USACE Hurricane Debris Estimating Model

ScopeFor the hauling contracts, for the disposal sites, and for the federal reimbursement request. The Corps of Engineers' model does it from the population and the storm: households (population divided by 3) times a per-household debris factor for the storm category (2, 8, 26, 50, or 80 cubic yards for categories 1 through 5), times multipliers for vegetative cover, commercial density, and a wet storm. The category carries most of the spread -- a category 5 produces forty times the debris per household of a category 1 -- and the result carries a stated accuracy of 30% either way, so the band is printed beside the figure. A county of 45,000 hit by a wet category 3 storm with medium tree cover and light commercial density comes to about 659,100 cubic yards, somewhere between 461,370 and 856,830. At the guide's default split of 30% clean woody debris, 461,370 cubic yards is construction and demolition debris -- 230,685 tons at 2 cubic yards per ton, the part that needs sorting and landfill space. The default split is from Hurricane Andrew and another storm produced the reverse, so the woody fraction is an input; reversing it cuts the landfill share by more than half. The guide's own Harrison County example, 6,992,374 cubic yards, is reproduced with the household count carried unrounded as the guide does. A planning forecast only: it does not replace field estimates or load tickets, and the model was not built for tornado, flood, earthquake, or wildfire debris. FEMA Public Assistance, the state, and the applicant's debris management plan govern.

Formula or tableQ (cy) = H x C x V x B x S, with H = population / persons per household (3, carried unrounded); C = 2, 8, 26, 50, 80 cy per household for categories 1 to 5; V = 1.1, 1.3, 1.5; B = 1.0, 1.2, 1.3; S = 1.0 or 1.3; band Q x 0.7 to Q x 1.3; woody = Q x woody fraction, C&D = the rest, split 42% burnable, 5% soil, 15% metals, 38% landfill; tons = cy / (softwood 6, hardwood 4, mixed 4, C&D 2).

Source and editionFEMA-325, Public Assistance Debris Management Guide (July 2007), Appendix B, USACE Hurricane Debris Estimating Model, Step 1 and its stated plus-or-minus 30% accuracy, with the Hurricane Andrew composition and C&D split from the same guide; volume-to-weight factors as restated in FEMA 329, Debris Estimating Field Guide (September 2010). FEMA-325 is superseded in part by the Public Assistance Program and Policy Guide; the model's factors remain the published USACE values.

Free accessFEMA-325 and FEMA 329 are free federal publications on fema.gov; every factor is a public-domain USACE or FEMA figure.

What governsEstimate. AHJ and licensed professional govern.

API field namespopulation, persons_per_household, storm_category, vegetation, commercial, precipitation, woody_fraction, wood_type, households, debris_cy, debris_low_cy, debris_high_cy, woody_cy, woody_tons, cd_tons, cd_burnable_cy, cd_soil_cy, cd_metals_cy, cd_landfill_cy

• Three persons per household the model's household count is population / 3 unless a local figure is enteredFEMA-325 Appendix B
• Plus or minus 30% a planning forecast, replaced by field estimates and load tickets as they come inFEMA-325 Appendix B
• Conversion factors are defaults C&D 2 cy per ton, hardwood and mixed 4, softwood 6; field tests may be needed to confirm themFEMA 329 (2010)