Current through Register Vol. 47, No. 17, September 10, 2024
Basis and Purpose: The statutory authority
for this rule is found in sections
37-91-101(1);
37-91-102;
37-91-104(1)(c),
(j), & (k);
37-91-106(3);
37-91-109(1); and
37-91-110(2),
C.R.S. The purpose of this Rule is to identify the minimum construction
standards for water wells or other excavations constructed in different types
of aquifers in Colorado, in order to ensure that such construction prevents
harm to the public health, will not impair water quality or cause contamination
of shared groundwater resources, and will ensure the safety of groundwater
resources for Colorado's existing and future populations.
10.1
General - To assist in the
orderly development of the groundwater resources of Colorado, to insure the
protection of the public health, and to prevent degradation of the groundwater
resource, all wells constructed to withdraw or inject water must be
constructed, maintained, or repaired in such a manner that will:
a. maintain existing natural protection
against contamination of aquifers;
b. prevent the entry of contaminants through
the borehole;
c. limit groundwater
production to one aquifer unless otherwise permitted by the State Engineer;
and
d. prevent the intermingling of
groundwater from different sources through the borehole.
10.1.1 The contractor is responsible for
constructing the well using standards that are more stringent than the minimum
specified in these Rules, if necessary to ensure the adequate integrity of the
well and protection of the aquifer. If conditions on the well permit specify
standards that exceed the minimum standards of these Rules, the well
construction contractor must comply with the conditions specified on the well
permit.
10.1.2 Prior to starting
construction, all persons authorized to construct wells must investigate and
become familiar with the geology of potential aquifers, confining layers,
anticipated water quality problems, and known contaminated water-bearing zones
that may be encountered in the area of the proposed drilling activity, and
where necessary, must advise the well owner of the potential for poor water
quality or contamination and plan for the resolution of such issues prior to
beginning construction.
10.1.3 All
wells and boreholes, when unattended, must be securely sealed, capped, or
covered. It is the responsibility of the well construction contractor and pump
installation contractor to ensure the well is securely covered while unattended
during well construction and pump installation and securely sealed or capped
upon completion of the well. Thereafter, it is the responsibility of the well
owner to ensure that the well is securely sealed or capped.
10.1.4 When hazardous contaminants are known
or suspected to be encountered during well construction, the contractor is
responsible for ensuring that his or her personnel are adequately trained and
that proper safety equipment is provided to handle and contain those
substances.
10.1.5 Nested wells
completed in different aquifers or production zones must be grouted to prevent
intermingling of groundwater.
10.1.6 Any hydraulic fracturing or
stimulation of a well must be restricted to the permitted production interval
and must not compromise the integrity of an adjoining confining layer or
aquifer.
10.2
Well
Location - When selecting a well location, consideration must be given
to topography, drainage, sources of contaminants, underground utility
locations, and other onsite conditions in order to promote sanitary conditions
and prevent contamination of the well and aquifer.
10.2.1 When locating wells, well construction
contractors and private drillers must comply with the regulations of federal,
state, county, municipal, or local governments, in determining the required
distance from sources of contaminants, when those regulations are more
stringent than the minimum standards of these Rules.
10.2.2 Wells must not be located closer than
one-hundred (100) feet horizontally to the nearest existing source of
contaminants or fifty (50) feet horizontally from a septic tank, sewer line or
other vessel containing contaminants. A request for variance (as provided for
in Rule 18) must be submitted and written approval from the Board must be
obtained prior to the construction of a well that cannot meet this spacing
requirement. The variance request must be prepared by a water well construction
contractor or authorized individual, must be based on hydrogeologic
information, and must comply with the minimum requirements shown in Figure 2a
or 2b (whichever is applicable) to the greatest extent possible.
10.2.3 In the event a well is constructed as
a replacement for an existing well that is located less than one hundred (100)
feet horizontally from a source of existing contaminants, the replacement well
must not be located closer to the source of contaminants. The distance between
the perimeter of that source and the base of the grout seal must not be less
than 100 feet, as shown in Figure 2a (or not less than 50 feet as shown in
Figure 2b), unless a variance request prepared in accordance with the
provisions of Rule 10.2.2, is granted.
FIGURE 2a MINIMUM DISTANCE FROM A SOURCE OF
CONTAMINATION
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image
Figure 2a. Schematic of the minimum distance (A)
to a well from a leach field or other source of contaminants (Rule 10.2.2).
