PORT ANGELES — Officials were still cleaning up on Saturday after an intense rainfall on Monday caused a discharge of 1.49 million gallons of combined sewer overflow into the Port Angeles Harbor during a deluge that flooded streets and strained facilities across the region.
Monday’s overflow was the largest spilled from permitted outflows since the $47 million combined sewer overflow (CSO) project, the largest public works project in the city’s history, was completed in 2016. It was the second overflow since the system was built; the first was of an estimated 451,800 gallons of untreated sewage and stormwater in February.
Thomas Hunter, Port Angeles Public Works director, described Monday’s rainfall — which preceded the first lowland snow of the season that day — as “a 100-year storm event,” not merely because of the amount of precipitation but how quickly it fell.
“We got hit by an extraordinary amount of intense rain, not just in quantity but in how fast it was coming down,” Hunter said Saturday.
The intensity of the storm combined with high tides made it “something of a perfect storm,” he added.
The city’s 5-million gallon CSO tank was filled to capacity, Hunter said.
“The amount of rain we got hit with was relatively unprecedented in our recent memories,” Hunter said. “The area was already so saturated with water, there wasn’t a lot of extra capacity to handle a 100-year storm event.”
A state Department of Ecology official, reached as the overflow occurred, said that flooding was happening all over the region, Hunter said.
Reports came in of standing water in Sequim and Port Angeles. Records were reportedly set Monday at the National Weather Service in Seattle (2.19 inches) , at Seattle Tacoma International Airport (1.64 inches) and Bellingham (1.82 inches).
Hunter estimated that 3 inches of rain fell in Port Angeles, coming down at a minimum of one-third inch per hour.
Two-thirds of the total rainfall was in an eight-hour time span between 6 a.m. and 2 p.m., with the peak at 11:53 a.m., city officials said on the website at cityofpa.us.
The overflow into the harbor prevented a complete failure of Port Angeles’ wastewater system, Hunter said.
The outflows provide a “short relief on the system to protect against catastrophic failure that could take the plant out for weeks at a time,” Hunter said.
Since then city workers have been treating the water stored in the CSO tank, a process that continued on Saturday, and are investigating reports of flooding at businesses and residences.
Direct questions or concerns in Port Angeles to publicworks@cityofpa.us.
________
Executive Editor Leah Leach can be reached at 360-417-3530 or at lleach@peninsuladailynews.com.
________
