Environmental Engineering Reference
In-Depth Information
•
Deine
: After contamination is found, the purpose of the define-type of investiga-
tion is to evaluate the nature and extent of contamination. Define-type investiga-
tions may consist of several phases requiring a greatly expanded scope compared
to the find-type of investigation. The resulting scope depends upon the following
factors:
• Federal- or state-specific requirements for each contaminant of concern
• The media being evaluated (e.g., soil, groundwater, sediment, surface water)
• The pathways being considered (e.g., ingestion, inhalation, dermal contact)
• Background concentrations of heavy metals such as lead or arsenic
The extent is derived laterally and vertically by these two equivalencies: (1) to the concen-
tration equal to or less than the lowest applicable cleanup criteria for nonnaturally occur-
ring compounds; and (2) to background concentrations for those compounds naturally
occurring in the environment, such as heavy metals.
•
Reine
: The purpose of the “refine” type of investigation is to gather addi-
tional information about the contamination and determine if an unacceptable
risk to human health and the environment exists and requires remedial action.
Refine-type investigations include collecting and analyzing samples from loca-
tions of highest risk for specialized analytical parameters to evaluate certain
remedial options, or to gather more specific data on the nature and extent of
contamination.
Phase II environmental investigations are conducted separately for soil and groundwater
and are discussed in Section 4.3.
4.2.4 Geophysical Investigation
There are occasions when direct sampling under a traditional Phase II investigation
approach does not adequately characterize a specific site. Examples may include areas not
accessible to sampling equipment, extremely large sites, or locations where buried objects
are of great concern or are under investigation. In these cases, surface geophysical tech-
niques may be used to fill in the data gaps.
Since geophysical investigations provide supplemental data, they rarely are the only
type of environmental investigation conducted at a site. There are a wide range of geo-
physical techniques to accommodate different objectives, investigative requirements, and
site limitations, and these techniques offer certain advantages, including
• Increasing the accuracy and area of coverage of subsurface investigations
• Increasing data density
• Collecting data on subsurface geology and hydrogeology at locations inaccessible
to other investigative techniques, or areas considered too dangerous to investigate
using other methods
• Decreasing the cost and time necessary to characterize certain sites, and are gen-
erally noninvasive
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