Techniques for managing landfill litter
Litter isn"t just an issue for urban waste management. Landfill sites also have to ensure that litter is kept under control - and this requires careful management at all stages of the process.
Litter is an issue faced by almost every municipal solid waste landfill, regardless of its size or location. Essentially, there are three main ways in which landfill operators can minimize litter: prevention, control and collection. Prevention techniques, such as load management, compaction, soil covers and other suppression systems, are used to minimize the amount of litter generated. Litter control then involves various different types of fencing, and is used to stop "blowing litter" getting off the site. Finally, litter collection methods, including manual picking and mechanical collection devices, are used when there is any litter that has not been prevented or controlled.
Landfill litter has been defined as any waste which is blown or washed away from the active face of the landfill. 1 In practical terms, this includes any uncovered or undisposed waste at a landfill, whether it came from the active face or not.
Although many state regulations do not specifically define landfill litter, US Federal Landfill Regulations (40 CFR 258) address litter control through a requirement for cover material to be placed at the end of each operating day, or at more frequent intervals if necessary. This is to ensure that blowing litter is minimized, in addition to controlling disease vectors, fires, odours and scavenging. Many state regulations go further than this, and require landfills to develop a litter control plan; this can entail patrolling the facility daily, refusing litter from uncovered vehicles or vehicles without tarpaulins, and implementing steps to minimize blowing litter (e.g. screens).
Other countries, such as England and Wales, also require measures to be taken so that any nuisance caused by wind-blown materials is minimized, though these regulations leave site-specific planning to the operators of the landfill itself. Australian guidelines, being somewhat more comprehensive than those of other countries, do provide recommendations on how to approach litter control, as well as some technologies for consideration.
Of course, it is not only legislation that influences landfill control. Other reasons for proper litter management include keeping the site aesthetically pleasing, minimizing additional disease vectors, and preventing potential blockage of drainage (such as smaller culverts).
Litter prevention techniques
The most effective approach to litter management is prevention. Preventative techniques commonly used at landfills include:
alternative suppression materials.
Staff at the active face of a landfill (which includes load spotters and landfill operators) must make sensible decisions about how to minimize blowing litter, a process referred to as "load management". Staff should evaluate waste loads based on how likely these are to generate litter. For instance, loads with large quantities of loose paper and plastic should be directed to areas protected from the wind, perhaps between two larger loads or at the base of a slope.
Having soil readily available to cover potentially high piles of waste is another load management method, while minimizing the size of a landfill"s active face will greatly influence the amount of wind-blown litter. A water truck can also be used to spray loads as they are being dumped and spread, to minimize litter during heavy winds. On excessively windy days, operations should be adapted as necessary. This might mean moving the active face, limiting waste tipping, and possibly even halting operations temporarily.
For example, at the City of Salina, Kansas Municipal Solid Waste Landfill in the US, winds can often exceed 40 miles/hour (64 km/hour). Consequently, operators used to struggle with controlling blowing litter. One of the measures they took to combat wind-blown litter was to enact a set of guidelines for load management based on wind speeds. Now, at winds greater than 20 miles/hour (32 km/hour), portable fences are moved closer to the active face. At winds greater than 35 miles/hour (56 km/hour), staff make extra efforts to ensure that litter control fences do not become clogged, as this could result in fencing being bent over or becoming permanently damaged. When winds are over 45 miles/hour (72 km/hour), loads are often covered with soil immediately rather than being spread and compacted, as this can be done once wind speeds have decreased. Other landfills commonly close their gates at higher wind speeds, typically at 35-45 miles/hour, although Salina chooses not to.
When loads are being dumped at the active face, waste piles present a greater risk of blowing litter than "pushed" piles. Loads should be pushed and compacted as soon as possible, as this will effectively anchor loose materials from the load.
Soil cover is the time-proven standard for preventing blowing litter, and as such requires little discussion. However, when this approach is used constantly, its cost-effectiveness is questionable, as it reduces available disposal capacity. Excessive use of soil cover throughout the day, above and beyond a single layer of daily cover, may also impact the soil balance at a "dirt poor" site. In other words, overuse could mean that a landfill with just enough soil on-site to meet operational and closure requirements might eventually have to purchase more.
If soil cover is used for litter prevention during the day, it is best to partially close areas of the landfill, thus decreasing the size of the active face; removing previously placed cover soils before additional waste is dumped is also an option.
Alternative suppression materials
Alternative suppression can involve spray-applied substances, or other materials based on waste or processed waste. Numerous manufacturers have developed products from various combinations of foam, post-consumer paper, wood and proprietary adhesive chemicals. These materials are typically very successful in meeting litter control requirements, and they also minimize airspace consumption when used as an alternative daily cover. However, they do add to operational costs, and this must be considered prior to purchasing necessary equipment and supplies.
Other alternative cover materials available include processed construction and demolition material, shredded tyres and chipped wood. All of these have a proven record of controlling blowing litter. While it would be impractical to try to identify all of the various materials that can be used for landfill cover, some form of suitable material is always needed to cover deposited waste.
