Checked the BOCW Act , there is no specific provision for medical check up of workers under the Act. However, there is a general clause that under Section 40, the appropriate government can make provision for:
(t) maintenance of medical facilities for building workers; &
(u) any other matter concerning the safety and health of workers working in any of the operations being carried on in a building or other construction work.
So it has to be checked up with each state rule on the position in this regard.
But by the way, why not free regular medical check up every year of all workers at your project sites as part of your social responsibility. The benefit would far outweigh the meager cost involved in it. Moreover it will show your genuine labour welfare concern for the poorest section of society.