December 2003 

03/12/WQPC-WWF 

EPA/600/R-04/035 

Environmental Technology

Verification Report 

Wet Weather Flow Monitoring 

Equipment 

ADS Environmental Model 3600 

Open Channel Flow Monitor 

Part I – Laboratory Test Results 

Prepared by 

NSF International 

Under a Cooperative Agreement with 

U.S. Environmental Protection Agency 
THE ENVIRONMENTAL TECHNOLOGY VERIFICATION 

PROGRAM 

U.S. Environmental NSF International 

Protection Agency 

ETV Joint Verification Statement 

TECHNOLOGY TYPE: AREA/VELOCITY FLOW METERS 

APPLICATION: FLOW METERING IN SMALL- AND MEDIUM-SIZED 

(10- to 42-inch) SEWERS 

TECHNOLOGY NAME: ADS ENVIRONMENTAL SERVICES MODEL 3600 OPEN 

CHANNEL FLOW METER 

TEST LOCATION: QUEBEC CITY, QUEBEC, CANADA, AND LOGAN, UTAH 

COMPANY: ADS ENVIRONMENTAL SERVICES 

ADDRESS: 5030 BRADFORD DRIVE PHONE: (800) 633-7246 

BUILDING 1, SUITE 210 FAX: (256) 430-6633 

HUNTSVILLE, AL 35805 

WEB SITE: http:\\www.adsenv.com 

EMAIL: info@adsenv.com 

NSF International (NSF) manages the Water Quality Protection Center (WQPC) under the U.S. 

Environmental Protection Agency’s (EPA) Environmental Technology Verification (ETV) Program. 

NSF evaluated the performance of the Model 3600 Open Channel Flow Meter manufactured by ADS 

Environmental Services. Utah Water Research Laboratory (UWRL) in Logan, Utah, and BPR of Quebec 

City, Canada, both NSF-qualified testing organizations, performed the laboratory and field verification 

testing, respectively. 

EPA created the ETV Program to facilitate the deployment of innovative or improved environmental 

technologies through performance verification and dissemination of information. The goal of the ETV 

program is to further environmental protection by accelerating the acceptance and use of improved and 

cost-effective technologies. ETV seeks to achieve this goal by providing high-quality, peer-reviewed data 

on technology performance to those involved in the design, distribution, permitting, purchase, and use of 

environmental technologies. 

ETV works in partnership with recognized standards and testing organizations; stakeholder groups 

consisting of buyers, vendor organizations, and permitters; and with the full participation of individual 

technology developers. The program evaluates the performance of innovative technologies by developing 

test plans that are responsive to the needs of stakeholders, conducting field or laboratory tests (as 

appropriate), collecting and analyzing data, and preparing peer reviewed reports. All evaluations are 

conducted in accordance with rigorous quality assurance protocols to ensure that data of known and 

adequate quality are generated, and that the results are defensible. 

03/12/WQPC-WWF The accompanying notice is an integral part of this verification statement. December 2003 

VS-i 
TECHNOLOGY DESCRIPTION 

The following technology description is provided by the vendor and does not represent verified 

information. 

Area/velocity flow meters are commonly used in wastewater collection, storm sewer, and combined 

sewer systems. The ADS 3600 flow meter utilizes a quad-redundant ultrasonic sensor that measures the 

time required for an ultrasonic pulse to travel from the sensor face to the surface of the water and back to 

the sensor. The meter converts the travel time to distance by calculating the speed of sound through air 

and adjusting for temperature, which is measured by two sensors inside the ultrasonic sensor head. The 

depth of the flow is then calculated using the pipe diameter and the range measured by the ultrasonic 

sensor. A pressure-depth sensor is also installed at the bottom of the pipe to measure surcharge levels and 

to provide a redundant depth reading when used with the ultrasonic level sensor. Doppler velocity 

measurements are made by transmitting an ultrasonic signal upstream using a submerged velocity sensor 

and measuring the frequency shift in the sound waves reflected by the moving particles in the water. The 

depth and velocity sensor readings are stored in the flow meter’s memory until the data can be 

downloaded to a computer through either a voice-grade telephone line or a cellular network. The 

computer software calculates flow rates using the depth and velocity readings. 

The ADS 3600 flow meter system includes the flow meter unit, sensors, and installation hardware. The 

flow meter unit is housed in a waterproof, marine-grade aluminum housing. The submersible pressure 

sensor, ultrasonic level sensor, and velocity sensor are attached to a circular stainless steel band installed 

around the inner circumference of the sewer pipe. Waterproof cables with sealed connectors convey 

power and signals between the flow meter unit and the sensors. The system is battery-powered, and can 

power the unit for about one year at a standard 15-minute measurement interval. The unit is intrinsically 

safe. According to vendor claims, after the unit is installed, minimal operation and maintenance (O&M) 

or unit calibration is required; the most common O&M procedure is cleaning the sensors. 

VERIFICATION TESTING DESCRIPTION 

Laboratory Test Site 

The laboratory testing was completed at the Utah Water Research Laboratory (UWRL), at Utah State 

University in Logan, Utah. The flow meter was installed in three nominal pipe sizes: 10-inch, 20-inch, 

and 42-inch. The straight lengths were sized so they were at least 40 times the pipe diameter for the 10- 

and 20-inch pipes and at least 22 times for the 42-inch pipes. Pipe slopes were adjustable to allow the 

flow meter to be evaluated under different slope conditions. Sluice gates at both ends of the pipes were 

used to regulate appropriate flow, head, and obstruction during testing. Reference devices were directly 

traceable to the National Institute of Standards and Technology (NIST), and were regularly calibrated. 

Uncertainty for the reference devices was less than 0.25 percent. 

Field Test Site 

Field verification testing was conducted in a section of the Quebec Urban Community’s sewer network, 

located in the City of Sainte-Foy, Quebec, Canada. The ADS flow meter and reference meters were 

installed in a 41.7-inch diameter interceptor pipe, near the downstream end of a straight run of pipe that 

had a mean slope of 0.169 percent. The reference devices, which consisted of a bubbler for reference level 

measurement, a reference flow monitor, and an Accusonic 4-path flow monitor, were installed 

downstream of the ADS flow meter. Upstream and downstream sluice gates were used to create the 

required flow conditions. 

Validation of the reference flow monitor and bubbler were performed by lithium tracer dye tests. Flow 

rates under the upstream and downstream gates were calculated using standard hydraulic equations for a 

redundant check of flow data. 

03/12/WQPC-WWF The accompanying notice is an integral part of this verification statement. December 2003 

VS-ii 
Methods and Procedures 

Laboratory evaluation of the flow meters consisted of collecting depth, velocity, and flow data from the 

ADS meter and comparing it to the depth, velocity, and flow data from the reference devices. These tests 

were performed under normal operating conditions of uniform flow, backwater flow, full pipe (manhole 

surcharged), and simulated silt. Water transmission through the pipes, as a ratio of flow depth versus the 

pipe diameter (d/D), ranged from 10 to 250 percent (surcharged conditions). Tests were also performed 

under the abnormal operating conditions of reverse flow and grease accumulation. 

Field evaluation of the ADS flow meter at the Quebec site consisted of a general evaluation of the flow 

meter (Test A) and the performance of the meter under varying flow conditions. Testing consisted of 

collecting depth, velocity, and flow data at regular time intervals and comparing the data to the 

corresponding depth, velocity, and flow data from the reference devices. Four test scenarios were used: 

1. Test B—accuracy under low weather flow (approximately 1.71 million gallons per day [MGD]), with 

back-flow conditions; 

2. Test C—accuracy under wet weather flow (1.71–29.7 MGD), without back-flow conditions; 

3. Test D—accuracy under wet weather flow (1.71–29.7 MGD), with back flow-conditions; and, 

4. Test E—accuracy under short-term (26-day) continuous operation, with various flow rates. 

Three conditions were identified during testing that created an unintended challenge to the ADS flow 

meter: 

1. The water used in the testing at UWRL did not contain the particulate concentrations of normal 

sewage, so small quantities of coffee creamer were added to the water on some test runs. The 

operating principle utilized by the ADS flow meter requires particles in the water to serve as 

reflectors for sound waves. The vendor maintained that the coffee creamer additive provided a level 

of reflectivity, but the particulate concentration in the test water did not approach that of sewage and 

could be a source of measurement error. 

2. During each field test, a portion of the ADS flow meter data collected at one-minute intervals was not 

recorded. ADS personnel indicated that this happened because the flow meter was configured for 

maximum error checking and sensor refiring. They further indicate that the ADS 3600 flow meter can 

be reconfigured to collect data at one-minute intervals by reducing the level of real-time error 

checking. 

3. The field testing results include data in which it appears that standing waves and troughs were present 

beneath the ADS 3600 flow meter’s ultrasonic depth sensor. During portions of the testing, the depth 

sensor was likely affected by standing waves and troughs up to +5 inches. The ADS flow meter 

measures depth with a downward-looking, narrow-beam ultrasonic sensor mounted on the top of the 

pipe, so depth measurements would be susceptible to influence by waves. Based on a review of the 

field data, it appears that waves were most prevalent at higher depths and flow rates. 

No editing was allowed on the metered data during field or laboratory testing. In actual applications, the 

flow monitoring service provider may implement post-monitoring quality control measures to attempt to 

improve the accuracy of final data. According to ADS, the company typically bundles flow meter sales 

with post-monitoring quality control and reporting services. 

03/12/WQPC-WWF The accompanying notice is an integral part of this verification statement. December 2003 

VS-iii 
VERIFICATION OF PERFORMANCE 

System Operation 

The testing organizations found the equipment durable and easy to use, and that it required minimal 

maintenance. The flow meter operation and data retrieval software programs were easy to learn. The 

ultrasonic sensors and stainless steel band did not promote accumulation of debris during testing. 

Laboratory Testing Results 

The mean deviations and the 95-percent confidence intervals under normal operating conditions (i.e., all 

test conditions except grease tests and reverse flow) are presented in Table 1. The width of the 95-percent 

confidence interval is a function of the variation in instrument deviation, and the number of test runs in 

each reported category. Categories with a fewer number of runs show wider confidence intervals. The 

calculations exclude “abnormal condition” tests, where grease was applied to the sensors or where 

reverse-flow conditions were created. The mean deviation for the abnormal operating conditions was 1.9 

percent for the 0.5-mm grease tests, -100.0 percent for the 2.0-mm grease tests, and –72.7 percent for the 

reverse-flow tests. 

Table 1. Deviation and 95-Percent Confidence Interval by Test Configuration for Lab Testing 

Deviation 95-percent 

Pipe size (inches) (percent) confidence interval 

10 2.8 0.2 – 5.4 

20 7.2 2.4 – 12.0 

42 1.6 -1.8 – 5.0 

Pipe slope (percent) 

0.1 4.9 -1.4 – 11.2 

0.2 1.6 -1.8 – 5.0 

0.5 5.6 1.6 – 9.6 

1.25 4.2 -1.6 – 9.9 

2.0 6.1 -3.8 – 16.1 

 Percent full (d/D, percent) 

10 3.6 -9.4 – 16.6 

30 11.1 6.5 – 15.7 

50 3.4 0.2 – 6.7 

80 1.3 -3.1 – 5.6 

150 0.9 0.9 – 2.8 

250 4.8 -5.0 – 14.6 

Condition 

Free-flow 2.6 -1.4 – 6.7 

Back-flow 5.8 2.9 – 8.7 

All conditions 4.5 2.1 – 6.9 

The overall accuracy of the ADS flow meter under normal operating conditions is shown in Figure 1. The 

meter deviation is segregated into two components—bias and precision. Overall bias was 1.6 percent, as 

calculated by the slope of the best-fit line. Precision, as calculated with the correlation coefficient (r2), 

was 0.45 percent. 

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VS-iv 
Figure 1. Laboratory metered flow rate versus reference. 

Field Testing Results 

Table 2 summarizes the field testing results in two categories: mean deviation and trimmed mean 

deviation. The mean deviation is the arithmetic mean of all of the one-minute–interval data. The trimmed 

mean deviation is calculated by eliminating values greater than ±99 percent, making it less susceptible to 

skewing from large outliers, such as those produced when the ADS flow meter recorded zero velocity. 

