ASTM C1745/C1745M-24

Standard Test Method for Measurement of Hydraulic Characteristics of Hydrodynamic Stormwater Separators and Underground Settling Devices

SIGNIFICANCE AND USE
5.1 Each device has unique flow patterns and turbulence characteristics. In addition, each device exhibits a wide range of efficiencies as discharge, particle size, particle density, and flow viscosity (that is, water temperature) change. The testing procedure in Section 7 will help develop the parameters necessary to input into a function that describes the performance of a device under a wide range of application conditions. Specifically, this test standard produces a characteristic curve that describes the hydraulic head-discharge relationship in a hydrodynamic separator over a range of flow rates typical in system operation.
SCOPE
1.1 This test method concerns measurement of selected hydraulic characteristics of hydrodynamic separators and underground settling devices critical to their function as stormwater treatment devices.  
1.2 Units tested shall be of a size commonly manufactured and available for purchase. In order to facilitate testing it is permissible to substitute alternate materials for the housing and structural components of the test units if operational components are at full size, with identical dimensions, configurations and materials specified for commercial use. Scale models are not permissible.  
1.3 As each stormwater treatment device is unique in design, so are its hydraulic characteristics (flow versus head and loss coefficients). A sufficient number of accurately measured data points are needed to properly define the hydraulic characteristics of each test unit. Therefore, it is imperative that the unit setup and subsequent testing methodologies be well defined and executed to ensure accurate flow and elevation data.  
1.4 The values stated in inch-pound units are to be regarded as standard, except for methods to establish and report sediment concentration and particle size. It is convention to exclusively describe sediment concentration in mg/L and particle size in mm or µm, both of which are SI units. The SI units given in parentheses are mathematical conversions, which are provided for information purposes only and are not considered standard. Reporting of test results in units other than inch-pound units shall not be regarded as non-conformance with this test method.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Dec-2023
• ICS: 13.060.30 - Sewage water
• Technical Committee: E64 - Stormwater Control Measures
• Drafting Committee: E64.01 - Lab Evaluation

Relations

• Replaces: ASTM C1745/C1745M-18 - Standard Test Method for Measurement of Hydraulic Characteristics of Hydrodynamic Stormwater Separators and Underground Settling Devices
• Effective Date: 01-Jan-2024
• Refers: ASTM E3318-24 - Standard Terminology for Standards Relating to Stormwater Control Measures
• Effective Date: 01-Jan-2024
• Referred By: ASTM E3373-24 - Standard Test Method for Scour of Hydrodynamic Separators and Settling Devices
• Effective Date: 01-Jan-2024
• Referred By: ASTM C1893-23 - Standard Practice for Laboratory Performance Verification of Hydrodynamic Separators for the Treatment of Stormwater Runoff
• Effective Date: 01-Jan-2024

Overview

ASTM C1745/C1745M-24 is the ASTM standard test method for the measurement of hydraulic characteristics of hydrodynamic stormwater separators and underground settling devices. This test method provides a detailed, reproducible procedure for evaluating the hydraulic behavior-such as flow, head loss, and velocity-of such stormwater treatment units under gravity flow conditions. The standard ensures accuracy in testing, facilitates the development of performance curves, and informs the technical selection and specification of devices used in stormwater management systems.

Hydrodynamic separators and underground settling devices play a critical role in stormwater treatment by separating sediments and pollutants from water before it is discharged. Understanding their hydraulic performance is essential to ensure they function effectively under varied real-world conditions.

Key Topics

• Hydraulic Characterization

  • Measurement of flow versus head relationships
  • Determination of head loss and loss coefficients
  • Analysis across a range of flows typical of system operation

• Device Testing

  • Only full-size, commercially available units may be tested (no scale models)
  • Testing may use alternate housing materials if core functional components match commercial specification

• Measurement Parameters

  • Flow, surface water elevation, and water temperature are measured to assess hydraulic performance
  • Precise calibration and setup are required for accuracy

• Test Method Procedural Integrity

  • Pipe diameters, lengths, slopes, and roughness values must mirror realistic installation parameters
  • Both manual and computerized data collection methods are referenced, with a strong preference for computerized data acquisition for continuous monitoring

• Reporting Requirements

  • Detailed reports to include diagrams of setup, measurement locations, and instrument types
  • Presentation of characteristic curves for system head loss versus flow rates

• Units of Measurement

  • Standard values are stated in both inch-pound and SI units; sediment concentrations in mg/L and particle size in mm or μm

