B+H West Seattle Bridge Replacement Proposal - Cost and Schedule by B+H Architects

BRIDGING SEATTLE COST | SCHEDULE ENVIRONMENT

The West Seattle Bridge Reimagined in Mass Timber Summer 2020

THE BEST OPTION It’s time to bring a new kind of infrastructure to Seattle. We’ve proposed a bridge constructed of mass timber steel composites. It would accommodate vehicular traffic, light rail, pedestrians, and bike traffic, and it could be a beautiful, symbolic representation of Seattle’s dedication to sustainability and our relationship with trees and timber. The benefits include longer lifespan than the typical concrete bridge, smaller carbon footprint, and the potential for immensely positive economical effect in the Pacific Northwest. A mass timber bridge also gets cars over the bridge and into West Seattle faster than the cast-in-place concrete option. B+H and SMEC partnered with industry veteran Lane Construction to assemble this cost and schedule comparison of West Seattle Bridge options. What we found is that a mass timber steel composite West Seattle Bridge can be finished in 28 months - 16 months faster than castin place concrete.

TABLE OF CONTENTS 1 OVERVIEW 2 BASELINE 1: CAST-IN-PLACE CONSTRUCTION 3 MT STEEL DESIGN: MASS TIMBER- STEEL COMPOSITE CONSTRUCTION 5 CONSTRUCTION SCHEDULE 6 CONSTRUCTION COST 7 CARBON FOOTPRINT 9 POSITIVE EFFECTS ON PHYSIOLOGY AND PSYCHOLOGY 10 AIR QUALITY HEALTH HAZARD DURING MANUFACTURING 10 COMMUNITY AND INDUSTRY IMPACTS 11 TEAM 13 APPENDIX

SCOPE: The scope of this comparative cost and schedule analysis includes the bridge superstructure and substructure, from Piers 15 to 18, incl.

OVERVIEW Our approach when examining options for the future West Seattle Bridge’s main bridge spanning over the river includes consideration of two types of structures. The first structure option involves replacement of the compromised superstructure of the main bridge utilizing a cast-in-place concrete segmental design (Baseline 1). This would be very similar to the existing structure type matching the same width. A comparison cost analysis has been performed on a precast variation of the above option (Baseline 2) but no significant economies were observed. Our proposed structure option (MT-Steel Design) is focused on replacing the West Seattle Bridge with a re-imagined mass timber and steel composite design.

Assumptions in both designs: • Assessment is relevant only to the structural unit of the main bridge spanning over the river (590 feet) and the two adjacent smaller spans (375 feet, ea.). No consideration has been given to any improvements associated with the approach span portion of the bridge. • The current bridge foundations and substructure for the three spans will be replaced in all options. Baseline 1 and 2 will require new, stronger piers and foundations to support a wider drive deck that includes LRT and bicycle lanes. The MT-Steel Design is a light-weight structure; new piers and foundations are less substantial than in the Baseline design structure

BASELINE 1: CAST-IN-PLACE CONSTRUCTION Cast-in-place is a technology of construction where structures are cast at the site in formwork. This differs from precast concrete technology (Baseline 2) where elements are cast elsewhere and then brought to the construction site and assembled. Following existing bridge demolition, the construction sequence would be as follows: • • • • •

Construct new foundations and piers at four pier locations. (Twin piers for Baseline 1 and 2) Install traveling form systems (8 required) on completed pier tables Construct balanced cantilever sections Construct 80-foot backspan tie in sections on falsework Complete joint connections and remaining deck works

Benefits: • the • •

General type and appearance of structure would mirror that which currently serves local community This design type affords long span crossings, thus limiting ground disturbance Process enables reduction in number of closures required in the maritime channel

This option costs less upfront, but the linear nature of cast-in-place construction yields slower overall production rates and is not preferred for projects requiring fast-track construction.

MT STEEL DESIGN: MASS TIMBER - STEEL ARCH COMPOSITE CONSTRUCTION This concept design includes side spans on either side of the main river crossing supported by an under the deck truss system. The main span over the river would be a composite Steel Arch and Mass Timber design. The work would be staged in the following phases: Stage 1: • Main bowstring structural steel element assembled at ground level of the underdeck support • Entire span to be lifted vertically into its final position at deck level using a multistrand heavy lift jacking system attached to the upper area of the bridge columns • Once secured to its permanent fixation points, the jacking system will be removed, movement joints installed at connection with approaches and remaining concrete riding surface of the deck would be cast in place at this location

Stage 2: • Main span steel arch pre-assembled on the ground in a staging area • Arch re-positioned to final lifting location • Entire span to be lifted vertically into its final position at deck level using a multistrand heavy lift jacking system attached to the upper area of the bridge columns • Once secured to its permanent fixation points, the jacking system will be removed, movement joints installed at connection with approaches and remaining concrete riding surface of the deck would be cast in place at this location Benefits: • Substantial times saving on overall project schedule with pre-assembly work taking place concurrently with new foundation and pier building activities • Timber design elements which reflect a main economic engine of the region • Overall safety of the workforce enhanced with primary assembly activities taking place at ground level This is initially more expensive but incorporates a construction approach that affords an accelerated project schedule since prefab components and installation are concurrent with demolition operations. Significant economies in the schedule can offset the more expensive direct cost of the mass timber and steel arch alternative design.

CONSTRUCTION COST

CONSTRUCTION SCHEDULE The design and demolition phases are the same for all three options, but the driving elements for each schedule are slightly different. The cast-in-place bridge can’t begin the work of casting-in-place until demolition has been completed. The Mass Timber - Steel composite bridge can begin fabrication earlier because fabrication is done offsite, so the design timeframe is the biggest impact. Cast-in-Place Schedule (Baseline 1): Because the “Demolition” phase must be completed first, the CIP construction is completely in the critical path and ahead of the completion of the “Demolition” phase. However, in this case, the “Design” phase is not as critical as per the “Mass Timber / Steel” option. Overall, the construction of this option is lasting 44 months from NTP. Precast Concrete Schedule (Baseline 2): The production of precast segments at the precast yard can start out of the critical path and ahead of the completion of the “Demolition” phase. Neither the “Design” phase nor the “Demolition” phase are impacting the schedule. Overall, the construction of this option is lasting 40 months from NTP. Mass

Timber/Steel Schedule: The steel fabrication can start out of the critical path and ahead of the completion of the “Demolition” phase. The “Design” phase is highly impacting the start of the steel fabrication. Overall, the construction of this option is lasting 34 months from NTP.

