(1) New Class II landfill units and lateral expansions must be constructed:

(a) in accordance with a design approved by the department that ensures that the concentration values listed in Table 1 at the end of this rule will not be exceeded in the uppermost aquifer at the relevant point of compliance, as specified by the department; or

(b) with a composite liner and a leachate collection system meeting the following requirements:

(i) The composite liner shall consist of 2 components.   The upper component must consist of a minimum 30-mil flexible membrane liner (FML) , and the lower component must consist of at least a 2-foot layer of compacted soil with a hydraulic conductivity of no more than 1 x 10^-7 cm/sec.   FML components consisting of high density polyethylene (HDPE) must be at least 60-mil thick.   The FML component must be installed in direct and uniform contact with the compacted soil component.

(ii) The leachate collection and removal system must be designed and constructed to maintain less than a 30-cm depth of leachate over the liner.

(2) When approving a design under (1) (a) of this rule, the department shall consider at least the following factors:

(a) the hydrogeologic characteristics of the facility and surrounding land, including depth to ground water, value and uses of the uppermost and any regional aquifers, type, depth, and hydraulic conductivity of soils and lithology below the waste disposal areas;

(b) the climatic factors of the area;

(c) the estimated volume and physical and chemical characteristics of the leachate;

(d) the hydraulic conductivity of the barrier layer;

(e) the barrier layer thickness;

(f) the slope of the barrier layer; and

(g) the hydraulic head on the barrier layer;

(3) A design of a landfill unit pursuant to (1) (a) of this rule must include a leachate collection and removal system and a barrier layer.

(4) The barrier layer must be an engineered improvement that may include, but is not limited to the following:

(a) compacted soil liner as defined in ARM 17.50.502;

(b) geosynthetic clay liners;

(c) soil admixtures;

(d) geomembranes;

(e) polymers;

(f) natural lithology when the uppermost soil layer of the landfill base is recompacted to achieve a minimum final thickness of 12 inches with a hydraulic conductivity of less than or equal to 1 x 10^-7 cm/sec; and

(g) variations or combinations of design components
described in this section that achieve compliance with (1) (a) of this rule.

(5) A barrier layer is not required for landfill units at a facility that has a department-approved no migration petition as specified in ARM 17.50.723.

(6) The leachate collection and removal system must be designed and constructed:

(a) to maintain less than a 30 centimeter (12-inch) depth of leachate at any point over the barrier layer or base of the landfill unit; and

(b) When a compacted soil liner or recompacted natural lithology is used as the barrier layer, to ensure that the minimum slope at the base of the overlying leachate collection layer is at least 2% and side slopes do not exceed 33%.

(7) The leachate collection system must be designed with consideration of the following factors and must be approved by the department:

(a) sized to water balance calculations or using other accepted engineering methods approved by the department;

(b) waste type;

(c) slope length;

(d) percent slope;

(e) barrier layer;

(f) hydraulic conductivity of the drainage layer; and

(g) long term performance during the active life and post closure care period.

(8) The leachate removal system must be designed, constructed, and operated to:

(a) allow the leachate collection system to perform as designed;

(b) allow for the safe removal of and treatment of the collected leachate; and

(c) account for potential increased hydraulic head in the removal system.

(9) The returning of leachate to the landfill unit or the recirculation of leachate in the landfill unit may be done only in landfill units that have a composite liner system.

(10) The relevant point of compliance specified by the department must be no more than 150 meters from the waste management unit boundary and must be located on land owned by the owner of the landfill unit.

(11) In determining the relevant point of compliance, the department shall consider at least the following factors:

(a) the hydrogeologic characteristics of the facility and surrounding land;

(b) the volume and physical and chemical characteristics of the leachate;

(c) the quantity, quality, and direction of flow of ground water;

(d) the proximity and withdrawal rate of the ground water users;

(e) the availability of alternative drinking water supplies;

(f) the existing quality of the ground water, including other sources of contamination and their cumulative impacts on the ground water, and whether the ground water is currently used or reasonably expected to be used for drinking water; and

(g) public health, safety, and welfare effects.

