Coyote Creek Restoration Project

COPYRIGHT 2015 BY CH2M HILL, INC. COMPANY CONFIDENTIAL

P re l im ina ry Eng inee r i ng S tudy

Coyote Creek Restoration Project

Prepared for City of San Jose

Department of Parks Recreation and Neighborhood Services

Public Works September 2015

1737 N 1st St, Suite 300

San Jose, California United States, 95112

COPYRIGHT 2015 BY CH2M HILL, INC. COMPANY CONFIDENTIAL 2

Coyo te Creek Res to ra t i on P ro jec t

Prepared for City of San José

September 2015


Executive Summary

The City of San José (City), in cooperation with the Santa Clara Valley Water District (District), is proposing to remove the existing Singleton Road low‐water crossing at Coyote Creek. The purpose of this study is to identify and evaluate different concepts for replacing the existing low‐water crossing, restoring the creek, and defining a preferred replacement bridge alignment.

The Coyote Creek – Singleton Road Fish Barrier, Stream Restoration, and Pedestrian Bridge Project (Project) has two core objectives; 1) barrier removal and creek restoration, and 2) construction of a replacement pedestrian bridge. The District is championing the barrier removal and restoration work. The City seeks to complete that work in conjunction with construction of a pedestrian bridge to ensure continuity of the regional Coyote Creek Trail system.

Removal of the fish barrier and restoration of Coyote Creek would provide opportunities for protected and endangered aquatic species to migrate upstream to better spawning areas. The existing low‐water crossing is a complete fish passage barrier under most hydraulic conditions. It is highly unlikely that a fish would be able to jump over the low‐water crossing or attempt to jump into a storm drain culvert to migrate upstream. There are no found records of the existing crossing’s construction. This study presumes that it was built as an access road to the former landfill west of the creek. As a part of this study, different approaches for how to re‐establish the steam bed and natural stream channel after this barrier is removed were evaluated. Two of these approaches are presented in Section 3.

The Coyote Creek Trail is partially developed as one of the City network’s longest trail systems, ultimately extending from the San Francisco Bay to the City’s southern boundary. The regional system extends beyond the City’s boundaries with reaches within the County’s jurisdiction. The existing low‐water crossing limits public passage during high water events. The existing trail system is currently approximately 17 miles long between Tully Road and Anderson Dam.

Upstream of the fish barrier, the trail is located on the west side of the creek. The trail crosses the creek using the low‐water crossing that is an extension of Singleton Road and continues downstream on the east side of the creek. The trail within the vicinity of the project does not meet current American Disabilities Act (ADA) standards. The City desires to maintain this trail link by modifying the trail to meet Class I standards and to provide a pedestrian bridge structure that will span the creek and not impede 100‐year flood flows.

The City, the District, and the resource agencies developed the design criteria to evaluate several different bridge crossing alternatives. Brief descriptions of the developed alignment and bridge concepts are presented in Sections 2 and 6, respectively.

Detailed analysis of each of the proposed bridge concepts is presented in Section 13. The preferred concept is also described in Section 13. This concept would minimize the environmental impacts of the project, while maintaining the flood capacity of the creek and continuous trail access. It can also be implemented in the shortest amount of time, to allow for creek restoration most quickly. The preferred pedestrian bridge concept would span the creek from the landfill top of bank on the west to the top of bank along Tuers Road, above the 100‐year water surface, in the approximate vicinity of the existing low‐water crossing. This alternative would minimize the amount of native riparian vegetation disturbed during construction and maintain the hydraulic capacity in the creek. After the pedestrian structure is installed and the fish barrier is removed, the stream can be restored by creating a pilot channel for the stream to re‐establish naturally over time. Other alternative bridge/trail alignments were considered but not preferred, because they would either cause greater disturbance to the creek, would cause greater disturbance to the vegetation and shaded canopy within the riparian corridor, would be more difficult to construct, or are estimated to be more expensive to construct.


This report concludes that it is feasible to return the reach of Coyote Creek adjacent to the crossing to its natural form while minimizing impacts within the riparian corridor. The recommended approach is to restore the channel by removing the barrier and construction of a pilot channel to encourage the channel to naturally mobilize and redistribute the accumulated sediment. To restore access for Coyote Creek Trail, a pre‐manufactured steel truss bridge is recommended to be constructed with an alignment within the footprint of the existing low‐water crossing.

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Contents Section Page

Executive Summary ................................................................................................................................... 3

Acronyms and Abbreviations .................................................................................................................... vii

Introduction and Project Background ......................................................................................... 1‐1 1.1 Introduction ........................................................................................................................... 1‐1 1.2 Project Description and Background ..................................................................................... 1‐1

Alignment Concept Development ............................................................................................... 2‐1 2.1 Background ............................................................................................................................ 2‐1

2.1.1 Environmental Criteria .............................................................................................. 2‐1 2.1.2 Hydraulic and Drainage Criteria ................................................................................ 2‐1 2.1.3 Trail Alignment Criteria ............................................................................................. 2‐1 2.1.4 Structure and Foundation Design Criteria ................................................................ 2‐2 2.1.5 Other ......................................................................................................................... 2‐2

2.2 Initial Three Alignment Concepts .......................................................................................... 2‐2 2.3 Refinement of Trail Alignments ............................................................................................. 2‐3 2.4 Select Preferred Trail Alignment Concepts ............................................................................ 2‐3 2.5 Description of Selected Conceptual Alternative Alignments ................................................. 2‐4

2.5.1 Alternative 2 ............................................................................................................. 2‐4 2.5.2 Alternative 5A ........................................................................................................... 2‐4

Fish Barrier Removal and Stream Restoration ............................................................................. 3‐1 3.1 Background ............................................................................................................................ 3‐1 3.2 Geomorphic Assessment and Channel Restoration Alternatives .......................................... 3‐1

3.2.1 Alternative A: Crossing Removal and Stream Simulation with Pilot Channel Excavation ................................................................................................................. 3‐2

3.2.2 Alternative B: Crossing Removal and Installing Roughened Channel ....................... 3‐2

Hydraulic Assessment ................................................................................................................. 4‐1

Environmental Clearance and Permit Requirements ................................................................... 5‐1 5.1 California Environmental Quality Act Clearance ................................................................... 5‐1 5.2 Permitting Requirements ....................................................................................................... 5‐1

5.2.1 Local Permits ............................................................................................................. 5‐1 5.2.2 State Permits ............................................................................................................. 5‐1 5.2.3 Federal Permits ......................................................................................................... 5‐2 5.2.4 Santa Clara Valley Habitat Conservation Plan .......................................................... 5‐2

Bridge Structure Types and Geotechnical Foundation Evaluation ................................................ 6‐1 6.1 Bridge Geometry and Location .............................................................................................. 6‐1 6.2 Bridge Type Selection ............................................................................................................ 6‐1 6.3 Foundations ........................................................................................................................... 6‐1 6.4 Substructure .......................................................................................................................... 6‐2 6.5 Bridge Deck ............................................................................................................................ 6‐2 6.6 Hydraulic Impacts and Scour Protective Measures ............................................................... 6‐2 6.7 Utilities ................................................................................................................................... 6‐2 6.8 Bridge Aesthetics ................................................................................................................... 6‐2 6.9 Bridge Alternatives ................................................................................................................ 6‐3

CONTENTS, CONTINUED

Section Page

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6.9.1 Alternative 2 Three‐Span Bridge ............................................................................... 6‐3 6.9.2 Alternative 5A Clear‐Span Bridge .............................................................................. 6‐3 6.9.3 Alternative 5A Three‐Span Bridge ............................................................................. 6‐3

Constructability Considerations .................................................................................................. 7‐1

Right‐of‐Way Requirements ........................................................................................................ 8‐1

Utility Requirements ................................................................................................................... 9‐1

Surface Improvements at Tuers Road ....................................................................................... 10‐1 10.1 Future Roadway Improvements ........................................................................................... 10‐1 10.2 Trailhead Connection at Surface Street ............................................................................... 10‐1

Estimate of Project Costs .......................................................................................................... 11‐1

Project Implementation Schedule ............................................................................................. 12‐1

Evaluation of Alternatives and Recommendations ...................................................................... 13‐1 13.1 Stream Restoration Evaluation ............................................................................................. 13‐1

13.1.1 Alternative A: Crossing Removal and Stream Simulation with Pilot Channel Excavation ............................................................................................................... 13‐1

13.1.2 Alternative B: Crossing Removal and Installation of Roughened Channel .............. 13‐2 13.2 Steam Restoration Recommendations ................................................................................. 13‐2 13.3 Trail Alignment Evaluation ................................................................................................... 13‐2

13.3.1 Alternative 2 ............................................................................................................ 13‐2 13.3.2 Alternative 5A .......................................................................................................... 13‐3

13.4 Trail Alignment Recommendations ...................................................................................... 13‐4

Appendixes

A Civil/Structural Design Criteria and Refined Conceptual Drawings B Preliminary Geomorphic and Hydraulic Assessment and Channel Restoration Recommendations C Initial Environmental Assessment D Landscape Design Criteria Memo and Conceptual Graphics E Revised Draft Report Preliminary Geotechnical Evaluation F Meeting Minutes G Cost Estimates H County of Santa Clara Assessor’s Maps

Tables

Table 5‐1 Permitting Requirements Matrix .............................................................................................. 5‐3

Table 8‐1 Property Owners for Alternative 2 ........................................................................................... 8‐1

Table 8‐2 Property Owners for Alternative 5A ......................................................................................... 8‐1

Table 9‐1 Utility Matrix ........................................................................................................................... 9‐1

Table 11‐1 Cost Summary for Crossing Removal and Stream Restoration Only ...................................... 11‐1

Table 11‐2 Cost Summary for Bridge and Trail Improvements Only ....................................................... 11‐1

Table 11‐3 Total Project Cost ................................................................................................................. 11‐1

CONTENTS, CONTINUED

Section Page

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Figures

1‐1 Project Location Map ........................................................................................................................ 1‐3

