Current through Register Vol. 18, September 20, 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;
