Modification of contract terms

If during the term of the contract (including contracts which have been executed and are presently in force) there has been a reduction of fifteen per cent or more in the volume of business of the concessionaire for a period of sixty days or more, computed on the average monthly gross income for the eighteen months just prior to the period or as long as the concessionaire has been in the business, whichever period is shorter, and such reduction as determined by the officer letting the contract is caused by construction work conducted during the period of time on, or within or contiguous to, the public property upon which the concession is located by either the state or county governments, or both, the officer, with the approval of the governor in the case of a state officer and the chief executive of the respective county in the case of a county officer, may modify any of the terms of the contract, including the agreed upon rent, for a period which will allow the concessionaire to recoup the amount lost by such reduction; provided that if the contract includes provisions allowing modification for the above contingencies, this section shall not be applicable thereto; provided further that this provision shall not apply to any particular concession if the application thereto may impair any contractual obligations with bondholders of the State or counties or with any other parties.