Planning and Design of Hydro-Electric Power Plants Course No: S04-002

Credit: 4 PDH

Gilbert Gedeon, P.E.

Continuing Education and Development, Inc. 9 Greyridge Farm Court Stony Point, NY 10980 P: (877) 322-5800 F: (877) 322-4774 info@cedengineering.com

CECW-ED

Engineer Manual

1110-2-3001

Department of the ArmyU.S. Army Corps of Engineers

Washington, DC 20314-1000

EM 1110-2-3001

30 April 1995

Engineering and Design

PLANNING AND DESIGN OFHYDROLECTRIC POWER PLANT

STRUCTURES

Distribution Restriction StatementApproved for public release; distribution is

unlimited.

DEPARTMENT OF THE ARMY EM 1110-2-3001U.S. Army Corps of Engineers

CECW-ED Washington, DC 20314-1000

ManualNo. 1110-2-3001 30 April 1995

Engineering and DesignPLANNING AND DESIGN OF HYDROELECTRIC

POWER PLANT STRUCTURES

1. Purpose. This manual provides guidance for structural planning and design of hydroelectric powerplants.

2. Applicability. This manual applies to HQUSACE elements, major subordinate commands, districts,laboratories, and field operating activities having responsibility for design of civil works projects.

FOR THE COMMANDER:

This manual supersedes EM 1110-2-3001, dated 15 December 1960.

DEPARTMENT OF THE ARMY EM 1110-2-3001U.S. Army Corps of Engineers

CECW-ED Washington, DC 20314-1000

ManualNo. 1110-2-3001 30 April 1995

Engineering and DesignPLANNING AND DESIGN OF HYDROELECTRIC

POWER PLANT STRUCTURES

Table of Contents

Subject Paragraph Page Subject Paragraph Page

Chapter 1IntroductionPurpose and Scope. . . . . . . . . . . . . . 1-1 1-1Applicability . . . . . . . . . . . . . . . . . . 1-2 1-1References . . . . . . . . . . . . . . . . . . . 1-2 1-1Codes. . . . . . . . . . . . . . . . . . . . . . . 1-4 1-1Criteria . . . . . . . . . . . . . . . . . . . . . . 1-5 1-1Hydroelectric Design Center. . . . . . . 1-6 1-1

Chapter 2General RequirementsLocation of Powerhouse. . . . . . . . . . 2-1 2-1Location of Switchyard. . . . . . . . . . . 2-2 2-1Highway and Railroad Access. . . . . . 2-3 2-1Other Site Features. . . . . . . . . . . . . 2-4 2-1Types of Powerhouse

Structures. . . . . . . . . . . . . . . . . . . 2-5 2-1Selection of Type of

Powerhouse . . . . . . . . . . . . . . . . . 2-6 2-2General Arrangement of

Powerhouse . . . . . . . . . . . . . . . . . 2-7 2-2Location of Main

Transformers. . . . . . . . . . . . . . . . . 2-8 2-3Powerhouse and Switchyard

Equipment . . . . . . . . . . . . . . . . . . 2-9 2-3Powerhouse Auxiliary

Equipment . . . . . . . . . . . . . . . . . 2-10 2-4

Chapter 3Architectural RequirementsExterior Design . . . . . . . . . . . . . . . . 3-1 3-1Exterior Details . . . . . . . . . . . . . . . . 3-2 3-1Interior Design . . . . . . . . . . . . . . . . 3-3 3-2

Interior Details . . . . . . . . . . . . . . . . 3-4 3-6Schedule of Finishes. . . . . . . . . . . . 3-5 3-6Painting . . . . . . . . . . . . . . . . . . . . . 3-6 3-6Design Memorandum. . . . . . . . . . . . 3-7 3-7Drawings . . . . . . . . . . . . . . . . . . . . 3-8 3-7

Chapter 4Structural RequirementsDesign Stresses. . . . . . . . . . . . . . . . 4-1 4-1Design Loads . . . . . . . . . . . . . . . . . 4-2 4-1Stability Analysis. . . . . . . . . . . . . . . 4-3 4-3Subgrade Conditions and

Treatments . . . . . . . . . . . . . . . . . . 4-4 4-5Foundation Drainage and

Grouting . . . . . . . . . . . . . . . . . . . . 4-5 4-5Substructure Functions and

Components. . . . . . . . . . . . . . . . . 4-6 4-5Joints . . . . . . . . . . . . . . . . . . . . . . . 4-7 4-6Waterstops . . . . . . . . . . . . . . . . . . . 4-8 4-8Draft Tubes. . . . . . . . . . . . . . . . . . . 4-9 4-8Spiral Cases . . . . . . . . . . . . . . . . . 4-10 4-8Generator Pedestals. . . . . . . . . . . . 4-11 4-10Bulb Turbine Supports. . . . . . . . . . 4-12 4-10Types of Superstructures. . . . . . . . . 4-13 4-10Superstructure-Indoor

Powerhouse . . . . . . . . . . . . . . . . 4-14 4-11Intakes . . . . . . . . . . . . . . . . . . . . .4-15 4-12Penstocks and Surge Tanks. . . . . . . 4-16 4-14Switchyard Structures. . . . . . . . . . . 4-17 4-16Reinforcing Steel. . . . . . . . . . . . . . 4-18 4-17Encasement of Structural

Steel . . . . . . . . . . . . . . . . . . . . .4-19 4-17Retaining Walls. . . . . . . . . . . . . . . 4-20 4-17

i

EM 1110-2-300130 Apr 95

Subject Paragraph Page Subject Paragraph Page

Area Drainage. . . . . . . . . . . . . . . . 4-21 4-17Chamfers, Grooves, and

Rustications . . . . . . . . . . . . . . . . 4-22 4-17

Chapter 5Physical SecurityProtection Plan . . . . . . . . . . . . . . . . 5-1 5-1

Chapter 6Retrofitting Existing ProjectsGeneral. . . . . . . . . . . . . . . . . . . . . . 6-1 6-1Hydraulic Design

Considerations. . . . . . . . . . . . . . . . 6-2 6-1Geotechnical Considerations. . . . . . 6-3 6-2

Tunnels in Rock Abutments. . . . . . . 6-4 6-2Cut and Cover Conduits. . . . . . . . . . 6-5 6-2Free Standing Penstock Within

Conduits. . . . . . . . . . . . . . . . . . . . 6-6 6-2

Appendices

Appendix AReferences

Appendix BTabulation of Generator and Turbine Data

ii

EM 1110-2-300130 Apr 95

Chapter 1Introduction

1-1. Purpose and Scope

This manual presents a discussion of the general, archi-tectural and structural considerations applicable to thedesign of hydroelectric power plant structures. It is in-tended for the guidance of those elements within theCorps of Engineers responsible for the planning and de-sign of such structures. It should also be used inestablishing minimum criteria for the addition of hydro-power facilities at existing Corps of Engineers projects,whether by Corps of Engineers or a non-Federaldeveloper.

1-2. Applicability

This manual applies to HQUSACE elements, major sub-ordinate commands, districts, laboratories, and field oper-ating activities having responsibility for design of civilworks projects.

1-3. References

Required and related publications are listed inAppendix A.

1-4. Codes

Portions of the codes, standards, or requirements publish-ed by the associations or agencies listed below are appli-cable to the work.

a. American Association of State Highway andTransportation Officials (AASHTO).

b. Institute of Electrical and Electronics Engineers(IEEE).

c. American Society of Civil Engineers (ASCE).

d. American Society of Mechanical Engineers(ASME).

e. National Board of Fire Underwriters (NBFU).

f. National Bureau of Standards (NBS).

g. National Electrical Manufacturers Association(NEMA).

h. National Fire Protection Association (NFPA).

1-5. Criteria

The design methods, assumptions, allowable stresses,criteria, typical details, and other provisions covered inthis manual should be followed wherever practicable.However, it is expected that judgment and discretion willbe used in applying the material contained herein. It isrealized that departures from these standards may benecessary in some cases in order to meet the specialrequirements and conditions of the work under consider-ation. When alternate methods, procedures, and types ofequipment are investigated, final selection should not bemade solely on first cost but should be based on obtain-ing overall economy and security by giving appropriateweight to reliability of service, ease of maintenance, andability to restore service within a short time in event ofblast damage or radiological contamination. Whetherarchitect-engineers or Hydroelectric Design Center per-sonnel design the power plant, the criteria and instruc-tions set out in Appendix A of guide specificationCE-4000 should be followed.

1-6. Hydroelectric Design Center

a. Utilizing installations. The engineering of hydro-electric projects is a highly specialized field, particularlythe engineering design and operational activities. Inorder to assist field operating activities (FOA), the Corpsof Engineers has established a Hydroelectric DesignCenter (HDC), located at Portland, Oregon, for utilizationfor all hydroelectric installations, including installationsat existing dams.

b. FOA services. The FOA will retain completeresponsibility and authority for the work, including fund-ing, inspection, testing, contract management, and admin-istration. The HDC will perform the followingengineering and design services in accordance withER 1110-2-109:

(1) Provide the technical portions of reconnaissancereports and other pre-authorization studies for inclusionby the requesting FOA in the overall report.

(2) Provide the architectural, structural, electrical,and mechanical design for the powerhouse includingswitchyards, related facilities, and all hydraulic transientstudies.

(3) Prepare preliminary design reports and the fea-ture design memoranda for hydroelectric power plants forthe requesting FOA.

1-1

EM 1110-2-300130 Apr 95

(4) Prepare plans and specifications for supply andconstruction contracts and supplemental major equipmenttesting contracts.

(5) Provide technical review of shop drawings.

(6) Provide technical assistance to the ContractingOfficer’s representative at model and field tests. TheHDC will analyze results and make recommendations.

(7) Assist in preparation of Operation and Mainte-nance Manuals.

(8) Provide necessary engineering and drafting totransfer “as-built” changes to “record” tracings andensure complete coordination of such changes.

(9) Participate in review of plans and specificationsfor non-federal development at Corps of Engineers proj-ects in accordance with ER 1110-2-1454.

1-2

EM 1110-2-300130 Apr 95

Chapter 2General Requirements

2-1. Location of Powerhouse

a. Determining location. The location of the power-house is determined by the overall project development.The factors affecting the location include:

(1) Location of the spillway (when powerhouse islocated adjacent to the dam).

(2) Location of navigation locks (on navigationprojects).

(3) Foundation conditions.

(4) Valley width.

(5) River channel conditions below dam.

(6) Accessibility.

(7) Location of switchyard and transmission lines.

b. Local conditions. At projects where the power-house is located at the dam adjacent to the spillway, localcondition such as width of flood plain, accessibility, anddepth of foundations will usually govern the location.On projects which will include a navigation lock, thepowerhouse is preferably located at the opposite end ofthe spillway from the lock. Where the river channelbelow the dam has an appreciable fall, economic studiesshould be made to determine whether a remote power-house location downstream from the dam is justifiable.

c. Sub-structures. At low-head projects, the sub-structure of the powerhouse may be wholly or partiallyincorporated into the design of the intake structure. Atmedium-head plants, the substructures of the generatingunits and the upstream generator room wall should beseparated from the toe of a concrete dam, and any part ofthe powerhouse supported thereon, by a formed joint.See paragraph 4.7 for additional joint details. Theamount of separation between the powerhouse substruc-ture and the toe of the dam at, or below, the elevation ofthe generator room floor may be dependent upon thefoundation conditions, but the separation is frequently asmuch as 10 feet or more to provide adequate space toinstall service facilities.

2-2. Location of Switchyard

The availability of suitable space will, in a great manycases, determine the location of the switchyard. Consid-eration should be given to the number and direction ofoutgoing transmission lines. The elevation of the switch-yard should be established above design high tailwater.The most desirable and economical location is usuallyadjacent to or near the powerhouse.

2-3. Highway and Railroad Access

In planning the development of the site, both highwayand railroad access to the powerhouse, switchyard, andother structures should be considered. Highway access tothe plant should usually be provided. At plants wherelarge generating units are to be installed, an access rail-road should be considered if feasible and economicallyjustified, consideration being given to utilizing the rail-road connection which will usually be required for con-struction of the dam. Trucking costs from the nearestrail point, together with all handling costs should becompared with the cost of constructing and maintaining arailroad to the plant. The location of the highway orrailroad access into the powerhouse will be determinedby the approach conditions in the valley and the arrange-ment of the powerhouse. The access facilities should,where possible, be located so that their use will not beimpaired by design high water. It is not essential that therailroad entrance be located above high water, especiallywhere the flooding period would be of short duration;however, provision for bulkheading of the railroadentrance should be provided, and an access protectedfrom design high-water conditions should be provided forpersonnel.

2-4. Other Site Features

Area should be provided for both public and employeeparking. Sidewalks, guard rails, fences, locked gates,parapets, and other safety features should be included inthe general plan. Adequate drainage, a water supply, andlighting should be provided in the areas near the power-house. Landscaping should also be considered in thestudies of the site development.

2-5. Types of Powerhouse Structures

Three types of powerhouses classified as to method ofhousing the main generating units are described:

2-1

EM 1110-2-300130 Apr 95

a. Indoor type. The generator room is fully enclosedand of sufficient height to permit transfer of equipmentby means of an indoor crane.

b. Semi-outdoor type.The generator room is fullyenclosed but the main hoisting and transfer equipment isa gantry located on the roof of the plant and equipmentis handled through hatches.

c. Outdoor type. In this type there is no generatorroom and the generators are housed in individual cubiclesor enclosures on, or recessed in, the deck.

2-6. Selection of Type of Powerhouse

This determination will be made on the basis of an eco-nomic analysis which takes into consideration, not onlyfirst cost, but operation and maintenance costs. Whilethere is some structural economy inherent in outdoor andsemi-outdoor plants, it does not necessarily offsetincreased equipment costs. An outdoor type of plantmay be competitive with an indoor type at a site havinglow maximum tailwater and where the number of gener-ating units to be provided is sufficient to minimizeincreased crane costs. The structural economy of a semi-outdoor plant is marginal since the only saving is in wallheight, while the roof, which is actually the workingdeck, must generally sustain higher live loads. It isemphasized, however, that selection of type, for anygiven site, can only be made after a thorough study.

2-7. General Arrangement of Powerhouse

In general, a powerhouse may be divided into threeareas: the main powerhouse structure, housing the gener-ating units and having either separate or combined gener-ator and turbine room, erection bay, and service areas.

a. Main powerhouse structure. The generator roomis the main feature of the powerhouse about which otherareas are grouped. It is divided into bays or blocks withone generating unit normally located in each block. Thewidth (upstream-downstream dimensions) of the genera-tor room for the indoor type should provide for a pas-sageway or aisle with a minimum width of 10 feetbetween the generators and one powerhouse wall. Theheight of the generator room is governed by the maxi-mum clearance height required for dismantling and/ormoving major items of equipment, such as parts of gen-erators and turbines; location of the crane rails due toerection bay requirements; the crane clearance require-ments; and the type of roof framing. All clearancesshould be adequate to provide convenient working space

but should not be excessive. The elevation of the turbineroom floor should be established so as to provide a mini-mum requirement of 3 feet of concrete over a steel spiralcase, or a minimum roof thickness of 4 feet for a semi-spiral concrete case. In establishing the distance betweenthe generator and turbine room floors, if they are notcombined, the size of equipment to be handled in theturbine room, the head room between platforms in theturbine pit, and the generator room floor constructionshould be considered.

b. Erection bay. In general, the erection bay shouldbe located at the end of the generator room, preferably atthe same floor elevation and with a length equal to atleast one generator bay. The above length should beincreased sufficiently to provide adequate working roomif railroad access is provided into the erection bay atright angles to the axis of the powerhouse; however, noadditional space should be required if the access railroadenters from the end of the powerhouse. In cases wherethe elevation of the crane rail would be dependent on therequirement that a transformer with bushings in place bebrought under the crane girder, consideration should begiven to the possible advantages of revising the layout topermit bringing the transformer in at the end of the struc-ture, at the end of the generator room, if the generatorroom is at a lower elevation than the erection bay, orremoving bushings before moving transformer intopowerhouse. If the height required for untanking a trans-former appears to be the controlling dimension, a studyshould be made of the economy of installing a hatchwayand pit in the erection bay floor to provide the requiredheight.

c. Service area. Service areas include offices, con-trol and testing rooms, storage rooms, maintenance shop,auxiliary equipment rooms, and other rooms for specialuses. For plants located at the toes of gravity dams, thespace available between the generator room and the faceof the dam is a logical location for most of the featuresenumerated above. However, in all cases an economicstudy, which should include the cost of any added lengthof penstock required, should be made before deciding toincrease the space between the dam and powerhouse toaccommodate these features. The offices are frequentlylocated on upper floors, and the control room and otherservice rooms on lower floors. The most advantageouslocation for the maintenance shop is usually at the gener-ator room floor level.

d. Space allocations.Space should be provided forsome or all of the following features and uses, asrequired:

2-2

EM 1110-2-300130 Apr 95

(1) Public areas: main public entrance, receptionarea, public rest rooms, exhibits, and elevator.

