CHAPTER 6INSTRUMENTATION AND MONITORINGGUIDELINES

6.0 GENERAL"Instrumentation of a dam furnishesdata to detennine if the completedstructure is functioning as intendedand to provide a continuing sur­veillance of the structure to warn ofany developments which endanger itssafety" (ICOW. 1969).The means and methods available tomonitor phenomena that can lead todam failure include a wide spectrumof instruments and procedures rang­ing from very simple to very com­plex. Any program of dam safetyinstrumentation must be properlydesigned and consistent with otherproject components. must be basedon prevailing geotechnical conditionsat the dam. and must include con­sideration of the hydrologic -andhydraulic factors present both beforeand after the prQject is in operation.Instruments designed for monitoringpotential deficiencies at existingdams must take into account thethreat to life and property that thedam presents. Thus. the extent andnature of the instrumentation dependsnot only on the complexity of thedam and the size of the reservoir. butalso on the potential for loss of lifeand property downstream of thedam.

An instrumentation program shouldinvolve instruments and evaluationmethods that are as simple and

.straightforward as the project willallow. Beyond that. the dam ownershould make a definite commitmentto an ongoing monitoring program orthe installation of insl{Uments prob­ably will be wasted

This chapter discusses deficiencies indams that maybe discovered and thetypes of instruments that may beused to monitor those deficiencies.Table 6. I describes deficiencies.their causes and generic means fordetecting them. Increased knowledgeof these deficiencies acquired througha monitoring program is useful indetermining both Ihe .cause of thedeficiency and the necessary remedy.

Sf

Involvement ofqualified personnel inthe design. installation. monitoring.and evaluation of an instrumentationsystem is of prime importance to thesuccess of the program.

6.1 REASONS FORINSTRUMENTATIONInstrumentation and proper monitor­ing and evaluation are extremelyvaluable in determining the perfor­mance of a dam. Specific reasons forinstrumentation include:

• Warning of a Problem - Often.instruments can detect unusualchanges. such as water fluc­tuations in pressure that are notvisible. In other cases. gradualprogressive changes in say see~

age flow. which would go unnoticedvisually. can be monitored regu­larly. This monitoring can warn ofthe development of a seriousseepage problem.

• Analyzing and Defining a Prob­lem - Instrumentation data isfrequently used to provide en­gineering information necessaryfor analyzing and defining theexte·nt of a problem. For example.downstream movement of a dambecause of high reservoir waterpressure must be analyzed todetermine if the movement isuniformly distributed along thedam, whether the movement is in.the dam. the foundation. or both.and whether the movement is con­tinuing at a constant. increasing ordecreasing rate. Such informationcan then be used to design correc­tive measures.

• Proving Behavior Is as Expected- Instruments installed at a dammay infrequently (or even never)show any anomaly or problem.However. even this information isvaluable because it shows that thedam is performing as designedand provides peace o( mind to anowner. Also, although a problemmay appear 10 be happening orimminent, instrument readingsmight show that the deliciency

52

(say increased seepage) is nonnal(merely a result of higher thannormal reservoir level) and wasforeseen in the dam's design.

• Evaluating RemedialAction Pel'­formance - Many dams, par­ticularly older darns, are modifiedto allow for increased capacity orto correct a deficiency. Instru­ment readings before and after thechange allow analysis and evalu..tion of the performance of themodification.

action, expansion resulting from tem­perature change, and heave resultingfrom hydrostatic uplift pressures.They can be categorized by direc­tion:• Horizontal Movement - Horizon­

tal or translational movementoonunonIy happens in an upstream­downstream direction in bothembankment and concrete dams.It involves, the movement of anentire darn mass relative to its

/

.... MIN1MUM

-.

I- REBAR

mU.n \\ URKS

J~~' ---r~r ~_~___ STATION

AXIS ~F DA\M LLo -1_ /

..,-~~,...:=:==;o~~~~~-- ~

~ ! ~~ -- ~- - ...

~:r.~I&:~ar:~~

Figure 6.1 b - Plan of Alignment Syslem

Figure 6.1a - Inslallallon of Permanent Points

6.2 INSTRUMENT TYPES ANDUSAGEA wide· variety of devices and pr~

cedures are used to monitor dams.The features of dams and dam sitesmost often monitored by instru­ments include:• Movements: (horizontal, verti­

cal, rotational and lateral)• Pore pressure and uplift pres-

sures• Waler level and now• Seepage now• Waler quality• Temperalure• Crack and joint size• Seismic activity• Weather and precipitation• Stress and slrainA listing of manufacturers and sup­pliers for the various instrumentationdevices is pr~vided in a rePort byDunnicliff () 98) ). Details of theinstallation, operation, and mairi­tenance of each device Bie describedin U.S. Bureau of Reclamation(J986).

6.2.1 Visual observations - As dis-. cussed in Chapter S, visual obser­

vations by the dam owner or theowner's representative may be themost important and effective meansof monitoring the performance of adam. The visual inspections shouldbe made whenever the inspectorvisits the dam site and should consistof a minimum of walking along thedam alignment and looking for anysigns of distress or unusual con­ditions at the dam.6.2.2 Movements - Movementsoccur in every dam. They are causedby Slresses induced by reservoirwater pressure, unstable slopes (lowshearing strength), low foundationshearing strength, settJement (c0m­pressibility of foundation and dammaterials), thrust due to arching

$3

abutments or foundation. In anembankment dam, instrumentscommonly used for monitoringsuch movement include:

• Extensometers• Multi-point extensometers• Inclinometers• Embankment measuring

points• Shear strips• Structural measurinl points

Installation of simple meaSurinapoints is illustrated iD Ape 6.], aand b, a simple crack monitoring sys­tem is shown in Figure 6.2, andinclinometer systems IIDd plots areshown in Figure 6.3.c.For a concrete dam, instruments formonitoring horizOntal movementsmay include:

• Crack measuring devices• Extensometers• Muhi-point extensometen• Inclinometers• Structural measuring points• Tape gauges.• Strain meters• PJumb lines• Foundation deformation gauges

CARPENTER'S UVEL(Spirfl Lntl)

YMINIMUMEMBWMENT

"OR"O,"I \ I.mS1'1 \C • \1.·'·1

•41n1tW)

~;..;exozou~ -L__-L_-\-_-,,-4

SECOND Rf.ADlNGn'"'''' :1_ --r--r ~=:gc::z::»~~,.

b(Sa........)

Figure 6.2 Monitoring Cracks on Embankment

+1.1

1ST READING•:-2ND READING,,

•,

•

,,I1.,,

-u

...wWl&.

Z

:z::Ii:wo

8- DIRECTION

+1.1

I 1•,•, 5,,,

,i,

I/

1

•

-uDEFUCTION IN INCHES

Figure 6.3b - Plot of tncllnomet... Readings

1ST READING +--..,

2ND READING

B-..-

INCLINOMETER

tnctlnomet... Syst.ms and Plots are Shown In Figure 6.3~c.

A • DIRECTION

A+- -A-

Figur. 6.3a - IncDnom.ter....D.tall at surfac.

A­

Figure 6.3c Incllnom.t.r and Casing

In a concrete dam. vertical move­ment monitoring devices mayinclude:

• Settlement sensors• Extensometers• Piezometers• Structural measuring points• Foundation deformation

gauges• Rotational Movement - Rota­

tionaJ mo··ernent is commonly aresuh nf high reservoir water pres­sure in combination with lowshe:>rin1- strength in an embank­ment or fowldalion and may occurin either component of a darn.This kind of movement may bemeasured in either embantmentor concrete dams by instrumentssuch as:

• Extensometers• I ndinomeh:rs• liltmeters• Surface measurement points• Crack measurement devices• Piezometers• Foundation deformation

gauges• Plumblines (concrete only)

• Lateral Movement - LateraJmovement (parallel with the crestor a dam) is common in concretearch and gravity dams. The struc­ture 01 an arch dam causes reser­voir water pressure to be translatedinto a horizontal thrust againsteach abutment Gravity damsalso exhibit some lateral rnove­ment because or expansion andcontraction due to temperaturechanges. These movements maybe detected by:

• Structural measurementpoints

• liltmeters• Extensomcters• Crack measurement devices• Plumblines• Strainmeters• Stressmeters• Inclinometers• Jointmeters• Thermometers• Load cells

6.2.3 Pore pressure and uplift pres­sure: As discussed in Chapter 2. acertain amount orwater seeps through.under. and around the ends 01 alldllJJlS. The water moves throughpores in the soil, rock. or concrete asweU as through cracks, joints. etc..The pressure of the water as it moves

movements may be monitoredby:

• Settlement plates/sensors• Extcnsometen• Piezometers• Vertical Internal movement

devices• Embankment measuring

points• Structural measuring points• Inclinometcl' casing mea­

surements

Ib) STRAIGHT EDGE AND TAPE. PLUS REFERENCE POINTS

PLUMB BOB OR WEIGHT

STRING OR TWINE

~s

STEEL TAPEI

---:'~"~'~'=.~.'~.. ~.-.~:=.~>~.Fr.~.~..=...~..~....=..=.~=.~I:":V~ERT1CAL DISPLACEMENT.:'. ~ ..

