Tosh Creek Watershed Restoration

Project Update - 5/25/2016

The design team has completed preliminary engineering for the six projects shown in the project map below. These projects are proposed for construction from 2016-2022 as shown on the project schedule.

We recently distributed a project newsletter to residents and businesses within the watershed. Here are a few project updates that were included in the newsletter:

  • 159th Avenue Vault Project   
    We are reducing costs and construction impacts by moving the proposed vault from the street onto three adjacent properties. The City owns one of these properties and is negotiating the acquisition of the other two with the property owners.

  • 50th Way Flood Reduction Project   
    We have reached final design and are conducting outreach for the project. We will advertise the project to contractors in June and construction will start this summer.

Public Meeting  Ice Cream Social – June 13

Join the project team and your neighbors for an ice cream social and project update! During the event, we’ll share new information about the Tosh Creek Watershed Restoration Projects, including upcoming construction on NE 50th Way and a design update for the 159th Avenue Vault project.

Date:          Monday, June 13, 5 p.m. – 7 p.m.
Location:    City-owned property between 4618 & 4702 NE 159th Ave NE

Online Open House – Starting June 8

If you can’t make it to our public meeting, visit the online open house to learn more about the Tosh Creek Watershed Restoration Plan and the six projects we are currently designing.

Date:         Join us online between June 8 and July 13

If you are interested in receiving project emails and notifications, please sign-up for our mailing list: Tosh Creek Mailing List

Purpose of the Plan

Tosh Creek The City is committed to fully restoring Tosh Creek to make it healthy for aquatic life, and a valuable natural asset for the people who live, work, and play in Redmond. Using a watershed approach (as documented in the 2013 Redmond Watershed Plan) to achieve healthy aquatic habitat has been a long-standing policy detailed in the City's Comprehensive Plan and is recognized by stormwater and surface water restoration practitioners as the recommended approach to accommodate healthy streams in an urbanized landscape. The Tosh Creek Restoration Plan, completed in February 2015, identifies potential stormwater retrofit and in-stream projects that will improve the hydrology and water quality of the stream and also mitigate flood hazards.

There are five main areas of focus in this Restoration Plan:

  1. Flow Control - Slow down stormwater flows to protect the stream       
  2. Water Quality Treatment - Clean up stormwater runoff for cleaner water in the stream
  3. Low Impact Development Infiltration - Soak stormwater into the ground       
  4. Instream Work - Repair damaged sections of the stream and add plants       
  5. Stormwater Infrastructure Repairs - Repair or replace failing pipes

Projects described in the Tosh Creek Restoration Plan from each of these focus areas form a capital improvement program that lays out a sequence of projects tailored to the prioritized needs that have been identified for the Tosh Creek watershed.

Proposed Projects

Feedback from Redmond residents played an important role in our decision-making by helping us understand where there are drainage, flooding and erosion problems. Along with public input, we evaluated proposed projects based on their feasibility, cost and the perceived benefit to the watershed. The projects we are moving forward with are shown on the map and table below.



Project name

Current problem

Planned solution

Anticipated timeframe for construction

Funding status

50th Way Flood Reduction

The stream along NE 50th Way frequently floods when there is a lot of rain

Install new pipes under the street to direct most stormwater away from the stream, reducing flooding


Summer 2016 for approx. 3 months

Source: King County (KC) Flood Control District, Redmond Stormwater Capital Investment Program (CIP)

159th Avenue Vault

The current series of pipe vaults under 159th Ave NE are old and need to be replaced to ensure reliability and to meet current standards that protect the stream

Install a new stormwater vault on three adjacent properties: 4612 159th Ave NE, 4618 159th Ave NE, and the adjacent vacant City parcel

Spring 2017
for approx. 6-9 months

Sources: Washington State Dept of Ecology (Ecology), KC Flood Control District, and Redmond Stormwater CIP


156th Avenue Flow Splitter

The existing flow splitter directs too much water to one of Tosh Creek’s tributaries


Modify the flow splitter to reduce the amount of water going to the tributary

Summer 2017
for approx. 3 months

Sources: Redmond Stormwater CIP

Onyx Pond

Onyx Pond is too small to store and treat the amount of water coming from the Tosh Creek watershed


Improve Onyx Pond by removing sediment and trees in the pond; expand the pond

Summer 2020
for approx. 3-6 months


Preliminary funding received for fieldwork and early design; additional funding requested. Ecology grant award pending availability of state funding.

In-stream work

Tosh Creek tributaries are eroded and the stream’s habitat is deteriorated


Repair the stream to reduce erosion, stabilize channels, and restore habitat

Tributary B: Summer 2020
for approx. 3-6 months

Additional projects planned for the future

Preliminary funding received for fieldwork and early design; additional funding requested

Prescott Vault (NE 44th Court)

The existing vault is not large enough to hold the amount of stormwater needed

Expand the vault so that it can hold more stormwater, and add system to treat water before releasing it into the creek


Approx. 6 months in 2022

Preliminary funding received for fieldwork and early design; Ecology grant award pending availability of state funding.


Community Benefits

Completion of the projects identified by this plan will:

  • Reduce flooding in neighborhoods       
  • Prevent erosion in Tosh Creek
  • Reconstruct stream channel segments to improve fish habitat
  • Remove invasive vegetation and re-plant bare portions of the stream buffer
  • Repair damaged stormwater pipes to avoid future flooding problems 

Ultimately, the combined suite of projects proposed in the Tosh Creek Restoration Plan will restore the ecological health of the stream and bring back larger populations of Coho salmon, cutthroat trout, and other fish. This healthy stream will be a valuable asset for our community for generations to come!

How to Stay Informed

Please visit this website for the most up-to-date information on the project. Additional materials and project information will be posted on the site as the project develops.

Please join the Tosh Creek mailing and notification list:  Tosh Creek Mailing List

Tosh Creek Watershed Plan Program Manager:  Steve Hitch, 425-556-2891
159th Vault Construction Project Manager:  Joseph O'Leary, 425-556-2738
50th Way Flood Reduction Project Manager:  Bassam Al-Ali, 425-556-2743
Tosh Creek Project email: