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A Review of The Boulder Dam Project

A Thesis Submitted to

The Faculty of
MICHIGAN STATE COLKBSE
OF

AGRICULTURE AND APPLIED SCIENCE

/' ._

o. F Ravell. BI LL; Greenman.

 

Candidates for the Degree of

Bachelor of Science

June 1930

THESIS

BIBLIOGRAPHY
N

Colorado River Dev‘eiopment- 'Deoum'ent ‘1235
Boulder Dam Today- Repfiint From ("Economic
factons' bi fir. liwood Head and "Technical
Phases"by'Rdjdond F: Waiter.)

Engineering News-RecordQFebffiHrj‘1§30.

Engineering Nefid'neoord,Apfil'1930.

FOREWORD
The wafer in and dfi fihe Sirths surface
is of odnsfantly increasing imporfianoe
to the life and comfort of man. As pop-
ulation increases and Eiiiltzation advances
so will the value of iéfer’inorease'and
the struggle over 115 dontrol will increase

‘in like measure.

REVIEWING THE BOULDER CifiYON PRUJFUT

The Boulder Canyon Prouect became effective June 21,
1929; six months after it's passage,and money was to be
made available at the regular 1929-30 meeting of Congress.

The branch railroad from the Union Pacific railroad,
to the damsite is now under construction,most of the work
beirg done by the Union Pacific.

It is expected that highway construction from Lae Vegas
to the damsite will start immediately. This road may be con-
structed as part of the project,since it is considered a
proper charge against the construction fund,because the
government will need prompt and efficient stage service
for express,light freight,std labor turnover.

Private corporations will be allowed to bid for fur-
nishing the power necessary for construction,and if theme
bids are not suitable the government will build it's own
plant.

A concrete gravity type dam,curved in plan is pronosed.

Excavations must be Fade to a maximum depth of 195
feet below the river bed to solid rock.

A coffer dam must be built both above and below the
damsite and tunnels excavated through the solid rock to
divert a maximum of 200,000 second feet of water around the
site(according to the"Colorado River Board" repert) before

excacation may begin.

(1)

It is anticipated that approximately 2,500 men will
be employed during the construction pericd,depending largely
on the construction methods used.

it is estimated that power will be ready for delivery
at the switchboards within five or six *ears 'fter the first
contract is let.

WOLLCKIEG IS A REVIFW OF ThE BOULDER CAEYCT PROJFCT

ACT: I

' 1. That the location of the project shall be at the
Eculder or the Black Canyon.(Sec.l)

2. That the purpose of the act is to coxirol the floods,
improve navi-ation,and regulate the flow of tge Col-
orado Piver,to provide for stvrsge and use exclunively
within the United States,and to generate electrical
energy as a refine of making the project a financially
solvent undertaLing.(Sec.ld

3. That any rights the states may have to water within
thig} boundaries,or the right to adapt such policies
and enact such laws «s they deem necessary,with respect
+0 tre approiation,cortrcl,snd use of “ater Within
their boundaries,shall not be ncdified except by tTB
"Colorado River Compact" or other interstate agree-
ment.(Soc.18)

4. That the Secretary of the Interior is authorised to
carry out the provisions of this act,subject +0 the
"Colorado River Compact".(Par.(b)sec.8)

5. That the~e is hereby appropriated $115,000,003 to

10.

ll.

carry Out the purpose of this act.(Sec.3)

That the secretary of the Interior is authorized to
acquire by proceedings,eminent domain,and otherwise
all rights of way,lands and other preperty necessary
to carry out this act.(Sec.l)

That no expenditures shall be made out of the fund
for Operations anr3 maintenance except from appropri-
ations therefor.

That interest shall be at the rate of 44 on all amounts
advanced from the fund und r prcvisicns of't is act,
an"1 all amounts advanced frem such funds shall be
checked by the Secretary of tie Interior at the close
of each fiscal year.(Par.(b)sec.s)

That no person shall be entitled to have the use of
the water for any purposes,ex ept by contract made
with thr Secretary of the Interior as herein stated.
($60.51

Trat after the 325,000,000 set aside for flood control
has been replaced from the 62 1/2 per cent of any
excess over the amounts due the government,after the
amortization period,it shall be placed in the fund

to be expended within the Colorado River basin as may
be hereafter prescribed by Congress.(8ec.5)

That the rights of the United states in,or to,the
Colorado Fiver and it's tribut°ries,shall be subject
to and controlled by the"Colorado River Compact"(Pa

(b)sec.lfi)

12.

14.

15.

16.

17.

4.

That 37 1/2 per cent of any'moneys collected by the
Secretary of the Interior,above the amoun+s due the
government shall go to Arizona and Ievada,presumably
in lieu of taxes,by virtue of their natural resources
being taken for a pu’lic service.(Far5b)sec.4)

That the power to be sold at a price Way le found

to be ”Justified by competitive conditions at distrib-
uting points or competitive centers" (Par.(b)sec.4)
Contracts will “e made with a view to secure reasonable
returns. (Par.(h)sec.7)

That the provision of the Feder 1 Water Power Act,

and regulations of the Federal power co mi~sien shall
be conformed with as far as possible in the operation
and administration of the project and for the protection
of the investor and the consumer. (390.5)

That there shall be readjustment periods for the sale
price of the pover,either upward or downward as the
conditions at the distributing pc;nts ray irdicate,
the first readjustment after fif*een years 6nd every
ten years thereafter.(Par(a)sec.5)

That no charge shall be made for water for irrigation
and potable purposes in the Imperial and Ccschella
Valleys. (390.1)

That the water may be sold for irrigation and potable
purposes in all districts other than the Imperial

and Coachella Valleys.(8ec.5)

5.

18. That a board may be arranged for,consistlng of one

19.

20.

21.

22.

H

member from each of the seven states,to advise With

the Secretary of the Interior on the sale price of

water and power,and matters relative to the states(8ec.ld)
That the sum of $25,000,000 set aside for flood control
to be replaced out of 62 1/9 per cent of any revenue

in excess of any amount necessary to repay the govern-
ment,and if not entirely replaced during the amortization
period,it may,thereafter be paid from the 62 1/2 per

cent of the net profits.(Par.(b)sec.2)

That the all American canal may be constructed,and

any dam and necessary works,under the reclamation act,
which provided that all expenditures be underwritten

by the lands benifited,prior to the beginning of con-

:struct:on,and shall not be paid for out of the sale

of water or power.(Sec.l)

That a dam be constructed with a reservoir capacity

of not less than 20,000,000 acre feet of water. (860.1)
That firm contracts be rade by the Secretary of the
Interior,for the sale of power generated,and the use

of water to generate power,and for the storage of

water for irrigation and domestic uses,and that Will
replace the government investment in the dam and power
plants in fifty years,before construction shall be
undertaken,and the charges foe the water for irrigation

and domestic purposes shall be for permanent services.(Sec,5

25.

That the consent of Congress is given to the seven
states of Colorado,New Mexico,Wyoming,xtah,Arizona,
California,ard Levada to enter into a compact or agree-
ment,supplemental to and in conformity with the
”Colorado River Compact".(Par.(a)sec.13)

That the consent of Congress is given to any six
states of hhe basin,including California,to enter

into a six state compact,if the said six states ratify
the Colorado River Compact without conditions except
to waive the provisions of the first paragraph of
article three of said compact,requiring seven states,
provided California limits itself,bv leglislative
action,to a consumptive use of not more than 4,CO0,000
acre feet of water from the Colorado River,and in the
event of the six state pact,the act shall become
Operative six months from date of passage. These

conditions have been complied with both as to the six

-state pact and the California limitation as to the

use of water(Par.(a)sec.4,psr.(a)sec.13)
The consent of Congress is given to the thre~ states
California,Arizona,and Kevada to enter into an agree-
ment,and especially provides for seven conditions
under which this agreement may be nade,vnd rat be
necessary to return to Congress for reratification,
as follows: (Par.(a)iec.4)

(1) That of the 7,500,000 annually apportioned to

the lower basin by paragraph (a) of article

(“)

(5)

three of the Colorado River Compact,there shall
be apportioned to the state of Kevada 300,000
acre feet,and to the state of Arizona 2,300,000
acre fest for exclusive beneficial and consump-
tive use in perpetuity.

That the state of Arizona may an ually use one
half of the excess or surplus waters unapportioned
by the Colorado River Compact.

That the state of Arizona shall have the cxclu-
sive beneficial use of the Gila River and it's
tributaries within the boundaries of the state.
That the waters of the Gila River and it's trib-
utaries except return flow after the same enters
the Colorado River shall never be subject to any
diminution whatever by any allowance of water

by treaty or otherwise to the United States of
sexico,but if as provided in paragraph (c) of
article three of the Colorado River Compact,it
shall become necessary to supply water, to the
United States of fiexico from the waters over

and above the quantities which are surplus as
defined by said compact,then the state of Cali-
fornia shall and will mutually agree with the
state of Arizona to supply,out of the main stream
of the Colorado River,one half of any deficiercy
which must be supplied to Hexico by the lower

basin.

(5) That the state of California shall and will
mutually agree with the state of Arizona and
Nevada that none of the said three states shall
withold water and none shall require the delivery
of water which cannot reasonably be applied to
domestic and agriculture uses.

(6) That all provisions of said tri~state agreement
shall be subject in all particulars to the pro-
visions of the Colorado River Compact.

(7) Said agreement to take effect upon the r tifi-
cation of the Colorado River Compact by Arizona,
California,and hevada.(Par.(a)sec.43

And further provides that the threw stetee may erter

into any compact,or any two thereof may enter into
any compact.subject to further approval of Congress.

(Par.(b)sec.8)

26.’The general and uniform regulations shall be prescrib-
Iby the Secretary of the Interior for awarding contracts
and for the renewal of contracts,and providing that
no contract shall be of longer duration than 50 years.
(860.5)

27. That any dispute or disagreement as to the fullfillment
of any contract made under this act,shall be deter-
mined by arbitration or by court proceeding.(Par.(a)
sec.6)

28. That contracts for use of power shall be made with
responsible applicants,who will pay the price set

by the Secretary,with a view to meeting the revenue

29.

30.

31.

52.

requirements provided for in this act.(Par.(c)sec.5)
That in case of conflicting applications for the
purchase of power and water,that the Secretary cf the
Interior shall determine the matter in conformity

with the policy expressed in the Colorado River pact

as to conflicting contracts for water aid power rights,
preference being first given to a State.(Par.(c)sec.5)
That preference shall be given to a State for the
purchase of power within six months after the Secretary
has‘giVen notice,provided,however,that time shall be
given for a State to'arrange for bond issues for
payment.(Par.(c)sec.5)

That any agency receiving a contract for electrical
energy equivalent to 100,000 horsepower may be requir-
ed by the Secretary of the Interior,if deemed feasible,
tc allow any other agency having contracts for less
than 25,000 horsepower to participate in the benefits
and to use any transmission line constructed for
carrying such energy,upon payment of a reasonable

share of the cost of construction,0peration,and
maintenance.(Par.(d)sec.5)

That the Federal Power Coemission is hereby directed
not to issue or approve any permits under the Federal
Water power act upon the Colorado River or any of

it's tributaries,except the Gila River,in the Colorado
River basin,until this act shall become effective.(Sec.5)
That the United States in constructing,managing,and
operating the project under this act,sha11 be subject

to,ard controlled by the terms of ary compact between

35.

56.

57.

10.

the States of Arizona,Colorado,and Eevada,or any two
thereof.(Par.(b)sec.8)

That all persons who have served in the United States
Army during the wars with Germany,Spain,or the inn-
surrection in the Philippines sh 11 have preference,
for three months,to the right of entry into any public
lands thrown open by the Secretary of the Interior.
(Sec.9)

That,as far as practicable,preference shall be given
to persons serving inthe wars with Germany,Spain,or
the insurrection of the Philippines,in all construction
work authorized by this act.(Sec.9)

That the Secretary of the Interior may,at his dies
cretion,lease the use of the water for generating
power,deliver power at the switchboard,or build ard
lease the power plants.(Se .6)

That the Secretary of the Interior,is authorized and
directed to make investigation and public reports

of the feasible projects for irrigation,and sites

for power projects in the States of Eew ~"exico,(301-
orado,Wyoming,Utah,Arizona,and Eevada.(Sec.lE)

That the Secretary of the Interior is authorized to
investigate the feasibility and determine the bound-
aries of the reclamation project known as the "Parker-
Gila valley reclamation project" in Arizona,and
determine the most feasible method of irrigation of

these lands.(Sec.ll)

11.

The project was to become effective when,either the
'six-State”or the "seven-State"compact was accepted by the
States involved.

The Congre s of the United States does not limit the
water supply of any State,without that State's consent.

In the ”six-State”compact,California is the only State in
which the amount of water supplied is to have a limit. No
attempt was made to limit the supply of either nevada,or
Arizona,hence no principle of State ri hts Pas been violaded.

The whole purpose of either the six or the seven State
compact is,to reserve a fair share in perpetuity in the
States where developement will necessarily be slow.

‘he California Legislature accepted the definite limmt-
ations and,Utah entered the ”six-State"com‘act by action
of it’s 1929 Legislature,therefore the Boulder Canyon Project,
became effective on proclamation of the President after
June 21,1929,Utah being the sixth State to adopt the “six—
State'compact.

