Sec. 26.13.05.11. Surface Impoundments

A. Applicability. This regulation applies to owners and operators of facilities that use surface impoundments to treat, store, or dispose of hazardous waste, except as Regulation .01 of this chapter otherwise provides.

B. General Design Requirements.

(1) A surface impoundment shall be designed to provide:

(a) At least 60 centimeters (2 feet) of freeboard; or

(b) An amount of freeboard other than 60 centimeters based on documentation acceptable to the Secretary that the specified amount of the freeboard will prevent overtopping. The amount of freeboard approved by the Secretary shall be specified in the permit.

(2) A surface impoundment shall be designed so that any flow of waste into the impoundment can be immediately shut off in the event of overtopping or liner failure.

(3) A surface impoundment shall be designed to prevent discharge into the land and ground water, and to surface water (except discharges authorized by a State discharge permit) during the life of the impoundment by use of a containment system which complies with §D. The Secretary shall include the design of the containment system as a term and condition of the permit.

(4) Dikes shall be designed with sufficient structural integrity to prevent massive failure without dependence on any liner system included in the surface impoundment design.

(5) For a surface impoundment, except for an existing portion of a surface impoundment, a leachate detection, collection, and removal system shall be designed so that liquid will flow freely from the collection system to prevent the creation of pressure head within the collection system in excess of that necessary to cause the liquid to flow freely.

(6) The owner or operator would be exempted from the requirements of §B(3), of this regulation, if the Secretary finds, based on a demonstration by the owner or operator, the alternate design and operating practices, together with location characteristics, will prevent the migration of the hazardous constituents (see COMAR 26.13.05.06-1B) into the ground water or surface water at any future time. In deciding whether to grant an exemption, the Secretary will consider:

(a) The nature and quantity of the wastes;

(b) The proposed alternate design and operation;

(c) The hydrogeologic setting of the facility, including the attenuative capacity and thickness of the liners and soils present between the impoundment and ground water or surface water; and

(d) All other factors which would influence the quality and mobility of the leachate produced and the potential for it to migrate to ground water or surface water.

(7) Any facility or facility unit subject to this regulation shall be constructed and installed as designed.

C. General Operating Requirements.

(1) A surface impoundment shall be operated to prevent any overtopping due to wind and wave action, overfilling precipitation, or normal or abnormal operations, malfunction of level controllers, alarms, and other equipment, or human error.

(2) A surface impoundment shall maintain enough freeboard to prevent any overtopping of the dike by overfilling, wave action, malfunctions of level controllers, alarms, and other equipment, human error, or a storm. There shall be at least 60 centimeters (2 feet) of freeboard.

(3) A surface impoundment shall be operated to maintain at least the amount of freeboard specified by the Secretary in the permit.

(4) For a surface impoundment, except for an existing portion of a surface impoundment, a leachate detection, collection, and removal system installed to comply with §D, of this regulation, shall be operated so that leachate flows freely from the collection system and is removed as it accumulates or with sufficient frequency to prevent backwater within the collection system.

(5) Earthen dikes shall be kept free of:

(a) Perennial woody plants with root systems which could displace the earthen materials upon which the structural integrity of the dike is dependent; and

(b) Burrowing mammals which could remove earthen materials upon which the structural integrity of the dike is dependent or create leaks through burrows in the dike.

(6) Run-on shall be diverted away from a surface impoundment.

D. Containment Systems.

(1) Earthen dikes shall have a protective cover, such as grass, shale, or rock, to minimize wind and water erosion and to preserve the structural integrity of the dike.

(2) The owner or operator of a surface impoundment, except for an existing portion of a surface impoundment or a surface impoundment covered by COMAR 26.13.06.19D(1) and (2), shall construct a liner system designed to prevent discharge into the land during the life of the surface impoundment:

(a) With:

(i) A highly impermeable liner system in contact with the waste which will prevent the discharge of the waste or leachate into the liner or liners during the life of the surface impoundment based on the liner or liners' thickness, the saturated permeability of the liner or liners, and the pressure head of waste or leachate to which the liner or liners will be exposed; and

(ii) A leachate detection, collection, and removal system beneath the liner or liners in contact with the waste to detect, contain, collect, and remove any discharge from the liner system in contact with the waste; and

(b) Above the water table, which may be controlled to comply with this requirement, to ensure the detection of any discharge of waste or leachate through the liner system in contact with the waste, prevent the discharge of ground water to the leachate detection, collection, and removal system, and to preserve the structural integrity of the liner or liners.

(3) A highly impermeable liner beneath the drainage layer (for example, the bottom liner) is a necessary part of a leachate detection, collection, and removal system.