WALL

STRAIGHT EDGE

•

Ca. STRAIGHT EDGE AND TAPE

LOOK FOR CHANGES

HERE ll-sun TAPE?-l

LOOK FOR CHANGES HERE

Ie) PLUM. Boa

STRUCTURAL _./CRACK oF.

SIDE OF >.

CONCRETE •... t:SPILLWAYWALL

Cd) MORTAR MARKER

LOOK FOR CRACKINGTHROUGH PATCH

Figure 6.4 - Measuring Displacements

..ExlilDples of monitoring of c:oocretestructure movements are shown inFigure 6.4.• YeTtkaI Movement - VerticaJ

movement is c:ommOoly a resultofc:onso6dation of embanlment orfoundation materials rmdting insettlement of the dam. Anothercause is heave (particularly at thetoe of • dam) caused by hyd~static uplift pressures.

In an embankment.da~ verticaJ

acts uniformly in all planes and istermed pore pressure. The upwardforce (caDed uplift pressure) has theeffect ofreducing the effective weightof the downstream portiOn of a damand can materially reduce damstability. Pore pressure in an em­bankment dam. a dam foundation orabutment. reduces that component'sshearing strength. In addition, excesswater, if not effectively channeled bydrains or filters. can result in pro­gressive internal erosion (piping) andfailure. Pore pressures can be m0n­

itored with the following equipment• Piezometers

electricalopen weDpneumatichydraulicporous tubeslotted pipe

• Pressure meters &. gauges

• Load cellsSimple piezometers may be as illus­trated in Figure 6.5, while a basicobservation weD ~ shown in Figure6.6.

6.2.4 Water Level and Flow· Formost dams, it is important to monitorthe water level in the reservoir andthe downstream pool regularly todetennine the quantity ofwater in thereservoir and its level relative to theregular outlet works and the emer­gency spillway. The water level isalso used to compute water pressure .and pore pressure; the volume ofseepage is usuaRy directly related tothe reservoir level. It is also impor­tant to establish the normal or typicalDow through the outlet works forlegal purposes.Water levels may be measured bysimple elevation gauges - either staffgauges or numbers painted on perma­nent, fixed structures in the reservoir- or by complex water level sensingdevices. Flow quantities are oftencomputed from a knowledge of thedimensions of the outlet works andthe depth offlow in the ouUet channel·or pipe.

55

6.2.5 Seepage flow - Seepage mustbe monitored on a regular basis' todetermine if it is increasing. decreas­ing. or remaining constant as thereservoir level fluctuates. A flow ratechanging relative to a reservoir waterlevel can be an indication of aclogged drain, piping. or internalcracking of the embankmenL Seepagemay be measured using the followingdevices and methods:

• Weirs (any shape such as V­notch, rectangular, trapezoidal,etc.)

• Flumes (such as a Parshallnume)

• Pipe methods• Timed-bucket methods• Flow metersExamples ofweirs. flumes, and buck­et measuring installations are ilJus.­trated in Figures 6.7. 6.8, and 6.9.6.2.6 Water quality - Seepagecomes into contact with variousminerals in the soil and rock in andaround the darn. This can cause twoprOblems: the chemical dissolution ofa natural rock such as limestone. orthe internal erosion of soil.

STANDPIPE

CONCRETE OR GROUT

•Figure 6.6 - Typical Observation wen Installation

OVERBURDEN

J-MINIMUMDIAMETERBORING

YNEUMATICTRANSDUCER

POROUS ----Ie.fiLTER

POROUS STONE SENSING UNIT

C;?~it:Uj~ndow.)

~~W.ln ~nltn htrt; prtssvrt is tlItf1td on adi.pltralrM al IItt tn. of Iht wnshtlr vnll.

TO PORE PRESSURE TERMINAL

INSTALLATION DETAIL(TYPICAL)

Figure 6.5 - Porous Stone Piezometer

56

Dissolution of minerals can often bedetected by comparing chemicalanalyses of reservoir water'andseepage water. Such tests ate sitespecifIC; for example, in a limestonearea. one would look for calcium andcarbonates, in a gypsum area, cal­chun and sulfates. Other tests, suchas ph can also sometimes provideuseful· information on chemicaldissolution.Internal erosion can be detected bycomparing turbidity of reservoirwater with that of seepage water. Alarge increase in turbidity indicateserosion.

6.2.7 Temperature - The internaltemperature of concrete dams iscommonly measured both during andafter construction. During construc­tion, the heat of hydration of freshlyplaced concrete can create highstresses which could result in latercracking. After construction is com­pleted and a dam is in operation, it isnot uncommon for very significanttemperature differentials to existdepending on the season of the year.For example, during the winter, theupstream face of a dam remainsrelatively wann because of reservoirwater temperature, while the down­stream face of the dam is reduced to acold ambient air temperature. Thereverse is true in the summer. Tem­perature measurements are impor­tant botIt to determine causes ofmovement due to expansion or con­traction and to compute actual move­menL Temperature measurementscan be made by using any of severaldifferent kinds of embedded ther­mometers or by making simultaneoustemperature readings on devices suchas ~tressand stram meters which pro­vide means for indirectly measuringtemperature of the mass.·6.2.8 Crack and joint size - Aknowledge of the locations andwidths of cracks and joints in con­crete dams and in concrete spillwaysand other concrete appurtenances ofembanbnent dams is importantbecause of the potential for seepagethrough those openings. Even more,it is important to know if the width ofsuch openings is increasing or de­creasing. Various crack and joint·measuring devices are available. andmost allow very accurate measure­menL Some use simple tape or dialgauges, while others use complexelectronics to gain measurements.

BULKHEAD

SEC. A-A

DEPTH OF FLUME

DEPTH INDICATOR

METAL STRIP.

'\.~----T

METAL SfRIP

~

,..: V-NOTCH WEIR

•

BULKHEAD

W~TER SURFACE

~JH

(H EIGHT OF WATERABOVE CREST

PARSHALL FLUME(Installation and I10w measunmenl

aceordinllo manufaaurcr's instr1lClions)PanMJlfIurM

Tllr..., Sbippinc Intate <mtalR.ln! Capacity W""h Dept'" We.... W"'" Lnol'itds. JPIIt. lin.) (ift.) (Ibs.) G.... (ilL) (ft_....)

.on )2 , 6 n 16 ,..,.. r· ," •..... 21O 2 1O 2S ,r- S"I.. T·roW

.64 2'7 ) 12 ~~ 12 iOJ,. )"·r'-134 ~ ) IS .1 16 10". )"·r

(HEIGHT OF WATEP L B_U_L_K_H_E_A_D ..."BOVE CREST

WAUR SIJRFACE

RECTANGULAR WEIR

"

ItI',I

". !I-ALTERNATIVE DEPTHINDICAJOR ,PLACEON UPSTREAM FACE>F BUUtHEAD)

Figure 6.7 - standard Weirs

FI9",e 6.1 Parshall Flume

_, \ \ \\\ W ,~~ \\/,\1.:' !r. '~fffl} ifIll

-----e------- -..., ~RECORD TIME iIT TAXES TO FILL COU.ECnONCONTAINER 7 onCH

DIXE TO CONTROLFLOW

Figure 6.9 Bucket and Stopwatch Method

57

6.2.9 Seismic activity - Seismicmeasuring devices record the inten­sity and duration of large-scale earthmovements such as earthquakes.Many federal and state dams usethese instruments because they arepart of the U.S. Geological Survey'snetwork of seismic recording stations.It ~ay or may not be necessary for apnvate dam to contain any seismicdevices depending upon whether it isin an area of significant seismic risk.Seismic instruments can also be usedto monitor any blasting conductednear a dam site.

6.2.1.0 'Yeather and precipitation­MODltonng the weather at a dam sitecan provide valuable informationa~ut both day-t~day performanceand developing problems. A raingauge, thermometer, and wind gaugecan be easily purchased, installedmaintained and monitored at ~dam site.

6.2.11 Stress and strain - Measwe-_ments to determine streSs and/or

strain are common in concrete damsand to a lesser extent, in embank­ment dams. The monitoring devicespreviously listed for measuring dammovements, crack and joint size andtemperature are also appropriate formeaswing stress and strain. Monitor­ing for stress and strain permits veryearly detection of movemenL

6.3 FREQUENCY OFMONITORINGThe frequency of instrument readingsor malting observations at a damdepends on several factors including:

• Relative hazar~ to life and prop­erty that the dam represents

• Height or size of the dam ,• Relative quantity of water im­

pounded by the dam• Relative seismic risk at the

site• Age of the dam• Frequency and amount of water

level nuctuation in the reservoirIn general, as each of the above fac­tors increases, the frequency of mon­itoring should increase. For example,very frequent (even daily) readingsshould be taken during the first fillingof a reservoir, and more frequentreadings should be taken during highwater levels and after significantstorms and earthquakes. As a rule ofthumb, simple visual observationsshould be made during each visit tothe dam and not less than monthly.Daily or weekly readings should bemade during the flrst filling. im­mediate readings should be takenfollowing a storm or earthquake, andsignificant seepage, movement, andstress-strain readings should ~ably be made at least monthly.

