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Madison Valley Project
Madison Valley Stormwater Project
What’s New
February 8, 2010 - City Council Concept Approval for Master Use Permit for Phase 2, Madison Valley Stormwater Facility
City Council concept approval was granted for the Master Use Permit for the Madison Valley Stormwater Facility (Phase 2) consisting of a 1.3 million gallon, partially below grade tank and a separate 0.9 million gallon above grade open stormwater storage area in the south end of Washington Park and Arboretum. View Council Clerk File 310085 (PDF)
Phase 1 - Stormwater Storage Facility at 30th Ave E and E John St
Regular construction days/hours: Monday - Thursday, 7:30 AM to 6 PM
"Local Access Only" - 30th Ave E between E John St & E Denny Way. Access will be maintained for residents on the block of 30th Ave E.
"No Parking" - between 7 AM to 6 PM (on working days) on 30th Ave E between E Denny Way & E John St, and for half the block on E Denny Way west of 30th Ave E. We’re working with impacted residents to address concerns about these traffic restrictions. Periodic parking restrictions - E Denny Way between 29th & 31st Ave E
Haul Route Map (PDF)
Phase 1 Construction Notice (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 purposes. These drainage improvements are scheduled to be completed by the end of 2009
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.
- • Phase 1 consists of expansion of an above-ground stormwater holding area at 30th Ave. E and E John Street.
- • Phase 2 consists of construction of a new stormwater pipeline and storage system in Washington Park that will have the capacity to hold approximately 2.1 million gallons of stormwater.
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 Adendum (PDF).
2006 Storm Investigation Report for Vicinity of Dewey Place
Following the storm in December 2006, Seattle Public Utilities contracted with CH2M Hill, a national engineering consulting firm, to investigate the 2006 flooding events in the vicinity of Dewey Place E. SPU held a public meeting to discuss the results of this investigation report in spring 2007.
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