In the office of the construction company where I work, a construction worker came in at lunch time from a job to fill out some insurance forms. We were not friends but we were friendly. He had been called into the office to fill out the form unexpectedly. He had to ask me a question about an item on the form and I could clearly smell alcohol on his breath. The job he was working on was a six-story building. Immediately I saw the ethical dilemma. We were friendly but the right thing to do was report him in order to prevent injury or death to himself and/or others. I could decide to remain silent and risk his life and others. If I reported him, he would probably lose his job. Drinking or using drugs on the job in construction work is as dangerous as driving a car while drinking.
I do not know his specific job on the construction site, but I tried to imagine a situa