Pontoon construction project overview

February 2013

• WSDOT is moving forward with pontoon construction to replace the aging and vulnerable SR 520 floating bridge on Lake Washington

• The $367.3 million Pontoon Construction Project broke ground in February 2011 at a 55-acre site in Aberdeen. • As part of this project, contractor Kiewit-General Joint Venture (K-G) has built a new casting basin facility and is constructing 33 concrete pontoons that will be used to replace the SR 520 floating bridge.

An aerial photograph of the pontoon casting basin and Grays Harbor in May 2012. Photo courtesy of Soundview Aerial Photography.

Seattle

Kenmore

Olympia

Tacoma

GraysHarbor

Lake Washington

MEDINA

MADISON PARK

West Connection Bridge

Barrier andrestriping

EastApproach

Bridge Maintenance Facility

Floating Bridge

SR 520 Floating Bridge and Landings Project elements

99

5

5

405

405

90

90

520

167

509

Puget Sound

ElliottBay

Shoreline

Seattle

MercerIsland

FederalWay

Port of Tacoma

Kent

Renton

Bellevue

Auburn

Fife

Snohomish County

King County

King County

Pierce County

BothellKenmore

Redmond

Sea-Tac

202

900

522

Lake Washington Lake

Sammamish

509

161

99

18

516

Floating bridge and landings project area

February 2013

Project elements include:Design and construction of:

• New six-lane floating bridge superstructure and roadway, including HOV lanes and a bicycle/pedestrian path. • 44 supplemental stability pontoons. • Anchors and anchor cables. • Permanent East Approach. • Final connection to Evergreen Point Road vicinity. • Transition structures between East and West Approaches and floating bridge. • New maintenance facility and dock in Medina.

Towing pontoons to Lake Washington.Assembly of the new floating bridge.Removal of existing floating bridge and landings.

SR 520 construction activities are taking place at multiple locations in Washington state.

99

5

5

5

405

405

90

520

167

167

509

18

161

99

516

Puget Sound

ElliottBay

Shoreline

Seattle

MercerIsland

FederalWay

Port of Tacoma

Kent

Renton

Bellevue

Auburn

Fife

Snohomish County

King County

King County

Pierce County

BothellKenmore

Redmond

Sea-Tac

202

900

522

Lake Washington Lake

Sammamish

B

C

D

E

SR 520 construction around the state

A. Grays Harbor (Feb. 2011 – 2014) • Pontoon construction• Pontoon moorage• Casting basin construction

B. Port of Tacoma (Nov. 2011 – early 2014)• Pontoon construction• Pre-cast concrete elements• Pontoon moorage and outfitting

C. Kenmore (Feb. 2012 – early 2014)• Anchors• Pre-cast concrete element• Deck sections

D. Lake Washington (Spring 2012 – 2016)• Bridge assembly• Bridge Maintenance Facility• East and West Approach connections• Decommission existing bridge

E. Eastside (Spring 2011 – Winter 2014)• Lid construction• Highway widening• Culvert installation

349 direct jobsJan. 2013

174 direct jobsDec. 2012

24 direct jobsDec. 2012

254 direct jobsDec. 2012

207 direct jobsDec. 2012

1,008 direct jobsWinter 2013

TOTAL

Seattle

Kenmore

Olympia

Tacoma

GraysHarbor

A

All towing will occur in designated shipping lanes.

Crews on site in Kenmore. Pontoon progress in Tacoma.

February 2013

In addition to direct employment listed above, SR 520construction creates opportunities for vendors, suppliers and other services like restaurants and retail.

Supplemental

stability pontoons(54)

Supplemental stability pontoon

Longitudinal pontoons(21)

Longitudinal pontoon

Superstructure

Cross pontoons(2)

Cross pontoon

The three types of pontoons that will support the new SR 520 floating bridge.

A representation of pontoons being assembled on Lake Washington.