For a period of from eight to ten years b fore the
bill was placed before'Comgress,engineers were going over
the ground,testing the rock strata,determining elevations,
selecting and rejecting different sited and locations,
trying to determine the most feasible point for the super-
dam,somewhere in the lower Colorado,that would hold back
in one great lake,the amount of water that would normally
empty from the mouth of the river over a period of one and

one half years.

Finally two sites were picked,one in the Boulder Canyon
and,the other farther downstream in the Black Canyon. Both
sites were considered as a feasible location for the dam,
but the site in the Black Canyon was decided to be prefer-
able to that in the Boulder Canyon,due to phases which will
be discussed later.

After deciding upon the damsite,it was considered to
be feasible,from an engineering standpoint,to build a dam
across the Colorado River,that would safely impound water.
to an elevation of 550 feet.

Due to this enormous head of water,the dan er to +he
country below the dam,in case of collapse,was realized,snd
therefore it “as decided that large factors of safty should
be used in all phases of the design. It was jud ed feasible
to make the necessary excavations,of approximately 125 feet,
but that the plans and the estimated costs should include
provision for the control and handling of a considerable
volume of water. This on account of any unexpected leakage

through the cofferdams during excavation.

The plans for the power house,which must be fitted to
a particular site,are considered feasiile as proposed.

It was decided that the All-Americ n canal,should be
concrete lined through the sand dunes,and Fe given enough
slope to carry away all inblown sand to a suitable place
of disposal and removal. Consequently the canal was pronoun-

ced feasible with additional cost.

13.

A dam of 550 feet above low water,across the Colorado
River at Black Canyon,impounding 26,000,000 acre feet,will
be adequate,to so regulate the flow of the lower Colorado
as to control ordinary floods,to improve the present nav—
igation possibilities,and to store and deliver the available
water for reclamation of public lands and for other bene-
ficial uses within the United States.

After it was determined that the project was feasible,
the necessity then arose to select the type of dam most
suitable,and to estimate the cost of construction.

The dam will be a curved gravity structure,designed
for a maximum stress cf 50 tons per square foot. It will
be more than 700 feet high and contain approximately three
and one half million cubic yards of concrete,of which about
one half million cubic yards will be below the low water
level,the lowest point of the excavation being approximately
125 feet below low water. After the river has been'diverted
into the diversion tunnels and the excavation has been com-
pbeted,the construction problem will be probably the great-
est mass-concrete manufacturing-job ever undertaken. That
is it may be considered the greatest,when the unusual height
is considered as over against the horizontal area involved.

It is believed that the mass-concrete work will take about
three years and eight months.

The stresses are determined by the trial load method,
and takes into account uplift at the base of the dam and
within the concrete;radial sides of cantilever elements;

tangential shear between the arches;temperature changes in

14.

the concrete,as produced by both setting heat and exterior
air and water temperature variations;transverse shear in
both arch and cantilever elements;the effect of twist;and
the effect of foundation and abutment deformations in both
arch and cantilever elements.

The cost of the dam is estimated at 37o,eoo,ooo.oo

For the discharge and regulation of irrigation water
it is prOposed to install needle valves in both sides of
the Canyon,connectsd to the reservoir by tunnels and fed
from the power intake tunnels.

Also because of the prOpOsed location of the power plant
and the great height of the dam,spillways of anple capacity
will be provided to prevent damaging the power house by
any abnormally large flood topping the dam.

The power plant will be an installation of 1,000,000
horsepower. It will be located immediately below the dam,
one half on the Nevada side and the other half on the Ari-
zona‘side,forming a U—shaped structure with the base of the
U resting on the downstream toe of the dam.

The estimated cost of the 1,000,000 horsepower devel-
opement is ess,2oo,ooo.oo

Also there is to be considered the construction of
the All-American canal,which will run in a southwesterly
direction,to the international boundary line then westerly
to a point about ten miles west of Calexico,Calif. The
length will be between 75 and 80 miles. rower can be de-

veloped at various sites along the canel,principally at

Siphon Drop,Pilot Knob,and possibly three or four places
west of the sand hills. The Coachella branch diverts from
the main canal at a point about 40 miles from tle Laguna
dam,runs northwesterly to a point near Indio,Calif.,north-
west of the Salton Sea,and thence southerly to a point near
the north boundary of the Salton Sea,the length of this
branch is about 140 miles. The cost of the All-American
canal and the Coachella canal is estimated at 349,5 0,000

The interest during the period of construction is
estimated at $17,700,030 giving a total estimated cost of
$176,ooo,ouc.oo

Up to this time it has been realized that water storage
is necessary to supply the demands,but nothing or practic-
ally nothing has been said as to the disposal of the water,
that is dividing the quantities such that each of the States
effected would get thier fair share. This qestion of water
disposal necessitated the drawing up of an agreement or
compact,which each of the States would have to sign in order
that the agreement be effective,such an instrument was
drawn up and is known as the ”Colorado River Compact".

' It provides in substance as follows: The Colorado River
basin consists of two great natural sub-divisions,the upper
basin and the lower basin. All of the streams and all drain-
age of the upper basin Join together to form a single stream
at Lee's Ferry,located at'the head of the great Canyon,in
the State of Arizona,a few miles southerly from the inter-

section of the Colorado River with the bOundary line common

16.

to the State of Arizona and the State of Utah,and is the
natural point of demarcation between the upper region and
the lower region.

The Compact conforms to this division and the seven
States are grouped into two political divisions. Colorado,
New Hexico, Utah,and Wyoming constitutes the ”States of the
upper division”,and the States of Arizona,0alifornia,and
Nevada constitute the lower division.

With the drainage area divided it was considered ad-
visable to apportion a certain arnnal amount to each division.

Seven million five hundred thrusand acre feet annually,
was apportioned to each division,and by reason of probable
future debelopement along the Gila River,the lower basin
is premitted to increase it's develOpement to the extent
of one silicon acre feet additional annual beneficial con-
sumptive use before being authorised to call for a further
apportionment from the surplus of the River.

The States of the upper basin shall not cause the flow
of the River to be depleted below 50¢ of the River flow at
Lee's Ferry during the lowest ten year period which is on
record.

Navigation is made subservient to all other uses. Power
is made subservient to domestic and agriculture uses.

State control of the appwmyfllation,use,and disposition
of the water Within each State is left undisturbed.

The compact may be terminated at any tine by tFe un-

aminous agreement of the signatory States.

17.

host of the items so far covered have dealt with those
articles which had to be passed by Congress or by some board
appointed by Congrese,now the discussion of why the dsvsite
in the Black Canyon was chosen rathe- than the one in the
Boulder Canyon,from the engineer's standpoint.

Approximately seventy different sites were carefully
tested,one after the other these sites were rejected as
being unsuitable for such an enormous project,due to some
defect found by the engineers,testing the foundation,ele-
vations,and canyon walls. After a number of years of testing
and discarding,the number of possible densites had dwindled
down to two,one in Boulder Canyon and tie other in the Black
Canyon.

, The Boulder Canyon site was found to he Suitable and
could be used,provfded no better site was lecated. The
foundations are of granite rock of excellent quality. Reg-
ular jOints and more irregular fractures are numerous,and
there was found to be occasional fault zonesyhowever,test
tunnels showed that these are of little consequenoe to with-
in a few feet of the surface.

Thane is no danger of the rock failing to meet the
requirements as adam foundation.-‘

The site considered to he most suitable for tie con-
struction of the dam was in'filack Canyon,whioh is about
forty miles from Las Vegas,fievsdn and the Union Pacific
railroad. At this site the rock formation is somewhat

jointed and eXhibits occasional fault displacements,which

18.

are completely healed. It is almOSt ideal rock for tunnel-
" I

ing,is satisfactory in every essential,snd is suitable for
a

4
1

use in construction.

The GeQIOgic conditions at Black Canyon are superior
tonthose at Boulder Canyon. The Black Canjon site isyhore
accessible,the walls are steeper,and a damkof the ease htight
here would cost less and have a slightly greater reservoir
capacity. \

There is no doubt whatever but that the rock foumations
of this site are competent to carry safely the heavy load
and the abutment thrusts contemplated. ‘

It is feasible from an engineering standpoint to build
a dam at Black Canyon that will safely impound water to‘=
an elevation of 560 feet above low water.

The proposed dam will be by far the highest ever con-
structed and will impound 26,000,000 acre feet of water.
Failure of such a structure would cause immense damage
to the country below,and therefore the dam should be con-
structed on very conservative lines.

In the Opinion of the board the maximum calculated
stresses should not exceed 30 tons per square foot. Keep-
ing the stress to as low a maximum as 50 tons per square
foot,will add materially to the cost of the structure.

NOt only was the rock formation an important factor
to be studied,but also the reservoir capacity. All of that
reservoir which lies between the damsite in the Black Can-

yon and the Boulder Canyon,is additional capacity to what

19.

would be obtained by constructing the dam in Boulder'Canyon.
A review of the entire reservoiriis as follows: At the dam-
site the reservoir is only about 400 feet Wide,from this
point it gradually widens until at a paint about one and

one half miles aboue the damsite the reservoir is four miles

wideaand maintains this width to a point ghout ten miles
above the damsite. The average depth is aboégiaso feet giving

‘;\, a
a capacity of 8,448,000 acre feet,or 49,065,03§,0CO gallons

of water. Tidy

We have now followed the re :ervoir up to the lower end
of the Boulder Canyon,and here the reservoir nanrovsxdown
from a width of 4 miles to about 5,000 feet. Forts distance
of seven miles the width gradually becomes its 9 and at the
upper end of the Boulder Canyon the reserVOir is only 1,000':
feet Wide. The average depth of this narrow channel is 010 R
feet,giving a capacity of 865,159 acre feet of water.' 3

It can readily be seen'hat all of the water up to this
point in the reservoir,is that additionap amount which is
obtained by placing the dam in the Black Canyon rather than
in the Boulder Canyon,or an additional capacity of 9,311,159
acre feet of water.

From the upstream end of the Boulder Canyon the reservoir
widens out until at a point 8 miles upstream the reservoir
is 9 miles wide. This extreme width id due to a wash extend-
ing 7 miles south;the width then gradually decreases until
at a point about 28 miles above the damsite the reservoir

is 4 miles wide and,at this point the Colnrado RLVBr branches

20.

off continuing on too the east and south as the Colorado
River and,northward as the Virgin River.

Suppose now we consider the north fork of the reser-
voir;first we find that in about five miles it narrows down
to two miles wide and,at the forks the depth is about 460
feet,five miles farther upstream the depth is about 400 feet.
The reservoir extends northward for about 18 miles with
approximately the same width,there it branches out,the right
branch continuing on to the north about 10 wiles,gradually
becoming shallower and shalloworduntil there is nothing
left but a muddy creek. It now we obServe the left fork,

' we find that it includes the towns of St Thomas and Kaolin,
this branch extends northward for 7 miles,and also dwindles
away to a muddy creek.flNot only fit Bhomas and Kaolin but
also U miles of railroad will be in the reservoir.

The reservoir along the Colorado River ‘aintains a
uniform width of about two miles for a distance of 10 miles
above the forks. From this point the reservoir narrows down
luntil at a distance of 12 miles upstream from the forks,
it is only about 2000 feet across. This is through the Vir-
gin Canyon which is about 6 miles long and will have a depth
of about 400 feet. After passing through the Virgin Canyon,
the reservoir widens out,covering a sand dune territory and
Greggs Ferry,then narrows down again as it enters Iceberg
Canyon. The River crosses the Nevada and Arizona line in
this Canyon. The depth at the line will be about 580 feet.
From this point on the width will rarely exceed 2,000 feet,

as the water passes through canyon after canyon,filling

the Grand Wash,the Grand Tash Canyon,the Grapevine Wash,

the lower granite gorge and,from a point Just about 100 ’
miles from the Black Canyon damsite;where the elevation

is 1050,upstream to the Bridge Canyon damsite,the river is
in a canyon having practically no reservoir capacity due
to it's width.

This then is the review of the greatest reservoir ever
contemplated,in which there will be stored approxiratly
26,000,000 acre feet of water. It can readily be seen that
it will take some time to fill and keap filled a reservoir
of such an enormous capacity,so at this time we will take
up a study of the Cdlorado River and'it's tributaries.

The United States Geological Survey has finished an
investigation to determine the possible ultimate develOp-
ment of the States‘of Wyoming,Colorado,New Mexico,and Utah
from the Colorado River and'it‘s tributaries. It has been
determined according to a recent ”press release" that approx-
imately 1,198,000 acres are now irrigated from the green
and the Colorado Rivers not including 160,000 acres on the
San Jaun River in New Mexico,with a possible ultimate acre-
age of 2,997,000'acaes on the Green and Colorado Rivers,
and of 600,000 acres on the San Jaun,making an ultimate
irrigated area of 5,597,000 acresgassuming a consumptive
wafer duty of 1.5 aore-feet per acre;which students of the
question agree to be liberal,makes aitotal consumptive use
of the water in the upper basin of 5,395,503 acre-feet of

possible ultimate transmountain diversions,brings the total

22.

possible use to approximately 5,720,000 acre-feet as con-
templated by the Colorado River Compact.

The total mean annual run-off at the junction is about
12,5p©,000 acre-feet of which 6,800,000 acre-feet flows in
the Colorado‘River and 5,730,000 acre-feet in the Green,
The available reports discuss in detail the extent to which
this flow is now being put to use and outline it's probable
future use. The bare facts are presented.

