# 2.13 Bridges and Structures

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## Document Metadata

- **Document Title:** Bridges and Structures
- **Section Number:** 2.13
- **Document Type:** Request for Proposal – General Provisions
- **Project:** I-405/Brickyard to SR 527 Improvement Project
- **Organization:** Washington State Department of Transportation (WSDOT)
- **Source PDF:** Users/z/Desktop/git/Brickyard/Project_Documents/Contract_Documents/02_Extracts_RFP/Chapter 2/Section_2.13_Bridges_and_Structures.pdf
- **Conversion Date:** 2025-12-15

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# 2.13 Bridges and Structures

## 2.13.1 General

The Design-Builder shall perform all Work necessary to complete the bridges and structures for the Project to satisfy the Basic Configuration requirements. Elements of Work shall include the following:

• **Bridge Removals:**
  - Bridge No. 405/70N-E (northbound I-405 to eastbound SR 522)
  - Bridge No. 405/70N-W (northbound I-405 to westbound SR 522)
  - Bridge No. 522/30E-N (eastbound SR 522 to northbound I-405)

• **New Bridges:**
  - Pedestrian bridge over I-405 at Brickyard BRT Station
  - I-405 direct access bridge at SR 522
  - Northbound I-405 over Sammamish River and SR 522
  - Northbound I-405 off ramp to SR 522
  - 17th Avenue SE direct access bridge over northbound I-405 at SR 527 BRT Station
  - Fish Passage structures as listed in Section 2.30, Water Crossings

• **Bridge Replacements:**
  - Bridge No. 405/104P (pedestrian bridge over northbound and southbound I-405 to SR 527 BRT Station)

• **Bridge Modifications:**
  - Bridge No. 522/28N (westbound SR 522 over North Creek) to add pedestrian pathway and incorporate requirements in Section 2.15, Roadside Restoration, and Transit Facilities Architectural and Urban Design Criteria (Appendix S)
  - Bridge No. 405/70E (northbound I-405 over Sammamish River/SR 522, due to removal of existing Bridge No. 522/30E-N)

• **Bridge Widenings and Seismic Retrofits:**
  - Bridge No. 405/103E (northbound I-405 over 228th Street SE)

• **Bridge Seismic Retrofits:**
  - Bridge No. 405/64 (NE 160th Street over I-405)
  - Bridge No. 405/73 (NE 195th Street over I-405)
  - Bridge No. 405/103W (southbound I-405 over 228th Street SE)

• **Bridge Joint Rehabilitations:**
  - Bridge No. 405/70W and 405/70E (southbound and northbound I-405 over Sammamish River/SR 522)
  - Bridge No. 405/70S-E (southbound I-405 to eastbound SR 522)
  - Bridge No. 405/103W and 405/103E (southbound and northbound I-405 over 228th Street SE)
  - Bridge No. 522/28N (westbound SR 522 over North Creek)

• **Bridge Deck Repair and Sealing:**
  - Bridge No. 405/70W and 405/70E (southbound and northbound I-405 over Sammamish River/SR 522)
  - Bridge No. 405/70S-E (southbound I-405 to eastbound SR 522)

• **Bridge Deck Overlay Replacement:**
  - Bridge No. 405/103W and 405/103E (southbound and northbound I-405 over 228th Street SE)
  - Bridge No. 405/72 (northbound and southbound I-405 over North Creek)

• Permanent and temporary retaining walls, moment slabs, buried structures, noise walls, traffic barriers, sign structures, toll structures, lighting structures, detention vaults, and stormwater vaults.

The plans showing the existing bridges and other structures are located in the As Builts (Appendix N). The plans are not guaranteed to be dimensionally accurate or complete. The Design-Builder shall field measure and verify existing dimensions as required for their Work.

### 2.13.1.1 Forward Compatibility

The Design Builder shall illustrate the Forward Compatible concept in design drawings in plan, section, and elevation. Design calculations shall include design and analysis of the Forward Compatible concept. Forward Compatible walls shall be designed for the current and Forward Compatible conditions and shall satisfy global stability for both conditions. Structure layouts shall dimension clear zones and locations of Forward Compatible elements.

All new bridge widenings, modifications, and retrofits shall be designed and constructed so they are Forward Compatible with the Forward Compatible Plans (Appendix M), except Bridge No. 405/104P (pedestrian access over northbound and southbound I-405 to the Canyon Park BRT Station) which shall be Forward Compatible with the Interim Forward Compatible Plans (Appendix M).

All new retaining walls and noise walls shall be designed and constructed so they are Forward Compatible with the Forward Compatible Plans, except the following:
• Wall 22.35R
• Wall 22.49L
• Wall 22.82L
• Wall 23.02L
• Wall 23.15L
• Wall 23.32L
• Wall 23.54R
• Wall 23.72R
• Wall 23.80R
• Wall 24.83R
• Wall 26.02R
• Wall 26.11R
• Wall 26.34R
• Wall 26.74L
• Wall L1

The following new retaining walls and noise walls shall be designed and constructed so they are Forward Compatible with the Interim Forward Compatible Plans:
• Noise wall NW6
• Noise wall NW7

Future construction of an additional lane on northbound I-405 will require excavation at the face of Wall 23.28R to a future ground line. Wall 23.28R shall be designed for the Forward Compatible condition without demolition as an element of the widening shown in the Forward Compatible Plans.

Stormwater treatment vaults shall be designed and constructed so they are Forward Compatible, except the following:
• Detention vault along southbound I-405, near MP 26.45

Fish passage structures shall be Forward Compatible as described in Section 2.30, Water Crossings.

The Design-Builder shall include in the design, structural concept and analysis demonstrating Forward Compatibility requirements.

## 2.13.2 Mandatory Standards

The following is a list of Mandatory Standards that shall be followed for all design and construction related to this Section as referenced in Section 2.2, Mandatory Standards.

1. Special Provisions (Appendix B)
2. Standard Specifications M 41-10 (Appendix B)
3. WSDOT Bridge & Structures Office Design Memoranda (Appendix B)
4. WSDOT Bridge Design Manual LRFD M 23-50 (Appendix D)
5. WSDOT Geotechnical Design Manual M 46-03 (Appendix D)
6. Sound Transit Design Criteria Manual (Appendix S)
7. AASHTO Guide Specifications for LRFD Seismic Bridge Design
8. FHWA Seismic Retrofitting Manual for Highway Structures: Part 1 - Bridges
9. AASHTO LRFD Bridge Design Specifications
10. AASHTO LRFD Guide Specifications for the Design of Pedestrian Bridges
11. FHWA Evaluating Scour at Bridges, HEC-18
12. AASHTO Manual for Bridge Evaluation
13. WSDOT Design Manual M 22-01 (Appendix D)
14. WSDOT Plans Preparation Manual M 22-31 (Appendix D)
15. WSDOT Construction Manual M 41-01 (Appendix D)
16. AASHTO LRFD Bridge Construction Specifications
17. AASHTO Guide Design Specifications for Bridge Temporary Works
18. WSDOT Materials Manual M 46-01 (Appendix D)
19. Standard Plans M 21-01 (Appendix D)
20. Qualified Products List (QPL) https://wsdot.wa.gov/engineering-standards/construction-materials/qualified-product-list-qpl
21. AASHTO LRFD Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals
22. AWS Structural Welding Code - Steel (AWS D1.1/D1.1M)
23. AWS Structural Welding Code - Reinforcing Steel (AWS D1.4/D1.4M)
24. AASHTO/AWS Bridge Welding Code (AWS D1.5M/D1.5)
25. American Concrete Institute Code Requirements for Environmental Engineering Concrete Structures (ACI 350)
26. AASHTO LRFD Road Tunnel Design and Construction Guide Specifications
27. International Building Code (IBC) with local amendments
28. AASHTO LRFD Guide Specifications for Accelerated Bridge Construction
29. AASHTO LRFD Guide Specifications for Design of Concrete-Filled FRP Tubes for Flexural and Axial Members
30. ASCE Pre-Standard for LRFD of Pultruded FRP Structures
31. National Cooperative Highway Research Program (NCHRP) Guidelines and Recommended Standards for Geofoam Applications in Highway Embankments (NCHRP Report 529)
32. AREMA Manual for Railroad Grade Separation Projects
33. AREMA Manual for Railway Engineering
34. City of Bothell Municipal Code Chapter 20.04, Building Regulations and International Codes

