At around 32 minutes in it appears James throws just two vials of drugs into the water however, when the camera shifts to the water it clearly shows three.
At about 3/4 through the movie, when Nicole confronts Kate about James, when Nicole enters, Kate tells her "Employees aren't allowed to be here". However, there are banks of lockers, stating that this is where employees store their personal effects. It's possible Kate meant that employees can't be there during their shift, for security purposes, but Nicole was in street clothes, she'd need access to the lockers if she was going on duty.