CHAPTER 9 OPERATIONS GUIDELINES 9.0 GENERAL An operations plan details each of the safety program components outlined in Chapter 4. and detailed in Chapters 5 through 8. The extent of an operations plan depends on the complexity ofthe dam itself- factors such as dam size, number and type of appurtenances and operating mech- anisms. The operation of a dam may involve adjusting the reservoir level. control- ling debris by opening and closing valves. keeping records, and, in general. ensuring public safety. Prop- er operation procedures is extremely' important for miUntaining a safe structure. Many small dams do not need a full-time operator. but should be checked regularly. Specialopera- tional procedures to be followed dur- ing an emergency should be posted, particularly if the owner/operator is not always available. 9.1 OPERATIONS PLAN . GUIDEUNES Establishing an operations procedure or plan calls for detailed documenta- tion of the following: • Dam and reservoir physical characteristics data • Descriptions of dam com- ponents (Chapter 2) • Operations instructions for operable mechanisms (Chap- ter 9) • Inspection guidelines (Chapter 5) • Instrumentation .and monitor- ing guidelines (Chapter 6) • Maintenance operations guide- lines (Chapter 7) • Emergency operations guide- lines (Chapter 8) • Bibliographical information (Appendix D) As recommended in Chapter 4. collection and review of existing infonnation on the dam design, con- struction and structural character- istics is the first step in developing a dam safety program. for 75 inspections, monitoring. main- tenance, and emergency action plan- ning are presented in the other indicated chapters. The operation plan should have several seperate sections: Section A: Background Data 1. Vital dam statistics 2. Description of appurtenances Section B: Operations Instructions and Records 1. Operating instructions for oper- able mechanisms 2. Inspection instructions and foons 3. Monitoring instructions and forms 4. Maintenance instructions and forms 5. Biblography 6. Telephone list Section C: Emergency Waming System Sections A and B are described brieny below and a schedule of routine tasks is included. Instructions are included for frequent inspections, monitoring. and follow-up main- tenance. The Emergency Warning System plan is discussed in Chapter 8. 9.].] Background Data ]. Vital dam statistics include: a. General -. Type of dam • Height of dam • Length of crest • Width of crest • Angle of upstream slope • Angle of downstream slope • Available freeboard • Capacity tables for reservoir • Top of dam elevation • Capacity tables of inflow and outflow works • County location • Township location • Stream name • Year completed • Hazard classification
Transcript
CHAPTER 9OPERATIONS GUIDELINES
9.0 GENERALAn operations plan details each ofthe safety program componentsoutlined in Chapter 4. and detailed inChapters 5 through 8. The extent ofan operations plan depends on thecomplexity ofthe dam itself- factorssuch as dam size, number and type ofappurtenances and operating mechanisms.The operation of a dam may involveadjusting the reservoir level. controlling debris by opening and closingvalves. keeping records, and, ingeneral. ensuring public safety. Proper operation procedures is extremely'important for miUntaining a safestructure. Many small dams do notneed a full-time operator. but shouldbe checked regularly. Specialoperational procedures to be followed during an emergency should be posted,particularly if the owner/operator isnot always available.
9.1 OPERATIONS PLAN. GUIDEUNESEstablishing an operations procedureor plan calls for detailed documentation of the following:
As recommended in Chapter 4.collection and review of existinginfonnation on the dam design, construction and structural characteristics is the first step in developing adam safety program. Guid~lines for
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inspections, monitoring. maintenance, and emergency action planning are presented in the otherindicated chapters.The operation plan should haveseveral seperate sections:Section A: Background Data
1. Vital dam statistics2. Description of appurtenances
Section B: Operations Instructionsand Records
1. Operating instructions for operable mechanisms
2. Inspection instructions andfoons
3. Monitoring instructions andforms
4. Maintenance instructions andforms
5. Biblography6. Telephone list
Section C: Emergency WamingSystemSections A and B are describedbrieny below and a schedule ofroutine tasks is included. Instructionsare included for frequent inspections,monitoring. and follow-up maintenance. The Emergency WarningSystem plan is discussed in Chapter8.9.].] Background Data]. Vital dam statistics include:a. General
-. Type of dam• Height of dam• Length of crest• Width of crest• Angle of upstream slope• Angle of downstream slope• Available freeboard• Capacity tables for
reservoir• Top of dam elevation• Capacity tables of inflow
and outflow works• County location• Township location• Stream name• Year completed• Hazard classification
b. Spillway
• Type of spillway• Length of spillway• Spillway channel elevation• Normal pool elevation• Available freeboard• Maximum observed flow
Operoting instTuctions fOr operoblemechanisms - The plan should pr0vide complete. clear. st~by stepinstructions for operating aD mechanisms associated with a dam including the outlet control valve andspillway gates. Proper sequencesshould be emphasized and sketches,drawings. and photographs to aid inidentifying specific handles, crmb.buttons, etc should be includcd.. Thecorred method of opening and closing pard gates. gate usage duringlow and high flow. openings at whichexcessive vibrations are experienced,and operating problems peculial'to •specifIC gate should also be listed.For hydraulic and electric gates. aschematic diagram should be pr0vided showing eacb component (including back-up equipment) and itsplace in the operating sequence.
Instructions on the general operatioaoftbe reservoir. including the regulation of inflow and outlet ditches.should be given. These should statethe maximum pool levels to beallowed at different times of the year,maximum and/or minimum carryover storage. maximum and/or minimum permissible outlet releases.They should also descn"be operatioaof the outlet to limit or. preventexcessive spillway flow, and themethod for periodic drainage of thereservoir to permit thorough outlet orupstream slope inspectioa.
l~ct;on and ;nstTumentatioll - Aclear. step-by-step set of instructionsfor conducting a comprehensive
inspection of the dam and its surroundings should also be provided.Forms. for re~ding data such asthose in Appendix A. should be usedand copies of all completed~tion records should be kept.
Monitoring instTuctions - Clearinstructions on how to use monitoring instruments and how to takemeasurements at monitoring pointsshould be prepared, a map identifying each instnunent and monitoringpoint should be mcluded, and formsfor recording the data shou_1eI be p~vided. The monitoring points themselves, plus any seepage or otherareas needinl special attention shouldbe kept clear ofobscuring growth andbe permanently marked, so they canbe found during inspection. The helpof • qualified engineer will be usefulin developing this section.
Monitoring can only be beneficial ifthe observations are recorded in anorderly way and form a clear performance record. Thus, plotting orcharting some of the readings will benecessary. Instructions on how to.make and record each measwementor observation must be provided. Ifthe owner's engineer is not going toplot or chart the data, instructionsand forms should be developed toallow owneR. operators. or maintenance penonnel to do this work.An experienced consulting engineermay be helpful in preparing theneeded formats.
Maintenance instructions - instructions for performing periodic maintenance should be given in detail. sothat new penonnel can understandthe task and experienced personnelcan verify that they have completedthe wort properly. AU needed maintenance work should be .identifiedand listed. This list includes the tasksdescribed in Chapter 7 sucb as:
1. Removing brush and trees2. Removing debris· .3. Regrading the crest ud/or access
roads4. Removing harmful rodentsS. Operating and lubricating gates6. Addina riprap when needed7. Sealingjoints in concrete facings8. Oeaning drainpipes and outlets9. Maintaining monitoring points
10. Maintaining security of operating equipment
Bibliography - All available referencematerial should be cataloged in asingle Iisl Other title. aUthor oragency responsible for publication.date and place ofpublication or briefdescription. and the permanent 1ocation of the material (for example fi1ing cabinet in basement) should beincluded. Even materials withouttitles or authors. sucb as photographsand maintenance information, shouldbe listed.
