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.