modified the original agreement. The modification required Empire to pay for the blasting
work on a time and materials basis for the remainder of the project. Rock Services,
thereafter, completed its work on the project.
Upon completion of the work, Empire refused to pay Rock Services for the remaining
balance due on the time and materials agreement in the amount of $58,686.63, and Rock
Services instituted this action. The trial court concluded that the later purchase order was a
valid and enforceable modification of the earlier contract. The trial court found that the
parties intended the purchase order to modify the earlier agreement and that Empire’s
assent to the modification was not made under duress but, rather, was a calculated business
* * *
In concluding that the modification was valid and enforceable, the trial court
determined that the later agreement was supported by sufficient consideration. * * *
“The doctrine of consideration is fundamental in the law of contracts, the general rule
being that in the absence of consideration an executory promise is unenforceable.”
[Citation.] While mutual promises may be sufficient consideration to bind parties to a
modification; [citations] a promise to do that which one is already bound by his
contract to do is not sufficient consideration to support an additional promise by the
other party to the contract. [Citations.]”
“A modification of an agreement must be supported by valid consideration and requires
a party to do, or promise to do, something further than, or different from, that which he
is already bound to do. [Citations.] It is an accepted principle of law in this state that
when a party agrees to perform an obligation for another to whom that obligation is
Our Supreme Court in [citation], however, articulated an exception to the preexisting
duty rule: “‘[W]here a contract must be performed under burdensome conditions not
anticipated, and not within the contemplation of the parties at the time when the contract
was made, and the promisee measures up to the right standard of honesty and fair dealing,
and agrees, in view of the changed conditions, to pay what is then reasonable, just, and fair,
such new contract is not without consideration within the meaning of that term, either in
law or in equity.’” * * * “‘What unforeseen difficulties and burdens will make a party’s
refusal to go forward with his contract equitable, so as to take the case out of the general