1‐2: Site Map .......................................................................................................................................... 1‐4

1‐3 Creek Pictures ................................................................................................................................... 1‐7

2‐1 Alternative 2 ..................................................................................................................................... 2‐5

2‐2 Alternative 5A ................................................................................................................................... 2‐6

6‐1 Singleton Road Pedestrian Bridge General Plan Alternative 2 ............................................................ 6‐4

6‐2 Singleton Road Pedestrian Bridge General Plan Alternative 5A Clear Span ........................................ 6‐5

6‐3 Singleton Road Pedestrian Bridge General Plan Alternative 5A Three Span ....................................... 6‐6

9‐1: Existing Utilities Map ....................................................................................................................... 9‐3

12‐1 Project Implementation Schedule ................................................................................................. 12‐2

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Acronyms and Abbreviations ADA American Disability Act BFE base flood elevation CEQA California Environmental Quality Act City City of San José CIDH cast‐in‐drilled‐hole CCCST Central California Coast Steelhead Trout CDFW California Department of Fish and Wildlife District Santa Clara Valley Water District DOT Department of Transportation EPA U.S. Environmental Protection Agency ESM engineered streambed mix FEMA Federal Emergency Management Agency NMFS National Marine Fisheries Service OHW ordinary high water PG&E Pacific Gas and Electric Company Project Coyote Creek – Singleton Road Fish Barrier, Stream Restoration, and Pedestrian Bridge

Project psf pound per square foot RWQCB Regional Water Quality Control Board SCVWRPC Santa Clara Valley Water Resources and Protection Collaborative Study Preliminary Engineering Study TAC technical advisory committee USACE U.S. Army Corps of Engineers USFWS U.S. Fish and Wildlife Services

SECTION 1

1-1 COPYRIGHT 2015 BY CH2M HILL, INC. COMPANY CONFIDENTIAL

1 Introduction and Project Background 1.1 Introduction The City of San José (City), in cooperation with the Santa Clara Valley Water District (District), is proposing to remove the existing Singleton Road low‐water crossing at Coyote Creek. The existing low‐water crossing of Coyote Creek at Singleton Road is a significant obstruction to fish passage upstream to spawning areas. The low water crossing also serves as a segment of the Coyote Creek Trail which is planned and partially developed as one of the City network’s longest trail systems, ultimately extending from the San Francisco Bay to the City’s southern boundary. The regional system extends beyond the City’s Boundaries. It is one of the most popular trails in the area but during high water events, this low‐water crossing limits public passage.

The Coyote Creek – Singleton Road Fish Barrier, Stream Restoration, and Pedestrian Bridge Project (Project) has two core objectives; 1.) barrier removal and creek restoration, and 2.) construction of a pedestrian bridge. The City and District is championing the project. The City also champions preservation of a continuous trail alignment with construction of a pedestrian bridge to ensure continuity of the regional Coyote Creek Trail system.

The purpose of this study is to identify and evaluate different concepts for replacing the existing low‐water crossing, restoring the creek, and defining a preferred trail/bridge alignment.

1.2 Project Description and Background The Project site is located in south San José, southeast of downtown and the Los Lagos Golf Course along Coyote Creek, between Capital Expressway and Yerba Buena Road. Access to the site from the west is from Senter Road via Singleton Road and from Tuers Road from the east. This segment of Coyote Creek is located within City Council District 7, as shown on Figure 1‐1. The Project includes developing a fish obstruction removal plan for the existing low‐water crossing and other nearby obstructions, an associated creek restoration plan, and preliminary engineering for a new pedestrian bridge that would generally align with Singleton Road and include connecting ramps to the existing trail system and a new gateway at Tuers Road (see Figure 1‐2).

The existing trail along Coyote Creek follows the west side of the creek, south of Yerba Buena Road. The trail continues north past the closed Singleton Road Landfill and then shifts to the east bank of Coyote Creek, south of Capital Expressway, via the Singleton Road low‐water crossing. The low‐water crossing is believed to be a remnant from the former land fill operation and was not originally developed as part of the City trail system. Both the west and east creek banks are heavily wooded. Re‐construction of the trail alignment to be exclusively on either the east side or west side of Coyote Creek, between Capital Expressway and Yerba Buena Road, is not considered a viable option at this time. Re‐aligning the trail and extending the trail inside the banks of Coyote Creek would result in large‐scale disruption of native trees and vegetation that provide canopy over Coyote Creek. Realignment would also require construction of new ramp structures and trail connections resulting in greater amount of earthwork and require modifications to existing bridges on either Capital Expressway or Yerba Buena Road to add a class 1 bike lane. Both of these vehicular bridges have high volumes of traffic that would likely be affected during construction of the bridge modifications. The proposed pedestrian bridge crossing location results in less earthwork, less impacts to shaded canopy, less impacts to the creek, and less mitigation and therefore it is less expensive than eliminating this crossing and shifting to a vehicular bridge. Therefore, the focus of the replacement structure is to develop and evaluate concepts in the vicinity of the existing crossing to minimize impacts to the riparian corridor.

SECTION 1 INTRODUCTION AND PROJECT BACKGROUND


The low‐water crossing spans Coyote Creek approximately 1,000 feet upstream of Capitol Expressway. This section of creek is characterized primarily by the low‐flow channel with a raised terrace and moderately steep‐sloped banks to the east and west. The width of the creek between top of bank at Tuers Road and top of landfill at Singleton Road is approximately 400 feet wide at the proposed crossing location. The ordinary high water (OHW) mark of the active flow channel in the Project area is approximately 60 feet wide with an average depth of 5 feet.

The existing low‐water crossing is an obstruction to fish passage upstream to spawning areas. The structure is constructed of one 36‐ and one 48‐inch‐diameter culvert and a Portland Cement Concrete base and asphalt concrete surface road. It is 40 feet wide and spans the entire width of the sediment transport channel. The streambed has degraded over time and the downstream inverts of the culverts are approximately 2.7 feet above the bottom of the creek at elevation 129.4 feet while the top of the roadway is at elevation 135.6 feet. The height of the structure is too high to allow for fish passage, even during normal storm events. It is highly unlikely that a fish would jump higher than 2 feet or jump into a storm drain culvert for fish passage. (see Figure 1‐3).

A closed landfill site exists along the west bank of the creek, on both the north and south sides of Singleton Road. Within the project limits, both the Coyote Creek trail and Singleton Road are asphalt‐concrete paved. North of Singleton Road and between the landfill and Coyote Creek, a gravel maintenance road exists near the toe of slope running adjacent to the channel.

A field topographic survey of the Project site was completed on February 6, 2015, and base mapping was developed for this Study. The survey included identifying the width and length of the paved surface for the low‐water crossing, size and location of the culverts; rock slope protection above and below the low‐water crossing; width of active channel at the time of the survey; location of trees and vegetation in the vicinity of the crossing; maintenance road and trail connections; street curb, gutter, and sidewalk along Tuers Road; existing ground grade breaks; visible utility structures and site contours of the landfill and creek banks. The survey does not include cross sections of the creek, which would be completed during final design phase.

A list of the civil and structural design criteria used to develop and evaluate the trail alignment concepts is included in Appendix A.

Some of the significant trail design criteria are:

Class I bikeway,

16‐feet wide with 12‐feet asphalt‐paved width, and

2‐feet aggregate base shoulders on each side.

The pedestrian bridge would be designed for:

90 pound per square foot (psf) of pedestrian loading,

AASHTO H‐10 truck live load to allow for small maintenance vehicle access (pickup truck only),

self‐weight dead load, and

12 feet bridge deck width with permitted intrusion for handrails.

The bridge type would likely be a pre‐manufactured steel truss‐type with weathered steel, and the deck would be cast‐in place concrete. The creek’s dense riparian tree cover and no direct views from surrounding neighborhoods warrants a non‐custom design solution.

Figure 1-2SITE MAP

1 OF 3COYOTE CREEK - SINGLETONROAD FISH BARRIER, STREAM

RESTORATION AND PEDESTRIANBRIDGE PROJECT DRAFT

PRELIMINARY ENGINEERINGSTUDY

Figure 1-2 SITE MAP

2 OF 3COYOTE CREEK - SINGLETON ROAD FISH BARRIER, STREAM

RESTORATION AND PEDESTRIAN

BRIDGE PROJECT DRAFT PRELIMINARY ENGINEERING

STUDY

Figure 1-2 SITE MAP

3 OF 3COYOTE CREEK - SINGLETONROAD FISH BARRIER, STREAM

RESTORATION AND PEDESTRIANBRIDGE PROJECT DRAFT

PRELIMINARY ENGINEERINGSTUDY

Figure 1-3

COYOTE CREEK – SINGLETON ROAD FISH BARRIER, STREAM RESTORATION AND PEDESTRIAN BRIDGE PROJECT DRAFT PRELIMINARY ENGINEERING STUDY

SECTION 2


2 Alignment Concept Development 2.1 Background The Project is of high interest to multiple regulatory agencies and jurisdictions and has two core objectives; 1.) barrier removal and creek restoration, and 2.) construction of a pedestrian bridge. The District is championing the barrier removal and restoration work. The City seeks to complete that work in conjunction with construction of a pedestrian bridge to ensure continuity of the regional Coyote Creek Trail system. The City established a technical advisory committee (TAC) to develop evaluation criteria and solicit feedback to make critical decisions. The TAC includes representatives from:

Santa Clara Valley Water District (District),

National Marine Fisheries Service (NMFS),

United States Fish and Wildlife Services (USFWS),

California Department of Fish and Wildlife (CDFW),

U.S. Environmental Protection Agency (EPA),

United States Army Corps of Engineers (USACE), and

City’s Emergency Response agencies, such as Fire and Police Departments.

Based on input from the TAC, the following evaluation criteria were used to develop and evaluate each alternative:

2.1.1 Environmental Criteria Reduce impacts to the existing riparian corridor by keeping the project footprint in the disturbed area of

the existing low‐water crossing and open riparian areas with low forest canopy density and small‐diameter riparian trees.

