No. It is required by the FMCSA.
Yes
You'll fail a drug screening with ANY detectable amount of THC in your system.
In order to get a Commercial Drivers License (CDL), you must first have a valid drivers license. Then you must pass the CDL test which includes the general knowledge exam and the driving test. You will also have to pass a medical exam and drug screening test. Once you pass all the tests you will have to pay for the actual CDL, which can cost between $25 to $100.
You can get a CDL. But no company is going to hire you with that on your record. While it is possible for someone with a felony to get a CDL job (albeit difficult), drug convictions and violence convictions make you untouchable.
No amount of water can mask or clean a drug screening.
does workers comp require a drug screening upon injury
It cannot be detected in any drug screening. :) There is no test that can detect it.
Yes
Synthetic urine, also known as Agent X is detectable in a DOT drug screening. It will show up in a drug testing lab.
It will.
It won't be easy.
The drug screen is a mandatory part of your CDL physical. If you don't take it then, you don't pass your DOT physical, and you won't get a medical card - hence, you don't get your CDL. If you already have a CDL, and you refuse to take a pre-employment drug screen, you don't get hired. If you're already employed as a CDL driver, and you refuse a quarterly or other periodic drug screen, you lose your job, and a big black mark goes on your MVR. If you refuse a mandatory post-incident drug screen... well, welcome to the wonderful world of implied consent. You'll lose your job and your licence.