Mohlendorph Creek

Carkeek Watershed Community Action Project (CWCAP) has worked since early March 2016 with Seattle Public Utilities (SPU) to solve local, rain-triggered flooding in a neighborhood along a branch of Mohlendorph Ravine at the boundary of Carkeek Park.  Community members and CWCAP are committed to helping solve surface water flooding in this watershed, but insist that a thoughtful and forthcoming solution is sought and implemented.

Here’s is a link to SPU‘s project introduction:

NW 120th Street and 9th Avenue NW Outfall and Drainage Improvements SEPA Determination of Non-Significance (DNS)

NW 120th Street and 9th Avenue NW Outfall and Drainage Improvements SEPA (State Environmental Policy Act) Determination of Non-Significance (DNS)

Here are a few of the serious problems with SPU‘s current solution that the community and CWCAP are helping with, but still need to be worked out:

Incomplete solution:

  • When completed, SPU‘s project will necessarily fall short of solving the local rain-triggered flooding in the neighborhood of NW 120th and 9th Ave NW.
  • Just one property/plot approximately 180 feet north of NW 120th on 9th Ave NE and one developer will see immediate help from SPU, and therefore taxpayer dollars.
  • The new pipe would run south down 9th NW and turn west onto NW 120th for a short distance to the dead end of NW 120th and tight-line into Mohlendorph Creek.
  • The developer on 9th Av NW will have a solution to a very serious problem of poor drainage engineering.  The rest of the neighborhood, particularly those residents that live along NW 120th east up the steep grade towards 6th Av NW will see little relief from rain events that flood their street-side drainage ditches and flow in sheets down NW 120th towards Mohlendorph Creek and the steep, destabilized ravine hill sides.

Water Quality:

  • “Sources of stormwater runoff include upstream neighborhood streets, sidewalks,
    driveways and impervious areas from privately owned rooftops and paved areas.
    Contaminants found in residential stormwater runoff would continue to be delivered
    to Mohlendorph Creek. Contaminants commonly found in urban stormwater include
    metals (including copper, zinc, and lead, for example), herbicides and pesticides, and
    microbes (including pathogens such as Giardia, Cryptosporidium, Campylobacter,
    Vibrio, Salmonella, Escherichia, and Pseudomonas). Primary sources of such
    contamination are residential activity (including lawn and garden care), vehicles,
    pollution from the air, and animal feces.” – from SPU‘s SEPA (State Environmental Policy Act) Checklist: Section B. Environmental Elements, 3. Water, (6) – page 8 of 27.


  • In order to file a Determination of Non-significance, SPU avoided identifying the resident Cutthroat trout living in Mohlendorph Creek.  Stating that trout live in Mohlendorph Creek, which has been known for decades, would have required professional biologists from the Washington Department of Fish & Wildlife to help determine if this project posed a threat to these fish.  Instead, SPU left this information off of their SEPA Checklist.  With the help of middle school summer camp participants, this video was taken in a pool in Mohlendorph Creek on July 27, 2016 some 20 feet above its confluence with Venema Creek.  Resident Cutthroat trout can be found year round in this system.

  • Here is a link to a copy of SPU’s SEPA Checklist for this project, but just below is a screen shot of Section B. Environmental Elements on page 11 of 27.  CWCAP is trying to help SPU’s Project Manager, Arnel Valmonte, with direct, professional, and unambiguous help in re-evaluating their assertions in the SEPA checklist (note that there are no fish selected).  This inaccurate information was used to produce a Determination of Non-significance (links to copy of DNS).
SEPA Checklist Section B5 - Animals
Screen shot taken from SPU‘s SEPA Checklist filed on Feb 4, 2016 by Arnel Valmonte in order for SPU‘s Betty Meyer to sign a Determination of Non-significance on Feb 11, 2016. Note that no fish are indicated, yet pigeon are.


SPU‘s NW 120th St. project would increase rain-triggered surges in volume and velocity into Mohlendorph Creek and then into Venema Creek. Since 70-100,000 salmon fry are released every Spring about 20 feet from where these two creeks converge, adult salmon may return here to spawn each Fall and build nests.

