For centuries, solid waste disposal was informal and largely consisted of burning and burying trash in small amounts near a home or business. As cities allowed people to live so close together, they simply couldn’t use those methods any longer. Thus, municipal, open dumps became the standard way for disposal. While the first open dumps rapidly shrank on their own, because they were largely food waste, wood, and fabric, modern materials changed the viability of just dumping waste on flat ground. Materials like plastic, glass, rubber, and scrap metal began to make up the majority of the waste stream, resulting in piles that took centuries or millennia to shrink rather than just a few years. This suddenly meant that a more nuanced approached to waste management was needed. What’s known as the sanitary landfill was the outcome of many years of development to build holding cells that didn’t let liquid or vaporous waste escape either. Open dumps are still in use in some parts of the country, but they’re very different from the much more advanced, sealed and capped landfill cells used elsewhere.
Amounts of Regulations and Permits
Open dumps were generally built across the US in the early 1900’s, with little to no regulations controlling their construction. This meant that some were designed to hold water or protect the environment, while others were located in sensitive environments that couldn’t handle the volume of waste. Many open dumps failed in specific ways that helped form the earliest regulations on landfill design and permits. Modern regulations on new landfills keep them from being located too close to existing waterways, delicate ecosystems, and housing developments. Today’s landfills have dozens of individual permits and approvals to secure before construction begins, making them far more work to build than the old, open dumps.
Design Oversight
As with permits and regulations, there was little design advice or oversight available for many decades for landfill design. On-site inspections of failed and successful open dumps helped engineers develop their theories of building better sealed and sanitary landfills. That has resulted in today’s extensive design processes that guide modern landfill cell creation. A new facility will require the attention of multiple engineers and designers, where original open dumps often had little more design and planning other than setting aside an open field of a certain acreage. While the design oversight definitely results in better quality landfills, it also adds to the cost and time frame of the project.
Liners
Liners were not a part of the original, open dumps used prior to the 1970’s for multiple reasons. First, polymer manufacturing was still developing, and large-scale production of flat, impermeable barriers was only possible for the last few decades of that period. Even once geomembranes were invented, they still weren’t widely available or affordable. It was simply impractical to try and line an entire landfill that stretched over 30, 50, or 100 acres. Modern cell design addresses the cost and challenge of lining this scale of land by breaking down the total surface area into small areas. Usually only one or a few cells are excavated and lined at once, spreading the cost of constructing the landfill out over many years.
Excavation and Grading
Open dumps rarely included much excavation, although some facilities took advantage of existing depressions like dry lake beds or sink holes. Placing waste mounds on the surface of the soil, without a liner, created obvious issues with the absorption of leachate into the soil. It also allowed for erosion and runoff since the water leaching out of the waste, and rainfall that soaked through it, had nowhere to accumulate. Modern landfill cells feature both excavation and raised berms around the edges to increase the total capacity for both solid and liquid waste. No matter how much a landfill works to dewater any particular waste stream before it enters the cell, it’s going to produce some amount of liquid as materials like yard trimmings and food waste break down. Excavation is essential to creating enough space for the expected amount of waste, but it can’t replace the use of liners to contain the leachate that is produced.
Secure Capping
Current EPA regulations require all landfill site operators and owners to contain the site properly when it’s no longer in use. This means capping and covering all existing materials so they can’t blow away, fill up with rainwater, or settle unevenly. As of 2020, landfill operators have to maintain and monitor the site for 30 years after closing it. This means using a durable and long-lasting cover material that won’t need replacing every few years just to secure the cell. Soil alone won’t work in anything less than the driest environments. Installing an impermeable cap material, that is similar in composition to the liner used at the base, is essential to truly secure covering that controls both liquids and gases.
Gas Production
Open dumps produce plenty of methane and other potentially hazardous gases, but they can’t be easily trapped for reuse due to the sprawling size of most facilities. Tapping the deposits from these older types of landfills generally results in low quality landfill gas that is only used for flaring on-site and not for heating or power generation. In contrast, properly managed, closed, landfill cells can produce valuable methane for years to come. This can pay for the maintenance of the facility and offset any upfront construction costs.
Leachate Control
Finally, open dumps were known for having extensive leachate issues. Many of the design features of landfill cells, including impermeable liners and multiple layers of leak control, are chosen specifically to address these risks. Even excavation and berm design are essential to controlling liquid waste. Without these features, open dumps tended to badly damage the environment around the facility in ways that required costly remediation. Excavation and relocation of old dump materials continue today, condensing the old waste in new, lined cells that are far safer.
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