through the system for another 23 hours. At the
pared detergent washes with plain water washes.
end of this time, they were still able to detect low
Method 1 involved injecting 30 gal warm water
(49C or 120F) with detergent (1%), followed by
ppb levels (1.1 to 18) of TCE in water pumped
through the system. They concluded that rubber
rinsing with 10 gal of ambient-temperature wa-
hose could not be decontaminated using this meth-
ter. Method 2 was similar, except that only half
od in an acceptable amount of time.
the previous amount of cleaning and rinsing so-
In all of their subsequent tests they used the
lutions were used (15 gal of detergent wash water
same methodology except that they used FEP tub-
and 5 gal of ambient rinse water). Method 3 in-
ing rather than the rubber hose and the original
volved washing with 30 gal warm water (no de-
exposure time was less, 30 minutes. In the third
tergent) followed by a 10-gal rinse with ambient-
test, they found that TCE concentrations were be-
temperature water. Method 4 was similar except
low the detection limit (0.5 ppb) after pumping
that the amount of water was again half (15 gal
clean water for 90 minutes. The initial level of
warm water, 5 gal ambient-temperature water).
TCE contamination was similar to the previous
The four solutions were pumped through a stain-
studies, approximately 1200 ppb. In the next
less-steel bladder pump (equipped with a PTFE
(fourth) trial, they were unable to completely de-
bladder) and PTFE-lined sample tubing. After re-
contaminate the system. They found that, after
moving the pump from the well, the external sur-
pumping clean water through the system for 120
faces of the pump and tubing assembly were steam
minutes, concentrations of Freon 113 (1,1,2-trichlo-
cleaned before circulating the cleaning fluids
ro-2,2,1-trifluoroethane) ranged from 1.7 to 21 ppb;
through the pump. The pump had been used to
initial concentrations of this analyte were approx-
sample VOCs; a minimum of five sampling
imately 3900 ppb. In the fifth test, 1,1-dichloroet-
pump/tubing assembly volumes of contaminated
hylene concentrations dropped below the detec-
water were pumped from the well between de-
tion limit (0.5 ppb) after pumping clean water for
contamination procedures.
only 7 minutes. However, the initial concentra-
In the first study, initial concentrations of TCE
tion of this contaminant was much lower, only
in the well water were 300 mg/L. They found that
about 120 ppb. In the sixth test, dimethyl nitro-
all four methods yielded rinse water with no TCE
samine concentrations fell below the detection lim-
contamination. In a field test, they found no VOCs
it (0.2 ppb) after pumping clean water for only 3
in 26 of 28 quality-control samples taken after us-
minutes. Again, initial concentrations were low
ing method 2 to clean the sampling device. Al-
(~30 ppb). The next two tests indicated that metal
though they claimed there was no effect of con-
contaminants are more readily decontaminated.
centration on decontamination efficiency, the data
(Selenium concentrations dropped below the de-
do not support this claim. TCE concentrations of
1.0 g/L and 1.8 g/L were found in the two sam-
tection limit--5 ppb--after pumping clean water
for only 3 min; initial concentrations were 610 ppb
ples that were pumped from the two wells with
the highest TCE concentrations (1600 g/L and
in the contaminated well. In another test, initial
2215 g/L, respectively). For the rest of the study,
chromium concentrations in the well water were
43,000 ppb. However after pumping with clean
initial concentrations of TCE in well water were
water for 20 minutes, concentrations were at the
much lower (all but one sample had concentra-
background level.) They concluded that residual
tions of 300 ppb or less) and initial concentrations
TCE concentrations dropped off more rapidly us-
of the other VOCs (1,1-dichloroethane, 1,1-dichlo-
ing Teflon than rubber hose. However, given that
roethylene, tetrachloroethylene, and 1,1,1-trichlo-
roethane) were in the low (< 10 g/L) range.
the initial contact time was 4 times longer for the
rubber hose than for the FEP tubing, a valid com-
Schuh et al. (1993) tested the effectiveness of a
parison cannot be made. It is clear from this data
distilled water rinse for removing seven pesticides
that decontaminating either type of tubing by
[bromoxynil, diclofop-methyl, dimethoate, 2-
steam cleaning the exterior and pumping clean
methyl-4-chlorophenoxyacetic acid (MCPA), me-
water through the system can be time-consuming
thyl parathion, propiconazole, and trifluralin]
and ineffective for certain organic contaminants,
from a PVC bailer. They found that the effective-
especially if the initial concentrations of the con-
ness of this procedure depended on the analyte's
solubility in water and its Kow value. Contact time
taminants are in the ppm range and contact times
was brief (1 minute); they felt that a 1-min con-
are 30 minutes or more.
tact time was representative for samples taken in
Fink et al. (1989) evaluated four methods for
a shallow well or gravelly aquifer. They found
decontaminating a sampling pump. This test com-
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