2007 Solid Waste Management Plan

3. Assessment of Municipal Solid Waste Management Systems

Appendix 3 contains a map and corresponding one-page solid waste profile for each county in Nevada. Each map provides a "snapshot" of the existing solid waste infrastructure. Each profile provides the following information:

The solid waste trends presented in the solid waste profiles are as follows:

4. Solid Waste Management Issues and Future Considerations

The disposal and recycling regulations that have been adopted and implemented in Nevada, since 1991, have significantly changed the way solid waste is managed in Nevada. In reviewing the current status of Nevada's solid waste management systems some "old problems" persist while some new issues have been identified. As Nevada's solid waste authority, we have to ask; do our solid waste management systems comply with applicable Federal and State standards, protect public health and the environment, enhance the beauty of the landscape and conserve natural resources? Are Nevada's solid waste laws and regulations adequate to achieve the goals for which they were adopted? This section of the Plan describes some issues that deserve attention and suggests strategies for addressing them. The issues are grouped under the general headings of: Landfills, Recycling and Waste Prevention, Importation of Solid Waste, Special Waste Management, Rural Solid Waste Management, Open Dumping and Open Burning, and State and Local Funding.

4.1 Landfills
Since the Federal Subtitle D of the Resource Conservation and Recovery Act (RCRA) criteria were established in 1991, landfill researchers and operators have pointed to problems with the criteria and suggested potential alternatives to address them. Liner requirements and alternative cover criteria have come to question in arid environments. In Nevada, recent proposals to develop large commercial facilities have raised concern about the current requirements for containment of landfill leachate and gas.

4.1.1 Liner Requirements
All municipal waste landfills in Nevada are required to conform to Federal standards adopted under RCRA Subtitle D. The Federal regulations and the approved State regulations require a composite liner of clay and plastic membrane for all new or expanding landfills that receive an average of more than 20 tons per day of waste (Class I facility). However, landfill owner/operators may apply to the Solid Waste Management Authority to approve an alternative design if a landfill owner/operator can demonstrate that the landfill design is sufficient to protect the waters of the State from degradation by pollutants or contaminants. This Plan recognizes that site-specific conditions should be considered and taken into account in further development of our disposal infrastructure, and that, with attention to detail and careful oversight of proposed designs, approved landfill designs can be protective of the environment.

4.1.2 Bioreactor Landfills
The standard approach to landfill design in Nevada is commonly known as the "dry tomb," achieved by the minimization of leachate generation by the exclusion of liquids from the buried waste. Some researchers have criticized the "dry tomb" design, contending that it delays decomposition of waste such that the waste will always present a threat to groundwater. An alternative technology, the "bioreactor" landfill, is gaining more attention among regulators and the waste industry to address this concern. A bioreactor landfill employs leachate recirculation and the controlled addition of liquids to promote waste decomposition. Bioreactor landfills are currently operating in other states, but it remains to be seen whether bioreactor designs will be safe and economical landfill alternatives for Nevada, where climatic and hydrogeologic conditions appear to favor the indefinite containment of solid waste in a "dry tomb."

In March 2004 the USEPA revised its municipal landfill criteria to allow states to issue Research, Development and Demonstration (RD&D) permits that allow variances from the standard landfill operation criteria, design criteria and final cover requirements in the closure and post-closure care criteria. The Federal RD&D rule requires that any permit issued under the rule must, "include terms and conditions at least as protective" as the standard municipal landfill design. One requirement of a permit with this flexibility is the requirement to collect data and report on the performance of the designs. These permits would be issued for 3 years extendable up to a maximum of 12 years. Data gathered under the RD&D rule will help regulators and landfill owners evaluate the performance of these designs under different climatic conditions. With the RD&D flexibility a variety of innovative landfill designs is possible. In order to have the flexibility to try new technologies, such as the "bioreactor" landfill, Nevada would have to amend the solid waste regulations by adopting the RD&D rule.

4.1.3 Postclosure Care Period
Landfill owners are required to provide postclosure care for a 30-year period following the site's final closure in order to maintain the final cover, monitor and manage explosive gas and if applicable, monitor groundwater, and maintain and operate the leachate collection system. Recent advocates for revision of the postclosure care criteria have noted that the 30-year time period is arbitrary and have suggested that the standard should be based on risk - that postclosure care should continue until the waste no longer poses a threat to groundwater. In addition to leachate management concerns, the long-term integrity of the final cover is a concern for all Nevada landfills because natural forces may eventually impair every final cover, thus compromising the integrity of the waste containment system.