Table 2. Deviation from Reference Flow: Tests B, C, and D 

Mean deviation Trimmed mean deviation 

Flow regime (percent) (percent) 

Test B -29.7 2.4 

Test C 5.0 5.0 

Test D -1.0 4.7 

Test B-D combined -5.7 2.1 

Simulated low flow -7.6 12.2 

Simulated high flow -4.3 -4.1 

Combined flows -5.7 2.1 

Analysis of the data collected during Test B (low flow) revealed that the deviation was –100 percent in 

nearly one-third of the samples. This occurred most frequently during back-flow conditions when the 

ADS 3600 recorded zero velocity and calculated zero flow. The data collected during Tests C and D 

showed a much lower occurrence of data with deviations exceeding ±99 percent. 

03/12/WQPC-WWF The accompanying notice is an integral part of this verification statement. December 2003 

VS-v 
Test E (not included in Table 2) evaluated the performance of the flow meter over an extended (26-day) 

time period. Generally, the data collected during Test E closely correlated with the reference flow monitor 

data. Spikes were noted in water level measurements collected toward the end of the test, which may have 

been the result of accumulated condensation on the ultrasonic depth probe. No debris accumulation was 

observed on the equipment, and, aside from a thin film of grease on the probes, the equipment was in 

good condition and did not require maintenance. 

QUALITY ASSURANCE/QUALITY CONTROL 

A complete description of the quality assurance/quality control procedures and findings are included in 

the verification reports. Calibration records were maintained by the testing organizations and validation of 

the reference flow devices fell within control limits. NSF completed a data quality audit of at least 10 

percent of the test data to ensure that the reported data represented the data generated during testing. 

Audits of the field and laboratory testing were conducted by NSF with no significant issues noted. 

Original Signed by Original Signed by 

Lee A. Mulkey March 31, 2004 Gordon Bellen April 26, 2004 

Lee A. Mulkey Date Gordon Bellen Date 

Acting Director Vice President 

National Risk Management Laboratory Research 

Office of Research and Development NSF International 

United States Environmental Protection Agency 

NOTICE: Verifications are based on an evaluation of technology performance under specific, 

predetermined criteria and the appropriate quality assurance procedures. EPA and NSF make no expressed 

or implied warranties as to the performance of the technology, and do not certify that a technology will 

always operate as verified. The end user is solely responsible for complying with any and all applicable 

federal, state, and local requirements. Mention of corporate names, trade names, or commercial products 

does not constitute endorsement or recommendation for use of specific products. This report is not an NSF 

Certification of the specific product mentioned herein. 

Availability of Supporting Documents 

Copies of the Draft 4.0 – Generic Verification Protocol, Flow Monitors for Wet Weather Flows 

Applications in Small- and Medium-Sized Sewers, September, 2000, the verification statement, and 

the verification report (NSF Report #03/12/WQPC-WWF) are available from: 

ETV Water Quality Protection Center Program Manager (order hard copy) 

 NSF International 

 P.O. Box 130140 

Ann Arbor, Michigan 48113-0140 

NSF web site: http://www.nsf.org/etv (electronic copy) 

EPA web site: http://www.epa.gov/etv (electronic copy) 

(NOTE: Appendices are not included in the verification report. Appendices are available upon 

request from NSF.) 

03/12/WQPC-WWF The accompanying notice is an integral part of this verification statement. December 2003 

VS-vi 
Environmental Technology Verification Report 

WET WEATHER FLOW MONITORING EQUIPMENT VERIFICATION 

ADS ENVIRONMENTAL MODEL 3600 

OPEN CHANNEL FLOW MONITOR 

PART I - LABORATORY TEST RESULTS 

UTAH WATER RESEARCH LABORATORY TEST SITE 

Prepared for: 

NSF International 

Ann Arbor, Michigan 

Prepared by: 

Utah Water Research Laboratory 

Logan, Utah 

December 2003 

Under a cooperative agreement with the U.S. Environmental Protection Agency 

Raymond Frederick, Project Officer 

National Risk Management Research Laboratory 

U.S. Environmental Protection Agency 

Edison, NJ 08837 
Notice 

The U.S. Environmental Protection Agency (EPA) through its Office of Research and 

Development has financially supported and collaborated with NSF International (NSF) under a 

cooperative agreement. This verification effort was supported by the Water Quality Protection 

Center operating under the Environmental Technology Verification (ETV) Program. This 

document has been peer reviewed and reviewed by NSF and EPA and recommended for public 

release. 

ii 
Foreword 

The following is the final report on an Environmental Technology Verification (ETV) test 

performed for NSF International (NSF) and the United States Environmental Protection Agency 

(EPA) by Utah Water Research Laboratory, in cooperation with ADS Environmental Services 

for the Model 3600 Open Channel Flow Monitor. The test protocol for flow monitors requires 

both laboratory and field testing. The final report for this verification is divided into two parts to 

address both portions of testing. 

This part of the report (Part I) describes the testing and summarizes the data from the laboratory 

testing. Part II: Field Test Results, describes the testing and summarizes the data of the field 

testing. Both parts of the report are available on the NSF and EPA websites. 

The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the 

Nation=s land, air, and water resources. Under a mandate of national environmental laws, the 

Agency strives to formulate and implement actions leading to a compatible balance between 

human activities and the ability of natural systems to support and nurture life. To meet this 

mandate, EPA’s research program is providing data and technical support for solving 

environmental problems today and building a science knowledge base necessary to manage our 

ecological resources wisely, understand how pollutants affect our health, and prevent or reduce 

environmental risks in the future. 

The National Risk Management Research Laboratory (NRMRL) is the Agency’s center for 

investigation of technological and management approaches for preventing and reducing risks 

from pollution that threaten human health and the environment. The focus of the Laboratory’s 

research program is on methods and their cost-effectiveness for prevention and control of 

pollution to air, land, water, and subsurface resources; protection of water quality in public water 

systems; remediation of contaminated sites, sediments and ground water; prevention and control 

of indoor air pollution; and restoration of ecosystems. NRMRL collaborates with both public 

and private sector partners to foster technologies that reduce the cost of compliance and to 

anticipate emerging problems. NRMRL’s research provides solutions to environmental problems 

by: developing and promoting technologies that protect and improve the environment; advancing 

scientific and engineering information to support regulatory and policy decisions; and providing 

the technical support and information transfer to ensure implementation of environmental 

regulations and strategies at the national, state, and community levels. 

This publication has been produced as part of the Laboratory’s strategic long-term research plan. 

It is published and made available by EPA’s Office of Research and Development to assist the 

user community and to link researchers with their clients. 

iii 
Contents 

Verification Statement ...............................................................................................................VS-i 

Notice.............................................................................................................................................. ii 

Foreword........................................................................................................................................iii 

Contents ......................................................................................................................................... iv 

Acronyms and Abbreviations ....................................................................................................... vii 

Acknowledgments........................................................................................................................viii 

Chapter 1 Introduction .................................................................................................................... 1 

1.1 ETV Purpose and Program Operation............................................................................... 1 

1.2 Testing Participants and Responsibilities.......................................................................... 1 

1.2.1 U.S. Environmental Protection Agency...................................................................... 2 

1.2.2 NSF International........................................................................................................ 2 

1.2.3 Laboratory Testing Organization................................................................................ 2 

1.2.4 Field Testing Organization ......................................................................................... 3 

1.2.5 Vendor......................................................................................................................... 4 

1.3 Laboratory Verification Testing Site................................................................................. 4 

Chapter 2 ADS Equipment Description and Operating Processes ................................................. 5 

2.1 Equipment Description...................................................................................................... 5 

2.2 Operating Process.............................................................................................................. 9 

2.2.1 Depth........................................................................................................................... 9 

2.2.2 Velocity..................................................................................................................... 10 

Chapter 3 Laboratory Report ........................................................................................................ 11 

3.1 Test Set-Up, Test Equipment, and Procedures................................................................ 11 

3.1.1 Test Description........................................................................................................ 11 

3.1.2 Reflectors .................................................................................................................. 19 

3.1.3 Laboratory Test Instrumentation............................................................................... 19 

3.1.3.1 Flow Measurement Tanks and Calibrated Flow Meters .................................... 19 

3.1.3.2 Precision Point Gauge ........................................................................................ 20 

3.1.3.3 Thermometer ...................................................................................................... 20 

3.1.3.4 Timer .................................................................................................................. 21 

3.1.3.5 Precision Calipers............................................................................................... 21 

3.1.4 Pretest Procedures..................................................................................................... 21

3.1.5 General Test Procedures ........................................................................................... 21 

3.1.5.1 Set Flow Condition............................................................................................. 21 

3.1.5.2 Allow Flow To Stabilize .................................................................................... 22 

3.1.5.3 Measure Water Temperature.............................................................................. 22 

3.1.5.4 Measure Reference Flow.................................................................................... 22 

3.1.5.5 Measure Reference Depth .................................................................................. 23 

3.1.5.6 Log Meter Data .................................................................................................. 24 

3.1.5.7 Measure Reference Flow and Depth (Second Time) ......................................... 24 

3.1.5.8 Calculate Reference Velocity............................................................................. 24 

3.1.5.9 Record Observations .......................................................................................... 24 

3.1.5.10 Review Reference Data...................................................................................... 25 

3.1.5.11 Download Meter Data........................................................................................ 25 

iv 
3.1.6 Test Conditions ......................................................................................................... 25 

3.1.6.1 Free Flow and Backwater Tests ......................................................................... 25 

3.1.6.2 Full Pipe Tests (Manhole Surcharged)............................................................... 25 

3.1.6.3 Silt Simulation Tests .......................................................................................... 26 

3.1.6.4 Grease Build-up Tests ........................................................................................ 26 

3.1.6.5 Reverse Flow Tests ............................................................................................ 27 

3.1.7 Data Management and Analysis ............................................................................... 30 

3.1.8 Quality Assurance..................................................................................................... 31 

3.2 Test Results...................................................................................................................... 31 

3.2.1 Preliminary Test Measurements ............................................................................... 31 

3.2.2 Test Data ................................................................................................................... 34 

3.2.2.1 Statistical Evaluation of Data............................................................................. 34 

3.2.2.2 Graphical Evaluation of All Flow Data.............................................................. 35 

3.2.2.3 Graphical Evaluation of Flow Data by Test Condition...................................... 37 

3.2.2.4 Data Analysis Discussion................................................................................... 38 

Appendices.................................................................................................................................... 58 

A Laboratory Equipment Calibrations and Information........................................................... 58 

B Raw Laboratory Test Notes and Data................................................................................... 58 

C Operational Procedure and Data Logging Method ............................................................... 58 

D Laboratory Test Data ............................................................................................................ 58 

Glossary ........................................................................................................................................ 59 

Tables 

Table 3-1. Test Conditions and Sequence: 10-inch Test Pipe ..................................................... 28 

Table 3-2. Test Conditions and Sequence: 20-inch Test Pipe ..................................................... 29 

Table 3-3. Test Conditions and Sequence: 42-inch Test Pipe ...................................................... 30 

Table 3-4. Preliminary ADS 3600 10-inch Pipe Test Measurements........................................... 32 

Table 3-5. Preliminary ADS 3600 20-inch Pipe Test Measurements........................................... 33 

Table 3-6. Preliminary Model 3600 42-inch Pipe Test Measurements ........................................ 33 

Table 3-7. Deviation by Test Configuration: Normal Operating Conditions ............................... 35 

Figures 

Figure 2-1. ADS Model 3600 Open Channel Flow Monitor.......................................................... 7 

Figure 2-2. ADS flow monitoring sensors (laboratory 20-inch installation).................................. 8 

Figure 2-3. Ultrasonic sensor illustration........................................................................................ 9 

Figure 2-4. Doppler velocity sensor illustration. .......................................................................... 10 

Figure 3-1. The 10-inch pipe test set-up. ...................................................................................... 13 

Figure 3-2. The 20-inch pipe test set-up. ...................................................................................... 14 

Figure 3-3. The 42-inch pipe test set-up. ...................................................................................... 15 

Figure 3-4. The access hole opening for testing. .......................................................................... 16 

