Section 1 – Finding of No Significant Impact
Section 2 – Section 7 of the Wild and Scenic Rivers Act Determination
Section 1

Finding Of No Significant Impact

Purpose and Need

This Finding of No Significant Impact (FONSI) documents the decision of the National Park Service (NPS) to adopt a plan to remove Happy Isles Gauging Station Bridge and the determination that no significant impacts on the human environment are associated with that decision. The National Park Service proposes to remove the Happy Isles Gauging Station Bridge in Yosemite Valley, within Yosemite National Park. The need for the proposed project arose as a result of the 1997 flood damage to the Happy Isles Gauging Station Bridge. Structural damage sustained during the flood, as well as subsequent deterioration and structural failure (including a large sinkhole on the river-left abutment), have resulted in the need to remove the failing bridge. The National Park Service intends to remove the failing structure, which has been closed to the public since 1997, in order to avoid uncontrolled bridge collapse and resulting environmental consequences. A complete description of the proposal and its environmental consequences are contained in the Happy Isles Gauging Station Bridge Removal Project Environmental Assessment.

Alternatives Analyzed

The Happy Isles Gauging Station Bridge Removal Project Environmental Assessment analyzed two alternatives, Alternative 1: No Action, and Alternative 2: Controlled Demolition. These alternatives were developed by the National Park Service based on the proposed action’s purpose and need, issues raised in scoping, and other public comment. The Happy Isles Gauging Station Bridge Removal Project Environmental Assessment disclosed the potential environmental consequences that may result from implementation of each alternative. Comments received during public review of the Happy Isles Gauging Station Bridge Removal Project Environmental Assessment were considered in preparation of this FONSI.

Alternative 1: No Action Alternative. The No Action Alternative represents conditions and management practices as they currently exist for the Happy Isles Gauging Station Bridge. It provides the basis for comparison for the action alternative. Under the No Action Alternative, Happy Isles Gauging Station Bridge would continue to degrade and would eventually fail. Bridge collapse would likely occur during high flow conditions. Bridge-related debris would be deposited downstream, possibly damaging the historic Happy Isles Gauging Station and disrupting the validity of measurements from the gauging station pool. Deposition of bridge-related debris would also adversely affect natural, cultural, and scenic resources and recreation. Sudden collapse of the bridge could result in serious injuries and/or fatalities to recreational users of the river. The National Park Service would remove bridge debris from the river as soon as possible following bridge collapse, although the retrieval effort may be delayed by several months, since debris removal activities would need to occur during periods of low flow. Diverted river flows and erosion could result in adverse impacts to vegetation, soils, and cultural resources along the riverbanks. Over the long term, uncontrolled failure of the bridge largely would restore free flow of the Merced River at this location.

Alternative 2: Controlled Demolition. Alternative 2, Controlled Demolition, would partially remove the Happy Isles Gauging Station Bridge. The river-right abutment, which is located on a large boulder on the riverbank, would be retained to protect the historic Happy Isles Gauging Station. Alternative 2 would involve separating the bridge into liftable segments and removing the segments using equipment located on the riverbank. A temporary containment system (e.g., a reinforced tarp, netting, cage, or floating barge) would be installed beneath the Happy Isles Gauging Station Bridge to catch small amounts of debris during partial bridge removal. This containment system would prevent slurry from concrete saws, as well as small debris, from falling into the Merced River.  However, not all demolition debris would be prevented from falling into the river; only masonry debris greater than 2 inches in any dimension and all metal debris would be removed. A temporary structural support system (e.g., scaffolding, jacks, or mechanical lifts) may be installed to prevent uncontrolled collapse of the bridge structure during demolition or to anchor the containment system.

Removal of Happy Isles Gauging Station Bridge would have short-term demolition-related impacts on natural, cultural, and social resources. Because demolition would occur in a controlled manner (e.g., within a delineated work area, during low-flow conditions, with the application of Best Management Practices), Alternative 2 would avoid the more pronounced adverse effects of uncontrolled bridge failure and debris retrieval activities described under Alternative 1. Demolition-related impacts would be reduced by application of Best Management Practices and resource-specific mitigation measures (refer to Chapter II). Minor regrading and revegetation would increase bank integrity, resulting in beneficial effects on soils, water quality, cultural resources, and biological resources. Similar to Alternative 1, controlled bridge removal largely would restore the free-flowing condition of the Merced River and return this portion of the river to a more natural condition, thereby enhancing its biological and hydrologic integrity. Alternative 2 would have a long-term, beneficial effect on natural and scenic resources because it would return a portion of the riverbank to a more natural state (benefiting wetland and aquatic resources), restore the active flood regime and fluvial processes, and improve views from the riverbank. Retention of the river-right abutment would have minimal impacts to river flow because the abutment is anchored on a large boulder that controls the majority of flow around the abutment.

Alternatives Considered but Dismissed.  The National Park Service considered three additional alternatives to the proposed action that were dismissed from further consideration because they did not meet the project's purpose and need. These included:

·         Complete Removal of Happy Isles Gauging Station Bridge.  To avoid damage to or loss of the gauging station, the National Park Service determined that the river-right abutment of the bridge should not be removed so that it could continue to protect the gauging station and streamflow gauge during high flows and flood events.

·         Repair of Happy Isles Gauging Station Bridge.  The National Park Service in consultation with the Federal Highway Administration determined that the existing bridge structure has been weakened and compromised in the vicinity of the river-left abutment due to the extent of concrete cracking, crushing, and displacement evidenced by the bridge.  Damage to the bridge is sufficiently extensive such that any attempted repair would require complete removal and replacement of the concrete for the entire west abutment, wingwalls, and a portion of the affected superstructure.

·         Uncontrolled Demolition of the Happy Isles Gauging Station Bridge.  This alternative was dismissed from further consideration because it would not take measures to prevent demolition material from falling into the Merced River, and it would not allow for protection of the river-right abutment during removal.

Environmentally Preferable Alternative

The environmentally preferred alternative is determined by applying criteria identified in Section 101 of the National Environmental Policy Act (NEPA) to each alternative considered. In accordance with the NEPA, the environmentally preferred alternative would best: (1) fulfill the responsibilities of each generation as trustee of the environment for succeeding generations; (2) assure for all generations safe, healthful, productive, and esthetically and culturally pleasing surroundings; (3) attain the widest range of beneficial uses of the environment without degradation, risk of health or safety, or other undesirable and unintended consequences; (4) preserve important historic, cultural and natural aspects of our national heritage and maintaining, wherever possible, an environment that supports diversity and variety of individual choice; (5) achieve a balance between population and resource use that will permit high standards of living and a wide sharing of life’s amenities; and (6) enhance the quality of renewable resources and approaching the maximum attainable recycling of depletable resources.

