system background

The Water & Wastewater The Water & Wastewater Authority of Wilson County, Authority of Wilson County,

TennesseeTennessee

Reducing Real Losses (Leakage) in a Rural Reducing Real Losses (Leakage) in a Rural System Using a Bottom-up ApproachSystem Using a Bottom-up Approach

Case Study Published: EPA 816-R-10-019Case Study Published: EPA 816-R-10-019water.epa.gov/drinkwater.epa.gov/drink

November 2010November 2010

System BackgroundSystem Background

• 100% purchased water via 15 supply 100% purchased water via 15 supply metersmeters

• 321 miles of main, 2” to 10”, mostly 6”, 321 miles of main, 2” to 10”, mostly 6”, nearly 100% PVCnearly 100% PVC

• System pressure ranges 25 psi to 140 psiSystem pressure ranges 25 psi to 140 psi

• 6,926 service connections, normally ¾” 6,926 service connections, normally ¾” copper or black rolled plastic copper or black rolled plastic

• The customer base is primarily residential The customer base is primarily residential serving a rural areaserving a rural area

• 12 employees12 employees

Indicators used for Real Loss Target Indicators used for Real Loss Target SettingSetting

AWWA Water Audit Operational AWWA Water Audit Operational Efficiency Indicators used for Efficiency Indicators used for

Real Loss Target SettingReal Loss Target Setting• Real Losses per length of main per day: Real Losses per length of main per day:

645.59 gallons/mile/day (0.45 gpm/mile)645.59 gallons/mile/day (0.45 gpm/mile)

• Unavoidable Annual Real Losses (UARL): Unavoidable Annual Real Losses (UARL): 60.78 million gallons/year (0.36 gpm/mile) 60.78 million gallons/year (0.36 gpm/mile)

• Infrastructure Leakage Index (ILI) (Real Infrastructure Leakage Index (ILI) (Real Losses/UARL): 1.24Losses/UARL): 1.24– In order for the ILI to equal 1.0 then the Real In order for the ILI to equal 1.0 then the Real

Losses need to equal the UARL or 0.36 gpm Losses need to equal the UARL or 0.36 gpm per mile of water mainper mile of water main

Trousdale Ferry DMATrousdale Ferry DMA• 56 miles of main56 miles of main

• Real Losses should be maintained at a Real Losses should be maintained at a level of 20 gpm (0.36 gpm per mile)level of 20 gpm (0.36 gpm per mile)

• The MNF should be maintained at 53 The MNF should be maintained at 53 gpm (LNC of 33 gpm + Real Losses of gpm (LNC of 33 gpm + Real Losses of 20 gpm) 20 gpm)

• Pump station & 500,000 gallon tank Pump station & 500,000 gallon tank level monitored via telemetry level monitored via telemetry

• Turn off pump station and measure Turn off pump station and measure tank level drop during MNF period tank level drop during MNF period

• If drop > 53 gpm consider interveningIf drop > 53 gpm consider intervening

January 11, 2010 MNFJanuary 11, 2010 MNF

• Trousdale Ferry DMA MNF = 120 gpmTrousdale Ferry DMA MNF = 120 gpm

• Trousdale Ferry DMA LNC = 33 gpmTrousdale Ferry DMA LNC = 33 gpm

• Trousdale Ferry DMA Real Losses Trousdale Ferry DMA Real Losses (Leakage) = 120 gpm – 33 gpm = 87 (Leakage) = 120 gpm – 33 gpm = 87 gpmgpm

• Trousdale Ferry DMA = 56 miles mainTrousdale Ferry DMA = 56 miles main

• 87 gpm/56 miles = 1.6 gpm/mile87 gpm/56 miles = 1.6 gpm/mile

Isolated Valves must not leak through Isolated Valves must not leak through

January 12, 2010 Step January 12, 2010 Step TestingTesting

• TF DMA West MNF = 87 gpmTF DMA West MNF = 87 gpm

• TF DMA West LNC = 11 gpmTF DMA West LNC = 11 gpm

• TF DMA West Real Losses (Leakage) TF DMA West Real Losses (Leakage) = 87 gpm – 11 gpm = 76 gpm= 87 gpm – 11 gpm = 76 gpm

