Current through Register Vol. 6, March 22, 2024
(1) An
owner or operator required to monitor under this subchapter shall install a
ground water monitoring system that consists of a sufficient number of wells,
installed at appropriate locations and depths, to yield ground water samples
from the uppermost aquifer, or underground drinking water source, as required
in ARM 17.50.1204, that:
(a) represent the quality of background
ground water that has not been affected by leakage from a unit. A determination
of background quality may include sampling of wells that are not hydraulically
upgradient of the waste management area when:
(i) hydrogeologic conditions do not allow the
owner or operator to determine the wells that are hydraulically upgradient;
or
(ii) sampling at other wells
will provide an indication of background ground water quality that is as
representative or more representative than that provided by the upgradient
wells; and
(b) represent
the quality of ground water passing the relevant point of compliance specified
by the department under ARM
17.50.1204(3).
The downgradient monitoring system must be installed at the relevant point of
compliance specified by the department under ARM
17.50.1204(3)
that ensures detection of ground water contamination in the uppermost aquifer,
or underground drinking water source, as required in ARM 17.50.1204. When
physical obstacles preclude installation of ground water monitoring wells at
the relevant point of compliance at existing units, the downgradient monitoring
system may be installed at the closest practicable distance hydraulically
downgradient from the relevant point of compliance specified by the department
under ARM 17.50.1204(3)
that ensures detection of ground water contamination in the uppermost aquifer,
or underground drinking water source, as required in ARM 17.50.1204.
(2) The department may approve a
multi-unit ground water monitoring system instead of separate ground water
monitoring systems for each Class II or Class IV landfill unit when the
facility has several units, if the multi-unit ground water monitoring system
meets the requirements of (1) and will be as protective of human health and the
environment as individual monitoring systems for each Class II or Class IV
landfill unit, based on the following factors:
(a) number, spacing, and orientation of the
Class II or Class IV landfill unit;
(b) hydrogeologic setting;
(c) site history;
(d) engineering design of the Class II or
Class IV landfill unit; and
(e)
type of waste accepted at the Class II or Class IV landfill unit.
(3) Monitoring wells must be cased
in a manner that maintains the integrity of the monitoring well bore hole. This
casing must be screened or perforated and packed with gravel or sand, where
necessary, to enable collection of ground water samples. The annular space,
i.e., the space between the bore hole and well casing, above the sampling depth
must be sealed to prevent contamination of samples and the ground
water.
(4) The owner or operator of
a Class II or Class IV landfill unit required to monitor under this subchapter
shall:
(a) submit a ground water monitoring
plan to the department for approval that includes:
(i) the location, number, depth, design,
installation, development, and decommission of any monitoring wells;
(ii) plans for the design, installation,
development, and decommission of piezometers or other measurement, sampling,
and analytical devices; and
(iii)
discussions of the anticipated ground water monitoring system and schedule of
sampling for closed portions of the facility, if applicable;
(b) update the ground water
monitoring plan at least once every five years, except that a ground water
monitoring plan for a closed facility must be updated at least every ten years;
and
(c) notify the department that
the approved ground water monitoring systems plan has been placed in the
operating record.
(5)
The monitoring wells, piezometers, and other measurement, sampling, and
analytical devices must be operated and maintained so that they perform to
design specifications throughout the life of the monitoring program.
(6) The number, spacing, and depths of
monitoring wells must be:
(a) determined
based upon site-specific technical information that must include thorough
characterization of:
(i) aquifer thickness,
ground water flow rate, ground water flow direction, including seasonal and
temporal fluctuations in ground water flow; and
(ii) saturated and unsaturated geologic units
and fill materials overlying the uppermost aquifer, or underground drinking
water source, as required in ARM 17.50.1204, materials comprising the uppermost
aquifer, or underground drinking water source, as required in ARM 17.50.1204,
and materials comprising the confining unit defining the lower boundary of the
uppermost aquifer, or underground drinking water source, as required in ARM
17.50.1204, including, but not limited to, thicknesses, stratigraphy,
lithology, hydraulic conductivities, porosities, and effective porosities;
and
(b) be certified by
a qualified ground water scientist and approved by the department. Within 14
days of this certification, the owner or operator shall notify the department
that the certification has been placed in the operating record.
(7) The drilling and construction
of a ground water monitoring well at a solid waste management system may be
subject to the requirements of Title 36, chapter 21, subchapters 4, 7, and
8.
75-10-204, MCA; IMP,
75-10-204,
75-10-207,
MCA;