Attack plan for brown water: Seattle Public Utilities plans large-scale West Seattle flush

(Reader photo from a brown-water situation earlier this month)

By Tracy Record
West Seattle Blog editor

After months of intermittent but intense West Seattle brown-water incidents that we’ve been covering – going back to last fall – the city is making plans for a major operation to try to attack the underlying problem: Rust in the pipes.

The rust isn’t unusual and isn’t unhealthy, Seattle Public Utilities stresses – but there shouldn’t be this much of it stirred up when something happens such as a hydrant opening or pipe break, and it should clear faster (as commenters have pointed out, it often lingers longer than they were told it would).

So SPU is planning a “unidirectional flush” – something that utility managers say hasn’t been done anywhere in the city in more than a decade.

It’s not one big operation at one time but will play out over the course of months. We got an early briefing during a visit to the SPU Operations Control Center, following up on our recent behind-the-scenes look at how water safety and quality is monitored.

We met there with drinking water quality director Wylie Harper and other SPU water managers, including operations director Dave Muto. First, some context. Two-thirds of the 1,800 miles of pipeline in SPU territory is unlined cast iron – and this is the primary source of what discolors the water in certain circumstances:

If there’s a pipe break/leak, if a hydrant is operated (including fire incidents), if something in the operational system requires a flow reversal, it could “stir things up … that’s part of the nature of the system.”

While SPU refers to it as sediment, it’s rust from those cast-iron pipes.

Harper says it’s not that the utility never flushes pipes – “it’s usually been more ‘spot flushing’,” compared to what’s in the works now, a “much more thoroughly planned and comprehensive effort,” at multiple locations involving a “large portion of the system.” It’s “hugely time-consuming and complex to do this,” so they’ve been having planning meetings.

They will start at the source – a tank, a transmission line, a large feeder main (12″ wide or larger), “working so that sediment is pushed from the source to the outer edges of the pressure zone, with valve closure along the way.” That means some effects at homes/businesses while it’s happening, and they promise you will get an advance alert when it’s scheduled to happen in your area.


Explaining how this works, they explained that West Seattle has “three planning zones” for water delivery, largely related to topography and how the water is delivered. The zone that’s primarily being focused on for this upcoming operation is known as 498 (the beige area in the map above), and Harper says “60 or 70 piping segments have been picked out” for the unidirectional flushing operation, starting in the north, where more problems have been reported in recent months. (We learn while at SPU that we too are in the 498 zone, toward its south, served by an unlined-cast-iron main, but we can’t recall having had a discoloration problem in the 20-plus years we’ve lived in the same place.)

This is all an intricate operation to be sure it doesn’t cause more problems than it solves. “To do it the right way … there’s a fair amount of technique involved,” Harper explains: A certain velocity – three to five feet per second – will suspend (the) rust and move it out. If it’s too slow, it’s not good. Too fast, not good” – that could break off “rust nodules” that have formed inside the pipes over the decades. So they have mapped out which hydrants, which pipe sections will be involved. And they plan to do most of the work late at night, when it will have less of an impact on customers, and when the pressure is higher because use is lower.

Following up post-visit with SPU spokesperson Ingrid Goodwin, we obtained more explanation: “The flushing needs to occur sequentially. So, when one flush is complete, crews will move to the next location. At this point, we are still determining how many crews will be required. It will likely be up to three, 2-person crews ( so 2 to 6 people) working in the field M-F, from about 11 pm to 5 am. Daytime flushing may occur at some point, as well. We estimate that it could take 3 to 6 months to flush all of West Seattle. However, once we get started in April, we’ll have a better idea of how long it’s actually going to take to complete.”

According to Harper, they’ll be able to measure the results via water-quality parameters. As for how customers will know it was a success – the primary result would be any future discoloration (for the same reasons, pipe breaks, hydrant uses, etc.) clears more quickly. Harper is careful to stress it doesn’t mean discoloration will never happen again – “we still have unlined cast iron pipe … what flushing WILL do is remove some of the sediment, so the intensity (of discoloration) is less.” Though the pipes are up to ~90 years old, removing and replacing them on a large scale isn’t an option, according to Harper. For one, they still, in general, “function properly,” with a “leak rate better than the industry average, fewer links per mile … and the pipe wall itself is robust.”

Also stressed: The reason for this is aesthetics, not a health risk, unlike the last time this kind of flushing was done, out of concern about coliform bacteria in the early ’90s. But the aesthetic concern is enough that they’ve decided to do this – “a lot of this is driven by customer interest and recent calls,” Harper said.

What happens to the water that’s “flushed”? Another question we asked Goodwin post-interview: “During flushing, water valves are closed to direct the water through designated parts of our main lines and flushed out of opened hydrants. The water is drained to either the combined or separate storm drain systems. Water that goes to the combined system (wastewater and drainage) ends up at the treatment plant. Water that goes to the separated system is dechlorinated onsite and flows to receiving bodies of water.”

