With respect to well casings, there have been relatively few systematic studies of

sorption and leaching, other than well documented reports describing the persistent effects of

PVC solvent cements (Sosebee et al., 1983) and the problems with corrosion of ferrous

casings.

6.2.2

Types of Casing Materials

Casing materials widely available for use in ground water monitoring wells can be

divided into three categories:

1)

Fluoropolymer materials, including polytetrafluoroethylene (PTFE),

tetrafluoroethylene (TFE), fluorinated ethylene propylene (FEP),

perfluoroalkoxy (PFA), and polyvinylidene fluoride (PVDF);

2)

Metallic materials, including carbon steel, low carbon steel, galvanized steel,

and stainless steel (304 and 316); and

3)

Thermoplastic materials, including polyvinyl chloride (PVC) and acrylonitrile

butadiene styrene (ABS).

In addition to these three categories that are widely used, fiberglass reinforced plastic

(FRP) has been used for monitoring applications. Because FRP has not yet been used in

general application across the country, very little data are available on their characteristics and

performance. Gillham and O'Hannesin (1990) examined sorption of dissolved aromatics

(ppm levels) by epoxy impregnated fiberglass. Generally, fiberglass was more sorptive of

these compounds than rigid PVC but less sorptive than PTFE. Fiberglass reinforced materials

are not included in the following discussion. However, owners/operators may conduct

technically based comparative studies between new well construction materials and standard

alternatives (e.g., PVC, stainless steel, and PTFE) on a site specific basis to demonstrate

performance of well materials.

All well construction materials possess strength related characteristics and chemical

resistance/chemical interference characteristics that influence their performance in site specific

hydrogeologic and contaminant related monitoring situations. The characteristics for each of

the three categories of materials are discussed below.

Fluoropolymer Materials

Fluoropolymers are synthetic materials consisting of different formulations of

monomers (organic molecules) that can be molded by powder metallurgy techniques or

extruded while heated. Fluoropolymers are technically included among the thermoplastics,

but possess a unique set of properties that distinguish them from other thermoplastics:

fluoropolymers are resistant to chemical and biological attack, oxidation, weathering, and

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