At the end of the day, ensure that your whole team understands the areas that add or decrease productive distances that can hurt efficiencies, stressing and managing proper layer heights for your waste and machine size, as well as keep them communicating. Don’t settle for anything less.
Waste industry applications are some of the harshest for operators and the equipment they run. For the past 20 years, we’ve been working closely with our customers to understand those applications and help them meet their goals while lowering costs. During site visits and evaluations, we are often asked: “What are some best practices that you have seen and trained?” The following best practices are a high level start on improving your operations while lowering overall costs.
All waste applications are inherently harsh environments. Safety programs that are not just lip service or “check the box” provide a growing ‘safety culture’ that does not end when the employee goes home for the day. Programs should create and sustain a culture of safety excellence. A good safety program should measure and manage the right safety activities, recognize workers for what they do right and ensure that all levels of the organization are involved/engaged in the safety system. As a top Caterpillar safety leader once said: “There should be visible commitment from top leadership; there should be a strong accountability system and there should be total engagement of those closest to the safety concerns or hazards.”
Plan for safety, production and efficiency. Keep working distances short enough to have good production while not jeopardizing safety and ability to layer and compact the waste. As an example: adding 25 feet of push distance to a D8T due to not cleaning the floor correctly, which keeps inbound from backing up to the working face … will decrease production approximately 16 percent. Customers tell us that increased distance due to inefficient work face operations affect safety, density, fuel, and wear on machines and overall maintenance.
Nothing robs airspace and density any quicker than improper layer height. Compaction density is affected by many variables. A large majority of landfills are primarily MSW. Add enough of MSW in to a layer and no matter whose compactor or what size compactor is used, density will diminish rapidly. In basic definition, landfill density is achieved by the ability of the compactor to compress and shred material. There will be arguments about moisture, tips, wheel width, etc., but these are the basics.
What we have found during past “Best Practice” testing is, that no matter what size compactor, more than a 2-foot layer of MSW, the top of the layer will compact but below a certain compression and shredding level, the rest will stay untouched and will act like a sponge or shock absorber. During the testing, we found that the difference between a 1-foot layer of MSW with four passes and a 4-foot layer of MSW with four passes could be as much as 1000 lbs./yd3 density loss. (Again, it depends on many variables but this was the average). Fuel consumption on the machines increased between 10 to 15 percent depending on the thickness of the layer of waste as it got deeper. When we train Best Practices, we always tell our attendees that ‘thin layers’ are best. One last addition, once a layer is added to a compacted area, that layer needs to be compacted prior to adding anymore waste. This seems simple and actually redundant, however, approximately 90 percent of the landfills we have performed site/machine assessments on in the past few years, have a tendency during peak times, to not only thick layer, but double layer just to get the tip floor cleared. For example, the dozer layers an area properly, a peak time starts, the compactor is running passes, but the dozer trying to keep up with inflow moves and layers more waste on top of an area that had been previously been layered before the compactor reaches that area. The waste layer now could be 4-foot deep or more. Communication between machines (compactors/dozers, etc.) is paramount when trying to achieve good compaction densities.
According to Caterpillar, SWANA and other reliable waste sources, consensus is that the minimum amount of passes for best density is three to five. What we see is normally one to two passes maximum. More to the point, when we ask the compactor operator how many passes they have on the waste, they tell us “about four,” when they really only have one to two. The discrepancy is due to not running a proper pattern. A pattern is defined as “a logical sequence of doing things.” For example: if the dozer/compactor starts on one side of the working face and they work across the face together, then that is an efficient pattern. Layering and compacting from left to right or right to left is a ‘logical sequence.’ Knowing that inbound haul vehicles do not always adhere to that logic, then the dozer/compactor operators need to plan, communicate and stay with a logical sequence so that they cover the whole area without under/over compacting and/or thick layering of material. This is not easy to do during peak times. Again, when helping customers with the best practice of planning and maintaining a pattern, we have seen increases of from 50 to 200 lbs./yd3 increase in density.
In today’s waste, making enough passes to compress and shred the material properly is imperative to achieving higher densities. As I said in the above “pattern efficiency”, a minimum of 3 to 5 passes are needed to obtain the highest densities. And, as I mentioned, the norm is two passes on most landfills. The machine wheels compress and the tips give traction and shred the material. The more passes, the higher the density. Having said that, most operators that achieve higher densities start on one side and go forward to the end of the waste and back in the same tracks achieving two machine passes over the waste. Continual moving over one wheel width will eventually achieve four passes. They continue that ‘pattern’ all the way across the waste and then start over. Someone is probably saying, “What about the edges that only achieve two machine passes?” Most operators will perform four machine passes (twice up and back) on the edges until they get to the point that their pattern starts to achieve four passes (repeat the four passes on the far side edge). As per the statement above in “pattern efficiency”, as the number of passes goes up, so too does substantial growth in the density achieved.
Finishing the Face
Customers have said, “How you leave the working face at the end of the day, prepares the working face for the amount of work performed during opening the following morning.” How many times have we looked across the working face as they prepare to cover and instead of flat and level, it looks like meteors have impacted the working face? Or, there is big ugly material sticking up? Simply put, the time it takes to run down, track in or perform 45 degree passes to the working face prior to cover or ADCs, the less time it takes to open the following morning and the less cover soil or problem with ADCs you will have. Tracking in or running 45 degree passes, “knit or blend” the working face materials together. The result is: less voids, harder surface, less big/ugly materials jutting up. Thus, the working face is easier to cover, easier to close, easier to open the next day, which translates to less time and money.
