1. Workshop developed by RCAP/AWWA and funded by the USEPA
System Operations:
Main Breaks
Instructors please mention that this is the second of two modules focused on distribution system operations. This module focuses on main breaks and cross connections, and describes how these events can compromise water quality in the distribution system.
Workshop developed by RCAP/AWWA and funded by the USEPA
Developed by American Water Works Association with funds from the U.S. Environmental Protection Agency, Published 2015

2. Learning Objectives
Be able to preserve water quality when responding to a water main break
Describe the difference between proactive and reactive responses to leaks
Be able to describe what a cross connection is and recognize a cross connection

3. Learning Objectives Continued
Be able to describe the seriousness of cross-connections and importance of cross-connection control
Describe requirements for cross-connection control
Be able to outline the emergency response in the event of a backflow

4. Main Break: How Does it Happen?
Aging infrastructure
“a significant water line bursts on average every two minutes somewhere in the country”
“$334.8 billion will be needed for pipe, treatment, storage, source and other infrastructure over the 20 year period ”
Pressure surge
Mechanical damage
3rd Party damage
Sabotage 4

5. Main Break: How Does it Happen?
“The rupture was caused by an emergency pump shutoff that increased pressure from 180 psi to 300 psi.”

6. Main Break: Consequences
Potentially a safety hazard
Flooding of surrounding area
Property damage
Traffic interruptions
Water service interruption

7. Main Break: Consequences (Continued)
Loss of pressure
Contaminant intrusion
May require boil water order or bottled water
Loss of finished water
High velocity scouring of pipes may dislodge sediments and increase turbidity

8. Reactive Response to Leaks
Valve off section of line if needed
Notify MSDH if pressure goes below 20 psi
Excavate
Repair leak
Make sure ALL valves are re-opened

9. Proactive Response to Leaks
Ensure your lines are marked in construction areas
Develop a protocol for response to main breaks to limit adverse water quality effects
Develop a program to anticipate main breaks
Asset Management
Buried pipes are the most costly asset of a water utility
Prioritize mains that need replacement and get them included in the Capital Improvement Plan

10. Proactive Response to Leaks
Being proactive can reduce costs and protect water quality

11. Proactive Response to Leaks
EPA Asset Management Program
Check Up Program for Small Systems
(CUPSS)

12. Disinfecting New Pipes and Returning New Pipes to Service
New water mains and those taken out of service should be disinfected before returning to service
For additional guidance and information go to:
AWWA Standard C – Disinfecting Water Mains 12

13. Disinfecting Pipe AWWA: 4-Step Process
Flush the line to remove any particulates
More effective than burning with chlorine
Velocity > 2.5 fps
Flush at least 2x the volume of the pipe
Chlorinate
Should target a dose of 50 mg/L
A 5 mg/L residual should remain after 24 hours
A higher chlorine dose can be used in exchange for shorter contact time
Do not use dry chlorine (HTH) as granules may not fully dissolve

14. 4-Step Process (Continued)
Flush to remove chlorinated water (at least 2 full pipe volumes)
Chlorinated water must be dechlorinated prior to discharge in some areas
Refill the line and perform coliform sampling
If results are negative the line is ready to be returned to service (with MSDH’s approval)
If results are positive, repeat from step 2
If positive results continue, pigging or additional flushing may be necessary 14

15. Activity A D Finished water C B E
5. Key Distribution System Components and Their Effects on Water Quality
Activity
Chlorine A B C
Finished water D E
Instructors move to the next slide to answer the question.
Developed by American Water Works Association with funds from the U.S. Environmental Protection Agency, Published 2015

16. 5. Key Distribution System Components and Their Effects on Water Quality
Activity
Describe how the following scenarios will affect water quality
What would be your concern?
What should you monitor for?
What else should you do?
A fire breaks out at Point D
Chlorine metering pump breaks down at Point B
Booster pump breaks down at Point C
Main break at Point E
A rainy week during the summer
Half time at the Super Bowl
Modeling of distribution system network with EPANet or other modeling software. The key infrastructure including WTP and storage tanks are identified.
Developed by American Water Works Association with funds from the U.S. Environmental Protection Agency, Published 2015

17. Questions?