Alternative Delivery as a Form of Risk Mitigation

Transcription

1 Alternative Delivery as a Form of Risk Mitigation Erika P. Moonin, P.E. Lake Mead Intake No. 3 Access Shaft Low feet Lake deep Level Pumping Station November 29, 2017

2 Outline Project Background - Lake Mead Intake No. 3 Risk Mitigation Benefits using Alternative Delivery Highlights on the Challenges during Construction Closing/Questions Lake Mead Intake No. 3 Low Lake Level Pumping Station

3 The Situation Drought in the Colorado River basin Colorado River supplies 90% of Las Vegas water 1983 Now!

4 Drought Impacts Intake No. 1 Out of Service Intake No. 2 Out of Service Spillway Gate - Elevation 1,224 Spillway gates Elevation 1,050 INTAKE NO. 1 INTAKE NO. 2 Elevation 1,000 Hoover Dam Saddle Island INTAKE NO. 3 Dead Pool - Elevation 897 Elevation 860

5 Lake Mead Intake No. 3 Project Project Approved: 2005 Construction: Estimated Cost: $1.4B Primary Project Purpose Preserve existing capacity Multiple Contracts: 01 Tunnel & Shafts Design-Build 07 L3PS UG & AG CMAR The Project Exist. Water Treatment Facility Pump Procurement Test Procurement CMAR Low Lake Level Pumping Station (L3PS) L3PS Discharge Aqueducts Design-Build Intake 3 Tunnel Saddle Island Design-Bid- Build Intake 3 Lake Mead Design-Bid- Build Intake No. 2 Connection Design-Bid- Build Intake No. 2 Connection & Modifications Exist. Intake 1 Exist. Intake 2 Completed Under Construction

6 Variable Geology: The Challenges Hard, fractured Metamorphic rock Weak sedimentary rock Volcanic rock High tunneling pressures 17 bar (250 psi) 15 bar actual Deep Water Intake Structure construction feet of water Intake Structure/TBM - docking within a 1-ft tolerance after 3 miles of tunneling Connection to existing operating intakes Precision drilling for well shafts State of the art submersible pumps

7 Risk Management Benefits Through Alternative Delivery Methods 1) Qualification Based Selection Competent Team Good Fit! 2) Early Contractor Involvement 3) Price and Schedule Advantage Innovative Approach This is why we chose alternative delivery! DBB Limitations

8 Risk Management Benefits 1) Qualification Based Selection 2 Step Short List and Final Proposals DB - RFPP & RFP w/ Presentations CMAR RFP & Presentations Technical Capabilities Risk Management Approach Key Staff - Culture and Team Interaction Build the Partnership during Tender Phase DB Proprietary Meetings GBR, Completion Date, etc

9 Risk Management Benefits Lake Mead Intake No. 3 Project 2) Early Contractor Involvement Underground High Risk! Design - Incorporates the Contractor s Means and Methods CMAR Jointly developed GBR 3) Price and Schedule Advantage Innovative Approach! Alternatives price and schedule comparison In all underground contracts jointly developed Rik Register Examples

10 DB Intake No. 3 Tunnel & Shafts Contract Access Shaft ~ 600 deep 30 finished interior diameter Construction Adit Connector Tunnel 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 ~ 15,000 long Intake Structure 96 high 16 diameter

11 Starter Tunnel Incursion of Unstable Ground Starter Tunnel - Flooded over 4 days Beginning of inflow Starter Tunnel June 28, 2010

12 Tunnel Reinstatement Work

13 New Alignment Area of Tunnel Inflows Tunnel Realignment January 2011

14 DB Completed Starter Tunnel Collaborative Approach to Design True Partnership Drill & Blast Starter Tunnel Completed July 2011

15 Tunnel Boring Machine (TBM) Hybrid Design Hard Rock Slurry Handle challenging ground conditions (water pressure of 17 bar, etc) Manufactured in Germany by Herrenknecht 23.5 outside diameter TBM Gantry Support Equipment 585 long, 1500 tons

16 TBM Cutter Head Underground TBM Excavation began December 27, 2011

17 3000+ feet at 13.5 bar Took a Toll on the Machine 2013 Mar 29

18 2013/2014 TBM Repairs 4 foot deep niche excavated in front of cutterhead Collaborative Approach to Design True Partnership

19 Intake Riser - Excavation Spring 2010

20 Intake Riser Construction & Transport DB proposed new location for Intake Structure Better Ground! DB proposed completely different approach to Intake Structure

21 Intake Riser Concrete Transport

22 February and March 2012 Total Tremie Concrete = 11,300 cy

23 10-ft.

24 Completed Intake Tunnel TBM Hole Thru - December 10, 2014 Operational September 26, 2015

25 Low Lake Level Pumping Station CMAR

26 L3PS Components Aboveground Well shafts - 34 steellined 6 ft diameter, 500 ft deep Access Shaft - 26 ft diameter 527 ft deep Riser Shaft Connector Tunnel - 20 ft long by 20 ft wide by 20 ft high D- shape Riser Shaft - 26 ft diameter 45 ft deep Forebay - 33 ft wide by 36 ft high by 377 ft long horseshoe-shaped Cavern Pumps 32 total, 22 low lift and 10 high lift pumps Underground

27 CMAR Underground Excavation - Well Shafts

28 L3PS Early Contractor Involvement Started 50% design UG co-located Reviewing plans/construction approach Attending weekly progress meetings Blind Bore vs. Raise Bore Workshop June 23, 2015 Risk Comparison Raised vs. Blind Bore Sub-Contractor Advertisement July 7, 2015 Short List Created July 27, 2015 Bids due (Drillers) Aug 20, 2015 Final Design Produced Sept 14, 2015 CMAR UG Package Award Sept 17, 2015 $209 M - $20 M Contingency Raise Bore Blind Bore

29 L3PS Early Contractor Involvement Blind bore was selected Mitigate ground risk better control of the ground Introduce other risk more difficult to comply with already tight drilling tolerance Worked together to develop innovative approach & Weighed the risks! Included coordination with pump manufacturers to determine allowable tolerance

30 CMAR Underground Excavation - Well Shafts

31 Test Pumps - Factory Performance Tests Indar pump Andritz pump Ebara pump

32 Underground Excavation - Shafts

33 Underground Excavation - Forebay

34 Underground Excavation - Forebay

35 SNWA Lake Mead Intake No. 3 Thank you MWH/Stantec & CH2M Barnard of Nevada & North American Drillers Vegas Tunnel Constructors Salini-Impregilo & SA Healy & ARUP Renda Pacific Parsons Questions?