MWRD Sewer Flow Metering Services

Transcription

1 Insert Slide Title Here MWRD Sewer Flow Metering Services Flow Metering and Uses of Flow Data Patrick L. Stevens, PE Rob Grob Chris Skehan ADS Environmental Services June 25 & 26, 2015

2 Agenda 1. How Flow Meters Work 2. Getting More Knowledge from Flow Metering (two types of information) 3. What to Do with Flow Data A. Locate Sources of I/I, B. Pre-Post Rehabilitation, C. Capacity Evaluation, D. Modeling. 4. Mistakes People Make in Flow Metering Programs. 5. Summary of Metering Program and Options

3 No Flow Meter on the Face of the Earth Measures Flow Directly All meters measure some other physical entity and calculate flow rate*. Flumes and Weirs measure only depth Open Channel Sewer Flow Meters measure Depth and Velocity. The Continuity Equation is used to Calculate Flow rate.

4 Open Channel Meters use Continuity Equation Flow Rate = Cross Sectional Area x Average Velocity 4" 3" Area of flow 2" 1" Depth

5 Typical Metering Installation Incoming Line Stable Hydraulics D & V measured in same place. Avoid Disturbances in MH Channel Far enough upstream to avoid drawdown

6 Open Channel Technologies Depth (only two) Pressure Sensor Ultrasonic Downlooker Ultrasonic Uplooker MWRD redundant Depth Velocity Average Doppler Peak Doppler Gated Doppler Time of Travel Faraday Surface Doppler Radar Cross Correlation

7 Pressure Depth Sensor water

8 Pressure Depth Basic Operation The cable contains wires and an air tube that opens at the top of the manhole air Diaphragm with Strain Gauge water Port to Sewer Air vent tube The sensor contains a gauge to measure the pressure difference of the water and air The pressure sensor is typically mounted to the bottom of the pipe above any silt

9 Ultrasonic Depth Sensor water

10 Ultrasonic Depth Sensors Can be Uplooker or Downlooker Measures up to Pipe Diameter Measurement Based on Time No Drift

11 Ultrasonic Down Looking Depth Sensor

12 Ultrasonic Up Looking Depth Sensor

13 Depth Sensor Technologies Offer Different Window of Precision Ultrasonic Depth Precision Pressure Depth Precision is based on a percentage of Full Scale Inches 4" 3" 2" 1" Ultrasonic Depth Pressure Depth M J J A gpm 0.2% of Full Scale (11.5') =0.28 inches

14 Velocity Technologies Cross Correlation ADS FlowShark Pulse Average Hach-Sigma 940 ISCO 2150 Continuous Wave Peak ADS FlowShark Doppler Surface Hach-MMB Flo-Dar Gated ISCO ADFM Electromagnetic Hach-MMB Flo-Tote Time of Transit Accusonic

15 Doppler Technology is Similar to Traffic Radar

16 "In theory, theory and practice are the same. In practice, they are not. Lawrence Peter Berra In this pipe: Peak Velocity = 2.1 fps Average Velocity = 1.9 fps In this pipe: Peak Velocity = 2.1 fps Average Velocity = 1.8 fps x x x2.1 fps 2.0 x 1.9 x x x x x x x x x 2.1 fps x Average Velocity is Difficult to Measure

17 TRITON+ Headlines TRITON+ is the new ADS flow monitor designed for versatility, safety, and low lifetime cost Internally (battery) or externally powered Certified to the highest level of Intrinsic Safety Internal 4G/3G/2G modem offers greater flexibility and choice Redundant sensing/processing for added reliability Analog and Digital I/O for simple SCADA integration Ultra low power electronics for longer battery life Proven ultrasonic sensor technology

18 Peak Combo Sensor Continuous Wave Peak Velocity with Uplooking Depth Three sensors in combination: Peak Velocity, Uplooking Ultrasonic Depth, and Pressure Depth in single sensor housing Sensor can be changed without changing meters Intrinsically Safe FlowShark Triton Monitor Direction of Wastewater Flow Peak Combo Sensor

