Environmental Engineering Reference
In-Depth Information
variation of the Kemmerer that lowers horizontally and is more appropriate for
estuary sampling.
Groundwater Sampling
Groundwater samples are collected from a well by a bailer or pumps of various types
(Fig. 4.4). A bailer is a pipe with an open top and a check valve at the bottom (3 ft
long with a 1.5 inch internal diameter and 1 L capacity). A line is used to
mechanically lower the bailer into the well to retrieve a volume of water. A bailer is
easy to use and transport but it may generate turbulence when the bailer is dropped
down to the well and it is exposed to atmospheric O
2
when the sampled water is
poured into a container. Bottom-filled bailers, which are more commonly used, are
suitable provided that care is taken to preserve VOCs.
A peristaltic pump consists of a rotor with ball-bearing rollers. Dedicated
tubings are attached to both ends of the rotor. One end is inserted into the well and the
other end is a discharge tube. A peristaltic pump is suitable for sampling wells of small
diameter (e.g., 2 inches) and has a depth limitation of 25 ft. Cross-contamination is
not of concern because dedicated tubing is used and the sample does not come in
contact with the pump or other equipment. It can result in a potential loss of VOCs
due to sample aeration.
(a)
(c)
Cable
1.14” O.D. ×1” ID Teflon
extruded tubing 18 to 36” Long
1/4” Air Line
Air line
to
pressure
Sample line
Lifting bal
Check valve
1” PVC pipe
Perforated
Flow tube
Flexible
diaphram
3.4” Diameter
Glass or Teflon
1” Diameter teflon
extruded Rod
Annular
space
Bladder
5.10” Diameter hole
(b)
Peristaltic
pump
Intake valve
assembly
(Inside screen)
Chock valve
Medical-grade silicone
tubing
Anti
clogging
screen
Rotor
Intake
Assorted lengths
of Teflon tubing
Discharge to
sample containers
Figure 4.4
Common sampling tools used for groundwater: (a) Bailer, (b) Peristaltic pump, and
(c) Bladder pump (U.S. Army Corps of Engineers, 2001)
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