Silicon Valley Clean Water Tunnels Sewer Tunnel Innovation in Silicon Valley

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1 Silicon Valley Clean Water Tunnels Sewer Tunnel Innovation in Silicon Valley Bruce Burnworth, Project Manager Breakthroughs in Tunneling Short Course Chicago August 2017 Regional Environmental Sewer Conveyance Upgrade

2 BELMONT REDWOOD CITY SAN CARLOS EMERALD HILLS MENLO PARK WEST BAY SANITARY DISTRICT WOODSIDE

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4 Three Major Innovations Progressive Design Build for a Tunnel Multiple Layers of Defense against Sewer Corrosion Diurnal and Wet Season Equalization

5 Need for Project

6 Community Reaction to Open Cut HDPE: The Black Dragon

7 140 Alternatives Considered Open Cut in Street Open Cut in Levee Lay in Slough Lay in Lagoon Microtunnel (shallow) Microtunnel (deep) Tunnel Boring Machine (deep) From SVCW Plant From near Airport Sliplining (w/ bypass) Parallel Smaller Pipes Pipe Bursting (w/ bypass) Pipe Splitting (w/bypass) Swege (w/bypass) Replace in place (w/bypass)

8 Evaluation Basis SUCCESS FACTORS Evaluate Capital and Life Cycle Costs COSTS How well does each alternative match up with SVCW definition of success RISK FACTORS Identify probability of risk & consequence of undesired outcome

9 5 Alternatives Evaluated & Scored 70 Conveyance Alternatives: Risk vs. Success Scores AE 5AE 7 Risk Score BE 4DE Success Score

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11 Cost Biggest Challenges 2013 CIP budget: $65million Current project budget: $220 million Current project cost estimate: $275 million Schedule Current pipeline failing Risk of catastrophic failure increasing over time Current schedule: completion year life requirement

12 Progressive Design Build Approach Faster Completion Leaner Project Better Value Alternative Corrosion Protection Approaches Lower Life Cycle Cost WATS modeling Increase Project Value Diurnal Flow Equalization to Reduce WWTP Future Costs

13 SVCW Progressive Design Build Two Step Selection Process 1. RFQ with SOQ and Interviews to arrive at Shortlist 2. RFP 10% design with Confidential Meetings and Interviews Two Stage Design-Build Agreement Stage 1: Design from 10% to 60% collaboratively Stage 2: Complete Design and Construction Multiple Phases of Construction (conceptual) Stage 2A: TBM Ordering, Segment Mold Ordering Stage 2B: Shaft Construction, Segment Fabrication Stage 2C: Tunnel Construction Stage 2D: Connections

14 Progressive Design-Build Advantages Faster start and completion All parties at the table during design & construction Combination of all good ideas from owner, designers, contractors - creativity Early contractor involvement Flexibility to achieve project objectives Single-point responsibility for design-build Ability to control costs and transparency Minimize confrontational contracting minimize contract change orders, claims and lawsuits Disadvantages Not done previously for tunnels in USA No firm price when Design-Builder selected Requires openness and solid project management skills Requires method to confirm that pricing is competitive (sub bids and independent reviews) Strong trust needs to be developed

15 Progressive Design Build Status Three teams shortlisted: Barnard/Bessac/Arup Kiewit/McNally/Stantec Obayashi/JayDee/McMillen Jacobs Interviews: August 9 and 10 Stage 1 Design-Build Agreement: Sept./Oct. Start of Construction: 2018 Completion: 2020 to 2024 (TBD)

16 Corrosion Protection Current estimate includes $90 million to put a pipe inside the tunnel Alternatives: HDPE lining (several methods) Multiple layers of defense including upstream dosing

17 Multiple Layers of Defense Upstream dosing to eliminate sulfides Sacrificial concrete thickness Enhanced air movement Corrosion resistant concrete Laminar flow design Biocide concrete additive Monitoring and inspections