Avoid removal of shaded canopy near the active channel.

Avoid removal of large‐diameter, native trees and minimize native understory vegetation removal.

2.1.2 Hydraulic and Drainage Criteria Meet District minimum freeboard requirements to pass the 100‐year storm event beneath the new

structure.

Avoid placing fill within the creek that may reduce the conveyance area and raise the water surface.

Provide a clear span over the Ordinary High Water (OHW), to the extent possible.

Maintain existing drainage patterns.

2.1.3 Trail Alignment Criteria Provide a standard Class 1 trail with maximum of 5 percent grade and minimum vertical clearance of

10 feet.

Minimize grading activities of the existing slopes and especially avoid excavation into the landfill materials.

Maintain all existing trail connections and maintenance road access connections.

SECTION 2 ALIGNMENT CONCEPT DEVELOPMENT


Avoid conflicts with overhead and underground utilities that may require costly and time consuming relocations to the extent possible.

Utilize as much of the existing trail system and maintenance road as possible.

2.1.4 Structure and Foundation Design Criteria Install bridge abutments and piers outside of the OHW mark.

Install bridge abutment outside the limits of landfill, if possible.

Provide perpendicular crossing of the creek and clear sight distance from City streets.

Provide adequate bridge width and reduce angle points in the bridge to allow small maintenance vehicles access across the bridge (pickup trucks).

2.1.5 Other Locate gateway pavement ideally to make use of legal intersection crossings, rather than require

connecting sidewalks or other improvements to lead trail users.

Avoid construction of concrete vertical walls and other flat surfaces subject to graffiti.

Include design enhancements to complement the existing gateways along Coyote Creek Trail.

The Preliminary Engineering Report includes developing and evaluating two trail alignments and three bridge types for the selected study alignments.

2.2 Initial Three Alignment Concepts The initial three alignment concepts were developed. All three concepts included connections to the existing trail system on the west bank at the corner of the landfill and at the trailhead at the Tuers Road and Brandybuck Way intersection. The initial alignment concepts were developed to:

minimize impacts to the native vegetation and canopy along Coyote Creek,

use existing contours and grading to minimize earthwork requirements,

meet Class I trail standards,

meet vertical clearance requirements for maintenance vehicles, and

meet District minimum freeboard requirements to pass the 100‐year storm event.

Alternative 1 provides a direct bridge connection on a skewed angle between the intersection of Singleton Road and Coyote Creek Trail on the west bank and the proposed trailhead at Tuers Road and Brandybuck Way on the east bank. This bridge alignment would cut through native riparian vegetation on the east bank and be approximately 360 long.

Alternative 2 proposes the bridge to be perpendicular to the stream crossing located in the approximate footprint of the existing paved low‐water crossing. This bridge alignment would connect the top of the landfill slope on the west with the top of bank at Tuers road on the east bank and require construction of a trail along the top of bank on the west side of Tuers Road. The approximate bridge length is 285 feet.

Alternative 3 is a hybrid of Alternatives 1 and 2. This would be a two‐span structure with one span perpendicular to the creek flow in the approximate location of the existing low‐water crossing and a second span with an angle point connecting the first span to the proposed trailhead location. The center pier is located outside the OHW channel and would be larger and have an angle point in the structure. This bridge



alignment has a total bridge length of approximately 345 feet and would have a more complicated pier construction and connection. All three initial alignment concepts are included in Appendix F.

2.3 Refinement of Trail Alignments Extensive constructive feedback on the initial three alignment concepts was provided by the Technical Advisory Committee (TAC). It was generally determined that Alternative 2 trail alignment was preferred because it most closely aligns within the existing low‐water crossing footprint and has minimal environmental impact on the riparian area. It also provides the most direct access across the creek with minimal removal of mature canopy near the bottom of the creek. Alternative 1 requires removing native vegetation and mature canopy near the water’s edge. Removal of native plant material is contrary to the project’s primary objective of creek restoration. Alternative 3 would be more difficult and expensive to construct. Higher cost might slow project development and the City seeks to advance work as early as possible. There was also a concern about maintenance vehicles being unable to navigate the turn on the bridge at the angle point without significantly widening the bridge beyond 12 feet. None of the three alternatives provides adequate vertical clearance between the proposed pedestrian bridge trail surface and the overhead telephone and electric lines. Since there was a preference to avoid PG&E relocations that may affect the overall schedule, additional design concepts that would avoid the need for relocation of overhead utilities were developed. Three additional alternatives were prepared: Alternative 4, Alternative 5A, and Alternative 5B. Conceptual drawings, including a plan view, cross section of the creek, and profile for the bridge were developed for each of these alternatives. Figures for each of these alternatives are included in Appendix A.

Alternative 4 would provide a perpendicular stream crossing similar to Alternative 2, but would be placed just downstream of the low‐water connecting the northwestern landfill abutment to Tuers Road. To avoid the conflict between the proposed bridge structure and overhead utility relocation, this trail alignment requires constructing a levee condition across Singleton Road to connect to the existing trail system located on the west side of the creek. This levee condition would eliminate access to Singleton Road and cause significant drainage problems unless the width of Singleton Road is regraded and filled as much as 200 feet away. The abutment and bridge piers for Alternative 4 may also be in conflict with existing underground utilities.

Alternative 5 would maintain all trail and maintenance road connections at Singleton Road while maintaining the maximum grades of five percent required for a Class I trail; however, this alternative would shift the new bridge crossing as much as 250 feet downstream. The alignment for Alternative 5 crossing of Coyote Creek would avoid the overhead and underground utilities and would be a shorter bridge span but it would require removing more mature vegetation and canopy near the water’s edge. Two options were developed for this trail alignment (Alternatives 5A and 5B). One alignment places the west abutment outside the footprint of the existing landfill inside the creek bank and the other one locates the abutment inside the landfill prism, which would require special pile considerations. The west abutment of Alternative 5A is proposed to be on top of the existing landfill with piles driven through the landfill and spans over the existing maintenance trail along the west side of the creek. This trail alignment provides all connections and avoids placement of fill inside the creek bank that could reduce the conveyance capacity of the creek. The west abutment of Alternative 5B is proposed to be placed on embankment fill outside the toe of the existing landfill and existing maintenance road. This alignment avoids impacts to the landfill but requires placing fill inside the creek and removing vegetation along approximately 500 feet of the west bank of the creek. Alternative 5B requires removing of valuable habitat and mature canopy near the OHW channel and potentially impacts the conveyance of the creek.

2.4 Select Preferred Trail Alignment Concepts After further evaluation of Alternatives 2, 4, 5A, and 5B, Alternative 4 was ruled out because it posed additional drainage and levee challenges to the project and would likely require underground utility



relocations that can be more expensive and time consuming than overhead utility relocations. Although Alternative 5 would avoid all utility relocations, there would be more impacts to existing vegetation along the riparian corridor. Alternative 5A would require temporary removal of vegetation in the footprint of the bridge, while Alternative 5B would require both temporary and permanent impacts to the riparian vegetation that resource agencies would find objectionable. Therefore, there were too many disadvantages with Alternative 4 and Alternative 5B and they were dropped from further consideration. The preferred trail alignments are Alternative 2 and Alternative 5A. Both are presented in the Bridge Type Selection Report. An order of magnitude cost for the relocation of overhead utilities will be included in the analysis for Alternative 2 and the additional foundation costs for the abutment piers located in the landfill will be included in Alternative 5A analysis.

2.5 Description of Selected Conceptual Alternative Alignments

As a result of the concept development and review process, the following two alignment alternatives were selected for further evaluation. Following is a brief description of the two selected trail alignment concepts. The evaluation of these concepts is included in the following sections of the report.

2.5.1 Alternative 2 Alternative 2 proposes a 280‐foot bridge to be perpendicular to the stream crossing and would be located in the approximate footprint of the existing paved low‐water crossing. To the east, the bridge would connect to a trail at the top of the east bank that would be parallel to Tuers Road and continues north to the intersection of Tuers Road and Brandybuck Way. To the west, the bridge would sit on the top of the landfill south of Singleton Road. The bridge would connect to a trail that extends southeast to the existing Coyote Creek Trail and to a maintenance road that extends southwest to existing Singleton Road. The existing maintenance road and Singleton Road on the west bank would remain (see Figure 2‐1).

2.5.2 Alternative 5A Alternative 5A proposes a 260‐foot bridge to be perpendicular to the stream crossing and would be located approximately 300 feet downstream of the existing paved low‐water crossing. To the east, the bridge would connect to the proposed trailhead at the intersection of Tuers Road and Brandybuck Way. To the west, the bridge abutment would be placed along the top of the landfill north of Singleton Road. The bridge would connect to a trail that extends south along the contours of the existing landfill and conforms to Singleton Road south of the low‐water crossing. The existing trail south of Singleton Road would be modified to meet the maximum slopes of five percent for a Class I trail. The existing maintenance road would be maintained north of the low‐water crossing at Singleton Road (see Figure 2‐2).

SECTION 3


3 Fish Barrier Removal and Stream Restoration 3.1 Background The City seeks to remove the existing culverts and low‐water crossing at Singleton Road across Coyote Creek. This low‐water feature has been identified as a significant migration barrier for Central California Coast Steelhead Trout (CCCST) in Coyote Creek. The proposed stream restoration and alternative trail crossing must comply with current fish passage design criteria (see Attachment A of Civil/ Structural Design Criteria in Appendix B for the fish passage and hydraulic design criteria).

The low‐water crossing consists of two approximately 65‐foot‐long corrugated metal pipe culverts that cross under the road surface. The culvert outfalls are perched above the bed. During moderate to high flows, water flows over the low‐water crossing, then plunges into a large pool, forming an approximately 2‐foot‐high hydraulic jump. Both culverts are in disrepair, both outfalls are largely rusted through, and both culvert entrances are bent. The culverts’ capacity has diminished over the years. Previous studies report that Singleton Road is a barrier for fish migration. The vertical height is too high, there is insufficient pool depth, and the minimum velocities are too high for fish passage (see Appendix B for additional discussion).

