Is paying two Riyals per ton to the site manager in exchange for concluding a quarry waste sale contract considered a bribe that incurs a warning of punishment, knowing that it was a condition for the completion of the contract and not sought by the payer?

It is not permissible for a company employee to stipulate something for himself to complete a contract without the knowledge of his company, because that is a forbidden bribe, according to the saying of the Prophet (peace and blessings of Allah be upon him): "The Messenger of Allah (peace and blessings of Allah be upon him) cursed the one who gives a bribe and the one who takes it." Therefore, it is not permissible to pay this amount to the employee or to accept contracting for works he obtains in exchange for this bribe, because it is cooperating in sin and aggression, and consuming wealth unlawfully. You have the right to report him to the company owner.