This, I think, was a BIG mistake. Are you saying you did not do ANY on campus interviews (through your career placement office) during your senior year? Most engineers get their first job through on-campus interviews. If I could hazard a guess, I would say that the majority of ChemE graduates had GPA below 3.0, so that threshold should not have been a deterrent.
In addition to the career placement center at your school (mentioned above), I would suggest that you reach out to some of your Chemical Engineering professors at your school who might have industry contacts or know of current openings at various companies. You could try to contact graduates from your ChemE program for possible job openings at their company, can provide job leads at other companies or are willing to “hand deliver” your resume to hiring managers (engineering) at their company.