I've looked and can't find anything terribly worthwhile. It appears that UC Davis did a study on the effectiveness of water as a dust control measure years ago, and the only people that quote it online is the san juaqin valley air pollution control district. In the PDF (http://www.valleyair.org/busind/comply/ ... Packet.pdf
) published by San Juaqin ... the application rate minimum is quoted as 650 gallons per acre for an unpaved traffic area, with only one application required for under 150 trips per day. Check page 20 of the PDF.
I couldn't believe SWRCB or EPA had anything about application rate.