Publication No. FHWA-NHI-01-007 February 2001 U.S. Department of Transportation Federal Highway Administration Hydraulic Engineering Circular No. 24 HIGHWAY STORMWATER PUMP STATION DESIGN Technical Report Documentation Page 1. Report No. 2. Governmental Accession No. 3. Recipient's Catalog No. 4. Title and Subtitle 5. Report Date Highway Stormwater Pump Station Design February 2001 Hydraulic Engineering Circular 24 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. Peter N. Smith 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Parsons Brinckerhoff 11. Contract or Grant No. Barton Oaks Plaza Two 901 Mopac Expressway South, Suite 595 DTFH61-97-C-00033 Austin, TX 78746 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Federal Highway Administration Final Report Office of Bridge Technology Applications, HIBT-20 14. Sponsoring Agency Code 400 Seventh Street, SW., Room 3203 Washington, D.C. 20590 15. Supplementary Notes FHWA COTR: Arlo Waddoups (Ayres Associates) formerly of FHWA Technical Assistance: Philip Thompson, Johnny Morris (Ayres Associates), Dan Ghere (Illinois DOT), 16. Abstract This circular provides a comprehensive and practical guide for the design of stormwater pump station systems associated with transportation facilities. Guidance is provided for the planning and design of pump stations which collect, convey, and discharge stormwater flowing within and along the right-of-way of transportation systems. Methods and procedures are given for determining cumulative inflow, system storage needs, pump configuration and selection, discharge system size, and sump dimensions. Pump house features are identified and construction and maintenance considerations are addressed. Additionally, considerations for retrofitting existing storm water pump stations are presented. 17. Key Words 18. Distribution Statement Pump Station, Pumps, Storm Drain, This document is available to the public from Stormwater Management, Hydraulic, National Technical Information Service, Hydraulic Engineering Circular, HEC, Springfield, Virginia 22151 Highway Hydraulic Design 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price Unclassified Unclassified 218 Form DOT F 1700.7 (8-72)Reproduction of completed page authorized This page intentionally left blank. Table of Contents 1. INTRODUCTION 1-1 1.1 Need For Stormwater Pump Stations 1-1 1.2 Intent of Manual 1-1 1.3 Organization of Manual 1-1 1.4 Unit Convention 1-1 1.4.1 SI versus Metric 1-1 1.4.2 Caution on Unit Usage 1-1 2. PUMP STATION COMPONENTS 2-1 2.1 Introduction 2-1 2.2 Collection System 2-1 2.3 Storage Unit 2-1 2.4 Wells 2-2 2.5 Pumps 2-2 2.6 Pump Controls 2-2 2.7 Pump Drivers 2-2 2.8 Station Housing 2-2 2.9 Sump Pump 2-3 2.10 Power Supply 2-3 2.11 Security and Access Features 2-3 2.11.1 Security 2-3 2.11.2 Access 2-4 2.12 Other Features 2-4 2.12.1 Hoists 2-4 2.12.2 Trash Racks 2-4 3. PUMPS AND PUMP STATION TYPES 3-1 3.1 Introduction 3-1 3.2 Classification of Pumps 3-1 3.2.1 Dynamic Pumps 3-1 3.2.2 Positive Displacement Pumps 3-1 3.3 Impeller Types 3-1 3.3.1 Axial-Flow Pumps 3-2 3.3.2 Radial-Flow Pumps 3-2 3.3.3 Mixed-Flow Pumps 3-2 3.3.4 Propeller versus Impeller 3-3 3.3.5 Comparison of Impeller Types 3-3 3.4 Pumps For Stormwater Use 3-3 3.4.1 Submersible Pumps 3-3 3.4.2 Vertical Shaft Pumps 3-4 3.4.3 Horizontal Pumps 3-6 3.5 Wet-Pit Stations 3-7 3.5.1 Vertical Pumps in Rectangular Wells 3-7 i 3.5.2 Vertical Pumps in Circular Wells 3-12 3.5.3 Submersible Pumps in Rectangular Wells 3-13 3.5.4 Submersible Pumps in Circular Wells 3-15 3.6 Dry-Pit Stations 3-18 3.6.1 Dry Well 3-18 3.6.2 Wet Well for Dry-Pit Station 3-19 3.6.3 Storage Unit 3-19 3.7 Comparison of Pit Types 3-19 3.7.1 Dry-Pit Station 3-19 3.7.2 Wet-Pit Station 3-20 3.8 Station Type Selection 3-20 3.9 Debris and Sediment Handling 3-20 4. PUMP STATION DESIGN PROCESS 4-1 4.1 Introduction 4-1 4.2 Overview of Pump System Hydraulic operation 4-1 4.3 Pump System Design Objectives 4-2 4.4 