7 ? '? / official file copy / i
TRANSCRIPT
,.
HYDRAULICS BRANCH 77�? '? � / OFFICIAL FILE COPY / I // /�
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * • * *
* * * * * * * * * *
UNITED STATES DEPARTMENT OF THE INTERIOR
BUREAU OF RECLAMATION
HYDRAULIC LABORATORY REPORT NO. 173
HYDRAULIC MODEL STUDIES FOR SPILLWAY ALTERATIONS AT ELEPHANT BUTTE DAM
RIO GRANDE PROJECT, NEW MEXICO-TEXAS
By
F. C, LOWE
Denver, Colorado June 5, 1945
* * * * * * * * * ... * * * * * * * * * * * * * *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
•
FOREWORD
Hydraulic model studies in connection with the spillv,ay alter
at ians at Elephant Butte Dam were made in the hydraulic laboratory
ef the Bureau of Reclamation, at Denver, Colorado. The studies were
begun by J. A. Lindsay, Assistant Engineer, in September, 1941, and
completed by R. C. Edge, Junior Engineer, about June, 1942. All
tests v;ere made under the immediate supervision of J. w. Ball, Engineer.
Centents
Forewerd
1. Introduction and summary of results.
2. The Elephant Butte Dam - Conditien iri 1939.
3 o The spillway.
4. Inadequacy of the existing spillway design.
5. The 1:40 hydraulic model ef the spillway.
6 . The procedure f the tests.
7. Model studies en the existing spillway (1941).
8. Pressures on west spillway well.
9. Temporary \''alls te protect against anticipated floods in 19420
10. Discharge of pretotype spillway in 1942 and comperiaen with model tests.
11. Model studies for permanent spilb:ay el teret ions - Baffles in transitien sectien,
12. Tests with dentates.
13. Tests with training walls.
14. Tests '.Alith channel cover and overhanging baffles on channel. walls-the final design.
15. Additi0nal tests on channel.
16. Revisiens to cylinder-gate cutlets.
17. Discharge of spillway into river channel.
18. Rating curves for existing and final designs.
19. Abstract of corresp0ndenceo
UNITED STATES DEPARTMENI' OF THE INTERIOR
BUREAU OF RECLAMATION
Branch of Design and Construction Engineering and Geological Control
and Research Division Denver� Colorado June 5, 1945
Laboratory Report No. 173 Hydraulic Laboratory Compiled by: F. C. Lowe
Reviewed by: J. E. Warnock
Subject: Hydraulic model studies for spilh,11ay alterations at Elephant Butte Dam - Rio Grande Project, New Mexico-Texas.
1. Introduction and summary of results. This report is concerned
primarily with model studies to improve the hydraulic design of the
spillway at Elephant Butte Dam. In addition, several dissertations con
cerning the prototype have been interposed to present a more complete
picture, or background, of the entire program concerning the spillvay
alterations.
Subsequent to the completion of the dam in 1916, the hydraulic
design of the spillway was questioned by several engineers. When
water discharged through this spillway for the first time in August
1941, it �as realized by all concerned that it was inadequate to handle
floods which occurred in the Rio Grande River. Accordingly, a program
for spilh1ay alterations was proposed, the alterations to be based upon
designs evolved from studies on a 1:40 hydraulic model.
In model tests of the existing design, '1-'Iater piled against the
walls of the spillway channel or chute, forming standing waves. These
waves topped the channel walls at discharges greater tban,8,000 second
feet, limiting the safe spill�ay capacity to this quantity because bed
rock upon which the spilhiay was built contained much shale, and would
easily erode, A maximum flood of 35 0 000 second-feet would cause very
serious damage, if not failure of the spillway.
Timber \"alls, to extend the height of the channel walls for tem
porary protection until permanent alterations could be completed f were
first studied on the model. Such ¥ialls ¥1ere actually erected in the
prototype in the spring of 1942 when it became apparent that the spill
way would be needed to bypass floods. On June 5, 1942, the spillway
disc�arged ? i OOO second-feet. It was then observed that the timber
walls were properly located to deflect the standing waves, and that
the waves would overtop the channel walls at a discharge of approximately
8 i 000 second-feet, as indicated by tte model studies. Observations of
the prototype also suggested tr.at air would mix v.1ith the v-:ater to have
the same effect as increasing the height of the �aves against the
channel wall, thus the spill�ay capacity in the prototype may be some
what less than that indicated by the model.
Model studies for permanent spillway alterations included tests
using baffles, dentates, training walls, and channel covers to force
the flow to change its direction, to enter the spilh:ay chute in a
uniform manner end not to pile against the walls. Baffles and dentetes
were not satisfactory. Training walls could be used but· structural
difficulties v,ould be encountered. A single training well wHb a
channel cover over a portion of the spill�ay, and overhanging sections
or baffles on tte channel walls immediately do¥rnstream from the crest
formed the arrangement selected for the final design (figure 1). ! This
design was adequate for discharges to 35, 000 second-feet.
2
FIGURE: I
6 --------D S. edge of bridge pier
L E
--,-+-.I-'--
-----·Controcl,on 10,nf 1n existing wall
' J
'\0· ,r;. ��,
s
'/>i
o""
� :;��;. -� L = 8712'
� o'r;.'
' <:- \
• 0
. • or;,
-Top of wall -�_,r:., 6'/"-l.._ [I 4-39765 ,• /
_(/'
------Contraction joint----....
"·--:,4" D10.
{,,
·�
crf� �--.. �'"""'"' \ - Top of existing.': . 1
4- 4 8 wall. El. 4369.59' r> .,, ,a.' , R.,,_,418
5,
1 -_ z7 · I L -
.· "'·
L -;-----------,-------;.,_--¥-----------+-
f---- _-_-_-_-_-_-_-_-_-_-_.,.:;,-... ---��,_· _- _ -_ -_·_-_-_-_- _-_ -_-__ \,!!11.�..L.---
0 ·--1"'-, ' ·'--Bridge pier
�·-.. 3133'
o-:N'.,<; ; : _ .. ·· Bolter f" per It.
>:ft'� SECTION A-A
----� -
· --- -----·········�
·" ,., C .
. //•
2167'
........ 20 0· ......... .. �{:t:-- · 20 o' . . ..... .. ':':Jr:�: ..
,,,· ...•.......... ·.·······.····. :·1 /4 ',
;.; •.• ____ 'If . !;:; :� .94;,s.· ,,1 .--r._ .. :� ·-... �(>1
PLAN OF CHANNEL COVER -,· c :c:; ·. 9"'
62 57'
/ .. -·f Spillway ---- ---��l __ y · .... ,;
·
- 5100'
__ .... -20" Depth of ro,I< wdh 4" of grout on top------- ............. .
�24':-<-
SECTION 8-8
...-·Barrer 1-"per ft /
8 .
Existing
:, -
SECT/ON C-C
_ .. -Batter f per ft
.. .. ... 62.67' ...
.
....... ... .
·2161'. ········>i ····· ····· ·····-··--·········-�----··········-··
. 27 ,5· --------------;--------r------13 35 ......... 1 ' '
ELEVATION 0-0
\·
J_,, "''"
Bottom
......... 2161' ......... ..... ,_;
,.. .. 53.00' · .,,
PLAN OF SPILLWAY SHOWING LOCATION OF BAFFLES
SECTION E-E with
;..----------· 9'-5" ...
SECTION F-F
-· ........... 9'-3" .. .... ..... ,.,
-� --'l'-
-�i< ... 5·-�-
:.a: "" . .. .,.:_,,,,. ··. -.. · .. •·
;.. ... .. 5'-0" . ....
SECTION 6-6
;
-----J ---,.-·--;::;;; / 117 "ii.
---
/ • .-·-Weep holes-.'
\ •
I
------I � co ,, '/Jcrete ................ J'o g,,,. ---. e ul7'1i'or ............
/lJ 9r ---
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.
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Key .... /·,1 :lo..,,--·.-··«·· : -</ • ,, ' ..i
(_-[ x,sf,ng jlra/1 .. ..-'.
SECTION H-H SECTION J-J
El 4347.39--.
I , I I
', I --.... I
,..._,_ I
....... _______ ,
Ul'I/ITED STATES
OF.PAR TAI ENT OF THE IAITCRtOR
BUREAU OF RECLAMATION
RIO GRANDE PROJECT-AIIE"WIIIIEXICO-TEXAS
ELEPHANT BUTTE DAM
SPILLWAY ALTERATIONS CONCRETE DETAILS OF CHANNEL COVER
DRAWN..... �.,(if._ Sl.lJIMITTCD .
TlfACED. If.JI..'! ........ IIECOMltl£MD£1J .•••••••...•.•• ---.
