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Ahwahnee Grease Interceptor Improvement (CFF 2020)

Yosemite National Park » Ahwahnee Grease Interceptor Improvement (CFF 2020) » Document List

This project proposes to add a grease interceptor to the existing grease management system at The Ahwahnee. A 1,500 galloon grease interceptor was originally constructed in 1984 and was replaced with a 6,000 gallon interceptor in 2014. These are both approximately 50 feet west of the northwest portion of the hotel (enclosure 1: Project Location Map/Area of Potential Effects). The current interceptor is not functioning adequately, such that substantial amounts of grease are getting through the grease interceptor and into the downstream sewer system and ultimately into the lift station. Investigation has shown that the interceptor outlet temperature is above 100 degrees, which does not allow the grease to coagulate and settle into the interceptor. By adding another grease interceptor (4,000 gallons) to the existing interceptor, the retention time of the system will increase allowing the grease wastewater to cool and coagulate properly.

The proposed grease interceptor will be positioned south of the existing interceptor and will include trenching to connect associated piping to the existing sewer line approximately 15 feet to the west. This will include construction of two new manholes. This new grease interceptor will bypass a section of the existing piping between the existing interceptor and the lift station, which is located approximately 130 feet to the northwest. The undertaking will require ground disturbance of approximately 15 feet wide x 40 feet long x 8 feet deep to install the equipment, and a maximum disturbance for trenching of 100 feet long x 24 inches x 60 inches deep for the associated piping and two manholes. The existing piping will be left in place . Fill will be replaced on top of the equipment and the area will be rehabilitated.

The tasks for this effort include the following:

1. Excavate and install new interceptor
2. Connect new interceptor to existing lines and/or tie into existing lines
3. Test and backfill
4. Re-grade and re-pave where disturbed in excavation