SMALL DAM DESIGN AND CONSTRUCTION MANUAL - pfra.ca

1 SMALL DAM DESIGN AND CONSTRUCTION MANUAL MAY, 1992 Agriculture Canada Prairie Farm Rehabilitation Administration Prairie Resources Service SMALL DAM DESIGN AND CONSTRUCTION MANUAL May, 1992 PREFACE This MANUAL has been developed by PFRA specifically for use by its staff in the DESIGN and CONSTRUCTION of the SMALL dams built under various PFRA water development and conservation programs. The investigation and DESIGN phases and the technical assistance during the CONSTRUCTION of these dams, as described in the MANUAL , are organized based on precedent delivery modes of these programs.

2 The MANUAL relies on the technical skills presently in place in the PFRA district offices and the engineering expertise available in headquarters and the regional offices. Any revisions to the recommended organization of the investigation, DESIGN and CONSTRUCTION roles, made necessary by changes in PFRA programs or redistribution of staff, will be incorporated into the MANUAL through amendments. The MANUAL presents engineering information for the DESIGN , CONSTRUCTION , operation and maintenance of SMALL dams on the Canadian Prairies. Under certain limiting conditions that consider size, potential hazards, CONSTRUCTION materials and level of investment, the MANUAL provides the basis for safe, cost-effective projects which can be designed by qualified engineering technicians or technologists, subject to the review of a qualified professional engineer. The MANUAL is arranged in logical, convenient sections, dealing with investigations, DESIGN , CONSTRUCTION , operation and maintenance, and includes various appendices presenting DESIGN aids and additional information.

3 The text was prepared by an engineering team comprising PFRA engineers under the overall direction of D. H. Pollock, Chief, Technical Resources, Development Service. The text was coordinated and edited by C. R. Campbell. Editorial guidance and review was provided by R. R. Weinberger. Other reviewers included J. Lebedin, F. R. J. Martin, M. Lu and R. E. Lien. The authors and their areas of contribution are: M. Mowchenko - hydrology; J. C. Oosterveen and T. A. Dash - geology; V. Klassen - geotechnical DESIGN , CONSTRUCTION ; and C. Campbell - hydraulic and structural DESIGN , CONSTRUCTION , operation and maintenance. As PFRA cannot satisfy itself that the MANUAL will not at some time be acquired and used inappropriately by others, PFRA shall be under no liability whatsoever to any individual or group using this MANUAL , and makes no warranty concerning the completeness, reliability or suitability of the information contained herein.

4 - i - TABLE OF CONTENTS Page INTRODUCTION General .. 1-1 Application of the MANUAL .. 1-3 Project Concept .. 1-3 Foundations and Embankment Materials .. 1-4 Size Classification .. 1-4 Hazard Potential Classification .. 1-4 DESIGN Responsibility .. 1-5 Project Life Cycle .. 1-6 INVESTIGATIONS General .. 2-1 Hazard Potential .. 2-2 Methods For Determining Hazard Potential .. 2-2 Hazard Potential Assessment.. 2-3 Geology .. 2-7 Classification and Engineering Characteristics of Geological Materials .. 2-7 Common Relationships Among Geologic Unit .. 2-16 Errors in Interpretation of Relationships .. 2-22 Geological Damsite Description .. 2-22 Hydrology.

5 2-29 Flood Potential .. 2-30 General Concepts .. 2-30 Development of Flood Determination Model .. 2-31 Procedures for Flood Peak Determination .. 2-33 Example of Flood Peak Calculation .. 2-35 Uses and Limitations .. 2-36 water Supply Potential .. 2-36 General Concepts .. 2-36 Development of water Supply Determination Procedures .. 2-38 - ii - TABLE OF CONTENTS (Cont'd) Page Procedures for water Supply Potential Determination .. 2-40 Examples of water Supply Potential Calculations .. 2-41 Users and Limitations .. 2-44 Hydrology Summary Report.

6 2-45 Geotechnology .. 2-63 Soil Classification .. 2-63 Laboratory Tests .. 2-63 Identification of Soil Groups .. 2-64 Field Investigations .. 2-70 Reconnaissance Investigations .. 2-70 Subsurface Investigations .. 2-73 Types of Foundations .. 2-76 Geotechnical Assessment .. 2-77 Surveys and Mapping .. 2-89 Site Investigation Guidelines .. 2-91 DESIGN General .. 3-1 DESIGN Inputs .. 3-3 Embankment DESIGN .. 3-4 Description .. 3-4 Criteria and Standards .. 3-4 Methods .. 3-9 Spillway System DESIGN .. 3-15 Description .. 3-15 Criteria .. 3-16 Standard Spillway Structures .. 3-21 Methods .. 3-21 Reservoir Outlet DESIGN .. 3-27 Description .. 3-27 Criteria.