Litter control techniques
No matter how well a landfill implements the litter prevention techniques listed above, there is always going to be blown litter outside the active face. This litter needs to be contained for quick recovery and prevented from leaving the site (or going any further than necessary, for that matter). To control blowing litter, landfill operators typically use the following methods:
The key to a successful litter control plan is the use of multiple rows of fencing and/or netting, so that any litter not intercepted by the first line of fencing is stopped by a second or third line. Regardless of the configuration and fencing or netting materials used, even the best fences need to be cleaned to prevent accumulation of litter. Otherwise, they will act like a wall, and wind could blow litter up and over the top.1
The first line of litter control should usually involve portable fencing. While designs and costs for this vary greatly, according to manufacturers and operators" preferences, portable fencing should be constructed in an appropriately sturdy fashion. Fences are usually around 20 feet tall (6 metres), and are heavily ballasted. By its nature, portable fencing is frequently moved to prevent litter at the active face of the landfill.
The useful life of portable fencing is extended significantly when it is properly reinforced and constructed with hook rings and push plates. Rings allow chains to be properly attached when the fence is being pulled, and plates mean that the fence can be pushed by landfill equipment while minimizing wear and tear. Some manufacturers have also designed portable fencing that can be lifted and moved using typical landfill equipment, such as bulldozers, without the need for operators to get out of their cab.
Temporary and permanent fencing
Temporary fencing is typically used as the next line of defence, followed by more permanent fencing. In contrast to portable fencing, both temporary and permanent forms use conventional types of fencing, and are in place for a longer period of time. Temporary fencing usually lasts about a year, and permanent fencing longer.
All forms of conventional fencing have been used for landfill litter fences, including chain link, chicken wire, wooden snow fence, plastic construction fence and golf fencing; but whichever type is used, it is typically supported by wood or steel posts. How often the fence is to be relocated as the active area moves, and how close the fence will be to the active area, are both factors that should be considered when choosing fence material. For instance, frequent relocation of fencing, and close proximity to an active face in heavy use, will clearly require a more durable product.
Temporary fencing, although attached to posts driven in the ground, often has a useful life as short as a year due to relocation of the active face. Permanent fencing, meanwhile, is generally constructed of more durable chain link materials and is often located at the site boundary, or at least sufficiently distant from the active operations that it does not have to be moved for a much longer period of time.
Although litter nets can be more expensive than average height chain-link fence, they can provide greater litter control efficiency, and are also extremely cost-effective (when bearing possible future labour costs in mind). Due to the cost, netting is typically deployed at the perimeter of the landfill or property as a permanent measure. Nets are highly recommended when the landfill is immediately adjacent to the property boundary or to trees or waterways; if litter gets into such environments, removal is a costly process.
Perimeter netting is typically mounted on wooden or steel poles, and extends 20-40 feet (6-12 metres) above ground. Poles should generally be mounted so that they are raked to the inside (i.e. towards the landfill), so that captured litter can drop when winds are slower.
Netting materials vary, although a more durable net is generally recommended due to the wide range of materials in contact with it and the heavy wear along the base during litter collection.
Litter collection techniques
Where litter remains, however, there is really no choice but to pick it up. Regardless of the approach chosen, this is typically the most arduous, time-consuming, and often the most expensive litter management method. Litter collection usually requires manual labour, although some landfills and manufacturers have developed mechanical vacuum devices, so that litter can be recovered in a less physically intensive manner.
Manual removal of litter is currently the most common method of litter collection. Labourers walk along the fence lines and remove the litter that has accumulated there.
Litter removal should be performed as required at each area of the site to prevent significant accumulation, as this renders fencing ineffective. A fair estimate of litter removal frequency is:
close to working face - remove daily, or as needed
perimeter - remove at least weekly, or as needed
off-site - remove after periods of high winds, or as needed.
If managed appropriately, litter removal can be performed by landfill staff, although periods of high winds typically require temporary workers to be contracted. Some landfills utilize prison inmates, or those on work release or community service, for low- or no-cost assistance with litter collection, as well as community groups.
Mechanical vacuum devices
Equipment such as litter vacuum devices can often increase collection efficiency. Manufacturers have responded to the needs of landfill operators, and numerous mechanical, pneumatic and blower-operated systems are available.
The Salina Landfill designed its own mechanical litter collection system. Having looked at other manufactured systems, the landfill operators were conscious of the critical design needs for their site; they needed something with a large diameter opening for larger pieces of litter, a large bin for holding more litter between dumping, and an open holding bin for spraying the litter with water before dumping it, to prevent it from being blown away when the device was emptied. The device they designed (seen in the photograph above), cost only US$15,000 to construct, $12,000 of which was for the compressor. With little maintenance, it has served the operators" needs for over seven years.
Landfill litter considerations
A landfill litter management plan needs to utilize a three-prong approach, comprising litter prevention, control and collection. Preventing litter from the active face reduces the need for later collection, and any litter that does escape should be contained within multiple layers of control, rather than a single row of fencing. Collection also needs to be carried out frequently, especially during periods of high winds, as this will prevent damage to fencing and other control measures. But, most importantly, the plan should be kept simple, as it will be used every day of the landfill"s active life.
Christopher M. Martel, P.E., works for Camp Dresser & McKee, Inc., Chicago, Illinois, US.
Robert J. Helm is at the Department of Public Works, City of Salina, Kansas, US.
1. Bolton, Neal. The Handbook of Landfill Operations. Blue Ridge Services, Inc. Atascadero, California, US. 1995. pp. 228-232.\\n\n