Design shall comply with the codes and standards of the jurisdiction in which the structure resides. The codes and standards of the Authority Having Jurisdiction (AHJ) shall govern design to the greatest extent required by law and good engineering practice. The Engineer of Record shall address any conflicts as part of a Basis of Design and submit to WSDOT for Review and Comment.

Combined building and bridge structures or building and roadside structures shall be analyzed for AASHTO LRFD Bridge Design Specifications, the Mandatory Standards, and the International Building Code and be designed for the most stringent forces, deformations, and requirements. Pedestrian bridges shall be governed by these Mandatory Standards and design requirements of the AHJ and be designed for the most stringent.

### 2.13.2.1 Bridge Design Manual Rights and Responsibilities

The WSDOT Bridge Design Manual, as modified by the WSDOT Bridge & Structures Office Design Memoranda, allocates responsibilities as follows:

• **Rights and Responsibilities** - The following clarifies which rights and responsibilities discussed in the WSDOT Bridge Design Manual are applicable to the Design-Builder:
  - The Design-Builder shall complete all analyses, evaluations, load ratings, Plans, and specifications discussed in the WSDOT Bridge Design Manual. All Chapters of the WSDOT Bridge Design Manual shall be followed as a part of the Mandatory Standard.
  - All analyses, evaluations, load ratings, Plans, and specifications are subject to Review and Comment by WSDOT.
  - All references to WSDOT Sections, offices, and engineers shall mean WSDOT.

• Where the WSDOT Bridge Design Manual or the WSDOT Bridge & Structures Office Design Memoranda requires approval, the Design-Builder shall be responsible for obtaining approval from the WSDOT Engineer prior to proceeding with the design.

## 2.13.3 Personnel Requirements

The Design-Builder shall provide a Structural Lead Engineer (SLE) to manage, coordinate, and review all aspects of the structural Work completed for the Project. The SLE shall provide written certification that the design and construction of all permanent and temporary Work is in conformance with the Contract requirements and the Quality Management Plan for each structural drawing, calculation package, temporary structure package, working drawings, and design revision during construction.

The SLE shall have a minimum of 10 years of experience in the design of bridges, retaining walls, shoring and temporary walls underpinning bridges, and other highway related structures. This individual shall be a Structural Engineer.

The Engineer of Record (EOR) for all structural engineering Design Documents for significant structures described in RCW 18.43.020(12) and for all bridges shall have a minimum of 10 years of experience in the design of bridges, retaining walls, and other highway related structures. The EOR shall be a Structural Engineer.

The EOR for all structural engineering Design Documents for all other structures in the Project shall be a Professional Engineer or Structural Engineer.

The Design-Builder shall designate a Structural Engineer, geotechnical engineer, and lead field engineer to design, manage, and review all aspects of Work for installation of walls and shoring under existing bridges and structures, such as Work under Bridge No. 405/103E. They shall have completed at least five similar wall and shoring projects under existing bridges, within the last 10 years. The Design-Builder shall submit documentation demonstrating minimum qualifications for Review and Comment.

## 2.13.4 Design Criteria

The Design-Builder shall analyze and design all new permanent bridges and structures, and all existing or modified structural elements whose structure or load-carrying capacities or demands are altered by the Work, using Load and Resistance Factor Design (LRFD) as defined in the WSDOT Bridge Design Manual and the AASHTO LRFD Bridge Design Specifications.

The Design-Builder shall design and construct permanent bridges and structures to achieve a minimum design life of 75 years.

Minimum clearances shall be as follows and shall be maintained at all times during and after construction:

• New vehicular structures over a roadway shall provide a minimum vertical clearance of 16ʹ - 6ʺ.

• New bike/pedestrian structures crossing a roadway shall provide a minimum vertical clearance of 17ʹ - 6ʺ. The vertical clearance from the top of the walkway to overhead obstructions shall be a minimum of 9ʹ - 0ʺ.

• New structures over the railroad adjacent to Woodinville Drive shall provide a minimum vertical clearance of 23ʹ - 6ʺ measured to the top of the rail, maintained over a minimum horizontal distance of 20ʹ- 0ʺ from the center of track. If the top of rail elevation is unknown at the time of construction, it shall be coordinated with King County and the WSDOT Engineer.

• New overwater structures shall provide minimum clearances that meet the following, except as modified for culverts in Section 2.30, Water Crossings:
  - 3 feet of freeboard above the 100-year Mean Recurrence Interval (MRI) water surface to the lowest point of the spanning member, unless otherwise stated.
  - 6 feet above the thalweg taken perpendicular to the stream bearing to the bottom of the spanning member, unless otherwise stated.
  - New structures over the Sammamish River shall provide a minimum navigational opening as required by the United States Coast Guard bridge permit (Appendix P).

• New deck overhang structures over a roadway shall provide a minimum vertical clearance of 17′ - 6ʺ.

• New structures over Sammamish River Trail shall provide a minimum vertical clearance of 14′ - 0ʺ over the trail and associated buffers. A horizontal buffer of 10ʹ - 0ʺ shall be provided from each edge of the paved trail.

• New pedestrian bridge at Brickyard BRT Station shall have a minimum walkway width of 10ʹ -0ʺ. Vertical clearance from top of walkway to overhead obstructions shall be a minimum of 9ʹ - 0ʺ.

• Pedestrian bridge (Bridge No. 405/104P) shall have a minimum walkway width to match the existing (10ʹ - 7ʺ minimum per the As Built drawings). Vertical clearance from top of walkway to overhead obstructions shall be a minimum of 9ʹ - 0ʺ.

• For modified existing structures, the minimum vertical clearance shall not be less than the existing clearance.

• The new northbound I-405 over Sammamish River/SR 522 bridge north abutment shall be located no further south than the existing bridge north abutments for bridges 405/70E and 405/7W.

• Slopes in front of new bridge abutments or in front of retaining walls supporting bridge abutments shall provide a minimum of 13 feet of overhead clearance from top of slope to bottom of superstructures, except for the north abutment of the new northbound I-405 over Sammamish River and SR 522, and north abutment of the I-405 direct access bridge at SR 522.

• When multiple minimum clearances are listed, the required minimum vertical clearance shall be the greater value.

Minimum foundation cover requirements for scour shall be in accordance with the WSDOT Bridge Design Manual. Existing structure foundations including spread footings, pile caps, shaft caps (or bottom of seal if used), and wall elements (including fascia panels, lagging, leveling pads, and footings) affected by the Work shall meet the minimum foundation cover requirements or be protected against scour to that level.

