HomeMy WebLinkAboutTrans 2007-06-25 Item 3B - Discussion - SR 518 Route Development Plan ModificationsTo:
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ISSUE
INFORMATION MEMO
Mayor Mullet
Public Works DirectordjT)
June 15, 2007
SR 518 Route Development Plan Proposed Modifications
Attachment III.B.
Present to the Transportation Committee the proposed modifications to the WSDOT adopted
Route Development Plan for SR 518 and authorize the City of Tukwila's concurrence.
BACKGROUND
WSDOT has prepared and adopted a Route Development Plan (RDP) for SR 518 from Tukwila
to Burien and an Environmental Assessment for the SR 518 SR 99 interchange. The project
is largely in response to the current desire by the Ports to implement improvements that will
support air traffic growth at SeaTac Airport as well as access to and from the cities of SeaTac
and Tukwila.
The adopted plan has since presented conflicts between the Port of Seattle trying to develop
property north of SR 518 and components of the RDP. The Port of Seattle has met with the
City of SeaTac and other stakeholders to develop alternative scenarios for the 24th Ave S S
154th St SR 99 interchange. The proposed changes are shown on the attached sheets and will
be presented at the meeting.
ANALYSIS
The Port of Seattle and the City of SeaTac have met and developed alternative plan concepts
for SR 518 that do not constrain future development of property owned by the Port of Seattle.
The proposed alternatives are shown on the attached sheets as well as the existing alternatives
that are proposed for removal from the RDP.
In order to have WSDOT re -open the RDP and make modifications to it, agreement by the
other affected agencies is required.
RECOMMENDATION
Discuss the proposed changes to the RDP as presented and authorize support for modifying the
RDP.
attachments: letter from Port of Seattle, sketches of proposed alternatives
(P:ali= TC 062507 SR $IS)
5
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Port of Seattle
April 6, 2007
Jim Morrow
Public Works Director
City of Tukwila
6300 Southcenter Blvd.
Tukwila, WA 98188
Dear Jim,
In the interest of developing and enhancing property north of SR -518, Sea -Tac
International Airport, in partnership with the City of SeaTac, has revisited the SR -518
Route Development Plan (RDP). Both the 1997 Airport Master Plan Update as well as
the 2005 Draft Sea -Tac International Airport Comprehensive Development Plan (CDP)
discussed the need for future development of the L -shape property north of SR -518. As
you know, the development of the L -shape requires the construction of a secure bridge to
allow pallet loaders and tugs to operate between the cargo facilities and aircraft. While
we were investigating the physical constraints associated with the bridge, we surfaced a
better solution not only to address structural conflicts with planned frontage roads, but to
remove unwarranted improvements such as the single point, urban interchange (SPUD at
SR 99 and SR 518.
Airport and City of SeaTac staff met in April of 2006 to develop alternative scenarios for
the 24 Ave. S. S. 154 St. SR -99 interchange. Each scenario had two common
components, removal of the frontage roads and the SPUI. Four scenarios were analyzed
for the years 2010 and 2024 without frontage roads, but with other modifications to ramp
geometry, signalization, and ramp terminal locations. Where appropriate, scenarios were
reanalyzed with a change in land use assumptions to reflect transit- oriented development
around the S. 154 St. Sound Transit LRT station. Supplementing the interchange
analyses are intersection Level -of- Service (LOS) tables provided by the CDP Surface
Transportation Report. As the airport reaches capacity in 2024, airport related traffic
plateaus and subsequently decreases in future years.
Intersection analyses of 24 Ave. S., S. 154 St., and WB SR 518 are attached to this
letter. I have also enclosed supporting documentation for the modeling methodology.
Overall LOS in the vicinity of SR 518 is acceptable with the modifications described.
With agreement from WSDOT, both the Airport and the City of SeaTac recommend
inserting Concept 2E as the revised concept for the 24 Ave. S. S. 154 St. SR -99
interchange. The new concept would replace the existing recommended RDP concepts
known as the Modified Split Diamond/Loop and the Phased Combined Diamond/SPUI,
and all their associated components
Seattle- Tacoma
International Airport
P.O. Box 68727
Seattle, WA 98168 U.S.A.
