Three sewage treatment plants on Whidbey Island were recognized by the state for achieving full compliance with their water quality permits in 2020.

By far the newest of the plants on the island, Oak Harbor’s state-of-the-art, $150 million facility was not among the top performers because of several problems the city self-reported to the state.

Facilities in Coupeville, Holmes Harbor and Langley were named as winners of the Department of Ecology’s Outstanding Wastewater Treatment Plant Award for 2020.

A total of 127 treatment plants in the state, or about 40%, received the award.

The Department of Ecology noted that wastewater treatment plants faced unprecedented challenges due to the pandemic.

“Facility staff kept the plants running 24 hours a day, seven days a week while also managing an influx of wipes, masks and gloves clogging up their systems and causing serious problems,” according to a statement from the department.

Documents from the state Department of Ecology outlined a few of the plant’s “noncompliance events” in 2020.

The most significant of the events was the discharge of 1.2 million gallons of untreated sewage into Puget Sound during a three-day period in early February 2020 because of “long-lasting rain showers” created an unusually high amount of rainwater infiltration into the collection system.

As a result, the city contacted the company that supplies the plant with the membrane filtration system to discuss the addition of modules to increase capacity.

Also, city staff continues to search for and repair areas of rainwater infiltration.

The city failed to submit a discharge monitoring report in March; it was later submitted in November. In addition, the pH of effluent was outside the allowable pH range for a few seconds in September, which the city said was due to a technical issue with the monitor.

The records show that the city also had problems with effluent being too acidic for a short period of time twice in June of this year.

The city’s explanation letter states that the incidents occurred following citric acid maintenance cleaning cycles.

Island County has a sewage treatment facility near Coupeville that handles septage pumped from septic tanks in the county.

Since the facility doesn’t dump effluent into any bodies of water, it doesn’t require a Department of Ecology permit.

The Department of Ecology reports that municipal wastewater treatment plants are the biggest source of nutrient pollution in Puget Sound by a very large margin.