4725.3450 FLOWING WELL OR BORING.
Flowing wells and borings are drill holes where the pressure in the aquifer is sufficient to force water
above the ground surface, so that water will flow without pumping. Flowing conditions typically occur at
lower elevations in groundwater discharge areas near rivers, lakes, or other water bodies. The most
common example of a flowing artesian aquifer consists of a low permeability confining layer, such as
clay or shale, which overlies the flowing aquifer. However, under some circumstances the presence of
faults, fractures, or solution cavities can cause a drill hole to flow. Also, flowing wells or borings can
occur without the presence of a distinct confining layer, near discharge areas, usually very near rivers. In
these cases, a drill hole can provide a vertical pathway through sediments that normally transmit water
better in a horizontal direction than a vertical direction.
Subpart 1. General construction; flowing well or boring. A well or boring from
which groundwater flows above the established ground surface without pumping
must be constructed to prevent erosion of the aquifer and the confining layer.
Casing must be installed into the flowing aquifer to prevent water flowing up the
outside of the casing. The requirements in this part are in addition to other
requirements of this chapter.
The purposes of these requirements are to contain the flowing groundwater within the well or boring
casing and to protect and conserve the groundwater resource. Flow outside the casing may result erosion
of the confining layer(s), subsidence of overlying formation(s), and eventually anuncontrollable flow.
Flowing wells and borings have caused drilling machines to tip over, caused significant damage to
property and structures, created serious safety threats, and accelerated aquifer dewatering.
Shallow, high flow wells deserve special caution. It is very important not to erode the confining layer.
Large diameter grout pipes and high volume grout pumps may be needed. The contractor should be
prepared prior to starting drilling in an area likely to have flowing conditions. Adequate equipment,
casings, grout, and personnel should be available. A well or boring should not be left uncontrolled in the
hope that conditions will stabilize later. This rarely happens, and usually creates much greater problems.
These requirements apply when the well or boring will flow at the land surface, even if the casing is
extended above the artesian head, or a device installed to reduce the flow. Subpart 1a. applies to flows
less than 70 gallons per minute or pressures less than 10 pounds per square inch measured at the land
surface. Subpart 2 applies to flows greater of 70 gallons per minute or greater, pressures of 10 pounds per
square inch or greater, or in flowing well and boring special construction areas. In numerous instances,
particularly as flow rates approach 70 gallons per minute or pressures approach 10 pounds per square
inch, it is safer to follow the standards of subpart 2 (install an outer casing and cement) even though it is
not required.
A cross-sectional geological diagram depicting confining layers and artesian conditions is located after
the definition of “confining layer” in Minnesota Rules, part 4725.0100.
Subp. 1a. Low flow and low pressure. A flowing well or boring that flows 70
gallons per minute or less, and that has an artesian pressure ten pounds per
square inch or less, must be constructed by either:
A. drilling a bore hole larger than the casing into the flowing aquifer, installing
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casing into the flowing aquifer, and grouting the annular space surrounding the
casing with neat-cement grout or cement-sand grout from the bottom of the casing
to the base of the pitless adapter or unit, or to the established ground surface
according to part 4725.3050; or
B. driving steel casing with welded, or threaded and coupled joints, into the
flowing aquifer.
Driven steel casing with welded or threaded and coupled joints is exempt from the cement grout
requirement described in subpart 1a, for wells and borings flowing less than 70 gallons per minute,
having a head less than 10 pounds per square inch, or not located in a flowing well or boring special
construction area.
The low-flow or low-pressure wells or borings do not require a minimum bore hole size. However,
annular space must be grouted with neat-cement or cement-sand grout from the bottom of the casing. In
many cases it may be prudent to drill a hole large enough to install a larger tremie pipe. Problems have
been encountered attempting to place cement grout in flowing wells through small-diameter grout pipes
with low flow pumps if the grout cannot be emplaced fast enough to overcome the water flow rate out of
the hole. Contractors have reported that thicker cement grout (5.2 gallons of water per 94 lb. of Portland
cement) or rapid-setting cement (high early) can be beneficial in grouting some flows.
Placing a screen or gravel pack within the confining layer is not allowed.
In some instances of low flow, it may be possible to raise the ground elevation around the casing to
prevent flow and make service and installation of the discharge easier.
The flow rate and the pressure are measured at the established ground surface, not at the top of the casing.
The flow rate and pressure conditions apply at the time the well or boring is placed in service. Under
certain conditions, a well may begin to flow only after drilling fluids are removed and/or well
development takes place. Contractors should carefully measure the flow rate and pressure.
Subp. 2. High flow, high pressure, or special construction area.
