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Wawona Wastewater Treatment System Rehabilitation Environmental Assessment

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

This project has three components as described below. The first component upgrades the plant's infrastructure including requirements associated with the issuance of a Time Schedule Order (TSO) by the California Regional Water Quality Control Board in 2013 that addresses the treatment plant's inability to remove dichlorobromomethane (a potential carcinogen). The NPS has until July 2018 to comply with these requirements. The second component was identified as a Category 2 action under the MRP, and calls for construction of a pump station and utility corridor connecting the Wawona Campground to the Wawona Wastewater Treatment Plant. The third component 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 flow from visitor facilities with failing leach fields, 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
• Replace 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

Component #2: Campground Wastewater Treatment System

This project will address the following:
• Replace the six saturated and failing Wawona Campground restroom leachfields with a new connection to the Wawona wastewater system
• Install one mile of six inch high density polyethylene (HDPE) gravity sewer conveyance pipe within Wawona Campground
• Install two lift stations in the Wawona Campground area
• Install a third lift station close to Wawona Road that collects the campground sewage, conveying it to the Wawona sewer collection system.
• Install a 10 feet by 14 feet pump house near the central lift station.

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
• Connect this flushing facility to the sewer being installed in the Campground