Mass

Timber/Steel Accelerated Schedule (New Location): Significant further savings could be achieved, if the replacement bridge was built adjacent to the existing bridge, i.e., a few yards away from its current location. This would save time and cost, because the new bridge foundations and subsequent erection work could take place while demolition of the existing bridge an foundations are underway. Overall, the construction of this option is lasting 28 months from NTP.

CIP CONCRETE

PRECAST CONCRETE

MASS TIMBER/STEEL

MASS TIMBER/STEEL MOVED AND REALIGNED

Direct CostSuperstructure Foundations Substructure Add for LRT Width Job Overhead Corporate G+A and Profit Total Cost Premium, Relative to Baseline 1

MT-Steel Design

MT-Steel Design (New Location)

Baseline 1 (CIP)

Baseline 2 (PC)

$123,022,000

$64,312,500

$68,670,000

$23,420,000

$27,125,000

$6,875,000

$7,980,000

incl.

$17,978,000

$23,463,000

incl. $25,500,000

$20,500,000

$33,000,000

$30,000,000

$26,823,000

$22,559,000

$23,586,000

$205,640,000

$200,640,000

19%

16%

$172,955,000 $180,824,000 5%

ASSUMPTIONS

Cost comparisons for the three bridge types: MT-Steel Design, MT Steel Design at new location adjacent to the current bridge, Baseline 1 (Cast-In-Place Concrete), and Baseline 2 (precast Concrete). Included in all options are the cost of the foundation, piers, and bridge deck structures, incl. LRT and bicycle lanes. No inclusion has been made for the cost of demolition, although this work activity has been noted In the schedule. The primary items that are not included in this pricing study include the following: • No improvements to the low level existing approach spans leading up to the main span. • No inclusion for costs associated with expansion joints or bearings. • No inclusion for costs associated with parapet walls. • No inclusion for costs associated with traffic signage, traffic control systems, traffic camera monitoring systems etc. • No costs to cover demolition and disposal of the existing bridge superstructure and substructure. • No electrical works. • No ballast or rail components or control systems to support light rail mass transit needs. • No electrical works. • No ballast or rail components or control systems to support light rail mass transit needs. • No architectural lighting or other forms of architectural treatments. • Bridge maintenance structures / platforms.

CARBON FOOTPRINT The design and construction industry plays an important role in mitigating climate change and seeks ways to reduce the amount of greenhouse gases -primarily carbon dioxide- that are released into the atmosphere. Steel and concrete have high CO2 emissions equivalents compared to engineered wood, or mass timber. Higher percentages of mass timber in a built structure result in a lower carbon footprint. Engineered wood is also a natural carbon sink; the sequestration and phased release of carbon is used to reduce climate change peak loads over time. Currently, in our design, the relatively small amount of mass timber compared to the amount of steel does not lead to a lower carbon footprint just yet. More iterative analyses will be necessary to maximize the use of engineered wood for our structure to significantly affect the carbon footprint balance. The positive, low-emissions equivalent of mass timber is shown in the graph below.

Cecobois

Mass timber is appropriate for long-span bridges and engineering applications can be further maximized for structures of this type. Engineered wood is a renewable product that can be sourced, manufactured, fabricated, and assembled in Washington state with local labor. Across the United States, there are 50,000 to 60,000 concrete posttensioned bridges -similar to the West Seattle Bridge- that have reached their end-oflife-cycle. Infrastructure is crumbling and the opportunities for engineered wood as an environmentally-friendly, innovative, 21st century design and construction technology are vast.

POSITIVE EFFECTS ON PHYSIOLOGY AND PSYCHOLOGY

AIR QUALITY HEALTH HAZARD DURING MANUFACTURING OF CONCRETE

Organic forms and wood surfaces positivley affect our personal health and are scientifically substantiated.

The manufacturing of concrete has a 60 percent higher emissions potential for ozone (O3) than steel/mass timber hybrid manufacturing. While ozone, high in our atmosphere, is important for protecting people from the sun’s ultraviolet radiation, at ground level it can be a significant health threat. Ground level ozone, or smog, is formed from a chemical reaction between nitrogen oxides and volatile organic compounds in the presence of heat and sunlight. Smog aggravates lung diseases such as asthma, emphysema, and chronic bronchitis.

Since the beginning of time we have been living in nature. And over this entire time the human body adapted to nature. Today, when we see natural materials, we automatically feel good because we are wired to the natural environment. There is a connection in the molecular database. We use “Biophilia” to describe this phenomenon. The sight of curvilinear form, shapes, and textures triggers positive responses in our emotional control center. They are judged more beautiful, as compared to their linear and orthogonal counterparts. Exposure to wood reduces the release of stress hormones, compared to other materials, and the sight of natural surfaces positively affects cortisol levels, a primary regulation hormone of the body.

COMMUNITY AND INDUSTRY IMPACTS Crossing the West Seattle Bridge has been a breathtaking experience for everyone who ever traversed the Duwamish River at height and enjoyed the scenic panorama of Mount Rainier, the Olympic Mountains, Puget Sound, the Seattle skyline and the Cascade Mountain ranges. In 2019, the bridge has been subject to over 100,000 vehicle trips and 390 bus trips per day. A bridge built with locally grown timber will compliment and ground the bridge to its community, industry, and shared value system that is deeply rooted in the heritage of Emerald City, a name manifesting our past and future. In Washington, the timber industry supports 101,000 workers, generates $5.5 billion in wages annually, and constitutes the third largest manufacturing industry.

