I’ve had a lot of conversations lately about whether stormwater really even matters. And all I want to do is jump up and down and yell, “Look around you! It’s everywhere!” All of our gutters direct stormwater. Our downspouts carry it. Catch basins capture it. Highways are tilted to redirect it. Roofs are too, and gardens are planted to harvest it. Swales slow it down, and barrels contain it. Every construction project deals with the mud (or prevents it in the first place), and every city watches it flush their streets and flow into their lakes, rivers, streams, and bays.

Here’s what a sewer map looks like at Seattle’s Pike Place Market.

What does this mean?

4 city blocks in Seattle, including streets, covers about 6 acres of land.

Seattle itself covers about 91,200 acres of land. So that’s about 15,200 times that of the little square of land shown above, give or take some density changes.

Excluding the King County mainline sewer, SPU (Seattle Public Utilities) manages 530 miles of sanitary mains, 500 miles of storm sewer drains, 1,020 miles of combined sewers (a pleasant mix of sanitary – that’s from your house – and stormwater), 277 storm drain outfalls, and 43 CSO (combined sewer outfall) control systems.

That’s it! One not-so-big city has enough storm and combined sewer lines to just about cross the entire country.

All of these sewer lines are in almost constant use, and they all require regular maintenance and upgrade. It’s the city’s job to do it, and with limited funds. Which is why we’re starting to see some pretty exciting innovation (if I do say so myself) in the stormwater industry as a result of the sheer volume of water we have to manage, and the infrastructure required to do it properly. With sea levels rising and large storms becoming more frequent, the need to prioritize infrastructure for upgrade and replacement continues to grow, but our budgets do not. That’s where we come in. We want to make it easy to get the data we need to make decisions across entire sewersheds and start building our first smart urban watersheds. StormSensor is incredibly proud to be a part of the movement to smart city infrastructure management, starting from the (under)ground up!


  • http://gisrevprxy.seattle.gov/wab_ext/DSOResearch_Ext/
  • https://www.seattle.gov/financedepartment/0207adopted/DWF.pdf

About the author

Erin Rothman

Talk stormwater with erin@stormsensor.io With more than 15 years of environmental consulting experience, Erin observed so many opportunities for innovation in the stormwater industry. With those in mind, she founded StormSensor to enthusiastically embrace new technology to help solve the problems of an age-old industry.