Project Name: Angels Penstock Emergency Repair

Status: Complete

Description

On Thursday April 10, staff observed a leak in the Angels Penstock drain valve assembly vault beneath the parking lot in Utica’s operations yard right next to the Angels Powerhouse. Staff determined the leak was bad enough to require, which required the penstock to be drained and excavation to expose the valves beneath the penstock.
By April 15, Utica staff had completed the critical repairs, with help from regional water and sewer districts.
Repair Activities and Timeline: On April 14, 2025, Utica staff coordinated material procurement efforts and contacted Tuolumne Utilities District (TUD) under the agencies’ mutual assistance agreement. TUD confirmed that all necessary valves, fittings, and ductile iron pipe were in their warehouse and made them available to Utica. Staff picked up the materials April 15.
Utica staff assembled the components and began installation work, including:
• Welding a new standard-class bung onto the penstock; completed by Mark Lowe.
• Installing new ductile iron piping and modern valves.
• Replacing all non-standard and failed components with new parts
• Replacing the original riveted drain pipe leading to the creek with C900
Current Status: As of April 16, 2025 Utica staff successfully completed a pressurization test of the penstock and conducted a full visual walk-down inspection to confirm that no leaks were present. Staff are currently in communication with PG&E regarding the status of their transmission outage and are awaiting clearance to begin restarting the Angels Powerhouse.
Agency Support: This complex repair was supported by multiple partner agencies:
• CCWD: Supplied a Vac-Con truck and construction crew
• Tuolumne Utilities District: Provided valves, pipe, materials and fittings
• Murphys Sanitary District: Provided a CCTV inspection camera for drain pipe
• City of Angels Camp: Provided valves, fittings, and pipe and marked USA

Timeline: April 10, 2025 -  April 16, 2025

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