You don't have to tell; they cannot legally ask.
Employees are eligible if they have worked for their employer for at least one year, and for 1,250 hours over the previous 12 months, and if there are at least 50 employees within 75 miles. -
U.S. Department of Labor
The above probably applies to your agency, not your assignment. Be careful- are there 50 employees within 75 miles?