Telephone List - A comprehensiveu~t<HIate listing of important telephone numben should be maintainedand include:
• The owner/operator (home andoffice) phones
• Employees actively involved withthe dam
• The local emergency management agency
• State police• The local police and fire depart
ments• ]be state agency responsible for
dam safety• Qualified local engineering c0n
sultants• Downstream residents
9.2 SCHEDULE OF ROunNETASKSA schedule should be establishedthat includes both day-to day tasksand tasks performed Jess frequentlyduring the year. Such a scheduleserves to formalize inspection andmaintenance procedures and makesit easy to determine when a tastshould be done. As suUested inTable 9.1. The frequency of arequited task is often dependent uponthe hazard classification of the dam(See Chapter 3).
9.3 RECORD KEEPING .As already suggested, operating adam should mclude keeping accuraterecords of:I. Observations: All observations
should be recorded. Periodicobservation of seepage is particularly important. Again, phot~graphs are valuable for recordingobservations and documentingchanges.
2. Maintenance: Written records ofmaintenance and major repainare important for evaluating thesafety of a dam.
3. Rai1ffaH and Water Lnelr Arecord of the date, time. BDd JDaXimmn elevation of utremely highwater and associated rainfall orrunoff b espcciaDy helpful inevaluating the performaDCe of 8
dam aDd its spillway system. Inparticular, records should be keptfor reservoirs that haVe widelyfhK:tuatio& water levels.
4. Drawdown: A record should bekept or the amount. rate, andreason for pool level drawdown.
S. Other Procetlurrr A completerecord or all operating procedw"esshould be maintained
,
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TABU 9.1OPERATION PLAN SCHEDULE OF ROUTINE TASKS
Hazard OassificatioDs
Category I Cate~ory 2 Category 3Higb Huard Sipiflcant Low HazardMany lives lost. Few lives lost. No lives lost.
10.0 SUPPLEMENTS TO ADAM SAFETY PROGRAMThis manual has stressed safety asboth a fundamental need and a primeresponsibility or the dam owner.Developing an effective dam safetyprogram is the single most importantmeasure a dam owner can take toreduce the possibility or consequences of dam failure. However, on anational scale, an acceptable level ofdam safety is stiD far from beingachieved. Losses are continuing toincrease and may intensify as papulation growth and migration con-.tinue. From both the perspective ofthe nation and the dam owner, othersteps must be taken to reduce loss oflife and property and subsequentliability.Uabilities which are determinedfolJowing a dam failure stronglyaffect bOth organizations and people,governments and dam owners. Determination of liability is the legalmeans developed by society torecover damages due to a "wrong"(in this case, lack of dam safety) andis another aspect of the dam safetyproblem. A thorough understandingof this legal process can help the damowner decide the steps to be taken toreduce liability.A discussion of liability and its relation to a dam owner is presentedbelow, followed by a discussion ofthree important measures beyondt,hat of individual dam safety· thatdam owners can promote to reduceliability - the use cf insurance, theprovision or governmental assislaDce, and the use of consultants.
10.1 LIABILITYThe following discussion reviewsgeneral principles concerning liabilityand the operation or reservoirs.Uability in specifIC instances, however, very much depends upon thedam. the accident, the owner and thejurisdiction in which the reservoiris located.The liability of an owner or a reservoir is considered general civil
79
("tort") liability, A tort is simply acivil wrong for which an injured partymay recover damages from the responsible party. In most circumst.ances, simply causing damage is notsufficient basis for the imposition ofliability. Negligence must accompany the injury before liability isincurred However, negligence is not·a fued concept; it has been modifiedand changed by court decisions overthe years. In simplest terms, it hasbeen described as the violation of aduty to act as a reasonable and prudent person would act; a violationwhich directly results in damage toanother.The questions of what "duty" isimposed by society and what standard or reasonable care is imposedby the duty have undergone enormous scrutiny and changes over thepast 25 years. In many instances theduty to make a product safe or theduty to insure that one's propertydoes not pose a danger to others, hasbeen significantly increased.While the concept of negligence hasbeen subs~tially broadened, changesin the limits of negligence do notdirectly affect dam owners because aseparate basis of liability has longbeen imposed upon them. This standard is one of "strict liability." Strictliability is not based upon fault ornegligence, rather it is based solelyupon resulting damage, regardless offautt. Strict liability is generallyapplied to those activities which aredeemed "ultra-hazardous" aDd Dotcapable ofbeing rendered reasonablysafe.
The whole concept of strict liabilitywas fIrSt established in a case involving a reservoir - the 1866 Englishcase, Fletcher vs. Ryfands, LR J,Ex. 265. A reservoir was built in thevicinity or abandoned coal mines; thewater from the reservoir found itsway into the abandoned shafts andfrom there into active shafts andcaused damage. ·Under present legalthought, the basis of liability for suchan occurrence may well be negligentdesign (i.e., failure to adequately
UIF WATER ESCAPES FROM A DAM,REGARDLESS OF FAULT, THE OWNERIS RESPONSIBLE FOR ALL DAMAGESSUSTAINED:'
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investigate the surrounding circumstances at the time the reservoirwas built). However, in the actualdecision, it was assumed that no onecould have known the abandonedmine shafts existed and specificallydecided that the owner was notnegligent. Nonetheless, the EnglishCourt established the concept ofstrict liability for reservoir owners,and the owner of the reservoir wasfound to be liable for the escape ofwater from the reservoir regardless offault.
Fletcher vs. Rylands has subsequently been adopted by most U.S.courts and has been cited whensimilar circumstances are considered. It is the basis for imposingliability on the owner of a reservoirfor all damages caused, regardless offauk and without need to provenegligence.
Thus, with a very limited number ofexceptions, the general statement ofliability for the owner or operator ofareservoir is:
It should be noted however, that allof the discussion concerning rompensation for damages due to releaseof water from a reservoir deal solelywith water that has previously beenstored. In all circumstances to date,and in most states by specific statute,a reservoir oWner may pass on allnatural flood waters without incurring any liability downstream.Strict liability has two relativelynarrow exceptions: acts of God, orintentional acts of third parties, overwhom the owner had no control.While acts of God are recognized asa defense, this does not include allnatural occurrences over which theowner had no control, but is morenarrowly limited to those events overwhich the owner had no control andalso which the owner could not, usingavailable expertise, have anticipated.The other exception - intentionalacts ofthird parties - was established·by the Wyoming Supreme Court inthe Wheatland case. The WheatlandIrrigation District asserted that theirreservoir had been damaged bysaboteurs, and the Wyoming Supreme Court recognized that illegal,
intentional acts by third partieswhich the owner could not protectagainst or anticipate were a viabledefense to strict liability.Still, where there is no remediallegislation, the circumstances inwhich a reservoir owner is not liablefor all damages caused by the leakingor breaking of his dam are severelylimited.While the standard of liability imposed on a reservoir owner affordsextremely limited relief, severalstates have enacted legislation whichlimits, in certain circumstances liability for damages. In many otherstates, by statute or common law, theowner of a reservoir is entitled to utilize (i.e., release water to) the "normal high water line" of a streamwithout incurring liability for property damaged within the "normal"flood area. However, the definition ofthe limits within which no liability isimposed vary from place to place andmay not be clearly designated. of!maps. Nonetheless, the right to titil-
ize dermed or "historic" floodplainregions downstream of a reservoircan provide substantial relief from
·strict liability for a reservoir owner.With the recent insurance crisis andsoaring Iiabililty insurance rates,many states are considering legislation which would limit either thebasis of liability or the amount ofliability that can be imposed on areservoir owner. Some states, forexample. are considering legislationwhich would change the standard ofliability for a reservoir owner from astandard of "strict liability" to one ofproven negligence.If coupled with a redefinition ofnegligent actions, statutory modification of the basis of a reservoirowner's liability could have a significant effect. However, as notedabove, the trend during the past 25years has been to broaden, notnarrow, the scope of negligent behavior by imposing broad expectations of prudence and foresight.Even if standards of "strict liability"are replaced by standards of "negligence," in the case of a reservoirowner, because the criteria of reason-
able care and foresight are broadlyinterpreted, the change may notgreatly affect the actual standard ofliability imposedIn summary, existing law holds areservoir· owner to the highest standard of care. Pending legislation maylimit liability in certain circumst2Jlces, however the general statementremains unchanged: the owner is liable for all damages caused by waterescaping from a reservoir - despitethe best efforts of the owner.
