Current through Register Vol. 6, March 22, 2024
(1) Class I ground
waters are those ground waters with a natural specific conductance less than or
equal to 1,000 microSiemens/cm at 25°C.
(a) The quality of Class I ground water must
be maintained so that these waters are suitable for the following beneficial
uses with little or no treatment:
(i) public
and private water supplies;
(ii)
culinary and food processing purposes;
(iii) irrigation;
(iv) drinking water for livestock and
wildlife; and
(v) commercial and
industrial purposes.
(b)
Except as provided in ARM
17.30.1005(2), a
person may not cause a violation of the following specific water quality
standards in Class I ground water:
(i) the
human health standards for ground water listed in DEQ-7;
(ii) for concentrations of parameters for
which human health standards are not listed in DEQ-7, no increase of a
parameter to a level that renders the waters harmful, detrimental, or injurious
to the beneficial uses listed for Class I water. The department may use any
pertinent credible information to determine these levels; and
(iii) no increase of a parameter that causes
a violation of the nondegradation provisions of
75-5-303, MCA.
(2) Class II ground
waters are those ground waters with a natural specific conductance that is
greater than 1,000 and less than or equal to 2,500 microSiemens/cm at 25°C.
(a) The quality of Class II ground water must
be maintained so that these waters are at least marginally suitable for the
following beneficial uses:
(i) public and
private water supplies;
(ii)
culinary and food processing purposes;
(iii) irrigation of some agricultural
crops;
(iv) drinking water for
livestock and wildlife; and
(v)
most commercial and industrial purposes.
(b) Except as provided in ARM
17.30.1005(2), a
person may not cause a violation of the following specific water quality
standards for Class II ground water:
(i) the
human health standards for ground water listed in DEQ-7;
(ii) for concentrations of parameters for
which human health standards are not listed in DEQ-7, no increase of a
parameter to a level that renders the waters harmful, detrimental, or injurious
to the beneficial uses listed for Class II water. The department may use any
pertinent credible information to determine these levels; and
(iii) no increase of a parameter that causes
a violation of the nondegradation provisions of
75-5-303, MCA.
(3) Class III ground
waters are those ground waters with a natural specific conductance that is
greater than 2,500 and less than or equal to 15,000 microSiemens/cm at
25°C.
(a) The quality of Class III ground
water must be maintained so that these waters are at least marginally suitable
for the following beneficial uses:
(i)
irrigation of some salt tolerant crops;
(ii) some commercial and industrial
purposes;
(iii) drinking water for
some livestock and wildlife; and
(iv) drinking, culinary, and food processing
purposes where the specific conductance is less than 7,000 microSiemens/cm at
25°C.
(b) Except as
provided in ARM
17.30.1005(2), a
person may not cause a violation of the following specific water quality
standards for Class III ground water:
(i) the
human health standards listed in DEQ-7, except that the nitrate nitrogen and
nitrate plus nitrite nitrogen standards listed in DEQ-7 do not apply to ground
waters with a specific conductance equal to or greater than 7,000
microSiemens/cm at 25°C. The nitrate nitrogen and nitrate plus nitrite
nitrogen standards for these waters are each 50 mg/l; and
(ii) for concentrations of parameters for
which human health standards for ground water are not listed in DEQ-7, no
increase of a parameter to a level that renders the waters harmful,
detrimental, or injurious to the beneficial uses listed for Class III water.
The department may use any pertinent credible information to determine these
levels.
(c) The
nondegradation provisions of
75-5-303, MCA, do not apply to
Class III ground water.
(4) Class IV ground waters are those ground
waters with a natural specific conductance greater than 15,000 microSiemens/cm
at 25oC.
(a) The
quality of Class IV ground waters must be maintained so that they are suitable
for some industrial and commercial uses.
(b) Except as provided in (5) and ARM
17.30.1005(2), a
person may not cause a violation of the following specific water quality
standards for Class IV ground water:
(i) the
human health standards for parameters categorized as carcinogens in
DEQ-7;
(ii) for concentrations of
parameters in DEQ-7 which are not listed as carcinogens, no increase of a
parameter to a level that would adversely affect existing beneficial uses. The
nitrate nitrogen and nitrate plus nitrite nitrogen standards are each 50
mg/l;
(iii) for concentrations of
parameters for which human health standards are not listed in DEQ-7, no
increase of a parameter to a level that would adversely affect existing
beneficial uses. The department may use any pertinent credible information to
determine these levels.
(c) The nondegradation provisions of
75-5-303, MCA, do not apply to
Class IV ground water.
(5) For Class III or IV waters, where it can
be demonstrated to the satisfaction of the department that the field hydraulic
conductivity is less than 0.1 feet per day in an affected or potentially
affected ground water zone, the nitrate nitrogen and nitrate plus nitrite
nitrogen standards in (3) (b) (i) and (4) (b) (ii) do not apply, provided that
all existing and anticipated uses of the ground waters are protected.
(6) The ground water quality standards for
metal parameters are based on the dissolved portion (after filtration through a
0.45 micron filter) of the contaminant in the ground water. The ground water
quality standards for other parameters in department Circular DEQ-7 are based
upon unfiltered samples. For inorganic parameters, compliance with standards
based on filtered samples must be assumed if analyses using the total
recoverable method demonstrates compliance with the numerical
standards.
75-5-301,
80-15-105,
80-15-201, MCA; IMP,
75-5-301,
80-15-201,
MCA;