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System Background

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

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System Background

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  1. The Water & Wastewater Authority of Wilson County, TennesseeReducing Real Losses (Leakage) in a Rural System Using a Bottom-up ApproachCase Study Published: EPA 816-R-10-019water.epa.gov/drinkNovember 2010

  2. 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

  3. Indicators used for Real Loss Target Setting

  4. 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

  5. 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

  6. 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

  7. Isolated Valves must not leak through

  8. 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

  9. 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

  10. 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

  11. 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

  12. Leak Sounding

  13. 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

  14. 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

  15. 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

  16. Economic Leakage Level COST OF LEAKAGE CONTROL AND WATER LOST Cost of Water Lost Background Leakage and Reported Breaks Cost of Leakage Control LOSSES (MGD) The Economic Balance Where the total cost is at a minimum

  17. 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: cleauber@wwawc.com Tel: 615-449-2951 Fax: 615-449-8310

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