19 Peak Combo Sensor During Normal Flow Pressure sensor calibrated to Ultrasonic once per day. Minimum Depth = 1.5 in. Uplooking Ultrasonic Depth

20 Peak Combo Sensor During Full Pipe Pressure Depth Automatically Switches Pressure sensor previously calibrated Can be raised on block above silt level

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24 What to Do with Flow Data (Getting More Knowledge) Without Flow Metering, symptom = problem. With Strategic Flow Metering, the problem(s) can be separated from the symptom. Knowledge of pipe s Operational Capacity may change the decision replace or rehabilitate a sewer. 24

25 Knights Branch Evaluation Operational Pipe Capacity (%) SSOs since 2006 Knights Branch Rehab Capture Coefficients

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27 Properly Deployed, a Flow Meter will look both Upstream to measure flow and Downstream to determine hydraulic conditions. Flow (MGD) Sat Mar in/hr 14:00 Storm Event - 3/13/ :00:00 AM Rainfall Gross Q Gross I/I Precomp(-) Weekends Weekdays Sun 15 Mon 16 Tue 17 Wed Date Rainfall (in) Storms Upstream Downstream Depth - Velocity Flowmeter 27

28 Storm Event - 3/13/ :00:00 AM Rainfall Gross Q Gross I/I Precomp(-) Weekends Weekdays Peak Rainfall in/hr 14:00 Peak RDII Flow Hydrograph RDII Hydrograph Flow (MGD) Rainfall Hyetograph Dry Day Hydrograph Weekend & Weekday Rainfall (in) Sat Mar Sun 15 Mon 16 Tue 17 Wed Date Storms

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30 Percentage of Rainfall and SSES Cost ($ 110,520) in 2 Mini Basins with Excessive I/I.

31 Q vs. i Mother Load of Flow Study Should be Linear Storm Period Net RDII Volume for (mg) mg (02/16/98) (02/19/98) (12/18/97) (03/31/98) (02/21/98) (03/13/98) (01/09/98) (05/04/98) (01/12/98) (01/29/98) (05/12/98) (03/27/98) (04/11/98) (03/05/98) (05/13/98) (01/31/98) Q vs i - Airbase Storm Period Net RDII Volume vs. Rainfall Depth (02/03/98) (02/14/98) (02/06/98) (02/07/98) (03/25/98) 2 inch 2.00 Inches (02/23/98) (12/05/97) y = *x r^2=0.96; t= Storm Period Rainfall Depth (Inches)

32 Q vs i - hc1 Storm Period Net RDII Volume vs. Rainfall Depth 0.35 Fall Summer Spring Winter Storm Period Net RDII Volume for (mg) (03/13/97) (02/04/97) (04/16/98) (01/07/98) (03/20/98) (02/17/98) (04/09/98) (05/25/97) (12/16/96) (01/27/97) (12/11/96) (04/25/98) (04/16/97) (04/12/97) (11/25/96) (05/02/97) (12/24/97) (03/28/98) (06/21/97) (06/25/97) (10/18/96) (09/21/96) (09/13/96) (12/10/97) (05/31/97) (09/27/96) (02/26/97) (09/06/96) Storm Period Rainfall Depth (Inches)

33 Site Volume Q vs i - LS403_ Total Event Net RDII Volume vs. Rainfall Depth 1.1 Pre-Rehab Post-Rehab 1.0 Total Event Net RDII Volume (mg) (4/22/2005) (12/31/2006) (12/20/2006) (12/25/2006) (12/12/2006) (1/4/2007) (11/15/2006) (5/13/2005) (10/27/2006) (11/30/2006) 0.1 (4/26/2005) (11/10/2006) (11/6/2006) (10/31/2006) Total Event Rainfall Depth (in)

34 Properly Deployed, a Flow Meter will look both Upstream to measure flow and Downstream to determine hydraulic conditions. Flow (MGD) Sat Mar in/hr 14:00 Storm Event - 3/13/ :00:00 AM Rainfall Gross Q Gross I/I Precomp(-) Weekends Weekdays Sun 15 Mon 16 Tue 17 Wed Date Rainfall (in) Storms Upstream Downstream Depth - Velocity Flowmeter 34

35 Scattergraphs A display of paired depth and velocity readings. The pattern should look like a pipe curve. A pattern that doesn t look like a pipe curve means that one of two things is occurring: 1. Normal open channel flow is not occurring 2. The meter is not working correctly.

