Highway Cover Uses: Screening and Assumptions Memorandum

MET.11.1.3.AH.06.20201007

Draft Key Number: K19071 Task: 11.1.3 FOR REVIEWODOT ONLY EA: PE002591000J71 METRO 20201007 August 25, 2020 MET.11.1.3.AH.06.20201007

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Contents Executive Summary ...... vi Sites for Consideration ...... vii Key Assumptions and Preliminary Takeaways ...... viii Design Options Summary ...... xii Memorandum Format ...... xiii 1 Screening for Technical Study ...... 1 1.1 Screening Criteria ...... 1 1.2 Land Use Categories Evaluated...... 2 1.2.1 Highway Cover Sites: ...... 3 1.3 Scoring ...... 4 1.4 Recommendations for Further Evaluation ...... 5 1.4.1 Public Open Space, North Site, 15% Submittal ...... 5 1.4.2 Public Open Space, North Sites A and B ...... 5 1.4.3 Public Open Space, Middle Site B ...... 5 1.4.4 Public Open Space, Middle Sites A and B ...... 5 1.4.5 PublicFOR Open REVIEW Space, South ONLY Site, 15% METRO Submittal ...... 20201007 ...... 5 1.4.6 Public Open Space, South Sites A and B ...... 5 1.4.7 Light Public Buildings, North Sites A and B ...... 6 1.4.8 Light Public Buildings, Middle Sites A and B ...... 6 1.4.9 Light Public Buildings, South Sites A and B ...... 6 2 Land Use Assumptions ...... 11 2.1 Land Use Regulations and Compliance ...... 11 2.1.1 Base Zones ...... 11 2.1.2 Overlay Zones ...... 12 2.1.3 Plan Districts ...... 12 2.1.4 Hierarchy of Regulations ...... 13 2.2 Incentive Programs: Inclusionary Housing and Affordable Commercial Space ...... 13 3 Environmental and Right-of-Way Considerations ...... 15 3.1 Right-of-Way Ownership Governance ...... 15 3.1.1 Right-of-Way Cover Use Screening Assumptions ...... 15 3.2 Relationship of Options to Environmental Class of Action ...... 16 MET.11.1.3.AH.06.20201007

3.2.1 Highway Covers Use ...... 16 3.2.2 Highway Covers Shape ...... 16 4 Structural Considerations ...... 17 4.1 Building Positioning and Foundation Support Considerations ...... 17 4.2 Design Code Changes for Occupied Space on Highway Covers ...... 17 4.3 Range of Types for Building-To-Bridge Structural Connections ...... 18 4.4 Implications for Directly Adjacent Building Foundations ...... 18 4.5 Building Loading Assumptions Table ...... 18 4.6 Long-Term Performance of Buildings Constructed on Bridges ...... 19 4.7 Defining Bridge Design Loads for Future Building Type and Placement ...... 20 4.8 Refined Structural Evaluation Based on Preliminary Technical Screening ...... 20 4.8.1 Design Implications of a Single (Combined) Highway Cover Shape ...... 21 4.8.2 Design Implications of Structural Irregularities ...... 21 4.8.3 Design Implications of Building Geometry and Position in Highway Covers ...... 22 4.8.4 Design Implications of Building Connections to Highway Covers ...... 25 4.8.5 Summary of Findings from Preliminary Studies ...... 29 4.8.6 OtherFOR Considerations REVIEW for Buildings ONLY on METRO the Highway 20201007 Cover ...... 30 5 Site Access, Parking, and Loading ...... 30 6 Utility Routing Considerations ...... 31 6.1 Gravity-Related Utility Routing ...... 31 6.2 Non-Gravity-Related Utility Routing ...... 32 7 Maintenance and Inspection Assumptions ...... 32 8 Fire and Life Safety Considerations and Assumptions ...... 33 8.1 Tunnels under the Highway Cover Structures ...... 34 8.2 Considerations for Buildings on Top of Highway Cover Structures ...... 35 8.3 Consequences for Buildings on the Highway Covers ...... 38 9 Conceptual Design Options ...... 39 10 Highway Cover Relevant Examples ...... 63 10.1 Relevant Example Projects ...... 63 10.1.1 Atlanta Financial Center – Atlanta, GA ...... 64 10.1.2 Copley Place/Prudential Center – Boston, MA ...... 65 10.1.3 The Rose Fitzgerald Kennedy Greenway – Boston, MA ...... 66 MET.11.1.3.AH.06.20201007

10.1.4 The Cap at Union Station – Columbus, OH ...... 67 10.1.5 Klyde Warren Park – Dallas, TX...... 68 10.1.6 Freeway Park/Washington State Convention Center – Seattle, WA ...... 69 10.1.7 Aubrey Davis Park Lid – Mercer Island, WA ...... 70 10.2 Other Examples: ...... 71 10.2.1 5th Street Pedestrian Plaza – Atlanta, GA ...... 71 10.2.2 Hartford Public Library – Hartford, CT ...... 72 10.2.3 George Washington Bridge Bus Terminal – New York, NY ...... 73 10.2.4 Eastside Parks on SR 520 – Seattle, WA ...... 74 10.3 Relevant Example Projects Findings ...... 75

Figures Figure 1. Highway Cover Sites ...... vii Figure 2: Building Feasibility of Middle Site within Existing Constraints ...... xi Figure 3: Building Feasibility of North Site within Existing Constraints ...... xi Figure 4. Example Images of Public Open Spaces ...... 2 Figure 5. ExampleFOR Images REVIEW of Light Public ONLY Buildings METRO ...... 20201007 ... 3 Figure 6. Highway Cover Sites ...... 4 Figure 7. Zoning Map for Highway Covers and Vicinity ...... 12 Figure 8. Plan Districts for the Highway Covers Sites...... 13 Figure 9. Analytical Models for Building Assessments (a) Middle and South Site 2-story building model, (b) Middle and South Site 4-story building model, (c) North Site 2-story building model.23 Figure 10. Conceptual details of the Type 1 connection...... 27 Figure 11. Conceptual details of the Type 2 connection...... 27 Figure 12. Preferred Block Frontages for Access and Loading ...... 31 Figure 13. Relationship of Building Ground Floor to Bridge Deck ...... 32 Figure 14. Minimum Highway Cover Edge Offsets ...... 33 Figure 15. Building Wall Positions at Offset Distances from Portal – 0 ft. (Top), 12 ft. (Middle), and 24 ft. (Bottom) for a Fixed Fire Position on I-5 ...... 36 Figure 16. Thermal Energy Mapping on a Building at 0 ft., 12 ft., and 24 ft. Offsets from Cover Structure Edge (Design Hydrocarbon Fire at Fixed Position) ...... 37 Figure 17. North Site, Design Options Explored ...... 39 Figure 18. Middle Site, Design Options Explored ...... 40 MET.11.1.3.AH.06.20201007

Figure 19. South Site, Design Options Explored ...... 41 Figure 20. Broadway/Weilder Site, Design Option Explored ...... 42

Tables Table 1: Summary of Findings for Cover Use Options Studied ...... viii Table 2. Identification, Scoring, and Screening Methodology ...... 1 Table 3. Preliminary Screening Matrix ...... 7 Table 4. Zoning Code Districts and Related Development Standards for Zones included in the Highway Cover Sites ...... 14 Table 5. Building Load Assumptions ...... 19 Table 6. Summary of Preliminary Girder Sizing for Various Loading Scenarios on the Middle and South Sites ...... 24 Table 7. Summary of Advantages and Disadvantage of Pilaster Connection Concepts ...... 28

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Acronyms and Abbreviations

A&E Architecture and Engineering AASHTO American Association of State Highway and Transportation Officials ASCE American Society of Civil Engineers CAC Community Advisory Committee COP City of Portland DOT Department of Transportation EA Environmental Assessment ESC Executive Steering Committee FAR Floor Area Ratio FLS Fire and Life Safety HCAC Highway Covers Advisory Committee LRFD Load and Resistance Factor Design ODOT Oregon Department of Transportation ROW Right-of-way WSDOT Washington State Department of Transportation

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Executive Summary

The purpose of this memorandum is to inform the Project Team about the technical considerations and constraints related to a range of potential uses and shapes for the highway covers. The information presented is considered to be preliminary in nature and does not conclusively support or eliminate specific cover use concepts from further consideration. It is critical to note that the Architecture and Engineering (A&E) Team was required to develop all design concepts presented herein, without the benefit of community engagement. Therefore, these design options are propositional and developed in order to study technical issues only. The A&E studied a range of building sites, shapes, and heights as well as a range of open space designs while maintaining the infrastructure elements of the House Bill 2017 project and staying within the currently assumed footprint and environmental class of action. Also important to acknowledge is that the design of the project elements – roadway alignments, vertical profiles, transit stops/stations and so forth – continue to change. Some of the design changes are not captured in this memorandum, but ongoing refinements to the project and the cover uses will be developed in tandem. This memorandum intends to summarize technical evaluations completed to date in order to inform the Highway Covers Advisory Committee (HCAC), Community Advisory Committee (CAC), and the Project Executive Steering Committee (ESC) in the investigation, evaluation, and potential refinement of the uses and shapes for the highway covers. It can also be used as an information source for the public process and community conversation about the character and use of the spaceFOR created REVIEW by the highway ONLY covers. METRO Information 20201007 contained herein might also be used to inform stakeholders and partners on the assumptions, constraints, and technical details surrounding the design of the structures and surfaces of the highway covers. The preliminary technical analysis was progressed in two phases. Phase 1 included a technical screening and initial evaluation, while Phase 2 included refined technical study and evaluation. Some Phase 1 design options were set aside prior to Phase 2 due to the magnitude of change or an increased cost to the project (i.e., placing 6-story buildings on the North Site). The decision to set these select design options aside are not project decisions, rather they reflect the A&E’s charge to be swift and efficient with the technical work, with the expectation that many ideas and explorations would be revisited in concert with the project partners and public process. Much more work is to be done regarding the selection and design development of community-supported cover shapes and uses. That work includes the development of policies and processes as well as technical design and coordination. The high-level findings, documented assumptions, and description of constraints should aid in the development of a workplan and next steps for the highway cover shape and use resolution. MET.11.1.3.AH.06.20201007

Sites for Consideration To acknowledge the unique constraints, challenges, and opportunities of the various regions of the highway cover, the highway cover extents were divided into three main sites, identified in Figure 1: North, Middle and South. A fourth area, between Broadway and Weidler Street, was not studied for including buildings on covers, due to its triangular shape and scale.

Figure 1. Highway Cover Sites

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A number of Open Concept and Public Buildings options were studied for each of the three sites, and in combination. A summary of those options and their relation to key project questions is presented in Table 1. MET.11.1.3.AH.06.20201007

Table 1: Summary of Findings for Cover Use Options Studied Does it fit within Does it Does it Does it add Option Site the NEPA increase the change the structure footprint? project cost? cover shape? depth?

Open Concept North Yes No No No Option 1: Maintain approximate cover Middle Yes No No No shape South Yes No No No

Open Concept North Yes Yes Yes No Option 2: Expanded single Middle Yes Yes Yes No cover South Yes Yes Yes No

Public Buildings North Yes Yes Yes Yes Option 1 (up to 2 stories) Middle Yes Yes Yes No

South Yes Yes Yes No

Public Buildings North No Yes Yes Yes Option 2 (over 2 stories) FORMiddle REVIEW Yes ONLY METROYes 20201007Yes Yes

South Yes Yes Yes Yes

Note: 1. Table summarizes cover use options for technical evaluation. Preliminary findings are not intended to provide final recommendations or reflect the entire spectrum of potential covers uses. 2. Red indicates that a change from the Open Concept (Option 1) is required.