IRRIGATION.- Approximately 1,158,000 acres are irrigated
at the present time with water from these drainage basins,
and it is estimated that this area may ultimately be increased
to nearly 2,997,000 acres.

TRAESKOUKTAIN DIVERSION.- At the present time there are
nine conduits that divert water frOm the Green River basin
into the Great Salt Lake basin,c1siming about 166,000 acre-
feet per year,and six conduits that divert water from the
Colorado River above the Green into the Hississippi River
drainage basin,with an annual diversion of 20,000 acre-feet.
'Aocording to es+imated that have been made the possible in-
creased diversion into the Great Salt Lake Basin may amount
to 50,000 acre-feet and that into the hississippi River
Basin to 262,000 acre-feet.

DEVELOPED POWFR.- Rot including all special plants such
as flourmills and sawmills,which generate hydroelectric
power for use incident to *heir business,there are 48 hyd-
roelectric ptants intthe basin having a total installed

capacity of about 49,000 horsepower. These plants are dis-

tributed by States as follows;wycming,one With an installed
capacity of 70,0010rado,fourty one having a total installed
capacity of 47,550,and Uthh six with an installed capacity
of 1,780.

UNDEVELOPED POWER.- The amount of the developed power
is practicably negligible compared with the undeveloped
power resources. The various reports describe some ninety
sites at which it would be possible to deve10pe1169,000
'horsepower for 90 per cent of the time,5ll,000 horsepower
‘ for 50 per cent of the time,or 1,080,000 horsepower with.
the flow regulated at described reservoir'sites. These sites
are located as follows sf states and”by msjss and'minor ',
drainagu basins: 1

The above figures do not include 7,500 horsepower now
in use and ten undeveloped sites capable of producing 200,
000 horsepower in New Hexico 0n the San Juan. The tota1,then,
in the four upper basin States-wyoming,Colorado,New Mexico,
and Utah—is developed 56,700 horsepower,undeveloped1,860,
000 horsepower.

The Coborado River Board,after revieWing in some detail
existing records of flow,in it's concluding paragraph on
water supply statesijlt is estimated that the present flow
is depleted by water taken for irrigationin the upper basin
0 by approximately 2,750,000 acre feet,which amount if added
to the above estimated flow,would increase ft td about 15,
000,000 acre-feet. This is the-amount appertioned bythe

seven-state compact for the division at Lees Ferry.

SILTIKG OF THE RESERVOIR.- It is decided that the efficien-
cy of the reservoir will not be seriously impaired during
the first fifty years,and is estimated that 137,000 acre-
feet of silt will be deposited in the preposed reservoir
annually.

It is estimated by engineers familiar with the situation
that well within that periodbother reservoirs will be con—
structed above which will store a greater part of the silt.
Five million acre-feet capacity in the Boulder Dam reservoir
is allocated to silt controll

‘As a closing paragraph for the tepie of the water supply
I would say that without regulation the river has little
value. When the nelting snows fill its thousands of little
feeders,the lower river becomes a turbulent,dangerous
force. Nearly a hundred miles of levees have to be maintain-
ed at a greet cost to keep the river floods from innundating
the farms of Yuma and Imperial valleys. When the snows are
gone, the river shrinks to a shadow of what it was two months
before. The quick runoff of the river and the absence of
summer rains accentuate this wide difference between high
and low water. The highest sunmer floods have exceeded
200,000 cubic feet per second; low flow has dropped to 1,299
cubic feet per second.

These conditions call for a large reservoir to regulate
the river's flow as the next step in protecting development
already made and in providing for its eXpunsion. To serve

all purposes the stonage must be large enough to equalize

‘25.

the wide variations in monthly discharges and reduce the
variation between years. The largsr‘the storagethe‘mose
valuable it will be.

During the months preceding the passage er the bill
the original purpose of the act,which was to protect the
Imperial and Yuma valleys from floods and drought,extendl
the irrigated area in Arizona and California and furnish
additional water for domestic use and other uses in the
coast counties of California,had been lest sight of: It
had ceased to be a measure to provide water and had become,
in the discussion and in popular opinion,a measure for the
production and disposal of pewer.

Enlisted in this controversy were the prfvate power
interests,opposed to all government construction of power
plants,the believers in state and and municipal ownership
and operation of power plants,and the different states
which wish to participate in power revenues. It became a
' struggle between different economic and social policies
and for the political advantages of the diffsnent states.
As a result it is‘hard to understand just what the bill,
as it was passed,means,h0w far the Secretary of the Interior
in the allocation of power is to be controlled by the pre-
ference given to municipalities and to states,and how far
he can exercise discretion in the protection of public wel-
fare.

One thing the Secretary cannot ignore. The law requires

26.

him to secure a contract for the power that will repay the
costs of certain parts of the work within fifty years. with-
out such contract the satire”isgfsrsttes falls and Boulder
dam_hou1d have to wait until Congress deals with it again.
(’ngn Opinion widely held that—- Boulder dam is being

pold for out of taxation-- is erroneous; It must be paid

for out of power revenues and charges for storing water.
,.hfter the Secretary has secured satisfactory contracts for
/powerfhe can then proceed to submit estimateszfos appocieticns
[ and make contracts for the building or the dam and poser
:ghousg.

/ 37 After s long and careful investigatiOn the power experts

I, fmployod fixed a price for the power privilege at the dam

‘/ of b.65 mills per killowatt-hour as meeting these require-

j ;ments.iThcse who pay this price will have to install and

g Operate the machinery. It simply means a fixing of the price

I to be paid for falling water,with the government having
nothing to do with the generating of hydro-electric energy.
{If/the charge is much greater than this,customers cannot

V berflfound.

While there have been protests that the price was ex-
cessive,two offers for the entire output have been recisved,
one from the Southern California Edison and related companies,
and one from the department of power and light ofjthe city
of Les Angeles. Both of these bidders are in a position to

dispose of all the power purchased. There have been‘other

offers,but'hhe abflity to dispose of the power is so prob-

lsmatical that the Secretary could not consider them with
the facts now before him.

The problem of disposing of the power is complicated
, by provisions in the bill giving to municipalities and to
the three lower states of the basin a preference right to
claim power. The act acquires that this preference right
of the states be exercised within six months. Only Nevada
has indicated a desire to acquire any definite quantity or
power. Certain municipalities in Arizona and California
have also applied for power.

There are,however,certain definite rights which must
be protected. Thefuetrcpolitan Water Distnict, comprising
the southern California municipalities whic are seeking a
source of domestic water supply in the Coloradc'Rfver,wil1
need a large amount of power'to pump this°hater over the
mountains. A number of other municipalities‘have preference
rights,as have the states of Arizona and Nevada. It is in
every way desirable that hhese states obtain this power
whenever it can be utilized to Operate mines or develops
latent recounces. The Secretary has been very successful
in his negotiations with the different interests,ln fihat
he has induced the two principal distributors of power to
agree that,thils they will contract for (and if necessary
take) all the power,thsy consent to surrender to,the iatro-
politan Water Uisfrlct one half of the total pOWer generated,
or so much thereof as may be necessary for pumping water

in the aqueduct. They agree to surrender‘tc each‘cf the

28.

states of Arizona and Nevada 18 per cent,or 36 per cent

of the total quantity of the power generated,and to munic-
ipalities a certain additional percentage,the amount of
which has not as yet been definitely fixed.

If all these withdrawal privileges were exercised,
it would mean that the original contractors would have less
than 10 per cent of the power left to meet their require-
ments. They are willing to assume this risk because of a
confident belief that not all of the withdrawal rights will
be exercised,or at least will not be exercised for many
years.

’If the power privilege is disposed of at 1.63 mills
per killowatt-hour,it will pay the‘entire cost of the dam
and leave a very considerable surplus to be divided between
the states of Arizona and Nevada,the bill providing for
such division. It would appear that each of these states
stands to recieve an annuity somewhere between $550,000
and $700,000 a year.

Based on the'estimates of the variatiOns of flow of!
the Colorado River,it is believed that*under present con-
ditions of irrigation a continous output er 550,000.horse-h
power,or 1,000,000 horsepower on a'55 per cent powerhfactor;
could be maintained even duaing the years of normal low flow.
A 1,000,000-horsepower hydroelectric plant fully loaded and
Operating continously on‘a 55 per cent load'factor,would
generate annually°5,600,000,000 kilowatt hours of current.

In actual practice this thecretici Output might be reduced

29.

by approximately 10 per cent.

With the uncertainties of the flow at Boulder Dam 1+
is impossible to estimate Closely the average annual output
of powerywhich would obtain during a fifty year period but,

' it will be concluded that with full irrigation development
in the upper basin,the 75,000,000 acre-feet can be delivered
at Lees Ferry,during any ten year period.

The above supply equalizedat Boulder Canyon is equal
to approximately 12,000 second-feet of continous flowfiwhich
in turn will generate,with head available,approximately
; 659,000 horsepower under hltimate development. For present
and near future conditions-- say for the next 25 to 60 years
the available water supply will develop 850,000 firm horse-
power. These conditions willrobtain until full irrigation
develoPment in the upper basin.

SEQUENCE OF CONSTRUCTIGN: Before work can be started
at the damsite it will'he necessary to build the construct-
ion railroad,to provide adequate housing'facilities and to
secure electric power for construction purposes. The first
step in the prOgram will be the construction of the rail-
road. The next step will‘be the building of a town with all
modern improxements,including sewer and water supply systems,
the water being obtained from the Colorado River. Construct-
ion of a temporary power plant,or of a transmission line
from some outside source,can proceed simultaneously‘with
the building of the railroad and the town.

’As soon as transportation,housing and pOWer facilities

50.

are available,the driving of the diversion tunnels will be
started. On completion of the tunnels,the river will be div-
erted and the upstream and downstream coffer-dams built so
that the foundation or the dam can be unwatered and the
foundation excavations made: Stripping of loose rock on the
canyon walls,excavation of highway approaches and such
abutment excavation as may berequired will be carried on
while the coffer-dams are being bailt. is soon as the founé
dation excavation is made,pouring of the mass-concrete will
be started. Concrete work in the spillway,power tunnels and
outlet works can proceed simultaneously with the pouring

of the mass-concrete in the dameIt is estimated that all
work can be completed in seven years.

The construction of the main line 0f the All-American
canal will be a six year program and work Will proceed sim-
'ultaneously with the work on the dam. No'estimate; of the
time required to build the Coachella branch of the Alléimer-

’ v *‘1 I: 4' . '-
ican Canal have been made thus far.

The object of this Thesis, being a part of the review of
the Boulder Dam Project, is to present a comprehensive view
of the general conditions confronting those interested in such
a project. It is not intended to be a technical report of the
subject, but is limited to things of‘a more general nature.
It is hoped that this knowledge may be obtained upon reading
the pacer as presented.

0. F. Ravell.

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The investigations of the feasible sites for the boulder
Dam included the investigation of two locations; namely the
Boulder canyon site and the Black canyou site. The board of
Engineers and Geologists appointed under authority of Joint
Resolution No. 65, Beventieth Congress, made the following rep-
ort to Tecretary Jest. At Boulder canyon the foundation rock
is granite and associated franitic rock of excellent quality.
Regular Joints and more irwegular fractures are numerous and
there is an occasional fault zone. Test tunnels prove that
these are of little consequence to within a few feet from the
surface. On the whole the rock is strong, substantial, durable,
and the whole mass is essentially tight. There is no danger of
the rock failing to meet requirements as a dam foundation. The
rock in the vicinity is suitable for construction materials,
and there are local courses of gosd gravel. If no other site
were available, The floulder canyon site could safely b: used
as far as geological conditions are concerned.

The most favorable site in Black canyon is about 40 miles
distant from Las Vejas, Nevada., and the Union *acific Rail-
road. A construction railroad from Las Vegas would pass near
available gravel deposits and the best quarry sites. The foun-
dation is a volcanic breccia 0f tuff, a well-cemented, teijh,
durable mass of rock standing with remarkable steep walls, and
resisting the attack of weather and erosion exceptionally well.
The rock formation is somewhat Jointed and exhibits occasional

fault displacements, which are now completely healed. It is

almost ideal rock for tunteling, is satisfactory in every ess-
ential, and is suitable for use in construction.

Geologic conditions at Black canyon are superior t3 those
at Boulder canyon. The Black canyon site is more accessible,
the canyon is narrower, the gorge is shallower below water lev-
el, the walls are steeper, and a dam of the arms height here
would cost less and would have a somewhat creator reservoir
capacity.‘rhe rock formation is less jointed, stands up in
sheer cliffs better, exhibits fewer open fractures, is better
healed where formerly brohen, and is less pervious in mass
than is the other site.

There is no doubt whatever but that the rock formatizns
of this site are conpetitent to carry the h avy load and abut-
ment thrusts contemplated. The board is of the opinion that
the Black canyon site is suitable for the proposed dam, and

is preferable to Boulder canyon.

rm-

ine Ceolo:y of the Foundation

{he Xudiy Creek formation occupies by far the greater
part of the surface within the Boulder canyon Reservoir site.
Overlying the Greg 3 braccia and the ruddy Creek formation is

a deposit of well-stratified sand and gravel With intercalated
flows of basalt. This has been described by Lee of the United

States Geological Survey, who named it the Temple Bar conglom-
erate. It is variable in thickness and from lee's descriptions
ap-ears to attain a maximum of over 2000 feet. He regarded it

as probably of early Quarternary are

0'" O

a

h still younger deposit of gravels forms bluffs and ter-
faces along the Colorado from the mouth of the Grand Canyon to

he Gulf of California. They have been named by Lee the Che.

