Portland’s East End Beach reopened Friday afternoon just in time for the annual open water swim from Peaks Island.

The race, a fundraiser for the YMCA of Southern Maine, is scheduled for Saturday and was in jeopardy after an estimated 1 million gallons of partially treated sewage spilled into Casco Bay on Thursday. The city announced Friday afternoon that a water-quality test showed reduced levels of bacteria near the beach.

“We are relieved that this is the case and are confident that participants will be safe during our event,” the YMCA of Southern Maine posted on its Facebook page.

The YMCA warned, however, that there still are routine weather concerns, such as fog, that will be evaluated closer to race time. About 450 people had signed up to attempt the 2.4-mile swim across Casco Bay that ends at East End beach.

The swim event was in doubt after the spill and into Friday afternoon because an initial water test showed elevated bacteria levels. The water tests take 24 hours to process. The results of the first sample taken Thursday morning found 160 colony forming units of bacteria, or cfu, per 100 milliliters of water. The state beach closure limit is 104 cfu per 100 milliliters of water, the city said.

But the results of a second sample taken Thursday afternoon showed the bacteria levels had gone down to 10 cfu per 100 mililiters. A third sample was taken this morning, but those results will not be available until Saturday.

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This is the first time Portland’s wastewater treatment plant has experienced an overflow of this type, said Michelle Clements, spokeswoman for the Portland Water District, which operates the plant. Few new details were available about the incident Friday.

The Maine Department of Environmental Protection is investigating the incident. The water district has five days to submit a report about the spill to the state, which could then change the plant’s operational plan or order a fine.

The wastewater overflowed from a treatment tank and poured into the bay to the west of the beach and the boat launch. It was in the final stage of the treatment process, when chlorination and dechlorination take place to disinfect the water.

One of the two chlorine-contact tanks was drained for cleaning Wednesday, and the valves to let wastewater back into the tank were not been reopened. The surge of water during the overnight storm overwhelmed the second tank and it began to overflow. Each tank can hold 400,000 gallons.

The water had been chlorinated, Clements said. But it did not sit for the required minimum 30 minutes in the contact tank, and the chlorine had not yet been removed as it normally would be before the effluent is released into Casco Bay.

The water district estimated the overflow occurred for less than an hour beginning at 6:45 a.m. A person on the Eastern Prom Trail reported the overflow to the city, which alerted the water district. Clements said there are two employees at the plant during evening hours and up to 14 during business hours. There are no alarms that would alert employees about an overflow of the contacts tanks, she said.

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Clements declined to answer questions about why the valves were not reopened, if procedures exist in the plant that should have prevented errors and whether any employees involved in the error will face disciplinary action.

“Again, we are conducting a thorough investigation and details of the incident will be in the report,” Clements wrote in an email.

The spill washed out a part of the Eastern Prom Trail, which will be closed until Wednesday for repairs. The water district is responsible for fixing the trail, which Clements said will cost between $30,000 and $50,000.

Megan Doyle can be contacted at 791-6327 or at:

mdoyle@pressherald.com

Twitter: megan_e_doyle


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