Unless required elsewhere in the RFP, fall protection shall be provided at the top of all new structures, buried structures, retaining walls, and retaining wall terraces in accordance with Section 1060 of the WSDOT Design Manual. Fall protection shall be a standard guardrail system (galvanized steel with black powder coated or vinyl coating), as described and in accordance with the requirements in the WAC 296-880-40005 and Appendix L. Fall protection shall have a top and middle rail. Timber, extended wall parapet, and wire rope shall not be used as a material type for standard guardrail. The Standard Plan Chain Link Fence Types 3 and 4, and Glare Screen Types 1 and 2 are not acceptable fall protection systems. Design calculations and/or product data shall be provided for all components and connections, including off-the-shelf fence connections, demonstrating design requirements are met. For fall protection features that are exposed to the public, design of railings shall be in accordance with Chapter 13 of the AASHTO LRFD Bridge Design Specifications. All fall protection exposed to the public shall be a minimum 54 inches in height, measured from the top of finished roadway, sidewalk, or platform.

The Design-Builder shall design and install all subsurface transit facility and BRT Station elements including foundation elements, anchors, conduit, junction boxes, sign attachments, and drainage. The Work shall be coordinated with local transit authorities and meet the requirements in Section 2.27, Transit; Appendix S; and this Section.

• All station elements shall be clearly laid out, detailed, and dimensioned in the structure design submittals to be locatable and installed in the future.

• Rebar clear zones shall be provided where future post-installed anchors are required. Clear zones shall be clearly defined and dimensioned in the structure design submittals to be locatable in the future.

• Utilities shall be concealed within the structures and penetrations through the bridge deck and structure shall be fitted with waterstop, gasket, or similar to ensure no passage of water.

• Conduits and drain pipes shall be capped with removable mechanical pipe plugs. Plugs shall be ABS plastic fitted with neoprene or rubber gasket capable of withstanding 5 psi. Conduit and drainpipes shall be left long protruding at least 2-feet above finish surface.

• All subsurface transit facility and station elements shall be protected and concealed beneath secured plywood covers that are marked with high visibility orange paint. The transit facility and station areas containing protruding subsurface station elements shall be completely cordoned off to prevent access with 4-feet high temporary chain link construction fence. Fencing shall be situated to maintain a minimum 6-feet wide public access past the areas.

### 2.13.4.1 Bridge Design Criteria

The following permanent bridge superstructure types are permitted for this Project:
• Prestressed concrete I Girders
• Prestressed concrete wide flange I Girders
• Spliced prestressed concrete girders
• Prestressed concrete tub girders
• Prestressed concrete wide flange thin deck girders (subject to limitations stipulated in the WSDOT Bridge Design Manual)
• Steel-plate girders
• Steel-box girders
• Post-tensioned concrete box girders
• Prestressed concrete slab girders for pedestrian bridges only

The Design-Builder shall not use steel trusses, rolled steel beams, prestressed concrete deck bulb-tee girders, tri-beam sections, and double tee girders for permanent bridge structures. Masonry or timber shall not be used as materials for permanent bridge superstructures or substructures.

For vehicular bridges, a minimum of three girder lines, with the exception of two girder lines for tub girders, shall be used to provide redundant load paths. Intermediate hinges shall not be used with permanent bridge structures.

Non-redundant, fracture critical pier caps shall not be used.

#### 2.13.4.1.1 Bridge Seismic Design Criteria

The seismic analyses and design for all new permanent bridge elements shall be in accordance with the AASHTO Guide Specifications for LRFD Seismic Bridge Design, as modified by the WSDOT Bridge Design Manual, and the code-based response spectra and coefficients applicable to this Project as defined in Section 2.6, Geotechnical, and the WSDOT Geotechnical Design Manual.

All new, widened, modified, and seismic retrofitted bridges carrying I-405 mainline and ramps to and from I-405 mainline shall have an operational classification of Recovery as defined in the WSDOT Bridge Design Manual. All other bridges shall have an operation classification of Ordinary. Where the WSDOT Geotechnical Design Manual identifies structures as Normal or Essential, they shall be treated as Ordinary or Recovery, respectively, in accordance with the classifications in the WSDOT Bridge Design Manual.

The seismic design of Recovery level bridges includes bridge approach slabs and walls or other structures supporting bridge elements. Following a Functional Evaluation Earthquake (FEE) event, seismic settlements of bridge elements, approach slabs and structures supporting bridge elements shall not exceed the post construction settlement limits in Section 2.6, Geotechnical.

##### 2.13.4.1.1.1 Liquefaction and Lateral Spread

All new and widened bridges shall be designed for the effects of liquefaction and lateral spreading in accordance with the requirements of the WSDOT Bridge Design Manual, WSDOT Geotechnical Design Manual, and Section 2.6, Geotechnical. Where the structural design cannot accommodate effects from liquefaction or lateral spreading or meet settlement requirements, the Design-Builder shall provide mitigation of liquefiable soils.

#### 2.13.4.1.2 Bridge Widening Design Criteria

The Work on bridges to be widened shall be in accordance with the WSDOT Bridge Design Manual and shall include the following analysis and retrofit criteria:

• Determination of minor and major modifications and widening projects as defined in the WSDOT Bridge Design Manual.

• Determination of strength Capacity to Demand (C/D) ratios for the existing and modified structure and determination of displacement C/D ratios for the existing and modified structure (such as deck slab, girders, crossbeams, columns, and footings) using the pushover method of analysis. A summary table of C/D ratios for all elements shall be provided for each structure.

• Elements of the existing structure with C/D ratios made worse by the Work or less than 1.0 shall be retrofitted to restore their C/D ratios to the greater of preconstruction values or 1.0. The Design Builder shall submit analysis and calculations evaluating the C/D ratios for all structural elements during all stages of Work to WSDOT for Review and Comment.

• Analysis and quantification of the seismic demand effects due to differential settlement, and liquefaction/lateral spreading.

• Analysis for seismic demand effects shall be separate from settlement due to liquefaction.

For Bridge No. 405/103E, the Work shall include the following seismic retrofit measures at a minimum:

• Provide infill shear walls between each column.
• Provide steel column jackets on each column as required.
• Provide crossbeam strengthening with bolsters at the intermediate piers as required.
• Provide full width transverse girder stops between each girder at each girder support.
• Provide seat extensions at the intermediate piers and abutments as required to meet seat length requirements.
• Provide foundation strengthening below top of existing footings to resist seismic inertial demands. Existing shallow spread footings at the intermediate piers shall be made continuous to form a catenary or deep beam across the pier.
• Ground improvements for liquefaction mitigation of the existing structure can be deferred to the Bridge Seismic Retrofit Program.

For all other bridges to be widened, the Work shall include the following seismic retrofit measures at a minimum:
• Provide steel column jackets on each column or infill shear walls.
• Provide crossbeam strengthening with bolsters at the intermediate piers as required.
• Provide full width transverse girder stops between each girder at each girder support.
• Provide seat extensions at the intermediate piers and abutments as required to meet seat length requirements.
• Provide foundation strengthening below the top of existing footings for Recovery level bridges.

All new structural elements required to retrofit existing structures shall be designed for HL-93 live load.

Foundations for widening of Bridge 405/103E shall use drilled shafts. They shall be designed to impose no load or deformation on the South Fork Perry Creek culvert and be a minimum of 8 feet clear of the culvert.