Figure 3-5. View of manhole for 20-inch pipe. ........................................................................... 17 

Figure 3-6. Simulated 20-inch sewer (riser-pipe-manhole shown from right to left).................. 18 

Figure 3-7. Reference depth point gauge..................................................................................... 20

Figure 3-8. ADS flow monitoring sensors (laboratory 10-inch pipe installation)........................ 22 

v 
Figure 3-9. ADS flow monitoring sensors (laboratory 42-inch pipe installation)........................ 23 

Figure 3-10. Silt simulation using a fixed bed (looking downstream). ........................................ 26 

Figure 3-11. ADS depth sensor shown during the 0.5 mm grease test........................................ 27 

Figure 3-12. Sensor installation locations..................................................................................... 32 

Figure 3-13. Metered flow rate versus reference flow rate........................................................... 36 

Figure 3-14. ADS 3600 data summary, 10-inch pipe, 0–600 gpm reference flow....................... 39 

Figure 3-15. Scatter-graph for 10-inch pipe test at 0.1 percent slope........................................... 40 

Figure 3-16. Scatter-graph for 10-inch pipe test at 0.5 percent slope........................................... 41 

Figure 3-17. Scatter-graph for 10-inch pipe test at 1.25 percent slope......................................... 42 

Figure 3-18. Scatter-graph for 10-inch pipe test at 2.0 percent slope........................................... 43 

Figure 3-19. Deviation of meter flow to reference flow for 10-inch pipe. ................................... 44 

Figure 3-20. Plot of reference flow versus meter flow in 10-inch pipe........................................ 45 

Figure 3-21. Scatter-graph for 20-inch pipe test at 0.1 percent slope........................................... 46 

Figure 3-22. Scatter-graph for 20-inch pipe test at 0.5 percent slope........................................... 47 

Figure 3-23. Scatter-graph for 20-inch pipe test at 1.25 percent slope......................................... 48 

Figure 3-24. Scatter-graph for 20-inch pipe test at 2.0 percent slope........................................... 49 

Figure 3-25. Deviation of meter flow to reference flow for 20-inch pipe. ................................... 50 

Figure 3-26. Plot of reference flow versus meter flow in 20-inch pipe........................................ 51 

Figure 3-27. Scatter-graph for 42-inch pipe test at 0.2 percent slope........................................... 52 

Figure 3-28. Scatter-graph for 42-inch pipe test at 0.2 percent slope with silt............................. 53 

Figure 3-29. Scatter-graph for 42-inch pipe test at 0.2 percent slope with 0.5mm grease. .......... 54 

Figure 3-30. Scatter-graph for 42-inch pipe test at 0.2 percent slope with 2.0mm grease. .......... 55 

Figure 3-31. Deviation of meter flow to reference flow for 42-inch pipe. ................................... 56 

Figure 3-32. Plot of reference flow versus meter flow in 42-inch pipe........................................ 57 

vi 
Acronyms and Abbreviations 

ADS ADS Environmental Services, a division of ADS Corporation 

BPR BPR, Quebec, Canada 

cfs Cubic feet per second 

ENS Event Notification System 

EPA United States Environmental Protection Agency 

ETV Environmental Testing Verification 

ft Foot or feet 

FTO Field testing organization 

gpm Gallons per minute 

in. Inch or inches 

lb Pound 

LTO Laboratory testing organization 

mg/L Milligrams per liter 

min Minimum 

NIST National Institute of Standards and Technology 

NSF NSF International (formerly National Sanitation Foundation) 

NTU Nephelometric turbidity units 

QA Quality assurance 

QUC Quebec Urban Community 

SAG Stakeholders Advisory Group 

SCADA Supervisory control and data acquisition 

UWRL Utah Water Research Laboratory 

VTP Verification test plan 

WWF Wet weather flow 

vii 
Acknowledgments 

The Laboratory Testing Organization, Utah Water Research Laboratory, and the Field Testing 

Organization, BPR, Quebec, Canada, were responsible for all elements in the testing sequence, 

including test set-up, calibration and verification of instruments, data collection and analysis, 

data management, data interpretation, and the preparation of this report. 

Utah Water Research Laboratory 

Utah State University 

8200 Old Main Hill 

Logan, UT 84322-8200 

Contact Person: Steven L. Barfuss 

BPR 

4655, blvd Wilfrid-Hamel 

Québec, Qc, Canada, G1P 4J7

Contact People: Denis Simard or Geneviève Pelletier 

The manufacturer of the equipment: 

ADS Environmental 

5030 Bradford Dr. 

Bldg. 1, Suite 210 

Huntsville, AL 35805 

Contact Person: Eugene C. Cullie 

The Utah Water Research Laboratory wishes to thank the UWRL shop for the many hours spent 

preparing the piping for these tests. Also, special thanks to Utah State University Engineering 

students Randy Geldmacher, Tyler Smith, John Nunley, and Garrett McMullen for their 

assistance in establishing proper test conditions and collecting test data. It is also necessary to 

thank ADS personnel for their support throughout the test program. ADS support was provided 

by George Kurz, Pat Stevens, Keith Waites, Christy Kennamer, Heather Hackett, Jeffrey White, 

Erica Blanken, Mark MacPherson, and Gillian Woodward. 

viii 
Chapter 1

Introduction

1.1 ETV Purpose and Program Operation 

The U.S. Environmental Protection Agency (EPA) created the Environmental Technology 

Verification (ETV) Program to facilitate the deployment of innovative or improved 

environmental technologies through performance verification and dissemination of information. 

The goal of the ETV program is to further environmental protection by substantially accelerating 

the acceptance and use of improved and more cost-effective technologies. ETV achieves this 

goal by providing high quality, peer-reviewed data on technology performance to those involved 

in the design, distribution, permitting, purchase, and use of environmental technologies. 

ETV works in partnership with recognized standards and testing organizations; stakeholder 

groups, which consist of buyers, vendor organizations, and permitters; and with the full 

participation of individual technology developers. The program evaluates the performance of 

innovative technologies by developing test plans that are responsive to the needs of stakeholders, 

conducting field or laboratory testing (as appropriate), collecting and analyzing data, and 

preparing peer-reviewed reports. All evaluations are conducted in accordance with rigorous 

quality assurance protocols to ensure that data of known and adequate quality are generated, and 

that the results are defensible. 

NSF International (NSF) operates the Wet Weather Flow (WWF) Technologies Area in 

cooperation with the EPA under the Water Quality Protection Center. The WQPC evaluated the 

performance of the ADS Model 3600 open channel flow monitor, which is an area/velocity flow 

meter used to measure flows in municipal sewers. The performance claim evaluated during 

laboratory testing of the ADS Model 3600 was that the instrument is capable of measuring 

depths and velocities in a wide range of pipe sizes and flow conditions. This document provides 

the laboratory verification test results for the ADS Model 3600 open channel flow monitor. 

1.2 Testing Participants and Responsibilities 

The ETV testing of the ADS 3600 Open Channel Flow Monitor was a cooperative effort of the 

following participants: 

• U.S. Environmental Protection Agency 

• NSF International 

• Utah Water Research Laboratory 

• BPR 

• ADS Environmental 

The following is a brief description of the ETV participants and their roles and responsibilities. 

1 
1.2.1 U.S. Environmental Protection Agency 

The EPA Office of Research and Development, through the Urban Watershed Branch, Water 

Supply and Water Resources Division, National Risk Management Research Laboratory 

(NRMRL), provides administrative, technical, and quality assurance guidance and oversight on 

all ETV Water Quality Protection Center activities. 

Contact Information: 

 EPA, NRMRL 

Urban Watershed Management Research Laboratory 

2890 Woodbridge Avenue (MS-104) 

Edison, NJ 08837-3679 

Phone: (732) 321-6627 

Fax: (732) 321-6640 

Contact Person: Raymond Frederick, Project Officer 

 Email: Frederick.Ray@epamail.epa.gov 

1.2.2 NSF International 

NSF is a not-for-profit testing and certification organization dedicated to public health, safety, 

and protection of the environment. Founded in 1946 and located in Ann Arbor, Michigan, NSF 

has been instrumental in the development of consensus standards for the protection of public 

health and the environment. NSF also provides testing and certification services to ensure that 

products bearing the NSF Name, Logo and/or Mark meet the organization’s standards. 

NSF had several different roles in completing this verification. NSF reviewed the verification of 

the verification test plan (VTP) and provided technical oversight of the verification testing, 

including auditing of the laboratory’s analytical, data gathering, and data recording procedures. 

NSF also provided review of this verification report. 

Contact Information: 

NSF International 

789 North Dixboro Rd. 

Ann Arbor, MI 48105 

Phone: 734-769-8010 

Fax: 734-769-0109 

Contact: Tom Stevens, Program Manager 

 Email: stevenst@nsf.org 

1.2.3 Laboratory Testing Organization 

The Utah Water Research Laboratory (UWRL), a Utah State University hydraulic research 

facility, is an NSF-qualified testing organization (TO) for the WQPC and conducted the 

verification testing of the ADS 3600 flowmeter. UWRL provided all needed logistical support, 

established a communications network, and scheduled and coordinated the activities of all 

participants. It was responsible for ensuring that the testing location and feed water conditions 

2 
could meet the stated objectives of the verification testing. UWRL prepared the VTP; oversaw 

the pilot testing; managed, evaluated, interpreted and reported on the data generated by the 

testing; and evaluated and reported on the performance of the technology. 

UWRL employees manufactured and prepared the test piping, set test conditions, and measured 

and recorded data during the testing. The UWRL’s Project Manager provided testing oversight. 

Contact Information: 

Utah Water Research Laboratory 

Utah State University 

8200 Old Main Hill 

Logan, UT 84322-8200 

Phone: (435) 797-3214 

Fax: (435) 797-3663 

Contact Person: Steven L. Barfuss 

Email: Barfuss@cc.usu.edu 

1.2.4 Field Testing Organization 

BPR is an NSF-qualified TO for the WQPC and was responsible for conducting the field 

verification testing of the ADS 3600 flowmeter. The testing was conducted on a section of the 

Quebec Urban Community’s (QUC) western sewer network located in the City of Sainte-Foy, 

along the east side of Boulevard Chaundière, approximately between Bombardier and Mendel 

Streets. 

BPR provided all needed logistical support, established a communications network, and 

scheduled and coordinated the activities of all participants. It was responsible for ensuring that 

the testing location and feed water conditions could meet the stated objectives of the verification 

testing. It prepared the VTP, oversaw the pilot testing; managed, evaluated, interpreted, and 

reported on the data generated by the testing; and evaluated and reported on the performance of 

the technology. 

BPR employees prepared the test site, set test conditions, and measured and recorded data during 

the testing. BPR’s Project Manager provided oversight of the daily tests. 

Contact Information: 

BPR-CSO 

4655, Boulevard Wilfrid-Hamel 

Québec, QC, Canada G1P 4J7 

Phone: (418) 871-3414 

Fax: (418) 871-9569 

Contact Persons: Denis Simard or Geneviève Pelletier 

E-mail: dsimard@bpr-cso.com or gepelletier@bpr-cso.com 

3 
1.2.5 Vendor 

The flow monitoring equipment is manufactured by ADS Corporation. ADS was responsible for 

supplying a field-ready open channel flow meter equipped with all necessary components, 

including an installation and operation manual. The manufacturer was also responsible for 

providing technical support personnel. This individual was responsible for installing and 

precalibrating the flow monitoring equipment in the simulated sewer for each test series, and was 

available during all tests to provide technical assistance as needed. 

Contact Information: 

ADS Environmental 

5030 Bradford Dr., Building One, Suite 210 

Huntsville, AL 35805 

Phone: (256) 430-3366 

Fax: (256) 430-6633 

Contact Person: Eugene C. Cullie 

1.3 Laboratory Verification Testing Site 

The Utah Water Research Laboratory, constructed in 1965, is one of the largest water research 

laboratories of its kind in the country. The laboratory, which occupies more than 50,000 square 

feet of floor space, contains a variety of flumes, channels, pumps, pipelines, equipment, and 

instrumentation for conducting hydraulic research, model studies, hydraulic valve testing, and 

flow meter calibrations. It is capable of performing an array of hydraulic tests and research 

programs. A network of steel piping (18-, 24-, 36-, and 48-inch diameter), located under the floor 

of the lab, provides maximum flexibility in constructing test lines from 1/2-inch to 60-inches. 