Washington Forest Protection Association

Sneek Bridge, Netherlands

A GLOBAL TEAM THAT BUILDS WORLD-CLASS INFRASTRUCTURE We’re an international team with local champions. B+H Architects, SMEC, and Robert Bird Group are members of the Surbana Jurong Group (SJ). With over 50 years of track record in successful project delivery, SJ has grown to become one of the largest industrial, infrastructure, urban design, and architecture consulting firms. SJ is headquartered in Singapore, and its global workforce of 13,500 employees across more than 120 offices are driven by progressive thinking and creative ideas.

The B+H Architects Seattle studio was established in 2013. For the last 65 years, we’ve been growing from our Toronto headquarters and we’re operating in offices around the world. We combine strategic thinking with a bold and inspiring design to transform spaces, communities, and economies. We’ve worked with clients across the globe to design buildings and environments that are inspiring, functional, and contextual, and we have several firstof-kind projects that pioneered materiality and sustainability. The local Seattle office, which functions as the U.S. headquarters of our global consulting practice, leads the West Seattle Bridge effort.

WITH LANE CONSTRUCTION Lane has built over 150 bridges throughout the US in its 130-year history, completing more than 80 design-build projects totally more than $13 billion. Lane understands that its client’s objectives are based on developing high-quality, reliable, and durable infrastructure that improves mobility and economic potential within geographic areas. Lane has a reputation for reliability, scheduling, and project cost reductions

Its parent company, Webuild Group, recently completed the Genoa Bridge(pictured) in Italy in just 12 months. Nicknamed “The Site that Never Stops”, Webuild completed this vital piece of infrastructure with 20 contemporary parallel construction sites working 24 hours per day, 7 days per week. Lane is currently under contract for over $500 million in projects in the Greater Seattle Area, including work on the I-405 Renton to Bellevue Widening and Express Toll Lanes project and the Ship Canal Water Project.

APPENDIX

8/27/2020

v WEST SEATTLE BRIDGE REPLACEMENT (MASS TIMBER / STEEL vs. CIP CONCRETE vs. PRECAST CONCRETE) Cod.

1 2 3 4 5 6 7

8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Activity

NTP, MOBILIZATION & DESIGN - Same for All Options NTP ON SITE MOBILIZATION DESIGN [Demolition] DESIGN [Demolition - Approval] DESIGN [New Bridge] DESIGN [New Bridge - Approval]

DEMOLITION - Same for All Options EQUIPMENT [Procurement] EQUIPMENT [Design, Fabrication, Delivery, Assemblt, Test & commissioning] DEMOLITION [Edge & Median Barriers] DEMOLITION [Deck Overhangs] DEMOLITION [Back Spans - Unbalanced Segments] DEMOLITION [Main Spans - Balanced Cantilever Segments] DEMOLITION [Main Piers 16 & 17 - Pier Heads] DEMOLITION [Main Piers 16 & 17 - Piers] DEMOLITION [Main Piers 16 & 17 - Pile Caps] DEMOLITION [Main Piers 16 & 17 - Foundations] - It is assumed that existing Piles can be reused DEMOLITION [Transition Piers 15 & 18 - Pier Heads] DEMOLITION [Transition Piers 15 & 18 - Piers] DEMOLITION [Transition Piers 15 & 18 - Pile Caps] DEMOLITION [Transition Piers 15 & 18 - Foundations] - It is assumed that existing Piles can be reused

23 MASS TIMBER / STEEL OPTION - Single Deck Section 130 ft wide 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

47 CIP CONCRETE OPTION - Twin Deck Box Section 65 ft wide each 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75

SUBSTRUCTURES [Main Piers 16 & 17 - Foundations] - It is assumed that existing Piles can be reused SUBSTRUCTURES [Main Piers 16 & 17 - Pile Caps] SUBSTRUCTURES [Main Piers 16 & 17 - Piers] SUBSTRUCTURES [Main Piers 16 & 17 - Pier Heads] SUBSTRUCTURES [Transition Piers 15 & 18 - Foundations] - It is assumed that existing Piles can be reused SUBSTRUCTURES [Transition Piers 15 & 18 - Pile Caps] SUBSTRUCTURES [Transition Piers 15 & 18 - Piers] SUBSTRUCTURES [Transition Piers 15 & 18 - Pier Heads] DECK CONCRETE STRUCTURE [E/B - Balanced Cantilever Segments over Main Pier 16 - 1U&D] DECK CONCRETE STRUCTURE [E/B - Form Travellers Assembly & Commissioning] DECK CONCRETE STRUCTURE [E/B - Balanced Cantilever Segments at Main Pier 16] DECK CONCRETE STRUCTURE [E/B - Back span Unbalanced Segments at Transition Pier 15] DECK CONCRETE STRUCTURE [E/B - Balanced Cantilever Segments at Main Pier 17 - 1U&D] DECK CONCRETE STRUCTURE [E/B - Form Travellers Assembly & Commissioning] DECK CONCRETE STRUCTURE [E/B - Balanced Cantilever Segments over Main Pier 17] DECK CONCRETE STRUCTURE [E/B - Back span Unbalanced Segments at Transition Pier 18] DECK CONCRETE STRUCTURE [W/B - Balanced Cantilever Segments over Main Pier 16 - 1U&D] DECK CONCRETE STRUCTURE [W/B - Form Travellers Assembly & Commissioning] DECK CONCRETE STRUCTURE [W/B - Balanced Cantilever Segments at Main Pier 16] DECK CONCRETE STRUCTURE [W/B - Back span Unbalanced Segments at Transition Pier 15] DECK CONCRETE STRUCTURE [W/B - Balanced Cantilever Segments at Main Pier 17 - 1U&D] DECK CONCRETE STRUCTURE [W/B - Form Travellers Assembly & Commissioning] DECK CONCRETE STRUCTURE [W/B - Balanced Cantilever Segments over Main Pier 17] DECK CONCRETE STRUCTURE [W/B - Back span Unbalanced Segments at Transition Pier 18] DECK CONCRETE STRUCTURE [E/B & W/B - Form Travellers Disassembly] DECK CONCRETE STRUCTURE [Longitudinal CIP Stitch between E/B & W/B] FINISHING WORKS CIP CONCRETE OPTION - SUBSTANTIAL COMPLETION