10.2 MEASURES TO REDUCETHE CONSEQUENCESOF DAM FAILUREA dam owner can directly andindirectly influence the introductionand use of a variety of measures thatwill reduce the consequences of damfailure. Insurance can be purchasedthus, spreading costs from a singledam owner to others. Land usemeasures, although difficult to institute, can be an even better means ofmitigating future disasters. (If peopleare restricted from living in inundation zones, safety is obviously radically improved.) Increasing publicawareness and governmental planning are also measures that canreduce the consequences of damfailure.A dam owner can obtain insurancedirectly and should do so. The othermeasures discussed here: land use,public awareness and preparednessplanning. are essentially controlledby local governments. Therefore,dam owners would be wise to toencourage as strongly as possibleawareness and action in the publicsector. Finally, a dam owner mayalso wish to hire consultants from thepriv"ate sector when the informationneeded for prudent decisions exceedstheir expertise.
10.2.1 Insurance - Insurance canprovide liability and asset protectionand thus, is important for damowners. In many states a minimumlevel of insurance coverage is mandated by law; in others it is not. Ineither case, the level of insurancecarried should be based on: state law,value of facilities at risk, potentialdownstream impacts,· condition andage of the dam, likelihood of an in~ident occurring and the cost of avaIlable of insurance. Insurance spreadsrisk among a large group of peopleand can not only provide protectionfor the person or organization owningthe dam, but also for employees and
Table10.1 :Comparison of warning success for selected dam failures
and nash floods
Early Potential Actual loss Fablit)'Event • direction loss or life or life rate (%)
&: wamina
Bil Thompson. Colo. No 2,500 139 S.6(Rash Flood)
Laurel Run Dam, Pa. No ISO 39 25.0Kelly Barnes Dam, Ga- No 200 39 20.0Buffalo Creek, W. Va. Some 4,000 125 3.1Teton Dam, Idaho Yes 3S,000 II <0.1Southern Conn. Yes Unknown 0 0June 1982(20 dams r.iJed)
governing boards who may be heldpersonally liable. Types or coverage,availability and cost will vary fromtime to time, so it is, advisable to seekprofessional advice when consideringthe purchase of insuranCe. Someinsurance companies and brokersspecialize in issues related to damfailure. Recommendations of insurerscan normally be obtained frominsurance industry representatives orfrom the state agency responsible fordam safety. Nol only can damageand liability be covered. the cost ofbusiness interruption, lost income,and workmen's compensation canalso be provided.
Insurance can spread and reducepotential loss and as such should bean accepted cost of doing business.Many persons have avoided this costand have paid severely for theirshortsightedness.
10.2.2 Governmental assistance One of the fundamential functions ofgovernment is to protect citizensfrom threats to their health, safety,and general welfare. Reducing theconsequences of dam failure isclearly a duty of federal, state andJocal governments which have jointand separate responsibilities to thepublic concerning dam safety.
Land use planning. public awarenessprograms, and emergency preparedness pJaruiing are typically conducted at the local level - the level ofgovenunent most immediate and responsive to the dam owner. Federalagencies have technical expertiseand can normally provide technicalassistance when requested. but ultimately, each state is responsible forits own dam safety program.
Localgovemment roles - Populationsettlement pattern and populationgrowth strongly affect the costs ofdam failures. More simply, if no onewere allowed to settle in hazardousareas, few, if any, lives would be lostand little property damaged. Conversely, as settlement continues neardams and in inundation zones, thepotential for disaster increases commensurately. "Low-hazard" damsare continually being transfonnedinto "significant hazard" and "highhazard" dams as this settlement continues. Increased losses are inevitable unless significant land usemeasures are enacted to restrict theuse of land in inundation zones. Thestrategjes used will reflect federal,state, and local efforts, but localgovernment must make the critical
decisions and only rely on state andfederal government for support. All.elements of mitigation planning arebased upon or affected by the way inwhich the affected land is used.
If the land has not been developed,the establishment of open spaceareas in potential inundation zones isa particularly effective way to reducefuture costs of dam failure. Indeed,this is the best mitigation strategy toreduce future loss. Despite thisutility, organized programs or strategies of land acquisition or settlement restriction exist in few states usually because of strong oppositionamong developers and land owners.
If land is already under development,zoning measures to limit high popul.tion density can be useful. Also, theestablishment of "green areas" parks or golf courses - can be lowcost means of limiting senlemeot ininundation zones. In some fullydeveloped areas, nood proofingdevices (walls, barriers) may proveuseful.
In much of the nation, land hasalready been developed and residential construction in inundation zonesis already in place. People that live insuch 8Jeas may have a false sense ofsecurity and not be aware that ahazard even exists.Experience bas clearly shown thatsimple warning and evacuation pr~
cedures can save a significant numberoflives. Table 10.1 demonstratesthis success and the correspoodin&failure wben c8Jly detection andwarning are not available. Oe8Jly,communities downstream from adam should establish an early n0tification and warning system.
a,The stimulation or public awarenessofthis hazard and the development ofwarning aDd evacuation plans isclearly the responsibility of localgovernment The utility of sUchefforts cannot be overlooked; theaggregate·retum will be large over thelong term.Existing levels of awareness varyacross the nation. Some people arefully aware of their exposure to thiShazard while many do not even realize that they reside in an inWldationzone. Obviously, tourists are usuallyless aware than pennanent residents;camp grounds for ex ample, are notnormally posted with signs that pOintout the existence of a dam hazard.Oearly. awareness is the fIrSt step inmitigating the hazard and increasing safety.
• To develop programs to inCreaseawareness of CJlisting dam fai~
ure hazards, aod more specifi~
ally, of who is in danger.• To de'felop plans for warning
and evacuating the population,• To increase public familiarity
with plans through publications,well publicized exercises andother means.
UsuaUy, a public awareness programwiD be well received and generateconfidence in government Media television, and newspapers - radioare potentiaDy the most effective wayto educate people. Dam ownersshould encourage pub6c awarenessas weD as warning and evacuationplanning.
12
State government roles - Most stategovernments have actively attemptedto reduce the possibility of and consequences ofdam failure through anyof several major programs.
While some local public and privateorganizations may capable of supervising dam safety, the authority and .responsibility for such measures restwith state agencies that approveplans and specifications for thedesign and construction ofdams, andconduct of inspections of existingdams. In most states, dam safety ismonitored by the department ofwater resources, state engineersotrlCe. or an equivalent agency in theexecutive branch of government1bese. agencies often determine therules and regulations governing thedesign, construction, and maintenance of dams.1be state office of emergency preparedness is also concerned withdam safety. However, it deals mainlywith planning for the protection ofpeople - awareness, warning andevacuation planning. Disaster (including dam failure) response andrecovery efforts are part of thisprogram.
Federal government roles - TheFederal Emergency ManagementAgency (FEMA) develops and maintains guidelines for dam safetypolicy, as well as programs for preparedness, emergency response andrecovery planning and mitigationplanning. FEMA coordinates allfederal dam safety programs, andotherwise promotes both federal andnonfederal programs to reduce thehazard posed by unsafe dams.The Federal Energy RegulatoryCommission (FERC) supervises thedam safety program mandated by theFederal Power Act It issues rulesand regulations to ensure that licensedprojects are adequately construct~
operated and maintained to protectlife, health and property. FERC"sjurisdiction includes dams at hydr<>electric prqects on navigable streamsor on federally owned land projectsusing surplus water or waterpowerfrom federally owned dams; anddams affecting interstate or foreigncommerce.
