Small Employer, Requirements For ObamaCare?

One of my colleagues from a small city (considered a small employer) asked me if they are required to offer insurance to an employee who works over 30 hours per week. I did not know the correct answer because Mankato is a large employer and I have not had to look into small employer requirements.

This city currently offers its full-time employees insurance through the city but they have a worker, who was hired as part-time, working over 30 hours per week. Is the city required to offer this employee health insurance even though they are considered to be a small employer?

I personally recommended that they should, based on a standard of fairness, but as I looked into it, they may not have to offer insurance. The information on large employers is easy to understand but the small employer information tends to be less clear. This subject has my interest now and I would really like to know the answer.

Thank you for your time.