The National Park Service has considered all alternatives in this analysis in accordance with NEPA and CEQ regulations (CEQ Regulations, Section 1505.2) and has determined that Alternative 2: Controlled Demolition, as presented in the Happy Isles Gauging Station Bridge Removal Project Environmental Assessment is environmentally preferable. After review of potential resource and visitor impacts, and developing mitigation for impacts to natural and cultural resources, the preferred alternative achieves the greatest balance between the necessity of removing the damaged bridge area with preserving resources and visitor experience in the park.

Why the Preferred Alternative Will Not Have A Significant Effect On The Human Environment

Removal of Happy Isles Gauging Station Bridge would have short-term demolition-related impacts on natural, cultural, and social resources. Because demolition would occur in a controlled manner (e.g., within a delineated work area, during low-flow conditions, with the application of Best Management Practices), Alternative 2 would avoid the more pronounced adverse effects of uncontrolled bridge failure and debris retrieval activities described under Alternative 1. Demolition-related impacts would be reduced by application of Best Management Practices and resource-specific mitigation measures (refer to Mitigation, below). Minor regrading and revegetation would increase bank integrity resulting in beneficial effects on soils, water quality, cultural resources, and biological resources. Similar to Alternative 1, controlled bridge removal largely would restore the free-flowing condition of the Merced River and return this portion of the river to a more natural condition, thereby enhancing its biological and hydrologic integrity. Alternative 2 would have a long-term, beneficial effect on natural and scenic resources because it would return a portion of the riverbank to a more natural state (benefiting wetland and aquatic resources), restore the active flood regime and fluvial processes, and improve views from the riverbank. Retention of the river-right abutment would have minimal impacts to river flow because the abutment is anchored on a large boulder that controls the majority of flow around the abutment.

Minor, short-term inconveniences to visitors in the bridge vicinity would occur in the form of noise, dust, and other activities during demolition. Over the long term, the public will benefit from the removal of the bridge as a result of increased public safety.

In addition, no highly uncertain or controversial impacts, unique or unknown risks, significant cumulative effects, or elements of precedence have been identified, and implementing the Alternative 2 will not violate any federal, state, or local environmental protection law.

Non-impairment of Park Resources

Based on the analysis provided in the Happy Isles Gauging Station Bridge Removal Project Environmental Assessment, the National Park Service concludes that implementation of Alternative 2: Controlled Demolition, would have no major adverse impacts to a resource or value whose conservation is (1) necessary to fulfill specific purposes identified in the establishing legislation or proclamation of Yosemite National Park; (2) key to the natural or cultural integrity of Yosemite National Park or to opportunities for enjoyment of the park; or (3) identified as a goal in the park’s General Management Plan or other relevant National Park Service planning documents. Consequently, implementation of the proposed action will not violate the National Park Service Organic Act.

Mitigation

The following mitigation measures (table 1) have been incorporated into the project to avoid or reduce impacts to park resources.

Public Involvement and Coordination

Public Involvement

Scoping History.  On April 9, 2001, the Yosemite National Park Superintendent mailed a letter announcing the beginning of the planning process for removal of the Happy Isles Gauging Station Bridge. This letter was sent to over 6,200 individuals and organizations on the park’s planning mailing list, and was posted on the park’s web site. The letter also detailed the time, location, and purpose of an on-site public meeting at the bridge.

The purpose of the planning process was to identify alternatives for the Happy Isles Gauging Station Bridge Removal Project. During the planning process, alternatives were developed that addressed bridge removal and compliance with the Wild and Scenic Rivers Act of 1968, as amended (16 United States Code [USC] 1274[d]). Through scoping and the public comment review process on the Happy Isles Gauging Station Bridge Removal Project Environmental Assessment, the planning process is being conducted in consultation with affected federal agencies, state and local governments, tribal groups, and interested organizations and individuals.

TABLE 1: Mitigation Matrix

Mitigation Measure

Responsibility

  

The project will avoid or minimize impacts to natural and cultural resources. The project will be designed to work in harmony with the surroundings, particularly the Yosemite Valley Cultural Landscape. The project will reduce, minimize, or eliminate air and water nonpoint-source pollution. The project will be sustainable whenever practicable, by recycling and reusing materials, by minimizing materials, and by minimizing energy consumption during the project.

Yosemite National Park

Contractor

Ensure that the extent of impacts stay within the parameters of the project so they do not escalate beyond the scope of the environmental assessment, as well as to ensure that the project conforms with the U.S. Army Corps of Engineers Section 404 permits.

National Park Service project manager

Implement a natural resource protection program. Standard measures include pre-construction briefing of natural and cultural resource protection measures, construction scheduling, erosion and sediment control, use of fencing or other means to protect resources adjacent to the project area, salvage of native materials (rock, cobbles, gravels, plants, soil, litter, and duff) and reuse on the site to minimize the need to import non-native materials, removal of all food-related items or rubbish to bear-proof containers, and regrading and revegetation. Food will be stored in accordance with park regulations.

National Park Service project manager

Contractor

  

All construction equipment will be stored within the delineated work limits. Excavated and stored materials will be located within the upland staging area and contained and stabilized to prevent reentry into the river.

National Park Service project manager

Contractor

  

Ensure an emergency notification program is in place. Standard measures include notification of utilities and emergency response units prior to demolition activities. Locations of existing utilities will be identified prior to demolition activity to prevent damage to utilities, particularly the water supply lines that pass through the work limits. The contractor will call Underground Services Alert and National Park Service maintenance staff 72 hours prior to any ground disturbance. Demolition will not proceed until the process of locating existing utilities is completed. To avoid damage to underground water supply lines located beneath the service road east of the restrooms, heavy equipment will access the river-left demolition area via the service road located west of the restrooms. Because impacts to the existing 8-inch drainage pipe (which is connected to the 12-inch water line) could damage the existing water line, measures will be taken to avoid such impacts. Measures will include protection of this line from being struck or disturbed during the demolition and any associated grading.

National Park Service project manager

Contractor

  

All tools, equipment, barricades, signs, surplus materials, and rubbish will be removed from the project work limits upon project completion. Any asphalt surfaces that are damaged due to work on the project will be repaired to original condition. All demolition debris will be removed from the project site, including all visible concrete and metal pieces. Disturbed areas will be graded and raked smooth to eliminate tire tracks and tripping hazards.

National Park Service project manager

Contractor

GEOLOGY, GEOHAZARDS, AND SOILS

  

Provide erosion and sediment control per Stormwater Pollution Prevention Plan measures, described below.

National Park Service project manager

Contractor

  

HYDROLOGY, FLOODPLAINS, AND WATER QUALITY

  

Small wheeled or tracked equipment would be allowed to enter the river to assist in the placement of the structural support system or to remove demolition debris from the river. To protect the riverbank, this equipment will be lifted from the riverbank by crane and placed on the riverbed, or will be driven on a ramp into the river. Heavy equipment used within the bed and banks of the Merced River should be placed on mats, or other measures will be taken to minimize disturbance.

National Park Service project manager

Contractor

  

Masonry debris greater than two inches in any dimension and all metal debris that inadvertently falls into the river will be removed during demolition.

