First-Arriving Placement at a Four-Story Residential Over Commercial
At 0312 you arrive alone as the first engine on a reported smoke investigation at a four-story building, 48 feet tall, apartments over a ground-floor restaurant. The building faces A Street. You approached eastbound on A Street, which is one-way eastbound. B Avenue, one block west, is one-way northbound. The next cross street east is 3rd Street. A working hydrant sits on A Street at the corner of B Avenue; the hydrant on 3rd Street is bagged out of service. The front setback from curb to building is 30 feet. A 20-foot-wide rear alley runs behind the building, but overhead wires cross it at 18 feet. Smoke is showing from a second-floor window on the A Street side. A truck company is two minutes out with a 100-foot aerial; its outriggers need 16 feet of width and a clear working arc. Civilian traffic is light.
1. Where do you position the engine, and what do you do first with the hydrant? Justify each with the details given.
Read the worked answer
Engine placement. Spot past the building on A Street, eastbound, leaving the frontage directly in front of the building open. Two details drive this:
- A Street is one-way eastbound, so the truck must approach from the west and travel east. Any apparatus parked in the block west of the entrance can block that approach.
- The smoke is on the A Street side, so the front of the building is the working side and the spot that the aerial will need.
Hydrant. Take the A Street hydrant at B Avenue. The 3rd Street hydrant is bagged out of service, so it is not a backup, and the B Avenue corner is the closest confirmed working supply. Lay supply line from that hydrant rather than drafting or relying on the booster tank.
Why not the alley? The rear alley is the obvious second choice, but the wires at 18 feet cross it. A 48-foot building needs the aerial raised over the roof line, and the alley does not give the clear arc the outriggers and boom require. Keep the alley open as a hand-line and egress route instead.
2. The truck officer asks by radio whether the aerial can be set in the rear alley. Answer with the numbers.
Read the worked answer
Answer: no. Set the aerial on A Street, front of the building.
Alley problems, in order of severity:
- Wires at 18 feet. The aerial must reach above 48 feet. Raising the boom in a 20-foot-wide alley crossed by wires at 18 feet puts the boom through the wire envelope before it clears the roofline.
- Outrigger width. The rig needs 16 feet of spread in a 20-foot alley. That leaves 2 feet on each side, with no margin for the boom's working arc and no room for a second rig to pass.
- Working arc. The requirement is a clear 35-foot arc. The alley does not provide it.
Front placement math. Setback is 30 feet, building height 48 feet. The boom length needed is the hypotenuse: square root of (48 squared + 30 squared) = square root of (2304 + 900) = square root of 3204, about 56.6 feet. A 100-foot aerial covers that with margin. Outriggers need 16 feet, which fits in a closed traffic lane on A Street with light traffic.
Conclusion: front of the building on A Street, west of the entrance so the truck approaches eastbound, outriggers into a closed lane.
3. What single fact, if it changed, would most change your answer about the alley?
Read the worked answer
The wires. If the wires crossing the alley at 18 feet were confirmed de-energized and moved, or confirmed as de-energized service drops that could be cut by the utility, the alley plan gains a serious advantage: it puts the aerial on the side away from the collapse zone and away from the A Street window that is showing smoke.
Why this beats the other possible changes:
- Building height dropping below about 30 feet would help, but smoke is already showing at the second floor on a 48-foot building, so the height is not going to be revised downward.
- The 3rd Street hydrant coming back in service changes supply, not aerial placement.
- More civilian traffic would make the A Street lane closure harder, but the alley would still be unusable.
Reasoning pattern the exam rewards: identify the binding constraint, then ask which single input, if altered, releases it. Here the binding constraint on the alley is the overhead wire envelope, not the pavement width. Width rules out a comfortable setup; wires rule out the setup entirely.