76 PRECAST CONCRETE OPTION - Twin Deck Box Section 65 ft wide each 77 78 79 80 81 82

Start

End

Months M1

0.00

11.00

0.00 1.00 0.00 1.00 0.00 1.00

0.00 1.00 2.00 3.00 10.00 11.00

0.00 0.00 2.00 2.00 10.00 10.00

0.00

18.00

0.00 1.00 2.00 3.00 4.00 6.00 12.00 14.00 16.00 18.00 12.00 13.00 15.00 17.00

1.00 6.00 4.00 6.00 8.00 12.00 14.00 16.00 18.00 18.00 13.00 15.00 17.00 17.00

1.00 5.00 2.00 3.00 4.00 6.00 2.00 2.00 2.00 0.00 1.00 2.00 2.00 0.00

11.00

34.00

23.00

18.00 19.00 21.00 23.00 17.00 18.00 20.00 22.00 11.00 17.00 24.00 25.00 27.00 25.00 26.00 28.00 17.00 23.00 25.00 28.00 31.00 30.00 34.00

19.00 21.00 23.00 24.00 18.00 20.00 22.00 24.00 23.00 25.00 25.00 27.00 27.00 26.00 28.00 28.00 23.00 25.00 25.00 32.00 33.00 34.00 34.00

1.00 2.00 2.00 1.00 1.00 2.00 2.00 2.00 12.00 8.00 1.00 2.00 0.00 1.00 2.00 0.00 6.00 2.00 0.00 4.00 2.00 4.00 0.00

18.00

44.00

26.00

18.00 19.00 21.00 23.00 19.00 20.00 22.00 24.00 26.00 28.00 29.00 32.00 27.00 29.00 30.00 33.00 26.00 28.00 29.00 32.00 27.00 29.00 30.00 33.00 36.00 39.00 40.00 44.00

19.00 21.00 23.00 26.00 20.00 22.00 24.00 27.00 28.00 29.00 37.00 38.00 29.00 30.00 38.00 39.00 28.00 29.00 37.00 38.00 29.00 30.00 38.00 39.00 40.00 41.00 44.00 44.00

1.00 2.00 2.00 3.00 1.00 2.00 2.00 3.00 2.00 1.00 8.00 6.00 2.00 1.00 8.00 6.00 2.00 1.00 8.00 6.00 2.00 1.00 8.00 6.00 4.00 2.00 4.00 0.00

8.00

40.00

32.00

18.00 19.00 21.00 23.00 17.00 18.00

19.00 21.00 23.00 26.00 18.00 20.00

1.00 2.00 2.00 3.00 1.00 2.00

M9 M10 M11 M12 M13 M14 M15 M16 M17 M18 M19 M20 M21 M22 M23 M24 M25 M26 M27 M28 M29 M30 M31 M32 M33 M34 M35 M36 M37 M38 M39 M40 M41 M42 M43 M44 M45 M46 M47 M48 M49 M50 M51 M52 M53 M54

NTP, MOBILIZATION & DESIGN ‐ Same for All Options NTP ON SITE MOBILIZATION DESIGN [Demolition] DESIGN [Demolition ‐ Approval] DESIGN [New Bridge] DESIGN [New Bridge ‐ Approval]

DEMOLITION ‐ Same for All Options EQUIPMENT [Procurement] EQUIPMENT [Design, Fabrication, Delivery, Assemblt, Test & commissioning] DEMOLITION [Edge & Median Barriers] DEMOLITION [Deck Overhangs] DEMOLITION [Back Spans ‐ Unbalanced Segments] DEMOLITION [Main Spans ‐ Balanced Cantilever Segments] DEMOLITION [Main Piers 16 & 17 ‐ Pier Heads] DEMOLITION [Main Piers 16 & 17 ‐ Piers] DEMOLITION [Main Piers 16 & 17 ‐ Pile Caps] DEMOLITION [Main Piers 16 & 17 ‐ Foundations] ‐ It is assumed that existing Piles can be reused DEMOLITION [Transition Piers 15 & 18 ‐ Pier Heads] DEMOLITION [Transition Piers 15 & 18 ‐ Piers] DEMOLITION [Transition Piers 15 & 18 ‐ Pile Caps] DEMOLITION [Transition Piers 15 & 18 ‐ Foundations] ‐ It is assumed that existing Piles can be reused

MASS TIMBER / STEEL OPTION ‐ Single Deck Section 130 ft wide SUBSTRUCTURES [Main Piers 16 & 17 ‐ Foundations] ‐ It is assumed that existing Piles can be reused SUBSTRUCTURES [Main Piers 16 & 17 ‐ Pile Caps] SUBSTRUCTURES [Main Piers 16 & 17 ‐ Piers] SUBSTRUCTURES [Main Piers 16 & 17 ‐ Pier Heads] SUBSTRUCTURES [Transition Piers 15 & 18 ‐ Foundations] ‐ It is assumed that existing Piles can be reused SUBSTRUCTURES [Transition Piers 15 & 18 ‐ Pile Caps] SUBSTRUCTURES [Transition Piers 15 & 18 ‐ Piers] SUBSTRUCTURES [Transition Piers 15 & 18 ‐ Pier Heads] DECK STEEL STRUCTURE [Fabrication & Delivery to site] DECK STEEL STRUCTURE [Back Spans Assembly] DECK STEEL STRUCTURE [West Back Span Delivery to Erection Site] DECK STEEL STRUCTURE [West Back Span Partial Lifting & Underslung Arch Assembly] DECK STEEL STRUCTURE [West Back Span Final Lifting] DECK STEEL STRUCTURE [East Back Span Delivery to Erection Site] DECK STEEL STRUCTURE [East Back Span Partial Lifting & Underslung Arch Assembly] DECK STEEL STRUCTURE [East Back Span Final Lifting] DECK STEEL STRUCTURE [Main Span Assembly] DECK STEEL STRUCTURE [Main Span Delivery to Erection Site] DECK STEEL STRUCTURE [Main Span Final Lifting] DECK CONCRETE SLAB MASS TIMBER FINISHING WORKS MASS TIMBER / STEEL OPTION ‐ SUBSTANTIAL COMPLETION

