I do not know how civil engineering is at your school, but many programs have students concentrate in some sort of subfield, such as transportation or structural, etc..
If your school has an environmental option or a water/hydrology option, these may be good ones for a pre-med student. Often times such concentrations have classes such as organic chemistry or microbiology as options (I know my school has those classes listed under the environmental option, as well as the hydrology option).
If your school does not have such concentrations, they may allow you to customize your own. You don't have to tell them you are pre-med, but you can say something about environmental or water stuff (ie. organic chemistry, microbiology, and molecular biology are good classes for water treatment stuff or air quality/purification)
I spoke to a civil engineering advisor and she said that she knew a few students who went to medical school from civil engineering, and actually felt it was beneficial to them (one student said that her fluid mechanics courses helped her a lot when learning about the circulatory system)