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Soil Swell & Haul-Off

Calculate loose cubic yards (LCY) for excavation haul-off based on bank volume and specific soil expansion swell factors.
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The Dirt on Swell 🚜

When you dig a hole, you're literalizing the concept of "fluffing" the soil. Compacted earth (Bank Volume) expands significantly once it's disturbed and air is introduced (Loose Volume). This is why you often have a pile of dirt that seems twice as big as the hole it came out of. Always calculate your haul-off based on Loose Cubic Yards (LCY) to avoid under-budgeting your trucking costs.

Bank Volume

29.63 BCY
Compacted measure in-ground

Loose Volume

40.00 LCY
Expanded measure for haul-off
Haul-Off Strategy3 Loads

Assuming standard 15-yard tandem dump trucks.

BANK (BCY)+35% SWELLLOOSE (LCY)
For estimation purposes only. Always consult a licensed professional before beginning work. Full Trade Safety Notice →
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What is The Mathematics of Soil Expansion?

When soil is excavated from its natural 'bank' state, the excavator bucket violently fractures the thousands of years of geological compaction. Small chunks break apart, and atmospheric air floods into the microscopic voids between the dirt particles. This causes the earth to swell, occupying significantly more volume than the original hole it came out of. This expanded volume is known as Loose Cubic Yards (LCY) and is the absolute basis for all trucking haul-off costs.

Mathematical Foundation

Geometric Bank Volume (BCY)
BCY=L×W×D27BCY = \frac{L \times W \times D}{27}
BCYBCY= Bank Cubic Yards. The rigid, exact volume of the hole in the ground.
L,W,DL, W, D= Length, Width, and Depth dimensions measured in Feet.
Aerated Export Pile (LCY)
LCY=BCY×(1+Sf)LCY = BCY \times (1 + S_f)
LCYLCY= Loose Cubic Yards. The larger physical volume of the dirt after being torn from the bank by an excavator.
SfS_f= Swell Factor percentage expressed as a decimal (e.g., 35 percent = 0.35).

Laws & Principles

  • Sand and Gravel Stability: Coarse materials like sand swell very little (around 15 percent). Because the particles are already large and naturally granular, they don't lock together tightly in the ground. Digging them up doesn't inject much extra air.
  • The Clay Expansion Penalty: Wet, heavy clay experiences massive swelling (often exceeding 35 percent). Because clay particles are microscopic and naturally compressed into dense, water-tight sheets, tearing them apart injects huge pockets of air that refuse to compress back down naturally.
  • The Blasted Rock Extremes: Solid bedrock blasted with dynamite can swell by up to 60 percent. The massive, jagged boulders stack against each other in the truck bed, leaving gigantic empty air cavities that you still must pay to have hauled away.

Step-by-Step Example Walkthrough

" An in-ground swimming pool contractor is digging a 40 foot by 20 foot rectangular pool that is 6 feet deep. The soil profile is extremely stiff, wet clay. They need to calculate how many 15-yard tandem dump trucks to hire. "

  1. 1. Calculate the rigid hole Bank Volume: (40 x 20 x 6) = 4,800 cubic feet.
  2. 2. Convert into Bank Yards: 4,800 / 27 = 177.7 Bank Cubic Yards (BCY).
  3. 3. Apply local Clay Swell Factor: Heavy clay expands by 35%. Multiply 177.7 * 1.35.
  4. 4. Calculate LCY: The 177 yard hole translates into a 240 Loose Cubic Yard (LCY) pile on the street.
  5. 5. Calculate Trucks: 240 yards / 15 yards per truck = 16.0 Full Trucks.
Final Result: The contractor must budget for exactly 16 dump truck loads. If they had ignored the 35 percent swell factor and only ordered trucks based on the 177 yard 'hole' (which equates to 11.8 trucks), they would be left with a massive pile of dirt in the client's front yard and no budget to remove it.

Quick Answer: How do I calculate haul-off volume?

To calculate the volume of dirt you must haul away, you must first calculate the Bank Cubic Yards (BCY) of the literal hole in the ground (Length × Width × Depth in feet ÷ 27). Next, you must multiply that number by the soil's Swell Factor (e.g., multiply by 1.30 for a 30% swell). The resulting number is your Loose Cubic Yards (LCY). LCY is the exact volume you use to order dump trucks and budget for hauling fees.

Swell & Trucking Formulas

Excavation Site Volume (BCY) = (L × W × D) ÷ 27

Haul-Off Pile Volume (LCY) = BCY × (1.0 + Swell_Factor_Decimal)

Dump Trucks Required = LCY ÷ Dumpster Capacity in Yards

Note: Dump trucks max out slightly below their stated water-level capacity. A 15-yard truck safely hauls about 14 yards of loose spoil over the road.

