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Yes. If it requires a tanker with an unrestricted CDL, so it does with a permit, as well.
They require a tanker endorsement, and most commodities they haul also require the driver to have a hazmat endorsement.
Yes. No differentiation is made between liquid and dry bulk tankers in this regard.
You will need a Class B CDL with tanker endorsement.
Yes. Tank trucks require a tanker endorsement, and the tanker endorsement can only be put onto a CDL. A permanently mounted tank requires one (the regs don't specify a minimum capacity), as do portable tanks of more than 1000 gallons.
Any tank vehicles, or anything defined as a portable tank with a capacity of greater than 1000 gallons.
There is no such thing as an air brake endorsement on any US license, CDL or otherwise. Only a restriction for CDL holders if they don't complete the written air brakes test and perform their pretrip and road tests in a CMV equipped with air brakes, which prohibits them from operating a vehicle requiring a CDL which is equipped with air brakes.
You would need the N (tanker) and H (hazmat) endorsements. Most states issue an X endorsement as a combination of N and H.
Yes. You'll need the CDL of a class appropriate to the vehicle being operated, a tanker endorsement, and a hazmat endorsement. 300 gallons puts you well past the 1000 lb. threshold for not needing one.
Yes. You need a CDL and a hazmat endorsement both. You're well above the allotted amount which can be transported without the tanker and hazmat endorsements.