LAKE MEAD WATER INTAKE NO. 3Constructing the highest pressure tunnel in the world

to preserve drinking water supply for two million people

Drought in the Colorado River basin Colorado River supplies 90% of Las Vegas’

water

1983 2013

The Situation

3

Lake Mead dropped 150 feet between

2000 and 2015

HIGH AND LOW LAKE LEVEL ELEVATIONS

Intake No. 1 Out of ServiceIntake No. 2 Out of Service

Saddle Island Elevation 860’

Spillway gates

Elevation 1,000’

Hoover Dam

Dead Pool - Elevation 897’

Spillway Gate - Elevation 1,224’

Elevation 1,050’

INTAKE NO. 3

INTAKE NO. 2

INTAKE NO. 1

Drought Impacts

If the lake level falls below 1,050 feet: Intake No. 1 will be out of service Pumping capacity will be reduced

A new intake system is needed to preserve existing

capacity and water quality if lake levels continue to decline.

Lake Mead Water Level Impacts

Lake Mead Intake No. 3 Approved by SNWA Board of Directors May

2005 Six contracts (originally), $817 Million total

(est)… Deferred Pumping Station - three major contracts $650M estimated construction value

Completion 2015 (2020 with Pumping Station)

Challenges Variable Geology:

Hard, fractured Weak sedimentary Volcanic rock

High tunneling pressures – 17 bar (250 psi)

Intake Structure installed in 350 feet of water

Intake Structure/TBM docking within a 1-ft tolerance after 3 miles of tunneling

Connection to existing operating intakes

Project Location

Lake Mead Las Vegas

Exist Water Treatment

Facility

L3P3 PUMPING STATION

Intake 3

INTAKE TUNNEL

DISCHARGE PIPELINES

INTAKE No. 2 CONNECTOR TUNNEL

Lake Mead Intake No. 3 Contracts

Exist Intake 1

Exist Intake 2

INTAKE No. 2 CONNECTION & MODIFICATIONS

Lake Mead

Saddle Island

Exist Water Treatment

Facility

Intake 3

INTAKE TUNNEL

INTAKE No. 2 CONNECTION

Exist Intake 1

Exist Intake 2

INTAKE No. 2 CONNECTION & MODIFICATIONS

Lake Mead

Saddle Island

Vegas Tunnel Constructors (Design-Build) ~ $450MAccess Shaft• ~ 600’ deep• 30’ finished interior diameter

Tunnel• Launch Chamber ~ 202’ long, 47’ W x 35’ H• Starter Tunnel ~ 450’ long, 27’ W x 25’ H • TBM tunnel

– 20’ finished internal diameter– ~ 14,904’ long– 14” concrete segmental lining

Intake Structure (elev 860)• 96’ high• 16’ diameter riser• Radial inlet

Shafts & TunnelAs deep as the Wynn is tall!

13

Top-Down Shaft Construction Sequence

1) Drill2) Blast3) Excavate4) Map the rock

face5) Initial Support6) Lower Form7) Cast ConcreteRepeat…

Shaft ExcavationCompleted

January 2010

TBM Assembly Chamber

TBM Chamber Excavating Top Heading – Nov 2009

TBM Assembly Chamber

Beginning of inflow in Starter Tunnel - June 28, 2010

Incursion of Unstable Ground

Tunnel Flooding

Flooding EventJune 28th – July 1st, 2010

Area of Tunnel Inflows

Tunnel Realignment

New Alignment

January 2011

20 Realigned Starter Tunnel viewed from Cavern – 03/29/11

Starter Tunnel

CompletedJune 2011

Drilling Jumbo Truck - Hoover Dam Diversion Tunnelshttp://www.usbr.gov/history/photos/dams007.jpg

Back then…

23

Tunnel Boring Machine• 24ft Outside Diameter• 600ft Long Trailing Gear • Total Weight 1500 Metric

Tons• TBM was designed to be

driven in rock with water head up to 17 bar (250 psi)

• Capable of grouting and soil improvement ahead of the face

• Machine designed and fabricated specifically for this project with strict cooperation between SNWA, Design-Builder, and Supplier (Herrenknecht)

Contract 01

TBM TRAILING / SUPPORT GEAR - 585’ long, 1500 tons

TBM

Strand Jacks Used to Handle Weight and Depth

Lowering TBM Down Shaft

27 TBM Lowering September 2011

TBM Positioned At Tunnel Face

December 27, 2011

Local Mfg. of Precast Segments

5 Segments + I keystone = Ring

30 Tunnel Segments delivered to Site

31

Segment Transport

3,000 feet at

13.5 bar WHAT PSI IS 13.5

BAR ?

195.80 PSI

Took a Toll on the Machine

2013 Mar 29

2013/2014 TBM Repairs

3 Repair Stops

4 foot deep niche excavated in front of cutterhead

36

Soft eye

25’ 10”

41 Stainless Steel Riser Assembly

42 Stainless Steel Intake Screen

Intake Riser - Excavation

Spring 2010

44

Preparations for Excavation at lake bottom

• Additional ground investigation• Bathymetry Survey• Excavation and Blasting done from

crane barge• Clam and airlift “Overburden”-

15,000 CY• Overburden was 6 ft of desert soil;

very small silt layer about 6 inch on top.

Shaped Charges Placed on rock surface 7.5 kg / charge Placement structure

30 ft x 30 ft Small blasts at surface – Fish Scare

23,000 charges

46 Rendering of final excavation at lake bottom

Intake Structure Installation

Total Tremie Concrete = 11,300 cy

February and March 2012

Assembled Intake Structure Conveyed to Intake Site

15 Feb 2012

Concrete Batch Plant

Concrete Transport Barge

Intake Structure Tie in

10-ft.

ROV Intake Inspection

Cleaning Seal with ROV

Lowering Bulkhead

Piece of soft eye during hole through

59

Breakthrough on December 10, 2014

60

TBM Removal

TBM Removal

TBM Removal - Completed Apr 27, 2015

Tunnel Steam Cleaner

Remaining Milestones

Intake No. 3 Shafts & Tunnel

Operational October 2015 Final Completion January 2016

600

800

700

900

1100

1000

1200

1300

Intake 3 Tunnel

Inta

ke 3

Inta

ke 1

Connector Tunnel

RMWTF

AMSWTF BROFIPS-1 IPS-2

IPS-2 Pump Operation Limit El. 1000

IPS-1 Pump Operation Limit El. 1050

Lake Elev. (feet above MSL)

Inta

ke 2

Isola

tion

Gate

L3PS

68

Low Lake Level Pumping Station

L3PS was approved by the SNWA on December 10, 2014

L3PS CONTRACT PACKAGES

Mass Excavation - Design-Bid-Build

Pumping Station - CMAR Underground Mechanical and Electrical

Discharge Pipelines – Design-Bid-Build

Electrical Feed & Substation – Design-Bid-Build (by CRC)

Questions? Questions ?