Pump Station Design Process Flowchart 4-2 4.5 Planning Phase 4-5 4.5.1 General Planning Considerations 4-5 4.5.2 Level of Effort for Planning 4-5 4.6 Schematic Development Phase 4-6 4.6.1 Data Collection 4-6 4.6.2 Evaluation of General Facility Design Criteria and Constraints 4-6 4.6.3 Evaluation of Alignment Alternatives and Value Engineering 4-7 4.6.4 Roadway Profile Guidelines 4-8 4.7 Design Phase 4-8 4.8 Development of Plans, Specifications and Estimates 4-12 4.8.1 Layouts and Details 4-12 4.8.2 Specifications, Provisions and General Notes 4-12 4.8.3 Design Review 4-12 4.9 Construction and Testing 4-13 4.10 Operation and Maintenance Phase 4-13 4.11 Retrofitting Stage 4-13 5. SITE PLANNING AND HYDROLOGY 5-1 5.1 Introduction 5-1 5.2 Considerations for Site Planning 5-1 5.2.1 Drainage Area 5-1 5.2.2 Proximity 5-2 5.2.3 Site Access 5-3 5.2.4 Power Sources 5-5 5.2.5 Storage 5-5 5.2.6 Environmental Quality 5-5 5.2.7 Safety 5-6 5.2.8 Security 5-7 5.2.9 Utilities 5-7 ii 5.2.10 Soil Investigations 5-7 5.3 Hydrologic Considerations and Criteria 5-7 5.3.1 Premise for Design 5-7 5.3.2 Design Frequency 5-8 5.3.3 Check Frequency 5-8 5.4 Design Hydrograph 5-8 5.4.1 Hydrologic Methods 5-9 5.5 Procedure to Determine Mass Inflow 5-10 6. STORAGE SYSTEM 6-1 6.1 Introduction 6-1 6.2 Storage Components 6-1 6.3 Storage Concepts 6-1 6.3.1 Storage Potential 6-1 6.3.2 Storage Design Philosophies 6-2 6.3.3 Available Storage 6-3 6.3.4 Procedure to Estimate Total Available Storage Required 6-3 6.4 Collection System 6-4 6.4.1 Procedure to Establish Collection System 6-5 6.5 Maximum Highwater Elevation 6-5 6.5.1 Roadway Low Point 6-5 6.5.2 Hydraulic Grade Line 6-5 6.5.3 Procedure to Determine Allowable Highwater in Wet Well 6-6 6.6 Wet Well System 6-6 6.6.1 Procedure to Select Preliminary Wet Well Dimensions 6-7 6.7 Storage Unit 6-7 6.8 Storage Calculations 6-8 6.8.1 Sloping Conduit 6-9 6.8.2 Example of Storage in a Sloping Pipe 6-10 6.8.3 Procedure to Establish Storage Unit Dimensions 6-11 6.8.4 Procedure to Develop Stage-Storage Curve 6-12 7. PUMP CONFIGURATION AND MASS CURVE ROUTING 7-1 7.1 Introduction 7-1 7.2 Criteria and Considerations for Pump Configurations 7-1 7.2.1 Number of Pumps 7-1 7.2.2 Size of Pumps 7-1 7.2.3 Pump Sequencing 7-1 7.2.4 Pump Switching Elevations 7-2 7.2.5 Procedure to Estimate Capacity and Number of Pumps 7-3 7.2.6 Pump Cycling 7-4 7.2.7 Allowable Minimum Cycling Time 7-4 7.2.8 Usable Storage 7-5 7.2.9 Pump Cycling Time 7-5 7.2.10 Usable Storage Calculations 7-9 7.2.11 Procedure to Determine Trial Switching 7-12 7.3 Mass Curve Routing 7-15 iii 7.3.1 Procedure to Perform Mass Curve Routing 7-16 7.3.2 Procedure to Check Routing Mass Curve 7-17 8. DISCHARGE LINE AND PUMP SELECTION 8-1 8.1 Discharge Line Components 8-1 8.1.1 Basic Line 8-1 8.1.2 Manifold System 8-1 8.1.3 Design Size 8-1 8.1.4 Procedure to Determine Discharge Pipe Size 8-2 8.1.5 Pump Discharge Pipe Material and Configuration Guidelines 8-2 8.1.6 Appurtenances 8-4 8.1.7 Preventing Reverse Flow 8-6 8.1.8 Hydraulic Transients 8-6 8.1.9 Accessories 8-6 8.1.10 Valves 8-6 8.1.11 Flap Gates and Flap Valves 8-8 8.1.12 Outfall 8-10 8.1.13 Friction Loss Equations 8-11 8.1.14 Appurtenance Energy Losses 8-13 8.2 Total Dynamic Head and System Curve 8-15 8.2.1 Total Dynamic Head 8-15 8.2.2 System Head Curve 8-16 8.2.3 Procedure to Determine System Curves 8-17 8.3 Pump Characteristics 8-21 8.3.1 Cavitation 8-21 8.3.2 Vortexing 8-21 8.3.3 Net Positive Suction Head Required 8-22 8.3.4 Net Positive Suction Head Available 8-22 8.3.5 Net Positive Suction Head Margin 8-23 8.3.6 Submergence 8-24 8.3.7 Specific Speed 8-24 8.3.8 Suction Specific Speed 8-24 8.3.9 Selection of Impeller Type 8-25 8.3.10 Pump Performance 8-25 8.3.11 Design Point and Operation Range 8-27 8.3.12 Example of Pump Selection 8-29 8.3.13 Procedure to Select Manufacturer’s Pumps and Discharge Piping 8-29 8.3.14 Pump Bell/Intake Diameter 8-32 8.3.15 Power and Efficiency 8-32 9.