Applications

• Stormwater Treatment Design

  • Hydraulic data supports engineers and municipalities in selecting and sizing hydrodynamic separators and underground settling devices for stormwater management
  • Performance curves developed under this method inform modeling and regulatory compliance

• Regulatory Compliance

  • Provides standardized data for authorities reviewing the capabilities of stormwater treatment devices for permitting or approval processes

• Manufacturing and Product Development

  • Enables manufacturers to validate and benchmark the hydraulic efficiency of new or existing designs under consistent testing conditions

• Operational Assurance

  • Facilities and operators can use the results to predict device behavior under a variety of realistic stormwater loading scenarios, thus supporting preventive maintenance and operational optimization

Related Standards

This test method references and aligns with several other established standards, including:

• ASTM D5242 – Open-Channel Flow Measurement of Water with Thin-Plate Weirs
• ASTM D5389 – Open-Channel Flow Measurement by Acoustic Velocity Meter Systems
• ASME MFC-3M – Measurement of Fluid Flow in Pipes Using Orifice, Nozzle, and Venturi
• Other withdrawn standards used for historical reference (e.g., ASTM D4409, D5640)

The approach in ASTM C1745/C1745M-24 is consistent with internationally recognized principles for the development of standards, supporting its applicability in global contexts.

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By adhering to ASTM C1745/C1745M-24, stakeholders in stormwater management can ensure reliable, accurate measurement and reporting of hydraulic characteristics, enabling informed design, regulatory review, and product validation in environmental water treatment applications.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C1745/C1745M − 24
Standard Test Method for
Measurement of Hydraulic Characteristics of Hydrodynamic
Stormwater Separators and Underground Settling Devices
This standard is issued under the fixed designation C1745/C1745M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.6 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This test method concerns measurement of selected
ization established in the Decision on Principles for the
hydraulic characteristics of hydrodynamic separators and un-
Development of International Standards, Guides and Recom-
derground settling devices critical to their function as storm-
mendations issued by the World Trade Organization Technical
water treatment devices.
Barriers to Trade (TBT) Committee.
1.2 Units tested shall be of a size commonly manufactured
and available for purchase. In order to facilitate testing it is
2. Referenced Documents
permissible to substitute alternate materials for the housing and
2.1 ASTM Standards:
structural components of the test units if operational compo-
E3318 Terminology for Standards Relating to Stormwater
nents are at full size, with identical dimensions, configurations
Control Measures
and materials specified for commercial use. Scale models are
not permissible.
3. Terminology
1.3 As each stormwater treatment device is unique in
3.1 Definitions:
design, so are its hydraulic characteristics (flow versus head
3.1.1 For definitions of common technical terms used in this
and loss coefficients). A sufficient number of accurately mea-
standard, refer to Terminology E3318.
sured data points are needed to properly define the hydraulic
3.2 Definitions of Terms Specific to This Standard:
characteristics of each test unit. Therefore, it is imperative that
the unit setup and subsequent testing methodologies be well
NOTE 1—The terms and definitions related to this standard also relate to
defined and executed to ensure accurate flow and elevation
other standards currently being balloted. As such they are being balloted
data. separately in a single terminology document, Terminology E3318.
1.4 The values stated in inch-pound units are to be regarded
4. Summary of Test Method
as standard, except for methods to establish and report sedi-
4.1 This test method describes procedures and equipment
ment concentration and particle size. It is convention to
required to measure the hydraulic characteristics of hydrody-
exclusively describe sediment concentration in mg/L and
namic separators and underground settling devices used for
particle size in mm or μm, both of which are SI units. The SI
treating stormwater runoff.
units given in parentheses are mathematical conversions,
which are provided for information purposes only and are not
5. Significance and Use
considered standard. Reporting of test results in units other
than inch-pound units shall not be regarded as non-
5.1 Each device has unique flow patterns and turbulence
conformance with this test method.
characteristics. In addition, each device exhibits a wide range
of efficiencies as discharge, particle size, particle density, and
1.5 This standard does not purport to address all of the
flow viscosity (that is, water temperature) change. The testing
safety concerns, if any, associated with its use. It is the
procedure in Section 7 will help develop the parameters
responsibility of the user of this standard to establish appro-
necessary to input into a function that describes the perfor-
priate safety, health, and environmental practices and deter-
mance of a device under a wide range of application condi-
