Hoover Dam1

8/12/2019 Hoover Dam1

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HISYORY OF TECHNICS

HOOVER DAM



Contents

Planning and agreements

Contractors Construction round!or"

Ri#er di#ersion

Roc" clearance

Concrete Arc$itectural st%le

Construction deat$s

Construction arti&actsO'eration

Po!er 'lant

Po!er distri(ution S'ill!a%s

En#ironmental im'act

)se &or road trans'ort

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Planning and agreements

Hoo#er Dam+ once "no!n as ,oulder Dam+ is a concrete arc$-gra#it% dam in t$e,lac" Can%on o& t$e Colorado Ri#er+ on t$e (order (et!een t$e ).S. states o& Ari/ona

and Ne#ada. 0$en com'leted in 1234+ it !as (ot$ t$e !orld5s largest $%droelectric

'o!er generating station and t$e !orld5s largest concrete structure. It !as sur'assed in

(ot$ t$ese res'ects (% t$e rand Coulee Dam in 1267. It is currentl% t$e !orld5s 37t$-largest $%droelectric generating station.

T$e &irst attem't to gain Congressional a''ro#al &or construction o&,oulder Dam came in 12** !it$ t$e introduction o& t!o (ills in t$e House o&Re'resentati#es and t$e Senate. T$e (ills !ere introduced (% Congressman P$il D. S!ing

and Senator Hiram 0. 8o$nson and !ere "no!n as t$e S!ing-8o$nson (ills. T$e (ills

&ailed to come u' &or a #ote and !ere su(se9uentl% reintroduced se#eral times. InDecem(er 12*:+ (ot$ t$e House and t$e Senate &inall% a''ro#ed t$e (ill and sent it to t$e

President &or a''ro#al. On Decem(er *1+ 12*:+ President Cal#in Coolidge signed t$e (ill

a''ro#ing t$e ,oulder Can%on Pro;ect. T$e initial a''ro'riation &or construction !asmade in 8ul% 123<+ (% !$ic$ time Her(ert Hoo#er $ad (ecome President.

Earl% 'lans called &or t$e dam to (e (uilt in ,oulder Can%on+ so t$e 'ro;ect !as

"no!n as t$e ,oulder Can%on Pro;ect. T$e dam site !as e#entuall% mo#ed do!nstream

eig$t miles =13 "m> to ,lac" Can%on+ (ut t$e 'ro;ect name remained t$e same. A ma;ormoti#e &or relocating to ,lac" Can%on !as t$at a dam at ,oulder Can%on !ould not $a#e

'ro#ided su&&icient '$%sical control o& t$e ri#er (elo! t$e damsite?t$e area o& !$at is

called t$e ,oulder (asin. ,lac" Can%on 'ro#ided a (etter total control o& t$e ri#er t$at &ardo!nstream.

S"etc$ o& 'ro'osed damsite @ reser#oir Her(ert Hoo#er

3



Contractors

T$e contract to (uild t$e ,oulderDam !as a!arded to Si Com'anies+

Inc. on Marc$ 11+ 1231+ a ;oint #enture

o& Morrison-Bnudsen Com'an% o&

,oise+ Ida$o )ta$ ConstructionCom'an% o& Ogden+ )ta$ Paci&ic

,ridge Com'an% o& Portland+ OregonHenr% 8. Baiser @ 0. A. ,ec$telCom'an% o& Oa"land+ Cali&ornia

MacDonald @ Ba$n td. o& os

Angeles and t$e 8.F. S$ea Com'an%o& Portland+ Oregon. T$e c$ie&

eecuti#e o& Si Com'anies+ Fran"

Cro!e+ $ad 're#iousl% in#ented man%o& t$e tec$ni9ues used to (uild t$e

dam.

During t$e concrete-'ouring and

curing 'ortion o& construction+ it !asnecessar% to circulate re&rigerated

!ater t$roug$ tu(es in t$e concrete.

T$is !as to remo#e t$e $eat generated (% t$e c$emical reactions t$at solidi&%

t$e concrete+ since t$e setting and

curing o& t$e concrete !as calculated to ta"e a(out 1*7 %ears i& cooling !as not done. SiCom'anies+ Inc+ did muc$ o& t$is !or"+ (ut it disco#ered t$at suc$ a large re&rigeration

'ro;ect !as (e%ond its e'ertise. Hence+ t$e )nion Car(ide Cor'oration !as contracted

to assist !it$ t$e re&rigeration needs.