National Park Service project manager

Contractor

  

Heavy equipment shall be steam cleaned prior to entering the park to prevent importation of non-native plant species, and repaired of all petroleum leaks prior to working near the Merced River. Hydraulic hoses will be fastened tight and will be in good condition.

National Park Service project manager

Contractor

  

To minimize the possibility of hazardous materials seeping into soil, or water, equipment will be checked frequently to identify and repair any leaks. Standard measures include hazardous materials storage and handling procedures; spill containment, cleanup, and reporting procedures; and limitation of refueling and other hazardous activities to upland/nonsensitive sites. An adequate hydrocarbon spill containment system (e.g., floatable absorption boom, absorption materials, etc.) will be available on site, in case of unexpected spills in the project area. All equipment allowed within the river channel will be equipped with a hazardous spill containment kit.

National Park Service project manager

Contractor

  

HYDROLOGY, FLOODPLAINS, AND WATER QUALITY (Continued)

  

Implement stormwater management measures as necessary to reduce nonpoint- and point-source pollution discharge from paved and other impervious surfaces. This could include street sweeping, and use of permeable surfaces and vegetated or natural filters to trap or filter stormwater runoff.

National Park Service project manager

Contractor

  

WETLANDS

  

Minimize adverse effects to aquatic resources in accordance with Executive Order 11990 (Protection of Wetlands), the Clean Water Act, and Director’s Order #77-1.

National Park Service project manager

Contractor

  

Monitor area to ensure success of bank restoration and stability.

National Park Service project manager

  

VEGETATION

  

Avoid damage to natural surroundings in and around the work limits. Provide temporary barriers to protect existing trees, plants, and root zones, if necessary. Trees and other vegetation would not be removed, injured, or destroyed without prior written approval. Ropes, cables, or fencing would not be fastened to trees. All existing resource protection fencing (post and rope) will be left in place and protected from heavy equipment.

National Park Service project manager

Contractor

  

Ensure that the spread of non-native plant species is controlled. Standard measures include the following elements: ensure construction-related equipment arrives on site free of mud or seed-bearing material, certify all seeds and cover material as weed-free, identify nearby areas of non-native vegetation before construction, avoid spreading non-native vegetation within the project area, and revegetate with appropriate native species.

National Park Service project manager

Contractor

  

Avoid impacts to vegetative communities and trees. If avoidance is not feasible, written permission from the National Park Service project manager must be granted before proceeding.

National Park Service project manager

Contractor

  

Use only native plants in revegetation. Comply with the Yosemite Vegetation Management Plan (NPS 1997g) for revegetation within and around the project work site.

National Park Service project manager

Contractor

  

WILDLIFE AND SPECIAL STATUS SPECIES

  
     

Educate workers on the dangers of intentional or unintentional feeding of park wildlife, and on inadvertent harassment through observation or pursuit.

National Park Service project manager

Contractor

  

Minimize night lighting during construction. Where night lighting is necessary, design lighting to be minimal, directed downward, and shielded.

National Park Service project manager

Contractor

  

Excavation sites (trenches or pits) would have suitable ramps to allow all small mammals to exit these areas.

National Park Service project manager

Contractor

  

Special-Status Birds

·         To avoid conflicts with nesting birds, construction activities within nesting habitat will occur outside the breeding season (typically March to August).

·         If it is determined that the action will not impact an active nest or disrupt breeding behavior, construction will proceed without any restriction or mitigation measure.

·         If it is determined that construction will impact an active nest or disrupt reproductive behavior then avoidance strategies will be implemented. Construction could be delayed within 500 feet of such a nest until a qualified biologist determines, in consultation with National Park Service wildlife biologists, that the subject birds are not nesting or until any juvenile birds are no longer using the nest as their primary day and night roost.

National Park Service project manager

Contractor

  

WILDLIFE AND SPECIAL STATUS SPECIES (Continued)

  

Special-Status Aquatic Species

·         Implementation of the following conservation and protection measures would reduce or eliminate potential taking of special-status aquatic species.

·         Work activities within potential special-status aquatic species habitat will be completed during low-flow conditions.

·         The aquatic construction boundary will be fenced to prohibit to control siltation and disturbance to aquatic habitat.

·         All construction adjacent to or within aquatic habitats will be regularly monitored.

·         All fueling and maintenance of vehicles and equipment will occur at least 20 meters (65 feet) from any aquatic habitat.

National Park Service project manager

Contractor

  

AIR QUALITY

  

Implement a dust abatement program. Construction contractors will implement the following measures:

·         Water all active work areas, access roads and paths, parking areas, and staging areas at least twice daily (use of dust abatement products would not be allowed). Ensure that applied water does not enter the Merced River.

·         Cover all trucks hauling demolition debris and other loose materials that could spill onto paved surfaces, or require all trucks to maintain adequate freeboard.

·         All paved areas that are subject to vehicular and pedestrian traffic will be kept clean of construction debris and soils. Sweeping of these areas will be implemented as necessary.

·         Cover all stockpiles.

·         Limit traffic speeds on unpaved roads and paths to 5 miles per hour.

·         Revegetate disturbed areas, if appropriate, upon completion of the project.

National Park Service project manager

Contractor

  

Implement vehicle emissions controls. Construction contractors will implement the following measures:

·         Use California on-road diesel fuel for all diesel-powered construction equipment.

·         Use construction equipment that is properly tuned and maintained in accordance with manufacturers’ specifications.

·          Use best management construction practices to avoid unnecessary emissions (e.g., engines of trucks and vehicles in loading and unloading areas would be turned off when not in use).

National Park Service project manager

Contractor

  

NOISE

  

If deemed necessary, demolition work on weekends or federal government holidays may be authorized, with prior written approval of the Superintendent. To the extent possible, all on-site noisy construction work above 76 dba (such as the operation of heavy equipment) will be done between the hours of 8:30 a.m. and 5:00 p.m. to minimize disruption to nearby campers.

National Park Service project manager

Contractor

  

All construction equipment will be equipped with mufflers kept in proper operating conditions, and when possible, equipment will be shut-off rather than allowed to idle. Standard noise abatement measures include the following elements: a schedule that minimizes impacts to adjacent noise-sensitive uses (campgrounds, etc.) between 8:30 a.m. and 5:00 p.m., use of the best available noise control techniques wherever feasible, use of hydraulically or electrically powered impact tools when feasible, and location of stationary noise sources as far from sensitive public use areas as possible. Trucks and other construction equipment will be equipped with standard muffling devices and will not be excessively loud.

National Park Service project manager

Contractor

  

Ensure cultural resources within and adjacent to the project area are protected. Standard measures include use of fencing or other means to protect cultural resources adjacent to demolition. This task includes specific demolition monitoring by resource specialists, as well as treatment and reporting procedures.

National Park Service project manager

Contractor

Conduct bridge demolition in accordance with the park’s 1999 Programmatic Agreement and Standard Mitigation Measures presented in the Yosemite Valley Plan. Standard mitigation measures include recordation, salvage, and interpretation.

