Guidelines for Design of Dams

1 NEWNew York StateDECD ivision of WaterGuidelines for Design of DamsJanuary 1985 Revised January 1989 New York State Department of Environmental ConservationGeorge E. Pataki, GovernorJohn P. Cahill, CommissionerGUIDELINES FORDESIGN OF DAMSNEW YORK STATEDEPARTMENT OF ENVIRONMENTAL CONSERVATIONDIVISION OF WATERBUREAU OF FLOOD PROTECTIONDAM SAFETY SECTION 625 BROADWAY ALBANY, NEW YORK 12233-3507 Guidelines FOR Design OF DAMSTABLE OF CONTENTSSECTIONTITLEPAGEP reface to the January 11989 Edition1 Introduction 22 Definitions 33 Hazard Classification 54 Design and Construction Documents 55 Hydrologic Criteria 76 Hydraulics of Spillways 106A Flashboard Policy 127 outlet Works and Conduits 158 Geotechnical Investigations 169 Earth Dams 1810 Structural Stability Criteria for 21 Gravity Dams11

2 Existing Dams: Rehabilitation and 25 Modification12 Cofferdams 2613 Miscellaneous 2714 Emergency Action Plan 2715 Approval to Fill Reservoir 2816 References 2917 DEC - Regional Directory 31 PREFACE TO THE JANUARY 1988 EDITIONThe January 1988 revision involves:PageItem2 Introduction4 Corrected definition for the Service SpillwayDesign Flood (SSDF)6 Construction Inspection11 Insertion of Section 6A, Flashboard Policy14 Filter and drainage diaphragm replacing antiseepcollars for pipe conduits19 Vegetation Control22 Insertion of Loading Condition 3A25 Cofferdams28 The addition of references 3, 4, 5 and 6 PREFACE TO THE JANUARY 1989 EDITIONThe January 1989 revision involves.

3 PageItem7 Hydrology Investigations7 Existing Dams - Service SpillwayDesign Flood Criteria 1 general The Department of Environmental Conservation receives manyrequests for detailed information about designs for damsrequiring a permit under Article 15, Section 0503 of theEnvironmental Conservation law. This brochure has been developedby the department for the general guidance of Design Guidelines represent professional judgment of the DamSafety Section's staff engineers. The Guidelines convey soundengineering practices in an average situation. Where unusualconditions exist and the Guidelines are not applicable, it is theduty of the Design engineer to notify the department which willthen consider deviation from the these are only general Guidelines for small damconstruction in an average situation, compliance will notnecessarily result in approval of the application.

4 Thedetermination by the department of the acceptability of thedesign and adequacy of the plans and specifications will be madeon a case-by-case basis. The primary responsibility of properdam Design shall continue to be that of the the administration of this law, the department is concernedwith the protection of both the health, safety and welfare of thepeople and the conservation and protection of the natural resources of the State. (See Reference 1 and 2).Water stored behind a dam represents potential energy which cancreate a hazard to life and property located downstream of thedam. At all times the risks associated with the storage of watermust be minimized. This document deals with the engineeringguidelines for the proper Design of a dam.

5 In order for a dam tosafely fulfill its intended function, the dam must also beconstructed, operated and maintained of construction or reconstruction of the dam by alicensed professional engineer is required to insure that the dam willbe built according to the approved plans. See Article 15-0503, Item 5 ofthe New York State, Environmental Conservation Law (Reference 1).For the proper operation and maintenance of a dam, see "An OwnersGuidance Manual for the Inspection and Maintenance of Dams in New YorkState" (Reference 6). ApplicationA permit is required if the dam:is at least 10 feet high or stores 1 million gallons ( acre feet) or has a drainage area of 1 square surface impoundments which are large enough to meet the abovementioned criteria shall not require an Article 15 dam permit.

6 Hazardouswaste surface impoundments will continue to be regulated by the Bureauof Hazardous Waste Technology, Division of Hazardous Substances3 Regulation of the Department of Environmental Conservation, under6 NYCRR-Part 373, Hazardous Waste Management Regulation. Surfaceimpoundments which are part of an approved waste water treatment processwill be regulated within a SPDES permit issued by the Division of Application FormsApplications, including the Supplement D-1 (hydrological, hydraulic andsoils information), can be obtained from and should be submitted to theRegional Permit Administrator. The addresses of the Regional PermitAdministrators are shown on page 31. Detailed information on applicationprocedures is contained in the Uniform Procedures Regulations, Part on all pertinent items should be given.

7 Construction plansand specifications should be prepared in sufficient detail to enablereview engineers to determine if the proposed Design and construction isin compliance with department Guidelines . Thorough engineering reviewwill be given each application. The time for this review and anyadditional time if revisions are necessary should be a consideration ineach DEFINITIONSA ppurtenant works are structures or materials built andmaintained in connection with dams. These can be spillways,low-level outlet works and spillway is a secondary spillway designed to operateonly during large is a temporary structure enclosing all or part of theconstruction area so that construction can proceed in the is an enclosed channel used to convey flows through or under is any artificial barrier and its appurtenant worksconstructed for the purpose of holding water or any other is the Department of Environmental Conservation (DEC).

8 Detention/Retention Basin is any structure that functions as a Dam is made by compacting excavated earth obtained from a Dissipator is a structure constructed in a waterway which reducesthe energy of fast-flowing Routing is the computation which is used to evaluate theinterrelated effects of the inflow hydrograph, reservoir storage andspillway discharge from the is the vertical distance between the Design high water leveland the top of the Dam is constructed of concrete and/or masonry and/or laid-upstone that relies upon its weight for is the vertical dimension from the downstream toe of the dam atits lowest point to the top of the outlet is an opening at a low level used to drain or lower Size Dam is at least 25 feet high and holds at least 15 acre feetof water or is at least 6 feet high and holds at least 50 acre feet Impoundment Capacity is the volume of water held when the watersurface is at the top of the Maximum Flood (PMF)

9 Is the flood that can be expected from theseverest combination of critical meteorologic and hydrologic conditionspossible for the particular region. It is the flow resulting from Maximum Precipitation (PMP) is the maximum amount ofprecipitation that can be expected over a drainage Collar is built around the outside of a pipe or conduit under anembankment dam to lengthen the seepage path along the outer surface ofthe Spillway is the principal or first-used spillway during Spillway Design Flood(SSDF) is the flow discharged through theservice is a structure which discharges Design Flood(SDF) is the largest flow that a given project isdesigned to pass of Dam is the junction of the downstream face of a dam and thenatural ground surface, also referred to as downstream toe.

10 For an earthdam the junction of the upstream face with the ground surface is calledthe upstream HAZARD GeneralThe height of the dam, its maximum impoundment capacity, the physicalcharacteristics of the dam site and the location of downstreamfacilities should be assessed to determine the appropriate hazardclassification. Applications should include the Design engineer'sdescription of downstream conditions and his judgment of potentialdownstream hazards presented in the form of a letter designation and awritten Letter DesignationClass "A": dam failure will damage nothing more than isolated farmbuildings, undeveloped lands or township or country "B": dam failure can damage homes, main highways, minor railroads,or interrupt use or service of relatively important public "C": dam failure can cause loss of life, serious damage to homes,industrial or commercial buildings, important public utilities, mainhighways, and Written DescriptionThe written description is an elaboration of the letter designation.