Key Assumptions and Preliminary Takeaways Summary of key assumptions, considerations, and high-level takeaways included in this memo are as follows (note: No market analysis has been performed as part of this work): Assumptions: • No building should be built with a portion of it on the cover and a portion on land due to long-term maintenance issues and constructability constraints. • Adding buildings, even if they were to remain in public-ownership only, could require a revision to the environmental document. Publicly-owned buildings may still allow for leased spaces for commercial or residential use or other civic and service uses. • City of Portland land use zoning requirements and development approval processes would apply to the spaces created on the highway covers, even though they are within ODOT right-of-way (ROW). This is especially true if buildings are included. MET.11.1.3.AH.06.20201007

• Buildings on the highway covers will not meet, and should not be required to meet, certain parking and access minimums or standards. It is assumed that exceptions will be negotiated in order to support community development. • Vibration of bridges due to the live load/transportation activities on and below the highway covers could influence the development viability and suitability of specific open space and building uses. • Based on preliminary findings, a buffer of 24’ from the edge of the highway cover, for Fire and Life Safety (FLS) reasons, is assumed for any design option that includes a building. Additional study and collaboration is needed to determine the building material type, allowable egress pathways/durations, and other considerations related to buildings on the highway covers. • A single cover, or multiple separate covers, have a similar fire suppression / smoke evacuation system for the freeway below. It is also assumed that no vertical penetrations for venting through the covers are provided. • Highway cover structures will not incorporate major vertical penetrations for elevators, tree wells, and building-supportive utilities. It is assumed that the buildings on highway covers will have “ground” floor elevations above the adjacent sidewalks, by a minimum of 2-6 feet, in order to accommodate these and other essential elements. • Significant further study is needed to ascertain the cost premium and design details for including the additional loading (dead load, live load, seismic load) of buildings on the highway covers. • The cost for the design and construction of buildings on the highway covers would exceedFOR that of REVIEW a comparable ONLYbuilding off METRO-cover. That cost20201007 premium should be included in any development economic feasibility analysis. Takeaways: • The accommodation of different open space and building uses influence both the cover shape and depth of structure. The highway covers can be designed to allow for a wide range of possible open concepts and a limited range of potential buildings. The taller the building, the more challenging the highway cover bridge(s) will be to design. Depending on the building height, a bridge solution that maintains the NEPA EA may not be possible. • The vertical constraints in the project area – between the freeway surface and the local roads surface – are constrained. It will be challenging to provide required clearances below and a “seamless urban environment” above. • Placing buildings on the highway covers results in different design codes, standards, and requirements that will require careful consideration and possible policy changes or innovations for ODOT and partner agencies. • For buildings taller than 2 stories, foundations may need to be built into the highway cover bridge structures at predetermined locations, thereby allowing only a very specific building to be built in the future. The specificity of that building design either reduces flexibility for future development or requires contemporaneous design of the building and bridges. • Buildings of 2 stories or less have more flexibility in shape, column spacing and timeframe of construction. MET.11.1.3.AH.06.20201007

• North Site: Taller buildings on the highway cover bridges north of NE Hancock/Dixon Streets are the most difficult to accommodate. This is due to the longer bridge spans and changes to surrounding cover grades. • Middle Site: Site development is most promising at this location for a number of reasons. First, it is the largest contiguous development site on the highway cover bridges. Second, it has long frontages that allow access parking, and/or loading. Third, it’s “address” on Broadway, Vancouver and Williams is potentially most attractive for a variety of development uses. • South Site: Viable buildings of any scale on the South Site are challenged, primarily due to highly constrained site access from NE Weidler Street. For this reason, only a 1-story building is shown in this Memo. Structural implications of various buildings are the same for the South Site as the Middle Site. • For the Middle and South Sites, buildings taller than 2 stories need further study, but are feasible up to approximately four stories. Buildings of 2 stories or less can likely be accommodated by the same bridge depth as the open cover concept. Additionally, 2-story buildings could likely accommodate “surface connections” that are more flexible for future building location and footprint, if built after the project. • Any building on the North Site would require modification to the assumed structure depth. A 1-story building could likely be accommodated with increased structure depth. Two story buildings may be possible with certain building constraints such as location and size limitations. Additional study, however, is required to confirm the permissible limitations. FOR REVIEW ONLY METRO 20201007 The A&E Team investigated the preliminary structural design implications for a select range of preliminary design options. Each of these sites present unique structural design considerations as well as provide differing urban design and cover use opportunities based on conditions both below (freeway) and above (local street network and land use) the highway cover. Due to the combination of site constraints and opportunities, the majority of the structural evaluations completed to date have focused on the Middle Site. A high level summary of those findings are reflected in Figure 2 and Figure 3 below. Additional information related to design assumptions for this preliminary evaluation are summarized in Section 4. MET.11.1.3.AH.06.20201007

Figure 2: Building Feasibility of Middle Site within Existing Constraints

Figure 3: Building Feasibility of North Site within Existing Constraints

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Design Options Summary North Site

Middle Site

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South Site MET.11.1.3.AH.06.20201007

Memorandum Format This memorandum has three main components: 1. Technical Screening (Section 1) 2. Assumptions (Sections 3-8) 3. Design Options (Sections 9-10) Technical Screening Section Purpose: The purpose of the screening process was to select a limited number of design options that enable the A&E Team to study a range of potential engineering, architectural, and landscape technical issues on an expedited timeline. This is not intended to replace the public process, provide a recommendation, or provide anything other than selecting a few informed, initial options that allow the A&E to focus and go deeper into interdisciplinary technical work. The reason for doing this is to uncover critical issues that will inform, impact, and constrain the feasible cover uses, shapes, and surface design. Assumptions Section Purpose: The purpose of the assumptions component is to share the assumptions and constraints the A&E Team has uncovered through exploration of the possible cover solutions. Documenting the identified assumptions or constraints is meant to inform and facilitate conversations with technical reviewers and project stakeholders related to the technical analysis completed to date. This information can be either accepted or modified as appropriate at the discretion of Oregon Department of Transportation (ODOT) and project partners. A high- level list of the key assumptions and major takeaways of the initial work are listed below. Design Options Section Purpose: The purpose of the design options component is to provide the Project TeamFOR an overview REVIEW of the range ONLY of Open METRO Concepts and 20201007 Buildings Concepts the A&E Team explored. While the design options are not informed by public process, the A&E Team believes the specific issues that were technically studied (e.g., how to accommodate trees, landscapes, urban design pavements and features; how to accommodate on-site vehicular access; what are possible building to bridge connections; how do we solve the need for elevator pits, building foundations and utilities, etc.) are all important and applicable to whatever eventual vision and solution set emerges from the project partners and public engagement process.

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1 Screening for Technical Study The purpose of this particular screening process is to select a limited number of potential design options that will enable the A&E Team to study a range of technical issues (related to different cover uses/shapes and architecture/landscape designs on the surface) on an expedited timeline. The A&E Team was directed by ODOT to focus this screening analysis on the feasibility of two broad land use categories applied to a series of variations of the highway cover shape, largely within the current project footprint: 1) Open Spaces and 2) Light Public Buildings. The screening process is not intended to suggest decisions, recommendations, or conclusions. It is not intended to limit or constrain the community engagement process and urban design visioning, nor is it intended to test every alternative and permutation of use, shape, and surface design, etc. By developing a limited range of options that can highlight potentially different values, priorities, and uses it allows the Project Team to delve deeper into interdisciplinary technical work to uncover critical issues that will inform, impact, and constrain the feasible cover uses, shapes, and surface design. The screening methodology consists of three steps identified in Table 2.

Table 2. Identification, Scoring, and Screening Methodology Step Description and Purpose

Identify potential uses and shapes ranging from landscaped public open Identification FOR REVIEW ONLY METRO 20201007 spaces to those with buildings and various cover shapes.

Use evaluation criteria to score projects (green, yellow, red) based on Scoring criteria which includes constructability, access, capacity to support community goals, and cost.

Screening Screen options for design refinement and additional analysis.

1.1 Screening Criteria The screening criteria include three overarching categories of considerations: 1. Structural, access, and utility considerations 2. Urban design and land use considerations 3. Environmental and cost considerations The final screening criteria is identified in Table 3.

The list of screening criteria was developed using the project goals from the environmental assessment (EA) and supplemented by a technical evaluation of project opportunities and constraints. The A&E Team was directed by ODOT to focus this screening analysis on the feasibility of two broad land use categories applied to a series of variations of the highway cover shape within the current environmental class of action and the project footprint: Public Open

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Spaces and Light Public Buildings. This screening process excluded private land uses, buildings above six stories, and design modifications that would result in significant changes to the project footprint and/or the shape or extent of the highway covers.

1.2 Land Use Categories Evaluated The screening process was focused on two broad land use categories: • Public Open Spaces • Light Public Buildings These categories do not encapsulate the full range of variation of uses that could exist on the highway covers, but rather focused the evaluation on two of the most likely uses, see Figure 4 and Figure 5.

Figure 4. Example Images of Public Open Spaces

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Figure 4 includes example images of pathways, plantings, water features, and public gathering spaces located on a highway cover. These images from Dallas, Texas are part of the five-acre Klyde Warren Park located over the eight-lane Texas Highway 366. Additional information is provided in Section 10: Highway Cover Relevant Examples. MET.11.1.3.AH.06.20201007

Figure 5. Example Images of Light Public Buildings

The images of Light Public Buildings located in Figure 5 represent examples of the occupancies, construction types, scale, and form of buildings that have been constructed on highway covers in other locations throughout the country. These buildings have active pedestrian-orientedFOR ground REVIEW-floor uses and ONLY upper stories METRO with leasable 20201007 space for commercial or residential uses.

1.2.1 Highway Cover Sites: To acknowledge the unique constraints, challenges, and opportunities of the various regions of the highway cover, the cover was divided into four main sites, identified in Figure 6. This memo identifies sub-options for three of the four sites based on variation in shape. The fourth site, between Broadway/Weidler includes the block bounded by Broadway, Weidler, Williams, and Victoria, referred to in this memo as the Broadway/Weidler site. Unlike the other sites identified below, roughly half of the Broadway/Weidler site is on the highway cover and roughly half is off cover. This assessment determined that the on-cover space on this block was not sufficient to support a building alone, due to the triangular shape and shallow parcel depth created by the highway cover cutting diagonally through the block. This site should still be evaluated with future Urban Design efforts as it relates to its opportunity to compliment and support urban uses off the physical limits of the highway cover. 1) North Site North Site A North Site B 2) Middle Site Middle Site A+B MET.11.1.3.AH.06.20201007

Middle Site B 3) South Site South Site A South Site B 4) Between Broadway/Weidler (B/W) Site

The 15% Basis of Design highway cover shape, which included a variation in shape of the “middle” site, is also identified and scored in the cover uses screening matrix within Table 3, for reference only.

Figure 6. Highway Cover Sites

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1.3 Scoring The A&E Team conducted preliminary scoring of the covers use alternatives to create a range of contrasting uses and scales that could be used to further inform a technical evaluation of the covers. This scoring exercise is not intended to provide official recommendations for cover use or shape but rather to inform the evaluation of key technical considerations and assumptions for a range of cover use options. For the two land use categories and highway cover sites, the screening matrix includes a scoring of the feasibility of those land uses on the highway cover sites using the following format:

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• Green: Further Technical Study Warranted • Yellow: Potential for Further Technical Study • Red: Not Recommended for Further Technical Study

1.4 Recommendations for Further Evaluation Options were evaluated based on structural, access, and utility considerations, urban design and land use considerations, and cost relative to benefit of the parcel created. Each bridge region contains its own set of unique conditions, constraints, and opportunities. The screening matrix found in Table 3 identifies the land use and sub option categories recommended for additional technical study. See Figure 18 through Figure 20 for visual references of the options for further evaluation.

1.4.1 Public Open Space, North Site, 15% Submittal This option provides a highway landscape buffer but has limited options for active uses. It is the smallest of the North Site options and would maintain the existing, proposed bridge shape with low-to-medium premium in structure cost.

1.4.2 Public Open Space, North Sites A and B This option allows for a larger area for open space with active and passive uses, streetscape supportive framing, and a highway landscape buffer. This is the largest of the North Site options and would include expansion of the bridge at a moderate-to-high premium in structure cost.

1.4.3 Public OpenFOR Space, REVIEW Middle Site ONLYB METRO 20201007 This option allows for a larger area for streetscape supportive framing, a highway landscape buffer, and a larger space for active use, without entirely closing the highway. This is the smaller of the two Middle Site options and most closely aligns with the current, proposed bridge shape with low-to-medium premium in structure cost.

1.4.4 Public Open Space, Middle Sites A and B This option most fully encloses the northbound and southbound highway on the Middle Site. It allows for streetscape supportive framing, a highway landscape buffer, and the largest amount of open space. This option also includes expansion of the bridge at a moderate premium in structure cost.

1.4.5 Public Open Space, South Site, 15% Submittal This option provides a highway landscape buffer, but limited options for open space use. It is the smallest of the South Site options and would maintain the existing, proposed bridge shape with low-to-no premium in structure cost.

1.4.6 Public Open Space, South Sites A and B This option is the larger of the two options for the South Site. It allows for streetscape supportive framing and a larger highway landscape buffer but is not large enough to support significant active uses. This option also includes expansion of the bridge at a low-to-moderate premium in structure cost.

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1.4.7 Light Public Buildings, North Sites A and B This option allows for an approximately 11,500 SF footprint, street-facing public building. It is the smallest of the North Site options that could support a viable building footprint and the necessary maintenance and service accessway. This option would result in a medium-to-high premium in structure cost to design the bridges to support an approximately one-story building.

1.4.8 Light Public Buildings, Middle Sites A and B This option allows for an approximately 16,400 SF footprint, Broadway-facing public building that could range in height from one story to taller. The site requires closure of the cover shape to maximize the flexibility and extent for building footprint and site access. The Middle Site is the most viable and likely most desirable development site due to its location on Broadway and the Vancouver/Williams couplet. This option would also include expansion of the bridge area at a moderate-to-high premium in structure cost.

1.4.9 Light Public Buildings, South Sites A and B This option allows for an approximately 4,400 SF footprint, one story, street-facing public building. It is the smallest of the South Site options that could support a viable building footprint and the necessary maintenance and service accessway. This option would also include expansion of the bridge at a moderate-to-high premium in structure cost.

