4725.5750 DUG WATER-SUPPLY WELLS.
A “dug well” is a water-supply well constructed by digging by hand, back hoe, bucket auger, excavating
or boring machines, or other “unconventional” equipment. Historically, dug wells were lined or cased
with stone, brick, wood, tile, concrete, or other nonwatertight casing. Dug wells obtained water from the
loose joints, bottom, and often the surface, creating water quality issues. Dug wells also presented safety
issues due to their often large diameter. Dug wells are sometimes referred to as “bored, augered, crock,
curbed, or tile” wells.
Previous rules allowed the use of concrete curbing or poured concrete subject to a number of restrictions.
Even with these precautions, a large percentage of concrete curbed dug wells demonstrated
contamination, so that in 2008 the use of concrete curbing or poured concrete was no longer permitted for
new wells. Existing wells may be still used and repaired, and new dug wells may be constructed using
conventional casing. Steel, and more recently plastic, casing is made in larger diameters, and can be made
with watertight joints.
Subpart 1. Construction. A dug well must be constructed in accordance with all
requirements of this chapter including the materials, grouting, and casing
standards. Where geological conditions preclude the possibility of completing a
water-supply well with conventional drilling methods, materials, or casing, a
variance may be granted under part 4725.0410 to install a dug well for a
residential water supply using unconventional techniques or materials. A dug
water-supply well may only be constructed in an unconsolidated formation.
All requirements of the general well and boring rules, and the water-supply well rules including grouting,
multiaquifer well prohibitions, and inner/outer casing combinations, apply to dug wells. A dug well may
not obtain water from more than one aquifer.
As an alternative to concrete or other older dug well materials, large diameter steel and plastic well casing
are made. Hydrofracturing can be used in conventional wells in some circumstances where before, a
conventional well would not produce an adequate quantity of water. Larger or multiple pressure tanks
can be installed on low yielding conventional wells. For those cases where unique geology may make
completion of a conventional well unlikely, a variance may be applied for to modify the required
materials or methods. The variance allows for review of the site-specific conditions, allows the well
owner to be fully informed of the risks, and allows precautions to be taken.
Subp. 2. Cover. A dug water-supply well must be protected with a cap or cover
meeting the requirements of part 4725.3150, subpart 1, or a precast, overlapping,
steel-reinforced, concrete cover at least four inches in thickness, or a locked,
overlapping, metal cover at least 3/16 inch in thickness. The junction of cover with
the well casing must be made with a watertight gasket and must be provided with a
well vent according to part 4725.5450.
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Subp. 3. Watertight openings. A pump opening and a connection below the
established ground surface for a dug water-supply well must be made watertight in
accordance with part 4725.4850, subpart 1, or with concrete or cement.
A “buried slab” construction of installing a small diameter upper casing and pitless on a large diameter
dug well is not approved.
Subp. 4. Location. Unless a dug water-supply well is grouted from the surface to
a depth of 50 feet or through a confining layer, the well must be located according
to part 4725.4450, subpart 2.
This subpart applies to contamination sources placed near existing dug wells. Minnesota Rules,
part 4725.4450, subpart 2, item A requires twice the isolation distance between contamination sources
entering the soil and “sensitive” wells. Sensitive wells include wells with screen, open hole, or water
intake areas within 50 feet of the surface or that don't penetrate 10 feet of a confining layer. The rules now
require grouting of new (dug) wells to a depth of 50 feet. However, many old dug wells still exist, and the
rule requires that new contamination sources not be placed closer to existing wells than the setbacks in
rule.
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
4725.5800 [Repealed, 17 SR 2773]
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