Davis Bacon testing concerns

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I am working on restating 2 Documents for a client. One Plan is a 401k Plan that excludes all employees performing work covered by Davis Bacon Contracts. The other Document is a Prevailing Wage Plan that excludes all classification of employees other than those covered byt the attached Davis Bacon Contract.

Question

1. It sounds to me that the 401k Plan is excluding all employees from the Davis Bacon Plan? The former TPA states no that they are excluding compensation made with the Davis Bacon Plan.

2. Doesn't 410b need to be done? If so for each Plan excludinig each classification? If compensation was excluded shouldn't 414s test be performed?

Any other thoughts?