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).

Conclusions

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

screening material.

November 1992

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