Landfill Cell Geometry

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Landfill Cell Geometry
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Want to See a Big Pile of Money?

• No, not this loose change
• I mean a LOT of money?

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Yeah, A Lot of Money!
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This is a Costly Procedure
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Cover Soil
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Why Use Cover Soil?

• It keeps litter in
• It keeps vectors and moisture out
• It provides a driving surface
• It keeps the landfill looking sanitary
• ITS THE LAW

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Well First what is Daily Cover Soil?

• Its soil thats used to cover waste every day
• How much soil do we use to cover a daily cell?
• 31 cover ratio?
• 6 of soil?
• The regulations require at least 6 whats real?

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Understanding a 31 Ratio

• At 1,200 pcy, 350 tons of waste will create a 583
  cy cell(15,750 cf).
• This cell, at 8 deep, 80 wide and a 25
  advance, will have surface area of 4,615 sf.
• At 31, 194 cy of soil would be used to cover
  this cell.
• At 6, only 85cy of soil would be required.
• It doesnt match!

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Whats the No. 1 Problem?Too Much Soil

• Using too much cover soil is the most common (and
  most costly) operational problem at most
  landfillsin my experience
• Regulations say 6
• Best Ive ever seen is 11
• Average is 16
• Worst Ive ever seen is 42
• What is the problem? Lost Airspace

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Daily Cover

• Its good
• It provides a barrier
• Its required
• Its bad
• It costs money to place
• It costs money to purchase
• It takes up lots of airspace

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What Does Soil Cover Cost?

• Whats it Cost (per square foot) to
  Cover?AirspaceMaterialLaborEquipment
• Lets assume that we use 16 if soil for daily
  cover

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Why Care About Airspace?

• Its not the employer who pays wages he only
  handles the money. It is the product that pays
  wages.
• Henry Ford
• Youre selling airspace!

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Airspace

• /cy
• Lets assume that on average it costs 10/cy
• That works out to 0.37 per cubic foot
• Since were using 1.33 cubic feet of airspace per
  square foot of cover, in terms of airspace, daily
  cover costs 0.49 per square foot (in lost
  airspace)

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Material

• Buying soil?
• Royalty or fee?
• Lets assume that adequate soil is available
  on-site

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Labor

• In this example, the only labor associated with
  daily cover is for the equipment operators
  included in the equipment cost (see next page)

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Equipment

• Lets say that it takes 1 hour to haul the soil
  with a 623 scraper at 140 per hour
• And 1 hour to place the soil with a D6 dozer at
  85 per hour
• All costs include the operator
• This totals 225 to cover a 4,615 sf cell
• and works out to approximately 0.05/sf

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The Bottom Line

• So how much does it cost (per square foot) to
  cover? Plenty
• In our example
• Airspace costs 0.49
• Equipment Labor 0.05
• Total 0.54 per square foot
• Thats nearly 2,500/day !!

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How Can We Reduce that Cost?

• Dont cover? yeah right
• Use less soil? maybe, but not today
• Use ADC? sure, thats always a good bet
• Make smaller cells? Lets take a look

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Making a Smaller Cell

• We can make a smaller cell by getting better
  compaction but today we arent talking about
  compaction
• We can also make a smaller cell by optimizing the
  geometry
• Consider this

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These Cells All Have the Same Volume

• But which will use the least cover soil?
• Its depends on the geometry

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Cell Geometry

• Today well be talking about Cell Geometry
• Pretty exciting, huh?
• Well, well see

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Definition of a Cell

• Before we start, lets make sure were all on the
  same page
• Of course when we talk about a cell, were
  talking about a landfills daily cell
• But pay attention, if you dont get the landfill
  cell right, the term could be expanded to include
  other types of cells!!

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If You Fail on the Landfill Cell
Microbe Phone
Jail
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A Landfill Cell!
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Why is Efficiency Important?

• Its something we do everyday
• Lets be good at it.

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Efficiency is vital

• If youre satisfied with mediocrity, youll
  seldom achieve excellence.