36 The target performance for a meter is a line. Low precision meters produce wide scatter. High Precision Low Precision

37 Normal Dry Weather flow Depth - Velocity Flowmeter

38 The combination of a Manning Curve, meter data and confirmations reveal a meter s accuracy.

39 Silt and Obstacles result in backwater at a meter. Silt

40 Dead Dog Dead Dog = 6.45 in.

41 High Technology proves the existence of the Dead Dog in sewers

42 Iso-Q Lines

43 In an ideal pipe, the pipe can surcharge and the Hydraulic Grade Line will be parallel to the pipe. In this situation the pipe should be carrying full capacity Hydraulic Grade Line Depth - Velocity Flowmeter

44 Surcharge By the Book

45 Bottleneck Downstream of Flowmeter HGL is Nearly Flat for Several MHs Upstream HGL Depth - Velocity Flowmeter ROOTS

46 Bottleneck & Capacity Loss Operational Capacity is 55%. Replacement or pipe bursting may be the solution here.

47 Upstream SSO SSO Upstream of Flowmeter Depth - Velocity Flowmeter ROOTS

48 Upstream SSO Operational Capacity is 50%. Replacement or pipe bursting may be the solution here. Signature of U/S SSO. (Cluster of data constant V constant D)

49 SSO and Bottleneck Downstream of Flowmeter Depth - Velocity Flowmeter ROOTS

50 Downstream SSO Operational Capacity is 50%. Replacement or pipe bursting may be the solution here. Signature of D/S SSO. (V increase at constant D) 50

51 Soft Restriction Roots create a restriction that does not follow an Iso-Q line.

52 Soft Restriction

53 Scattergraph Poster

54 Fate of Sewer Rehabilitation (RDII) Projects Sewer Rehabilitation Projects A. RDII Reduced Everyone Happy Promotion B. RDII Reduced But Can t Demonstrate or Quantify C. No Apparent Reduction SSOs & Basement Flooding Continue Followed Recipe Plan for Post-rehab Extremely Lucky Toilet Paper is Not as High in the Trees as it Used to be Do Not Try to Measure Forensic RDII Reveals Twelve Stumbling Blocks Followed No Recipe Did Not Address Private Sources Piecemeal Repair Rely on Smoke Testing Only Rely on TV only Repaired only Manholes Repaired only Mainlines Did Not Control Basin Size Use Poor Rehab Technology Upstream Restricted Sewer

55 The Tell-Tale Language of a Failed Rehab Analysis Conclusions by Consultant for City of Cedar Lake Due to the inequality of the conditions in Post-rehab flow monitoring versus Pre-rehab flow monitoring...the magnitude of improvements made to the collection system cannot be measured. Given equal antecedent conditions in Post-rehab versus Prerehab, significant improvements will be clearly evident. Therefore, this comparison does not show the totality of the improvements made to the collection system. What have you done with the money?

56 12 Stumbling Blocks to Demonstration of Success 1. Rain Gauge Strategy 2. Basin Size 3. KPI - Scattergraphs & Q vs. i 4. Metering Depth Technology 5. Duration 6. Season 7. Rainfall Data Frequency 8. Tight Subtractions 9. Method of Calculating RDII 10. Dynamics of Sewers (restricted) 11. Control Basin 12. Site Hydraulics at Metering Manhole

57 Recommended Densities

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59 Green band (>1/2 in) is 6 Mi. wide, Yellow band (>1.2 in) is 0.6 Mi. (1 Km) wide

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61 Rain Gauge Density Rain Gauge Density: 4 mi 4 9mi 2 /RG Rain Gauge Grid Size: 2 3migrid Recommended Quantity: 10

62 Rain Gauge Density Never Less than Two (always assume one will fail) 1-2 Mi 2 /RG in convective storm season or in hilly area. 3-4 Mi 2 /RG in cyclonic storm season.