Under-the-floor channels conduct water from the experiments back to the river, to recirculating 

pumps, or to the precise flow measurement facilities. 

The primary water supply for the laboratory is an 85-acre-foot reservoir approximately 500 feet 

from the facility. The water supply, which is conveyed to the laboratory through a 48-inch pipe, 

provides a constant 25 feet of head to the main level of the laboratory and 35 feet of head to the 

lower level at shutoff. Flow can also be supplied from either high-pressure pumps or a constant 

level tank within the laboratory. 

For direct National Institute of Standards (NIST) traceability, flow rates are measured using the 

laboratory’s weigh and volumetric tanks. These tanks are calibrated regularly and are NISTtraceable by weight. The UWRL primary flow measurement system consists of one 1,000 lb 

weigh tank, two 30,000 lb weigh tanks, and a 222,144 lb (3,560 ft3

) volumetric tank. Flow rates 

up to 40 cubic feet per second (cfs) can be accurately measured with the primary flow 

measurement system. 

A number of venturi meters—6-, 12-, 20-, 24-, and 48-inch—are installed in various test lines 

throughout the laboratory. These master meters are calibrated in place using the UWRL primary 

flow measurement system. As a secondary standard with NIST-traceability, these meters allow 

accurate flow measurements to be made for flow rates up to approximately 200 cfs. 

4 
Chapter 2

ADS Equipment Description and Operating Processes 

The information contained in this chapter is provided by the vendor and does not represent 

verified information. The information is intended to provide the reader with a description of the 

ADS 3600 flow monitor and to explain how the technology operates. The verified performance 

characteristics of the ADS 3600 are described in subsequent chapters. 

2.1 Equipment Description 

The ADS 3600 flow monitor is specially designed to meet the demands of measuring flow over 

long-term periods in open channel applications, such as wastewater collection systems, storm 

sewer systems, and combined sewer systems. The battery-powered system acquires highly 

accurate depth and velocity data, and transmits the data through telemetry to a remote computer. 

The ADS 3600 is certified as Intrinsically Safe (IS) by Factory Mutual (United States), and by 

SIRA Certification Services (International). IS certification confirms that it meets both U.S. and 

international standards for electrical apparatus installed in potentially explosive environments. 

The ADS 3600 is used for many project applications, including: 

• Infiltration/inflow analysis and reduction; 

• Master plan studies; 

• Interagency billing networks; 

• Combined sewer overflow characterization; 

• Storm sewer monitoring; 

• Sewer capacity analysis; and 

• Sewer system performance studies/trending. 

Precise pipe dimensions (height and width) are measured during installation because they are 

critical to both depth and cross-sectional area. ADS depth sensors measure the distance from the 

down-looking sensor to the water surface (range) and depth of flow is obtained by subtracting 

the range from the diameter. This is an important step since the inside diameter of most sewer 

pipe is not equal to its nominal diameter. Velocity sensor confirmation is another critical-toquality activity. While the ADS 3600 velocity sensor will perform in most sites using factory 

default settings, it can be adjusted by a trained technician to improve performance in unique 

hydraulic conditions. 

The ADS 3600 features: 

• Quad-redundant Ultrasonic Level Sensor. This nonintrusive, zero-drift sensing method 

results in a stable, accurate, and reliable flow depth calculation. 

• Peak Velocity Sensor. Readings from this sensor are used to calculate average velocity. Its 

miniature size minimizes fouling and flow disruption. 

• Pressure Depth Sensor. This sensor is used to measure surcharge levels or to provide a 

redundant depth reading when used in conjunction with the ultrasonic level sensor. 

5 
• Water Quality Sampler Interface. A variety of industry standard water quality samplers are 

compatible and easily interfaced with the Model 3600. Sampling is initiated automatically 

based on a fixed-time or flow proportional basis. The sampler must be certified to maintain 

IS certification. 

• Tipping Bucket Interface. Where installation criteria allow, the flow monitor can be 

interfaced to a tipping bucket unit to record rainfall amounts. 

• Supervisory Control and Data Acquisition (SCADA) System Interface. An external modem 

unit can communicate both with a SCADA system remote computer and via telemetry with 

QuadraScanTM Software. 

• QuadraScanTM Software. This enables a SCADA system to retrieve various data entities, 

including depth of flow, average velocity, flow rate, daily flow totals, etc. 

• Accurate Flow Measurement. This technology has been shown to be highly accurate in both 

laboratory and in-field tests. It measures flow under open channel, free flow conditions, and 

non-free flow conditions, including surcharge and backwater. 

• QuadraScanTM Software Interface. This complete hydraulics and analysis package provides 

telemetered data collection, trending, reporting, and file management. 

• Automated Data Collection. Data can be collected at user-defined times, including group 

collections of multiple monitoring units, increasing the efficiency and flexibility of flow 

data analysis. 

• Event Notification System (ENS) Capability. Consisting of the ADS 3600 Monitor, 

QuadraScanTM Software, and event reporting software, this versatile system can initiate an 

alarm to a remote location and/or activate other instrumentation activity such as water 

quality sampling based on preset conditions. 

• Low Cost Telemetry. The standard telemetry interface allows remote communications and 

diagnostics, resulting in a significant reduction in field labor. 

• Manufacturing Quality Control. Each unit undergoes factory testing and certification by 

qualified technicians. 

• Ultra-low Power Consumption. Batteries can last more than one year under most operating 

and environmental conditions. 

• Fully Water-Resistant Housing. The housing reliably withstands harsh sewer environments, 

even under surcharge conditions. 

• Low Battery Warning. Each unit monitors battery voltages to warn the operator in advance 

of battery failure. 

• Optional Non-IS Configuration. This unit is suitable for installations where protection from 

explosive environments is not required. 

Figure 2-1 is a view of the ADS 3600 meter’s canister. Figure 2-2 shows the stainless steel ring 

and sensing devices installed inside a pipe. 

The ADS meter installation is similar to nearly all depth velocity meters, but the ADS meter 

differs in that only its velocity sensor is mounted in the flow. The velocity sensor offers a crosssectional area of around one-half square inch, and measures velocity in depths of less than one 

inch. Both the depth and velocity sensors are mounted on a stainless-steel ring that is expanded 

into place with a hand crank and spreader bars. The meter is either attached to rungs in the 

manhole or to an attachment hook drilled into place on the manhole wall. The meter is activated 

6 
by downloading BASIC code with monitor and sensor configuration. The monitor clock is 

synchronized with the central computer each time data are collected. 

Figure 2-1. ADS Model 3600 Open Channel Flow Monitor. 

It is important that the actual pipe dimensions be measured for two reasons: (1) the correct 

diameter will be used to calculate cross-sectional area of the pipe; and (2) the depth of flow 

equals the actual diameter minus the range measured by the depth sensor. An incorrect diameter 

translates directly to an incorrect depth. The inside diameter of most sewer pipe is not equal to its 

nominal diameter. For example, a 15-inch PVC sewer line with SDR 35 wall thickness has a 

maximum manufactured diameter of 14.4 inches. 

The monitor and software manuals offer approximately 600 pages of instruction, including 

graphics, on installing the meter, activating the meter, collecting data, and processing data. 

ADS provides hardware as well as flow monitoring services throughout the United States. 

Technical support is provided by its headquarters office as well as by 16 regional and local 

7 
offices. Most offices are staffed with data analysts and operations people who will readily assist 

with any hardware, software, or operational problem. Parts can be ordered through any office. 

Pressure Depth Sensor 

Depth Sensor 

Velocity Sensor 

Stainless Steel Ring 

Figure 2-2. ADS flow monitoring sensors (laboratory 20-inch installation). 

No special tools are required for installation. Most installations are accomplished with standard 

wrenches, screwdrivers, wire ties, and a drill and bits. 

Once placed in service, continued calibrations are not required to obtain valid data, but periodic 

site visits are recommended to spot hydraulic changes. The ultrasonic sensor has zero drift, but it 

is recommended that the sites with silt be visited regularly to verify silt depth. Silt reduces the 

cross-sectional area of flow and creates inaccuracy in the continuity equation. Hydraulic changes 

can also affect the average-to-peak ratio, which should be confirmed periodically through 

velocity profiles. 

The unit operates with little routine maintenance. The most common maintenance needed is 

cleaning the ultrasonic depth sensor should it become coated with grease during a surcharge 

event in a greasy sewer. In most sewers the ultrasonic sensors are not affected by surcharging, 

and they immediately begin reporting depth the moment surcharging subsides. The velocity 

8 
sensor is not affected by grease, but can be impaired by heavy silt or debris covering the sensor. 

In such cases, the sensor can be rotated off the bottom of the sewer to avoid silt and debris. 

Ultrasonic depth sensor crystals that deteriorate with age can be diagnosed and taken out of 

service remotely. A visit to the site can be avoided by switching to an inactive sensor pair. There 

are 12 possible sensor pairs, and the meter will operate with only one pair in service. 

2.2 Operating Process 

2.2.1 Depth 

Depth is measured by a quad-redundant ultrasonic sensor installed at the top of the pipe facing 

down toward the water surface. The meter measures the time of travel of an ultrasonic pulse 

from the sensor to the water and back to the sensor. The meter converts the time of travel to 

distance by calculating the speed of sound through air and adjusting for temperature, which is 

measured by two temperature sensors inside the ultrasonic sensor head. 

Each of the four transducers can operate in either transmit or receive mode, allowing for 12 

possible transmit–listen pairs, as illustrated in Figure 2-3. A crystal cannot transmit and listen for 

its own signal. The paired sensors essentially eliminate the dead zone inherent to a single 

ultrasonic crystal that transmits and then listens. The dead zone is usually less than one inch. 

Ultrasonic Sensor Pairs

0 3

1 2

Pair crystals 

can transmit 

40 kHz crystals 1 - 0 0 

2 0 - 1 

3 - 0 2 

4 - 0 3 

5 - 1 0 

and receive. 

6 - 1 1 

7 1 - 2 

8 - 1 3 

9 - 2 0 

10 2 - 1 

11 2 - 2 

12 2 - 3 

13 3 - 0 

14 3 - 1 

15 3 - 2 

16 3 - 3 

page 8

Figure 2-3. Ultrasonic sensor illustration. 

Up to four of the 12 sensor pairs are in operation at any moment, and the operator can remotely 

diagnose the operating pairs for strength and quality of signal. The operator can remotely add 

and remove sensor pairs from operation. When activated for a reading, each pair in turn 

measures distance 32 successive times for a total of 128 readings. Errant readings from each 

sensor pair are discarded and four depth readings are recorded. The sensors are designed to have 

zero drift, where only extremely noisy or wavy sites affect performance. 

9 
2.2.2 Velocity 

Doppler velocity measurements are made by transmitting an ultrasonic signal upstream and 

measuring particle velocity, similar to police radar. The sensor receives echoes from the particles 

and records the frequency shift (velocity) and strength of each echo. The ADS 3600 uses Peak 

Velocity Doppler, which is ADS’s third generation velocity technology (V3). V3 technology 

takes advantage of the fact that the fastest particle in sewage remains constant from moment to 

moment, regardless of its size. V3 technology measures the velocity of the fastest particle 

(particle C in Figure 2-4) in sewage and converts it to average velocity. The ratio of average to 

peak velocity is around 0.9 in most sewers, and velocity profiles are used to determine the ratio 

in unusual flow. 

page 46

Doppler Sensors Measure Velocity 

and Echo Strength of Particles 

Echo Strength 

Side view of sensor in sewer 0 

top view 

a

a

a

b

b

b

c

c

c

d 

d 

d

e 

e 

e

f 

f 

f

Velocity 

Figure 2-4. Doppler velocity sensor illustration. 

10 
Chapter 3

Laboratory Report 

This chapter presents the procedures used in generating the laboratory performance data for the 

ADS 3600, along with the test data generated from the verification testing. This chapter 

addresses only the laboratory portion of the verification. Chapter 4, contained in Part II of the 

report, addresses the field testing portion of the verification testing. 