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Cell Components

• A typical cell has three surfaces
• Top
• Side
• Face

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Measuring the Cell

• Depth is measured vertically
• Width is measured horizontally
• Advance is measured in the direction of the
  advancing cell

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Optimum Cell

• Lets apply this to a typical landfill

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Team Project

• How big is the cell?
• 600 tons of waste
• 1,200 pcy density

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First, how much waste are we talking about?

• 600 tpd
• 1,200 pcy (waste density)
• Volume of waste?
• 600 x 2,000 / 1200 1,000 cy

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Any other Factors?

• Minimum width of tipping area?Lets say 100

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Optimum Cell Depth?

• Okay, how can we determine the optimum cell
  depth?
• How about trial and error?
• Lets try 8

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Team Project

• Calculate surface area
• 100 wide
• 8 feet deep
• 1,000 cy of waste

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Cell Dimensions at 8 deep

• Run through the math to find dimensions
• 1,000 x 27 / 100(wide) / 8(deep)
• 34(advance)

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See How it Works?

• Dimensions are
• 100 wide
• 8 deep
• 34 advance

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Calculate the Surface Area

• Now the surface areaTop 100 x 34 3,400
  sfSide 34 x square root (576 64) 860
  sfFace 100 x square root (576 64) 2,530 sf
  Total surface area 6,790 sf

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How Much?

• So, whats it cost?6,790 sf x 0.54/sf 3,667
  per day
• How much soil are we using?16 1.33 ft1.33 x
  6,790 / 27 334 cy per day

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Is 8 the Optimum Depth?

• But is 8 feet really the best?Lets try 9 feet
  10 feet 7 feet? what depth is best?
• Lets change to 675 tons of waste per day
• Lets also change to an excavator and trucks
  hauling soil and a D7 dozer spreading soil
• Want to re-calculate this?
• Neither do I

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Put Your Computer to Work

• Lets put this together into a spreadsheet so
  that we dont spend the rest of the summer
  calculating the best cell geometry.

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Here is the Goal

• In general, we want to construct a cell that has
  the minimum surface area.

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Review Spreadsheet

• Variables
• Analysis
• Output

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This Spreadsheet Makes it Easy

• You can adjust all of the variables and calculate
  the best cell geometry
• Any other issues?
• What if we use ADC

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ADC
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ADC its the true fat-free diet for landfills

• Looking for high-fiber and low-fat?
• ADC could be the answer
• Sure, ADC can be more economical

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How Much Does ADC Cost?

• Typically, ADC costs less than soil when we
  factor in the value of airspace
• Some types of ADC cost less than soil even
  without considering lost airspace

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ADC Cost Analysis

• Lets take a quick look at the cost of ADC
• This is a simple spreadsheet

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Lots of Choices

• Tarps
• Film
• Spray-on
• Auto shredder fluff, green waste, and a variety
  of other types of waste materials

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Calculating the Cost of ADC

• Its not all economics. Sometimes site
  characteristics, local conditions, or even
  personal preference will dictate what type of
  ADC is best

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Our Goals Change When We Use ADC

• But what if were using ADC? Things changeWere
  no longer concerned with minimum surface area
  just in minimizing the area that receives soil
  because ADC is usually less costly than soil
  when we factor in airspace

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Maximize the Face When Using ADC

• Lets combine the soil costs with the ADC costs
  and see how it looks
• Not surprisingly, with ADC, the deeper the better
  up to a point.

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ADC Changes the Optimum Cell

• Lets look again at the spreadsheet

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But Dont Stop Here

• Theres another cost that we still havent
  considered

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Dozers Cost

• Dont forget about Dozer costs

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Pushing Costs Money
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And the Longer the Push the More it Costs
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We Have to Compromise

• Soil only looks to minimize overall surface
  area
• ADC maximizes the face and minimizes remaining
  soil area
• Dozer tends to reduce the face size to avoid
  excessive pushing costs

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Review Spreadsheet

• When we include the pushing costs, we get a new
  optimum cell depth. This is what weve been
  looking for. Its the real bottom line
• Now go do the right thing

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Wrap Up

• Any Questions or Comments?