 

 

 

 

 

COLORADO RIVER. NO. 92

Looking downstream into Boulder Canyon from point of rock on Nevada side rear the
entrance. The lower part of the Arizona abutment fora darn at the upper ("C") site is
shown in the lower left corner. A dnll barge ls shown in the center of the picture. work-
ing at the "A" darn snte. February 19, 1921

 

n huevia gravel and were considered by his as of late Cust-
ernary age. Their maximum thickness is given as about 700
feet. .

In addition to the intrusive granite rocks of pre-Camb-
rian age such as are exposed in Boulder Canyon and the late
Tertiary basalt flows, such as occur in the ruddy Creek for-
mation and Temple Ear conglomerate, the region contains two
rather complex masses of predominantly igneous rock of con.
sidereble volume and extent. One of these lies J~st nurth of

‘ ‘

Boulder Canyon and stretches westward tonard Callville Sash
and eastward to the valley of the Virgin; the other occupies
many square miles on both sides of the Colorado, in the vic-
inity of “lack Canyon. Information concerning these rocks will
not be given. for practical convenience of reference in the
present report, however, the first of these may be referred

to as the Boulder wash group and the second as the Black Canyon
group. The Black Canyon group is he more homogeneous and con—
sists of intrusive masses, floss, breccias, and volcanic cede
iments that are probably all of Tertiary age. The Boulder Wash

trons, in addition to volcanic and intrusive rocks, contains

(e

some limestone and shale. The volcanic rocks are probably
Tertiary but some of the stratified rocks and possibly some
of the intrusive rocks may be older than the Tertiary.

At the base of the Boulder bash group, on the north side

of Boulder Canyon, 1,070 feet or more above the river, is a

hard, siliceous yellowish limestone which rests directly upon

the pre-Cambrian schist and ¢ranite. Ho fossils have been

found in it and its a e is unkne.?n. Shis li eat one, which
is perhaps from 100 to 203 feet thick, is overlain by sev-
eral hundred feet of coarse brecoia con os;d 1M ggely of
fra3 Wen s of ere-oarnrian rock. Apnarently so7e lenses of
limestone are interhedded.with this.hreccia. The general-
dip of the whole is to the north

The i3neous rocks of the flack Canyon group constitute
an extensive mass that lies athwart the course of tbe Colo-
rado, about 3 miles south of the mouth of has Ve3as tech,
and stretches east and west for 2 or 3 miles on each side
of the river. Through this mess the stream has cut the deep
gor3e of “ oulder Canyon and i‘lou s wholly within it for about
8 mile a, to 3-point where the wal.s become lo sprecipitous
and pre—Cambrian.3ranitic and schistose rocks ener3e from
beneath the volcanic group. For about 7 miles farther, down
to Jumbo Vash, the river flows 'ainly tn ou3h mour ntains of
pre—Canbrian crystalline rocks, but men we rs of the Black Can-
yon grouu.anpear at the water's edge. felon Junho Tash the
Can; on was not traversed, but a reconnaissance suggests that.
the Black Canyon volcanic 3roup may he generally continuous
with the thick volcanic series that makes up most of the

B lack Tountains zartli er south, in the vicinity of Catnan,

drizona

The gen rel form of the entire as Jla e of rocks con
prisin; the'hlack Canyon {roue is difficult to ascertain and
in so:. e resrects w uld re:7ain in dou’; t even aft er detailed

geologic napning. It is clear, however, that the rocks are

chiei ly lava flows an brecoia deposits that originally

were 11s a rly horizontal. They evidently occupy a basin of
which the deepest part is under the present ‘1ack Canyon.
The shape of this basin and the depth {rem the river level
to the Dre-Cambrian crystalline rocks upon which the lavas

as a whole rest are not at firesent determinable. There is
some evidence to show that_the bottom of the hasin subsid-
ed after the first eruptions and perhans continued to sink
throu5hont the period Of volcanic activity. Such movement
is indicated by tlze exposxre within t: c cenpr gel 5 of lay-
ers of'volcanic sandstone which new Cal? at en3les up to 65°
and leve been faultam , nieras t e hL,her flows have genern
ally a much 10 er GL9 to. .ard. the east-northeast. There is
eviience at one locality that the andesite broke through
the older rocks in the vicinit; of Elect Cnsyom in 0 her
words, that the seat ef_cruntion was lecsl and tLat the
flows and Urecrias are not tfie product of out? rats at so~
mc tflgfflgi iittugp :"int, I; psi: is true, it is probable
that in some parts of tbe Pasin h e ~tcit’c lavas est-

eni doW'n are to their point of orikin within the earth.

The basaltic dikes and masses that are exooned in the

anyon ta lls belon.3 to a late stage in tz1e eruptive act-

ivity and nrooahly xxtend downward far below the bot on of
the basin. They apwear to have risen through branching and
irregular fissures which cross he general stratification
of the flows and breccias.

From the occurrence of ere-Cambrian granitic and sch-

istose rocks both north and south of Black Canyon it is

fairly certain that the Flack Canyon volca ic grout as a

whole rests on these rocks. finch a relation is cleurly shown
on the river about 8 miles below the head of llack Canyon.
Tere the andesite rests on the ore-Cambrian. It nee not era-
cticable to exerine the cont ct closely at this place but,
as seen from the river, it apoears to be fairly close. It is

certain that loose grav is or broccies are aheent at this

point, and if any detrital material intervenes between the

1

levee and the ere-Cambrian it is not of a cirraoter to cau-
se any anxiety as regards possible leakage from a reservoir
8 miles away.
REG RVCIR LEiKAGi

n brief, the ester of the nrooosed Black Canyon Pes-
ervoir will be confined by mountains of hard rock or by
natural dams of softer but not particularly pervious mater-
ial throngs which it would have to pass for 20 miles or
more before finding an outlet.‘In other words, there is no
point at which escaoe of water from the reservoir through
a relatively thin barrier of pervious material need be feared.
The shortest route of escape through the inclosing rocks
would be throujh the mass between Hemenway Wash and Color»
ado Hiver, to some point of emergence below the dam site.
To accomolish this passage the water would have to pass thr-
ough at least a mile of rock, partly intrusive dioritio pore
phyry and partly the volcanic rocks of the slack Canyon

is no evidence of the existence of any cont-

grouo. There
iouous porous rock member as for example, a layer of cone
glomerste or loose breccia, through.which water could es-

J

cape by this route.

7.

O

The possibility of leakage around the dam on the Aria-
ona side of the river, under the gravel-covered slopes that
intervene between the Black Canyon volcanics and the pre-
Cambrian rocks of the main ridge of the Black rountains. was
also carefully considered. To escape by this general route
the water would have to penetrate at least 2 miles of mater-
ial, mostly solid. impervious rock. As the flows of the Black
Canyon group dip mostly northeast, away from the dam site,
the water would have to find its way not merely between but
across these flows and the possibility of escape by this une
derground route may safely be dismissed.

B’ZACK CAIE E101} DALE SITE Iii-1D I..E.AE{AGEE
LRO ED BAH

The river here is from 250 to 300 feet wide, and the
walls rise so steeply that at the 1,100 contour. or about
450 feet above the river, they are only from 600 to 700 feet
apart. For s.considereb1e part of their height they are com-
posed of andesite tuff breecia, consisting of angular frag.
ments of andesite and of other fine-grained igneous rocks in
a matrix of finer particles, all firmly cemented to a hard
rock or generally reddish gray color..Although.not separ-
alle into distince beds, the rock exhibits indefinite lines
of stratification, emphasised on weathered surfaces by the
alignment of irregular pits of cavities which.give the rock
the suoerficial apnea ance of being somewhat porous or spon-
fiy. the pits, however. are not original cavities but are due
to the disintegration and weathering out of certain fragments

in the broccia, In eertain spots in the walls the cement of

 

the breccia, which is partly calcite and probably-partly
oxide of iron, is more readily acted upon by the weather
than elsewhere and the breccia disintegrates so as to pro-
duce cavities or shallow caves in the cliffs. This action,
however, is superficial and the rock back of a very thin
surface layer is apnarently nearly or quite as strong, hard,
and igficrvicus as elsenhere. The breccia as a Whole is a
stronC. hard, impervious rock and would be excellent mater-
ial on and against shich.to construct a dam. Th;re is no
deep decomposition and less than 10 feet would.have to be
removed to secure good anchorage for a concrete structure.
The breccia is traversed by some joints, but these are sup-
' erficially accentuated by’seathering. Joints are probably
much less abundant than in the granit at Boulder Canyon.
Then a den is constructed on granite there is not lik-
ely to be much concern about the foundation. There is reas~
enable certainty that the granite extends downward far bey-
ond any depth that need be considered in planning an engin-
eering structure. Then, however, a dam is built on volcanic
rock it is necessary not only to consider the character of
the rock in sight but to inquire what may be beneath it. It
is possible, for example that a firm massive lava may rest
on loose gravel or aztlonerate through which water might es-

cape and perhaps in time undermine the foundation of the dam.

I

n

no one can tell at present what is under the andesite bree-

cia at the lower dam site at 313°}: 95’ "on: but. it is reason—

able certain that the breccta extends so far below the river

bed at this point to insure an adequate foundation for any-

9.

preperly constructed dam. The lines of stratification in the
breccia dip uostream at about-5* degrees. The same breocia
extends downstream for at least 1203 feet, V th gradually de-
ore sin: dip. The average dip can safely be taken at 30 deg-
ress. This would give a thickness of at least 703 feet of br-
eccia below the surface of the river at the dam site. The act-
ual thickness is probably greater than this, as the dip tnd
distance used in the calculation were very conservatively
taken. If anywhere beneath the breccia were soft or porous
deposits, these nowhere come to the surface and consequently
would not be likely to permit the scans of‘weter held back
by the proposed dam..¥herever the base of any member of the
Black Canyon volcanic group has been seen no considerable
quantity of loose or porous material has been found. About
1,700 feet downstream from he lower dam site an irregular
intrusive mess of basalt is exposed on both sides of the riv-
er and extends for some hundreds of feet above the water.
This mass has presumably come up from great de pth and con.
stitutes a natural impervious diaphragm which would prevent
free pessege of water tbrough a buried porous stratum, did
such exist. About a mile below the dam site the breccia disc
ainears and an intrusive diotitid rock forms the lower wall!
of the canyon. The precise piont of change was not recognized
in passing up and down the river and the contact between the
two rocks is certainly inconspicuous and presumably, there-
fore, close. In short, th re is no reason to apnrehend.that
water impounded,hehind a high dam at tie lower dam site could

escape around or under the dam.

10.

iZLFCIION or 7’? TIT?

Ewe ass sit es were investi5ated in Black Baryon; one
about 1/00 feet b: low the entrance, known as the A site and
the other about 1? miles below the entrance, known as the 3
site. Due to the greater width of river channel at the uno-
er site it the anticipated that bed rock would be found at
comparatively shal‘ow depths. however, the shallow depth did
not materialize, and this in combination with the character
of the rock and 16 large amount of concrete necessary to
build the dam, made the D site preferable.

fhe river at the D site is from about 253 to 353 feet
wide at low ester and the walls rise so steeply that at an
elevation A50 fe-t above the river they are only from 550
to 650 feet apart. For a considerable po rt of their height
the azlls are composed. of andisite tuff brecoia, previous-
ly described, overlain by flow breecia.

Dril ing of site D was undertaken in Zeptcsber, 1922.
Due to the fact that the rock is of volcanic ori5in, usual-
ly looked upon as re airing careful investigation before acc-
eptance for a foundation for a hi h dam, it was desire cl to
obtain a high core recovery. To acoo plish til 3 a core 13/8
inches in diameter and don oleotube core barrels replaced the
s ingleetube type.