While thirty years is the standard postclosure period under Nevada regulations, the solid waste authority may alter the time frame. A shorter period may be approved if the owner demonstrates that it is sufficient to protect the environment; a longer period may be required if the authority determines that this is necessary to protect the environment. Lacking an agreed-upon method for making such a demonstration, a 30-year period has been accepted as default in Nevada, as in most states. As a result, planning and cost estimates for postclosure care are developed on the assumption that it will last thirty years. In order to interject the flexibility in the regulation, a methodology needs to be developed to evaluate landfill performance and environmental risk during the postclosure period. Such a methodology would provide regulatory agencies with criteria for approving demonstrations, as well as an incentive for landfill owners to design, operate and close landfills in a manner that would reduce the time during which they pose a threat of contaminant release. The Environmental Research and Education Foundation (EREF) has initiated the development of such a methodology and published its progress in the document A Performance-Based Approach to Ending Post-Closure Care at Municipal Solid Waste Landfills available at http://www.erefdn.org

4.1.4 Final Cover Design
The current prescriptive standard for a municipal solid waste landfill cover consists of an 18-inch thick layer of compacted clay topped by a 6-inch layer of soil capable of supporting vegetation. The clay layer provides the barrier to impede moisture percolation into the waste mass. In the last few years, researchers have asserted that the wetting-drying cycles resulting from direct exposure to the atmosphere cause cracks to develop in the clay. New data suggest that such covers may quickly fail within only a few of these wetting-drying cycles.

While the literature contains several alternative final cover (AFC) design concepts, the evapo-transpiration cover (ET cover) is showing the most promise for Nevada's arid climate. Such covers can be designed to exceed the percolation reduction performance of conventional covers and also offer other advantages, such as ease of construction and increased long-term cover integrity. While Nevada regulations allow Solid Waste Management Authorities to approve AFC designs that achieve an equivalent reduction in percolation as the prescriptive cover design, few permit applications have incorporated them to date. The absence of AFC design work in Nevada may be due to the lack of familiarity with AFCs, the lack of a standardized approach to demonstrations of equivalency, and applicants' fears of the inevitable delay involved with a regulatory review of an innovative design.

As noted previously in Section 4.1.2 above, US EPA recently amended the Federal landfill standards to allow states to issue RD&D permits that authorize variations from certain of the criteria, including the final cover design. While the RD&D rule would require that any alternative cover be at least as protective as the prescriptive design, the owner/operator of the landfill must demonstrate that no moisture will escape from the landfill to the surrounding surface and groundwater.

4.1.5 Landfill Gas
Since the Federal municipal waste landfill criteria were adopted in 1991, landfill design and operation has become increasingly important for the proper management of landfill gas. The landfill gas regulations were written primarily to prevent explosion hazards due to the generation and migration of methane. It was a commonly held belief that arid landfills do not generate significant quantities of landfill gas, and that this issue was of little importance in Nevada. However, the Apex in southern Nevada collects and continually flares gas that is generated at the facility.

Due to changes in Federal clean air regulations and information accumulated from landfill research and operational data, landfill gas issues are beginning to be seen in a different light. Three points deserve mention:

4.1.6 Items for future consideration, Sec. 4.1 - Landfills

1. In reviewing any request for a new or expanded landfill that proposes to use an alternative liner design, the Solid Waste Management Authorities (SWMA's) should conduct a comprehensive detailed engineering evaluation to ensure that the application conclusively demonstrates that the proposed design is sufficient to protect the waters of the State from contamination.

2. The SWMA's could consider seeking amendment of the Nevada Administrative Code to allow solid waste management authorities to issue RD&D permits for bioreactor landfills and alternative final covers in conformance with federal requirements contained in CFR 40 §258.4 (Appendix 9).

3. The SWMA's should monitor the development of tools, methods and criteria (EREF and others) that can be used to establish the end of postclosure care based on landfill performance (e.g., whether the landfill has ceased to pose a threat to human health and the environment).

4. The SWMA's should continue to monitor and evaluate landfill gas detection and collection data at Nevada's municipal waste landfills and investigate the conditions of landfill gas generation.



¹ Murray, R., Samorano, D., Masbruch, K., and Petersen, N. 1991. An Empirical Model for Vapor Transport in Arid Landfills. Seminar Presentation, 1991.

Home Page – Waste Management
Site Index -- Topic Index
NDEP Home Page