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Madison Valley Stormwater Project

Update – December 19, 2011

  • 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.

Good News! Phase 2 Madison Valley Stormwater Project is now operational

The project team is excited to announce that the new 6.5-block long pipeline that conveys stormwater from the NW section of Madison Valley to the new 1.3 million gallon stormwater tank in the SW section of Washington Park during large rain storms, is now operational! In addition, there is a 0.9 million above-ground stormwater holding area adjacent to the new tank that can be used to temporarily store stormwater during very extreme storms. Furthermore, major improvements to the drainage system on E Madison St, near 29th Ave E are complete. These improvements greatly reduce the potential of sewer backups and stormwater flooding in the vicinity of 30th Ave E and E John St, as well as greatly reduce the potential of stormwater flooding in the vicinity of E Madison St near 29th Ave E.

Final grading & landscaping activities in Washington Park on hold until spring 2012 - Crews temporarily demobilizing for the winter

Crews are clearing the staging area at 29th Ave E and E Roy St, temporarily demobilizing equipment and cleaning up the streets. In November, we informed the community that work in the park was on hold until next spring. The soil conditions in the park are too wet at this time to complete final grading and landscaping. We have installed temporary erosion control measures in the park to protect the slopes from wet weather disturbances this winter.  We will follow-up with the community when we know more information about a start date in spring 2012.

While the project is on hold, the community can expect the following:

Next spring, we will complete the final grading and landscaping in Washington Park, pavement restoration near 29th Ave E and E Roy St and install a permanent sidewalk on E Madison St near the former project construction entrance into the Washington Park.

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

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)

200 Block Drainage Improvements (vicinity of 31st Ave E & E Denny Way)

On August 11, 2009, the City Council's Environment, Emergency Management and Utilities Committee approved the bill authorizing the acceptance of six easements on five real properties known as 201, 205, 209, 215 and 217 31st Avenue East, Seattle, Washington for stormwater drainage improvement purposes. These improvements were completed in October 2009. They will help alleviate surface ponding from Seattle rain storms that are average in size. The Phase 1 & 2 of the project were designed to substantially improve the storm and sewer infrastructure in the vicinity of 30th and John St., which will greatly reduce flooding potential in that area during large rain storms.

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).

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