(2) Employee areas: employee entrance, equipmententrance, offices, office storage, rest rooms for officeuse, control room, rest rooms for control room operators,kitchen for control room operators, repair and test roomfor instruments, main generator rooms, main turbinerooms, station service or fish water units area, erectionand/or service areas.

(3) Shops: machine, electrical, electronic, pipe,welding, sheet metal, carpenter, and paint with spraybooth.

(4) Storage and miscellaneous areas: storage batteryand battery charger rooms, cable galleries, cable spread-ing room under control room, telephone and carriercurrent equipment room, oil storage tank room, oil purifi-cation room, storage for paints and miscellaneous lubri-cants, storage rooms, locker rooms with showers andtoilet facilities, first aid room, lunch room with kitchenfacilities, elevator, heating, ventilation, and air condition-ing equipment rooms, and auxiliary equipment rooms.

2-8. Location of Main Power Transformers

The choice of location of the main power transformers isinter-related with the selection of the type and rating ofthe transformers. The selection of single-phase or3-phase type of transformers, the method of cooling, andthe kVA rating are also directly related to the basicswitching provisions selected for the plant, the numberand rating of generators associated with each transformeror transformer bank, and the location of the transformers.In order to determine the most suitable and economicalinstallation, including the type, rating, and location of themain power transformers, adequate studies, includingcomparative estimates of total installed first cost and totalannual cost for each scheme studied, should be madeduring the preliminary design stage along with studies todetermine the basic switching arrangement and generalarrangement of the powerplant. Locations at which themain power transformers may be placed are: betweenthe powerhouse and dam, on the draft tube deck, in theswitchyard, and near the powerhouse but not in theswitchyard. From the viewpoint of electrical efficiency,the power connections between the generators and trans-formers should be as short as practicable. This consider-ation favors the location of the transformers at or nearthe powerhouse. In deciding between the upstream ordownstream location at the powerhouse, considerationshould be given to the location of the switchyard and the

nature of the high-voltage connections between it and thetransformers. In some cases the location of the trans-formers on the draft tube deck may increase the cost ofthe powerhouse structure. However, if such a locationmakes possible a direct overhead connection to theswitchyard, this feature may more than balance anyincreased cost of the structure. At small plants and,where the switchyard can be located close to the power-house, a transformer location in the switchyard may beeconomical. Where transformers are located between thepowerhouse and dam, special high-voltage cable connec-tions to the switchyard may be required. In selecting thelocation for the transformers, as well as in planning thegeneral plant arrangement, consideration should be givento the requirements for transporting and untanking thetransformers.

2-9. Powerhouse and Switchyard Equipment

The connection between items of equipment in thepowerhouse and switchyard will require special study ineach individual case. The connections fall into threeclasses described below:

a. Main power connections. In general, when themain power transformers are located in the switchyard,the main power connections between the powerhouse andswitchyard should be carried in an underground tunnel orduct bank. When the transformers are at the power-house, consideration should be given to the economy andadvantages of overhead connections.

b. Control cables and power supply to switchyard.The number and types of these connections require thatthey be run underground. For best protection fromdampness and for ease of inspection and replacement, acable tunnel is usually justifiable in major plants. Insmall plants, the cables are sometimes run in conduits orduct banks from the powerhouse to a distributing point inthe switchyard.

c. Oil piping. It is desirable to concentrate oil puri-fication operations and oil storage in the powerhouse.This concentration requires connections between theswitchyard and powerhouse for both clean and dirtyinsulating oil. If a tunnel is required for electrical con-nections, these pipes can be run in the same tunnel;otherwise, they must be buried underground. If theswitchyard is some distance from the powerhouse, aseparate oil purification and storage system may be moreeconomical. Oil piping or tanks buried undergroundmust meet local, state, and Federal regulations for envi-ronmental protection.

2-3

EM 1110-2-300130 Apr 95

d. Drains. Any drains that may handle a mixture ofoil and water should be connected to an oil/waterseparator.

2-10. Powerhouse Auxiliary Equipment

In planning the general arrangement of the powerhouse,space must be assigned in all of the auxiliary electricaland mechanical equipment that will be required. Thelocation of the auxiliary equipment must also be consid-ered with respect to the location of the main equipmentwith which it is associated. The following is a list ofauxiliary equipment and systems usually required forpowerplants. It is not expected that all items listed willbe incorporated in all plants. The size, service, andgeneral requirements of the plant will usually determinewhich items are necessary: water supply systems forraw, treated, and cooling water, unwatering systems,insulating and lubricating oil transfer, storage and puri-fications systems, compressed air systems, turbine

governing equipment, fire protection, detection andannunciation, heating, ventilating, and air conditioningsystems, turbine flow meters, water level transmitters andrecorders, elevators, main generator excitation equipment,station service power generating units, station servicetransformers and switchgear, main unit control boards,station service control boards, storage battery and charg-ers, inverter, electronic equipment (carrier current micro-wave), telephone and code call system, maintenance shopequipment, sewage disposal equipment, auxiliary equip-ment for oil-filled or gas-filled cables, emergencyengine-driven generator, incinerator, station drainagesystem, generator voltage switchgear, metal-enclosedbuses, and surge protection equipment, air receivers fordraft tube water depressing system, heating, ventilationand air conditioning switchgear, lighting transformers andswitchgear, unit auxiliary power centers, electrical shop,transformer oil pumps and heat exchangers (when locatedremote from the transformers), and generator neutralgrounding equipment and switchgear.

2-4

EM 1110-2-300130 Apr 95

Chapter 3Architectural Requirements

3-1. Exterior Design

a. The importance. Exterior design should be con-sidered throughout the design process. In general, thedesign should receive most attention once the generalarrangement of the powerhouse including floor and cranerail elevations and crane clearances is determined. Itshould utilize scale, proportion, rhythm, and compositionto achieve an aesthetically pleasing structure which fits inwith its natural surroundings. In achieving these endseconomy is important, and, although decoration andcomplexity are not to be ruled out, simplicity should bethe keynote.

b. Aesthetic appearance. The arrangement anddimensions of the various masses is determined by thephysical requirements of the powerhouse components.However, in the design of the ensemble of these masses,the architect should be allowed freedom consistent withan efficient and economical plant layout. In addition,some of the devices that may be used to define and com-pose the masses and give scale, proportion, and rhythmare changes in texture and materials, emphasis of hori-zontal pour joints and vertical contraction joints, andplacement and sizing of fenestration and openings. Theexact size and location of openings should be determinedfrom the standpoint of aesthetics after the structural,mechanical, and functional requirements have been inves-tigated. Windows need not be used, but they may bedesirable in order to let in natural light and increaseemployee morale. When used, their form and locationshould relate to their function and the aesthetic appear-ance of the structure. In general, large glass areas inoperating portions of the powerhouse should be avoidedto minimize blast damage, but small windows high in thepowerhouse walls may have value in this respect as blastpressure relief openings.

c. Final selection. Selection of the final powerhousedesign should be made after a careful study of at leastthree designs having basically different exterior treat-ments. Each proposed design should be carefully devel-oped and perspective drawings prepared. The point ofvision for the perspectives should be a point from whichthe general public will view the structure. The sketches,which are to be used for the selection of exterior treat-ment, should include all of the adjacent structures andsurroundings.

3-2. Exterior Details

Exterior details are discussed in the followingsubparagraphs.

a. Roofing. Powerhouse roofs may be pitched(gabled, hipped, vaulted, etc.) or flat (pitch not greaterthan 1 inch per foot nor flatter than 1/2 inch per foot).Pitched roofs are preferred because of lower maintenancecosts (flat roofs must be waterproof, whereas pitchedroofs need only be watershedding). Parapets that meetcurrent safety codes should be provided at all roof edges.Cants should be provided at the intersection of roof andall vertical surfaces in order to eliminate sharp angles inthe roofing. In designing the roofing system, i.e. insula-tion, roofing, flashing, and expansion joint covers, themost current roofing technology should be utilized.Whenever roofs are exposed to public view from the topof the dam or the abutments, special materials may beused for appearance, e.g. marble chips in place of gravelsurfacing.

b. Decks. Exterior concrete decks covering interiorspaces should be of watertight construction. Where thedeck is covering habitable areas, or areas containingequipment which could be damaged by water, a water-proof membrane with concrete topping shall be added tothe structural slab.

c. Walls. Due to structural considerations, e.g. theusual necessity to support crane rails, and the fact thatconcrete is the main material used in powerhouse con-struction, concrete is the most commonly used materialfor the exterior walls of superstructure. However, othersystems such as prefabricated insulated aluminum orstainless steel wall panels, concrete masonry, brick, etc.may be used provided an overall economy is effected.Concrete should always be used below maximum power-house design tailwater elevation. The finish of the exte-rior surface of powerhouse superstructures is discussed inparagraph 4-14b. All details for concrete constructionsuch as joints, rustication, V-grooves, corner chamfers,and fillets should be studied and considered in the archi-tectural design. The V-grooves, where required shouldnot be less than 1 inch across the face and 1/2-inch deep.The angle at the bottom of the V-grooves should beabout 90 degrees. All contraction joints in the substruc-ture should be continued through the superstructure andconsidered in the design, regardless of the material usedfor the walls. Wall panels should not be laid continu-ously across such joints. Flashings or waterstops shouldbe used in all exterior vertical contraction joints.

3-1

EM 1110-2-300130 Apr 95

Flashing, jamb closures, corner plates, parapet and eaveclosure plates for insulated metal walls should be of thesame material and the same gage as specified for exteriorwall plates.

d. Entrances. Entrances should conform to OSHArequirements. Not only should all entrances be locatedfor proper and efficient operation of the plant, but theyalso should be placed to obtain a pleasing exterior archi-tectural design. The dimensions of the door openingsshould be governed by the required use and should notbe sized for the exterior appearance alone. Doorsrequired for proper operation of the plant should not beof monumental type, but should give the impression thatthe doors are for plant operation. The public entrancemay be more decorative than other plant doorways and,if desired, may be massive when used as a design fea-ture. Doors of structural glass or of glass and aluminumare recommended for public entrances. Large doorsshould either be hinged at the sides and supported at thetop by a trolley for folding-door operation or should beof the motor-operated, vertical-lift or overhead rollingdoors type where clearances are adequate and whereconsidered desirable from an operation standpoint. Apilot door should be provided in any large door, when asmall entrance door is not nearby.

e. Fenestration. The openings in the exterior wallsof the generator room should be confined to the neces-sary access doors and to ventilation louvers or smallwindows above the crane rails. All sash, trim, orexposed exterior metal should be of aluminum orcorrosion-resisting metal requiring no painting and, ingeneral, should be detailed for standard manufacturedproducts. The use of specially designed sash and trimshould be limited to the public entrance. When the maintransformers are to be located close to the powerhousewall on either the upstream or downstream decks, nowindows should be planned in the adjacent portion of thewall. Where possible, the use of windows in office areasand lunch rooms is encouraged. They should be operablefor ventilation and easy to clean such as tilt-turn win-dows. Glazing should generally be insulating glass.Full-length glass doors and sidelights should be glazedwith tempered glass. In certain cases, where the admis-sion of light is desired but a clear view is not necessary,the use of double skin insulating plastics may be consid-ered. Wire glass and glass block will give security andlight blast protection. Glass block may be used as adesign element.

f. Draft tube deck. The draft tube deck should bewide enough to provide safe clearances for operating the

gantry crane, painting and repairing the crane and gates,and removing and reinstalling the gratings. Hose bibbsof the nonfreeze type should be recessed in the wall ofthe powerhouse. A concrete parapet, with or without apipe handrailing on top, should be provided on the down-stream side of the deck and should have an overall heightabove the deck of three and one-half feet or as requiredby current safety codes. The design of the lighting sys-tem for the draft tube deck may include provisions in theparapet to accommodate lighting fixtures. Drainage linesfrom the deck should be as short and direct as possible,but the outlets should be concealed. To avoid a trippinghazard, crane rails should be installed in blockouts withthe top of the rail approximately flush with the deck.Blockout should be partially filled with non-shrink grout,and the top remainder of the recess filled with a two-component, cold-applied, self leveling type sealant. Thethickness of the sealant is determined by the compressivespace required for the crane wheel flange depth.

g. Stairs and railings. Exterior stairs should beprovided with safety treads made of a material that willnot rust or require painting and may consist of abrasivematerial troweled into the finish or abrasive stripsembedded in the tread and nosing. Handrailings shouldbe made of concrete, concrete and metal, or metal only.The metal railings should be treated or a material speci-fied so that maintenance painting will not be required.All railings should be designed to comply with the mostcurrent safety codes.

h. Skylights. Skylights can present leakage andmaintenance problems and should therefore be limited touse in visitor’s areas where a special effect is desired.The framing should be aluminum or corrosion-resistingmetal. They should be glazed with insulating glass ordouble-skin insulating plastic. Insulating glass shouldconsist of a top layer of tempered glass and a bottomlayer of laminated safety glass or as required by currentlocal codes.

3-3. Interior Design

Interior details are discussed in the followingsubparagraphs.

a. Visitor’s facilities. All attended power plants willnormally be provided with limited space for the visitingpublic. This space should be kept to the minimumrequired for the estimated attendance. The items men-tioned in the following paragraphs should be consideredin planning the public spaces for all power plants. Thepublic entrance for small plants may be combined with

3-2

EM 1110-2-300130 Apr 95

the employee entrance, and when so located it should beproperly marked as a visitors’ entrance. For largerplants, a separate, prominently located visitors’ entranceshould be provided. The entrance to the visitors’ areashould be as direct as possible from the avenue of publicapproach and should be accessible to handicapped visi-tors. An entry vestibule is desirable, but not essential.The design of the visitors’ area should take into consider-ation provisions for exhibits, and location of drinkingfountains, public toilet rooms, and vertical transportation,e.g. elevators for handicapped access. The visitors’ areasshould be arranged so that they are isolated from allother parts of the plant except for access through lockeddoors. The room finishes should be attractive, service-able, and easily maintained. Some of the materials thatshould be considered for use are terrazzo, ceramic andquarry tiles, plaster coated with a durable enamel paint,acoustical tile ceilings, etc. Each material should beevaluated on the basis of cost, appearance, durability, andease of maintenance.

b. Control room facilities. The control room spaceshould be planned for the ultimate development of thepowerhouse, regardless of the number of units installedinitially. The control room should be planned for con-venience in operation and the equipment should bespaced to permit easy circulation, easy access to equip-ment for repair or replacement, and convenient installa-tion of future equipment. A minimum space of 4 feetshould be provided between the switchboards and thewalls and between switchboards and other major equip-ment. Doors or removable panels of adequate sizeshould be provided to accommodate the installation offuture switchboard panels. Items such as speciallydesigned operator’s desks, control consoles, and key andmap cases should be considered in planning the controlroom.

(1) Rooms which should be provided as auxiliariesof the control room at attended power plants usuallyinclude a small kitchen, a toilet, a supplyroom, and aclothes closet. These rooms should be directly accessibleto the operators without the use of hallways. The toiletroom should contain one water closet and a lavatorycomplete with necessary accessories. The supply roomshould include shelving for storage of forms and suppliesused by the operators. The clothes closet should have ahat shelf and clothes rod.

(2) The control room floor may be carpeted or haveresilient floor covering such as rubber or vinyl-plastictile. The walls should be smooth, e.g. plaster or sheet-rock, and painted. The ceiling should be suspended

acoustical tile. Special thought should be given to soundcontrol. Sound-absorbing wall panels should be consid-ered. They should be covered with perforated vinyl forease of maintenance. Windows between the controlroom and the main powerhouse area should have insu-lated glazing and sound absorbing insulation in theframe. The control room will usually have special light-ing, carefully placed to prevent annoying reflections onthe instrument panel glass.