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Table 3. Preliminary Screening Matrix DRAFT I-5 Rose Quarter Cover Uses Screening Matrix Structural, Access, and Utility Considerations Urban Design and Land Use Considerations Additional Considerations Next Steps Supports a Provides Leasable Provides Opportunity for Feasibility of On- Complexity of Utility Relative Cost of Infrastructure vs. Benefit Environmental Study Move Forward for Alternatives Structural Feasibility Seamless Urban Commercial Programmable Open Cover Site Access Needs and Routing of Parcel Created Impacts Technical Study Context Space/Mixed Use Space Ability of Vehicles to Includes Gravity Fed Provides Modifies Structural Rough Order of Estimate of "Benefit" Potential Effect on Access and Serve Utilities and other Continuity and Use Alternative Sub-Options Shape and Type from Magnitude of Parcel for Wealth Environmental Studies and the Site from Local Building-Specific Enclosure at Street Baseline Infrastructure Cost Creation or Civic Use Class of Action Roads Services Level provides screening does not include shape results in reduced North Site 15% limited on-site space minimal utility needs - but only limited footprint and ownership same as baseline leasable commercial options for programmable baseline minimal civic use Yes Submittal for vehicular access to be determined opportunity for remain EA consistent space/mixed use open space public open space larger area for increased area street framing + does not include shape creates more options North Site A+B allows for enhanced minimal utility needs - hwy landscape larger area for civic footprint and ownership possible further study leasable commercial for programmable open $$ Yes Expanded uses and vehicular to be determined buffer, and greater use remain EA consistent space/mixed use space access opportunity for public open space No. Additional provides screening technical evaluation does not include shape results in reduced Middle Site limited on-site space minimal utility needs - but only limited footprint and ownership not recommended due same as baseline leasable commercial options for programmable baseline minimal civic use 15% Submittal for vehicular access to be determined opportunity for remain EA consistent to similarity to other space/mixed use open space public open space alternatives being studied. complexity of shape and vehicular access does not include shape results in reduced minimal utility needs - available area for footprint and ownership Middle Site B possible further study needed to multiple leasable commercial options for programmable $ minimal civic use Yes FOR REVIEWto be determined ONLYstreet framing + METRO 20201007 remain EA consistent small sites space/mixed use open space Public Open hwy landscape Spaces buffer larger area for increased area street framing + allows for enhanced does not include shape creates more options Middle Site minimal utility needs - hwy landscape larger area for civic footprint and ownership possible further study uses and leasable commercial for programmable open $$ Yes A+B to be determined buffer, and greater use remain EA consistent consolidated space/mixed use space opportunity for vehicular access public open space

provides screening does not include shape results in reduced South Site 15% least on-site space minimal utility needs - but only limited footprint and ownership same as baseline leasable commercial options for programmable baseline minimal civic use Yes Submittal for vehicular access to be determined opportunity for remain EA consistent space/mixed use open space public open space

No. Additional provides screening does not include shape results in reduced technical evaluation limited on-site space minimal utility needs - but only limited footprint and ownership South Site A+B possible further study leasable commercial options for programmable $ minimal civic use not recommended due for vehicular access to be determined opportunity for remain EA consistent space/mixed use open space to option yielding low public open space value results. MET.11.1.3.AH.06.20201007

No. Additional technical evaluation not recommended because space does inadequate on-site insufficient space for increase to structure complex building insufficient space minimizes unprogrammed footprint and ownership not allow for viable Building up space for viable building site, insufficient space for depth anticipated, supportive utility for viable building site area by maximizing $$ remain EA consistent, needs building footprint to 2 stories development and therefore no leasable viable building site further study required routing site building footprint further study options, and/or vehicular access space possible eliminated due to similarity to other alternatives being North Site15% studied. Submittal No. Additional technical evaluation not recommended because space does requires sig. larger inadequate on-site insufficient space for complex building insufficient space minimizes unprogrammed footprint and ownership not allow for viable Building up structure to space for viable building site, insufficient space for supportive utility for viable building site area by maximizing $$$$ remain EA consistent, needs building footprint to 6 stories accommodate, further development and therefore no leasable viable building site routing site building footprint further study options, and/or study required vehicular access space possible Light Public eliminated due to Buildings FOR REVIEW ONLY METRO 20201007 similarity to other alternatives being studied.

increased area complex building building can minimizes unprogrammed footprint and ownership Building up allows for enhanced provides active ground limited development possible further study supportive utility enclose the street site area by maximizing $$ remain EA consistent, needs Yes to 2 stories uses and vehicular floor commercial space parcel created routing and buffer the hwy building footprint further study access

No. Additional technical evaluation heavier building not recommended North Site A+B ground floor space is requires added because space does requires sig. larger increased area severely compromised complex building structure depth minimizes unprogrammed compromised footprint and ownership not allow for viable Building up structure to allows for enhanced by structural complexity, supportive utility which creates site area by maximizing $$$ development site remain EA consistent, needs building footprint to 6 stories accommodate, further uses and vehicular upper story leasable routing blank building building footprint created further study options, and/or study required access space comes at a walls at sidewalk eliminated due to significant premium level similarity to other alternatives being studied. MET.11.1.3.AH.06.20201007

No. Additional technical evaluation not recommended because space does inadequate on-site insufficient space for complex building insufficient space minimizes unprogrammed footprint and ownership not allow for viable Building up space for viable building site, insufficient space for possible further study supportive utility for viable building site area by maximizing $ remain EA consistent, needs building footprint to 2 stories development and therefore no leasable viable building site routing site building footprint further study options, and/or vehicular access space possible eliminated due to similarity to other alternatives being Middle Site studied. 15% Submittal No. Additional technical evaluation not recommended because space does requires sig. larger inadequate on-site insufficient space for complex building insufficient space minimizes unprogrammed footprint and ownership not allow for viable Building up structure to space for viable building site, insufficient space for supportive utility for viable building site area by maximizing $$$ remain EA consistent, needs building footprint to 6 stories accommodate, further development and therefore no leasable viable building site routing site building footprint further study options, and/or study required vehicular access space possible eliminated due to similarity to other FOR REVIEW ONLY METRO 20201007 alternatives being studied. No. Additional technical evaluation not recommended because space does insufficient space for complex building insufficient space minimizes unprogrammed footprint and ownership not allow for viable Building up limited on-site space viable building site, insufficient space for possible further study supportive utility for viable building site area by maximizing $ remain EA consistent, needs building footprint to 2 stories for vehicular access therefore no leasable viable building site routing site building footprint further study options, and/or space possible eliminated due to similarity to other alternatives being studied. Middle Site B No. Additional technical evaluation not recommended because space does requires sig. larger insufficient space for complex building insufficient space minimizes unprogrammed footprint and ownership not allow for viable Building up structure to limited on-site space viable building site, insufficient space for supportive utility for viable building site area by maximizing $$$ remain EA consistent, needs building footprint to 6 stories accommodate, further for vehicular access therefore no leasable viable building site routing site building footprint further study options, and/or study required space possible eliminated due to similarity to other alternatives being studied. MET.11.1.3.AH.06.20201007

DRAFT I-5 Rose Quarter Cover Uses Screening Matrix Structural, Access, and Utility Considerations Urban Design and Land Use Considerations Additional Considerations Next Steps Supports a Provides Leasable Provides Opportunity for Feasibility of On- Complexity of Utility Relative Cost of Infrastructure vs. Benefit Environmental Study Move Forward for Alternatives Structural Feasibility Seamless Urban Commercial Programmable Open Cover Site Access Needs and Routing of Parcel Created Impacts Technical Study Context Space/Mixed Use Space Ability of Vehicles to Includes Gravity Fed Provides Modifies Structural Rough Order of Estimate of "Benefit" Potential Effect on Access and Serve Utilities and other Continuity and Use Alternative Sub-Options Shape and Type from Magnitude of Parcel for Wealth Environmental Studies and the Site from Local Building-Specific Enclosure at Street Baseline Infrastructure Cost Creation or Civic Use Class of Action Roads Services Level increased area complex building building can minimizes unprogrammed footprint and ownership Building up allows for enhanced provides active ground largest development possible further study supportive utility enclose the street site area by maximizing $$ remain EA consistent, needs Yes to 2 stories uses and vehicular floor commercial space parcel created routing and buffer the hwy building footprint further study Middle Site access A+B requires larger increased area complex building building can minimizes unprogrammed footprint and ownership Building up structure to allows for enhanced provides active ground largest development supportive utility enclose the street site area by maximizing $$$$ remain EA consistent, needs Yes to 6 stories accommodate, further uses and vehicular floor commercial space parcel created routing and buffer the hwy building footprint further study study required access No. Additional technical evaluation not recommended because space does inadequate on-site insufficient space for complex building insufficient space minimizes unprogrammed footprint and ownership not allow for viable Building up space for viable building site, insufficient space for possible further study supportive utility for viable building site area by maximizing $ remain EA consistent, needs building footprint to 2 stories development and therefore no leasable viable building site routing site building footprint further study options, and/or vehicular access space possible eliminated due to similarity to other alternatives being South Site 15% studied. Submittal No. Additional FOR REVIEW ONLY METRO 20201007 technical evaluation not recommended because space does requires sig. larger inadequate on-site insufficient space for complex building insufficient space minimizes unprogrammed footprint and ownership not allow for viable Building up structure to space for viable building site, insufficient space for supportive utility for viable building site area by maximizing $$ remain EA consistent, needs building footprint to 6 stories accommodate, further development and therefore no leasable viable building site routing site building footprint further study options, and/or study required vehicular access space possible eliminated due to similarity to other alternatives being studied. increased area complex building building can minimizes unprogrammed footprint and ownership Building up allows for some provides active ground limited development possible further study supportive utility enclose the street site area by maximizing $ remain EA consistent, needs Yes to 2 stories enhanced uses and floor commercial space parcel created routing and buffer the hwy building footprint further study vehicular access

No. Additional technical evaluation limitations in site ground floor space is not recommended South Site A+B access and compromised by site because space does requires sig. larger increased area complex building supportive-on access and supportive minimizes unprogrammed compromised footprint and ownership not allow for viable Building up structure to allows for some supportive utility street conditions street design, upper site area by maximizing $$$ development site remain EA consistent, needs building footprint to 6 stories accommodate, further enhanced uses and routing suggest that story leasable space building footprint created further study options, and/or study required vehicular access additional height is comes at a significant eliminated due to not viable premium similarity to other alternatives being studied. MET.11.1.3.AH.06.20201007

2 Land Use Assumptions Once constructed, the highway covers would create new space which could be utilized for open space, buildings, or a combination of both. The form, function, and use of the land created by the highway covers has the potential to improve east-west connections across I-5 and reconnect the urban fabric on both sides of the interstate. A community-supported vision for the land use on the highway covers will be identified through a public process, involving community members and stakeholders, including people from historically underrepresented groups, and those who do not typically participate in city planning public processes.

2.1 Land Use Regulations and Compliance The geography of the I-5 Rose Quarter highway covers is regulated by Portland’s Zoning Code (Title 33). The zoning code is intended to implement Portland’s Comprehensive Plan and related land use plans in a manner that protects the health, safety, and general welfare of the citizens of Portland. There are several types of zoning regulations that may affect the highway covers. For the purposes of the technical work underway and described in this memorandum, it is assumed that current City of Portland (COP) zoning designations would apply to the spaces on the covers, even though a final determination on the applicability of zoning codes on spaces within ROW has not yet been made.

2.1.1 Base Zones All properties within the COP have a base zone. There are four zones that apply to the highway covers, see FigureFOR 7. REVIEW ONLY METRO 20201007 1. Commercial/Mixed-Use-3 (CM3) 2. Central Commercial (CX) 3. General Industrial (IG1)1 4. General Employment (EG1)

1 Re-adoption of Central City 2035 may occur later in 2020 and could change IG1 to EX

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Figure 7. Zoning Map for Highway Covers and Vicinity

2.1.2 Overlay ZoneFORs REVIEW ONLY METRO 20201007 Each part of the highway cover is also within a Design Overlay Zone, which means additional Design Review is required for future development.

2.1.3 Plan Districts All parts of the highway covers are either included in the Central City Plan District or the Albina Community Plan District, see Figure 8. Plan districts include additional regulations to support community goals for connectivity, land uses, and building heights. MET.11.1.3.AH.06.20201007

Figure 8. Plan Districts for the Highway Covers Sites

2.1.4 Hierarchy of Regulations In general, an area with base zoning, overlay zoning, or a plan district designation is subject to all the regulationsFOR of each. REVIEW Where a land ONLY division is METRO requested, the 20201007 land division regulations also must be met. When the regulations conflict, unless specifically indicated otherwise, the following rules apply: • Plan district regulations supersede regulations in overlay zones, base zones, and land division series of chapters. • Overlay zone regulations supersede regulations in base zones and land division series of chapters. • Plan districts and overlay zone regulations supersede conflicting regulations for a specific use or development stated in the additional use and development regulations series of chapters. • The regulations in the additional use and development regulations series of chapters supersede regulations in the land division series of chapters. • When regulations at the same level conflict, those that are more specific to the situation apply.

2.2 Incentive Programs: Inclusionary Housing and Affordable Commercial Space In order to meet the identified need for both 1) additional housing to serve low- and moderate- income households and 2) affordable commercial space for small businesses, the COP has established an Inclusionary Housing Program and an Affordable Commercial Space Bonus Program. The incentives made possible through these programs apply to the highway covers sites.

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The COP’s Inclusionary Housing Program requires all residential buildings proposing 20 or more units to provide a percentage of the new units at rents affordable to households at 80 percent of the median family income. The Affordable Commercial Space Bonus Program allows mixed-use development projects a FAR and building height bonus in exchange for additional space for residential, commercial, office, or hotel projects. Buildings that include a housing component must include 20 or fewer new residential units. Priority tenants for the affordable commercial space are local businesses owned by women and/or people of color; local businesses primarily owned by individuals who are members of historically underserved populations; and non-profit organizations which serve historically underserved communities, including communities of color.

