The Leaking Acid Drum and the Carbide
At a chemical distributor's dock you are handed a shipping paper and a load for a 300-mile run. The paper lists four entries: 1,100 lb of UN 1993, Flammable liquid n.o.s., Class 3, PG II; 600 lb of UN 1789, Hydrochloric acid, Class 8, PG II; 400 lb of UN 1479, Oxidizing solid n.o.s., Class 5.1, PG III; and 5 lb of UN 1402, Calcium carbide, Class 4.3, PG I. All are in non-bulk packages. Nothing has been placarded yet. While checking the load you find white crystalline crust around the bung of one acid drum, a faint sharp odour, and a wet patch at its base. The loader tells you to "just get rolling, it's always like that," and that the carbide can ride on the floor next to the acid because "they're both in drums."
1. Which placards does this load require? Show the reasoning, not just the answer.
Read the worked answer
Four placards: FLAMMABLE, CORROSIVE, OXIDIZING, and DANGEROUS WHEN WET.
The reasoning runs in two steps.
- Table 1 materials need a placard at any quantity. Division 4.3 is on that list, so the 5 lb of calcium carbide alone requires the DANGEROUS WHEN WET placard, no matter how small the shipment.
- Table 2 materials need placards once the aggregate gross weight reaches 1,001 lb. Class 3 (PG II), Class 8 (PG II) and Class 5.1 (PG III) are all Table 2. Adding the package weights: 1,100 + 600 + 400 = 2,100 lb, well over the threshold. When the threshold is met, every Table 2 hazard class present must be placarded - you do not get to pick the two biggest.
So all three Table 2 classes are placarded, plus the carbide. Placards go on both sides and both ends of the vehicle, and the shipping paper must travel with the load, with emergency response information and a 24-hour contact number. If you placard one class you must placard all of them; selective placarding is a violation.
2. What do you do about the acid drum, and why does the carbide placement matter so much?
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The drum does not get loaded, and the carbide does not ride next to it.
- The crystalline crust at the bung is dried acid from a leaking closure; the wet base and the sharp odour confirm it. A leaking package may not be accepted for transport. The shipper must repair, overpack, or replace it before it goes on any truck.
- Calcium carbide plus water produces acetylene gas - flammable, and capable of forming an explosive mixture in a trailer. A leaking acid drum sitting beside it is an acid source and a moisture source in the same place. Even with intact drums, carbide belongs where it stays dry and away from acids and oxidizers.
- The oxidizer and the flammable liquid are also a poor pairing on the same deck; keep them separated and never let anything leak onto a package below.
Practical sequence: refuse the drum in writing, note the condition, notify your company's hazmat contact, and do not attempt cleanup without the right PPE and spill kit. "It's always like that" is a description of a recurring violation, not a release from your responsibility.
3. The run ends at 11 p.m. and the only nearby truck stop backs onto a residential subdivision. What parking rules apply to this load?
Read the worked answer
This load is Class 3, 8, 5.1 and 4.3 - it is not in the Division 1.1/1.2/1.3 or 2.3 poison-gas set that triggers the strictest parking rules, so the general hazmat parking rules govern rather than the 300-ft separation rule. That still leaves real constraints:
- Never park within 5 ft of the travelled portion of the roadway.
- Keep away from people, congested areas, tunnels, bridges and overpasses. A lot backing onto a residential subdivision is the opposite of what you want; find a designated hazmat parking area or an isolated spot in the lot.
- Attend the vehicle. Do not leave it unattended where someone can walk up to a leaking drum.
- No smoking, no open flame, and nothing that can spark anywhere near the trailer, which matters more than usual with a flammable liquid and an oxidizer aboard.
- Local rules can be stricter than the federal ones - in a mountain town, assume they are, and check before you commit to a spot.
And do the obvious thing first: get the leaking drum off the load before you park anywhere near people.