(3) The toilet should have ceramic tile floor andwalls and painted plaster ceiling. The other small roomsshould have the same floor covering as the control roomand should have painted plaster or gypsum wallboardwalls and ceilings. Cove bases of rubber, vinyl, orceramic tile should be used in all of the rooms. In someplants, an instrument and relay testing room and a tele-phone and electronic equipment room may be required.Such rooms should be located near the control room. Aphotographic darkroom should also be provided in thisarea for plants using oscillographic equipment. In thedarkroom, there should be a stainless steel sink anddrainboard for developing and washing films, storagespace for developing apparatus, and a storage cabinet forfilms. A workbench with the necessary electrical con-nections and a storage cabinet or closest should be pro-vided in the instrument and relay test room. Thetelephone and electronic equipment room should also belocated convenient to the control room and preferablyshould be above maximum design tailwater elevation.This room must be kept clean and free from dust andshould be located with this in mind.

c. Generator room and auxiliary spaces. Thearrangement of the rooms and spaces that will house theelectrical and mechanical equipment essential to theoperation and maintenance of the plant should be deter-mined on the basis of an over-all study of the require-ments of the functions involved. A workable,convenient, economical arrangement should be developedthat is structurally and architecturally sound.

(1) The criteria governing the layout of the gener-ator room are given in paragraph 2-7a. A sufficientamount may be added to the minimum clearancesrequired for installation, operation, repair, and overhaulto secure reasonably convenient space for carrying outthese functions. It is not intended that clearances andoperating spaces should be arbitrarily overdesigned, butreasonable operating convenience should not be sacrificedin order to secure minimum cost. The space allotmentfor the erection bay is discussed in paragraph 2-7b. Asthe erection bay is merely an extension of the generator

3-3

EM 1110-2-300130 Apr 95

room, the entire space should be treated architecturally asone room. In general, the treatment should be as simpleas possible. The floor finish selected should be the eco-nomic one for the plant under consideration. It should beone that will not dust, will resist damage during minorrepairs to equipment, and can be satisfactorily repaired ifaccidentally damaged. Also, a finish shall be used thatwill clean easily and will not deteriorate with frequentcleaning. Terrazzo is usually justified due to its extremedurability, ease of maintenance, and attractive appear-ance. In certain cases a wainscot of ceramic tile or someother material may be justified, however, concrete wallsare usually sufficient. Concrete walls and ceiling shouldbe painted or sealed to prevent dusting. Special con-sideration should be given to the design of the roof fram-ing, as well as any ventilation duct work and piping thatmust be carried under the roof, in order to obtain aspleasing an appearance as possible.

(2) The allotment of space for a maintenance shopshould be determined from a layout of the equipmentconsidered necessary to maintain the plant. This roomshould be located on the generator room floor level andshould adjoin the erection bay if possible. The ceilingheight should be adequate to provide for the use of asmall overhead crane for handling equipment beingrepaired. The capacity of the crane must be determinedby the weight of equipment to be handled. Where parti-tions form a wall of this room, the partition should be ofconcrete or concrete masonry units. Partition and wallsmay be painted or sealed.

(3) The general arrangement of auxiliary equipmentis usually determined in making the basic plant layout.An economical and convenient arrangement of thisequipment may be achieved only by thorough study of allthe requirements and by careful coordination of the vari-ous systems. The auxiliary equipment and services forwhich space will usually be required are listed underparagraph 2-10.

(a) The spaces allotted for the electrical shop, forsewage disposal, and for oil purification and storageshould be enclosed; but it is not essential that separaterooms be provided for all of the other functions. Inmany cases, open bays housing several functions will bepracticable, and such an arrangement will usually bemore economical than a layout that provides separaterooms for each function.

(b) Storage battery and charging rooms shall bedesigned to conform to Corps, OSHA, and NEC safetycodes. Storage battery and battery charging rooms

preferably should be located above high tailwater eleva-tion and should be adequately ventilated. A sink con-structed of acid-resistant material should be provided inthe battery room. Drainage from the sink and floordrains should flow to an acid neutralization tank, thendischarge to the sewer system. All piping to theneutralization tank and floor drain, including the drainsthemselves, should be acid resistant. The walls and floorof this room should be painted with an acid-resistantenamel. The ceiling may be painted to improve lightingconditions if desired. Access to the rooms should beadequate for easy installation and replacement ofequipment.

(c) The floors of the oil purification and storagerooms should be trowel- finished concrete, painted withoil-resistant paint or sealed. The lower 6 feet of thewalls should have an oil-resistant painted dado, with thewalls above the dado and the ceiling unpainted. Allother rooms should receive no special finishes.

d. Personnel facilities. Employee facilities requiredfor efficient plant operation should be based uponapproved design memorandum on plant staffing. Thesefacilities usually include the offices, toilet, shower, lockerrooms, employees’ lunchroom, stairways, corridors, andelevator. In the larger plants, it is usually necessary toprovide a conference room suitable for employee man-agement meetings.

(1) The requirements for office space will probablyvary with each plant, but at all attended powerplants it isrecommended that offices be provided for the plantsuperintendent and for general clerical space. Therequirements of each plant should govern the allotmentof additional space for offices, and the expected operat-ing organization must be determined before the planningcan be completed. A fireproof vault, file and recordrooms, storage closets, and clothes closets should beprovided as required and should be conveniently locatedwith respect to the offices. Plants should provide toiletrooms for both male and female employees in the officearea. The minimum requirements for the men’s toiletshould be one water closet, one urinal,and one lavatory;and for the women’s toilet, the requirements should beone water closet and one lavatory, but in all cases shallmeet the requirements of local codes. Floors should beof rubber or vinyl-plastic tile with a light but serviceablecolor with a nondirectional pattern that will hide scuffmarks and a dark cove base. Dark, patterned carpetingwith rubber or vinyl cove base may be considered.Plastered masonry walls, gypsum wallboard, or metalpartitions should be painted with interior enamel.

3-4

EM 1110-2-300130 Apr 95

Ceilings should be suspended acoustical tile. The closetsand storage rooms should be finished the same as theoffices. The toilet rooms should have ceramic tile floors,tile cove bases, and glazed tile wainscot with paintedplastered or concrete masonry walls above. The stalls intoilet rooms should be metal with factory-applied enamelor other durable coating.

(2) A minimum width of 5 feet should be used forall office corridors and a minimum of 6 feet for all corri-dors in work areas where corridors may be used forhandling equipment. In planning corridors and openings,consideration should always be given to the desirability(and in some cases the necessity) of bringing bulky equi-pment into the plant and installing it intact. The corri-dors on the office floor levels will normally be finishedsimilarly to the offices. Floors of corridors on the otherlevels should be trowel-finished concrete with hardeneradded. Where floors are likely to remain wet a lightbrush finish after troweling should be specified to pre-vent slipping. Painted concrete floors should be avoidedbecause of the maintenance involved. Partitions shouldbe concrete or concrete masonry as desired. Unfinishedconcrete ceilings should be used and may be painted ornot as required to improve lighting.

(3) Stairways, aside from entrance steps or stairs,may be classed under three general types: office stairs,work area stairs, and limited-use stairs or ladders. Theoffice stairways should have concrete or masonry walls,painted to match the finish in the adjacent areas; soffitsor ceilings may be painted or left unfinished. The finishas described above should extend to the floor levelsbelow and above the office floor. The office stairsshould be of the pan type, steel- supported; with concretesafety treads with safety nosings and metal risers.Painted metal, galvanized pipe or extruded aluminumhandrails may be used for these areas. Work area stairsshould be similar to office stairs or concrete with safetytread nosings, and the walls and ceilings should be unfin-ished concrete. Limited-use stairs and ladders, whichprovide access to places requiring no regular service,may be of concrete or steel of simple design andprovided with adequate protection as required by currentsafety codes.

(4) Both male and female personnel of the plantshould be provided with adjoining locker, shower, andtoilet rooms, located near the maintenance shop anderection bay. In large plants, additional toilet roomsshould be provided toward the far end of the plant. Thelocker rooms should have forced ventilation and shouldcontain benches and built-in type metal lockers. The

shower rooms should have gang-type showers for menwith one shower head for each ten men to be accommo-dated per day, and individual shower and drying stalls forwomen with one shower for each ten women to beaccommodated per day. In general, an increasing per-centage of female workers should be planned for. Thetoilet rooms adjoining the locker and shower room shouldhave one water closet, one lavatory and for men, oneurinal for each ten personnel to be accommodated perday. The additional toilet rooms shall be limited to onewater closet, one lavatory and for men, one urinal. Insome cases unisex toilet rooms may be used. A drinkingfountain should be located in the corridor adjacent to thearea. Walls should be concrete, masonry or gypsum wallboard on steel studs. Shower and toilet room wallsshould have a standard height, glazed tile wainscot,except in the showers, where it should extend to theheight of the shower head. Ceilings and concrete portionof the walls of the shower room subject to steam vaporsshould be given a prime coat of primer-sealer (conform-ing to the latest edition of Federal SpecificationTT-P-56), one coat of enamel undercoat (conforming tothe latest edition of Federal Specification (TT-E-543) fol-lowed by one coat of gloss enamel (conforming to thelatest edition of Federal Specification TT-E-506). Con-crete masonry walls should receive one coat of concreteemulsion filler prior to the above treatment. A janitor’scloset should be provided and should have a service sinkand shelves for supplies. The walls of the janitor’s closetshall be painted gypsum wall board or unpainted concreteor masonry. The floor shall be trowel-finished concretewith no base.

(5) A lunch and break room should be provided. Itshould include adequate counter space and storage cabi-nets and a range top with ventilation. It should providespace for a refrigerator, microwave ovens, and vendingmachines. There should be adequate electrical outlets forcoffee pots, microwave ovens, vending machines, etc. Itshould have sufficient room to accommodate anticipatedplant personnel. Finishes should consist of rubber orvinyl plastic resilient flooring with cove base, paintedwalls, and suspended acoustical tile ceiling. Insofar aspractical, the lunch room should be located so as to mini-mize the noise and vibration of the powerplant. The useof sound absorbing wall panels covered with perforatedvinyl should be considered. Sound dampers may have tobe used for the lunch room HVAC system. Unnecessarywall penetrations should be avoided. If practical, consid-eration should be given to locating the lunch room at alevel where windows to the outside can provided. Thisis highly desirable considering the indoor nature of thework.

3-5

EM 1110-2-300130 Apr 95

(6) A first-aid room should be planned adjacent tothe control room, if practicable, or otherwise on eitherthe office or locker floor level. This room should con-tain a first-aid cabinet, a cot, and a lavatory and shouldhave rubber or vinyl-plastic tile floor and cove base,painted walls, and ceiling. The door should be wideenough to accommodate a stretcher.

(7) A powerhouse having more than three floorlevels should be provided with one or more elevatorsdesigned in conformance with the ANSI Safety Code forElevators and Dumbwaiters, Escalators and MovingWalks, A 17.1. The location should be established toenable omission of a penthouse above the roof of thestructure if possible and to reduce corridor travel to aminimum. The elevator should be a passenger typehaving minimum inside dimensions of five feet by sevenfeet, and a minimum capacity in conformance with ANSIA 17.1. Car speed should not be less than 200 feet perminute and controls should be of the pushbutton, auto-matic selective, collective type. Car and hoistway doorsshould be of the horizontal sliding type equipped withautomatic, two-speed power operators. In large power-houses, a freight elevator may also be provided.

3-4. Interior Details

In order to obtain reasonable uniformity and to establisha high standard of quality, certain interior details aredescribed in the following paragraphs. However, thesedetails are not mandatory. The designer should use hisknowledge of equipment and materials to achieve sim-plicity and first-cost economy consistent with utility,safety, aesthetics, and low maintenance costs.

a. Floor and wall finishes. All floors should bedesigned for serviceability and appearance and shouldadjoin all walls with a cove base if practical. These covebases should be of concrete, ceramic or quarry tile, orrubber or vinyl-plastic material. Where wet walls andfloors may be expected because of seepage, condensa-tion, and similar conditions, gutters should be providedaround the room at the walls. Cove bases are notrequired where gutters are used. Floors in rooms whereoil or water is stored, processed, or handled should beadequately drained. A floor slope of 1/8-inch per foot isrecommended where floor drains are installed. Curbsshould not be provided at doors in these rooms except asa last resort. The floors should be recessed below adja-cent floor whenever feasible. Steps should not be locatedat the immediate entrance. A platform or a ramp withnonslip finish and maximum slope of 1 in 12 should beprovided.

b. Acoustical tile ceiling. Where flat acousticalceilings are required, acoustical tile of suitable designmay be supported on steel supports.

c. Door trim. All trim for doors throughout theplant should be of metal. It is recommended that bucksbe used for mounting all trim. Poured-in-place, integraljambs, and trim are not desired except in areas wherestructural shapes are used as the finish trim.

d. Plumbing fixtures. Maintenance of the toiletrooms of the plant will be made easier if the floor area isclear of fixture mountings. For this reason, wall-hungurinals, water-closets, and lavatories should be usedthroughout the plant. Wall-hung, foot-operated flushvalves should be furnished for water closets and urinals.Unit coolers should be provided for drinking water, posi-tioned in such manner as not to unduly restrict passagethrough corridors. Because of possible damage due toleaks and to facilitate access for repairs, plumbing fix-tures, water supply, or drain piping should not be locatedabove the control room or directly over electrical switch-gear and similar equipment.

3-5. Schedule of Finishes

The finishes of some of the rooms in the plant aredescribed above in detail. The finishes for all rooms in aplant should be shown in the form of schedules to beincluded in the contract drawings. The schedules shoulddefine the “finish” and “color” of the various componentsof each room, such as floors, walls, ceilings, trim, doors,and equipment and should indicate the number and typeof prime and finish coats of paint required. Paint colorsshould be specified by the numbering system of the paintcolor chips shown in Federal Standard No. 595, “Colors”.

3-6. Painting

The painting requirements for both the above and belowwater level portions of the powerhouse are adequatelycovered, both as to the surface preparation and paintsystems to be specified in Guide SpecificationCW-09940, provisions of which should be followed inpreparing the painting portion of the Schedule ofFinishes.

a. Special formulations. The special formulationslisted in the above guide specification, or StandardFederal Specifications should be used to procure thepaint ingredients required in lieu of reference to a spe-cific manufacturer’s product.

3-6

EM 1110-2-300130 Apr 95

b. Aesthetic goals. Paint used to achieve aestheticgoals and super-graphics used to convey information anddirections are considered appropriate in areas open to thepublic.

c. Reasons for painting. With the few exceptionsalready listed, painting should not be used for decorativepurposes but should be confined to preventing corrosionof the surfaces requiring protection, to improving lightingefficiency, and to stopping dusting of concrete. Whenpainting is required for concrete walls, the concrete inarea visible to the public should have a sack- rubbedfinish before applying the paint.

d. Requirements. Painting requirements should becovered by general provisions in the specifications anddetailed information shown on the Schedule of Finishes.Some painting requirements may need to be indicated onthe details.

3-7. Design Memorandum

The architectural design of the powerhouse should bethoroughly discussed in a design memorandum. Generaland specific consideration that influenced the exteriordesign and type of construction should be given. Thereasons for designing a windowless plant or for usingwindows and also the reasons for using various materialssuch as precast concrete panels, concrete poured mono-lithically, prefabricated aluminum or stainless steel wallpanels for the exterior finishes of the powerhouse shouldbe stated. The method of determining the amount ofspace allotted for public use and for offices should beexplained.

