GATED OUTLET APPURTENANCES EARTH DAMS TECHNICAL RELEASE NO. - - - - - -- - - - - - - UNITED STATES DEPARTMENT of AGRICULTURE SOIL CONSERVATION SERVICE ENGINEERING DMSION UNITED STATES DEPARTMENT OF AGRICULTURE SOIL CONSERVATION SERVICE Regional Technical Service Center Engineering & Watershed Planning Unit Portland, Oregon This manual has been prepared to assist the design engineer in development of plans for gated outlet appurtenances associated with small earth dams. The original and resourceful charts provide both ready solution to design and show the full range of compatible alternatives in related design details. The basic design phtlosophy, criteria and procedure are presented in the accompanying narrative. Judicious use of both design charts and standard construction details will offer opportunity for a marked improvement in the quality of most plans and an equally significant reduction in time required for their preparation. Harry W. Firman, Design Engineer, is responsible for the con- cepts and content of this manual. Robert Morland prepared the chapter, Hydraulic Controls. Valuable counsel and assistance were provided by Frank Muceus, Design Section Head, and other staff members. June 1969 TABLE OF CONTENTS FRONTISPIECE Section - A INTRODUCTION - B HYDRAULICS - C INLET STRUCTURE - D CONTROLS - E CONDUITS - F OUTLET STRUCTURES - G MISCELLANEOUS STRUCTURES - H DRAWING LAYOUT AND SUMMARY - I BIBLIOGRAPHY - J APPENDIX - SECTION A INTRODUCTION Contents Page . . . . . . . . . . . . . . . . . . . . . . . . . . . General A- 1 Figures . . . . . . . . . . . . . . . . A-1 Standard-Equivalent Dam A- 3 . . . . . . . . . . . . . . . . . . . A-2 Procedure Flowchart A- 5 SECTION A - INTRODUCTION This design manual contains procedure, design aids, standard details and drawings, useful for developing construction drawings for gated outlets and appurtenances common to earth dams used for storage of water Tor irrigation. As the cover graphically indicates, the planner needs only the basic data to enter this guide and come out with essentially the completed drawings for the outlet appurtenances. Design aids in the form of nomographs, charts and tables have been developed wherever possible to provide ready solution of design analyses Examples have been placed on each of the more complex charts and nomo- graphs to facilitate their use and help the designer grasp the rela- tionship between dependent variables in identifying most alternatives. Some of the figures may appear complicated and require some study of the example to understand the relationships expressed. Once vaster of a chart, the designer has a comprehensive understanding and perspective of the relationship between elements attainable in no other way. Each section of the manual is presented in adequate detail for treat- ment of its specific subject in design of small irrigation storage structures. An example is continued through the manual. As each section is finished, the progressive example is completed to include the system components discussed in that section. The hydraulics section is a general treatment of hydraulic design of gated outlet systems. It is in adequate detail for preliminary design purposes and in many cases satisfactory for final design. Refined analysis is recommended where critical design factors and cost alter- natives are involved. Discussion of hydraulic systems for operation of control gates on earth dam conduits is presented in detail since the application is somewhat unique. The hydraulic system offers advantages under certain condi- tions over the mechanical gate stem control that makes it worth consideration. The importance of proper conduit design and installation cannot be overstressed to insure safety of the structure. It is usually impract- ical if not impossible to repair deficiencies in conduits through embankments; this unit of the system must be done right the first time. Every item presented in this section deserves careful consideration. Outlet structures for stilling high velocity flows from conduits have taken a variety of forms depending on physical and economic factors of the site and structure. Performance characteristics, general site adaptab.ility and economic consideration to facilitate judgment i n