Si Com'anies+ Inc. !as contracted to (uild a ne! to!n called ,oulder Cit% &or

!or"ers+ (ut t$e construction sc$edule &or t$e dam !as accelerated in order to createmore ;o(s in res'onse to t$e onset o& t$e reat De'ression+ and t$e to!n !as not read%

!$en t$e &irst dam !or"ers arri#ed at t$e site in earl% 1231. During t$e &irst summer o&construction+ !or"ers and t$eir &amilies !ere $oused in tem'orar% cam's li"e Ragto!n

!$ile !or" on t$e to!n 'rogressed. Discontent !it$ Ragto!n and dangerous !or"ing

conditions at t$e dam site led to a stri"e on August :+ 1231. Si Com'anies res'onded (%sending in stri"e-(rea"ers !it$ guns and clu(s+ and t$e stri"e !as soon 9uelled. ,ut t$e

discontent 'rom'ted t$e aut$orities to s'eed u' t$e construction o& ,oulder Cit%+ and (%

t$e s'ring o& 123* Ragto!n $ad (een deserted. am(ling+ drin"ing alco$ol+ and

'rostitution !ere not 'ermitted in ,oulder Cit% during t$e 'eriod o& construction. To t$isda% ,oulder Cit% is one o& onl% t!o locations in Ne#ada not to allo! gam(ling+ and t$e

sale o& alco$ol !as illegal until 1242.0$ile !or"ing in t$e tunnels+ man% !or"ers su&&ered &rom t$e car(on monoide

generated (% t$e mac$iner% t$ere. T$e contractors claimed t$at t$e sic"ness !as

'neumonia and !as not t$eir res'onsi(ilit%. 0$en Ne#ada o&&icials tried to en&orce state

mining air-9ualit% la!s+ t$e contractors too" t$em to court. O&&iciall%+ onl% 24 !or"ersdied constructing Hoo#er Dam. Some o& t$e !or"ers sic"ened and died (ecause o& t$e

so-called 'neumonia. Most are uncounted on t$e o&&icial deat$ list.T$e ,ureau o&

Reclamations &atalit% statistics s$o! t$at 6* deat$s !ere attri(uted to 'neumonia duringt$e construction 'eriod+ more t$an an% ot$er cause.In 8anuar%+ 1234+ t$e Si Com'anies

made out-o&-court settlements+ in undisclosed amounts+ !it$ &i&t% gas-suit 'lainti&&s

6



Construction

diagram o& 'arts o& t$e o'eration

7



Hoo#er Dam arc$itectural 'lans

4



O#er#ie! O& dam mec$anisms



Groundwork

To 'rotect t$e construction site &rom &looding+ t!o co&&erdams !ere constructed.

Construction o& t$e u''er co&&erdam (egan in Se'tem(er 123*+ e#en t$oug$ t$e ri#er $adnot %et (een di#erted. A tem'orar% $orses$oe-s$a'ed di"e 'rotected t$e co&&erdam on t$e

Ne#ada side o& t$e ri#er. A&ter t$e Ari/ona tunnels !ere com'leted+ and t$e ri#er

di#erted+ t$e !or" !as com'leted muc$ &aster. Once t$e co&&erdams !ere in 'lace andt$e construction site de!atered+ eca#ation &or t$e dam &oundation (egan. For t$e dam to

rest on solid roc"+ it !as necessar% to remo#e all t$e ri#er(ed5s accumulated erosion soilsand ot$er loose materials until sound (edroc" !as reac$ed. 0or" on t$e &oundationeca#ations !as com'leted in 8une 1233. During eca#ations &or t$e &oundation+

a''roimatel% 1+7<<+<<< cu(ic %ards =1+17<+<<< m3> o& material !as remo#ed. Since t$e

dam !ould (e a gra#it%-arc$ t%'e+ t$e side-!alls o& t$e can%on !ould also (ear t$e &orce

o& t$e im'ounded la"e. T$ere&ore t$e side-!alls !ere eca#ated too+ to reac$ #irgin =un-!eat$ered> roc" !$ic$ $ad not e'erienced t$e !eat$ering o& centuries o& !ater see'age+

!intertime &ree/e crac"ing+ and t$e $eatingGcooling c%cles o& t$e Ari/onaGNe#ada desert.