3-8. Drawings

The architectural drawings required for the constructionof the powerplant should include the layout of groundsand access roads, exterior and interior elevations of thepowerhouse, cross sections through the powerhouseshowing all types of construction and floor elevations,detail elevations of all tile work and special interior

treatments, detail sections of stairs, stair and handraildetails, window and door schedules and details, plans ofall floors and roofs, detail plans of special areas such aspublic reception room, details of special decorative items,details of dado and tile finishes, details of roofing andflashings, and any other architectural details that will beneeded for the construction of the powerhouse. A rec-tangular system of column reference lines should beestablished and, in general, all dimensions should be tiedto these reference lines.

a. General layout. The general layout should bedrawn at such a scale as to require only one sheet andshould show means of access to the plant, public andemployee parking facilities, grading, drainage, lighting,and landscaping. Details of architectural features of thelayout, such as floodlighting arrangements and land-scaping, should be shown at a larger scale on otherdrawings.

b. Elevations. The exterior elevations of the power-house should be made at a scale that will allow the fulllength of the powerhouse to be shown on a standard sizesheet. These elevations should show all roof and floorelevations, finish grade elevations, all windows, doors, orother openings, V-rustications, surface treatments andspecial decorations and should make reference to theproper drawings for details. Interior elevations of power-house walls may usually be shown adequately on thecross sections. All tile wainscots should be drawn inelevation at not less than a 1/4-inch scale and shouldshow the vertical and horizontal courses of tile andshould give dimensions of the tile and of wall openings.All wainscots, floors, and door openings should be laidout, using the 4-inch modular system as proposed by theAmerican Standards Association.

c. Plans. Construction drawings required for theconstruction of the powerplant shall be in accordancewith specific requirements of Paragraph 7c of CE-4000,“Lump-sum Contract for Engineer Services for Design ofHydroelectric Power Plant.”

3-7

EM 1110-2-300130 Apr 95

Chapter 4Structural Requirements

4-1. Design Stresses

Allowable stresses will depend on the materials involved,the conditions of loading, and severity of exposure.

a. Allowable stresses. Structural steel and weldedjoints should be designed in accordance with the allow-able stresses outlined in the latest version of the AISCconstruction manual. Welding details should be as out-lined by the latest version of AWS D1.1 “StructuralWelding Code-Steel.” Gates, Bulkheads, Trashracks, andassociated guides should be designed using the allowablestresses outlined in EM 1110-1-2102. Steel andaluminum/switchyard structure should be as designedwith the loading and allowable stresses contained inNEMA publication SG-6 “Power Switching Equipment,”part 36.

b. Concrete structures. Concrete structures loadedhydraulically should be designed in accordance with theprocedures outlined in EM 1110-2-2104 “Strength Designfor Reinforced Concrete Hydraulic Structures.” Thoseportions of a powerhouse that will not have water load-ing, such as the superstructure, may be designed inaccordance with the latest version of ACI 318 “BuildingCode Requirements for Reinforced Concrete.”

4-2. Design Loads

a. General considerations. The structures should bedesigned to sustain the maximum dead, live, hydrostatic,wind, or earthquake loads which may be imposed uponthem. Where only partial installation is to be madeunder the initial construction program, considerationshould be given to the temporary loading conditions aswell as those anticipated for the completed structures.The stability of all powerhouse monoliths should beinvestigated for all stages of construction; and loads thatmay be imposed or absent during the construction periodshould be accounted for in the design memoranda.

b. Dead loads. Dead loads to be considered in thedesign consist of the weight of the structure itself, includ-ing the walls, floors, partitions, roofs, and all otherpermanent construction and fixed equipment. Theapproximate unit weights of materials commonly used inconstruction can be found in the AISC Manual. Forthose materials not included, refer to ASCE (1990). A

check should be made of the actual weights where avariation might affect the adequacy of the design, or incases where the construction may vary from normalpractice.

c. Live loads. In general, floors are designed for anassumed uniform load per square foot of floor area.However, the floors should be investigated for the effectsof any concentrated load, minus the uniform load, overthe area occupied. Equipment loads should take intoaccount installation, erection, and maintenance conditionsas well as impact and vibration after installation. In mostcases, it will be necessary to proceed with the design onthe basis of estimated loads and loaded areas until suchtime as the actual data are available from the manufac-turers. All live loads used in design should be recordedwith notations as to whether the loads are actual orassumed. The weights of turbines and generators ofCorps of Engineers hydroelectric power projects aretabulated in Appendix B1. However, weights will varyconsiderably for units of the same capacity. Estimates ofthe weights of the machines should always be requestedfrom the manufacturers for preliminary use in the design.Assumed loads should be checked later against actualloads, and, where differences are appreciable, the neces-sary modifications in the design should be made.

(1) The live loads shown in Table 4-1 are recom-mended for the design of slabs, beams, girders, and col-umns in the area indicated. These loads may bemodified, if necessary, to suit the conditions on indi-vidual projects, but will ordinarily be considered mini-mum design loads. These loads may be reduced20 percent for the design of a girder, truss, column, orfooting supporting more than 300 square feet of slab,except that for generator room and erection floors thisreduction will be allowed only where the member underconsideration supports more than 500 square feet of slab.This differs from ASCE (1990) recommendations for liveload reduction because of the loadings historicallyrequired in powerhouse floor slabs.

(2) Draft tube decks, gantry decks, and erection baysare often made accessible to trucks and Mobile Cranes,the wheel loads of which may produce stresses greaterthan those caused by the uniform live load. Under theseconditions, the loading used for design should include theweight of the heaviest piece of equipment, such as acomplete transformer including oil plus the weight of thetruck or crane. Stresses should be computed in accor-dance with AASHTO “Standard Specifications of High-way Bridges.” As a safety measure it would be

4-1

EM 1110-2-300130 Apr 95

Table 4-1Minimum Uniformly Distributed Live Loads

Element lb/sq ft

Roofs 50Stairways 100Floors:

Offices 100Corridors 100Reception rooms 100Toilets and locker rooms 100Equipment and storage rooms 200Control room 200Spreading room 150Generator room *500Turbine room 1,000Erection floor 1,000Maintenance shop 300Pump rooms and oil purification rooms 200

Gantry deck (outdoor powerhouse) 300 or H 20Transformer deck 300Intake deck--general 300 or H 20Intake deck--heavy lift areas 1,000Powerhouse access 300 or H 20Draft tube deck 300 or H 20

*300/lb/sq ft should be used for mezzanine floors and 1,000lb/sq ft for areas which may be used for storage or erection ofgenerator or turbine parts

advisable to post the load limit in all cases where such aload is used in design. Where mobile cranes are in use,the design should include outrigger loads. Where thepowerhouse monoliths include the headgate structure andintake deck, moving concentrated loads such as mobilecranes and trucks handling equipment parts and trans-formers should be considered in the design of the deckand supporting structure. In case the deck carries a high-way, it should be designed for standard highway loadingalso.

(3) Impact factors for vehicle wheel loads are givenin AASHTO “Standard Specifications for HighwayBridges.” Impact factors for crane wheel loads on run-ways are given in paragraph 4c(9).

(4) Wind loading should be applied to the structureas outlined in ASCE (1990). Members subject tostresses produced by a combination of wind and otherloads listed under group II in EM 1110-2-2105 should beproportioned on the basis of increased allowable stresses.For concrete structures, ACI 318 and EM 1110-2-2104provide appropriate load factors to be used for windloading. The design of switchyard and take-off structures

for wind is covered in the reference cited in para-graphs 4-2dand 4-15.

(5) Construction loads should be carefully consid-ered to determine if provision should be made in thedesign of these temporary loads or whether false work ortemporary bracing will suffice. It will be noted thatconstruction loads are classified as Group II loading inEM 1110-2-2105, and should have the applicable loadfactor combinations for concrete structures.

(6) The possibility of seismic activity should beconsidered and appropriate forces included in the design.The structural analysis for seismic loading consists oftwo parts: The traditional overturning and sliding stabil-ity analysis using an appropriate seismic coefficient, anda dynamic internal stress analysis, using either sitedependent earthquake ground motions or a static seismiccoefficient. The use of the seismic coefficient should belimited to sites where the peak ground acceleration forthe maximum credible earthquake is less than 0.2 g.Where a dynamic analysis is involved the powerhouseshould be investigated for both the maximum credibleearthquake and the operating basic earthquake. Earth-quake motions should be picked by procedures outlinedin ETL 1110-2-301 “Interim Procedures for SpecifyingEarthquake Motions.” General guidance for seismicdesign and analysis is found in ER 1110-2-1806 “Earth-quake Design and Analysis for Corps of Engineers Proj-ects.” Specific criteria for powerhouses should be asoutlined in ETL 1110-2-303 “Earthquake Analysis andDesign of Concrete Gravity Dams.” This referenceshould be followed closely when the powerhouse intakeforms a part of the dam. Site-dependent earthquake timehistories or response spectra should be carefully chosenthrough geological and seismological investigation of thepowerhouse site.

(7) All loads resulting from headwater and fromtailwater should be accounted for. Since it is sometimesimpracticable to protect the powerhouse against floodingat maximum tailwater elevation, a level should beselected above which flooding and equalization of inter-ior and exterior water loads will occur. This elevationshould be determined after careful consideration of allfactors involved, particularly the cost of initial construc-tion and of rehabilitation in relation to flood levels andfrequencies. The structures should be designed to with-stand tailwater pressures up to the chosen level and posi-tive provisions should be incorporated in the structure topermit rapid flooding and equalization of pressures after

4-2

EM 1110-2-300130 Apr 95

the tailwater rises above this level. Provisions shouldalso be made for rapid draining of the powerhouse whenthe tailwater drops. A maximum tailwater elevation(below that selected for flooding the entire powerhouse)should also be chosen for unwatered draft tubes andprovisions for automatic flooding of the water passageswhen that level is exceeded should be considered. It isnearly always advisable to reduce the uplift pressures onthe draft-tube floor by means of a drainage system.When “floating” or relatively flexible floor slabs areused, they are not considered in the stability analysis,either as contributing weight or resisting uplift. Whenthe floor slabs must take part of the foundation load, asis sometimes the case when the foundation is soil or poorrock, uplift should be assumed and the slab made anintegral part of the draft-tube structure.

(8) Snow loading should be applied to the structureas outlined in ASCE (1990) “Minimum Design Loads forBuildings and other Structures.” Members subject tostresses produced by snow loading should be propor-tioned by treating it as a Group 1 loading inEM 1110-2-2105 or, in the case of concrete structures, asa basic live loading.

(9) Wheel loads should be treated as moving liveloads in the design of crane runways. Maximum wheelloads should be computed from the dead load of thecrane and trolleys plus the rated live load capacity, withthe load in position to produce maximum truck reactionat the side of the runway under consideration. Dimen-sional data, weights, and truck reactions for cranesinstalled in Corps of Engineers powerhouses are given inEM 1110-2-4203. An impact allowance of 10 percentfor cranes over 80-ton capacity, and from 12 percent to18 percent for smaller cranes, should be added to thestatic loads. Side thrust at the top of the rail should betaken as 10 percent of the summation of the trolleyweight and rated capacity, with three-fourths of thisamount distributed equally among the wheels at eitherside of the runway. This may vary in the case ofunequal stiffness of the walls supporting the runway. Forinstance, if one wall is relatively massive, the entire sidethrust may be taken by this wall with little or no thrusttaken by the more slender wall. The runway designshould provide for longitudinal forces at the top of railequal to 10 percent of the maximum vertical wheel loads.Crane stops should be designed to safely withstand theimpact of the crane traveling at full speed with poweroff. Only the dead weight of the crane will be con-sidered and the resulting longitudinal forces should beprovided for in the design of the crane runway.

d. Load on switchyard structures. Switchyard struc-tures should be designed for line pull, equipment load,dead load, wind load, snow load, and ice load in accord-ance with the requirements of the NEMA PublicationSG-6-Power Switching Equipment. Take off tower lineloading should conform to ANSI Standard C2, NationalElectrical Safety Code, Section 25, and shall includeapplicable combinations of dead load, and line tensiondue to wind, ice and temperature changes.

4-3. Stability Analysis

a. Outline of investigation. A stability analysisshould be made for each monolith of the powerhouse andall critical levels should be investigated for the mostsevere combination of horizontal and vertical forces. Inthe case of a monolith in which the power unit will notbe installed with the initial construction, the stabilityshould be investigated for the interim as well as the finalcondition. Analysis should be made for the applicablecases indicated below and for any other combinations ofconditions which might prove critical. Cases S-1, S-2,S-3, and S-4, below are applicable when the powerhouseis separated from the dam, and Cases M-1, M-2, M-3,and M-4 are applicable when the powerhouse and head-works form a part of the dam.

(1) Applicable when powerhouse is separated fromdam.

(a) Case S-1: head gates open--headwater at top offlood-control pool, hydraulic thrusts, minimum tailwater,spiral case full, draft tube full, uplift, and wind orearthquake.

(b) Case S-2: head gates open, tailwater at power-house flooding level, spiral case full, draft tube full,uplift, and wind or earthquake.

(c) Case S-3: head gates closed, tailwater at draft-tube flooding level, spiral case empty, draft tube empty,uplift, and wind or earthquake.

(d) Case S-4 (Construction): no tailwater, and nouplift.

(2) Applicable when powerhouse and headworks,form part of dam.

(a) Case M-1: head gates closed, headwater at topof flood-control pool, minimum tailwater (ice pressure (if

4-3

EM 1110-2-300130 Apr 95

applicable)), draft tube and spiral case open to tailwater(uplift), and wind on upstream side or earthquake.

(b) Case M-2: head gates open, headwater at maxi-mum flood level, tailwater at powerhouse flooding level,spiral case full, draft tube full (uplift), and wind onupstream side or earthquake.

(c) Case M-3: head gates closed, headwater at topof flood-control pool, tailwater at draft-tube floodinglevel, spiral case empty, draft tube empty, uplift, andwind on upstream side or earthquake.

(d) Case M-4 (Construction): no headwater, notailwater, no uplift, and wind or earthquake.

(3) In some cases, the maximum overturningmoment will occur when tailwater is at some intermedi-ate level between minimum and maximum.

(4) In analyzing monoliths containing draft tubes, thefloor of the draft tube should not usually be consideredas part of the active base area since it is generallydesigned to take neither uplift nor foundation pressure.(See paragraph 4-2c(7)).

(5) Monoliths should also be checked for lateralstability under applicable conditions, and the possibilityof flotation at high tailwater levels should be borne inmind.

b. Vertical forces. The vertical forces that should beconsidered in the stability analysis are the dead weight ofthe structure, fixed equipment weights, supported weightsof earth and water, and uplift. The weights of movableequipment such as cranes and heavily loaded trucksshould be included only where such loads will decreasethe factor of safety against overturning.

c. Horizontal forces. The horizontal forces thatshould be considered are those due to headwater, tail-water, ice, earth, and wind or earthquake pressures.Force due to waves should also be included if the fetchis great enough to cause waves of considerable height.The forces resulting from temperature changes in steelpenstocks need not be considered, but the pressure ofwater in the penstocks should be included as hydraulicthrust resulting from wicket gate closure, depending uponthe assumed conditions. The application and intensity ofwind pressure or earthquake should be as prescribed inparagraphs 4-2c(4) and 4-2c(6).

d. Uplift assumptions. Effective downstream drain-age whether natural or artificial will in general, limit theuplift at the toe of the structure to tailwater. If thepowerhouse is separate from the dam, uplift from tail-water should be assumed 100 percent effective on theentire foundation area. If the powerhouse forms part ofthe dam, uplift assumptions should be the same as thosefor the dam, as described in EM 1110-2-2200. For thosestructures founded on soil, uplift should be assumed tovary from headwater to tailwater using the line of seep-age method as outlined in EM 1110-2-2502, “Retainingand Floodwalls.” For a majority of structures, thismethod is sufficiently accurate, however there may bespecial situations where the flow net method is requiredto evaluate uplift.

e. Base pressures and stability. Ordinarily the maxi-mum base pressures do not govern the design of power-house on sound rock. However, regardless of thefoundation material, they should always be checked tomake sure they do not exceed the safe working valuesestablished as a result of the geological or soils investiga-tions. For conditions that include earthquake, the resul-tant of all forces may fall outside the kern but within thebase a sufficient distance so that the allowable foundationpressure is not exceeded. The location of the resultant ofall forces, including uplift, acting on the structure shouldfall within the kern of either a rectangular or irregularlyshaped base. In pile foundations, the allowable material,bearing, and tension valves for the piles should not beexceeded. If the foundation at the selected site is entirelysoil, or is a combination of soil and rock, special consid-eration should be given to the possibility of unequalsettlement. It may be necessary to investigate the shear-ing strength of the foundation or, in case of a hillsidelocation, to investigate the stability of the structure andfoundation together by means of one of the methodsdiscussed in EM 1110-2-1902.

f. Sliding factor. EM 1110-2-2200 contains the crite-ria and guidance for assessing the sliding stability fordams and related hydraulic structures. Required factor ofsafety for major concrete structures are 2.0 for normalstatic loadings and 1.3 for seismic loading conditions.Horizontal earthquake acceleration can be obtained fromseismic zone maps and the seismic coefficient method isthe most expedient method to use when calculating slid-ing stability.

