Litter Catch Fences

Are you using fences to manage litter at your landfill?   

"If you don't use a variety of fences at your landfill, yet your complaining about litter, you're not dealing with the problem, your chasing symptoms"  (Who Says You Have a Litter Problem, Neil Bolton, MSW Management, July/August 2000)

Relying on one line of defence for managing your litter will help, but it won't solve the blowing litter issues.  You need to look at a variety of fencing options.  This includes, using perimeter fences,  wind-break fences, and portable catch fences.  You may need to erect temporary or semi-permanent lines of fences across your site between your action operations and the perimeter fences to catch litter.  In some circumstances, you may need to use tall baseball netting.  

Fencing systems must be designed to keep litter inside the landfill.   You want to focus on keeping blowing litter to a minimum by using operating practices that include operation of small working faces, apply cover,  and good compaction.   In some wind conditions, you may even need to limit your landfill operations.  

Perimeter Fence

Perimeter fences serve more than one purpose.  They provide site security, can limit animal access, and they are the last line of litter catchment before litter can escape the site. 

Perimeter fencing is most commonly constructed as a chain-link fence mounted on steel post.  Some designs include extension of the fence fabric below the ground surface and addition of electric fencing wire to discourage bear intrusion.    To prevent human intrusion, the fences should be a heavy gauge mesh and mounted on sturdy fence posts.  Some facilities will include barb-wire strands on top (as in the photo above).  Signs should be posted that clearly state 'no entry', and if the fence is electrified. 

To be effective as a litter catchment fence, the mesh wire should not be greater than 2 inches.    A unique design that I've seen installed in a couple of location in Southern Alberta is a sloping perimeter fence.  The fence is slope into the prevailing wind direction on the downwind side of the active landfill.   The concept behind this design is to drive the blowing litter to the bottom of the fence for easier retrieval and to minimize plugging of the fence that can happen with vertical fences. 

With either a vertical fence or sloping fence design, it is essential that the fences be cleaned of any litter that is trapped by the fence for both aesthetic reasons and to maintain the fence.  If litter is allowed to collect on the fence fabric, it may eventually plug the free flow of air through the fence and litter will then blow over the fence, or it may result in the fence being blown over. 

Intermediate Fencing

What I mean by intermediate fencing is fencing that is placed at strategic locations between the active areas of the landfill and the site perimeter fences.  Intermediate fencing may be temporary, semi-permanent, or even permanent when it makes sense to do so. 

The purpose of intermediate fencing may be to establish fence boundaries for different operations on the landfill and to provide added security if needed.  For purpose of this writing, it is fencing that is placed at location through the site to catch blowing litter.  The more of this fencing that is used, there will be less litter collecting along perimeter fences, and by logic, the less litter that will escape the landfill property.  

Intermediate fencing can consist of single rows of fencing or multiple rows.  Of course this will be determined by blowing litter direction, wind conditions experienced at the site, site topography, and budget allowances. 

When permanent fences are used, the fence could consist simply of a wire mesh fence (with no greater than a 2 inch mesh) mounted on angle iron posts, or it could be constructed similar to the chain-link perimeter fencing. 

Using semi-permanent fences allows for the fencing to be easily moved as the landfill expands.  The angle iron post design could be established as a temporary fence and used where it will be in that location for longer periods of time.   Some fence designs marketed by fencing companies are intended to be even more temporary.  Some vendor designs are simple fabric mounted on light weight posts and are anchored with wires.  Others are designed to angle into the wind.  The intent of the design is so that these fences can be easily and quickly moved. 

The baseball netting fences, may also be considered as an intermediate fence.  These fencing systems are usually a permanent installation, so their choice of location needs to be well planned out.  they need to be placed where the litter blows and where they won't interfere with landfill operations and development.   Some netting designs can be installed in a temporary location and be moved as the landfill operations move.  See photo examples below. 

Portable Catch Fences

Portable catch fences are used in close proximity of the active working face.  The are designed to be quickly moved so they can move with the continually moving working face and when the wind direction changes. 

Most designs consist of a heavy frame structure that is mounted on a skid frame.  The fence mesh is typically a heavier gauge 2 inch wire mesh.  The skid frame acts as the base to hold the fence erect.   My view is that the base (or skid frame) needs to be 2/3 the height of the vertical fence frame.   Ideally, at least 2/3 of the base should extend to the downwind site of the fence to reduce the potential for the fence blowing over.   These fence designs are moved by pulling the fence sections with the landfill equipment. 

Portable fencing sections can also be designed to slope into the wind.  This helps contain the litter at the bottom of the fence and reduce plugging of the fence.  

