Chabot Dam Chabot Dam Seismic Upgrade Project Seismic Upgrade - - PowerPoint PPT Presentation

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Chabot Dam Chabot Dam Seismic Upgrade Project Seismic Upgrade - - PowerPoint PPT Presentation

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Chabot Dam Chabot Dam Seismic Upgrade Project Seismic Upgrade Project Tom Boardman, Project Manager November 14, 2018 Project Location North EBMUD Chabot Dam Project Location North Oakland Chabot Reservoir (10,350 acre-ft) Outlet

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Chabot Dam Seismic Upgrade Project Chabot Dam Seismic Upgrade Project

Tom Boardman, Project Manager November 14, 2018

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Project Location

Chabot Dam EBMUD North

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Project Location

Chabot Reservoir

(10,350 acre-ft)

Outlet Works North Hayward fault zone Chabot Dam San Leandro Oakland Castro Valley

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Chabot Dam and Outlet Works

Chabot Dam

Outlet Works

Release Spill

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Project Description

  • 140-yr old dam and 90-yr old outlet works
  • During M7.25 earthquake on Hayward fault:

Earth dam settles and slides Outlet works collapses; can’t drain lake

  • In 2006, DSOD directed EBMUD to develop

plans to upgrade earth dam and outlet works to improve seismic performance

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Chabot Dam built in 1875

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Earth Dam – Seismic Displacement Model

Reservoir Level Expected displacements due to Mw 7.25 earthquake

Dam before retrofit

135-ft high

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Outlet Works Retrofit

Outlet Works, July 2013

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Outlet Tower Retrofit

Reservoir Level Release Hillside Outlet Tower 8-ft Shaft

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Temporary Park Closures

Work Area

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Site Access Issues

12-ft Spillway Bridge 

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Site Access Issues

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Site Access Issues

Cliff Swallow Dusky Footed Wood Rat Wood Rat Midden Swallow Nests

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Earth Dam Seismic Upgrade

Max Lake Level Max Lake Level 100-ft wide CDSM buttress to reduce seismic displacements Expected displacements due to Mw 7.25 earthquake

Existing Dam Dam After Upgrade

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CDSM Rig Onsite

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CDSM Buttress Drilling Pattern

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CDSM Mixing Blades

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CDSM Mixing Blades

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Seepage Trench

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Seepage Trench

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Earthwork and Seepage Trench

Before Project During Seepage Trench During Final Grading

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Outlet Works Retrofit

Outlet Works in 1924 Outlet Tower Demolition

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Outlet Works Retrofit

Shaft Liner Installation Shaft Liner Grouted in Place Brick Lined Access Shaft

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Outlet Works Retrofit

During Pipeline Removal New 42” Intake Pipeline - Lakeside After Pipeline Removal

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Outlet Works Retrofit

New Outlet Works in Rock Hillside Outlet Works After Demolition

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End of Construction

Final Downstream Slope of Dam Replacement Staff Gage and Safety Buoys View of Former Outlet Tower across Lake

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2016/2017 Winter Rainfall

  • Record breaking rainfall ~44-inches
  • Spilled Jan to May 2017
  • Delays to earthwork on dam
  • Chabot fish go over spillway

Main Spillway Jan 26, 2017 San Leandro Creek below Dam

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San Leandro Creek – Fish Flows

  • Rescued ~80 rainbow trout; returned to Chabot
  • Currently releasing ~80 gpm (0.2 cfs)
  • EBMUD still working with CDFW to develop

long-term strategy for fish flows in creek

Rescued Rainbow Trout Team of EBMUD & EBRPD rangers/biologists May 25, 2017

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Spillway Repair

During Repair Cracked Spillway After Repair

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Earthquake Monitoring

During Repair Seismograph

  • n Dam

After Repair

Mw 3.0 earthquake July 15, 2018 ~ 2 miles from Chabot Dam

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Questions?

During Repair Cracked Spillway After Repair