3.1 Solid Waste Management

Municipal Solid Waste (MSW), commonly known as trash or garbage, encompasses everyday items discarded by the public. The management of this waste is a critical component of environmental health, directly impacting soil, water, and air quality. The Resource Conservation and Recovery Act (RCRA) Subtitle D provides the federal framework for managing non-hazardous solid waste, setting minimum criteria for municipal solid waste landfills (MSWLFs) to ensure the protection of human health and the environment.

Municipal Solid Waste Characteristics

Municipal Solid Waste consists of organic and inorganic materials generated by residential, commercial, and institutional sources. The composition of MSW significantly dictates the necessary waste management strategies.

Primary Components of MSW

According to the EPA, the largest components of MSW generated include:

1. Paper and Paperboard: Historically the largest fraction, though declining due to digital media and recycling.
2. Food Waste: A rapidly growing segment, presenting significant challenges for methane generation in landfills.
3. Plastics: Highly persistent in the environment and challenging to recycle uniformly.
4. Yard Trimmings: Often diverted to composting facilities to reduce landfill burden.
5. Metals, Glass, and Wood: Represent smaller, yet significant, portions that are highly recyclable.

Understanding the waste stream is crucial for sanitarians to evaluate the effectiveness of local diversion programs and the potential environmental impacts of disposal facilities.

Sanitary Landfills: RCRA Subtitle D Regulations

Sanitary landfills are meticulously engineered facilities designed to isolate waste from the surrounding environment. Under RCRA Subtitle D, MSWLFs must adhere to strict location, design, operation, and closure standards.

Location Restrictions

Landfills cannot be sited in sensitive environmental areas, including:

• Fault areas and seismic impact zones
• Floodplains (must not restrict the base flood flow)
• Wetlands (unless no practical alternative exists)
• Near airports (to prevent bird strike hazards, typically within 10,000 feet of turbojet runways)

Liner Requirements and Leachate Collection

To protect groundwater from contamination, RCRA requires a robust barrier system at the base of the landfill.

• Composite Liner System: The standard requires a two-part liner. The upper component must be a flexible membrane liner (FML), often a high-density polyethylene (HDPE) geomembrane at least 30 mils thick (60 mils for HDPE). The lower component must consist of at least 2 feet of compacted clay with a hydraulic conductivity of no more than 1x10^-7 cm/sec.
• Leachate Collection and Removal System (LCRS): Installed directly above the composite liner, the LCRS collects percolating liquids (leachate) so they can be pumped out and treated. The system must be designed to maintain a leachate head of no more than 30 cm (12 inches) on the liner.

Operational Criteria

Proper daily operation is vital to mitigate immediate environmental and public health hazards.

• Daily Cover: Operators must apply at least 6 inches of earthen material (or approved alternative daily cover) over the disposed waste at the end of each operating day. This crucial practice serves multiple purposes: controlling disease vectors (rats, flies, birds), minimizing odors, preventing blowing litter, and suppressing fires.
• Disease Vector Control: Facilities must implement programs to prevent or control on-site populations of disease vectors.
• Prohibited Wastes: MSWLFs cannot accept regulated quantities of hazardous waste, bulk liquids, or certain medical wastes.

Environmental Monitoring

Landfills generate hazardous byproducts, specifically landfill gas (methane and carbon dioxide) and leachate, requiring continuous monitoring.

• Methane Gas Monitoring: Anaerobic decomposition of organic waste produces methane, a highly combustible gas. RCRA mandates that methane concentrations must not exceed 25% of the Lower Explosive Limit (LEL) within facility structures. At the facility property boundary, methane concentrations must not exceed 100% of the LEL.
• Groundwater Monitoring: A network of monitoring wells must be installed to detect any escape of leachate. This includes background (upgradient) wells and compliance (downgradient) wells. Monitoring is conducted for a specific list of heavy metals and volatile organic compounds (VOCs).

Closure and Post-Closure Care

When a landfill reaches capacity, it must be capped with a final cover system designed to minimize infiltration and erosion.

• Post-Closure Care Period: Following closure, the facility owner/operator must conduct maintenance and environmental monitoring (groundwater and gas) for a mandated period of 30 years. This ensures the long-term integrity of the containment systems and detects any delayed environmental impacts.

Recycling and Source Reduction

The EPA's waste management hierarchy prioritizes source reduction and recycling over treatment and disposal.

• Source Reduction (Waste Prevention): The most preferred strategy, involving designing, manufacturing, purchasing, or using materials in ways that reduce the amount or toxicity of waste created. Examples include lightweighting packaging and reducing food waste.
• Recycling and Composting: The process of collecting, sorting, and processing materials that would otherwise be thrown away and turning them into new products. Composting manages organic waste, converting it into a valuable soil amendment, thereby significantly reducing landfill methane emissions.