Exceptions to Rule 10.2.2 may be granted through a variance request; if
distance A is less than 100 ft., distance C must equal 100 feet or more.
Click to view
image
FIGURE 2b MINIMUM DISTANCE FROM A VESSEL CONTAINING
CONTAMINANTS
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image
Figure 2b. Schematic of the minimum distance (A)
to a well from a sewer line, septic tank, or other vessel containing
contaminants (Rule 10.2.2). Exceptions to Rule 10.2.2 may be granted through a
variance request; if distance A is less than 50 ft., distance C must equal 50
feet or more.
Click to view
image
10.3
Well Casing Well casing
must consist of materials that will ensure adequate protection against failure
for the intended use of the well
10.3.1 All
casing must be new or unused pipe, except that casing recovered when a well is
modified or replaced may be reused in the new well if it will ensure
satisfactory well performance. PVC casing must not be exposed above the ground
surface. All surface casing must be steel pipe and be undamaged, free of pits
and corrosion, and free of contamination. Used oilfield pipe must not be
installed in any well.
10.3.2 The
well casing inside diameter (ID) or pitless adapter must be sufficient to
accept a pump capable of producing the desired production rate. The following
minimum ID (nominal) requirements apply to the specified type of well casing:
a. Steel well casing: 4.5 inch ID
b. PVC well casing: 4.0 inch ID
10.3.3 All casing wall thickness
must be adequate to prevent collapse due to hydrostatic pressures. The
following minimum wall thicknesses apply to the specified type of well casings:
a. Steel well casing: 0.188 inches
b. PVC well casing: 0.237 inches (Schedule
40)
c. Precast concrete rings: 3.00
inches
10.3.4
Casing Perforation - Casing perforation methods or designs must
not result in inclusions or debris inside of the well casing. Any inclusions or
debris must be removed after perforation. Oxygen-acetylene torch-cut
perforations on well casing are prohibited on well casings less than 5 inches
ID.
10.4
Construction Procedures The excavation of the borehole, selection
and installation of the casing, grouting, development and disinfection of a new
well, and repair or deepening of an existing well, must protect the health and
safety of the public utilizing workmanship and materials that match the
intended use of the well.
10.4.1
Centralizers -
a. Centralizers
must be installed in all grouted intervals of the production casing of a well.
The distance between centralizers must not exceed fifty (50) feet for intervals
that will be grouted for more than fifty (50) feet. If the grouted interval of
the production casing is less than fifty (50) feet, centralizers must be
installed at the top and bottom of the grouted interval. Production casing must
be hung in tension during the placement of grout material.
b. Centralizers must also be installed on
grouted surface casing within five (5) feet of the bottom of the surface
casing.
10.4.2
Wells with Surface Casing - Wells that will be constructed with a
surface casing string must have watertight steel casing and joints installed
from a minimum of one (1) foot above to a minimum of nineteen (19) feet below
ground level. The annular space between the borehole wall and surface casing
string must, at a minimum, be grouted in accordance with the requirements of
Rule 10.5 . Centralizers must also be installed on grouted surface casing
within five (5) feet of the bottom of the surface casing.
10.4.2.1
Driven Surface Casing for
wells in Type II and Type III aquifers - The annular space between
surface casing that is driven and the production casing string must be grouted
in accordance with the following requirements for Type II and Type III
aquifers. Additional grouting below the base of the driven surface casing may
be necessary to comply with the requirements for a particular type of aquifer.
See Figure 3.
a. For Type II aquifers
(unconfined bedrock aquifers) with driven surface casing, the grout interval
must extend from at least twenty (20) feet below to at least ten (10) feet
above the base of the surface casing.
b. For Type III aquifers (unconsolidated
aquifers) with driven surface casing, the grout interval must extend from at
least ten (10) feet below to at least ten (10) feet above the base of the
surface casing. See Figure 3.
FIGURE 3 WELLS WITH DRIVEN CASING
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image
Figure 3. Schematic diagram for grout placement
in wells with driven steel casing. In each aquifer type, the minimum continuous
grout interval must extend a minimum of 10 feet into the annulus between the
driven casing and the production casing.