3.1 Test Set-Up, Test Equipment, and Procedures 

3.1.1 Test Description 

The laboratory flow meter verification was performed in three different nominal pipe sizes: 

10-inch, 20-inch, and 42-inch. Figures 3-1 through 3-3 show the piping prepared for the tests in 

the three respective sizes. Although the schematic drawings are not to scale, the dimensions and 

the relative locations of flow meters, risers, valves, and manholes are accurate. Each set-up was 

constructed using steel pipe. 

An opening was cut in the top of the pipe near where the vendor test sensors were installed. The 

opening provided access to the sensor location so that a precision point gauge could be used to 

accurately measure flow depths and to allow test participants to view the installation from above 

and to observe flow conditions around the flow meter. The access opening had a watertight cover 

that was closed during pressurized (full-pipe) tests. Figure 3-4 shows the 20-inch pipe with the 

access hole open and closed. The other pipe sizes were similarly constructed. 

A manhole was also constructed in each test set-up near the location of the test flow meter. The 

size and location of the manhole was sufficient to provide access for the installation of the test 

flow meter, and to provide a suitable location for monitoring surcharge flow conditions. The 

manhole consisted of a cylindrical steel tank with a watertight bottom. Each manhole was 

constructed to the dimensions indicated in the figures. The section of pipe passing through the 

manhole had its top removed (down to the spring-line). A sloping steel floor was installed in the 

bottom of the manhole, so that all water drained to the pipe spring-line. Figure 3-5 is a 

photograph of the outside and inside of the manhole in the 20-inch pipe set-up. The other pipe 

size set-ups were similarly constructed. 

The test flow meter sensors were installed in the upstream pipe adjacent to the manhole. The 

precise location of the meter in the test pipe depended on ADS’s specifications for the meter and 

its installation requirements. The crown of the pipe was removable near the installation location 

for access to the installed flow meter, but this access location was not used to install the flow 

meter. The access hole was covered and sealed for tests requiring surcharged flow conditions. 

All cables and wires connected to the sensor were directed into the test pipe through the 

manhole. 

In the 10- and 20-inch test pipes, the length of straight pipe installed upstream of the 

manhole/flow meter test location was at least 40 times the pipe diameter. This length of straight 

pipe was necessary to provide near-uniform flow to the flow monitoring equipment during tests 

11 
with no backwater effects. In the 42-inch test pipe, the length of straight pipe upstream of the 

manhole/flow meter test location was at least 22 times the pipe diameter. This shorter length was 

sufficient to provide near-uniform flow at the single pipe slope (0.2 percent). 

12 
Figure 3-1. The 10-inch pipe test set-up. 

13 
Figure 3-2. The 20-inch pipe test set-up. 

14 
Figure 3-3. The 42-inch pipe test set-up. 

15 
(a) Closed pipe. 

(b) Open pipe. 

Figure 3-4. The access hole opening for testing. 

16 
(a) Outside view. 

(b) Inside view. 

Figure 3-5. View of manhole for 20-inch pipe. 

17 
A minimum of 10 diameters of straight pipe was installed downstream of each manhole to 

simulate the flow conditions exiting the manhole. Figure 3-6 shows the 20-inch set-up. The other 

pipe size set-ups were similarly constructed. 

Figure 3-6. Simulated 20-inch sewer (riser-pipe-manhole shown from right to left). 

Each test line was laid at a constant slope along the full length of the pipe. The test set-up 

allowed for the adjustment of pipe slope in the 10- and 20-inch sizes. The supports for these two 

test lines were capable of supporting pipe from a slightly negative slope condition to a maximum 

slope of 2.0 percent. The 42-inch pipe set-up was set at a constant slope (0.2 percent) for all tests. 

The vertical pipe supports prevented the pipe from sagging under the weight of the water. The 

spacing between vertical pipe supports for the three steel pipe set-ups was no greater than ten 

pipe diameters. No horizontal supports were needed. 

A control valve was placed both upstream and downstream of the model piping. The valves were 

used to control the rate of flow through the simulated sewer. The upstream valve was used to 

control the rate of flow entering the riser supplying the test line. The downstream valve was used 

to impose a downstream control to the test line, providing backwater during surcharge test 

conditions. 

A vertical riser was installed upstream of each test pipe to help dissipate the energy of the 

incoming flow, to provide a smooth pour-over into the model pipe for open channel tests, and to 

18 
provide a surcharge stand-pipe during full-pipe tests. The dimensions of each riser are shown in 

Figures 3-1 through 3-3. 

The test pipe was connected to the vertical supply riser with a flexible coupling that allowed for 

the required adjustment of pipe slope. The point of connection was high enough on the riser to 

allow the test pipe to be set at a maximum slope of 2.0 percent along its entire length. (The 

coupling can be seen on the right side of the photograph in Figure 3-6. In the photograph, flow is 

from right to left.) The elevation of the pipe at the coupling was always the same. The adjustable 

stands were raised or lowered to set the appropriate slopes for each test so that the entire test line 

rotated about the upstream coupling. 

Water was supplied by a reservoir near the laboratory. This constant head source was capable of 

maintaining constant and steady water depths in the test pipe for the duration of each test run. A 

turbidity test was performed in the Environmental Quality Laboratory at UWRL and found to be 

at a level of 0.58 nephelometric turbidity units (NTU). One NTU is the limit for public drinking 

water supplies. The lower limit on the laboratory meter that made the measurement is 

approximately 0.1 NTUs. A turbidity measurement of 0.58 NTU indicates water with high 

clarity. 

3.1.2 Reflectors 

The Doppler shift principle requires particles in the water to serve as reflectors for sound waves. 

The clear water used in the UWRL contains considerably fewer particles than sewage. Since it 

was not practical to replicate the particulate concentrations of normal sewage, coffee creamer 

was added to the water in small quantities on some test runs. The vendor maintains that although 

the coffee creamer additive did provide a level of reflectivity, the particulate concentration in the 

test water did not replicate that of sewage, and thus could be a source of measurement error. It 

was not necessary to add creamer while the laboratory was making reference measurements. 

For test configurations where particulate levels were especially low, ADS technicians made 

compensations during confirmations by changing adjustable parameters on the ADS 3600 

velocity subsystem. This sensitivity adjustment was made using the Fieldscan standard field 

configuration software. It allowed the meter to register the faint echoes from the few particles 

that were in the fastest portion of the flow, and adequately compensated for the clarity issue. In 

typical sewer installations, this type of adjustment is not necessary. 

3.1.3 Laboratory Test Instrumentation 

The laboratory instruments used during the verification tests are described in this section. 

Calibration records for the instruments are shown in Appendix A. 

3.1.3.1 Flow Measurement Tanks and Calibrated Flow Meters 

Laboratory weigh tanks and master venturi meters were used to determine the reference flow rate 

for each test run. The measurement tanks are directly traceable to the National Institute of 

Standards and Technology (NIST) by weight. The master venturi flow meters are regularly 

19 
calibrated and are NIST-traceable. Uncertainty for the tanks and flow meters is less than 0.25 

percent. 

3.1.3.2 Precision Point Gauge 

A precision point gauge was used as the reference depth measurement in determining the depth 

of flow near the test flow meter focal point (Figure 3-7). The precision point gauge is readable to 

the nearest one-thousandth (0.001) of a foot. The point gauge was mounted as close as possible 

to the downstream edge of the access hole. Likewise, the ADS depth sensor was also mounted as 

close as possible to the downstream edge of the access hole. The reference depth measurement 

was compared to the indicated depth measurement from the meter. 

3.1.3.3 Thermometer 

A calibrated thermometer was used to measure the temperature of the water flowing through the 

test pipe. The temperature measurement was used for spreadsheet calculations requiring 

temperature. The thermometer was calibrated for accuracy before the verification tests. 

Figure 3-7. Reference depth point gauge. 

20 
3.1.3.4 Timer 

A calibrated stopwatch/timer was used to measure the collection time of the water entering the 

weigh tanks. The time measurement was used with the weight reading to calculate the actual 

flow rate for each test in which the master venturi meters were not used. The timer was 

calibrated before the verification tests. 

3.1.3.5 Precision Calipers 

Precision calipers were used to measure the inside diameter of the model piping and to verify the 

roundness of the pipe. An accurate measurement of each pipe diameter was necessary for correct 

area calculations. 

3.1.4 Pretest Procedures 

The VTP included a detailed set of test procedures that was followed during the verification 

tests. The procedures were consistent with the requirements established in the protocol. 

Laboratory personnel performed the following tasks before beginning the verification test on a 

specific pipe set-up: 

• The geometry of the test pipe and location of the vendor instrument within the pipe was 

measured and documented. 

• A digital photograph was taken of the installed flow meter sensors in each pipe size 

(Figures 2-2, 3-7, 3-8, and 3-9). 

• The time required for flow meter installation and set-up by the vendor was recorded. 

3.1.5 General Test Procedures 

Flow, depth, and velocity data from the test flow meter was logged electronically as recorded by 

the vendor-supplied electronics. Average recorded values were entered into a computer 

spreadsheet. 

Tables 3-1, 3-2, and 3-3 define each run that was tested in 10-, 20-, and 42-inch pipe, 

respectively. 

The procedures described in this section were conducted for each set of test conditions 

established in Tables 3-1 through 3-3. The procedures were repeated each time the flow 

conditions were changed. The following procedural steps were taken for each run. 

3.1.5.1 Set Flow Condition 

Both the upstream and downstream control valves were used to set the flow. Uniform flow (free 

flow) tests had no downstream control. Conversely, the downstream control valve was throttled 

for submerged and backwater tests. Tables 3-1 through 3-3 list the target flow conditions for 

each run. 

21 
Figure 3-8. ADS flow monitoring sensors (laboratory 10-inch pipe installation). 

3.1.5.2 Allow Flow To Stabilize 

Test measurements were not made until the water had stabilized in the pipe. The flow was 

stabilized when the depth in the pipe did not change over time. The precision point gauge 

mounted on the centerline of the flow path acted as a gauge for setting and stabilizing the flow. 

The flow depth was set within .02 D (D = diameter of the pipe) of the flow depths specified in 

Tables 3-1 through 3-3. 

3.1.5.3 Measure Water Temperature 

The temperature of the water in the test pipe was measured using a calibrated mercury 

thermometer. This manual reading was recorded after the mercury in the thermometer had 

stabilized. 

3.1.5.4 Measure Reference Flow 

The reference flow rate was measured and recorded utilizing the laboratory instrumentation 

before and after each logging period. Laboratory personnel measured the actual flow rate using 

the laboratory master flow meters. The master venturi flow meters are used often and are 

regularly calibrated at the laboratory. Flows too small to be accurately measured by the master 

venturi meters were measured using the laboratory weigh tanks. 

22 
Figure 3-9. ADS flow monitoring sensors (laboratory 42-inch pipe installation). 

3.1.5.5 Measure Reference Depth 

The actual depth was measured and recorded before and after the logging period of each run. 

Laboratory personnel measured the actual flow depth at the centerline of the pipe. This 

measurement was made very near the focal point for the sensor depth measurement. The depth 

was determined by taking the difference between the water surface measurement and the 

reference pipe invert measurement made by the centerline point gauge. 

If the water surface was mounded slightly at the measurement location, a measurement of the 

complete cross-sectional water surface profile was necessary to generate the correct flow area for 

mean velocity calculations. An evaluation of each water surface profile was performed to decide 

the necessity of conducting either a single centerline depth or a complete cross-sectional water 

surface profile. This check was made by comparing the depths at the centerline and near the wall 

of the pipe. 

23 
If the peak-to-peak difference in depth across the water surface profile was greater than 0.02 D 

inches, a complete cross-sectional water surface profile was necessary. A special adjustable point 

gauge was used to measure water surface depths at five equally spaced locations across the water 

surface. Since the water surface width changes with increased depth, the spacing and position for 

the five equally spaced point gauges also varied. 

3.1.5.6 Log Meter Data 

Average flow, depth, and velocity measurements were electronically logged and recorded from 

the ADS output device. ADS provided a laptop computer to retrieve the logged data. The logged 

data was manually entered into a desktop computer spreadsheet at the end of each day of testing. 

