EP 1110-1-27
27 Jan 00
Chapter 6
Chemical Dosage for Wells
Chemical treatment in a preventive mode is a major aspect of maintenance of well and fluid system
performance. ASTM D 5978, which addresses the maintenance of monitoring wells, does not recommend
the use of chemicals, but redevelopment only. This restrictive guidance is not extended to pumping and
injecting wells on HTRW sites, for which the responsible use of chemicals in PM redevelopment is
usually needed to improve the well's effectiveness. Experience shows that chemical choices in well
treatment are often made based on incomplete information or vendor sales literature. And while
information should not be dismissed if it comes from a commercial source (as vendors frequently seek to
educate), it is crucial that personnel engaged in the planning of well system O&M seek expert advice and
review publications specifically written for these types of sites to become well acquainted with the
features of chemical choices, both for effectiveness and safety.
6-1 Lists of Chemicals to be Used
a. Issues in chemical choices. The listings of chemicals in this section include brief summaries of
the chemicals' uses. Detailed information is provided in Borch, Smith, and Noble (1993), ADITC (1997),
and Smith (1995).
(1) Reactivity with constituents of contaminated ground water is an issue in HTRW remediation
and monitoring well maintenance. Table 2-4 provides a summary of common reactions.
(2) Cost is frequently cited as an issue in choices made as to whether to use chemicals and
electing which ones and how much to use.
(a) Three factors affect the market price of chemical products used in well cleaning:
Actual process and shipping costs.
Premiums for purity and standard certification.
Degree of commercial exclusivity (particularly with proprietary products).
(b) In terms of effectiveness, a more expensive chemical may be a better choice and therefore
cost-effective. Among the acids, for example, organic-based and more concentrated products are more
expensive than inorganic acids, primarily due to process costs. However, their effectiveness against
biofouling and relative handling safety may outweigh the actual material cost differential.
(c) The USACE directs that HTRW site project and O&M management take a "long-view"
approach to O&M cost-effectiveness calculations, i.e., to consider cost-effectiveness on a life-cycle cost
basis. Available research (Sutherland, Howsam, and Morris 1994) in water supply applications indicates
that even aggressive PM is cost-effective compared to losses in efficiency, equipment repair, and well
failure. HTRW ground water plume management adds the factor of the project mission, i.e., the cost of
failure to control contaminated ground water.
(d) Warning. The chemicals used in O&M are all reactive and pose risks to skin, mucous
membranes, and other soft tissues of humans, and are potentially harmful to the environment if handled
improperly. They should only be used by trained personnel familiar with their safe use, and who are
equipped with proper respiratory and skin protection. Material Safety Data Sheets (MSDS) and other
safety information must be reviewed by all personnel involved (mandatory). No HTRW remediation
6-1
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