River diversion

To di#ert t$e ri#er5s &lo! around t$e construction site+ &our di#ersion tunnels !eredri#en t$roug$ t$e can%on !alls+ t!o

on t$e Ne#ada side and t!o on t$e

Ari/ona side. T$ese tunnels !ere 74&eet =1 m> in diameter. T$eir

com(ined lengt$ !as nearl% 14+<<<

&t =6+2<< m> or more t$an 3 mi =6.:"m>. Tunneling (egan at t$e lo!er

'ortals o& t$e Ne#ada tunnels in Ma%

1231. S$ortl% a&ter!ards+ !or"

(egan on t!o similar tunnels in t$e

Ari/ona can%on !all. In Marc$123*+ !or" (egan on lining t$e

tunnels !it$ concrete. First t$e (ase+ or in#ert+ !as 'oured. antr% cranes+ running onrails t$roug$ t$e entire lengt$ o& eac$ tunnel !ere used to 'lace t$e concrete. T$e

side!alls !ere 'oured net. Mo#a(le sections o& steel &orms !ere used &or t$e side!alls.

Finall%+ using 'neumatic guns+ t$e o#er$eads !ere &illed in. T$e concrete lining is 3 &t=<.21 m> t$ic"+ reducing t$e &inis$ed tunnel diameter to 7< &t =17 m>.

Follo!ing t$e com'letion o& t$e dam+ t$e entrances to t$e t!o outer di#ersion

tunnels !ere sealed at t$e o'ening and $al& !a% t$roug$ t$e tunnels !it$ large concrete

'lugs. T$e do!nstream $al#es o& t$e tunnels &ollo!ing t$e inner 'lugs are no! t$e main (odies o& t$e s'ill!a% tunnels.

Rock clearance

T$e t!o #ertical &oundations &or eac$ o& t$e arc$ !alls =t$e Ne#ada side and

Ari/ona side> $ad to (e &ounded on sound #irgin roc" &ree o& crac"s and t$e !eat$eringt$at t$e sur&ace roc" o& t$e can%on !alls $ad &rom t$ousands o& %ears o& !eat$ering and

e'osure.

:



T$e men !$o remo#ed t$is roc" !ere called $ig$-scalers. 0$ile sus'ended &romt$e to' o& t$e can%on !it$ ro'es $ig$-scalers clim(ed do!n t$e can%on !alls and

remo#ed t$e loose roc" !it$ ;ac"$ammers and d%namite.

Concrete

T$e &irst concrete !as

'laced into t$e dam on 8une4+ 1233. Since no structureo& t$e magnitude o& t$e

Hoo#er Dam $ad (een

constructed+ man% o& t$e

'rocedures used inconstruction o& t$e dam

!ere untried. Since

concrete $eats u' andcontracts as it cures+ une#en

cooling and contraction o&

t$e concrete 'osed a serious 'ro(lem. T$e ,ureau o&

Reclamation engineers

calculated t$at i& t$e dam!ere (uilt in a single continuous 'our+ t$e concrete !ould $a#e ta"en 1*7 %ears to cool to

am(ient tem'erature. T$e resulting stresses !ould $a#e caused t$e dam to crac" and

crum(le. To sol#e t$is 'ro(lem t$e dam !as (uilt in a series o& interloc"ing tra'e/oidal

concrete 'ours. To &urt$er cool t$e concrete eac$ &orm contained cooling coils o& 1 inc$=*7 mm> t$in-!alled steel 'i'e. Ri#er !ater !as circulated t$roug$ t$ese 'i'es to $el'

dissi'ate t$e $eat &rom t$e curing concrete. A&ter t$is+ c$illed !ater &rom a re&rigeration

'lant on t$e lo!er co&&erdam !as circulated t$roug$ t$e coils to &urt$er cool t$e concrete.

A&ter eac$ la%er $ad su&&icientl% cooled+ t$e cooling coils !ere cut o&& and 'ressuregrouted (% 'neumatic grout guns. T$e concrete is still curing and gaining in strengt$ as

time goes on.T$ere is enoug$ concrete in t$e dam to 'a#e a t!o-lane $ig$!a% &rom San

Francisco to Ne! Yor".

