The Philadelphia School District has sent layoff notices to more than 1,400 additional members of its blue-collar union, effectively threatening the dismissal of all the men and women who drive buses, clean schools, and keep buildings warm, dry, and operational.

District officials said, however, the number of union employees to be let go was dependent on whether a dispute over contract concessions could be resolved.

Pink slips went out to 1,406 members of Local 32BJ, Service Employees International Union, on Dec. 31. The layoffs are effective Dec. 31, 2012 - by contract, union members require a full year's notice.

Those layoffs are in addition to 848 pink slips sent in September.

It's a sign of the bleakest budget picture anyone can remember.

Even though the district shed thousands of employees and made steep cuts before the current school year began, it has issued hundreds more layoff notices and slashed school budgets by an additional $10 million in recent weeks.

And officials have said the midyear cuts aren't finished.

Spokesman Fernando Gallard said the new 32BJ layoffs, which he characterized as a "difficult decision," were necessary because the union's members rejected a contract extension that contained $16 million in concessions to the district.

"As a result of this rejected agreement, there remains a budget gap that the district must close this year, and the district now anticipates it will face significant budget challenges in the coming years," Gallard said in a statement. "The district is now forced to take other steps to achieve needed savings and to keep all of its options open regarding staffing in future years."

Union leaders have said their members rejected the deal in part because of a payout approaching $1 million given to former Superintendent Arlene C. Ackerman days before the blue-collar workers were asked to make concessions.

District officials have said that layoffs might not be necessary if the concessions were made.

"We continue to be in contact with 32BJ's leadership to discuss ways to meet our goal of savings and to find alternatives that may reduce the need for actual layoffs to occur in December 2012," Gallard said.

In all, 276 building engineers, 126 custodial assistants, 503 general cleaners, and 501 bus attendants received walking papers last week.

The average 32BJ worker is paid $18.43 an hour, less than $40,000 a year. But the benefits are good; if the layoffs go through, presumably the district could contract out services.

Members say they help keep schools running, and that contract workers could not perform all the jobs they do. The union has "been decimated" in the past few years, president George Ricchezza has said, with layoffs chipping away at its ranks.