Feasibility Study. October Bicycle and Pedestrian Bridge over the North Channel of the Boise River. Eagle Road/Highway 55

Transcription

1 October 2015 Feasibility Study Bicycle and Pedestrian Bridge over the North Channel of the Boise River Eagle Road/Highway 55 Prepared for: Community Planning Association of Southwestern Idaho (COMPASS) City of Eagle, Idaho Prepared by: J-U-B ENGINEERS, Inc. Alan Cukurs, P.E.

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3 Table of Contents Executive Summary... 1 Introduction... 3 History... 3 Existing Bridge... 4 Eagle Road... 4 Purpose of Feasibility Study... 5 Bike/Pedestrian Bridge Design Criteria... 6 City of Eagle Approval Process... 7 ITD District 3 Conditions and Considerations... 8 Initial Concept Explored... 9 Initial Concept: Lightweight Aluminum Bike/Pedestrian Bridge... 9 J-U-B s Investigation of this Concept... 9 Other Options Explored Concrete Beams Supported by Additional Pile Supported Piers Adjacent to Existing Bridge Three Span Steel Truss Attached to Existing Bridge Steel Truss Clear-Span Bridge Additional Considerations Funding Options Summary Ownership and Maintenance Cost Considerations Recommendation Next Steps Agencies and Other Parties Consulted Agencies Other Involved Parties... 17

4 Executive Summary 1 Executive Summary This document is a feasibility study that examines attaching a bike/pedestrian bridge to the existing Eagle Rd/SH-55 Bridge crossing the north channel of the Boise River in Eagle, Idaho. The proposed bridge would provide north-south connectivity to existing and future Greenbelt pathway and neighborhoods. J-U-B ENGINEERS, Inc. (J-U-B) was hired by COMPASS to perform this study. As part of the feasibility study process, J-U-B: Reviewed work that was completed prior to this study Reviewed existing bridge plans Performed a site visit Analyzed the existing bridge foundations for supporting a lightweight aluminum structure Investigated other options for widening the bridge for bicycle and pedestrian use Developed planning-level cost estimates for bike/pedestrian bridge structure options Coordinated this effort with Idaho Transportation Department (ITD) Attended two Eagle City Council meetings, presented information, sought input Attended an Eagle Parks and Pathways Development Commission meeting, presented Draft Feasibility Study, sought input Prior to J-U-B s involvement in this project, an aluminum bridge was investigated by others. A lightweight aluminum bridge option was originally proposed to avoid the need for additional pile foundations, and to minimize or eliminate in-stream construction; thereby reducing the cost. J-U- B determined that the originally proposed aluminum structure would overload the existing foundation pile capacities at the piers and would require additional piles. Other bridge options were investigated after J-U-B determined that in-stream work and additional pile foundations would most likely be required for an aluminum bicycle and pedestrian structure attached to the existing SH-55 Bridge. The three other options considered in this study are: OPTION 1: Widen the existing bridge with precast concrete beams supported by extending the existing piers and abutments with additional pile foundations OPTION 2: Widen the existing bridge with steel trusses supported by extending the existing piers and abutments with additional pile foundations OPTION 3: An independent steel bike/pedestrian truss bridge spanning the entire north channel of the Boise River J-U-B recommends Option 1. Table 1 includes a summary of the pros and cons for the options.

