Costs for expansion of the University Area Joint Authority sewage treatment facility, slated for completion by mid-1992, could total $18 million, UAJA Manager Dave Allison said yesterday.

The plant, located in College Township, is now operating at more than 85 percent capacity and must be expanded to comply with state regulations.

The State College borough diverts about half of its sewage to the plant, which it shares with College, Ferguson Patton and Harris townships. About 42 percent of UAJA's sewage comes from the borough, Allison said.

Borough Public Works Director, Lee Lowery said in order to pay for the expansion borough officials plan to raise sewer user rates. In effort to help offset part of the cost hike, sewer authority officials recommended that council approve a tap-in-fee for all new construction projects.

Allison said he does not know how much authority sewage handling rates will increase as a result of the expansion.

Centre Region officials are now in the process of compiling a state-mandated Act 537 sewage facilities plan which outlines the current status of its sewage facilities and identifies current growth areas.

Robert Bini, Centre Region planning director, said the plan should outline financing methods for the growth of some sewage facilities in the region, but added he was unsure whether the plan takes into account the UAJA expansion.

Allison said it is up to the municipalities who use the plant to determine their means of financing the expansion.

The plan must be adopted by all the region's municipalities and submitted to the state's Department of Environmental Resources before the facility can be expanded.

The plant's expansion provides for: a sludge management facility; an additional disinfecting facility; a new tertiary treatment building; additional primary settling tanks; a main control building; expansion of the administration building and new settling tanks.