National Park Service project manager

Contractor

  

SCENIC RESOURCES

  

Avoid or minimize adverse effects on natural communities and visual intrusion into the natural landscape.

National Park Service project manager

Contractor

  

RECREATION

  

Implement measures to reduce effects of demolition on visitor safety and experience. Visitors, contractors, and park personnel will be safeguarded from demolition activities. A barrier plan indicating locations and types of barricades will be used to protect public health and safety.

National Park Service project manager

Contractor

  

On-Site Public Meeting.  On April 18, 2001, the National Park Service held an on-site public meeting at the Happy Isles Gauging Station Bridge to discuss its potential removal. The purpose of the meeting was to: (1) provide participants with an overview of existing conditions and the proposed action; (2) ask participants to identify key issues that should be analyzed during the environmental review and compliance process; and (3) provide an opportunity for participants to ask questions regarding project alternatives and the overall environmental review and compliance process.

Results of Scoping.   The notice to interested agencies and public was released on April 6,2001. Scoping comments were received through April 27, 2001. As a result of the scoping effort, 60 responses were elicited. All comments received in response to the scoping notices have been duly considered and will remain in the project record throughout this planning process.

Public Comment.  The Happy Isles Gauging Station Bridge Removal Project Environmental Assessment was released for a 30-day public review period beginning August 9, 2001 and closed September 8, 2001. Comments received consisted of 30 letters, emails, and faxes from 35 individuals with a total of 74 comments, of which 66 comments pertained to the Happy Isles Gauging Station Bridge Removal Project while 8 comments were beyond the scope of this planning effort. Issues raised included document length and format, NEPA compliance, alternatives, protection of the historic Happy Isles Stream Gauge, interpretation, aesthetics, use of Best Management Practices during project implementation, and restoration.  None of the comments received introduced substantive new information nor raised any issues not fully considered in the Happy Isles Gauging Station Bridge Removal Project Environmental Assessment.  No modifications to the Proposed Action were made as a result of comments. A copy of the Happy Isles Gauging Station Bridge Removal Project Environmental Assessment Summary of Public Comments and Responses is on file at Yosemite National Park and can be requested from the National Park Service at:

Superintendent, Yosemite National Park

ATTN.:  Happy Isles Gauging Station Bridge Removal Project

P.O. Box 577

Yosemite, California 95389

FAX: 209/379-1294

EMAIL:

Coordination

U.S. Army Corps of Engineers.  The U.S. Army Corps of Engineers issued a verification letter to the National Park Service on October 2, 2001 granting the use of Nationwide Permit Number 13 for the Happy Isles Gauging Station Bridge Project (Project Number 199900464). A copy of the verification letter is on file at Yosemite National Park.

Central Valley Regional Water Quality Control Board.  Pursuant to Sections 401 and 404 of the Clean Water Act, the Central Valley Regional Water Quality Control Board issued a waiver for the Happy Isles Gauging Station Bridge Removal Project on September 3, 1999.The National Park Service received confirmation on August 23, 2001 (CVRWQCB 2001) from the Central

Valley Regional Water Quality Control Board that the 1999 waste discharge waiver for the project remains valid throughout the duration of the project. A copy of the waste discharge waiver is on file at Yosemite National Park.

Federal Highway Administration.  The Federal Highway Administration examined the Happy Isles Gauging Station Bridge (Federal Highway Administration Structure No. 8800-037S) on three occasions since the January 1997 flood, including on June 22 and 23, 1997, June 1998, and August 2000. In 1997, the Federal Highway Administration determined that the bridge was in poor condition due severe scour, full-length undermining of the bridge, and loss of support of the river-left abutment, all of which were attributed to the January 1997 flood. The Federal Highway Administration determinations on the Happy Isles Gauging Station Bridge are on file at Yosemite National Park.

U.S. Fish and Wildlife Service. The U.S. Fish and Wildlife Service has determined that the Happy Isles Gauging Station Bridge Project is not likely to adversely affect any threatened or endangered species or critical habitat (U.S. Fish and Wildlife Service Letter, October 11, 2001, Reference Number 1-1-01-I-3366).

California State Historic Preservation Officer. The National Park Service reviewed the documentation regarding historic properties under stipulations of the 1999 Programmatic Agreement and found that there would be adverse effects to a single historic property, the Happy Isles Gauging Station Bridge itself, under section 106 of the National Historic Preservation Act.  However, this impact is not considered a significant adverse effect in terms of NEPA. The National Park Service forwarded the documentation and a formal letter to the California State Historic Preservation Officer (SHPO) requesting review and comment on the finding.  A letter of concurrence was received from the California State Historic Preservation Officer on October 25, 2001, stating there is no objection to any aspect of the notification regarding the adverse effects, provided the proposed mitigation measures are implemented (table 1). A copy of the verification letter is on file at Yosemite National Park (Reference Number NPS011023Y).

 Culturally Associated American Indians. The National Park Service conducted consultation with culturally associated American Indian tribes according to stipulations of the Programmatic Agreement and specific agreements. As a result of the consultation, no comments were received from these groups concerning the proposed action.

Conclusion

Based on information contained in the Happy Isles Gauging Station Bridge Removal Project Environmental Assessment as summarized above, the nature of comments of agencies and the public, and the incorporation of the mitigation measures to avoid or reduce potential direct, indirect, and cumulative impacts, it is the determination of the National Park Service that the Proposed Action is not a major federal action significantly affecting the quality of the human environment.  No long-term adverse impacts to floodplains or wetlands would occur from the Proposed Action.  Therefore, the National Park Service finds the Proposed Action to be acceptable under Executive Order 11988 for the protection of floodplains and Executive Order 11990 for the protection of wetlands.  Therefore, in accordance with the National Environmental Policy Act of 1969 and regulations of the Council on Environmental Quality (40 CFR 1508.9), an environmental impact statement will not be prepared. The Proposed Action as detailed in the Happy Isles Gauging Station Bridge Removal Project Environmental Assessment may be implemented immediately.

Recommended:

Superintendent, Yosemite National Park                                                      10/31/2001           Date

Approved:

Director Pacific West Region, National Park Service                                   10/31/2001           Date

Errata for the Environmental Assessment

This section provides a catalog of the corrections and changes made to the Happy Isles Gauging Station Bridge Removal Project Environmental Assessment since its original release for comment. Revised or new language is underlined. Deleted text is marked by strikethrough.

Where a change is made as part of a response to a comment on the Happy Isles Gauging Station Bridge Removal Project Environmental Assessment, the comment number is noted in brackets at the end of the text change.

