Janitors who clean MBTA stations say their employers plan to sweep nearly one third of the jobs off the payrolls in September as a cost-saving measure.

“If you let the vendors decide how many janitors it takes to clean, you will see them cutting corners and putting it on backs of workers and leading to what we think will be a mess,” Roxana Rivera, district leader of 32BJ SEIU District 615, told the state Transportation Board Wednesday. She said the cuts will create “an unsustainable workload for those workers that are retained.”

Transportation Secretary Richard Davey told the News Service the MBTA has moved to a “performance-based contract as opposed to a you-must-have-X-number-of-people-in-place kind of contract” and he expects the companies will use more advanced cleaning techniques to meet the standards.

“A little push-broom is not going to help clean these stations in a meaningful way, so my expectation is that we’re going to be using better equipment, better cleaning supplies, etc. So that is part of the question as opposed to how many people you have,” said Davey, who said he is “very sympathetic” to the workers who will be laid off, and they will be able to participate in MassDOT job fairs and possibly move into positions elsewhere in the agency.

MBTA spokesman Joe Pesaturo told the News Service that before last September, the T had 13 separate cleaning contracts managed by four different departments and held by five different companies. Two companies now hold the five-year contracts with a total value of $61.8 million, and the companies were allowed to propose staffing reductions starting in the second year of the contract, as long as there is not detriment to service, Pesaturo said. The proposals were approved in the bid process, he said.

The contracts are now overseen by a single department, engineering and maintenance, and the contractors are required to share half of any incentive payments with employees, Pesaturo said.

Contractor SJ Services does work on the southern portion of the Red Line, the Blue Line and the northern portion of the Green and Orange lines, according to a map provided by the union. American Building Maintenance has the rest of the system.

The union obtained the staffing reduction plans through a public records request, Rivera told the News Service, and an SEIU analysis indicates 90 of the 315 janitors will lose their jobs. That will result in a 29 percent cut to the labor force and a 25 percent cut in total cleaning hours worked, with most of the cuts undertaken by SJ Services. The Danvers-based SJ Services’ plans will account for 79 of the 90 staff reductions, according to SEIU, which cast doubt on the ability to maintain cleanliness under the plan.

“In an environment in which workers are routinely called upon to clean not only soil and trash, but urine, vomit and feces, this has significant quality and public health ramifications,” the analysis states. “This outcome is clearly inconsistent with the MBTA’s stated goal of providing exceptional cleaning standards at all times.”

A voicemail left with SJ Services Thursday morning was not returned.

The union doubts that equipment upgrades will enable cost savings, citing “existing supply shortages” and Rivera said the T is “headed toward a cliff” when the layoffs go into effect Sept. 1.

“We’ve laid off employees in the past, cut services, our riders have paid more, and so I think it’s fair that our contractors do more with less,” Davey said. He said, “We’re going to hold our contractor to performance-based standards of cleanliness, etc., so no, it shouldn’t be cause for concern.”