evaluation of cso control alternatives in small communities michael sullivan limno-tech, inc
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Evaluation of CSO Control Alternatives2
Elements of an LTCP for Small CSO Communities
Required in CSO Control Policy:
Consideration of sensitive areas
Public participation
Evaluation of CSO control alternatives
Useful or likely to be required:
Characterization (not necessarily monitoring and modeling
Maximization of treatment at the POTW
Post-construction compliance monitoring
Evaluation of CSO Control Alternatives3
Most Widely Used CSO Controls
Rank LTCP Control Activity1 Sewer separation
2 Sewer rehabilitation
3 Retention basins
4 Disinfection
5 Primary sedimentation
6 Storage tunnels and conduits
7 Upgraded WWTP capacity
8 Outfall elimination
Evaluation of CSO Control Alternatives4
CSO Controls for Small Community Consideration
1. Maximization of treatment at the POTW.
2. Inflow control.
3. Sewer separation.
4. Storage.
Emphasis placed on these controls, but there
are many other types of controls available.
Evaluation of CSO Control Alternatives5
1. Maximization of Treatment at the POTW
Take advantage of existing infrastructure
Increase conveyance and pumping capacity where excess POTW treatment capacity is available
Increase POTW treatment capacity where conveyance is available
Build on Existing Infrastructure: Increase Pump Station Capacity
Wilmington, DE
Evaluation of CSO Control Alternatives6
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Increase POTW CapacityCity of Frankfort, KY (pop 27,750)
In Frankfort the 2001 expansion increased the POTW capacity from a 6.6 MGD facility to a 9.9 MGD facility.
Evaluation of CSO Control Alternatives9
2. Inflow Reduction
Various techniques used to reduce the amount of water that enters a CSS through:
Roof leaders
Area drains
Foundations drains
Basement sump pumps
Downspout Extension and Redirection
Milwaukee Metropolitan Sewer District
Evaluation of CSO Control Alternatives
Rain Garden Solution:Downspout and Basement Sump
RedirectionSweetwater Alliance, Duluth, MN
Evaluation of CSO Control Alternatives
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Inflow ReductionSouth Portland, ME (Pop: 23,200)
CSS covers 5,250 acres
Surveyed 6,000 residential buildings.
Found 380 roof leaders connected to CSS.
Notified property owners and established rebate program:
$75 for roof leader diversion*$400 for basement sump pump diversion*
Achieved substantial reduction in CSO discharge for relatively low cost.
* 1995 dollars
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Inflow ReductionBurlington, IA (Pop 26,800)
Inspected 1,300 manholes (GPS opportunity).
Smoke testing on 300,000 lf sewer line.
Surveyed 4,500 homes
Disconnected all but 50 of 1,400 roof leaders.
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3. Sewer Separation
A widely used CSO control – especially in small communities.
Can be expensive and disruptive.
Often implemented with other projects – road work, utility work, and redevelopment.
Solves CSO problem, but adds to storm water problem.
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Sewer Separation: Onondaga County, NY
Tallman and Onondaga Avenue Areas
Sub Areas Acres
Taylor Street 10
Tallman Street West 12
Onondaga Avenue 1 15
Onondaga Avenue 2 16
53
Evaluation of CSO Control Alternatives22
Onondaga County, NYDetails
New sanitary sewers constructed.
Old sewers become storm sewer.
Cost is $90,000 per acre
70% funding from Corps of Engineers
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Onondaga County, NYAdditional Improvements
Replacing sewer laterals from street to curb line.
Making spot repairs to existing combined sewer.
Replacing active lead or galvanized iron water lines from water main to curb stop.
Gas utility replacing gas main in some portions of work areas.
Evaluation of CSO Control Alternatives24
Onondaga County, NYDisruption Considerations
Development of traffic plan.
Construction done during normal work hours.
Advance notification of water service disruption and alternative water source provided.
Minimization of gas service interruptions.
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Sewer Separation Example Randolph, VT (Pop: 2,270)
Separated 44 of 52 catch basins.
Cost to date is $2.7M
25% State grant
50% State revolving fund loan
25% City of Randolph
CSOs reduced but not eliminated.
Achieving full separation is difficult.
Planning to spend another $0.5M.
