Violent surging, as with compressed air, should not
be permitted.
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Surging of the well shall require use of a circular block which is
approximately 25 mm 1 inch smaller in diameter than the inside diameter of
the relief well and is constructed of a material which will not damage the
screen if the block comes in contact with the screen, and a bailer or pump
to remove materials drawn into the well. The surging shall be continued
for a period of approximately one hour or until little or no additional
material from the foundation or filter pack can be pulled through the
screen. The surge block shall be moved by a steady motion up and down the
full length of the well screen. Prior to commencing surging, and
periodically during development by this method, all sand and/or other
materials shall be removed from inside the screen. All materials pulled
into the well by the surging process shall be removed by the Contractor.
3.5
BACKFILLING
[After the well has been developed, additional filter pack should be added
if necessary to meet the requirements of paragraph FILTER PACK PLACEMENT.
Then the annular space above the filter pack, shall be backfilled by first
placing a 300 mm 12 inch minimum layer of concrete sand on the filter pack
and then filling the remainder of the space up to the [finished ground
surface] [well pit] with grout or concrete. The concrete backfill shall be
placed to a depth at least equal to the existing impervious blanket, but in
no case less than [_____] m feet.] [For PVC riser pipe, after the well has
been developed, additional filter pack should be added if necessary for it
to meet the requirements of paragraph FILTER PACK PLACEMENT. Then the
remaining annular space above the filter pack shall be backfilled by first
placing a 300 mm 12 inch minimum layer of concrete sand on the filter pack
and then filling the remainder of the space up to the [finished ground
surface] [well pit] with bentonite.] The temporary casing, if used, shall
be withdrawn in increments as the backfill is placed. The Contractor shall
fill with impervious material to original grade all pits such as those
incidental to the reverse rotary circulation method of drilling.
3.6
PLUGGING OF ABANDONED WELLS
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NOTE: Regulatory requirements shall be stated along
with applicable paragraphs to direct Contractor on
how a well is to be abandoned. If there are no code
requirements the following should be used.
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[The Contractor has the option of attempting to remove the well screen. If
the well screen can be removed, the Contractor will grout the bore hole
starting from the bottom of the hole to within 1 m 3 feet of ground
surface. The grouting shall start at the elevation of the bottom of the
tailpipe of the well. If the well screen could not be removed or broke off
during the removal attempt, the Contractor shall still be responsible for
grouting the well from the bottom of the tailpipe to within 1 m 3 feet of
ground surface. Either of the above abandonment procedures may require the
Contractor to redrill the hole so that the bore hole can be grouted.][The
well shall be grouted from the bottom of the tailpipe to within 1 m 3 feet
of ground surface. After the grout has setup the riser pipe shall be cutoff
1 m 3 feet below ground. Then the hole shall be backfilled.] The cement
grout mixture proportion to be used shall be submitted for approval.
SECTION 02525A
Page 22
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