Table 4. Zoning Code Districts and Related Development Standards for Zones included in the Highway Cover Sites Applicable Development Standards Max. Zoning Min. Site* Height / District Max. FAR Building Coverage Landscape Other Number of Area Floors 100% allowed; landscape Eastern part 3:1 (ratio of 65′-0″ requirements must be met Commercial/ of North Site development Ground Floor via urban green alternative Mixed-Use A and B, part area to 5 floors (15′ first 15% of site area Window landscaped areas i.e. roof (CM3) of Middle Site block/parcel floor, 12′ upper Standards apply garden, or other AFOR and B REVIEWarea) ONLYfloors) METRO 20201007 landscape solution 4:1 (ratio of South Site 75′-0″ Central development Ground Floor A and B, part Commercial area to 6 floors (14′ first 100% allowed 0% of site area Window of Middle Site (CX) block/parcel floor, 12′ upper Standards apply A and B area) floors) General Part of North No limit No limit 100% allowed 0% of site area N/A Industrial (IG1) Site A and B 3:1 (ratio of General development Part of North Pedestrian Employment area to No limit 85% allowed 15% of site area Site B Standards apply (EG1) block/parcel area)

* See Figure 7. Zoning Map for Highway Covers and Vicinity MET.11.1.3.AH.06.20201007

3 Environmental and Right-of-Way Considerations

3.1 Right-of-Way Ownership Governance The proposed highway covers are located within the active interstate ROW and the bridge infrastructure is assumed to be under ODOT ownership. Typically, local street overcrossings of interstate ROW involve a maintenance and ownership agreement between the Department of Transportation (DOT) and local jurisdiction outlining ownership and maintenance responsibility as well as designating road authority and responsibility. In the case of interstate crossings, it is common for the overcrossing structure, and in many cases the crossing street within the interstate ROW prism, to remain under DOT ownership. ODOT has established guidance related to the sale or lease of ODOT owned land or structures. Below are several excerpts from “Property Management Chapter 9, ODOT ROW manual 8/31/18.” ODOT Policy ROW 10 (3/22/11) states in general that authority over ODOT real property is divided between: 1. ODOT Region has authority to proceed with the use of an excess parcel, when that use is the one for which the property was acquired and is for transportation system improvement. 2. Support Services Branch, Facilities Management Section has authority to proceed with the use of an excess parcel when that use is the one for which the property was acquired FORand is for REVIEW construction ofONLY an ODOT METRO-owned facility. 20201007 3. Technical Services, Right of Way Section has all other authority over excess property. This authority extends to the temporary use of excess property prior to its use in a transportation system improvement or its development as an ODOT facility. It also includes authority over the permanent use of excess property by ODOT, when that use is one different than the use for which the parcel was originally acquired. When it is determined that it is feasible or desirable to rent a property, either because the property is surplus to the needs of a project or the construction schedule is far enough in the future; a month-to-month rental agreement may be used. ORS 270.105 dictates that for properties valued at $100,000 and above, the State Agency (ODOT) will invite public comment on the sale of the property. Recommended notification procedure is to place an ad in the public notice section of the local newspaper. The ad should be published at least once, approximately one week prior to the advertisement of sale.

3.1.1 Right-of-Way Cover Use Screening Assumptions The process for leasing, sale, or transfer of ownership typically involves coordination with multiple agencies including ODOT’s Property Management group, Federal Highway Administration (FHWA), and the Department of Administrative Services (DAS). This process typically takes into consideration the existing functionality, access, maintenance, and operational needs for the property and impacted infrastructure in addition to the long-term lifecycle management (i.e. replacement or rehabilitation) of the facilities.

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All potential uses of the highway covers and the surrounding ROW will need to establish clear ownership, maintenance, and operations agreements to guide the short and long term uses of the proposed facility. As the highway cover and adjacent property is assumed to be part of the functioning interstate right-of-way, it is assumed for the purposes of this screening exercise that this area would not meet the criteria of “vacant or excess land” and would not comply with the criteria for surplus property. It is also assumed that any infrastructure including community open space or building infrastructure would remain under public ownership and would require multijurisdictional intergovernmental agreements to outline the terms and conditions of the operations and ownership of said facilities.

3.2 Relationship of Options to Environmental Class of Action

3.2.1 Highway Covers Use The existing Draft EA for the I-5 Rose Quarter Improvement Project describes the use of the I-5 covers as follows: an “added surface space would provide an opportunity for new and modern bicycle and pedestrian facilities and public spaces when construction is complete, making the area more connected, walkable, and bike friendly.” Additional impacts analysis would be required if, through design refinement, the project were to propose features inconsistent with the cover use described in the EA. Structures may be considered consistent with the intent of the EA if those structures do not prohibit bicycle and pedestrian facilities and are used as public spaces. Impact analysis would be required if proposed structures do not meet those criteria or would require modifications to the structure that would increaseFOR grades REVIEW across the covers ONLY or impact METRO additional 20201007 areas or adjacent uses. If the covers are constructed to accommodate private or public structures, impact analysis may require the reevaluation of noise impacts to sensitive receptors not previously captured, land use impacts to review potential induced growth through the creation of development space previously considered used for right of way purposes, and a review of potential air quality impacts of the new development space.

3.2.2 Highway Covers Shape Section 2.2 of the EA provides the following general description of the covers: “with the Build Alternative, the existing N/NE Weidler, N/NE Broadway, and N Williams overcrossings would be removed and rebuilt as a single highway cover structure over I-5 (see Section 2.2.2). The existing N Vancouver structure would be removed and rebuilt as a second highway cover…” Section 2.2.2.1 of the EA provides additional clarification of the proposed covers: “the structure replacement would be in the form of the Broadway/ Weidler/Williams highway cover. The highway cover would be a wide bridge that spans east-west across I-5, extending from immediately south of N/NE Weidler to immediately north of N/NE Broadway to accommodate passage of the Broadway/Weidler couplet.” Section 2.2.2.2 of the EA describes the Vancouver/Hancock highway cover as “a concrete or steel platform that spans east-west across I-5 and to the north and south of N/NE Hancock” While the shape of the highway cover is generally described in the EA, the description is somewhat vague and does not prescribe the precise shape. Minor modifications to the shape of the highway cover that stay within the geographical confines described in Section 2.2.2.1 and

16 | August 25, 2020 MET.11.1.3.AH.06.20201007 Higway Cover Uses: Screening and Assumptions Memorandum

Section 2.2.2.2 would be consistent with the EA Project Description. Potential impacts would need to be analyzed if design refinements result in a highway cover shape that can no longer perform the functions anticipated in the EA or extends outside the geographical confines described in Section 2.2.2.1 or Section 2.2.2.2. Differing impacts to a variety of resources such as ROW, land use, active transportation, noise, and air quality, etc. could result pending the extent of the highway cover shape refinement. If the impacts are determined to not be significant, then the highway cover shape modifications could be captured in a reevaluation of the EA. If the impacts analysis determines significant impacts would result, then an Environmental Impact Assessment would be required.

4 Structural Considerations Structural considerations related to open spaces and buildings on the highway covers are generally focused on the available positions for buildings relative to available support conditions and how that load path impacts designs; additional design requirements with buildings on the highway covers; and structural performance considerations of the individual buildings and highway covers, as well as the combined integral system. These considerations are discussed more within this section.

4.1 Building Positioning and Foundation Support Considerations Foundation design is based on the supporting soil deflecting elastically as it is loaded, with deflections being related to the underlying soil stiffness. Because of this, building foundations must have uniform support conditions from the material beneath them in order to function properly and provideFOR adequate REVIEW support tONLYo the building METRO structure. 20201007Placing an element on non- uniform support conditions causes different amounts of vertical movement between the separate support conditions. If not appropriately accounted for in the design, this differential deflection condition can propagate up through the building, causing damage to the foundation and other building elements. In the case of the highway cover structures, non-permanent loadings such as vehicular and truck traffic will traverse the highway cover structures and produce transient vertical deflections across the highway cover structure spans. A building foundation partially on and partially off the highway cover structure would experience differential deflections. As a result, this investigation will only consider buildings completely supported on either the highway cover structure or the ground adjacent to the highway cover structure to achieve uniform support conditions.

4.2 Design Code Changes for Occupied Space on Highway Covers The urban design plan for the top surfaces of the highway cover structures will likely dictate the design codes and standards that will be required for the design of the structures. If buildings are not part of the urban design use for the highway cover structures, then the structures will be designed according to the ODOT Bridge Design Manual, ODOT Geotechnical Design Manual, and applicable American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) codes. If buildings are part of the urban design use for the surfaces of the highway cover structures, then the AASHTO LRFD, 2019 Oregon Structural Specialty Code (Oregon’s adaptation of the

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2018 IBC), and American Society of Civil Engineers (ASCE) 7-16 will all likely be the required design codes for the structures. The different seismic and non-seismic loading and resistance requirements for each of these codes will likely need to be met. In addition to meeting multiple design codes, incorporating buildings into the design will also increase the complexity of how the seismic analysis is conducted. Based on ASCE 7-16, seismic design requires considering the interaction between the buildings and highway cover structures in designing the combined system, taking account the relative seismic weights and structure natural frequencies. It will be difficult to account for future building construction for the design of the highway cover structures. Detailed coordination will be required to design the highway cover structure to account for buildings and to incorporate building design. As the building height and weight increase, the structural design implications become increasing dependent on the specific design assumptions and parameters of the intended future building configuration. It is expected that the highway covers would have to be designed and constructed to accommodate a specific building, not a range of possible buildings or varying sizes, shapes, structural systems, or connection points to the highway cover bridges.

4.3 Range of Types for Building-To-Bridge Structural Connections Any building constructed on the highway cover structure will need to be positively connected to the deck of the bridge structure. This connection will anchor the building in place and will need to resist wind and seismically generated building loads. Potential anchorage includes fixed or pinned column base connections via anchor bolts, seismic isolation bearings at column bases, or simple dowelled connections of a strip footing under a wall. The choice of the connection will depend on the typeFOR of bu ildingREVIEW framing syONLYstem, capacity METRO of the bridge 20201007 deck to support the connection, and the need to seismically isolate the building from the highway cover bridge structure. Isolation bearings can sometimes reduce seismic loads in the bridge highway cover structure or building, but they can also lead to differential movement of the building during earthquakes and may result in unintended consequences. A range of heights (measured from the top of the bridge deck to the ground floor elevation of the building) to accommodate the building-to-bridge connections (along with building utilities and vertical circulation systems) is discussed in Section 4.8.4. Use of seismic isolation bearings warrants more investigation in future efforts once potential building geometries and heights are better envisioned in the project.

4.4 Implications for Directly Adjacent Building Foundations Buildings constructed on the ground adjacent to or in the proximity of the highway cover structures can produce increased lateral earth pressures on the abutments of the highway cover structure. These additional loadings on the highway cover structures, or building foundation types avoiding such increased loadings, will be considered. These considerations could influence potential future development immediately adjacent to the highway covers.

4.5 Building Loading Assumptions Table Assessment of building loads requires an estimation of the dead and live loads of the building. These loads will be based on the building footprint configured, number of floors, expected framing (i.e. light or heavy), and expected occupancy (for live load). Table 5 lists the assumed loads being investigated as part of the screening analysis.

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Table 5. Building Load Assumptions

Expected Type of Loading per Floor Occupancy Framing Dead Load* Live Load** Roof Load*** Light 50 psf. 100 psf. 50 psf. Commercial (Retail) Heavy N/A N/A N/A

Light 50 psf. 40 psf. 50 psf. Residential Heavy N/A N/A N/A

* Dead Load includes floor slabs and walls with an allowance for stairs/elevators ** Live Load for retail is for first floor if mixed use building is provided *** Roof Load includes dead and snow loads

4.6 Long-Term Performance of Buildings Constructed on Bridges The highway cover structure bridge will support several local streets and two streetcar tracks. The diagonal configuration of the street grid in relation to the proposed building sites results in the highway cover bridge structure supporting vehicle/streetcar live loads in the same unit, and often by the same beams that the buildings are supported on. Heavy trucks and streetcars cause the highway cover bridge structure to deflect and vibrate (bounce). Current AASHTO provisions require the structure be stiff enough to limit these live load deflections to (1/1000) of the span length, roughly one inch. Based on our conceptual designs we expect these deflections due toFOR vehicles REVIEW to be less than ONLY one inch, METRO probably one 20201007-half to three-quarter inches. The only way to reduce these deflections is to increase the structure stiffness by using deeper or more girders or a different structure type such as spliced girders. These methods are expected to add significant cost and are not considered as part of this study. The addition of buildings on top of the highway cover structure adds several complications. The buildings add significant dead loading, creating a structure with a very high dead to live load ratio. The sustained dead load will cause long-term deflection (sag) in concrete structures due to concrete creep. While the structure can be constructed with a camber to ensure clearances below on I-5 are maintained over the long-term, deflection will still occur. In addition, highway cover structure deflections will impact the long-term performance of the supported buildings. Structural issues include the potential for cracking and impacts to framing, fixtures, and utilities due to differential settlement at the building foundation. This differential settlement can also result in non-structural damage: doors and windows can stick, leaks can form, and utilities can be damaged. In a similar fashion, deflections and vibrations from live load resulting from passing vehicles and streetcars can impart structural damage over time. Expected deflections and vibrations in buildings are much less than the deflection expected in bridge structures and impacts the perceived quality of the building. Deflection and vibration of the foundation can result in deflection and vibration that exceed allowable limits, especially where they may be magnified in multistory buildings. Identification of potential damage will help make an informed decision concerning long-term building performance and liability. Vibration on the bridges, transmitted to

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the buildings and ultimately transmitted to occupants of the buildings could also influence viable development typologies. For instance, vibration from streetcar tracks and general street traffic could discourage consideration of housing as a desirable development type on the covers.