10.4.3
Wells without Surface
Casing - All wells that will be constructed without surface casing must
have watertight steel casing and joints installed from a minimum of one (1)
foot above to a minimum of nineteen (19) feet below ground level. The annular
space between the borehole wall and production casing string must be grouted in
accordance with grouting requirements for the particular type of aquifer in
which the well is constructed and the requirements of Rule 10.5.2.1.
10.4.4
Annular Space Requirements for
All Grouted Intervals - The borehole must be constructed to provide
sufficient annular space for the placement of grout. The borehole diameter for
every well must not be less than two (2) inches larger than the outside
diameter of the casing (minimum one (1) inch of annular space, as defined in
Rule 5.2.1). If grout is poured from the surface and the casing is not
vibrated, the borehole diameter for the well must not be less than four (4)
inches larger than the outside diameter of the casing (annular space of two (2)
inches).
10.4.5
Wells
Constructed Into Type I Aquifers (Confined Aquifers):
10.4.5.1
Type I Well Penetrating Only
One (1) Confining Layer (Excluding Those Penetrating the Laramie-Fox Hills
Aquifer see Rule 10.4.8) -
a. Wells
completed in a Type I aquifer (confined aquifer-see Rule 5.2.2.1), where the
borehole penetrates only one (1) confining layer (see Rule
5.2.12), and are constructed without surface casing must have watertight solid
casing with watertight joints installed from the base of the confining layer
directly above the permitted production zone to the top of the well.
b. Wells completed in a Type I aquifer
(confined aquifer), where the borehole penetrates only one (1)
confining layer, and are constructed with surface casing must have solid casing
with watertight joints installed from the base of the confining layer directly
above the permitted production zone to at least ten (10) feet above the base of
the surface casing (see Figures 4a and 4b).
c. For wells constructed into Type I
aquifers, where the borehole penetrates only one (1) confining
layer, the annulus between the borehole wall and the casing string must be
grouted with cement or cement-bentonite from the base of the confining layer
back to a level that is not less than sixty (60) feet above the base of the
confining layer or to the level required to withstand the maximum potential
hydrostatic pressure differential between the aquifers.
d. If the well is constructed with steel
casing, the interval from the base of the confining layer directly above the
production zone to the depth required by Rule 10.5.2.1 must be grouted with
approved grout (Table 2). If surface casing is used, the grout must extend 10
feet above the base of the grouted surface casing.
e. The upper part of the well must be grouted
with cement to a minimum depth of thirty nine (39) feet as shown in Figures 4a
and 4b, and in accordance with Rule 10.5.2.1 . Grout must also be placed
between casing strings when fluctuating static or water table levels could
cause interconnection or intermingling of water from different aquifers unless
such interconnection or intermingling has been specifically permitted by the
State Engineer.
10.4.5.2
Type I Well Penetrating More than One (1) Confining Layer-
a. Wells completed in a Type I aquifer
(confined aquifer-see Rule 5.2.2.1), where the borehole penetrates more than
one (1) confining layer, and are constructed without surface casing must have
watertight solid steel casing with watertight joints installed from the base of
the confining layer directly above the permitted production zone to the top of
the well.
b. Wells completed in a
Type I aquifer (confined aquifer), where the borehole penetrates more than one
(1) confining layer, and are constructed with surface casing must have solid
steel casing with watertight joints installed from the base of the confining
layer directly above the permitted production zone to at least ten (10) feet
above the base of the surface casing (see Figures 4a and 4b).
c. For wells constructed into Type I aquifers
(confined aquifers), where the borehole penetrates more than one (1) confining
layer, the annular space between the borehole wall and the casing string must
be grouted with approved grout using positive displacement from the base of the
confining layer overlying the permitted production zone up to sixty (60) feet
above the base of the uppermost confining layer, or to the depth required by
Rule 10.5.2.1 .
FIGURE 4a
TYPE I AQUIFER
WELLS PENETRATING ONE CONFINING LAYER
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image
Figure 4a. Schematic diagram for wells that penetrate only
one confining layer and are constructed into a Type I (confined)
aquifer.
Note:
If the well is
constructed with steel casing, the interval from the base of the confining
layer directly above the production zone to the depth required by Rule 10.5.2.1
must be grouted with approved grout (Table 2). If surface casing is used, the
grout must extend 10 feet above the base of the grouted surface
casing.
