You can notify 311 all day long, but they probably won't do anything. When I talked to them, they said they had been told to ignore folks complaining about homeless encampments. According to the policeman I spoke with, letters are the way to get through. If you write a letter to the chief of police, your city supervisor, and the health department, these homeless encampments wil be gone shortly. Just write the same letter three times. Make sure to sign the letter with ink and also hand-write in the address on the envelope. It is a health hazzard to have these folks camping on the sidewalk.

I had the same problem by my house and after over 30 calls/posts to 311, I sent letters and it was solved within 2 days. Good luck!