For this topic, I am going to start with cover soil. Everyone normally has enough cover soil starting out, but when coming to the end of ‘closure,’ they start hoping for inbound inert soils or they have to buy soils. Most landfills over use their cover soils. Of course, depending on whether they are covering for daily, intermediate or final, the layer height changes. Let’s start with excavation and tracking of your cover soil. Most customers do not track their cover soil use. A best practice is to track the amount of loads of cover soil moved daily. Keep track of where the cover soil goes also. (Does it go to a: preplanned stockpile, or stockpile ready to use for daily that day or within the week, intermediate cover areas, road building, etc.?) Most of our customers agree on the following: put the correct layer height in the first time. (For example: if it is a 6″ daily cover, then layer it in 6″ layers (some put it in slightly thicker for erosion and depending on weight of daily traffic). The more times over the waste while putting down daily cover, the more soil is incorporated in to the waste. (Make as few passes as possible so that you do not have to add more cover soil.) Another best practice is to not fill holes or ‘level’ the waste with cover soils/materials. Large holes in the work face, low spots, etc., should be filled with waste and brought up to level prior to adding cover. Finally, some customers attempt to remove or “mine” soils prior to starting their day. They will “skim,” “mine,” “recover” the top few inches of soils and stockpile off to the side. This enables them to use this ‘mined’ soil as a beginning layer when adding daily cover at the end of the shift. Adding 2″ of previously mined cover and then 4″ or so of excavated cover, helps their daily cover soil use by 30 percent. Most customers say that mining their daily or intermediate cover soils and then reusing as a base layer, has helped them save 20 to 40 percent on cover soil use. Of course, as we all know, ADCs are preferred, but not cheap. Just like the working face, cover soil should be planned, tracked and managed closely.
Prior to coming onsite to perform a site/machine assessment, we normally ask the customer for a ‘normal’ weeks’ worth of scale data. We ask them for the tonnage to the working face by the hour, each hour of daily operation, for a full week. If they provide this data, we then chart daily tonnages and vehicle traffic for each hour of each day. Of course, this will show us peak times of tonnage and vehicles inbound to the working face. Everyone knows that most landfills have two to three peaks times of inbound tonnage/vehicles per day. Approximately 60 to 70 percent of total tonnage comes in during these two to three times. Most of the time these peak times are when the working face team struggles the most. The reason is that during these times, approximately 60 to 75 percent or more of landfills are undermachined and undermanned. Other than the early morning rush, most of these peak times coincide with breaks, lunches, fueling or cleaning times. During these times, the customer should be adding machines and personnel, not taking them away. Bottom line here: track, chart, then plan. Understand when your peak times are; do not fuel or clean machines during these times. Alternate operators during breaks/lunches, so that peak times are covered by running machines, etc. One final word on peaks. We have been on a few sites where they thought they had enough machines and manpower to handle peaks. When we arrived, their operators were telling us, “We just can’t keep up with what we have for some reason.” They had tracked, charted and planned for their peaks. So where was the problem? During our observation, we basically sat and observed their worst peak day for two to three hours. We took vehicle truck counts and tonnages of each type of inbound haul vehicle for 10 minute segments during each hour. This is where the term “super peak” was coined. We observed that during one hour of peak time of 150 tons/hr., one 10-minute segment received more than half of the inbound vehicles with approximately 80 tons of the 150 for the total hour. Again, 80 tons of the 150 tons/hour of the peak arrived in a 10-minute time span. Think about it! At that point, the objective was to keep the tipping floor clean and get the waste in place. Simply put, 80 tons was placed in a 10-minute time where that amount is normally placed and compacted in a one-hour time. Most managers and operators say that they will come back and work the waste, but it never happens. Once you have lost initial density with a deep layer, it will never be recovered. That is why we say: track, chart and plan.
At the End of the Day
In conclusion, best practices are simple:
- Safety first. Include the whole team. Make everyone accountable.
- Plan working distances to be efficient and productive. Work with your team and help them understand the areas that add or decrease productive distances that can hurt efficiencies.
- Improper layer heights will be your biggest loss of density. Talk with your team stressing and managing proper layer heights for your waste and machine size.
- Run patterns so that you achieve maximum passes. Keep your team communicating. Do not allow them to settle for anything less.
- At the end of the day, leave the working face so that cover soil can be added easily and efficiently. This also allows a quick start the next shift/morning.
- Track the use of your cover soil wherever it goes. This will allow you to cut down on ‘overuse’ of cover soil and helping you manage cover soil usage.
- “Mine or recover” soil when opening the next day. Use it as the “base” layer of the next day’s cover. Customers have told us this can save them 20 to 40+ percent on their cover soil use.
- Chart your working face tonnage to understand peak times. Do not fuel or clean machines during peak times nor take breaks or lunch during peak times unless you have another crew to take their place. Super peaks will take place at the worst time possible. Observe and understand possible super peaks to help your operators cope.
Tom Griffith is a Market Professional of Waste Applications and Products for Caterpillar Corporate Waste Group. He can be reached at (309) 675-5463.