Although 5901 051321 exa:ninatio ns indicated that the
foundation rock extended to a depth of at least 730 £9 at be-
low river level; that it does res t on a la3 er of material
throu5h which wrter under great pre3sure mi5ht ease, and
that if this pervious layer did exist the passage of water

would be prevented by a diaphragm of basalt across the can-

yon below the dam site, it r:s thou_1t best to toe t the r ck
to a considerable depth. A hole was therefore drilled on the

*Jiosite the center of the base of the pro-

'15
*5
Ha
I
9
S
6
.4.
a.
d)
E
' *3

posed d::, to a depth of 575 feet (575 feet below low-tater
surface). Ti5hty five per cent of tie core was rec overed.
The hole remained in breccia or compact lati e of snu7=esite
for the entire distance. The rock toried "latite" or "anaes-
its" was encountered several times. It isa smooth, dark red-
brown rock, similiar to the volcanic breCoia but without the
angular fra5rents. there the change from one rock to the other
occurs there is no definite 3; int. The chan5e is rrrdusl, one
merginr into tbe other, and in all nrobability the two are es-
sentially the sa: e rock with a different distribution of the
an'1ular frc gnents. Tllree concertt ivol;~r soft streaks were one.
count .eI ed, one at depth 335 feet, one at 459 feet, and 016
at 5T5 feet. The drill water was lost once when the hole had
rcsclod a depth of h7fi feet, but it is not known_whethor the
water was lost above or below water level in the river. A
great deal of tro Mel was excerienced toward the end on ace
coant of lacn 0T proper equipment for so deep a hole. It was
no essary to "niece out” with snallor drill rods which.vib-
rated badly. There was dan5er of stickin5 the diamond bit
and as tzc additional info mtion to be obtained was of a
nature to satisfy curiosity rather than of practical value,
he hole was discontinued.
The entire area of fountetion of the lar5est dam prop~

osed was developed by drilline on lines 2e) feet abart as

«as done at Boulder Canyon. In addition, the sites of the

proposed cofferdaas for diverting the river during const-

 

12

ruction of the Gem were drilled.
ts a usual practice all holes at the lower dam site were

drilled into befl rock for a distance of 33 f et. The records

to

how that 100 per cent of core was recovered free several holes

and 13?.at core recovere selfiom fell below 90 per cent. “be foun-

Q:
{6.)
(O-
’J

on rock wre founu to oe the some enleeitio tuff breecia
that aoweere in the cany on walls at th= dam site. At times

317333 of core 3 and 4 I‘eot more r3oove Pea. In one hole on

lino :2-3 3 and ine on 3633 oomoect letite or a: ':.1te without
angular frefiments was encountered, similar to that found in

the fleet laud hole. frief y, the aril in: firovei the foundat-

‘)

ion to be exoe Ml .ent beyond u03-t Iho eoek is vasoive, sound,
and of a revarkoble uIMi o.m marector.
the matinim deeth below low water we; found to be 110 feet

for 430 foot l>etwe n limos 0-233 e33 1-337, inoroaeinfi to 123.3

.a‘
q
I

feet at line 3-403 and 132.5 feet at 1.43 D~530. Zhere is
point just aoove line TJ-E 3”) and anotger near 113: D-oOD, where

at noveuent has a3 arently taken place Although they

I. . O ‘

are con? '27:? :1 of no ore otical in porta -3 tge mom has been

nlaced as to avoid them- thus the downstroa: toe of the larg-

est 1:;‘1 “rovo ml falls about 50 feet downstzeea from line D-4OO

and it is as aged that at this point t“e fluxlwom lepth is 125
In fisheral t 39 rJ-vor c‘tniel is fillea with fine sand

and silt to a deotg of Yvon 20 to ?3 fe t everL M ; gravel

and Small boulders with the excootion that at line 3 large

v o: -\ I} .qm- .2..- . v '~ t .. r o 3 .fi p"v< 7 ‘ -.. ’-, lfio ‘ ‘
bouluols, presu golf t3c resalo o- a 1»c: Sigue iron tee can-

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v... we”; ., « '. .LC €..'.Lv‘...-1bta.£'-‘u.o (39,, ct. 3.4-.- s- Von). JJDn-n-"J .-.es 8.43."

04

ow the materla bel3w thy fine sand to be well graded and suit-

 

 

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BUREAU or RECLAMATION
COLORADO RIVER STORAGE

BOULDER CANYON DAM
. GENERAL LAYOUT 0F DAM AND DIVERS/0N WORKS
25,000,000 ACRE FEET

POWER pLANT ON BOTH SIDES OF RIVER

4 — 50 Fr DIA. DIVERSION TUNNE
.omwm....-.5’.MeF.SUBMITT£D
TRACED. .KM¢.§.-.... chmhguozo” . ...--..4 .-.-....
curcxeo. &.'13.5.-.. .. APPROVED . ..

23 96 D"-(n.cow, Nbv ’I',z'.--S'D.

 

ARIZONA

  
  
 
 

 

 

ICC 200 300 400 500 " ‘ , STUDY No. 3A
1 l I I |

SCALE OF FEET

 

 

REV. NulZ’m

 

 

 

 

 

 

 

\\ 2-30

\

able far are in conc¢cte. Ig-v y»? n pructicul value since

~. ,. . --~ ,~. .. .. . .... -. 'I‘. a .3
1:39 213.73.318.12; CAU’iUCt'JJ for 1313-: 1011‘: 331-0133.}. 2.“; a? .362 St-DI‘G.L [01'

,ofi~ifier'biua hfifi :iVCA to £11113; bzfl “'vcr gorge ”y
Elast‘lg r03 the c3nyou 3178, :3L alch a 9133 was aland-
033' as iagractical. There 13 with 31Mc an idea a aractical

c3rtai EL? of excesaive sob?wl Igcnc 5nd 3 rczzlt 33 m “d‘ce to
the 'tfe*" of tlu 333. 1th a dam of unpraceacnbed high and

13:33 331*333 no 3: via in cost 530313 fie attemptefl at the

Yue Deaign
The unprecedented hci_ht of the Uropcved.dnm, roughLy
twice that of any drm neret ofsre built, nece sitac3s a con-
SCTVPtive dtcflr‘ The concrefie gravity dam, Quilt of homo-
geneous material zvnd dong Mdgt; only on its «313ht to resist

the w tar prefievre, rtt or than uncertain stres es of thick

arcacr, is Lest suited to thin conxition. For enhanced Safety

craze 3rcvity d3.ns to cain’s t 0027 versus fiouvl=r s theory
for 2310 culntln3 pTeS‘UPOS in the concrete. Cain's theory 301-
ves for maximum yres arcs perpendicular to the facss cf the
dam, whxle ”ouvier's t33ory solves for Er Asvr(s normal to the.
r63u1tenfi of forces.

itxon of construcb€d dams 33 33:3 tnecrles show-

ed the foliowing stresses wit” 9 full ressrvoir.

13.

design purposes. The weijht of 143 pounds per cubic fo:t will
effect a small r duction in the required dam section.

?ith r ference to as umntion (f), although uplift is re-
cognized in the design, precaution against its occurrence is
taken by extensive drainage and grouting of both the foundv
ation and the dam itself, with resulting increase in dam str-
ength. Further as to assumption(f) the intent is that pressure
at either end of the dam will he that corresnonding to the
height of the water above that point with water at the tap of
the an at the upper end and at the low-water level at the
lower end. This pressure has been presumed to be effective
over two-thirds of the area, the other one-third of the area
distributed uniformly from one end to the other of the dam,
which is assumed adequately drained to prevent the formation
of pressures over one-third of its area.

With regard to assumetion(H), it annears that the stres-
ses were computed by as using a slice through the dam from
front to beck face 1 foot in thickness; that is, 1 foot thick
between parallel planes throujh the section of the dam. This
amounts to assuming a gravity dam with a straight plan instead
of an arched plan and wiht such a straiént plan the pressure
of #0 tons per square f03t would be attained. In fact, however,
the plan of the dam Being an arch, the stresses should enter
and leave the dam on radial lines with the result that the str~
eases entering the dam at the upner end over a width of 1 foot
or more would be concentrated in the lower end of the dam over
a width materially less, the concentration depending on the
shortening of th radius. Offsetting this tendency toward inc-

rease in stresses there is a shifting of the center of gravity

19.

‘
k‘

toward the upstream toe by reaso n of greater thicxness at
that point. If we now assume that all stresses of the arched
dan are carried by gravity only then the maximum stress at
the downstream toe, as computed by Fr. 3. F. Jahobsen who is
associated with Kr. La us, at 68.10 tons ner sfiuare fo t. The
Government engineers have made a similiar computation and
found a stress of 68.3 t ns Der square foot under the r: 9
conditions. It is to be borne in mind, however, that this
result could only be obtained if arch action were entirely
destroyed. It is the belief of the bureau engineers, based
unon the results of careful analyses of other dams, that the
fears entertained by :r. Jakobson re ardin; the ineffect-
ivness of arch action are largely without foundation. The
Weymouth design in not considered as inal but was selected
fromlexoorience as renresinting sufficient yardage for a
final design in which the question of stresses could be more
fully considered.

Further with reference to assumption (h), although inv~
estigetions indicate that the stress at the toe, reservoir
full, is materially increased by this reduction of lenjth if
the dam is considered as resisting the pressure by gravity
action alone, it is probable that the arch form adds security
in even creater pronorticn since the stress can not exist
with-out first deselepiig both horizontal and vertical arch
action.

In the event silt accumulates in the reservoir to the
top,(an event quite unlikely by reason of upstream storage
develonment) the foundation fresnure will be increased mater-

.‘

i

ially over that produced by

.atcr alone

pressures, however, will remain within

. The resultant

20.

of

the middle third of

the base at all heights and the sliding coefficient will be

.less

than that required to satisfy uplift assumptions.

dilt and unlift are not assumed to act at the some time.

For this and other dams the computed stresses are as

follows:

 

ww—-

 

 

uEW. Tax. Eressures en}. in
can. heiiht tons per sq. ft.
in acre to road by Cain's theory.
feet. way in :0 with : t1
feet. uplift up- silt
or silt lift to
hes. ton
full of
dam.
sax, pre§~ure u.s. face 14,000,07fi ?h0 41.3 8.5 19-2
' n.1, " 34,000,0ao 7&0 39.7 39.6 45.6
Jax. sliding factor. 34,0fi0,0®0 740 .51 .71 .74
Tax. pressure v.9. face 90,000,090 540 40.4 3.1 9.1
' s.s " ac,oso,ooo one 79. 39.7 49.4
tax. slidinz factor 20,000,000 ~4. .V2 .72 .67
Tax. "ressure U.S.faco 10,300,070 593 35.5 ““"*‘-“
" " 3.3. " 10,01o,039 533 34.9 35.0 #1.1
Iaximum sliding factor 1“,OW0,000 533 .51 .59 .61

 

The section chosen
that could exist at the
inf

.1

As a

that bed rock in the narrow tron

for investigati
lower dam site

I
5.
.1

l’ 1- 1‘ ‘
on wee the maximum
‘ .‘fi ‘9' ‘1 '9 Car .1
in b130$ Lanyon .asum-

is level.

rock is 14 feet higher than at the downstream toe.

Over the

at about elevation 600,

rock at the downstream toe

+ 1‘s r)

30 feet above t

of the dam .

lowest point

LLV

*1

meter of fact, at the unstream heel of the dam the

gveater part of the foun stion area the rock is

of

Inns, there is only

a very 7511 33LL101 of tve don that is as hijh as as um-

(D
m

e” ezd if the foundation wer ssum-d as bein: at elev-
ation 500 the ma rtimgm desi yusd stress for the highest d8
would not be in excess of about 33.? tone at the dov .stree.m
side and it is believed the t this stress could be reduced
to 35 tors without ad in concrete by changing tne shape of
t‘ie d wnstreem face slightly. Certainly, the loads would be
distributedto the side benches in the riber channel in such

siy as to relieve the higher stresse at the toe at the
deeoest paint in the narrow trench. Furthermore, with add?
itionsl work on the design than is warranted in the prelim-
inarw deci n, the stress could undouttedly be made to incr-
ens e uniformly toward t e tottom ratMi r than s.s worE':.ed out
in this deciMn. "he comoaratively hifh stress at the u stream
13:1 iiffl TCTTlTfil r e‘pty is not of much import nee since
t.e re crvo ir can never be empty-at least not below river
level and nrooably not bzlow the lower set of nermanent ou’
lets '

lhe stresses due to silt are thhr3r th.a. those due to
water alone. However, the sssumation tuft the res rvoir will
at some Lime be filled to the top with: llt is rates stir-
eme aid it is questionable if the silt deposit will not relieve
the o_ssnures ratner than incre. so then. Authorities do not
agree ueon this point and experiments are not conclusive.
A study was :ad e of e effect of varying the top width.

Reduc1. i; the Width fro: 50 t: 25 feet did not result in ap -

the 5136 pro-

“3

presisble saving in concrete and for a dam o
posed the wider top is believed to be more in keeping with

other dimensions.

A design and estimate was prepared of a dam at the
lower dam site in Black Canyon to develop a maximum press-
ure of 33 tons per square foot by Cain's theory. The concrete
required to build such a dam would be about 25 per cent in ex-
cess of t-at for a pressure of 40 tons per s~usre foot, and
the total eatimat ed cos t uoOAt 1.? per cent more. It might be
posolble to reduce the pressures and the cost of the dam thr-
ou3h tie use of sore sort of E;ollow or perforated construction
instead of fol' win3 the usual pr?ctice in desi3ning Rtevity
dams, but it is questionzlle if any "freak dosifn" would be
aporove' where the inte3rity of the structure is of such g eat
importance.

In all cases the est mates assume that it will be neces—
sery to remove foundation and abutment rock to a depth of 10
foot to secure absolutely round rock. It is proposed that \
each do: be built on a curve to best fit the dam site.

In the prepcsed la 3out of the den site if the pots
house were moved upstream to shorten the pressure tunnels its
cost would be materially increae=d, and it would be located
at tzae be se of the vary steep canyon tell w1;erc roclis falling
from 22>;ve mi3ht damage the maehinor; as well as the building.
It wvs also found that the saving in cost of the tunnels by
movin3 the den downs trea;n did not ofIset the ir .crensed cost

of the dam due to its greater volume.

23.

COT”TRUCTICN EPTEEIAL?

The estimated cement revuiro"e>ts :15 4, 033, 033 barrels
for s r sorvoir of 34,033,033 sore-feet capacity and nroport-
ionnll' less for smaller reservoirs. The Touthern California
and Ut 11 mil s are ver3 nvorobly located with re nest to dis-
ance and rail connectionn to the dam site n;d their combined
daily coneciuy is about 23,330 barrels, or 6,333,333 bur rols
annual y for 333 working days per year. This is 53 per cent
in excess of the total ccTez‘lt requiren nonts for the den if
built in a single year.