The Department of the Anny, Corpsof Engineers, is authorized by theFederal Water Pollution Control Actof 1972 and the River and HarborAct of1899 to issue permits for workinvolving the nation's waterways.Under the National Dam Safety Actof 1972, the Corps, working withindividual states, inventoried 68,153dams, inspected 8,818, and established a list of hazard criteria.Five agencies within the DepartmentofAgricuhure are involved with noDfederal dams. These include theAgricultural Stabilization and Conservation Service (ASCS)~ theFarmer's Home Administration(FMHA), the Forest Servker theRuraJ ElectrifICation Administration(REA) and the Soil ConservationService (SCS). Technical engineering is the responsibility of the SoilConservation Service.The U.S. Department of tile Interior,Office of Surface Mining (OSM)provides support to state regulatoryagencies that conduct dam inspection.and monitoring as it relates to surfacemining. The Department's Bureau ofReclamation also manages a pr<>gram or water development whichincludes providing water for irrigation, the hydroelectric power industry, and recreation.10.2.3 Consultants role in damsafety - A dam is a special kind ofstructure which is conceptually simple but made or many complicated"components. Several engineeringskiDs are needed to design, build,inspect and repair a dam, and it isuncommon that a dam owner has aDof these technical skins. Even if thedam owner did have these skiDs, it isunlikely that an owner .could devote
•
the time and effort necessary to dothe work properly. Thus, private consuhants can play an important role ina dam safety program, and ownersshould consider contracting withconsuhing firms for assistance.When hiring a consultant, certainsteps will insure that an ownerobtains what is really needed Theinitial screening of possible c0n
sultants should be based on pr<>fessional qualifications. A Jist ofconsultants who have experiencewith dams may be available from thestate office managing dam safety.The owner should then investigatethe background and experience oftilecompany and the specific experienceof the individuals who will do thework.
The owner should be sure to defme asclearly as possible the wort to bedone. Although some ownen select aconsulting fum based on qualiflCa-
. tions and then work with the fmn todefine the work to be done, an ownercan often define the scope or workhimself, and then receive bids andproposals from several consultants.This latter arrangement usuallyresults in the lowest cost for • givenpiece of wort.H many of the items discussed in thisguidebook are new and unfamiJiar toa dam owner, a consultant should becontacted immediately. Professionalconsultants help conduct a properand safe evaluation ofa dam, ·and canhelp develop and execute an effectivedam safety program. Of course. adam owner should· have confidencein the consultant he hires. When aconsultant makes recommendations,they must be taken seriously.
APPENDIX AINSPECTION FORMS
•
13
INSPECTION D TE:NAME OF DAM: A
EMBANKMENT CHECK ( )ACTION
Q 1 of 2 NEEDED
il '" e",0 g '"z c:oHDmON OUIIVATlONS -:II Z~~ ~
~0 :l2 _CI
I SUIU'ACE CMCKING
% CAVIl IN. ANIMAL BUJUl.OW
3 LOW AJ\.EAlS)
B4 HOlUZONTALAUGNMENT, RUTS ANDiOR PUDOLES
6 VIlGETAnON CONomON
7
•9 SUDE. SLOUGH. SCARP
10 SLOPE PROTEcnON
! II SINKHOLE, ANIMAL BURROW
U EMB.·ABUT. CONTACT
I q EROSION
14 VIlOETAnONCONomON ..13
16
AD0l110NAL COMMENTS: REFER TO ITEM NO. IF APPUCABLE.
INSPECTION DATENAME OF DAM: :
EMBANKMENT CHECK ( )ACTION
Q 2012 NEEDED
i§=I ,
i i= ~ =CONDITION OBSERVATION - -~
Z ~~ ::0 ~I: :s ~O =17 WET A.REA(S) (NO PLOW)
18 SEEPAGE
!19 SLIDE, SLOUGH, SCARP
20 EMB.·ABUT. CONTACT
! 21 CAVE IN, ANIMAL BURROW
=22 EROSION
! 23 UNUSUAL MOVEMENT
24 VEGETATION CONTllOL•
2$
26 .27 PIEZOMETEIWOBSERV. WEU.S
,28 STAPP GAUGE AND RECORDER
i 29 WEIRS
30 SUaVEY MONUMENTS \
31 DRAINS:I~
PREQUENCY OP READINGSi 31
33 LOCATION OP RECORDS
343S
ADDITIONAL COMMENTS: UPER TO ITEM NO. IP APPLICABLE.
NAME OF DAM' INSPECTION DATE:
COWNSTREAM AREA CHECK ( )
AND MIse. ACTIONa NEEDED
i§ 1 of 1al:i ~ s ..:.
I- al:CONDITION ONERVATIONS - ~lU -:z lUI- 0(
~ 0 >0( c..\I,l
2 ~O al:
36 ABUTMENT LEAKAGE
is 37 POUNDAnON SEEPAGE
=38 SUD£. SLOUGH. SCARP
I39 DRAINAGE SYSTEM
40
4\
42 DOWNSTREAM HAZARDDESCIUPTtON
43 DATE Of LAST UPDATE OFEMERGENCY AcnON PLAN
44 RESERVOIR SLOP~S
.. 4.5 ACCESS ROADS
I46 SECURITY DEVICES
,.
47
48
49 ' ,
30
ADDITIONAL COMMENTS; UPER TO ItEM NO. If APPLICABLE.
83 ..ADDITIONAL COMMENTS: REFER TO ITEM NO. IF APPLICABLE.
INSPECTION DATENAME OF DAM: :
CONCRETE/MASONRYCHECK ( )DAMS ACTION
Cl NEEDED
~~ 1 of 1=:; '" .:.! 0 0
t:: ... '"z CONDITION OIl$ERVATIONS [21>.1 -::s z <0 ~~
..'" ~t: ::E _t.7
8<1 SURFACE CONDITIONS
8S CONDITION OF JOINTS
;g 86 UNUSUAL MOVllMENT
87 ABUTMENT-DAM CONTACTS
88:)
89
90 SURFACE CONDITIONS
91 C,ONDITION OF JOINTS •
~92 UNUSUAL MOVEMENT
93 ABUTMENT-DAM CONTACTS
SU 94 DRAINSj~
9S LEAKAGEg96
97
98 SURFACE CONDITIONS
99 HORIZONTAL ALIGNMENT
Ii; VIlRTlCAL ALIGNMENT
~ CONDITION OF JOINTS
UNUSUAL MOVEMENTS
ADDITIONAL COMMENTS: REFER TO ITEM NO. IF APPLICABLE.
APPENDIX BREPORT FORM
•
95
DAM INCIDENT REPORT FORM
DATE TlME _
NAME OF DAM --'----
STREAM NAME _
WCATION _
COUNTY _
OBSERVER _
OBSERVER TELEPHONE _
NATURE OF PROBLEM _
WCATION OF PROBLEM AREA ~ _(Looking Downstream)
EXTENT OF PROBLEM AREA .:..- _
FLOW QUANTITY AND COLOR _
WATER LEVEL IN RESERVOlR _
WAS SITUATION WORSENING ~-------------------
EMERGENCY STATUS _
CURRENT WEATHER CONDITIONS _
ADDITIONAL COMMENTS: -'-- _
APPENDIXCGLOSSARY
99
ABUTMENTThat part of a valley side against which a dam is constructed. An artificial abutment is sometimes constructed as a concrete gravity section, to take the thrust ofan arch dam where there is no suitable natural abutment. Right and left abutments are those on respective sides of an observer looking downstream.
ACTIVE STORAGEThe volume of a reservoir that is available for power generation, irrigation, noodcontrol, or other purposes. Active storage excludes nood surcharge. It is thereservoir capacity less inactive and dead storages. The terms "useful storage,""unable storage," or "working storage" are sometimes used but are notrecommended.