5 Executive Summary 2 Table 1: Concept Pros and Cons Concept/Option Initial Concept: Lightweight Aluminum Cantilever Bridge Based on preliminary analysis, this option does not appear to be feasible. The existing pile foundation cannot support the additional weight of the aluminum pedestrian bridge, along with the pedestrian loads. This option has been eliminated as an option for this study. Concept/Option Pros Cons OPTION 1: Concrete Beams Attached to Existing Bridge with Additional Pile Supported Pier adjacent to existing bridge. Vertical Pedestrian bridge loads are supported independent of the existing bridge. OPTION 2: Three Span Steel Truss Attached to Existing Bridge with Additional Pile Supported Pier adjacent to existing bridge. Vertical Pedestrian bridge loads are supported independent of the existing bridge. OPTION 3: Separate Steel Truss Clear-span Bridge Cost effective Similar in appearance as the existing bridge. Shallow profile will not change the visual appearance of the site. Future widening of the bridge by ITD would include sidewalks for pedestrians and bicyclists, therefore the only cost to the city would be the initial cost for widening. Preliminary estimated cost of bridge structure is approximately $600,000. Lighter than precast concrete which may reduce the cost of the additional foundation A low profile truss may be visually appealing Future widening of the bridge by ITD would include sidewalks for pedestrians and bicyclists, therefore the only cost to the city would be the initial cost for widening After ITD widens the bridge, the steel truss could be salvaged for use on other City pathway projects. Would not impact the SH-55 Bridge in the immediate future and in the future when SH-55 Bridge is replaced. Design life is not dependent on the existing SH-55 Bridge. Preliminary estimated cost of bridge structure is approximately $800,000. Service life of the new pedestrian bridge will not be fully utilized as the new construction will be replaced once the older existing bridge has reached its service life. Instream work will be required to construct new piles and piers. Greater level of coordination between the State and the City for construction and maintenance of the pedestrian structure. The steel truss bridge would likely be more costly compared to precast concrete. Similar Cons as Option 1 regarding service life and coordination with other agencies. Initial cost may be the greatest for this option. Relatively tall structure and may be a visual distraction for the site because it is adjacent to the relatively low profile SH-55 bridge.

6 Introduction 3 Introduction History The City of Eagle (City); Walk and Ride Eagle, LLC; Two Rivers Community; and the Idaho Transportation Department (ITD) have been collaborating together for a new proposed bicycle pedestrian bridge adjacent to the west side of State Highway 55 (SH-55) over the north channel of the Boise River. The City applied for Project Development funding from Community Planning Association of Southwest Idaho (COMPASS) to study the feasibility of the project. The ultimate goal is to provide the needed technical analysis and details for the City to seek federal funding in the near future for design and construction of the project. Project Location Map Currently, there is no separate north-south bike/pedestrian river crossing on Eagle Rd/SH-55. It is currently improved with five lanes (four thru-lanes and one center lane) and shoulders on both sides. The function of the center lane is to provide adequate room for vehicle stacking at the intersections of Riverside Drive to the north and Island Woods Drive to the south. With the increase of developing neighborhoods and businesses in this area, bike/pedestrian use of the existing bridge shoulders on SH-55 have increased. Citizens walking along the shoulder of the SH-55 bridge (June 2015) The northeast corner of the bridge is in close proximity to a Hotel with a number of other businesses located near the north side of the bridge on both sides of SH-55. An existing east-west bike/pedestrian path is located on the north side of the river crossing underneath the bridge at the north abutment. Utilities such as overhead power are located adjacent to the east side of the bridge. East Side of SH-55 bridge, utilities, hotel, pathway connection (June 2015)

7 Introduction 4 Existing Bridge West side of SH-55 bridge, looking south (June 2015) The existing SH-55 Bridge was constructed in two phases. The east half of the bridge was constructed in 1974 and the west half of the bridge was constructed in In general, the bridge is in good condition. However, the typical design life for a bridge such as this is approximately 75 years, which would give a remaining theoretical service life of 34 years based on the original construction year. Eagle Road Future Plans In addition to the remaining service life of the existing bridge structure, it is important to consider if there are any plans to widen Eagle Road. Currently, there are no plans to widen this section of Eagle Road. It is not identified in the COMPASS 2040 Communities in Motion (CIM) long-range plan nor any of ITD s plans. Right-of-Way and Easements There is approximately 90-feet of ROW along the bridge portion of SH-55 and established public access easements on the west side of the existing bridge to the north where the bike/pedestrian underpass connects to the greenbelt and to the south where the bike/pedestrian underpass connects to an existing dirt detached pathway. Once the preferred bridge option is selected, an evaluation of any additional right-of-way and/or easements should occur as part of the project development process. An easement from the Idaho Department of Lands for the Bridge crossing over Boise River will likely be required. Additionally, consultation with the Shoshone Bannock Tribes will be required as part of the environmental process associated with federal funding. All other required permits will be identified as part of the project development process (next phase).