Mohlendorph Creek converges with Venema Creek about 20 feet from where 70-100,000 Chum salmon fry are released each Spring.  The fish fry are imprinted in an off-channel imprint pond so that the adults will return in 3-5 years to these waters, their home waters, each Fall to spawn.  Adult Chum salmon swim into Piper’s Creek to spawn and many will take the “left turn” up Venema Creek in search of spawning opportunities.  They may pass the confluence of Mohlendorph Creek in their way to upper reaches of Venema Creek.

Hundreds of spawners each Fall excavate nests (redds), deposit eggs and sperm, and die.  Rain-triggered storm water tears down from the watershed developments through storm pipes increasing volume and velocity within minutes.  These flash events scour the creeks of recently buried eggs making natural spawning survival all but impossible.  This is due to the flash volume and velocity increases from rain-triggered events and the way developers and city engineers have managed storm water for more than a century.

How does the community find a remedy for local flooding in this neighborhood?

The intended outcome of this project is to divert local rain-triggered surface water flooding into a new, larger, and efficient storm water pipe directly into the upper reaches of Mohlendorph.  The resulting compression of time frame in which the rain fall is conveyed into Mohlendorph and ultimately through the system into Puget Sound, suggests a common sense change in volume/velocity/contaminants (reduction in biofiltration) and hence the potential impact on habitat stability (e.g., weirs, pools, meanders, bank stability/erosion) and animals (e.g., resident trout, salmon redds) in the downstream direction from the project area.  A change that would warrant something beyond what is stated in Section B. Environmental Elements, 3. Water, b. Ground of the SEPA Checklist (page 8 of 27):

“However, the completed project is anticipated to reduce localized flooding, which has the potential to permanently reduce the amount of stormwater infiltrating to groundwater tables. The volume or magnitude of that reduction is not known.

Inputs notwithstanding, using fish bearing systems as a storm water conveyance in this manner is an antiquated approach given what SPU has learned from such work as the Venema Creek Natural Drainage System above 3rd Av NW on NW 120th & 122nd.

One could read the multiple appeals to this common sense concern by CWCAP in the filings to the City Examiner’s Office in the documents linked below.  One would also find filings by SPU denying that CWCAP has any proof that water volume/velocity will change in Mohlendorph Creek and downstream to Venema and Piper’s Creeks after the project.  Yet the quote taken from SPU‘s SEPA Checklist used to produce their Determination of Non-significance (DNS) is worth repeating once again:

“However, the completed project is anticipated to reduce localized flooding, which has the potential to permanently reduce the amount of stormwater infiltrating to groundwater tables. The volume or magnitude of that reduction is not known.

[SPU] NW 120th Street Outfall and Drainage Improvements Project

Addendum Filings (May 12, 2016) posted at

NW 120th Street Outfall and Drainage Improvements Project Update (e-mail invitation sent June 20, 2016)

The project team will host a walk and talk from 5:30 – 6:30 p.m. on Wednesday, July 20, to answer questions about the project and to discuss construction impacts. We will meet at the corner of 9th Avenue NW and NW 120th Street. See attached flyer for more information.

Case Details for HE File Number: W-16-002
Case Name: Nancy R. Malmgren Property
Address: NW 120th St and 9th Ave NW
Business Name: Outfalls and Drainage Improvement Project
Mailing Address:
Date Received: 3/2/2016
Date Filed: 3/2/2016
Filing Fee: $85.00
Nancy R. Malmgren
Carkeek Watershed Community Action Project
386 NW 112th St
Seattle, WA 98177
Phone: (206) 363-4116

Appellant Case Contact
Rick Henry
Phone: (206) 235-7431

Betty Meyer
PO Box 34018
Seattle, WA 98124
Phone: (206) 386-1999
Arnel Valmonte
PO Box 34018
Seattle, WA 98124
Phone: (206) 615-1438
Department Legal Counsel:
Liza Anderson
City Attorney’s Office
701 Fifth Ave, Suite 2050
Seattle, WA 98104
Phone: (206) 684-8202
Alicia Reise
City Attorney’s Office
701 Fifth Ave, Suite 2050
Seattle, WA 98104

Phone: (206) 684-8247
4/20/2016, 9:00 AM
Addition Case Contact
Marisa Johnson

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