4.7 Defining Bridge Design Loads for Future Building Type and Placement The unusual situation of placing a building on top of a highway cover structure affects the design of both the buildings and highway cover structure. Highway cover structures are designed as bridges with large live loads from trucks, which cause deflections and vibrations which are acceptable when within design code limits. Current bridge design practice for earthquakes is to provide structure ductility to allow structure plastic displacement to dissipate seismic loads rather than resist these forces by the elastic strength of the highway cover structures. Adding a building structure results in three major changes. First, the additional dead load of the building changes the typical ratio of dead to live load, resulting in potential deflection due to concrete sag. Second the mass and stiffness of the buildings change the seismic response of the highway cover structure. This seismic response can be affected by the building construction materials, the building’s seismic lateral resisting system, and even the connection methods between the building foundations and the highway cover structure. Finally, the vibration and deflection caused by bridge loading may cause magnified vibration and deflection in the buildings. This vibration and deflection are affected by the specific building construction. If buildings are included in the urban design use, the loading and behavior of the highway cover structure will be interconnected to the building configuration. If full design details of the building(s) are notFOR known REVIEW, then the highway ONLY cover METROstructure can 20201007only be designed according to a detailed design criteria for building footprints, number of stories and height, dead and live loads, framing layout, support locations and connection to bridge, lateral resisting system configuration for building stiffness, and all other required design details. The detail and thoroughness of the design criteria will be critical to designing the highway cover to support future buildings. If the decision for building configuration is delayed to the future, the highway cover structure will need to be designed more conservatively or may limit certain future building configurations. Also, if a future building of unknown and different configuration is planned, then the original cover structure design is voided and a new detailed analysis of the as-constructed cover structure must be completed to certify that the cover can safely support this future building configuration. Finally, if it is planned to design and construct buildings in the future on the highway cover, plans for future buildings are vulnerable to changes in building codes. Regardless of how well the design criteria is defined for the future building, future building codes will dictate the future designs.

4.8 Refined Structural Evaluation Based on Preliminary Technical Screening To investigate some of the structural considerations in Sections 4.1 to 4.7, the A&E Team performed preliminary analyses involving select loading conditions in specific bridge regions based on the initial screening exercise. These focused preliminary analyses were selected for further evaluation as they: 1) Addressed some of the most critical design parameters affecting the structural feasibility and impacts of different uses; 2) Considered specific design elements

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(such as building connection details and seismic behavior with buildings attached to the cover) that were not previously evaluated as part of the project; and 3) represented a range of cover uses and representative regions of the highway cover. These preliminary analyses represent only a small range of potential uses and required a number of discrete design assumptions. However, the findings from these limited analyses are useful to develop a general understanding of the cover design implications for the various urban design concepts and potential uses.

4.8.1 Design Implications of a Single (Combined) Highway Cover Shape Urban design concepts and potential loadings associated with those concepts assume that the individual North and South Covers be combined into a single, closed highway cover. There are various benefits that result from combining the highway covers, and from a structural perspective. One of the largest benefits is the improved framing plan that can be implemented. The single highway cover concept implements a more consistent highway cover geometry over the freeway, which in turn allows for traditional two-span bulb-tee girder designs to be implemented in a larger portion of the highway cover. The preliminary analyses utilize two-span bulb-tee girders representative of the Middle and South Sites. Similar analyses were conducted for the 2-span cast-in-place, post-tensioned box girder bridges in the North Site of the highway cover. These analyses are discussed in Sections 4.8.2 to 4.8.6.

4.8.2 Design Implications of Structural Irregularities It was previously discussed in Section 4.2 that multiple design codes become applicable if buildings are includedFOR in theREVIEW urban design ONLY concepts METRO on top of th e20201007 highway covers. In the preliminary analyses that were completed, the ASCE 7-16, IBC, and OSSC codes were used to assess the design implications of that code to the design of the highway covers when the structures support buildings. One of the largest implications identified in this limited investigation is the more stringent design requirements for the girders imposed by the ASCE code when they support buildings. When the highway covers support buildings, the columns of the buildings will not always align with the bents of the highway cover to provide a continuous vertical lateral force resisting element. This type of discontinuity is addressed in ASCE 7 Table 12.3-1 and is referred to as a “Type 4 Out- of-Plane Offset Irregularity.” In accordance with ASCE 7 Section 12.3.3.3, this type of irregularity requires that the structural elements supporting these walls or frames and their connections be design to resist seismic load effects that include an overstrength factor. Assuming ordinary moment frame type construction for the buildings on top of the highway cover, the overstrength factor as given in ASCE 7 Table 12.2-1 is 3.0. This overstrength factor is used to amplify the resulting seismic demands for this critical type of irregularity as specified in ASCE 7 section 12.4.3. Stated more plainly, because the girders serve as the supporting elements that serve in the load path between the building columns and substructure/foundation elements of the highway covers, the code amplifies the seismic loadings to be used in the design of these elements above what would be required if the AASHTO codes were used to design these elements for highway loadings. These additional design requirements by the ASCE code will likely drive designs to increases in girder sizes and superstructure depths as building loadings on the highway covers are investigated.

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4.8.3 Design Implications of Building Geometry and Position in Highway Covers Preliminary designs for the highway covers utilized BT48 girders for the open urban design concept, however a combination of design progression and a revised approach to structural protection utilizing sacrificial concrete overbuild resulted in a recommendation for modified BT60 girders for the open cover urban design concept. To further support the urban design use evaluation, the A&E Team conducted more detailed technical assessments including several preliminary analyses to investigate the feasibility of seismic design for various building loading conditions within the Middle Site and North Site of the highway covers. The Middle Site offers both the largest potential area for development of buildings and a shorter 2-span configuration that better supports additional loading. The North Site offers limited space for buildings, and due to the longer spans of the highway cover in this area, building loadings must be limited in order to be feasible within these spans. The design implications of building height for assumed building footprints and positions with the highway cover was the primary item being investigated in these analyses. In multiple scenarios, the girders sizes required to support the considered building loadings were compared to the modified BT60 girder sizes of the open urban design concept as a high-level indicator of the design implication of the considered building loading to the highway cover. The building loadings that were considered in all scenarios are hypothetical because actual building designs are not known. In these analyses, the building loadings were estimated assuming mixed-use structures that would geometrically fit within the sites of the highway cover. Multiple assessments were performed for each site to investigate how the number of stories within each building footprint impacted the girder designs of the highway cover. Each assessmentFOR generally REVIEW included the ONLY following: METRO 20201007 • RISA software was utilized to develop a reasonable and representative building design for the analysis. • SAP structural analysis software was utilized to generate analytical models to study the structural behavior and interaction of building structures and the highway cover during a seismic events. Images of the SAP models for select analyses of the Middle and South Sites, as well as the North Site, are presented in Figure 9. • LEAP Bridge software was used for preliminary designs of the girders supporting the buildings. It was assumed that each building reaction at the pilasters is distributed to three girders. Building footprints and locations used in the assessments were as follows: • Middle and South Sites: The building footprint was rectangular, assumed to be 50 feet by 200 feet in size, and centered within one span of the two-span structure. The building was oriented with the long edge parallel to the abutment. While this analysis only evaluated a single building shape, the findings provide a preliminary estimated range of feasible building heights that are thought to be applicable for many regular-shaped buildings that fit on the highway cover. However, it should be noted that irregular building shapes could structurally behave differently and load the highway cover differently than what has been analyzed. In all cases, additional detailed structural assessments are required to determine the structural feasibility of a building condition. MET.11.1.3.AH.06.20201007

• North Site: The building footprint was assumed to be rectangular, 70 feet by 175 feet in size, and was assumed to straddle over the median bent with part of the building in each span of the two-span structure. • For all sites, 2 feet of landscaping loading was assumed to accompany the building in the spans containing a building footprint. Future efforts must coordinate the desired landscape loading with the building being considered.

Figure 9. Analytical Models for Building Assessments (a) Middle and South Site 2-story building model, (b) Middle and South Site 4-story building model, (c) North Site 2-story building model.

FOR REVIEW ONLY METRO 20201007 MET.11.1.3.AH.06.20201007

(c)

For the Middle and South Sites, the assessment findings suggest that the following building heights have varying levels of feasibility: • 1- & 2-Story Buildings: Likely feasible (with no increase in structure depth) • 3-Story Building: Probably feasible (with increased structure depth) • 4-Story Building: Possibly feasible with some design constraints (with increased structure depth) • 5-Story andFOR Higher: REVIEW Unlikely to be ONLY accommodated METRO 20201007 Estimated girder sizes in the highway covers supporting these buildings are summarized in Table 7. Note that the 4-story building in these assessments is estimated to require modified BT84 girders, and the girder analyses indicated that additional design constraints may be required to make these girders satisfactory to support the building loadings. With limited remaining girder sizes larger than BT84, it was determined to be unlikely to accommodate buildings taller than 4 stories at this site. This was further reinforced when the A&E Team conducted an analysis of a 6-story building at this site with a non-rectangular footprint and was unable to develop a girder design that met the assumed design parameters.

Table 6. Summary of Preliminary Girder Sizing for Various Loading Scenarios on the Middle and South Sites 2-Story 4-Story 6-Story Non- Open Cover Rectangular Rectangular Rectangular Building Building Building Modified BT84 (Fail) BT60 (Pass) BT60 (Pass) BT84 (Pass) Girder Size* Assumed Type 2 or N/A Type 1 Type 2 or Type 3 Connections** Type 3 * “Modified” means additional sacrificial concrete cover added to standard shape for structural protection during design fire event. ** Connection details and summary of findings are included in Section 4.8.4. MET.11.1.3.AH.06.20201007

For the North Site, assessments for 1- and 2-story buildings were completed with an assumed 8-foot structure depth. Both of these assessments confirmed that building loadings in the longer spans greatly magnify the required structure depths. Both initial assessments resulted in unsatisfactory girder analyses. As a result, structural demands from the buildings must be greatly reduced relative to what was analyzed. Reducing the building loads, reducing the building size, or both, may be required to accommodate any building in these spans. As a result, the feasibility of buildings in these spans of the highway cover are considered to be the following: • 1-Story Building: Probably feasible with some design constraints • 2-Story Building: Possibly feasible with significant design constraints Overall, the preliminary assessments confirmed that there are design implications to adding buildings to the urban design concepts on top of the highway cover. The assessments further confirmed that the design implications differ in magnitude depending the height of the building and the length of the girder spans supporting the buildings. It should be noted that the general rectangular building footprints were used in these assessments. Buildings with non-rectangular geometries will have different seismic behavior, and therefore, they will load the girders differently and potentially in different locations than the buildings in these assessments. Additional analyses are warranted to further investigate the feasibility of buildings on the highway cover once potential building geometries and height are better envisioned, along with the landscape design that is desired around the buildings.

4.8.4 Design Implications of Building Connections to Highway Covers Construction of buiFORldings REVIEWon the highway ONLY cover requires METRO consideration 20201007 of suitable connections in the form of pilasters between the building columns and superstructure of the highway cover. It was illustrated in the previous section that design implications for the girders differ for the various building loading scenarios that were investigated, and that is because the force demands from the building columns and pilasters to the highway covers differ among the various scenarios that were considered. As a result, preliminary concepts for structural connections between the buildings and highway covers were developed to accommodate varying levels and types of building connection forces. A fundamental assumption for all connection designs is that the connection must distribute the loading from the pilaster to three girders of the highway cover in order to lessen the girder size by lowering demands that are distributed to a single girder. Descriptions of the three connection concepts are described in the following paragraphs. Figures 8-9 illustrate conceptual details of the connections, and Table 8 summarizes advantages and disadvantages of the connections. Type 1: Surface Connection Figure 10 illustrates this deck surface connection constructed by drilling and bonding post- installed reinforcing bar anchors with epoxy resin. Because this connection is primarily transferring loading to the girders through the deck (as compared to through connections to the girders themselves), it provides more future flexibility in the potential building placement after the initial bridge construction. Also, as this connection has no structural elements passing below the top surface of the supporting girders, this conceptual connection is considered feasible of being constructed from the deck surface without the need to have construction operations below the deck, and without the need for lane closures on the below freeway. The connection incudes

25 | August 25, 2020 MET.11.1.3.AH.06.20201007 Higway Cover Uses: Screening and Assumptions Memorandum tall stem and flange walls that distribute loads to adjacent girder webs. These walls are important to ensure that compressive and uplift loads are distributed equally to three adjacent girders and that uplift loads are evenly distributed to the hooked shear stirrups where they can be resolved into the girders. It should be noted that pre-installed precast inserts could be used instead of drill and bond dowels in this type of connection. Locations for the inserts could be installed during construction of the highway cover at pre-determined locations for pilasters. The benefit to using precast inserts is that they can be installed during construction instead of future construction. However, a disadvantage of using precast inserts is that pilaster locations are fixed for future buildings. Type 2: Through Connection Figure 11 illustrates the through connection made by passing reinforcing or high strength bars through the deck into a diaphragm that is connected to the girder webs below the deck level. This type of connection can likely accommodate higher uplift loads than the Type 1 surface connection (and therefore larger building demands). For high loadings, anchor plates may need to be added to the high-strength bars passing through the deck, and transverse post-tensioning may be needed in the diaphragm. Type 3: Hybrid Connection Another type of connection could be considered that is a combination of the Type 1 and Type 2 connections. This type of connection could be used after construction of the bridge in locations where the Type 1 surface connection does not have sufficient uplift or moment capacity. In this conceptual type of connection, the shear transfer would occur with post-installed anchors into the deck and an FORadditional REVIEW uplift restraint ONLY would pass METRO through the 20201007 deck and engage a diaphragm below the deck level. This type of connection could be installed on a limited scale after the construction of the bridge, but would have many of the construction disadvantages of the Type 2 connection.

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Figure 10. Conceptual details of the Type 1 connection.

Figure 11. Conceptual details of the Type 2 connection.