59TABLE 7.1MAINTENANCE GUIDEUNES

DIRECTORY

~~Or-:~-::c ....~~REQUIRED -< :«

MAJNTENANCE---.. 1J1~

Tobit 7.1 lis's i'tms to bt moin,ointd at adam and Ilrt mainltnona lasks la lit ptr­formtd. T1rt sp«jfic s«'wns wlrert 1M ma;~

tenanu 'asks art diseusstd art also '101M

X

x

XX

~,!

IIIX ,--

I -L ---.-I __ I JI -,-- ~ ---

t-- ,-------j-- - 1-: --.- :----. X--X

-X i -)( x-----i

I r i- i

! I ! If X X-----

j_._". Ii-. ----I---.f------­i- _-~= - -- .!- -- *----- *-. -I'.- -~ ------ -I-'~-== ~

-- 1--- X - i- X _._--.!I X- l-- -~---- f-~-X

I ... ,--.1--1- i---t1--- x--- Jf. .-- -- X-'--'*.-j - I--. I - x-- -- x·· ---- --I t 1 * f -- fl-*j,:----.--Jf,.--i-- *·~~rX -- - --- '--'----·'-1-- x---

I I t I· - I-T---:--'1-'- ~_ -.~ I -~--=l1- -- x-- x- -~-

11==-i I=·=-~II ~ .. ~ ..--;:'·-31_ . --- . J~-=-*.~~ -- !--~

I i I-- x---x·--_·

X

xXXX

Xi

X

XX

I

I:

X

x

•X

I

x

XXXX

X

x,-i

XX-I,,

x

X

X

XXXX

x

X,

XX

x

XX

X

X

xI

X

x

XX

·X

XX

xXXX

X

IXX

.I

IIIIXI

x

SPIUWAYSApproach ChannelInlet/outlet structureStilling BasinDischarge conduit!Channel

Control FeaturesErosion ProtectionSide Slopes

CONCRETE DAMSUpstream SlopeDownstream SlopeuNRight AbutmentsCrestInlernal Drain. SystemRelief DrainsGalleriesSluiceways/Controls

FEATURE

EMBANKMENT DAMUpstream SlopeDownstream SlopeLeNRight AbutmentsCrestInternal Drainage Sys.Relief DrainsRiprap & SlopeProtection

GENERAL AREASReservoir SurfaceMech/elect. syslernsShorelineUpstream WatershedDownstream Channel

OUTLETS. DRAINSInlet/outlet structureStilling BasinDischarge ChannelTrashracltlDebris ControlEmergency Systems

CHAPTER 7MAINTENANCE GUIPEUNES

7.0 GENERALA good maintenance program willprotect a dam against deteriorationand prolong its life. A poorly main­tained dam will deteriorate and canfail Nearly aD the components of adarn and the materials used for damconstruction are susceptible to dam­aging deterioration if not properlymaintained A good maintenanceprogram provides not only protectionfor the owner, but for the generalpublic as wen. Moreover, the cost ofa proper maintenance program issmaJl compared to the cost of majorrepairs, Joss of life and property andresultant litigation.A dam owner should develop a basicmaintenance program based primarilyon systematic and frequent inspec-­tions. Inspections, as noted in Chap­ter S, should be done at least monthlyand after major nood or earthqualeevents. During each inspection, achecklist of items calling for main­tenance should be used.

7.1 MAINTENANCEPRIORITIESMaintenance is a task which shouldnever be neglected. If it is, severalareo ultimately wiD need attention­some of greater concern than others.The foUowina outline lists, by rela­tive priority, the various problems orconditions that might be encounteredin • deteriorated darn7.1.1 I mmediate maintenance -Thefollowin, conditions are critical andcall for immediate attention:..• A darn about to be overtopped or

being overtopped

• A darn about to be breached (byprqgressive erosion, slope failure,or other circwnstances)

• A dam showing signs of piping orinternal erosion indicated byincreasingly cloudy seepage orother symptoms

• A spillway being blocked. orotherwise rendered inoperable, orhaving normal discharge re­stricted

6t

• Evidence of excessive seepageappearing anywhere at the damsite (an embankment becomingsaturated, seepage exiting on thedownstream face of a dam)increasing in volwne.

Although the remedy for some criti­cal problems may be obvious (suchas clearing a blocked spillway), theproblems listed above generally

. require the services of a ProfessionalEngineer familiar with the construc­tion and maintenance of dams. Theemergency action plan (discussed inChapter 8) should be activated whenany of the above conditions arenoted.7.1.2 Required maintenance atearliest possible date - The follow­ing maintenance should be com­pleted as soon as possible after thedefective condition is noted:

• All underbrush and trees shouldbe removed from the dam. and agood grass cover should beestablished

• Eroded areas and gullies onembankment dams should be re­stored and reseeded

• Defective spillways, gates. valves.lind other appurtenant features ofa darn should be repaired

• Deteriorated concrete or metalcomponents of a darn should berepaired as soon as weatherpermits

7.I.j Continuing maintenance ­. Several tasks should be perfonned on

a continuing basis: .

• Routine mowing and generalmaintenance .

• Maintenance and filling of any. cracks.and joints on concrete

dams

• Observation of any springs orareas of seepage

• Inspection of the dam (as dis­cussed in Chapter 5)

• Monitoring of development inthe watershed which wouldmaterially increase runofffrom storms

62

• Monitoring of developmentdownstream and updating theemergency notification plan toinclude new homes or otheroccupied structures within thearea

7.2 SPECIFIC MAINTENANCEITEMS7.2.1 Earthwork Maintenance andRepair - Deterioration of the sur­faces of an earth dam may occur forse~ral reasons. For example, waveaction may cut into the upstreamslope, vehicles may cause rots in thecrest or slopes, or runoff waters mayleave erosion gullies on the down­stream slope. Other special pro~

lems, such as shrinJtage cracks orrodent damage, may also occur.Damage of' this nature must berepaired on a continuing basis. Themaintenance procedures describedbelow are effective in repairing minorearthwork problems. However, thissection is not intended to be a techni­cal guide, and the methods discussedshould not be used to solve seriousproblems. Conditions such as em-

:b~ent slides, structural cracking,and sinkholes threaten the immediatesafety of a dam and require immediaterepair under the direction of an

. engineer.

The material selected for repairingembankments depends upon the pur­pose of the earthwork. Generally,earth shou~d be free from vegetation(Jrganic materials, trash, or larg~rock. Most of the earth should befine-grained soils or earth clodswhich easily break down whenwork.ed wi~ compaction equipmentThe IDtent IS to use a material whichwhen compacted, fonns a finn, solidmass, free from excessive voids.If Oow-r~sistant portions of anemb~ent. are being repaired,n;tatenals which are high in clay orslh content should be used. If thearea is to be free draining or highlypenneable. (i.e., riprep bedding, etc.)the matenal should have a higherpercentage of sand and gravel. As ageneral rule, it is usually satisfactoryto. repl~ce ?'" repair damaged areas~th sods Similar to those originallym place.

An important soil property affectingcompaction is moisture content.Soils which are too dry or too wet donot compact well. One may roughlytest repair material by squeezing it

into a tight ball. If the sample main­tains its shape without cracking andfalling apart (which means it is toodry), and without depositing excesswater onto the hand (which means itis too wet), the moisture content isprobably near the proper levelBefore placement of earth, the repairarea must be prepared by removingall inappropriate material. Vegeta­tion such as brush, roots, and treestumps must be cleared and any largerocks or trash removed. Also, unsuit­able earth, such as organic or loosesoils, should be removed, so that thework surface consists ofexposed fmnclean embankment material.

Following cle~up, the affected areashould be shaped and dressed, so thatthe new fiU can be compacted andwill properly tie into the existing fiU.If possible, slopes should be trimmed.and surfaces roughened by scarifyingor plowing to improve the bond be­tween the new and existing fi)) and toprovide a good base to compactagainst. ..'

Soils should be placed in loose layersup to 8 inches thick and compactedmanually or mechanically to fonn adense mass free from large rock ororganic material. Soil moisture mustbe maintained in the proper range.The fiU should be watered and mixedto the proper wetness or scarified andallowed to dry if too wetDuring backfilling, care should betalen that fiU does not become too­wet from rainstonn runoff. Runoffshould be directed away from thework area and repair areas should beoverfilled so that the fiJi maintains acrown which will shed water...As mentioned eariler,. occasionallyminor cracks will fonn in an earthdam -b«ause of surface drying.These are called dessication (drying)cracks and should not be confusedwith structural or settlement cracks.Dryingqacks are usually parallel tothe main axis of the dam, typicallynear the upstream or downstreamshoulders of the crest These cracksoften om intennittently along thelength of the dam and may be up to 4feet deep. Drying cracks can be dis­tinguished from more serious struc­tural cracks because the former areusually no wider than a few inchesand have edges that are not offsetvertically.

