*** edit *** I missed part of the questions.
Depending on what your company policy it might be better to call a lawyer. If you single someone out you can set your self up for a lawsuit.
It might be better to do 100% on site test and after the testing have everyone sign an updated drug policy. On site testing for 12 people would run about a grand where I’m at.
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If there is a suspicion of drugs or alcohol someone off our safety staff will drive them to the local drug testing offices. It's best to do a random test and uses something like everyone with a 5 in there SSN and make sure the person in question is in the group.
Every few months at the morning meeting we will draw names and take a van full to get tested.
If needed we have the testing company come to our office and test everyone in office.
If someone test positive they do a second round of testing on the spot. Both samples are sent to a second lab for more testing. It takes 7 to 10 days to get the results back and they go on paid administrator leave for this time. If they are positive they are fired.
If someone turns them self in then rehab. After rehab they can come back to work, but some kind of random drug testing system will be in place for them. I have been though this once and it was a pain in the butt.
Anyone that is taking something that will show up on the drug test then they have to go to our company doc, before they can go back to there normal job. We do offer office jobs to these people till they get into the company doc and it's normally takes about half a day. We also offer office jobs to people with colds taking over the counter drugs if needed.
With our insurance we are required to test a % of office staff, CDL holder, heavy equipment operators, and maintenance.