Is it legal for my employer to take a percentage of my prevailing wages for health care costs?

I work for a company that has two type hourly rates. One is a base wage and the other is prevailing wage. Prevailing wages typically pay twice as much as the base wage. The type of wage is determined by the type of contract the company bids on and wins. All of the employees come out of the same pool. Some will end up on a base wage type of job and others on prevailing wages. This can be for different reasons such as proximity to the job or who is available at the time. My employer pays 100% of my medical/dental when I am on a base wage job. However, if I go on prevailing wages, my employer takes a percentage of my wages and the cost out of my pay check is very high (a few hundred dollars a month). Is it legal for my employer to purchase group insurance at a fixed cost yet charge me a percentage of my prevailing wages and make me pay more than when I am making a base wage?
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part of receiving "prevailing wage" is the employee accounting for all there own benefits. prevailing wage is set for government contracts and government funded projects and is based on the average wage in the area for the type of employment and it requires that benefit cost be added as well even though by law the employer does not have to pay benefits. that is why you make the higher wage but must pay for the benefits. the contract is set for a certain cost for labor due to prevailing wage but the employer is not expected to pay that benefit cost them self. YOU the employee is being paid accordingly so that you can pay for the benefits. for info on prevailing wages and how they work see this site: http://www.dol.gov/compliance/topics/wag…
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