Waste Settlement and Recovered Airspace
Splits settlement into primary, recoverable as airspace while the cell is open, and secondary.
Example
You enter
- Waste thickness (ft) 100
- Filled area (acres) 50
- Primary settlement (% of thickness) 8
- Secondary settlement (% of thickness) 12
- In-place density (lb/cy) 1200
- Tipping fee ($/ton) 45
- Cap drainage slope (%) 4
- Slope run length (ft) 300
- Adjacent fill thickness (ft) 50
You get
- Total settlement 20.0 ft -- 8.0 primary, 12.0 secondary
- Primary settlement (ft) 8
- Secondary settlement (ft) 12
- Volume the settlement creates 1613330
- Recoverable airspace 645333
- Recoverable (ton) 387200
- What that carries 17424000
- Differential against the adjacent fill 10.0 ft (10.0 ft there against 20.0 ft here)
- Design fall (ft) 12
- Remaining slope (%) 0.666667
- Fall consumed (%) 83.3333
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
ScopeWhich only lowers the final grades, then checks the differential against the cap's design fall. The worked cell recovers $17.4M of airspace and loses 83% of its cap slope to differential settlement.
Formula or tablesettlement = waste thickness x the primary and secondary fractions; recoverable airspace = primary settlement x area; differential = the settlement difference between adjacent fill thicknesses, against the cap's design fall over its run.
Source and editionSettlement as a fraction of waste thickness. The site's own settlement monitoring, the closure plan, and the permit's minimum final-cover slope govern.
Free accessPublic arithmetic; the settlement fractions come from the site's own monitoring.
What governsEstimate. AHJ and licensed professional govern.
API field nameswaste_thickness_ft, filled_acres, primary_settlement_pct, secondary_settlement_pct, in_place_density_lb_per_cy, tipping_fee_per_ton, cap_slope_pct, slope_run_ft, adjacent_thickness_ft, total_settlement_ft, primary_settlement_ft, secondary_settlement_ft, total_volume_cy, recoverable_airspace_cy, recoverable_tons, recoverable_revenue, differential_settlement_ft, design_fall_ft, remaining_slope_pct, fall_consumed_pct
- Differential not the total, is the number that governs the cap; final grades are designed with the settlement added back inclosure plan
- Settlement fractions entered; they are highly waste and site specific and are not predicted heresite settlement monitoring