Water Shuttle Operations, Dump Site Selection, and Large-Volume Water Movement
Cycle time drives everything
A water shuttle moves water by repeating a cycle: fill, travel loaded, dump, travel empty, and reposition. Total cycle time includes all five elements. A tender's effective delivery rate is tank volume divided by cycle time. The number of tenders needed is the required fire flow divided by each tender's effective rate, rounded up.
Dump site selection
Place the dump site as close to the fireground as safe access allows, but keep it out of the immediate hazard area and clear of fireground apparatus movement. The site needs a large firm area for portable tanks, turn-around room, overhead clearance, drainage control, and room for the drafting pumper. A water shuttle officer tracks cycle times, tank levels, and radio traffic.
Worked example
A 2,000-gallon tender fills in 5 minutes, travels loaded in 8 minutes, dumps in 3 minutes, travels empty in 6 minutes, and spends 2 minutes positioning. Cycle time = 5 + 8 + 3 + 6 + 2 = 24 minutes. Effective rate = 2,000 / 24 = 83 gpm per tender. For a required 500 gpm, 500 / 83 = 6.0, so six tenders are needed. Reasoning: travel distance alone is not cycle time; fill, dump, and positioning must be counted.
Traps
Do not use tank size as usable water without allowing for residual water and vent limits. Do not ignore setup time at both sites. Do not place the dump site where tenders must back into traffic. Do not calculate tenders from one-way travel time only.