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ERDC/CRREL TR-02-1
APPENDIX C: GROUNDWATER SAMPLING
Guide:
1. Review of historical records
2. Site clearance
3. Monitoring well installation
4. Groundwater sampling for the detection of EM
5. If EM are detected, groundwater contaminant monitoring
When a military range extends over a very large area, sampling the ground-
water on a potentially contaminated site can help establish whether an environ-
mental impact exists. Therefore, a sampling plan involving the collection of
groundwater samples during the initial phases is not only prudent but may help
limit the costs associated with sampling and analysis. When contamination is
found in the groundwater, a more detailed sampling plan to identify sources in
the surface and subsurface (vadose zone) should be undertaken. All related work
concerned with the installation of wells should be conducted with the participa-
tion of a hydrogeologist and after explosives clearance has been granted.
In general, there are two principle reasons for sampling groundwater: to
detect the presence of a contaminant or to monitor contaminant concentrations on
temporal and spatial scales. When sampling groundwater for energetic materials
(EM), dedicated or disposable systems are more suitable for a surveillance
program than the re-use of equipment following extensive cleaning procedures.
When the principle objective is to establish the presence or absence of explo-
sives, sampling can be performed using a variety of fairly simple techniques. One
of the most common and economical methods is to use a dedicated or disposable
bailer. However, when groundwater sampling is being used to monitor spatial
and temporal trends within a contaminant plume, the sampling protocol needs to
enhance the representativeness of the samples taken from the formation. Low-
flow (or low-stress) sampling is recommended to meet this more stringent objec-
tive (U.S. EPA Region 1 1996, Pennington 1996).
Purging of the wells is necessary for all groundwater sampling activities
because the water within the well casing may be stagnant, degassed, influenced
by the screen or casing material, or chemical oxidation may have occurred due to
contact with air. It is therefore necessary to purge a sufficient volume of water
from the well to ensure that the sample collected for analysis will be composed of
water from the formation. Purging may be accomplished using either a pump or a
bailer, depending on the objective of the sampling plan (i.e., contaminant detec-
tion or temporal and spatial monitoring). When using a bailer, this task is subject-
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