4-4

EM 1110-2-300130 Apr 95

4-4. Subgrade Conditions and Treatments

a. Rock foundation. It is very important that thestructure rest on sound material, unweathered and unshat-tered by blasting, in order to develop full resistance toshearing and sliding. The character of some rock foun-dations is such that disintegration will take place uponshort exposure. In these circumstances it will be neces-sary to preserve, insofar as possible, the natural charac-teristics of the unexposed foundation material.Disintegration may be prevented either by delaying theexcavation of the last foot or two of material until justprior to placing concrete, or by excavating to final gradeand immediately applying asphalt or a similar waterproofcoating to the exposed surface. Another method is toplace a light concrete cover immediately upon exposure,which provides a better surface for workmen and equip-ment as well as protection for the foundation. An other-wise sound rock foundation may contain seams of clay orother unsuitable materials which must be excavated andfilled with concrete, or areas for broken rock which mustbe consolidated by pressure grouting.

b. Soil foundation. The design of powerhouse foun-dation on earth is based on the in situ shear and bearingstrength of the underlying soil, with consideration beingtaken of weak seams at deeper depths below the founda-tion line. Weak materials may require excavation tofirmer material or the use of piles as a foundation. Aclose cooperation between the designer and the founda-tion and materials engineer must exist even in prelimi-nary design. Factors of safety against sliding should becomputed using procedures discussed in paragraph 4-3f.

4-5. Foundation Drainage and Grouting

a. Rock foundation. Provisions should be made forfoundation drainage, particularly under the draft-tubefloor slabs, to reduce uplift and permit the unwatering ofdraft tubes. Usually, a network of drains under the drafttubes is all that is required. Holes drilled into the rockconnect with these drains, which discharge through weepholes in the slab into the draft tubes. Drain holes shouldbe cleared on a routine basis, perhaps every 5 years, toensure their functional capability. For unwatering, adrain in each draft tube leads, through a valved connect-ing pipe, to a header which drains to a sump from whichthe water is pumped outside the powerhouse. Theoreti-cally, the drill holes in the rock should be deep enoughso the hydrostatic uplift (due to maximum tailwater withdraft tube unwatered) on a horizontal plane at the bottomof the holes will be more than balanced by the weight ofthe rock above the plane plus the weight of the draft tube

floor slab. A lesser depth will usually be satisfactory, asthe rock may be assumed to “arch” to some extent acrossthe end piers of the draft tube. It is recommended thatthe drain holes extend to a depth at least equal to one-half the monolith width below the floor slab. Drainholes should be spaced about 12 feet to 15 feet oncenters with weep holes in the slab 6 feet to 7-1/2 feeton centers. Where the nature of the rock indicates perco-lation of such magnitude as to render the unwatering ofdraft tubes difficult, perimeter grouting, area grouting, orboth may be used within the powerhouse foundation area.Care should be taken that this grouting does not interferewith drainage essential to the dam or the powerhouse. Ifperimeter grouting is used, a system of relief drains nearthe upstream side of the monoliths is necessary to pre-vent possible building up of headwater pressure under thestructure in case of leakage through or under theupstream grout curtain. Because of the possibility thatheadwater may enter the area and cause worse unwater-ing and uplift conditions than would have been the casewithout curtains, it is desirable to avoid perimeter grout-ing if possible. For additional information on the pur-pose, theory, and methods of foundation grouting refer toEM 1110-2-3506.

b. Soil foundations. When powerhouse structuresrest on soil, it is necessary to protect the foundationmaterial against scour and piping. The potential foreffective drainage and grouting in soil materials is verysensitive to the exact nature of the material. Upliftreduction may be more effective if underlying drainageblankets are used rather than drain holes.

4-6. Substructure Functions and Components

The powerhouse substructure supports the turbines andgenerators as well as a superstructure for their protectionand equipment related to their operation. The substruc-ture also contains the water passages, includes rooms andgalleries needed for certain mechanical and electricalequipment and services, and furnishes most of the massneeded for stability. It is usually desirable, where theturbines have steel spiral cases, to provide recesses in thesubstructure for accommodation of these parts and todesign the structure so that concreting operations cancontinue without interruption during their installation.Access galleries to the draft tube and spiral case shouldalso be provided in the substructure. Except as providedin Table 4-2, substructure concrete should be placed inlifts, generally not more than 5 feet thick. Each liftshould be divided into pours by vertical joints as deter-mined by equipment installation needs and as required tominimize shrinkage and temperature cracking.

4-5

EM 1110-2-300130 Apr 95

Table 4-2Powerhouse Concrete Lift Height Limitations (in feet)

Temperature-Controlled Concrete Normal ConcreteType of Placement Watertight Other Watertight Other

Mass or semi-mass areas such 7-1/2 7-1/2 5 5as draft tube or spiralcase roofs

Walls and piers over 7 ft thick 7-1/2 10 5 10

Walls and piers 5 ft to 7-1/2 15 5 107 ft thick

Walls 18 in. to 5 ft thick 15 20 10 20

Walls less than 18 in. thick 10 10heavily reinforced

Walls less than 18 in. thick 15 15moderately reinforced

4-7. Joints

a. General. The purpose of joints is to facilitateconstruction, to prevent destructive or unsightly cracks,and to reduce or eliminate the transmission of stressesfrom one portion of a structure to another.

b. Types of joints. Joints may be classified asexpansion, contraction, construction, or control. Selec-tion of the location and type of joint is governed by botharchitectural and structural requirements. Reinforcingsteel or structural steel should not cross expansion orcontraction joints, but may be continued across construc-tion and control joints. The functions of the variousjoints are as follows:

(1) Contraction joints are used to divide the structureinto separate monoliths, the principal purpose being toreduce the tendency to crack due to shrinkage resultingfrom the cooling of the concrete from the maximumtemperature. The location and spacing of the transversecontraction joints will be determined by the spacerequired for the unit. Where the powerhouse structure islocated immediately downstream or adjacent to the con-crete gravity dam, a contraction joint will be provided toseparate the dam and powerhouse. In the above casewhere more than one generating unit is involved, thespacing of the transverse contraction joints of the intakemonoliths must be the same as in the powerhouse sub-structure, although not necessarily on the same align-ment. Other detailed criteria for contraction joints aswell as the necessary construction joints are given in

EM 1110-2-2000. Ordinarily, no initial opening ortreatment of the vertical concrete surfaces at the joint isnecessary. However, the longitudinal formed jointbetween the toe of the dam and the powerhouse (seeparagraph 6) should have an initial opening of about1 inch filled with a suitable premolded compressive-typefiller to permit possible movement of the dam withouttransfer of load to the powerhouse substructure. Contrac-tion joints in the substructure should continue through thesuperstructure. Offsets in contraction joints are undesir-able and should be avoided if possible.

(2) Construction joints are required primarily for thepractical purpose of dividing the structure into satisfac-tory and convenient working units during concrete place-ment. Also, in large or irregular pours, it is usuallydesirable to require construction joints in order to mini-mize the influence of shrinkage on the formation ofcracks. Construction joints should be so located anddesigned that they will not affect the continuity of thestructure. Reinforcing steel should be continued acrossthe joint and provisions made to transmit any shear fromone side to the other. Horizontal construction jointsnormally do not require keying, because the roughenedsurface resulting from water jetting, greencutting, or sandblasting is adequate for transferring shear. This type ofjoint preparation is not feasible for vertical constructionjoints where shear keys are usually necessary.

(3) Control joints are adequately described anddetailed in EM 1110-2-2000 and in Guide Spec.CW-03301.

4-6

EM 1110-2-300130 Apr 95

c. Criteria for location of construction joints. Con-struction joints should be located to minimize cracking inthe more massive concrete placements. Greater restric-tions are necessary where concrete is to be watertight,such as in draft tubes and spiral cases; cracking is causedby heat generated during curing of the concrete andexternal and internal restraint to attendant volumechanges. This type of cracking is minimized by reducinglift heights, using low slump mixes, replacing cementwith pozzolan, increasing cure time between lifts, insulat-ing to control the rate of cooling, and reducing the plac-ing temperature of the concrete. Concrete placed underthese conditions is termed “temperature-controlledconcrete.”

(1) For less massive concrete placements, construc-tion joints should be located to facilitate forming andplacing of concrete. Lift height is controlled by form,shoring, and bracing design requirements to resist theconcrete pressure and dead weight. Reduced lift heightsare often necessary when concrete placement is madedifficult because of heavy, closely spaced reinforcing, orother physical constraints to placing and compactionequipment.

(2) Basic lift heights (in feet) should not exceed thelimitations shown in Table 4-2.

(3) Powerhouse substructures often use a two stageconcreting operation where the downstream wall andtailrace structure, and some or all of the spiral case piersare placed in the first stage concrete forming a skeletonstructure. The embedded turbine parts, and the slopingfloor and roof of unlined concrete spiral cases are cast inthe second stage concrete. This arrangement allows early“water-up” of the project, and also allows each unit to beplaced “on-line” upon its completion while constructioncontinues in neighboring bays. Keys should be formedin the vertical construction joints of the first stage con-crete, and reinforcing dowels provided so the completedstructure acts monolithically. Where the vertical jointsare subjected to headwater or tailwater pressure, reinforc-ing should also be adequate to resist the hydrostaticloading created in the joint. When embedding steel linedspiral cases, the lift heights below the center line of thedistributor lift heights are limited to 5 feet.

(4) To prevent distortion of the turbine liner concreteshould be placed in layers such that there is no morethan a one foot height differential of fresh concreteagainst the liner. The liner is to be continuously sprayedwith water during cure of the concrete.

(5) Where main structural slabs frame into walls, itis preferable to locate a horizontal construction joint inthe wall at the elevation of the bottom of the slab. Theslab is then cast over the prepared wall joint. Keying ofmainslabs into walls or piers pose design and construc-tion problems, and should be used only when the con-struction schedule dictates a need for delaying the slabplacement. When main slabs are keyed, it is necessaryto dowel heavy reinforcing through the forms and thenlap splice closely spaced slab reinforcing at a point ofmaximum stress. Deep key ways interfere with the verti-cal curtain of wall reinforcing particularly if it is neces-sary to waterstop the keyed joint. These problems areless evident in thin, lightly loaded slabs, and it is oftenmore economical to key these slabs into the walls.

(6) Exterior concrete decks covering interior areasrequired to be dry should have a minimum thickness of12 inches. Minimum reinforcement should be 0.75% ofthe cross sectional area with half distributed to each face.Waterstops should be provided at contraction joints, andconstruction joints should be treated as specified in guidespecifications CW 03301.

(7) Vertical construction joints should be used todivide lift placements covering large areas into two ormore smaller placements based on the following:

(a) Maximum rate concrete can be batched andplaced without developing cold joints.

(b) Watertight concrete or other serviceabilityrequirements affected by shrinkage cracking.

(c) Openings, blockouts or other discontinuities inthe placement that tend to generate cracks.

(d) A need for a vertical construction joint, such asthe one normally used between the intake and power-house structures, to allow flexibility in concrete placingschedules for different construction areas.

(e) The tempera ture-cont ro l led concre terequirements.

(8) As a general guide, base slabs up to 100 feetwide, can be placed, without need for intermediate verti-cal joints, using a 3-inch aggregate, temperature-controlled concrete, and a batching and placing capabilityof 150 cubic yards per hour. Because of the tendencyfor shrinkage cracks to radiate out from the turbine pitblockout, the greatest dimension for a spiral case roof

4-7

EM 1110-2-300130 Apr 95

pour should be limited to 70 feet, using 3-inch aggregatetemperature-controlled concrete. By using additionalreinforcing to minimize crack widths for satisfying thewatertight concrete requirements, pour widths can beincreased. With the added reinforcing, and by carefullyestablishing the temperature control requirements, it isseldom necessary to resort to segmented, waterstoppedroof placements used in the past for unlimited concretespiral cases.

(9) When vertical construction joints are required inthe substructure, they should extend upward through themassive part of the structure, but need not extend intoless massive piers, slabs or walls. Vertical constructionjoints should be keyed, and adequate shear friction rein-forcing should be provided across the joint to develop therequired shear capacity.

(10) A sloping construction joint should be locatedat the top of the main intermediate piers in the intake anddraft tube. The roof of the water passage is then placedacross the top of the prepared surface of the piers. Dueto the slope of the roof, several horizontally placed liftsare usually required to complete the roof. Where the lifttends to feather out to the roof form, the pour line shouldbe dubbed down 12 inches to eliminate the featherededge.

(11) Consideration should be given to the locationof horizontal construction joints on exposed faces. AV-notch rustication can be chamfering the joints in keep-ing with the architectural treatment.

4-8. Waterstops

Waterstops across contraction joints are necessary toprevent leakage and obtain satisfactory dry operating andworking conditions. They are required to exclude waterunder head in the substructure and to ensure weather-tightness of the joints in the superstructure. Material ofrubber or polyvinylchloride (PVC) is suitable for thispurpose. Extensive experience in the use of moldedrubber or extruded polyvinylchloride waterstops in jointsof conduits and hydraulic structures have proved thepracticability and advantages of using either of thesematerials. Copper waterstops were used in the past,however, they will fail where yielding foundations orother conditions result in differential movement betweenmonoliths. They are also easily damaged during installa-tion. PVC or rubber waterstops with a center bulb canwithstand this type of movement and are recommendedfor use in hydroelectric products. A wider width is indi-cated for waterstops in the substructure where large

aggregate is used and higher water pressures exist thanfor waterstops to be installed in low-pressure areas or forweather-tightness only. Waterstops should be placed asnear to the surface as practicable without forming weakcorners in the concrete that may spall as a result ofweathering, or impact, and should create a continuousbarrier about the protected area. All laps or joints inrubber waterstops should be vulcanized or satisfactorilycemented together, and joints in “PVC” waterstopsshould be adequately heat sealed. Waterstops in contactwith headwater for structures founded on rock shouldterminate in a recess formed by drilling holes 6 inchesdeep into the rocks and should be carefully grouted inplace. Occasionally, double waterstops are required inpier joints, one on either side of a formed hole, contain-ing bituminous material. In some important locations,two waterstops and a drain should be used to ensurewater-tightness.

4-9. Draft Tubes

The outline of the draft tube is usually determined by theturbine manufacturer to suit the turbine operating require-ments. However, in most cases, the manufacturer will belimited by certain physical requirements, such as thespacing and setting of the units, depth of foundations,and elevation of tailrace. The draft-tube portion of thesubstructure should be designed to withstand all loadsthat may be imposed on it, including superstructureloads, foundation reactions on the piers, tailwater on theroof, and the bursting effect of tailwater inside the draft-tube. Uplift under the floor of the draft-tube should alsobe considered in the design of the slab even when reliefdrains are provided. The upstream ends of intermediatepiers should have heavy cast or structural steel nosing(usually furnished by the turbine manufacturer) to with-stand the concentrated vertical load and to protect thepiers from erosion. Piers between adjacent draft-tubesare usually bisected by the monolith contraction jointfrom which water is excluded by seals near the gate slot.Therefore, each half pier must be designed for the pres-sure of tailwater on the inside of the draft tube as a nor-mal condition. It is advisable to consider also thepossibility of unbalanced load in the opposite direction incase of failure of a contraction joint seal with the draft-tube unwatered.

4-10. Spiral Cases

a. General. Spiral cases should be designed towithstand the bursting pressure of maximum headwaterplus water hammer.

4-8

EM 1110-2-300130 Apr 95

b. Types of spiral cases. The type of spiral casedepends on the power plant being considered.

(1) For low-head plants they may be of unlinedconcrete with engineered reinforcement to withstandapplied dead, hydraulic and equipment loads.

(2) For medium and high head plants, they should bemade of steel plate with shop welded longitudinal joints.Circumferential joints may be either field welded or highstrength bolted, depending on the turbine manufacturersdesign. Welded joints should be double-vee butt jointsmade under strict quality control and in accordance withthe provisions of ASME. It is preferred that the “c”sections of spiral cases requiring field welding be butt-welded to skirt plates which should be shop-welded tothe stay rings. All longitudinal welds should be radio-graphed. Ordinarily, stress relieving will not be required.When considering spiral cases under high head, andwhen shipping, handling, and erection cost would control,consideration should be given to the use of high strengthsteels. Completed spiral cases should be proof testedhydrostatically with a test pressure equal to 1-1/2 timesthe maximum design pressure.

c. Construction details.

