STANDARD
ATV - A 128E
Standards for the Dimensioning
and Design of Stormwater Structures
in Combined Sewers
April 1992
ABWASSER • ABFALL • GEWÄSSERSCHUTZ
GERMAN ASSOCIATION FOR THE WATER ENVIRONMENT
W A S T E W A T E R - W A S T E
STANDARD
ATV - A 128E
Standards for the Dimensioning
and Design of Stormwater Structures
in Combined Sewers
April 1992
ISBN 3-934984-17-7
ATV-A 128 E
2 December 1992
The ATV ad hoc Working Group 1.9.1/1.9.3 in the ATV Specialist Committee 1.9 "Assessment and Treatment of Stormwater Discharge", who prepared this ATV Standard A 128, is made up from the following members:
Dr.-Ing. Göttle, Kempten, (Chairman) Prof. Dr.-Ing. Brunner, Karlsruhe Dr.-Ing. Durchschlag, Bochum Dipl.-Ing. Freund, Wiesbaden Prof. Dr.-Ing. Geiger, Essen Dr.-Ing. Gniosdorsch, Frankfurt Dipl.-Ing. Jacobi, Darmstadt Dr.-Ing. Meißner, München Dipl.-Ing. Pawlowski, Berlin Dr.-Ing. Pecher, Erkrath
Dipl.-Ing. Schitthelm, Düsseldorf Dr.-Ing. Schmitt, Kaiserslautern Dipl.-Ing. Sperling, Essen Dr.-Ing. Verworn, Hannover Dipl.-Ing. Willems, Essen Prof. Dr.-Ing. Wolf, Kassel
The Standard presented here has been prepared within the framework of the ATV committee work, taking into account the ATV Standard A 400 "Principles for the Preparation of Rules and Standards" in the Rules and Standards Wastewater/Wastes, in the January. 1994 .version. With regard to the application of the Rules and Standards, Para. 1 of Point 5 of A 400 includes the following statement "The Rules and Standards are freely available to everyone. An obligation to apply them can result for reasons of legal regulations, contracts or other legal grounds. Whosoever applies them is responsible for the correct application in specific cases. Through the application of the Rules and Standards no one avoids responsibility for his own actions. However, for the user, prima facie evidence shows that he has taken the necessary care.
All rights, in particular those of translation into other languages, are reserved. No part of this Standard may be reproduced in any form by photocopy, microfilm or any other process or transferred or translated into a language usable in machines, in particular data processing machines, without the written approval of the publisher.
Gesellschaft zur Förderung der Abwassertechnik e.V. (GFA), Sankt Augustin 1992 German 0riginal produced by: Druck Carl Weyler KG., Bonn
Contents
1 Scope of Application and Terms 7
2 Objective of Stormwater Treatment 7
2.1 Principles 7
2.2 Method of Approach 7
3 Requirements on Stormwater Treatment 8
3.1 Technical Requirements for the Normal Case (Normal Requirements) 8
3.2 Advanced Requirements 9
3.3 Overall Consideration of a Lake or River 9
3.3.1 Common Requirements in the Overall Drainage Area 9 3.3.2 Combined Requirements with Different Surface Waters 10
4 Planning Principles 10
4.1 Reduction of the Amount of Wastewater Produced 10
4.1.1 Rainwater Run-off 10
4.1.2 Domestic and Industrial Wastewater Flow 10
4.1.3 Sewer Infiltration Water Flow 11
4.2 Measures for Wastewater Treatment in the Combined Wastewater System 11 4.2.1 Intermediate Storage of Combined Wastewater 11
4.2.2 Redistribution of Rainfall Run-offs 11
4.2.3 Wastewater Treatment Measures 11
4.3 Structures with Overflow 12
4.3.1 Stormwater Overflows 12
4.3.2 Stormwater Tanks with Overflow 13
4.3.2.1 Stormwater Tanks Retaining the First Flush of Stormwater 14 4.3.2.2 Stormwater Tanks with Overflow for Settled Combined Wastewater 14
4.3.2.3 Composite Tanks 14
4.3.2.4 Sewers with Storage Capacity and Overflow 15
4.3.2.5 Main and By-pass Streams 16
4.3.3 Arrangement of Several Stormwater Tanks with Overflow 19
4.3.3.1 Parallel Stormwater Tanks with Overflow 19
4.3.3.2 Series Stormwater Tanks with Overflow 20
4.3.4 Stormwater Holding Tanks 20
