The U.S. Postal Service plans to consolidate more than 80 mail-processing centers next year, but communities are almost entirely in the dark about how the changes will impact service in their areas, federal auditors said Wednesday.

The USPS inspector released a report on Wednesday saying the agency did not complete impact studies for any of the 95 facilities that are scheduled to absorb the operations of other centers starting in January.

The review also found that the agency has not informed stakeholders about the expected service changes, despite a 2006 law that requires public input before they take effect.

The Postal Service plans to close more than 80 processing centers and move their operations into 95 other facilities. (Matt Rourke/AP)

The changes will increase delivery times and eliminate overnight delivery for “a large portion of First-Class Mail and periodicals,” the report said.

USPS could not complete the impact studies on time because it had not yet finalized its new processing guidelines, according to the report. But instead of postponing the consolidation plan, Postmaster General Patrick Donahoe announced in June that the agency was ready to move forward with the initiative early next year.

Auditors said the lack of information and public disclosure could degrade USPS services and harm the agency’s brand, in addition to causing carriers to work later into the evening — one postal worker was fatally shot last year while finishing his route at night.

The Postal Service has estimated that consolidation will cause overall delivery times for First-Class Mail to increase from an average of 2.14 days to 2.25 days, according to a fact sheet from the agency. Some areas could see much larger increases.

The inspector general said USPS should complete impact studies for all the facilities that are scheduled for consolidation. The agency agreed with the recommendations but disagreed that its failure to complete the analyses would harm quality of service.

The consolidation plan is expected to save more than $750 million per year, providing some financial relief for an agency that has experienced years of multibillion-dollar losses due in large part to declining mail volume.

The Postal Service expects the plan to help it match current and future mail volumes. The number of processing centers has already shrunk dramatically in recent years, with the agency closing more than half of the facilities since 2005. Last year, there were 320 of them.

Postal unions and many lawmakers oppose service cuts for USPS. With revenue increasing lately in areas such as package delivery, labor groups say the only thing holding the agency back from returning to profitability is a 2006 law requiring about $5 billion per year in advanced payments toward the agency’s retirement benefits — the agency has defaulted on that obligation for the past several years.

The postmaster general has asked Congress to eliminate or restructure the prefunding requirement.