If you enter US from any

conjoint land by driving (not flight, boating, walk), you can use the valid I-94 to enter US within 30 days for reenter. However, sometimes, Canadian Immigration may ask you to surrender your I-94 as exchange for accepting the your landing inquiry. If you were in a case like this, you would go back to US immigration side at the same day before 8:00 pm and ask US officer to replace your I-94. Canadian Imm supposed to send your surrended I-94 back to US before the end of the day.