EP 1110-1-27
27 Jan 00
(a) Sizing. Compressors, airlines, hoses, fittings, etc., should be of adequate size to pump the well
by the airlift method at l-l/2 to 2 times the design capacity of the well. Each case is specific in terms of
depth, submergence, well diameter, and screen hydraulic conductivity. For wells less than 300 ft (91.4 m)
in depth, with 60% submergence possible, approximately 0.75 cfm of air compressor capacity is needed
per gpm (0.133 cfm) (~5.6 m3/sec of air per 1 m3/sec water) of anticipated pumping rate (Driscoll 1986,
Fig. 15.12). In practice, a 375-cfm compressor developing 100 psi can usually pump 400 to 500 gpm
(approximately 44 to 67 cfm or 1.25 to 2.0 m3/sec) of water with proper airline submergence.
(b) Development process. The first goal is to establish a piston effect (surging) and not to conduct
airlift pumping. In surging, sufficient air is fed to raise the water level as high as possible, then released to
let it drop. Airlift pumping is then used to pump the well periodically to remove sediment from the screen
or borehole. When the well yields clear, debris-free water, the airline is lowered to a point below the
bottom of the eductor line and air introduced until the water between the eductor pipe and the casing is
raised to the surface. At this time the airline is raised back up into the eductor line causing the water to be
pumped from the well through the eductor line. The procedure of alternating the relative positions of the
air and eductor line is repeated until the water yielded by the well remains clear when the well is surged
and backwashed by this technique.
(6) Combination tools and methods: The better features of several tools and methods can be
combined. For example, combination surging and jetting tools are used to surge while jetting in acid.
d. Care in performing development. To avoid applying forces on the casing, screen, and grout that
are beyond their capacity for resistance, care and attention to detail are required in development and
redevelopment. Sufficient force, efficiently supplied, is needed to set formation particles in motion and to
sheer off encrustation. However, this does not have to be violent force that damages the well. For
example, causing an excessive difference in hydrologic pressure between the outside and inside of a
casing may result in casing distortion. Sharp shock loading or unloading of some well screens may cause
distortion or collapse.
(1) Development typically should proceed in 2.74- to 4.57-m (3- to 5-ft) segments.
(2) Tools should not impact sharply against casing joints or screen rods.
(3) In air development, especially, there is a tendency to "overdo it." Sufficient air flow volume
(cfm) should be available (paragraph 9-5d(5)(a)) to mobilize the water in the well and the near-well
formation, but being careful to not disturb the filter pack. Exceeding a 10:1 air-water volume ratio can
actually reduce airlift pumping flow rates because the well is impeded by excessive air volume.
9-6 Maintenance Monitoring Well Deterioration and Redevelopment Evaluation
a. Evaluation in the PM plan. Including recommendations, processes, and checklists for methods
to evaluate well performance, its deterioration, and repair and treatment results in the well system PM
plan permits evaluation of treatment effectiveness, the need for additional actions, or changes in
subsequent treatment. An overview of maintenance monitoring schedule and parameter recommendations
is provided in Sections 5-2 and 5-3.
recommendations for maintenance monitoring:
(1) Physical-chemical monitoring for maintenance water quality testing. Electronic colorimetric
or spectrophotometric instruments and electronic pH-mV, temperature, and conductivity meters are
9-7
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