Some other innovative designs use a steel bar section on the vertical section of the fence that is built so the top of a loader bucket can hook under the bar to lift the fence and carry to the desired location

There are numerous manufacturers that market portable fence systems and can be easily found on an Internet search.   Landfill operators often develop their own innovated designs and work with local welding shops. 

What I think is important in portable fence design is:

• use heavy frames to reduce damages that occur with light frames
• use a wire mesh that is no greater than 2 inches
• design the fence with a substantial base to prevent it from blowing over
• design the fence so the ends butt up against each other, or even so they can over lap

Placing portable catch fences

The placement and use of portable litter catchment fences is just as important as their design.  Poorly placed, they can be completely ineffective.  The fences must be placed closed to the source of the litter and downwind.  Some operators will place these fences in a circular pattern around their active working face.  

Neil Bolton suggest using multiple rows of fences.  With a single row, the fence can be plugged and the litter will then blow over the fence.  Some litter may be trapped behind the fence if a sheltered zone is created by the plugged fence, but by placing a second row of fence, secondary trapment exists.  A third row provides an even higher degree of litter trapment.   A good example of this technique being applied is in the photo of the Lethbridge Regional Landfill at the top of this blog entry.

Ultimate Fencing Systems

If one searches around the Internet, you'll come across some fencing systems that entirely enclose the active working face under a mesh tent-like structure.   One example is shown below.  

Litter Controll at Lethbridge Waste & Recycling Centre

This landfill is located in southern Alberta and is in an area that is subjected to frequent windy conditions.  The City has the distinction of being the 2nd most windiest City in Canada.   Because of historical issues with litter problems at the landfill, the City and the site operators have implemented a comprehensive litter management program.  This is a brief summary of that program. 

Prevent Litter From Customer Vehicles

A secure load policy has been implemented and a surcharge is applied for all loads that are not enclosed, covered with a tarp, or firmly secured.  The surcharge rate is $20/load for loads under 1 tonne, or $40/load for loads over 1 tonne.  

Haulers may also be subject to fines for transporting unsecured loads and causing litter along public highways.

Monitoring & Litter Collection

Regular monitoring is conducted and the site operators retrieve litter along roads, ditches, and nearby irrigation canals. Depending on the road, this retrieval occurs daily to weekly. 

Fence lines around the landfill are monitored and litter is retrieved to keep the site clean. 

Litter is collected from private property adjacent to the landfill site and along road ways with access permission from the land owner.  

Illegal Dumping

To prevent illegal dumping, the City offers a large item service to residents, and provides a free Saturday disposal program. The City conducts regular monitoring for illegal dumping and works with enforcement agencies. 

Litter Controls

A combination of techniques are used at the landfill to prevent litter from occurring and to prevent litter from escaping.  

Portable wind screen fences to shelter the working face and catch fences are used downwind to catch any blowing litter.  The working face is kept as small as possible to minimize exposure of waste to wind.  

An 8 meter tall 'primary' entrapment fence is placed at the edge of the landfill operations, and a 12 meter tall 'secondary' entrapment fence is placed downwind (east side) of the landfill. 

The landfill operations are closed when winds exceed limits set out under the Environmental Approval.  Walking floor transfer trailers are prohibited from unloading when wind gust exceed 60 km/hr, and all loads are prohibited when wind gusts exceed 70 km/hr. 

Transfer Station & Baler

To address the issues with collection systems because the landfill is shut down high wind conditions, the City has constructed a transfer station with a baler.  The waste bales are 'wrapped' and when placed at the landfill, they are not a source of blowing litter.  

Other Technologies

The City and the site operators continue to investigate other technologies to add to the existing litter controls.  For example, a trial for application of a spray on mulch alternative daily cover was used.  

Exposed to Wind

How much waste that is exposed to the wind can be directly related to the amount of wind blown litter you will have.  A large working face that is un-sheltered will certainly result in a high amount of wind blown litter.   Keeping an active working face as small as possible, or practical, is an important part of litter control.  In high wind conditions, it may be necessary to reduce the size of the exposed face, even if it means that inbound vehicles need to line up in a cue and await their turn. 

Sheltering the working face by taking advantage of surrounding topography may be effective in some circumstances and not so much in others.  More on this later when we discuss wind patterns and turbulence.   Using artificial wind breaks can provide some reduction in wind speed, and this will be discussed in a later post.   In this photo, this landfill is using a combination of fencing systems to provide shelter and to catch litter.  But most importantly, the working face is kept as small as possible to reduce the amount of waste exposed to the wind. 