(1) Consideration should be given to under-drainageof the turbine floor to intercept seepage upward throughthe spiral case roof. Under-drainage should consist of agrid of shallow trenches in the concrete subfloor coveredby porous concrete planks, and overlaid by a 3 inchgravel bed. The vertical joint between the intake struc-ture and the spiral case roof should contain a doublewaterstop and drain. Where the spiral case piers areplaced in the first of a two-stage concreting operationdescribed in paragraph 4-7c, and extend above the spiralcase roof line, the joint between the piers and roof shouldbe double waterstopped. Consideration should also begiven to providing a grouted contact strip in the contrac-tion joint between adjacent spiral case piers at approxi-mately mid-height of the pier. When a unit is unwatered,unbalanced hydrostatic load will be shared by both piers.The contact strip is constructed by injecting grout into aformed recess about 3 inches wide and 12 inches highlocated in the contraction joint. A waterstop should belocated just above and below the recess to prevent grout-ing the entire joint.

(2) The substructure may be “skeletonized” and thedownstream wall and portions of the side walls or pierscompleted prior to embedment of the spiral case. In thiscase a minimum clearance of 2 to 3 feet must be left

between the spiral case liner and the concrete walls ofthe recess. The transition section from penstock to spiralcase extension should not be encased. A penstock roomor gallery should be provided to house the transition,penstock coupling, and when required, a butterfly orspherical closure valve. A Dresser-type coupling shouldbe used to connect the penstock to the spiral case. Thelifts of concrete around the spiral case liner should belimited to the depth specified in paragraph 4-7c. A mini-mum of 72 hours per lift shall elapse between the placingof each successive lift. Bent steel ’J’-pipes 6 inches ormore in diameter should be provided for placing concreteunder the stay ring, discharge ring, and spiral case. Thenumber of ’J’ pipes required depends on the size of thespiral case. Concrete may be pumped through the ’J’pipes using a positive displacement concrete pump.After concrete placement is complete the ’J’ pipes shouldbe filled with concrete and left in place.

d. Embedment conditions. Two methods of embed-ment of steel spiral cases in concrete are commonly used:

(1) When steel spiral cases are to be embedded inconcrete in an unwatered condition, the top portion of thespiral case should be covered with a compressible mem-brane to ensure that the spiral case liner resists internalpressure by ring tension with only a small load beingtransmitted into the surrounding concrete. The compress-ible membrane should consist of sheets of closed cellfoam material with the property that a 1/4-inch-thickpiece deflects 0.10 inch under a 50-psi uniform pressureapplied normal to the surface. Polyvinylchloride foamand polyurethane foam are acceptable, and the sheets ofthis material should be attached to the spiral case linerwith an adhesive. The thickness of the membranedepends on the diameter and thickness of the spiral caseliner, and the internal pressure being resisted. The com-pressible membrane should extend to the first construc-tion joint below the horizontal centerline of the spiralcase. A drain should be provided along the lower limitsof the compressible membrane in order to prevent trans-mitting stress to the concrete through a water medium.

(2) When steel spiral cases are to be embedded inconcrete under a pressurized condition, a test barrel isused to close off the opening between the upper andlower stay rings, and a test head is attached at the inletof the spiral case extension. The spiral case is filled withwater and pressurized to the test pressure or to a pressureequal to head water plus water hammer while encasementconcrete is placed. Grout and vent holes in the stay ringare fitted with plugs which remain in place until thespiral case is unwatered. After concrete has been placed

4-9

EM 1110-2-300130 Apr 95

at least one lift above the top of the spiral case, and thetop lift has set at least 72 hours, the spiral case should beunwatered and the test barrel and test head removed.Workable concrete should then be placed through thebent steel ’J’ pipes to fill the void under the stayring/discharge ring. Neither a compressible membrane ordrains are required for embedding spiral cases under thepressurized condition, except when low alloy steels orhigh strength quenched and tempered alloy steels areused for spiral case construction, consideration should begiven to providing drains.

e. Concrete placing. The use of mechanical vibra-tors will not be permitted closer than 5 feet to any partof the spiral case, stay ring/discharge ring, or draft tubeliner, except that small vibrators may be lowered throughthe grout holes in the stay ring to vibrate concrete placedthrough the steel ’J’ pipes.

(1) Concrete placement through the steel ’J’ pipesshould be accomplished in a single lift operation whichbrings the concrete to within about 1 inch of the lowerstay ring. After a minimum seven day cure period, groutfill pipes shall be attached to grout holes spaced evenlyaround the stay ring, and non-shrink grout injected at ahead not exceeding 6 feet. A vent hole shall be locatedapproximately midway between grout holes to permitescape of entrapped air and water.

(2) Concrete reinforcement above the spiral caseshould be designed to distribute the generator pedestaland turbine floor loads to the stay ring and the spiralcase piers and walls.

4-11. Generator Pedestals

The generator, except in some low-head plants, is usuallysupported on a heavy concrete pedestal. The details ofthis pedestal will depend on the make and type of gener-ator to be installed. It should be of massive constructionand should be designed to resist vibrational forces fromthe moving mechanical parts, the heavy loads from thethrust bearing, and the short circuit torque of the genera-tor. It is usually designed to support the generator roomfloor also. Openings in the pedestal should be providedon all four sides when practicable for access to and ven-tilation of the turbine pit. Adequate head room should beprovided between the underside of the generator and thegenerator platform, if one is used, and between this plat-form and the turbine walkway.

4-12. Bulb Turbine Supports

Bulb turbines are supported in a much different mannerthan the typical vertical shaft Francis or Kaplan unit. Atypical cross section of a bulb unit is shown in Fig-ure 4-1. The main element of support for a bulb turbineis the stay column. It must carry the weight of the rotat-ing parts, most of the stationary parts, and the hydraulicloads due to thrust, hydrostatic pressure, and transientloading. A typical stay column consists of an upper andlower support column fixed to the inner and outer staycones. The inner stay cone forms the inner water pas-sage and houses the turbine parts. The outer cone formsthe outside water passage surface. This cone and bothsupport columns are embedded in concrete, thereby trans-mitting all loads to the structure.

4-13. Types of Superstructures

The main superstructure may be one of three types:indoor, semi-outdoor, or outdoor. The indoor type com-pletely encloses the generators and the erection bay andhas an inside crane runway supported by the walls of thestructure. The semi-outdoor type consists of a continu-ously reinforced slab over generators and erection baysupported by heavy transverse walls enclosing 2 or3 units. The powerhouse crane is an outdoor gantry withone runway rail on each side of the low superstructure.Sliding hatches in the roof over each generator and in theerection bay provide access for handling equipment withthe crane. In the outdoor type, each generator is pro-tected by a light steel housing which is removed by theoutdoor gantry crane when access to the machine isnecessary for other than routine maintenance. The erec-tion and repair space is in the substructure and has a roofhatch for equipment access. Choice of type should bedictated by consideration of first cost of the structurewith all equipment in place, cost of maintenance ofbuilding and equipment, and protection from the ele-ments. The indoor type affords greatest protection fromthe weather and facilitates operation and maintenance ofequipment. The semi-outdoor type may sometimes havea marginal economic advantage insofar as it pertains tothe cost of the structure, but this advantage will notalways offset the increased equipment cost. The outdoortype is structurally the most economical at sites with lowmaximum tailwater. The structural economy must, how-ever, be weighed against increased cost of generatorhousing, greater crane costs, and increased maintenanceof equipment.

4-10

EM 1110-2-300130 Apr 95

Figure 4-1. Typical cross section thru bulb unit

4-14. Superstructure - Indoor Powerhouse

a. Framing. The framing of the superstructure maybe cast-in-place or precast reinforced concrete, pre-stressed concrete, structural steel, or a combination. Thechoice is dependent on economy and architecturalrequirements.

b. Concrete walls. Concrete exterior walls may becast-in-place with uniform thickness, column and spand-rel wall, precast panels, or prestressed precast units.They must all be designed to withstand the stresses frompossible loading combinations and at the same time pro-vide the necessary space requirements, both for embed-ded items and interior clearances. Provisions mustusually be made for carrying loads imposed by bridgecranes and the rails are usually supported by continuouscorbels or wall offsets at the elevation of the rails.Exterior concrete should not be rubbed nor should formliner be used, but a rigid specification for forming shouldbe set up to insure reasonably smooth, plane surfaces. Insome cases, special finishes, such as bush hammered orstriated concrete, may be considered for special architec-tural effect. Matched tongue-and-groove lumber of2-inch nominal thickness is satisfactory for sheathing.

Wall pours should not be made more than about 10 feetin height. Horizontal rustications should be used at thepour joints on the exterior side where practicable in orderto prevent unsightly spalling; hence, locations of jointsand pour heights will depend partly on the exterior archi-tectural treatment. In the interior of the powerhousewhere neat appearance is essential, it will be necessary toprovide a smooth, dustless surface. The requirements forobtaining such a surface are contained in EM 1110-2-2000. Sack rubbing of the concrete surfaces should beavoided insofar as practicable. Contraction joints in thesame vertical plane as those in the substructure should beprovided in the superstructure walls. Criteria for open-ings in exterior walls are given in paragraph 3-1.

c. Steel framing and walls. While self-supportingconcrete walls are usually preferred in the generator anderection bays, their justification is dependent upon econ-omy and tailwater limitations. Where economicallyfeasible, steel framing with curtain walls or insulatedpanels should be used where the generator floor is abovethe maximum tailwater. The use of steel framing may,in some cases, be desirable to permit the early installa-tion and use of the crane runways and crane. Thisadvantage should, however, be evaluated only in terms of

4-11

EM 1110-2-300130 Apr 95

overall cost. The steel framing for each monolith shouldbe a separate unit, with no steel except the crane railscrossing the contraction joints. Crane rail splices shouldbe staggered a few inches with the joints. One bay ineach monolith should be diagonally braced in both roofand walls. Bents may be composed of columns support-ing simple beams or girders or may be rigid frames.Trusses should be used only if dictated by unusuallyheavy loads and long spans. In case it will usually beadvantageous to weld shop connections and bolt fieldconnections. Exceptions should be made for field splicesin long rigid frames, which should be welded for struc-tural continuity.

(1) If steel framing is used in other parts of thestructure, it is usually of the conventional beam andcolumn type used in office buildings.

(2) Suspended ceilings should be avoided unlesseconomically justifiable. Inner tile walls to conceal thesteel columns or rigid frames should be avoided. Notonly is concealment of the steel considered unjustifiedbut high thin walls are a hazard structurally.

d. Floors. Floors systems should be reinforcedconcrete flat slabs or one or two-way slabs with a 6-inchminimum thickness. The types of floor finishes and covedetails designated for the various parts of the super-structure are given in paragraph 3-4a. Placement ofconcrete in floor slabs should be stopped sufficientlybelow finish grade to allow for appropriate finishes. Thethickness of the structural slab will in many cases bedetermined by the member and size of electrical conduitswhich it must encase. Separate concrete fill placed ontop of the structural slabs to encase conduits is uneco-nomical but can be used where large numbers of conduitsmust be accommodated, or where reinforcement in thestructural slab is closely spaced. If used, it is recom-mended that the generator room floor be designed as aslab of uniform thickness, supported on the upstream anddownstream walls and at the generator pedestal and car-ried on double columns at the contraction joints. Build-ing contraction joints with water stops should be carriedthrough all floor slabs. Shrinkage and temperature steelshould be provided in the tops of all slabs. At hatchwaysthrough floors, flush sockets should be provided for theinstallation of temporary railings for protection of person-nel at times when the covers are removed.

e. Roofs. Roof framing will usually consist of pre-cast, prestressed units such as tee’s, double tee’s or hol-low core plank. If structural steel framing is used, it willusually be fabricated steel girders supporting steel

purlins, which in turn, support the roof deck. Slope fordrainage should be provided by the slope of the roofdeck or the use of sloped insulation. The use of light-weight or sawdust concrete should be avoided. Insula-tion, embedded in hot bitumen or mechanically fastenedshould be applied over a vapor seal course to the roofslab or deck. Foam insulation should be avoided due tothe unevenness of application. Thickness of insulationshould be determined by an analysis of heating and cool-ing requirements. Roofing criteria are given inparagraph 3-2.

f. Future extensions. A temporary end wall must beprovided for a superstructure which will at some futuretime, be extended to house additional units. The con-struction of the temporary wall should be such that itmay be easily removed, and with a minimum of interfer-ence in the operation of the station. The temporary wallbelow the maximum tailwater elevation should be madeof precast concrete slabs, supported on a steel frame-work, designed to resist the tailwater pressure, and sealedwith rubber or polyvinylchloride water seals at all joints.The remainder of the temporary wall could be made ofprefabricated metal panels which can be removed andpossibly utilized in the future permanent end wall.

g. Vibration. The superstructure in the generatormonoliths will be subject to vibration caused by thegenerating units. In order to minimize the effect ofvibration on the main structural framing, the superstruc-ture should be made as rigid as practicable. Concretecolumns and walls should be integral with floor slabs andgirders. Steel beams should be framed into columns andgirders with full depth connections and not with seatangles alone. In some cases it may be desirable to usetop flange clip angles also. Special attention should bepaid to framing connections in light floors, balconies,stairways, and roofs and to fastenings of gratings, prefab-ricated metal panels, precast slabs and handrails.Threaded or welded handrail connections are preferred topin connections. The effect of vibration in a generatormonolith is, of course, greater on members close to theunit than on those at a distance. Also, members in partsof the structure separated from the generator monolithsby contraction joints will be less affected. Therefore, thedesigner must use careful judgment in determining theextent to which vibration will influence the design ofsuch members.

4-15. Intakes

a. Type of intakes. Intakes may be classified as lowpressure, or high pressure, according to the head on the

4-12

EM 1110-2-300130 Apr 95

inlet, but there is no definite line of demarcation separat-ing the two types. For low-head plants and for develop-ments where the pool drawdown is small, low-pressureintakes are used. If the pool drawdown is to be large,such as on many multipurpose projects, the intake will beof the high-pressure type. It is advantageous to locatethe intake high as practicable in order to minimizeweights and travel distance of gates, size of hoist, etc., aswell to keep the sill above possible silt deposits. Low-pressure intakes are usually incorporated in the dam and,for low-head plants, are also part of the powerhousestructure. High-pressure intakes may be in the dam itselfor may be in a separate structure or structures in theforebay. The essential requirement if the two types arethe same, but the details and equipment may be radicallydifferent. Features common to practically all intakes are:trash racks, gates, steel bulkheads, concrete stoplogs, orall three, and converging water passage or passages.

b. Shape of intake. The lines of the intake should becarefully laid out to obtain water velocities increasinggradually from the racks to the penstock, or to the spiralentrance. Abrupt changes in area of the water passageshould be avoided in order to minimize turbulence andconsequent power loss. The sections between the rectan-gular gate and the round penstock entrance is particularlyimportant. The transition is ordinarily made in a distanceabout equal to the diameter of the penstock. Model testsare of great value in determining a satisfactory shape ofintake, especially if Juvenile Fish Bypass is a designconsideration.

c. Trash racks. Trash racks are usually vertical inorder to economize on length if intake structure. Forlow-head intakes, however, where the increase in lengthof structure would be small or where considerable trashaccumulation may be expected, they are often sloped tofacilitate raking. Water velocities at the racks should bekept as low as economically practicable with a maxi-mum, for low-pressure intakes, of about 4 feet per sec-ond. For high-pressure intakes, greater velocities arepermissible but should not exceed about 10 feet persecond.

(1) The racks are usually designed for an unbalancedhead of 10 to 20 feet of water and are fabricated bywelding in sections of a size convenient for handling.For low-head intakes, stresses due to complete stoppageand full head should be investigated and should notexceed 150 percent of normal stresses. If the racks areto be sheathed for the purpose of unwatering the intake,case II working stresses should not be exceeded for thatloading condition. The clear distance between rack bars

varies from two to six inches or more, depending on thesize and type of turbine and the minimum operatingclearances. Bar thickness should be consistent withstructural design requirements, with the vibrationaleffects resulting from flowing water being considered. Athick bar should be used with the depth of the bar con-trolled by the allowable working stress.