The sand found along the river banks Ind in the unner

$.19
.4-

oortions of tie river bed witl nrndoninstlng groin amet~

ers of 0.331 to 0.035 inch is too fine for general use in
concrete other than to sup ly s pos~ible derisioncy of "fines'
in a unturs or crwshed send. This .snd contains ver3r little
orgsni c matzer, being finely broken and worn rock fragments
of great vsrio+y niht quartz predominating. $he coarser send
and gravel found in the lower portion of the river bed are
suitstle for concrete, and it is proposed to store such mat-
erial from the excsvetiou for1;he den at flack Conyon to be
later used for concrete.

Concrete aggregate could “e made by crushing the grenit-
ic r3!) is of Boulder Us'yon or title fln.ssy levns at Flack Can-
yon. The "ls tits"1 at Black Canyon is very brittle and could

rovci “1' be made into eanl 9rd grs e1, but the process would
be comparitlvely erpeusive.

So large dipos ts of clean send and gravel tore located

in the innedle e vicinity of any of he den sites. The clean

est deosits are fo*1d in Callville Tash., but these are not

*

favorably located with resooct to the dam sites. in Hesenway

lash are very large doses its of so ani and rat1Lr argular gravel

cgst Ti 12% considerable fin Lgtcrial. lie most or0119im3 de-

.l

0

posit lies about 3% miles fPOfl the co1t d dam site in Black

Canyon on the route of the proposoi construction railroad

D ‘ arA :‘ r—u r- c? s I
ial ior t 9 largest can du:2£ con.iucratioa.
r. Cf' | D, J‘ E ‘_ .- ‘
121ple1, ran ing ir LL} it from lo: DOLuab to 1,333 oou-

”do, of various materials 11 tne vic izity of tn: dam sites
which in the field apoeor to be Gil able for colorete a; reg-
ate mere tested hr the Bureau of Standsr s. The tests Show
that the florenwsv sand and firmvol, although apparently dirty
tn; forbidding in an earance, is the moat suitaLle of any of
the titsrials submitted for test as to concrete ctrerfitn,
workability, oni .11at-‘itv Crushiz; tests of concr to made
from the unweob material, Just as fonn“
nefrly the some stre.gtn as washed material, and better wors-

f0

ability. Twenty-cig t day torts o; concrete cylinders of this

I'v_-\

material showed average 5 rcnjhh of over l,;:. pounce pnfl L1.
inch for the more snitaile mixtures, comparinfi favorably with
concrete concurror ‘.tly sale t1t11 prov.;n gravols from the K..sh—
infton vicinity. The voight cf Fened.1 gravel concrete avert
aged 14} pounds per CUElC f at ago Hi st 146 oounus for the

U.c:i~~ton arTVel With extended researc n to (ioterzr zine the
best crops rtionin; and pretaration of Ucaenway gravels cons

crate of the highest gtality ca. be expected. It apnear:

h)

that washing may be found necessary and that screening may
be limited to a simple separation if tFe coarse aggregates
from the fine. There was some doubt about the dirty films
on the 3r*vel, but microscopic examination showed these to
be calcium carbonate and iron oxide, both stable minerals,
and dispelled suspicion.

A light-weight concrete without sacrifice of strength
would be desirable in that its use would result in a smalla
er dam section and therefore a less cost, provided the 115-
htweight concrete could be produced cheaply. A possilility
in this direction lies in the use of crushed latite which
is to be found.at the adopted dam site in Black Canyon in a
very advantageous position to be quarried cheaply. It is
brittle and could be crushed readily. Its aposront Specific
gravity is about 2.27 and the weight per cubic foot of con-
crete resulting in its use was fozn to be 131 pounds aga-
inst 143 pounds for the Heminway grevol. The crushed egg-
regete is sharp, and when used alone, results in a harsh
mix of poor workability. The subsitution of fine river sand

for 25 oer cent of the crushed send imoroved both the str-

ength and workability of he concrete. It is believed, howev~

er, that the saving in concrete with the lightweight latite

would be more than offset by the additionelcost crushing ago

regate in comparison with.Hemenway gravels.

- 25,
Diversion florks

Balanced 72-inch needle valves were adopted because-
First: They are narticularly adapted to working under high
heads.

Second: The discharge into open air, which avoids difficulties
arising through the creation of vacuum around the contracted
Jet. .

fhirl: Ihe energy of the jet is destroyed in the river chan-
nel where no damage can result.

Jourth: Regardless of the stage of water in the reservoir

the valves are under observation and may be renaired or re-
nlaoed at any time.

Ehe valve conduits are to be lined with somistoel to
prevent the water in the conduits from exerting uplift within
tLe dam.to transmit the compressive forces inthe dam and to
resist the wear and tear of silt which will in time be car-
ried through the dam.

Zach conduit is provided with a 5 by 9 foot hydraulic-
operated emergency slide gate near the upstream end operat-
ed from a gallery in the dam.

Trash racks have been provided on the upstream face of
the den with provision for mechanical rah n3.

Ehe trash rack piers contain two grooves to guide bulk-
heads to position in case it becomes necessary to do some
repair work in the conduit unstrean from the emergency gate

before the water in the reservoir is drawn down. A travel-

in: crane on ton of the dam will handle needle valves,~trash
racks, and bulkheads.

r11 , .7. 1 fl. rm 6 ‘ "- ‘
ihe AEXith irrigation demand is assumed as 30,000 '

'27.

second-feet. In case of the dam to store 20,0efi,3®3 acre~
feet, t; is outlet vor r.:s will Operate as follows.
(a) The lower set of valves begin discharging with 2,000,
000 acre-feet in the reservoir.
(b) ‘Tith 5,70“, 030 acr e-feet in the reservoir tie discharge
is 30,000 second-feet.
(c) The under set begins discha: in: at the time the lower
set is carrying 26, 000 secon d- fer t.
(d) T‘s up‘er set with full reserve! r will discharge 38, 000
second-feet under a head of 200 feet.
(9) hcth sets will discharge 85,3“0 secondnfeet with water
surface standing st to . of paraeets. Taxirum head 315 feet.
In the estimates it has has n assured that all needle valves
for any one dam are of the same design, although the heads
on the two tiers cre different in order that they may be
interc‘11sngeeble in an enerve‘cv

The only excuse for operating valves in the higher dam
under heads greater_i¥cn 275 feet would ‘
(a) It might be desired to discharge'the 40,000 secondvfeet
flood-control water before the water surface in the reser-'
voir reached the bottom of the 5,0fi0,010 acre-foot flood-
ccntrol storage reserve, in which case the lower set would
be require d to operate under a head of 365 feet. Tith water
surface above this level the under valves alone would pass
the 40,000 second-feet.
(b) At very long intervals of time it might be necessary to

Operate the lower set of valves under heads as great as 415

28.

feet to prevent water overtopoin: the perspets on the dam.
Even this head is not considered excessive for emergency use
durih3,e short neriod.

The outlets at river level are not a part of the per-
nanent outlet works as they are to be "plugged" when their
usefulness has ceased. Their function is to carry the low-
weter flow of the river during the time the diversion tun-
nels are being closed and until the water surface in the res-
ervoir is raised to the loser set of valves.

In the event a power house is built as a part of the
develoomeut a large part of the irrigation requirement, and
at times all of it, would ones through the power house thus
relieving tge outlet works. Tith the outlets provided it is
possible that overtoppong may Occur at very long intervals-
perhans once in 500 years if it is attempted to control the
flood to 43,000 second-feet. Overtopsinx could be prevented
by opening the gates to discharge at the rate of about 80,-
900 second-feet at a time when it becomes ecidcnt that over-
tooiing would otherwise occur.

finillwey

qtudies of various tynes of spillweys were made. In
one the discharge was carried downward into the tunnels
used for dicerting the river dueing construction of the dam.
.In another the discharge was carried at high.velocity in
larfie tunnels through the point of rock on the Arizona side
and dropped over the cliff downstream from the dam. In anoth-
er the discharge was carried at comparatively slow velocity

through the ridge east of the dam site and dropwed into a

wash, entering the river about 1% miles by river below the
dam site.

In the case of the concrete dams the plan of carrying
the abnormal flogds occurring at very long intervals over
the den was adepted as being the nest econ nical and the
safest manner in which to handle the discharge. As was
considered in making the computations for the dam, the des-
ign allows for water to pass over the central portion with

the water surface in the reservoir standing 21 feet above

C"P
,. o
o
3
O
90
Q
:5
4

r with the resultant foroes falling within the
mivdle third of the critical point.

To keep he possible overflow from striking he abut~
ments of the dam the latter has been raised at each end 25
feet above the roadway.

The flow will be at right angles to the crest toward
the center of curvature. Any overtopping would be of short
duration and the only damage anticipated would be the poss-
ible breaking oif of the parapets. This, however, might re-
sult in a sudden increase in flow downstream and defeat to
a certain extent the fled-control.

Ihere was an article published in the Takineering howl

statin; that there is a movenent to increase th

} in

height 95 feet there-by making it more effecfive in flood-

control.

30.

(1f\-‘?'_‘;:1"Yflffl rrx'm T"? 'V’
J\J‘.‘l.— .A...-.-J LJ—lg-g.‘ -- n-j-A&

Tiversion works.
In designing the his? osed diversion works the flow of
the Colored) fiver at ;"*a bet: :eon the years 1902 and 1923

use used as a basis for calculating nrcheble discharges at

The relative peek discharge at points widely separated
on the river desends upon the magnitude and ‘uration of the
fTO‘S. Large floods build up gradually .nd are "ironed out”

by the effect of channel sto rage nrenortionslly less than

J

" originating in streets like the San

are the "flasny flo:ds
Juan, Little ‘c‘c-a o, and Virgin. The impending danger of
1cs113 coffe rdrns will be die to the flashy floeds which
are apt to occu r at any time during the working season.

is an exauple of the absorbing power of the river cheno
nel the £10 d of 'ctober, 1911 was sited. T116 discharge at

f‘

lune suddenly rose from 5,033 to 60,033 foot-second, 2,000

"I
.7)
O
C)
. 4

id-feet of which came from the Gila and the remainder

nrincipally from the San Juan and Dolores iivers. At Ship

‘4

Hcc:,h. Tezico (about 325 m les above tees Ferry), the dis-
charge of the San Juan Fiver was esti ated to be150,0fi0
second-feet. ssirirf tth the San Juan and holores peaks
did. not coincide this peak discharge of?_),309 second-feet
at Yuma had dininifihed to 58,003 second- fest or at the aver-
uge rate of aLout lOO second-feet per mile. Upon this basis
the discharge at Lees Perry is assured to have been about
117,090 second-feet and at 301.1d2r Canyon spout 90,000 sec-

end-feet.

31.

Luring the years in mhicn record were taken on stream
flow the fol1owing gives some ids ca of ti 1o torking seasons
nd+J'1e quantities of f1os that would have had to been taken
care of by diversion works. The dischorges exceeded 75,000
scccn6—feet a total of nine ti.e s in the 19 seasons after
work would prohebly have been started. Ehe flood of Sept.
$23, which is estimated to have been cloee to 100,030 sec.-
ft. at noulder Car yon, would have overtooned the cofferdama.
Only four of tbese overtopoings would have been serious,
since in other instances work would not have been far adv.
enced. Tfie serious floade would have occurred as follows:
October, l9ll,e stI e.ted pee.k, 82,000; work advanced 23 mo.
Larch, 1915, est ir‘ eted beak, 8),000; “or a lvenced 83-. mo.
February, 1Q20, esti eted peeL, 96,000; wk. adv. 7 3/4 mo.
Sent., 1923,estimeted peek, 100,030; Wk. adv. 2 months.
In the season 1909-10 conditions were extreeely severe, and
even with diversion works of 75 .000 second-feet capacity
only 73 months would have been available for com: leting the
seasons worL.

The sorrec iable lo_ger working season and lessened dan-
gar from overton in: Justifies the construction of temporary
diversion works having a capacity of 100,000 second~feet
since the loss of a cof;erdLe m after the work was well under
way would undoubtedly defer the corplcticn of the da m et
least a year.

Temporary diversion of
100,000 second-feet is accompl«

ished by means of tree concre te-linod tunnels at lZO-foot

32.

CCLters on the Leveia sir1 e of the river, and rock-earth

f 11 cofferaems, t e tu uLm1 ls to be later used for power

Ho

development.

Estimates of tunnels of varying $176 and tne neces-
sary coffordnms for each size indicrted that a combination
utilising 33-fort din“: :r tu 75L: was the most economical,
but since ttznnels 35 fee t in diameter Ler:= best suited to
th; requirements of flower develoement this size was adopted
at very little greater cost. The la rges t tun11 els justified
'y other conditions ere desirable to effectively pa. as the
large quantities of drift and denris carried by the Colorado

River. That portion of he tunnels uses later for power pur-

poses is lined with 1:2:4 concrete witl an average thickness
of 30 inches. It is proposed to grout between t11e concrete
and rock n36? a pressure slightly in ex‘ess of the pressure
to '11ich t:1e tur.aeLs will be subjected in operation as pen-
stoc:s.

The portions of the tuLcels not used as penstoc‘L s are

)

li:od with l:;§:5 concrete having an average thickness of
18 inches, the least thought to be practicable. High rock
points would be pcrmitte lto eiteafl to wit! lin 6 inches of
the face of the concrete.

Althoufh horseshoe tunnels Lould Le TOPS easily dug,
on account of the flatter bottom, circulsr tunnels were
aiopted for the reason that they are better adapted to dis-
tributing uniformly he great rroscures to which they will

be euljectefi under full reservoir 1m c1.

