8224

• UCREFRP Catalog Number: 8224
• Author: Lapham, W. W., F. D. Wilde and M. T. Koterba.
• Title: Ground-Water Data-Collection Protocols and Procedures for hte National Water-Quality Assessment Progra
• USFW Year: 1995.
• USFW - Doc Type: Selection, Installation, and Documentation of Wells, and collection of Related Data.
• Copyright Material: NO

Well Completion
Well completion ensures that the hydraulic head measured in the well is that of the aqui-
fer(s) of interest, ensures that only the aquifer(s) of interest contribute(s) water to the well, and
prevents the annular space from being a vertical conduit for water and contaminants. Such com-
pletion steps are critical to the long-term goals of NAWQA, which dictate that many of the wells
installed by the program are to be used for water-quality sampling for decades. Well completion
in unconsolidated deposits for the NAWQA Program consists of installing the well casing and
screen, and filling and sealing the annular space between the well casing and borehole wall, and
completing the documentation required, as discussed on page 43 in the section "Documentation."
Compliance with State regulations for well completion, as for well drilling, is mandatory.
Specific details of well completion require consideration of several hydrogeologic factors,
including (1) the depth to water, to the top of the aquifer of interest, and to the zone in the aquifer
to be monitored; (2) the nature of materials that make up the aquifer to be monitored and that
overlie the aquifer--for example, whether the materials are consolidated or unconsolidated; (3)
expected water-level fluctuations; (4) expected direction of the vertical head gradient--down-
ward, upward, or fairly uniform with depth; (5) whether the aquifer is confined or unconfined;
and (6) the design of the monitoring well(s) (figs. 4-6). Completion requirements and practices
can differ considerably among wells (W. Lapham, U.S. Geological Survey, written commun.,
1995--see footnote 1).
In most cases, wells installed for NAWQA Land-Use or Flowpath Studies will consist of
flush-threaded PVC pipe with short (2- to 10-ft) well screens (table 3). Installation of a filter
pack around the well screen and sealing of the annular space between the well casing and the
borehole wall also will be necessary for those installations in which the annular space could re-
main open after well installation. Each major element of well completion has specific design
objectives, which are discussed briefly here. A more detailed discussion of the major elements
of well completion has been written (W. Lapham, U.S. Geological Survey, written commun.,
1995--see footnote 1), and additional information related to completion procedures is given in
ASTM (1992) and Driscoll (1986).
The well casing and/or screen is installed in the borehole as the first step in well comple-
tion. After installation of the well casing and, if needed, the well screen, the major elements of
well completion consist of the following:
1. If a well screen is used and a filter pack is required, the primary filter pack is installed
around the well screen.
2. A secondary filter pack is installed above the primary filter pack.
3. Annular seals are installed to about frost level.
4. A surface seal is installed.
5. A protective casing is installed around the well at land surface.
An example of these major elements of well completion, in this case for a shallow well with
a filter-packed well screen installed in unconsolidated materials, is provided in figure 4. This is
a typical design for wells for Land-Use and Flowpath Studies.
36