an appropriate material selection. In the absence
of water quality data, it is prudent to choose
conservative materials.
Stainless steel (SS) piping offers high strength and
rigidity sufficient to withstand virtually any
subsurface condition, and is highly resistant to
corrosion. SS is susceptible to degradation in
long-term exposure to highly corrosive environments,
including saline and certain acidic environments.
This degradation results in the leaching of nickel
and cadmium into the sampling regime.
PVC piping is lightweight, corrosion resistant,
durable, and generally chemically resistant. PVC is
susceptible to degradation in long-term exposure to
high concentrations of certain organic solvents.
These include tetrahydrofuran (THF), methyl ethyl
ketone (MEK), methyl isobutyl ketone (MIBK), and
cyclohexanone.
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2.1.1
Stainless Steel Piping
ASTM A 312/A 312M, Type 304, Schedule 40S, with flush threaded joint end
fittings. Threaded joints shall be wrapped with flouropolymer tape, and
provided with nitrile O-ring gaskets.
2.1.2
PVC Piping
ASTM F 480, Type 1, Grade 1, PVC 12454, NSF wc or NSF pw, Schedule [40]
[80], with flush threaded joint fittings. Threaded joints shall be wrapped
with flouropolymer tape, and provided with nitrile O-ring gaskets.
2.2
WELL SCREEN
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NOTE: Well screens are located in the most reactive
zone of the well environment. The material
selection should be made based on similar criteria
as the well casing materials. However, in some
situations, well screen material may be different
from the material selected for the casing. Strength
of the screen is important, as it has large open
area. The width of the slotted openings should be
sized relative to the filter pack material, and
should retain between 90 and 99 percent of that
material. The open area of the screen should allow
flow through the screen at approximately the same
rate as the natural permeability of the aquifer.
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Well screens shall be located as indicated. The length of [each] [the]
screen shall be as indicated. Slot size shall be [_____] mm inch. Slotted
openings shall be distributed uniformly around the circumference of the
screen. Open area shall approach the formation's natural porosity.
SECTION 02525N
Page 9
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