CIP CONCRETE OPTION ‐ Twin Deck Box Section 65 ft wide each SUBSTRUCTURES [Main Piers 16 & 17 ‐ Foundations] ‐ It is assumed that existing Piles can be reused SUBSTRUCTURES [Main Piers 16 & 17 ‐ Pile Caps] SUBSTRUCTURES [Main Piers 16 & 17 ‐ Piers] SUBSTRUCTURES [Main Piers 16 & 17 ‐ Pier Heads] SUBSTRUCTURES [Transition Piers 15 & 18 ‐ Foundations] ‐ It is assumed that existing Piles can be reused SUBSTRUCTURES [Transition Piers 15 & 18 ‐ Pile Caps] SUBSTRUCTURES [Transition Piers 15 & 18 ‐ Piers] SUBSTRUCTURES [Transition Piers 15 & 18 ‐ Pier Heads] DECK CONCRETE STRUCTURE [E/B ‐ Balanced Cantilever Segments over Main Pier 16 ‐ 1U&D] DECK CONCRETE STRUCTURE [E/B ‐ Form Travellers Assembly & Commissioning] DECK CONCRETE STRUCTURE [E/B ‐ Balanced Cantilever Segments at Main Pier 16] DECK CONCRETE STRUCTURE [E/B ‐ Back span Unbalanced Segments at Transition Pier 15] DECK CONCRETE STRUCTURE [E/B ‐ Balanced Cantilever Segments at Main Pier 17 ‐ 1U&D] DECK CONCRETE STRUCTURE [E/B ‐ Form Travellers Assembly & Commissioning] DECK CONCRETE STRUCTURE [E/B ‐ Balanced Cantilever Segments over Main Pier 17] DECK CONCRETE STRUCTURE [E/B ‐ Back span Unbalanced Segments at Transition Pier 18] DECK CONCRETE STRUCTURE [W/B ‐ Balanced Cantilever Segments over Main Pier 16 ‐ 1U&D] DECK CONCRETE STRUCTURE [W/B ‐ Form Travellers Assembly & Commissioning] DECK CONCRETE STRUCTURE [W/B ‐ Balanced Cantilever Segments at Main Pier 16] DECK CONCRETE STRUCTURE [W/B ‐ Back span Unbalanced Segments at Transition Pier 15] DECK CONCRETE STRUCTURE [W/B ‐ Balanced Cantilever Segments at Main Pier 17 ‐ 1U&D] DECK CONCRETE STRUCTURE [W/B ‐ Form Travellers Assembly & Commissioning] DECK CONCRETE STRUCTURE [W/B ‐ Balanced Cantilever Segments over Main Pier 17] DECK CONCRETE STRUCTURE [W/B ‐ Back span Unbalanced Segments at Transition Pier 18] DECK CONCRETE STRUCTURE [E/B & W/B ‐ Form Travellers Disassembly] DECK CONCRETE STRUCTURE [Longitudinal CIP Stitch between E/B & W/B] FINISHING WORKS CIP CONCRETE OPTION ‐ SUBSTANTIAL COMPLETION

PRECAST CONCRETE OPTION ‐ Twin Deck Box Section 65 ft wide each SUBSTRUCTURES [Main Piers 16 & 17 ‐ Foundations] ‐ It is assumed that existing Piles can be reused SUBSTRUCTURES [Main Piers 16 & 17 ‐ Pile Caps] SUBSTRUCTURES [Main Piers 16 & 17 ‐ Piers] SUBSTRUCTURES [Main Piers 16 & 17 ‐ Pier Heads] SUBSTRUCTURES [Transition Piers 15 & 18 ‐ Foundations] ‐ It is assumed that existing Piles can be reused SUBSTRUCTURES [Transition Piers 15 & 18 ‐ Pile Caps]

WEST SEATTLE BRIDGE_Construction Schedule_R2

1/2

8/27/2020

WEST SEATTLE BRIDGE REPLACEMENT (MASS TIMBER / STEEL vs. CIP CONCRETE vs. PRECAST CONCRETE) Cod.

83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113

Activity

SUBSTRUCTURES [Transition Piers 15 & 18 - Piers] SUBSTRUCTURES [Transition Piers 15 & 18 - Pier Heads] PRECAST YARD [Setting & Ready to Start] PRECAST YARD [Production - About 300 Segments - 4 Short-Line Moulds] DECK CONCRETE STRUCTURE [E/B - Balanced Cantilever Segments over Main Pier 16 - 1U&D] DECK CONCRETE STRUCTURE [E/B - Segments 1U&D - CIP Stitches with Pier Head] DECK CONCRETE STRUCTURE [E/B - Lifting Frames Assembly & Commissioning] DECK CONCRETE STRUCTURE [E/B - Balanced Cantilever Segments at Main Pier 16] DECK CONCRETE STRUCTURE [E/B - Back span Unbalanced Segments at Transition Pier 15] DECK CONCRETE STRUCTURE [E/B - Balanced Cantilever Segments at Main Pier 17 - 1U&D] DECK CONCRETE STRUCTURE [E/B - Segments 1U&D - CIP Stitches with Pier Head] DECK CONCRETE STRUCTURE [E/B - Lifting Frames Assembly & Commissioning] DECK CONCRETE STRUCTURE [E/B - Balanced Cantilever Segments over Main Pier 17] DECK CONCRETE STRUCTURE [E/B - Back span Unbalanced Segments at Transition Pier 18] DECK CONCRETE STRUCTURE [E/B - Lifting Frames Disassembly] DECK CONCRETE STRUCTURE [E/B - Mid Main Span & Back Spans CIP Stitches] DECK CONCRETE STRUCTURE [W/B - Balanced Cantilever Segments over Main Pier 16 - 1U&D] DECK CONCRETE STRUCTURE [W/B - Segments 1U&D - CIP Stitches with Pier Head] DECK CONCRETE STRUCTURE [W/B - Lifting Frames Assembly & Commissioning] DECK CONCRETE STRUCTURE [W/B - Balanced Cantilever Segments at Main Pier 16] DECK CONCRETE STRUCTURE [W/B - Back span Unbalanced Segments at Transition Pier 15] DECK CONCRETE STRUCTURE [W/B - Balanced Cantilever Segments at Main Pier 17 - 1U&D] DECK CONCRETE STRUCTURE [W/B - Segments 1U&D - CIP Stitches with Pier Head] DECK CONCRETE STRUCTURE [W/B - Lifting Frames Assembly & Commissioning] DECK CONCRETE STRUCTURE [W/B - Balanced Cantilever Segments over Main Pier 17] DECK CONCRETE STRUCTURE [W/B - Back span Unbalanced Segments at Transition Pier 18] DECK CONCRETE STRUCTURE [W/B - Lifting Frames Disassembly] DECK CONCRETE STRUCTURE [W/B - Mid Main Span & Back Spans CIP Stitches] DECK CONCRETE STRUCTURE [Longitudinal CIP Stitch between E/B & W/B] FINISHING WORKS PRECAST CONCRETE OPTION - SUBSTANTIAL COMPLETION