decision between alternate choices is presented. The several design charts eliminate many steps and hours of work for quantity and cost estimating. Perhaps the most time saving operation in this manual is the summary sheet and procedure for preparing construction drawings. This conclud- ing step opens the door to the several alternatives and considerations i n composing a set of construction drawings for gated outlet appurte- nances for earth dams. Clarity of construction plans that present the design decisions made i n preceding sections of the manual is important. Neatness, legibi- l i t y and clarity i n plans create a psychological response in the builder conducive to better quality work than the response to poorly drafted and vaguely presented details. The ideas offered permit maximum clarity and minimum effort to make a professional presentation of plans, consistent with the quality of design and helpful to both builder and construction engineer i n getting a good job done. It is beyond the scope of this manual to evaluate storage requirements and downstream water needs. In this respect each installation is unique and cannot be standardized. Embankment analysis has also been omitted as a subject requiring individual attention. The concept of the STANDARD DAM for purposes of hydraulic design is a basic embankment shape and a full reservoir discharging a t the toe of the dam through a conduit. As used in this manual, the cross section * of the standard dam consists of an upstream slope of 3:1, a top width fi + of 2 5 feet, and a downstream slope of 2 :1. The standardized inlet, stem pedestal and l i f t pedestal are detailed for the 3:l slope. Hydraulic losses are based on a conduit length associated with the described embankment profile, full reservoir, and a free outfall. Some of the design charts and details are based on this configuration and are not applicable where these conditions are not met. Specific charts where these conditions apply are: Figures B-1, 2, 3, 4; C-4, 5; F-1, 2, 3, 4, 11. If the conduit is extended beyond the toe of the dam, the outlet is submerged or the reservoir only partially full, the hy- draulic system, using these figures, should be sized using an EQUIVALENT DAM height. See Figure A-1. The equivalent dam has a fictitious height that makes it equivalent to the standard dam with respect to hydraulic operation. Art overall perspective of the manual content and use is presented in Figure A-2, Procedure Flow Chart. This chart follows the normal sequence i n selection and development of the details of gated outlet appurtenances. It shows the major decisions that might affect alternate selection re- quired at various points in the development. + * H 35 The difference between this top width compared with one based on 5 w i l l have little effect on the preliminary hydraulic proportion- ing of the conduit. uf/et Structure I STANDARD DAM Out/et Structure e - - 1 L- -A Extended Conduit EQUIVALENT DAM Portio//y Fu// Reservoir fCrifico/ Conditionl m-e-rge-d -O-utj et I EQUIVALENT DAM FIGURE A-l STANDARD- EQUIVALENT DAM EWPUnit Portland Oregon 7 I\ I FIG. E-7 / YES ADJUST SYSTEM HEAD. SAF BASIN NEH 14 - PWD BASIN ---b 7 FIG. F-1 POOL ? CONSIDER IMPACT BASlN , CANTILEVER ADEOUAT NO ARMOR FIG. F- 4 i + 7IMPACLT BASIN CONSIDERATI CANTILEVER WITH ARMOR ARMOR SUMMARY = SHEETS ' ' DRAFTING STOP COMPLETED . SECTION B HYDRAULICS Contents Page . . . . . . . . . . . . . . . . . . . . . . I INTRODUCTION B-1 . . . . . . . . . . . . . . . . . . . I1 LOCATIONOFCONTROL B-2 . . . . . . . . . . . . . . . . . . . . . I11 FULL PIPE FLOW B-2 . . . . . . . . . . . . . . . . . . . . IV PARTIAL PIPE FLOW B-3 . . . . . . . . . . . . . . . . . . . . . . . V CAVITATION B-3 . . . . . . . . . . . . . . . . VI USE OF CHARTS AND GRAPHS B-3 . . . . . . . . . A Full Pipe Flow With Gate Fully Open B-4 . . . . . . . . . . . . . 1 Figures B-1 through B-4 B-4 . . . . . . . . . . . . . 2 Figures B-5 through B-10 B-4 . . . . . . . . . . . . . . . . B Partial Gate Opening B-5 . . . . . . . . . 1 Partial Pipe Flow. Figure B-11 B-5 . . . . 2 Full Pipe Flow. Figures B-12 through B-17 B-5 . . . . . . . . . . . . . . . . . . . . . . . . VII. REVIEW B-7 . . . . . . . . . . . . . . . . . . . . . VIII EXAMPLE PROBLEM B-7