AIRVENT PIPEA pipe designed to provide air to the outlet conduit to reduce turbulence duringrelease of water. Extra air is usually necessary downstream of constrictions.
APPURTENANT STRUCTURESAncillary features of a dam, such as the outlet, spillway, powerhouse,tunnels, etc.
AQUEDUCTAn artificial channel for conveying water, i.e., a canal, pipe, or tunnel; hence theterms "connecting aqueduct" and "diversion aqueduct."
ARCH DAMA concrete or masonry dam that is curved so as to transmit the major part of thewater pressure to the abutments.
Double Curvature Arch DamAn arch dam that is curved vertically as well as horizontally.
Arch BuHress DamSee Buttress Dam.
Arch Gravity DamSee Gravity Dam.
AUXIUARY SPillWAYSee Spillway.
AXIS OF DAM •A plane or curved surface, arbitrarily chosen by a designer, appearing as a line ina plan or cross section to which the horizontal dimensions of the dam canbe -referred.
BACKWATER CURVEThe longitudinal profile of the water surface in an open channel where the depthof now has been increased by an obstruction, an increase in channel roughness, adecrease in channel width, or a nattening of the bed slope.
BASE WIDTH (Base thickness)The maximum width or thickness of a dam measured horizontally betweenupstream and downstream faces and nonnal to the axis of the dam but excludingprojections for outlets, etc.
BERMA horizontal step or bench in the sloping profi!e of an embankment darn.
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BLANKET
Drainage BlanketA drainage layer placed directly over the foundation material.
Grout BlanketSee Consolidation Grouting.
upstream BlanketAn impervious layer placed on the reservoir floor upstream of a dam. In thecase of an embankment dam. the blanket may be connected to the impermeable element in a dam.
BunRESS DAMA dam consisting of a watertight upstream face supported at intervals on thedownstream side by a series of buttresses.
Arch Buttress Dam (Curved Buttress Dam)·A buttress dam that is curved in plan.
Multiple Arch DamA buttress dam whose upstream part comprises a series of arches.
CofferdamA temporary structure enclosing all or part of a construction area so that construction can proceed in a dry area. A udiversion cOfferdam" diverts a riverinto a pipe, channel, or tunnel.
CONCRETE unIn concrete work the vertical distance between successive horizontal construction joints.
CONDUITA closed channel for conveying discharge through or under a dam.
CONSOUDATION GROUTING (Blanket Grouting)The injection ofgrout to consolidate a layer ofthe foundation, resulting in greaterimpermeability and!or strength.
CONSTRUCTION JOINTThe interface between two successive placings or poUr~ of concrete where abond, not permanent separation is intended.
CORE WAllA waD built of impervious m.aterial, usua))y concrete or asphaltic concrete, in thebody of an embankment dam to prevent leakage.
CREST GATESee Gate.
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CREST LENGTHThe length of the top of a dam, including the length of spillway, powerhouse,navigation lock, fish pass, etc. where these structures form part of the length of adam. If detached from a dam, these structures should not be included
CREST OF DAMThe crown of an overflow section of a dam. In the United States, the term "crestofdam" is often used when "top ofdam" is meant.. To avoid confusion, the terms"crest ofspillway" and "top ofdam" may be used to refer to the overflow sectionand the dam proper, respectively.
CRIB DAMA gravity dam built up of boxes, cobs, crossed timbers, or gabions and filled withearth or rock.
CULVERT(a) A drain or watenvay builtlransversely under a road, railway, or embankment, usually consisting of a pipe or covered channel of box section. (b) Agallery or waterway constructed through any type ofdam, which is normally drybut is used occasionally for discharging water, hence Ibe terms "scour culverl,"·udrawofT culvel\" and Uspillway culvert."
CURTAINSee Grout curtain
CURVED BUTTRESS DAM (Arch Buttress Dam)See Buttress Dam.
CURVED GRAVITY DAMSee Gravity Dam.
CUTOFFAn impervious construction or material which reduces seepage or prevents itfrom passing through foundation material. .
CUTOFF TRENCHAn excavation later to be fined wilb impervious material to form a cutoff. Sometimes used incorrectly 10 describe Ibe culoff itself.
CUTOFF WALLA wall of impervious material (e.g., concrete, asphaltic concrete, steel sheetpiling) built into Ibe foundation .to reduce seepage under Ibe dam. .
DAMA barrier built across a watercourse for impounding or diverting Ibe flow ofwater.
DEAD STORAGEThe storage Ibatlies below Ibe invert ofthe lowest ouUet and Ibal, Iberefore, cannot be wilbdrawn from Ibe reservoir.
DESIGN FLOODSee Spillway Design Flood.
DIAMOND HEAD BUnRESS DAMSee Buttress Dam.
DIAPHRAGMSee Membrane.
DIKE (Leve.)A.long low embankment whose height is usually less Iban 4 to 5 meters andwhose length is more Iban 10 or IS times Ibe maximum height Usually applied10 embankments or structures built to protect land from flooding. lfbuilt ofcoDcrete or masonry Ibe struclore is usually referred to as a Dood wall. Also used todescribe embankments Ibat block areas on a reservoir rim Ibat are lower Iban Ibelop oflbe main dam and Ibat are quite long. In Ibe Mississippi River basin, wherethe old F,encli word levee has survived, the term now applies to flood protectingembankments whose height can average up 10 10 to IS meters.
DIVERSION CHANNEL CANAl. OR TUNNELA walerway used 10 divert water from its natural course. These lerms aregenerally applied 10 temporary structures such as Ibose designed to bypass wateraround a dam sile during construction. "Channel' is normally used instead of"canal" when the walerway is short OccasionBlly these terms are applied topermanent structures.
DRAINAGE AREAAn area that drains naturally 10 a particular point on a river.
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DRAINAGE lAYER OR BlANKETA layer of penneable material in a dam to relieve pore pressure or to facilitatedrainage of ftIl.
DRAINAGE WELlS (Relief WelOA vertical well or borehole, usually downstream of impervious cores, grout curlains, or cutoffs, designed to collect and direct seepage through or under a dam toreduce uplift pressure under or within a dam. A line of such wells fonDS adrainage curtain.
DRAWDOWNThe lowering of water surface level due to release of water from areservoir.
EARTH DAM OR EARTHFill DAMSee Embankment Dam.
EMBANKMENTA slope of fill material, usually earth or rock, that is longer than it is high. Thesloping side of a dam.
Embankmenl Dam (Fill Dam)Any dam constructed of excavated natural materials or of industrialwaste materials.
Earth Dam (Earlhflll Dam)An embankment dam in which rnore than 50,*, ofthe total volume is formed ofcompacted fine-grained material obtained from a borrow area.
Homogeneous Earthflll DamAn embankment dam constructed ofsimilar earth material throughout, exceptinternal drains or drainage blankets; distinguished from a zoned earthfJlIdam.
Hydraulic Fill DamAn embankment dam constructed of materials, often dredged, that are conveyed and placed by suspension in flowing water.
Rocldlll DamAn embankment dam in which more than 50% of the total volume comprisescompacted or dumped pervious natural or crushed rock.
Rolled Fill DamAn embankment dam of earth or rock in which the material is placed in layersand compacted by using rollers or rolling equipment.
Zoned Embankment DamAn embankment dam, of which is composed of zones of selected materialshaving different degrees of porosity, permeability, and density.
EMERGENCY ACTION PlANA predetennined plan of action to be taken to reduce the potential for propertydamage and loss of lives in an area affected by a dam break.
EMERGENCY GATEA standby or reserve gate used only when the normal means ofwater control arenot available.
EMERGENCY SPIllWAYSee Spillway.
ENERGY/DISSIPATING VALVEAny device constructed in a waterway to reduce or destroy the energy of fast"owing water.