Compacted Waste

Litter will be more easily wind blown when it is not compacted than if it is compacted.  Waste collection vehicles with compacted loads will have less litter wind blown as they unload than will the un-compacted loads.  Waste that is compacted on the working face is less likely to become wind blown than waste left in piles and exposed to the wind.    It should be remembered though that by pushing waste in windy conditions may actually add to the wind blown litter problem. 

It is important that the equipment operator understands that when spreading waste piles, the waste should be  pushed along the fill surface and not carried and dropped.  

Soil Cover

Covering the working face with soil will eliminate exposed waste and it cannot be pick up in the wind.    The equipment operator should advance the soil cover over the top bench of the daily cell to minimize exposure during the day.  Soil cover or an alternative cover is normally placed over the face at the end of a day's operation.  In some high wind conditions, the operator may need to apply a 'sprinkling' of soil cover over the working face during the day's operation to help control blowing litter. 

Blowing in the Wind

It is quite intuitive to think that things that are lighter will be more prone to be wind blown than heavier objects.  Items less likely to be blown about if they are heavy, such as a large metal object, or that have a high moisture content like food waste, or  that have been compacted as in a compactor truck. 

We also have to think about surface area as well.  For example, a flat sheet of paper has a great surface area that easily becomes wind blown, yet if it is crumpled into a ball, it has a lower surface area and is less easily wind blown.   We are all aware of the problem with plastic bags being blown about.  Plastic bags are not only light and have a large surface area, but wind will blow into an open bag and carry them aloft.  

Studies carried out in the late 70's for the Crowsnest Pincher Creek Regional Landfill showed how far a variety of objects could be blown at different wind speeds.  The study was based on an object dropping about 1.5 M (as it would from an unloading collection vehicle), and that it would be blown away from the working face of the landfill.  

Wind Speed                    Objects

10 - 25 km/hr                    Envelopes, dry paper

25 - 30 km/hr                    Empty plastic bags

30 - 50 km/hr                    Corrugated cardboard sheets, crumpled paper towels

50 - 60 km/hr                    Plastic strips, empty tissue boxes, tightly crumpled paper

60 - 90 km/hr                    Milk cartons, cardboard boxes

over 90 km/hr                   Metal cans

The energy in the wind is cubically proportional to the wind speedThe strength of the wind should never be under estimated.  (E = v3).  If wind speed is doubled, the energy increases by 8 times (2 x 2 x 2 = 8).  Never under estimate the power in the wind.  In strong winds, large objects, as shown here, can be blown out of the active landfill working face.   

Example Landfill with Litter Issues

This landfill is located on the Canadian Prairies in an area that is un-sheltered and is exposed to windy conditions that are typical of the southern portion of the Canadian Prairie Provinces.   

At this point in time, the operators maintained a large open working face that was about 25 to 30 feet high.  Waste was unloaded from self-haul customers at the bottom (toe) of the working face, and commercial customers unloaded at the top.   

Vehicles unloading at the bottom of the face were somewhat sheltered and litter catchment fences were around the tipping area, but were not well positioned for best protection.

The commercial vehicles unloading at the top were exposed to high winds and there was no litter control fencing provided for shelter or litter catchment. 

To add to the litter issues, effective bylaw and bylaw enforcement was lacking.  Loads on inbound vehicles were often unsecured.  This led to litter along roads leading to the site and contributed litter issues at the landfill. 

The operators were provided with well designed portable litter catchment fences.  The fences were not effectively used around the working face.  Fences were placed around the lower tipping area, but they were not well positioned to closed the gaps between fence sections.    These fences were not effective in catching blowing litter off the working face, simply because of the height of the working face.   The tipping area at the top of the face, which was the most exposed to the wind,  had no litter fencing available.  

THE RESULTS

Recommendations

The recommendations for litter management at this site included:

-  minimize and control the size of the working face

-  increase the amount of portable litter catch fences

-  place portable fences where they will be effective and close gaps

-  add portable wind-break fences to shelter exposed tipping areas

-  establish effective controls for un-secured loads

-  implement a litter retrieval program

Looking After Stuff

I've spent most of my life looking after the stuff that most of you toss out and never pay much attention to where it goes or what happens to it. I've been fortunate to work with people who try new things and share their knowledge about what works and doesn't work. One of the things I have spent time learning about is litter control and waste management facilities, or more specifically, at landfills. Much of what I have learned is from the landfill operators who have been frustrated by this never ending challenge, but who have been inovative in their ways of controling this perpetual problem.

Litter control at landfills takes an effort to understand wind patterns and know where and how to operate and use these patterns to advantage. It takes knowledge on how to handle waste in windy conditions and knowledge of fencing systems to trap litter and sheltering methods to prevent litter from blowing.

Over a period of time, I hope to share what I have learned, and I hope that you will, in return, share your experiences and knowledge.