Seismic improvements of Ordinary bridge foundation elements below the top of the existing footing can be deferred to the Bridge Seismic Retrofit Program.

Hold points shall be provided upon exposing bridge foundation elements below bottom of spread footing and pile or shaft caps, and before the start of any bridge seismic retrofit work.

#### 2.13.4.1.3 Load Rating Report

All new bridges, widened bridges, modified bridges, rehabilitated bridges, seismic retrofit bridges, and detour bridges that carry vehicular loads and are 20 feet or more in span length (measured from back-to-back of pavement seats along the centerline of the roadway) shall be load rated in accordance with the WSDOT Bridge Design Manual. Detour bridges, for the purpose of load rating, are defined as bridges that will be in place for more than 90 Calendar Days. The Design-Builder will not be required to retrofit the existing structures for a reduction in the load rating due to existing bridge overlay replacements, removal and replacement of traffic barriers, or both. However, the Design-Builder shall be required to retrofit the existing structures where load rating factors fall below 1.0 as a result of all other Work.

#### 2.13.4.1.4 Precast Prestressed Concrete Girders

Precast prestressed concrete girders include both pre-tensioned and post-tensioned girders.

The Design-Builder shall provide continuity reinforcement at intermediate piers in the bridge deck to resist negative moments due to live load and superimposed dead loads. Prestressed concrete girders shall be designed as simple span for all single span and multi-span bridges.

#### 2.13.4.1.5 Steel Plate Girders and Steel Box Girders

The main longitudinal load-carrying girders shall be cambered during fabrication. Heat cambered rolled girders shall not be used except as secondary members or temporary girders. Steel superstructures shall have a cast-in-place reinforced concrete bridge deck designed to be composite for live loads.

Drip plates shall be provided on the bottom flanges on the exterior side of the exterior steel plate girders to direct water runoff away from bearings and bridge seats.

Structural steel shall be painted in accordance with Section 6-07 of the Standard Specifications.

#### 2.13.4.1.6 Bridge Foundations

The Design-Builder shall construct bridge abutments, wingwalls, and curtain walls with precast or cast-in-place reinforced concrete. Where structural earth walls adjoin bridge abutments or curtain walls, the joint shall be a single vertical joint full height to the bottom of the traffic barrier. Curtain walls at bridge abutment wall corners shall be cast-in-place walls integral with the abutment walls and extending at least to the back of the footings. All girder seats at abutments and pier caps shall be sloped transverse to the abutment or pier cap to drain moisture accumulation.

The Design-Builder shall use wingwalls, curtain walls, and retaining walls as required by slope geometry and under-bridge clearances. These walls shall prevent soil slopes from spilling onto girders and bearings. End slopes shall meet stability requirements defined in Section 2.6, Geotechnical and the WSDOT Geotechnical Design Manual and shall be no steeper than 1.5H:1V.

#### 2.13.4.1.7 Bridge Decks and Expansion Joints

The Design-Builder shall design and construct all vehicular bridge decks using cast-in-place reinforced concrete or stay-in-place concrete deck panels in accordance with Section 15.5.5 of the WSDOT Bridge Design Manual. The bridge deck protection system for vehicular bridges, including bridge widenings, shall be in accordance with Section 15.5.5.D of the WSDOT Bridge Design Manual. Widened bridges with original concrete decks that do not meet a Type 1 Protection System, shall have a Type 1 Protection System on the new deck and shall have a Type 2 Protection System with a 1.5-inch concrete overlay on the existing deck, in accordance with Section 5.7.4B of the WSDOT Bridge Design Manual. Bituminous or bituminous-with-membrane overlays for permanent bridge deck construction on new vehicular bridges shall not be used.

Bridge deck texturing shall be in the longitudinal direction, except for bridge widenings, where the bridge concrete texturing shall match the existing bridge deck concrete finish adjacent to the widening.

The bridge deck for widened structures shall be continuous between expansion joints and shall match the existing expansion joint locations. Expansion joint headers shall be re-built the entire width of the new and existing bridge deck. Strip seals and compression seals and any associated armoring or anchorages shall be removed and replaced with new seals, in one continuous piece, for the entire width of the new and existing bridge deck.

The Design-Builder shall not use steel finger expansion joints on new bridges. All expansion joints shall be watertight. Longitudinal expansion joints shall not be used on new bridges or widened bridges. The maximum skew for expansion joints on new bridges shall be 30 degrees as measured perpendicular to the centerline of the bridge deck. Longitudinal joints in overlays on existing bridges needed for construction staging shall be placed along permanent lane lines.

In addition to Hold Points in Section 2.28, Quality Management Plan, a Hold Point shall be provided upon completion of existing header concrete removal and prior to placement of new header concrete for expansion joint replacement.

#### 2.13.4.1.8 Slope Protection

Slope protection shall reduce or eliminate the need for maintenance; lessen or eliminate negative visual impacts associated with soil erosion, weed growth, trash accumulation, and vandalism; and conform to the requirements described in the WSDOT Bridge Design Manual; Section 2.15, Roadside Restoration; and Appendix L. At a minimum, the Design-Builder shall provide concrete slope protection on slopes beneath new and widened bridges in accordance with Section 2.8 of the WSDOT Bridge Design Manual and Standard Plan A-30.10-00. Concrete slope protection shall be placed the full width of the bridge.

#### 2.13.4.1.9 Bridge Barriers and Railings

All new bridge and structure traffic barriers and railings shall be designed in accordance with the WSDOT Bridge Design Manual. The minimum Test Level design criteria shall be set as TL-4, except where pedestrian barrier is required shall be set as TL-3. Existing bridge barriers requiring modification shall be replaced by removing the existing barrier to the next joint.

Unless stated otherwise in the RFP, bridges with pedestrian or bicycle access shall have: 1) 32-inch high pedestrian barriers with pedestrian context sensitive solutions (CSS) railing adjacent to sidewalks, BRT Platforms, or raised rockscapes, or 2) 42-inch high single-slope barrier with pedestrian CSS railing elsewhere. Barriers and pedestrian railings shall also meet the requirements of Appendices L, and Section 2.15, Roadside Restoration.

Pedestrian CSS railing shall be designed in accordance with Appendices L, Sections 15.10.5 and 10.5.1 of the WSDOT Bridge Design Manual, and meet the strength and detailing requirements of Bridge Railing Type BP. The aesthetic requirements of Section 2.15, Roadside Restoration, shall not adversely affect the strength, extreme, and service limit states and safety requirements for traffic barriers and railings.

At a minimum, the following criteria shall also be met:

• New pedestrian bridge at Brickyard BRT Station shall have 32-inch height pedestrian barrier, curvilinear CSS railing with throw fence, and canopy structure, in accordance with Appendix L and Appendix S. The throw fence shall be 7.5 feet above walking surface.

• On Bridge No. 522/28N, the existing precast median barrier shall be replaced with new permanent 42-inch cast-in-place single slope barrier with rectilinear CSS railing.

• The existing metal pipe rail on the south side of Bridge No. 522/28N shall be removed and replaced with a rectilinear CSS railing. All existing anchors shall be removed to provide 1.5-inch clear cover and repaired in accordance with Section 6-01.16(2) of the Standard Specifications. Groups of closely spaced anchors shall be repaired as one continuous repair.

• New 42-inch height barrier shall be provided as a part of the required reconstruction of Bridge No. 405/70E, due to removal of Bridge No. 522/30E-N. The outside face barrier treatment shall be fractured fin to match the existing.

