The Indianapolis Deep Tunnel Surge Analysis: Debugging Future Operational Issues in the Present

Transcription

1 The Indianapolis Deep Tunnel Surge Analysis: Debugging Future Operational Issues in the Present Karen Ridgway, P.E., Applied Science Inc. Chris Ranck, P.E., BCEE, D.WRE, RW Armstrong Dave Klunzinger, P.E., DLZ John Morgan, Citizens Water June 20, 2012

2 Agenda Background The Indianapolis Tunnel System & The TAP Model Precursors to TAP Analysis TAP Analysis TAP Model Refinements TAP Results Recommended Surge Strategy Discussion

3 Background Why Do a Surge Analysis?

4 Background The TAP Model (Transient Analysis Program) State-of-the-Art Computational Hydraulics Program Fully-dynamic one-dimensional program Uses a finite-volume solution technique Properly simulates open channel and pressurized wave fronts created during rapid filling Validated to laboratory data, Method of Characteristics (MOC) and Implicit Methods (i.e. WHAMO)

5 Background Indianapolis Tunnel System December 2010 CD Amendment: 250 MG Total Tunnel Storage 90 MGD Dewatering Pump Station Physical Parameters: ~ 130,000 ft, 18 diameter ~ 100 CSOs connected 3 Retrieval Shafts, 4 Working/Intermediate Shafts ~ 35 Drop Shafts Design Progress DRTC In Construction DRTCPS 90% Design Complete FCWRTS 60% Design In Progress PRDT AFP Complete LPgRT AFP Complete

6 Precursors to TAP Analysis Screening of Surge Relief Locations SWMM Model Review 10,700 MGD Aggregate Peak CSO System Discharge 4600 MGD (7000 cfs) Discharge at Consent Decree Perf. Criteria Four Events to Evaluate One Synthetic, Three Historical

7 TAP Analysis Level 1 Tunnel Only Level 2 Tunnel & Drop Shafts Level 3 Tunnel, Drop Shafts, Consolidation Sewers, CSO Outfalls, CSO Weirs Level 4 Ventilation

8 TAP Analysis TAP Model Schematic Level 1 (Tunnel) 7 Inflow Points 4 Shaft Overflows 3 Surge Tanks

9 TAP Analysis L1 Passive Preliminary Surge Tanks Pleasant Run = 0.0 MG Pogues Run = 0.1 MG Fall Creek = 1.0 MG Preliminary Shaft Overflow Peak Rates Southport = 1,500 cfs White River at Pleasant Run = 1,500 cfs White River at Pogues Run = 1,500 cfs White River at Fall Creek = 2,700 cfs

10 TAP Analysis L1 Gated 5 Min Gate Closure Single Control Fall Creek/White River Intermediate Working Shaft Open/Close Elevation Upstream Crown (534 feet) CLOSE Deadband OPEN

11 TAP Analysis L1 Gated No Surge Tanks Required Shaft Overflows May be Necessary if Too Many Gates Fail Gates Need to Convey the Flow Rate for the Consent Decree Perf. Criteria (~4600 MGD) 18 Tunnel System Cannot Convey 10,700 MGD Peak Restriction at Drop Shafts or Consolidation Sewers are Required

12 TAP Model Schematic Level 2: Gated Model 35 Gated Inflow Points 4 Shaft Overflows (w/ BC) 3 Surge Tanks

13 TAP Analysis Level 3 TAP Model All CSOs represented Incorporated Headloss Curves for Drop Shafts based on physical modeling Taper Approach Channel CSO Weir to Collection System CCS CSO OF Drop Shaft

14 IIHR Physical Model of Vortex Dropshaft TAP representation calibrated to Headloss data Scaled for other dropshafts TAP Analysis

15 TAP Analysis Evaluated impacts of gate closure and surge on CCS and existing CSO system

16 Level 3 TAP Model TAP Analysis

17 TAP Analysis Level 3 Tunnel -> CSO Weirs Refined Shaft Overflow Peak Rates Southport = 1,500 cfs 100 cfs / 0.5 MG stored White River at Pleasant Run = 1,500 cfs White River at Pogues Run = 1,500 cfs 700 cfs 600 cfs White River at Fall Creek = 2,700 cfs 500 cfs Gate Closure Elevation in Intermediate Working Shaft 534 feet 550 feet Identified 15 CSOs where backflow may occur over CSO weirs after inflow gates have closed

18 Maximum Allowable Flow (cfs) TAP Analysis When do we need redundancy for Gate Failure? 2,500 2,000 2,100 1,500 1,300 1, July 18, 1996 Event June 15, 1998 Event November 7, 1996 Event

19 Level 4 Ventilation Utility Shafts Required after Pump Station submerges Area of concern for trapped air pocket Vent Orifice restriction considered TAP Analysis

20 Level 4 Ventilation Retrieval Shaft Ventilation on all Branches TAP Analysis

21 TAP Model Refinements Model Size 250 Junctions -> 450 Junctions 150 Conduits -> 250 Conduits Air Volume Tracking Volume of water & air reported in all conduits at all time steps Allows for post-processing to track movement of air and calculate ventilation rates in shafts

22 Recommended Surge Strategy Restrict peak inflow to tunnel system 18 Tunnel has capacity for peak inflow per the Consent Decree requirement Inflow Gates at all Drop Shafts Central Monitoring Point at Intermediate Working Shaft Redundancy for Inflow Gates Passive Shaft Overflows based on real storms Or Redundant Inflow Gates at largest drop shafts

23 Current Status Analysis Completed December 2010 Intermediate Working Shaft Moved ~ 1.7 Miles Upstream Feb 2011 Monitoring site change close elevation from 550 to 560 feet No longer practical shaft overflow site Additional strain on remaining 3 shaft sites Constructability limitations for shaft peak flow rates Shifting Preference to redundancy on largest gates Additional Ventilation Study for Utility Shafts is under consideration

24 Lessons Learned Interface with SWMM model (and modelers) is essential Physical Geometry influences surge strategy Fixed Diameter (CD Amendment) Slope (Geology, Constructability) Shaft Overflow Envelope (River to CSO Weir) Shaft Proximity to Largest CSOs Need to keep model up to date Need to keep up to date on research Conveyance Capacity Passive Feasibility

25 Acknowledgements John Morgan Citizens Water Dave Klunzinger DLZ Surge Modelers: Brittany Vrzina, Stephen Rowe Iowa Institute of Hydraulic Research (IIHR) Tunnel Designers: AECOM, Black & Veatch, B&N

26 Questions? Discussion