sample was collected to determine the initial con-
Sampling devices. The wall of the dual-check
centrations of the analytes in the well or standpipe.
valve bailer was made of fluorinated ethylene
The system was then left for 24 hours, and then
propylene (FEP), and the top and bottom check
another ten volumes were pumped through the
assemblies were made of PTFE. The bailer had a
system. Another sample was taken at this point to
350-mL capacity, was 12 in. in length, and had an
determine analyte concentrations in the well, or
outside diameter of 1.88 in. It was raised and
standpipe, at the time the system was decontami-
lowered on a nylon line.
nated. The pump was then removed from the
The bladder pump consisted of a stainless steel
well, drained, and decontaminated (described later
(type 316) body with a PTFE bladder. The pump
in the text).
was 1.5 in. in diameter and approximately 41 in.
After decontamination, the devices were used
in length. The pump was attached to either 96 ft
to sample distilled (DI) water. For the bailer, this
or 135 ft of twin-line bonded tubing. The com-
was done by lowering the bailer (without the sam-
pressed air supply line was polyethylene (0.25-in.
pling line) into a 1-L, glass graduated cylinder
o.d.) and the sample discharge line was FEP-lined
filled with DI water and allowing it to sit for two
polyethylene (0.50-in. o.d., with the FEP lining
minutes. Again, a two-minute contact time was
0.0165 in. thick and the PE layer 0.042 in. thick).
used to simulate the time it took us to retrieve a
Air was supplied to the bladder pump with an
bailer from our deeper well. For the bladder pump,
oilless gasoline-driven compressor capable of de-
the DI water sample was taken by lowering the
livering 2.1 standard cubic feet per minute (SCFM)
pump into a clean standpipe containing DI water
at 165 psig providing lifts to 320 ft. Regulation of
and then pumping the DI water out of the
air pressure, fill and discharge cycle times, and
standpipe.
hence sample flow rates were accomplished with
The decontamination efficiency was determined
a portable pneumatic control unit. The tubing
by measuring the amount that was desorbed from
length in the deeper well was 135 ft and 96 ft in
the decontaminated sampling devices back into
the shallower well.
the distilled water during the (DI water) sampling
Virgin sampling tubing. In our third TCE study,
event. The decontamination treatment was con-
a 6-ft piece of virgin FEP tubing was used to
sidered effective if we were unable to detect any
pump DI water. This was done to separate the
residual contaminant in the distilled water sample.
r e l a t i v e contaminant contributions of the
"cleaned" bladder pump and tubing. Prior to
Materials
the study, the virgin tubing was cleaned by
TCE-contaminated monitoring wells. Four-in.-
running DI water through it for several min-
diameter PVC casing and screen were used in
utes. A blank sample was then taken and no
the two monitoring wells. One well was ~139 ft
TCE was found.
deep with a static water level of 130 ft. This well
Pressure washer. A tap outside of our laboratory
had consistently high TCE concentrations (~150
building supplied ambient temperature tap water
to a high-temperature (~99C) pressure (1000 psi)
mg/L). The other well was ~100 ft deep with a
static water level of 87 ft, and it had consis-
washer. The pressure washer supplied the hot
tently low concentrations (~0.02 mg/L) of TCE.
detergent solution and the hot water rinse water.
Both wells contained bladder pumps that had
Detergent solution. A 1% Liqui-Nox detergent
been left in the well for one year. Thus, the
solution was used. Liqui-Nox is a phosphate-free
contaminants had had time to permeate the
liquid detergent with a pH of 8.08.5, is biode-
polymeric materials in the bladder and lines.
gradable, and is recommended by the manufac-
Standpipes. The standpipes used to hold the
turer for cleaning equipment that is used for envi-
contaminated well water and the distilled water
ronmental sampling and testing.
consisted of 8-in.-diameter, schedule 40 PVC
DI water. DI water was provided by running a
pipe, approximately 8 ft long. A PVC end cap
virgin LDPE line out the window of our chemis-
was pounded on one end of the pipe; no organic
try laboratory to either our washing station or to
solvent was used to join the end cap and casing.
the DI-water standpipe (both directly outside of
Another small standpipe was used in some
the laboratory). The tubing was cleaned by run-
experiments for washing the pump. It consisted
ning several volumes of DI water through the line
of a 3-in.-diameter, schedule 40 PVC pipe ap-
and then collecting a blank sample. No TCE, pes-
proximately 4 ft long. The PVC end cap was in-
ticides, or munitions were found in any of the
stalled as described previously.
blank samples.
5
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