According to your case, you have the right to cancel this agreement because the performance of the contract is based upon permission of the forest department for initiation of work. However, tender is issued and completed according to the law but at that time it might be presumed that the forest department may give permission so no saving clause was included in the contract.
This contract is frustrated because not getting permission from the forest department. Section 56 of the Indian Contract provides a right to cancellation of the contract on the ground of frustration. Frustration is an act outside the contract due to which the completion of a contract becomes impossible.
After the parties have concluded a contract, events beyond their control may occur which frustrate the purpose of their agreement or render it very difficult or impossible, or as even illegal, to perform. You should take a plea of frustration because permission from the forest department is an event which is out of your control. And permission was a sine qua non for the performance of the contract.
In Nirmala Anand vs. Advent Corporation Pvt. Ltd AIR 2002 SC: it is held by the supreme court that the competent authority has been moved and application for consent or sanction have been rejected once and for all and such rejection renders impossible the performance of the contract due to frustration under section 56 contract act. The relief must be given to the party and keep them in the same position as they were before the contract.
When a contract becomes impossible to perform due to its frustration then it cannot be enforced by the court. You shall not be liable to pay any compensation.