Disaster Response and Recovery
The calculators a crew needs after a flood, a storm, or a collapse, gathered from every trade in the order the work happens. Each one is a check, not the stamp, and each names the authority that governs it.
Emergency water and sanitation
- Emergency Drinking Water Bleach Dose Water and Wastewater Operations - The EPA's emergency bleach table is the most-printed water number in any disaster.
- Boil-Water Time and Boiling Point at Altitude Water and Wastewater Operations - A rolling boil is the standard emergency disinfection, and altitude lowers the temperature it happens at.
- Well Shock-Chlorination Dose Plumbing and Gas - The household bleach to shock-chlorinate a private well from the casing diameter and standing water column.
- Water Main Chlorination Dose Plumbing and Gas - The chlorine to charge a newly installed or repaired water main the AWWA C651 way.
- Chlorine Demand and Dose for a Target Residual Water and Wastewater Operations - Chlorine the water consumes, and the dose needed to hold a target residual.
- Disinfection Contact Time from a Baffling Factor Water and Wastewater Operations - The CT a disinfection step earns depends on T, the time by which only 10% of the water has passed through.
- Disinfection CT (USEPA SWTR) Water and Wastewater Operations - CT achieved against the USEPA SWTR requirement for 3-log Giardia inactivation.
- UV Dose and Target Check Water and Wastewater Operations - Delivered UV dose, checked against a validated target.
- Chlorine Residual Decay (First-Order) Water and Wastewater Operations - First-order residual C(t) = C0 x exp(-k t), time to a target residual, and an optional booster distance.
- Dechlorination Chemical Dose Water and Wastewater Operations - The sulfur-based chemical to neutralize a chlorine residual before an NPDES discharge or a fish-bearing stream.
- Total Coliform Routine and Repeat Sample Count Water and Wastewater Operations - Restoring a water system after a flood or a main break ends in sampling.
- Well Casing Storage, Purge Volume, and Disinfection Water and Wastewater Operations - How much water stands in a well casing, how long purging it takes, and what disinfecting it costs in chlorine.
- Water Main Flushing Volume, Duration, and Velocity Water and Wastewater Operations - How much water a main flush takes, how long it runs, and whether it reaches a scouring velocity at all.
- Cistern / Storage Reserve Days and Required Volume Water and Wastewater Operations - The reserve a storage tank carries and the tank a target reserve needs, a straight mass balance.
- Rainwater Harvesting Yield Cross-Trade Utilities - Annual gallons from catchment area, rainfall, and collection efficiency.
- Catchment Area for a Target Harvest Cross-Trade Utilities - The roof footprint needed to harvest a target volume a year.
- Rainwater First-Flush Diversion Volume and Standpipe Length Water and Wastewater Operations - The first rain off a roof washes it, carrying dust, pollen, bird droppings, and after a storm or a fire, debris and ash.
- Solar Water Pump Array Sizing Water and Wastewater Operations - A solar pump is sized from the water, not from the load.
- Pump Total Dynamic Head (TDH) Cross-Trade Utilities - Total dynamic head from static lift, static discharge, and Hazen-Williams suction / discharge / fittings friction.
- Friction Loss Plumbing and Gas - Water-pipe friction loss by Hazen-Williams or by Darcy-Weisbach with the Colebrook friction factor.
- Water Pressure Zone HGL and Service Pressure Water and Wastewater Operations - What pressure a service sees, and which elevations one pressure zone can serve.
- Design Flow from Population (Average, Peak, Minimum) Water and Wastewater Operations - Average, peak, and minimum design flow from a service population.
- Lift Station Outage: Time to Overflow and Pump-and-Haul Loads Water and Wastewater Operations - When a storm takes out power to a sewage lift station.
- Lift Station Wet-Well Volume and Cycle Time Water and Wastewater Operations - The active volume a lift station wet well needs so its pump does not start more often than the motor allows.
- Sump / Ejector Basin Drawdown and Cycle Check Plumbing and Gas - Drawdown volume, run and fill times, cycles per hour.
- Worksite Toilet and Handwash Count Cross-Trade Utilities - A recovery site fills with crews faster than it fills with portable toilets.