Page III-17, paragraph 3, sentence 3 is revised as follows:

The Cowardin system also recognizes that many unvegetated sites (e.g., mudflats, stream shallows, saline lakeshores, playas, deepwater) or sites lacking soil (e.g., rocky shores, gravel beaches) are wetland habitats. (Agency, Denver, CO - HI-EA-10)

Page III-17, paragraph 5, sentence 2 is revised as follows:

No riparian wetland communities (palustrine forest or palustrine scrub shrub) occur within the immediate project area (ESA 2001). (Agency, Denver, CO - HI-EA-10)

Page IV-50, paragraph 4, sentence 1 is revised as follows:

Partial removal of the Happy Isles Gauging Station Bridge would have local, short-term, adverse, demolition-related effects to approximately 0.3 0.6 acre of aquatic habitat. Effects would result from heavy equipment and demolition activities and could include soil compaction, dust, vegetation removal, root damage, erosion, and potential introduction and spread of non-native species. The addition of silt, the resuspension of sediment, or the introduction of construction-related pollutants (fuels, lubricants, etc.) could degrade the quality of aquatic habitats. Because demolition would occur in a controlled manner (e.g., within a delineated work area, during low-flow conditions, with the application of Best Management Practices), Alternative 2 would avoid the more pronounced adverse effects of debris retrieval activities described under Alternative 1. The application of mitigation measures described in Chapter II (Best Management Practices) would further reduce the potential adverse impacts to aquatic habitats. Therefore, Alternative 2 would have a local, short-term, negligible, beneficial effect on the aquatic environment compared to Alternative 1.

 

Section 2

Section 7 of the Wild and Scenic Rivers Act Determination

Introduction

Purpose of This Determination

The purpose of this determination is to evaluate the impact of the proposed Happy Isles Gauging Station Bridge Removal Project on the free-flowing condition and the Outstandingly Remarkable Values for which the Merced River was designated Wild and Scenic.

Authority

The authority for this determination is found in Section 7(a) of the Wild and Scenic Rivers Act (Public Law 90-542, as amended, 16 U.S.C. 1271-1278). Section 7(a) states:

      “no department or agency of the United States shall assist by loan, grant, license or otherwise in the construction of any water resources project that would have a direct and adverse effect on the values for which such river was established, as determined by the Secretary charged with its administration.”

While the Wild and Scenic Rivers Act does not prohibit development along a river corridor, it does specify guidelines for the determination of appropriate actions within the bed and banks of a Wild and Scenic River. As the designated river manager for the Merced River segments located within the boundaries of Yosemite National Park and the El Portal Administrative Site, the National Park Service must carry out a Section 7 determination on all proposed water resources projects [1] to ensure they do not directly and adversely impact the values for which the river was designated. [2]

Wild and Scenic River Designation

In 1987, the U.S. Congress designated the Merced a Wild and Scenic River to protect the river’s free-flowing condition and to protect and enhance its unique values for the benefit and enjoyment of present and future generations (16 United States Code [USC] 1271). This designation gives the Merced River special protection under the Wild and Scenic Rivers Act.

The passage of Public Law 100-149 on November 2, 1987 and Public Law 102-432 on October 23, 1992 placed 122 miles of the main stem and South Fork of the Merced River, including the forks of Red Peak, Merced Peak, Triple Peak, and Lyell into the Wild and Scenic River System. The National Park Service manages 81 miles of the Merced River, encompassing both the main stem and the South Fork in Yosemite National Park and the El Portal Administrative Site . The U.S. Forest Service and the Bureau of Land Management administer the remaining 41 miles of the designated river.

Happy Isles Gauging Station Bridge Removal Project Wild and Scenic Rivers Act Section 7 Determination

Table 1 presents the Section 7 evaluation for the Happy Isles Gauging Station Bridge Removal Project. This evaluation is based on guidance provided in the Wild and Scenic Rivers Act: Section 7 Technical Report (Interagency Wild and Scenic Rivers Coordinating Council), Appendix C, Evaluation Procedure under “Direct and Adverse.” The “direct and adverse” evaluation procedure is carried out for water resources projects licensed by the Federal Energy Regulatory Commission or other federally assisted water resources projects within the Wild and Scenic River Boundary of the designated river. The Happy Isles Gauging Station Bridge is within the bed and banks of the Merced River. All proposed activities will occur within the Wild and Scenic boundary of the Merced River. The Section 7 Determination process applies only to the proposed action.

TABLE 1: Section 7 Evaluation for Happy Isles Gauging Station Bridge Removal Project

Evaluation Criteria

Project Data

Define the Proposed Activity

Project proponent

National Park Service, Yosemite National Park

Purpose and need for the project

The purpose of the Happy Isles Gauging Station Bridge Removal Project is to:

·          Protect visitor health and safety by eliminating the threat posed by the failing concrete bridge.

·          Protect park resources from localized flooding that could result from uncontrolled bridge collapse during a high water period.

·          Prevent the difficult and potentially dangerous removal of bridge debris from the river that would be required if the bridge collapsed.

·          Protect park infrastructure (e.g., the historic Happy Isles Gauging Station and Happy Isles Vehicle Bridge, as well as water supply lines) from possible damage due to uncontrolled bridge collapse by removing the bridge before it collapses of its own accord.

·          Protect Happy Isles Gauging Station from gauge calibration distortion caused by an uncontrolled bridge collapse.

·          Enhance the free-flowing condition of the river.

The need for the proposed project arose as a result of the 1997 flood damage to the Happy Isles Gauging Station Bridge. Structural damage sustained by the bridge during the 1997 flood, as well as subsequent deterioration and structural failure (including a large sinkhole on the river-left abutment), have resulted in the need to remove the failing bridge before it collapses of its own accord. The National Park Service intends to remove the failing structure, which has been closed to the public since 1997.

Initial and subsequent evaluations by the Federal Highway Administration in 1997, 1998, and 2001 (letters on file at Yosemite National Park) indicate that the bridge is in danger of collapse due to severe flood damage, and total collapse of the river-left side of the structure is imminent. The undermined river-left abutment and subsequent settlement have rendered the Happy Isles Gauging Station Bridge unsafe.

Geographic location of the project

The Happy Isles Gauging Station Bridge is located on the main stem of the Merced River in Yosemite National Park, at the far east end of Yosemite Valley (Latitude 37°43'54", Longitude 119°33'28" NAD27). Refer to Figure I-1 of the Happy Isles Gauging Station Bridge Removal Project Environmental Assessment.

Project description

The proposed action is the Controlled Demolition Alternative, which involves partially removing the Happy Isles Gauging Station Bridge. The river-right abutment, which is located on a large boulder on the riverbank, will be retained to protect the historic Happy Isles Gauging Station. The Controlled Demolition Alternative will involve separating the bridge into liftable segments and removing the segments using equipment located on the riverbank. A temporary containment system (e.g., a reinforced tarp, netting,  cage, or floating barge) will be installed beneath the Happy Isles Gauging Station Bridge to catch small amounts of debris during partial bridge removal. This containment system will prevent slurry from concrete saws, as well as small debris, from falling into the Merced River. However, not all demolition debris would be prevented from falling into the river; masonry debris greater than 2 inches in any dimension and all metal debris that inadvertently fall into the river would be removed. A temporary structural support system (e.g., scaffolding, jacks, or mechanical lifts) may be installed, if necessary, to prevent uncontrolled collapse of the bridge structure during demolition or to anchor the containment system.