FOR REVIEW ONLY METRO 20201007 MET.11.1.3.AH.06.20201007

Table 7. Summary of Advantages and Disadvantage of Pilaster Connection Concepts Connection Type Advantages Disadvantages Type 1 Construction can likely be performed from the Requires a large quantity of drilled anchors or Surface Connection deck surface. pre-installed precast inserts Lane closures are not anticipated on the Requires a tall plinth and walls to evenly below freeway distribute loads to adjacent girders, which increases the footprint size of the connection Can be readily constructed after construction Requires thickening the deck to get adequate of the highway cover embedment for the anchors Can be easily applied to different locations to Requires increasing the number of stirrups in accommodate varying building column the girders to transfer the uplift force layouts (i.e. flexibility in future building placement) - May require field bending girder stirrups around the top mat of steel - Cannot accommodate large uplift loads (i.e. limits the loading capacity and therefore building sizes that could be accommodated by this type of connection type) Type 2 Can accommodate higher uplift loads than Cannot be easily constructed after the Through the Type 1 surface connection (and therefore construction of the highway cover (requiring Connection larger building demands connections to be constructed as part of the initial construction or severely limits the feasibility and flexibility of future foundation loads and placement) Does not require walls above the deck level Requires girder penetrations near prestressed FOR REVIEW ONLY METROstrands that 20201007 would require that sleeves be placed in the girders during girder fabrication Does not require increasing the deck Requires thick diaphragm below the deck level thickness Does not require increasing the number of Not good at accommodate varying or girder stirrups “unknown” column layouts Does not require field bending stirrups Would likely result in a cost premium if installed around top mat of deck slab after construction of the highway cover Type 3 Can accommodate higher uplift loads than Cannot be easily constructed after the Hybrid Connection the Type 1 surface connection construction of the highway cover - May require girder penetrations near prestressed strands that would require expensive non-destructive evaluation (NDE) location of strands prior to drilling through girders - Requires constructing a diaphragm below the deck level - Requires advanced coordination and design considerations - Would require lane closures on I-5 during construction - Would likely result in a cost premium if installed after construction of the highway cover MET.11.1.3.AH.06.20201007

Takeaway from conceptual development of these connections are as follows: • Types and magnitudes of force demands between the building columns/pilasters and the highway cover require different types and sizes of connections depending on the potential building size and location. • Connections for smaller force demands, likely resulting from smaller buildings, are considered to be more amenable to being installed after construction of the highway covers. As a result, this type of connection allows for more flexibility in column locations for future buildings that are developed when drill and bond dowels are used and other structural components are designed for flexibility in column placement. • Connections for larger force demands, resulting from larger and taller buildings, likely need to be installed during construction of the highway covers. Doing so would lock in column locations and impact potential loads and shapes for future buildings that are developed. It should be noted that preliminary assessments suggest that seismic isolation between the building and highway cover may not be advantageous for force attenuation. However, use of seismic isolation bearings warrants more investigation in future efforts once potential building geometries and heights are better envisioned in the project.

4.8.5 Summary of Findings from Preliminary Studies The preliminary analyses described in the previous sections were completed with preliminary design details of typical two-span, precast girder sections of the highway covers. General takeaways of theseFOR analyses REVIEW include the ONLY following: METRO 20201007 • Analyses supported initial assumptions that applicable building code provisions applied with building loadings will have design implications on the design of the highway cover. High-level magnitudes of the design implications are evident by comparing girders sizes supporting buildings to the modified BT60 girder size anticipated to support the open cover concept. • Confirmed initial statements that it will be difficult to design covers without knowing final building concepts or parameters. This is supported in the preliminary analyses by the changes in girder designs that resulted from variable considerations in building height with assumed building footprints and locations. • Review of results suggest that that magnitude of the design implications to the girders of the highway cover and base connections to the buildings are less with structures that are shorter (i.e. 2-story buildings vs. 5-story buildings). • Since girder designs are influenced by building positions and loadings, designing for flexibility in future building locations on the highway covers will result in a cost premium to develop one structural design that will be satisfactory for the numerous possible loading conditions that result by changing the building location on the highway cover. These increased costs will accrue in the increased design time needed to account for the numerous possibilities of building locations on the highway cover, and during the construction phase to construct larger and potentially more complex structures.. Establishment of future building size, footprint, and column locations during design of the covers will avoid some of the cost premium, but in return, it will place limits on building geometries in future developments. MET.11.1.3.AH.06.20201007

• Analyses confirmed significant long-term creep and shrinkage in the girders that results in downward movement of the girders. This behavior inflects a settlement into the buildings that are supported by the girders, and future building designs will need to account for this behavior to avoid experiencing damage that would shorten the service life of the building. Similarly, horizontal drift of the building is dependent up the building framing and was not evaluated in these preliminary assessments but will need to be confirmed in the final building design.

4.8.6 Other Considerations for Buildings on the Highway Cover Preliminary analyses were completed assuming relatively flat top deck of the highway cover. In addition, it was assumed that the earthquake resisting components include the median bent and passive soil resistance on the end diaphragms of the girders. • Not all regions of the highway cover will have full passive soil resistance on the end diaphragms to assist with structural resistance during seismic events. As a result, additional design enhancements may be required to the highway cover in these areas to replace this lost seismic resistance. These scenarios have not been evaluated to confirm the design enhancements that are needed. • The East-West profile at the extreme north end of the highway cover along the proposed Hancock Street extension has larger elevation changes than other areas of the highway cover. This elevation changes creates a significant challenge given that buildings require a generally flat surface for their foundations. Accommodating a building in this area of the structure is expected to require walls to overcome the elevation changes and develop anFOR adequate REVIEW supporting ONLYsurface for METRO a building of 20201007any height, and implementing those wall will result in a cost premium. The overall change in site grading as you traverse the cover will also influence building access and incorporation to the urban environment.

5 Site Access, Parking, and Loading Site access is prohibited along highway on- and off-ramps and for all blocks within 25 feet of intersections. The combination of the highway access ramps and several one-way thoroughfares in the study area lead to access challenges for existing blocks and potential future spaces created by the highway covers. Figure 12 identifies block frontages which are preferred for access drives and loading. These are block frontages with the least anticipated modal and design conflicts. Access assumptions and limitations are part of the on-going design progression process and additional requirements or limitations may apply. Access for all sites is subject to change based on future land use and a thorough evaluation of modal conflicts. It is expected that the limitations to site access and on-street parking/loading will influence the development feasibility of the spaces created on the covers. Additionally, coordination will be needed with partners to modify the street designs along frontages to create on-street parking, accessible parking areas, boarding/alighting, and/or loading zones.

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Figure 12. Preferred Block Frontages for Access and Loading

FOR REVIEW ONLY METRO 20201007 6 Utility Routing Considerations For either open space cover uses or buildings, utility routing and placement will be a key consideration during the highway cover design. While some utilities may provide more flexibility to maintain utility services, others such as gravity related systems must be considered in the functionality and feasibility of potential uses.

6.1 Gravity-Related Utility Routing Gravity systems, such as storm or sanitary lines rely on positive grade lines with minimum slopes to function properly. These systems must be designed within the constraints and confines of the structural members that comprise the highway cover bridge system. It is assumed that these gravity fed utilities must either be routed above the structural members of the bridge, or be routed within the voids between girder lines, following the structural members to the bridge abutments on either end of the structure. This assumption is based on the vertical clearance limitations between the highway covers and freeway, the practicality of locating the utility between the bridge structural elements and FLS protection measures which include heat resistant fire board utility coverings. These design considerations will need to be further investigated to confirm the feasibility and viability of delivering utility services for the intended sites, as well as the ability to provide ongoing inspection and maintenance access to said utilities which would likely included elements such as utility access ports, vaults, and access to utility meters.

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6.2 Non-Gravity-Related Utility Routing Non-gravity feed utilities such as electrical, communications, gas, and potable water provide more flexibility as compared to gravity services. However, similar access and service connection considerations must be investigated when considering potential uses. For the purposes of initial highway covers uses memorandum, it is assumed that these services would stem from main lines delivered along several of the approaching public roadways. It is also assumed that these services could be delivered using utility duct banks located between structural members running in parallel to the proposed bridge girders. As the bridge design anticipates multiple closely spaced girders to minimize bridge depths, these utility duct banks will likely require unique access needs including vaults and integration into the bridge abutment systems. The placement, scale, and shape of vertical and horizontal penetrations of the primary bridge structural members and deck will require further and very specific coordination. It is likely that specific routing, penetrations, and other elements for future buildings would have to be coordinated, designed, and constructed with the bridges. Therefore, the costs to do so would be incorporated into the Project and specific design limitations would be placed on future development of buildings.

Figure 13. Relationship of Building Ground Floor to Bridge Deck

FOR REVIEW ONLY METRO 20201007

7 Maintenance and Inspection Assumptions In order to access, inspect, and maintain areas of the highway covers, the Project assumes some level of accessibility to the perimeter of the highway cover structure is maintained. This provides typical maintenance access of the surface elements such as protective fencing, landscaping, vegetation, and lighting as well as routine maintenance access for structural features. In particular, the ability for maintenance and inspection vehicle to access along the north and south highway cover edges is anticipated to be critical to maintain the facility. Service

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and inspection access from the freeway are limited due to the impact on high volume travel lanes. For the purposes of this conceptual screening memorandum, small service trucks and light-weight bucket “snooper” cranes are anticipated to access and inspect areas of the bridge. It is assumed that these vehicles would access from the adjacent local street and be able to traverse the perimeter of the structure by way of a 12 foot access route. Additional offset and setback requirements may be identified as part of other considerations. The 24 foot minimum highway cover edge offset for Light Public Buildings and 12 foot minimum highway cover edge offset for Open Space is shown in Figure 14.

Figure 14. Minimum Highway Cover Edge Offsets

Light Public Buildings 24′ highway cover offset

FOR REVIEW ONLYLight Public METRO 20201007 Buildings 24′ highway cover offset

Open Space 12′ highway cover offset

8 Fire and Life Safety Considerations and Assumptions Fire and Life Safety (FLS) considerations pertain to requirements for occupancy egress (tenability) and structural performance during an extreme event occurring under or adjacent to

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the highway cover structures. According to the governing FLS code, the National Fire Protection Association (NFPA) 502, an engineering analysis is required with an appropriate design fire resulting from an emergency event under or near the highway cover structures. The engineering analysis must demonstrate successful tenability and performance of the structural elements during such a design fire. The design fire for the project is the 300 megawatt fire with a hydrocarbon growth rate. This fire represents a hydrocarbon tanker spill fire and is the worst-case scenario per NFPA 502 (Table A.11.4.1) for a tunnel that has no cargo restrictions. Occupant tenability and structural protection requirements for this design fire apply to various locations under and adjacent to the highway cover structures. When unmitigated tunnels do not satisfy FLS requirements, passive and/or active system components must be added to the tunnels to assist in creating an environment that can achieve FLS requirements.

8.1 Tunnels under the Highway Cover Structures Preliminary FLS analyses were completed to investigate the feasibility of unmitigated tunnels under the highway cover structures to satisfy tenability and structural performance requirements for a hydrocarbon design fire. These preliminary analyses revealed that the unmitigated tunnel will not be able to maintain tenability levels for occupant egress from within the tunnels of the cover structures, and the extreme temperatures will likely result in structural damage if the temperatures are prolonged. As a result, additional preliminary analyses were completed to investigate supporting FLS system components (active and passive) that would be required to achieve FLS tenability and structural requirements. The anticipated supporting FLS systems developed in theseFOR studies REVIEW include the following:ONLY METRO 20201007 • Early Detection Systems: Automated systems such as Close Circuit Television Video Image Smoke Detection to detect a potential fire and send notices to appropriate personnel for confirmation and necessary action. • Early Notification Systems: Automated live directive voice and display monitors directing egressing occupants to the nearest exits routes to safety. • Median Wall with Intermittent Exits: A median wall incorporated into the interior bent of the highway cover structures to protect a safe holding area in the non-fire event tunnel for egressing occupants. Intermittent exit doors through this median wall provide shortened egress distances to the safe holding area. • Sacrificial Concrete Cover on Girders: Additional thickness of concrete cover on the girders of the highway cover will be used to protect the girders during an extreme fire event. This structural protection concept is being advanced in the project instead of cover board protection in order to reduce long-term maintenance costs and to provide means for traditional bridge access and inspection in the highway cover. • Active Ventilation: When combined with intermittent median wall exits, active jet fan ventilation (each approximately 4.5 feet in diameter) positioned at strategic locations throughout the tunnels of the highway cover structures are estimated to be capable of achieving a tenable environment for egressing occupants. Ventilation concepts include jet fans at multiple locations throughout the highway cover structures. Jet fans were transversely positioned near the sides of the tunnels to avoid impacts to vertical clearances over vehicular travel lanes. MET.11.1.3.AH.06.20201007 Higway Cover Uses: Screening and Assumptions Memorandum

Use of intermittent vertical ventilation throughout the highway cover structures was considered undesirable because it would likely hinder and limit urban design concepts on the top side of the highway cover structures. It would also require additional safety considerations involved with venting vertically through the structures. As a result, additional preliminary analyses were completed to investigate the feasibility of providing all active jet fan ventilation in the longitudinal direction (parallel to I-5) with no vertical ventilation. Results of those analyses support that vertical ventilation will not be required for urban design scenarios considering separated highway cover structures and for scenarios considering a single highway cover structure.

8.2 Considerations for Buildings on Top of Highway Cover Structures Additional FLS considerations are introduced into the project with buildings placed on top of the highway cover structures. Typical FLS requirements within buildings will likely be consistent with local building code requirements, but design fire events on I-5 and corresponding impacts to nearby buildings must additionally be considered. During an extreme fire event on I-5 near the edge of a highway cover structure, thermal energy from the hydrocarbon design fire will propagate upward and radially, potentially impacting the buildings on top of the highway cover structures. The thermal energy impacting a structure can cause heating that leads to ignition of building materials. The magnitude of the thermal energy radiated to the buildings depends on multiple factors. Two significant factors include the position of the design fire on the below freeway and the position of the building relative to the edge of the highway cover structures. To better understand the risk of fire to the buildings on top of the highway cover structures, a preliminary building safety radiation study was performed to evaluate the thermal energy that would be receivedFOR by str ucturesREVIEW and the ONLY hazards associated METRO with 20201007 it. This building safety study evaluated the 300 megawatt hydrocarbon fire on I-5 at multiple offset positions outside of a tunnel portal and the resulting thermal energy (incident heat flux) received on a structure located on top of the highway cover structure at different offset distances from the edge or the portal. Considering a fixed design fire location on I-5, Figure 16 visually illustrates thermal energy mapping on a nearby building and how the received thermal energy on a building changes (decreases) with increased offset from the edge of a highway cover structure. Building offset distances evaluated were 0, 12, and 24 feet from the portal edge as indicated in the figures. Required building offsets from the edge of a highway cover structure will depend on threshold heat flux values related to ignition temperatures of building materials. Future detailed work will continue to investigate the received thermal energy on buildings and the building materials considered in urban design concepts to determine recommended building positions relative to the edge of highway cover structures. A minimum offset distance of 12 feet will be used in the investigation to satisfy ODOT requirements for maintenance vehicles as previously discussed. The preliminary analyses to date indicate that a building offset greater than 24 feet may be required based on thermal energy considerations and depending on the types of building materials used.

