Anderson Dam SeismicRetrofit Project

Joint SCVWD/City of San Jose Meeting | April 28, 2017

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| Joint SCVWD/City of San Jose Meeting 4-28-2017

Project Overview

Anderson Dam Existing Configuration

Spillway Outlet Pipe Dam Embankment Crest of Dam

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| Joint SCVWD/City of San Jose Meeting 4-28-2017

Project Overview

Problem Definition

► Magnitude 7.2 Earthquake on the Calaveras Fault or M6.6 on the Coyote Creek Fault► Embankment slumps up to 25 feet due to

liquefaction of lower fine fill and alluvium► Outlet conduit buckles up to 4 feet due to fault

rupture on the Range Front Fault

► Changes in Regulatory Requirements (DSOD and FERC)► Outlet works does not meet current emergency

drawdown criteria► Spillway undersized for Probable Maximum Flood

Attachment 1Pg. 3 of 11

| Joint SCVWD/City of San Jose Meeting 4-28-2017

2013 Project: Liquefaction, New Intake and Outlets, Spillway / Crest Modifications

New sloping intake

10 feet high cofferdam (drained reservoir)

Spillway modifications New High Level Outlet conduit

Upstream embankment buttress

Downstream embankment buttress

New lower level conduitright abutment alignment

Abandon existing outlet pipe

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| Joint SCVWD/City of San Jose Meeting 4-28-2017

June 2016: Dam Failure by Fault Rupture

XX

X

X

X X

X

Shown: Mapped traces of Coyote Creek Fault

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| Joint SCVWD/City of San Jose Meeting 4-28-2017

2016 Modified Project

Cross-Section: 2013 Recommended Project

Cross-Section: 2016 Modified Project

New Gravel FillNew Gravel

Fill

New Filter & Transition ZonesNew Transition Zone

Bedrock

“ ““ “

Core

Core Remnant

Attachment 1Pg. 6 of 11

| Joint SCVWD/City of San Jose Meeting 4-28-2017

2016 Modified Project Footprint

Existing dam clay core

Remnant dam clay core to remain

Post Project dam footprint

Existing dam footprint

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8 Joint SCVWD/City of San Jose Meeting 4-28-2017

Retrofit Includes High-Level and Low-Level Outlets

10% of Storage90% of Storage

Low-Level Outlet – 6-foot diameter

High-Level Outlet12-ft diameter

Spillway Invert

Max Water Surface EL 628 ftDam Crest

Anderson Dam Cross-Section

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| Joint SCVWD/City of San Jose Meeting 4-28-2017

2016 Modified Project Construction Sequence

Year 1:

Lower Dam to Interim Height

(El 570 ft)

Lower Dam to remnant core;

Dry Season*Year 2:

Dry Season Year 3:

Dry Season Year 4:

Winter Year 4:Reservoir begins

to re-fill

Full Height Over Winter

(El 647 ft)Interim EL

(570 ft)Winter 1

Interim EL (570 ft)

Winter 2

Complete Construction

(El 656 ft)

Build Dam to Full Elevation

(El 656 ft)

Dewatering, OutletTunnel Construction

* Dry Season = April to October

re-build to Interim Height

(El 570 ft)

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| Joint SCVWD/City of San Jose Meeting 4-28-2017

Project Schedule

2017 2018 20192013 2014 2015 2016

We are here

2020

Design

Construction

NEPA/CEQA/Permitting

Original Baseline

Legend

NEPA / CEQA / Permitting

Design

Construction through 2024

2021 2022

December, 2016

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Summary

► 2016 Modified Project

► More extensive embankment retrofit

► Increases total cost of Project from $200M to $400M

► Start of Construction extended to 2020

► Supported by dam regulators and Board of Consultants

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