CH£Clt'£0 »@. A,.,.,,IWCIJ ..
Dt£11YE11, COiOIIAIJO .,_c,.,o, -.s 24- 0- 724
Upon completion of the studies of the spillway channel, revisions
to the four outlets under the spillway crest were studied by the model
{figure 2) p and the flow from the spillway chute into the river bed, or
tail race, was observed. The relation of discharge to reservoir eleva
tion was determined, to furnish rating curves to estimate prototype dis
charge, for tbe existing and final designs.
2. The Elephant Butte Dem - Condition- in 1939. The Elephant Butte
Dem is located on the Rio Grande River at Elephant tlutte, New Mexico,
about 120 miles northwest of El Peso, Texas {figure 3). This concrete
gravity-type dam is 1 P 674 feet long 1 with the spillv·ay crest at eleva
tion 4,407 P 191 feet above tte normal tailv-ater in the river belOY!.
However, the maximum height of the structure itself, above the bedrock,
is 306 feet. Upon its completion in 1916, the reservoir, having a
capacity of 2,638 P 000 acre-feet, was used for flood control and for
storing •rater to irrigate tl:'e surrounding region; In 1941, the power-
house v·as completed so the dam now serves t tree purposes - flood con
trol, irrigation storage, and power development.
Naturally, through more than t·wenty-five years of service the dam
has suffered a certain t:l.lllount of deterioration, In a letter to the
Chief Engineer, dated Januory 3, 1940, R. S. Lieurance end R. F. Blanks
describe the condition of the dam and its appurtenant works as they
found it on an inspection trip during the 1neek of December 10, 1939, and
in this letter made recommendations for repairs. With the exception of
the spillway, no unusual repairs were considered necessary. It was
recommended thet portions of the downstream face of the dam be resur
faced; all drains be opened to carry eway leakage; the lighting circuits
4
f Of gate
:------5'-o" ------------
-------4·-sJ" -------� &';<- ,· -.-..c- 1'-�- l1-*--/'�
: l . :,. :'--r,';:l::::::i1:---I �:�
Ellipse-'
' � '
· SECTION A-A
Existing cu t-off wolf-'
PLAN OF SPILLWAY
�-------10'- "--------->i
ELEVATION B-B
f Spillway __
.-Connect cut-off wall to ex,st1ng , cut-off wall on both sides.
•.
.:,o" ,, - \,
,:t·---El. 4382.00,, ' \I
�--
'·Blackout for grouting gate guides
SECTIONAL PLAN E-E
Vorle x e//mina1or - _
Max. H.W El. 4415.00,,,
El. 4396.00-.,,
,· 8 Guide rod---- -- -,
6''
,.-----'. Bottom of existing ,
concrete - - ___ f ___ . ; 15'' ·o'
Hr:i, /'' Pipe sleeve- __ ":. ___ ": r------r-----'---;r=;==�--lT qi -- � � :: -I ' I E14395.50--r��
: ::: ' ':' ' "' ' : �---6'-o"--:---
' '
,, C, _,
,.--u 4382.00 1--�_._.,___�����--�..,__.,...... _ _,=-,------·-.l'. �===========j : t---::.-::.-::.-::.-:;.-::.-::.-::.-::.-:j / I
I I I
G'"1"""iifl��n--'-'---'.:�-� a ���-,........ Blackout for grout,n · ·, �-: ·
gate seal - - ______ - - -
-<: D
SECTION C-C
J .. o·
,A Conduit
-Crest El. 4407.00
SECTION F-F
_ --Gate r
ems--- -
I
SECTION o-o
F:GURE 2
I [ Br,dge- \
e<· � to-'
�ier o�d
\_ \
SECTIOWAL PLAN 6-6
tine ""f!d concrete-,
/
' /
SECTION H-H
. J'.·\. - �,' 1:L 1·.
·J·l..,-��.,.-,-�
, ..
· · :� > _ -Blackout for gate guides
., .
UNITED STATE$ OEPARTIIIIENT OF' THE INTERIOR
BUREALJ OF RECLAMATION
RIO GRANDE PRO,IECT-NEW MEXICO-TEXAS
ELEPHANT BUTTE DAM
SPILLWAY ALTERATIONS
CONCRETE DETAILS OF GATE STRUCTURE
DRAWN.
TlfACED.
K.J. G .
£.E.B.
CHECKED .
. . SUBMITTED.
. . ,RECOMMENDED •.
DENVER, COLO ADO, IIIA CH
FIGURE
3
be rewired; channel improvements be continued; and repairs be made to
the parapets and the roadway on top of tl:e dB!'l.
Some damage to the spillway was observed. Compression failures
were noted on the spandrel extensions which form the roadway above the
spillway, and cracks were observed on the ogee section downstream from
the crest. More important, however, the hydraulic design of the spill
way was questioned seriously, and it was doubted that the spillway
could safely carry the quantity of water for which it was designed.
It was recommended -
"that detail flood-control and spillway capacity studies be made in the light of present-day conditions and all available information. Depending upon the results of such study i
hydraulic model tests to determine the spillway operating conditions and required remodeling should be made."
3. The Spillway. The spilh,ay is located at the west or right
end of the dam �ith its crest parallel to the axis of the dam
(figure 3). The crest, at elevation 4p 40? P is 295 feet long, and 1L2
feet below the roadway over the top of the dam. This spillway may be
described as consisting of three sections: (1) the crest section P
(2) e transition channel, and (3) a chute. The crest section consists
of a shelf upstream from the crest, et elevation 4396. 0, end the
spillway apron downstream to elevation 4381.6 (figure 4). This sec
tion includes four 10-foot diameter cylinder-gate outlets which pass
underneath the crest and discharge upon the apron. These cylinder
gate outlets increase the spillway capacity and permit the spillway
to discharge when the water surface in the reservoir is between
elevations 4396. 0 and 4407. 0. The transition channel begins on the
7
r.. 1:;,,.
,, ,
REi'ORT Oi, rll.GH PKESSURl RESEF<VOIR OUTLETS
£/er 4422.5,
\.>·· �-.· ....... ""_=-=����=======l t=========::!c:::: '=======
CAM
UJ/?Cr&le Slabs1 �?eY.4'41867� I / J·. ,.· .·,• l• .. • .. , "·'· .-<·.•!" ,_./ •. ,_.,•
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H,�I.•)··· ' .. ·: �-/; . 'l . ' . ' .
· · � ,1--_____ _.....,.0c;-�_,.-;1.,-.!#_c,_;,,_'f:la_a_e._,ls__.: �..
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• • • • • • • • • • 0 . • • • • • • • •
11
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SECTIONC-C ,z· o
5UILE
.. ,.
'
295' 57'{j" 60'0' 60·0· 60'0' 57i5'
�----------------- - ------------------1------------� l5 ·or=
0 0 0
Der44ZZ5
E,eva//on
0 0
a .. . I
I
.
0 0
0
. "---__,. . '---� A L------------+-------- ________ J PLAN J . f3
.Sp1!I//Va Crest 4407
.SEC TION.4L .ELE//,4T/ON .4-.4 0 I,,
10' zo· I
30· ' 40' '30'
FIGURE 4
!),:,-p,4,qrMCNT or TM£ INTCR/OR t./NIT£0 5T.4 TES R.CCLAMAT10N S.C'Jf>VICC
RIO 6/?ANfJf PROJf'CT-NfJ11Mfl/CO-Tf'XAS f'LLPl1ANT BUTT£ OAM
SPILL WAY & CYLINDER GATE. frown C.4M Checked• r,J· <'.:
20400
\ -..... ,
1
spillway apron at elevation 4381.6, station O+o0, and joins the chute
at elevation 4347.50 P station 1+20076 (figure 5). The chute 9 50 feet
wide, extends to station 7+15 0 at elevation 4205.0. The total drop
from the crest, elevation 4407.0 to the mouth of the chute, elevation
4205.0 is 202 feet.
With the water surface at elevation 441.t.0, four feet above the
crest O the spillway will discharge approximately 16, COO second-feet,
8,000 second-feet over the crest and B P 000 second-feet through the
cylinder-gate outlets. As tbe water surface rises above elevation
4411 0 0, the spandrel arches forming the roadway above the crest will
restrict the flow somewhat. However, before the v.'ater could rise so
high, that there would be danger of overtopping the dam, the spillway
discharge would reach 35,000 second-feet, the maximum flood that is
anticipated in the Rio Grande River.
