PORTLAND, Ore. (KOIN) — Swimmers and boaters are no strangers to sewage spills into the Willamette River, and with that typically comes a warning to stay out of the water for 48 hours. However, officials did not notify the public of Saturday’s overflow until 45 hours later.

In a release sent Monday, the Portland Bureau of Environmental Services said heavy rain triggered a sewer overflow to the Willamette River between 7:34 p.m. to 7:36 p.m. Saturday. In those couple of minutes, about 344 gallons of combined sewage reportedly flowed into the river.

BES officials told KOIN 6 this particular outfall structure overflows at 4.3 feet, despite the alarm’s trigger being set for 4.5 feet. The depth on Saturday, however, only rose to 4.37 feet — falling short of the trigger’s threshold.

“We weren’t aware this particular CSO (Combined Sewer Overflow) happened because it didn’t trigger the alarm,” said Andy Kiemen with BES.

Kieman says that even if people were swimming in the water during that time, they don’t need to be examined by a doctor.

I wouldn’t presume that they would be in danger. We are talking about 340 gallons in a river,” Kieman said. “It’s a drop in the bucket.”

Less than 12 hours after the overflow happened, people were gathering at the river for the Portland Rose Festival Dragon Boat Race. A spokesperson for the festival said organizers were not notified of any contamination.

BES officials said the overflow wasn’t discovered until engineers analyzed the data Monday morning. The release notifying people of the contamination was not distributed until 4:16 p.m. Monday, however.

BES’ full statement:

“We are auditing that discrepancy in the alarm setting. Previous overflows at this site had gone over the 4.5 feet setting, causing an alarm. We didn’t see an overflow squeaked by without an alarm until we did a data verification for this weekend’s event on Monday.

We’re always looking to improve our data as we encounter issues and do our best to verify and check things to ensure the system is working correctly – or how to make it work better. And sometimes, we can’t figure out whether a problem is apparent until an alarm does or doesn’t go off in real-world conditions. We test the instruments regularly, but that only takes things so far as ensuring measurements are made correctly. This late call was an edge case that’s difficult to troubleshoot ahead of when the actual event happens, especially since these events happen so infrequently and at the level of precision we saw this weekend.”

KOIN 6 News’ reporter Liz Burch contributed to this story.