• New pedestrian bridge at the SR 527 BRT Station shall have 36-inch height pedestrian barrier, curvilinear CSS railing with throw fence, and canopy structure to match the existing bridge (405/104P), in accordance with Appendix L and the Transit Facilities Architectural and Urban Design Criteria (Appendix S). The throw fence shall be 7.5 feet minimum above walking surface.

• The SR 527 BRT Station shall have 32-inch height pedestrian barrier along the transit platforms and 42-inch height single sloped barrier elsewhere, in accordance Section 2.31, Vertical Construction. Temporary fall protection railing shall be installed to provide a minimum combined height of 42-inch. Pedestrian railing shall meet the requirements in this Section.

• The 17th Avenue SE direct access bridge over northbound I-405 at SR 527 BRT Station and approach shall have 42-inch single slope barrier with pedestrian CSS railings, in accordance with Appendix L and Appendix S.

Transitions between barrier types and height shall be provided in accordance with this Section and Appendix L. Transitions shall be gradual and provide a seamless appearance.

The Design-Builder shall not use precast concrete barriers for permanent applications on bridges or bridge approach slabs. Permanent barriers shall be reinforced concrete cast-in-place in the final position.

The Design-Builder shall cast a minimum of two spare 2-inch-diameter conduit pipes with junction box pairs (one for each conduit pipe) spaced at 180 feet maximum into all new concrete bridge barriers for the full length of the barrier, including barriers on bridge approach slabs and barriers on walls that abut approach slabs or bridges. Each conduit pipe shall terminate at separate Type 1 junction boxes within 15 feet of the exit from a barrier. The Design-Builder shall furnish and install conduit expansion, deflection devices, or both at all expansion joints, points where the conduit exits from the barrier and any other location where movement is expected. Additional conduit shall be installed as needed to meet the Project utility requirements. Conduit installed but not utilized for this Project shall be considered spare for future utility needs.

#### 2.13.4.1.10 Bridge Canopies

Bridge canopies shall meet the requirements in Section 2.31, Vertical Construction, and the Transit Facilities Architectural and Urban Design Criteria (Appendix S).

#### 2.13.4.1.11 Bridge-Mounted Utilities

Utility installation requirements on new and existing structures shall be in accordance with Section 2.10, Utilities and Relocation Agreements, Appendix L, and Section 15.10 of the WSDOT Bridge Design Manual.

#### 2.13.4.1.12 Temporary Structures

Temporary structures refer to any temporary bridge, detour bridge, portion of a bridge, or buried structure that will not remain upon Physical Completion of the Project. Temporary structures shall accommodate vehicular and pedestrian traffic and meet the following criteria:

The Design-Builder shall design temporary structures in accordance with the WSDOT Bridge Design Manual, WSDOT Geotechnical Design Manual, AASHTO LRFD Bridge Design Specifications, and AASHTO Guide Specifications for LRFD Seismic Bridge Design. Welding on any steel elements shall be in accordance with AWS D1.5. Components of temporary structures that will be incorporated into the permanent structures shall meet the requirements for the permanent structures. All temporary structures shall be designed for live load deflection less than or equal to L/800 as defined by AASHTO LRFD Bridge Design Specifications. Temporary structures with vehicular traffic shall be designed for minimum 75 percent of the HL-93 live load as defined in the AASHTO LRFD Bridge Design Specifications, except when there is no practical detour route available for freight, then 100 percent of the HL-93 live load shall be used.

The driving surface of the temporary detour structure shall be durable and skid resistant as defined in Section 10.13 of the WSDOT Bridge Design Manual. Temporary traffic barriers shall be in accordance with Section 1610 of the WSDOT Design Manual and the WSDOT Bridge Design Manual.

The Design-Builder may use new and salvaged structure members for the temporary structure, but it shall be the responsibility of the EOR to ensure all members meet all appropriate material properties for their intended function, such as dimensions, yield strength, tensile strength, ductility, toughness, chemical composition, weldability, and corrosion resistance. Material testing of the structure members may be required in order to provide assurance that the appropriate requirements of material properties have been met. For salvaged steel materials where the grade of steel cannot be positively identified, the design stresses for the steel shall conform to Section 6-02.3(17)B3 of the Standard Specifications. Salvaged structure members include previously used members from other bridges or structures, members that have been fabricated but never installed in a structure, and members from a prefabricated structural system designed specifically for repeated temporary use. Concrete girder design sheets shall be provided indicating concrete strength, strand type and pattern, shear reinforcement, and other pertinent information. The Design-Builder shall provide supporting documentation for all selected temporary members to the WSDOT Engineer for Review and Comment.

All foundations of the temporary structures shall be located outside the horizontal limits of the Ordinary High Water for the Sammamish River, Par Creek, North Fork Perry Creek, North Creek, Stream 25.0L, Juanita Creek, Queensborough Creek under I-405, and Queensborough Creek under SR 527, and the bottom of foundations shall be located a minimum of 2 feet below scour estimated for the 2-year MRI water flows. Before Substantial Completion of the Project, the foundations for temporary structures shall be completely removed.

Design Plans and specifications for all temporary detour structures shall be reviewed and approved by the SLE. Prior to opening to traffic, all temporary detour structures shall be reviewed in the field for compliance with the Plans and specifications by the SLE, who shall advise WSDOT of any deviations. The Design-Builder shall be responsible for the maintenance and removal of all temporary structures. Temporary structures shall be removed in accordance with 2-02.3(2) of the Standard Specifications.

#### 2.13.4.1.13 Bridge Security

Bridges shall be designed for security in accordance with the WSDOT Bridge Design Manual and shall employ both the natural surveillance and territorial reinforcement strategy and the hard armoring strategy.

Alcove spaces and ledges within abutment-superstructure interfaces shall be omitted or completely sealed off between girders above the abutment seat to the deck soffit with bridge security fencing in accordance with Section 15.2.11 of the WSDOT Bridge Design Manual.

Abutments supported by mechanically stabilized earth walls (commonly referred to as perched abutments) and bent-type abutments shall include concrete enclosing fascia walls that extend to the bottom of the superstructure and infill between girders from bottom of girder to deck soffit. The design shall minimize any gaps in the enclosing fascia, such as those needed to allow bridge movements. Bridge security fencing, meeting the requirements of Section 15.2.11 of the WSDOT Bridge Design Manual, may be used to infill between girders above the concrete enclosures in lieu. Inspection access and ventilation shall be provided and meet the requirements of WSDOT Bridge Design Manual 7.5.1.A.4.

Concrete enclosing fascia and bridge security fencing shall be designed in accordance with AASHTO LRFD Bridge Construction Specifications and the loads specified in Article 13.8.2 of that standard. The retaining wall and concrete enclosing fascia shall incorporate the aesthetic treatments for abutment walls in accordance with the I-405, Brickyard to SR 527 Project Urban Design Criteria (Appendix L).