As a precaution, suspected dryingcracks should initially be monitored

57

with the same care used for structuralcracks. The problem area should bemarked with swvey stakes. andmon­itoring pins should be installed oneither side of the crack to allowrecording of any changes in width orvertical offsel Once satisfied that

. observed cracking is the result ofshrinkage or drying. an owner maystop monitoring.However, these cracks will close asclimatic or soil moisture conditionschange. If they do not, it may benecessary to backfiD the cracks toprevent entry of surface moisturewhich could resuh in saturalioD of thedam. 1be cracks may be simply fiUedwith earth that is tamped in placewith hand or tools. It is also re~mended that the crest of a dam begraded to direct nmoff waten awayfrom areas damaged by dryingcracks.

As Chapter 5 suggests, erosion is oneof the most common maintenanceproblems at embanbnent structures.Erosion is a natural process, and itscontinuous forces will eventuallywear down almost any surface orstructure. Periodic and timely main­tenance is essential to prevent con­tinuous deterioration and possiblefailure.Sturdy sod. free from weeds andbrush, is an effective means of pre­venting erosion. Embankment 'slopesare nonnally designed and construct­ed so that surface drainage will bespread out in thin layers (sheet now)on the grassy cover. When embank­ment sod is in poor condition or Oowsare concentrated at any location, theresuhing erosion will leave rills andguJJiesin the embankment slope. Anowner should look for such areas andbe aware of the problems that maydevelop. Eroded areas must bepromptly repaired to prevent moreserious damage to the embanbnent.RiDs and gullies should be fdled withsuitable soil (the upper 4 inchesshould be top soil, if possible,) c0m­pacted, and then seeded. A local SoilConservation Service Officer can bevery helpful in selecting the types ofgrass to use for dam surface prote<rtion. Erosion in large gullies can beslowed by stacking bales of hay orstraw across the gully until penna­nent repainl can be made.Not only should eroded areas berepaired, but the cause of the erosionshould be found to prevent. rontinu­in& maintenance problem. Erosion

~ght be caused or aggravated byimproper drainage, settlement.. ped­estrian traffic, animal burrows. orother factors. The cause of the ero­sion will have a direct bearing on thetype of repair needed

Paths due to pedestrian or two-wheeland four-wheel vehicle traffic are aproblem on many embankments. If apath bas become established. vegeta­tion will not provide adequate protec­tion and more durable cover will berequired unless traffic is eliminated.Small stones, asphalt, or concretemay be used effectively to cover foot­paths. In addition, railroad ties orother treated wood beams can beembedded into an embankment slopeto form an inexpensive stairway.Erosion is also common at the pointwhere an embankment and the con­crete walls of a spillway or otherstructure meel Poor compactionadjacent to such a wall during con­struction and subsequent settlementcan result in an area along the walllower than the grade of the embank­ment. Runoff, therefore, often con­centrates alon~ these structures,resulting in erosion. People also fre­quently walk along these walls. wear­ing down the vegetal cover. Possiblesolutions include regrading the areaso that it slopes away from the wall,adding more resistant surface protec­tion, or constructing wooden steps.Adequate erosion protection is alsoneeded along the contact between thedownstream face of an embankmentand the abutments. Runoff from rain­fall can concentrate in gutters con­structed in these areas and can reacherosive velocities because ofrelativelysteep slopes. Berms on the down­stream face that collect surface waterand empty into these gutters add tothe runoff volume. Sod-surfaced gut­ters may not adequately prevent ero­sion in these areas. Paved concretegullers may not be desirable eitherbecause they do not slow the waterand can be undermined by erosion.Also, small animals often constructburrows underneath these guttersadding to the erosion potential.

A weD- graded mixture of rocks up to9 to 12 inches in diameter (or larger)placed on a layer of sand (filter)generally provides the best protec­tion for these gutters on small dams.Riprap slushed with a thin concreteslurry has also been successful inpreventing erosion on larger damsand should be used if large stonematerial is not available.

As with erosion around spillways,erosion adjacent to gutters resultsfrom improper construction or a poordesign in which the finished gutter istoo high with respect to adjacentground. This condition preventsmuch of the runolf water from enter­ing the gutter. Instead. the flow con­centrates along the side of the gutter,erodes and may eventuany under­mine the gutter.Care should be taken when replacingfailed gutters or designing new gut­ters to assure that:

• The channel has adequatecapacity

• Adequate erosion protection anda satisfactory filter have beenprovided

• Surface runoff can easily enter thegutter

• The outlet is~equatelyprotectedfrom erosion

7.2.2 Riprap maintenance andrepair - A serious erosion Proble111called "beaching" can develop on theupstream slope of a dam. Wavescaused by high winds or hi~speedboats can erode the exposed face ofan embankment by repeatedly strik­ing the surface just above the poolelevation. rushing op the slope. thentumbling back into the pool. Thisaction erodes material from the faceof the embankment and displaces itdown the slope, creating a "beach."Erosion of tmprotected soil can berapid and. during a severe stonn,could -lead to complete failure of adam.The upstream face of a dam is com­monly protected against wave ero­sion and resultant beaching byplacement on the face of a layer ofrock . riprap over a layer or filtermaterial. Sometimes. materials suchas steel. bitwnmous or concrete fac­in~ .bricks or concre~ blocks areused for this upstream slope protec­tion. Protective beaches are some­times actually ·blblt into smaU damsby placing a berm (8 to 10 feet wide)along the upstream face a short dis­tance below the normal pool levelthereby providing a surface on whichwave energy can dissipate. Generally,however, rock riprap provides themost economical and effectiveprotection.Nonetheless, beaching can occur inexisting riprap if the embankmentsurface is not properly protected by afilter. Water running down the slope

under the riprap can erode theembankment. Sections of rip-rapwhich have slwnped downward areoften signs of this kind of beaching.Similarly, concrete facing used toprotect slopes may fail becausewaves wash soil from beneath theslabs through joints and cracks.Detection of this problem is difficultbecause the '1oids are hidden andfailure may be sudden and extensive.Effective slope protection must pre­vent soil from being removed fromthe embankmenlWhen erosion occurs and beachingdevelops on the upstream slope or adam, repairs should be made as soonas possible. The pool level should belowered and the surface or the damprepared for repair. A small berm or"bench" should be built across theface of the dam at the base ofthe newlayer of protection to help hold thelayer in place. The size of the benchneeded depends on the thickness ofthe protective layer.A riprap layer should extend aminimum of 3 feet below the lowestexpected normal pool level. Other­wise, wave action during periods oflow lake level will undermine anddestroy the protection.If rock riprap is used, it should con­sist of a heterogeneous mixture ofirregular shaped stone placed over asand and gravel filter. The largestrock must be .Iarge enough In bothsize and weight to break up theenergy of the maximum expectedwaves and hold smaller stones inplace. (An engineer may have to beconsulted to determine size.) Thesmaller rocks help to fill the spacesbetweenthe larger pieces and to forma stable mass. The filter prevents soilparticles on the embankment surfacefrom being washed out throuBh thespaces between the rocks in the rip­rap. H the filter material itselfcan bewashed out through these voids andbeaching develops, two layers offilters may be required. The lowerlayer should. be composed or sand orfilter fabric to protect the soil surfaceand the upper layer should be com- .posed of coarser materials.A dam owner should expect someriprap deterioration because ofweathering. Freezing and thawing.wetting and drying. abrasive waveaction and other natural processeswill eventually break down thematerial. Therefore. sufficient main­tenance funds should be allocated forthe regular replacement of riprap.

64

The useful life of riprap variesdepending on the characteristics ofthe stone used. Thus. stone for riprapshould be rock that is dense and wellcemented. When riprap breaks down,and erosion and beaching occur moreoften than once every three to fiveyears, professional advice should besought to design more effectiveslope protection.

7.2.3 Vegetation maintenance- Theentire dam should be kept clear ofunwanted vegetation such as brush Ortrees. Excessive growth may causeseveral problems:

• ]t can obscure the surface of anembankment and prevent a thor­ough inspection of the darn

• Large trees can be uprooted byhigh wind or erosion and leavelarge holes, that can lead tobreaching of the dam

• Some root systems can decay androt. providing passageways forwater, and thus· causing erosion

• Growing root systems can liftconcrete slabs or structures

• Weeds can prevent the growth ordesirable grasses

• Rodent habitats can developWhen brush is cut down, it should beremoved from a darn to permit a clearview of the embankment Followingremoval of large brush or trees, theleft over root systems should also beremoved if possible and the resulting

·holes properly rtJled In cases wherethey cannot be removed, root sys­tems can be treated with herbicide(properly applied) to retard furthergrowth. After the removal of brush,cuttings may need to be burned. Ifthis is done, dam owners shouldnotify the local fire ~epartment,

forest service. or other agency re­sponsible for flTe control.

