Reconstructing Critically Eroded Sections of the El Portal Road

Section of El Portal Road that is failing
 

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Overview

The El Portal Road begins at the western boundary of Yosemite National Park. This road climbs 7.5 miles through the Merced River canyon, gaining almost 2,000 vertical feet before it intersects the Yosemite Valley Loop Road at Pohono Bridge. Along the way, this road parallels the Merced Wild and Scenic River and passes Arch Rock Entrance Station.
Significant damage occurred during the 1997 flood, necessitating an almost complete reconstruction of the El Portal Road. Since then, the National Park Service has rebuilt the westernmost 6.5 miles of the road—referred to as Segments A, B, and C— but prior to completion, reconstruction of the final one-mile segment of the project, referred to as Segment D, was halted as a result of a successful legal challenge. The court decision directed the National Park Service to prepare a comprehensive management plan for the Merced Wild and Scenic River in advance of completing that project.

During the following nine years, the roadway and embankment continued to be undermined by the river. As a result, the National Park Service completed five emergency repairs to Segment D, including three retaining wall repairs to prevent roadway collapse. However, these emergency repairs did not address the fundamental instability of the roadway and did not eliminate the potential for a complete roadway failure. Such a failure could have endangered motorists, caused a long-term road closure, and potentially severed Yosemite Valley’s primary electrical and sewage lines, which would have had serious environmental consequences for the Merced Wild and Scenic River. A roadway collapse would have prohibited access to Yosemite Valley from three park entrances.

Reconstructing Critically Eroded Sections of the El Portal Road EA focuses on the area that starts at the Big Oak Flat Road intersection and extended east 1,350 feet; it focused specifically on those areas in need of emergency repair. The El Portal Road Reconstruction project was originally intended to address various motorist safety and configuration issues in such a way that would align the road structurally and aesthetically with the three road segments previously completed. Because the original project that entailed completely reconstructing the entire road segment was on hold pending the approval of a valid Merced River Plan, the National Park Service addressed the immediate situation with a scaled-down reconstruction project that would stabilize the roadway, protect park resources, and ensure continued visitor access to Yosemite Valley. Other issues not directly related to the emergency repairs, such as intersection configuration, bicycle lanes, and parking were not addressed in this project.

The public scoping period took place from November 11 to December 29, 2006. Following the scoping period, the National Park Service analyzed the comments that were received from the public and identified a range of issues and concerns. The issues and concerns were then used to inform the development of alternative approaches to reconstruct this portion of El Portal Road.
In February and March, 2007, the National Park Service convened experts in natural and cultural resources, construction and engineering, and park operations and transportation planning to develop a range of reasonable and feasible alternatives based on the project’s purpose and need as well as input gathered during public scoping. After analyzing a number of potential solutions, the park identified two reasonable and feasible action alternatives that are analyzed in detail in the Reconstructing Critically Eroded Sections of El Portal Road Environmental Assessment. The public comment period on the Environmental Assessment occurred from June 4 to July 3, 2007 and a Finding of No Significant Impact (FONSI) was signed in August 2007. The preferred alternative reconstructs the road with 11-foot travel lanes, a 4-foot paved drainage ditch, a 1-foot shoulder, and a short cantilever road section at the roadway’s narrowest point. The work on this section of road was completed in 2008.

 

Documents

Last updated: February 10, 2020

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