ENVIRONMENTAL BORE HOLES
4725.7450 ENVIRONMENTAL BORE HOLES.
ENVIRONMENTAL BORE HOLE DEFINITION
In order for an excavation or drill hole to be an environmental bore hole, it must meet ALL three conditions:
A. THE DRILL HOLE MUST INTERCEPT A WATER-BEARING LAYER. For the purposes of the rules,
a water-bearing layer is interpreted to mean an aquifer. An aquifer is a saturated geologic material than can
transmit sufficient quantity of water to supply a well. An aquifer will have a hydraulic conductivity of 10-6
cm/sec or greater. Typically, an aquifer will have a sustained yield of .25 gallons per minute or greater. For
the purposes of the rule, an artificially created basin, not hydraulically connected (less than 10-6 cm/sec
hydraulic conductivity) to the earth outside the artificial basin, is not considered a water-bearing layer. Such
basins may include a landfill liner or an excavated basin in clay for petroleum tanks.
B. THE DRILL HOLE MUST BE EITHER DEEPER THAN 25 FEET OR PENETRATE A
CONFINING LAYER. The depth is measured to the deepest penetration of the drill hole. A confining layer
in unconsolidated materials, bedrock including the Paleozoic confining layers as specified in Minnesota
Rules, part 4725.2020 except for the Decorah and Glenwood formations, must be a minimum of 10 feet
thick. The Decorah or Glenwood must be a minimum of 2 feet thick to be considered a confining layer. If a
confining layer is penetrated, the drill hole is an environmental bore hole. Peat and muck-swamp deposits are
not considered confining layers.
C. THE DRILL HOLE MUST BE USED FOR TESTING WITHOUT EXTRACTING WATER OR BE
USED FOR VENTING, VAPOR RECOVERY, OR SPARGING TO REMOVE SOIL OR
GROUNDWATER CONTAMINATION. Testing includes measuring a water level, testing earth
properties or obtaining geologic samples for identification or other testing.
Examples of environmental bore holes include piezometers, soil borings, geologic test holes, push probe holes,
inclinometers, pressure transducers, and vents or air sparging points that meet the requirements of the definition
above.
An excavation or drill hole from which a water sample is removed, even if only a single sample is removed, and
regardless of depth, is a monitoring well not an environmental bore hole.
REGISTRATION/LICENSING TO CONSTRUCT OR SEAL AN
ENVIRONMENTAL BORE HOLE
A person must be either licensed as a well contractor or registered as a monitoring well contractor to construct,
repair, modify, or seal an environmental bore hole as detailed in Minnesota Rules,
part 4725.0475.
Environmental bore holes must be constructed, maintained and sealed according to the requirements of Minnesota
Rules, parts 4725.2010 to 4725.3875 and this part.
391
PERMITS AND REPORTS
Neither a permit nor a notification is required to construct or seal an environmental bore hole. A construction
report must be submitted unless the boring is sealed within 30 days. A sealing report must be submitted within 30
days of sealing. Environmental bore holes with similar geology and construction and on a single continuous piece
of property may be reported on one sealing report (provided the differences in depth is less than 25 feet) and a
drawing is submitted describing the locations of the bore holes.
A flow chart is included after part 4725.0100, subpart 30m that details the definitions and permitting requirements
for environmental bore holes and monitoring wells.
Subpart 1. Construction. An environmental bore hole must be constructed, repaired,
maintained, and sealed according to the general standards in parts 4725.2010 to
4725.3875. In addition, an environmental bore hole that is cased must be constructed to
conform to the monitoring well requirements in parts 4725.6650 to 4725.6850.
In addition to the general construction standards that apply to all wells and borings in Minnesota Rules, parts
4725.2010 to 4725.3875, an environmental bore hole must follow the requirements in this rule part, and
environmental bore holes which are cased must follow the monitoring well construction requirements in
Minnesota Rules, parts 4725.6650 to 4725.6850.
Subp. 2. At-grade bore holes. An environmental bore hole cased and completed
at-grade must conform to part 4725.6850.
Subp. 3. Sealing. An environmental bore hole that is not in use or that serves as a
potential or actual source of contamination must be sealed according to this chapter.
The sealing standards of Minnesota Rules, part 4725.3850 apply, except for the exception in subpart 4.
Subp. 4. Exception to sealing requirements. An environmental bore hole less than 50
feet in depth, in an unconsolidated formation, and not encountering a confining layer
may be sealed by removing the casing and screen and allowing the bore hole to collapse,
except for a flowing boring which must meet the requirements of part 4725.3850.
A. The bore hole must not encounter pollution or contamination or have been installed
to detect pollution or contaminants.
B. The collapse must not be induced other than by removal of the screen or casing.
C. The portion of the bore hole that does not collapse must be sealed immediately
upon removal of the casing as specified in part 4725.3850 with bentonite grout, neatcement grout, or cement-sand grout.
392
Subp 5. Screen or open hole across an unconsolidated formation and bedrock
contact. An environmental bore hole may be constructed to test contaminants without
extracting water, or to vent, recover vapor, or sparge contaminants from the water
surface, by placing a screen or open hole across the contact of an unconsolidated
formation and bedrock according to part 4725.6050, subpart 3.
Environmental bore holes constructed with multiple casings completed at different intervals in a single bore hole
are prohibited. Environmental bore holes constructed with multiple ports in multiple aquifers or confining layers
in a single bore hole are prohibited.
Environmental bore holes that flow may only be sealed with neat-cement grout or sand-cement grout.
An environmental bore hole may be located inside a building if the boring is sealed within 72 hours of the time
construction begins on the bore hole.
An environmental bore hole may be within 3 feet of a building if it is sealed within 72 hours of the time
construction begins on the well or bore hole.
INCLINOMETERS
“Inclinometers” are environmental bore holes if the inclinometer meets the conditions explained at the beginning
of this rule part (penetrates a water-bearing layer and is deeper than 25 feet or penetrates a confining layer).
Inclinometers meeting these conditions must be constructed to the standards of these rules except that ABS
inclinometer casing Standard Dimension Ratio 21 or less, with solvent-welded joints may be used. Rivets or
screws may not be used to connect casing sections.
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
4725.7500 [Repealed, 17 SR 2773]
4725.7600 [Repealed, 17 SR 2773]
4725.7605 [Repealed, 17 SR 2773]
393
End
of
Environmental Bore Holes Section
394