Tanker Shuttle Fill-Site-Limited Fleet Size
How many tankers is enough: past some fleet the water supply stops climbing because the bottleneck is the slowest fixed site, not the truck count. bottleneck = max(tank/fill_gpm, tank/dump_gpm); fleet = ceil(cycle / bottleneck); ceiling flow = tank / bottleneck. A 3,000-gal operation at 1,000 gpm fill and dump over a 2-mile haul needs 5 tankers to reach its 1,000-gpm ceiling; a sixth just queues. Slow the fill to 500 gpm and 3 tankers cap it at 500 gpm - the fix is a faster site, not more trucks. A planning aid, not incident command.
Formula and source
fill_min = tank_gal / fill_gpm; dump_min = tank_gal / dump_gpm; travel_min = 2 x distance_mi / speed_mph x 60; cycle_min = fill_min + dump_min + travel_min; bottleneck_min = max(fill_min, dump_min); fleet_for_max = ceil(cycle_min / bottleneck_min); site_limited_flow_gpm = tank_gal / bottleneck_min.
IFSTA / NFPA 1142 rural water-supply fill-site-limited fleet size, by name.
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