TELEX 703433
FAX (206) 431 -5912
APR 12 Z007
TtJKWIL A
PUBLIC WORKS
Port of Seattle
AdMi Concept 2e would include a new westbound off -ramp from SR 518 to SR 99, but would
permit only right turns from this new ramp. The loop ramp to southbound International
Blvd would remain, and a ramp to S 154 St at 32 Ave S or another location farther
west, would be included. Portions of the project could be completed in phases to be
determined at a later date. Total cost for Alternative 2e would be approximately $33
million in 2006 dollars, not including programmatic costs. In comparison, costs for
concept 2b were $32 million with similar parameters.
Both estimates included widening of westbound SR 518 to the north between the 51 Ave
S ramps and SR 99 to add a new auxiliary lane, widening of the bridge over 42 Ave S,
and development of a new exit gore to the westbound collector- distributor road. Costs
estimates were established for concepts 2e and 2b only since they were considered the
most conservative project from a scope perspective. For these estimates, HNTB has used
costing templates from the SR 518 3' Lane Project. Costs reflect a 30% contingency due
to high demand for labor and materials. We have also added a row to reflect engineering
and construction management tasks for the alternatives.
Included with this letter are three documents: 1) a signature page, 2) the intersection
traffic analysis, and 3) cost estimates. The signature is necessary for WSDOT to verify
that the interested parties have at least read and agree with the changes to the RDP. The
traffic analysis explains the various concepts considered by the group and their respective
intersection Levels of Service (LOS). The third document includes two pages of cost
estimates for the improvements seen in concept 2b and 2e. The Airport is eager to begin
development of the L -shape property and is ready to complete the addendum process for
the SR 518 RDP. If there is any additional information necessary please feel free to
contact me.
Regards,
Peter LindsaY
Senior Planner
Sea -Tac International Airport
PL:pl
Enclosures
Seattle Tacoma
International Airport
P.O. Box 68727
Seattle, WA 98168 U.S.A.
TELEX 703433
FAX (206) 431 -5912
F�1
8
Approved By:
Washington State Department of Transportation
Strategic Planning and Programming Division
Urban Planning Office
WSDOT, Northwest Region Administrator
Concurrence:
City of SeaTac, Public Works Director
City of Burien, Public Works Director
City of Tukwila, Public Works Director
ROUTE DEVELOPMENT PLAN
State Route SR 518 Addendum
From State Route 509 to Interstate 5
Date
Date
Date
Date
Port of Seattle, Managing Director Aviation Planning Date
WSDOT State Program Lead, UCO Date
SR 518 Interchange at International Boulevard South 154th Street
Interchange Alternatives Analysis
Alternative 1 a (Existing)
Altemative 1 c
1: 444733 \traffickepo rt\aitsa nalysisv3b.doc
Printed 3/21/2007
DRAFT
Page 2
Alternative 2b
Alternative 2e
Leaend
Active Roadway
Vacated Roadway
Signalized Intersection
Unsignalized Intersection
Traffic Lanes
Figure 1
International Boulevard South 154 Street Interchange Alternatives
/0
C. LA RegNrr R P Car%) GE P
Figure EX-5
24th Avenue S/Airport/SR 99 Interchange Concepts
Split Diamond
Features:
•Ramps to/from the east at SR-99.
•Ramps to/from the west at 24th Ave S.
•Onevay frontage roads connecting
20 Ave S and SR-99.
•Ramp terminal intersections at SR-99
and 20 Ave S are signalized.
Modified Split
Diamond/Loop
Features:
•WB ramp from SR-518 to NB SR-99.
WB ramp that diverges from NAE
offramp to SB SR-99 (via loop ramp)
and 24g Ave S (via frontage road).
•Frontage roads connecting ramps at
20 Ave S and SR-99.
•Slip ramp from 150 Ave S to WB
frontage road for WB traffic from SR-
99.
•Ramp terminal intersections at SR-99
(EB ramp only) and 20 Ave S are
signalized.
Phased Combined
Diamond/SPUI
Features:
Phase 1
Full SPUI at SR-99.
Partial 20 Ave S Interchange.
Optional Phase 11
Complete 20 Ave S Interchange
concurrent with, or after, 3
eastbound lane on SR 518.
PARSONS
Concept refinement and evaluation to be confirmed at
Advisory Meeting on November 29th
Executive Summary DRAFT Route Development Plan