Susceptibility of ABS, FEP, FRE, FRP, PTFE, and
PVC Well Casings to Degradation by Chemicals
THOMAS A. RANNEY AND LOUISE V. PARKER
previous report [Ranney and Parker 1994]). Also,
INTRODUCTION
previous studies by this laboratory (Hewitt 1989,
Ideally, any material used as either a well cas-
1992, 1993, Parker et al. 1990, Ranney and Parker
ing or a screen in a groundwater monitoring well
1994) and others (Reynolds and Gillham 1985,
should retain sufficient strength once installed in
Gillham and O'Hannesin 1990, Reynolds et al.
the well, should resist degradation by the envi-
1990) have shown that none of these materials are
ronment, and should not affect contaminant con-
chemically inert with respect to sorption and
centrations in samples by leaching or sorbing or-
leaching of analytes of interest. In these studies,
ganics or metals. Recent guidance by the U.S. En-
PVC and PTFE sorbed organics, and PVC and SS
vironmental Protection Agency (U.S. EPA 1992)
sorbed and leached metals.
acknowledges that none of the most commonly
Recently we started a series of laboratory
used well casing materials in groundwater moni-
studies to determine the overall suitability of four
toring (polytetrafluoroethylene [PTFE], polyvi-
other pipe and casing materials (acrylonitrile bu-
nyl chloride [PVC], or stainless steel) can be used
tadiene styrene [ABS], fluorinated ethylene pro-
for all monitoring applications. Strength consid-
pylene [FEP], fiberglass-reinforced epoxy [FRE],
erations limit the depth to which PTFE, and to a
and fiberglass-reinforced plastic [FRP]) for ground-
lesser extent PVC, can be used. The maximum
water monitoring applications. In the first study
depth PTFE can be used is 225 to 375 ft (69 to 114
we (Ranney and Parker 1994) compared sorption
m), while the maximum depth PVC can be used
of a suite of dilute organic solutes by these four
is 1200 to 2000 ft (366 to 610 m). While PTFE is
materials, along with PVC and PTFE. We found
very inert to degradation by chemicals (App. A,
that ABS sorbed organic contaminants much
B), PVC is degraded by several neat organic sol-
more rapidly and to a greater extent than the
vents, including low molecular weight ketones,
other five materials; losses ranged from 19 to 74%
aldehydes, amines, and chlorinated alkanes and
after only eight hours. On the other hand, FRE
alkenes (Barcelona et al. 1984). (See App. A and B
and PVC were relatively nonsorptive, and by the
for specific chemicals.) PVC can also be degraded
end of the study (6 weeks) losses were no greater
by high concentrations (near solubility) of these
than 25%. FEP, FRP, and PTFE were intermediate
organic chemicals in aqueous solution (Berens
in their performance, and none of these materials
1985, Vonk 1985, 1986). Stainless steel will rust if
performed consistently better than the other.
corrosive conditions exist. These include a pH
We also found that ABS, FRP, and FRE leached
<7.0, a dissolved oxygen content >2 ppm, H2S
contaminants into the test solution. These con-
levels ≥1 ppm, total dissolved solids content
taminants were observed as spurious peaks in the
>1000 ppm, CO2 levels >50 ppm, and Cl- concen-
HPLC analyses. FRE leached one contaminant
trations >500 ppm (Aller et al. 1989, modified
while FRP and ABS leached several contaminants
from Driscoll 1986). (Additional information on
(five and eleven, respectively). Several of these
the susceptibility of stainless steel 304 and 316 to
peaks were identified by purge and trap GC/MS
a wide range of chemicals can be found in the
analyses. With respect to leaching, our results
Cole-Parmer catalog [Cole-Parmer 1992] or in our
agree well with those of Cowgill (1988) for FRE
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