Architectural style

T$e dam crosses t$e (order (et!een t!o time /ones+ t$e Paci&ic Time one and

t$e Mountain Time one.T$e initial 'lans &or t$e &inis$ed &acade o& (ot$ t$e dam and t$e 'o!er 'lant

consisted o& a sim'le+ unadorned !all o& concrete to''ed !it$ a ot$ic-ins'ired (alustrade and a 'o!er$ouse t$at loo"ed li"e little more t$an an industrial !are$ouse.citation neededJ T$is initial design !as critici/ed (% man% as (eing too 'lain and

unremar"a(le &or a 'ro;ect o& suc$ immense scale+ so os Angeles-(ased arc$itect

ordon ,. Bau&mann !as (roug$t in to redesign t$e eteriors Bau&mann greatl%streamlined t$e (uildings+ and a''lied an elegant Art Deco st%le to t$e

entire 'ro;ect+ !it$ scul'tured turrets rising seamlessl% &rom t$e dam &ace and cloc" &aces

on t$e inta"e to!ers set &or t$e time in Ne#ada and Ari/ona+ in t$e Paci&ic Standard Timeone or Paci&ic Da%lig$t Time one and Mountain Standard Time one time /ones

res'ecti#el% =alt$oug$ (ecause Ari/ona does not o(ser#e da%lig$t sa#ing time+ t$e t!o

2



cloc"s s$o! t$e same time during t$e $al& o&t$e %ear around t$e nort$ern summer>.

One o& t!o 0inged Figures o& t$e

Re'u(lic (% Os"ar 8.0. Hansen+ 'art o& t$emonument o& dedication on t$e Ne#ada side

o& t$e dam.

At Bau&mannKs (e$est+ Den#er artistAllen Tu''er True !as (roug$t on (oard to

$andle t$e design and decoration o& t$e

!alls and &loors o& t$e ne! dam. True

concei#ed o& incor'orating moti&s o& t$e Na#a;o and Pue(lo tri(es o& t$e

region.Alt$oug$ some initiall% !ere

o''osed to t$ese designs+ True !as gi#ent$e go-a$ead and !as o&&iciall% a''ointed

Consulting Artist.citation neededJ 0it$ t$e

assistance o& t$e National a(orator% o&Ant$ro'olog%+ True researc$ed aut$entic

decorati#e moti&s &rom Indian sand

'aintings+ !ea#ings+ (as"ets and ceramicsT$e images and colors are (ased on Nati#e American #isions o& rain+ lig$tning+ !ater+

clouds+ local animals-li/ards+ ser'ents+ (irds-and on t$e Sout$!estern landsca'e o&

ste''ed mesas. In t$ese !or"s !$ic$ are integrated into t$e !al"!a%s and interior $alls

o& t$e great dam+ True also re&lected on t$e mac$iner% o& t$e o'eration ma"ing t$es%m(olic 'atterns at once a''ear (ot$ ancient and

modern.

T$ese Nati#e American moti&s+ em(edded in t$eterra//o &loors+ loo" li"e t$e cogs o& t$e giant

tur(ines+ %et t$e% are distinctl% American Indian in

origin. For True+ t$e s$a'es and designs associated!it$ t$e American Indians !ere a"in to t$ose o& t$e

ancient ree"s and Romans. TrueKs designs 'la%ed!ell o&& Bau&mannKs monumental arc$itecture and it

could (e said t$at toget$er t$e% created an Americantem'le to modernit%.

0it$ t$e agreement o& arc$itect Bau&mann and t$e

engineers+ True also de#ised an inno#ati#e colorcoding &or t$e 'i'es and mac$iner%+ !$ic$ !ould (e

im'lemented t$roug$out all t$e Federal ,ureau o&

Reclamation 'ro;ects. TrueKs Consulting Artist ;o(lasted t$roug$ 126* and !as etended so t$at $e also

com'leted design !or" &or t$e Par"er+ S$asta and

rand Coulee dams and 'o!er 'lants. At t$e time+TrueKs !or" on t$e ,oulder Dam !as $umorousl% noted in a 'oem !$ic$ a''eared in t$e

Ne! Yor"er maga/ine+ 'art o& !$ic$ read+ Llose t$e s'ar"+ and ;usti&% t$e dream (ut also

!ort$% o& remar" !ill (e t$e color sc$eme.

Construction deaths

1<



T$ere !ere 11* deat$s associated !it$ t$e construction o& t$e dam. T$ere are di&&erent

accounts as to $o! man% 'eo'le died !$ile !or"ing on t$e dam and !$o !as t$e &irst

and last to die. A 'o'ular stor% $olds t$at t$e &irst 'erson to die in t$e construction o&Hoo#er Dam !as 8. . Tierne%+ a sur#e%or !$o dro!ned !$ile loo"ing &or an ideal s'ot

&or t$e dam. Coincidentall%+ $is son+ Patric" 0. Tierne%+ !as t$e last man to die !or"ing

on t$e dam+ 13 %ears to t$e da% later. Ninet%-si o& t$e deat$s occurred duringconstruction at t$e site.