This spillway was not built as one project. The crest section,
including the cylinder-gate outlets, a1;3 shown in figure 4 was com
pleted in 1916. The construction of the transition channel and chute
downstream was delayed for several ye:ars, end was not completed until
1922 0 From the beginning there was uncertainty as to the proper
location and alignment of the chute. While it would have been desirable
to locate the chute at right angles, or normal, to the axis of the
spillway crest the terrain was unfavorable. When the crest section
was under construction, before 1916 0 it was evidently planned to turn
the chute about 23 degrees 45 minutes to the right of the normal of
the crest, looking dov·nstream e Accordingly, the tunnels of the
. -J
.....
.•
Pre5en L So /,no{/ Sl.-:.1cf .. 1rc -�.st:..,, c-,v�fe
, ''loor h, b• ?:m.Jvt"d \ >
GRAVITY WALL
lop Of /Yo!/ f/43:Jll
if7naLle (,111/7. 50)
0
,For Numrer or !JtJ'0 Long'/ !Jor.5 m lb.rr��nl roofino.5 5::,: Tab/� "
Canh/t:¥er rYa//.5
. ?ro/ilc al frf'I trail :· .Prof;h on t
SECTION ON fi
50 100 150 el t 11 I 1rl r I rlt I 111111 I 11
Scale of Feet
rf Spi!lw0t,1 ,
P L A N
' ' I L _ _ _ _ _ _ _
l
---�,?,!,�: !' _:__ 5h:, J;/5 rhw,
I A -+- _J
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Ir.as and orouf Z' o.F l?�f o,r fil/. .-- .
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GeNeRAL PLAN
N ote ·-Sluhon 6+37 lo 7 r/5 Aftn. Thi,:;!< or rloor Z4'
3cale ,,100'
Confrod,on Joinf.5 al cbouf ZS'c.foc. as shown /n flan. Pour ffoll in c.('::r. --:ch- secfions .. ...
.·· 4' Hooks · � t : *'"J,lg's I, ?,3 : and 4 lJars -- ·· ,,::
F I G U R E 5
ELEV. A-A
, r� F �=::,4--1--. __ .__J'. T ---,�=-...::.....J
C r , + I--- - - .B - - - - -k{i: ,. Con.sfrucfion �55
l
!'or Ya/u,,s o.F A -.B-c; and .F Sec Tobie.
\
CONTRACTION JOINTS
E5 T/MATED QUANTITlcS. Concrefe !'Yifh Plums 1650 /i"ein;f'orced Conr::rck .3500 fi'einf"orcinq Sled 48000
DEPART.ENT 0, TH• INTElnOlf.
UN1T•D STAT&'B RECLAMATION 8._..,�-.
"' RIO <JRAND/: STORAGE N.eW ML?f/CO
"" ELEPMANT .8UTTc SPILLWAY L/Neb CHANNEL " , · .
cylinder-gate outlets did not go under the crest at right angles to
the axis but turned to the right 23 degrees , 45 minutes to discharge
directly into the chute, figure 4 0 When constru ction of the chute
began , it was found that better foundat ion rock wou ld be available
and that a large savings in constructi on costs would be possible if
the cr-ute turned the opposite directi on; that is , to the left of the
normal of the ax is of the crest. Accordi ngly, the chute ·was located
40 degrees, 45 minutes, to the left of the normal of the crest and
j oined to the crest sect ion by the transition channel between stat ions
Ot- 00 and 1+20. ?6 (f igure 5).
4. Inadequacy of the existing spillway design. This location of
the chute means trat water flowing over the spillway crest must turn
40 degrees, 45 minutes, to flow into the chute, and that water flowing
through the cylinder-gate outlets must eventually turn through an
angle of 64 degrees, 34 minutes. Actually, water from t he outlet ad
jacent to the west channel wall P the right well looking dovmstream,
must turn through an angle of 91 degrees to flow along t h is ad jacent
west wall. At the time of the constructi on of the spillway, before
1922v flow in steep channels v<:as understood only vague ly , or not at
all , and model studies to assist in th e hydraul ic design of such
structures ·were not commonly used . While the chute was designed to
carry a flood as large as 35 0 000 second-feet, insuff icient consid
eration was given to the effects of a change in directi on of the flow.
Water flowing dovm a steep chute in which there i s a curve , w ill
pile �p or fo�n a standing wave on the outside wall at the curve. This
11
wave will b e reflected to the opposite channel wall further downstream,
then reflected back again, and so on to the end of the channel. * In
a chute as steep as that at tbe Elephant Butte spillway the height of
such a standing wavd could be several times the depth of flow in the
channel ,
Prier to the inspection of the darn by R. S, Lieurance and R. F.
Blanks , December 10 , 1939, the spillway bad never been used, but, as
inferred in t heir report of January 3, 1940 , silting of this dam
would eventually reduce th e storage to a point ·where the spillway
would be needed. On July 11 , 1941, the cylinder-gate outlets dis
charged for the first time. A maximum flow of 2 , 742 second-feet
occurred on July 17. The operation of the cylinder-gate outlets
du ring the months of July end August is described in a chronological
record in a letter from Pro ject Superintendent L. R. Fieck to the
Chief Engineer, dated September 4, 1941 . Photographs in that report,
two of which are shown on figure 6, show water flowing through the
tunnels, striking the ad jacent west wall of th e chute to form waves
which are almost as high as the channel wells o The waves tended to
reflect on the east wall of tte chute further d o-Y.n stream, although
their height was greatly diminished. In tbe letter of September 4 1
Fieck emphasizes in paragraphs 6 to 9 , inclusive, t�at the existing
channel is completely inadequate to handle large floods, and that
* For additional information on this type of flo¥1 see the report by A o T. Ippin and R . T. Knapp "A Study of High Velocity Flow in Cu�ved Sections of Open Channels" prepared at the California Institute of Technology for the Los Angeles Flood Control District, March 29, 1936 0
A, ALL FOOR SPILLWAY CYLINDER GATES OPl!N FULI., DIS::HARGE 2, 093 c , t, s,
B, SPILLWAY CHANNEL, ALL FOOR CYLINDER GATES OPEN FULI., DISCHARGE 2,093 c .t ,s .
ELEPHANT BUTTE DAM SPILLWAY DISCHARGE IN SPILLWAY AUGUST 1, 1941
FIGURE 6
model studies should be made to show the action of the spillway et
large di scharges and to determine necessary alterat i ons to make it
safe.
5 . The 1: 40 hydraulic model of the spillway. A model of the
spillway was bu ilt on a scale of l :40 i wh ich included a small por
t i on of topography upstream from the spillv·ay es well as the spill
way crest sect ion, transition channel, and chute, f igure ?. It was
also contemplated that disch arge from t be chute into the river bed
might be studied but the model was not extended beyond the mouth of
the chute, station ?+15 . 00, until the major problem, wr ich concerned
flow down the transit ion channel and in the chute, had been solved
( secti on l?).
The topography upstream from the sp illway was formed with sand
and wh ile only approximate, in conjuncti on with a rock baffle it was
suff icient to cause flow to approach the spillway crest properly,
(f igure ?B) . The crest section , which included the spillway above
elevati on 4281.6, tte cylinder-gate outlets, piers and arch roadway ,
was built as a box in wh ich there were set sheet metal templates �ith
neat cement cast between them . The cyl inder-gate outlets of three
inch seamless tuping were cast in place . The cylinder gates were
mounted on pin supports and fastened to the pier�. The piers and
arch roadway were made of redwood held in place on the crest by p ins.
It was necessary to include tr. e arch roac"way in the model because , as
aforementi oned, the spr ing line o f the br idse arch at elevati on 4, 4 11
14
-IN ,n · ' en , I t_
'
L--f,'1--..,.,.-...., '
' '
,, 00
C h u to --_
C -<-7
-<J
Redwood 0.3'.':,. <· "N splash stri p - - - - -
�
- --, ! ! __ 1 --
t
�
D E T A I L "A"
, " C . ' - · · - - - - - - - - · - · - - - - - --- - 1 4 - 10 - - - - - - - - -- - -- - -- - - . - - - - --.