If properly maintained. grass is notonly an effective means ofcontrolJmgerosion. it also enhances the appear­arice of a dam and provides a surface'that can be easily inspected Grassroots and stems tend to trap fme sandand soil particles, forming an erosion­resistant layer once the plants arewelJ established Grass is least effec­tive in areas ofconcentrated runofforin areas subjected to wave action.

7.2.4 Livestock control - Livestockshould not be allowed to gaze on anembankment surface. When soil iswet. they can damage vegetation anddestroy the uniformity of the surface.

Moreover, livestocl tend to wall inestablished paths and thus can pro­mote severe erosion. Such pathsshould be regraded and seeded, andthe livestock should be permanentlyfenced out of the area.

7.2.5 Rodent damage control ~

Rodents, such as groundhogs (wood­chucks), muskrats, and beavers arenaturally attracted to the habitatscreated by dams and reservoirs andcan, by their behavior, endanger thestructural integrity and proper perfor­mance of embankments and spillways.Groundhog and muskrat burrows canweaken embankments and can serveas pathways for seepage. Beavers canplug a spilJway and raise the poollevel. Rodent control is essential tothe preservation of a darn.

The groundhog is the largest memberof the squirrel family. Its coarse fur isa typically grayish brown with a red­dish cast Occupied groundhog bur­rows are easily reCognized in thespring because of the groundhog's_habit of keeping them "cleaned out"Fresh soil is generally found at themouth of such active burrows. Hatr­round mounds, paths leading from theden to nearby ftehls, and clawed orgirdled trees and shrubs also indicateinhabited burrows and dens.

When burrowing into an embank­ment, groundhogs stay above thephreatic surface (upper surface ofseepage or saturation) to stay dry.The burrow is rarely a single tunnel. Itis usually forked, with more than oneentrance and with several side pas­sages or rooms from I to 12 feet inlength.

Controls should bC implemented dur­ing early spring when active burrowsare easy to fmd, young groundhogshave DOl yet scauered. and there isless likelihood of damage to otherwildlife. In summer, faU, and winter.game animals may scurry..into gr0und­hog burrows for brief protection andmay even take up permanent residenceduring the period of groundhogtu"bemation.

Groundhogs can be controlJed withfumigants or fIrearms. Fwnigation isthe most practical method althougharound buildings or high fire hazardareas, .shooting may be preferable.Gas cartridges for fumigation may bepurchased 8t local farm exchanges,fann supply centers, and many countyextension offices.

. Groundhogs will be discouraged frominhabiting an embankment ifthe grasscover is kept mowed.

The mushat is a stocky rodent with abroad head, short legs, small eyes,and rich dark brown fur. Muskrats arechieOy nocturnal and can be foundwherever there are marshes, swamps,ponds. lakes, and streams havingcalm or very slowly moving waterwith vegetation in the water and along.the banks.

Barriers, such as properly construct­ed riprap and filter layers, provide themost practicaJ protection from musk­rats by preventing burrowing. As amuskrat tries to construct a burrow,the sand and gravel ofa mter layer willcave in and discourage den building.Filter layers and riprap should extendat least 3 feet below water line. Heavywire fencing laid Oat against a slopeand extending above and below the

.waterline can also be effective. Elim~nating or reducing aquatic vegetationalong a shoreline will also discouragemuskrat habitation. Trapping withsteel traps is normally the most practi­cal method of removing muskrats thathave already inhabited a pond.The easily recognized beaver, if in­habiting an area around a dam. will tryto plug the spillway with their cut­tings. Routinely removing the cuttingscan aJleviate the problem or an elec­trically charged wire or wires can beplaced around the spillway inlet.Beaver may be trapped during theproper season and sometimes a localfur trapperwill perform the work at lit­tle or no expense to the owner.

Methods of repairing rodent damagedepend upon the nature of the damage.but in any case. extermination of therodent population is the required firststep. If the damage consists mostly ofshallow holes scattered across anembankment. repair may be necessaryto maintain the appearance or thedarn, to keep runoffwaters from infil­trating the dam, or to discouragerodents from subsequently returningto the embankment In these cases,tamping of earth into the rodent holeshould be sufficient repair. Soil shouldbe placed as deeply as possible andcompacted with a pole or shovelhandle.

Large burrows on an embankmentshould be ftned by mud-packing. Thissimple, inexpensive method involvesplacing one or two lengths of met21stove or vent pipe verticaJly over theentrance of the den with a tight seal

behteen the pipe and den. A mud­pack mixture is then poured into thepipe until the burrow and pipe arefilled with the earth-water mixture.The pipe is removed and additionaldrY earth is tamped into the entr8l)ce.The mud-pack mixture is made byaddingwater to a 90 percent earth and10 percent cement mixture until 8

slurry ofthin cement is attained. Allentrances should be plugged withweD-compacted earth and vegetationre-established. Dens should be elim­inated promptly because one btmowcan lead to failure of a dam.

Different repair measures are neces­sary if a dam has been damaged byextensive small rodent tunneling or by

. beaver or muskrat activity. )n thesecases, :t may be necessary to excavatethe damaged area down to competentsoil and repair as described in Sec­tion 7.2.1.Occasionally, rodent activity willresult in passages which extendthrough the embankment that couldresult in leakage of reservoir water,piping. and, ultimately, failure. Inthese cases, the downstream end ofthe tunnel should not be pluggedsince this wiD add to the saturation ofthe dam. Tunnels of rodents orground squirrels will nonnaUy beabove the phreatic surface withprimary entrance on the downstreamside of the dam. while those of beaverand muskrat nonnally exist below orat the water surface with entrance onthe upstream slope. H8 rodent hole isfound that extends through the dam.the best procedure is first to locatethe upstream end of the passage. Thearea around the entrance should beexcavated and then backfilled withimpervious material. This places 8

plug or p'atch at the passage entranceso that reservoir water is. preventedfrom saturating the interior of thedarn. This should be considered atemporary repair. Excavation andbackfilling of the entire tunnel or fill­ing of the tunnel with cement groutare possible Iong-tenn solutions, butpressure cement grouting is anexpensive and sometimes dangerousprocedure. Indeed, pressure exertedduring grouting can cause additionaldamage to the embanlment in theform of hydraulic fracturing (anopening of cracks by high pressuregrouting). Thus, grouting should beperformed only under the direction ofan engineer.

1.2.6 Traffic damage control - Asmentioned eariler. vehicles drivingacross an embankment dam cancreate ruts in the dam crest if thecrest is not surfaced with roadwaymaterial. The ruts can then collectwater and cause saturation and sof­tening of the dam. Other ruts may beformed by vehicles driving up anddown a dam face. These ruts cancollect runoff and result in severeerosion. Vehicles should be bannedfrom darn slopes and kept out by fen­ces or barricades. Any ruts should berepaired as soon as possible using themethods outlined in Section 1.2.1.1.2.1 Mechanical maintenance ­Proper operation of a dam's outletworks is essential to the safe andsatisfactory operation of a dam.Release of water from a dam is nor­mally a frequent or ongoing function.However, on some reservoirs usedfor recreation. fish propagation. orother pwposes that do nol requirecontinual release of· water, an oper­able outlet· provides the only means _for the emergency lowering of the·reservoir and is therefore, essentialfor the safety of the dam.

If routine inspection of the outletworks indicates the need for main­tenance, the work should be com­pleted as soon as access can begained. Postponement of main­tenance could cause damage to theinstallation. significantly reduce theuseful life of the structure, and resultin more extensive and more costlyrepairs when finally done. Moreimportantly. failure to maintain anoutlet system can lead directly tofailure of the dam.

The simplest procedure to insure thesmooth operation of outlet gates is tooperate all gates through their fullrange at least once and preferablytwice annually. Many gate manufac­turers recommend operating gates asoften as four times a yeh. Becauseoperating gates under fuJI reservoirpressure can result in large outlet dis­charges, gate testing should bescheduled during periods of lowstorage. If this cannot be done, theyshould be operated during periods oflow stream now. If large releases areexpected, outlets should be testedonly after coordinating releases withwater administration officials andnotifying downstream residents andwater users.

65

Operation of the gates minimizes thebuildup of rust in the operati~g

mechanism and therefore, the likeli­hood of seizure of the operatingmechanism. During this procedure.the mechanical parts of the hoistingmechanism - including drive gears.bearings, and wear plates - should bechecked for adverse or excessivewear, all bolts. including anchorbolts, should be checked for tight­ness, worn and corroded parts shouldbe replaced, and mechanical andalignment adjusbnents should bemade as necessary.

The way the gate actually operatesshould also be noted. Rough. noisy.or erratic movement could be the firstsigns of a developing problem. Thecause ofoperational problems shouldbe investigated and correctedimmediately.