33.

It is proposed to drive and line all tunnels complete
before the rock-fill cofferdans are started. All tunnels may
be driven simultaneously from both ends, the muck being rem-

"muck tunnels" at each end, constructed on a

ov ed through
grade of about 5 per cent from the invert of tie large tun-
nels to a point above high water. The uct unnels, cross-
ing all diversion tunnels below low-water surfece in the
river and with exits above high water, would permit the triv-
ins of the diversion tunnels regardless of the stage of the
river. The inlet and outlet ends of the diversion tunnels
will have to be completed behind cofferdees during low water.

It is nrooosed to use rock-fill cofferdems to turn the
river, as they apneer to be the most erecticrble type for
the situation, having been successfully seed at other points
on the river and exclusively in recent years in closing
breaks on the lower river.

Test holes were out down on the sites of the temporary
cofferdrms, the location of the lines d llled being based
uoon the assumption that a percolation factor of 6 would be
sufficient for the gravelly material in the river bed below
the fine sand. The results of the investigations are favor-
able for such requireuents.

'n the othe hand in order to insure the safety of the
rock-fill cofferdenc, they must rest upon a better found-
ation then is offered by the sand and silt in the river bed.
It is believed that great floods scour out the channel fil—
ling clear to bedrock while ordinary floods probably scour

out the send and silt down to the more stable gravel and

boulders.

34.

It is preposed to start dumping large rock obtained
from the canyon walls at the cofferdam sites from cable-
ways spanning the site as soon as the flood begins to recede
in July, he diversion tunnels having been comoleted before
the spring £10 d. It is assumed that at this time the river
channel will be scoured out to at least elevation 620, perv
hens dceper under the lower cofferdam. Ehe rocks first drop-
ped would be as large as would be practicable to handle.
Tome of these rocks would be carried downstream beyond the
linits of the coffordam section, but at some stage a part

i

of them would begin to "hang‘ within the sectioz. fit this
point smaller rock would be dropped simultaneously which
would be caught by the larger rocks and held within the intn
erstices. is the flood receded sore rocks would stay in place.
The estleates assume that 25 her cent of the rock dropped
would be carried away. ruring the rock placing process the
diversion tunnels would be discharging at full capacity, and
to refluce the head on the cofferdams these would be built
simultaneously, the lower one being kept half as high as the
upper one.

Cue to the velocity of the overflowing water, the low-
er side of the rock-fill nay trke a rlooe as flat as l on 4
or 5 and by the time the rock fill is raised sufficiently
high to turn the entire flow through the tunnels, a blanket
of sand and silt will, no doubt, have deposited on the upper
slope to approximately normal river bod level. Experiments

at “oulder ggnyon have demonstrated this material to be

very tight if undisturbed. above the too of the send, and

\.A 9’

U1
0

to the top of the rock fill, an earth blanket will be cla-
ced on the water side, materiel for which may be obtained
free fiewecwey Tech.

For additional safety the channel excevetion for the

main am not euiteble for making concrete may be dumped on

The arguments in favor of using rock-fill cofferdems
constructed as proposed, are as follows:
(a) The brocess and nrc¢ssary equipment is not complicated.
(b) If the £111 is placed during the recession of the flood,
the rock will be deposited on a bottom as established by the
flocd which is uncuestionebly much more stable than the nor-
mal river bed at low Water.
(c) A fill built as here planned will ffcct a saving of time
of enproximctely two months for other work since if built
from treetles, or if a type is built requiring caissons,
31133, cribs, etc., construction could not be undertaken un-
til about the let. of chtember or until the return of low
water in the river.
(d) The rock-fill type placed by cableways is particularly
adapted to fighting flouds. Any type recuiring the building
of treetles across the river would be in inminent danger of
being eetroyed by the flush floods which may occur at any
time. Loss of e cofferdem during its construction might
result in a year's delay in completing the main dam.
(e) If the rock fill were built at low water s‘ege, its

inundation would be such.thet a blowout of the send on

which it rested would be apt to occur under the herd to

36.

which it would be subjected.

(f) Sitn the csblewsys left in place over the crest of the
cofferdcm it could be reicod rapidly if e"*rn3ered by flood
and if the rock fill in vrrticlly or entirely lost, it could
be reoleced without having to wait to rebuild trestles,
drive piles, etc,

Echind the temporery cofferdnms it is preposed to build
nortions of tits u73tresm end downstroen feces of the dam to
the height necessary to permener tly divert the river. The
work to be sccomolished in bringin3 the whole don up to the
elevstion of the river would be entirely too 3reat to be
acconnlished between seasonal flo do. ”ith the river per-
memently diverted, excavation of the foundation end'pour-
ing of the concrete between the permanent cofferdemo ould
orcceed without undue haste.

?ernenent coffcrddms to force 237,330 second-fee
throut3l the diversion twntels were 3iven consiicretion but
the lee i3n *7 as not considered practicable and, moreover
a flood of that proportio: has only oczurrcd once in the 20
year period of recori- in 921- when the discharge at lune
was about 200,007 second-feet. For the rer*'ro t cofferdsms
the diversion capacity is calculatoi to be 1,5,3 0 second-
feet in case or the long tunnels disc ~3rri13 belo*x the
po;er house and 154, 030 second—feet if the shorter tunnels

are used-sufficient to pass ordinary floods. The cofferda s

might be overtooned in a hi:h year, but no damage could res-
ult beyond filling the Hole wit: send, or possibly frevel.

It is nrooosed to first b151d a nrotlon of the gravity

37.

section at the upetreen side of the den on esch bench,

‘ ‘I

leaving a 333 about 153 feet wide over tee seen trench. The
rock ezesvetion on the benches would be uider sev while the

loose material in the do men trenc1 788 being excavated and
he pouring of concrete would be sts rted st t11e earlies

possible moment.

ed excavation

0.;

g
t
;o
n

In order to reduce the in J ezs
and concrete qw ntities across t :e de:e trench to a min-
imum, a thin arch with short red us has been desirncd for
the coffordan. The gravity sections have sufficient sec-
tion to keep the tnngenticl thrust cft.he arch well with-
in the middle of the section. Both the wavity and arch
sections would be stepoei and dov tailed onthe do

stress side and steel :3 s, or rails, would be left project-

C.

in3 to secure a 390d bend 31th the concrete to be let r
added.

I

The lower eernanent coffe dam is designed

to

s a gravity
don to tek water nressure from either side. Its construction
would be carried on simultaneously it: that of the upper
cofferdem. The problem here is less difficult and there is
less concrete to be placed. There is a possibility that the
lower cofferdam may not be needed, depending on conditions

found when the dam site is unwetered. If tlie loose ethrough

the rock-fill coffe den and the underlying 3reve1 and bould-
ers can be handled at a reasonable ex sees and it ennesrs
fesssble to complete the person nt upper cofferden on sch-
edule, then the temporary loner rock-fill could be raised

to the necessary eleven. bl on.to avoid.overton in3 by the

eerivg £1033, an: the permanent cofferdem dieyeneed with.
On the othcr hand, if the term1anent upper COLierL¢ can
only be cofioltt i to riV3r "r"qo, or a little above, it
would be tet3er to build the permanent 13;: W coffe rdem
than ‘3 take a chance of losing the lower rock—fill dam
dur n; tie flo d. tince the additional cxeouve of build-
ing the permanent lower cofferdem is smell, it is prob-
able that it should be built. The only objection to it
is the fact that it introduces Wfiet "cy be corei 1e red 3
line of weakness in the comglsted den Where the stresses
are hifih. However, in the design, an effort Iee berm meoe
to miniflize this fault by making the general direction of
he joint more 9.1 to the flirecticn of prcnewrem. The up-
stream face wouli be dovetail ecfl steel ‘tpuae" Wonld.te
lc-ft projectfl -n3 as izl ceee of tke cpoer flex.
The crit ic 31 time in the construction pariod is that
during Which the pereanent cofferdems are t :ins3 built.
It will, in an ordinary season, be necessary, in about
eighto nine months' time, to bu: d the cofferdams, and
place the concrete to at least lrw-Wcter surface. The cut-
off tre nch in the founaation hes bee: 1 :12 Gel jaet down-
str re: m from the permanent upeer cofferism es a timesever,
as With ‘he trench et the ubstreen sifle of the Qam, con-
struction of tze pe rlezoct cofferflot would be delayed
We itin: completion of the trench ex‘eve"o:.
Then it is iesirea to bemin storing water in the res-
oir the éivereion tunnels Will be plugged near the res-

ervoir end With conc‘ete and the river discharge erzied

by the conduits through the concrete dams at about river
:rede. After the tunnel plugs have been placed the lower
tier of cttlets Without gates will be plugged with con.
crete behind a ball to be placed at the upstream end and
a low cofferdnm built on the den at the lower end, the
water in the meantime being controlle by the outlets
provided with gates. After weter level reaches the higher
valves the conduits at river level are to be permanently

nlu3"ed with concrete.

-' I ‘ ‘ V r I ‘

1&0,

CON‘TRGCTION PLEN

It is assumed that all construction machinery at the
dam site will be electrically Operated. Due to the magnio
tude of the work it is as umed that the construction rail-
road to the dam site and the plant for furnishing power
will be built before work at the dam site is undertaken,
the latter either at Las Vegas or the dam site, depending
upon whether it would be more economical to transport fuel
or transport power. During the construction of the railroad
and power plant a construction ergo would be built at the
dam site, including housin5.fecilities, shOps, water sup-
ply, etc.

From the detailed studies of various construction
plants it apeears that a cableway plant is best adapted for
use at the proposed dam site. The cableways would span the
canyon in positions to handle both the excavation and conc~
rete. Cableways used to build the rock-fill cofferdams would
after their completion, be moved to new positions over the
main dam. Nine cableways are proposed, each capable of hand-
ling a 12-ton rock or five cubic yards of concrete each trip.

The first work to be done is the driving of the three
diversion tunnels, involving about 15,500 linear feet of 38
to 40 feet diameter tunnel and lining them with concrete.
Electric shovels and muck trains would probably be used, the
shovels digging themselves in at both ends of each tunnel
through the muck tunnel described under the heading "diver.
sion works? with its portal above high-water surface. The

large tunnels would not be "blown through" at either end

41.

until the concrete lining had been completed,since other-
wise work could not be carried on durin: sigh water. Exc-
avation would be started during low water so that the six
shovals could be taken to the tunnel portals on barges. To
get the shovels from the railroad at elevation 1,375 to the
barges, cablewsys Nos. 1 and 2 would be used. These two cab.
leways and the railroad trestle under them would be the
first equipment installed at the dam site. The longest tun-
nel has a length of 5,700 feet. If it is assumed that work
would be carried three shifts per day for six days a week,
with an average daily progress of 15 linear feet, it would
require about 15 months to complete excavation. Concrete
lining would follow the excavation closely. Therefore if
work were started in December it should be completed by the
middle of the second Harch, prior to the beginning of the
spring flood. Upon completion of the diversion tunnels the
shovels would be moved.to the rock quarries to furnish rock
for the temporary cofferdams.

During construction of the diversion tunnels the camp
would have been completed; three cableways would have been
erected over each rock-fill cofferdam; oabloway No.9 would
have been erected over the lower permanent cofferdam; and
the quarries above the rock-fill cofferdams would have
been opened up. Diversion capacity has been enlarged from
100,033 to 200,000 second‘feot, in accordance with a spec-
ial enjineerin; boards report.

As stated under " iversion works" the rock-fill coffer-

dams would be started as soon as the £10 d began to recede,
probably in July. The upwer cofferdam is much the larger
and would require the longer time in building, requiring
620,000 cubic yards of loose rock, including the 25 per

cent assumed to be swept away. The material will be handl-
ed in 8 by 2% foct skips, the loaded skips weighing from 8
to 8} tons. The skips would be filled by the electric shove
els, with some hand work, and taken to the cableways on flat
cars. The skips would be dumped automatically without lower-
ing down into the canyon, permitting high speed and large
-output. The quarry equipment to maintain the pace set by the
cableways would have to be efficient. Work would be carried
on in three shifts per day without interruption, at least
until the river had been turned. The crest of the fill would
be kept level in order to avoid concentrated flow at any one

" each successive

point. Allowing 30 seconds for "hooking
skip, each cebleway should average 33 trips per hour. On
similiar work of this kind these ships averaged 4.3 cubic
yards of lo:se material per load. Assuming this as a basis
of computations each cableway would handle 12? yards per
hour or 3,100 yards per day. Three cableways would place
about 9,000 yards per day, and it would require 69 days to
complete the cofferdam or conservatively three months. By
the middle of October therefore the rock fill should be
completed. The fill would be made water-tight by placing
sand and gravel from Hemenway Wash on the upstream face.

The river should be turned at least by the middle of

September, at which time the fill then in place could be

2‘73 .

made water-tight so that unwaterin; of the dam site could
be started. The lower cofferdam would have been completed
and cableways Ros. 7 and 8 moved to positions 71 and 8?
over the lower permanent cofferdam. As soon as the site was
unwatered, excavation of the river bed would be started at
both permanent cofferdams-probably about october 1.

The lo se excavation for the lower p:rmancnt cofferdam
is the greater and amounts to 343,030 cubic yards. however,
the time element is more important in :sse of the upwer
permanent cofferdam where there are 133,000 cubic yards to
be removed. By October 1, cableway £0. 3 could have been
removed to position 32 leer Hg ho. 4i and 53 to finish the
up er rock fill cofferdam. There would thus be three cable-
ways com ending each permanent cofferdam site.