5 Planning Scope 21
5.1 Determination of Actual Status 21
5.2 Determination of the Planning Status 21
5.3 Planning Periods 21
5.4 Standard and Variant Investigations 22
6 Calculation Principles 22
6.1 Sizes of Catchment Areas 22
6.1.1 Annual Precipitation hPr 22
6.1.2 Surface Areas ACA and Ais 22
ATV-A 128 E
4 December 1992
6.2 Discharges 23
6.2.1 Combined Wastewater Discharge to the Sewage Treatment Plant Qcw 23
6.2.2 Dry weather Flow in Daily Average Qdw24 24
6.2.3 Hourly Peak Flow with Dry Weather Flow Qdwx 24
6.2.4 Rainwater Run-off from Separate Areas QrS24 25
6.2.5 Rainwater Run-off Qr24 25
6.2.6 Critical Rainwater Run-off Qrcrit 25
6.2.7 Critical Combined Water Flow Qcrit 25
6.2.8 Mean Rainwater Run-off During Overflow Qro 26
6.3 Discharge Rates 26
6.3.1 Dry Weather Discharge Rate qdw24 26
6.3.2 Rainwater Run-off Rate qr 26
6.4 Dry Weather Concentration cdwc 27
6.5 Mean Mix ratio in Overflow Water m 27
7 Determination of the Necessary Total Storage Volume 27
7.1 Determination of the Permissible Overflow Rate 27
7.1.1 Influence of Heavy Polluters ap 28
7.1.2 Influence of Annual Precipitation ah 28
7.1.3 Influence of Sewer Deposits aa 29
7.1.4 Dimensioning Concentration in the Dry Weather Flow cd 30
7.1.5 Theoretical Overflow Concentration ccc 30
7.1.6 Permissible Annual Overflow Rate eo 30
7.2 Necessary Total Storage Volumes 32
7.3 Accountable Storage Volumes 33
7.4 Minimum Storage Volumes 33
8 Dimensioning of Individual Structures with Overflow 34
8.1 Simplified Distribution Method 34
8.1.1 Approach 34
8.1.2 Scope of Application 34
8.2 Verification Procedures 35
8.2.1. Special Basic Facts 35
8.2.1.1 Precipitation Loading 35
8.2.1.2 Registration of the Sewer Network 35
8.2.1.3 Fictitious Central Tanks 36
8.2.2 Approach 36
8.2.2.1 Preliminary Calculation to Determine Permissible, Model-Dependent,Overflow Loads 36 8.2.2.2 Determination of the Rehabilitation Requirement 37
8.2.2.3 Planning of Measures 37
8.2.2.4 Further Verification Parameters 38
8.2.3 Requirements on Pollution Load Calculation Methods 38
9 Dimensioning of Individual Structures with Overflow 39
9.1 Stormwater Overflow 39
9.3 Sewer with Storage Capacity and Overflow 42 9.3.1 Sewer with Storage Capacity with Top-end Overflow 42 9.3.2 Sewer with Storage Capacity with Bottom-end Overflow 42
9.4 Stormwater Holding Tanks 42
10 Construction and Operation of Structures With Overflow 43
10.1 Stormwater Overflows 43
10.1.1 General 43
10.1.2 Method of Construction of Stormwater Overflows with Overflow Weirs 44 10.1.3 Method of Construction of Stormwater Overflows with Floor Opening
(Spring Overflow) 45
10.2 Stormwater Tanks with Overflow 46
10.2.1 Method of Construction of Separation Structures and Overflows 46 10.2.2 Method of Construction of Stormwater Tanks with Overflow 47 10.2.3 Method of Construction of Sewers with Storage Volume 48
10.2.4 Method of Construction for Discharges 48
10.3 Maintenance and Operation 49
10.3.1 Maintenance Facilities 49
10.3.2 Cleaning and Flushing Facilities 50
10.3.3 Measurement Facilities 50
10.3.4 Other Records 50
11 Dimensioning Example 50
11.1 Local Situation 50
11.2 Necessary Total Storage Volumes 52
11.2.1 Simplified Distribution Procedure 53
11.2.2 Verification Procedure 53
11.2.2.1 Hydrologic Method 56
11.2.2.2 Hydrodynamic Method 56
11.2.2.3 Presentation of Results 57
11.3 Dimensioning of Stormwater Overflows 58
11.3.1 Stormwater Overflow SO1 in Commercial Area 2 58
11.3.2 Stormwater Overflow SO2 in Sub-area 3 58
12 Terms 59
13 References 60
Appendix 1 64
Notes on Advanced Requirements 64
Protection or Management Need 64
Effects 64
Assessment Criteria 66
Measures 67
ATV-A 128 E
6 December 1992
Appendix 2 68
Pollution Load Calculation Methods 68
2. Hydrologic-Empirical Methods 68
3. Deterministic Models 68
