How to choose a civil engineer?

[Forrest Shealy]

This will be my first time needing a civil engineer, or any engineer. I will mostly need them to overcome some challenges getting sewer service to the property. It is a basically flat property with good drainage and we are using a standard size steel frame construction, so the other questions should be easy. It is only a 6000sf building and affordability is and affordability is a major concern. How do I choose? What questions should I ask? 

I understand I will have to spend money, but I want to know if these sewer issues push us over budget or just eat the margins, before we spend too much.

Thank you!