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4 EPICENTERThe point on the earth’s surface directly above the focus of an earthquake.
FACEThe external surface of a structure, e-g, the surface of a wall of a dam.
FACINGWith reference to a wall or concrete dam, a coating of material, masonry orbrick, for architectural or protection purposes, e.g., stonework facing, brickworkfacing With reference to an embankment dam, an impervious coating or face onthe upstream slope of the dam.
FAILUREThe uncontrolled release of water from a dam.
FILTER (Filter Zone)A band or zone of granular material that is incorporated into a dam and is graded(either naturally or by selection) so as to allow seepage to flow across or downthe filter without causing the migration of material from zones adjacent tothe filter.
FLASHBOARDSA length of timber, concrete, or steel pl aced on the crest of a spi llway to raise theretention water level el but that may be quickly removed in the event of a flood .either by a tripping device or by deliberately designed failure-of the flashboard orits supports.
FLOODPLAINAn area adjoining a body of water or natural stream that has been or may becovered by flood water.
FLOODPLAIN MANAGEMENTA management program to reduce the consequences of flooding - either bynatural runoff or by dam failure - to existing and future properties in a flood-plain.
FLOOD ROUTINGThe determination of the attenuating effect of storage on a flood passing througha valley, channel, or reservoir.
FLOOD SURCHARGEThe volume or space in a reservoir between the controlled retention water leveland the maximum water level. Flood surcharge cannot be retained in the reser-voirbut will flow over the spillway until the controlled retention water level isreached. (The term “wet freeboard” for describing tbe depth of flood surchargeis not recommended; see Freeboard),
FL OOD WALLA concrete wall constructed adjacent to a stream for the purpose of pieventingflooding of property on the landward side of the wall; normally constructad inlieu of or to supplement a levee where the land required for levee construction isexpensive or not available.
FOUNDATION OF DAMThe natural material on which the dam structure is placed.
FREEBOARDThe vertical distance between a stated water level and the top of a dam. “Netfreeboard,” “dry freeboad, ” “flood freeboard,” or “residual Freeboard” is thevertical distance between the estimated maximum water level and the top of adam, “Gross freeboard” or “total freeboard” is the vertical distance between themaximum planned controlled retention water level and the top of a dam. (Thatpart of tbe “gross freeboard” attributable to the depth of flood surcharge is some-times referred to as the “wet freeboard,” but this term is not recommended; it ispreferable that freeboard be used with reference to the top of the dam
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GAWRY(a) A passageway within the body of a dam or abutment; hence the tenns "grouting gallery," "inspection gallery," and "drainage gaDery." (b) A long and rathernarrow hall; hence the following terms for a power plant "valve gallery,"·"transfonner gaDery," and "busbar gallery."
GATEA device in which a leafor member is moved across the waterway from an external position to control or stop the now.
Bulkhead GoteA gate used either for temporary closure of a channel or conduit to empty it forinspection or maintenance or for closure against nowing water when the headdilTerence is smaD, e.g., for diversion tunnel closure. Although a bulkhead gateis usually opened and closed under nearly balanced pressures, it neverthelessmay be capable of withstanding a high pressure dilTerential when in theclosed position.
ere.t Gote (Spillway Gote)A gate on the crest of a spillway to control overflow or reservoir waterlevel.
Emergency GateA standby orreserve gate used only when the nonnal means ofwater control isnol available.
Fixed Wheel Gate (Fixed Roller Gate, Fixed Axle Gate)A gate having wheels or rollers mounted on the end posts of the gate. Thewheels bear against rails fIXed in side grooves or gate guides.
Flap GateA gate hinged along one edge, usually either the top or bottom edge. Examplesof bottom-hinged nap gates are tilting gates and belly gates, S<H:aDed due totheir shape in cross section.
Flood GoteA gale to control flood release from a reservoir.
Guard Gate (Guard Valve)A gate or valve that operates fully open or closed It may function as a secondary device for shulling off the now ofwater in case the primary closure devicebecomes inoperable, but is usually operated under balanced pressure, noflow conditions.
outlet GoteA gate controlling the oulOow of water from a reservoir.
RadIal Gate (Talntlll Gote)A gate with a curved upstream plate and radial arms hinged to piers or othersupporting structures.
Regulating Gote (RegUlating Valve)A gale or valve that operates under fuJI pressure and flow conditions to throttleand vary the rate of discharge.
Slide Gote (SluIce Gote)A gate that can be opened or closed by sliding il in supporting guides.
GRAVITY DAMA dam constructed of concrete and/or masonry that relies on its weight forstability.
Arch Gravity DamAn arch dam in which part of the water pressure is transmitted to the abutments by horizontal thrust and part to the foundation by cantileveraction.
Curved Gravity DamA gravity dam that is curved in plan.
Hollow Gravity Dam (Cellular Gravity Dam)A dam that has the outward appearance of a standard gravity dam but that is ofhoUow construction.
GROSS STORAGE (Reservoir Copaclty (Gross Copaclty 01 Reservoir)The gross capacity of a reservoir from the river bed up to maximum controlledretention water level. It. includes active, inactive, and dead storage.
GROUT BlANKETSee Blanket.
GROUT CAPA concrete pad or waD constructed to facilitate pressure grouting of the groutcurtain beneath it. .
GROUT CURTAIN (Grout Culofl)A barrier produced by injecting grout into a vertical zone, usually narrowhorizontally, in the foundation to reduce seepage under a dam.
HEIGHT ABOVE LOWEST FOUNDATIONThe maximum height from the lowest pointofthe general foundation to the topofthe darn.
HYDRAUUC HEIGHTThe height to which water rises behiod a dam and the difference between thelowest point "in the original streambed at the aXis of the dam and the maximumcontrollable water surface.
HYDROGRAPHA graphic representation of discharge, stage, or other bydraulic property withrespect to time for a particular point on a stream. (At times the term is applied tothe phenomenon the graphic representation describes; bence a flood bydrograpbis the passage of a llood discharge past the observation point.)
INACTIVE STORAGEThe storage volume of a reservoir measured between the invert level of thelowest ouUet and minimum operating level •
INCUNOMETER (tnclomeler)An instrument, usually consisting ofa metal or plastic lube inserted in a drill boleand a sensitized monitor either lowered into the lube or flIed within the lube.This measures at different points the tube's inclination to the vertical. By integration, lhe lateral position at different levels of the tube may be found relative to apoint, usually the top or bottom ofthe lube, assumed to be flIed. The system maybe used to measure setUement.
INTAKE.Any structure in a reservoir, darn, or river through whicb water can be drawn intoan aqueduct.
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INTENSITY SCAlEAn arbitrary scale used to descn"be the severity ofearthquake-induced shaking ata particular place. The scale is not based on measurement but on direct observation. Several scales are used (e.g., the Mndified Mercalli scale,the MSK scale)all with grades indicated by Roman numerals from I to XIL
INTERNAL EROSIONSee Piping.
INUNDATION MAPA map delineating the area that would be inundated in the event of a darnfailure.
lEAKAGEUncontrolled loss of water by flow through a hole or crack.
UNINGWith reference to a canal, tunnel, shaft, or reservoir, a coating of asphaltic concrete, reinforced or unreinforced concrete, shotcrete, rubber or plastic to providewatertightness, prevent erosion, reduce friction, or support the periphery of thestructure. May also refer to lining, such as steel or concrete, of outlet pipeor conduit.
UVE STORAGEThe sum of active. and inactive storage volumes. When there is no inactivestorage, as in some irrigation reservoirs, the tenns "live storage" and lI'activestorage" are equivalent. -
lOW lEVEl OUTlET (Bottom outlet)An opening at a low level from a reservoir generally used for emptying or forscouring sediment and sometimes for irrigation releases.
