Completion of a $10-million Shirley sewer district that is expected to help create more than 500 jobs has been delayed by the harsh winter, Brookhaven Town officials said.

The 200,000-gallon-per-day sewage treatment plant will allow for building and expansion on the remaining 96 acres of the 235-acre Brookhaven R&D Plaza, a light industrial complex south of the Long Island Expressway, officials have said.

Officials said a year ago that the sewers should be completed by June 2011. But the construction, held back by winter weather, is just reaching the halfway mark, town spokesman Jack Krieger said yesterday. The new expected completion date is October, he said.

Brookhaven Supervisor Mark Lesko, Councilman Daniel Panico and Rep. Tim Bishop (D-Southampton) will hold an event at the R&D Plaza at 3 p.m. Tuesday to mark the half-way point of the construction. The eventual completion will “allow expansion of existing and new businesses” within the park, the officials said in a statement.

The project is being funded through the creation of a special district and the use of federal stimulus money, officials have said.