O'erationPower plant

Two intake towers on the Arizona side.

0ater &lo!ing &rom a"e Mead t$roug$ t$e

graduall%-narro!ing 'enstoc"s to t$e 'o!er$ouse reac$es a s'eed o& a(out :7 m'$

=13 "mG$> (% t$e time it reac$es t$e tur(ines.

T$e entire &lo! o& t$e Colorado Ri#er 'assest$roug$ t$e tur(ines =ece't &or see'age

around t$e edges o& t$e dam t$roug$ t$e semi-

'orous #olcanic roc" it rests against>. T$es'ill!a%s are rarel% used.

The hydroelectric generators at Hoover dam

Follo!ing an u'rating 'ro;ect &rom 12:4 to 1223+ t$e total

gross 'o!er rating &or t$e 'lant+ including t!o *.6

mega!attcitation neededJ electric generators t$at 'o!er t$e 'lant5s o'erations+ is a(out *<:< mega!atts.

Eca#ation &or t$e 'o!er$ouse !as carried out

simultaneousl% !it$ t$e eca#ation &or t$e dam &oundation

and a(utments. Eca#ation &or t$e )-s$a'ed structurelocated at t$e do!nstream toe o& t$e dam !as com'leted in

late 1233 !it$ t$e &irst concrete 'laced in No#em(er 1233.

enerators at t$e Dam5s Hoo#er Po!er'lant (egantransmission o& electricit% &rom t$e Colorado Ri#er to os

Angeles+ Cali&ornia *44 miles =6*: "m> a!a% on Octo(er *4+ 1234. Additional

generating units !ere added t$roug$ 1241. Original 'lans called &or 14 large generators+: on eac$ side o& t$e ri#er =see arc$itectural illustrations> (ut t!o smaller generators !ere

installed instead o& one o& t$e large ones on t$e Ari/ona side+ &or a total o& 1. T$e

smaller generators !ere used to ser#e smaller munici'alities at a time !$en t$e out'ut o&

eac$ generator !as dedicated to a munici'alit%+ (e&ore t$e dam5s total 'o!er out'ut !as 'laced on t$e grid and made ar(itraril% distri(uta(le.

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Power distribution

T$e ,ureau o& Reclamation re'orts t$at t$e energ% generated is allocated as &ollo!s

Area Percentage

Metro'olitan 0ater District o& Sout$ern Cali&ornia *:.7323

State o& Ne#ada *3.3<4State o& Ari/ona 1:.27*

os Angeles+ Cali&ornia 17.6**2Sout$ern Cali&ornia Edison Com'an% 7.73

,oulder Cit%+ Ne#ada 1.4*

lendale+ Cali&ornia 1.7:6

Pasadena+ Cali&ornia 1.34*2Ana$eim+ Cali&ornia 1.16:

Ri#erside+ Cali&ornia <.:417

Vernon+ Cali&ornia <.41:7,ur(an"+ Cali&ornia <.7:4

A/usa+ Cali&ornia <.11<6

Colton+ Cali&ornia <.<::6,anning+ Cali&ornia <.<66*

pillways

T$e dam is 'rotected against o#erto''ing (% t!o s'ill!a%s. T$e s'ill!a%

entrances are located (e$ind eac$ dam a(utment+ running roug$l% 'arallel to t$e can%on!alls. T$is s'ill!a% entrance arrangement &orms a classic side-&lo! !eir. 0ater &lo!ing

1*



o#er t$e s'ill!a%s dro's s$ar'l% into s'ill!a% tunnels and connects to 'art o& t$econstruction di#ersion tunnels+ and reenters t$e main ri#er c$annel (elo! t$e dam. T$is

com'le s'ill!a% entrance arrangement com(ined !it$ t$e a''roimate << &t =*1< m>

ele#ation dro' &rom t$e to' o& t$e reser#oir to t$e ri#er (elo! is a di&&icult engineering 'ro(lem and 'oses se#eral design c$allenges. T$e o#erall s'ill!a% ca'acit% !as

em'iricall% #eri&ied in 'ost construction tests in 1261. T$is test also s$o!ed t$at t$e

s'ill!a% tunnels could (e damaged &rom ca#itation created (% t$e $ig$ #elocit% &lo!!$en running near &ull #olume. A&ter &urt$er damage !as incurred during use in si

!ee"s in t$e summer o& 12:3+ t$e tunnel linings !ere re'aired and t$e s'ill!a% tunnel

design !as modi&ied to minimi/e ca#itation 'otential.

