Sanitary Landfill Design for Civil Engineers

Sanitary Landfill Design for Civil Engineers

Civil engineers design landfills to serve as safe and sanitary sites to store and manage waste. [1] The sites protect modern communities from toxic gases and chemicals that synthesize when waste degrades. Local and state officials plan, regulate and manage nonhazardous consumer and industrial solid waste using Resource Conservation and Recovery Act (RCRA) Subtitle D, while hazardous materials fall under RCRA Subtitle C or the Toxic Substance Control Act (TSCA). As the topic of sustainability moves toward the forefront of the waste management field, legislators are transiting from asking if recycling is feasible to educating officials on how to operate financially successful sustainable waste management operations.

Regulations for Sanitary Landfills

Roughly 2,000 Municipal landfills operate in the United States, typically under federal regulation. Some states might enforce regulations that surpass federal requirements. [2] Any non-state regulated municipality must follow minimum federal regulations. Municipal solid waste landfills (MSWLFs) only accept common consumer debris. However, households also produce hazardous materials. As a result, municipalities commonly establish separate disposal sites for:

  • Paint
  • Cleaning compounds
  • Motor oil
  • Batteries
  • Insecticides

Some municipalities also accept nonhazardous industrial materials, such as nontoxic sludge, limited generator waste and harmless industrial solid waste.

Industrial landfills only accept commercial solid debris deemed unsafe for municipal landfills. Each state enforces federal RCRA Subtitle D regulations for municipalities handling nonhazardous industrial waste products.

Some industrial landfill operators reduce expenses, environmental impact and space consumption by recycling and repurposing waste materials. The Environmental Protection Agency (EPA) enforces additional rules for asbestos and lead waste disposal at these sites. Industrial landfills accept construction and demolition materials, such as:

  • Concrete
  • Doors
  • Drywall
  • Glass
  • Metal
  • Windows
  • Wood

RCRA Subtitle C landfills treat, store and dispose of only toxic materials and hold them until they no longer pose a threat to public safety. Sometimes referred to as treatment, storage and disposal facilities (TSDFs), the enterprises incinerate or oxidize some hazardous materials, rendering them inert. RCRA laws dictate practices for hazardous material creation, use, transport and disposal. While some processes reduce chemical activity, others reconstitute waste for reuse. Prior to treatment, landfill operators store hazardous materials using RCRA compliant structures, such as:

  • Containers
  • Containment structures
  • Drip pads
  • Geographic depressions
  • Tanks

The federal government outlines regulations for hazardous materials storage under Title 40 of the Code of Federal Regulations (CFR). Landfill operators treat hazardous materials and then contain them in specially prepared depressions or long-term containment units.

Common Sanitary Landfill Practices

It is mandatory that a civil engineer research a potential site and then design a construction and operation plan based on local geological characteristics before an operator can safely build a landfill. [4] Civil engineers also design the plans to gather, deliver and manage waste.

Landfills in developed nations establish a precedent for global waste disposal practices. [3] These landfills incorporate attractive landscaping, while producing little noise or fumes, but not all economies can afford these amenities. However, landfill sanitation has little to do with aesthetics or olfactory comfort. In fact, basic landfill sanitation costs relatively little and presents less risk of failure compared to complex operations. Sanitary landfills generally meet four criteria:

    1. Hydrogeological isolation
    2. Environmental engineering
    3. Managed operations
    4. Land use management

For each landfill location, civil engineers create a site plan that meets these criteria or will eventually bring the sites into compliance.

Civil engineers practice hydrogeological isolation to keep toxic runoff (called leachate) from draining into nearby water supplies. Leachate represents the largest safety concern among landfill operators. As the facility continues operations, precipitation soaks into debris and washes, or leeches, harmful chemicals out of the waste. Organic and artificial substances combine to create this harmful waste byproduct. The closer waste rests near the surface or underground water networks, the higher the risk of contamination. When possible, site designers choose locations with natural hydrogeological isolation features, such as:

  • Bedrock
  • Geological formations
  • Ground water networks
  • Naturally occurring chemicals

If the engineers cannot locate one or more of these features, they will design artificially lined waste depressions or divert leachate into a natural or artificial treatment system.