The new NB I-405 over Sammamish River and SR 522 bridge shall meet the bridge security requirements stated above in this Section and shall also have 8-foot tall bridge security chain-link fencing installed to deny access to the area beneath span(s) north of SR 522 to the northern abutment. The bridge security chain-link fencing shall seamlessly interface with the wire mesh with vines on low wall behind the BRT transit stations shown in the Transit Facilities Architectural and Urban Design Criteria (Appendix S) to deny access. Widened bridges with a clear height of 10-feet or less on any side (measured from the ground line at face of abutment to girder seat) shall have 8-foot tall bridge security chain-link fencing, which shall deny access to spaces between girders at the abutment and areas where the superstructure is less than 10-feet from finished grade. Bridge security chain-link fencing shall terminate at the abutment, beneath the bottom flange of the exterior girders, and shall not extend in front of the exterior girder webs and curtain or wing walls. Bridge security chain link fencing shall be 9-gauge, 0.5-inch mesh, black vinyl-coated chain link fence fabric and shall have a continuous top pipe rail. High-security locking gates shall be provided as required for maintenance and inspection. The fencing shall be designed for the loads specified in Article 13.8.2 of AASHTO LRFD Bridge Design Specifications.

#### 2.13.4.1.14 Bridge Seismic Retrofit Design Criteria

Provided the bridges to be retrofit are not widened, the Work shall include seismic analysis and retrofit measures for the elements noted on the following bridges in accordance with Section 4.4 of the WSDOT Bridge Design Manual:

• Determination of strength C/D ratios for existing and modified structures and determination of displacement C/D ratios for all elements of the existing and modified structures (including crossbeams, columns, and footings) using the pushover method of analysis. A summary table of C/D ratios for all elements shall be provided for each bridge.

The Work on Bridge Nos. 405/64, 405/73, and 405/103W shall include the following seismic retrofit measures at a minimum:

• For Bridge No. 405/64, provide steel column jackets for the two southern columns at pier 2 (columns built prior to 1980).

• For Bridge No. 405/73, provide steel column jackets for the two center columns at Pier 2, 3, and 4 (columns built prior to 1980).

• For Bridge No. 405/103W, provide steel column jackets for the three western columns at Pier 2 and 3 (columns built prior to 1980).

• Provide crossbeam strengthening with bolsters at the intermediate piers as required.

• Provide full width transverse girder stops between each girder at each girder support.

• Provide seat extensions at the intermediate piers and abutments as required to meet seat length requirements.

All new structural elements for the seismic retrofit shall be designed for an HL-93 live load. Pedestals at the top of the footings shall be considered part of the columns for retrofit requirements and shall be retrofitted as required.

Seismic improvements of the existing foundation elements below the top of the existing footing can be deferred to the Bridge Seismic Retrofit Program.

Hold points shall be provided before placement of column jackets, bolsters or girder stops to assess conditions of the structure.

#### 2.13.4.1.15 Bridge No. 405/70E Modification Design Criteria

Removal of Bridge No. 522/30E-N shall be considered a modification of the existing NB I-405 bridge (Bridge No. 405/70E). Analysis of the modified Bridge No. 405/70E shall meet the requirements of a bridge minor widening in accordance with the WSDOT Bridge Design Manual. The Design-Builder shall be responsible for determining the limits of removal of Bridge No. 522/30E-N, and elements of the existing structure with C/D ratios made worse by the Work or less than 1.0 shall be retrofitted to restore their C/D ratios to the greater of preconstruction values or 1.0. The Design-Builder shall submit analysis and calculations evaluating the C/D ratios for all structural elements of the existing and modified structure, and a summary table of C/D ratios for all elements shall be provided to WSDOT for Review and Comment.

At the location where the existing bridge superstructure will be removed as a part of the Work, the Design-Builder shall provide new concrete fascia to enclose all voids and enclose the end of the box girder along the full width of the bridge, and finish with a Class 2 surface finish and pigmented sealer to match existing. Concrete fascia shall be designed in accordance with AASHTO LRFD Bridge Design Specifications and the Mandatory Standards. Inspection access and lighting for any box girder cells to remain shall be provided and meet the requirements of WSDOT Bridge Design Manual 5.2.6.

New cast-in-place concrete barrier shall be installed on the bridge to close gaps left in the barrier from removal of Bridge No. 522/30E-N. New bridge drain inlets and downspouts shall be installed to eliminate any possible ponding that may occur as a result of the modification. Barrier scuppers and freefall of water to the ground below are not allowed.

Seismic retrofit of the existing structure below top of columns can be deferred to the Bridge Seismic Retrofit Program.

The modified bridge shall be load rated in accordance with this Section.

#### 2.13.4.1.16 Bridge No. 522/28N Modification Design Criteria

Work on Bridge No. 522/28N shall incorporate aesthetic and landscape requirements of Section 2.15, Roadside Restoration, and Appendix L. Bridge analysis shall meet the requirements of a bridge widening in accordance with the WSDOT Bridge Design Manual. At a minimum, the Work shall include the following analysis and retrofit criteria.

• Determination of minor and major modifications and widening projects as defined in the WSDOT Bridge Design Manual. The Work may be considered a minor modification and widening provided the net mass increase is equal to or less than 10 percent of the original superstructure, and substructure and foundations are unchanged.

• Elements of the modified structure with strength and service limit states C/D ratios less than 1.0 shall be retrofitted to restore their C/D ratios to be greater than 1.0. Steel stresses at the applicable services limit states shall also be evaluated and control of cracking by distribution of reinforcement shall be met for a Class 2 exposure condition, in accordance with AASHTO LRFD Bridge Design Specifications. Where seismic evaluation is required, determination of displacement C/D ratios for all elements of the modified structures (including crossbeams, columns, and footings) shall be performed using the pushover method of analysis. A summary table of C/D ratios for all elements shall be provided for each structure.

• The Design Builder shall submit analysis and calculations evaluating the C/D ratios for all structural elements during all stages of Work, including, but not limited to, construction loading, and new hard-scaping placement to WSDOT for Review and Comment. Analysis shall evaluate the short- and long-term effects of added deadloads.

The landscaping, hardscaping, pedestrian path, bridge joints and waterproofing system components, shall be designed for HS-20 live load and pedestrian live load full width, barrier-to-barrier, in accordance with AASHTO Guide Specification for Pedestrian Bridges. Dynamic load allowance need not be considered for HS-20 live load.

All new structural elements required to retrofit existing structures shall be designed for HL-93 live load.

Seismic improvements of the existing foundation elements below the top of the existing footing can be deferred to the Bridge Seismic Retrofit Program.

The bridge shall be load rated in accordance with this Section.

A waterproofing assembly shall be provided in accordance with this Section.

Hold points as described in Section 2.28, Quality Management Plan, shall be provided before the start of any bridge seismic retrofit work.

#### 2.13.4.1.17 Bridge No 405/104P Design Criteria

The existing portion of Bridge 405/104P structure may be left in place and incorporated into the replacement bridge structure provided that elements of the existing structure with C/D ratios made worse by the Work or less than 1.0 are retrofitted as required to restore their C/D ratios to the greater of preconstruction values or 1.0. Seismic analysis and design of the new and existing structure shall be in accordance with this Section.

The bridge shall maintain the same superstructure and substructure type as the existing portion and adhere to the requirements in Section 2.15, Roadside Restoration, and Appendix L. The overall appearance and geometrical dimensions shall be the same as those of the existing structure. Portions of unused structure shall be removed in accordance with the Standard Specifications.

#### 2.13.4.1.18 Bridge Drainage

Where new bridge drain inlets, pipes, and downspouts are installed, they shall be placed to capture stormwater runoff on the bridge and shall meet the requirements in Section 2.14, Stormwater; Section 15.10 of the WSDOT Bridge Design Manual; and the following:

• Downspout parts shall be accessible for maintenance and cleaning.
• Drain pipes and drainage accessories shall not be installed within the bridge substructures elements, within box girder cells, within the box girder top flange or deck, or on the exterior (visible) sides of the bridge.
• Drain pipes and downspouts shall be located in accordance with Appendix L.
• Pipes and downspouts shall be ductile iron pipe.

