Dust Control Calculator

This calculator estimates how much water an unpaved construction site needs each day to keep fugitive dust suppressed, starting from an EPA AP-42-informed base application rate of 0.5 gallons per square yard per pass. That base rate gets scaled up by a wind factor — emissions from unpaved surfaces increase disproportionately with wind speed, so the model raises (wind speed / 10 mph) to the power 1.3 relative to a 10 mph baseline, meaning windier sites need noticeably more water per application, not just proportionally more. Separately, an evaporation factor combines temperature and humidity relative to a 75°F/50% baseline (higher temperature and lower humidity both speed drying) to determine how many applications per day are needed, rounded to a whole number and capped between 1 and 8. Water per application is area times the base rate times the wind factor; multiplying that by the number of daily applications gives the Daily Water Needed figure, which then rolls up into a monthly estimate (assuming 22 working days) and a rough cost at $0.005/gallon bulk water pricing, plus how many 4,000-gallon truck loads that represents per day.

Because wind and evaporation factors compound multiplicatively, a hot, dry, and windy day can require dramatically more water than the defaults suggest — don't assume a linear relationship between conditions and water need. The target soil moisture output (3–5%) is a simple three-tier lookup based on humidity alone and is a suppression-effectiveness reference, not a measured value from your site — real soil moisture depends on soil composition and depth, which this calculator can't see. It also doesn't account for traffic volume, surface type, or dust palliatives/binders, which can substantially reduce water needs; treat this as a planning estimate for water trucks and budgets, not a regulatory compliance calculation.