Abstract
The design, performance, and analysis of a soil vapor
extraction system to identify zones most conductive to air
transport and quantify kair in sequential soil layers is
presented. A multi-level extraction well, with alternating
solid and screened sections, was utilized to characterize
multi-layered media. The field site, located in the Carolina
Slate Belt within the physiographic region known as the
Piedmont, is comprised of alternating layers of different soil
types of varying kair , including thin bands of clay, silt, and
sand.
The pneumatic test consisted of one multi-level
extraction well and four multi-level pressure monitoring
wells. Screen locations were based on previous site
characterization. Vapors were extracted at one screen while
pressure, temperature, and volumetric flow rate were monitored
using a computer data acquisition system. Data was analyzed
by both steady-state and transient solution techniques using
pressure drawdown versus time data collected at various
locations.
Results from vapor extraction tests indicate that the
multi-level approach is advantageous when dealing with
heterogenous media, since the most permeable layer was
identified. Transient and steady-state solutions indicate
that a kair= 2.0 X 10-7 cm2 is representative of the located
permeable layer within the subsurface. Vacuum system,
formation, and extraction well characteristics are evaluated
to determine pressure as a function of volumetric flow rate.
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