T$e large s'ill!a% tunnels $a#e onl% (een used t$ree times in t$e $istor% o& t$edam. In addition to use in 1261 and 12:3+ s'ill!a% use !as re9uired in 1222 !$en $ea#%

'reci'itation in t$e !aters$ed &illed a"e Mead.

En#ironmental im'act

Hoo#er Dam and its

associated c$anges in !ater

use $ad de#astating im'acton t$e Colorado Ri#er

Delta at t$e mout$ o& t$e

Colorado Ri#er. T$econstruction o& t$e dam $as

(een 'ointed to as t$e

(eginning o& an era o&

decline o& t$is estuarineecos%stem. For si %ears in

t$e late 123<s+ a&ter t$e

construction o& t$e dam and!$ile a"e Mead &illed+

#irtuall% no &lo! o& !ater

reac$ed t$e mout$ o& t$eri#er. T$e delta5s estuar%+

!$ic$ once $ad a &res$!ater-salt!ater miing /one stretc$ing 47 "ilometres =6< mi>

sout$ o& t$e ri#er5s mout$+ !as turned into an in#erse estuar% !$ere t$e le#el o& salinit%!as actuall% $ig$er closer to t$e ri#er5s mout$.

oo"ing u'stream &rom Hoo#er Dam in 8ul% *<<2+ t$e !ater le#el $as decreased

drasticall%.

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T$e Colorado Ri#er $ad e'erienced natural &looding (e&ore t$e construction o&t$e Hoo#er Dam. T$e dam eliminated t$e natural &looding+ !$ic$ im'eriled man% s'ecies

ada'ted to t$e &looding+ including (ot$ 'lants and animals.

T$e construction o& t$e dam decimated t$e 'o'ulations o& nati#e &is$ in t$e ri#erdo!nstream &rom t$e dam. Four s'ecies o& &is$ nati#e to t$e Colorado Ri#er+ t$e ,on%tail

c$u(+ Colorado 'i"eminno!+ Hum'(ac" c$u(+ and Ra/or(ac" suc"er+ are currentl% listed

as endangered (% t$e ).S. &ederal go#ernment.

)se &or road trans'ort

).S. Hig$!a% 23 on Hoo#er Dam

T$ere are t!o lanes &or automo(ile tra&&ic across t$e to' o& t$e dam. It ser#es as t$eColorado Ri#er crossing &or t$e $ig$!a% ).S. Route 23. T$e t!o-lane section o& road

a''roac$ing t$e dam is narro!+ $as se#eral dangerous $air'in turns+ and is su(;ect to roc"

slides.

16



Hoo#er Dam ,%'ass

To 'ro#ide muc$ more $ig$!a% ca'acit%+ and (etter sa&et%+ t$e ne! Hoo#er Dam,%'ass is sc$eduled to (e com'leted in *<1< and it !ill di#ert t$e ).S. 23 tra&&ic 1+7<< &t

=64< m> do!nstream &rom t$e dam. T$e (%'ass !ill include a com'osite steel and

concrete arc$ (ridge+ tentati#el% named t$e Mi"e O5Callag$an-Pat Tillman Memorial,ridge. Once t$e (%'ass is com'leted+ t$roug$ tra&&ic !ill no longer (e allo!ed across

Hoo#er Dam.

Additionall%+ in t$e !a"e o& t$e Se'tem(er 11+ *<<1 terrorist attac"s t$ere are

signi&icant securit% concerns. ,ecause o& t$e attac"+ t$e Hoo#er Dam ,%'ass 'ro;ect !ase'edited. Tra&&ic across Hoo#er Dam is 'resentl% restricted. Some t%'es o& #e$icles are

ins'ected 'rior to crossing t$e dam !$ile semi-trailer truc"s+ (uses carr%ing luggage+ and

enclosed-(o truc"s o#er 6< &eet =1* m> long are not allo!ed on t$e dam at all.36J T$attra&&ic is di#erted sout$ to a Colorado Ri#er (ridge at aug$lin+ Ne#ada.

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,I,IORAPHY

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http://www.wikipedia.com/

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http://www.hooverdambypass.org/

http://www.wikipedia.com/

http://www.sunsetcities.com/hoover-dam.html

http://www.hooverdambypass.org/

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Hoover Dam1