8 Introduction 5 Purpose of Feasibility Study J-U-B was retained by COMPASS to further develop the concept and feasibility of attaching or supporting a bike/pedestrian bridge adjacent to the existing SH-55 Bridge. Previously, there was some investigation done by others for the use of a three span aluminum bridge with an aluminum bridge deck for its relatively lightweight material properties. This concept was conceived to eliminate or minimize impacts to the existing bridge. J-U-B investigated the feasibility of attaching an aluminum bike/pedestrian structure to the existing bridge without additional foundations. Furthermore, this feasibility study includes an investigation of alternative bridge concepts for bike/pedestrian crossing at this location. Upon ITD s approval of this feasibility study, the Project Development phase will begin. During the Project Development phase, a project description, scope of work, purpose and needs statement, list of permits needed, maps, cost estimates, a public/stakeholder outreach plan and an environmental scan will be prepared. The intent of the Project Development phase is to further develop the preferred concept, develop a funding strategy, and prepare adequate project information to support a future grant application.

9 Bike/Pedestrian Bridge Design Criteria 6 Bike/Pedestrian Bridge Design Criteria The American Association of State Highway and Transportation Officials (AASHTO) Guide for the Planning, Design, and Operation of Pedestrian Facilities and the AASHTO Guide for the Development of Bicycle Facilities require the pathway on the bridge to be a minimum of 10 feet of clear width for bike/pedestrian traffic. Additionally, the bridge and the approaches to the bridge would need to meet Americans with Disabilities Act (ADA) requirements. The minimum design life of the structure is 75 years. The bike/pedestrian Bridge would not adversely impact the existing SH-55 Bridge.

10 City of Eagle Approval Process 7 City of Eagle Approval Process In consultation with City Planning and Zoning Staff and Parks and Recreation Staff, the following considerations will need to be made as the project moves forward: POINT OF CONTACT: Mike Aho, Director, City of Eagle Parks and Recreation is the point of contact and will distribute the plans to the staff responsible for the review of the project. DESIGN REVIEW: This project lies within a Scenic Overlay District. Therefore, the City Planning and Zoning Department requires Design Review. Since it would be a City application, no formal applications or paperwork other than plans would be necessary for submittal, and the project would be a staff level review. TIMELINE: Staff level review may take 3-4 weeks depending on internal workload. City staff would present the project through its various phases to the Eagle Parks and Pathways Development Commission and City Council.

11 ITD District 3 Conditions and Considerations 8 ITD District 3 Conditions and Considerations The following is an excerpt from an from Greg Vitley with ITD District 3 Environmental Planning and needs to be considered as this project progresses. 1. Use of the existing shoulder is not viable due to current standards/safety on a high speed facility. 2. Be responsible for all costs associated with development and operations (engineering studies, environmental clearances, plans, mitigation, construction, coordination with ITD for construction inspection, and long term inspection and maintenance of the structure and pathway). a. ITD s impression is that the cost estimates provided at the previous meeting may not be sufficient for the work being contemplated, and suggests you consider obtaining an independent assessment and estimate by a professional engineer. 3. Demonstrate to ITD through engineering analysis what potential impacts, connection mechanisms, and load reduction the additional structure will have on the bridge. 4. Provide required width for two way traffic throughout the length of the pathway and provide an ADA compatible facility for liability purposes if the structure is in ITD ROW. Facilities for a shared-use pathway are required to be a minimum of 10 wide. ADA accommodations will be required for the connection between the new pathway and the existing greenbelt/pathway at the northwest corner of the bridge. Please refer to the AASHTO Guide for the Planning, Design, and Operation of Pedestrian Facilities AND the AASHTO Guide for the Development of Bicycle Facilities. 5. If ITD gives access for parking on the southwest side, the southeast parking would be eliminated. ITD District 3 s Development Services Manager, Jim Morrison, has been coordinating with the City of Eagle on this particular request. 6. Continue close coordination with ITD and obtain ITD approval of the project plans prior to construction. ITD realizes the increase in development in the area and your proposal has merit to mitigate your concerns regarding bike and pedestrian circulation. Generally, state highways are not constructed for bike and pedestrian circulation, therefore, it is encouraged that comprehensive planning for bike and pedestrian circulation to the extent possible, be apart from state highways (i.e.: greenbelt connections from the south slough to the north slough). Thanks again for your proposal. If you have any questions please call me.