Excessive force should be neitherneeded nor applied to either raise orlower a gate. Most hoisting mech­anisms are designed to operate satis­factorily with a maximwn force of40pounds on the operating handle orwheel. Ifexcessive force seems to beneeded, something may be bindingthe mechanical system. The applic.tion of excessive force may result inincreased binding of the gate ordamage to the outlet works. H theredoes seem to be undue resistance, thegate should be worked up and dowDrepeatedly in short stroke~ until thebinding ceases, and/or the cause ofthe problem should be investigatedor course. the problem should becorrected as soon as possible toassure the continued operability ofthe gate.n a gate does not properly seal "t!henclosed; debris may be lodged underor around the gate leafor frame. Thegate should be raised at least 2 to 3inches to nush the debris. and theoperator should then attempt toreclose the gate. This procedure

. should be repeated until proper seal­ing is achieved However. if thisproblem or any other problem per­sists, a manufacturer's representativeor engineer experienced in gatedesign and operation should beconsuhed.

An outlet gate operating mechanismshould always be well lubricated inaccordance with manufacturer'sspecifICations. Proper lubricationwiD not only reduce wear in themechanism, but also protect itagainst adverse weather. Gates with

66

oil-filled stems (i.e.• stems encased ina larger surrounding pipe) should bechecked semiannually to assure the

. proper oil level is maintained If suchmechanisms are neglected. watercould enter the encasement pipethrough the lower oil seal and couldcause failure of the upper and/orlower seals which in tum could leadto the conosion ofboth the gate stemand interior of the encasementpipe.The metal used in gate seats isusually brass. stainless steel. bronze,or other rust-resistant alloys. Okleror smaller gates may not be fittedwith seats, making them susceptibleto rusting at the contact surfaces be­tween the gate leaf and gate frame.Operation of gates should preventexcessive rust buildup or seizure.

For satisfactory operation, a gatestem must be maintained in properalignment with the gate and hoistingmechanism. Proper alignment andsupport is supplied by stem guides insufficient number and properly spacedalong the stem. Stem guides arebrackets or bearings through which astem passes. They both preventlateral movement of the stem andbending or buckling when a stem issubjected to compression as a gate isbeing closed.

The alignment of a stem should bechecked during routine inspections.Alignment milY be checked by sight­ing along the length of the stem, ormore accurately by dropping aplumbline from a point near the topof the stem to the other end. The stemshould be checked in both anupstream/downstream direction aswell as in a lateral direction to ensurestraightness. While checking align­ment, aU gate stem guide anchors andadjusting bolts should be checked fortightness. A loose guide provides nosupport to the stem and could causebuckling of the stem at that poinL

Ifd!lring normal inspection. the stemappears out of alignment, the causeshould be repaired. The gate shouldbe completely lowered and an ten­sion or compression taken ofT thestem. Any misaligned stem guidesshould be loosened and made tomove freely. The hoisting mechanismshould then be operated to put ten­sion on the stem. thereby straighten­ing it, but the gate should not beopened The affected guides shouldthen be aligned and fastened so thatthe stem passes exactly throughtheir centers.

Many outlet gates are equipped withwedges that bold the gate leaf tightlyagainst the gate frame as the gate isclosed, thus causing a tight seal.lbrough years ofuse, gate seats maybecome worn, causing the gate toleak increasingly. If an installationhas a wedge system, the leakage maybe substantially reduced or eliminatedby readjusting the wedges.Because adjustment of these gates iscomplicated, inexperienced person­nel can cause extensive damage to agate. Improper adjustment couldcause pl"emature seating of the gate.possible scoring of the gate seats,binding or the gate. gate vibration,leakage, uneven closing of the gate,or damage to wedges or gate guides.Thus, only experienced personnelshould perform adjustments, and· agate supplier or manufacturer shouldbe consulted to obtain names ofpeo­ple experienced in such wort.

Ice can exert great force on and causesignificant damage to an outlet. &at~leaf. Storage levels in a reservoir dm­ing winter should be low enough thatice cannot form behind a gate. Toprevent i~e damage. the winter waterlevel should be significantly higherthan the gate if storage is maintainedthrough the winter or, if the reservoiris to remain empty over the wintermonths, the outlet should be left. fullyopen. Ifoperations caU for the waterlevel to move across the gate durin"gthe winter, a bubbler or other anti- .icing system may be needed.

7.2.8 Electrical maintenance ­Electricity is typically used at adam to:

• Provide lighting• Operate outlet gates• Operate recording equipment

. • Operate spillway gates• Operate other' miscellaneous

equipmentIt is important that an electrical sys­tem be well maintained. Main­tenance should' include a thoroughcheck of fuses and a test of the sys­tem to ensure that all parts are pr0p­erly functioning. The electrical systemshould be free from moisture and dirt,and wiring should be checked for cor­rosion and mineral deposits. Anynecessary repairs should be com­pleted immediately. and records ofthe repair work should be kept.Generators used for auxiliary emer­gency power must also be main­tained This work includes changingoil, checking ba"eries and antifreeze

and ensuring that fuel is readilyavailable.7.2.9 Cleaning - As already sug­gested. the proper operation ofspill~ays. slui~ways, approachchannels, inlet!outlet structures. stiD­ing basins, discharge conduit, damslopes, trashracks. and debris controldevices require regular and thoroughdebris reinoval and cleaning. Clean­ing is especially important afterupstream storms which tend to sendmore debris into the reservoir.

7.2.10 Concrete maintenance ­Also as mentioned, periodic main­tenance should be performed on allCODa-ete surfaces to repair deteri­orated areas. Concrete deteriorationshould be repaired inunediately whennoted; it is most easily repaired in itsearly stages. Deterioration canaccelerate and. if left unattended, canresult in serious problems or dam

. failure. An experienced engineershould be consulted to determineboth the extent of deterioration andthe proper method of repair.

7.2..11 Metal component main­ttnanee - AU exposed. bare ferrousmetal on an outlet installation,whether submerged or exposed to air,will tend to rusL To prevent corro­sion, exposed Cerrous metals musteither be painted or heavily greased.H painted, the paint should beappropriate and applied·foUowing thepaint manfacturefs directions.When areas are repainted, stepsshould be tak~n to' assure that paintdoes not get on gate seats, gatewedges, or gate stems where thestems pass tlvough the stem guides,or on other friction surfaces where

. paint could cause binding. Heavygress·c should be used on surfaceswhere binding can occur. Becauserust is especiaUy damaging to contactsurfaces, existing rust should beremoved before the periodic applica­tion of greaSe.

Ta~ 8./ is Q nif~renc~ dirrcrory ofoC'C"llrrrn- TABLE 8.167

en and ~m~rg~lICY acriolU 10 ~ rak~" if EMERGlHCY ACnONlIudrdGUIOEUHES DIRECTORY

0 ...~Z 0

ffi~Z ~Z b.J b.Jo ...0:~ 0 ~~ >-1: ~~ Z0. Z

t~ 0 <::> ~III0 0~~

Zm ~~ ~u ~~. O~t 11I- O~ ..J::> m~ ..J~>m =0 !:)d (l)Q =::> ..Ju =1: ~::>III<~ ~g ~~> ;::;:-

~a 0:< ~b.J g~OCCURRENCE .. 0 ~b.J b.J~ u:l~ O~ b.J{I) (I) = u:l{l)

EMERGENCY ACTIONII

HYDRAUUC iLower water level X k X X X X X X .~Increase outlet Rows X I i

X X iControlled Breach X X ISandbags (increase X Xfreeboard) I

!Plug leak entrance X X XClose outlet X . i. IEROSION CONTROl i. IiSandbags X- X X . __ .. 'iRiprap X r XWeight toe area i

X X I :.. ·1I I II I !! I ~ IOPERATIONS I ! i..... __ .~Inspect X X X X X ! . X

Monitor X ! X X X X X I. X ···--ij-

Repair &:. maintain I ! X X x- .... ,:._-- ki ' .

Emergency notification X. I

X , fC -- ._-- ---- _.. rOperate at reduced X X X X X X X··· ·_--xlevel

...

CHAPTER 8EMERGENCY ACTION PLAN GUIDELINES

8.0 THE EMERGENCY ACTIONPlANAlthough most dam owners have ahigh level or confJdence in the struc­tures they own and are certain theirdams will not fail. history has shownthat on occasion dams do fail andthat often these failures cause exten­sive property damage and de aths. Adam owner should prepare for thispossibility by developing an- emer­gency action plan which provides asystematic means to:

• Identify emergency conditionsthreatening adam

• Expedite effective response ac­tions to preve~t failure

• Reduce .loss or life and propertydamage sbouJd failure occur -

A dam owner is responsible· for pre­paring a plan stating the above pur­poses and listing actions that theowner. the operating personnel andlocal government authorities shouldtake. A plan should include sectionson:Purpose: (indicated above)Situation:• A list of problem indi~ators (see

the checklist included in Table8.3)

• A sununary ofcommunities in thepotential inundation zone andOood travel times

•

69

• A list of anticipated failure situa­tions that can be used as a guidefor appropriate responses suchas:

• Failure pending - structure canlikely be saved with inunediateremedial action

• Failure imminent - structuremay possibly be saved withimmediate remedial action

• Failure in progress - no chanceto save the structure

• Flooding expected or in pro­gress upstream from the damsite

• Any other conditions peculiarto this dam

Execution:• A list of remedial actions to pre­

vent failure (see Section 8.2.)