mine the applicability of regulatory limitations prior to use.
tions. Specifically, this test standard produces a characteristic
This test method is under the jurisdiction of ASTM Committee E64 on
Stormwater Control Measures and is the direct responsibility of Subcommittee
E64.01 on Lab Evaluation. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Jan. 1, 2024. Published February 2024. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2011. Last previous edition approved in 2018 as C1745/C1745M - 18. Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/C1745-24. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1745/C1745M − 24
curve that describes the hydraulic head-discharge relationship 7.1.1.2 Flow measurements shall be made to a precision of
in a hydrodynamic separator over a range of flow rates typical 1 % of measured flow. The accuracy of the flow measurement
in system operation. shall be within 610 % of the target value for controlled
laboratory testing. The acceptable coefficient of variation of
measurements should not exceed 0.03.
6. Apparatus
7.1.1.3 All flow meters used in this protocol must be
6.1 The test unit shall be set up to reflect actual field
calibrated as required by the instrument manufacturer. Copies
installation parameters to the greatest degree possible. Influent
of flow meter calibrations shall be included in the final report.
and effluent pipes shall be the same diameter and shall be equal
The flow meter data logger must record flows at a minimum of
or less than 25 % of the test unit inside diameter or inside width
once per minute so that samples can be compared to corre-
of the unit, being the smallest measured dimension.
sponding flow rate values. The average flow rate shall be
6.2 The experimental setup includes an influent straight pipe
reported.
(without bends) of minimum length equivalent to ten pipe
7.1.2 Temperature—Tests shall be run at water temperatures
diameters to ensure stable flow conditions upstream from the
not to exceed (80°F). At a minimum, water temperatures shall
test unit. The effluent pipe length is to be from 3 ft to 5 ft long
be recorded three times, at the beginning, the middle, and the
aswith a free-fall condition at its end. No fittings are allowed in
end of each test. The average temperature shall be used in data
the straight pipe with the exception of:
reduction and reporting.
(1) Sediment injection port
(2) Water sampling port(s)
8. Procedure
(3) Fitting connecting the inlet pipe and outlet pipe to the
8.1 All associated instrumentation shall be calibrated to the
test unit
manufacturer’s specification before testing. The flow measure-
(4) Pressure transducer taps and temperature sensors
ment apparatus must be calibrated for the flow or range of
6.3 Pipe slopes for the influent and effluent pipes shall be
flows to be tested. Multiple flow measurement apparatus may
1-2 %.
be required depending on the range of flows to be tested. Flow
6.4 Both influent and effluent pipes shall have smooth,
conditions shall be stable for
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C1745/C1745M − 18 C1745/C1745M − 24
Standard Test Method for
Measurement of Hydraulic Characteristics of Hydrodynamic
Stormwater Separators and Underground Settling Devices
This standard is issued under the fixed designation C1745/C1745M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method concerns measurement of selected hydraulic characteristics of hydrodynamic separators and underground
settling devices critical to their function as stormwater treatment devices.
1.2 Units tested shall be of a size commonly manufactured, not a scale model.manufactured and available for purchase. In order
to facilitate testing it is permissible to substitute alternate materials for the housing and structural components of the test units if
operational components are at full size, with identical dimensions, configurations and materials specified for commercial use. Scale
models are not permissible.
1.3 As each stormwater treatment device is unique in design, so are its hydraulic characteristics (flow versus head and loss
coefficients). A sufficient number of accurately measured data points are needed to define properly define the hydraulic
characteristics of each test unit. Therefore, it is imperative that the unit setup and subsequent testing methodologies be well defined
and executed to ensure accurate flow and elevation data.
1.4 This test method addresses gravity flow operation only. It does not address performance of units operating under pressurized
conditions.
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard.as standard, except for methods to establish and report sediment
concentration and particle size. It is convention to exclusively describe sediment concentration in mg/L and particle size in mm
or μm, both of which are SI units. The SI units given in parentheses are mathematical conversions, which are provided for
information purposes only and are not considered standard. Reporting of test results in units other than inch-pound units shall not
be regarded as non-conformance with this test method.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
This test method is under the jurisdiction of ASTM Committee E64 on Stormwater Control Measures and is the direct responsibility of Subcommittee E64.01 on Lab
Evaluation.
Current edition approved May 1, 2018Jan. 1, 2024. Published May 2018February 2024. Originally approved in 2011. Last previous edition approved in 20112018 as