Start

End

20.00 22.00 8.00 20.00 26.00 26.75 27.00 28.00 30.00 27.00 27.75 28.00 29.00 31.00 32.50 33.00 26.00 26.75 27.00 28.00 30.00 27.00 27.75 28.00 29.00 31.00 32.50 33.00 35.00 36.00 40.00

22.00 25.00 20.00 30.00 27.00 27.00 28.00 32.00 32.00 28.00 28.00 29.00 33.00 33.00 33.50 35.00 27.00 27.00 28.00 32.00 32.00 28.00 28.00 29.00 33.00 33.00 33.50 35.00 37.00 40.00 40.00

Months M1

M9 M10 M11 M12 M13 M14 M15 M16 M17 M18 M19 M20 M21 M22 M23 M24 M25 M26 M27 M28 M29 M30 M31 M32 M33 M34 M35 M36 M37 M38 M39 M40 M41 M42 M43 M44 M45 M46 M47 M48 M49 M50 M51 M52 M53 M54

2.00 3.00 12.00 10.00 1.00 0.25 1.00 4.00 2.00 1.00 0.25 1.00 4.00 2.00 1.00 2.00 1.00 0.25 1.00 4.00 2.00 1.00 0.25 1.00 4.00 2.00 1.00 2.00 2.00 4.00 0.00

SUBSTRUCTURES [Transition Piers 15 & 18 ‐ Piers] SUBSTRUCTURES [Transition Piers 15 & 18 ‐ Pier Heads] PRECAST YARD [Setting & Ready to Start] PRECAST YARD [Production ‐ About 300 Segments ‐ 4 Short‐Line Moulds] DECK CONCRETE STRUCTURE [E/B ‐ Balanced Cantilever Segments over Main Pier 16 ‐ 1U&D] DECK CONCRETE STRUCTURE [E/B ‐ Segments 1U&D ‐ CIP Stitches with Pier Head] DECK CONCRETE STRUCTURE [E/B ‐ Lifting Frames Assembly & Commissioning] DECK CONCRETE STRUCTURE [E/B ‐ Balanced Cantilever Segments at Main Pier 16] DECK CONCRETE STRUCTURE [E/B ‐ Back span Unbalanced Segments at Transition Pier 15] DECK CONCRETE STRUCTURE [E/B ‐ Balanced Cantilever Segments at Main Pier 17 ‐ 1U&D] DECK CONCRETE STRUCTURE [E/B ‐ Segments 1U&D ‐ CIP Stitches with Pier Head] DECK CONCRETE STRUCTURE [E/B ‐ Lifting Frames Assembly & Commissioning] DECK CONCRETE STRUCTURE [E/B ‐ Balanced Cantilever Segments over Main Pier 17] DECK CONCRETE STRUCTURE [E/B ‐ Back span Unbalanced Segments at Transition Pier 18] DECK CONCRETE STRUCTURE [E/B ‐ Lifting Frames Disassembly] DECK CONCRETE STRUCTURE [E/B ‐ Mid Main Span & Back Spans CIP Stitches] DECK CONCRETE STRUCTURE [W/B ‐ Balanced Cantilever Segments over Main Pier 16 ‐ 1U&D] DECK CONCRETE STRUCTURE [W/B ‐ Segments 1U&D ‐ CIP Stitches with Pier Head] DECK CONCRETE STRUCTURE [W/B ‐ Lifting Frames Assembly & Commissioning] DECK CONCRETE STRUCTURE [W/B ‐ Balanced Cantilever Segments at Main Pier 16] DECK CONCRETE STRUCTURE [W/B ‐ Back span Unbalanced Segments at Transition Pier 15] DECK CONCRETE STRUCTURE [W/B ‐ Balanced Cantilever Segments at Main Pier 17 ‐ 1U&D] DECK CONCRETE STRUCTURE [W/B ‐ Segments 1U&D ‐ CIP Stitches with Pier Head] DECK CONCRETE STRUCTURE [W/B ‐ Lifting Frames Assembly & Commissioning] DECK CONCRETE STRUCTURE [W/B ‐ Balanced Cantilever Segments over Main Pier 17] DECK CONCRETE STRUCTURE [W/B ‐ Back span Unbalanced Segments at Transition Pier 18] DECK CONCRETE STRUCTURE [W/B ‐ Lifting Frames Disassembly] DECK CONCRETE STRUCTURE [W/B ‐ Mid Main Span & Back Spans CIP Stitches] DECK CONCRETE STRUCTURE [Longitudinal CIP Stitch between E/B & W/B] FINISHING WORKS PRECAST CONCRETE OPTION ‐ SUBSTANTIAL COMPLETION

WEST SEATTLE BRIDGE_Construction Schedule_R2

2/2

MT-Steel Design Bridge Dimensions Total Deck Length Main Span Back Span Total Deck Width No. of carriageways Total Deck Area

m m m m No. 2 m

13,912,800.00

Summary of Quantities (Balanced Cantilever Option)

1380 130 179400

18,333,477.69

1.31774177

Top Slab Thickness Average Deck Depth Web Thickness Average Bottom Slab Thickness Bottom Slab Width Average Cross-Section Area Total Deck Cross-Section Volume Volume of Diaphragms Total Deck Volume

No.

