I think that we can all sympathize with Michelle Murphy’s situation where her Rucker Hill home is flooded with sewage every time there is an extremely large rainfall.
As she pointed out in her Thursday guest commentary, “Sewage flooding must stop, be repaired”, the sewage flooding is caused by stormwater runoff that enters the combined sewer system in her neighborhood and overwhelms the existing pipe system. Fortunately, not all of Everett is serviced by a combined sewer system, but for older neighborhoods like hers this is a real and continuing problem. As a hydrologist specializing in stormwater problems, I know that, despite promises otherwise from the city, these sewage flooding problems will continue to occur in the future whenever we receive unusually heavy rainfall like we have seen in August and September of this year.
The recommendation for homeowners to create rain gardens in their yards to collect stormwater runoff is good and will help the environment, but it is unlikely that it will solve this combined sewer flooding problem. The vast majority of the stormwater that is flooding the combined sewer system is from impervious surfaces, primarily city streets. Backyard rain gardens are not going to collect, store, and infiltrate this street stormwater runoff.
Real solutions are expensive. The best solution, as noted by Ms. Murphy, is to separate the stormwater sewer system from the sanitary sewer system. Separate systems were built in most of Everett (and surrounding communities) once engineers recognized the flooding problems produced by combined systems. But that doesn’t help neighborhoods like Rucker Hill. Other solutions include increasing the size and capacity of the combined sewer pipes, which it sounds like the city tried to do, and/or providing stormwater storage systems (tanks or underground vaults) to collect, store, and slowly release the stormwater runoff into the combined sewer system.
Combined sewer overflows can also be used to dump the excess water directly into Port Gardner Bay, but require special regulatory permits. Regardless of the solution selected, the city needs to act quickly. Unless it does so, I predict that Everett will end up spending more money on settling homeowner lawsuits than it would have spent on constructing a better system that actually works. And that would be a city-wide tragedy.
Doug Beyerlein, P.E.
Clear Creek Solutions, Inc.
Mill Creek
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