Evaluation of CSO Control Alternatives26
4. Storage FacilitiesMany possibilities for small
communities
In-line storage—oversized conduits and regulators; in-line tanks; parallel relief sewers.
Off-line storage—retention basins/tunnels to store wet weather flow for subsequent treatment.
On-site storage / flow equalization—storage at WWTP to manage excess wet weather flow.
Off-Line StorageExcavation of Retention Basin
Massachusetts Water Resources Administration, MA
Evaluation of CSO Control Alternatives
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On-Site Storage Example Oakland, ME (Pop: 6,000)
Restoration of unused flow equalization basin:
Had sufficient conveyance capacity.
Needed additional wet weather capacity.
Restored unused flow equalization basin from closed textile mill.
New storage volume is 0.2 MG
Cost was $27,600 (14 cents per gallon)
Evaluation of CSO Control Alternatives31
On-Site Storage Example South Paris, ME (Pop: 2,237)
Restoration of unused pretreatment facility:
Wastewater treatment system designed with two pretreatment facilities – tannery and cannery.Tannery closed in 1985.Tannery pretreatment facility brought back on line in mid-1990s.New storage volume is 1.5 MGCost was $110,000 (7 cents per gallon)
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CSO Technology References
Report to Congress on Impacts and Control of CSOs and SSOs
http://www.epa.gov/npdes/pubs/csossoRTC2004_AppendixL.pdf
EPA Municipal Support Division Fact Sheetswww.epa.gov/owm/mtb/mtbfact.htm
Rouge River National Wet Weather Demonstration Project (MI)www.wcdoe.org/rougeriver/
Columbus Water Works National Demonstration Program (GA)www.cwwga.org/NationalPrograms/Index.htm
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Screening and Evaluation of CSO Controls
The screening and evaluation of controls should:
Include WQ considerations
Consider site specific control needs
Address performance of control technologies
Describe implementation issues
Explain reasons for selecting CSO control alternatives
Explain reasons for rejecting other controls
Note: Looking for logical decision-making process
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Selecting the Best CSO Control Alternatives
Will water quality and designated uses be protected?
Have sensitive areas been considered?
Has a reasonable range of CSO control alternatives been considered?
Has public input been obtained and used?
Has financial capability been assessed?
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Final Selection of CSO Control Alternatives
Should be based on:
Control priorities
Site specific conditions
Protection of WQS and designated uses
Public input
Cost-effectiveness of controls
Financial capability
Other considerations
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CSO ControlWest Lafayette, IN (Pop 28,900)
The 20 Year plan for CSO control that began in mid-1990s includes:
An $18 million upgrade to the POTW
A $2.2 million foundation drain disconnect program in the BarBarry neighborhood (1999)
Construction of the $2.3 million North River Road lift station (1999).
The $1.9 million rehabilitation of the Happy Hollow interceptor (2001).
Construction of the $5.9 million wet weather treatment facility to reduce CSO impacts on the Wabash River (2003).
CSO Control: Auburn, IN (Pop 12,000)
Improvement Date Effect on CSOsBuilt relief sewer and
Swirl concentrator
1981 Increased storage
Partial treatment
POTW expansion 1985 Eliminated some CSOs
NW sewer separation 1986 Decreased CSS area
NW sewer separation 1988 Eliminated one CSO
SW sewer separation 1993 Decreased CSS area
POTW Expansion 1999 Added capacity: 2.5 MGD average, and 5.0 MGD maximum
Evaluation of CSO Control Alternatives
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CSO ControlSaltsburg Borough, PA (Pop. 955)
Small population and limited
budget required emphasis on
NMCs:
Proper O&M of existing sewer system.
Installed baffles to control floatables in catch basins.
Notification signs at CSOs
Community bulletin board for education abut CSOs.
Limited monitoring of CSO volume and freq.
Evaluation of CSO Control Alternatives39
CSO ControlSouth Portland, ME (Pop: 23,200)
Achieved 90 percent reduction in CSO volume
Wet weather primary capacity expanded from 12 mgd to 56 mgd
Adjusted weir heights
Upgraded pump stations
Inflow reduction (roof leaders and sump pumps)
Select sewer separation
Eliminated 25 of 30 CSO outfalls