(12) Verification of construction of the final cap, liner, and leachate collection and removal system approved by the department is required by means of construction quality control (CQC) and construction quality assurance (CQA) plans and testing for construction of these elements of design in accordance with submitted specifications.

(13) CQC and CQA plans must be approved by the department.

(14) A report of all CQC and CQA procedures and results of all testing and monitoring provisions performed during construction of the design features for a landfill unit as specified in the approved plans must be submitted to the department and approved in writing before acceptance of waste by a landfill unit is allowed.

(15) (a) Owners or operators of all existing landfill units, new landfill units and lateral expansions that meet the criteria for a small community exemption and are approved by the department are not required to comply with this rule.

(b) Petitions requesting the small community exemption must be in writing and must contain sufficient information for the department to make its determination.

(c) Any change in a facility's compliance with the mandated criteria automatically revokes the exemption and the facility must comply with all applicable requirements in this subchapter.

(d) The department must be notified of any change in the facility's eligibility under the following criteria within 30 days of the change.

(16) The small community exemption will be approved only if all of the following criteria are met:

(a) there is no evidence of existing ground water contamination; and

(b) the landfill receives less than 20 tons per day of all types of solid waste, based on an annual average; and

(c) the landfill is in an area that annually receives less than 25 inches of precipitation; and

(d) the landfill serves a community that has no practicable waste management alternative.   For the purposes of this section, the lack of a practicable waste management alternative may be demonstrated by the following:

(i) no access to licensed Class II landfill within 100
miles of the community; and

 (ii) the cost per household of using an alternative disposal method, and the cost per household of complying with the requirements of the landfill design and operation distributed over the entire estimated active life of the landfill, will each exceed on an annual basis 1% of the median household income for the service area.

 

          

TABLE 1
Chemical	MCL (mg/l)
Arsenic	0.05
Barium	1.0
Benzene	0.005
Cadmium	0.01
Carbon tetrachloride	0.005
Chromium (hexavalent)	0.05
2,4-Dichlorophenoxy acetic acid	0.1
1,4-Dichlorobenzene	0.075
1,2-Dichloroethane	0.005
1,1-Dichloroethylene	0.007
Endrin	0.0002
Fluoride	4
Lindane	0.004
Lead	0.05
Mercury	0.002
Methoxychlor	0.1
Nitrate	10
Selenium	0.01
Silver	0.05
Toxaphene	0.005
1,1,1-Trichloroethane	0.2
Trichloroethylene	0.005
2,4,5-Trichlorophenoxy acetic acid	0.01
Vinyl Chloride	0.002

 

(17) Landfill units and lateral expansions must be designed, constructed, and operated in a manner to prevent harm to human health and the environment.

(18) Class IV landfill units and lateral expansions must be constructed in accordance with a design approved by the department that ensures that the concentration values listed in Table 1 of this rule will not be exceeded in the uppermost aquifer at the relevant point of compliance, as specified by the department.

(19) A Class IV landfill unit is exempt from liner requirements if:

(a) the department determines, based upon site-specific information such as soil or rock types, average net infiltration or percolation rates, depth to ground water, and contaminant
migration velocities, that the unit does not have the potential to cause ground water contamination during the active, closure, and post closure care periods;

(b) the unit is located at a Class II facility and is monitored by the facility's ground water monitoring system in accordance with this subchapter; or

(c) the unit is located at a Class II facility that meets the requirements of ARM 17.50.723.

(20) Returning leachate to a Class IV landfill unit, or recirculating leachate in the landfill unit may only be done in a landfill unit that has a composite liner system.

(21) The relevant point of compliance for Group IV units is the same as specified in (10) of this rule for Class II units.   The requirements of (11) of this rule apply to Class IV units.

(22) At sites where Class IV units require liners and for closure activities at all Class IV units, the CQC/CQA requirements for Class IV units are the same as for Class II units contained in (12) , (13) and (14) of this rule.

(23) The requirements of this rule are effective October 9, 1993, except for the existing landfill units and lateral expansions to existing units defined in ARM 17.50.501(4) , which must comply by April 9, 1994.