A. A well or boring must be constructed according to the requirements in this
subpart when:
(1) the artesian flow rate at the established ground surface is greater than 70
gallons per minute;
(2) the artesian pressure at the established ground surface exceeds ten pounds
per square inch; or
(3) the commissioner designates an area where the use of standard
construction techniques have resulted in uncontrolled flows, or where
hydrogeologic conditions such as eroded or unstable confining layers require
special construction to successfully complete a well or boring and confine the
artesian pressure.
B. A well or boring meeting the criteria in A must be constructed by:
(1) installing an outer steel casing into, but not through the confining layer
overlaying the flowing aquifer, except that the outer casing may terminate in
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competent bedrock above the confining layer. The outer steel casing is not
required to meet the material specifications for casing in part 4725.2350 if the
casing is of sufficient strength to withstand the structural load imposed by
conditions both inside and outside the well or boring. The casing must be installed
by drilling a bore hole a minimum of 3.0 inches larger, or 3.5 inches larger for
casings deeper than 100 feet and larger than 12 inches inside diameter, than the
outside diameter of the casing or couplings, whichever is larger, into the confining
layer overlying the flowing aquifer. The bore hole must not penetrate the entire
thickness of the confining layer. Steel casing must be installed into the confining
layer; and neat-cement grout or cement-sand grout must be pumped into the
annular space surrounding the casing from the bottom of the casing to the
established ground surface or base of the pitless adapter or unit;
(2) drilling a bore hole a minimum of 3.0 inches larger, or 3.5 inches larger
for casings deeper than 100 feet and larger than 12 inches inside diameter, than
the outside diameter of the inner casing or couplings through the confining layer
into the flowing aquifer;
(3) installing an inner casing into the flowing aquifer in accordance with part
4725.2250, subpart 8; and
(4) grouting the annular space surrounding the inner casing with neat-cement
grout or cement-sand grout from the bottom of the casing to the established ground
surface or base of the pitless adapter or unit.
Grouting must comply with part 4725.3050.
The designated areas are known as “Flowing Well or Boring Special Construction Areas” and will be
established by the MDH when necessary. Maps showing flowing well and boring areas will be provided
to contractors as they become available. At the present time, only one such area, located near Kabekona
and Benedict Lakes in Hubbard County, has been designated.
Wells and borings which exceed the flow rate or pressure, or are in special construction areas must be
double cased and double grouted using either neat-cement or cement-sand grout.
It is extremely important that the outer casing be firmly sealed into the confining layer. The drill hole
must not penetrate all the way through the confining layer. Ideally, the casing should be set approximately
one-half way into the confining layer. The outer casing may terminate in a “competent bedrock” above
the confining layer – this applies only to formations meeting the definition of “bedrock” found in
Minnesota Rules, part 4725.0100, subpart 21b, and does not include alluvium, glacial drift, glacial
outwash, glacial till, saprolite, or soil.
The outer casing must be steel, but does not need to meet the casing standards; it may be used, nonprime,
or “light-weight” pipe. It may not be plastic. The inner casing may be steel, plastic, or stainless steel
meeting the specifications of the rules (Minnesota Rules, part 4725.2250).
The neat-cement or sand-cement grout must be pumped through the casing or a tremie pipe.
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After grouting the outer casing, drilling may not be done for 24 hours (12 hours if rapid-setting cement is
used) to allow time for the cement to set. Refer to Minnesota Rules, part 4725.3050, for more information
on grouting.
The inner casing must be cement grouted from the bottom of the casing (which is installed into the
flowing aquifer) to the ground surface or base of the pitless unit or pitless adapter.
These requirements are designed to prevent uncontrolled flows which can erode an uncased bore hole,
making it difficult and expensive to control.
These standards apply to wells and borings within a flowing well or boring special construction area, and
also to any well or boring, regardless of location, which when completed, will have an artesian flow rate
of 70 gallons per minute or greater, or artesian pressure of 10 pounds per square inch (psi) or greater at
the land surface. Contractors should anticipate flowing conditions, and design, bid, and construct the well
or boring accordingly.
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Subp. 3. [Repealed, 33 SR 211]
Subp. 4. Flow control. A flowing well or boring must be provided with flow
control capable of stopping all flow, consisting of a valved pipe connection,
watertight pump connection, specially designed pitless unit, or a receiving tank set
at an altitude corresponding to that of the artesian head.
This rule does not require flow from a well or boring to be permanently stopped; only that the well is
constructed so flow can be completely stopped. The MDH recommends using an approved flowing well
pitless unit where possible, which stops the flow, because it provides the best protection from freezing
and conserves groundwater. Contractors are cautioned that flowing wells may exert considerable pressure.
Removal of the spiders or fittings from a flowing well pitless spool may cause the spool to rapidly eject
from the casing and potentially cause injury.