One more note from Harper – he said they would like to do more in the future; other areas of the city have unlined cast-iron piping such as North Ballard and Green Lake, and “might benefit,” according to Harper.

In the meantime, watch for the first round of formal announcements from SPU about the flushing operation in about a week. (added) Goodwin told us, “We are planning to mail a public notice, FAQ and map to customers by the end of next week (by April 8). This information will go to the first group of neighborhoods in West Seattle that are scheduled to have the water mains on their streets flushed. These will be the neighborhoods in the northern part of the 498 zone.”

And if you experience discolored water (as did residents in Fairmount Springs after a truck took out a hydrant last night) – call SPU’s 24-hour hotline, 206-386-1800. Speaking of which:


COMING UP ON WSB: Within a few days, we’ll publish part 2 of the report on our visit to the Operations Center will take a look at what happens when you call in a complaint as well as more extensive background on where your water comes from and what happens to it along the way, including a behind-the-scenes look at the center – which includes controls for facilities of all sizes, as well as the call centers where operators talk with SPU customers reporting problems (photo above), calling with questions, etc.

11 Replies to "Attack plan for brown water: Seattle Public Utilities plans large-scale West Seattle flush"

  • Mike E March 31, 2016 (1:09 pm)

    Very cool stuff, and thanks so much for all the investigation and sharing of how this all works.  It is very much appreciated.

  • chemist March 31, 2016 (1:12 pm)

    Should people in area 498 experience any big changes in the city delivered water pressure during this ? I have a pressure reducing valve on the house that needs replaced, eventually, and only have about 20 psi left before pressure relief valves should trigger.

  • Aaron March 31, 2016 (2:48 pm)

    I have 3 years worth of back and forth emails about our brown water with little to show for it.  Spu told us it was just us.  Glad to know there will be some action

  • Diane March 31, 2016 (3:53 pm)

    re “they promise you will get an advance alert when it’s scheduled to happen in your area”

    how will they give advance alert?  will they notify you, so it will be published?  as a renter, we are rarely notified of anything like this if the owner were contacted by SPU

    not looking forward to having more brown water while they spread it out over months

    • WSB March 31, 2016 (4:01 pm)

      I need to add this to the story – it’s from my followup questions to Ingrid Goodwin today: “We are planning to mail a public notice, FAQ and map to customers by the end of next week (by April 8). This information will go to the first group of neighborhoods in West Seattle that are scheduled to have the water mains on their streets flushed. These will be the neighborhoods in the northern part of the 498 zone.”

      And yes, we’ll have the info, they promise – the whole reason we got this advance info that it’s being planned is because we’ve been reporting on the brown-water situation in recent months, and that ostensibly in turn led to more citizen reporting of the problem. – TR

  • Ckup March 31, 2016 (6:37 pm)

    Confused about the large green areas along the water edge. We’re on Beach Drive near Ehe Emma viewpoint.  When might we be impacted by this or will we not be?

    • WSB March 31, 2016 (8:02 pm)

      The explanation will be in part 2 but … along the water you’re in an entirely different sort of delivery zone, gravity rather than pumping, since you’re at sea level. I don’t know for sure whether the flushing will be done in that zone too – but we’ll be sure to ask. – TR

  • Neighbor March 31, 2016 (6:41 pm)

    Fascinating! I love wonky infrastructure stuff like this. Thanks for covering this. Looking forward to learning more about this process as it unfolds. 

  • Question Mark March 31, 2016 (10:41 pm)

    Some advice for those in areas being flushed.

    1) If possible, turn OFF your water service at the meter while the mains are being flushed.
    2) Turn OFF water to the inlet of your tank water heater(s), especially if you see rusty water appear from the mains (filling the hot water tank with rusty water will take much longer to flush from your household system).
    3) After the mains have been flushed and you turn on your water service, you will likely see rusty water at first, from your own plumbing.
    4) Flush the cold water tap at your bathtub (usually the greatest flow in the house) until it is clear before
    5) turning the water back on to the inlet of water tank(s).

  • Wylie Harper April 1, 2016 (9:42 am)

    Customers in the 498 zone should expect pressure to stay the same in general since it’s a large zone. However, connections along each particular pipe segment when they’re flushed, and possibly immediately adjacent for a block or two, may experience decreased pressure temporarily when a hydrant is opened (10 min – 1hr depending on the flushing duration at each hydrant).

  • Truthteller April 4, 2016 (5:34 pm)

    Thank you to the West Seattle Blog for the advance warning this time around. Last month I had 3 rounds of the rustiest water you have ever seen. Because I did not have warning, I turned on my hot water, ran a load of clothes (ruined) and had to flush my tank 3 times, not to mention running water forever to get it clear only to have it happen again and again. Finally had to buy 10 gallons of water for cooking and drinking. After Flint, it’s hard to trust what SPU was saying because they told my neighbors and me who called, 5 different versions of why it was brown. I would think that some of my $520.00 water bill could have been spent notifying me earlier so I could have turned off my valve. Oh, and the rust from “my” pipes? How does that work if you have Pex? 

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