(4) The owner or operator of each new surface impoundment, each new surface impoundment unit at an existing facility, each replacement of an existing surface impoundment unit, and each lateral expansion of an existing surface impoundment unit, shall install two or more liners and a leachate collection system between the liners. The liners and leachate collection system shall protect human health and the environment. The requirements of this section shall apply with respect to all waste received after the issuance of the permit. The requirement for the installation of two or more liners in this subsection may be satisfied by the installation of a top liner designed, operated, and constructed of materials to prevent the migration of any constituent into the liner during the period the facility remains in operation, including any post-closure monitoring period, and a lower liner designed, operated, and constructed to prevent the migration of any constituent through the liner during this period. For the purpose of the preceding sentence, a lower liner shall be deemed to satisfy this requirement if it is constructed of at least a 3-foot thick layer of recompacted clay or other natural material with a hydraulic conductivity of no more than 1 x 10(-7th power) centimeter per second.

(5) Section D(4) of this regulation does not apply if the owner or operator demonstrates to the Secretary and the Secretary finds for the surface impoundment, that alternative design and operating practices, together with location characteristics, will prevent the migration of any hazardous constituent into the ground water or surface water at least as effectively as the liners and leachate collection systems.

(6) The double liner requirement set forth in §D(4), of this regulation, may be waived by the Secretary for any monofill, if the monofill contains only hazardous wastes from foundry furnace emission controls or metal casting molding sand, and the wastes do not contain constituents which would render the wastes hazardous for reasons other than the toxicity characteristic in COMAR 26.13.02, and one of the following applies:

(a) All of the following:

(i) The monofill has at least one liner, as defined in §D(7) of this regulation, for which there is no evidence that the liner is leaking;

(ii) The monofill is located more than 1/4 mile from an underground source of drinking water as that term is defined in 40 CFR §144.3;

(iii) The monofill is in compliance with generally applicable ground water monitoring requirements for facilities with permits under COMAR 26.13.07;

(b) The owner or operator demonstrates that the monofill is located, designed, and operated to assure that there will be no migration of any hazardous constituent into ground water or surface water at any future time.

(7) For the purposes of this section, the term "liner" means a liner designed, constructed, installed, and operated to prevent hazardous waste from passing into the liner at any time during the active life of the facility, or a liner designed, constructed, installed, and operated to prevent hazardous waste from migrating beyond the liner to adjacent subsurface soil, ground water, or surface water at any time during active life of the facility.

(8) In the case of any surface impoundment which has been exempted from the requirements of §D(4) of this regulation on the basis of a liner designed, constructed, installed, and operated to prevent hazardous waste from passing beyond the liner, at the closure of the impoundment, the owner or operator shall remove or decontaminate all waste residues, all contaminated liner material, and contaminated soil to the extent practicable. If all contaminated soil is not removed or decontaminated, the owner or operator of the impoundment shall comply with appropriate post-closure requirements, including but not limited to ground water monitoring and corrective action.

(9) A containment system shall have a containment life equal to or greater than the life of the surface impoundment. (See "Landfill and Surface Impoundment Performance Evaluation", EPA, SW/869, September 1980 for methods to evaluate the containment life and effectiveness of a containment system.)

(10) Liner systems shall be:

(a) Constructed of materials which have appropriate chemical properties and strength and of sufficient thickness to prevent failure due to pressure head, physical contact with the waste or leachate to which they are exposed, climatic conditions, and the stress of the installation and daily operations;

(b) Constructed on a foundation capable of providing support to the liner or liners and resistance to the pressure head above the liner or liners to prevent failure of the liner or liners due to settlement, compression, or uplift (see "Lining of Water Impoundment and Disposal Facilities", EPA/870, September 1980 for data and discussion of liner system materials, design, construction, operation, and maintenance);

(c) Installed to cover all surrounding earth likely to be in contact with the waste or leachate.

(11) The sides and bottom of the impoundment shall be constructed of a material which prohibits the discharge of contaminants to ground water unless specifically authorized by a State discharge permit.

E. Waste Analysis and Trial Test. In addition to the waste analyses required by Regulation .02D, whenever a surface impoundment is to be used to chemically treat a hazardous waste which is substantially different from waste previously treated in that impoundment, or chemically treat hazardous waste with a substantially different process than any previously used in that impoundment, the owner or operator shall, before treating the different waste or using the different process:

(1) Conduct waste analyses and trial treatment tests (for example, bench scale or pilot plant scale tests); or

(2) Obtain written documented information on similar treatment of similar waste under similar operation conditions to show that this treatment will comply with Regulation .02H(2) of this chapter.

