Distribution System Issues

1
Distribution System Issues

• Cross-Connections and Backflow
• Research/Information Needs
• Possible Ranking Process
• Doug Owen
• TWG Representative
• TCRDS Federal Advisory Committee
• October 17-18, 2007

2
This Meetings Presentations

• Objectives

Provisions
Distribution System Issues Issues and Attributes
Rankings
System compliance
Improvement
Distribution System Issues Information and
Research needs
Research
3
Presentation objectives

• Focus on the first 4-5 priority issues from the
  expert panels or workshops
• Start with cross-connections and backflow -
  educate the FAC about the magnitude of risk and
  opportunities for risk reduction
• Identify where information gaps might define
  research needs
• Find or develop a decision support tool to
  provide for more systematic evaluation of
  priorities

4
Background September Meeting FAC Priority
Issues from Workshops/Panels
5
Distribution System Definition

• The public water distribution system consists of
  pipes, pumps, valves, storage facilities, meters,
  fittings, and other hydraulic appurtenances that
  connect water treatment plants or well supplies
  to consumers premise plumbing with the function
  to deliver water to all customers of the system
  in sufficient quantity for potable drinking water
  and fire protection purposes, at the appropriate
  pressure, with minimal loss, of safe and
  acceptable quality, and as economically as
  possible.
• (adopted from NRC, 2006, Drinking Water
  Distribution Systems Assessing and Reducing
  Risks).

6
Cross-connection

• A point in the plumbing system where the potable
  water supply is connected directly, or has the
  potential of being connected, to a source of a
  non-potable substance
• Any tee off the customers service line such as
  underground irrigation or a fire sprinkler
  system.
• Internal plumbing connections such as threaded
  faucets, water makeup lines for boilers, troughs,
  and autopsy tables, so
• Anything that uses water

7
Backflow

• The flow of water or other liquids, gases or
  solids from any source back into the piping of
  the water supply system
• An unprotected cross connection under certain
  hydraulic conditions can allow backflow to occur
• Incidents where potable water could be
  compromised by a
• Non-health hazard impairment of the water that
  creates adverse aesthetic qualities
• Health hazard an actual health hazard through
  poisoning or spread of disease

8
Backflow Incidents

• The EPA White Paper describes information about
  450 chemical, biological and physical backflow
  incidents, and over 12,000 illnesses (1970
  2001).
• These were obtained from public information and
  media reports and in do not indicate the complete
  extent of the problem
• Most incidents are not reported or the
  information is incomplete
• reporting is not required
• dont know how or to whom to report
• liability issues are a deterrent to reporting
• dont know that it occurred
• Some states have active CCCP
• WA as able to document 5 backflow incidents in
  Sept 2007

9
Hydraulic Conditions

• Backsiphonage Backflow due to a negative or
  reduced pressure within the potable water supply
• Backpressure Backflow due to pressure from an
  external source which exceeds the operating
  pressure of the potable water supply
• Water flows from high pressure areas to low
  pressure areas
• A hose submerged in a water trough can allow
  water to flow back into the piping system if the
  supply pressure drops (a break in a main, high
  unexpected water demand)
• The pressure exerted by elevated piping (i.e. a
  tall building) can exceed the water supply
  pressure forcing water to flow backwards

10
Cross-Connection Control

• Plumbing Code
• Internal plumbing (e.g. air gaps on all faucets)
• State County Health Rules
• Protect the distribution system
• Water Systems Policies
• Implement CCC programs
• Industry Standards AWWA, USC
• EPA Guidance

11
What information does the FAC need from the TWG
to help you evaluate issues and priority?What
information is needed to populate a decision
support tool
12
Information and Research Availability Spreadsheet
13
Who is studying cross-connections and backflow?

• Two AwwaRF Projects that Focus on Cross
  Connections
• Impacts of Cross-Connections in North American
  Water Supplies (90928 -Year 2003)
• Completed
• Covers the occurrence of cross connections in
  North America.
• Cross Connection and Backflow Vulnerability
  Monitoring and Detection
• To be completed in 2009
• Researching how to detect and monitor for cross
  connection and backflow events in the
  distribution system

14
Development of a Risk Assessment / Decision
Support Tool
15
Risk Assessment Management Model
16
DS Risk Assessment Difficulties

• Typical risk assessments rely on occurrence and
  concentration data
• It is extremely difficult to do that in the
  distribution system environment
• Variety of contaminants in the DS
• Variety of concentrations throughout the DS
• Concentrations can be intermittent and fleeting
• The following decision support tool is one way to
  assess and rank risks

17
Issues and Attributes Matrix
18
Issues and Attributes Matrix
19
Deteriorating Infrastructure

• The FAC requested that the TWG consider
  deteriorating infrastructure when addressing
  distribution system issues.
• Addressing deteriorating infrastructure could
  help to address other distribution system issues,
  such as biofilm and microbial ecology, pressure
  transients and intrusion, and storage facility
  integrity.
• TWG is evaluating compilation and synthesis
  documents, such as
• AWWA Evaluations Papers
• EPA Aging Infrastructure White Paper
• TWG is also investigating the EPA Sustainable
  Water Infrastructure program

20
Appendix

• AwwaRF Cross-Connection Control Research
• NRC/NAS Committee Recommendations

21
Impacts of Cross Connections in North American
Water Supplies (90928 -Year 2003)

• Objective assess the impacts, financial and
  otherwise, of cross-connections and
  cross-connection control in North American water
  utilities.
• Over 700 utilities surveyed - 91 were found to
  have a cross-connection control program.
• Sudden changes of water demands in piping
  networks can cause sub-atmospheric pressures
  within systems resulting in backflow incidents.

