HomeMy WebLinkAboutTrans 2011-08-15 Item 2C - Discussion - Tukwila Urban Center Pedestrian-Bicycle Bridge ReportCity of Tukwila
Jim Haggerton, Mayor
INFORMATIONAL MEMORANDUM
TO: Mayor Haggerton
Transportation Committee
FROM: Bob Giberson, Public Works Director w;
DATE: August 12, 2011
SUBJECT: TUC Pedestrian Bicvcle Bridqe
Project No. 90510403
Type, Size and Location Report
ISSUE
Presentation of the Pedestrian /Bicycle Bridge project from inception to the draft Type, Size, and
Location Report.
BACKGROUND
In 2007, the City contracted with KPFF to begin the design of a pedestrian /bicycle bridge
crossing the Green River. This work was partially funded by an Enhancement Grant of
$200,000.00. The first step in designing a new bridge involves a Type, Size, and Location
(TS &L) Study to determine the best placement for the bridge and what kind of bridge is
appropriate. The first draft of the TS &L was completed in August 2008. Additional funding was
necessary to complete the design of the bridge and staff continued to pursue grant
opportunities. With recent awards of two grants totaling approximately $1,251,000.00, adequate
funding is available to complete the bridge design.
DISCUSSION
The TS &L Report has been reviewed by staff and is being finalized for presentation to the
Council for acceptance and selection of the bridge type to complete design. A presentation on
the history of the Pedestrian /Bicycle Bridge project, along with highlights of the forthcoming
TS &L Report, will be presented to the Transportation Committee on August 15, 2011. The Final
Draft of the TS &L Report will be distributed to the Committee under separate cover sometime
the following week. The TS &L Report will be formally presented to the Committee at the
September 6, 2011 meeting. The draft Executive Summary is attached.
RECOMMENDATION
Information Only.
Attachment: Draft Executive Summary
w: \pw eng\old p drive\cyndy \pedestrian bridge \information memo is &I presentation 8- 15- 11.docx
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1. Executive Summary
The primary goal of the Tukwila pedestrian bridge is to create a strong link between transit oriented
development related to Tukwila Sounder Station and the Tukwila Urban Center. In analyzing potential
bridge locations across the Green River, it became apparent that bridging the river is just one link that
needs to be considered. There are no clear connections with Chrmstonsen Road to west or the
Interurban Trail and future Tukwila Station to the east. It also became apparent there are two rivers to
cross: the Green River and West Valley Highway (SR 181). The West Valley Highway acts as a barrier
as much as the Green River because of its width, amount of traffic, anc€ no direct access across.
This report provides the results of the type, size, ario Iopation (TS &L) studyfor. the Green River crossing
and the associated trail alignment beginning at &ikr Boulevard crossing ove #1 Green River, and
terminating at the West Valley Highway. The TS &L phase includes the study of tf}' ,locations and
alignments, bridge types and sizes, and project aesthetics, and defines permitting requirements
related to the trail approaches and river, crossing.
Hydraulic, geotechnical, and environmerltak` aaKs were performmlE
trail alignment and bridge structure alternatives The hydraulic t
Corps of Engineers, King County, and theVty to establish the cu
floodplain and the required•.vertical ciearan'cefor structures abo
geotechnical study was performed to evaluate the genetat, geol
alignments and provide recommendations for ea h erpinkmer
foundations. A preliminary environmental evaluat orl"Was condu
define possible permits.
to support the development of both
>k included coordination with the
ant location of the 100 -year
the 104 -year floodplain. A
conditions along the proposed
>,.:retaining walls, and bridge
ed to identify critical areas and
Site constraints affecting the bridge kicatido -wo trail alignment include the proximity of private
propel'ty�#nd the loc tlon_of a major waterline o i 'ad. by the Seattle Public Utilities (SPU). Properties
incl'ude'Riverview Plaza Park,. Embassy Suite's, Marriott Courtyard, Residence Inn, a 76 Gas
Station, and a private residbrice. Each alignment alternative balances the need for right -of -way
acquisition while not encroaching within the CPU right -of -way with the bridge structure.
The bridge alternatives evaluated for the main spans over the Green River were a twin tied arch bridge,
a single inclined arch bridge, a single tied arch bridge, and several truss alternatives. These options
were selected due to the long spans 200 feet) required to span the Green River. The structure
alternatives were developed to Xfbvel that enabled the preliminary sizing of structural member that
could then be used to develop cost estimates.
Three trail alignments were studied for the approach west of the river. The alternatives travel at -grade
through or around the Riverview Plaza. East of the river, both a structural ramp alternative and an
elevator /stairway combination alternative were considered for the approach to the main river span.
Cost estimates were developed for each bridge and trail alignment alternative. The cost estimates
included three trail alignment alternatives for the western approach, five Green River pedestrian bridge
alternatives, and two structural approach styles for the eastern approach.
City of Tukwila
Pedestrian /Bicycle Bridge