F. Inspections and Testing.

(1) Liners.

(a) During construction or installation, for purposes of this section, liners (except for existing portions of surface impoundments exempt from liner installation) shall include all cover systems, membranes, sheets, and/or coatings.

(b) During construction or installation, liner systems shall be inspected for uniformity, damage, and imperfections (for example, holes, cracks, thin spots, and foreign materials).

(c) Earth material liner systems shall be tested for compaction density, moisture content, and permeability after placement.

(d) Manufactured liner materials (for example, membranes, sheets, and coatings) shall be inspected to ensure tight seams and joints and the absence of tears or blisters.

(2) The owner or operator shall inspect:

(a) A surface impoundment which contains free liquids at least once each operating day to ensure compliance with §C(1)-(3), of this regulation, and to detect any leaks or other failures of the impoundment.

(b) Each surface impoundment including dikes, berms, and vegetation surrounding the dike, at least once a week and after storms to detect any evidence of or potential for leaks from the impoundment erosion of dikes, and to ensure compliance with §C(4) of this regulation.

(3) The structural integrity of any dike, including that portion of that dike which provides any freeboard, shall be certified against massive failure by a qualified engineer before the issuance or reissuance of a permit, or if the impoundment is not in service before being placed in service and after construction or before being returned to service. In certifying the structural integrity of the dike it shall be established that the dike will withstand the following:

(a) The stress of the pressure head of liquids placed into the impoundment;

(b) The weakening effect of earth materials being scoured due to leakage from the impoundment through and under the dike without relying on any liner system; and

(c) The weakening effect of earth materials being scoured due to leakage from the impoundment through and under the dike assuming leaks develop in the liner system.

(4) The requirements of §F(3) of this regulation, shall be followed, at a minimum, at 6-month intervals after the initial certification.

G. Closure and Post-Closure Care.

(1) At closure, the owner or operator shall:

(a) Remove or decontaminate all waste residues, contaminated containment system components (liner, etc.), contaminated subsoils, and structures and equipment contaminated with waste and leachate, and manage them as hazardous waste unless COMAR 26.13.02.03D applies, or he shall do §G(1)(b)-(e), of this regulation, if all hazardous waste is not removed or decontaminated;

(b) Eliminate free liquids by removing liquid wastes or solidifying the remaining wastes and waste residues;

(c) Stabilize remaining wastes to a bearing capacity sufficient to support final cover;

(d) Cover the surface impoundment with a final cover designed and constructed to at a minimum:

(i) Provide long-term minimization of the migration of liquids through the closed impoundment;

(ii) Function with minimum maintenance;

(iii) Promote drainage and minimize erosion or abrasion of the final cover;

(iv) Accommodate settling and subsidence so that the cover's integrity is maintained; and

(v) Have a permeability less than or equal to the permeability of any bottom liner system or natural subsoils present; and any other requirements established by the Secretary; and

(e) Apply for a permit pursuant to Regulation .14 and COMAR 26.13.07.

(2) If some waste residues or contaminated materials are left in place at final closure, the owner or operator shall comply with all post-closure requirements contained in Regulation .07 including maintenance and monitoring throughout the post-closure care period. The owner or operator shall:

(a) Maintain the integrity and effectiveness of the final cover, including making repairs to the cap as necessary to correct the effects of settling, subsidence, erosion, or other events;

(b) Maintain and monitor the leak detection system, where such a system is present between double liner systems;

(c) Maintain and monitor the ground water monitoring system and comply with all applicable requirements of Regulations .06-.06-7 of this chapter;

(d) Prevent run-on and run-off from eroding or otherwise damaging the final cover.

(3) If an owner or operator plans to close a surface impoundment in accordance with §G(1)(a), of this regulation, and the impoundment does not comply with the liner requirements of §D(2)-(5) of this regulation, then:

(a) The closure plan for the impoundment under Regulation .07C shall include both a plan for complying with §G(1)(a), of this regulation, and a contingency plan for complying with §G(1)(b)-(e), of this regulation, if not all contaminated subsoils can be practicably removed at closure.

(b) The owner or operator shall prepare a contingency post-closure plan under Regulation .07H of this chapter, for complying with §G(2), of this regulation, if not all contaminated subsoils can be practicably removed at closure.

(c) The cost estimates calculated under Regulation .08 for closure and post-closure care of an impoundment subject to this paragraph shall include the cost of complying with the contingent closure plan and the contingent post-closure plan, but are not required to include the cost of expected closure under §G(1)(a) of this regulation.