12 Initial Concept Explored 9 Initial Concept Explored Initial Concept: Lightweight Aluminum Bike/Pedestrian Bridge The initial concept bridge is a three-span aluminum truss bridge. The spans would be the same as the existing bridge span lengths of 75 feet, 90 feet, and 75 feet. The bridge would have a 10-foot-wide clear pathway and would meet ADA requirements. The initial concept would involve supporting the aluminum bridge with new cantilever supports attached at the abutments and piers (eliminating the construction of additional foundations in the Boise River at abutments and piers). The riding/walking surface (the bridge deck) of the bike/pedestrian bridge was assumed to be at the same elevation, or nearly the same elevation as the existing SH-55 bridge deck. This maintains the vertical clearance below the bike/pedestrian bridge; allows for greater visibility of pedestrians for safety; better fits the site conditions at the existing abutments and river banks, and integrates well with the existing sidewalks at the northwest corner of the bridge. Locating the bridge on the west side of the existing highway facilitates maintenance for debris removal, which tends to collect on the east side (upstream side) of the bridge. J-U-B s Investigation of this Concept Initial Concept: Lightweight Aluminum Bike/Pedestrian Bridge Connecting the proposed aluminum bridge to the existing bridge without additional foundation support is not feasible. The existing bridge piles will not support the additional load of: the aluminum bridge, the weight of bicycle and pedestrian traffic, and the additional cantilever supporting the aluminum bridge. These additional loads would increase the total loads beyond the available capacity of the existing piles. The capacity of the existing piles and loads are shown on the existing bridge drawings. The reserve capacity of the existing foundation was computed and found to be less than the additional loads imparted by the aluminum bridge and the bike and pedestrian traffic supported by the aluminum bridge. Additional steel piles are required to support the proposed aluminum bridge option.

13 Other Options Explored 10 Other Options Explored J-U-B s preliminary analysis indicates that using lightweight material such as an aluminum bridge does not result in eliminating the need for additional foundation elements to support the bike/pedestrian bridge. Therefore, other bridge materials and types were investigated for attaching to the existing bridge. A three span steel truss bridge option and three span precast concrete beam option attached to the existing bridge were considered. The options attaching to the existing bridge assumed the same span lengths, pathway width and overall geometry as the initial aluminum bridge option. A single clear span steel truss bridge independent of the existing bridge was also considered. Concrete Beams Supported by Additional Pile Supported Piers Adjacent to Existing Bridge Attachment of any bike/pedestrian structure to the existing bridge abutments and piers is in essence, widening the existing bridge. Along with the aluminum and steel truss options, precast concrete beams similar to the existing bridge can be used to support a pedestrian pathway. Precast concrete beams are readily available and are likely to be less costly compared to the steel and aluminum truss options. Because the same materials and structural elements are used, the precast concrete beams may be more harmonious with the existing bridge and pathway. Any option of attaching a bike/pedestrian structure to the existing SH-55 Bridge should consider the remaining service life of the existing bridge. The new bike/pedestrian bridge may likely be limited to a remaining service life of 34 years, at which time the existing SH-55 Bridge along with the newly built bike/pedestrian bridge would be replaced. Concrete Beams Attached to Existing Bridge Option, looking southeast Before photo (left) After rendering (right)