· · - _ - ----"'
),<:,- - - -· - - -- - - - - - - - 9'- 4¼� - -- - - - - - - - - - - - ---
., " � "' C
! ' ' A - P L A N
0 I 2 3 •
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P R O T O. M O D E L 1 + 2 0.76 4369.00 3 8.00 0. 950
+50 4360. 0 1 4 6.99 I . I 7 4 + 75 4352.42 5 4.58 I . 364
2 + 00 4 344.80 6 2 .20 I . 15 5 5 + 25 4337.28 6 9.72 I . 7 4 3 +50 43 29.58 7 7.42 I . 9315 +75 4 324,67 8 2.33 2 .0 5 8
3 + 00 4 3 1 9.67 8 7.33 2. I 83 + 25 4 3 1 4 . 75 9 2 .25 2 . 306 + 50 4 3 1 0.06 96.94 2 , 4 2 3 + 75 43015. 1 7 I O 1 .83 2. 545
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'T + 00 4UO.OO I H. 00 4 . 425 7 + IS 4 30. 1 77,00 4 . • n
T A B L. E II
ltlODEl v•LU£S Of �LEYATIOMI I N TRANIIT\011 CIIANNEl DATUM• CR£11l EL,.4411.0
ELEVATION F E E T BELOW CREST
P ROTO t,'I O O E L 4 � 0 1 . 43 5 . 5 7 0 . I 3 9 4 n 1. r o 9.90 0 . 2 4 7 4369.00 3 8. 00 o. 9 5 0 4405. 1 9 1 . 8 1 o.oo 4 398.67 8. 33 0. 208 4 3 9 1 .86 I �- I � o . 3 7 8 4 3 84. 1 0 22.90 o . 572 4 3 8 1 .0� 25. 96 0 . 6 4 t 4377. 1 8 2 9 a2 fl . 7 4 5 4 369.00 �8.00 0 . 950 438 1 .60 25.40 0. 6 3 6 4 377.30 21.70 0 . 742 4347. 1 0 69. 90 1 . 497 438 1 .60 29.40 a. 6 3 5 43 77.30 29. lO Q , 7 4 2 4370. 1 0 31.90 0. 9 2 2 4 3611.40 47.60 I. 1 90 4 3 5 3.20 5 3 . 80 1 . 3 4 5 4347, 10 59.90 I . 497
P ROTO. 4 3 4 7. 1 0 59.90 4 3 3 9.00 68.00 4 3 3 2.20 74. 80 4 3 2 5.20 8 1 . 80 4 3 1 8. 1 0 88. 90 , 4 3 1 1- . 1 0 95.90 4 306.60 1 00.40 4 302. 1 0 1 0 4.90 . 4 297.80 1 09.20 4 2 9 3.60 1 1 3.40 4 2 8 9. 1 0 I 1 7.90
4 2 80.20 1 26.80 4 2 7 5.80 l 3 1 .20 4 2 7 1 ,50 1 35.SO 4 t87, 1 0, 1 ::19.90 4 2&1.80 1 44.20 4 2 5 8.50 148.50
4 2. S l.70 i !U- 30 4 242.70 1 84.JQ 4 2 30.6.0 1 76,40 Ott,IG 1 84.IO 4 105.00- aot.oo
05,00 202.00
M O D E L 1 . 497 I . 700 1.870 2.045 2.222 2. 397 2.5 1 0 2.625 2. 730 2.835 !:. 947
3. 1 70 3'.280 3 . 3 87 3.497 �805 3. 7 1 2 �"2 •• 1 0 7 4.4 1 0 4 6.to S,Q50
, 5.0&o
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1"1 10· Forms ... ,:
b •. J P C
0 - P L A N O F S P I LLWAY C R EST S EC i l Q.N A N O T RA N S I T I ON C H A N N EL
10 20 30 40 � 60 S C A l E I N F E E T
E - E L E V A T l°
ON OF S P I LLWAY C REST S EC T I ON ''-Floor at modei.
A N D T RA N S I T I O N C H A N N EL
R I O G R A N D E PROJECT- N EW MEXICO·TEXA.S
E L E P H A N T B U TT E D A M S P I L L W A Y A LT E R ATI O N S
a. o W ....
D,ETA I LS OF 1 : 40 H Y D R A U LI C M OD E L O F S Pl L1.WA Y l'.C,L.
0 � 0 .... � u
was only four feet above the crest and discharge s greeter than 16 P OOO
second-feet would be atfected by the arches.
The t ransition channel, beginning at the downstream edge of the
spillway crest se �tion, at elevation 4381 .6 or station o+-oo , was
built by forming plywood sides secured by one -inch lumber forms or
templates. Neajt cement '4/8S then poured between these sides to form
the floor of thf channel a
The chute, beg inning at station 1+ 20.?6 and extending to station
7+ 15 . 00 was built with treated redwood sides and vri th the bottom of
asbestos-cement board. A special survey was made i� the field to
ascertain the elevations of the floor of the chute and transition
channel so the model could be built sccurately as possible .
6. The procedure of the tests. In testing the mode l the prin
cipal objective was to observe the manner end extent to which the
water piled against the channel walls of the transition section and
chute. Photographs were adequate to re cord most obse rvations and
only a few p hysical measurements were required, which we re discharge ,
water surface elevation in the rese rvoir, a nd, in some te sts , pres
sure s. Each mode l arrangement was studied at discharge s of 2, 0C O,
4 9 000, s , ooo , 121 000 second-feet , and so on until the capacity of the
spillway was exceeded - or the d esired capacity of 35 1 000 second-feet
was reached . Discharge was measured by the laboratory venturi meters .
The v;ater surface of the reservoir was measured by a hock e;age, sue h
records being made only dur ing calibration tests on the mode l (section
18) . Pressures were measured by piezometric connections l ocated as
the require ments demanded, (section 9 end 14 ) .
15
S lope adjustments to correct for roughness in the model were not
attempted because the nature of t he correction �as uncertain as far
as t he particular type of study was concerned. By the very nature of
the problem th� tests were mostly qualit at i ve studies in wh ich the
effects of slope corrections would be immaterial.
?. Model studies on the existing spill\''ay ( 1941) . The existing
spillway design , as of 1941 , was studied wit h the model a t discharges
from 2,000 to 20 9000 second-feet. At e disch arge of 2,000 second-feet
t r.rough tbe cylinder-gate outlets - comparable with the prototype flows
which occurred in 1941 - there was sufficient resemblance to the proto
type to assure that t he model studies would be reliable (figure 8).
Water from the cylinder-gate outlets st riking the west wall of the
transition channel ( the left wall looking upstream in figure 8) piled
up to form stand i ng waves along t�is wall. Entering the chute t he
water spread, but tended to form, or reflect, a standing \'lave on the
ea st v:all near station 2+46. This general pattern remained t he same
as disch arge i ncreesed althoue;h the height of t he waves on tre west
wall increased, the wave on the east wall near station 2+ 46 became
pronounced, and another wave formed on the west wall further down
stream , ne ar st ation 4+90.
At e disch arge of 8 9 000 second-feet , water began to splash over
the west wall near station 1+ 20. ?6 where the transition channel joins
the cr.ute (figure 9A ) . As the discharge increased t he spill over the
channel wall became gre ater , occurring also where the other waves
1.7
A, THE PROTOTYPE, DISCHARGING ABOUT 2, 000 c, f ,e , THROUGH CYLINDER-GATE OUTLEJ'S. AUGUST, 1941.
B. THE 1 :40 MODEL, DISCHARGING 2, 000 c . r . s. ( in prototype) THROUGH CYLINDER-GATE OUTLE!'S, AUGUSJ', 1941.
ELEPHANT BUTTE DAM SPILLWAY COMPARISION OF FLOW IN MODEL AND PROTOTYPE
>zj
� ro
A, DISCHARGE B, 000 c. f. s. , CYLIND�.R-GATES OPEN. B. DISCHARGE 20,000 c . r. s . , CYLINDER GATES OPEN.
'° 1: 40 MODEL OF ELEPHANT BUTTE DAM SPILLWAY
were located. At a discharge of 20 8 000 sec ond-feet, weter spilled ever
the west wall in front of the exit of the left cylinder-gate outlet,
over the west wall near station 1+ 20 . ?6, ove r tre east wall near
station 2+46, and over the west wall near station 4+ 90 (f igure 9B ) .
Increasing the discharge beyond 20 0 000 se c ond-feet rapidly increased
the quantity spilled.
However, no attempts were made to measure the rate of flow over
the walls although it was guessed that there would be as much as 100
se cond-feet at a discharge of 20 8 000 se c ond-feet. Regardless of the
quantity , this spill over t he walls could not be tolerated because
the backfill and foundation rock contained shale which would quickly
erode . It f ollows that tte capa city of the existing design was,
therefore, only 8 8 000 se cond-feet.
8 . Pressµres on west spillway wall. Studies on the existing
design included pressure measurements on the west wall o f the tran
sition channel and chute for discharges of 8 8 000 , 12, 000 and 16 , 000
se cond-feet with the cylinder gates both opened and closed . The
location of piezometric conne ctions and a table c ont aining meesurements
are shown on figure 10. As anticipated, there was a p ressure in c-r-ease
where water piled ar,ainst the wall. No unusual pressure conditionP,
such as negative pressures , could be observed . It we� c oncluded t r.at
no additional pressure measurements would be necessary until the
f i nal design was obtaine d .