Once the river-left abutment has been removed, the existing void in the riverbank will be filled and shaped to match adjacent bank composition (boulders, cobbles, and gravels) and contour. The large size of substrate materials along this stretch of the river provides for bank stability. Riparian vegetation will be planted to match conditions of adjacent portions of the riverbank, but would not be relied upon to provide for bank stability along this steep gradient section of the river.  A viewing platform will be established on the river-right abutment of the bridge. The platform will allow visitors views of the Merced River.

Duration of the proposed activities

The U.S. Army Corps of Engineers requires that demolition activities occur during low water months. In-channel activities therefore will take place during the fall of 2001, when flow of the Merced River is expected to be less than 200 cubic feet per second (approximately 95% of the time). Bridge demolition will be avoided during higher flow periods.

Magnitude and/or extent of the proposed activities

Refer to the Happy Isles Gauging Station Bridge Removal Project Environmental Assessment, Chapter IV, Environmental Consequences for detailed data concerning potential impacts of the proposed action.

Mitigation

The proposed action will protect Outstandingly Remarkable Values from possible damage from uncontrolled collapse of the bridge, make a small improvement to the free-flowing condition of the river, and restore natural fluvial processes in the vicinity of the river-left abutment of the bridge. Mitigation (e.g., Best Management Practices, and resource-specific measures) is incorporated into the proposed action. Refer to the Happy Isles Gauging Station Bridge Removal Project Environmental Assessment, Chapter II, Alternatives for mitigation measures incorporated into the proposed action.

Relationship to past and future management activities

The Yosemite Valley Plan calls for the replacement of the Happy Isles Gauging Station Bridge. The Happy Isles Gauging Station Bridge Removal Project is being executed consistent with the Merced Wild and Scenic River Comprehensive Management Plan and General Management Plan. Implementation of the proposed action will not alter management of this river segment.

Describe How the Proposed Activity Will Directly Alter Within-Channel Conditions

The position of the proposed activity relative to the streambed and streambanks

The Happy Isles Gauging Station Bridge is located within the bed and banks of the Merced River. The demolition activities to remove the bridge will occur within the bed and banks of the Merced River as well.

Any likely resulting changes in:

Active channel location

Removal of the Happy Isles Gauging Station Bridge will eliminate an existing constriction to the natural flow of the Merced River. Currently, the bridge is causing localized bank erosion, stream widening, and can result in storm-related flooding that adversely impacts areas beyond the riverbanks and threatens park facilities. Once removed, the river channel is expected to return to a more natural flow condition, similar to what existed prior to bridge construction. The river-right abutment, which will be left in place, will not impede river flows during normal flow conditions because the abutment is anchored on a large boulder that controls the majority of flow around the abutment. The active channel location will not be altered. The bridge removal action will improve the active channel by returning it to more natural conditions.

Channel geometry (cross-sectional shape, width, depth characteristics)

The project will remove the river-left abutment and bridge deck leaving the river-right abutment intact to protect the Happy Isles Gauging Station from flood damage and excessive scour. The bridge removal will eliminate a constriction to natural river flow and removing the river-left abutment will reduce the occurrence of stream bank erosion and scour that form downstream eddies adjacent to the abutment. The river reach in the immediate vicinity of the bridge will be returned to flow conditions similar to those that existed prior to the bridge construction. Overall channel geometry, both in the project vicinity and along the entire reach will be unaffected.

Channel slope (rate or nature of vertical drop)

The current configuration of the bridge does not alter the slope of the river channel and the overall channel slope through this segment will remain unaffected by the bridge removal.

Channel form (straight, meandering, or braided)

The Merced River through the project area is a straight river channel underlain by boulders and cobbles. Removal of the bridge will not affect the channel form.

Relevant water quality parameters (turbidity, temperature, nutrient availability)

The removal of the bridge will not result in a long-term net increase or decrease of turbidity, temperature, nutrient availability, or other pollutant loads (sediment, bacteria) within the Merced River.

Navigation of the river

River navigation is not applicable to this section of river.

Describe How the Proposed Activity Will Directly Alter Riparian and/or Floodplain Conditions

The position of the proposed activity relative to the riparian area and floodplain

The Happy Isles Gauging Station Bridge is located within the bed and banks of the Merced River – below ordinary high water and within the 100-year floodplain.

Any likely resulting changes in:

Vegetation composition, age structure, quantity, or vigor

Project implementation could result in the possible removal of one mature tree. The tree would be removed only if deemed necessary. Should the tree be removed, the National Park Service would either cut and remove the tree from the site, cut and retain the tree to contribute woody debris to the river, or destabilize and control the fall of the tree to retain woody debris and a natural-appearing fallen tree with the root ball attached. Such activities would occur subsequent to bridge demolition. Removal of the river-left abutment will somewhat improve free-flow of the Merced River and return this portion of the river to a more natural state, thereby enhancing its biological integrity. Minor regrading and revegetation will increase bank and vegetation integrity in this area.

Relevant soil properties such as compaction or percent bare ground

No long-term adverse impact to soil resources is anticipated.  The project may decrease concentrated visitor use on the riverbank in the river-left abutment area thereby reducing soil compaction and improving riverbank soil conditions.

Relevant floodplain properties such as width, roughness, bank stability, or susceptibility to erosion

Currently, the Happy Isles Gauging Station Bridge constricts river flow. As was observed during the January 1997 flood, the bridge can act as a debris dam, forcing flood waters to leave the riverbanks and flood areas adjacent to the river. Because the project will remove the constriction and the river has ample capacity, the river is not expected to overflow its banks at flood stage. The project restores the river to more natural flow conditions and therefore, will reduce the potential for flooding due to river constriction. The project will not affect the natural floodplain properties within this reach.

Once the river-left abutment has been removed, the existing void in the riverbank will be filled and shaped to match adjacent bank composition (boulders, cobbles, and gravels) and contour. The large size of substrate materials along this stretch of the river provides for bank stability. Riparian vegetation will be planted to match conditions of adjacent portions of the riverbank, but would not be relied upon to provide for bank stability along this steep gradient section of the river. Because this reach of the Merced River is underlain by large granitic boulders and these boulders naturally armor the riverbank, the placement of boulders in the vicinity of the river-left abutment would essentially replace boulders that were removed when the bridge was built. This will return the bank to a more natural condition, as can be seen immediately upstream and downstream of the bridge.

Describe How the Proposed Activity Will Directly Alter Upland Conditions

The position of the proposed activity relative to the uplands

The proposed action is located within the bed and banks of the Merced River. Uplands will not be affected by the proposed action.

