Pumping Downhill Can Be A Good Solution Unique Challenges To Pumping Downhill Hydraulic Transient Analysis Case Study City Of Indianapolis, IN Randy Vanderwerf, P.E., Clark Dietz, Inc. Omkar Ghavi, E.I., Clark Dietz, Inc.

March 20, 2012

Belmont North Service Area

Belmont North Interceptor (BNI)

BNI System • Separate Sanitary Sewer System Sewers 27 inch to 54 inch

• Limited Interceptor Capacity • Wet Weather Sanitary Sewer Overflows

• Separate Relief Interceptor • Eliminate Wet Weather Capacity Limit 20-year Build-out of Service Area

BNRI Advanced Facility Plan ~ 25 ft

~ 40 ft

50 ft Drop

BNRI Advanced Facility Plan Value Engineering

• Population Projection • Rainfall Pattern

Flow Reduction

Alternative Routes • Constructability • Environmental Impacts

• Construction Costs • Present Worth

Project Costs

BNRI Advanced Facility Plan

780

Belmont North Lift Station Flows 760

740

720

700

680

Peak Hour … 38 MGD Daily Average … 7 MGD Daily Minimum … 3 MGD

Pumps 3 Operating 1 Standby

BNRI Force Main Profile Force Main Static HGL

Air Pockets

Steady State HGL at 38 MGD

Standpipe Standpipe 745.00

Belmont Belmont North Lift Lift North Station Station

735.00

50 ft Drop

BNRI Force Main Force Main Present Worth Analysis Electrical Cost Ferric Chloride Cost

Pump Cost

42” Force Main

BNRI Advanced Facility Plan

• Project Cost: $222 Million • Lift Station & Force Main Savings $ 49 Million Belmont North Lift Station

42”

42”

42”

Standpipe 42”

Surge Analysis: Criteria Criteria

✓• • ✓ ✓• ✓• ✓•

TDH > 50 ft Flow > 500 GPM Pipe > 1,000 ft High Points Profile: ‘Knees’

BNRI Conditions • • • • •

TDH ~ 116 ft Flow = 26,200 GPM Force Main ~ 28,350 ft Valleys and Peaks Knee at ~ 15,000 ft

Investigate Hydraulic Transients

Typical Causes • Valve Movement : Opening / Closing • Starting or Stopping Pump(s) with

Other Pump(s) Operating • Change in Flow Demand

• Frequent Variation in Water Level • Pump Trip due to Power Failure

Impacts of Transients • High Pressure Failure Pumps, Valves Pipe Rupture Disintegration of Pipe Lining Pipe Leaks

• Low Pressure Cavitation and Column Separation Collapsing of Pipe Intrusion of Contaminants Vapor Cavities: Very High Pressures

Surge Analysis: Importance • Select & Design Pipe to Withstand

Pressures • Select Appropriate Check Valves • Surge Control Devices Alleviate Adverse Transient Effects Proper Selection and Location Start-up / Shutdown Procedures

Surge Control Devices

Active Devices

Modify Conditions by Providing Liquid or Air to Piping System

Surge Tank

Surge Control Devices

Passive Devices

Limit Extent of High or Low Pressure

Air Release Valves

Surge Tanks • Normally Located at Lift Station Protection against Pump Power Loss

• Pressurized Vessels (Air + Water) • Supply Liquid to Pipeline Must Not Empty / Allow Air to Enter

• Initial Air Quantity: Large Limit Rate of Pressure Drop

Surge Analysis Model

Peak Flow at 38 MGD • Steady State • Pump Trip: 100% to 0% in 4 seconds • Monitor Pressures for 320 seconds

Surge Model Layout

Surge Analysis at 38 MGD 1600

840

820

No Surge Steady State Protection

1400 800

780 1200

Several Times Steady State Pressure

720 800

700

• Max. Pressure Belmont • Min. Pressure North Lift • Conditions Station • Location • Duration

HGL after 16 seconds Pressure Envelope

Very High Positive Head

Standpipe

760

1000 740

Force Force Main Main Steady Steady State State HGL HGL at at 38 38 MGD MGD

183 psi -14.4 psi Full Vacuum Everywhere 320 sec

Negative Head Elevation

Important ARV Features • Avoid Rapid Air Expulsion Secondary Surges Two / Three Stages: Restrict Air Release

Proprietary Designs: Surge Check Valves Bias Mechanisms Throttling Devices

• Sealing Pressure < Static Head Valve Doesn’t Seal: Discharge Sewage

ARV Selection Air Valve Considerations • Non-slam Feature • Sealing Pressure • Materials • Cost

Force Main Static HGL Steady State HGL at 38 MGD Air Valve

Standpipe Belmont North Lift Station

ARV Sealing Pressure Criteria Force Main Static HGL Steady State HGL at 38 MGD Air Valve Valve Sealing Head

Standpipe Belmont North Lift Station

Surge Analysis Model: Modifications

Surge Analysis at 38 MGD Force Main Steady State HGL at 38 MGD HGL after 16 seconds Pressure Envelope

Air Valves

840 1600

Surge Conditions with No Protection

820

1400 800

780 1200

760

740

720

• • • • •

Max. Pressure Min. Pressure Conditions Location Duration

55 psi -14.4 psi Partial Vacuum Several 320 sec 1000

800 700

Surge Tanks: Sewage Applications Hydro-pneumatic Tank • Air Compressor: Control Gas Volume

Bladder Tank • Pre-charged Pressurized Bladder

Hybrid Tank • Air Vent: Utilize Atmospheric Air

Surge Tanks: Sewage Applications Hybrid Tank

Courtesy: Charlatte America

Sewage Surge Tanks Evaluation HydroPneumatic

Bladder

Hybrid

O&M ✓ Issues

✓

✓

✓ Effectiveness

✗

✓

Cost

Surge Analysis at 38 MGD Force Main Steady State HGL at 38 MGD HGL after 16 seconds Pressure Envelope

Air Valves & Hybrid Tank

840

820

800

780

760

740

720

700

• • • • •

Max. Pressure Min. Pressure Conditions Location Duration

52 psi -12 psi Partial Vacuum One