9. Temporary walls to protect against ant�. c i pated flcods in 1942.
A spillway capacity o f 8 0 000 se cond-feet was completely i nade quate,
20
I · . 2-. : - . 3 ._ - -4 · ->.
-- ---- - - -t·- -, -
We s t w a l l --
>
I
F I G U R E 1 0
- - - . · 1· - - ::,-, I I I I
C h a nnel floor- - - - - ·
E L E VA T / O N - WE� T
P I E ZO M E T R I C P R E S S U R E S O N WAL L
DIS CHARGE I N C.F. S, POSITION OF GAT ES O P E N P I E ZO M ET E R N O.
I 2 . 4 2 1 0 . 0
8000 I
CLO S E D
2 . 0 4 . 0
1 2 ,000 O P E N
4 . 8 1 6 . 0
- ·-
CL O S E D
4.8 -- -- ·--8 . 0
! 1 6,000 O P E N C L O S E D
3 . 2 2 ,0 1 2 .8 1 0 .0 --� - - - -- - - - - - -- �-
- - --4 ---- - -5 -- - --6 7
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8 . 0 8 .0
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9 . 2 -7. 2 - -8 .8 6 . 4 6 . 0 --�- J- -6 . 8
8 .0 � - --------· --� ---1 9 4 . 0 2 0 8 .8
-
4 . 8 f---
6 . 4
3 . 6 ---4 , 0 7 . 6 -6 . 4
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1 6 . 0 - -· 1 6 .4 --1 0 .0
- - -1 2 . 8 -1 6 .0 --- -
- -- - -
- -
1 8 .4 i o .o ----1 2 .4 I I . 2 --- ·--
6 .0 1 3 . 6 2 . 0 8 . 8 - -4 . 0 1 2 ,0
8 . 8 1 0 . 0 4 . 0 1 2 . 0
>--- - ---7. 2 8 . 8 4 .8 1 2 .4
1 2 .8 1 4.0
-4.0 -8 .0
1 2 .0 1 5 . 6 1 4 . 0
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1 6 .8 1 0.0
-1 2 . 0 1 0 .0 1 1 . 2 -- -1 0 , 0 1 2 .0
-t-- -- ·--- -- --- -- ---� 4 . 0 8 . 0 8 . 8
1----- -- -1 2 .0-8 . 0 1 2 .0
R 1 0 G R A NDE P R O J E C T - N EW M E X I C O -T E XAS
E L E P H A N T BUT TE D A M
-
I 0 .0 1 2 .0 -
6 .8 -6 .0 8 .8
-- I-9 . 2 S:-o
8 . 0 7 . 6 6 .0 7 . 6 4 .0 5 . 2 2 .0 4.8 3 . 6 -6 . 0 - � - --6 .4
1 6 .0 ·-- ----1 6 .0 - ---6 . 0 - -
1 0 . 0 1 0 . 0 -1 9 . 2 18 .0 20.0 --1 6 . 0 -1 9 .2 1 2 .8 1 6 .0 1 2 .0 12 . 0 1 2 . 0 1 4-.0 1 0 .0
- -
---
- --
-
-
---
14.�
S P I L LWAY A LT E R AT I O N S BY HY D RAU L I C M O DE L- 1 : 40 S_CA LE P R E S S U R E S ON WES T WAL L O F EX I S TI NG DES I G N
and from the model t est s it was hoped that a method could be de
vised whereby the spillway could be altered to accommodate a maxi
mum flood of 35 p 000 second-feet . However 9 et the time the tests
were planned (November 1941 ) there was en •unusually large quantity
of water stored in the Elephant Butte Reservoir , end should large
tloods occur in the spring of 1942 it was almost certain that the
spillway would again overflow o Therefore , the first model tests
were used to develop a temporary and relat ively inexpensive
method for making the spillway safe .
T imber bulkheads or walls placed on top of the channel walls
were sugge sted as a temporary protect ive works s ince they could
be installe d on short noticeo The se walls were eight feet high ,
built wit� 3- by 10-inch lagging fastened to 6- by 6- inch post s o
The post s , 16 feet long , were t o be fastened on the outside of the
walls of the transition channel and chute ( figure 11 and 12A) o
The walls were installed in the model to scale , figure 12 .A.
and a series of runs were made at discharge s up to 35 , 000 second
feet . It was found that the 8-foot walls would be sat isfactory
for d i scharges up to 28 � 000 second-feet �igure 12Bo This maximum
discharge could be increased by increasing the height of the
temporary walls , but this was not considered necessary for
temporary proteet ion o
It would be possible to use such a scheme for pennanent
spillway alterat ions by increasing the height of the exist ing
channel walls . However, such a plan would not be pract ical because
the addit ional weights of the extended walls , in concrete , would be
22
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0 I I
----� ------,- , o u r. c. 1 1
1 00 I I I I I S C A L E OF F E E T
200 I
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. - .� - - - Sta . 1 + 2 0 .7 6
6 11X 61 1X l 61
Posts
-tO · - - . . . _ Locat ions of temporary wa l l s -
N
_y_ . . .__ _ _ 3 1 1 x 1 0 1 1
L a gg i n g
_ _ _ j'_ _ _
S E C T I O N O F WA L LS
I N C H U T E
w I-::) -,_- - - I 0
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611 X 61 1X l 6 1
Posts - - - . _ co ·-. I:,, .. ,:< ....
3" x 10" La g g i n g
· o . . , ,, ' .i?
S E C T I O N O F W A L L S I N
T R AN S I T I ON C H A N N E L
-N IJI
y f
�-- Sta. 7 + 1 5 I I
R I O GRANDE P R O J EC T - N E W M EX I CO - T EXAS
E LE P HA N T B U T TE DA M SPILLWAY A LT E R AT I ONS BY HYD RAUL IC MODEL- 1 : 40 SCA L E
T E M PO RA R Y WA L L S TO P R O T E CT S P I L LW A Y A G A I N S T F LOOD S
A. LOCATION OF WALLS B , DISCHARGE 28, 000 c , f, s , , CYLINDER GATES OPEN.
1 : 40 MODEL OF ELEPHANT BUTTE DAM SPILLWAY TEMPORARY WALLS TO PROTECT AGAINST ANTICIPATED FLOODS IN 1942 f-' ro
so great that the foundations would have to be enlarged o Moreover 0
t he f inal resuit would appear so haphazard and unsightly that it
would invite much adverse crit ic ism .
lO o D ischarge of prototype spillway in 1942 and comparison
with model tests o As ant ic ipated , the reservoir hav ing rema ined
nearly full throughout the season of 1941 fille d again early in
1942 0 On April 23 1 t he spillway was d ischarging 2 0 500 second
feet , and a much larger flow appeared inevitable . In a telegrB.lll
dated April 24 , the Chief Engineer d irected Superintendent Fiock
to begin construct ion of the protect ive t imber walls ( figure ll ) o
Inspecti on of t he spillway was made June 5 0 by D . C .
McConeughy , senior engineer from the Denver office , in the company
of Mr . Fiock , Mr. Caylor , and other members of the pro ject staff .
On that day the water surface stood at elevat ion 4408 .18 , 1 .18
feet above the spillway crest o By fully opening the cylinder gates
a spillway discharge , estimated to be 7 , 000 second-feet , was ob
tained . In a "Memorandum for Mr. Keener , " dated June 16 , 1942 ,
which described this inspection trip Mr . McCo Eughy states :
"3 o The action of the water followed that in the model
very closely , and temporary protect ive works 9 cons ist ing of
t imber walls 9 wh ich may be seen in the photographs ( figure
13 ) ; were evidently et the correct locat ions . These locat ions
were predicted from the model ; it had been expected t hat the
protective work would not be necessary for di scharges smaller
than about 8 9 000 second-feet , end this seemed to be the cese o
Alt hough the timber was wet by spray to such an extent that
25
A. SI'ANDING WAVES rn WES!' Y'ALL OF TRANSITION c'ECTION BELOW CYLINDER-GATE OUTLEl'S,
S!'ANDIID WAVE CN WES!' WALL NEAR SI'ATION 1 +20. 76.
ELEPHANT BUTTE DAM SPILLWAY
B. REFLECTED V'AVE ON EASI' VIALL OF CHUTE NEAR Sl'ATION 2 +46 , 00.
D . EAST WALL OF TRANSITION SECTION BELOW CYLINDER-GATE OUTLE!'S.
