CEMP-E
TI 814-01
3 August 1998
b. Corrosion. The best method to prevent corrosion is to use a metal which is resistant to
the attack. Once a screen has deteriorated, the only method of rehabilitation may be to
remove it and install a new screen. The design of the initial installation should allow for
removal of the screen in the future. Corrosion is also a problem in pumps. The use of pumps
constructed of special non-corrosive materials will help. Care should be taken to use pumps
with single metal types. Chemical inhibitors can be injected into wells to prevent corrosion, but
this is costly.
c. Down Hole Inspections. Special television equipment has been developed to permit a
visual inspection of a well. Special lighting will permit high resolution pictures even under
water. Wells as deep as 900 m (3000 ft), in casings as small as 100 mm (4 in) diameter can
be inspected. The entire inspection can be videotaped for later review.
d. Well Cleaning. Where incrustation is a problem, periodic well cleaning (also called "well
stimulation" or "well rehabilitation") may be practiced. An effective cleaning procedure should
be developed and applied annually or more often if necessary. Maintenance procedures are
given in "Ground Water and Wells" by Driscoll, Fletcher G.
5-9. ABANDONMENT OF WELLS AND TEST HOLES . It is essential that wells, test wells,
and test holes that have served their purpose and are abandoned, be effectively sealed for
safety and to prevent pollution of the ground water resources in the area. The abandonment
of wells shall follow the guidance of AWWA A100 and state/local regulations. Figure 5-5
illustrates the configuration of a filter-packed well in operational condition and figure 5-7
illustrates a well after sealing.
5-10. CHECK LIST FOR DESIGN.
a. Topographic maps of area where wells could be located.
b. Reports on area geology and ground water resources from U.S. Geological Survey,
State Geological Survey, and other state and local agencies that have an interest in or have
conducted ground water investigations. Records obtained from drilling contractors familiar with
the area. Reports of test drilling and pumping.
c. Copies of logs of existing water supply wells, drawdown data, pumpage, water table
elevations. Estimates of safe yield of aquifers.
d. Records of physical, chemical, and bacteriological analyses of water from existing
wells.
e. Assessment of probable treatment requirements, such as iron, manganese, and sulfide
removal; softening; and corrosion control.
f. Summary of sanitary survey findings, including identification of possible sources of
5-26
Previous Page
