in the annulus above the bentonite seal rather than
cement grout. Advantages and disadvantages of using
a bentonite grout instead of cement grout are
discussed in EM 1110-1-4000. There may be a need
for a provision to grout the annular space in lifts
in deep wells to ensure that any PVC or other type
casing will not be collapsed by the weight and/or
heat created by the chemical reaction of cement
grout. If grouting in lifts is for some reason not
acceptable, the well should be designed to withstand
greater external pressures. This may mean using
higher schedule casing, or steel instead of PVC, for
example.
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After the inner casing and [well screen] [filter pack] have been installed,
a [non-shrinking cement] [high-solids bentonite] grout, shall be
mechanically mixed in accordance with paragraph CEMENT AND BENTONITE GROUT,
and placed by tremie pipe, in one continuous operation into the annulus
between the inner and outer casings above the bentonite seal to [within
[_____] mm feet of] [the ground surface] [the maximum depth of frost
penetration (frost line)]. Grout injection shall be in accordance with
AWWA A100. If the casing interval to be grouted is less than 4.5 m 15 feet,
and without fluids after any drill casing is removed, the grout may be
placed either by pouring or pumping. The tremie pipe shall be thoroughly
cleaned with high pressure hot water/steam before use in each well. The
bottom of the tremie pipe shall be constructed to direct the discharge to
the sides rather than downward. The discharge end of the tremie pipe shall
be submerged at all times. Additional grout shall be added from the
surface to maintain the level of the grout [within [_____] mm feet of the
ground surface] [at the land surface] as settlement occurs. Work shall not
be conducted in the well within [24] [_____] hours after cement grouting.
The alignment of the well shall be verified by passing a 1.5 m 5 foot long
section of rigid [PVC] [stainless steel] [PTFE] [_____] pipe 6 mm 1/4 inch
smaller in diameter than the inside diameter of the casing through the
entire well. If the pipe does not pass freely, the well will not be
accepted. The pipe section shall be thoroughly cleaned with high pressure
hot water/steam prior to each test.
3.4
WELL DEVELOPMENT
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NOTE: There is a provision for predevelopment, or
development after the filter pack is installed, but
before the bentonite seal is installed.
Well development criteria, such as the measurement
of certain ground-water parameters, may be deleted
if the well is not installed at an HTRW site.
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Within 7 days of completion of each well, but no sooner than [48] [_____]
hours after cement grouting is completed, the well shall be developed.
[Predevelopment, or development after the filter pack has been installed,
but before the annular seal is installed, may be initiated before this
minimum 48 hour period.] The well shall be developed in accordance with the
Well Installation Plan, by approved methods until the water pumped from the
well is substantially free from sand, and until the turbidity is less than
5 on the Jackson Turbidity Scale specified in AWWA EWW. Developing
SECTION 02521
Page 27
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