18 WATS Model Wastewater Aerobic/anaerobic Transformations in Sewers Developed over 3 decades at Aalborg University, Denmark. Computer simulation of all relevant biological, chemical and physical processes including interphase mass transport, wastewater hydraulics and sewer air... using a matrix of non-linear differential equations

19 Microbially Induced Corrosion Formation of H2S in biofilm Chemical oxidation of sulfide in bulk water Biological oxidation of sulfide in bulk water Biological oxidation of sulfide in biofilm Emission of H2S from water phase to gas phase H2S oxidized to sulfuric acid on concrete surface

20 San Francisco Results & Targets Some locations showed that corrosion can results in 5-10 cm (2 4 in) over a 100 year period, but in general corrosion is a minor issue in the drainage area Recommended Target Parameters Dissolved Sulfide (DS) < 0.5 mg S/L H2S (gas) <10 ppm inside the selected monitoring manhole Shear stress >0.5 Pa if a new pipe is installed

21 Flow Equalization Diurnal flows Average ~14 mgd Each day varies from 2 mgd to 24 mgd Wet Season Peak Flows ~103 mgd Treatment plant capacity is 80 mgd WWTP operates well at 60 mgd

22 Wet Season Peaks With 11 ID tunnel (pipe in tunnel) additional surface storage needed With 13 ID tunnel (no pipe in tunnel) all equalization can occur in tunnel

23 Diurnal Equalization With 11 ID tunnel (pipe in tunnel) air flow to plant blocked every day creating upstream odor issues With 13 ID tunnel (no pipe in tunnel) all air flows to plant for odor control (dry season)

24 Hydraulics Design Storm Equalization Diurnal Equalization San Carlos Drop Structure

25 Tunnel Excavation Rate Tunnel excavation rate of 100 feet per day average is expected based on a nearby tunnel project (after first 1,000 feet) Soil exploration every 250 feet along the alignment indicates consistent lens for tunneling of upper alluvial sediments (medium stiff clays and sand lenses) Herrenknecht thinks that average tunneling rates can be improved significantly with current TBMs by operating the TBMs as a moving production line

26 Greatest Pleasure Cost of public projects increases potentially cutting project cost in half ($275m to $135m) Public projects always get delayed potentially cutting project duration in half (2024 to 2020 completion) Cost Schedule Quality: You can t have all three. I sure try. Motivation: Deliver the best possible project.

27 Questions For more information and copies of documents visit /gravitypipeline.aspx Regional Environmental Sewer Conveyance Upgrade

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29 Recommended Alternative 4BE

30 Solution Varies MIC attacks increase in ferocity as temperatures rise, detention times increase, dissolved oxygen is not available, air flow slows, concrete is easily penetrated by acids allowing steel rebar to corrode and concrete spall. Corrosion varies dramatically with these variables. Understanding how these variables affect MIC for a specific section of sewer is critical to an appropriate design that defends against MIC attack at every MIC step.

31 Future treatment processes only need to be designed for 60 mgd instead of 80 mgd If flushing is needed, can be done using upstream pump stations

32 Notes

33 Innovations flow from necessity. A cut and cover HDPE 66 force main sewer project through an exclusive residential neighborhood in Silicon Valley (California) was being referred to as the Black Dragon and was doomed to years of lawsuits. A nearby 5 mile long water tunnel gave us a potential cost effective solution but the need for corrosion protection drove the cost way over budget. Progressive design-build is being used to complete the 3.3 mile long 15 OD tunnel project to under our budget and ahead of schedule. A multi-layer defense is being studied to more cost effectively address sewer corrosion while diurnal and seasonal flow equalization in the tunnel provide additional value. Additional valuable ideas are expected to flow from the collaborative Progressive Design Build approach.