• A plan for notification of down­stream communities that allowsthe greatest possible time to warnand evacuate residents shouldfailure occur and a Jist or te~

phone numbers or emergency pre­paredness officials in eachcommunity (There is an impor­tant distinction between notifica­tion and warning. Notification isthe responsibility of the damowner. he or she must notify com­munity emergency officials ofimpending failure. These officialsmust then warn the public andevacuate them from the inunda­-tion zone if necessary. Publicwarning processes need not befully specified in the dam owners'"emergency action plan.)

Resources and CoordinatingInstructions:• A list of those who can be ofassis­

tance, related telephone numbers.and radio call signs

• A list of materials for use inremedial action; for example,sandbags, high intensity lightingfor night repairs

TABLEa.2POTENTIAL PROBLEMS

AND IMMEDIATE RESPONSE ACTIONS

OVERTOPPING BY FLOOD WATERS• OpeD outlet to its maximum safe capacity• Place sandbap aJona the crest to incTease freeboard aDd force more water throop the

spillway and outlet• Provide erosio&-resistant protectioa 10 the dowDstream slope by placiDa plastic sheets

or odter materials over erodiDa aieas• Di-rert flood waten arowxt the reservoir bum if possible• Creale 8dditionaI spiUway capacity by makinc a cootroDed breach ma Jow embank-

ment 01' dike see:tioa where the foundation inaterials are erosion resistantLOSS OF FREEBOARD OR DAM CROSS SECTION DUE TO STORMWAVE EROSION• Place additiooaJ riprap or saodbap in damaged aRas to preveDt fuJ1bei-

embllDlmeDt erosion• Lower the water level to aa elevaOOo below the damazed area• Restore &eeboardwitb sandbap or euth and rockfiU• Continue close inspection or the damaged area until the storm is overSLIDES ON THE UPSTJlEAM OR DOWNSTREAM SLOPE OF THEEMBANKMENT• Lower the water level at a rate and to an ele.,.tion eoasidered safe liveD the slide COD­

ditioa. H the outlet is damllled or bIoct~pumpiDs. sipboDiDs. 01' a CODb'oIIed breachmay be required

• Restore lost freeboard if required by p1acins sandbap 01' rl1lin& ill the Ic?P or theslide ,

• Stabilize slides 011 the downsbam slope by weiBbtiDs the toe area with additiooal soil.rock, 01' sravel

EROSIONAL FLOWS THROUGH TIlE EMBANKMENT, FOUNDATION.OR ABUIMENTS• PluS die Dow with whatever material is available (hay bales. beDtoaite. or plastic

lbeetioa if the entrance to the leat is ill the reservoir bum)• Lower the water level uutiJ the I10w decreases "to a aoa-erosive velocity oc uutil it

~ '_1_·• Place a protective sand and gravel filter over the exit area to bold materiau 1D

place• ContiDue Iowerina the water level until a safe elevation is reached• Continue operatins at a reduced level uutil repain can be made .

10

A dam owner should male full use orother persons who we c:oocemedwith dam safety. Cooperative plan­ning cm peatly benefit all partjesand result in a more concrete,intepated, plm. People and organi­zations with whom a dam ownershould coordinate emergency~nina inc~WCAL PARTICIPANTSThe dam's owners, shareholders, aDd

beneficiariesOfficials ornearby downstream cities

and townsLocal police, county sheriff .local emergency officialsLocal fare departmentCounty highway departmentLocal construction companiesNews media serving the area (radio,

TV, newspaper)Nearby engineering finDsProfessional diving servicesHelicopter servicesHospital and'or ambulance services

STATE AGENCIESState Engineers office

State EDJineerDam Safety BranchLocal water commissionerDivisioa enPoeer

State offICe responsible for disasteremergency servicesState Highway Patrol

Department or highwaysDep~ent of health

FEDERAL AGENCIESBureau of ReclamationU.S. Forest ServiceNational Park ServiceU.S. Army Corps of EngineersFederal Bureau of InvestigationFederal Emergency Mma,eDJent

Agency"Federal EnerlY Regulatory

CommissionUnited States <koIogicaJ Survey

A checklist to assist in the develop­ment of an emergency action plUlisprovided at the end of this chapter. Adam owner should use this Jist todevelop a plan and to update the planperiodically thereafter as conditionschange (see Table 8.3).

8.t IDENTlFICAnON OFEMERGENCY CONDlnONSAND INITIATION OFEMERGENCY RESPONSEACnOHSAs discussed in earlier chapters, adam owner should observe a damstructure and the dam site OD aregular basis. Failure 1s most oftencaused by overtopping, water nowin&through a dam's key components,and weaknesses in the foundationand outlet works. As discussed inChapters S and 6, a nwnber ofindicators can signal the beginnin& ofproblems that might cause failure.

At a minimum, a dam owner shouldinclude in the II Situation" portion ofthe plan a reminder to check the his­tory and location or hazards whichcould lead to overtopping or otheracute problems. These are discussedin detail in Chapter 3 and include:

• Earthquakes and active faults• Flooding, storms, SDOW melt

runolf

• LandslidesReporting a Dam Safety Incident­WbeD reportin& a dun incident, aDdirections for example ·'left of" or"right from") are from the point ofvie,!, of an observer facing down­stream.

When an "indicator" or dangerouscondition appears, a dam owner orresponsible agent must tale immed­iate action. Ir failure is possible, thatperson should report the situation tostate and local dam safetyautboritiesimmediately. The report shouldinclude:

• The name of the pem>o makingthe report and how he or she canbecODtacted

FAILURE OF APPURTENANT STRUCTURES SUCH AS OUTLETS ORSPILLWAYS• JmpJement temporal}' measures to protect the damaged stnJctwe, such as closing aD

outlet or providiq temporary pmtedioo for a dam-sed spillway• Employ experienced professional divers if DeCeSSuy to assess the problem an4 0

possibly impIemeDt ~pair

• Lower the water level to a safe devation. H the outlet is inoperable, pumpiD&, sipboD-ins. or a cootroIIed breach may be required

MASS MOVEMENT OF mE DAM ON ITS FOUNDATION,(SPREADING Ok MASS SUDING FAILURE)• hnmediately lower the ....ter lenl UDti1 esc:essive JDOYcmenl stops• CootiDue loweriDa the water until a safe level is ~ached

• Continue operatiDg at a reduced level UDtiJ repairs CaD be madeEXCESSIVE SEEPAGE AND HIGH LEVEL SATURATION OF THEEMBANKMENT• Lower the water to a safe level• Cootinue frequent monitoring for signs of slides. cracking or concentrated seepage• Cootinue operation at • mtuced lnel uutil repairs CaD be madeSPILLWAY BACKCUTTING mREATENING kESERVOIREVACUATION• Reduce the now over the spillway by fuJly openina the maiD outlet• Provide temporary protectioo at the point of erosion by placinl sandbags. riprap

materials, or plastic sheets weighted with saDdbap• WIlen inDow subsides, lower the water to • safe level• Continue operating at a low water level in Older 10 minimize spillway DowEXCESSIVE SEITLEMENT OF THE EMBANKMENT• Lower the water level by ~leasiDgit tbroup the outlet or by pwnpin.. siphoning. Or a

CODtroUed breach• H necessary, ~sto~ littboard, preferably by placing saudbap• Lower water to a safe level• Continue opelating at a reduced level uutil repairs CaD be madeLOSS OF ABUTMENT SUPPORT OR EXTENSIVE CRACKING INCONCRETE DAMS• Lower the water level by releasing it through the outlet• Implement notification procedures• Auempt to block water movement throop the dam by placiDg plastic sheets on the

upstream face

• Lowering water to a safe level

• The name of the dam. lake orreservoir, and river, stream. ortributary the dam is located on

• The location of the dam by thenearest highways. roads or townsand by township and section, andrange and principal meridian, ifknown

• A description of the problem (forexample, excessive leakage,cracks, sand boils, slides, wetspots, etc.)

• The location of the problem areaon the dam relative to embank­ment height (for example. "about1/3 up from the toe") and relativeto the dam's crest (for example.100 feet to the right of the outletor abutment) and in terms of whatpart or the dam is actually affected(for example, upstream slope,crest, or downstream slope)

• A description of the extent of theproblem area

• An estimate of the °quantity ofunusual Dow as weD as 8 descrip­tion of flow quality (clear,cloudy, muddy)

• A reading of the water level in thereservoir relative to· the dam'screst, spillway 8JWJ/or the gaugerod

• An indication of whether thewater level is rising or falling

• An indication of whether thesituation appears to be worsenin&

• An indication of whether theproblem appears to be conw.able or is an emergency

• The cunent weather CODditions atthe site

• Anytiling else that seemsimportant

7t

A reporting form is included inAppendix B of this manual Ownersshould use it as a guide and supple­ment it with additional site-specificdetails.AdditionaDy. the items on the reportform should be periodically reviewedby owners and operators who ~quentiy visit the dam site. An u~to­

date report fonn and accurate reportwill permit intelligent assessment ofaproblem situation and proper imple­mentation of an emergency actionplan.