C1745/C1745M - 11.C1745/C1745M - 18. DOI: 10.1520/C1745_C1745M-18.10.1520/C1745-24.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1745/C1745M − 24
2. Referenced Documents
2.1 ASTM Standards:
D3858E3318 Test Method for Open-Channel Flow Measurement of Water by Velocity-Area MethodTerminology for Standards
Relating to Stormwater Control Measures (Withdrawn 2023)
D4409 Test Method for Velocity Measurements of Water in Open Channels with Rotating Element Current Meters (Withdrawn
2023)
D5089 Test Method for Velocity Measurements of Water in Open Channels with Electromagnetic Current Meters (Withdrawn
2023)
D5242 Test Method for Open-Channel Flow Measurement of Water with Thin-Plate Weirs
D5389 Test Method for Open-Channel Flow Measurement by Acoustic Velocity Meter Systems
D5413 Test Methods for Measurement of Water Levels in Open-Water Bodies
D5640 Guide for Selection of Weirs and Flumes for Open-Channel Flow Measurement of Water (Withdrawn 2023)
2.2 ASME Standard:
MFC-3M Measurement of Fluid Flow in Pipes Using Orifice, Nozzle, and Venturi
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 inlet (or outlet) rounding, n—radius of fillet at inside pipe junction with separator structure.
3.1 Definitions:
3.1.1 For definitions of common technical terms used in this standard, refer to Terminology E3318.
3.2 Definitions of Terms Specific to This Standard:
NOTE 1—The terms and definitions related to this standard also relate to other standards currently being balloted. As such they are being balloted
separately in a single terminology document, Terminology E3318.
4. Summary of Test Method
4.1 This test method describes procedures and equipment required to measure the hydraulic characteristics of hydrodynamic
separators and underground settling devices used for treating stormwater runoff.
4.2 Other standards that may be useful to reference include: Test Methods D3858, D4409, D5089, D5242, D5389, D5413, Guide
D5640, and ASME MFC-3M (see Section 2).
5. Significance and Use
5.1 Each device has unique flow patterns and turbulence characteristics. In addition, each device exhibits a wide range of
efficiencies as discharge, particle size, particle density, and flow viscosity (that is, water temperature) change. The testing procedure
in Section 7 will help develop the parameters necessary to input into a function that describes the performance of a device under
a wide range of application conditions. Specifically, this test standard produces a characteristic curve that describes the hydraulic
head-discharge relationship in a hydrodynamic separator over a range of flow rates typical in system operation.
6. Apparatus
6.1 The test unit shall be set up to reflect actual field installation parameters to the greatest degree possible. Influent and effluent
pipes shall have a Manning’s roughness coefficient not greater than 0.013 be the same diameter and shall be the minimum diameter
recommended by the device manufacturer. Pipe type, diameter, slope (2 to 3 %), orientation, and inlet/outlet roundings shall be
recorded and reported for each test. The influent pipe shall be a minimum of ten pipe diameters in length, or 6 m [20 ft] whichever
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
C1745/C1745M − 24
is less, to ensure a uniform approach flow to the test unit, and an effluent pipe of length equivalent to three pipe diameters with
a free-fall condition at its downstream end. equal or less than 25 % of the test unit inside diameter or inside width of the unit, being
the smallest measured dimension.
6.2 The experimental setup includes an influent straight pipe (without bends) of minimum length equivalent to ten pipe diameters
to ensure stable flow conditions upstream from the test unit. The effluent pipe length is to be from 3 ft to 5 ft long aswith a free-fall
condition at its end. No fittings are allowed in the straight pipe with the exception of:
(1) Sediment injection port
(2) Water sampling port(s)
(3) Fitting connecting the inlet pipe and outlet pipe to the test unit
(4) Pressure transducer taps and temperature sensors
6.3 All components of the experimental setup shall be inspected immediately before any testing to confirm that no damage or
obstruction is present and that there are no sediments or other deleterious materials therein. Leakage in system piping or from the
unit during the test is allowable as long as the leakage rate is less than 0.1 % of the measured flow rate.Pipe slopes for the influent
and effluent pipes shall be 1-2 %.
6.4 Both influent and effluent pipes shall have smooth, non-corrugated interior walls with an accepted Manning’s n value of <0.022
or a roughness of <5 mm.
7. Test Parameters and Methodologies
7.1 Three major parameters shall be measured and recorded for use in establishing a unit’s hydraulic characteristics: flow, surface
water elevations, and water temperature.
7.1.1 Water Surface Elevation—Pressure heads or water elevations shall be recorded to a minimum accuracy of 0.25 in. for each
condition tested to determine the head elevations. The locations of elevation measurements shall be fixed for all flow conditions.
Elevation measurements shall be recorded in the influent and effluent pipes at locations 2 6 0.11-2 6 0.1 pipe diameters upstream
and downstream of the unit using piezometer taps in the pipe inverts. Internal measurements shall be recorded at a location that
allows determination of bypass flow. Measurements are to be r
...