Landfill Airspace Consumption and In-Place Density
Converts tonnage and in-place density into waste and cover airspace, the airspace utilisation factor.
Example
You enter
- Tonnage placed (tons) 250000
- In-place density (lb/cy) 1200
- Cover as a share of waste volume (%) 20
- Committed airspace cost ($/cy) 8
- Improved density to compare (lb/cy) 1500
You get
- Waste airspace consumed 416,667 cy at 0.600 tons/cy
- Cover airspace 83333.3
- Total airspace consumed 500,000 cy
- Airspace utilisation factor 0.500 tons per cy
- Cover share (%) 16.6667
- At the improved density 400,000 cy total, AUF 0.625
- Improved airspace utilization factor 0.625
- Airspace saved 100,000 cy (20%) from a 25% density gain
- Airspace saved (%) 20
- What that is worth $800,000 -- no capital and no permit
Checked against published worked examples from: University of Massachusetts Amherst, Dept. of Civil & Environmental Engineering...; Stormwater Solutions (Endeavor Business Media), Daniel P. Duffy, P.E.
Details, formula, and sources
ScopeConverts tonnage and in-place density into waste and cover airspace, the airspace utilisation factor, and what a density improvement is worth. The worked site saves 100,000 cy a year, 20% of its airspace, from a 25% compaction gain for no capital and no permit. Density is an operating result, not a property of the waste.
Formula or tablewaste airspace = tons / in-place density in tons per cubic yard; cover airspace = waste airspace x the cover ratio; airspace utilisation factor = tons placed / total airspace consumed.
Source and editionVolumetric bookkeeping. In-place density is commonly 1,000 to 1,600 lb per cubic yard and cover commonly adds 20 to 50% of the waste volume (EPA's Decision-Maker's Guide prints waste-to-soil ratios of 2:1 to 5:1 and plans on 3:1; USACE EM 1110-3-177 plans on 4:1 to 3:1). The site's own airspace survey and its permitted capacity govern.
Free accessPublic arithmetic; the densities and cover ratios come from the site's own survey.
What governsEstimate. AHJ and licensed professional govern.
API field namesannual_tons, in_place_density_lb_per_cy, cover_ratio_pct, airspace_value_per_cy, improved_density_lb_per_cy, waste_airspace_cy, cover_airspace_cy, total_airspace_cy, airspace_utilization_factor, cover_share_pct, improved_total_airspace_cy, improved_airspace_utilization_factor, airspace_saved_cy, airspace_saved_pct, airspace_saved_value
- Cover counted alongside the waste; reporting density on waste alone while measuring capacity on total volume mixes two basessite airspace survey
- Airspace value the committed construction, cover, closure, and post-care cost per cubic yardsite financial assurance