14 Other Options Explored 11 Concrete Beams Attached to Existing Bridge Option, looking under the west side of the bridge Before photo (left) After rendering (right) Three Span Steel Truss Attached to Existing Bridge West side of SH-55 bridge, north abutment (June 2015) A preliminary analysis indicates that the foundation type and substructure type for a steel truss bridge would be similar to that of an aluminum bridge. The length of a single steel pile would be greater than what would be required for an aluminum structure. However, the cost for the additional pile length may not be substantial. A steel truss bridge may be a more cost effective bridge compared to an aluminum bridge. A steel truss bridge tends to be less costly compared to aluminum. A steel superstructure is also more resistant to corrosion compared to aluminum. However, the steel structure is heavier and imparts greater load at the supports. This can increase the cost of the foundation and substructure. If a truss type structure attached to the existing bridge is desired, an overall cost comparison between an aluminum and steel bridge should be developed to determine the most cost effective truss option to attach to the existing bridge.

15 Other Options Explored 12 Steel Truss Clear-Span Bridge A separate steel truss bridge clear spanning the Boise River on the west side of SH-55 may be a feasible option. This would consist of a 240-foot-long single-span, 14 foot-tall steel truss bridge, which would not be attached or supported by the existing SH-55 Bridge. Some benefits of clear spanning the River with a detached steel truss bridge include: A minimum 75 year design life can be achieved by keeping the new bridge Steel Truss Clear-Span Bridge Detached from Existing Bridge Option, independent of the existing looking southeast After rendering SH-55 Bridge. In the future, when the SH-55 Bridge is replaced, the bike/pedestrian bridge would remain. A clear span structure eliminates and or minimizes any adverse impacts on the current and the future SH-55 Bridge. Namely, a clear span bike/pedestrian structure eliminates the risk of increasing scour of the existing or future bridge foundations. Furthermore, the clear span structure minimizes impacts to the environment. Additional Considerations An aluminum bridge deck may not be desirable if it propagates sharp sounds from bike and pedestrian use. The issues of deck noise from bicyclists and pedestrians should be considered. Steel Truss Clear-Span Bridge Detached from A concrete deck may be the most durable and Existing Bridge Option, looking under the west side of quiet deck type for this application. A wood deck the bridge - After rendering may not be desirable from a durability and maintenance aspect. A single span truss bridge, regardless of the materials being used, will require a truss that is approximately 14 feet tall. This height would extend above the existing traffic barrier by approximately six feet.

16 Other Options Explored 13 The visual appearance of aluminum, steel, and concrete should be considered in the context of the bridge site. Shiny metallic materials may not be desirable in a pathway setting. Weathered steel, which develops a reddish patina may be more desirable. It has the added benefit of being relatively maintenance free as painting is not required. Precast concrete beams may be more visually harmonious with the existing bridge. A bridge with a pathway width of 12 feet provides greater safety for bicyclists and pedestrians. This would moderately increase the cost of the bridge, but should not significantly change any environmental impacts compared to a bridge with a 10-foot-wide pathway. Option 1 with precast concrete beams, will be less costly to increase the pathway from a 10 ft. wide to a 12 ft. wide pathway, compared to the singles span steel truss option.

17 Funding Options 14 Funding Options It is the City s intent, in partnership with COMPASS, to apply for federal and/or state funding sources to fund the design and construction of the Bridge and associated pathway connections. Potential funding sources include but are not limited to: SURFACE TRANSPORTATION PROGRAM-TRANSPORTATION MANAGEMENT AREAS-TRANSPORTATION ALTERNATIVES PROGRAM (STP-TMA-TAP): this funding source is managed by COMPASS. Funds could be used for design and construction of the bike/pedestrian bridge. A local match of 7.34 percent would be required. TRANSPORTATION ALTERNATIVES PROGRAM (TAP): this funding source is managed by ITD. Funds could be used for design and construction of the bike/pedestrian bridge. A local match of 7.34 percent would be required. RECREATIONAL TRAILS PROGRAM (RTP): this funding source is managed by Idaho Department of Parks and Recreation (IDPR). Funds could be used for trailhead improvements, trail connections, abutments, shared costs, etc. A local match of 20 percent would be required. LAND AND WATER CONSERVATION FUND (LWCF): this funding source is managed by IDPR. Funds could be used for planning, acquisition and development of needed land and water areas and facilities. A local match of 50 percent would be required. Partnerships, donations, and local matching dollars are also possibilities for leveraging grant funds.