Any likely resulting changes in:

Vegetation composition, age structure, quantity, or vigor

No measurable effect to age, vigor, quantity, structure or composition of upland vegetation. Minor regrading and revegetation would increase local bank and vegetation integrity. Implementation of these measures under the proposed action would result in localized beneficial effects on vegetation. The extent and quality of vegetation throughout the remainder of the Yosemite Valley segment of the river would be unaffected.

Relevant soil properties such as compaction or percent bare ground

No measurable effect to upland soil resources. Site restoration and stabilization would repair eroded areas and increase the protection of riverbanks, adjacent trails, and Yosemite Valley’s water supply line, resulting in a localized beneficial impact on soils. Native soils throughout the remainder of the Yosemite Valley segment of the river would be unaffected.

Relevant hydrologic properties such as drainage patterns or the character of surface and subsurface flows

No measurable effect to upland hydrologic properties. No portion of the proposed action, including equipment staging, demolition activities, or materials storage, would be located within or otherwise affect surface or subsurface drainage patterns from the uplands to the Merced River.

Potential changes in upland conditions that would influence archeological, cultural, or other identified significant resource values

All actions would be performed in accordance with stipulations in the park’s 1999 Programmatic Agreement. The proposed action would have no measurable effect to archeological, cultural, or other identified significant resource values in upland areas.

Evaluate and Describe How Changes in On-Site Conditions Can or Will Alter Existing Hydrologic or Biologic Processes

The ability of the channel to change course, re-occupy former segments, or inundate its floodplain

Currently, the Happy Isles Gauging Station Bridge constricts river flow. As was observed during the January 1997 flood, the bridge can act as a debris dam, forcing flood waters to leave the riverbanks and flood areas adjacent to the river. Because the project will remove the constriction and the river has ample capacity, the river is not expected to overflow its banks at flood stage. The project restores the natural river flow conditions and therefore, will reduce the potential for storm-stage flooding due to river constriction.

Streambank erosion potential, sediment routing and deposition, or debris loading

Streambank erosion potential is highest when river flow is constricted by an in-stream structure such as a bridge. The proposed action will remove the bridge, thereby removing the constriction, restoring flows to more natural conditions, and restoring natural erosion, sedimentation, and depositional processes. The presence of the river-right abutment will not initiate or increase streambank scour caused by upstream eddies because the abutment is anchored on a large boulder that controls the majority of flow around the abutment.

Once the river-left abutment has been removed, the existing void in the riverbank will be filled and shaped to match adjacent bank composition (boulders, cobbles, and gravels) and contour. The large size of substrate materials along this stretch of the river provides for bank stability. Riparian vegetation will be planted to match conditions of adjacent portions of the riverbank, but would not be relied upon to provide for bank stability along this steep gradient section of the river. Because this reach of the Merced River is underlain by large granitic boulders and these boulders naturally armor the riverbank, the placement of boulders in the vicinity of the river-left abutment would essentially replace boulders that were removed when the bridge was built. This will return the bank to a more natural condition, as can be seen immediately upstream and downstream of the bridge.

The amount or timing of flow in the channel

Removal of the bridge deck and river-left abutment will not affect flow rates or discharge of the river.

Existing flow patterns

Removal of the bridge deck and river-left abutment will eliminate an existing constriction to the natural flow of the Merced River. Once removed, the river channel is expected to return to a more natural flow condition, similar to what existed prior to bridge construction. By removing the bridge deck and river-left abutment, constriction of flood waters behind the bridge will be eliminated and the river should remain within its banks during flood stage. Retaining the river-right abutment will not impede river flows during normal flow conditions because the abutment is anchored on a large boulder that controls the majority of flow around the abutment.

Surface and subsurface flow characteristics

The proposed action will have no measurable effect on surface or subsurface flow characteristics. No portion of the proposed action, including equipment staging, demolition activities, or materials storage, would be located within or otherwise affect surface or subsurface drainage patterns from the uplands to the Merced River.

Flood storage (detention storage)

By removing the bridge deck and river-left abutment, constriction of flood waters behind the bridge will be eliminated and the river will remain within its banks during flood stage. Otherwise, there will be no measurable effect to flood storage as a result of the proposed action.

Aggregation and/or degradation of the channel

No measurable effect to aggregation and/or degradation of the channel. The proposed action will remove the bridge deck and river-left abutment, thereby removing the river-constricting bridge, restoring natural flows, and restoring natural erosion, sedimentation, and depositional processes.

Biological processes such as:

  

Reproduction, vigor, growth and/or succession of streamside vegetation

Removal of the river-left abutment will somewhat improve the free-flow of the Merced River and return this portion of the river to a more natural state, thereby enhancing its biological integrity. Minor regrading and revegetation in this area will improve bank and vegetation integrity.

Nutrient cycling

No measurable effect is anticipated. The proposed action will not adversely affect riparian vegetation, woody debris or free-flowing characteristics (major contributing components of riverine nutrient cycling) of the Merced River. Local nutrient availability and cycling may be temporarily affected during the 2-month demolition period due to an increased amount of fine sediment released in the river. However, the sediment dislodged by construction associated with the proposed action is anticipated to be less than would occur under the No Action Alternative, as construction activities would be centralized in one location along the riverbank. In the long-term, nutrient availability will be enhanced because the minor regrading and revegetation will improve bank and vegetation integrity.

Fish spawning and/or rearing success

No measurable effect is anticipated. The river in the vicinity of Happy Isles Gauging Station Bridge is swift and lacks fish spawning or rearing habitat (e.g., riffles, pools, gravel substrate). Minor regrading and revegetation would increase bank integrity, somewhat improving fish habitat. The extent and quality of fish habitat throughout the remainder of the Yosemite Valley segment of the river would be unaffected.

Riparian dependent avian species needs

No measurable effect is anticipated. The river in the vicinity of Happy Isles Gauging Station Bridge supports no riparian vegetation. No riparian vegetation would be removed under the proposed action. The extent and quality of avian habitats throughout the remainder of the Yosemite Valley segment of the river would be unaffected.

Amphibian/mollusk needs

No measurable effect is anticipated. The river in the vicinity of Happy Isles Gauging Station Bridge is swift and lacks amphibian or mollusk habitat. The proposed action would not have an adverse effect on amphibian or mollusk needs. The extent and quality of amphibian and mollusk habitats throughout the remainder of the Yosemite Valley segment of the river would be unaffected.

Species composition (diversity)

No measurable effect is anticipated. Upon project completion, the biological integrity of the site would be enhanced.

Estimate the Magnitude and Spatial Extent of Potential Off-Site Changes

Consider and document:

  

Changes that influence other parts of the river system

The effects of the proposed action are localized and will not result in changes that will influence other portions of the Merced River system.

The range of circumstances under which off-site changes might occur (for example, as may be related to flow frequency)

Once the bridge is removed, river flow will no longer be constricted in this area, and natural flow processes will largely prevail. There are no obvious circumstances under which offsite change will occur.

The likelihood that predicted changes will be realized

The predicted change for this project is that more natural, unconstricted flows will be restored under the proposed action. There is every indication that these predicted changes will be realized.