- Responder Base Camp Sanitation and Water Cross-Trade Utilities - Utility, line, and debris crews brought in after a disaster often sleep where they work.
Emergency and temporary power
- Generator Sizing Electrical - Continuous and surge wattage from running totals and the largest motor's starting draw.
- Generator Sizing for Motor Starting Electrical - Required generator kW / kVA from running load and motor-starting kVA at the 30% voltage-dip criterion.
- Generator Output Derate for Altitude and Temperature Electrical - A rental generator shipped to a mountain town in a heat wave does not make its nameplate.
- Generator Fuel at Part Load and Minimum-Load Check Electrical - Emergency generators are nearly always oversized for the load they carry.
- Generator Fuel Runtime and Backup Duration Electrical - How long a standby generator runs on its fuel, the fuel-supply companion to generator-sizing and battery-runtime.
- Generator Fleet Fuel Resupply Trucking and Logistics - After a hurricane a county's temporary power is dozens of generators of different sizes at hospitals, lift stations.
- Paralleled Generator Droop Load Sharing Electrical - Temporary power often means paralleling whatever units arrived -- different sizes, different governors.
- 120/240 V Generator Leg Balance Electrical - A portable generator's wattage is split across two 120 V legs, and each leg has its own limit.
- Critical Load Priority Shedding Electrical - When the available source is smaller than the connected load.
- Generator Output Conductor at 115% (NEC 445.13) Electrical - The conductor rule from a generator to its first overcurrent device, which estimators routinely get wrong.
- Power Distro Per-Leg Loading Stage and Live Production - Current per leg, percent of service rating, headroom.
- Voltage Drop Electrical - Single-phase or three-phase voltage drop over length.
- Existing-Facility Load by Peak Demand (NEC 220.87) Electrical - Adding load without a service upgrade, on the metered peak.
- Battery Runtime Electrical - Hours of runtime from Ah, voltage, depth of discharge, and load (optional Peukert).
- Off-Grid Battery Bank Sizing Electrical - Required nameplate capacity (Wh and Ah) from daily load, days of autonomy, depth-of-discharge, and round-trip efficiency.
- Battery Bank Series/Parallel Configuration Electrical - The series/parallel wiring of a battery bank.
- Battery-to-Inverter DC Conductor and OCPD (NEC 690.9 / 706) Electrical - Sizes the DC conductor and fuse between a battery bank and an off-grid or ESS inverter.
- Battery Room Hydrogen Ventilation (IEEE 1635) Electrical - The cells-not-jars exhaust rate that keeps a battery room under the LEL.
- Generator-Battery Hybrid Fuel Savings Electrical - A generator carrying a light load around the clock burns fuel inefficiently and wet-stacks.
- PV Array Size from a Target Annual Energy Electrical - The DC array size needed to offset a target annual production.
- Solar PV String Sizing Electrical - Cold-Voc max series and warm-Vmp min series for an inverter MPPT window.
- PV Circuit Maximum Current and Ampacity (NEC 690.8, the 156% Rule) Electrical - PV circuit maximum current and the minimum conductor ampacity it requires.
- MPPT Charge Controller Output Current Electrical - An MPPT charge controller is sized by the current it delivers to the battery.
- Radio and Communications Site Duty-Cycle Battery Electrical - A radio draws a lot of current while it transmits and very little while it listens.
- Propane Tank Vaporization Capacity Plumbing and Gas - How fast a propane tank can turn liquid into vapour.
- Propane Run Time and Refill Interval Plumbing and Gas - How long the propane in a tank lasts, and when the next delivery has to be.
Collapse shoring and rescue support
- Collapsed or Damaged Floor Load for Shoring Carpentry and Construction - Every emergency shore starts from the same question.
- US&R Vertical Shore Post Capacity Carpentry and Construction - Emergency vertical shores are designed with the US&R guides' own simplified column formula.
- US&R Box Crib Capacity and Height Limit Carpentry and Construction - A box crib's capacity is not the wood's column strength; it is the bearing where one layer crosses the next.
- US&R Raker Shore Geometry and Wall Force Carpentry and Construction - A damaged masonry wall is held with rakers.