February 2013

SR 520 floating bridge pontoons The new SR 520 floating bridge will be supported by three types of concrete pontoons:

Longitudinal pontoons (21) – These are the largest pontoons at approximately 360 feet long. They form the backbone of the bridge and support the roadway superstructure. • Constructed in Aberdeen facility • Weight: 11,100 tons

Cross pontoons (2) – These mark the ends of the floating bridge section and the transition to the East and West Approach structures. • Constructed in Aberdeen facility • Weight: 10,100 - 10,550 tons

Supplemental stability pontoons (54) – These smaller pontoons help stabilize and support the weight of the new floating bridge. • Constructed in Aberdeen facility (10) and Tacoma facility (44) • Weight: 2,500 - 2,820 tons

February 2013

FOR ILLUSTRATION PURPOSE ONLY - NOT TO SCALE

???

Wall forms

Keel slab

Wall formsupports Wall form

supports

Wall formsupports

Precast panelInternalwatertightcell

Rebar

Rebar

Rebar

Post-tensioning ducts

Post-tensioning duct

Exterior wall slab

Wall FormSupports

How to build a pontoon

bals leek ni etercnoc ruop dna slenap tsacerp roiretni llatsnI stcud gninoisnet-tsop llatsni dna ,raber ,smrof llaw teS • Longitudinal pontoons: 90 precast panels • Cross pontoons: 57 precast panels • Supplemental stability pontoons: 9 precast panels

Pour top slab rebar and post-tensioning ducts Remove wallforms and perform post-tensioningto add strengh

Pour concrete for exterior walls and joints between interior precast pannels

1 2 3

64

Post-tensioning duct

Wall formsupports

Pour top slab concrete5

Remove wall forms

Remove wall forms

Post-tensioninghead

Post-tensioning cable

End wall

Top slabTop slab

Computer analysis shows rebar in pontoons provides required structural capacity; expert review panel adds two new members

who will assist in the panel’s review of the design, materials, construction methods, and overall integrity of the pontoonsFloating bridge assembly continues on Lake Washington

Crews encounter spalling and end-wall cracking after a

pontoon is post-tensioned

Crews completed repairs to the first pontoon and pre-emptive

modification in remaining pontoons

WSDOT convenes an expert review panel to

address causes of spalling and end-wall cracking

Repaired pontoons are floated out of the casting basin; crews complete

pre-tow inspections

Pontoons are towed into Lake WashingtonA leak is found and then repaired between two internal cells where

ballast water was placed; Crews find additional moisture and WSDOT begins analysis of additional repair options

WSDOT reconvenes expert review panel to conduct additional analysis of pontoon design, repairs

and construction management processes

KG rejects 9 of 345 precast panels for Cycle 2 pontoons in accordance with

quality assurance process

2012 Aberdeen pontoon issues and repairs

Location of leak between cells

Expert review panel issues its report, and recommends WSDOT revise post-tensioning design

and maintain rigorous concrete thermal controlsWSDOT starts Cycle 2 construction with revised post-tensioning

design and other panel recommendations

May June July Aug Sept Oct Nov Dec

February 2013

February 2013

Pontoon joining on Lake Washington

N

Note: For illustrative purposes only. Not to scale. All joints are sealed with concrete grout.

W

W

VU

V U

Joining bolt (total of 80)

Alignment key

Recess frame

VNEVNW

VNW, VNE, VSW, VSE

VSEVSW

Alignment key

Recess frame

Post-tensioning strand (total of 28)

Joining bolt (total of 16)

Post-tensioning strandJoining bolt

Rubber gasket seal

Rubber gasket seal

Cross pontoon

Longitudinal pontoons

Supplemental pontoons

February 2013

SR 520 longitudinal pontoons design components

Lake Washington

TB C D E F G H I J K L M N O P Q R SA U V W

For illustration purposes only - not to scale

Longitudinal pontoon

Final six-lane bridge configuration on Lake Washington

Other components include:• Inserts for electrical conduit• Walkways and ladders for crew access• Maintenance access hatches

Pre-cast interior walls1

2

4

5

Post-tensioningducts

Cast in place concrete (bottom, sides and top)

Bolt beam that allowspontoons to be joinedtogether.

3aHole for bolt shaft connection between pontoons

3bPost-tensioning heads at the end wall of the pontoon

Cross pontoons

LongitudinalpontoonsSupplementalstability pontoons