(2) The design of the guides and centering devicesfor the rack sections should receive careful attention.Clearances should be small enough to prevent offsetsinterfering with removal of the racks, or operation of arake if one is provided. Embedded members on theguide slots should have corrosion-resisting exposed sur-faces. Corrosion-resisting clad steel is satisfactory forthe purpose.

(3) For high-pressure intakes in concrete dams, thetrash rack supporting structure is sometimes built outfrom the face of the dam in the form of a semicircle inorder to gain rack area to maintain low velocities.

d. Gates. Provisions for emergency closure of theintake downstream from the racks is necessary to protectthe generator unit. A vertical lift gate in each waterpassage is usually provided and is normally suspendedjust above the roof of the intake from a fixed hoist. Onvery low-head multiunit plants a single set of intake gatesoperated by a gantry crane is adequate and will be lessexpensive than individual gates operated by fixed hoists.In either type of installation, self-closing tractor gatescapable of operating under full flow are provided. Fixedwheel gates may be the most economical type for intakeswhere a gantry crane will be used for operation. Bronze-brushed wheel bearings should be used if the wheels willbe submerged when the gate is in the stored position,otherwise, antifriction bearings can be used. For all butthe lowest head intakes, “caterpillar” type gates withcorrosion-resisting steel rollers and tracks have beenfound to be the most economical.

(1) In selecting the position of the gate slots, limit-ing velocities of flow as well as economical gate sizeshould be considered. If the slots are located too fardownstream, where the opening is small, power reductionfrom eddy losses may be more costly than a larger gate.The duration of peak demand on the plant will also affectthe location of the slots, since a higher velocity may betolerated for a short time. In any case, however, it isadvisable to keep the maximum velocityV in feet persecond below that given by the expression:

V 0.12 2gh

4-13

EM 1110-2-300130 Apr 95

in which h is the head on the center line of the gate atnormal power pool.

(2) Slots for stop logs or bulkhead gates are usuallyprovided just upstream from the gates so the gate slotsmay be unwatered for maintenance operations. In casewhere headwater is never far above the top of the intake,the racks are sometimes designed to support sheathingfor unwatering.

(3) Essential fixed metal in the slop-log slots shouldhave corrosion-resisting exposed surfaces, since theseslots cannot be easily unwatered for repairs.

e. Air vents. Since emergency closure must be madeunder full flow conditions, negative pressures will tend tobuildup at the top of the intake just downstream from adownstream-sealing gate as the gate is lowered. Toprevent excessive negative pressures from occurring inthe penstock during emergency gate closure and toexhaust air during penstock filling operations, one ormore air vents should be provided just downstream fromthe gate. The air vents should be of sufficient size tomaintain a pressure of not less than 1/2 atmosphere inthe penstock at the maximum rate of depletion of waterfrom the penstock under emergency closure conditions.The opening in the intake roof should be as close aspracticable to the gate. The upper end of the air passageshould be open to the atmosphere well above maximumheadwater and in a location not readily accessible topersonnel. Gates sealing on the upstream side are some-times used. Air vents in the penstock may then be elimi-nated, as enough air will be introduced into the waterpassage through the opening between the downstreamside of the gate and the concrete structure. Gate slots forboth the upstream and downstream seal gates should beadequately vented by the use of open grating covers orby other means.

f. Prevention of ice troubles. Periods of freezingweather are likely to cause trouble with ice at low-pressure intakes, and the design of plants in northernlatitudes should take this into account.

(1) Frazil and anchor ice may cause loss of head byforming on, or clogging rack openings, or may immobi-lize racks and gates by massing in the slots. Continuoussurface ice tends to prevent the formation of frazil andanchor ice, and for this reason an ice sheet in the forebayis more beneficial than otherwise, except as it interfereswith raking, or at breakup when it must be chuted to thetailrace or passed over the dam.

(2) Formation of ice may be prevented in the slotsby means of electric heaters in casings embedded in thepiers next to the guides and on the racks by a bubblersystem with outlet nozzles just below the bottom of theracks and far enough upstream for the released air tocarry the ice particles to the surface without coming incontact with the racks. At the surface the ice is sluicedto the tailrace.

4-16. Penstocks and Surge Tanks

a. Details and design. The determination of thediameter of penstock and the selection of size, type, andlocation of surge tank, if one is used, involve rathercomplex economic considerations. Therefore, onlydetails of design will be discussed.

b. Free standing penstocks and surge tanks. Thepenstock should be designed for full pressure due tostatic head caused by maximum elevation of the operat-ing range for the intake pool plus waterhammer.Waterhammer studies should be conducted to determinetransient pressures at any point along its length. Thefollowing design conditions and their correspondingallowable stresses for carbon steels (see ASME, Boilerand Vessel Pressure Code, Sections 8 and 9 when othersteels are used) are to be considered for these structures.

(1) This condition includes maximum, minimum,and rated turbine static heads plus waterhammer due tonormal operation, load rejection and load acceptance. Italso includes stresses due to gravity loads and longitudi-nal stresses due to penstock movement. The allowablestress for this basic condition is equal to the smaller of1/4 of the specified tensile strength or 1/2 of the speci-fied yield strength. The load acceptance conditionincludes minimum static head and loading the turbinefrom speed no load to full gate opening at the maximumrate of gate opening. This condition will indicate a mini-mum pressure grade line for the determination of subatmospheric conditions. Amstutz buckling criteria shouldbe used for embedded conduits. Stewart buckling criteriashould be used for non-embedded conduits. If a valve isused as an emergency closure device, the conditions atmaximum flow and maximum head with maximum valveclosure rate must be analyzed.

(2) This includes conditions during filling and drain-age of the penstock or surge tank and seismic loadsduring normal operation. The allowable stress for thiscondition is equal to 1/3 of the specified tensile stress or2/3 of the specified yield point, whichever is less.

4-14

EM 1110-2-300130 Apr 95

(3) This condition includes the governor cushioningstroke being inoperative and partial gate closure in 2L/aseconds at a maximum rate, whereL equals the conduitlength in feet anda equals the pressure wave velocity infeet per second. The allowable stress for this conditionis equal to 1/2 of the specified tensile strength, but in nocase shall this stress exceed the specified minimum yieldstress.

(a) After combining longitudinal and circumferentialstresses in accordance with the Hencky-Mises Theory,whereSe² = Sx²+SxSy+Sy², the allowable stresses are not tobe exceeded by the resulting equivalent stress at anypoint on the penstock or surge tank.

(b) Minimum shell thicknesses are recommended forall steel penstocks to provide the rigidity needed duringfabrication and handling. This minimum may be com-puted from the formulaT = D + 20/400, whereD equalsthe diameter in inches andT equals the minimum shellthickness in inches. A thinner shell may, in some cases,be used if proper stiffeners are provided during fabrica-tion, handling, and installation.

(c) Welded joints should be butt-welds made understrict procedure control by qualified operators, and inaccordance with the provisions of CW-05550, weldedpower penstock and surge tanks. All longitudinal seamsshould be examined radiographically in accordance withCW-05550.

(d) Completed penstocks with an operating headgreater than 100 feet, should be hydrostatically testedwith an internal pressure that will produce a hoop stressof 1.5 times the allowable stress. Penstocks with operat-ing heads less than 100 feet should be pressure tested ifthey are unusually long, as may be the case of powertunnels or some conduits. Care should be taken whenspecifying test pressures to indicate where on the pen-stock the pressure is to be measured. This will ensurethat the penstock is not overstressed during the test. Ifthe entire penstock cannot be tested as a unit, individualsections are to be tested in the shop after they have beenradiographed. The pressure should be applied threetimes, being increased and decreased slowly at the uni-form rate. The test pressure should be held for a lengthof time sufficient for the inspection of all plates, joints,and connections for leaks or signs of distress. It is desir-able that the test be performed when the pipe and waterhave a temperature of not less than 60 °F. The penstockshould be vented at high points during filling to preventformation of air pockets.

(e) Upon completion, and prior to insulation andpainting, surge tanks should be tested by filling the tankwith water to a point 1 foot from the top of the shell andmaintaining this water level for not less than 24 hours, orsuch additional time as may be required to inspect allplates, joints, and connections for leaks or signs of dis-tress. Preferred water and shell temperatures for the testshould be not less than 60 °F.

(f) In long penstocks, a surge tank may be necessaryto prevent the fluctuation of water-hammer flow fromseriously interfering with turbine regulation (see 4-16(f)).Free-standing penstocks should be constructed so as topermit any leakage to drain to tailwater without pressur-izing the surrounding regulating outlet conduit. Carefulattention should be given to anchorage of the penstockagainst longitudinal thrust.

c. Power conduit linings. The function and many ofthe details of construction and erection for an integrallyembedded steel liner are similar to a free-standing pen-stock; however, the loading conditions are different. Thesteel lining, concrete encasement, and if present, thesurrounding rock act together to resist the pressures.EM 1110-2-2901 outlines in detail the loading conditionsand allowable stresses for a conduit under embankmentsor rock. In both instances, external pressures must beaccounted for as well as the internal pressures.

d. Water velocities and water hammer. The velocityof flow in penstocks depends largely upon turbine regula-tions but is seldom lower than 6 feet per second. In veryhigh-head plants velocities as high as 30 feet per secondhave been used. For medium-head plants at maximumdischarge, velocities of about 12 to 18 feet per secondare typical. It should be noted that the allowable stressesfor the components of the turbine spiral case, spiral caseextension, valve, and valve extensions are different thanthose for the penstock. Refer to the guide specifications(CE-2201.01, CE-2201.02, and CE-2201.03, etc.) forthese allowable stresses. The point of division betweenthe penstock and spiral case/valve extension is custom-arily defined as the limit of supply for the turbine and/orvalve manufacturer.

(1) Changes in the rate of flow in penstocks causevariations in pressure known as water hammer. Thesechanges in flow rate can be caused by the turbine wicketgate motions due to power changes or load rejections,unit runaway, and closure of the emergency valve orgate. The magnitude of the pressure variation is depen-dent upon the length of penstock, the velocity of the

4-15

EM 1110-2-300130 Apr 95

water, and the rate of change of the flow. When theturbine gates close due to a decrease in load, the pressureincreases above the steady full load gradient. As the gatemovement ceases, the gradient drops below that forsteady full load, then fluctuates with diminishing ampli-tude between the maximum and minimum positions untilthe movement is damped out by friction. When anincrease in load causes the turbine gates to open, thegradient first drops below that for steady full load, thenfluctuates in a manner similar to that described for gateclosure. The penstock must be designed at every point towithstand both the maximum and minimum pressure atthat point as determined by the highest and lowest posi-tion of the water-hammer pressure gradient.

(2) The subject of water hammer is covered inHydroelectric Handbookby Creager and Justin,Hand-book of Applied Hydraulicsby Davis, Engineering FluidMechanics by Jaeger, andWaterhammer AnalysisbyJohn Parmakian. Prior to development of plans andspecifications, the hydraulic system should be modeledusing a digital computer to simulate the various designconditions and configurations of the hydroelectric facility.The Corps has had a computer program (WHAMO)especially developed to simulate water hammer and massoscillation in hydro-power and pumping facilities. Thisprogram or one equal to it should be used for thispurpose. The Hydroelectric Design Center should beconsulted prior to usage of WHAMO.

e. Bends, wyes, and tees. The distance from anelbow or bend in a penstock to the turbine inlet shouldbe as great as the layout will permit in order that distur-bances in the flow at the bend will not affect turbineperformance. If a butterfly valve is used, its center lineshould be at least 3 penstock diameters upstream fromthe center line of the unit. The penstock must beanchored at bends to withstand the centrifugal forces ofthe water as it changes direction. Anchorages are usuallyblocks of mass concrete encasing the pipe. Wyes andtees involve internal pressures on noncircular sectionsand require special design. Often the entire wye branchor tee is encased in reinforced concrete, sometimes withembedded steel girders and tie rods, to prevent deforma-tion and concentration of stresses in the shell. An exam-ple is the tee at a surge tank riser. Stress analysis ofwyes and tees can be done as outlined in “Design ofWye Branches for Steel Pipe” published in the June 1955edition of Journal of The American Water Works Associ-ation. For large structures or unusual configuration, afinite element analysis may be necessary.

f. Surge tanks and stability. For isochronous (iso-lated from the power grid) operation, a minimum ratio ofwater-starting time to mechanical starting time is requiredfor stability. Usage of a surge tank (which decreaseswater starting time) or a flywheel (increases mechanicalstarting time) may be employed. Surge tanks also mod-erate water-hammer pressures. In long penstocks thefluctuation of water-hammer pressure may seriouslyinterfere with turbine regulation unless relief is provided.For this purpose, a surge tank is generally used at thelower end of a penstock longer than about 400 feet. Forsimple surge tanks, the minimum area is usually 50 per-cent larger than the Thoma area. Isochronous operationcapability should be provided for all but the smallestunits. Surge tanks are of three basic types: simple,restricted-orifices, and differential. Also for undergroundstations where the rock is suitable, a surge chamber(accumulator) can be employed. A discussion of theadvantages and disadvantages of each type as well as anoutline of design procedures,is contained in Chapter 35of Hydroelectric Handbook by Creager and Justin.Waterhammer Analysisby Parmakian also covers solu-tions of simple surge tanks. The WHAMO program isalso capable of medeling all types of surge tanks as wellas predicting hydraulic instability. It is recommendedthat the Hydroelectric Design Center or an engineer whohas a successful record in surge tank design be retainedto analyze the flow regulation problem and design thetank at any power project where long penstocks are to beused and isochronous unit operation is a requirement.

4-17. Switchyard Structures

The most suitable and economical general arrangementand design of outdoor high-voltage switchyards should bebased on consideration of the scheme of high-voltageswitching employed, the voltage and capacity of the mainbuses and transmission lines, the number of generator ortransformer and transmission line bays required, thelocation of the main power transformers, the direction oftransmission lines leaving the yard, and size and topo-graphy of the space available.

a. The switchyard should be arranged to provideadequate space for the safe movement of maintenanceequipment and for the future movement of circuitbreakers and other major equipment into position withoutde-energizing existing buses and equipment. A chainlink woven wire fence approximately 7 feet with lockablegates should be provided to enclose the entire switchyard.

4-16

EM 1110-2-300130 Apr 95

b. An arrangement using high truss-type structuresand either strain or rigid-type buses required a minimumof ground area and is generally used for yards rated161 kv and below. An arrangement using low flat-typestructures with rigid buses is generally used for yards230 kv and above and may also be used for lower-voltage yards where adequate space is available. Thisdesign utilizes separate A-frame structures for dead-ending the transmission lines and individual lightweightstructures for supporting the buses, disconnects and otherequipment. This arrangement is considered the mostreliable and all equipment is easily accessible for inspec-tion and maintenance.

c. The switchyard structures and transmission linetake-off towers have special requirements in regard toloading, rigidity, resistance to shock, installation, andmaintenance. Standards for the design of switchyardstructures to meet these special requirements have beendeveloped on the basis of long experience of the powerindustry and are summarized in NEMA PublicationSG 67, “Power Switching Equipment.”

d. The switchyard structures should be designed forthe initial power installation but with provision forexpansion as additional generating units and transmissionlines are installed in the future.

4-18. Reinforcing Steel

Reinforcement should be designed using the requirementsset forth in the latest edition of ACI 318 “Building CodeRequirements for Reinforced Concrete,” and as amendedby EM 1110-2-2104 “Strength Design for ReinforcedConcrete Hydraulic Structures.” Guide specificationCW-03210 “Steel Bars, Welded Wire Fabric and Acces-sories for Concrete Reinforcement” provides the neces-sary details for tests, cutting, bending, and splicing ofreinforcement.

4-19. Encasement of Structural Steel

When the framing of the powerhouse is structural steel,the members shall not be encased, except for certainlocations where appearance is a factor, such as officespace and lobby, or where a fire hazard exists.

4-20. Retaining Walls

Walls subject to earth pressure, such as tailrace walls andfoundation walls at the shore end of the powerhouse,may be of the gravity, semi-gravity or cantilever type,depending upon economy, and should be founded onsolid rock wherever possible. Where sound rocks risesabove the bottom of the tailrace at the shore side, exca-vation may be saved by anchoring a concrete facing tothe rock and building the gravity wall above.