MAGNIWDE (see also RIchter SCale)A rating of an earthquake independent of Ibe place of observation. It iscalculated from seismographic measurements and is properly expressed inordinary numbers and decimals based on a logarithmic scale. Each higher number expresses an amount of earthquake energy that is 10 times greater than thatexpressed by the preceding lower number, e.g., a magnitude 6 earthquake has 10times more energy than a magnitude S.
MASONRY DAMA dam constructed mainly of stone, brick, or concrete blocks that mayor maynot be joined wilb mortar. A dam having only a masonry facing should not bereferred to as a masonry dam.
MAXIMUM CREDIBlE EARTHQUAKE (MeaThe severest earthquake that is believed to be possible at a site on the basis ofgeologic and seismological evidence. It is determined by regional and localstudies including a complete review of all historic earthquake data ofevents sufficiently nearby to ~ct the site, all faults in the area, and attenuations due tofaults to the site.
MAXIMUM CROSS SECTION OF DAMA cross section of a dam at the point of maximum height of the dam.
MAXIMUM WATER lEVELThe maximum water level, including flood surcharge, Ibe darn is designedto withstand.
MEMBRANE (Diaphragm)A sheet or thin zone or facing made of a flexible material that is sometimesreferred to as a diaphragm waIl or diaphragm.
MINIMUM OPERATING UVELThe lowest level to which the reservoir is drawn down under nonnal operating
.conditions.
MORNING GLORY SPILLWAYSee Spillway.
NORMAL WATER UVELFor a reservoir with a fIXed overflow sill the lowest crest level oCthat sill. For areservoir whose outllow is controlled wholly or partly by movable gates, siphonsor other means, it is the maximum level to which water may rise under normaloperating conditions, exclusive oC any provision Cor llood surcharge.
OPERATING BASIS EARTHQUAKEA hypothetical earthquake used Cor design purposes. A more moderate standardthan the Maximum Credible Earthquake·(see), it is based on regional and localgeology and seismology studies and is considered likely to occur during the liCe oCthe dam.
ONE-HUNDRED YEAR (100·Year) EXCEEDANCE INTERVALThe Dood magnitude expected to be equalled or exceeded on the average ofonCein 100 years. It may also be expressed as an exceedance frequency with a percent chance of being exceeded in any given year.
ounnAn opening through which water can be Creely discharged Crom a reservoir.
OVERFLOW DAM (Overtoppable Dam)A dam designed to be overtopped
PARAPnWALLA solid wall built along the top of a dam Cor ornament, Cor the safety oC vehiclesand pedestrians, or to prevent overtopping.
PEAK FLOWThe maximum instantaneous discharge that occurs during a llood. It is coincident with the peak of a Dood hydrograph.
PERVIOUS lONEA part of the cross section oC an embankment dam comprising material oChigh penneability.
PHREATIC SURFACEThe Cree surface oC groundwater at atmospheric pressure.
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PIElOMmRAn instrumentconcrete.
Cor measuring pore water pressure within soil, rock. or
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PIPINGThe progressive development of internal erosion by· seepage, appearingdownstream as a hole or'seam discharging water that contains soil particles.
PORE PRESSUREThe interstitial pressure oC water within a mass of soil rock. or concrete.
PRESSURE CELLAn instrument Cor measuring pressure within a mass ofsoil, rock. or concrete orat an interface between one and the other. .
PRESSURE REUEF PIPESPipes used to relieve uplift or pore water pressure in a dam Coundation or in thedam structure.
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PROBABLE MAXIMUM FLOOD (PMF)A flood that would result from the most severe combination of criticalmeteorologic and hydrologic conditions possible in the region.
On.Hol. PMFA flood with a peak flow equal to one-halfof the peak flow ora probable max-imum flood. .
PROBABLE MAXIMUM PRECIPITATION (PMP)The maximum amount and duration of precipitation that can be expected tooccur on a drainage basin.
PUMPED STORAGE RESERVOIRA reservoir filled entirely or mainly with water pumped from outside its naturaldrainage area.
REGUlATING DAMA dam impounding a reservoir from which water is released to regulate the flowin 8 river~
REUEF WEllSee Drainage Wen.
RESERVOIR AREAThe sunace area of a reservoir when fined to controlled retention waterlevel.
RESERVOIR ROUTINGThe computation by which the interrelated effects of the inflow hydrograpb,reservoir storage, and discharge from the reservoir are evaluated.
RESERVOIR SURFACEThe sunace of a reservoir at any level.
RICHTER SCALEA scale proposed by C.F. Richter to descnoe the magnitude of an earthquake bymeasurements made in well-dermed conditions and with a given type of seismograh. The zero of the scale is fixed arbitrarily to fit the smallest recordedearthquakes. The largest recorded earthquake magnitudes are near 8.7 and arethe result ofobservations and not an arbitrary upper limit like that of the intensityscale. .
RIPRAPA layer of large uncoursed stones, broken rock, or precast blocks placed in random fashion on the upstream slope of an embankment dam, on a reservoir shore,or on the sides of a channel as a protection against wave and ice action. Verylarge riprap is sometimes referred to as armoring.
RISK ASSESSMENT •As applied to dam safety. the process of identifying the likelihood and consequences of dam· failure to provide the basis for informed decisions on •course of action. .
ROCKFill DAMSee Embankment Dam.
ROllCRETEA no-slump concrete that can be hauled in dump trucks, spread with a bulldozeror grader. and compacted with a vibratory roller.
SEEPAGEThe interstitial movement of water that may take place through a dam, its foundation, or its abutments.
SEEPAGE COUAIA projecting collar, usually ofconcrete, built around the outside of a pipe, tunnel,or conduit under an embankment dam, to lengthen the seepage path along theouter surface of the conduit
SIll(a) A submerged structure across a river to conlrolthe water level upstream. (b)The crest of a spiDway. (c) A horizontal gate seating, made ofwood, stone, concrete or metal at the invert of any opening or gap in a structure, hence theexpressions "gate siD" and "stoplog sill:'
SlOPE(a) The side of a hill or mountain. (b) The inclined face of a cutting or canal orembankment (c) Inclination from the horizonia!. In the Untied States, it ismeasured as the ratio of the number ofunits ofhorizontal distance to the numberor corresponding units or vertical distance. The term is used in English for anyinclination and is expressed as a percent when the slope is gentle, in which casethe tenn "gradient" is also used. .
SLOPE PROTECTIONThe protection of a slope against wave action or erosion.
SlUICEWAYSee low-level outlet
SPillWAYA structure over or through which nood nows are discharged. H the now is con;trolled by gates, it is a controlled spillway; if the elevation or the spillway crest isthe only control, it is an uncontrolled spillway.
AUXiliary Spillway (Emergency Spillway)A secondary spiDway designed to operate only during exceptionally largennods.
Fuse Plug SpillwayAn auxiliary or emergency spillway comprising a low embankment or anatural saddle designed to be overtopped and eroded away during a very rareand exceptionally large flood.
Primary Spillway (PrincIpal Spillway)The principal or rust-used spillway during nood flows.
Shan Spillway (Momlng Glory Spnlway)A vertic"a1 or inclined shaft into which flood water spills and then is conductedthrough, under, or around a dam by means of a conduit or tunnel; If the upperpart of the shaft is splayed out and terminates in a circular horizonial weir, it istermed a "bellmouth" or "morning glory" spillway.
Side Channel Spillway •A spillway whose crest is roughly parallel to the channel immediatelydownstream of the spillway.
Siphon SpillwayA spillway with one or more siphons built at crest level. This type of spillwayis sometimes used for providing automatic surface-level regulation withinnarrow limits or when considerable discharge capacity is necessary within ashort period of time.
SPillWAY CHANNEL (Spillway Tunnel)A channel or tunnel conveying water from the spillway to the riverdownstream.
