3 August 1998
(a) Explosives can be used to break rock formations. However it may be difficult to
tell in advance if the shooting operation will produce the required result.
are opened up in the aquifer surrounding the well hole by the action of the acid dissolving the
(c) Sand fracking is the action of forcing high pressure water containing sand or
plastic beads in to the fractures surround a well. This serves to force the crevices open.
b. Disinfection of Completed Well. The disinfection of the completed well shall conform to
AWWA A100. Bacteriological samples must be collected and examined in accordance with
Standard Methods for the Examination of Water and Wastewater.
c. Disinfection of Flowing Artesian Wells. Flowing artesian wells often require no
disinfection, but if a bacteriological test, following completion of the well, shows contamination,
disinfection is required. This can be accomplished as follows. The flow from the well will be
controlled either by a cap or a standpipe. If a cap is required, it should be equipped with a
one-inch valve and a drop-pipe extending to a point near the bottom of the well. With the cap
valve closed, stock chlorine solution will be injected, under pressure, into the well through the
drop-pipe in an amount such that when the chlorine solution is dispersed throughout all the
water in the well, the resultant chlorine concentration will be between 50 and 100 mg/L. After
injection of the required amount of stock chlorine solution, compressed air will be injected
through the drop-pipe, while simultaneously partially opening the cap valve. This will permit
the chlorine solution to be mixed with the water in the well. As soon as chlorine is detected in
the water discharged through the cap valve, the air injection will be stopped, the cap valve
closed and the chlorinated water allowed to remain in the well for 12 hours. The well will then
be allowed to flow to waste until tests show the absence of residual chlorine. Finally, samples
for bacteriological examination will be collected in accordance with Standard Methods for the
Examination of Water and Wastewater. If the well flow can be controlled by means of a
standpipe, disinfection can be accomplished as described for a water table well.
5-8. RENOVATION OF EXISTING WELLS. Well yield can be maintained by proper operating
procedures. The most common cause of declining capacity in a well is incrustation which
results from material being deposited on the well screen and thereby clogging the openings. A
second cause is corrosion of the screen which is a chemical reaction of the metal. This action
results in the screen being dissolved and enlarging the openings, allowing caving to occur.
Records of pump performance and pumping levels are very important in a good maintenance
a. Incrustation. The effect of incrustation is usually decreased capacity due to clogging of
the screen openings. For incrustation due to calcium deposits or precipitation of iron and
manganese compounds, treatment with an acid solution will dissolve the deposits and open up
the screen. For bacterial growths and slime deposits, a strong chlorine solution has been
found effective. In some instances, explosives may be used to break up incrustation from
wells in consolidated rock aquifers.