PART 3
EXECUTION
3.1
DRILLING
Wells may be drilled by the reverse rotary circulation method or other
method approved, which will insure proper placement of the well screen,
riser pipe, and filter pack. Methods which involve radical displacement of
the formation, or which may reduce the yield of the well, will not be
permitted. Excavated material shall be disposed of as directed.
3.1.1
Reverse Circulation Method
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NOTE: Where the Contracting Officer approved use of
drilling fluid, it shall be a suspension of fine
grained soil or commercial product of a recognized
manufacturer. The drilling fluid shall have the
characteristic of being readily removable from the
filter pack and the walls of the foundation by
development as specified in paragraph DEVELOPMENT.
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If the reverse circulation method is used for drilling wells, all of the
drilling fluid shall be removed from the filter pack and the natural
pervious formation. If in the opinion of the Contracting Officer the walls
of the hole above the top of the filter pack require support during
development operations, a temporary casing similar to that specified in
paragraph TEMPORARY CASING shall be placed. The diameter of the hole shall
be such as will permit the placement of the minimum thickness of filter
pack as specified in paragraph FILTER PACK PLACEMENT. The drilling fluid
shall be a suspension of fine grained soil or shall be a commercial product
of a recognized manufacturer, shall be approved by the Contracting Officer,
and shall have the characteristic of being readily removable from the
filter pack and the walls of the formation by development as specified in
paragraph DEVELOPMENT. The use of bentonite will not be permitted.
3.1.2
[Temporary Casing
Temporary well casing of either iron or steel of sufficient length to case
to the bottom of all borings shall be available at the construction site.
The Contracting Officer will direct the use of a temporary casing to the
bottom of the boring during drilling and placement of screen, riser, and
filter pack when he believes it is necessary to provide adequate support to
the sides of the hole. When the walls of the boring will require support
only during development operations a temporary casing will be required to
extend only to a depth 1 m 3 feet below the top of the filter pack. The
temporary casing, shall have an inside diameter of not less than [_____] mm
inches, shall have sufficient thickness to retain its shape and maintain a
true section throughout its depth, and may be in sections of any convenient
length. The temporary casing shall be such as to permit its removal
without disturbing the filter pack, riser, or well screen. The setting of
temporary casing shall be such that no cavity will be created outside of it
at any point along its length. In the event the temporary casing should
become unduly distorted or bent it should be discarded and a new casing
should be used during installation of any additional relief wells.]
SECTION 02525A
Page 17
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