Electric shovels or dregline excavators would be used
in the hole to load the same ships that were used in build-
ing the rock-fill cofferdaes. The ships would average 4.3
yards per trio. Allowing 30 seconds for "hooking: each cab-
leway could make 13 trips per hour,”lifting out of the hole
and dumping into a "dirt trap" at the top of the canyon.
Work would be carried on continuously for 24 hours a day.
Each cableway would handle 56 yards per hour or 1,340 yards
per day, and three cableways would handle 4,000 yards per
day. At this rate the excavation would require 47 days or
conservatively 2 months. By December 1, therefore, the er
cavation of loose material at the upcer site should be fin-
ished.‘Tork of preparing the foundation would take another

month and it would be the let of January before concreting

could be started. Excavated material suitable for use, in
concrete would be stored in the spillway basin under cable-
ways Hos. 1,2 and 3 B.

There are 150,000 yards of concrete inthe upper per-
manent cofferdam and 85,000 in the lower. by December 1, the
concrete mixing plant would have been completed and the era-
vel pit in Hemenway Wash would have been Opened up, the sho-
vels used in the diversion tunnels, quarries, and dam exc-
avations, having b an moved to the gravel pit. Concrete bu-
ckets would be of the bottomndumning type with capacity of
5 cubic yards per trip. It is assumed that concrete would
be placed on two shifts per day only, the third shift being
devoted to cleaning up and heapina the job going. Each cab-
leway could make 13 trips per hour allowing 30 seconds for
hocking trips. fiach cableway could place 65 yards per hour
or about 1,000 yards per day. One cablevay would be reser‘
ved for gene a1 service, leaving two outfits to place 2,000
yards per day. If this rate could be maintained it would re~
quire 75 days, or until fiarch 15, to finish the work, If
concrete were placed at half the rate assumed, the coffer-
dam could still be finished by the end of Fay in time to
turn the seasonal flood which does not usually occur until
late in June.

One of the characteristics of the Colorado is its ten-
dency toward flashy floods of comparatively small volume.
Although of small volume and short duration thty cause a

great deal of anxiety and would be a source of great dan-

45.

ger. The river may rise from 10 to 15 feet in a few hours

at rest any time during the workin: season. During such a
time the temporary rock-fill cofferdaes would be in d*n-

yer and in order to be in a position to combat the flood

two cableways would be left in position over the upper
rock—fill and one over the lower fill until the perman-

ent coffernam- have been completed. After that they would be
moved to their new positions over the main dam.

t ap ears that the work of diverting the river can be
accomplished in the time avialabls and certainly the per»
manent cofferdans could be at least be brought up to riVer
level from where they could be completed after high water
without rebuilding temporary cofferdams. Tron tie time con-
struction of the railway is started until the nermanent cof-
ferdans are finished will be at least 30 months, allowing 3
months to build the railroad.

Any diversion scheme which does not contemplate build-
ing the p rmanent cofferdvms in one low-water period will
be a very expensive one, since it will involve the part-
ial of total loss of both temporary cofferdans and their re-
placement, and the excavation of the river—bed material at
the dam site for the second time-at least down to the un-
completed structure. While the monetary loss would not be
especially serious, the loss of time, necessary shutdown,
and the demoralizing of the orflanisation would have a ser-
ious effect upon the work.

With the permanent cofferdams successfully completed

the construction of the dam would be a comparatively easy
matter and would resolve itself, more or less, into the dev-
elopment of a plant to put concrete into the den at the

are test practicable spe d and at the least possible cost
comparable with good quality.

Excavation of the remaining lo se material between the
finished cofferdams and work of preparing the foundation
rock would be takes up im ediately. By the time this work
was done the heat of the sumser would slow up Operations
and concreting on a large scale would not be started until
about September 1, three years after beginninfi construction
of the railroad. m

The volume of concrete inuthe dam, exclusive of that
in appurtenant structures, is estimated to be 3,560,000
cubic yards. Assuming 250 working days per season and an
average daily fate of progress of 3,500 cubic yards, it
would require A years to place the concrete. As the dam is
raised the area over which concrete can be placed becomes
less, so that in order to maintain the everege rate of pro-
gress it may be necessary to place concrete in the lower
portion of the dam at twice the average rate. fork would be
carried on for three shifts per day, ‘ut one shift would be
necescarily be devoted to repairing equipment and getting
the work cleaned up in order that concreting ontho other
two shifts may not be delayed.

The maximum rate at which c ncrete would be placed in

estimated to be 3,500 cubic yards per shift of 8 hours,

47.

w bic1 ado cunts to 433 yards per hour and, considering loads
of 5 yards, the requirieents of cal :19 we .service are 87}
trips per hour. The oableways proposed averaae 1? tries
nor hour ecc1, carrying concrete the average distance and
lowerin: to the averafe depth of tie lower two-thirds of
the concrete in the dam. Thus it will require seven or ble-
ways to do the work. However, nine cablensgs are proposed
partly on account of ad ante ed a spacing of cablenays over
the work and partly on account of the fact that some of these
cableways will be used for handling forms and miscellaneous
material. The total time being 7 years after s‘arting. I

The plant proposed for building the dam is very simple
and is one which should perforn the work at a ninimam cost.
It is proposed to locate t;:e mi :ir3 pla .nt on the rim of the
canyon in a pos tion to be under the csblenays but above
fhe top of tbe completed dam so that t31e concrete ms y be
handled by gravity. The mixing plant would be des i3ned to
produce 3,537 on :ic vsrds per 8-hour sb ft or at the rate
of 7. 3 cubic yards per minute._lf EE-yard mixers were ado-
pted it would require a ::ottery of five mixers with prob-
ably a spare mixer to insure the eve 1‘s bility oi‘ five at all
tires. The mixer would be set '11 r t1: material bins and
would dun: into hon are holding at least 9 batches. The

ablewayfl skips would be carried to the minis: plant on
flat cars running on t ac]: under all; "-213.13: cablezmys.

The cement, sand, 3ravel, and cobbles would be troufiht
in on the railroad built over the :Tat r 'al bins and dumned
directly into the bins. For each yar* of concr ate 1. L cusmi

yards of material exclusive of cement are r nuired, or for

-?
(u
C

the construction of the dam 5,130,9é0 cubic yards. If 33-
yerd dune cars are used it will riouire l7l,fi0fi cerloade
of materiel from the grevel hits 7% miles away. Trains will
operate three shifte a day so that when runs of 7,000 gerds
“er day are being made at the dam 336 cerloeds of material
will be required at the rate of 14 cars per hour continu-
ously. In operetion a 7 oer train would probably be brought
from the switching yards to the mixing plant every half hour.
Two recioroceting locomotives with one spare could pra-

bebly benflle the trains between the gravel wit and the swit-

,3.

ching yard. Three geared engines e th e seere could handle

the ctrs fron the switching yard to tre mixing plant. Two

I

switch engines would be required

‘4-

n the yards. A large num-
ber of gravel cers would be required not only to insure
flexibility in Operation but to provide live storage in
cars in the switchinj yards where they could be drawn upon

in cese of an accident on the railroad.

49.

UNIT COSTS
In July. 192} letters were written to several large
manufacturers of cement requesting quotations on gement
snip ed in bulk in very large quantities to be used in

estin ting purposes. The following quotations were rece-

ived: Per
Ebls

fionolith Portland cement 00., Colton, Calif. 32‘50
Colton Portland Cement 00., Colton, Calif. 2.30
Cash 10 days 2:25

Ogden Portland Cement Co.. Ogden, Utah 2.10

Southwestern Portland Cement 00,,Victoria, Califl 2.00

Colorado Portland Cement Co.. Fortlend, Colo. 2.00
Cash 10 days 1.90

Riverside Portland Cement 00,, Riverside, Calif. 2.00

The asnumed costs are as follows:

 

fiesumed cost of cement at mill 12.00

Freight Riverside to Searchlight, 380 lbs. at 23}

per hundred~weight .88

Freight Riverside to dam site,48 miles at its

per ton-mile. .14

Storage and rehandling at mixing plant .10
Total estimated cost in bins at plant 33.12

Rogk_ intern,u n.9,-ar1‘zogk;til;‘goiferdam
Sourse of material, rock in the canyon walls at the

cofferdam sites.

Per Cu.
uarrying and loading into skips on cars: h Yd.
BEE} 1&3? ifigl Edi? t1Harrichsmnovels and hand ”O‘gg
P 0W6? ’ 0
Repairs and supnlies . ’18

Plant depreciation

20
31f55

Total by solid measurement

at: 9;

It is assumed that 1 cubic yard of solid rock will build

1} cubic yards of rock fill dreamed from cablenays (331/3 %

voiie). . Per Cu.

I Ed.

The resulting cost of rock measures in the fill is $1.00

Hauling to cableways .15

Placing by cableways .15

Total estimated cost in dam. 1.30

gravel_and_ cobbles £03; gogcgete_ Per ou.yd.
Steam shovel operation 70.15
Hauling to screening plant .15
Operation of screening plant .35
Plant depreciation .15
Hauling to mixing plant .10

Total estimated cost in bins at mixing plant
30.90

Assuming 50 percent natural send mixed with 50 per

cent crushed sand. ?er Cu.
Yd.
Katnral sand came as gravel 30.90

Crushed sand:
Quarrying and loading rock at $1.50 per cu. yd.,

solid 35 % voide crushed .97
Hauling to crushing plant .15
Cperation of crushing plant:
Crushing .25
mol‘ing .40
Plant depreciation .20
Transportation to mixidi plant .15 -
Total crushed sand 2.12
Tota1.estimated cost mixed sand in
bins at mixing plant 1.50

11th reference to the following estimates it will be
noted that the dost of a den 550 feet hign, with a resern

vcir capacity of 26,000,000 acre-feet, was increased from
$41,500,000 to $76,600,030 by the Special engineering board.

Three items entered into the increased cost of the dam.

(a) Increased spi'lway capacity over top of dam.

(b) Decreased allowable pressures on foundation from 40
tons to 30 tons per square foot.

(0) anr0 ace in size of diversion works.

It is not ass med, however, that the board v ried the unit

costs materially.

 

Biversion works ”4,37 ,350. 00
Dam 19 ,400, 400. 00
Outlet works 4,540,356.00
Spillway 210,060.00
Tailroac 1,3+0,;l0. 00
Construction ca mp 500, 0’0 .00
Eerza..ent izsprc venents 52:22',2W‘
Right of way 250.003.01“

lotel es tizetod field cost
Administration, engineering and
Construction 22} p 7.024 253.0)
al estir'ted cost:
Exclusive of p awer dove looment _
and interest durin3 const. j33,135, :
Ereliminarz estm a;e_
Capacity 34,000,000 acre-feet. Tax. tater surface,e1. l,f50
feet. Fiversion tunnels discharging below power house
To be increased according to Colorado River board report.

Diversion works, sane as for 20,002,000 acre-feet res.

34,258,200
Foundation excavation 1,112,000 cu.yds. 1,840,500
ratinj and drainage 113,434

Cone. in body of dam 3,% ' 0,000 on. yds.Ӥ7 24,920,000
“"”€2e s lizht n;j, r112. in; roalaa; at abutments,

.C-u‘ tha’

railing, and eXtra conc. on abyttents 18 ,415
Outlet conduits - 2,097, " '6
Outlet works, trash racks 304,159
Va-ves and gates 2,082,140
Closing sluiceways 383,915
Track, crane, and elevators 250,193
Const. R.R. as per 20,000,000 acre-foot 2T8. 1,840,810
Const. camp 500,000
Permanent imorovements 60,000
Sight of way . 500,000
Field cost. f ,425,0
Administration, engineering and contin- 9,077,706

gencies 22%;

'4» A n. . 2:14. 1.23.».
Cflgfiflti 11,000,010 root-i.wu; 1711;11

2,733 f at. Diversion tuxdels flisekarginfi a‘ove -
4,.
1L0.
Iii'rersi m. nor-1:“, total 18:1“ t‘rl of tax: ‘el 11,500 ft.
Foundation or c,,total 8m,o10 cu. yds.
21811tinf :H1i “rair'-W;
Cone. in to: ;r of de m, 1,320,000 cu. ydo.
i; tir

- ‘. ~‘
"' ’ PW I x‘ "' l ‘
- .' 12.1.“. .. JI.’ \J. 121‘." '1', ‘.

Outlet condiiits
Trash racks
Valves
Tree“,crane, &
Construction railroad
Coaetruction 3823
Permanent imorovenents

"‘ I o ‘

~
" 1 3' '\ w r) -'
H‘ l o- x) "J ,3. I?( v”:

1C,,K‘j to.

.-
‘ .J

an r1

bgks

fates

21¢“r21r2*?

Total field cost.

fill-x . . r - ._ A
13* - ui_; 8211.»»noii- aioioe .;

Total estimated cost

Rouxhly

.. . 1‘
~ (“.171 (J .‘I ~. ..
XI: 4t! .1; ~31};- a..r

$8, elev.

1_ ,._4
. '3

U‘:

z+\:,} 42 I’QU4
1&9: 50’), O )0

”5.515.730
1,198,500
71,594
9,240,020
51’ Cr”
1,511 284
571,460
1,305,596
235 937
1, 5425: 543
501,010
75,000
200.010
22.955. 593
59 155:032

523,120,730
228,000,000

 

 

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