FIGURE 4b
TYPE I AQUIFER
WELLS PENETRATING MORE THAN ONE CONFINING
LAYER
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image
Figure 4b. Schematic diagram for wells that penetrate more
than one confining layer and are constructed into a Type I (confined)
aquifer.
10.4.5.3
Hydraulic fracturing of a
water well in Type I Aquifers: Any hydraulic fracturing or stimulation
of the producing interval of a water well drilled into a Type I Aquifer must
not compromise the integrity of a confining layer. Before initiating any
hydraulic fracturing operations in a water well drilled into a Type I Aquifer,
the driller and/or consultant (Authorized Individual) must provide detailed
plans for such operations to be reviewed by Board Staff at the State Engineer's
Office, and may only initiate such operations upon (1) advance written approval
of the Board, and (2) at least 24 hours advance notification of the initiation
of such operations to the Chief Well Inspector by telephone or email. Upon
request of the Chief Well Inspector or other staff of the State Engineer, the
driller or authorized individual must provide reports or other data concerning
the hydraulic fracturing of the water well.
10.4.6
Wells Constructed Into Type II
Aquifers (Unconfined Bedrock Aquifers): Wells constructed into a Type II
Aquifer must have at least forty (40) feet of solid casing, from at least one
(1) foot above to at least thirty nine (39) feet below ground level, and must
have at least thirty (30) feet of continuous grout. The uppermost twenty (20)
feet of solid casing (including surface or production) must be steel casing.
10.4.6.1
Casing Requirements -
a. Wells completed in a Type II aquifer
(unconfined bedrock aquifer-see Rule 5.2.2.2) that are constructed without
surface casing must have solid casing with watertight joints installed from the
top of the permitted production zone to the top of the well.
b. Wells completed in a Type II aquifer
(unconfined bedrock aquifer) that are constructed with surface casing must have
solid casing with watertight joints installed from the top of the permitted
production zone to at least ten (10) feet above the base of the surface
casing.
10.4.6.2
Grouting Requirements for Type II Aquifer (unconfined bedrock aquifer)
Not Overlain by Type III Aquifer (alluvial/colluvial aquifer) - Wells
completed in a Type II aquifer (unconfined bedrock aquifer) that do not
penetrate through a Type III aquifer (unconsolidated) must have at least thirty
(30) feet of continuous grout and must be grouted in accordance with the
following:
a. If no surface casing is
installed, grout must be placed in the annular space between the production
casing and the borehole wall from a depth of at least thirty-nine (39) feet up
to the depth required by Rule 10.5.2.1 . See Figure 4c.
b. If surface casing is installed to a depth
less than thirty-nine (39) feet below the land surface and grouted to the depth
required by Rule 10.5.2.1, the annulus between the borehole wall and the
production casing string must be grouted from a depth of at least thirty nine
(39) feet below the surface back to a level that is at least ten (10) feet
above the base of the surface casing. See Figure 4c.
c. If surface casing is installed to at least
thirty-nine (39) feet below the surface, the annulus between the surface casing
and the production casing string need not be grouted if the annular space
between the borehole wall and the surface casing is grouted from a depth of at
least thirty-nine (39) feet up to the depth required by Rule
10.5.2.1.
10.4.6.3
Grouting Requirements for Type II Aquifer Overlain by a Type III Aquifer
(Alluvial/Colluvial) - Wells completed in a Type II aquifer (unconfined
bedrock aquifer) that penetrate through a Type III aquifer (unconsolidated
aquifer) must fully isolate the entire Type III aquifer interval with grout or
driven steel casing. See Figure 4d.
FIGURE 4c
TYPE II AQUIFER
WELLS COMPLETED IN TYPE II AQUIFER (UNCONFINED BEDROCK)
NOT OVERLAIN BY TYPE III AQUIFER
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image
Figure 4c. Schematic diagram for wells
constructed into Type II (unconfined bedrock) aquifers, not overlain by a Type
III (unconsolidated) aquifer.
10.4.7
Wells Constructed Into Type III
Aquifer (Unconsolidated Material) - Wells constructed into a Type III
aquifer (unconsolidated aquifer) must have at least twenty (20) feet of solid
steel casing in accordance with Rule 10.4.2 or Rule 10.4.3, and at least ten
(10) feet of continuous grout.
10.4.7.1
Casing Requirements - All wells completed in a Type III Aquifer
(unconsolidated aquifer--see Rule 5.2.2.3), with or without surface casing must
have solid steel casing with watertight joints installed from a depth of at
least nineteen (19) feet to the top of the well.