THE PROTOTYPE, DISCHARGING APPROXIMATELY 7000 c , f, s . , JUNE 5, 1942 I-' ul
swelling had caused some of the legging t o bulge ou�ward ,
there was no considerable volume of water against the t imber
at t he maximum attainable discharge ot 7 j 000 second-feet .-
--" The photographs of Mr . McConaughy ' s report furnish en oppor
tunity for e model-prototype comparison o The s imilar views of
f igure 14 indicate that waves in the prototype j et a di scharge of
7 9 000 second-feet P are as high es corresponding wave s in the model
at the larger discharge of 8� 000 second-feet . The cause for this
d ifference is apparent for considerable air is mixed with t he water
in the prototype whereas the water surface in the model is com
parat ively smooth . In other words , the model cannot dupl i cate the
prototype es far as effects concerning surface tension end entrain
ment of air are concerned o Therefore � in the prototype the waves
will be higher for similar discharges 9 and the model re sult s
should be modified in some manner t o account for this phenomenon .
Unfortunately , there is not suffic ient knowledge on the subject
at the present to apply proper correct ions to the model so this
factor must be neglected . At t he same t ime it should be real ized
that the capac ity of the prototype may be somewhat less than that
indicat ed by the model .
11 . Model studies for permanent apillwey elteret ions - Baffles
in the transition sect ion . Following test s involving temporary
protect ive walls , the model was used to study plans for permanent
spillway alteret ions o Several schemes were proposed by which the
water could be directed into the chute without spilling over the
A. THE PROTOTYPE, DISCHARr.IJ,K; APPROXIMATELY 7 , 000 c . f. s . JUNE 5, 1942.
B. 'J'l!E 1 : 40 MODEL, DISCHARGING 8, 000 c . f. s .
ELEPHANT BUTTE DAM SPILLWAY
COMPARISI ON OF MODEL WITH PROTOTYPE
FIGURE 14
channel walls . These included baffles , dentates , training walls ,
and channel covers o
It at f irst appeared desi rable to c reate a series ot drop
pools with baffle s in the transit ion sect ion p the last pool
arranged so water would drop int o the chute at a low velocity and
in a uniform manner. In al.1 9 four different arrangement s of
battles were placed across the transit ion sect ion and tested
( f igure 15 ) o None of these arrangements reduced the amount of
water topping the channel walls for the pools formed by the
battles were completely ineffect ive at large d ischarges . There
fore , no further consideration was given to the use of baffles o
12 . Test s with dentates a Dentates on the spillway apron and
on the floor of the transition channel were suggested as en
effect ive method for dissipating the energy of flow and d isturb ing .
the water over the trans it ion channel so as to enter the chute in
a more uniform manner o Therefore , wedge-shaped dentates were
placed on the spillway apron in horizontal rows 6 feet 8 inches
apart , and on the floor of t he trans ition sect ions in similar
hori zontal rows but forming a radial pattern . The dentates in
each row were spaced eight feet on c enters , and staggered with
respect to dentetes in the ad jacent rows . Eech dentate was four
feet wide , four feet high , three feet tour inches t hick et the
base , and one foot thick at t he t op c
These · dentatee were sat isfact ory tor small discharges but
eppeBred t o be worse than none at all at large discharges in that
they tended to ra ise the water surface , spilling more wate r than
29
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cii z � a: �
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F I G U R E 1 5
3 11 . 3 1 1 1 4 (5.83'h-, ,;rl 4 ( 5.83')
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1 ' - A - } \ A rLJ1fU7' ' ' - ,-.· ,-3 " ( 1 0.0 ' )
- r"', ,,._} . IL'' - X- -� - X
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1 " ( 3 34' ) ' ' ', 3"( 1 0.0 'f 9" (96·6 ') A .
B AN D C A R R A N G E M E N T No . 4
I " ' 2 2 (8.33 )- , , ·4" (1 3.33') 6 " (20' )- _ - ,._ - -
�-- -� - A:,: ' . - f -
y I ' ' I - .Y°'.: ' ··2 "(6.67'
< - 2 1 " (70') · ;'tf� ' ' · ':...- 2 " (6.67') B
A R R A N G E M E N T No. 3
-Sta . 1 +20.76
2 " (6 67')- , 2 .5 " (8.33')-,, ' I
C .,i - :J r-'
:-.::- - 1 5 " (50')- - >-'
A
1 " ( 3.33')- 2 .5" (8.33 'h
2 2"(7 3.3 ')· B
I I 7 {"-' '
>-'
A R R A N G E M E N T N o. 2
1 -¾"(5.83 1) - --:; - 2"(6.67 ' ) - - 1 ¾" (5.83'h-, 2"(667'h �\. \ i),. '.
I
[1illLi7illj • t) r7. r r< >- 2 1 " ( 70') .,._
l . 5 " (50'h 3. 5 " ( 1 1 ,67 ' ) -, I
r=��; __ 7__,: �--:,.._ _ _ 36" ( 1 2 0' ) >"
D
1 -43 ''(5.s 3'h-,
I '
...,Y,,.'t. 2 " (6,67 ') -,
\
� I
;,-"-
� -} _ _ ,"""-, \ \
1 5 "(50')
A -< 29" (96 6')
8 AND C
r< 30" ( 1 0 0 ' )- >- I
\ 3"( 10.0 ') l .5"(5 0')'1
D
A R R A N G E M E N T No. I
D ETA I LS O F BAFFLE A R R ANGE M E N TS TEST E D N OT E : D i m e n s i o n s i n m o d e l , p rotot y p e i n p a r e n th e s i s
R I O G R A N D E P R O J E C T - N E W M E X I C O - T E X A S
E LEPHANT BUTTE DAM
S P I L LWAY A LT E R ATIONS B Y HYD RAUL IC MODE L - I : 40 SCALE
T E STS W ITH B A FF L E S I N T R A N S IT I ON S EC T I O N
ever over the channel walls o As in the case or the baffles 9
changes in the spacing and alignment of the dentetes d id not
1.niprove materially the flow cond it ions in the spillway � and it
was concluded that the use of dentates alone would be unset is-
It was suggested that training walls be used in conjunct ion
wit h the dentates o Two training walls 16 feet 8 inches high were
placed as shown in figure 16 0 The obj ect of the walls was to as
s i st the dentates to d ivide and spread the flow in the transit ion
sect ion . Thie arrangement was good for discharges to 20 , 000
second-feet , but at greeter discharges water overtopped the west
wall of the trans ition sect ion (f igure 16'8) o This arrangement I
worked better with the cylinder gates closed as water flowing over
the c rest attained a more uniform d istribution than water flowing
t hrough the tunne ls o
A third combinat ion was tried by plac ing dent ate s on t he
spillway apron above the beginning of the trans iti on section,
station o+oo , and a series or low tra ining walls in t he trans ition
sect ion below ( figure 17A) . This comb inat ion did not work as well
as t he former arrangement , with high t raining walls , for water
overtopped the channel wells at d ischarges greater than 16 , 000
second-feet { figure 17 B) o However, in c ontrast with the former
arrangement (f igure 16 ) the comb ination with low training wells
( figure 17 ) operated better with the cylinder gates open.
13 . Tests with treining walls o It became apparent that
schemes tor dissipatins the energy ot flow and spreading the water
�1
FIGURE 16
A. ARRAN:}D«ENT 01" D!ffl'ATES AND LOCA'l'ION OF TRAINING WALLS.
B. DISCHARGE 20, 000 c . f.s . , CYLIND,:R GATES OPEN.
1: 40 MODEL OF ELEPHANT BUTTE D.AM SPILLWAY
CONTROL OF SPILLWAY FLOW BY DENTATES .AND TWO HIGH TRAINING WALLS
FIGURE 17
A. ARRANGEMENT OF DENTATES AND LOW TRAINING WALLS.
B. DISCF.AR:E 16. 000 c . r . s . , CYLINDER GATES OPm.
l: 40 MJDEL OF ELEPHANT BUTJ'E DAM SPILLWAY
CONTROL OF SPILLWAY FLOW BY DENTATES .AND LOW TRAINING WALLS
over the transition section would not work on the Elephant Butte
spillway , and thet the water would have to be guided into the
chut e in some other menner. Therefore the dentates were rem.oved
and a number or tests with training walls were made . The 6 . 67-
foot walls ot the previoue test were used except that a high wall P
16 . 67-feet high, replaced a port ion of one low wall above stat ion
1+ 20076 ( figure 18 ) o Also three 3 .33-toot walls were set at each
end ot the spillway immediately below the crest to prevent water
from overtopping the channel walls of the transition sect ion o
This comb ination operated satisfactorily for discharges up to
25 i 000 second-feet . The principal difficulty was that the low
walls at each end of the crest reduced the discharge over t he
c rest . Accordingly P these crest walls were replaced by over
hanging sect ions or baffles on the channel walls immediately d own
stream from the crest ( figure 18 ) o The discharge capacity was
then increased to 30 p 000 second-feet , and later to 35 p 000 second
feet when eight-inch lips were placed on the outer edge of the
overhanging baffles to turn the water dowm;erde .