7 3-27 Standard Reservoir Outlet Structures .. 3-28 - iii - TABLE OF CONTENTS (Cont'd) Page Methods .. 3-29 DESIGN Output .. 3-30 CONSTRUCTION General .. 4-1 Earthwork .. 4-2 Quality Control Inspection for Earthwork CONSTRUCTION .. 4-7 Concrete .. 4-16 CONSTRUCTION Supervision and Quality Control Testing .. 4-17 As-Constructed Drawings .. 4-18 OPERATION AND MAINTENANCE General .. 5-1 Operation .. 5-2 Maintenance .. 5-3 Inspection .. 5-4 Operation and Maintenance MANUAL Model .. 5-5 Appendix A Standard Drawings Appendix B Specifications for CONSTRUCTION Appendix C Cost Estimating Appendix D DESIGN Example Appendix E Definitions References Attachments - iv - LIST OF TABLES Table No.

8 Project Hazard Potential Classification Drainability Factors Selection Chart Elevation-Storage-Area Relationship for Standard Reservoir Table of Divertible Flow Factors Soil Classification and Description Chart Auxiliary Laboratory Identification Procedure Classification of Foundations and Embankment Materials for Homogeneous SMALL Storage Dams DESIGN Standards for Upstream Slope Protection General Guide to Spillway Selection DESIGN Floods Cost Estimate - Joe Smith Dam - v - LIST OF FIGURES Figure No. Project Life Cycle Project Flow Chart Hazard Potential Assessment Summary Two Major Groups of Geologic Units Disturbance Due to Mountain-Building Forces Disturbance Due to Salt-Solution Collapse Disturbance Due to Glacial Thrusting Minor Pre-Valley Units and Their Relationship to Major Pre-Valley Units Valley Units Channel (Sand & Gravel) and Floodplain (Clay & Silt) Units Migration of Dune Sand Down Flank of Valley and onto Floodplain Various Relationships for Slump Debris Some Hypothetical Opportunities for Error in Interpretation Geological Damsite Description - Summary Sheet Index Flood Selection Graph Index Flood Multiplier Selection Graph Rainfall Isopleths for a 1.

9 100 Six-hour Rain Flood Peak Adjustment Factor Based on the Rainfall Component Isopleths of Average May-June Net Evaporation Flood Peak Adjustment Factor Soil Moisture Component Median Annual Unit Runoff for the Prairie Provinces Runoff-Draft Regions for the Prairie Provinces Storage-Draft Curves for Region No. 1 Storage-Draft Curves for Region No. 2 Storage-Draft Curves for Region No. 3 Storage-Draft Curves for Region No. 4 - vi - LIST OF FIGURES (Cont d) Figure No. Storage-Draft Curves for Region No. 5 Hydrology Summary Report Grain-Size Distribution Curve Proposed Hole Locations for an Investigation of a SMALL Dam Example PFRA Testhole Log Geotechnical Assessment Report Configurations for Internal Filter Systems Proposed Embankment DESIGN Cross-Section Example Freeboard Allowances Flow Chart For Spillway DESIGN Inclined Filter CONSTRUCTION Methods Volumeter Field Density Test Apparatus Standard Proctor Laboratory Test Apparatus Typical Five-Point Standard Proctor Curve One-Point Proctor Field Test for Clays Project Area Sketch Project Watershed Stereogram Hazard Potential Impacts Hazard Potential Assessment Summary (Joe Smith Dam) Geological Damsite Description - Summary Sheet (Joe Smith Dam) PFRA Testhole Log (Joe Smith Dam) PFRA Testhole Log (Joe Smith Dam) Geotechnical Assessment Report (Joe Smith Dam)

10 Other Soil Logs Capacity Curves Weighted Average Back Slope Hydrology Summary Report (Joe Smith Dam) - 1-1 - INTRODUCTION GENERAL Since inception in 1935, the Prairie Farm Rehabilitation Administration (PFRA) has been involved with dams - planning, designing, constructing, operating, inspecting and maintaining. More than 12,000 on-farm, group, and community dams have been built throughout the Canadian Prairies, all but a few with a successful record of operation and performance. Currently, all PFRA dams above a minimum size with the potential to impact on public safety are designed by a qualified, multi- discipline engineering team. On-farm dam facilities of lesser size which would not impact on the public safety are designed by technicians and technologists within various PFRA organizational areas and reviewed by a qualified professional engineer to ensure designs represent good engineering practice.