63 Stumbling Block #5 Basin Size is an Important Variable Meter Basins Should be Small and Uniform in Size Small Basins Isolate RDII (80/20 Rule) Smallest Amount (Least Cost) of Rehabilitation Easier to Demonstrate Improvement

64 ONE MONITOR - 385,000 LF 100% OF BASIN HAS EXCESSIVE INFLOW FOUR MONITORS - 85,000 LF 70% OF BASIN HAS EXCESSIVE INFLOW 12 MONITORS - 31,000 LF 60% OF BASIN HAS EXCESSIVE INFLOW 57 MONITORS - 8,100 LF 42% OF BASIN HAS EXCESSIVE INFLOW

65 Smaller Basin Size Advantage Ignored Inspected 12 MONITORS - 31,000 LF 60% OF BASIN HAS EXCESSIVE INFLOW

66 Basin Size Affects Capital Project 57 MONITORS - 8,100 LF 42% OF BASIN HAS EXCESSIVE INFLOW

67 CITY OF SACO The City of Saco is located on Maine s southern coast, approximately 14 miles south of the City of Portland. Saco is an attractive destination for both residents and visitors due to Saco s beautiful beaches, the Saco River, and the historic downtown and shopping district. 67

68 Bear Brook Pump Station The Bear Brook Pump Stat & Sewer Shed 109,000 LF of Sanitary Sewers Sizes from 8 to 14 inch

69 Findings from Phase I

70 Findings from Phase II

71 Near Thornton Academy, a storm water plunge pond and a storm drain were connected to the sanitary sewer.

72 Saco, ME Savings in SSES costs There are three possible options for locating sources of RDII; 1. The old way of doing SSES over the entire Bear Brook sewers 2. Doing SSES on the worst of the five large basins 3. Doing SSES on the worst of the micro-basins. Strategy Length of Sewer LF Cost of SSES at $4/LF Savings SSES entire system no metering 109,000 $424,000 None SSES on worst of Large Basins 64,365 $257,460 $166,540 SSES on 3 Micro Basins 24,106 $96,424 $327,576 The metering cost for both phases of the work was $25,000 and the payback over straight SSES was greater than 15:1

73 Summary of Metering Program and Options

74 Overview of Program Fee Structure ITEM QTY Flow Meters Installation $2, $2, Monthly O&M $ $ Rain Gauges Installation $ $ Monthly O&M $50.00 $50.00 Fee Structure Based on Normal Site Conditions for pipes up to 72 Diameter with One Month Minimum Duration Fee Structure for Adverse Conditions Approx. 10% Higher: 1. Heavy Traffic 2. Manhole Depth > 25 ft. 3. Manhole located > 330 ft. off road 4. Work required outside of normal hours

75 Sample Project Costs Project Duration (months) # Meters $ 15,500 $ 18,000 $ 20,500 $ 23, $ 31,000 $ 36,000 $ 41,000 $ 46, $ 46,500 $ 54,000 $ 61,500 $ 69, $ 62,000 $ 72,000 $ 82,000 $ 92, $ 77,500 $ 90,000 $ 102,500 $ 115, $ 93,000 $ 108,000 $ 123,000 $ 138, $ 108,500 $ 126,000 $ 143,500 $ 161,000

76 What is Included 1. Inspection of flow meter and rain gauge sites selected by the Owner 2. Recommendation of alternate sites based on findings during initial inspection 3. Installation and calibration of flow meters and rain gauges 4. Data collection via wireless telemetry 5. Review of raw data for signs of maintenance issues 6. Maintenance of flow meters and rain gauges 7. Raw data access via web based data hosting program 8. Removal of flow meters and rain gauges at end of monitoring period

77 Web based data delivery

78 Data Tools

79 What is NOT Included 1. Editing of raw data 2. Capacity or I/I Analysis of flow and rain data 3. Hydraulic modeling 4. Alarming or event notification

80 The End