Allowing a well to flow wastes groundwater resources, reduces artesian pressures, may accelerate casing
corrosion and/or mineral encrustation, may lead to land subsidence or erosion problems, and may
adversely affect nearby wells. Minnesota Statutes, section 103I.103 allows the DNR to order a person to
prevent the waste of groundwater. The DNR has authority in matters relating to groundwater use and may
require an appropriation permit.
The use of mineral oil, antifreeze, or other chemicals in a well or boring to control flow and prevent
freezing is not allowed. Contractors have reported success in some situations by pressurizing the casing
with air to depress the water level and prevent flow. However, this practice is not recommended since it is
difficult to maintain the air pressure long term, and the casing seal, cover or cap may be forcefully
detached from the casing causing damage or injury.
Special flowing spool pitless units will often provide the best solution to both controlling flows and
providing freeze protection. Some manufacturers report that units are capable of withstanding pressures
up to 50 psi. To prevent injury or damage, it is advisable to label or otherwise place a warning
identification on a casing under pressure. Drawdown seals are not recommended for heads over 5 psi or
11.5 feet of water (for each 1 psi, water will rise approximately 2.3 feet). Clamp-on pitless adapters, used
for buried discharge lines, are generally not recommended, since the gaskets will not always remain under
positive pressure. “Snifter” valves are prone to failure due to iron or calcium deposits. “Overflow” lines
are not recommended. If an overflow must be installed, it is recommended that the flow be reduced as
much as possible. Reports indicate that as little as 1 g.p.m will prevent freezing.
Subp. 5. Overflow discharge. A water discharge from a flowing well or boring
that disposes of water to the surface, a surface water body, sewer, or subsurface
must:
A. be protected with an air gap according to part 4715.2010;
B. have a valve or other mechanism as required in subpart 4 capable of
stopping all flow; and
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C. have the outlet screened with a noncorrosive mesh screen having openings of
1/16 inch or less.
The purpose of the air gap is to prevent back-siphoning of surface water into the well which may occur if
the discharge pipe is submerged and the water level drops in the well, as is likely with low volume flows
when the pump turns on. Minnesota Rules, Chapter 4715 (Minnesota Plumbing Code) requires an air gap
based on the diameter of the discharge pipe. The air gap calculations described in Minnesota Rules,
part 4715.2010 are intended for indoor plumbing applications and may not provide adequate protection
for discharge to an open body of water. The MDH recommends that a discharge pipe be elevated 1 foot
above the regional flood level.
If the discharge pipe is fitted with a valve for stopping the flow, the valve must remain accessible. It may
not be buried unless it can be operated from the surface. If the discharge pipe is fitted with a valve, it is
recommended that the well or boring be designed so that if the valve is closed, water will not freeze inside
the casing, or flow out of the cap, vent, electrical conduit or another opening. This will typically require
the use of a sanitary seal without a casing vent.
Subp. 6. Temporary wells and borings. Temporary wells and borings that flow,
and are sealed within 30 days of the time construction begins, are not required to
be constructed in accordance with this part, but must be constructed to prevent
erosion of the aquifer, drill hole, or surrounding property, and must be sealed to
stop all flow with neat-cement grout or cement-sand grout according to part
4725.3850.
The MDH advises contractors that a “temporary” flowing well or boring may quickly become difficult
and expensive to seal, or may cause erosion or subsidence problems, if precautions such as installation of
an outer casing and/or cement grout are not taken at the time of construction
For information about sealing flowing wells and borings, including the requirement to use neat-cement
grout or cement-sand grout see Minnesota Rules, part 4725.3850, subpart 7.
STAT AUTH: MS s 103I.101; 103I.111; 103I.205; 103I.221; 103I.301; 103I.401;
103I.451; 103I.501; 103I.525; 103I.531; 103I.535; 103I.541; 103I.621; 144.05;
144.12; 144.383; 157.04; 157.08; 157.09; 157.13
HIST: 17 SR 2773; 33 SR 211
4725.3500 [Repealed, 17 SR 2773]
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FLOWING WELL AND BORING SPECIAL CONSTRUCTION AREA
KABEKONA AND BENEDICT LAKES
HUBBARD COUNTY
NOTIFICATION OF SPECIAL FLOWING WELL AND BORING
CONSTRUCTION REQUIREMENTS
The MDH is issuing a FLOWING WELL AND BORING SPECIAL CONSTRUCTION AREA for
portions of Lakeport and Steamboat River Townships. The area is located in east-central Hubbard
County, Minnesota.
The MDH has initiated special construction restrictions due to considerable flowing well problems which
have been encountered in this area. High capacity flowing wells are common. Contractors have
experienced problems with uncontrolled flows which have resulted in erosion of land, and damage to
buildings and property.
Wells constructed within the boundaries of this area must follow the special construction
requirements.
BOUNDARIES OF THE SPECIAL CONSTRUCTION AREA
The special construction area includes properties on the southeast shore of Kabekona Lake and on the
southwest shore of Benedict Lake which are within 25 feet of lake level, or generally below an elevation
of 1320 feet as indicated on the accompanying map. The standard lake levels recognized by the U.S.