- Steel Picket Anchor Lateral Capacity and Count Rigging and Heavy Lift - Raker soles, rope anchors, and guy lines in the field are held by steel pickets driven into the ground.
- Wood Column Capacity (Slenderness) Carpentry and Construction - Slenderness ratio, column stability factor Cp, allowable Fc-prime.
- Wood Bearing Perpendicular to Grain (NDS 3.10) Carpentry and Construction - The crushing check a framer skips until the beam sinks into the plate.
- Formwork Shore Post Load and Spacing (ACI 347) Carpentry and Construction - The vertical load path of an elevated pour.
- Excavation Protective System and Egress Triggers (OSHA Subpart P) Carpentry and Construction - Whether an excavation requires a protective system at all.
- OSHA Trench Sloping Cross-Trade Utilities - Maximum slope ratio per soil class A/B/C and benching geometry.
- Excavation Slope and Bench-Step Plan Carpentry and Construction - OSHA Appendix B slope ratios A 0.75:1 / B 1:1 / C 1.5:1 turned into spoil volume (yd^3), surface footprint.
- OSHA Appendix C Timber Trench Shoring Lookup Carpentry and Construction - OSHA's Appendix C timber tables answer the question a utility repair or a trench rescue asks first.
- Trench Spoil Pile Setback and Surcharge Carpentry and Construction - Required spoil-pile setback (the larger of the OSHA 2 ft minimum and the depth-based surcharge), the pile toe spread.
- Lateral Earth Pressure and Thrust (Rankine) Carpentry and Construction - How hard retained soil pushes on a wall, active and passive.
- Soil Vertical Total and Effective Stress (Terzaghi) Carpentry and Construction - The vertical effective stress at a depth, from the soil profile and the water table.
- Confined Space Air Change Time Fire-Ground Engineering - Minutes to reach target air changes from blower CFM.
- Confined Space Retrieval Winch Force Cross-Trade Utilities - The force a confined space retrieval system has to produce: the entrant and their equipment, plus line friction.
- Rope Rescue Mechanical Advantage Fire-Ground Engineering - Theoretical and actual MA across rig types with pulley losses, tracking the tension through each pulley.
- Sling Angle Load Multiplier Fire-Ground Engineering - Tension per leg from load, configuration, and included angle.
- Required Fall-Arrest Clearance (ANSI Z359) Fire-Ground Engineering - The clearance a personal fall-arrest system needs below the anchor so the worker does not strike the level.
- Fall Arrest Anchorage and System Force Check (OSHA 1926.502(d)) Fire-Ground Engineering - What a fall-arrest anchorage and system must WITHSTAND -- and the two governing numbers are not the same number.
- Guy Anchor Holding Capacity in Soil Electrical - The guy-tension calculator gives the pull in the guy.
- Crane Ground Bearing Pressure and Mat Size Rigging and Heavy Lift - Outrigger / crawler ground bearing pressure vs an allowable soil bearing, the area required to pass.
- Relief Supply Pallet Floor Load Cross-Trade Utilities - Relief supplies land in gyms, church halls, and offices that were never designed as warehouses.
Flood fight and storm damage
- USACE Sandbag Levee Bags and Sand Cross-Trade Utilities - The first order a flood fight places is for sandbags and sand, and the count rises with the square of the height.
- USACE Emergency Earth Levee Section and Seepage Creep Check Cross-Trade Utilities - An emergency earth levee is built to a handful of USACE flood fight rules.
- Flood Hydrostatic and Hydrodynamic Load on a Wall Carpentry and Construction - Floodwater against a wall pushes with a triangle of still-water pressure and, where it flows, with drag.
- FEMA Flood Debris Impact Load Carpentry and Construction - A flood carries debris -- pieces of other buildings, poles, tanks.
- Flood-Head Uplift on a Slab, Hatch, or Manhole Cover Carpentry and Construction - Water under head pushes up on whatever is in its way.
- Buried Pipe Flotation and Anti-Flotation Backfill Carpentry and Construction - Flotation check for an empty large-diameter pipe in a flooded trench.
- Excavation Dewatering Pump Rate Carpentry and Construction - Pump rate to draw an open excavation down in a target time and hold it against a steady inflow.