All new drainage conveyance shall be supported in accordance with the requirements for utilities installed with new construction in Section 15.10 of the WSDOT Bridge Design Manual.

All new exposed drainage conveyance and associated supports attached to bridges shall be painted in accordance with Section 6-07 of the Standard Specifications and Appendix L.

Runoff shall be captured at each end of new and widened bridges. Approach drains shall be placed at each end of bridges to prevent stormwater from running onto the structure and where surface drainage is modified resulting in stormwater running onto the structure.

Refer to Section 2.31, Vertical Construction, for additional design criteria.

#### 2.13.4.1.19 Waterproofing Assembly for Bridge No. 522/28N

The Design-Builder shall design, furnish and install a complete vertical and horizontal waterproofing assembly below all hardscaping and landscaping features on the existing Bridge No. 522/28N. The waterproofing assembly shall be continuous and extend full width barrier-to-barrier, over bridge joints, and beyond each bridge approach slab, to provide a complete lateral conveyance system with positive drainage that discharges all subsurface flows off the bridge deck. The waterproofing assembly shall include, but not be limited to, surface conditioner, monolithic waterproofing membrane, prefabricated drainage mat, drainage course, filter fabric, separation layers and related cant strips, metal flashing and bridge expansion joint seals. The waterproofing membrane shall be a hot, fluid applied, self-healing, rubberized asphalt membrane. Base course and fill beneath hardscaping shall be closed-cell expanded polystyrene geofoam. Normal weight aggregate base course or soil shall not be used.

All waterproofing assembly components shall be obtained as a single-source from the membrane manufacturer to ensure total system compatibility, function, and integrity. Upon completion of the Work, the Design-Builder shall supply to the owner with a single-source 15-year total system warranty of United States origin direct from the manufacturer.

Penetrations through the waterproofing assembly shall not be allowed. However, foundations for illumination and sign poles may be attached directly to the existing bridge deck, and the waterproofing membrane and flashing/reinforcing shall extend up the sides of the element pursuant to the waterproofing manufacturer's recommendations and to ensure depth of subsurface water does not exceed the vertical height of the protection.

The prefabricated drainage mat and drainage course shall be sized to provide full lateral conveyance of all surface flows. The drainage mat and drainage course shall have sufficient compressive strength to support all overburden, including but not limited to hardscaping dead loads, pedestrian loads, HS-20 vehicular loads, and all other surface elements over the mat. Calculations and product documentation shall be provided for WSDOT Review and Comment.

Positive drainage shall be provided as flow transitions from the waterproof assembly to a conveyance system at the outside edges of all structures or retaining type elements. At these locations, the top of the conveyance system shall be located below the bottom of the prefabricated drainage mat. Clean-outs, accessible from the bridge deck, shall be provided at the inlet to each conveyance system. Backwater conditions resulting from this transition is prohibited.

The Design-Builder shall perform chain drag testing, ASTM D4580, Method B, across the entire bridge deck and approaches. Areas of spalling, delamination, unsound concrete, and rebar deterioration shall be documented in a Chain Drag Report (Appendix J) and submitted to WSDOT for Review and Comment at least 14 Calendar Days prior to installation of the waterproofing assembly. A Hold Point shall be provided prior to any further deck preparation and repair. The WSDOT Engineer shall approve the areas of the existing bridge deck requiring further deck preparation.

The Design-Builder shall include in their bid an area of further deck preparation equal to 25 percent of the area of the bridge deck. If WSDOT determines that the quantity of further deck preparation exceeds this area, additional compensation will be made in accordance with Section 1-04 of the General Special Provisions.

In addition to Hold Points in Section 2.28, Quality Management Plan, a Hold Point shall be provided upon completion of the repairs and prior to placement of the waterproofing assembly. A Hold Point shall be provided prior to placement of hardscaping elements on the bridge.

See Section 2.14, Stormwater, for additional conveyance requirements.

#### 2.13.4.1.20 Existing Bridge and Wall Demolition

During all stages of demolition, existing structures (or portions of structures as applicable) shall remain stable and shall be removed in a controlled fashion that does not damage surrounding existing structures, roadways or utilities. The Design Builder shall submit structural stability analysis to support the selected demolition sequence.

Bridge and wall demolition plans and procedures, including falsework plans, shall be submitted to WSDOT for Review and Comment as Type 3E Working Drawings, and be prepared in accordance with the Standard Specifications and this Section.

Falsework and shoring used for demolition shall be designed in accordance with the requirements for falsework in the Standard Specifications.

#### 2.13.4.1.21 Barges, Flexi-Floats, and Crane Mats

If barges, including flexi-floats, crane mats, and similar, are used to transport construction materials or demolitions debris, temporarily store and stockpile materials, or temporarily store or transport liquid or sediment removed during the Work, the work surface of the barge deck shall include containment to prevent any discharges into the Sammamish River. No rubblization, processing of material, or breaking down of any existing bridge or structural materials shall be allowed on vessel, barge, flexi-float, crane mats, or other Design Builder equipment used over existing waterways.

Barges shall not be allowed to ground-out during in-water construction. Barges and other floating equipment shall be operated so that there is a minimal suspension of sediments. Barges and walkways between barges shall be cleaned as necessary and kept free of material with the potential to enter waters of the State.

Should the Design-Builder choose to moor barges outside of the Project Limits, the Design-Builder shall obtain all necessary concurrence or approvals, or both, to do so in writing from the authority(ies) having jurisdiction. The Design-Builder shall provide copies of all such concurrences and approvals to WSDOT prior to mooring barges in the areas(s).

The use of barges shall be done in accordance with the requirements outlined in the applicable environmental permits, and the United States Coast Guard bridge permit.

For permit requirements and commitments list, see Appendix P and Appendix C.

#### 2.13.4.1.22 Navigation Channel Requirements

At the Sammamish River, the Design-Builder shall maintain a minimum navigation opening at all times during and after construction, as dictated by the United States Coast Guard Bridge Permit.

For permit requirements and commitments list, see Appendix P and Appendix C.

### 2.13.4.2 At-Grade Traffic Barriers

Refer to Section 2.11, Roadway, for design criteria regarding barrier type and height.

At-grade traffic barriers shall be designed in accordance with the WSDOT Bridge Design Manual and shall use the design criteria for TL-4, at a minimum. Existing barriers that require modification shall be replaced by removing the existing barrier to the next joint.

Where changes to the roadway beneath or adjacent to existing bridges results in abutments or piers located within the clear zone, as defined by the WSDOT Design Manual and AASHTO Roadside Design Guide, collision shall be addressed by either providing structural resistance or by redirecting or absorbing the collision load in accordance with Section 3.16.7 of the WSDOT Bridge Design Manual.

Traffic barriers with a grade difference greater than the Standard Plans shall meet requirements for both barriers and retaining walls, including slope stability, wall drainage, and horizontal bench requirements, in accordance with this Section; Section 2.6, Geotechnical; and the Mandatory Standards.