Once the flow stabilized, and after recording the first reference depth and flow measurements, 

laboratory personnel logged data from the flow monitoring equipment. Data was recorded in 

accordance with the operational procedures provided by the vendor, except that average flow 

rate, depth, and velocity readings were logged and recorded at one-minute intervals over a fiveminute period. Data was reported for each one-minute interval. ADS prepared the instrument so 

that each one-minute sample was independent and was not averaged with prior samples. The 

operational procedure and data-logging method devised and utilized by ADS is given in 

Appendix C. 

3.1.5.7 Measure Reference Flow and Depth (Second Time) 

After the ADS flow meter completed its logging cycle (during the five-minute period), the 

reference flow and reference depth measurements were repeated. This was done to ensure that 

the flow conditions had remained constant during the five-minute logging period. 

3.1.5.8 Calculate Reference Velocity 

Using the measured cross-sectional water surface profile, the flow area was calculated using a 

computer spreadsheet. The mean velocity for the test was calculated by dividing the flow area 

into the reference flow measurement. The mean velocity was based on the average reference 

depth and flow measurements for the run. 

3.1.5.9 Record Observations 

The flow conditions for each run were recorded. Appendix B contains the raw data and notes 

documented by laboratory personnel during the verification tests. 

24 
3.1.5.10 Review Reference Data 

Once all pertinent reference data for a single run had been entered into the computer, the results 

were reviewed before the flow conditions were changed for the next run. If flow conditions 

changed during a logging period, the test run was repeated. A run was repeated if the difference 

between the flow measurements taken at the start and end of the logging period were greater than 

one percent of the lesser value. Before repeating any given run, the vendor technician and 

laboratory personnel came to agreement that flow conditions had changed. 

After all measurements for the run had been made, the flow conditions were changed and a new 

run was started. Each step listed above was repeated for each run. 

3.1.5.11 Download Meter Data 

The data was retrieved from the meter at the end of each test day. The five flow rate, depth, and 

velocity readings for each run were manually entered into a computer spreadsheet. The average 

of all five one-minute samples was calculated and reported. 

3.1.6 Test Conditions 

3.1.6.1 Free Flow and Backwater Tests 

Free flow conditions were established by setting the desired depth in the pipe with no 

downstream control. Partial backwater conditions were simulated by closing the downstream 

control valve in the pipe. Each backwater test (nonuniform flow condition) had a corresponding 

uncontrolled flow test (uniform or free flow condition). The flow velocities for the backwater 

tests were set to approximately one-half the flow velocities for the uncontrolled tests by using the 

supply master venturi device. No backwater tests were performed for slopes greater than 

0.5 percent. 

3.1.6.2 Full Pipe Tests (Manhole Surcharged) 

For tests in which there was downstream control and the pipe was full and pressurized, the 

opening on the top of the pipe through which the sensor is accessed and point gauge readings 

taken was closed. The access opening was covered with a watertight lid (see Figure 3-7). During 

these tests, the depth of water (hydraulic grade line) was not measured. For runs where the pipe 

was full during surcharged conditions, this report indicates the pipe diameter as the flow depth. 

The reference flow measurement was divided by the pipe area to determine mean velocity. Flow 

and velocity were compared, but no comparisons of surcharged pressures were made. The ADS 

output indicated that the depth of flow in the pipe was equal to the diameter of the pipe. A 

piezometric measurement of the submergence was made and reported as an indication of the 

magnitude of submergence only, and not as a reference pressure measurement. 

25 
3.1.6.3 Silt Simulation Tests 

A simulated deposit of silt or sediment in the bottom of the pipe was conducted during the 

42-inch pipe tests. A rigid flat bed was installed in the bottom of the 42-inch pipe at a depth of 

three inches. The simulated fixed sediment bed was constructed of wood, and extended five pipe 

diameters at a depth of three inches. A 5:1 smooth sloped transition was installed at the leading 

edge of the fixed bed to reduce turbulence. 

ADS personnel adjusted installation of the flow measurement device so that it sat above the 

simulated silt bed. Runs were made as indicated in Table 3-3. Figure 3-10 shows the fixed bed in 

the bottom of the 42-inch pipe. 

Figure 3-10. Silt simulation using a fixed bed (looking downstream). 

3.1.6.4 Grease Build-up Tests 

Tests were performed with thin layers of grease (Crisco) placed on all submerged components of 

the flow monitoring equipment. These tests evaluated the ability of the meter to continue 

functioning accurately when grease built up on the wetted components, and also allowed 

technicians to observe and record whether the grease remained on the components. Both a 

26 
0.5-mm and 2.0-mm layer of grease was tested under three different flow conditions (six runs). 

Runs were made as indicated in Table 3-3. Figure 3-11 shows the depth sensor with a thin layer 

of grease applied. The grease thickness in the photograph is 0.5 mm thick. The 2.0-mm tests had 

four times the thickness of grease, which was applied manually. Figure 3-11 shows the flow 

sensor after grease was applied. 

Figure 3-11. ADS depth sensor shown during the 0.5 mm grease test. 

3.1.6.5 Reverse Flow Tests 

A reversed pressure flow condition was also tested. This was accomplished by elevating the test 

pipe to a slightly negative slope, installing the flow meter in the test line backwards, submerging 

the manhole, and forcing water uphill. The sensor was installed on the downstream side of the 

manhole (uphill side) and runs were made as indicated in Tables 3-1 and 3-2. Reverse flow tests 

were performed on the 10- and 20-inch pipes, but not the 42-inch pipe. 

27 
Table 3-1. Test Conditions and Sequence: 10-inch Test Pipe 

Nonuniform 

Uniform flow flow 

Pipe slope (downstream­ (downstreamRun number (percent) Water depth uncontrolled) controlled) 

1 0.1 0.1 D Yes 

2 0.1 0.3 D Yes 

3 0.1 0.5 D Yes 

4 0.1 0.8 D Yes 

5 0.1 0.1 D Yes 

6 0.1 0.3 D Yes 

7 0.1 0.5D Yes 

8 0.1 0.8 D Yes 

9a

 0.1 ~1.5 D Yes 

10a

 0.1 ~2.5 D Yes 

11 0.5 0.1 D Yes 

12 0.5 0.3 D Yes 

13 0.5 0.5D Yes 

14 0.5 0.8 D Yes 

15 0.5 0.1 D Yes 

16 0.5 0.3 D Yes 

17 0.5 0.5D Yes 

18 0.5 0.8 D Yes 

19a

 0.5 ~1.5 D Yes 

20a

 0.5 ~2.5 D Yes 

21 1.25 0.1 D Yes 

22 1.25 0.3 D Yes 

23 1.25 0.5D Yes 

24 1.25 0.8 D Yes 

25a

 1.25 ~1.5 D Yes 

26a

 1.25 ~2.5 D Yes 

27 2.0 0.1 D Yes 

28 2.0 0.3 D Yes 

29 2.0 0.5D Yes 

30 2.0 0.8 D Yes 

31a

 2.0 ~1.5 D Yes 

32a

 2.0 ~2.5 D Yes 

33b

 -0.1 ~1.5 D Yes 

34b

 -0.1 ~2.5 D Yes a

 Manhole is surcharged. b Flow meter installed backwards, pipe slope set negative, surcharged conditions.

28 
Table 3-2. Test Conditions and Sequence: 20-inch Test Pipe 

Uniform flow Nonuniform flow 

Pipe slope (downstream­ (downstreamRun number (percent) Water depth uncontrolled) controlled) 

1 0.1 0.1 D Yes 

2 0.1 0.3 D Yes 

3 0.1 0.5 D Yes 

4 0.1 0.8 D Yes 

5 0.1 0.1 D Yes 

6 0.1 0.3 D Yes 

7 0.1 0.5D Yes 

8 0.1 0.8 D Yes 

9a

 0.1 ~1.5 D Yes 

10a

 0.1 ~2.5 D Yes 

11 0.5 0.1 D Yes 

12 0.5 0.3 D Yes 

13 0.5 0.5D Yes 

14 0.5 0.8 D Yes 

15 0.5 0.1 D Yes 

16 0.5 0.3 D Yes 

17 0.5 0.5D Yes 

18 0.5 0.8 D Yes 

19a

 0.5 ~1.5 D Yes 

20a

 0.5 ~2.5 D Yes 

21 1.25 0.1 D Yes 

22 1.25 0.3 D Yes 

23 1.25 0.5D Yes 

24 1.25 0.8 D Yes 

25a

 1.25 ~1.5 D Yes 

26a

 1.25 ~2.5 D Yes 

27 2.0 0.1 D Yes 

28 2.0 0.3 D Yes 

29 2.0 0.5D Yes 

30 2.0 0.8 D Yes 

31a

 2.0 ~1.5 D Yes 

32a

 2.0 ~2.5 D Yes 

33b

 -0.1 ~1.5 D Yes 

34b

 -0.1 ~2.5 D Yes a

 Manhole is surcharged. b

 Flow meter installed backwards, pipe slope set negative, surcharged conditions.

29 
Table 3-3. Test Conditions and Sequence: 42-inch Test Pipe 

Uniform flow Nonuniform flow 

Pipe slope (downstream­ (downstreamRun number (percent) Water depth uncontrolled) controlled) 

1 0.2 0.1 D Yes 

2 0.2 0.3 D Yes 

3 0.2 0.5 D Yes 

4 0.2 0.8 D Yes 

5 0.2 0.1 D Yes 

6 0.2 0.3 D Yes 

7 0.2 0.5D Yes 

8 0.2 0.8 D Yes 

9a

 0.2 ~1.5 D Yes 

10a

 0.2 ~2.5 D Yes 

11b

 0.2 0.1 D Yes 

12b

 0.2 0.7 D Yes 

13b

 0.2 ~1.5 D Yes 

14c

 0.2 0.1D Yes 

15c

 0.2 0.3D Yes 

16c

 0.2 0.8D Yes 

17d

 0.2 0.1D Yes 

18d

 0.2 0.3D Yes 

19d

 0.2 0.8D Yes a Manhole is surcharged. b

 Silt simulation test. c

 Grease build-up test with 0.5-mm grease layer. 

d

 Grease build-up test with 2.0-mm grease layer.

3.1.7 Data Management and Analysis 

All raw data, notes, observations, and test descriptions were recorded using Microsoft Excel. 

Reference values for flow, depth, and velocity were calculated for each test run. These reference 

values provided the basis for determining the accuracy of the values from the flow meter output. 

The reference flow value for each run was the arithmetic average of the flow at the beginning 

and at the end of logging period, as determined using the calibrated master venturi meter or 

weigh tank. 

The reference depth value for each run was the arithmetic average of the depth at the beginning 

and at the end of the logging period, as determined using precision point gauges. 

30 
The reference velocity value for each run was the arithmetic average of the velocity values 

calculated from the depth and flow measurements taken at the beginning and end of the logging 

period. 

Meter output of flow, depth, and velocity was recorded in the Microsoft Excel spreadsheet for 

each of the five one-minute samples. When no data was available, the one-minute sample field 

was left blank. An average of the five one-minute samples was made to indicate the five-minute 

average for the meter. 

3.1.8 Quality Assurance 

The Utah State University Research Foundation has an active quality control program at UWRL. 

Flow meter manufacturers and nuclear power plants regularly audit the laboratory for quality 

assurance. Under the laboratory quality assurance program, equipment is calibrated for accuracy 

on a scheduled cycle or occasionally as-needed. Instrumentation calibrations are normally 

subcontracted to outside organizations, although some are performed using the calibration 

facilities at the laboratory itself. Where applicable, calibrations indicate traceability to NIST. All 

laboratory instrumentation that was used during this testing program was calibrated prior to 

performing verification tests. Calibration sheets for all applicable instrumentation are provided in 

Appendix A. The laboratory master venturi flow meters were used during most of the test 

program as the reference flow measurement. These venturi meters have uncertainties less than 

0.25 percent, which falls within the desired accuracy for the measurement. 