10.4.7.2
Grouting Requirements -
a. In wells constructed with surface casing
into Type III aquifers (unconsolidated aquifer), the annulus between the
borehole wall and the surface casing must be grouted from a depth of at least
nineteen (19) feet up to the depth required by Rule 10.5.2.1 . If the surface
casing is driven, grout must be placed between the production casing and driven
casing from not less than ten (10) feet below to at least ten (10) feet above
the base of the driven casing (see Figure 3). At least ten (10) feet of
continuous grout is required.
b. If
surface casing is not installed, the annulus between the borehole wall and the
production casing string must be grouted from a depth of at least nineteen (19)
feet up to the depth required by Rule 10.5.2.1 . (see Figure 4e). At least ten
(10) feet of continuous grout is required.
FIGURE 4d
TYPE II AQUIFER
WELLS COMPLETED IN UNCONFINED BEDROCK AQUIFERS
(OVERLAIN BY TYPE III AQUIFER)
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image
Figure 4d. Schematic diagram for wells constructed into Type
II (unconfined bedrock) aquifers, overlain by a Type III (unconsolidated)
aquifer.
FIGURE 4e
TYPE III AQUIFER
WELLS COMPLETED IN UNCONSOLIDATED
ALLUVIAL/COLLUVIAL MATERIALS
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image
Figure 4e. Schematic diagram for wells constructed into Type
III (unconsolidated) aquifers.
10.4.8 Wells Constructed into Laramie-Fox
Hills Aquifer:
10.4.8.1
Casing
Requirements:
a. Wells completed in the
Laramie-Fox Hills aquifer that are constructed without surface casing must have
watertight solid steel casing with watertight joints installed from the top of
the permitted production zone to the top of the well.
b. Wells completed in the Laramie-Fox Hills
aquifer that are constructed with surface casing must have solid steel casing
with watertight joints installed from the top of the permitted production zone
to at least ten (10) feet above the base of the surface casing (see Figure
4a).
10.4.8.2
Grouting Requirements - For wells constructed into the Laramie-Fox
Hills aquifer, the annular space between the borehole wall and the casing
string must be grouted with cement or cement-bentonite from the top of the
permitted production zone up to at least ten (10) feet above the base of the
surface casing, or to the depth required by Rule 10.5.2.1 if no surface casing
is installed.
10.4.9
Surface Completion - In the event the outermost casing is cut off
and does not extend more than one (1) foot above ground surface, the annulus
between the outer casing and the casing that extends above the surface must
have a watertight mechanical seal (e.g, a welded seal) or be sealed with a
minimum of ten (10) feet of cement grout up to the depth required by Rule
10.5.2.1 . If additional filter pack materials are to be added after the well
has been completed, those materials must be inserted through the use of a
filler tube, as required by Rule 10.4.10.
10.4.10
Filter Pack - If a
filter pack is installed in a well, the interval of the filter pack materials
must be limited to the producing aquifer and must not extend to the ground
surface. If additional filter pack materials are to be added after the well has
been completed, those materials must be inserted through the use of a filler
tube.
10.4.10.1
Filter Packs in Type
III aquifers with grouted surface casing: If a well in a Type III
aquifer (unconsolidated) has surface casing properly grouted in accordance with
Rule 10.4.7.2, and the annular space between the surface casing and production
casing is sealed with a watertight mechanical seal (e.g., a welded seal), then
a filter pack may be installed from the permitted production zone up to the
mechanical seal. Under these circumstances, the filter pack may only be
installed through a filler tube welded in place with a water-tight sanitary
seal.
10.4.11
Gallery Wells or Infiltration Galleries - Prior to the
construction of infiltration galleries or gallery type wells, written plans
detailing the location and size of the proposed excavation, size and materials
to be installed, amounts, types, and placement method of grout and backfill
materials to be used and other information pertinent to the construction and
use must be submitted to the Board of Examiners. If the Board finds the
proposed gallery acceptable, it will approve the construction plan in writing
and impose any conditions necessary to reduce the risk to public health by
contamination of the aquifer. Acceptable examples of gallery type wells are
shown in Figure 5.