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Figure 15. Building Wall Positions at Offset Distances from Portal – 0 ft. (Top), 12 ft. (Middle), and 24 ft. (Bottom) for a Fixed Fire Position on I-5

FOR REVIEW ONLY METRO 20201007 MET.11.1.3.AH.06.20201007

Figure 16. Thermal Energy Mapping on a Building at 0 ft., 12 ft., and 24 ft. Offsets from Cover Structure Edge (Design Hydrocarbon Fire at Fixed Position)

FOR REVIEW ONLY METRO 20201007 MET.11.1.3.AH.06.20201007

8.3 Consequences for Buildings on the Highway Covers For screening we have assumed a minimum building setback of 24 feet due to the combination of access to the perimeter of the structure as well as the potential implication of heat radiation from a potential combustion incident near the highway cover portal. If a design option includes buildings on the highway cover, additional investigation of building placement and building materials is required.

FOR REVIEW ONLY METRO 20201007 MET.11.1.3.AH.06.20201007

9 Conceptual Design Options

Figure 17. North Site, Design Options Explored North Site

FOR REVIEW ONLY METRO 20201007 Public Open Space, North Site A Public Open Space, North Site A + B Light Public Building, North Site A + B

Design Development Highlights for Consideration: 1) The North Site requires the longest spans within the highway covers and is not a candidate site for large/tall buildings that would require deeper structural supports. Those deeper supports cannot be accommodated below the cover surface and would therefore need to step up, above the adjacent urban context. For this same reason, lightweight landscape areas (with fewer trees) are being explored as viable options 2) The location of a construction joint (running approximately east to west, just north of the Hancock Street alignment) between two separate bridge types, further complicates the design of buildings and open spaces on this site. It is assumed and recommended that a building not span this constructions joint. Landscapes and pavements will have to be design carefully in order to present a seamless open space environment. 3) Access to this site for vehicles is from Vancouver Avenue only. Due to the construction joint and the difference in structure depth that will occur along this joint, vehicular access from Hancock Street to the north edge of the cover is unlikely. That may require a vehicular turnaround on the site that will take up otherwise developable or usable site area. 4) The western edge of the cover structure is significantly higher than the roadway elevation directly adjacent, resulting in a tall wall adjacent to the sidewalk. A building built on this cover site would not have a frontage on the lower street. MET.11.1.3.AH.06.20201007

Figure 18. Middle Site, Design Options Explored

Middle Site

FOR REVIEW ONLY METRO 20201007

Public Open Space, Middle Site B Public Open Space, Middle Site A + B Light Public Building, Middle Site A + B

Design Development Highlights for Consideration: 1) The Middle Site represents the largest and most central development site on any of the three cover sites being investigated and as such, lends itself to the study of larger/taller buildings. With its frontage on NE Broadway– a civic corridor in the City of Portland’s Urban Design designation – it has the greatest exposure to the travelling public and may be the site best suited for a civic use and destination. 2) Complete closure of the highway cover shapes to accommodate a single large site is not assured. However, the cover would have to be fully closed in order to provide a viable building site. 3) With a taller building comes the need for accessible vertical circulation in the form of an elevator. Current elevator technology still requires a “pit” below the floor level of the lowest floor ranging in depth of 4-5 feet. It is expected that the bridge structure cannot accommodate an elevator-sized rectangular penetration of the bridge deck to accommodate this “pit” so it would need to exist above the bridge deck and below the building’s finished floor. That means the building’s ground floor will be approximately 6 feet or more above the some areas of adjacent sidewalk level. Significant ramping and stairways will be needed for pedestrians to circulate from the accessible sidewalk to the building entries. Conditions like this – wherein the ground floor is above a pedestrian’s eye level – do not best support viable “ground floor” retail environments and active, pedestrian supportive uses. MET.11.1.3.AH.06.20201007

Figure 19. South Site, Design Options Explored

South Site

Public Open Space, South SiteFOR A REVIEWPublic OpenONLY Space, South SiteMETRO A + B 20201007Light Public Building, South Site A + B

Design Development Highlights for Consideration: 1) The South Site represents a uniquely constrained development area for buildings and landscapes. Because of its location between two highway ramps, with only one street frontage, all vehicular access and circulation needs to occur from Weidler. Committing this area to vehicular use limits the area available for development and open space, but also constrains the viable uses due to the limitations of on-street frontage for loading and/or parking in relation to the site. For that reason, a simple, one-story building was selected as most viable for technical study. 2) It is expected that all trees (which require a minimum 3 feet of soil depth) will need to be planted in berms or structure planters above the bridge deck. While specific trees in specific locations between girders could be placed within the depth of structure, the current baseline project assumes “tip to tip” prestressed concrete bulb “T”s with no gaps in the structure large enough for a tree trunk to rise up through. Ongoing maintenance, drainage and replacement considerations further complicate this solution. With all trees located “above” deck, landscape establishment period and irrigation of landscape on an ongoing basis is likely to require truck watering. MET.11.1.3.AH.06.20201007

Figure 20. Broadway/Weilder Site, Design Option Explored

FOR REVIEW ONLY METRO 20201007

Design Development Highlights for Consideration: 1) The Broadway/Weidler site located east of N Williams, between NE Broadway and NE Williams is located off the highway cover, but adjacent to the highway cover structure. 2) Buildings constructed on the ground adjacent to or in the proximity of the highway cover structures can produce increased lateral earth pressures on the abutments of the highway cover structure. These additional loadings on the highway cover structures, or building foundation types avoiding such increased loadings, should be considered. 3) Providing a buffer distance between the footings of cover-adjacent buildings and the highway cover structure will be necessary. Buffer distance is yet to be determined but should be at least 10 feet. MET.11.1.3.AH.06.20201007

FOR REVIEW ONLY METRO 20201007 MET.11.1.3.AH.06.20201007

LEGEND

ON-COVER DEVELOPMENT SITES

OFF-COVER DEVELOPMENT SITES

PLAZA

SHRUBS & CROUNDCOVER

LAWN

ON-COVER TREES

I-5

OFF-COVER TREES

N HANCOCK

NE HANCOCK

I-5 ON-RAMP

N DIXON

REVU O C N A V N SMAILLIW N FOR REVIEW ONLY METRO 20201007

NE BROADWAY

N WILLIAMS N NE VICTORIA NE

N BROADWAY

N WEIDLER NE WEIDLER

I-5 OFF-RAMP I-5 ON-RAMP

I-5

DEVELOPMENT SITES 8.13.2020 MET.11.1.3.AH.06.20201007

N VANCOUVER

COURTYARD30+ STAIR

WALL / PLANTED SCREEN

24’-0”

8’-0”

PARKING

COURTYARD29+ COVER OUTLINE

FOR REVIEWSTAIR ONLY METRO31+ 20201007 COVER EXTENSION MEP AREA COMMERCIALFFE: 132’

PLAZA RR

31.95+ BS 29.9+

TS 32+ TS 31.9+ N HANCOCK

1 BS 28+ 2%

5’-0” EMERGENCY ACCESS EMERGENCY

NE HANCOCK

COVER JOINT COVER OUTLINE COVER

NORTH SITE - ONE-STORY FLOOR PLAN SCALE: 1” = 30’-0” MET.11.1.3.AH.06.20201007

HANCOCK

1 N VANCOUVER N WILLIAMS N

2 BROADWAY

WEIDLER 3

FOR REVIEW ONLY METRO 20201007

NORTH SITE - SECTION 1 SCALE: 1/16” = 1’-0” MET.11.1.3.AH.06.20201007 N WILLIAMS

I-5 ON-RAMP N VANCOUVER N

EMERGENCY ACCESS

COVER OUTLINE

FOR REVIEW ONLY METRO 20201007

RESIDENT

PATIO

COVER OUTLINE

ADMIN. 2 PLAZA LOBBY FFE: 132’ WALL/PLANTED SCREEN WALL/PLANTED

N BROADWAY

MID-SITE - FOUR-STORY (OPTION A) - FIRST FLOOR PLAN SCALE: 1” = 30’-0” MET.11.1.3.AH.06.20201007 N WILLIAMS

I-5 ON-RAMP N VANCOUVER N

EMERGENCY ACCESS

COVER OUTLINE

FOR REVIEW ONLY METRO 20201007

COVER OUTLINE

N BROADWAY

MID-SITE - FOUR-STORY (OPTION A) - LEVELS 2-4 FLOOR PLAN SCALE: 1” = 30’-0” MET.11.1.3.AH.06.20201007

HANCOCK

1 N VANCOUVER N WILLIAMS N

2 BROADWAY

WEIDLER 3

FOR REVIEW ONLY METRO 20201007

MID-SITE - FOUR-STORY OPTION - SECTION 2 SCALE: 1/16” = 1’-0” MET.11.1.3.AH.06.20201007 N WILLIAMS

I-5 ON-RAMP N VANCOUVER N

EMERGENCY ACCESS

COVER OUTLINE

FOR REVIEW ONLY METRO 20201007

PATIO

COVER OUTLINE

PLAZA 2 WALL/PLANTED SCREEN WALL/PLANTED

N BROADWAY

MID-SITE - TWO-STORY (OPTION B) - FIRST FLOOR PLAN SCALE: 1” = 30’-0” MET.11.1.3.AH.06.20201007 N WILLIAMS

I-5 ON-RAMP N VANCOUVER N

EMERGENCY ACCESS

COVER OUTLINE

FOR REVIEW ONLY METRO 20201007

COVER OUTLINE

N BROADWAY

MID-SITE - TWO-STORY (OPTION B) - SECOND FLOOR PLAN SCALE: 1” = 30’-0” MET.11.1.3.AH.06.20201007

HANCOCK

1 N VANCOUVER N WILLIAMS N

2 BROADWAY

WEIDLER 3

FOR REVIEW ONLY METRO 20201007

MID-SITE - TWO-STORY OPTION - SECTION 2 SCALE: 1/16” = 1’-0” MET.11.1.3.AH.06.20201007

COVER OUTLINE

NE BROADWAY

31+ 30.5+ P1 P12 P2 P13 P14 STAIR P3 COMMERCIAL 3% FFE: 131’ MEP

P4 P15 NE VICTORIA

N WILLIAMS WILLIAMS N SIX-STORY BUILDING SECTION N WILLIAMS WILLIAMS N P5 P16 RESIDENTIAL USE 3.8%

FOOD 30.8+ TRUCK 2% COMMERCIAL USE P17 P6 LOBBY

P7 P18 EL EL (TO I-5 NB) I-5 (TO

FOOD 4 TRUCK FFE: 131’ (TO I-5 SB) I-5 (TO P8 P19 1-BR FOR REVIEW P9ONLY P20 METRO 20201007 1-BR

FOOD TRUCK P10 P21 1-BR 1-BR P11 P22 3% STAIR

2% STOR. COVER OUTLINE FOOD TRUCK 15’-0” MIN. 1-BR 1.5% 27.2+

27+ 28+

NE WEIDLER BLOCK 8 - FLOOR 1 SCALE: 1” = 30’-0” 7.10.2020 MET.11.1.3.AH.06.20201007

COVER OUTLINE

NE BROADWAY

1-BR 1-BR

1-BR STAIR

1-BR

NE VICTORIA

N WILLIAMS WILLIAMS N 1-BR SIX-STORY BUILDING SECTION N WILLIAMS WILLIAMS N RESIDENTIAL USE 1-BR 1-BR COMMERCIAL USE

1-BR EL EL

(TO I-5 NB) I-5 (TO 4 (TO I-5 SB) I-5 (TO FOR REVIEW ONLY METRO 202010071-BR 1-BR

1-BR 1-BR

STAIR STOR. COVER OUTLINE 1-BR

NE WEIDLER BLOCK 8 - FLOORS 2-6 SCALE: 1” = 30’-0” 7.10.2020 MET.11.1.3.AH.06.20201007

1 N VANCOUVER HANCOCK N WILLIAMS N

2 BROADWAY 4

WEIDLER 3

FOR REVIEW ONLY METRO 20201007

BLOCK 8 - SECTION 4 SCALE: 1/16” = 1’-0” 7.10.2020

N WILLIAMS N N WILLIAMS N

NE VICTORIA NE MET.11.1.3.AH.06.20201007

ONE-STORY BUILDING SECTION COVER OUTLINE RESIDENTIAL USE

COMMERCIAL USE

COVER OUTLINE

NE WEIDLER

29.5+

FOR REVIEW ONLY METRO30.95+ 29.75+ 20201007 COMMERCIAL 3 FFE: 131’ MEP

I-5 OFF-RAMP I-5 ON-RAMP I-5 24’-0”

