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Version 1.4 May 09
5.
Check the drill hole to ensure that the full depth
is clear and free of obstructions and that any
casing can be withdrawn.
6.
CHECK BASE READING OF PIEZOMETER.
Where necessary, record a reading from the
piezometer to confirm that it has not been
damaged since establishing the base readings
( see Section 5.1 )
7.
Where necessary and possible, fill the borehole
with clean water.
8.
If a Bentonite plug is required at the base of the
borehole, pull any temporary casing back so
that it lowest level corresponds to the top of the
intended plug. Slowly drop Bentonite pellets /
balls down the borehole. Be sure not to let the
pellets / balls plug or stick to the inside of the
casing by checking the depth using a weighted
tape. Ensure that the Bentonite level always
remains below the bottom of the casing.
( Feeding pellets / balls in to the borehole too
quickly will result in ‘bridging’ of casing and
make completion of the installation very
difficult ). The top of any base-plug must be
below the intended piezometer installation
elevation.
9.
Once the plug has been formed ( where
required ), the casing should be pulled to about
500mm (or in accordance with specification)
above the new base of the borehole ( the
intended piezometer installation elevation ) and
filter sand should be slowly added to fill the
borehole up to the depth at which the
piezometer is to be installed.
(Continued from page 18)
(Continued on page 20)