3.1 Hydrologic-Deterministic Models 69
3.2 Hydrologic-Hydrodynamic Models 69
4. Characterisation of Pollution Load Calculation Methods 70
Appendix 3 72
Appendix 4 73
Calculation Formulas for Figs. 12 and 13 73
1
Scope of Application and Terms
These Standards apply for structures with overflows in the overall system of a combined wastewater sewer system within the catchment area of sewage treatment plants. It replaces the previous ATV Standard A 128 from 1977/1.
Structures with overflows in combined systems are structures with an overflow into a lake or river such as, for example, stormwater overflows (SO), stormwater tanks with overflows (STO) and sewers with storage capacity and overflow (SSCO).
Stormwater holding tanks (SHT) are dealt with in ATV Standard A 117.
Stormwater sedimentation tanks (SST) serve for the treatment of stormwater with separate systems. They are also not dealt with here. Information is given in the ATV Working Report in "Korrespondenz Abwasser" (1980), Vol. 1.
2
Objective of Stormwater Treatment
For water management and cost reasons the priority task of the planning of measures for wastewater collection and stormwater treatment is the avoidance of stormwater overflow into the sewer system wherever this is possible. For the remaining discharges, for technical water management and economic reasons, stormwater structures with overflow are located in combined wastewater sewers.
With precipitation run-off, high pollutant loads can occur which, with discharge into lakes and rivers, could load these heavily. Although the loadings appear only temporarily these can exceed those from the effluents of sewage treatment plants several times over during rainfall run-off. The task of stormwater treatment is so to limit the rainfall run-off into the sewage treatment plants that there the desired effluent values are maintained and, at the same time, the surge-type loadings of the lakes and rivers remain within acceptable limits. The aim of stormwater treatment must be the best possible reduction of the total emissions from stormwater overflows and sewage treatment plants within the scope of water management requirements. An effective protection of lakes and rivers and of sewage treatment plants from excessive loadings is to be expected if the necessary stormwater treatment takes place according to the criteria of these Standards.
2.1
Principles
The objective can be achieved with various formulations - from discharge avoidance to substance retention. Stormwater overflows are fundamentally to be assessed together with the sewage treatment plant for interrelated catchment areas of a section of a lake or river. Requirements on the sewage treatment plant run-offs and on the stormwater overflow installations should be matched in their effectiveness for the lake or river.
The regional and network specific quantities precipitation, flow time, gradients, sewage storage capacity, heavy pollutants and areas drained with a separate system have a considerable influence on the overflow quantity and concentration. These are therefore taken into account.
2.2
Method of Approach
Having taken into account the given possibilities of discharge reduction or discharge avoidance, both prerelieved and non-prerelieved overflow structures are to be dimensioned for the remaining discharges. The effectiveness of a stormwater treatment here depends not only on the available storage volume but also particularly on the arrangement, design and operation of the installations (Chaps. 4 and 5).
Basically, there two procedures available for the dimensioning and verification of the objective of the stormwater treatment:
- simplified dimensioning procedure using diagrams (Chap. 8.1), - verification procedure using pollutant load lculations (Chap. 8.2).
