this sub-contract in accordance with instructions from defendant's superintendent, the plaintiff notified defendant when plaintiff came upon rock excavation for which a claim for payment would be made. Upon such notice the defendant prime contractor then sent its own Registered Surveyor to make the necessary measurements. This was done in this case. Under the procedure agreed upon, defendant would then notify plaintiff of the quantities so measured so that plaintiff could bill defendant for the amount so excavated. This was never done because the records were destroyed. This same certification was the basis upon which defendant would make its claim for payment to the Government.
The defendant's Registered Surveyor hired for this purpose was Mr. Aires. Upon plaintiff's requests he came to the excavation site and made the necessary measurements and computations. Mr. Aires was hired and paid by defendant and was defendant's agent under defendant's prime contract with the Government.
Before Mr. Aires could make the computations of quantities and transmit them to plaintiff his records were destroyed by fire. Without these measurements the Government has refused payment to defendant. Defendant refuses to pay plaintiff for the amount of excavation claimed by plaintiff under the proofs that plaintiff is able to submit for the reason that plaintiff cannot submit it to the computation and certification of quantities by a Registered Surveyor under the same terms and conditions required of defendant in submitting such claim to the Government.
Defendant relies on the language of the sub-contract that plaintiff sub-contractor assumes the same duties to defendant prime contractor as the prime contractor assumed to the owner, the United States.
We do not read the prime contract between defendant and the Government as allowing the defendant to pass on or sublet the duty of defendant to hire a Registered Surveyor to compute and certify quantities of excavation for payment. The contract requires the defendant to do this as a condition of payment by the Government. The defendant in turn under the sub-contract could require the plaintiff, its sub-contractor, to provide the same type of proof in support of its excavation claim, but in actual practice the parties in carrying out the sub-contract relied upon the measurements and certification to be made by defendant's Registered Surveyor.
We find that there is an ambiguity between the terms of the general contract between defendant and the Government, which places the responsibility for measurement and certification upon the Registered Surveyor hired by defendant, and the terms of the sub-contract which requires the sub-contractor to satisfy the same requirements as are imposed on the general contractor. In the face of such ambiguity we may turn to the practice of the parties in carrying out the sub-contract as the best guide to the intention of the parties. Aetna Casualty & Surety Co. v. United States, 365 F.2d 997 [8th Cir., 1966]; Nassif et al. v. United States, 187 F.2d 794 [1st Cir., 1951]; Pittsburgh Railways Co. v. Equitable Life Assurance Society, 198 F. Supp. 602 [W.D. Pa., 1960], affd. 288 F.2d 640 [3rd Cir.].
A clause in a sub-contract incorporating the prime contract into it, does not require the sub-contractor to act in place of the contractor in all areas. The Government does not recognize or deal with the sub-contractor, and the sub-contractor is only required to perform its obligation to the prime contractor. United States for Use of B's Co. v. Cleveland Electric Co., 373 F.2d 585 [4th Cir., 1967]; John A. Johnson & Sons v. United States ex rel. Bal. Brick Co., 153 F.2d 534 [4th Cir., 1946]; Fanderlik-Locke Co. v. United States for the Use of Morgan, 285 F.2d 939 [10th Cir., 1960].
Plaintiff testified that the instructions to call upon defendant to do the survey work were received from Mr. Gordon Sutherland, defendant's superintendent on the job. Mr. Sutherland also instructed him to excavate all trenches to a five foot width despite the Government's limitations of paylines in the prime contract.
It is clear here that both parties treated the sub-contract as not imposing upon plaintiff any separate obligation to make independent rock measurements. Defendant sent its own Registered Surveyor to make the measurements. This is a construction of the contract accepted by both the defendant and the plaintiff at the time. It was defendant who prepared the sub-contract. In case of any ambiguity as to its meaning the contract should receive the interpretation against the party who has drawn it. United States Aviation Underwriters Inc. v. WTAE Flying Club, 300 F. Supp. 341 [W.D. Pa., 1969].
Defendant's conduct in sending its Surveyor to make the measurements at the request of plaintiff also amounts to a subsequent oral modification or a waiver of the condition upon which defendant now relies. Even though a written contract provides that it can only be modified in writing it may be modified by subsequent oral agreement of the parties, or conduct which constitutes a waiver of the condition. Universal Builders, Inc. v. Moon Motor Lodge, Inc., 430 Pa. 550, 244 A. 2d 10 . Where a party is aware that extra work is being done without proper authorization, yet he stands by without protest while the extra work is being incorporated into the project, there is an implied promise that he will pay for the extra work. Universal Builders, Inc. v. Moon Motor Lodge, Inc. supra. The evidence here shows that defendant recognized its obligation to supply plaintiff with the measurements by assurance that they would be supplied when received from the surveyor.
We, therefore, hold that it was not a condition of payment that plaintiff supply an independent certification of measurement. All that is required is that plaintiff supply adequate proof in support of his claim for the amount of rock excavated.
Defendant insists that its obligation to pay rests upon a condition that the amount excavated be certified by a Registered Surveyor. Following the practice adopted by the parties, plaintiff called upon the Registered Surveyor employed by the defendant under the provisions of defendant's prime contract with the United States. This surveyor made measurements, but because of a destruction of his records is now unable to certify all of the quantities. This should not defeat plaintiff's right to recover.
Sec. 303 provides:
"Where a certificate of an architect, surveyor or engineer is a condition precedent to a duty of immediate payment for work, the condition is excused if the architect, surveyor or engineer
(a) dies or becomes incapacitated. * * *"