Thia was the first arrangement to accomplish the desired
results but it was not satisfactory trom the standpoint ot appear
ance and the low training walls would cause much spray. Accordingly ,
high training walls were next c ons idered ( figure 1 9 ) . The object
was to r eplace several low walls with a single high wall . In
addit ion the overhanging baffles on the channel wells were removed .
A number of combinations of we.lls were t ried from which a com
bination of two walls wee selected tor further test s , wells E
3 . 3 3 1 C re st w a l l s - -
W e st c h a n n e l w a l l - -
to rep lace 3 .33' / c r e s t w a l l s - - - - '
. ,<- 5' _ _ _ :,.;
f-" Li p
E - S E C T I O N O F B A F FLE O N W E S T WA L L
1 6. 67 ' W a l l · · · ( H i g h w a l l)
/ '
r • -�
l . 2 1 ->l r<· ,
_ : - ---i-
I '
I /
• /
A - PLAN
I G U R E r 8
" L , 1 8 , p - - · · . Jt f- S E C T I O N_ O F B A F F L E
O N E A ST W A L L
-- - -East c hanne l W O I I I I ' - 3 . 3 3 C r e st w a l l s
', 6 . 6 7 1 W a l l s _ _ (Lo w t r a i ni n g w a l l s) :._
- o ve rh a n g i n g ba f f l e t o - - - S t a. 1 + 2 0 . 7 6
:1[ '
rep lace 3. 33 ' c r e s t w a l l s
9 5 0 1 00
I I I I I I I I I I I S C A L E I N FEE T - P R O TO T Y P E
- � -< - I 01
lD - i- -2r--·· -' l _ _ _ y_ _
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1' - --- 2 . 9 1 R _y __
(D
'° D - P RO B A B L E S E C T IO N • I ' '
-� 4 . 1 61 ;..:;.
8 - S E C T I O N O F
LO W WA LLS
� :CT O F C R E S T WA L L S
->h .o' � -• I
C - P R OBA B L E S E C T I O N O F H I G H WA L L
N O T E
N o d at a g i v e n a s t o t h e s e ct i ons o f t he hi g h w a l l a nd c res t wa l l
R I O G RANDE P R OJ E C T - N EW M E X I CO - T E X A S
E LE PHA N T B U T T E DA M
SP I L LWA Y A LT E R AT I O N S B Y H Y DR A U L I C M O D E L - 1 , 4 0 S C A L E T ES T S W I T H LO W TR A I N IN G WA L LS I N TRA N S I T ION S E CT I ON
Wa l l C- --- -
Sto. 1 +20.76-,,
' - -- -wa l l E
' -- -wa I I A
50 ; 1 1 I
10'- - - ,- -:--!l : : ,, - - 1 0 1 0
F I G U R E
S C H E D U L E O F T EST S
US I N G H I G H WA L LS
TEST
2
3
4 - -5 6 7
WALL COMBINATION A & C A , B & C - -
A , B , C & D w i t h A,B & C exte nded as s h o w n b y d otted l i n e s .
E & F , S �c_t�'2_ E I E & F , S_ec:_! io� E 2 E & F , S ect ion E 3 E & F , Sect ion E4
50
\ t I ..,[ I I � :t.>Kr,;<1>1<-:>-'-< ' SCALE I N F E E T - P ROTOT Y P E
8 33 '---_lf��
_!�
I �[ - - 1 1 .67 1
1 5 '- -�_;
N r<"l W W
---1 I ->-:�-<-
C: C: 0 0
u u , - -1 25' 1 .25'--, w w "' ' (/) (/) -� r :-.:- I ->fy' � _I _
I I 1 y
, - - 5.32' I 'r' I
;' - , p,- - -3.33' I I� - >- I
I - _\'. I -<C,
1 9
�"
-
-:-- - x -g- - · · = i,, � � r -71- - · ==t'- - 1 20' I\ <!) a) I I •
� I '-1 25' --=..=,, : r() � :
I \ - - 1 -, - 1 • : 'f-- -- --- -R = 5.46 1
: � .
' '
<.Q <!)
- j -
- >-! � 3'
P ROBABLE S ECT ION OF WALLS A , B , C, D & F .
r() ',� -\ 1
' L '-R = 1 0.0' y _ ' - R = 1 6.67 ' I
-< - i;- - >, , -- --8.33' I
r" ft_>-- -6.67 ' E l E 2 , E 3
S EC T I O N S F O R WA L L E
I I I ' \,
· _, ' , , _R_= l 2 .67' y _ .__ _ _..
-<- ,_
-
->, - -- - -6.33' E4
N O T E : S e c t i o n o f wa l l s A, B , C , D a n d F n o t g i v e n b u t wa l l s i m i l a r to proba b le sect ion s hown A l l d i m e n s i o n s in p roto t y p e.
R I O G R A N DE P R O J E CT - N EW ME X I CO -T E X A S E L E PHANT B UTTE DA M
S P I LLWAY ALT E RAT I O N S BY HYDRAU L I C M O D E L - \ : 40 S C A L E T ES T S W IT H H I G H T R A I N I N G WA L LS
and F o The sect ion of wall E was made c onvex to form a roller
to turn the water t owards the east channel wall o Four d ifferent
sections of this type of wall were tried • all working fairly well p
holding water in the channel tor flows up to 20 p 000 second-teet o
However i when the overhanging battles on the channel walls were
replaced t o prevent water from splashing over the t ransit ion
channel P the discharge capacity was increased to 30, 000 second-
140 Taste with channel cover end overhanging battles on
channel walls - the final designo Training walls were better
than any previous scheme tried . nevertheless they would not be
sat isfactory because a large amount of spray would be thrown
into the eire end the pressure of water against the well s would
cause a cantilever act ion requiring a heavy foundat ion . To
avoid these undesirable features a channel cover over a port ion
of the trans it ion sect ion was suggested , for the cover would
retain much spray , and the cant ilever act ion on the training walls
would be eliminated . The arrangement shown on figure 20A. was
first tried . The east port ion of the transit ion sect ion was
covered . b etween stat ion o+oo end the chute entrance . eta . J:t- 20076 0
The overhanging baffle s on the channel walls were also included
s ince they were found to be necessary in previous test s o
water flowing down the trans it ion sect ion and into the chute
did so in a uniform manner, the undesirable standing waves being
elimineted o The design was adequate tor the maximum d ischarge
ot 35 9 000 second-feet , and was therefore cons idered as an approach
t o the final design ( figure 20B ) . Pressure measurement s were made
A. L C"'l-::R AND GV":RRA"!GING BAFFLES ON CHANNEL WAI.LS.
B. DISCHARlE :35, 000 c . f . a . , cYLINDER GATES OPEN.
1 : 40 MODEL OF ELEPHANT BUTTE DAM SPILLWAY
CONTROL OF SPILLWAY FLOW BY CHANNEL COVER
AND OVERHANGING BAFFLES ON CHANNEL WALLS
FIGURE 20
were made on both sides of the training wall , on the underside ot
the channel cover , and on t he unders ide of the overhanging baffles
to determine loading condit ions for the structural de sign
( figure 2l } o
The final des ign was evolved by moving the entrance of the
covered sect ion downstream t o reduce the large span of the cover
at its entrance o Cond itions were not materially changed by
moving the entrance cover 2o�reet downstreem from the beginning
of the trans it i on sect ion at stat ion o+oo ( figures 1 and 22.&.) .
At maximum discharge ot 35 9 000 second-feet P all conditions 1'18re
sat isfactory except that waves would splash over the entrance of
t he channel cover ( f igure 22'13) . Such splash was not crit ical,
however p because the channel cover would be of concrete and eo
arranged t hat the water splashing over the top would reenter
the chute below. Moreover a wall or bewn four feet high would
reduce the amount of splash on t he cover.
15 0 Addit ionsl tests on spillway ohannel o The channel cover
ot the f inal design was not considered a desirable solut ion of
the problem for the arrangement and appearance made it obvious
t hat it was an expedient to force the spillway t o funct ion properly o
Four additi onal tests were made , three using t raining walls and
the fourth a channel cover .
The test s with training walls were p ract ically a repet it ion
of previous tests o A single training wall down the trans it ion
was good for discharges to 20p000 second-feet ( f igure 23) o The
next arrangement consisted of three walls or fins partially
Baffle on west channel wall
I I
/ ,, / / ,: I ,' I I
,' L-l ' I I
I / I
/' I / I /
I
"c./ ..,.