22
Impacts of Cross Connections in North American
Water Supplies (90928 -Year 2003)

• Systems with larger variances in ground
  elevations have the greater possibility of
  creating sub-atmospheric pressures as water
  demands in the systems change.
• Computer modeling clearly indicates that sudden
  changes in water demand (e.g., a hydrant opening)
  caused drastic transient flow conditions,
  resulting in significant pressure loss and flow
  reversal in a system of any size.
• Often the pressure could reach below atmospheric
  pressure. The extent of the affected area could
  not be generalized and depended on spatial
  variations in network grids and scenarios of
  changes in water demand.

23
Impacts of Cross Connections in North American
Water Supplies (90928 -Year 2003)

• No geographic trends were found in North America
  in relation to the type of cross-connections
  being experienced.
• Indirect cross-connections accounted for 65 of
  cross-connections while 35 were direct
  cross-connections.
• Survey data suggested
• the number of incidents per utility is not
  necessarily changing over time
• reporting is becoming more prevalent as agencies
  develop cross-connection control programs.

24
Two other AwwaRF projects that partially
considered cross connection control

• Pathogen Intrusion Into Distribution Systems
  (90835- Year 2001)
• Researched how pathogens can enter the DS
• Not focused on cross connection control but
  confirmed that backflow and cross connection
  events were considered important routes of entry
  for pathogens into distribution systems.
• Guidance for Management of Distribution System
  Operation and Maintenance (90803-Year 2000)
• Included cross connection control as part of a
  larger guidance manual for distribution system
  operations and maintenance.

25
AwwaRFs ongoing project

• Cross-Connection and Backflow Vulnerability
  Monitoring and Detection (3022- ongoing)
• Objectives
• Establish useful or practical monitoring
  approaches that might help prevent or more
  rapidly detect cross-connection and backflow
  incidents.
• Assess how to identify and contain chemical and
  microbiological contamination using current
  technologies and capabilities.

26
Cross-Connection and Backflow Vulnerability
Monitoring and Detection (3022- ongoing)

• Tasks
• Identify distribution system characteristics that
  provide susceptibility to backflow incidents.
• Determine critical monitoring locations.
• Develop risk factor evaluation methodology.
• Identify and evaluate existing technologies for
  prevention of backflow incidents.
• Identify and evaluate existing technologies for
  monitoring and detection of backflow incidents.

27
Cross-Connection and Backflow Vulnerability
Monitoring and Detection (3022- ongoing)

• Tasks (Contd.)
• Provide guidelines for identifying potential
  sources of contamination and tracing existing
  contamination sources.
• Evaluate techniques for determining the most
  effective application of existing monitoring
  technologies for rapid detection of backflow
  incidents.
• Case study modeling evaluations for determining
  the most effective placement of monitoring
  technologies.
• Pilot and field scale evaluations.

28
NRC/NAS Committee

• Recommendations Pertaining to a Possible
  Distribution Rule
• Cross-connection control should be in place for
  all water utilities.
• EPA should work closely with representatives from
  states, water systems, and local jurisdictions to
  establish the elements that constitute an
  acceptable cross-connection control program.
• Residual disinfectant choices should be balanced
  to meet the overall goal of protecting public
  health.

29
NRC/NAS Committee

• Recommendations Research Needs
• Epidemiological studies that specifically target
  the distribution system component of waterborne
  disease are needed.
• Distribution system ecology is poorly understood,
  making risk assessment via pathogen occurrence
  measurements difficult.
• Current microbial monitoring is limited in its
  ability to indicate distribution system
  contamination events, such that new methods and
  strategies are needed.
• Distribution system integrity is best evaluated
  using on-line, real-time methods to provide
  warning against any potential breaches in
  sufficient time to effectively respond and
  minimize public exposure.
• Research is needed to better understand how to
  analyze data from on-line, real-time monitors in
  a distribution system.
• Communities should squarely address the problem
  of Legionella, both via changes to the plumbing
  code and new technologies.

30
NRC/NAS Committee

• Recommendations - Information Collection Needs
• More attention should be paid to having adequate
  facilities, instructors, and apprentice programs
  to train utility operators, inspectors, foremen,
  and managers.
• There is inadequate investigation of waterborne
  disease outbreaks associated with distribution
  systems, especially in premise plumbing.
• Other General Recommendations
• EPA should create a homeowners guide and website
  that highlight the nature of the health threat
  associated with premise plumbing and mitigation
  strategies that can be implemented to reduce the
  magnitude of the risk.
• Research projects are needed that specifically
  address potential problems arising from premise
  plumbing.

31
Issues and Attributes Matrix