Unusual Rain Event to Hit the Northwest. From one to 5 inches of rain is expected in various parts of the region, more rain than we typically get in the entire month of September around here.
In my neighborhood, the runoff goes into storm drains that tie directly into the sanitary sewer. The combined sewer lines carry all that waste water to pumping stations that send it to a treatment plant.
Because stormwater runoff is the major source of pollution in Puget Sound, you might think that sending that stormwater off to a treatment plant is a good idea. But it isn't that simple. When we have big storms, like the one heading our way as I write this, the extra volume of waste water can overwhelm the sewer system. To prevent flooding and sewage from backing up into people's homes, Combined Sewer Overflows (CSOs) release combined stormwater and raw sewage into the Sound.
Is a CSO near you discharging raw sewage? You can find out by checking this real-time map showing CSO status. The information is updated every few minutes. The time of the most recent data capture is shown at the top of the map. I've linked this to my area, SW Seattle. To check other locations, look for the options listed in the upper left hand corner of the page.
I took a walk last night at sunset and saw a man swimming in the Sound. I can't imagine that he will be out there again tonight, but he and anyone planning to swim, wade or fish in these waters might want to check the local CSO status first.