Seattle.gov Home Page
Seattle.gov This Department
SPU Home Page SPU Home Page Contact Us
Reliable water, sewer, drainage & solid-waste services

Drainage & Sewer System Branding Image

Madison Valley Stormwater Project

Update – May 14, 2012

  • Construction of Stormwater Storage Tank in Washington Park taken September 2011Construction of Stormwater Storage Tank in Washington Park taken in September 2011.
  • Construction of Stormwater Storage Tank in Washington Park taken September 2011Construction of Stormwater Storage Tank in Washington Park taken in September 2011.

Work restarts in Washington Park

After a thorough evaluation of the soils in Washington Park, we have determined with our contractor that work can restart. Our geotechnical engineers have reviewed and approved the import soils for the slopes in Washington Park which allows us to start work to finish the project. This work is weather sensitive, the community will be notified of any major changes to the schedule or activities.

Here are details about the work:

Parking

No Park signs will be placed along East Madison Street, adjacent to Washington Park.

The area on 29th Avenue East between East Roy Street and East Valley Street, adjacent to Washington Park, will be utilized as a materials storage space and as a secondary entrance to Washington Park. Placing No Park signs will provide room for large vehicles to access this area and maintain a safe working environment along the truck route. No Park signs will be placed on one side of the street along 28th and 29th Avenues East and East Valley Street.

Please be sure to read the No Park signs carefully.

Each sign has information about the dates and times parking is allowed. Street parking is allowed during non-working hours and weekends.

Working hours

Approved working hours are Monday through Friday, 7:30 a.m. to 6:00 p.m.

Activities in Washington Park

Activities outside Washington Park

Although most of the construction work will occur inside Washington Park, there will be some repair and maintenance work happening along the pipeline alignment:

Coordination with other construction projects

The Parks Department has started the Washington Park Playfield Renovation Project. SPU is coordinating activities with the Parks Department and their contractor to keep impacts to a minimum. Learn more.

SPU would like to thank the residents, businesses, and drivers in the area for their patience.

Four public meetings were held regarding E. Madison Stormwater Improvements

SPU has heard concerns from more than 30 E Madison St merchants that daytime construction work would significantly impact parking, traffic, and business access. At the March 5th public meeting The Madison Valley Merchants Association provided a letter (pdf) signed by many merchants stating their preferences for night work.

In response to these concerns, SPU has decided to conduct night work to complete stormwater infrastructure improvements, located near 29th Avenue E and adjacent to Washington Park. Night work would also greatly reduce the overall timeframe that construction work is occurring on E. Madison St. See project flyer (pdf) for more details. Repaving work will need to occur during the day.

Meeting summary notes from:

Project Update

Phase 1 – Stormwater Storage Facility at 30th Ave E and E John St. has been completed.

Learn more about Phase 1.

Phase 2 Update of Madison Valley Stormwater Project

Phase 2 includes building a new 48 inch, 6 ½ block long stormwater pipeline in the NW section of the Madison Valley basin and the construction of 2.2 million gallons of stormwater storage in the SW corner of Washington Park, 1.3 million gallons in a mostly underground tank, and 0.9 million gallons of additional stormwater storage in a bermed landscaped area adjacent to the tank only to be utilized during extreme storms.

Below are some key project dates:

Graphic Overview of Project with Pipeline Route (pdf)

Graphic of Landscape Plan (pdf)

Graphic of Landscape Details (pdf)

Phase 2 – Art Wall (pdf)

Project Schedule (pdf)

Overview

The Madison Valley area has experienced substantial surface flooding and sewer backup events. After the August 2004 storm, which resulted in significant flooding in the valley, Seattle Public Utilities (SPU) began an in-depth process to develop and evaluate many options to reduce the potential for flooding in the valley. SPU is currently designing a new stormwater conveyance and storage system to greatly reduce the potential for stormwater flooding in the valley. The project will be completed in two phases that, together, will be designed to contain the amount of stormwater that caused flooding in the two largest storms in 157 years of record - August 2004 and December 2006. The combined cost for Phase 1 and 2 is between $24 and $33 million. The cost range will narrow as Phase 2 design progresses.

Background

The Madison Valley drainage basin in Seattle is an area that is located east of Capitol Hill, west and south of Washington Park, and north of the Central District. Shaped by a glacier and eroded by floods, the valley has steep hillsides and was once drained by a stream that emptied into Union Bay via what is now the University of Washington Arboretum.

In the late 1860s, a wagon road was cut through from downtown to Madison Park along the current route of E Madison St. In the 1880s, a cable railway with a trestle across the valley was constructed to provide better access to Madison Park and environs. In the early 1900s, the trestle was replaced with fill, which blocked the natural watercourse, and a combined sewer trunk pipe (54” diameter south of Madison, 60” and 72” diameter north of Madison) was built to carry sewage and stormwater under the fill and northward. Today, the Madison Valley trunk line is connected to the King County combined sewer interceptor that conveys sewage and stormwater to the West Point Sewage Treatment Plant.

Over the past several decades, there have been a number of instances of flooding and sewer back-ups in Madison Valley during times of heavy rain fall. The City has taken actions since the 1980s to mitigate the risk of these flooding occurrences through installation and modification of sewer and drainage infrastructure; however, on August 22, 2004 and December 14, 2006, storm events which hit the city and the Madison Valley neighborhood were especially severe, causing some residents around 30th Ave. E and E John St. to have up to 5 feet of water in their basements and flooding in their backyards.

After the August 2004 storm, SPU began an extensive effort to monitor and model the storm and wastewater flows in the valley to better understand the causes of the flooding. The results of that effort informed a highly in-depth process of analyzing project alternatives that would reduce flooding in Madison Valley, especially in the vicinity of 30th Ave. E and E John St., an area that experienced the worst historic flooding.

SPU built an interim stormwater holding area at 30th Ave. E and E John Street which was completed in late December 2006 and holds up to 1 million gallon of stormwater during large rain storms.

As the alternatives for the long-term solution were considered, improving stormwater infrastructure on E Madison St. near 29th Ave. E also was an important consideration. SPU undertook an extensive public involvement effort through the development and selection of the preferred alternative, which was approved for implementation by Seattle City Council and the Mayor in June 2008.

SEPA Completed Spring 2008 for Project

In spring 2008, Seattle Public Utilities completed the required State Environmental Policy Act (SEPA) Environmental Checklist (pdf) for the construction of the two preferred long-term solution alternatives to alleviate sewer backups and system-related stormwater flooding in Madison Valley during very large storms. A SEPA Addendum was published by SPU on June 22, 2009. View SEPA Addendum (pdf) and cover letter to Addendum (pdf).

Newsletters