Immediate Response Actions ­Response actions should be listed inthe o"Execution" section of theemergency action plan according tothe problem or indicators beingaddressed (as in Table 8.2).

8.2 GUIDEUNES FOREMERGENCY NOnFICAnONAn essential part of the "Execution"Section of an emergency ac:tion-pipis • list of ageocies/persoDs to benotified iI. the event of a potentialfailure. Names for this list should beobtained from and coordinated withlocal law enforcement agencies BOdlocal disaster emergency servicesoff'JCes. The list should include keypeople or agencies woo can activatewarning and evacuation proceduresfor the public or who might be able toassist a dam owner in delaying orpreventing failme. "The foUowinJagencies can offer emerxency assis­tance if faiJure ofa dam appearsimminent:• Local sheriff. police, and/or

rare departments• Local disaster emergency agency• County engineer• State department responsible

for dam safety• State disaster emergency serv-

ices officeA copy of the notification list shouldbe posted in a prominent, accessiblelocation at the dam - near •telephone and/or radio transmitter, ifpossible. It should be periodicaUy(once or twice a year) verified andupdated as necessary. It shouldinclude individual names and titles,locations, office and home telephonenumbers, and radio frequencies andcall signals if appropriate. Specialprocedures should be developed fornighttime, boliday, and weekendnotification and for notification dur­ing a severe storm when telephones

72

may not be working or highways maybe impassable. . .

The notification element or anemergency action plan should bebrief, simple. and easy to implementunder any conditions. Notification ofimpending failure is the filst step inthe process that leads to public warn­ins. A dam owner should be carefulto quickly notify the key official re­sponsible for warning and evacuatingthe public. NormaUy, this is thecounty sheriff or city police chief.

• Notification or that official is theclear responsibility of the dam ownerwho should toow the roles and re­sponsibilities or both the official andthe agency that will cany out publicsafety actions. Often. if a reservoir islarge, the potential inundation zonewiD extend for many miles, andfailure will threaten several c0m­

munities and counties. A dam ownershould include the proper official foreach jurisdiction in the notificationplan, so all can be notified as quicklyas possible, (usc position· titles forofficials SO that the plan does notrequire updating every time a personchanges jobs). n

Certain key information must beincluded in every notification planincluding information about potentialinundation areas and travel times forthe breach (flood) wavc. Inundationmaps showing potential areas offlooding from a dam failure areespeciaUy useful in local warning andevacuation planning. Detailed infor­mation about the identification ofinundation zones and the develop­ment of maps can be found by con­tacting a state engineer's office orlocal planning office.

TABLE 8.3. CHECKLIST FORDAM EMERGENCY

PLANS

J. Development of Plan

IL Overview: Use format suggestedin paragraph 8.0.

I. Are reportinl procedulesclear in showinl what datamust be collected and whatinformation shOuld be re-·ported?

2. Are terms in the plan definedso that useR will have DO

questions about the natUre ofthe situation?

L failure vs. impendinlfailure

b. emergency situation vs.potential problem

c. rapidly vs. slowly devel­opinl situation

B. Problem Identification

I. Are all indicatOR of poten­tial failure covered in theplan?

L Siumpin&lsloughin,b. Erosionc. Riprap displacementd Slides on dam or abul­

mente. Increased amount of

seepager. Cloudy or dirty seepageg. Boilsh. Pipingi Whirlpools 1vortices)

. j. SettlementIt. CracksI. Bogsm. Sinkholesn. Abnormal instrument.

tion readings0. Failure of operating

equipmentp. Water in the intake towerq. Other

2. Are all emergency situationscovered in the plan?

L earthquakesb. floods •c. stormsd massive landslidesCo vokani<: eruptionsr. firesg. civil disturbanceh. sudden water releasesi. other potential disasteR

3. Does the problem identific.lion section list all the possi­ble ~ations of a problem?

4. Are the above elements.indicators and events suf­f-eentJy defmed so that theuser can understand them?

s. Does the plan identify th~cause or the problem?

6. Can the user ascertiin theseriousness of the problem?(i.e.• when: the problem be-­comes an emergency)

7. Can the user determine whataction is needed?

8. Can the user ascerbm exact­ly when to notify localoffICials and which ~al

offICials to notify dependingon the D8tuR oflhe problem?

9. Can the user determine whatequipment or supplies areneeded fOl' each type ofproblem?

10. Does the format of the planeasily lint· problem iden­tifICation with the action totake, notification to make.and equipment and suppliesto use?

II. Does the plan include a listof historical problems ormost common problems forthe type crdam ill questioo?

C. Notification

I. Does the plan contain • listof key agency personneland show:

L their office and 24-hourtelephone number

b. the name of their alter­nate

c. which officials to callflTSt

d. responsibilities cr theoff"lCials

2. Does the plan show the damtender or p~ect managersresponsibility in the event ofa total loss of communic.tions?

3. Does the plan's format allowthe user to fmd the name ofthe primary con~ets quick­ly? Has the order ofnotific.tioa been prioritized?

4. Does the plan·s list of localofficials in cbarge of evacua­tion include:

L otrlCe and 24-hour tele­phone number

b. names of alternatesc. which officials should be

. contacted ramd at what point offICials

should be called. "C. how messages should

be worded

S. Does the plan descn"be thecommunication system?

L under normal conditionsb. when backup is neces­

saryc. Are radio call numbers

and frequencies included___ for own radios

for those tobe notifaed

6. Does the plan include pr0­

cedures for downstreamnotification?

L downstream operatorsb. other damsc. industriesd. other agenciese. recreational users

D. local Coordination

I. Was the development of theplan coordinated with localoffICials?

a. did agencies contributeb. wa. the plan integrated

into the local plan

2. Do inundation maps providesufficient infonnation andexplanation?

L is language understand-able

b. are terms explainedc. is map usage explainedd. are criteria explainede. is travel time shownr. are hazardous elevations

shown~ is Oood plain infonnation

available

E. ~sources

I. Are resources adequatelyidentified? Does the planindicate how to locate emer­gency equipment?

L are equipment and sour­ces specifically deS­en"bed with the contactname and telephonenumber included

b. are supplies and sup­pliers specifically·des­cribed with the name ofthe contact and tele­phone number included

c. are repair material anderosion protection mater-.ial described

d. are memos of under­standing to share resour­ces with governmententities described

F. Review

I. Was there a comprehensivereview of the plan at the timeit was developed? Was it:

L technically accurateb. workablec. in compliance with cri­

teria• d. sufficiently comprehen-

sivee. presented effectively

II.Implementation of Plan

A. I..ocal Coordination

I. Were emergency plans (in­cluding notification lists andinundation maps) sent to aUappropriate officials? Is thelist maintained?

2. Have local officials had abriefmg or other explanationof the plan? Is a record ofsuch briefmg maintained?Did the briefmg explain:

a. basic project datab. mapsc. communication networksd. points of contacte. notifICation procedures··

3. Have effective lines of com­munication for critical c0n­

ditions been set up?

4. Have the dam owner andlocal officials aueed on theirrelationship, roles and re­sponsibilities during a damfailure. Is the agreement inwriting?

5.· Has the dam owner reviewedlocal evacuation plans anddiscussed them with localo.ncials?

B. Training

I. Has a plan for exercising theplan been developed?

2. Have exercises been conduc­ted? Is a schedule of exer­cises maintained'?

3. Have the foUowing elementsof the plan been exercised?

L problem identificationb. emergency scenariosc. notir~ation of dam owner

and operating stalfd. notification of otherse. communication systemf. resource list

4. Were aD appropriate person­nel involved in tbe test?

Ii- owner"s personnelb. dam safety personnelc. maintenaoce personneld. support staffe. local officialsr. contractors and suppliers .

73

C. Personnel and Resource Readi­ness

I. Are aD appropriate employ­ees familiar with theemer­gency action plan?

2. Do aU appropriate employeeshave access to the plan?

3. Have aU appropriate person­nel received training in thefoUowing?

a. how to use the planb. identifying a problemc. identifying the severity of

a problemd. using the communication

equipmente. using the notification

subplanf. overall dam safety

4. Are Itey personnel available24 hours a day?

5. Is the division of personnelinto emerceocy responseteams appropriate?

6. Do employees understandtheir roles during emergen­cies?

7. Do key employees haveaCcess to the dam duringemergeocies?

8. Are resources ready?

a. equipmentb. list of contractorsc. supplies on hand or read­

ily available

D. Updating and Reviewing

1. Is the plan reviewed atleast annually?

2. Are notification proceduresregularly updated?

L names and telephonenumbers of Itey staff

b. names and telephonenumbers of local off~

cialsc. names and telephone

nmnbers of contractors

3. Is the plan reviewed to makesure that:

a. exercises are conductedb. personnel are trainedc. communication equip-.

ment is maintainedd other equipment is

maintainede. the downstream warning

system is in place andoperational

r. any new problems areincluded

~ inundation maps are stiDcurrent