Quantity

1.0 Concrete Volume 2.0 Prestressing Tonnage 3.0 Reinforcement Tonnage

408 180 130 15.5 2 12,648

250 7,750 500 825 7,500 17.81 14,535 465 15,000

mm mm mm mm mm m2 m3 m3 3 m

Value 15,000 m 750 t 2,550 t

Main Spam

9,552 t

$ $ $ $ $ $

123,021,756 23,420,000 6,875,000 incl. 25,500,000 26,822,513 205,639,270 19%

Baseline 1 (CIP) $ $ $ $ $ $ $

Baseline 2 (PC)

64,312,500 27,125,000 7,980,000 17,978,325 33,000,000 22,559,374 172,955,199

$ $ $ $ $ $ $

68,670,000 27,125,000 7,980,000 23,463,025 30,000,000 23,585,704 180,823,728 5%

Varies from 11 250 mm at pier to 4 250 at midspans Varies from 1400 mm at pier to 250 at midspans `

Superstructure only

Unit

Remark

Calculated assuming 50 kg/m3 of concrete Calculated assuming 170 kg/m3 of concrete

Summary of Quantities (Steel and MT Timber Arch and Underslung Deck) Value Unit No. Quantity 1.0 Steelwork Tonnage

Direct Cost - Superstructure Foundations Substructure Add for LRT width Job Overhead Corporate G&A & Profit Total [Seattle, 2020] Cost premium, relative to Baseline 1

MT-Steel Design (new location) $ 123,021,756 $ 23,420,000 $ 6,875,000 incl. $ 20,500,000 $ 26,822,513 $ 200,639,270 16%

136,142.00 SF

Cost Estimates 150,000,000 37,500,000 38,250,000 225,750,000

CIP

19,620.00 CY 1,650,000.00 LB 5,610,000.00 LB

$ $ $

2,500.00 $ 49,050,000.00 5.00 $ 8,250,000.00 1.25 $ 7,012,500.00 $ 64,312,500.00 $ 472.39 174,200.00 SF

Remark

Calculated assuming 0.5 t/m2 of deck for 120 m span

382,075,000

Steel 1.692469546 timber deck temp. works Relocate RR & Road

21,014,125.00 4,237.76 9,677.78 1.00 1.00

LB MBF CY LS LS

$ 4.50 $ 94,563,562.50 $ 1,600.00 $ 6,780,416.00 $ 1,000.00 $ 9,677,777.78 $ 10,000,000.00 $ 10,000,000.00 $ 2,000,000.00 $ 2,000,000.00 $ 123,021,756.28 $ 706.21 136,142.00 SF

PC Segm

19,620.00 CY 1,650,000.00 LB 5,610,000.00 LB

3,500.00 $ 68,670,000.00 5.00 $ 8,250,000.00 1.25 $ 7,012,500.00 $ 83,932,500.00 $ 616.51

West Seattle Bridge Replacement Narrative (Lane Construction)

Construction Information

General Information

The following narrative provides some additional information regarding the types of construction we have reviewed, and offers additional details on how some of the work may be carried out.

This assessment is relevant only to the structural unit of the main bridge spanning over the river (the “main bridge”). No consideration has been given to any improvements associated with the approach span portion of the bridge.

Removal of Existing Main Span Bridge

Our general approach when examining options for the future of the West Seattle Bridge included consideration of two fundamental types of structures. Given the limited time available to consider the various options, a scope including a broader cross-section of bridge types was not reasonably possible.

Demolition of a cast-in-place segmental structure is a complex undertaking and significant engineering analysis must be carried out to ascertain the safest and most stable sequence. Essentially, the bridge must be demolished in the exact reverse sequence used during construction. These types of bridges must be “de-constructed” following a specific staged plan. From our past experience, we envision the following general operation.

We have assumed the current West Seattle Bridge foundations and substructure columns as being inadequate to receive additional loads related to LRT deck widening and have therefore approached the project with the view that these components would be part of the replacement structure.

As a preliminary activity, to reduce the maximum required lifting capacity of the lowering equipment, edge and median barrier sections will be cut in advance. Overhang deck sections (through to the most exterior longitudinal post-tensioning tendons are encountered) will be cut in advance as well.

To establish a baseline, we initially produced a cost estimate associated with replacement of the compromised superstructure and substructure of the main bridge utilizing a cast in place concrete segmental design (Baseline 1). This would be very similar to the existing structure type, however, for an equal comparison, we matched the width of the mass timber steel bridge and included structural provisions for LRT and bicycle lanes. Some changes would be included with the replacement structure, and of course, any new structure would be fully compliant with current design standards. The general type of structure would mirror that which currently serves the local community; however, the approaches would need to be widened to accommodate LRT and bicycle lanes.

The existing bridge main span deconstruction would then commence with the 80 ft long out of balance deck section at each backspan. These segments will be supported by means of temporary towers and removed with the aid of a crane positioned on the approaches or at ground level.

Our second cost analysis was focused on replacing the West Seattle Bridge with a reimagined mass timber and steel composite design (MT-Steel Design). As noted above, the foundations and substructure columns would be replaced. salvaged from the current structure and utilized for construction of the new span atop the existing works. From a schedule perspective, keeping the existing foundations and substructure would afford significant time savings in the overall replacement schedule. This is a key component to a fast track delivery for either of the new bridge options contemplated herein. The bridge type developed by B+H utilizing the composite mass timber and steel arch design proves to be less economical than the concrete baseline structure. However, given the fact that many components can be pre-fabricated and positioned for installation concurrent with the performance of bridge substructure operations, significant economies in the schedule are achievable and these efficiencies serve to offset the more expensive direct cost of the mass timber and steel arch alternative design.