18 Summary 15 Summary All bike/pedestrian bridge options involving attachment to the existing SH-55 Bridge would require extending the existing concrete bridge abutments and piers and require additional steel piles. All bike/pedestrian bridge options involving attachment to the existing SH-55 Bridge would likely have a service life of 34 years (same as the remaining service life of the original SH-55 Bridge). Precast concrete beams similar to the existing bridge beams should be used to widen the existing bridge for a bike/pedestrian path. This would likely be comparable to the cost of other options that attach to the existing bridge. An agreement between the City and ITD should be investigated to determine how this option would be funded along with how the future bike/pedestrian path would be funded once the entire bridge is replaced. An example might be that the City provides the funding to construct the widening for the bike/pedestrian pathway in the near future, followed by ITD funding the future replacement of the entire bridge to include the bike/pedestrian pathway once the service life has been reached for the SH-55 Bridge, or when the bridge is replaced. Clear spanning the North Channel of the Boise River with a 240-foot-long single-span steel truss bridge would maintain a 75-year service life and would eliminate and or minimize impacts to the existing SH-55 Bridge. Ownership and Maintenance As part of the project implementation process, the City and ITD will need to communicate and agree on responsibilities for maintenance of the pedestrian bridge. Cost Considerations Based on planning-level cost estimates, it is anticipated that the precast concrete option (Option 1) would be approximately $200,000 less expensive compared to the single span steel truss option (Option 3). If it is decided that a 12 foot wide pathway is desired, Option 1 consisting of three relatively short spans would have a significantly smaller increase in cost compared to Option 3 which is a single long span. Shorter span bridges are exponentially more effective in resisting loads resulting in significantly less expensive superstructures. Therefore, the cost is less sensitive to widening for shorter span bridges compared to longer span bridges; thus Option 1 would be better suited to consider widening the pathway from a 10 foot wide to a 12 foot wide pathway than Option 3.

19 Recommendation 16 Recommendation J-U-B recommends that Option 1, precast concrete beams with supports located at the same locations as the existing bridge, be advanced into the project development phase. Furthermore, we recommend that the recommendation be confirmed by updating the cost comparison of the two options (Option 1 and Option 3) by quantifying costs associated with pathway approaches, environmental and other non-bridge specific costs. A 10 foot wide pathway on the bridge is the minimum recommended width. However, for a shared use facility, which could see significant use, a bridge with a 12 foot wide path should be considered in the cost estimate for the recommended option. Next Steps Next steps to be completed in the project development phase (Phase 3) include: Confirm total project costs for the two options to include those costs not related to the bridge structure type such as environmental and bridge pathway approach costs. It is anticipated that incorporating these costs will not change the recommendation. However, for purposes of evaluating options in a complete fashion, we recommend that the total anticipated project costs be quantified. Begin project development on the recommended (preferred) option. Pursue the funding applications for the recommended option.

20 Agencies and Other Parties Consulted 17 Agencies and Other Parties Consulted Agencies COMPASS Don Matson Principal Planner, Transportation ITD Aaron Bauges District III Project Manager Sabrina Minshall Director of Planning Mary Ann Waldinger Principal Planner, Modeling City of Eagle Mike Aho Director, Parks & Recreation , Ext 214 Steve Noyes Trails Coordinator, Parks & Recreation Mike Ebright, P.E. Group III Design Leader, Bridge Section Matt Farrar, P.E. Chief Bridge Engineer Trii Buu, P.E. Construction and Materials Greg Vitley ITD District III Environmental Planning Nichoel Baird-Spencer, AICP Planner III, Planning and Zoning , Ext 211 Other Involved Parties MAADI Group Inc. Alex de la Chevrotiere President Ext: 225 Provided weight of aluminum bridges for 8 feet and 10 feet wide pathway. Rick Tholen Two Rivers; Walk and Ride Eagle, LLC f4ister@gmail.com Initiated the project in the initial/early project stages (aluminum bridge concept)