Gasoline Tanker Rollover with Product Entering a Storm Drain
At 14:10 on a 96°F afternoon, a 4,000-gallon MC-306 cargo tank rolls onto its side on a freeway frontage road after a tire failure. The tank was carrying about 2,800 gallons of unleaded gasoline. The top dome cover has sheared, and product is running out at an estimated 50–75 gpm, forming a pool roughly 20 by 30 feet. The pool is moving along the crowned roadway toward a storm drain inlet about 60 feet away; the drain discharges to a bayou roughly 900 feet downstream. The driver self-extricated and is walking around, smelling of product. Wind is from the south at 8 mph. Downwind at 150 feet is a strip center with about 40 people in the parking lot, and an occupant is standing 30 feet from the tank smoking. Ambient temperature is climbing, and the tank skin in the sun is hot to the touch. There is no fire.
1. Set the zones and the initial actions for the first five minutes. Be specific about what you do about the smoking occupant, the driver, and the drains.
Read the worked answer
This is a flammable liquid release with an ignition source already present and a pathway to a waterway, which makes it a defensive, isolate-and-contain operation from the first minute.
Isolation and zones. Gasoline is heavier than air (vapor density roughly 3–4) and its flammable range is about 1.4–7.6% by volume, so the vapor travels along the ground and collects in the drain and any low spot. ERG Guide 128 sets the initial isolation at 50 m (150 ft) for a small spill and 300 m (1,000 ft) for a large spill; a tanker with a sheared dome losing product at 50–75 gpm into a storm drain is a large spill, so I establish a 1,000-foot initial isolation in all directions and a protective action distance downwind on the order of half a kilometer - and I confirm it against the current ERG green-table pages rather than trusting memory. The strip center at 150 feet downwind is inside the isolation and gets evacuated, not sheltered.
Order of actions:
- Kill the ignition sources first, starting with the smoker. One person with a cigarette inside the vapor envelope is the single highest-probability cause of a mass-casualty event on this scene. This is a verbal command from a distance with a loud hailer if possible, escalating to a police escort out - nobody walks into the hot zone to tap him on the shoulder. Traffic is stopped, engines off, no apparatus driven into the vapor area.
- The driver becomes a patient, not a bystander. He is saturated with product, which means his clothing is a vapor source and a burn risk. He is moved upwind, clothing removed and bagged, and he is decontaminated and transported for evaluation. Gasoline exposure plus a hot day also carries a hydrocarbon aspiration risk if he vomited.
- The drain. The drain inlet is the highest-consequence pathway on the scene. A plug, a boom, or a temporary dam built from dirt, sand, or a salvage cover and weighted with anything available stops the product from reaching the bayou. If product has already entered, containment booms go downstream, and the wastewater and bayou authorities are notified immediately, not after the fire is out.
- No entry to the tank, no attempt to right it, no patching by fire crews. Ops-level response is defensive: foam, containment, and turning the scene over to the responsible party and a hazmat contractor.
Zones: hot zone to the 1,000-foot isolation, warm zone for decon at the upwind edge, cold zone for command, EMS, and staging upwind and uphill.
2. You are an operations-level responder at this scene. What PPE and extinguishing agent do you commit, and what will you not do?
Read the worked answer
The PPE answer has to be tied to what the product actually threatens, which here is vapor exposure and flash fire, not corrosivity or toxicity at a level that demands fully encapsulating suits.
PPE: Level B - SCBA with a positive-pressure facepiece, plus chemical-protective clothing with flash and fuel resistance (a turnout coat over chemical splash garments is a common field compromise, but the correct choice is a garment rated for both), chemical-resistant gloves, and chemical boots. Structural firefighting turnout gear alone is not chemical-protective clothing against a gasoline soak. Level A is not indicated: gasoline is not a gas that requires vapor-protective encapsulation, and Level A in a Houston afternoon creates a heat-stress casualty faster than the product creates a chemical casualty. The PPE decision must include a rehab and work-rest cycle: at 96°F ambient, a Level B responder in the sun has a very short safe work window.
Agent: fluorine-free foam (or AFFF where that is what the department carries) applied as a blanket over the pool. For gasoline, the application rate runs on the order of 0.10 gpm/ft² for a hydrocarbon - a 20×30 pool is 600 ft², so roughly 60 gpm of foam solution, well within one or two handlines with an air-aspirating nozzle. Foam here does two jobs: it suppresses vapor generation, which reduces the flammable atmosphere, and it buys time to get the drain plugged. Water alone without foam would spread the product.
What I will not do:
- I will not attempt to stop the leak at the dome, plug the shell, or right the tank. That is a technician-level task and a tank under load.
- I will not apply foam into the storm drain. It does nothing useful and pushes product downstream.
- I will not let a crew work the pool edge without a charged backup line and a clear escape route, and I will not run an apparatus through standing product.
- I will not declare the scene stabilized because the pool stopped growing; the drain and the bayou are the exposure until booms are confirmed.