Then, the segments of the remaining balanced cantilever deck sections will be removed simultaneously on either side of the cantilever itself. After lowering equipment has been firmly attached to the deck and segments have been secured to their spreader beams, wire cutting operations would be carried out to free these elements from the rest of the structure. Once cut free, the segments would be lowered to the ground on to lowbed trailers (in backspans) or to the river on barges (in the main span) for secondary transport to a demolition area established on site. The first main span segment removal will include a section of deck 2 typical segments in length plus the mid-span closure segment. Only after the lowering equipment has been firmly attached to the deck, wire cutting operations would be carried out. The central section would be lowered to a barge below and staged on trailers for final transfer to a demolition area established on site. Demolition will then proceed with removal of deck segments working back towards the main pier. We will follow the general joint layouts used in the original construction but may vary this approach in certain locations where larger elements may be handled. This approach will enable us to reduce the number of closures required in the channel. To expedite joint preparation, separate dedicated work crews will carry out limited joint precutting activities several segments back from the leading tip of the cantilever. To further mitigate the need for channel closures, we will be utilizing four separate deconstruction teams, one situated on each side of the center channel and on each structure (Eastbound and Westbound). Segments which have been cut free (one on each cantilever on each side of the channel) will be also lowered concurrently to maximize the benefit of each

channel closure. We will continue our operations in this manner as we progress towards the main piers until the entire bridge superstructure has been safely removed. Secondary Demolition at On-Site Facility For maximum efficiency, we would plan to establish a concrete breaking crushing operation on site to handle the larger concrete elements which have been removed from the existing structure. Maintaining the theme of environmental vigilance, our staff will look for any opportunities to recycle products that are derived from the deconstruction operations. We currently forecast that at least 30 thousand tons of recycled concrete can be utilized on site or sold for use in other regional construction and endeavors. All reinforcing and prestressing steel which is recovered from bridge demolition activities will also be sold for recycling purposes. Any materials which must be disposed of off-site will be handled through properly licensed and approved locations. Mass Timber – Steel Design - Arch Composite Side Spans Construction Sequence Since the concept design for the side spans includes and under deck truss system to support the overall span, the construction of the sides spans on either side of the primary river crossing would be staged in two primary phases. The first stage would address the assembly at ground level of the main bowstring structural steel element of the under-deck support. We have envisioned assembly of the structural steel frame without the installation of the tension cables in this first phase. Once the primary steel frame had been completely assembled within a separate supporting framework, the overall bow string frame would be raised vertically on for short towers to facilitate installation of the tension cables. Once the cables were installed, they will be stressed to their prescribed forces to provide adequate support for the total deck assembly at this stage of the construction sequence. Then, utilizing a multi-strand heavy lift jacking system attached to the upper area of the bridge columns, the entire span will be lifted vertically into its final position at deck level. Once secured to its permanent fixation points, the jacking system will be removed, movement joints installed at connection with approaches and remaining concrete riding surface of the deck would be cast in place at this location. The same system will be utilized for the bowstring spans on either side of the primary arched main span crossing. As pointed out earlier, with much of this pre-assembly work being permitted to take place concurrent with new foundation and pier activities, a considerable amount of time can be saved on the overall project schedule. Main Span Construction Sequence Again, to take advantage of schedule time savings through overlapping activities, pre-assembly of the main span would also be undertaken while new pier activity was underway. We foresee the main span steel arch, along with its side cantilevered roadway portion, being pre-assembled on

the ground in a staging area specially prepared for this activity. Speed of assembly will be greatly improved, and overall safety of the workforce enhanced, as the primary assembly activities would all take place directly at ground level. Once all pre-assembly operations have been completed and the tops of the main span support piers prepared to receive the new main span structure, the preassembled span would be loaded onto a specially outfitted barge utilizing multi axle self-propelled modular transporters (SPMT’s). Once the main span structure was properly positioned and stabilized on the barge, the SPMT’s would be driven off and returned to the staging area. Following receipt of approval for any necessary waterway channel closures, the barge carrying the preassembled main span would be floated into position in between the existing bridge columns. A multi-strand heavy lift jacking system, similar to that used to raise the side span preassemblies, would then vertically hoist the main span arch and cantilevered roadway structure vertically into its final service position. Once permanently positioned onto its support bearings and the lifting system removed, work will continue in place at deck level to pour the concrete riding surface for the structure. Baseline 1, Cast-in-Place Segmental Bridge Another alternative we have investigated for the West Seattle Bridge replacement is to cast the segments in their final position in the structure with the same methodology originally used. This would essentially be the bridge type that is currently in place on site and is what we have considered as the “base line structure” in our analysis. Cast-in-place construction proves to be very advantageous when large, very heavy segments are encountered. Instead of handling the segments in a completely precast state, with cast-in-place methodology, only materials have to be transported during construction, thus influencing the type and size of required equipment. The commonly used method for casting segments in place is with the use of a traveling form system, known as form travelers. Form travelers are moveable forms supported by steel cantilever trusses attached to previously completed segments. The usual production rate for a form traveler is one segment every week. Balanced cantilever erection will probably be the most commonly used method for constructing segmental bridges. It solves problems such as environmental or existing traffic constraints. Conversely, the linear nature of cast-in-place construction yield slower overall production rates. For a project requiring fast-track construction, this bridge type is less preferable. When balanced cantilever cast-in-place construction is used, a minimum of two form travelers is required. The segment production rate for form travelers is usually one segment every week per traveler. Therefore, to approach more reasonable production capacities, a total of eight form travelers would be required.

B+H | SMEC | RBG | LANE | DCI

MATTHIAS OLT Design Director, Architecture, USA B+H Architects matthias.olt@bhadvancestrategy.com 206.679.0922 bharchitects.com

B+H West Seattle Bridge Replacement Proposal - Cost and Schedule

Articles inside

APPENDIX

OVERVIEW

TEAM

POSITIVE EFFECTS ON PHYSIOLOGY AND PSYCHOLOGY

COMMUNITY AND INDUSTRY IMPACTS

CONSTRUCTION SCHEDULE

CONSTRUCTION COST