City officials may finally get an answer from the Navy base Monday on whether it will partner with Oak Harbor on a new sewage treatment facility.

The answer could affect ratepayers’ bills to the tune of about $6 a month.

Capt. Mike Nortier, commanding officer of Whidbey Naval Air Station, will be at City Hall at 10:30 a.m. Monday to deliver the answer in person.

The city will host Nortier during a special meeting open to the public, said Mayor Scott Dudley.

“I’m assuming what we will hear is the official ‘yay’ or ‘nay,’” he said, “and from what I’ve heard so far, it will most likely be a ‘nay.’”

Dudley said Navy officials usually ask Councilwoman Beth Munns to attend meeting with city officials in regard to the issue; she is the wife of a former base commander and has been communicating with a top Navy official at the Pentagon, the mayor said.

Instead of including just one council member, Dudley said he thought it would be better to open the meeting to all elected officials ­— as well as the general public.

The city currently partners with the Navy for sewage treatment. The city runs the treatment lagoons on Navy property at Crescent Harbor. They are near capacity and will not meet future water quality standards.

A draft study created for the Navy states that the city’s engineering firm overestimated the cost of the facility and that a less-expensive technology would significantly cut costs.

Several council members were outraged when Dudley shared the draft study — a public document under state law — with the Whidbey News-Times.

Dudley said he hasn’t seen the completed study.

The city originally asked for a decision from the Navy on July 1. Navy leaders later said they would have an answer by Oct. 31.

The estimated cost for the treatment plant varies depending on several factors, including inflation.

The estimated cost for the entire project, to serve the city until 2030, was $93.5 million in 2011 dollars.

The estimate for just the first phase, to serve until 2021, increases to $96.3 million in 2015-2016 dollars, according to a memo from the city engineer to the mayor.

The facility plan for the proposed sewage treatment plant estimates what residents’ sewer rates will have to be in 2017 to fund the wastewater treatment plant.

For a 30-year debt service at 4.5 percent interest, the engineering firms estimates $83.26 a month if the Navy partners with the city.

Without the Navy, the estimate increases to $90.48 a month.