By Mike DeNardo

PHILADELPHIA (CBS) – We could know by tonight whether the school district’s blue collar workers will ratify an agreement on concessions that the union says will save jobs.

Some 2,700 school district building engineers and mechanics are voting by mail on a tentative agreement on concessions that the union says will save jobs.

Without the deal, reached July 11th, the cash-strapped school district was set to begin laying off union workers on July 15th. The district has said it needed to save $50 million by modernizing custodial and maintenance expenses. Terms of the deal haven’t been released.

The mailed-in ballots from members of 32BJ, Local 1201 are being counted today by the American Arbitration Association.

Should the rank and file ratify the agreement, it would then go before the School Reform Commission.