Today, more than ever, you need to understand both the big picture of how to fill your site’s airspace as well as the nitty-gritty details of daily fill sequencing and overall operation in order to have a clear understanding of where to fill and how to do it most effectively.
By Troy Kechely
Do you know how much money you are losing at your landfill every year? Here is a hint: It is probably a lot. Especially during these uncertain times, not knowing how efficiently you are managing your airspace can create big financial problems down the road.
While nothing can be 100 percent efficient, the impact of being inefficient versus efficient can be dramatic. Let’s take landfill airspace for example. Anyone who has been in the waste management business more than a few years understands that the more efficient you are with the daily process of placing waste and covering it, the more money you make. It is simple math. If you have steady tonnage coming in that consumes a certain amount of airspace every day, but you increase your efficiency so that the same amount of tonnage consumes less airspace, then your site lasts longer, and you make more money. Achieving this often requires looking at a few important factors, like compaction, waste handling and cell construction. In the long run, simple operational changes can mean big savings. But what about how you sequence your fill? Can that save you money? You bet it can.
Just like improving efficiency in your daily waste placement, how you sequence your landfill can have dramatic cost and operational benefits. The best part is that it can be done before you even start placing waste. Here is how it works.
Changing Waste Streams
Every landfill has a general fill sequence plan, usually created during the permit process. This generally shows how the lined cells will be constructed and filled based on approved design base and final grades. The problem with these plans is two-fold: First, they usually have the cells sized for symmetry rather than for fiscal and operational efficiency. Second, they are rarely revised to reflect changes in the waste stream and other operational factors, like what we are facing in 2020 as a result of COVID-19 and national economic impacts that have potentially long-term impacts on waste streams.
We have seen clients experience massive fluctuations in their tonnages since February. First, there has been a dramatic drop in commercial waste and simultaneous increase in residential and self-haul tonnage.
And while many businesses shut down, large construction projects and home improvement projects remained steady, resulting in a big increase of construction and demolition waste. Although we are starting to see a return to business and a slight increase in commercial waste as the economy picks back up, most sites are still not seeing the tonnages they used to. Some have even seen as much as a 15 percent decrease.
No one knows how long this uncertainty will last but one thing is certain: tonnage will likely continue to fluctuate for the foreseeable future. Now is the time for sites to reassess their sequencing and perhaps even revamp their long-term plans for their site.
Airspace Management Plan
This is when your initial site sequencing plan just does not cut it. You really need what we call an Airspace Management Plan (AMP). Let’s take a deeper look at what exactly an AMP entails.
Because of the sheer size of each lined landfill cell, you want to look at not only basic design constraints—such as leachate collection systems (LCS) and construction limitations—but also at the cost/benefit for each cell. The primary costs are typically the excavation and stockpiling of soil, liner installation, leachate collection system and access road construction. The primary benefit is the amount of airspace gained from the liner placed. At first look, it would make sense to have a large area of liner put in because it gives the most airspace. There is just one problem with this: time. You might think putting enough liner down to provide 10 years of airspace is a good thing, but when you calculate how much it costs and then look at options of deferring some of that cost down the road, it becomes evident that bigger is not always better.
Let’s take a look at an example: On a recent project, a landfill’s biggest operational cost was soil excavation and stockpiling. The original permitted phasing had a cumulative cost for the life of the site of $37.4 million. By looking at alternatives, we were able to push some of those costs down the road by changing when each phase was constructed. The alternative option had a total cost or only $26.5 million, which is a difference of $10.9 million over the life of the site from the original calculated cost. Calculate the net present value of that savings and you get $5.7 million in savings in today’s dollars. These savings simply come from taking a hard look at the size and order of how—and most importantly when—each phase was constructed. With drops in tonnages due to COVID-19 and economic slowdowns, it might be worth a lot of money to take another look at your long-term sequencing.
Ultimately, an AMP must be dynamic and updated every five to seven years to respond to the ever-changing landfill environment. Factors like waste tonnages fluctuating or waste types changing due to regulation or population growth will require ongoing updates to the AMP.
Armed with a good AMP, a landfill will have the optimized big picture plan and can then focus on the short-term details related to the daily operations of the site. If you look at the life of the site, the largest costs are not liner or closure, it is the daily placement of waste. The pushing, the packing and the covering every day until the site closes. The AMP must be operationally optimized to not only save money, but also make the site safer and more efficient. These optimizations include looking at criteria like long and short-term access/haul roads, temporary stormwater management and stockpiles.
Fill Sequence Plan
You might wonder why details matter and if your site can get by with just an AMP. The answer is you can, but it will not be nearly as efficient as it could be. Here is why. Think of the life of your landfill as one big road trip across the entire country. The AMP shows you the overall route, but does not show any of the details along the way, like where to turn, where to get gas, what hotels and restaurants to pick, etc. All of those details—while seemingly less significant—can add up in terms of time and money. Remember, the biggest cost of a landfill is the daily operations. Just like a road trip, unexpected detours and delays can have a big impact and without question, COVID-19 and the economic uncertainty from it is a big detour on your site’s journey to completion.
A Fill Sequence Plan (FSP) addresses this. It provides the detailed turn-by-turn directions to get you through a 12 to 18-month period. Just like with the AMP, a good FSP needs to be operationally optimized for your specific site to be truly effective. This means it is focused on operational efficiency and safety factors such as:
• Optimal push distance and daily cell construction based on site equipment and current and projected tonnage
• All-weather tipping pad requirements
• Short-term haul roads and cover material stockpiles
• Temporary stormwater management structures
• Litter mitigation measures through daily cell construction and litter fence placement determined through wind modeling
• Traffic flows
• Etc.
When combined, a site-specific Airspace Management Plan with annual Fill Sequence Plans can:
• Maximize airspace
• Delay large cost events
• Deal with environmental factors that affect operations
• Reduce operational costs
Perhaps most importantly, the specifics of the fill sequence plan must be effectively communicated to the heavy equipment operators and landfill spotters, because they are the ones actually building the daily cell. If they do not understand the roadmap, they are not going to arrive at the desired location. There are many ways to communicate the fill sequence plans, including training, surveying markers and even 3D views of the plans that can be viewed in virtual reality. Regardless of what method is used, do not skimp on this step. It is the final piece of the puzzle that will make the plan into reality.
Are You Prepared?
Today, more than ever, you need to understand both the big picture of how to fill your site’s airspace as well as the nitty-gritty details of daily fill sequencing and overall operation. If landfill tonnage fluctuates, landfill managers and equipment operators need to adapt and have a clear understanding of where to fill and how to do it most effectively.
So, ask yourself a question. Do you know how your site is being filled and will be filled? Is it optimized to save you money? Are you prepared to respond quickly and effectively if tonnage fluctuates in the future? If you are not sure, it is time to step back, take a look at your airspace management and start planning for uncertainty. | WA
Troy Kechely is Airspace Management Planning Project Manager for Blue Ridge Services (Charlottesville, VA). He has more than 25 years of experience in large scale grading and airspace management planning in solid waste, civil site and environmental super fund projects throughout North America. He has created dozens of fill sequence and airspace management plans for landfills, as well as transfer station studies, site expansion design, wind modeling, litter mitigation planning and construction oversight. He can be reached at t[email protected].