1970, PVC manufactured in other countries may be stabilized with lead or cadmium
compounds that may leach from the PVC (Barcelona et al., 1983).
Composite Alternative Materials
In certain conditions it may be advantageous to design a well using more than one
material for well components. For example, where stainless steel or fluoropolymer materials
are preferred in a specific chemical environment, costs may be saved by using PVC in
non critical portions of the well. These savings may be considerable, especially in deep wells
where only the lower portion of the well has a critical chemical environment, and where tens
of feet of lower cost PVC may be used in the upper portion of the well. In a composite well
design, dissimilar metallic components should not be used unless an electrically isolating
design is incorporated (i.e., a dielectric coupling) (USEPA, 1986).
The available open and limited distribution literature on materials used in well
construction and sampling equipment for ground water quality monitoring strongly suggest
that well casing and screen material selection should be made carefully to prevent serious
errors in analytical results. When performance studies (laboratory or field) are conducted by
the owner or operator to demonstrate the appropriateness of a particular casing material, the
studies should demonstrate chemical sorption characteristics, physical strength, and
manufacturing tolerances on the inner diameter of the casing, at a minimum. Table 11
provides a summary of recommendations for the use of certain well casing materials under
various physical and geochemical conditions which may be encountered.
The Agency discourages the practice of selecting well construction materials based on
historical preference, unless supporting scientific studies or field data collected from facilities
located in similar hydrogeologic settings and with similar wastes justify the preference.
Consideration should be given to site specific factors such as: ground water geochemistry,
chemical characteristics of present or potential contaminants, structural integrity and chemical
resistance of the well construction material, and site specific comparative performance studies
of various materials. In all cases, the Regional Administrator has the authority (40 CFR
270.32(b) and 3005(c)(3) of RCRA) to make the final determination regarding the
appropriate well casing and screening materials for RCRA ground water monitoring systems.
Facilities may need to use combinations of screen and casing materials (either as a composite
or independently) in a ground water monitoring network, depending upon what constituents
the wells will sample. Further, the owner or operator may need to conduct site specific
comparative performance studies to justify their preference for a particular well casing or