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Picture of the existing Wawona Wastewater Treatment Plant. This is a view of the plant upper level looking into the treatment basins.

Wawona Wastewater Treatment System Rehabilitation Environmental Assessment

Yosemite National Park » Wawona Wastewater Treatment System Rehabilitation Environmental Assessment » Document List

The National Park Service plans to improve visitor facilities, address deferred maintenance, and increase efficiency and capacity in the Wawona Wastewater Treatment System. The finding of no significant impact for the project has been released (click the "Document List" link on the left side of the screen to view the document). The National Park Service plans to begin implementation of the project in fall of 2019.

This project will address deferred maintenance, improve visitor experience, and improve the operational efficiency of the Wawona Wastewater Treatment System. The selected action has has three main components (summarized below):


Component #1: Upgrade the Wastewater Treatment:

• Expand plant capacity to accept sewage from Wawona campground, unserved parcels, and eventual community buildout.
• Install solids handling capabilities
• Replace and reconfigure spray field equipment at the Big Trees Golf Course
• Construct disposal trenches at Big Trees Golf Course for winter effluent disposal
• Decommission effluent discharge system to the South Fork Merced River
• Repair/upgrade plant head works, grit removal, and septage receiving equipment
• Construct a plant office addition to the existing building
• Renovate the system's two main lift stations
• Install a new system instrumentation system and provide arc flash protection
• Ensure compliance with current and anticipated sewage treatment standards
• Improve energy efficiency and system controls
• Address safety hazards posed by water inundation in plant facilities


Component #2: Connect Wawona Campground Central Sewage Treatment:

• Decommission the individual leachfields at Campground
• Install a forcemain from Wawona Campgroud to the Wawona Wastewater Treatment Plant
• Install sewer conveyance forcemains and gravity sewers within Wawona Campground
• Install lift stations in the Wawona Campground area to convey sewage


Component #3: Install Flushing-toilet Restroom at South Fork Picnic Area (pending funding)

• Remove the existing single-stall vault toilet
• Construct an accessible, double-stall flushing toilet facility
• Install a lift station for sewage conveyance
• Connect this restroom to the sewer forcemain along Wawona Road