Corps of Engineers are 1296 above sea level for Kabekona Lake and 1295 feet for Benedict Lake. The
map indicates the general area affected. A more detailed map is available from the Bemidji office of the
MDH.
REQUIREMENTS FOR WELL AND BORING CONSTRUCTION WITHIN THE FLOWING WELL
AND BORING AREA
Within the area, a well or boring must be constructed by:
A. Drilling a bore hole a minimum of 3.0 inches larger than the outside diameter of the casing or
couplings, whichever is larger, into the confining layer overlying the flowing aquifer. Casings larger
than 12 inches and deeper than 100 feet must be installed in a 3.5 inch larger bore hole. The confining
layer in these areas generally extends from the surface to a depth of approximately 45 feet.
Occasional sand formations up to several feet thick with possible low flows may be encountered in
the upper 20 feet of the confining layer. The bore hole must not penetrate the entire thickness of the
confining layer;
B. Installing steel casing into the confining layer;
C. Pumping neat-cement grout or cement-sand grout into the annular space surrounding the casing from
the bottom of the casing to the established ground surface;
D. Drilling through the confining layer into the aquifer;
E. Installing an inner casing into the aquifer in accordance with Minnesota Rules, part 4725.2250,
subpart 8; and
F. Grouting the annular space surrounding the inner casing with neat-cement grout or cement-sand
grout. Grouting must be in accordance with Minnesota Rules, part 4725. 3050.
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As a caution, be aware that flowing conditions may be encountered outside the designated area. If flow
rates outside the area exceed 70 g.p.m or have pressures exceeding 10 psi at the land surface, well and
boring construction must be in accordance with the requirements listed for the Kabekona/Benedict special
construction area. If flows encountered outside the special construction area are less than 70 g.p.m or
10 psi, the well or boring must be grouted with neat-cement grout or cement-sand grout if rotary drilled,
or constructed with driven plain-end or threaded and coupled steel casing.
If you have any questions regarding this special flowing well and boring construction area, contact Kelly
Jorgensen at 218-308-2112, or Mark Malmanger at 218-308-2118.
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4725.3550 WELL LABEL.
Subpart 1. Label required. A person who has constructed a well must attach a
well identification label provided by the commissioner to the well before placing
the well into service unless the well is sealed within 90 days of construction.
All wells, including potable water-supply, nonpotable water-supply, monitoring, and dewatering, which
are not sealed within 90 days of construction must be labeled. The label is not required if the well is
sealed within 90 days of construction. Borings, including vertical heat exchangers, environmental bore
holes, and elevator borings, are not required to be labeled; however, it is recommended that permanent
borings, such as piezometers, be marked with the Minnesota unique well number for identification
purposes.
The licensed contractor who constructs a well (including water supply, monitoring, and dewatering) must
attach a well identification label to it before placing it into service. Well labels are provided by the MDH
Well Management Section with the Well and Boring Record form, and consist of a 2-inch by 3-1/2-inch
rectangular aluminum tag with the Minnesota unique well number stamped on its face.
Subp. 2. Attachment. The well identification label must be attached to the well
casing in a visible location using a stainless steel clamp, band, or strap.
Alternatively, the label may be attached to a concrete pump base or pedestal, or
at-grade well vault using screws or fasteners.
The well label must be attached to the outside of the well casing in a visible location above the finished
grade, with a stainless steel clamp, band, or strap. Wire, twist ties, plastic bands, or plastic fasteners are
not acceptable. Stainless-steel “hose clamps” are recommended. The label for at-grade wells completed in
a vault must be attached to the well casing with a stainless steel clamp, band, or strap; or to the inner wall
of the vault with screws or rivets. The label must not be fastened to the vault cover. For municipal wells,
or other wells with a pump sitting on a concrete pump pedestal, the label may be attached to the concrete
pump base using screws or fasteners suitable for concrete.
Subp. 3. Maintenance. The property owner must maintain the well identification
label in a readable condition.
The property owner (unless a written agreement exists identifying a different well owner) is responsible
for replacing lost or damaged well labels. Replacement labels are available from the MDH Well
Management Section.
Subp. 4. Removal; reattachment. The well identification label must not be
removed except to work on the well. On completing work, the label must be
reattached.
STAT AUTH: MS s 103I.101; 103I.111; 103I.205; 103I.221; 103I.301; 103I.401;
103I.451; 103I.501; 103I.525; 103I.531; 103I.535; 103I.541; 103I.621; 144.05;
144.12; 144.383; 157.04; 157.08; 157.09; 157.13
HIST: 17 SR 2773; 33 SR 211
4725.3600 [Repealed, 17 SR 2773]
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