Transcript Reducing Real Losses (Leakage) in a Rural System Using a Bottom

The Water & Wastewater Authority
of Wilson County, Tennessee
Reducing Real Losses (Leakage) in a Rural
System Using a Bottom-up Approach
Case Study Published: EPA 816-R-10-019
water.epa.gov/drink
November 2010
System Background
• 100% purchased water via 15 supply
meters
• 321 miles of main, 2” to 10”, mostly 6”,
nearly 100% PVC
• System pressure ranges 25 psi to 140 psi
• 6,926 service connections, normally ¾”
copper or black rolled plastic
• The customer base is primarily residential
serving a rural area
• 12 employees
Indicators used for Real Loss Target Setting
AWWA Water Audit Operational
Efficiency Indicators used for Real
Loss Target Setting
• Real Losses per length of main per day:
645.59 gallons/mile/day (0.45 gpm/mile)
• Unavoidable Annual Real Losses (UARL):
60.78 million gallons/year (0.36 gpm/mile)
• Infrastructure Leakage Index (ILI) (Real
Losses/UARL): 1.24
– In order for the ILI to equal 1.0 then the Real
Losses need to equal the UARL or 0.36 gpm
per mile of water main
Trousdale Ferry DMA
• 56 miles of main
• Real Losses should be maintained at a
level of 20 gpm (0.36 gpm per mile)
• The MNF should be maintained at 53 gpm
(LNC of 33 gpm + Real Losses of 20 gpm)
• Pump station & 500,000 gallon tank level
monitored via telemetry
• Turn off pump station and measure tank
level drop during MNF period
• If drop > 53 gpm consider intervening
January 11, 2010 MNF
• Trousdale Ferry DMA MNF = 120 gpm
• Trousdale Ferry DMA LNC = 33 gpm
• Trousdale Ferry DMA Real Losses
(Leakage) = 120 gpm – 33 gpm = 87 gpm
• Trousdale Ferry DMA = 56 miles main
• 87 gpm/56 miles = 1.6 gpm/mile
Isolated Valves must not leak through
January 12, 2010 Step Testing
• TF DMA West MNF = 87 gpm
• TF DMA West LNC = 11 gpm
• TF DMA West Real Losses (Leakage) = 87
gpm – 11 gpm = 76 gpm
• TF DMA West Miles of Water Main = 22
• 76 gpm/22 miles = 3.5 gpm/mile
January 12, 2010 Step Testing
• TF DMA East MNF = 33 gpm
• TF DMA East LNC = 22 gpm
• TF DMA East Real Losses (Leakage) = 33
gpm – 22 gpm = 11 gpm
• TF DMA East Miles of Water Main = 34
• 11 gpm/34 miles = 0.3 gpm/mile
January 12, 2010 Step Testing
• TF DMA SW MNF = 70 gpm
• TF DMA SW LNC = 8 gpm
• TF DMA SW Real Losses (Leakage) = 70
gpm – 8 gpm = 62 gpm
• TF DMA SW Miles of Water Main = 14
• 62 gpm/14 miles = 4.4 gpm/mile
Additional Step Testing within TF DMA SW
• Leakage isolated 3:15 AM to 1,700’ area
• Step tested 56 miles in 2 hours
• No water surfacing
• 6” PVC main located under soil conditions
over 20’ off road , 90 psi
• No low pressures complaints
• Leak rate estimated @ 65 gpm, 94,000
gallons per day, 34,000,000 gallons per
year
Leak Sounding
After Repairs
• Trousdale Ferry DMA MNF = 50 gpm
• Trousdale Ferry DMA LNC = 33 gpm
• Trousdale Ferry DMA Real Losses
(Leakage) = 50gpm – 33 gpm = 17 gpm
• Trousdale Ferry DMA Miles Main = 56
• 17 gpm/56 miles = 0.3 gpm/mile
• System Target is 0.36 gpm/mile
Yearly Comparison
• FY08/09 – ILI = 1.24; Real Losses @
645.59 gallons/mile/day
• FY09/10 – ILI = 1.11; Real Losses @
575.49 gallons/mile/day
• FY10/11 – ILI = 1.10; Real Losses @
573.82 gallons/mile/day
• FY 11/12 – ILI = 1.07; Real Losses @
557.75 gallons/mile/day
Plans to Improve
• Improve accuracy of AWWA water audit
• Program existing telemetry
• Install telemetry on 15 input meters
• Do AWWA water audits at DMA level
• Install AMR/AMI (advanced metering
infrastructure)
• Increase frequency of sounding
• Implement pressure monitoring/management
Where the total cost is at a minimum
Economic Leakage Level
Background Leakage
and Reported Breaks
COST OF LEAKAGE CONTROL
AND WATER LOST
The Economic Balance
Cost of Leakage Control
LOSSES (MGD)
Contact Information
Chris Leauber
Executive Director
Water & Wastewater Authority of
Wilson County
P.O. Box 545
680 Maddox Simpson Parkway
Lebanon, TN 37088
E-mail: [email protected]
Tel: 615-449-2951
Fax: 615-449-8310