A roughly 2.7‐foot jump in the long profile occurs at Singleton Road. The estimated drop has been measured between the culvert invert at the upstream edge of the low‐water crossing and the elevation of the plunge pool downstream of the existing low‐water crossing.

In this section, a brief summary of The Technical Memorandum: Coyote Creek – Singleton Road Fish Barrier, Stream Restoration, and Pedestrian Bridge: Preliminary Geomorphic and Hydraulic Assessment and Channel Restoration Recommendations is presented. The technical memorandum describes the geomorphic assessment and channel restoration approach in more detail (see Appendix B).

3.2 Geomorphic Assessment and Channel Restoration Alternatives

The City plans to remove the current Singleton Road low‐water crossing structure, restore the bed and banks for Coyote Creek, and replace the existing trail crossing with a pedestrian bridge to provide continuous trail access along the Coyote Creek stream corridor. The overarching habitat goals are as follows:

Protect or improve habitat for CCCST, a special status species, by removing this critical barrier.

Restore and protect riparian corridor by removing the antiquated low‐water crossing.

Additional channel restoration goals include the following:

Enhance existing reach conditions to provide additional geomorphic and ecological functions that extend habitat for aquatic and terrestrial wildlife species, to the extent possible.

Minimize in‐channel impacts and disturbances affecting aquatic species including CCCST, Pacific Lamprey and rainbow trout, and maximize both CCCST passage and habitat potential for other life stages.

Field reconnaissance suggests that there are two potential appropriate approaches to stream restoration and fish passage design in keeping with CDFW’s Fish Passage Manual (CDFW, 2009). These approaches include 1) developing a pilot stream simulation (i.e., replicate site‐specific form and process, thereby minimizing hindrance to fish passage and 2) a roughened channel (i.e., strategic placement of boulders and large rock). These two approaches have been developed into two channel restoration alternatives and are presented as follows along with a summary of the benefits and drawbacks of each approach.

SECTION 3 FISH BARRIER REMOVAL AND STREAM RESTORATION


3.2.1 Alternative A: Crossing Removal and Stream Simulation with Pilot Channel Excavation

The reach of Coyote Creek in the vicinity of the project site is straight, low‐gradient, and incised. Preliminary geotechnical work and our geomorphic reconnaissance indicate the stream banks consist of alluvial terrace deposits that are primarily cohesive sandy and silty clays. These factors present the potential opportunity to implement a restoration design that may minimize construction impacts and reduce the need for installation of rock‐slope bank protection.

Alternative A would consist of the following:

Removing the low‐water crossing and associated hardscape.

Restoring the channel using stream simulation techniques to emulate the natural channel, elevation, slope, and geometry based on diligent geomorphic interpretation.

A pilot channel would be excavated (approximately 275’ along the length of the channel) through the sediment “delta” that has been deposited in Coyote Creek, downstream of Upper Silver Creek to encourage remobilization of the sediment. The initial pilot channel slope would be 1.5 percent, similar to other downstream riffle faces in the vicinity of the site. (See Figure 5 in the Preliminary Geomorphic and Hydraulic Assessment and Channel Restoration Recommendations Technical Memo in Appendix B.)

Natural scour would likely occur in the stream gravels upstream of the low‐water crossing, and deposition would likely occur downstream.

Eventually, the channel slope and dimensions would likely evolve to be similar to the adjacent channel.

This alternative is compatible with all three bridge design alternatives and can be adapted to include bank protection around the outfall downstream of the low‐water crossing on the west bank, and bridge piers, as needed.

3.2.2 Alternative B: Crossing Removal and Installing Roughened Channel Alternative B adopts a roughened channel fish passage approach to preserve the approximately 2.7‐foot jump in the long profile at the low‐water crossing by constructing a roughened channel. Roughened channels are known to pass fish when designed correctly. Designing the roughened channel just under the maximum 5 percent grade, at 4 percent (CDFW, 2009) would reduce the construction impacts by reducing the overall length of the roughened channel ramp.

A roughened channel would require over‐excavation of the stream bed and banks to accommodate installation of engineered streambed mix (ESM). Logs and root wads may be installed to provide velocity and predation cover for migrating fish.

SECTION 4


4 Hydraulic Assessment A hydraulic assessment was performed on the two stream restoration alternatives. This section will briefly identify the hydraulic design criteria that was used to model the stream restoration and bridge alternatives.

Hydraulic design criteria that the stream restoration needs to meet include the following:

1. Comply with Federal Emergency Management Agency (FEMA) requirements for construction within the approximately 200‐foot‐wide regulatory floodway and the wider Special Flood Hazard Area. Encroachments, including fill (such as pier bents and abutments), are typically prohibited within the floodway unless it can be demonstrated that there would be no increase in the base flood elevations. If there is an increase to the 100‐year water surface, the flood map would be revised following all associated notification procedures for all adjacent landowners.

2. Comply with District requirement for bank protection and grade control. Bank protection must be adequate against a 10 percent chance flood event, and the channel design must be stable.

3. Comply with all requirements for design flows, freeboard, and channel design from the Santa Clara Valley Water Resources and Protection Collaborative (SCVWRPC) (2006). The District provided topography information within the channel to supplement field survey information. The District also provided a hydraulic model with flow data for use in this preliminary analysis. Based on this information, the preliminary HEC‐RAS model yielded a value of 3.7 feet minimum freeboard. It was decided to set the pedestrian bridge soffit at least 4 feet above the 100‐year water surface elevation.

Appendix B contains additional detailed discussion of the hydraulic design criteria.

Given the three bridge alternatives (Alternative 2 – Three‐Span, Alternative 5A – Clear‐Span, and Alternative 5A – Three‐Span) and two alternatives for channel restoration (Alternative A – stream simulation with a constructed pilot channel, and Alternative B – roughened channel), five hydraulic models were run using HEC‐RAS to estimate the 100‐year water surfaces. All combinations of bridge and channel restoration alternatives, along with both free‐span and three‐span options for each bridge alternative were analyzed in HEC‐RAS with the exception of the three‐span option of Bridge Alternative 5a paired with channel restoration Alternative A. For the purposes of this study, the other model runs suggest that the three‐span option of Bridge Alternative 5a paired with channel restoration Alternative A would produce results not significantly different from the free‐span option of Bridge Alternative 5a paired with channel restoration Alternative A. The models were configured to characterize the range of possible changes in the 100‐year water surface based on the instream restoration options and the new bridge alternatives. Appendix B provides a detailed discussion of the hydraulic assessment.

Results from comparison of the existing condition model to the proposed conditions models indicate the following preliminary findings:

In general, with the proposed removal of the Singleton Road culverts and channel restoration, the 100‐year water surface elevation in the immediate vicinity of the existing low‐water crossing is estimated to be approximately 2.5 to 3.0 feet lower than existing conditions. This is approximately equivalent to the height of the current hydraulic drop at the crossing.

Upstream of the channel restoration, the 100‐year water surface elevation is also significantly lowered. The water surface is lowered from approximately 3 feet at the crossing to 0.5 foot 1,000 feet upstream of the crossing.

The 100‐year water surface elsewhere was generally unchanged downstream of the channel restoration.

SECTION 4 HYDRAULIC ASSESSMENT


Downstream of the channel restoration, at the location for the bridge for Alternative 5A (downstream bridge), it is estimated the presence of piers possibly raises the water surface approximately 0.06 foot, relative to a clear span alternative. This is within the precision of the HEC‐RAS model and comparable to likely surface waves during a 100‐year flood event. The effect is likely the same for pilot channel and the roughened channel options.

As the calculation of the existing 100‐year water surface (BFE) is further refined during final design from updated District modeling, additional survey data is collected, and detailed modeling of proposed designs in the bridge study reach is performed, water surface elevations would be recalculated. If minor increases (less than 0.5 foot) in the calculated BFE are of concern, channel widening, and restoration in the vicinity of the bridge piers for Alternative 5A would offset increases in the BFE. These design modifications are to be determined as additional information on bathymetry is collected and further hydraulic modeling is performed.

Estimated 100‐year water surface elevations for Alternative 2 for both the pilot channel and roughened channel are still well below the existing BFE, including the presence of proposed bridge piers.

Channel velocities are estimated to range from 2 feet per second to 14 feet per second in the 100‐year flow, with the higher velocities in the center of the channel away from the proposed piers.

Based on preliminary analysis from scour algorithms in the HEC‐RAS model, which is also based on estimated and preliminary bathymetry, anticipated scour depth is estimated to be about 10 to 11 feet below the adjacent ground surface. Applying a factor of safety of 1.5, the estimated scour depth for bridge foundation design is about 15‐feet to 17‐feet below the ground surface, which places scour just below the design or existing thalweg. Additional analysis would be required to provide more accurate estimates of scour depth at the bridge piers once a preferred alternative is identified.

SECTION 5


5 Environmental Clearance and Permit Requirements This Project was initiated as a fish barrier removal and stream restoration project by the resource agencies and project sponsors with the construction of a pedestrian bridge as a means to preserve continuity of the trail. It is expected to be a self‐mitigating project. A brief discussion of the CEQA approach and permitting approach are provided in this Section.

5.1 California Environmental Quality Act Clearance Because of the environmentally sensitive nature of Coyote Creek, potential presence of endangered species of plants and animals, and anticipated public interest in this project, a California Environmental Quality Act (CEQA) checklist will be completed to identify temporary and permanent impacts from the construction of the bridge. It is anticipated that this study would lead to a Mitigated Negative Declaration for the Project, assuming impacts can be sufficiently mitigated by the proposed stream restoration and re‐vegetation plan. The typical mitigation ratio for cottonwood/willow riparian forest is 3:1, however because of the stream restoration component for this project, CDFW and NMFS may decrease the mitigation ratio for tree removals and trail impacts to the understory. The Technical Memorandum: Coyote Creek ‐ Singleton Road Fish Barrier, Stream Restoration, and Pedestrian Bridge Project Initial Environmental Assessment in Appendix C contains additional information about the CEQA clearance process.

