I work in an area and industry which has historically blurred overtime vs exempt status. I was hired as a "Project Manager", salaried, to review reports, supervise (technician) employees, and provide technical oversight. I was told that "ocassionally", if specific problems arose in my area of expertise, I might have to visit project sites to provide professional assistance. Fine.
As it turns out, over 75% of my daily work assignments are low-level assignments covering tasks that would, and could, normally be handled by hourly employees. My days are often 12 or more hours, and significantly more physically demanding than advertised. Other exempt employees are routinely used in the same manner. Corporate HR is NOT an option, and outright complaints are generally answered with "everybody has to do this".
At my age, finding new employment is an extremely risky venture, but the job I am performing is NOT now, or likely to be, the one I agreed to; and it is wearing on me, particularly physically. Do I have any viable options?

You are free to contact the DOL and discuss the classification of your position.

Also, just to be clear, there are something like 100 or so exceptions to overtime or minimum wage in the FLSA law. These exceptions are a function of job duties and sometimes the industry.The OPs question was worded in such a way as to not be clear which specific Exempt exception was being discussed. No job duties or industry was mentioned. Other employees were discussed, even though legally each employee's Exempt status legally stands alone. I am not saying that the OP should not contact DOL, but they would get better results if the question was a lot more tightly focused. IMO, very general questions that do not really say anything tend to get very general answers that also do not say anything in response.

I am going to include a pointer to the so-called White Collar (http://www.dol.gov/esa/whd/regs/compliance/fairpay/main.htm) exceptions. This group of 5 or so exceptions is one of the more common groups. There is no certainty that the employer is using one of these classifications, but it is a good starting point.

If I was going to try to claim that I was not Exempt, I would be likely to get a better result if the argument I made bore some relationship to the actual classification rules.

The field is construction engineering and inspection. I believe the exempt status (how would I find out?) is in the "technical or professional expertise" area, but that is not what the job assignments involve.

Your starting point is to read the White Collar exception rules. Have you?

Your employer is allowed to pick any of Exempt classification they feel they can support. You need to at least briefly read the rules I cited and see if a reasonable person could support you as falling under one of those exceptions. This is going to take some actual work on your part. You will need to make a list of all of your actual duties with an estimate of what percent each duty takes each week. If you later want to file a wage claim or court action, you need to basically be able to show that whatever Exempt classification your employer chooses fails to cover your actual job duties.

And no one on this website has physic abilities that will tell us what Exempt classification your employer will claim. Which is why you need to make your list of actual job duties and why you need to read the rules for the White Collar exceptions.