(4) During the post-closure care period, if liquids leak into a leak detection system the owner or operator shall notify the Secretary of the leak within 24 hours after detecting the leak. The Secretary shall modify the permit to require compliance with the requirements of Regulations .06-.06-7 of this chapter.

H. Containment System Repairs; Contingency Plans.

(1) Whenever there is any indication of a possible failure of the containment system, the system shall be inspected in accordance with the provisions of the containment system evaluation and repair plan required by this section. Indications of possible failure of the containment system include at least an unplanned and non-sudden drop in the liquid level in the impoundment, liquid detected in the leachate detection system, evidence of leakage or the potential for leakage in the dike, erosion of the dike, apparent or potential deterioration of the liner or liners based on observation or test samples of the liner materials, any mishandling of wastes placed in the impoundment, and foreign objects in the impoundment.

(2) Whenever there is a positive indication of failure of the containment system, the impoundment shall be removed from service. Indications of positive failure of the containment system include an unplanned sudden drop in the liquid level in the impoundment, waste detected in the leachate detection system, active leakage through the dike, or a breach (for example, a hole, tear, crack, or separation) in the liner system.

(3) If the surface impoundment must be removed from service as required by §H(2), of this regulation, the owner or operator shall:

(a) Immediately shut off flow of or stop the addition of waters into the impoundment;

(b) Immediately contain any leakage which occurred or is occurring;

(c) Immediately cause the leak to be stopped;

(d) If the leak cannot be stopped by any other means, empty the impoundment;

(e) Take any other necessary steps to stop or prevent catastrophic failure; and

(f) Notify the Secretary of the problems within 24 hours after detecting the problem.

(4) As part of the contingency plan required in Regulation .04, of this chapter, the owner or operator shall specify:

(a) A procedure for complying with the requirements of §H(3) of this regulation;

(b) A containment system evaluation and repair plan describing testing and monitoring techniques, procedures to be followed to evaluate the integrity of the containment system in the event of possible failure, a schedule of actions to be taken in the event of a possible failure, and a description of the repair techniques to be used in the event of leakage due to containment system failure or deterioration which does not require the impoundment to be removed from service.

(5) A surface impoundment that has been removed from service in accordance with the requirements of this section may not be restored to service unless the portion of the impoundment which was failing is repaired and the following steps are taken:

(a) If the impoundment was removed from service as the result of actual or imminent dike failure, the dike's structural integrity shall be recertified in accordance with §F(3) of this regulation;

(b) If the impoundment was removed from service as the result of a sudden drop in the liquid level, then:

(i) For any existing portion of the impoundment, a liner shall be installed in compliance with §D(5), of this regulation;

(ii) For any other portion of the impoundment, the repaired liner system shall be certified by a qualified engineer as meeting the design specifications approved in the permit.

(6) A surface impoundment that has been removed from service in accordance with §H(2), of this regulation, and that is not being repaired shall be closed in accordance with §G of this regulation.

I. Special Requirements for Ignitable or Reactive Waste. Ignitable or reactive waste may not be placed in a surface impoundment, unless the:

(1) Waste is treated, rendered, or mixed before or immediately after placement in the impoundment so that the resulting waste, mixture, or dissolution of material no longer meets the definition of ignitable or reactive wastes under COMAR 26.13.02.11 or .13, and Regulation .02H of this chapter is complied with; or

(2) Surface impoundment is used solely for emergencies.

J. Special Requirements for Incompatible Waste. Incompatible wastes, or incompatible wastes and materials (see Regulation .24 of this chapter, for examples), may not be placed in the same surface impoundment, unless Regulation .02H(2) of this chapter, is complied with.

K. Special Requirements for Hazardous Wastes F020, F021, F022, F023, F026, and F027.

(1) Hazardous Wastes F020, F021, F022, F023, F026, and F027 may not be placed in a surface impoundment unless the owner or operator operates the surface impoundment in accordance with a management plan for these wastes that is approved by the Secretary under the standards set out in this section, and in accordance with all other applicable requirements of this chapter. The factors to be considered are:

(a) The volume, physical, and chemical characteristics of the wastes including their potential to migrate through soil or to volatilize or escape into the atmosphere;

(b) The attenuative properties of underlying and surrounding soils or other materials;

(c) The mobilizing properties of other materials co-disposed with these wastes; and

(d) The effectiveness of additional treatment, design, or monitoring techniques.

(2) The Secretary may determine that additional design, operating, and monitoring requirements are necessary for surface impoundments managing hazardous wastes F020, F021, F022, F023, F026, and F027 in order to reduce the possibility of migration of these wastes to ground water, surface water, or air so as to protect human health and the environment.