3.2 Test Results 

3.2.1 Preliminary Test Measurements 

Prior to each test series the geometry of the test pipe and location of the vendor instrument 

within the pipe were measured and documented. Figure 3-12 shows the size and location of the 

access hole in each of the three test set-ups and establishes the location of the ADS stainless steel 

mounting ring for each test set-up. Tables 3-4 through 3-6 summarize the preliminary 

information recorded for each pipe size. The reference inside-pipe-diameter measurements were 

made using precision calipers at the location in the pipe where the flow meter sensors were 

installed. Measurements were made in four directions and averaged (every 45 degrees). Only 

three measurements were made in the 10-inch pipe because it was quite round. The time required 

to install and set up the flow meter was also recorded. 

31 
Dimension A is the distance from the access 

hole to the opening inside the manhole. 

Dimension B is the distance from the 

opening inside the manhole to the leading 

edge of the sensor band. 

Access Hole 

10-Inch Access Hole 7 5/8W x 5 7/8L 

A (inches) 7 5/8 

B (inches) 2 1/8 Meter Sensors 

Flow Direction 

Manhole 

B 

A 

20-Inch Access Hole 13 13/16W x 11 7/8L 

A (inches) 13 

B (inches) 8 1/4 

42-Inch Access Hole 29 3/4W x 23 7/8L 

A (inches) 16 1/2 

B (inches) 11 1/2 

(Note: All dimensions are in inches) 

Figure 3-12. Sensor installation locations. 

Table 3-4. Preliminary ADS 3600 10-inch Pipe Test Measurements 

Meter (monitor) serial number: 02527 

Ultrasonic serial number: 16405 

Velocity sensor serial number: 11652 

Pressure transducer serial number: 8710 

Test size: 10-inch 

Test dates: 5/2/01 to 5/11/01 

Sensor location U.S. of manhole opening: 2.125 in. 

Straight pipe U.S. of manhole: 63.9 ft 

Straight pipe D.S. of manhole: 28.7 ft 

Three pipe inside diameter measurement: 10.285 in., 10.29 in., 10.27 in. 

Average pipe inside diameter: 10.282 in. 

ADS pipe diameter measurement: 10.250 in. 

Pipe invert point gauge reference: 1.731 ft 

Time required to install the sensor: 15 min 

Time required to set up the sensor: 90 min 

Calibration performed by: Steven Barfuss, Randy Geldmacher, Tyler Smith 

Vendor technicians: Keith Waites, Christy Kennamer 

32 
Table 3-5. Preliminary ADS 3600 20-inch Pipe Test Measurements 

Meter (monitor) serial number: 02527 

Ultrasonic serial number: 16405 

Velocity sensor serial number: 11652 

Pressure transducer serial number: 8710 

Test size: 20-inch 

Test dates: 5/30/01 to 6/4/01 

Sensor location U.S. of manhole opening: 8.25 in. 

Straight pipe U.S. of manhole: 74.0 ft 

Straight pipe D.S. of manhole: 17.6 ft 

Four pipe inside diameter measurement: 19.435 in., 19.555 in., 19.615 in., 

19.553 in. 

Average pipe inside diameter: 19.535 in. 

ADS pipe diameter measurement: 19.500 in. 

Pipe invert point gauge reference: 0.907 ft 

Time required to install the sensor: 30 min 

Time required to set up the sensor: 120 min 

Calibration performed by: Steven Barfuss, Randy Geldmacher, Tyler Smith 

Vendor technicians: Jeffrey White, Heather Hackett 

Table 3-6. Preliminary Model 3600 42-inch Pipe Test Measurements 

Meter (Monitor) Serial Number: 02527 

Ultrasonic Serial Number: 16405 

Velocity Sensor Serial Number: 11652 

Pressure Transducer Serial Number: 8710 

Test Size: 42-nch 

Test Dates: 5/30/01 to 6/4/01 

Sensor Location U.S. of manhole opening: 11.5 in. 

Straight Pipe U.S. of manhole: 84.0 ft 

Straight Pipe D.S. of manhole: 36.6 ft 

Four Pipe Inside Diameter Measurement: 3.424 ft, 3.455 ft, 3.437 ft, 3.448 ft 

Average Pipe Inside Diameter: 3.441 ft 

Average Pipe Inside Diameter: 41.292 in. 

ADS Pipe Diameter Measurement: 41.250 in. 

Pipe Invert Point Gauge Reference: -0.100 ft 

Time required to install the sensor: 60 min 

Time required to set up the sensor: 150 min 

Calibration Performed by: Steven L. Barfuss, Randy Geldmacher, Tyler Smith 

Vendor Technicians: Erica Blanken, Gillian Woodward 

33 
3.2.2 Test Data 

The data obtained during testing was compiled in both graphical and statistical formats. The 

graphs are presented in the following sections, while the statistical tables are included in 

Appendix D. The time listed for each run in the statistical tables represents the start time for the 

five-minute logging period. This recorded time was critical to the success of the tests since the 

logged data was retrieved some time after the run was finished. It was necessary to find the 

recorded start time in the logged data to retrieve the corresponding set of five flow, depth, and 

velocity readings. For this reason, the times for the UWRL computer and the laptop computer 

used to log the data from the ADS flow meter were synchronized each day. 

For each run, the data include the pipe slope, desired flow condition, and the date and time when 

the five-minute logging period occurred. Up to five depth measurements were made for each 

logging period. It was usually not required to make all five depth measurements since the 

transverse water surface profiles were normally quite flat. During submerged tests, the depth 

readings in the tables in Appendix D show “FP,” indicating that the pipe was running full. 

Select runs were either not practical or not possible, and are indicated by “NA” in the data tables 

in Appendix D. In some cases, the meter did not record data during a particular one-minute 

interval or a reference depth reading was not made, and hyphens (-) were placed in the table 

when no data was collected. ADS was allowed to re-test certain runs due to changes in the test 

protocol subsequent to the original tests. An “R” following the run number indicates these runs 

in the data tables. 

3.2.2.1 Statistical Data Evaluation 

Deviation is summarized by the various test configurations in Table 3-7. Deviation is calculated 

as the mean of the percentage deviation for each given category. Depth, velocity, and flow data 

for each test run is outlined in Appendix D. 

The tables also contain the 95-percent confidence interval for the deviation data. The equation 

used to establish the confidence bounds is: 

  s  Confidence = x ±  t ×  

 n 

 

Where: 

x = sample mean

s = standard deviation

n = sample size

t = Student's t - distribution with (n − 1) degrees of freedom 

Therefore, the width of the interval is a function of not only the variation in instrument deviation, 

but also the number of test runs in each reported category. In general, the categories with the 

greatest number of runs will show the narrowest confidence intervals. 

34 
Table 3-7. Deviation by Test Configuration: Normal Operating Conditions 

95-percent Pipe size (inches) Deviation (percent) confidence interval 

10 2.8 0.2 – 5.4 

20 7.2 2.4 – 12.0 

42 1.6 -1.8 – 5.0 

Pipe slope (percent) 

0.1 4.9 -1.4 – 11.2 

0.2 1.6 -1.8 – 5.0 

0.5 5.6 1.6 – 9.6 

1.25 4.2 -1.6 – 9.9 

2.0 6.1 -3.8 – 16.1 

Percent full (d/D) 

10 3.6 -9.4 – 16.6 

30 11.1 6.5 – 15.7 

50 3.4 0.2 – 6.7 

80 1.3 -3.1 – 5.6 

150 0.9 0.9 – 2.8 

250 4.8 -5.0 – 14.6 

Condition 

Free flow 2.6 -1.4 – 6.7 

Backwater 5.8 2.9 – 8.7 

All normal conditions 4.5 2.1 – 6.9 

The ADS 3600 was also tested under “abnormal conditions,” defined previously as tests where 

grease was applied to the depth sensor and reverse flow conditions existed. During the tests 

where 0.5 mm of grease was applied to the ultrasonic depth sensors, the mean deviation was 1.9 

percent. When 2.0 mm of grease was applied to the ultrasonic depth sensors, the meter was 

unable to read depth, resulting in zero flow. The mean deviation for reverse flow tests was –72.7 

percent. The grease was not removed significantly by the flow during the grease tests. 

3.2.2.2 Graphical Evaluation of All Flow Data 

The overall accuracy of the ADS flow meter under normal operating conditions is shown in 

Figure 3-13, the plot of measured flow rates versus the laboratory reference. This plot excludes 

tests where grease was applied to the sensors and tests with reverse flow. 

35 
y = 0.9841x 

R2

 = 0.9955 

0 

2,500 

5,000 

7,500 

10,000 

12,500 

15,000 

17,500 

20,000 

22,500 

25,000 

ADS 3600 Flow (GPM) 

Zero deviation reference line (dashed) 

Best fit line (solid) 

0 2,500 5,000 7,500 10,000 12,500 15,000 17,500 20,000 22,500 25,000 

Reference Flow (GPM) 

Figure 3-13. Metered flow rate versus reference flow rate. 

Figure 3-13 was generated using formulas available in Microsoft Excel for characterizing a 

linear trend line. The line is fitted through the origin (y-intercept of zero). The slope of the 

regression line is computed as: 

∑ xy slope = 2

∑ x 

Where: 

x = reference flow rates 

y = ADS flow rates 

The correlation coefficient, r2, is defined as: 

SSE 

r

2 

= 1− SST 

Where: 

SSE is the sum of squares for the error component 

SST is the sum of squares total 

36 
With the slope and correlation coefficient, bias and precision can be calculated. Bias and 

precision are expressed as functions of the slope and correlation coefficient, respectively, using 

the following equations: 

 slope of zero deviation reference line  Bias =  1− × 100%   slope of best fit line 

2  r of zero deviation reference line 

Precision 



1− 

 = × 100%

r

2 of best fit line 

Values of 1.0 for both slope and correlation coefficient would yield results of zero percent for 

both bias and precision, and would indicate a one-to-one relationship between the metered flow 

and the reference flow, with changes in the reference flow accounting for all of the variation in 

the metered flow. 

Evaluation of the ADS 3600 data for the three pipe sizes (10-inch, 20-inch, and 42-inch) under 

normal operating conditions yields a bias of 1.6 percent and precision of 0.45 percent. 

3.2.2.3 Graphical Evaluation of Flow Data by Test Condition 

The flow, depth, and velocity readings, in addition to the average of the readings, are compared 

to the average reference flow, depth, and velocity for each run. The average reference flow, 

depth, and velocity are equal to the mathematical average of the initial and final reference 

measurements made for each run. 

The graphical evaluation of the flow data by test condition is provided in Tables 3-15 through 

3-32. The free flow and backwater data have been differentiated in each figure. The scattergraph figures for slopes of 0.1 percent and 0.5 percent have both free flow and backwater data 

shown on the same figure. Scatter-graph figures for pipe slopes of 1.25 percent and 2.0 percent 

do not have backwater data shown because no backwater data was collected for these slopes. It 

should be noted that the free flow curves are not always smooth. Laboratory personnel attempted 

to eliminate all backwater effects during free flow tests, but in some cases were not able to 

completely eliminate the effect of the valve at the downstream end of the test pipe. As an 

example, Figure 3-16 shows the free flow curve dropping off on the upper end. This shows that 

the velocity was lower than the desired free flow condition, indicating some backwater effect. 

Even though this occurred periodically, it did not affect the test results, since the verification is a 

direct comparison between the reference measurements and the meter data regardless of the flow 

condition. 

Two sets of plots are presented for each pipe size illustrating the deviation from reference flow. 

One series of plots (Figures 3-19, 3-25, and 3-31) show deviation as percent of reference across 

the full range of reference flows. Another series of plots (Figures 3-20, 3-26, and 3-32) show 

flow meter quantities compared to reference quantities. The reference line is the point of equality 

between the ADS flow meter and the reference measurements, where the deviations between the 

37 
two would be zero. The slope and correlation coefficient of the best-fit line are measures of bias 

and precision, respectively, where 1.0 is the ideal value. 

For the tests performed in the 10-inch pipe, Figures 3-15 through 3-18 are scatter-graph plots of 

the free flow and backwater tests, Figure 3-19 shows the deviation from the reference flow, and 

Figure 3-20 is a plot of reference flow versus meter flow. 

For the tests performed in the 20-inch pipe, Figures 3-21 through 3-24 are scatter-graph plots of 

the free flow and backwater tests, Figure 3-25 shows the deviation from the reference flow, and 

Figure 3-26 is a plot of reference flow versus meter flow for all tests. 