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SPillWAY DESIGN FLOOD (SDF)The largest flood that a given project is designed to pass safely. The reservoirinflow-discharge hydrograph used to estimate the spillway discharge capacityrequirements and corresponding maximum surcharge elevation in thereservoir.
mWNGBASINA basin constructed to dissipate Ibe energy of fast-flowing water, e.g., from a
spillway or bottom outlet, and to protect the river bed from erosion.
STOPLOGSLarge logs or timber or steel beams placed on top of eacb other wilb their endsheld in guides on each side of a channel or conduit providing a cbeaper or moreeasily handled temporlll}' closure than a bulkhead gate.
STORAGEThe retention of water or delay of nmolf either by planned operation, as in areservoir, or by temporlll}' fIlling of overIJow areas, as in the progression of aflood crest through a natural stream channel.
STORAGE RESERVOIRA reservoir that is operated with cbanging water level for the purpose of storingand releasing water.
TAILRACE .The tunnel, channel, or conduit that conveys the discharge from the turbine tothe river; hence the terms "tailrace- tunnel" and Utailrace canal.'"
TAILWATER LEVELThe level ofwater in the tailrace at the nearest free surface to Ibe turbine or in thedischarge channel immediately downstream of the dam.
TOE OF DAMThe junction of Ibe downstream face of a dam with the ground surface, alsoreferred to as downstream toe. For an embankment dam the junction of theupstream fac~ with ground surface is called the upstream toe.
TOP OF DAMThe elevation of the uppermost surface of a dam, usually a road or walkway,excluding any parapet wall, railings, etC.
TOP THICKNESS (Top Width)The thickness or width of a dam at the level of the top of the dam. In general, theterm "thickness" is used for gravity and arcb dams and "width" is used foroIherd~ ~
.TRANSmON ZONE (SemlpervioUi Zone)A part of the cross section of a zoned embankment dam comprising material ofintermediate size between that of an impervious zone and that of apermeable zone.
TRASH RACKA screen located at an intake 10 prevent the ingress of debris.
TUNNELA long underground excavation usually having a uniform cross section. Types oftunnel include: headrace tunnel, pressure tunnel, collecting tunnel, diversion tuRnel, power tunnel, tailrace tunnel, navigation tunnel, access tunnel, scour tunnel,drawofT tunnel, and spillway tunnel.
UNDERSEEPAGEThe interstitial movement of water through a foundation.
UPLIFTThe upward pressure in the pores of a material (interstitial pressure) or on thebase of a structure.
UPSTREAM BlANKETSee Blanket
VALVEA device filted to a pipeline or orifice in which the closure member is eitherrotated or moved transversely or longitudinally in the waterway so as to controlor stop the flow.
WATERSHED DIVIDEThe divide or boundary between catchment areas (or drainage areas).
WATERSTOPA strip ofmetal, rubber, or other material used to prevent leakage through jointsbetween adjacent sections of concrete. .
WEIR(a) A low dam or waD built acro" a stream to raise the upstream water level,tenned filled-crest weir when uncontroDed. (b) A structure built across a streamor channel for the purpose ofmeasuring now, sometimes called ameasuring weir .or gauging weir. Types of weir include broad-crested weir, sblUJH'rested weir,drowned weir, and submerged weir.
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APPENDIX DSELECTED BIBLIOGRAPHY
STATE MANUALS
Arkansas Soil and Water Conservation Commission (1980) Safely Evaluationof Small Earth Dams LillIe Rock, Arkansas.
Colorado State Engineer's Office, Division of Water Resources (1983) DamSafely Manual Denver, Colorado.
State of minois Department of Water Resources (1980) Guidelines and Formsfor Inspection of minois Dams, Springfield, Illinois.
Kentucky Natural Resources and Environmental Protection Cabinet, DivisionofWater Resources (1985) Guidelines for Maintenance and Inspection ofDamsin Kentucky.
Michigan Edition, STS Consultants, Dam Safety Guidebook.
North Carolina Department of Natural Resources and Community Development, Division of Land Resources, Land Quality Security Dam OperationMaintenance and Inspection Manual.
North Dakota Dam Design Handbook, North Dakota State Engineer.
Ohio Department of Natoral Resources (1983) Operation, Maintenance, andInspection Manual for Dams, Dikes, and Levees.
Pennsylvania Department of Environmental Resources, Division ofDam Safety(1986) A Manual for the Inspection, Maintenance, and Operation of Damsin Pennsylvania.
Virginia State Water Control Board, Bureau of Water Control Management(1983) Safety Evaluation ofSmalJ Earth Dams, Information Bulletin 549, Richmond, Virginia.
Wyoming Disaster and Civil Defense Office (1984) Dam Safety: A Manual forPrivate Dam Owners.
Selected BIbliographyAmerican Society of ,Civil Engineers (ASCE)/U.S. Commission on LargeDams (USCOLD) (1975). Lessons from Dam Incidents, USA NewYork: ASCE.
American Concrete Institute (ACI) (1968). "Guide for Making A ConditionSurvey of Concrete In Service", Journal of the American Concrete Institute,Vol. 65, No. I I: ACI.
(1982). "Materials and General Properties of Concrete." In ACI Manual ofConcrete Practice, Part J. Detroit: ACI.
Bartholomew, C.L, et al (1986). Embankment Dam InstrumentationManual U.S. Bureau of Reclamation, Washington, D.C., GoverrunentPrinting Office.
(1987). (To be published) Concrete Dam Instrumentation Manual, U.S.Bureau of Reclamation, Washington, D.C., Government Printing Office.
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Chiefof Engineers (1915). "Recommended Guidelines for Safely Inspection ofDams." National Program of Inspection of Dams, Vol. I, Appendix D,Washington, D.C., Department of the Army.
Concrete Construction Publication, Inc. (1983). "Four Steps to SuccessfulConcrete Repair." Vol. 28, No. I. Addison, Illinois: Concrete ConstructionPublication, Inc.
(1985) "Crack Repair." Vol. 30, No.1. Addison,lUinois: Concrete ConstructonPublication, Inc.
Dunniclilf, J. (1981). Measurements Commitee Report, U.S. Committee onlarge Dams Section VI, Inventory of Geotechnical Instruments, Manufacturersor Suppliers.
Golze, A.R., ed (1911). Handbook of Dam Engineering, Van NostrandReinbold Co., New York.
Graham, W.J. (1983). Dam Failure Warning EfTectivness, Denver,Colorado, U.S. Bureau of Reclamation. Unpublished report.
Interagency Committee on Dam Safely, Subcommittee on Emergency ActionPlanning (1985). Emergency Action Planning Guidelines fnr Dams,Washington, D.C., Federal Emergency Management Agency.
Interagency Committee on Large Dams (ICOID) (1-969). General Considerations Applicable to Instrumentation for Earth and Rock/ill Dams, Committee on Observations of Dam and Models, Bullelin, No. 21, Boston,Massachusetts.
(1981). Automated Observation for Instantaneous Safety Control of Damsand Reservoirs, Bulletin No. 4 I, Boston, Massachusetts.
International Conference of Building Officials (1919). Uniform BuildingCode, 1919 Edition, Whittier, California.
Jansen; R.B. (1968). A Prescription for Dam Safely - Instrumentation andSurveillance, Conference of CoDege of Engineering, Uuiversity of California, Berkeley.
(1980). Dams and Public Safely, U.S. Bureau of Reclamation, GovemmentPrinting Office, Washington, D.C.
Mine Safely and Health Administration, Mine Waste and· GeotechnicalEngineering Division (1984). Construction Inspection of Dams and CoalRefuse Embankments, BrucetOn Mills, Pennsy~vania.
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Responsibility and Liability of Public & Private Interest..; on DamsSepteml::er 1975
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Safety of Small DamsAugust 2974
A/1ERICAN SOCIETY OF CIVIL ENGINEERS
Current Trends in Design and Construction of flnbankIrent Dams1979 •
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