Traffic barriers along the eastern edge of northbound I-405 between MP 22.35 and 22.55 in the vicinity of the Brickyard BRT Station along the existing noise walls shall stand at least 2 feet clear of the existing noise walls, measured from back of barrier to face of existing noise wall. Where an offset of 4 feet or less is provided between the back of barrier and existing noise wall, the barrier shall be designed to transfer no collision load to the existing noise wall and its foundations. The barrier shall also be designed as a non-yielding retaining structure that restores the resistance at the existing noise wall foundation. The Design-Builder shall design the barrier and retaining structure for no deflection and at-rest earth pressures, as described in Section 15-4.8 of the WSDOT Geotechnical Design Manual.

### 2.13.4.3 Retaining Wall Design Criteria

The Design-Builder shall design and construct permanent retaining walls for the Project. Retaining walls shall be of the following types:

• Proprietary structural earth walls in accordance with Section 6-13 of the Standard Specifications.
• Standard permanent geosynthetic retaining walls in accordance with Sections D-3.09, D-3.10, and D-3.11 of the Standard Plans and Section 6-14 of the Standard Specifications.
• Standard reinforced concrete cantilevered retaining walls in accordance with Sections D-10.10 through D-10.45 of the Standard Plans and Section 6-11 of the Standard Specifications.
• Soil nail walls in accordance with Section 6-15 of the Standard Specifications.
• Soldier pile walls in accordance with Sections 6-16 and 6-17 of the Standard Specifications.
• Soldier pile tieback walls in accordance with Sections 6-16 and 6-17 of the Standard Specifications.
• Secant pile and tangent pile walls in accordance with Section 6-19 of the Standard Specifications

Rock walls, block walls, masonry walls, permanent shotcrete and gabion cribbing shall not be used for retaining earth or as retaining walls.

The Design-Builder shall design walls in accordance with Section 2.6, Geotechnical; the WSDOT Geotechnical Design Manual; the WSDOT Bridge Design Manual; and the AASHTO LRFD Bridge Design Specifications. The Design-Builder may modify the Standard Plan retaining walls to meet Project requirements, such as seismic design criteria and aesthetic requirements per Section 2.15, Roadside Restoration, by providing special design analysis. Aesthetic modifications shall not adversely affect the strength and safety requirements of the retaining walls. Special design retaining walls shall be stamped and signed by the EOR. Wall drainage, including cement concrete gutters, shall be provided for all walls in accordance with the WSDOT Geotechnical Design Manual and the WSDOT Bridge Design Manual.

The Design-Builder shall evaluate potential impacts to Utilities and other facilities (stormwater pipe, Intelligent Transportation System [ITS] conduit, etc.) crossing under proposed walls and bridges and incorporate mitigation measures to avoid conflicts and detrimental effects including, but not limited to, settlement and surcharge loading.

Walls supporting Recovery level bridges and bridge structure elements, including approach slabs, shall remain at full-service level as defined by the bridge seismic design criteria in this Section and the WSDOT Bridge Design Manual. They shall also meet the serviceability requirements in Chapter 15-4.7 of the WSDOT Geotechnical Design Manual and the post construction settlement limits in Section 2.6, Geotechnical, under the Functional Evaluation Earthquake (FEE) event.

#### 2.13.4.3.1 Retaining Walls Beneath Existing Bridges and Structures

During all stages of temporary and permanent retaining wall and shoring construction under existing bridges, structural elements shall not be overstressed with a C/D ratio of less than 1.0, or less than the C/D ratio of the existing structure. Design and construction staging shall be based on three-dimensional deformation-based analysis that provides predicted displacements of the structure during each stage of construction. The Design-Builder shall submit to WSDOT for Review and Comment structural and geotechnical analysis and calculations demonstrating existing structural elements are not overstressed during all stages of the Work. The analysis and calculations shall be submitted as a structure design submittal together with the design of the retaining wall or shoring. At a minimum, the analysis shall investigate the following:

• Deformations in all bridge structure and foundation elements caused by the Work at all stages.
• Short-term, long-term, and total and differential settlement and lateral movements.
• Any potential impacts to the bridge structure as a result of the Work.
• Geotechnical analysis required in Section 2.6, Geotechnical.

All structure design submittals for retaining walls beneath existing bridges shall include detailed plans, elevations, and section layouts of all existing and new structure elements identifying clearances and areas of potential conflicts. The Design-Builder shall submit Type 3E Working drawings detailing specific procedures for retaining wall and shoring installation and remedies for potential conflicts.

A pre-activity meeting with WSDOT and the Design-Builder shall be held at least 14 Calendar Days prior to beginning any temporary or permanent retaining wall Work under bridges. The conference will be used to discuss construction procedures, personnel and equipment to be used.

In addition to the Hold Points required in Section 2.28, Quality Management Plan, the following shall be provided:
• Prior to excavating below bottom of spread footing, or pile or shaft caps and within a zone sloping away from bottom of footing or cap.
• Upon exposing any foundation elements below bottom of spread footings or footing caps.
• Prior to placing any shotcrete facing.

#### 2.13.4.3.2 Temporary Retaining Walls

Temporary retaining wall refers to any wall, portion of wall, or shoring that retains earth adjacent to public vehicular traffic and will not remain functional upon Physical Completion of the Project.

The Design-Builder may reuse structural components of temporary retaining walls as part of permanent retaining wall systems, provided all of the structural support elements and materials of the temporary retaining walls are in as-new condition and meet the requirements of the permanent structure standards. Timber piles will be allowed only as foundations for temporary retaining walls where allowed by the Project's permits. Maintenance of temporary retaining walls shall be the Design-Builder's responsibility.

The Design-Builder shall remove all portions of temporary retaining walls before Substantial Completion of the Project.

### 2.13.4.4 Buried Structures Design Criteria

The Design-Builder shall use only cast-in-place or precast reinforced concrete, metal structural plate, or a composite arches system for buried structures.

Buried structures and associated headwalls, wingwalls and connected barriers shall be designed and constructed in accordance with the WSDOT Geotechnical Design Manual, WSDOT Bridge Design Manual, Standard Specifications, AASHTO LRFD Bridge Design Specifications, and the AASHTO LRFD Bridge Construction Specifications. The AASHTO operational classification load modifier for the buried structure shall be that for typical bridges unless noted otherwise.

Fall protection on buried structures and associated headwalls, wingwalls and connected barriers shall follow requirements in this Section.

Corrosion and abrasion shall be considered as specified in the WSDOT Bridge Design Manual.

The Structural Clear Span of a buried structure shall be used to determine the buried structure class. When supporting a Roadway, the Structural Clear Span shall be the widest horizontal opening from interior face to interior face of the end walls measured parallel to the roadway centerline. When not supporting a Roadway, the Structural Clear Span shall be the widest horizontal opening from interior face to interior face of the end walls measured perpendicular to the buried structure centerline.

| Structure Class | Structural Clear Span |
|---|---|
| Class 1 | Less than 20.0 feet |
| Class 2 | 20.0 feet and greater |

Class 2 buried structures shall be considered bridges and satisfy seismic requirements for Ordinary or Recovery operational classifications, as defined in this Section. Class 2 buried structures and associated headwalls and wingwalls shall include seismic design and ground failure mitigation in accordance with the AASHTO LRFD Road Tunnel Design and Construction Guide Specifications. Seismic analysis shall include the loading effects resulting from ground shaking and ground failure. This includes, at a minimum, design for the seismic effects of transient racking, ovaling deformations, liquefaction, lateral spreading and lateral flow effects. The AASHTO LRFD Bridge Design Specifications exemption from seismic loading shall not apply.

Seismic Design need not be considered for Class 1 buried structures. However, wingwalls and headwalls shall