Common Landfill Practices

Civil engineers monitor landfill operation and revise plans over time, as circumstances change of the course of many years. [5] A safe and sanitary landfill requires a sufficient number of trained staff members. Municipalities determine staffing requirements based on the engineer’s recommendation.

Most municipalities operate area landfills, where facilities deposit waste in impressions or pile debris into mounds. In a trench landfill, operators move land, deposit waste and then cover the debris with nearby earth. Municipalities operate naturally or artificially created ramp landfills by pushing waste over a ledge, then covering the debris with earth moved from the ramp or bank face.

Landfill workers compact waste and spread it in layers, versus simply dumping the debris randomly. By filling small sections as outlined in landfill regulations, the workers reduce insects and animals incursions.

Before depositing debris, the workers clear away stagnant water and natural vegetation, typically piling waste up to six feet high and maintaining a slope not exceeding 18–degrees to ensure compaction efficiency.

Landfill workers commonly compact debris by face-tipping, or tipping out debris then smoothing it down into a face rising no more than two feet high, or onion skinning, which mimics face tipping except with a flatter gradient. Workers prefer face-tipping, because it is simpler. However, onion skinning results in less debris drift and allows for a higher rise. When appropriate, some facilities combine the two methods.

Cultivating Funding Sources for Sustainable Initiatives

The Environmental Financial Advisory Board (EFAB) operates under the Federal Advisory Committee Act to advise the EPA on financing projects that reduce waste and protect the United States water supply. [6] The EFAB pursues five primary objectives:

    1.Chemical safety and pollution prevention
    2.Clean communities and sustainable development
    3.Climate change and air quality management
    4.Societal and environmental protection via regulation and enforcement
    5.Water protection

The group promotes reduced financing costs for projects that reduce pollution and protect the environment. Through regulatory initiatives, the EFAB encourages private sector investment in environmentally friendly projects. The organization seeks out new, cost-effective environmental financing solutions, while endorsing the best current funding alternatives available for green projects. The group believes that joint private and public sector investment in sustainable environmental projects will increase the resources available for green initiatives.

The EPA and the EFAB jointly publish the “Strategic Action Agenda,” which outlines past and present environmental projects. The collaborative notes that while the projects generate interest they lack long-term financial vision. To remedy this situation, the group recommends instruments, such as:

  • Annuities
  • Bonds
  • Escrow accounts
  • Funded Trusts
  • Utility structures

The collaborative categorizes small United States water systems as particularly vulnerable and recommends that small municipalities improve their financial analysis, funding procurement and management capabilities.

In the future, civil engineers must improve coordination with enterprises that promote sustainability, such as the EPA, the United States Department of Agriculture (USDA) and the National Rural Water Association (NRWA). This collaboration may indeed hold the key to protecting America’s water supply, as a new breed of civil engineers incorporates recycling and repurposing into waste management planning.

Learn More

Civil engineers play a crucial role in engineering the structural solutions of tomorrow and plan, design, construct, and operate the infrastructure essential to our modern lives. As a student in the online Master of Science in Civil Engineering program, you can enhance your quantitative decision-making skills and learn how to justify managerial decisions with data. You will also explore the capabilities of modern management technologies and discover how to successfully leverage these tools to maximize efficiencies in your projects and on your teams.

Sources:

[1] http://web.mit.edu/urbanupgrading/urbanenvironment/sectors/solid-waste-landfills.html
[2] https://www.epa.gov/landfills/basic-information-about-landfills
[3] http://documents.worldbank.org/curated/en/685291468739570943/pdf/multi0page.pdf
[4] http://www.eawag.ch/fileadmin/Domain1/Abteilungen/sandec/E-Learning/Moocs/Solid_Waste/W1/Decision_Makers_Guide_Solid_Waste_Landfills.pdf
[5] http://www.bvsde.paho.org/bvsair/e/repindex/repi49-50/lesson8/lesson8.html
[6] https://www.epa.gov/envirofinance
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