Also, lead is soluble in even a mild acid, and most rainfall contains carbon dioxide and nitric oxide both of which in water solution form acids. Under such conditions, the hygiene and other practices proposed by NRA for indoor ranges are applicable to outdoor ranges. Further discussion of airborne dust is outside the scope of this paper. Water's particulate carrying capacity is proportional to the square of the water's velocity. Clear water moving at 100 feet per minute can carry a lead particle 10,000 times heavier than water moving at a velocity of 10 feet per minute.
Muddy water can carry even larger particles.
The five factors that most influence velocity of runoff are described below and shown on Table 1. Rainfall Intensity . The greater the volume of rainfall during a short period of time, the faster the velocity created to carry the rainfall off-site. The higher the annual rainfall, the greater the number of periods of heavy rainfall. The steeper the topographic slope, the faster will be the velocity of storm water runoff, other things being equal.