Dependability Below Kensico Pressurization of Catskill Aqueduct from Kensico Reservoir to the UV Facility at Eastview Kensico – City Tunnel (Previously known as City Tunnel No. 3 Stage 3) The Bronx – Queens Tunnel (Previously known as City Tunnel No. 3 Stage 4) City Tunnel No.3 (Stage 2, Manhattan Leg)
2007 RWBT Identified as Primary Area of Concern 7 RWBT conveys Delaware system water and is the primary source for Towns of Newburgh and Marlborough and approximately 50% of New York City’s supply
Project Background - Roseton Surface Expression A dozen or so surface expressions Flow observed on west bank of Hudson River Testing program and analysis estimates leakage of 15 to 35 mgd. Roseton Leakage
9 How Long will the Tunnel be Out of Service? 2007 Shutdown Schedule
2008 Shortfall Curve
Potential Solutions for Dependability Demand Reduction Interconnections Expand Groundwater Use Croton Pump Stations Increase Aqueduct Capacities Hudson River and Harbor Surface Water, Hudson Groundwater Abandoned Sources (Westchester Co.) Parallel Tunnels
Project Tiering/Prioritization – Focuses Effort on Best Projects and Combinations Augmentation Project Screening
Delaware Repair: Alternative water sources Project evaluation to identify a group of projects to meet NYC’s alternate water supply needs (2008) 39 Projects 26 Projects Factors: Cost Schedule DEP Control Key: Redundant tunnels Optimization of existing system Groundwater Desalinization of Hudson River or Harbor water Interconnections to New Jersey or Connecticut
Delaware Repair: Alternative water sources Top 26 Projects falls to 17 with the removal of mutually exclusive projects.
Duel path – Alternate Supply / Parallel Tunnel
16 Moving to Design In 2008 and 2009 DEP hired new consultant team to develop parallel tunnel and bypass tunnel concepts to address the RWBT leaks
Wawarsing Roseton EL 840 Rondout Reservoir Rondout Creek Shawangunk Mountains Walkill River Hudson River Shaft 6 Tunnel Unwatering Shaft Shaft 8 West Branch Reservoir El 503 El Repair of the Leaks Shaft 1 Shaft 2 Shaft 3 Shaft 4 Shaft 2A Shaft 5 Shaft 5A Shaft 7 Shaft 9 Wawarsing Repairs: Possible from within tunnel Access via Shaft 2A Confinement Relatively good Roseton Repairs Not possible from within tunnel Access requires new shafts Best Solution is Bypass
Bypass Tunnel Construction 18
Recent Modeling In 2010 DEP shifted from evaluating a full repair of the RWBT to constructing a bypass around the leak in Roston, NY This bypass included the use of inundation plugs to handle tunnel inundation, resulting in approximately a month shutdown period for the connection 19
OST Supply Curve ( ) 20 OSTv _Aug-SC_000 Runs were conducted for these four supply levels
Objectives (during an outage): Provide advance notice of potential shortfall conditions Provide DEP with enough time to take some preventive action Objectives (now, during the planning process): Accurately simulate operations during an outage Provide a fuller picture of how various augmentation projects perform Provide a framework to help support DEP’s risk analysis Uncertainties in augmentation project capacity Uncertainties in RWB repair duration Threshold Approach - Objectives 21
Likelihood of Emergency Actions for 15-Month Outage 22
Big Break Through!!! Inundation Plugs not necessary!!! This resulted in the following: A shorter shutdown period for the connection of approximately 10 months A phased connection of the bypass tunnel to the RWBT Allowed for an evaluation of shorter shutdown periods and bailout contingencies We evaluated four phased approaches: Fixed Staging 4 month / 3 month / 3 month 5/5 6/4 Variable Stage (10 months total but can be broken and phased over 3 years) 23
Tunnel Outage Duration Evolution The design of the connection work always considered outage duration and risk mitigation Subsequent iterations improved risk picture Drainage Tunnel Preemptive Plug Base Plan Reactive Plug
Recent Modeling Results Where we are now!
26 Water Demand and Dry Weather Wastewater Flows Historic Flows and Future Projections 2012
Water Supply System Augmentation and Improvement Conservation / Demand Management Upper Catskill Aqueduct Optimization Queens Groundwater Rehabilitation 27
Modeling Results End of As a result of three workshops, extensive modeling, and shutdown design updates: Variable Stage Shutdown allows for complete shutdown in one phase Includes a repair start on Oct 1 with augmentation starting June 1 Provides for a singular phase repair based on modeling using forecasted 60 day look ahead for continuation of shutdown or bailout from repair Provides for allowance for remaining repair to be completed in subsequent years, if necessary 58 mgd of augmentation (33 mgd Groundwater + 25 mgd Demand Management) Catskill Aqueduct maximum flow increased to 636 mgd via Catskill Rehabilitation Project Croton WFP flow at 250 mgd to account for diurnal demand pattern.
Outage Surface Plot: Variable Outage 29 Year 1Year 2Year 3 Most outages start in October Index560 Outage_PatternVar SourceNY_Q58 New_Crot_Aq_max290 CatAq_max636 Reserve_Buffer10% NYC_Demand_level1070 Temp_vary_Demand0 Substantially longer Stage 1 outage duration with 10% reserve and CAT 636
Likelihood of Completion: Variable Staging 30 Month # lines for each color – these represent: NCA 250 / Demand Pattern NCA 290 / Demand Pattern NCA 250 / Demand Regression NCA 290 / Demand Regression This plot shows the likelihood of completing 300 total outage days over a period of up to 3 years. Likelihood of Completing x Outage Days Shows probability of successfully completing the variable stage shutdown repair during a three consecutive year period Allows for three chances to complete the 10 month (300 day) repair Could complete entire 10 months in first year Or could complete remaining repair period during subsequent one or two years if insufficient supply is available in first year Fixed stage shutdowns do not allow for this flexibility since entire three year period is required for each repair period
Likelihood of Completion: Summary Table 31 99% Probability of Success!
Next Steps 32 Continue refining shutdown design and modeling Continue thinking about issues that could arise Develop operational plans for shutdown