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

Agenda

• Background – The Indianapolis Tunnel

System & The TAP Model

• Precursors to TAP Analysis

• TAP Analysis

• TAP Model Refinements

• TAP Results – Recommended Surge

Strategy

• Discussion

Background – Why Do a Surge Analysis?

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)

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

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

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

TAP Model Schematic

– Level 1 (Tunnel)

7 Inflow Points

4 Shaft Overflows

3 Surge Tanks

TAP Analysis

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

TAP Analysis – L1 Passive

OPEN

CLOSE

Deadband

5 Min Gate Closure

Single Control Junction @ Fall Creek/White River

Intermediate Working Shaft

Open/Close Elevation – Upstream Crown (534 feet)

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

TAP Analysis – L1 Gated

TAP Model Schematic – Level 2: Gated Model

35 Gated Inflow Points

4 Shaft Overflows (w/ BC)

3 Surge Tanks

TAP Analysis

Level 3 TAP

Model

All CSOs

represented

Incorporated

Headloss Curves

for Drop Shafts

based on

physical

modeling

CSO Weir to

Collection System

CSO OF

Approach Channel

Taper

Channel

Drop Shaft

CCS

TAP Analysis

IIHR Physical

Model of Vortex

Dropshaft

TAP

representation

calibrated to

Headloss data

Scaled for other

dropshafts

Evaluated

impacts of

gate closure

and surge on

CCS and

existing CSO

system

TAP Analysis

TAP Analysis

Level 3 TAP Model

TAP Analysis

Level 3 – Tunnel -> CSO Weirs Refined 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

Gate Closure Elevation in Intermediate Working Shaft 534 feet

Identified 15 CSOs where backflow may occur over

CSO weirs – after inflow gates have closed

100 cfs / 0.5 MG stored

700 cfs

600 cfs 500 cfs

550 feet

TAP Analysis

When do we need redundancy for Gate Failure?

2,100

1,300

500

-

500

1,000

1,500

2,000

2,500

Max

imu

m A

llow

able

Flo

w (

cfs)

July 18, 1996 Event June 15, 1998 Event November 7, 1996 Event

TAP Analysis

• Level 4 – Ventilation

• Utility Shafts

Required after

Pump Station

submerges

• Area of concern

for trapped air

pocket

• Vent Orifice

restriction

considered

TAP Analysis

• Level 4 – Ventilation

• Retrieval Shaft

Ventilation on

all Branches

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

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

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

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

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

Discussion

• Questions?