Specify processes involved, such as water and sediment, and the movement of nutrients

Natural fluvial processes such as free-flow and sediment transport would be enhanced upon completion of the proposed action.

Define the Time Scale Over Which the Above Effects are Likely to Occur

Review the above effects, looking independently at the element of time.  Define and document the time scale over which the effects will occur

Demolition will occur over a period of about 2 months. Riverine system adjustment to a natural hydrologic regime will be immediate.

Compare Project Analyses to Management Goals

Identify and document project effects on achievement, or timing of achievement, of management goals and objectives relative to free-flow, water quality, riparian area, and floodplain conditions, and the Outstandingly Remarkable Values, and river classification. The following evaluates the project’s effects and relationship to the goals of the set forth in the Merced River Plan for the management of the Merced Wild and Scenic River.

Protect and Enhance River-Related Natural Resources

The proposed action will partially remove a human-made structure from the bed and banks of the Merced River. Free flow and natural fluvial processes (e.g., erosion, sediment transport, and deposition) will be largely enhanced. Removal of the river-left abutment will return this portion of the river to a more natural state, thereby enhancing its biological integrity. Minor regrading and revegetation in this area will improve bank and vegetation integrity. The proposed action is consistent with this management goal.

Protect and Restore Natural Hydrological and Geomorphic Processes

The proposed action will partially remove a human-made structure from the bed and banks of the Merced River. Removal of the Happy Isles Gauging Station Bridge deck and river-left abutment will eliminate an existing constriction to the natural flow of the Merced River. Currently, the bridge is causing localized bank erosion, stream widening, and can result in storm-related flooding that adversely impacts areas beyond the riverbanks and threatens park facilities. Once removed, the river channel is expected to return to a more natural flow condition, similar to what existed prior to bridge construction. The river-right abutment, which will be left in place, will not impede river flows during normal flow conditions because the abutment is anchored on a large boulder that controls the majority of flow around the abutment. The bridge removal action will improve the active channel by returning it to more natural conditions. The proposed action is consistent with this management goal.

Protect and Enhance River-Related Cultural Resources

Partial removal of the Happy Isles Gauging Station Bridge will require demolition operations along the banks of the Merced River. Ground-disturbing activities could result in an adverse impact to historic archeological resources. Any ground disturbing activity will be conducted in accordance with the 1999 Programmatic Agreement.

Based on a cultural resources inventory of Yosemite National Park, completed in 1994, the Happy Isles Gauging Station Bridge is a contributing feature of the Yosemite Valley Cultural Landscape, that is eligible for listing in the National Register of Historic Places. The controlled demolition of the Happy Isles Gauging Station Bridge will result in the loss of this cultural resource, resulting in an adverse effect on this historic structure. The bridge, however, is damaged beyond repair, and its uncontrolled failure is imminent. Should the bridge collapse, it could damage the historic Happy Isles Vehicle Bridge or Happy Isles Gauging Station downstream of the bridge. Controlled removal of the bridge prevents damage to these important historic resources, which beneficially effects cultural resources.

Protect and Enhance River-Related Cultural Resources (Continued)

Removal of the Happy Isles Gauging Station Bridge will be conducted in accordance with the 1999 Programmatic Agreement. In 1991, the bridge was documented to Historic American Engineering Record standards, which included historical and descriptive data, measured drawings, and archival photographs. In accordance with the protocols agreed upon by Yosemite National Park and the State Historic Preservation Officer on March 20, 1997, the current level of documentation for the Happy Isles Gauging Station Bridge was determined sufficient. The proposed action is consistent with this management goal.

Provide Diverse River-Related Recreational and Educational Experiences

The proposed action will not alter river-related recreational or educational experiences within the river corridor. The proposed action is consistent with this management goal.

Provide Appropriate Land Uses

The proposed action will not alter land use within the river corridor. The proposed action is consistent with this management goal.

Make the Section 7 Determination

Based on the above analysis, document:

The effects of the proposed activity on conditions of free flow, including identification of any proposed measures to minimize those effects.

The proposed action will partially remove a human-made structure from the bed and banks of the Merced River enhancing free flow and natural fluvial processes (e.g., sediment transport, natural erosion and deposition) in the immediate area. Upon removal of the Happy Isles Gauging Station Bridge deck and river-left abutment, the localized flow within the channel will no longer constrict river flows thereby reducing riverbank erosion and the potential for storm-stage flooding caused by material accumulation behind the bridge structure. Short-term impacts associated with bridge removal will be reduced through the application of Best Management Practices.

Any direct and adverse effects on the Outstandingly Remarkable Values for which the river was designated.

The proposed action will result in localized, beneficial effects to scenic, recreation, biological, and hydrologic processes Outstandingly Remarkable Values and localized adverse and beneficial effects to the cultural Outstandingly Remarkable Value. On a segment-wide basis, Outstandingly Remarkable Values would not be appreciably affected.

Section 7 Determination

The proposed action will partially remove a human-made structure from the bed and banks of the Merced River. Free flow and natural fluvial processes (e.g., sediment transport, natural erosion and deposition) will be enhanced in this area of the river. Upon removal of the Happy Isles Gauging Station Bridge deck and river-left abutment, the localized flow within the channel will no longer constrict river flows thereby reducing riverbank erosion and the potential for storm-stage flooding caused by material accumulation behind the bridge structure. Reduction of the flood hazard will reduce over-bank flooding and associated erosion during large storm events. The proposed action will result in localized, beneficial effects to scenic, recreation, biological, and hydrologic processes Outstandingly Remarkable Values and localized adverse and beneficial effects to the cultural Outstandingly Remarkable Value. On a segment-wide basis, Outstandingly Remarkable Values would not be appreciably affected. The National Park Service concludes that the proposed action will enhance free-flow of the Merced River and will not have a segment-wide direct and adverse effect on the Outstandingly Remarkable Values for which the river was designated Wild and Scenic.

Recommended:

Superintendent, Yosemite National Park                                              10/31/2001                Date

Approved:

Director Pacific West Region, National Park Service                            10/31/2001               Date
[1]     A water resources project is any dam, water conduit, reservoir, powerhouse, transmission line, or other works project under the Federal Power Act, or other developments that would affect the free-flowing characteristics of a wild and scenic or congressionally authorized study river. In addition to projects licensed by the Federal Energy Regulatory Commission, water resources projects may also include: dams, water diversions, fisheries habitat and watershed restoration, bridges and other roadway construction/reconstruction projects, bank stabilization projects, channelization projects, levee construction, boat ramps, fishing piers, and activities that require a Section 404 permit from the U.S. Army Corps of Engineers (Interagency Wild and Scenic Rivers Coordinating Council 1999).
[2]      This description of the Wild and Scenic Rivers Act Section 7 determination process is adapted from a technical report by the Interagency Wild and Scenic Rivers Coordinating Council (Interagency Wild and Scenic Rivers Coordinating Council 1999).

 

 

 

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