Safety 1st Advancer Manual do Operador descarregar pdf (Página 29)

Environmental Remediation Drilling

Safety Guidelines

Page 29 of 132

2.11 - Clearance Methodologies cont.

As the stream leaves the nozzle, it expands concentrically, since it is surrounded by atmospheric air. This

high velocity air penetrates the ground to a depth of about a foot, creating a momentary cavity of about a

foot in diameter, in which the soil structure is crumbled.

Hard clays and other very hard soils will be slow during the first several inches of depth, and will produce

increased scatter. But somewhat deeper, where the soil has usually retained greater moisture, the scatter will

reduce, and the excavation rate will improve.

Both dry and wet applications of these technologies can be performed. Both methods have inherent

problems associated with compromising the borehole for collection of environmental samples. Typically,

dry air knifing and vacuum extraction are preferred where soil samples must be collected in the top 5 feet of

profile. Water jetting or wet vacuuming may also compromise future collection of groundwater samples, so

is usually selected for boreholes advanced for remediation wells only.

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Safety 1st Advancer Manual do Operador Página 29