Depends on the company. Some companies require 3.0, some 3.2, some 2.5, some 3.5, some no requirement. Some take students after freshman year of the curriculum (aka the student has taken calc 1-2, some physics, etc.); some prefer students after junior year, when they’ve taken most of the classes in their major.
For informational purposes, you could look up civil or environmental internship postings on Indeed or Monster (two job-search websites) and see what companies are looking for.