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Embankment Dams Design Standards No. 13 Embankment Dams Chapter 21: Water Removal and Control: Dewatering and Unwatering Systems Phase 4 Final U.S. Department of the Interior Bureau of Reclamation September 2014 Mission Statements The U.S. Department of the Interior protects America’s natural resources and heritage, honors our cultures and tribal communities, and supplies the energy to power our future. The mission of the Bureau of Reclamation is to manage, develop, and protect water and related resources in an environmentally and economically sound manner in the interest of the American public. Design Standards Signature Sheet Design Standards No. 13 Embankment Dams DS-13(21): Phase 4 Final September 2014 Chapter 21: Water Removal and Control: Dewatering and Unwatering Systems Foreword Purpose The Bureau of Reclamation (Reclamation) design standards present technical requirements and processes to enable design professionals to prepare design documents and reports necessary to manage, develop, and protect water and related resources in an environmentally and economically sound manner in the interest of the American public. Compliance with these design standards assists in the development and improvement of Reclamation facilities in a way that protects the public's health, safety, and welfare; recognizes needs of all stakeholders; and achieves lasting value and functionality necessary for Reclamation facilities. Responsible designers accomplish this goal through compliance with these design standards and all other applicable technical codes, as well as incorporation of the stakeholders’ vision and values, that are then reflected in the constructed facilities. Application of Design Standards Reclamation design activities, whether performed by Reclamation or by a non- Reclamation entity, must be performed in accordance with established Reclamation design criteria and standards, and approved national design standards, if applicable. Exceptions to this requirement shall be in accordance with provisions of Reclamation Manual Policy, Performing Design and Construction Activities, FAC P03. In addition to these design standards, designers shall integrate sound engineering judgment, applicable national codes and design standards, site-specific technical considerations, and project-specific considerations to ensure suitable designs are produced that protect the public's investment and safety. Designers shall use the most current edition of national codes and design standards consistent with Reclamation design standards. Reclamation design standards may include exceptions to requirements of national codes and design standards. Proposed Revisions Reclamation designers should inform the Technical Service Center (TSC), via Reclamation’s Design Standards Website notification procedure, of any recommended updates or changes to Reclamation design standards to meet current and/or improved design practices. Chapter Signature Sheet Bureau of Reclamation Technical Service Center Design Standards No. 13 Embankment Dams Chapter 21: Water Removal and Control: Dewatering and Unwatering Systems DS-13(21):1 Phase 4 Final September 2014 Chapter 21 – Water Removal and Control: Dewatering and Unwatering Systems is a new chapter within Design Standards No. 13 and includes: Water Removal and Control Applications for Embankment Dams Dewatering, Unwatering, Pressure Relief and Seepage Control Methods Considerations During the Design Process, and Data Collection and Hydrogeologic Parameter Development Considerations During the System Design, Installation, and Operation and Performance Processes 1 DS-13(21) refers to Design Standards No. 13, chapter 21. Prepared by: Robert Thibot, RE. Date Geologist, Engineering Geology Group, 86-68320 Peer Review: , 7 - t.„ M. Jonathan-Harris, RE. Date Civil Engineer, Geotechnical Engineering Group 3, 86-68313 Security Review: aL51-01 c •ccr7 Robert L. Dewey, RE. Technical Specialist, Geotechnical Engineering Group 3, 86-68313 Rec ended for Technical Approval: Thomas McDaniel, P.E. Date Geotechnical Engineering Group 2, 86-68312 Submitted: ' I/te Karen Knight, RE. Date Chief, Geotechnical Services livision, 86-68300 Approved: Thomas A. Luebke, P.E. Director, Technical Service Center, 86-68010 Contents Page Chapter 21: Water Removal and Control: Dewatering and Unwatering Systems 21.1 Introduction ......................................................................................... 21-1 21.1.1 Purpose .................................................................................. 21-1 21.1.2 Scope .................................................................................. 21-1 21.1.3 Deviations from Standards .................................................... 21-2 21.1.4 Revisions of Standard ............................................................ 21-2 21.1.5 Applicability .......................................................................... 21-3 21.2 Acronyms and Definitions/Terminology ............................................ 21-3 21.2.1 Acronyms .............................................................................. 21-3 21.2.2 Definitions/Terminology ....................................................... 21-4 21.3 Water Removal and Control: Applications for Embankment Dams .......................................................................................... 21-13 21.3.1 General ................................................................................ 21-13 21.3.2 Design and Contracting Considerations .............................. 21-14 21.3.3 Performance Considerations ................................................ 21-15 21.4 Water Removal and Control: Dewatering, Unwatering, Pressure Relief, and Seepage Control Methods .......................... 21-16 21.4.1 General ................................................................................ 21-16 21.4.2 Types of Dewatering Systems ............................................. 21-19 21.4.2.1 Deep Well System......................................... 21-19 21.4.2.2 Well-Point System ........................................ 21-19 21.4.2.3 Eductor Well System (also Eductor-Jet Pump or Jet Pump) .................................. 21-19 21.4.2.4 Sumps ............................................................ 21-19 21.4.2.5 Vertical Sand Drains ..................................... 21-19 21.4.3 Types of Unwatering Systems ............................................. 21-19 21.4.3.1 Sumps ............................................................ 21-19 21.4.3.2 Ditches .......................................................... 21-20 21.4.3.3 Drains ............................................................ 21-20 21.4.3.4 Open Pumping .............................................. 21-20 21.4.3.5 Well Points .................................................... 21-20 21.4.4 Types of Pressure Relief Systems ....................................... 21-20 21.4.4.1 Pressure Relief Well ..................................... 21-20 21.4.4.2 Vacuum Pressure Relief Well ....................... 21-21 21.4.5 Types of Seepage Control Systems ..................................... 21-21 21.4.5.1 Well Points .................................................... 21-21 21.4.5.2 Eductor Systems............................................ 21-21 21.4.5.3 Ditches and Drains ........................................ 21-21 21.4.5.4 Filters and Seals ............................................ 21-21 21.4.6 Cutoff Walls for Groundwater Control ............................... 21-21 21.4.6.1 Sheet Piles ..................................................... 21-21 21.4.6.2 Slurry Trenches ............................................. 21-22 DS-13(21) September 2014 21-i Contents (continued) Page 21.4.6.3 Secant Walls.................................................. 21-22 21.4.6.4 Deep Soil Mixing .......................................... 21-22 21.5 Water Removal and Control: Design Process Considerations ......... 21-22 21.5.1 General Description ............................................................. 21-22 21.5.2 Appraisal Level Design ....................................................... 21-24 21.5.3 Feasibility Level Design ...................................................... 21-24 21.5.4 Final Design ........................................................................ 21-25 21.5.5 Performance Considerations ................................................ 21-26 21.6 Water Removal and Control: Data Collection and Hydrogeologic Parameter Development Considerations .......... 21-26 21.6.1 General Description ............................................................. 21-26 21.6.2 Problem Definition .............................................................. 21-27 21.6.3 Defining Potential Critical Design Parameters ................... 21-28 21.6.4 Field Data Collection: Identifying Needs ........................... 21-29 21.6.4.1 General and Regional Information................ 21-30 21.6.4.2 Construction Plans ........................................ 21-30 21.6.4.3 Surface .......................................................... 21-31 21.6.4.4 Subsurface ..................................................... 21-31 21.6.4.5 Specialized Hydrogeologic Data................... 21-32 21.6.5 Field Exploration Request ................................................... 21-32 21.6.6 Laboratory Testing .............................................................. 21-33 21.6.6.1 Gradation Analysis for Estimating K ............ 21-33 21.6.6.2
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