5.2 Permitting Requirements Based on the preliminary assessment of the existing condition and the proposed pedestrian bridge configurations that would be installed to replace the existing low‐water crossing, several permits would likely be required. Local, state, and federal agencies have jurisdiction for work proposed within Coyote Creek. Included is a description of the agency, its purpose, its jurisdiction, and why the project may or may not trigger the agency’s permit requirements. A list of the relevant permit application requirements is provided in Table 5‐1: Permitting Requirements Matrix.

5.2.1 Local Permits The District manages watercourses within Santa Clara County for purposes of watershed stewardship, flood protection, water supply and quality protection, water supply distribution, and maintenance. Project proponents must secure an Encroachment and Construction Permit from the District before construction of any project within 50 feet of top of bank of District facilities. A District permit would not be required because the project is not located within District property although the bridge would cross Coyote Creek, which is a designated watercourse under District jurisdiction. A District Encroachment and Construction permit would not be required.

5.2.2 State Permits CDFW is charged with the protection and conservation of fish and wildlife resources under Section 1601‐1607 of the California Fish and Game Code. The CDFW must be notified of any activity that impacts riparian corridors and wetlands so that they may conduct an onsite investigation to review the impacts of the project on any wildlife resources that may exist. Project proponents are required to enter into a Streambed Alteration Agreement with CDFW before construction of any project that would change the flow, bed, channel, or bank of any river, stream, or lake, or use materials from the streambed. Installation of the proposed bridge abutments and piers would impact the existing riparian vegetation and potentially may alter the banks of Coyote Creek, triggering CDFW involvement and requiring a Streambed Alteration Agreement. A CDFW permit would be required.

SECTION 5 ENVIRONMENTAL CLEARANCE AND PERMIT REQUIREMENTS


The Regional Water Quality Control Board (RWQCB) protects the water supply quality by managing construction‐related discharge of stormwater runoff and the discharge of materials into “waters of the State.” Project proponents are required to file a Notice of Intent under the General Permit for Stormwater Discharges Associated with Construction Activity with the State Water Resource Control Board. They also must prepare a stormwater pollution prevention plan before construction of any project whose stormwater runoff would disturb one or more acres of land. Because the area that would be impacted by the bridge construction would be approximately 1 acre of land, need for a General Permit (SWPPP) should be anticipated. Project proponents are required to secure a Section 401 Water Quality Certification from the RWQCB before any fill activity can begin within “waters of the State.” Coyote Creek is considered a “water of the State,” so it is anticipated that a Section 401 Water Quality Certification would be required to remove the concrete low‐water crossing and pedestrian bridge construction. A RWQCB permit and certification would be required.

5.2.3 Federal Permits USACE, under Section 404 of the Clean Water Act, protects the waters of the U.S. to preserve interstate or foreign commerce. Project proponents are required to secure a Department of the Army permit for work that results in the discharge of dredged or fill material into waters of the U.S. Because the bridge piers may be located within the creek channel, below the ordinary high tide line, fill material may be within waters of the U.S. A USACE permit would be required.

USFWS, under the direction of the United States Endangered Species Act, regulates federal activities that affect endangered or threatened species beyond the marine environment. Federal agencies are required to request a Section 7 Consultation with USFWS representatives if their project may potentially impact species listed under the Endangered Species Act. The California tiger salamander and the California red‐legged frog are endangered species known to exist in the Coyote Creek area, but are not likely to be present at the Project site according to available survey results. Potential project effects would be addressed by complying with the Santa Clara Valley Habitat Conservation Plan, including required avoidance and minimization measures and fee payment for offsite compensatory habitat mitigation. Consultation with USFWS is not likely to be required.

NMFS, under the direction of the United States Endangered Species Act, regulates federal activities that affect endangered or threatened species within a marine environment. Federal agencies are required to request a Section 7 Consultation with NMFS representatives if their project may potentially impact marine species listed under the Endangered Species Act as endangered, threatened, or as a candidate for listing. Steelhead and the Chinook salmon are federally listed species known to migrate in Coyote Creek and are expected to be present between October 15 and June 15 of every year. Although it is anticipated that the Project can be designed to avoid and minimize impacts to endangered species, consultation would be required as work would be conducted within the creek channel. A consultation with NMFS would be required.

5.2.4 Santa Clara Valley Habitat Conservation Plan The Santa Clara Valley Habitat Agency leads the implementation of the Santa Clara Valley Habitat Plan. The Habitat Plan is a 50‐year regional plan to protect endangered species and natural resources while allowing for future development in Santa Clara County. In 2013 the Habitat Plan was adopted by all local participating agencies and permits were issued from the USFWS and CDFW. It is both a habitat conservation plan and natural community conservation plan. The project area is within the Santa Clara Valley Habitat Plan area and is subject to the conditions and fees contained in the Habitat Plan. The project region is located in areas designated by the Habitat Plan as Golf Course/Urban Parks and Willow Riparian Forest and Scrub. The Habitat Plan’s wildlife survey of covered animal species identified tricolored blackbird on the project site. The project site is within Land Cover Fee Zone B and Land Cover Fee Zone ‐ Urban Area (which has no land cover fee). A Santa Clara Valley Habitat Conservation Plan permit would be required.

Table 5-1 - Permitting Requirements Matrix for Coyote Creek – Singleton Road Fish Barrier, Stream Restoration and Pedestrian Bridge Project Draft Preliminary Engineering Study

Agency Name Type of Permit Activity Requiring Permit Jurisdiction Reference Address Application Fee

California Department of Fish and Wildlife (CDFW)

Streambed Alteration Agreement

Modification of streambed or bank within Coyote Creek

Coyote Creek, from top of bank (levee) to top of bank (levee).

Section 1602 of Fish and Game Code

California Department of Fish and Wildlife, Region 3 Post Office Box 47 Yountville, CA 94599 (707) 944-5500

Fee ranges from $200 to $4,000 according to the estimated cost of the project.

Regional Water Quality Control Board (RWQCB)

NPDES General Permit for Discharges of Storm Water Associated with Construction Activity

Construction on one acre of land, or more. Construction-related discharge of surface or groundwater in Coyote Creek.

Construction sites of one or more acres

Clean Water Act, Section 402

San Francisco Bay Regional Water Quality Control Board 1515 Clay Street, Suite 1400 Oakland, CA 94612 (510) 622-2300

Fee ranges from $237 to $2,607 per year for construction areas of <1 acre to >100 acres (for 1 acre fee is $261)

Regional Water Quality Control Board (RWQCB)

Water Quality Certification Discharge of dredged or fill material in Waters of the State.

Waters of the State. Clean Water Act, Section 401

(same as above) $500 Base Price + (Discharge area in hundredths of an acre x $21.50)

United States Army Corps of Engineers (USACE)

Department of Army Permit

or Nationwide Permit

Discharge of dredged or fill material into Coyote Creek

Waters of the United States

Section 10 of the Rivers and Harbors Act or Section 404 of the Clean Water Act

United States Army Corps of Engineers, South Pacific Division 333 Market Street, 8th Floor San Francisco, CA 94105-2197 Attn: SPNCO-R (415) 977-8462

N/A

United States Fish and Wildlife Services

Section 7 Consultation Work impacting plant or wildlife species listed by the Endangered Species Act

Projects requiring a USACE Permit affecting threatened/endangered species beyond marine environment

U.S. Endangered Species Act

United States Fish and Wildlife Service, Sacramento Field Office 2800 Cottage Way Room W-2605 Sacramento, CA 95825 (916) 414-6600

N/A

National Marine Fisheries Service

Section 7 Consultation Work impacting wildlife species listed by the Endangered Species Act, notably salmon.

Project requiring a USACE permit affecting threatened/endangered species within marine environment, including anadromous fish

U. S. Endangered Species Act

Nation Marine Fisheries Service 777 Sonoma Avenue Room 325 Santa Rosa, CA 95404 (707) 575-6050

N/A

US Coast Guard Approval Letter Bridge construction in Coyote Creek

Navigable waterways in USA

Title 33, United States Code, Section 525

Eleventh Coast Guard Dist. Bldg 50-6, Coast Guard Island Alameda, CA 94501-5100 (510) 437-5836

N/A

Santa Clara Valley Habitat Agency

Santa Clara Valley Habitat Plan Permit

Bridge Construction in Coyote Creek

Coyote Creek U. S. Endangered Species Act

Santa Clara Valley Habitat Agency 535 Alkire Avenue Morgan Hill, CA 95037 (408) 779-7261

Permanent impact fees for Zone B are $11,806/ acre + $142,838/acre for permanent impacts to willow riparian forest and mixed riparian forest habitat. Temporary impact fees for Zone B are $11,806/acre/0.04 + $142,838/acre/0.04 for temporary impacts to willow riparian forest and mixed riparian forest habitat.

SECTION 6


6 Bridge Structure Types and Geotechnical Foundation Evaluation The City has selected two alternative trail alignments to reconnect the west and east side segments of the Coyote Creek Trail to allow for removal of the existing low‐water crossing. This section will identify appropriate bridge types for each of these alignments and discuss the advantages and disadvantages of various bridge types for the two selected trail alignments.

6.1 Bridge Geometry and Location In accordance with environmental requirements, the bridge abutments and piers shall be installed outside of the OHW mark and closer to the top of bank in disturbed area, if possible. Because the OHW mark varies from approximately 100 to 150 feet and the creek banks are a maximum of approximately 300 feet apart, a two‐span bridge would place a column within the ordinary high water limits; thus, the two‐span bridge option was eliminated.

There were many considerations for choosing the proposed abutment locations. One important consideration is to avoid raising the water surface elevation during a 100‐year flood event. This could be prevented by constructing the abutment as close to the existing channel banks as possible to not restrict the channel flows. A second consideration is to avoid placing the abutment within the existing landfill. Due to poor soils within the landfill, costlier foundations would be necessary to be constructed and any soil excavation from the landfill would need to be specially handled. Finally, it is preferable to avoid retaining walls to minimize flat surfaces that can be tagged and result in extensive maintenance.