For the tests performed in the 42-inch pipe, Figures 3-27 through 3-30 are scatter-graph plots of 

the free flow and backwater tests, Figure 3-31 shows the deviation from the reference flow for all 

tests, and Figure 3-32 is a plot of reference flow versus meter flow. 

3.2.2.4 Data Analysis Discussion 

The protocol outlines the procedure for characterizing flow meter accuracy by calculating 

deviation using the following formula: 

percent deviation (%D) = (XM-XR) / XR x 100% 

Where: 

XM = mean value recorded by test flow meter 

XR = mean reference value 

Calculating deviation as a percent of the reference value can exaggerate the apparent deviation at 

low flows. During low flow conditions, a low absolute |XM-XR| deviation results in a high 

percent (%D) deviation, creating a disproportionate percent deviation bias at low flow 

conditions. 

For example, during the ADS 3600 tests with the 10-inch pipe, test run number 16 recorded a 

test flow meter reading of 99.91 gallons per minute (gpm) and a reference reading of 87.01 gpm. 

This results in an absolute deviation of 12.90 gpm but a percent deviation of 14.83 percent. By 

contrast, test run number 26, which had the highest reference reading for the 10-inch pipe tests at 

1,293.89 gpm, had a corresponding test flow meter reading of 1,274.39 gpm, which computes to 

a larger absolute deviation (19.50 gpm) when compared to test run 16 but a much lower percent 

deviation (-1.51 percent). 

This phenomenon can also be represented graphically. Evaluating the ADS 3600 10-inch pipe 

test runs with an arbitrary “low flow” range of 0–600 gpm, the same data can be expressed on 

two separate plots: absolute deviation and percent deviation. When this is done, the absolute 

deviation data shows a strong correlation in absolute terms despite the relatively high percent 

deviation, as shown in Figure 3-14. 

38 
-10% 

-5% 

0% 

5% 

10% 

15% 

0 200 400 600 800 1000 1200 1400 

Re f e r enc e Fl ow ( GP M ) 

0 

200 

400 

600 

800 

1000 

1200 

1400 

0 200 400 600 800 1000 1200 1400 

Re f e r enc e Fl ow ( GP M ) 

(a) Absolute deviation (b) Percent deviation 

Figure 3-14. ADS 3600 data summary, 10-inch pipe, 0–600 gpm reference flow. 

The percent deviation data is presented in the ETV verification report because it is a common 

statistical method of computing the difference between a measured value and a reference value. 

This statistical anomaly is presented to inform the end-users of flow monitoring equipment that 

using percent deviation data when evaluating the performance of flow monitoring equipment at 

low flows may result in misleading information. During low flow conditions, a flow meter can 

report flow very close to a reference or actual flow but can be off by a disproportionately high 

percent deviation, especially when compared against high flow condition data. This phenomenon 

is reflective of a statistical limitation rather than a flow meter limitation. 

39 
2.50 

Velocity (ft/sec) 

2.00 1.50 1.00 0.50 0.00 

Free Flow Reference Data Free Flow ADS Data Backwater ADS Data Backwater Reference Data 

Free Flow 

Backwater 

10-inch pipe at 0.1% slo

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 

Depth (d/D) 

Figure 3-15. Scatter-graph for 10-inch pipe test at 0.1 percent slope. 

40 
0.00 

0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 

Depth (d/D) 

Velocity (ft/sec) 

Free Flow Reference Data Free Flow ADS Data Backwater ADS Data Backwater Reference Data Free Flow 

Backwater 

10-inch pipe at 0.5% 

Figure 3-16. Scatter-graph for 10-inch pipe test at 0.5 percent slope. 

41
0.00 

1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 

Depth (d/D) 

Velocity (ft/sec) 

Free Flow Reference Data Free Flow ADS Data 

Free Flow 

10-inch pipe at 1.25% 

Figure 3-17. Scatter-graph for 10-inch pipe test at 1.25 percent slope. 

42
0.00 

1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 

Depth (d/D) 

Velocity (ft/sec) 

Free Flow Reference Data Free Flow ADS Data 

Free Flow 

10-inch pipe at 2.0% s

Figure 3-18. Scatter-graph for 10-inch pipe test at 2.0 percent slope. 

43 
-100% 

-80% -60% -40% -20% 

0% 

20% 40% 60% 80% 

100% 

0 100 200 300 400 500 600 700 800 900 1,000 1,100 1,200 

Reference Flow (GPM) 

Deviation (Percent of Reference) 

10-inch Pipe at All Slopes (Normal Flow Co

Figure 3-19. Deviation of meter flow to reference flow for 10-inch pipe. 

44 
Slope = 0.987x 

Correlation = 0.9991 

0 

200 400 600 800 

1000 1200 1400 

0 200 400 600 800 1000 1200 

Reference Flow Rate (GPM) 

Metered Flow Rate (GPM) 

Zero deviation reference line (dashe

Best fit li

10-inch Pipe 

Figure 3-20. Plot of reference flow versus meter flow in 10-inch pipe. 

45 
0.00 

0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 

Depth (d/D) 

Velocity (ft/sec) 

Free Flow Reference Data Free Flow ADS Data Backwater ADS Data Backwater Reference Data 

Free 

Flow 

Backwater 

20-inch pipe at 0.1% 

Figure 3-21. Scatter-graph for 20-inch pipe test at 0.1 percent slope. 

46 
0.00 

1.00 2.00 3.00 4.00 5.00 6.00 7.00 

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 

Depth (d/D) 

Velocity (ft/sec) 

Free Flow Reference Data Free Flow ADS Data Backwater ADS Data Backwater Reference Data 

Free Flow 

Backwater 

20-inch pipe at 0.5% 

Figure 3-22. Scatter-graph for 20-inch pipe test at 0.5 percent slope. 

47 
0.00 

1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 

10.00 

0 0.1 0.2 0.3 0.4 0.5 

Depth (d/D) 

Velocity (ft/sec) 

Free Flow Reference Data Free Flow ADS Data 

Free Flow 

20-inch pipe at 1.25% 

Figure 3-23. Scatter-graph for 20-inch pipe test at 1.25 percent slope. 

48 
12.00 

Velocity (ft/sec) 

10.00 

8.00 6.00 4.00 2.00 0.00 

Free Flow Reference Data Free Flow ADS Data 

Free Flow 

20-inch pipe at 2.0% slop

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 

Depth (d/D) 

Figure 3-24. Scatter-graph for 20-inch pipe test at 2.0 percent slope. 

49
-100% 

-80% -60% -40% -20% 

0% 

20% 40% 60% 80% 

100% 

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 

Reference Flow (GPM) 

Deviation (Percent of Reference) 

20-inch Pipe at All Slopes (Normal Flow Cond

Figure 3-25. Deviation of meter flow to reference flow for 20-inch pipe. 

50 
Slope = 1.0653x 

Correlation = 0.9785 

0 

500 

1000 1500 2000 2500 3000 3500 4000 4500 5000 

0 500 1000 1500 2000 2500 3000 3500 4000 

Reference Flow Rate (GPM) 

Metered Flow Rate (GPM) Zero deviation reference line (d

20 Best fit line (solid) -inch Pipe 

Figure 3-26. Plot of reference flow versus meter flow in 20-inch pipe. 

51
0.00 

1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 

Depth (d/D) 

Velocity (ft/sec) 

Free Flow Reference Data Free Flow ADS Data Backwater ADS Data Backwater Reference Data 

Free Flow 

Backwater 

42-inch pipe at 

Figure 3-27. Scatter-graph for 42-inch pipe test at 0.2 percent slope. 

52 
0.00 

1.00 2.00 3.00 4.00 5.00 6.00 

0 0.2 0.4 0.6 0.8 1 

Depth (d/D) 

Velocity (ft/sec) 

Free Flow Reference Data Free Flow ADS Data 

42-inch pipe at 2.0% slope with simulated silt 

Figure 3-28. Scatter-graph for 42-inch pipe test at 0.2 percent slope with silt. 

53 
0.00 

1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 

Depth (d/D) 

Velocity (ft/sec) 

Free Flow Reference Data Free Flow ADS Data 

0.5 mm 

Grease 

42-inch pipe at 2.0% slope with 0.5 mm g

Figure 3-29. Scatter-graph for 42-inch pipe test at 0.2 percent slope with 0.5mm grease. 

54 
0.00 

1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 

0 0.2 0.4 0.6 0.8 1 

Depth (d/D) 

Velocity (ft/sec) 

Free Flow Reference Data Free Flow ADS Data 

2mm 

Grease 

42-inch pipe at 2.0% slope with 2.0 mm grea

Figure 3-30. Scatter-graph for 42-inch pipe test at 0.2 percent slope with 2.0mm grease. 

55 
-100% 

-80% -60% -40% -20% 

0% 

20% 40% 60% 80% 

100% 

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 

Reference Flow (GPM) 

Deviation (Percent of Reference) 

42-inch Pipe at All Slopes (Excluding Gre

Figure 3-31. Deviation of meter flow to reference flow for 42-inch pipe. 

56 
Slope = 0.9757x 

Correlation = 0.9956 

0 

5000 

10000 15000 20000 25000 30000 

0 5000 10000 15000 20000 25000 

Reference Flow Rate (GPM) 

Metered Flow Rate (GPM) Best fit line (solid) 

Zero deviation reference line (dashed) 

42-inch Pipe 

Figure 3-32. Plot of reference flow versus meter flow in 42-inch pipe. 

57
Appendices 

A Laboratory Equipment Calibrations and Information 

B Raw Laboratory Test Notes and Data 

C Operational Procedure and Data Logging Method 

D Laboratory Test Data 

58
Glossary 

Accuracy - a measure of the closeness of an individual measurement or the mean of a number of 

measurements to the true value and includes random error and systematic error. 

Bias - the systematic or persistent distortion of a measurement process that causes errors in one 

direction. 

Comparability – a qualitative term that expresses confidence that two data sets can contribute to 

a common analysis and interpolation. 

Completeness – a qualitative term that expresses confidence that all necessary data have been 

included. 

Precision - a measure of the agreement between replicate measurements of the same property 

made under similar conditions. 

Protocol – a written document that clearly states the objectives, goals, scope, and procedures for 

the study. A protocol shall be used for reference during vendor participation in the verification 

testing program. 

Quality Assurance Project Plan – a written document that describes the implementation of 

quality assurance and quality control activities during the life cycle of the project. 

Representativeness - a measure of the degree to which data accurately and precisely represent a 

characteristic of a population parameter at a sampling point, a process condition, or 

environmental condition. 

Wet Weather Flows Stakeholder Advisory Group - a group of individuals consisting of any or 

all of the following: buyers and users of flow monitoring technologies, developers and vendors, 

consulting engineers, the finance and export communities, and permit writers and regulators. 

Standard Operating Procedure – a written document containing specific procedures and 

protocols to ensure that quality assurance requirements are maintained. 

Technology Panel - a group of individuals with expertise and knowledge of flow monitoring 

technologies. 

Testing Organization – an independent organization qualified by the Verification Organization 

to conduct studies and testing of flow monitoring technologies in accordance with protocols and 

Test Plans. 

Vendor – a business that assembles or sells flow monitoring equipment. 

Verification – to establish evidence on the performance of flow monitoring technologies under 

specific conditions, following a predetermined study protocol(s) and test plan(s). 

59
Verification Organization – an organization qualified by EPA to verify environmental 

technologies and to issue verification statements and verification reports. 

Verification Report – a written document containing all raw and analyzed data, all quality 

assurance/quality control (QA/QC) data sheets, descriptions of all collected data, a detailed 

description of all procedures and methods used in the verification testing, and all QA/QC results. 

The test plan(s) shall be included as part of this document. 

Verification Statement – a document that summarizes the Verification Report reviewed and 

approved and signed by EPA and NSF. 

Verification Test Plan – a written document prepared to describe the procedures for conducting 

a test or study according to the verification protocol requirements for the application of flow 

monitoring technology. At a minimum, the test plan shall include detailed instructions for 

sample and data collection, sample handling and preservation, precision, accuracy, goals, and 

QA/QC requirements relevant to the technology and application. 

60