4-21. Area Drainage

Roof drains should be provided with basket-type strainersand should be connected to interior leaders discharginginto the headwater or the tailrace. All floors should haveflush drains to carry wash water, seepage, and possibleleakage from tanks to the station sump or, if the areadrained is well above maximum tailwater, to the tailrace.

a. Angles and abrupt bends in drain lines should beavoided insofar as possible, and cleanouts should beprovided where necessary to facilitate clearing the pipes.

b. Floors should be sloped so that drains are wellremoved from electrical equipment, and particular atten-tion should be paid to all details to avoid damage to suchequipment caused by leaks or clogged drains.

c. In cold climates drain piping must be locatedwhere temperatures will not drop below freezing or mustbe properly insulated. Outlets should be well belowtailwater to prevent formation of ice at the discharge.

4-22. Chamfers, Grooves, and Rustications

Exterior square corners are undesirable in concrete con-struction because of their tendency to break removal offorms or as a result of weathering or impact. Chamfersare usually formed on all exposed corners, but particularattention should be paid to this detail on the exteriorwalls. Chamfers of ample size should be provided at theends of monoliths, forming V-grooves at the contractionjoints. Horizontal V-grooves, or rustications are some-times used for architectural reasons and lift heightsshould then be planned so that the rustication will occurat the horizontal joints.

4-17

EM 1110-2-300130 Apr 95

Chapter 5Physical Security

5-1. Protection Plan

For every hydropower installation a detailed, writtenprotection plan shall be developed, which will use avail-able resources in the most efficient manner. Althoughthe primary area of concern should be protection fromterrorist threats, all aspects of protection design should beaddressed. (A recommended source of advice is theMissouri River Division (MRD), the Corps’ TechnicalCenter of Expertise for Protection Design.)

a. Type of protection. In determining the type andextent of physical protection required at an installation,the following pertinent factors should be taken intoconsideration in the indicated sequence.

(1) Importance of the power supply to NationalSecurity, to the regional power base, and project opera-tional requirements.

(2) Definition and analysis of area to be protected,and other pertinent consideration inherent to the problemsuch as existing hazards, either natural or man-made.(Threats from the stored water in the reservoir, fromlandslide or avalanche, from forest or brush fire, etc.)

(3) Operation, maintenance, and other requirementswhich must be integrated into the security plan.

(4) Environment-political, economic, legal,surrounding terrain, weather and climate.

(5) Costs of material and equipment to be installed,as well as availability of funds to provide at least mini-mum protection for all critical areas.

(6) Feasibility, personnel and equipment costs, andthe best method of providing adequate cost effectiveprotection.

b. Architectural design. The architectural design ofthe structure should incorporate necessary security designfeatures.

(1) A minimum of windows, particularly nearground level.

(2) Well anchored steel doors and frames.

(3) Transformers and power transmission lineslocated, or protected, to discourage threat activities.

c. Key elements in developing the protection plan.The response analysis should be assessed. The criticalitem to be estimated is the response time for securityforces (project guards, local law enforcement agents, etc.)to reach the installation once they are alerted. Thepowerhouse operator should not be considered a part ofthe security forces. Once the response time is estimated,then a threat analysis should be performed. This wouldconsider the most probable route of intruders to the mostvulnerable areas of the hydropower installation. Thenvarious delay zones (fences, walls, etc.) should be con-sidered, each with its own intrusion detection system.The threat analysis should result in a series of delayzones so that the total time for the intruders to reachcritical area of the hydropower installations, from firstdetection, exceeds the response time by security forces.

5-1

EM 1110-2-300130 Apr 95

Chapter 6Retrofitting Existing Projects

6-1. General

The addition of hydropower facilities at the existingCorps of Engineers projects must not jeopardize thepublic interest relative to water control management forflood control, navigation, water supply, water quality,recreation and other project proposes. In addition, thoseaspects of the design that could affect the safety of theproject must be consistent with Corps standards as torequirements of this manual and all referenced manualsand regulations. To ensure compliance with this policywhen development is by non-federal licenses, the Corpsof Engineers will review and approve the proposeddetailed design analysis and plans and specifications forthose hydraulic, structural and mechanical features thatcould affect the integrity and safety of the total project.Major items of concern, but not necessarily limited to,are discussed as follows:

6-2. Hydraulic Design Considerations

a. Proposals. Proposals to add hydropower facili-ties at Corps of Engineers projects must thoroughlyaddress the hydraulic design details and the overall func-tional capability. Items that must be addressed includethe following.

(1) Streamlining of entrance to power penstock fromflood control conduit must be addressed.

(2) Streamlining to preclude cavitation in flood con-trol conduit at junctions with penstock or gate slots mustbe addressed.

(3) Positive and negative pressure surges due topowerhouse load rejections, load acceptance, and unitrunaway is another important item to address.

(4) Reassessment of water quality provisions toinclude size and location of multi-level intakes and com-patibility of powerhouse release requirements with waterquality requirements is an important item.

(5) Means of dewatering power facilities withoutinterrupting water quality and/or flood control releasesmust be addressed. However, some powerhouses withlong penstocks, or those with only gates or valves imme-diately upstream of the powerplant need not be

dewatered except under emergency conditions. Thisprocedure can be followed only if it does not impactupon dam safety of flood control regulations. This typeof penstock can be inspected using divers or remotelyoperated cameras.

(6) Effects of adding trashracks in the existingintake if required for equipment protection must beaddressed.

b. Submittals. Submittals proposing inclusion oraddition of hydropower combined with water quality andor flood control facilities at Corps of Engineers projectsmust include a hydraulic design analysis covering alloperating and emergency conditions. Presentations needto address all items discussed above. Information onenergy and pressure grade lines throughout the hydraulicpassages covering maximum and minimum conditionswith local pressure drops at such places as bends, junc-tions, transitions, gate slots, etc., is necessary. The pre-sentations must include an analysis of the effects of apowerhouse load rejection. The degree of detail is to besufficient for the study stage being presented, although atfinal design stage. a transient analysis utilizing state-of-the-art computer programs must be performed andreviewed by a Design Center. The requirements apply toproposals from others (to be accomplished at theirexpense) as well as to in-house proposals.

c. Penstocks. The existing regulating outlet conduitsoffer an available connection between the reservoir andpotential hydropower facilities. Regulating outlet con-duits ar flood control or other non-power projects areusually designed for non-pressurized (open channel) flowconditions. for the most part, these conduits are of rein-forced concrete designed to withstand external rock orembankment loads and external hydrostatic pressures.Once hydropower facility is connected, the primary struc-tural concern is that an existing regulating outlet conduitbecomes a power penstock subject to internal pressuresequal to full pool plus any transient pressures due towater manner effects. Submittals proposing inclusion oraddition of facilities at Corps of Engineers projects mustinclude structural and geotechnical analysis covering alloperating and emergency conditions. Presentations needto address all items covered in this guidance. The degreeof detail presented should be sufficient for the studystage being presented. This applies to proposals fromothers (to be accomplished at their expense) as well as toin-house proposals. The following paragraphs presentacceptable design criteria for converting regulating outletconduits to power penstock (downstream control).

6-1

EM 1110-2-300130 Apr 95

6-3. Geotechnical Considerations

Original geologic conditions upon which project designwas based, and upon which cut and cover or lines orunlined tunnels were constructed, must be known so thatsafety and original design benefits are not reduced.Water must not be allowed to escape into the dam abut-ments from pressurized tunnels to cause slope stabilityproblems or groundwater changes that might affect thedam. An investigation of geologic conditions relative tothe design proposed for a pressurized tunnel must bemade. Existing lined tunnels may conceal voids, shearzones, rock of low deformation modulus, etc. Whenmodifying existing lined tunnels, design shall recognizeand provide for the above possibilities, just as it wouldfor unlined tunnels containing geologic weaknesses. Fulllength grouting behind linings or other measures may benecessary. If an existing tunnel is acting as a drainagefeature in an abutment, intentionally or unintentionally,the possibility of groundwater pressure changes occurringafter modification should be evaluated. The function andmany of the details of construction and erection for anintegrally embedded steel liner are similar to a free-standing penstock; however, the loading conditions aredifferent. The steel lining, concrete encasement, and ifpresent, the surrounding rock act together to resist thepressures. EM 1110-2-2901 outlines in detail the loadingconditions and allowable stresses for a conduit underembankments or rock. In both instances, external pres-sures must be accounted fro as well as the internalpressures.

6-4. Tunnels in Rock Abutments

An existing outlet tunnel (unlined or lined with otherthan steel) should be investigated to determine to whatextent the tunnel should be lined with steel plate to pre-vent leakage that could present a danger to the dam orabutment. The extent of steel liner plate should be suffi-cient to prevent leakage along rock fissures or joints thatintercept the dam or downstream of the impervious zone.An existing tunnel liner must be investigated for internalpressures that will occur once the hydropower facility isinstalled. In regions of an existing regulating outlettunnel liner where the rock cover is insufficient to offsetinternal pressures, or where geologic weaknesses exist, anew liner may be required fro structural reasons. A steellinerplate could be grouted in place and designed ascomposite with an existing concrete liner, provided theexisting liner reinforcement is adequate for all loads (seeEM 1110-2-2901). If the tunnel is unlined of if theexisting liner reinforcement is inadequate, a separate

free-standing penstock or new reinforced concrete linerwith composite steel liner plate should be provided.

6-5. Cut and Cover Conduits

a. General. In its existing non-pressurized condi-tion, these conduits are generally reinforced concretestructures without steel plate liners. To prevent leakagethat would endanger the embankment dam, a steel liningis required from the upstream face of the imperviouszone to the powerhouse. A reinforced concrete linercomposite steel liner plate, or a free-standing penstock,may be required to structurally accommodate the internalfull pool pressures resulting from downstream controlplus additional pressures due to water hammer effects.

b. Circular conduits. A steel liner grouted to beintegral with the existing concrete liner may be usedprovided the requirements of EM 1110-2-2901 are met.If the existing concrete reinforcement does not meet theabove requirements, a free-standing type penstock or newreinforced concrete liner with composite steel liner plateshould be provided.

c. Non-circular conduits. A free-standing penstock,erected within and independent of the existing regulatingoutlet conduit, should be provided.

6-6. Free-Standing Penstocks Within Conduits

Free-standing penstocks constructed within an existingconduit shall be designed in accordance with para-graph 4-16, penstocks and surge tanks. Plates and jointsshould be designed for full pressure due to static headplus water hammer as well as any negative pressuresdeveloped by hydraulic transients. All joints should bewelded except for the connection of the penstock to thespiral case, which is normally a flexible type. Free-standing penstocks should be constructed so as to permitany leakage to drain to tailwater without pressurizing thesurrounding regulating outlet conduit. Careful attentionshould be given to anchorage of the penstock againstlongitudinal thrust.

a. Gates and valves. The addition of hydropowerfacilities must include provisions for isolating the power-plant so as not to interfere with the project original pur-pose. When the existing flood control conduit ismodified for penstock use, a closure device such as abutterfly or spherical valve or a gate must be provided atthe powerhouse end of the penstock for shutoff of flow

6-2

EM 1110-2-300130 Apr 95

during emergency closure or during normal maintenanceof the equipment.

(1) The closure device should be designed for maxi-mum penstock head including water hammer andhydrostatically tested for 150 percent of the maximumdesign conditions. The valve operator must be capableof closing the device in from 2 to 5 minutes as practicalfor its size. The closure capability must be achievablewithout outside power. Thus, an energy storage devicesuch as an accumulator or counterweight is required.

(2) The closure of the normal water passage at thedownstream end for diverting flow to the turbine is sub-ject to the specific project layout. Gates or valves usedfor this purpose must be designed for the maximumwater pressure, including water hammer, and subject tohydrostatic testing in place.

b. Vents. When the existing flood control facilitiesare utilized for hydropower purposes, all the existing

components require careful analyzing and investigationfor any adverse cavitation or structural effects. One suchitem subject to structural loading greater than originallythorough analysis of the effects such changes would haveon the system when used in the original operation modefor the project purpose. During powerhouse operationthe vents are subject to full hydrostatic pressure includingwater hammer, and therefore structural adequacy shouldbe thoroughly investigated for this condition as well asthe seismic condition.

c. Bifurcation. In most instances, the utilization ofthe existing regulating conduit requires diverting thewater flow from the conduit to the power producingfacilities. The method of accomplishing this objectiverequires a bifurcation or diverting box depending of thespecific site conditions. The method chosen must bethoroughly analyzed for potential cavitation or structuraleffects and may require model testing to verify thedesign. For further structural requirements, seeparagraph 4-16e.

6-3

EM 1110-2-300130 Apr 95

Appendix AReferences

A-1. Required Publications

TM 5-809-1Load Assumptions for Buildings

TM 5-809-10Seismic Design of Buildings

TM 5-810-1Mechanical Design, HVAC

ER 1110-2-109Hydroelectric Design Center

ER 1110-2-1454Non-Federal Hydropower

ER 1110-2-1806Earthquake Design and Analysis forCorps of Engineers Dams

EM 1110-2-1902Stability of Earth and Rockfill Dams

EM 1110-2-2000Standard Practice for Concrete

EM 1110-2-2104Strength Design for Reinforced-Concrete Hydraulic Structures

EM 1110-2-2105Design of Hydraulic Steel Structures

EM 1110-2-2200Gravity Dam Design

EM 1110-2-2502Retaining and Floodwalls

EM 1110-2-2901Tunnels and Shafts in Rock

EM 1110-2-2906Design of Pile Foundations

EM 1110-2-3506Grouting Technology

EM 1110-2-4203Design Data for Powerhouse Cranes

EM 1110-2-4205Hydroelectric Power PlantMechanical Design

ETL 1110-2-256Sliding Stability for Concrete Structures (ETLsare temporary documents and subject to change)

ETL 1110-2-301Interim Procedures for Specifying EarthquakeMotions

ETL 1110-2-303Earthquake Analysis and Design ofConcrete Gravity Dams

CE-1602Dam Gantry Cranes

CE-1603Draft Tube Gantry Cranes

CE-1604.01Indoor Electrically Operated Traveling Cranes

CE-1604.02Indoor Electrically Operated Traveling Cranes

CE-4000Lump-Sum Contract for Design ofHydroelectric Power Plant

CW-03210Steel Bars, Welded Wire Fabric and Assessoriesfor Concrete Reinforcement

CW-03301Standard Guide Specifications for Concrete

CW-03305Standard Guide Specifications for Concrete

CW-05550Welded Power Penstocks and Surge Tanks

CW-09940Painting Hydraulic Structures andAppurtenant Works

A-1

EM 1110-2-300130 Apr 95

American Society of Civil Engineers 1990American Society of Civil Engineers. 1990. "MinimumDesign Loads for Buildings and other Structures(ASCE 7-88), New York.

A-2. Related Publications

Creager and Justin 1950Creager, W. P., and Justin, J. D. 1950.HydroelectricHandbook, Second edition, John Wiley & Sons, Inc.,New York.

Davis 1952Davis, C. V. 1952. Handbook of Applied Hydraulics,Second edition, McGraw-Hill Book Co., New York.

Jaeger 1949Jaeger, C. 1949.Engineering Fluid Mechanics, Blackie& Son, Ltd., London. (A translation by P.O. Wolf ofTechnische Hydraulik, Verlag Birkhauser, Basle, 1949.)

Miles Yanick and Company 1972Miles Yanick and Company. 1972.Visitors Facilities,Guidelines & Criteria Corps of Engineers, North PacificDivision.

Parmakian 1955Parmakian, J. 1955.Waterhammer Analysis. PrentissHall, New York.

Westergaard 1933Westergaard, H. M. 1933. “Water Pressures on Damsduring Earthquakes,” American Society of CivilEngineers, Transactions, vol. 98, (1933), pp. 18-433.Discussion, pp. 434-472.

A-2

EM 1110-2-300130 Apr 95

Appendix BTabulation of Generator and Turbine Data

B-1

EM 1110-2-300130 Apr 95

B-2

EM 1110-2-300130 Apr 95

B-3

EM 1110-2-300130 Apr 95

B-4

EM 1110-2-300130 Apr 95

B-5

EM 1110-2-300130 Apr 95

B-6

EM 1110-2-300130 Apr 95

B-7

EM 1110-2-300130 Apr 95

B-8

EM 1110-2-300130 Apr 95

B-9

EM 1110-2-300130 Apr 95

B-10

EM 1110-2-300130 Apr 95

B-11

EM 1110-2-300130 Apr 95

B-12

EM 1110-2-300130 Apr 95

B-13