches in contaminated areas would fall under both Subpart P and HAZWOPER. Workers who do not work in trenches fall under HAZWOPER only when working in contaminated areas and would not be covered by either standard when working solely in clean areas, provided they are not exposed to safety hazards resulting from hazardous waste operations. 

The Brio refining site is approximately 58 acres in size and is the location of a former chemical production, recovery, refinery, and regeneration facility. The site includes closed impoundments into which hazardous substances were disposed in bulk, storage tanks, and approximately 1,750 drums of hazardous substances. Remediation activities included the excavation and incineration of contaminated soil, installation of protective liners around selected pits, and the installation of a groundwater extraction system adjacent to a gully. 

Raghavan, A., Coles, E. and Dietz, D., Cleaning excavated soil using extraction agents a state-of-the art review, J. Hazard. Mater., 26, 81-87, 1991. 

It should be noted that early remedial actions for contaminated soil consisted primarily of excavation and removal of the contaminated soil from the site and its disposal at a landfill. SARA strongly recommends on-site treatment that permanently and significantly reduces the volume, toxicity, or mobility of hazardous substances, and utilizes cost-effective permanent solutions. The legislation prohibits land disposal of hazardous wastes unless U.S. EPA determines otherwise (as in the Hazardous and Solid Waste Amendments, HSWA). 

High-permeability passive perimeter gas control systems entail the installation of highly permeable (relative to the surrounding soil) trenches or wells between the hazardous waste site and the area to be protected (Figure 16.6). The permeable material offers conditions more conductive to gas flow than the surrounding soil, and provides paths of flow to the points of release. High-permeability systems usually take the form of trenches or wells excavated outside the site, then backfilled with a highly permeable medium such as coarse crushed stone. 

Remedying hazards posed by excavated soils resulting from response activities... 

In June of 2003, the U.S. Army unearthed 113 bacteria-containing vials, including live strains of brucellosis and non-virulent anthrax, during excavation of its Fort Detrick site to eliminate toxic chemicals and hazardous waste. (Credit The Council for Responsible Genetics)... 

Well construction minimizes the generation of significant quantities of potentially hazardous soils in contrast to significant volumes potentially generated by trench excavation. 

The normal cost for treatment of soils is under 100 per ton treated. The vendor claims that this is less expensive than excavation and hauhng and eliminates the need for hazardous waste disposal and the associated liabihty (personal communication, James Roma, KEECO, 9/97). 

Metal reclamation of sediments uses many of the same approaches as for soils, except that sediment access is often more difficult. Once removed from the bottom of a lake or river, sediments can be treated and replaced, or landfilled in a hazardous waste containment site. The actual removal of sediments involves dredging. This can pose serious problems since dredging includes the excavation of sediments from benthic anaerobic conditions to more atmospheric oxidizing conditions. This can result in increased solubilization of metals, along with increased bioavailability (see Section 10.3) and potential toxicity, and increased risk of contaminant spreading (Moore, Ficklin Johns, 1988 Jorgensen, 1989 Moore, 1994). There are ongoing discussions as to whether it is more detrimental to remove sediments, whether for treatment or removal, or simply to leave them in place. 

Describe possible mechanisms by which hazardous substances could be released from a disposal facility. A credible series of processes and events that could result in release of hazardous substances from the disposal site to a portion of the environment that is accessible to humans and the probability that these processes and events would occur, often called a release scenario, is developed. Release scenarios for waste disposal facilities generally should include considerations of inadvertent human intrusion resulting from normal activities, such as excavation or drilling, as well as releases to air and groundwater due to natural processes and events. 

Site investigation and remediation projects usually include the disposal of investigation-derived waste (IDW), for example, soil from cuttings or excavations, equipment decontamination water, purged groundwater from well installation, etc. To determine whether these waste streams may be hazardous, we should consider their source, and, if necessary, chemically characterize the streams for the determination of disposal options. The disposal facility acceptance criteria would be the action levels in this case. 

The costs of cleaning up hazardous waste, petroleum, and other contamination can be significant. Superfund sites commonly cost more than 30 million to remediate. The State of New York estimates that it would cost approximately 15— 20 million to excavate and dispose of wastes at a small industrial landfill, or approximately 3 million for the lower-cost alternative of capping [New York Department of Environmental Conservation (NYDEC) 2007]. Although costs are highly variable, it is clear that environmental cleanup is very expensive, and that like site assessments, cleanup will not happen without significant financial support. 

Location of buried materials at a hazardous waste site is usually for the purpose of remedial action l.e., excavating these materials and ultimately disposing of them. The key unknowns are type (bulk-dumped or packaged in drums or other containers), quantity (volume of waste number of drums), and location, particularly depth of burial. The concerns are for safe excavation without puncturing containers or breaching any existing trench liners and thus aggravating the cleanup problems. 

Destressing blasting serves to loosen up the rock mass in order to distribute high compressive loads more uniformly and to counteract the hazard of rockbursts. Rockbursts are particulary violent fracture processes, accompanied by considerable earth tremors. They mainly consist of a sudden thrust or ejection of the rock involved (coal salts massive rocks) and abrupt closure of the excavation. In coal seams,... 

The extent of cleanup that is necessar> to protect human health and welfare arics with different use categories. Residential development is probably the most sensiti e type of land use because of the long-term and multiple e.xposure routes and because of potential e. posurc to tlie most sensitive population segments (e.g., children and elderly persons). Excavation and removal appears to be the remedial action alternative selected at most sites where there is redevelopment. This is because no one can guarantee tliat a site is safe (i.e.. offers zero risk) unless all contaminants are removed. Neitlier a de eloper nor a municipality can accept responsibility for site safety as long as hazardous materials remain there. In situ treatment approaches are seldom icwed as the best option because they arc unproven and because 100% detoxification or stabilization caimot be achieved. 

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