• TF DMA West Miles of Water Main = TF DMA West Miles of Water Main = 2222



• TF DMA East MNF = 33 gpmTF DMA East MNF = 33 gpm

• TF DMA East LNC = 22 gpmTF DMA East LNC = 22 gpm

• TF DMA East Real Losses (Leakage) TF DMA East Real Losses (Leakage) = 33 gpm – 22 gpm = 11 gpm= 33 gpm – 22 gpm = 11 gpm

• TF DMA East Miles of Water Main = TF DMA East Miles of Water Main = 3434



• TF DMA SW MNF = 70 gpmTF DMA SW MNF = 70 gpm

• TF DMA SW LNC = 8 gpmTF DMA SW LNC = 8 gpm

• TF DMA SW Real Losses (Leakage) = TF DMA SW Real Losses (Leakage) = 70 gpm – 8 gpm = 62 gpm70 gpm – 8 gpm = 62 gpm

• TF DMA SW Miles of Water Main = 14TF DMA SW Miles of Water Main = 14


Additional Step Testing within TF DMA Additional Step Testing within TF DMA SWSW• Leakage isolated 3:15 AM to 1,700’ Leakage isolated 3:15 AM to 1,700’

areaarea

• Step tested 56 miles in 2 hoursStep tested 56 miles in 2 hours

• No water surfacingNo water surfacing

• 6” PVC main located under soil 6” PVC main located under soil conditions over 20’ off road , 90 psi conditions over 20’ off road , 90 psi

• No low pressures complaints No low pressures complaints

• Leak rate estimated @ 65 gpm, Leak rate estimated @ 65 gpm, 94,000 gallons per day, 34,000,000 94,000 gallons per day, 34,000,000 gallons per year gallons per year

Leak SoundingLeak Sounding

After RepairsAfter Repairs

• Trousdale Ferry DMA MNF = 50 gpmTrousdale Ferry DMA MNF = 50 gpm

• Trousdale Ferry DMA LNC = 33 gpmTrousdale Ferry DMA LNC = 33 gpm

• Trousdale Ferry DMA Real Losses Trousdale Ferry DMA Real Losses (Leakage) = 50gpm – 33 gpm = 17 (Leakage) = 50gpm – 33 gpm = 17 gpmgpm

• Trousdale Ferry DMA Miles Main = 56Trousdale Ferry DMA Miles Main = 56


• System Target is 0.36 gpm/mileSystem Target is 0.36 gpm/mile

Yearly ComparisonYearly Comparison

• FY08/09 – ILI = 1.24; Real Losses @ FY08/09 – ILI = 1.24; Real Losses @ 645.59 gallons/mile/day645.59 gallons/mile/day

• FY09/10 – ILI = 1.11; Real Losses @ FY09/10 – ILI = 1.11; Real Losses @ 575.49 gallons/mile/day 575.49 gallons/mile/day

• FY10/11 – ILI = 1.10; Real Losses @ FY10/11 – ILI = 1.10; Real Losses @ 573.82 gallons/mile/day573.82 gallons/mile/day

• FY 11/12 – ILI = 1.07; Real Losses @ FY 11/12 – ILI = 1.07; Real Losses @ 557.75 gallons/mile/day557.75 gallons/mile/day

Plans to ImprovePlans to Improve

• Improve accuracy of AWWA water auditImprove accuracy of AWWA water audit

• Program existing telemetryProgram existing telemetry

• Install telemetry on 15 input metersInstall telemetry on 15 input meters

• Do AWWA water audits at DMA levelDo AWWA water audits at DMA level

• Install AMR/AMI (advanced metering Install AMR/AMI (advanced metering infrastructure)infrastructure)

• Increase frequency of soundingIncrease frequency of sounding

• Implement pressure Implement pressure monitoring/managementmonitoring/management

The Economic Balance The Economic Balance

Cost of Leakage Control

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Cost of Water Lost

Economic Leakage Level

Where the total cost is at a minimum

Contact InformationContact InformationChris LeauberChris Leauber

Executive DirectorExecutive DirectorWater & Wastewater Authority Water & Wastewater Authority

of Wilson Countyof Wilson CountyP.O. Box 545P.O. Box 545

680 Maddox Simpson Parkway680 Maddox Simpson ParkwayLebanon, TN 37088Lebanon, TN 37088

E-mail: E-mail: [email protected] Tel: 615-449-2951Tel: 615-449-2951Fax: 615-449-8310Fax: 615-449-8310

system background

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