- Pit Dewatering Total Head, Staging, and Suction Limit Carpentry and Construction - In a deep pit the static lift dominates the head, and the suction side is what stops bad plans.
- Flooded Basement Staged Pump-Down Schedule Water Damage and Mold Restoration - Pumping a flooded basement dry in one go can collapse its walls or heave its floor.
- Standing Water Volume Water Damage and Mold Restoration - Gallons, ft^3, and weight from affected area and depth.
- Water Extraction Volume, Time, and Waste-Tank Dumps Water Damage and Mold Restoration - The three numbers that plan day one of a water loss, and the first rule of the trade stated as arithmetic.
- Wicking-Height Flood Cut and Demolition Takeoff Water Damage and Mold Restoration - Turns a wall run and flood-cut height into the demolition takeoff a tech marks on the wall.
- Flood-Cut Demolition Take-Off Water Damage and Mold Restoration - Drywall area removed, 4x8 sheet count, baseboard linear feet, and batt-insulation area from wall run and cut height.
- NFIP Substantial Improvement 50% Rule (44 CFR 59.1) Carpentry and Construction - The rule that decides whether a remodel in a flood zone is a remodel or a rebuild.
- NFIP Flood Opening Area (44 CFR 60.3) Carpentry and Construction - One square inch of NET area per square foot of enclosed area, a minimum of TWO openings.
- Existing Roof Snow and Ice Weight Against Design Load Carpentry and Construction - After a heavy snowfall the question is not the design load but the load on the roof now, measured with a ruler.
- Flat-Roof Snow Load Carpentry and Construction - The design snow load on a flat roof, from the ground snow load for the site.
- Snow Drift Surcharge at a Roof Step or Parapet (ASCE 7 Ch. 7) Carpentry and Construction - The triangular surcharge that collapses lower roofs, which the flat-roof snow-load never adds.
- Roof Rain Load and Secondary-Drainage Flow (ASCE 7 Ch. 8) Carpentry and Construction - The load that collapses flat roofs: standing water at the blocked-primary case.
- Trapped Ceiling-Cavity Water Load and Collapse Screen Water Damage and Mold Restoration - The distributed load (a foot of water is 62.4 psf), total weight.
- Wind Velocity Pressure Carpentry and Construction - The wind pressure on a wall or roof at a design wind speed.
- Wood Structural Panel Opening Protection Takeoff Carpentry and Construction - Before a hurricane every hardware store sells out of plywood.
- Manufactured Home Diagonal Tie-Down Anchor Count Carpentry and Construction - Manufactured homes are the housing most damaged by wind.
Debris management
- USACE Hurricane Debris Estimating Model Carpentry and Construction - Before a single truck rolls, a county has to estimate how much debris a hurricane left.
- FEMA Building and Contents Debris Estimate Carpentry and Construction - A debris estimate for a street of destroyed houses, a mobile home park.
- Demolition Debris Weight Carpentry and Construction - Tons of debris and recommended dumpster size by structure type.
- Debris Management Site Acreage and Volume Reduction Carpentry and Construction - Storm debris goes first to a temporary site where it is stacked, sorted, ground, or burned.
- Brush Chip Volume and Haul Loads Agriculture and Forestry - Loose chip volume and the number of chip-truck loads from the green weight of the wood.
- FEMA Debris Load Ticket Eligible Cubic Yards Trucking and Logistics - Debris haulers are paid by the cubic yard on a load ticket.
- Dump Truck Governing Payload and Load Count Carpentry and Construction - Whether the box volume or the legal weight limit fills the truck first, and the load count.
- Haul-Cycle Production and Fleet Match Carpentry and Construction - Truck cycle time, loads per hour, single-truck and matched-fleet production.
- Wheel-Loader / Excavator Bucket Production Rate Carpentry and Construction - Loose-yards-per-hour a wheel loader or excavator digs and dumps from the rated bucket capacity, fill factor.
- Roll-Off Dumpster / Haul Count Carpentry and Construction - Turns a demolition debris volume and weight into a haul count, where either the box volume or the weight cap governs.
- FEMA Hazardous Tree, Hanger, and Stump Screen with Extraction Volume Agriculture and Forestry - After a storm, tree crews on public property work to FEMA's thresholds.