FIGURE 5
GALLERY WELLS OR INFILTRATION GALLERIES
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image
Figure 5. Schematic diagram of various
gallery-type well designs
FIGURE 5 (CONTINUED)
GALLERY WELLS OR INFILTRATION GALLERIES
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Figure 5 (continued). Schematic diagram of
various gallery-type well designs.
10.4.12
Directional Drilling -
All wells must be constructed vertically and in accordance with Rule 10.4.13,
unless directional drilling has been specifically approved by the State
Engineer in a well permit and a variance has been approved by the
Board.
10.4.13
Plumbness and
Alignment - All wells must be constructed so that the horizontal
deviation of the borehole from its surface location is a practical minimum at
all times. An unintentional deviation of the borehole due to adverse drilling
conditions will not be considered directional drilling. The casing must be
sufficiently plumb and straight so that it will not interfere with the
installation and operation of the pump.
10.5
Grout and Grout Placement -
All wells must be grouted to prevent contaminants from entering the borehole,
to separate groundwater in different aquifers, and to seal off water bearing
zones known or suspected to contain contaminants. To achieve these objectives,
the selection, mixing, and placement of all grout is the responsibility of the
person authorized to construct the well. All grout seals must be installed
before completion of the well and the installation of the production equipment.
10.5.1 Only the grout materials that meet the
requirements set forth in Table 2 may be used. Grout must be uniformly mixed
prior to placement in the well. The grout mixture density and the volume
percent of each additive used in the grout mixture must be reported on the well
construction report.
TABLE 2: GROUT MATERIALS
|
Approved
Grouts |
|
A.
Neat Cement: a slurry of
cement and water with no more than six (6) gallons of water per 94-pound sack
(Portland cement ASTM C-150). Fly ash may be blended with Portland cements for
grouting wells. The water-cement ratio for grout slurries blended with fly ash
must not exceed 5 gallons of water per 86-pound sack of blended
cement. |
|
B.
Cement-Bentonite: a
slurry of cement, bentonite and water. The amount of bentonite added must not
exceed 8% bentonite per dry weight of cement. The volume of additional water
used in preparing these slurries is limited to three quarters (0.75) of a
gallon per 94-pound sack of cement for each 1% of bentonite added. |
|
C.
Non-shrinking Cementitious
Grouts of differing composition may be reviewed and approved by the
Board. |
|
Prior to the use of other grout materials, a
written request must be submitted to and written approval obtained from the
Board. |
|
Bulk Grouts -
restricted use (see Rule 10.5.3.3) |
|
A.
Cement-Sand: a slurry of
cement, sand and water. The amount of sand added must not exceed 140 pounds for
each 94-pound sack of cement. Not more than six (6) gallons of water per
94-pound sack of cement may be used in the preparation of these slurries. These
slurries should be used where extra strength or bulk is required. |
|
B.
Concrete: a slurry of
cement, sand and gravel aggregate. The amount of aggregate added must not
exceed 400 pounds for each 94-pound sack of cement. Not more than seven (7)
gallons of water per 94-pound sack of cement may be used in the preparation of
these slurries. These slurries should be used where extra strength and bulk is
required and the annular space allows the placement of the slurry. |
|
Bentonite -
restricted use pursuant to Rule 10.5.3.4 . Before use in water well
construction, a variance must be obtained from the Board. The Board may approve
the following types of bentonite products. |
|
Only high-solids bentonite products that are clearly
marked by the manufacturer as "grout" may be used. Mixing of bentonite grouts
must strictly adhere to the manufacturer's recommendations and must achieve a
slurry of not less than 20% solids by volume and a density of not less than 9.8
pounds per gallon. |
|
A.
Bentonite Slurry: a
slurry of bentonite clay (chips and pellets) and water. Mixing of bentonite
grouts must strictly adhere to the manufacturer's recommendations and must
achieve a slurry of not less than 20% solids by volume and a density of not
less than 9.8 pounds per gallon. The density must be measured using a "mud
balance" and reported on the well construction and test report. |
|
B.
Granular Bentonite:
solid granular bentonite (pellets and chips) may only be used as grout material
in saturated zones and must be placed directly into the appropriate interval.
|
|
Fill Materials:
Fill material, such as clean native clay, drill cuttings, or other inert rock
material may be used to fill the annular space in any interval where grout is
not required by these Rules. These materials are not grouts and must not be
placed where grout is required. Fill materials placed in the annulus near the
land surface must be less permeable than the surrounding soil and must be
adequately compacted to prevent settling. |
10.5.2 The following minimum grout intervals
apply to all wells intended for the withdrawal of groundwater or for the
injection of water into an aquifer.