Standard Geotechnical Swell Factors

Material Designation Visual Identification Swell %
Dry Natural Sand Falls apart instantly through fingers, no clods 10% - 15%
Loam (Farm Topsoil) Dark brown/black, holds slight shape, organic 20% - 25%
Stiff / Dry Clay Light colored, fractures into sharp angular pieces 25% - 30%
Wet / Sticky Clay Sticks directly to excavator bucket, heavy clods 30% - 40%
Solid Sedimentary Rock Requires ripper tooth or blasting to extract 50% - 60%
Note: If you physically mix solid rock boulders with wet clay during a deep dig, the large bedrock chunks will create massive unfillable air voids in the truck, vastly increasing your effective swell hauling volume.

Haul-Off Disasters to Avoid

The Scale Weight Trap

A superintendent calculates they have 300 Loose Cubic Yards of dirt. Standard tri-axle dump trucks hold 15 yards visually. The super orders 20 trucks (300/15). Unfortunately, the soil is rain-soaked heavy clay which weighs over 3,000 lbs per cubic yard. While the truck box could fit 15 yards of volume, 15 yards of wet mud exceeds the Department of Transportation (DOT) highway weight limit by 6 tons. The drivers are forced to short-load the trucks to 11 yards to stay street legal, requiring 28 total truck trips instead of 20.

The Import Shrinkage Error

A landscaper needs to fill a 100-yard hole on a property grade. They order exactly 100 cubic yards of Loose common earth from the local quarry. When the 100 LCY arrives, the landscaper dumps it into the hole and compacts it down with a vibratory roller to prevent the lawn from settling. The action of compaction squeezes all the air out of the loose dirt. The 100 LCY "shrinks" into only 80 yards of Compacted Cubic Yards (CCY), leaving a massive 20-yard low spot in the yard.

Professional Trucking Strategies

Do This

  • ✓Smash big clods while loading. When dropping wet clay into a dump truck, use the back of the excavator bucket to gently tap and break up the massive clods inside the truck bed. Breaking the clods allows the dirt to settle and eliminates massive empty air voids, allowing you to fit 1 to 2 extra yards per truck.
  • ✓Stockpile efficiently. If you must stockpile dirt on-site before truck arrival, keep the pile as tall and tightly grouped as possible. A low, sprawling pile acts like a sponge for overnight rain, ruining your haul-off weight. A tall, peaked pile sheds water immediately.

Avoid This

  • ✗Don't load sloppy spoil over the tailgate. Very soupy mud cannot be mounded inside the truck bed. It will self-level and pour straight backward over the tailgate when the truck accelerates up an incline on the highway. You must load "sloppy" mud severely short (maybe 8 yards total) to avoid DOT fines.
  • ✗Don't rely strictly on visual yardage. Do not pay haul-off truckers strictly per visual load unless you trust them implicitly. Pay per ton using scale tickets from the dump site, or explicitly stipulate a strict 'yardage per load' factor in their subcontract.

Frequently Asked Questions

What does BCY vs LCY vs CCY mean?

BCY (Bank Cubic Yards) is the volume of the undisturbed dirt still in the ground. LCY (Loose Cubic Yards) is the fluffy volume of the pile after you dig it up. CCY (Compacted Cubic Yards) is the tight volume after you place the dirt back down and mechanically roll it. The progression is always: Hole → Pile (Swells 30%) → Trench (Shrinks back down).

Does my excavator bucket measure Bank Yards or Loose Yards?

All earthmoving machine buckets measure Loose Cubic Yards (LCY). A 1-yard excavator bucket cannot remove a 1-yard piece of solid earth because the dirt instantly fractures and swells as the teeth hit it. You must divide your bucket capacity by the swell factor to find true bank production rates.

Are typical dump trucks limited by weight or volume?

It depends entirely on the soil's moisture content. For loose, dry topsoil, the truck will hit the volumetric capacity (e.g., 15 yards) long before it hits the legal DOT highway weight limit. For saturated, soggy clay, the truck will become dangerously overweight while the bed is visually only half full.

Why do we care about the shrinkage factor?

If you are exporting dirt away from the site, you solely care about Swell. But if you are importing dirt to build up a berm or structural pad, you must account for Shrinkage. Because you are buying Loose compacted dirt, but your blueprints require a dense, compacted fill, 100 LCY of imported soil might crush down into only 85 compacted yards in place.

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