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

important precaution to prevent possible cross-contamination between sites. At sites where
well clusters are being installed, decontamination of equipment between drill holes will help
prevent cross-contamination between boreholes. The degree to which each step of the six-step
protocol that follows must be completed, however, depends on the Study-Unit data-collection
requirements, including target contaminants and concentrations in ambient samples; the con-
fidence level needed for the data; and the contaminants expected to be contributed by the
equipment and methods used for installation and completion of the well.
Table 7. Six-step procedure for decontamination of well-installation equipment and
materials (modified from Aller and others, 1989, p. 62)
1. Select a location for decontamination procedures:
• Avoid spilling decontamination fluids at drilling site;
• Prepare clean area for cleaned equipment.
2. Select equipment requiring decontamination.
3. Determine the frequency of decontamination of the equipment.
4. Select the cleaning technique and type of cleaning solutions to be used for decontamina-
tion. The routine procedure for NAWQA for cleaning well-installation equipment and
materials is:
• Wash outside (and inside where applicable--for example, well casing and screen) of
equipment and materials used during well installation using a low-sudsing, non-
phosphate detergent;
• Complete decontamination procedure with high-pressure steam cleaning using
potable tap water.
5. Contain residual contaminants and cleaning solutions, if necessary, and dispose according
to regulations.
6. Plan to collect some quality-control samples to evaluate the effectiveness of decontami-
nation procedure (for example, a sample of the rinse water that was used to steam clean or
remove all residues and additional samples of rinse water taken from the equipment after
it has been decontaminated).
Well Drilling
Selection of a drilling method from among the methods available requires consideration
of the study objectives, as well as site conditions and economics (tables 8 and 9). Because a
primary purpose of installing the wells for NAWQA Land-Use and Flowpath Studies is for
water-quality sampling, a drilling method that has minimal effect on ground-water chemistry
should be a primary consideration during selection of a method.
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