10.5.2.1
At or near the ground surface, the annulus between the borehole and the
outermost casing must be sealed with at least the minimum amount of continuous
cement grout required for the particular type of aquifer in which the well is
constructed (see Rule 10.4), and considering whether a pitless adapter or unit
will be installed. The top of the grout seal must not exceed the depths below
ground level as set forth below:
a. Not more
than three (3) feet below ground level if no pitless connection is installed on
the casing.
b. Not more than three
(3) feet below any pitless adapter or pitless unit to be installed. The annular
space above the pitless connection must be filled with materials not more
permeable than the surrounding ground that are adequately compacted.
c. Not less than ten (10) feet above the base
of the surface casing that has been driven for a well in a Type II or Type III
aquifer. If the well is constructed into a Type II aquifer, the grout interval
must extend at least twenty (20) feet below the base of the surface casing. If
the well is constructed into a Type III aquifer, the grout interval must extend
at least ten (10) feet below the base of surface casing. See Rule
10.4.2.1.
10.5.2.2 All
known zones containing contaminants must be sealed off by placing grout
throughout the interval from twenty (20) feet below to twenty (20) feet above
those zones.
10.5.3 The
method of grout placement must achieve a permanent watertight seal for the
required interval(s). Grout must be selected and placed to withstand the
maximum potential hydrostatic pressure differential between aquifers.
10.5.3.1 Grout placed by positive
displacement must be placed through well casing or through a tremie pipe.
Grouting of each interval or stage must be installed from the bottom up in one
continuous operation unless placed in accordance with Rules 10.5.3.2 or
10.5.3.3 . The outside diameter of the tremie pipe must not exceed the annular
space between the casing and the borehole.
10.5.3.2 Where grout is poured from the
surface, only neat cement or cement-bentonite may be used except as provided in
Rule 10.5.3.3 . Grout may only be poured into a dry annulus where the placement
depth does not exceed forty (40) feet below ground surface.
10.5.3.3 Cement-sand or concrete grout
mixtures may only be poured into a dry annulus where the borehole diameter is
at least twelve (12) inches larger than the outside diameter of the casing (at
least six (6) inch annular space) and the placement depth does not exceed forty
(40) feet.
10.5.3.4 Bentonite grout
may be used in required grout intervals only pursuant to a variance from the
Board and if its use is consistent with the requirements of Rule 10.5 and Table
2. Bentonite must not be used to seal the outermost casing of a well within
forty (40) feet below ground surface. A fully-hydrated bentonite slurry must
not be used as a grout where a difference in hydrostatic head exists across the
grout interval.
10.5.4
It is the responsibility of the person authorized to construct the well to
allow the grout to set before resuming construction. The minimum setting time
is six (6) hours for cement grout with accelerators and twenty-four (24) hours
for cement grout without accelerators.
10.6
Well Development and
Cleaning All wells must be initially cleaned and developed by the person
authorized to construct the well in order to establish proper conditions in the
well for installation of the permanent pumping equipment. At a minimum, well
development and cleaning must include removal of drill cuttings, drilling
fluids, and any foreign materials introduced into the borehole as a result of
the borehole drilling and well completion processes.
10.7
Disinfection Prior to
leaving the well site, the person authorized to construct the well must
disinfect the well according to the provisions of Rule 15.
10.8
Static Water Level
Measurement The static water level in all newly-constructed or modified
wells must be measured by the method described in Rule 5.2.49 by the well
construction or pump installation contractor, private driller, private pump
installer, or authorized individual, within seven (7) days after the well has
been cleaned and developed and the well yield estimate performed (see Rule
12.2). Static water level measurements must be reported on the well
construction and/or pump installation report.
10.9
Flowing Wells Flowing wells
must be constructed to prevent leakage around the casing or adjacent to the
well. Upon completion of grouting, flowing wells must be equipped with a device
to completely control the flow from the well, or the well must be plugged,
sealed, and abandoned in accordance with Rule 16. It is the responsibility of
the well construction contractor or private driller to install such control
equipment at the time of well construction. Thereafter, it is the
responsibility of the well owner to ensure the control equipment is maintained
and operational.
