Oak Harbor officials had yet another financial surprise regarding the new sewage treatment plant. This time it was in the midst of negotiation with the Navy over hooking the Seaplane Base to the city’s facility.

Larger than anticipated rate hikes will put pressure on city officials to finalize an agreement with the Navy to treat its wastewater.

Doing so would cut residents’ rates, though nobody can say by how much.

City leaders should stick to their guns and ensure the Navy pays its fair share, even if it means staying with the rate hikes.

A consultant’s rate study calls for a series of increases in wastewater rates this year and the following four years to cover costs associated with the $149-million plant located downtown adjacent to Windjammer Park.

If adopted by the council, the rate would increase by about 29 percent over the next five years. It would jump from about $103 to nearly $133 a month in 2024. The reason for the proposed rate hikes is the cost of flood insurance, which wasn’t planned for, and higher-than-anticipated electricity charges.

The impact of proposed rate changes would be compounded by increases in solid waste, water and stormwater rates.

This comes after city leaders were twice surprised by giant increases in the cost of the treatment plant itself. The saving grace in those controversies was that city officials were able to obtain grants and low-interest loans to keep rates lower than they otherwise might have been. But apparently that’s no longer the case.

City council members vowed that Oak Harbor ratepayers would not subsidize the Navy when it comes to treating its dirty water. The membrane bioreactor system cleans the water so well that it’s safe to drink and will meet environmental standards for many years to come.

Hooking the Navy in would increase the operational expenses and significantly reduce the capacity and lifespan of the facility.

In the negotiations between the city and Navy, it’s David and Goliath. Hopefully David stands firm and Goliath plays fair.