34 SVCW is a public agency joint powers authority that conveys sewage from four cities in Silicon Valley, treats the sewage and discharges it to the San Francisco Bay as clean water. Our existing interceptor pipe is more than 45 years old and is failing due to soft soils and corrosion. When the pipe was constructed there were no houses in the area. Now the pipeline alignment has $2 million houses along tree lined streets. Open trench replacement of the pipe is not acceptable. A 3.3 mile tunnel will be built and serve as a gravity sewer pipeline to avoid major community disruption. Innovative concepts include: Tunnel to be used for wet season flow equalization to allow 103 million gallons per day (mgd) of storm inflow and infiltration to be equalized to 60 mgd for treatment to lower treatment costs. Tunnel to be used for diurnal flow equalization to provide a consistent 12 mgd of flow to the plant 24 hrs per day to equalize the current variation of 2 mgd to 24 mgd flow. This diurnal flow equalization will further decrease the cost of sewage treatment especially in the area of operations and maintenance allowing more consistent flow and more process automation. Launch shaft alternative to reduce community and environmental impacts A launch shaft on the middle with tunneling in both directions minimizes impacts A ramped launch shaft at the end on a wildlife refuge and airport clear zone would reduce costs if environmental and safety issues can be addressed. Tunnel excavation rate of 100 feet per day average is expected based on a nearby tunnel project (after first 1,000 feet) Soil exploration every 250 feet along the alignment indicates consistent lens for tunneling of upper alluvial sediments (medium stiff clays and sand lenses) Elon Musk is challenging the tunnel industry to increase tunneling rates by 5 to 10 times. He plans to use his Tesla production line experience and hiss SpaceX technology to accomplish these higher production rates. Herrenknecht thinks that average tunneling rates can be improved significantly with current TBMs by operating the TBMs a moving production line. First Progressive Design Build tunnel project in the USA (currently we are in the PDB selection process) Select Progressive Design Builder (PDB) based on experience, qualifications, approach and price Stage 1 bring current 5% to 10% design to 60% to 70% design PDB then provides a fixed price to complete design and construct the project Owner reviews price and negotiations completed (owner has off-ramps if negotiations not successful) Stage 2 involves 100% design, construction and start up by PDB Advantages: Practical and innovative ideas brought to project by PDB Faster completion of project by overlapping design and construction Minimize confrontational contracting minimize contract change orders, claims and lawsuits Alignment Horizontal alignment minimizes community disruption 3.3 miles through urban area and only four private properties and three public agencies affected. Private property impacts limited to small corners of parcels to allow reasonable TBM turning radii of 800 foot minimum Vertical alignment keeps TBM below soft young bay mud layer in medium stiff clays and sand Corrosion protection alternatives Pipe in Tunnel Tunnel Lining Multiple Layer Defense against Corrosion (could reduce project costs by $60 million) Corrosion in sewers... the process (all of these above steps need to happen to have a concrete structure fail): Solids in sewage provide a food source for bacteria that create H2S if there are no oxygen or nitrate molecules available. H2S in solution comes out of solution into the air in the sewer if the ph is low and with turbulence. H2S in the air is converted by bacteria on the moist surface of the pipe to create H2SO4 H2SO4 eats away at cement paste in concrete Multiple Layers of Defense against Corrosion (a defense for every step of the corrosion process): Continuation of upstream Bioxide dosing to reduce H2S formation in the wastewater, Adjustments to ph and laminar flow to reduce the movement of H2S from water to air, Enhanced air movement and biocide to reduce conversion of H2S to H2SO4, and Acid resistant precast concrete tunnel segments with sacrificial thickness to provide for long useful life of the concrete structure in an acid environment. (Metakaolin seems like a great solution for acid resistance... early strength and workability for pre-casters and acid resistance for sewer applications). The above layers of defense act together independently to achieve long concrete structure life with 95% to 99% confidence (joint probability). Project: 3.3 miles of 15 foot outside diameter soft ground tunnel with a construction cost of $100 million to $160 million with tunneling scheduled to start in 2018.