This study considers a three‐span bridge crossing for Alternative 2 and both a clear‐span and a three‐span bridge crossing for Alternative 5A (see Figures 6‐1, 6‐2, and 6‐3, respectively). All three alternatives are based on a tangent bridge alignment which accommodates anticipated City and Water District maintenance vehicles as well as emergency vehicles (pick‐up truck type vehicles).

6.2 Bridge Type Selection The proposed structure type for each alternative is a pre‐manufactured steel truss bridge with a cast‐in‐place concrete bridge deck on pile‐supported cast‐in‐place concrete foundations. Rapid delivery of the project is an important goal for all agencies, so this cost efficient and readily available structure type is preferred. Benefits to this type of structure include the following:

Rapid construction with minimal disturbance to the creek and to the neighborhood

Good economy

Minimal required maintenance

A functional, pleasing appearance

The space beneath the bridge deck can readily accommodate utility conduits, if necessary

Other structure types considered but dismissed include cast‐in‐place concrete structures, which would require construction on falsework within the Creek channel and longer duration of construction, and precast concrete structures, which were considered to have a less pleasing appearance for a trail environment.

6.3 Foundations The proposed foundation system for the bridge crossings were developed based on the results and recommendations from a preliminary geotechnical investigation, presented separately. Six‐foot‐diameter cast‐in‐drilled‐hole (CIDH) concrete piling are proposed for the bents adjacent to the creek, to minimize disturbance in this sensitive area. The piles would be located outside of the OHW line. Either smaller‐

SECTION 6 BRIDGE STRUCTURE TYPES AND GEOTECHNICAL FOUNDATION EVALUATION


diameter CIDH or driven concrete piling would be used at abutments. Appendix E contains additional detail on foundations.

For Alternative 5A structure layouts, the westerly abutment would be founded immediately adjacent, or within the limits of the Singleton Road Landfill. Because exploratory soil borings prepared for this project phase were located nearer to the Alternative 2 alignment, no specific soil data are available for Alternative 5A. Based on previous studies by others, the depth of waste material in the location of the western abutment is roughly estimated to be between 5 and 15 feet. Landfill waste and its soil cover should be ignored when calculating lateral soil resistance to seismic loads for the bridge abutment foundation. Larger‐diameter piling would be required in these locations to transfer lateral loads into native soil materials beneath the landfill debris.

6.4 Substructure Four‐foot round, cast‐in‐place concrete single columns with hammerhead caps are proposed at bents. Cast‐in‐place concrete cantilever abutments with wing walls are proposed at abutments.

6.5 Bridge Deck The proposed deck provides a 12‐foot‐wide travel path for pedestrians and bicycles. The bridge deck surface would be reinforced concrete supported by a steel deck for minimal maintenance. Both the bridge deck and the structure approach ramps would be American Disability Act (ADA) compliant. If it is determined that bird exclusionary measures will require the space beneath the bridge deck to be enclosed, this will be evaluated during final design. Other measures to address possible enhancements to the truss configuration in this regard will likewise be considered in conjunction with City staff and potential bridge fabricators.

6.6 Hydraulic Impacts and Scour Protective Measures Columns for the proposed three‐span bridge configurations are currently located a minimum of 10 feet beyond the estimated limits of OHW to minimize creek bed disturbance. These locations are subject to reevaluation during final design. Column and abutment locations are expected to have minimal impact on creek hydraulic performance. Appendix B provides a detailed assessment of hydraulics and scour.

The potential for scour has been evaluated separately. Scour protective measures are currently anticipated and their implementation will ensure that the pile‐supported foundations are not susceptible to damage during the design flood event.

6.7 Utilities The structure is not anticipated to carry any utilities. Section 9 presents discussion on utility relocations required for each alternative.

6.8 Bridge Aesthetics Although pre‐manufactured steel truss bridges may have many common features, a variety of subtle enhancements to shape, color, and texture are proposed to add uniqueness to this design solution. Unpainted weathering steel is recommended for use on all three bridge alternatives. This steel readily forms a surface layer of rust that inhibits long‐term corrosion and minimizes maintenance by eliminating painting. A byproduct of the use of this material can be surface rust staining on supporting concrete elements. In practice, this staining can be avoided by painting the end portions of the structure, by detailing to minimize the flow of run‐off water to the supports, or by using protective coatings on supporting concrete surfaces. Using this material greatly reduces future maintenance needs compared to painted steel structures and is consistent with other San José trail bridges.

End span lengths of the three‐span structures have been kept equal for economy and appearance. The middle span (of multi‐span structures, or the only span in a single‐span alternative) is proposed to have an

SECTION 6 BRIDGE STRUCTURE TYPES AND GEOTECHNICAL FOUNDATION EVALUATION


arching, bow‐shaped top chord (Bowstring), whereas the ends spans are proposed as parallel chord trusses for a pleasing appearance. Other proposed aesthetic treatment of various bridge elements will be developed by the project architect during final design. Treatments that are being considered include stamped or sandblasted patterns in the bridge deck concrete, and/or stained concrete bridge deck, a steel picket safety railing with decorative leaf or tree branch patterns, and textures or patterned concrete for the abutment faces and piers. Their implementation is not expected to have significant cost or structural impacts.

6.9 Bridge Alternatives The following structure configurations met the considerations previously outlined and are feasible for the alignments considered.

6.9.1 Alternative 2 Three-Span Bridge This alignment has a symmetric three‐span configuration with 70‐foot end spans and a 140‐foot main span. The total length of the bridge is 280 feet. The end spans will be parallel chord steel trusses that will extend 4 feet, 1 inch above the bridge deck. The main span will be a modified bowstring truss that will vary from 4 feet, 1 inch above the bridge deck at the bents to approximately 7 feet, 8 inches above the bridge deck at midspan. The bridge will have a concrete deck with a tangent alignment on a 1.7 percent longitudinal grade (see Figure 6‐1).

6.9.2 Alternative 5A Clear-Span Bridge This alignment has a single span arrangement of 260 feet. The main span would be a steel arch with a parallel chord box truss. The arch element would result in a maximum structure depth of approximately 45 feet. The box truss will accommodate the bridge deck with a structure depth of approximately 12 feet, 6 inches. The bridge will have a concrete deck with a tangent alignment on a 2.2 percent longitudinal grade (see Figure 6‐2).

6.9.3 Alternative 5A Three-Span Bridge This alignment has a symmetric three‐span configuration with 55‐foot end spans and a 150‐foot main span. The total length of the bridge is 260 feet. The end spans will be parallel chord steel trusses that will extend 4 feet, 1 inch above the bridge deck. The main span will be a modified bowstring truss that will vary from 4 feet, 1 inch above the bridge deck at the bents to approximately 7 feet, 8 inches above the bridge deck at midspan. The bridge will have a concrete deck with a tangent alignment on a 2.2 percent longitudinal grade (see Figure 6‐3).

Appendix G provides preliminary cost estimates for the three alternatives.

SECTION 7


7 Constructability Considerations Construction access to the project site would likely be via Tuers Road at the existing trailhead from the east and Singleton Road from the west. No temporary construction access easements would be needed since the entire project and access would be within City right‐of‐way. Construction staging would be located off of Singleton Road, west of Coyote Creek or possibly at the gated landfill.

For Alternative 2, construction of the truss can be done within the existing paved roadway, so environmental impacts would be minimal. Construction of the pedestrian bridge would require temporary closure of the trail at the low water crossing and diversion of bicycle traffic around the site.

For Alternative 5A, construction of the truss that spans over the low flow channel is expected to be done using temporary support bents between the abutments and piers. The weight of the completed truss segment prohibits lifting the entire span with one crane. These temporary supports might consist of driven steel piles, which would subsequently be removed once construction is complete. Sections of the truss would be lifted into place and field spliced. As an alternative, the contractor may elect to assemble the trusses adjacent to the alignment and then lift each completed span into place using two cranes.

During construction, it is likely the contractor would construct temporary timber or gravel surfaced pads parallel to the bridge alignment within the creek. These pads would provide construction access to piers and crane access for truss erection. These pads would be removed and the channel restored upon completion of construction.

SECTION 8


8 Right-of-Way Requirements Based on the field topographic survey and base mapping developed for this Study (see Figure 1‐2) and latest County of Santa Clara Assessor’s maps (see Appendix H), the entire project site is located completely within City right‐of‐way. The property ownership in and adjacent to the project area is summarized in Table 8‐1 for Alternative 2 and Table 8‐2 for Alternative 5A.

Table 8‐1 Property Owners for Alternative 2

APN Project Feature Ownership Area

494‐24‐014 Trailhead and Trail Connection to East Abutment

City of San José Coyote Creek North of Singleton Road

494‐24‐015 Construction Access/Staging City of San José Landfill North of Singleton Road

494‐22‐016 West Abutment and Trail Connection to West Abutment

City of San José Landfill South of Singleton Road

494‐26‐044 East Abutment City of San José Coyote Creek South of Singleton Road

Table 8‐2 Property Owners for Alternative 5A

APN Project Feature Ownership Area

494‐24‐014 Trailhead, Pedestrian Bridge, Trail Connections, and West and East Abutments

City of San José Coyote Creek North of Singleton Road

494‐24‐015 Maintenance Road and Trail Connection to West Abutment

City of San José Landfill North of Singleton Road

494‐22‐016 Construction Access/Staging City of San José Landfill South of Singleton Road

494‐26‐044 Trail Connection to West Abutment City of San José Coyote Creek South of Singleton Road

Even though the City owns the property encompassing the site and there will be no acquisition required for the project, the City will have to coordinate with the City Department of Transportation (DOT) to construct the portion of the trail adjacent to Tuers Road. Further discussion about future plans to widen the road are provided in Section 10.

