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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 environmental assessment for the project has been released and the comment period is open until December 9, 2018 (click the "open for comment" link on the left side of the screen to view the document and comment).

This project has three components as described below. The first component upgrades the Wawona Wastewater Treatment System infrastructure to increase efficiency, increase treatment capacity, address employee safety hazards, and improve the effluent disposal system to comply with the permitting requirements from the California Regional Water Quality Control Board. The second component was identified as a Category 2 action under the Merced Wild and Scenic River Plan (2014), and calls connecting the Wawona Campground to central sewage treatment at the Wawona Wastewater Treatment Plant. The third component eventually replaces a single-stall vault toilet with flushing toilet facility at the South Fork Picnic Area.

Component #1: Sewage Plant Updates and Improvements:

In 2010, the NPS conducted a facility assessment which identified specific items and recommended improvements to ensure that the plant would comply with future permit regulations, address deferred maintenance, and improve reliability and inefficiencies.

This component of the project will achieve the following outcomes:
• Provide additional plant capacity to accept additional flows from the Wawona campground, unserved parcels in the community currently served by septic systems, and future services on currently undeveloped parcels (ultimate buildout).
• Install solids handling capabilities
• Replace and reconfigure spray field equipment and install leach fields for effluent disposal during the winter months to eliminate direct river discharge
• Repair head works structure by replacing cracked concrete; replacing grit removal equipment with an improved screening, washing, and handling system; and improving septage and grease receiving equipment
• Build needed office space as an addition to the existing building
• Renovate the facility's two main lift stations
• Install a new instrumentation system and provide arc flash protection
• Ensure compliance with current and anticipated treatment standards
• Improve energy efficiency and system controls
• Address safety hazards posed by water inundation in plant facilities


Component #2: Campground Wastewater Treatment System

This project will address the following:
• Decommission the six saturated and failing Wawona Campground restroom leachfields
• Connect the Wawona Campgroud to the central sewage treatment at the Wawona Wastewater Treatment Plant by installing a forcemain along Wawona Road
• Install sewer conveyance forcemains and gravity sewers within Wawona Campground
• Install lift stations in the Wawona Campground area to convey sewage

Component #3: Installation of flushing toilet facilities at South Fork Picnic Area (pending funding availability)

This component of the project will achieve the following outcomes:
• Remove the existing single-stall vault toilet
• Construct an accessible, double-stall flushing toilet facility
• Install a lift station for sewage conveyance
• Connect this flushing facility to the sewer forcemain along Wawona Road