COVER EXTENSION EMERGENCY ACCESS AREA

BLOCK 10 - FLOOR PLAN SCALE: 1” = 30’-0” 7.10.2020 MET.11.1.3.AH.06.20201007

1 N VANCOUVER HANCOCK N WILLIAMS N

2 BROADWAY 4

WEIDLER 3

FOR REVIEW ONLY METRO 20201007

BLOCK 10 - SECTION 3 SCALE: 1/16” = 1’-0” 7.10.2020 MET.11.1.3.AH.06.20201007

FOR REVIEW ONLY METROBroadway 20201007

Weidler St

BUILDING MASSINGS MET.11.1.3.AH.06.20201007

10 Highway Cover Relevant Examples This section features examples of places where buildings and civic spaces have been created on highway covers over freeways or state highways. Relevant example projects are in the United States and profiles include the specific location, size, year built/open to the public, hazardous materials classification, and information about the project developer, designer, engineer/construction lead, and ownership. The example projects demonstrate how the FHWA has worked with state and local agencies to support development above existing interstates and state highways. Each State or Indian tribe is required to report any changes to its highway routing information to the Federal Motor Carrier Safety Administration (FMCSA). Roadway restrictions and/or designations are included for each example project profile according to the National Hazardous Materials Route Registry (NHMRR). (Source: https://www.federalregister.gov/documents/2018/08/09/2018-17060/national- hazardous-materials-route-registry)

10.1 Relevant Example Projects The following list of relevant example projects are summarized below in one-page factsheets. Projects with “*” after the name have current projects to expand or add covers to highways. • Atlanta Financial Center, Atlanta, GA * • The Rose Fitzgerald Kennedy Greenway, Boston, MA • Copley Place/PrudentialFOR REVIEW Center, ONLYBoston, MA METRO 20201007 • The Cap at Union Station, Columbus, OH • Klyde Warren Park, Dallas, TX • Freeway Park/Washington State Convention Center, Seattle, WA * • Aubrey Davis Park Lid on Mercer Island, Seattle, WA * Other projects, considered but not studied in more detail, are identified in the final section. MET.11.1.3.AH.06.20201007

10.1.1 Atlanta Financial Center – Atlanta, GA

Description The sites over the highway include office buildings and structured parking. The tunnel below the east tower includes automobile traffic and the Metropolitan Atlanta Rapid Transit Authority Red Line. The transportation infrastructure is shielded from the direct contact with the building to protect from hazards, noise, and vibrations. The hazardous materialsFOR restriction REVIEW class 0 (anyONLY materials METRO requiring placards) 20201007 was put in place in 1995 on Georgia Highway 400 between I-85 and Exit 2 (Lenox Road / Buckhead Loop). The restriction is directly related to the tunnel underneath the East Tower. Overview Facts

Year(s) Built 1990 Freeway/Highway Georgia State Route 400 Area/Size 10 acres; 900,000 ft2 office space (3 towers) Hazard Level Restriction Class: 0 – ALL Hazardous Materials Ownership Sumitomo Corp. of Americas (2016) Design/Engineering Firms Involved Smallwood, Reynolds, Stewart, Stewart and Association MET.11.1.3.AH.06.20201007

10.1.2 Copley Place/Prudential Center – Boston, MA

Description Copley Place and the Prudential Center is a large mixed-use complex that includes a retail center with two department stores, two major hotels, four office towers, restaurants, cinemas, and a parking garage located in Back Bay.FOR (Source: REVIEW https://www.fhwa.dot.gov/ipd/project_profiles/ma_copley_place.aspx ONLY METRO 20201007 ) Copley Place and Prudential Center sites are part of a long and detailed development history in Boston’s Back Bay. Built above the Massachusetts Turnpike (I-90), just east of the Hynes Convention Center which is also atop the turnpike and Huntington Avenue highway interchange. It includes connections to the MBTA Rapid Transit, Commuter Rail, and Amtrak service. I-90’s hazardous materials restriction is 0 from Logan Airport to Massachusetts Avenue, including all hazardous materials. The developer holds a 99-year lease with the Massachusetts Turnpike Authority and paid $1.2 million rent annually (February 1992 to February 2002). The escrow account includes security deposit in U.S. Treasury Bonds paying interest at not less than $1.2 million annually. As of 2002 the annual lease is $1.00 through 2077. Overview Facts Year(s) Built 1977-1984 Freeway/Highway I-90 Massachusetts Turnpike Area/Size 9.5 acres Hazard Level Restriction Class: 0 – ALL Hazardous Materials Ownership Urban Investment and Development Company Design/Engineering Firms Involved The Architects' Collaborative, Charles Luckman (Prudential Center) and Howard Elkus (Copley Place) MET.11.1.3.AH.06.20201007

10.1.3 The Rose Fitzgerald Kennedy Greenway – Boston, MA

Description The Greenway sits atop I-93, which was put underground through the Central Artery project (“Big Dig”). While the overall project itself suffered from significant setbacks, the new open spaces are a positive and lasting element of the city center. The parks central location helps link Boston’s downtown to the waterfront area and creates new open destinations for residentsFOR and REVIEW visitors. ONLY METRO 20201007 A key challenge of this project was building major infrastructure in the middle of a major U.S. city without shutting down transportation, businesses and neighborhoods. Team needed to understand conditions at all parts of the tunnel, some of which were still under construction. Utilities created shallow depths in some areas that affected park design. Had to maintain clear goals for public engagement to meet milestones and move design process forward. Owned by Massachusetts Department of Transportation; 2008 legislation established a 50/50 percent public/private funding model; Rose Kennedy Greenway Conservancy took over park management in 2009; 2017 funding agreement to solidify support from Commonwealth, City of Boston, and property owners. Overview Facts Year(s) Built 1991-2006 Freeway/Highway I-93 (Thomas P. O’Neill Tunnel) Area/Size 17 acres, 1.5 miles Hazard Level Restriction Class: 0 – ALL Hazardous Materials Ownership Massachusetts Department of Transportation Design/Engineering Firms Involved • Highway: Bechtel/Parsons Brinkerhoff • Park: Chinatown Park - CRJA-IBI Group; Wharf District Parks - EDAW and Copley Wolff Design Group; North End Parks - Crosby | Schlessinger | Smallridge and Gustafson Guthrie Nichol MET.11.1.3.AH.06.20201007

10.1.4 The Cap at Union Station – Columbus, OH Description The Cap at Union Station is a retail development built along High Street above the Inner Belt Highway (I- 670) in Downtown Columbus. (Source: https://www.fhwa.dot.gov/ipd/project_profiles/oh_cap_union_station.aspx) The project is a public-private partnership between the City of Columbus and Continental Real Estate Companies in response to the Ohio Department of Transportation proposed widening of I-670 in 1996. In 1999, the developer, Continental Real Estate Companies, signed a Memorandum of Understanding with the City of Columbus, which stated that if the city could gain the title to the development rights above the highway and obtain permission from FHWA and Ohio’s Department of Transport to build the Cap platforms, then the company would enter a lease agreement for the platforms and build the retail buildings. As of 1985, Interstate 670 from Interstate 70 to Interstate 270 has a Designation A: only for the delivery of NRHM within the City of Columbus. Overview Facts Year(s) Built 2002-2004 Freeway/Highway I-670 Inner Belt Highway Area/Size 25,500 sf Hazard Level Designation A: ALL Hazardous Materials Ownership Public-private partnership Design/Engineering Firms Involved Continental Real Estate Companies (Owner), Meleca Architecture and Urban Planning (Architect), Jezerinac Geers and Associates (Structural Engineer), FOR REVIEW ONLY METRO 20201007 MET.11.1.3.AH.06.20201007

10.1.5 Klyde Warren Park – Dallas, TX

Description FOR REVIEW ONLY METRO 20201007 The Klyde Warren Park connects Downtown Dallas to the Uptown neighborhood and is owned by the City of Dallas but privately operated and managed by the Woodall Rodgers Park Foundation. The $110 million project was funded through a public-private partnership, which included contributions in bond funds from the City of Dallas, state and federal highway funds, and private donations. (Source: https://www.klydewarrenpark.org/about-the-park/our-story.html) The park is heavily programmed by the Woodall Rodgers Park Foundation with public events scheduled regularly and several dining options. Overview Facts

Year(s) Built 2009-2012 Freeway/Highway Texas State Highway Spur 366 (Woodall Rodgers Freeway) Area/Size 5.2-acres Hazard Level Restriction Class: 0 - ALL Hazardous Materials (from US 75 to Interstate 35E) Ownership Owned by City of Dallas; Privately operated and managed by the Woodall Rodgers Park Foundation Design/Engineering Firms Involved Bjerke Management Solutions (Owners Rep), The Office of James Burnett (Design), Jacobs Engineering Group (Construction), Archer Western (Construction), McCarthy Building Companies, Inc. MET.11.1.3.AH.06.20201007

10.1.6 Freeway Park/Washington State Convention Center – Seattle, WA

Description Freeway Park is an urban park that sits above a section of I-5 that connects downtown Seattle to the First Hill neighborhood. FORThe Washington REVIEW State Convention ONLY Center METRO was built 20201007in 1985-1988 after the state legislature established a public nonprofit corporation in 1982 to manage construction and operations, which included a 40 percent enlargement of Freeway Park. (Source: https://www.freewayparkassociation.org) The freeway’s air rights were leased from the Washington State Department of Transportation by the private development. The center was further expanded in 2001 and 2010. The project used a mix of public and private financing, including state contributions, hotel tax revenue, and private developers. As of 1989, flammable loads cannot be transported through the tunnel under convention center when the sprinkler systems are not operational or being tested. Overview Facts

Year(s) Built 1976; Expansion in 1990 Freeway/Highway I-5 Area/Size 5.2 acres Hazard Level Restriction Class: 3 – Flammable Ownership Owner is Washington State Department of Transportation (WSDOT), airspace rights leased to private development; Freeway Park is City of Seattle public park, managed by Seattle Parks and Recreation Design/Engineering Firms Involved Designed by Lawrence Halprin and Associates, Angela Danadjieva; 1990 Extension to Convention Ctr (Danadjieva and Koenig); 2020 Improvements (Walker Macy, HDR, etc.) MET.11.1.3.AH.06.20201007

10.1.7 Aubrey Davis Park Lid – Mercer Island, WA

Description FOR REVIEW ONLY METRO 20201007 The highway widening project was proposed right after the NEPA was passed. This was the first highway project that was subject to NEPA, therefore requiring a long design and approval process starting in 1974. The lid is owned by WSDOT and built as mitigation for the expansion of the highway. The amenities above the lid such as parks are owned by the City of Mercer with an airspace lease agreement. WSDOT still owns most of the landscaping and trails on and along the lid and pays the City to maintain them through an interlocal agreement. As of 1990, flammable loads cannot be transported through the Mercer Island tunnel or the tunnel on the west side of Lake Washington when the sprinkler systems are not operational or being tested. A 2019 Park Master Plan is being led by the City, Parks and Recreation Commission, and Mercer Island Arts Council with consultant support from HBB Landscape Architecture, BERK consulting, Toole Design Group, David Evans and Associates, Rolluda Architects Inc., and 4Culture. (Source: https://letstalk.mercergov.org/AubreyDavis/widgets/13805/documents) Overview Facts Year(s) Built 1992 Freeway/Highway I-90 Area/Size 90 acres, 2.8-mile long Hazard Level Restriction Class 3: Flammable Ownership Owned by WSDOT, managed by the City of Mercer Island Design/Engineering Firms Involved Jongejan, Gerrard and McNeal, Lee Kobayashi Burke; Robert Josephson, PE (WSDOT now HNTB) MET.11.1.3.AH.06.20201007

10.2 Other Examples:

10.2.1 5th Street Pedestrian Plaza – Atlanta, GA The Fifth Street Bridge was built in 2007 and connects Georgia Tech to Technology Square in Midtown. It spans across 16 lanes of interstate (the Downtown Connector) and includes three- quarter acre of green space. (Source: http://aspirebridge.com/magazine/2008Winter/5th_street_win08.pdf)

FOR REVIEW ONLY METRO 20201007 MET.11.1.3.AH.06.20201007

10.2.2 Hartford Public Library – Hartford, CT The Main Building of the Hartford Public Library system is built on top of a cap on the Conland- Whitehead Highway, a short spur between I-91 and the State Capitol at Pulaski Circle. It was built in 1957, and a renovation and expansion project took place from 1998 to 2007.

FOR REVIEW ONLY METRO 20201007 MET.11.1.3.AH.06.20201007

10.2.3 George Washington Bridge Bus Terminal – New York, NY The George Washington Bridge Bus Terminal was built in 1963 and is located above I-95 on the eastern end of the George Washington Bridge in Washington Heights (Upper Manhattan). The terminal was renovated in 2013 and re-opened in 2017 to improve ADA accessibility, transit connections, and to add 90,000 square feet of retail space.

FOR REVIEW ONLY METRO 20201007 MET.11.1.3.AH.06.20201007

10.2.4 Eastside Parks on SR 520 – Seattle, WA There are three parks located on SR 520 in the Eastside of King County. The lids were completed in 2015 and are landscaped open spaces—two of which include bus stations. The lids were part of roadway improvement project for SR 520 and help noise-reduction and stormwater retention. (Source: https://www.wsdot.wa.gov/sites/default/files/2018/07/11/SR520- factsheet-EastsideProject-July2018.pdf)

FOR REVIEW ONLY METRO 20201007 MET.11.1.3.AH.06.20201007

10.3 Relevant Example Projects Findings The relevant highway cover example projects identified in this section are typically owned by a state department of transportation. The buildings or open spaces located on highway covers are typically privately developed and managed, or privately developed with airspace leases for other organizations to manage. Most relevant example projects are located above freeways with restriction classes for hazardous or flammable materials.

FOR REVIEW ONLY METRO 20201007