Strategy%20to%20Control%20CSOs%20in%20Winnipeg

1
Strategy to Control CSOs in Winnipeg

• Presentation To

April 27, 2005
2
Outline

• Background
• Existing System Response
• Possible Control Options
• Cost/Benefit Analysis
• 2003 CEC Recommendation
• Conceptual CSO Mitigation Plan

3
Background

• 5 Interceptor Sewer systems
• 3 Pollution Control Centres
• 79 CSO locations
• 231 Land drainage outlet
• 101 to Red and Assiniboine
• 2 Major Rivers

4
Wastewater Treatment Plants
NEWPCC
NEWPCC SEWPCC WEWPCC
Population Served 374,000 160,000 86,000
ADWF Recorded in 2002 160 50 27
ADWF Design Capacities 302 59 32
WEWPCC
SEWPCC
ADWF Average Dry Weather Flow (ML/d)
5
Winnipegs Wastewater Sewers

• Older parts of the City (pre 1960)
• Approximately 30 of City has combined sewers
• CSO dilute mixture of sewage and land drainage

6
Combined Sewers Exist Worldwide

• Many European cities have combined sewers
• control strategies being developed
• In North America, about 850 communities have
  combined sewers
• e.g., Boston, Chicago, San Francisco
• In Canada, cities include Halifax, Quebec City,
  Montreal, Toronto, Edmonton, Vancouver
• In Manitoba, portions of Winnipeg, Brandon and
  Selkirk sewer systems have combined sewers.

7
Existing Systems Response
8
Receiving Stream Impacts

• On average, CSOs occur 18 times per recreation
  season (May 1 to Sept 30)
• Overflows are wet weather driven
• During dry weather, all sewage is intercepted and
  conveyed to WPCCs for treatment
• 1 of total annual sewage is lost to overflows
• Effects of CSOs on River Quality relate to
• Microbiological water quality
• Aesthetic quality (Visual)

9
GM 200
10
ILLNESS RISK

• CSO Advisory sub-committee concurred in
  following
• CSO control will be costly and the benefits are
  subjective
• There are many reasons to consider CSO control
• CSOs should not be considered a significant
  public health issue
• CSO control is fundamentally a public policy and
  a regulatory compliance issue.

11
Control Methods

• Several control options possible
• Separation
• End-of-pipe treatment
• Storage and dewatering
• Off-line tanks / Tunnels
• In-line storage

• Target of 4 overflows per season common practice
  in USA

12
Sewer Separation

• Estimated at about 1.5 Billion (no inflation)
• Very disruptive to community

13
End-of-Pipe Treatment

• Vortex Solids Separator (VSS)
• Very costly, large structure, requires land at
  outfalls
• Requires chemicals, operational considerations
• NOT recommended

14
End-of-Pipe Treatment

• Retention Treatment Basins (RTBs)
• Very costly, large structure, requires land at
  outfalls
• Requires chemicals, operational considerations
• NOT recommended

15
Off-line Storage Tanks

• This will comprise large, near-surface tanks
  located at the end of the combined sewer trunks

• This method is used in
• Saginaw, Mich.
• Toronto, Ont.
• Sarnia, Ont.

16
Deep Tunnels

• Large tunnels could be used to store and convey
  combined sewage to WPCCs for treatment
• This method is used in
• Chicago, Ill.

17
In-line Storage

• Large old trunk sewers offer potential storage
  for combined sewage during smaller storms

• Relief sewers constructed for basement flooding
  also provide large volumes of potential storage

Trunk Sewer
Relief Sewer
7.55 ft
9.75 ft
9.0 ft
18
Latent Storage

• If these pipes are dewatered, storage could be
  available for inline storage

19
In-line Storage

• In-Line storage involves retaining wet-weather
  flow in the pipe for small rainstorms
• The stored wastewater is dewatered at a
  controlled rate and sent to WPCC
• If the rainstorm threatens basement flooding, all
  flow is released to river

• Needs Local Testing
• Sediment deposition
• Odours
• Minimize risk of basement flooding
  (reliability/liability)
• Has been used successfully in other jurisdictions
  
• Cleveland and
• Detroit

In-Line Storage
Inflatable Dam
To Interceptor
20
CSO Control Benefits
21
(No Transcript)
22
(No Transcript)
23
(No Transcript)
24
(No Transcript)
25
Overview of Plan
Tunnel Storage (Zero overflows)
In-line Storage plus Distributed Storage and
Transfers plus Off-Line Storage
Complete Sewer Separation
In-line Storage plus Distributed Storage and
Transfers
Available In-line Storage
Disinfection at WPCCs
CSO Control Options
26
Integration with Other Programs

• Basement Flood Relief
• Combined Sewer Renewal
• Potential Opportunities
• Oversizing of proposed relief pipes for storage
• Allowance for localized separation
• Cleaning of trunk sewers for storage
• New Developments

27
Cost/Benefit Trade-off
28
2003 CEC Hearings

• Clean Environment Commission (CEC) held public
  hearings in January and April 2003, and
  recommended
• Combined Sewer Overflow Reduction
• 7. The City directed to shorten the timeframe to
  complete its CSO plan a 20 to 25 year period.
• 8. The City directed to reduce CSOs by
  instrumenting outfalls, adjusting weirs,
  accelerating combined sewer replacement,
  advancing the pilot project within two years.
• Public Notification System
• 9. The City directed to develop and implement a
  notification system to inform the public whenever
  there is a release of raw sewage to the local
  Rivers
• Provincial Implementation (to be confirmed)
• Accept City plan to reduce overflows to 4/year on
  average
• Complete CSO plan by 2030

29
Public Notification Information

• Keep our rivers clean!
• What goes into the sewer can end up in our
  rivers.
• Responsible at source control

30
Long-term Goal 4 Overflows/year
31
Winnipeg's CSO Control Plan

• Citys current CSO control plan reflects many
  important considerations
• 2003 CEC Hearings recommendations
• Manitoba conservation guidance and priorities
• Consistency with prevailing international
  practice
• Understanding of benefits and costs
• Fiscal responsibility and environmental
  stewardship
• Initiation of near-term actions to reduce CSOs
• Confirmation of long-range control program

32
(No Transcript)