- Stump Grinding Volume, Chip Yield, and Backfill Agriculture and Forestry - THE GRIND IS WIDER THAN THE STUMP, and estimating on the visible diameter is where the job goes wrong before it starts.
- Timber Cruise (Doyle / Scribner / International 1/4) Agriculture and Forestry - Board feet per log by Doyle, Scribner Decimal C (Koch table, by diameter and length), or International 1/4.
Relief logistics, shelter, and temporary housing
- Relief Commodity Demand and Truckloads Trucking and Logistics - The first logistics order after a disaster is water, meals, ice, and tarps by the truckload.
- Points of Distribution Lanes, Types, Staff, and Footprint Trucking and Logistics - A point of distribution is a drive-through, and its capacity is set by lanes, not by the commodities it holds.
- Pallet Cube and Trailer Loadout Trucking and Logistics - Pallets per trailer by floor area and weight, cube fill, cube-out vs weigh-out.
- Dock Door Count from Arrivals and Turn Time Trucking and Logistics - Converts trucks and turn time into door-hours and a door count at a practical utilisation.
- Storage Position Count and Cube Utilisation Trucking and Logistics - Counts pallet positions from the module pitch and bay layout, then divides occupied cube by building cube.
- Congregate Shelter Capacity and Sanitation Cross-Trade Utilities - A school gym becomes a shelter overnight, and the facility crew needs to know how many cots fit and how many toilets.
- Building Occupant Load from Area and Use (IBC Table 1004.4) Carpentry and Construction - The one number the whole life-safety chain hangs on.
- Minimum Plumbing Fixtures by Occupancy (IBC Table 2902.1.1) Carpentry and Construction - The minimum water closets, lavatories, drinking fountains.
- Heat Stress (WBGT and Heat Index) Cross-Trade Utilities - Heat index, WBGT estimate, and OSHA-style work / rest cycle.
- Storm Safe Room Occupant Capacity Carpentry and Construction - A tornado safe room packs people at 5 sq ft each and a hurricane safe room gives them 20.
- Temporary Housing Park Service Demand Electrical - After a large disaster, displaced households live in travel trailers and manufactured housing units on group sites.
Buildings in an outage and restoration
- Building Temperature Drift in a Heating Outage HVAC - When the power or the gas goes out in a winter storm, the question for an occupant, a building manager.
- Whole-Building Heat-Loss Coefficient UA HVAC - The whole envelope rolled into one number a degree-day estimate and a balance-point calc both start from.
- Water Pipe Freeze Time Plumbing and Gas - Frozen and burst pipes are the most common damage in a winter outage.
- Freeze-Protection Heat-Trace Cable and Circuit Plumbing and Gas - The heat-trace cable and wattage a run needs to stay above freezing.
- Walk-In Cooler Outage Holdover and Dry Ice HVAC - When a storm takes out power to a restaurant, a grocery, or a food bank's walk-in.
- Walk-In Cooler Heat Load HVAC - Box load = transmission (U x area x deltaT) + infiltration + product + internal, times a safety factor.
- Carbon Monoxide Alarm Requirement and Count (IRC R311) Carpentry and Construction - Where carbon monoxide alarms are required -- and where, unlike smoke alarms, they are not.
- S500 Class-of-Loss Screen by Wetted-Surface Fraction Water Damage and Mold Restoration - Turns a wetted-surface field read into a candidate IICRC S500 Class of water intrusion.
- Dehumidifier Sizing Water Damage and Mold Restoration - Required pints per day by AHAM and field methods.
- Drying-System Balance (Installed Dehu vs Evaporation Load) Water Damage and Mold Restoration - Checks whether the installed dehumidification keeps up with the estimated evaporation load.
- Antimicrobial Mix and Coverage Water Damage and Mold Restoration - Concentrate and water split, per-tank dose, and tank fills from area, label coverage, and dilution (oz/gal or 1:N).
- Category 3 Loss Disposal Volume, Containers, and Routing Water Damage and Mold Restoration - The waste stream a Category 3 loss produces.
- Mold Remediation Scope by Area Water Damage and Mold Restoration - EPA / NYC DOHMH remediation level, containment, PPE tier, and clearance from affected square footage.