SECTION 9


9 Utility Requirements Based on the field topographic survey and base mapping developed for this Study and a collection of utility maps, the approximate location of existing utilities are shown on Figure 9‐1. The existing utilities within the project area are summarized in Table 9‐1.

Table 9‐1 Utility Matrix

ID No. Type Owner Size Quantity Location

Disposition

Alt 2 Alt 5A

1 Overhead Electric

PG&E 21KV 3 Along Singleton Road, crossing Coyote Creek

To be relocated

To remain

2

Overhead Fiber Optic Cable

Comcast ‐‐ 6 Along Singleton Road, crossing Coyote Creek

To be relocated

To remain

3 Utility Vaults

AT&T ‐‐ 2 150’ Southwest corner of the west bank of Coyote Creek, South side of Singleton Road

To be relocated

To be adjusted

4 Telephone AT&T Unknown 1

Along Singleton Road, crossing Singleton Road, connecting to vaults and manhole, crossing Coyote Creek, connecting manholes, up to Tuers Road

To remain To remain

5 AT&T Manhole

AT&T ‐‐ 2 Between existing Coyote Creek Trail and ramp on the east bank of Coyote Creek

To remain To remain

6 Manhole AT&T ‐‐ 1 120’ Southwest corner of the west bank of Coyote Creek, North side of Singleton Road

To remain To remain

7 Utility box Unknown ‐‐ 1 Next to AT&T manhole To be relocated

To remain

8 Utility Poles and guy poles

PG&E, Comcast

‐‐ 2 120’ Southwest corner of the west bank of Coyote Creek, South and North side of Singleton Road

To be relocated

To be adjusted

9 Storm drain Manhole

City of San José

‐‐ 1 120’ Southwest corner of the west bank of Coyote Creek, North side of Singleton Road

To remain To remain

10 Storm drain Line

City of San José

27” 1 Along Singleton Road, outfall to Coyote Creek

To remain To remain

11 Water City of San José

12”, 6” 1 Along Singleton Road, crossing Coyote Creek, to Tuers Road

To remain To remain

12 Telephone AT&T Unknown 1 Along Tuers Road Protect in place

Protect in place

13 Sanitary Sewer

City of San José

10” 1 Along Tuers Road To remain To remain

14 Storm Drain

City of San José


SECTION 9 UTILITY REQUIREMENTS


Table 9‐1 Utility Matrix

ID No. Type Owner Size Quantity Location

Disposition

Alt 2 Alt 5A

15 Water City of San José


16 Gas PG&E 4” 1 Along Tuers Road To remain To remain

17 Electric PG&E 21KV 3 From utility pole on east side of low‐water crossing to Tuers Road north

To remain To remain

18 Cable Comcast Unknown 1 From utility pole on east side of low‐water crossing to Tuers Road north and south

To remain To remain

On April 20, 2015, the City and the design team met with Pacific Gas and Electric Company (PG&E) at the project site to discuss minimum vertical clearance requirements between the final traveled surface and the overhead electric lines. PG&E indicated that they typically require a minimum of 10‐foot minimum vertical clearance between the highest point on the bridge and their lowest overhead line which acts as a common neutral. Because there would be vehicles accessing the bridge, the minimum vertical would be 18 feet. Furthermore, to be in compliance with the State of California GO95 minimum clearances, the 21kV overhead utility would need to be a minimum of 25 feet above the trail surface. This 25‐foot requirement will be the criteria used for the project.

Based on survey information collected on the height of the electric lines and the proposed bridge elevation, there is not adequate vertical clearance to meet the 25‐foot clearance requirement. PG&E indicated that they could replace existing poles with three taller poles and raise the overhead lines to meet the vertical clearance requirement. The existing joint pole located on the east bank has a riser. This pole would likely be relocated up the bank to the east towards Tuers Road. Appendix F provides a meeting summary.

For Alternative 2, the proposed pedestrian bridge and maintenance road would not provide the minimum required vertical clearance below the existing 21KV (PG&E) and fiber optic cable (Comcast) overhead lines (ID numbers 1 and 2 in Table 9‐1) crossing over the Singleton Road low‐water crossing. Since the lines cannot be raised high enough, relocating these overhead lines and associated utility boxes would be required. During installation of pile foundations, column and bent cap construction, and bridge erection, the overhead electric would be de‐energized when necessary.

For Alternative 5A, the proposed trail and Singleton Road would be raised west of the low‐water crossing. Raising the profile of the trail and Singleton Road would reduce the vertical clearance to the overhead lines but the minimum vertical clearance would still be provided so no relocations of the overhead lines would be necessary. The existing AT&T vaults (ID number 3) may need to be adjusted and utility and guy poles (ID number 8) may need to be buried.

For both alternatives, the existing City 6‐ and 12‐inch water and AT&T telephone crossing the creek downstream of the low‐water crossing are anticipated to remain. The same existing AT&T telephone conduit, which is also located under the proposed trailhead plaza, would need to be protected. No utility impacts are anticipated on the east side of Coyote Creek along Tuers Road.

Potholing activities would be performed during final design to verify existing underground utility location and depth. Coordination with AT&T would be needed to discuss how to provide access to existing manholes located at the existing Coyote Creek Trail and Singleton Road intersection on the east side of the channel.

SECTION 10


10 Surface Improvements at Tuers Road

10.1 Future Roadway Improvements Per discussion with the City, the minimum public right‐of‐way width of Tuers Road is 60 feet, so an additional 10 feet of additional roadway width is anticipated to be constructed in the future. The proposed design assumes that Tuers Road would be widened 10 feet on the west side of the street (creek side). The trail alignment is located outside the footprint of the future roadway widening project.

As part of this Project, sidewalk, curb and gutter would be constructed along the west side of Tuers Road from the trailhead north to Capitol Expressway.

10.2 Trailhead Connection at Surface Street A trailhead would be constructed at the intersection of Tuers Road and Brandybuck Way outside the limits of the future roadway widening project. The trailhead would include directional signage and architectural features. Following are two options for consideration for the architectural design of the trailhead (see Appendix D for landscape design criteria and conceptual graphics):

Leaf Motif – The leaf motif would include colored concrete paving of a leaf shape on the trailhead plaza. The gateway feature would be a ribbon spiral of rebar around rebar “trunk” and “branches.” Custom “leaf” arcs would be incorporated into the bridge railings.

Branch Motif – The branch motif would include colored concrete paving with a tree silhouette with sandblast finish and stained. The gateway feature would be rebar wrapped around 6x6 powder‐coated tubular steel members. Custom metal “branches” would be incorporated into the bridge railings.

Cobbles would be incorporated possibly around the abutment, used as a surface material beneath the branch structure supports of the seating feature, and would also appear in the gateway element for continuity.

SECTION 11


11 Estimate of Project Costs Cost estimates were developed based on historical Caltrans Cost Data from 2013. Costs for furnishing the various bridge alternatives were developed based on Vendor quotes. Costs for truss erection were built up costs using labor, equipment, and materials. A contingency of 35 percent was applied to overall project costs to reflect uncertainties associated with this level of design development. This level of contingency may not be sufficient, nor was there any attempt made, to estimate possible impacts from natural disasters on the overall future costs of construction. Appendix G provides a cost estimate backup.

The cost estimates also include a 30 percent allowance for City Project Development and a 25 percent allowance for engineering design and construction administration support.

Cost estimates assume no right‐of‐way acquisition, design, or construction of off‐site environmental mitigation. Costs for these items are unknown at this time and could be significant but would be further evaluated in subsequent phases of project development.

Table 11‐1, 11‐2 and 11‐3 provides estimated project costs for each alternative.

Table 11‐1 Cost Summary for Crossing Removal and Stream Restoration Only

Stream Simulation with Pilot

Channel Excavation Installation of Roughened Channel

Alternative 2 – Three Span $ 894,000 $ 1,999,000

Alternative 5A – Clear Span/ Three Span $ 908,000 $ 2,007,000

Table 11‐2 Cost Summary for Bridge and Trail Improvements Only

Bridge and Trail Improvements

Alternative 2 – Three Span $ 4,533,000

Alternative 5A – Clear Span $ 5,919,000

Alternative 5A – Three Span $ 5,185,000

Table 11‐3 Total Project Cost

Stream Simulation with Pilot

Channel Excavation Installation of Roughened Channel

Alternative 2 $ 5,427,000 $ 6,532,000

Alternative 5A ‐ Clear Span $ 6,827,000 $ 7,926,000

Alternative 5A ‐ Three Span $ 6,093,000 $ 7,192,000

SECTION 12


12 Project Implementation Schedule Figure 12‐1 shows the preliminary project implementation schedule, which includes approximately 2 years for project design, CEQA clearance, utility relocation, and regulatory permits after completion of this Study.

Construction would follow completion of the construction documents and receipt of all construction permits, and would take approximately 1 year to complete.

The Preliminary Project Schedule includes the following assumptions:

Schedule assumes funding available, as needed

CEQA task includes preparation of an Initial Study and City Council adoption of a Mitigated Negative Declaration for this project

Bird Exclusion Measures include pre‐construction surveys

Design and construction of off‐site environmental mitigation is not anticipated

For Alternative 2 the trail must be temporarily closed to the public during bridge erection.

Work within the channel banks (which includes the entire project except for work along Tuers Road) will only be allowed to occur between June 15 and October 15 of each year. Therefore, there would need to be consideration as to when the Project will be advertised and awarded to complete the work within one season.

ID Task Name Duration Start Finish

1 Complete Preliminary Engineering Study

0 days Fri 8/28/15 Fri 8/28/15

2 Phase II Survey and Geotechnical Investigation

30 days Mon 8/31/15 Fri 10/9/15

3 CEQA (Mitigated Negative Declaration)

6 mons Mon 10/12/15 Fri 3/25/16

4 Final Design 155 days Mon 10/12/15 Fri 5/13/16

5 Permitting 12 mons Mon 2/1/16 Fri 12/30/16

6 Relocate Utilities 6 mons Mon 2/29/16 Fri 8/12/16

7 Advertise & Award 40 days Mon 1/9/17 Fri 3/3/17

8 Construction 155 days Mon 3/6/17 Fri 10/6/17

9 Mobilization 70 days Mon 3/6/17 Fri 6/9/17

10 Bird Exclusion Measures 150 days Mon 3/6/17 Fri 9/29/17

11 Truss Fabrication 40 days Thu 4/6/17 Wed 5/31/17

12 Work Allowed in Channel 87 days Thu 6/15/17 Sun 10/15/17

13 Foundations & Substructure 60 days Thu 6/15/17 Wed 9/6/17

14 Truss Erection 15 days Thu 9/7/17 Wed 9/27/17

15 Restore Channel Bottom 12 days Thu 9/28/17 Fri 10/13/17

16 Misc.Work Outside Channel (Ramps/Trails/Etc)

85 days Fri 9/1/17 Thu 12/28/17

8/28M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12 M13 M14 M15 M16 M17 M18 M19 M20 M21 M22 M23 M24 M25 M26 M27 M28 M29 M30 M31 M32 M33 M34 M35 M36 M37

Year 2 Year 3 Year 4

Task

Split

Milestone

Summary

Project Summary

External Tasks

External Milestone

Inactive Milestone

Inactive Summary

Manual Task

Duration-only

Manual Summary Rollup

Manual Summary

Start-only

Finish-only

External Tasks

External Milestone

Progress

Deadline

COYOTE CREEK - SINGLETON ROAD FISH BARRIER, STREAM RESTORATION AND PEDESTRIAN BRIDGE PROJECTPROJECT IMPLEMENTATION SCHEDULE

Fig 12-1

Project: COYOTE CREEK - SINGLETON ROADDate: Thu 5/28/15

SECTION 13


13 Evaluation of Alternatives and Recommendations This section summarizes the results from the analysis described above and provides project recommendations.

13.1 Stream Restoration Evaluation 13.1.1 Alternative A: Crossing Removal and Stream Simulation with Pilot

Channel Excavation The following are benefits of Alternative A:

Consistent with the geomorphology of the reach.

Allows for sediment entering Coyote Creek from Upper Silver Creek to move downstream, likely improving habitat for target species in the nearly 2,500‐foot‐long run that continues from Yerba Buena Road and the confluence with Upper Silver Creek.

Reinvigorates sediment transport and encourage formation of short‐ to mid‐term channel gravel bars.

Encourages transient bed features (pools and riffles) to form and degrade naturally, especially if gravel augmentation/relocation occurs in the future.

Reduces the depth, and perhaps length of the continuous pool/glide that extends for nearly 1,800 feet between Yerba Buena Road and the Confluence with Upper Silver Creek, thereby improving habitat and passage through that reach.

Allows for a smaller construction footprint, shallower excavation depths, and overall reduced impact.

Minimizes channel slope, and in all likelihood, flow velocities, at the future bridge site (Bridge Alternative 2). In the long term, this alternative would probably provide the most freeboard for Bridge Alternative 2.

Reduces cost due to reduced material needs.

Enables large Streamwood better than a roughened channel (Channel Alternative 2), because little to no large rock would be used.

The following challenges are associated with Alternative A:

Adaptive management may be required because the bed and banks upstream may evolve in an unpredictable manner. Additional data, including more detailed survey data from approximately 1,000 feet upstream and sediment cores of the delta formed at the mouth of Upper Silver Creek, may minimize these concerns.

The beneficial effects on the channel upstream and downstream may be short lived. Gravel augmentation or restoration of geomorphic flows are not planned for Coyote Creek, but may support the long‐term benefits of channel enhancements.

There may be impacts to existing infrastructure, including, potentially, the Yerba Buena Road Bridge, if significant channel incision continues. Analyses planned for the final design phase will minimize these impacts to the extent practicable.

The buried telephone and water lines that traverse the stream at the Crossing may need to be protected or relocated.

SECTION 13 EVALUATION OF ALTERNATIVES AND RECOMMENDATIONS


Fish passage issues may emerge, as the channel upstream of the Site adjusts, and adaptive management measures may need to be taken. More data may be necessary to evaluate the thickness of the stream gravels and location of potential impediments to fish passage.

13.1.2 Alternative B: Crossing Removal and Installation of Roughened Channel

The following are benefits of Alternative B:

Allows for more control over the channel geometry and hydraulics in the vicinity of the bridge, if designed properly.

Is less likely to require adaptive management.

May enable the reduction in pier scour, and avoidance of the existing culvert outfall downstream of the Crossing on the left bank.

The following are challenges associated with Alternative B:

May be challenging to design a roughened channel that provides fish passage at low flows and that is stable at high flows. Preliminary modelling as part of this feasibility phase would provide more information.

Does not simulate the geomorphology of Coyote Creek in the vicinity of the Site.

Reduces the likelihood of transient bedforms, and would reduce the likelihood of the channel to adapt.

Maintains a steepened channel under the planned bridge (Alternative 2) and may accelerate flows in the vicinity of the bridge. Two bridge piers are planned for Alternative 2.

May be more costly to build when compared to Alternative A, because the roughened channel would require a large amount of imported streambed material.

Would likely cause greater impacts to the channel during construction.

May cause a change in the management of the reservoirs and percolation ponds upstream of the site. While it is unlikely that flooding would worsen, creating a roughened channel and reducing the number of hardened channel bed and bank features in Coyote Creek may afford the District water managers reduced flexibility in the future.

May cause large streamwood to get jammed on the roughened channel, affecting the hydraulics and/or damaging the roughened channel.

13.2 Trail Alignment Evaluation 13.2.1 Alternative 2 Alternative 2 places a bridge along the approximate alignment as the existing low‐water crossing. This bridge would be a symmetric three‐span configuration with a total length of 280 feet. The end spans would be parallel chord steel trusses and the main span would be a modified bowstring truss.

Following are benefits of this alternative:

Uses the footprint of the existing paved trail, thereby reducing temporary and permanent environmental impacts.

Keeps the estimated 100‐year water surface elevations for Alternative 2 for both the pilot channel and roughened channel well below the existing BFE, including the presence of proposed bridge piers.

Avoids costly bridge foundations and disposal of waste materials from landfill by constructing the proposed west bridge abutment on the edge of and outside of the landfill limits.



Provides more gradual trail connections to the bridge.

Requires less earthwork utilizing existing contours.

Provides full maintenance access and all existing connections.

Provides a stable base to place any necessary temporary supports for falsework required for bridge construction.

Is estimated to be lower in cost than Alternative 5A even with an allowance for utility relocations for raising overhead utilities.

Following are challenges associated with this alternative:

Requires relocation of the overhead utility lines, which may delay the project schedule.

Affects trail access since it would be constructed within the existing trail crossing, so a detour would need to be provided.

Is a longer bridge than Alternative 5A.

Requires more roadway work along Tuers Road and potential conflict with future widening plans.

13.2.2 Alternative 5A Alternative 5A places a bridge downstream of the existing low‐water crossing. Two bridge types are proposed for this alignment. The three span bridge option would be a symmetric three‐span configuration with a total length of 260 feet. The end spans would be parallel chord steel trusses and the main span would be a modified bowstring truss. The single span bridge option would be a single span arrangement of 260 feet. The main span would be a steel arch with a parallel chord box truss.

Following are benefits of Alternative 5A:

Requires adjustments of existing utility vaults and poles but should not delay the project schedule, because the utility vaults and poles are located outside the bridge footprint.

Is a shorter overall bridge length.

Requires less roadway work along Tuers Road.

Does not require alternate trail access or detouring during construction since the proposed bridge footprint is not over the existing trail.

Following are challenges associated with Alternative 5A:

Causes greater environmental impacts since the proposed bridge footprint would be constructed over an undisturbed area of the creek.

Requires a more complex bridge construction staging than Alternative 2 since the bridge footprint would be constructed over an undisturbed area of the creek.

Raises the water surface approximately 0.06 foot relative to a free span alternative, at the location for the bridge for Alternative 5A (downstream bridge).

Increases disposal costs for the landfill materials since proposed west bridge abutment would need to be constructed within the existing landfill limits.

Requires a more complicated and expensive foundation design of bridge abutments since they are located within the landfill.

Requires cyclists to walk their bikes across the bridge due to the right angles of the bridge trail connections on the west bank.



Is estimated to have higher bridge construction costs than Alternative 2.

It requires more earthwork to construct the trail on the west bank than Alternative 2.

13.3 Stream Restoration and Trail Alignment Recommendations

It is recommended that the project move forward with Alternative A for channel restoration and Alternative 2 for the trail alignment.

A preliminary review of the channel history and geomorphology suggests that channel restoration Alternative A, barrier removal, and construction of a pilot channel to encourage the channel to naturally mobilize and redistribute the accumulated sediment appears to be desirable. Alternative A may offer the unique opportunity in the Santa Clara Valley to remove the Crossing and return the reach of Coyote Creek adjacent to the Crossing to its natural form and process regime thereby minimizing engineering interventions and reducing associated costs and impacts within the riparian corridor.

A pre‐manufactured steel truss bridge with a cast‐in‐place concrete bridge deck on pile‐supported cast‐in‐place concrete foundations is the recommended structure type. Alternative 2 is the recommended crossing alternative for the following reasons:

Easier construction access and constructability because the existing low‐water crossing can be used as a foundation for falsework and staging.

Least disturbance for vegetation and shaded canopy within the riparian corridor.

Least impact to existing maintenance access roads along the west channel bank.

Estimated to be the lowest potential cost.

After confirmation from PG&E that the schedule would not be dramatically affected by raising the overhead utility lines, it is clear that Alternative 2: Low‐Water Crossing with Overhead Utility Conflict is the preferred alternative for this project.

It is therefore recommended that design development activities, including detailed geotechnical, hazardous material investigation, and potholing, be conducted as soon as funding is available.

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Coyote Creek Restoration Project

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