10 0' 1s.o' -
P,e zometr,c connections -
Center framing wall
Ta be deter,n1ned
:.
- '{
:? . .,,
.sf· N ' =o "'
:;;
-� 0
·2
·� ,,.
� �
Vories, see plan
-'i SECTION 8-B
C HANNEL COVER
: 11: ,' Y 1 / / / I I , / I I
' /L...f " I I
(!)_/ / I
/ I
. ·-·· ·· ·
")..,.
Sta. 0+00 · . . . - �
·o 2
East channel wall
.,_
I f / � '/' l I ,� 1 1
/ l l ,' / ,' 1' 1
1
,/ ,' j / ' / c-f',I>,. \� 1'1-/ / I / / ,� 1') '\ C)
DI • , 3 3 n' , ·. ,, "•"" Baffle on east . ! ' 1q ,�
\!!l 'Jo · channel wai f -
v '< >16.8'< •302'• ')43!J< �\ �� , •
0,__-'c •100'• �214• !368' · C'\,,- NOTE
� ' s .G A l l dimensions in prototype
,;;, � � � ,..., _ ·,.
/ PLAN
)"
RIO GRAND( PROJEC'·HEW M[XICO· T(US
ELEPHANT BUTTE DAM
· 1
Design tested Design adopted
Design adopted Des,gn tested
� 5'-2" ··,
1'-6 '. ; :,�< i'- 5" P1ezometr1c connections
,�� -· · r � �
'
SECTION C-C
BAFFLE ON E AST CHAN NEL WAL L
I 25'
Piezomelric connecf1ons :� .-l-i: �.. . - 2 oe'
�'
J�·;, ,
I I
Design tested Design odop�ed
SECTION A-A
BAFFLE ON WEST CHANNEL WALL
SPILLWAY ALTERATIONS BY HYDRAULIC MODE L 1, 40 SCA LE THE FINAL DES IGN- LOCATION OF PIE ZOMETERS AND PRESSURE DATA
PIEZOMETRIC PRESSURES ON CENTER WALL, CHANNEL COVER, AND BAFFLES I I I
71 ---,-2 73
7; 76 7 7 -:-9
79 tio 8 1 .,T 1 ni j I � � � ! 88 , ::5 ... eg ., z 6 I 96 I " i2 � 9 ,
PRESSURES I N FEET O F WATER PIIOTOlYP'l
0=?'.PQO -
1 < v o b ? 0 4 0 ·, 2 ,
0
I 2 0
! : 9 4 0 6 C
• V 4 0 G e -t 200 4 0 2 -·, 2 0 4
I a ., a r t0i)
I ., ' <l O 4
2 0 , 2 , 2
. � 2.Ji. _40 3 ?. l I!
•
A. ARRANGEMENT OF CHANNEL COV':R AND OVERHANGING BAFFLES IN FINAL DESIGN.
B. DISCHARGE 35,000 c . f. s . , OUTLE'J' GATES OPEN. NOTE WAVE TOPPING CHANNEL COVER.
1 : 40 MODEL OF ELEPHANT BUTTE DAM SPILLWAY
CHANNEL COVER AND OVERHANGING BAFFLES ON CHANNEL \l.'ALLS
THE FINAL DESIGN
FIGURE 22
A. SIN'.lIE TRAINING WALL DOWN TRANSITION SECTION.
B. DIOOHABGE 20,000 c.t'. a. , CYLINDER GATES OPEN.
1: 40 MODEL OF ELEPHANT BUTTE DAM SPILLWAY
CONTROL OF SPILLWAY BY SINGLE TRAINING WALL
FIGURE 23
traversing the channel to act as a combinat ion baffle and
training well ( f igure 24 ) . The three f ins ��re good only for
d ischarges up to l6 p 000 second-feet for the upstream f in appeared
to hold back water and push it over the channel walls ( f igure 24 ) o
When it was removed the d ischarge capacity was increased to about
20 p 000 second-feet .
A final test was made by plac ing a c over over the ent ire
trans iti on sect ion . Ho��ver , such a scheme was not pract ical
because water p iled against the west wall of the chute P forming
st anding waves in the same manner as if no channel cover ex isted o
16 . Revision s to cylinder gate outlet s . Upon completion or
studies on the spillway channel P attent ion was g iven t o revis ing
the cyl inder-gate out let s . Trenche s were cut int o the natural
shelf , or bench , upstre8.11l from the crest sect ion i n line with the
ten-foot diameter tunnels undor the crest ( f igures 2 and 25A) .
The cylinder gates we re replaced by rectangular gates P wooden
blocks in the model , which fit into the cylinder-gate frames ,
thus ut ilizing as much of the existing structure as possible .
The purpose of this alte ration was to permit water to flow into
the t renches and through the tunne ls under the crest when the
water surface in the reservoir was above e levat ion 4382 .0 ; whereas
in the existing structure the water had to rise above the rock
shelf at elevat ion 4396 . 0 . E y such alteration a greater emergency
storage could be ut ilized for flood control a
Model tests indicated that the tunnels would operate sat is
factorily, except that a ,rortex would form at the entrance of eech
A. THREE Hlr.H FINS 'IO ACT AS COMBINATION BAFFLE AND TRAINING WAll,.
B , DISCltARGE 16. 000 c . f . a . , CYLINDER r.ATES OPm.
1 : 40 MODEL OF ELEPHANT EIJTTE DAM SPILLWAY
CONTROL OF SPIUWAY FLOW WITH THREE IDGH FINS
FIGURE 24
A . THE CHANNELS IN '1HE SIELF UPS!'REAM FROM THE CREsr.
B. DISCHARGE THROUGH OU'l'LETS SHOWnt VORTEX IN ONE CUTI.El' AND FLOAT OVER OTHER OUTLEl' TO ELIMINATE AIR FILAMENT OF VORTEX.
1: 40 MODEL OF ELEPHANT BUTTE DAM SPILLWAY
REVI SIONS TO CYLINDER GATE OUTLETS
FIGURE 25
outlet ( figure 25B) . It was shown that the quantity of water
flowing into the out lets �ould be reduced when an air f ilament
as shown in figure 25 J3 was permitted to form o However , it was
found t hat a float would reduce this vertex action to the extent
that the ai r fileJ11ent would be eliminated and such a device was
adopted in the final design ( figure 2 ) o
17 0 Discharge of spillway into river che.nnel e At first the
tests were concerned with flow in the transition sect ion and into
the c hute , and the model as built originally extended only to
the mouth of the chute P station 7+15 . 0 ( f igure 7 ) . The river
bed at this point formed the tailrace t o the power plant and
some concern was expressed as to the poss ibility of dem5ge by
f low from the chute washing out the opposite banks o Therefore ,
the model was enlarged t o include topography downstream f rom
t he chute , the river bed and the ad jacent banks et the foot of
the dam ( f igure 26A) o
Teets indicated that a hydraulic jump would occur in the
mouth of the chute for discharge s less t han 3 , 700 second-feet
under normal f ield condit i ons ; that is p with the tailwater near
elevat ion 4 216 . At larger discharges the jump swept out of the
chute end the water entering the ta ilrace t ended to p ile upon
t he opposite bank e This cond it ion was also observed in the pro
t otype at di scharges as large as 7 P OOO eecond-feet e.nd described
in D . C . McConsughy ' s report of June 16 9 1942 .
At a discharge grea ter than 16 , 000 second-feet the model in
dicated t hat the oppos ite bank would virtually wash away
46
A. LOOKING IJOWNS'lllEAM WlmlE CHUTE JOINS TAilllACE.
B . DISCHA.llGE 35 ,000 c . r . s . , SHOWING now FROM CHUTE WASHING AWAY OPPOSITE BANK.
1 : 40 MODEL OF ELEPHANT BUTTE DAM SPILLWAY
DISCHARGE OF SPILLWAY INTO RIVER CHANNEL
FIGURE 26
( figure 25 ) o This condit ion suggested t he need of a st illing pool ,
but0 as Mr. Mcconaughy �teted in his report 0 such pools ere expensive
to build end in view of the infrequent intervals et which large dis
charges will occur it is more exped ient to repair the result ing
demege o For this reason no teat s were made on a st illing pool or
othe r structure s to avoid this sweep-out of the tailrece .
18c Rat ing curves for the existing end final designs o The
re lat ionship of d ischarge to water surface elevation is shown on
f igure 27 for both the existing and f inal des igns . These curves
include d ischarge through the four outlet s under the crest with
the ir gates wide open at water surface elevat ions les s than 4407 9
t he comb ined d ischarge over the crest and through the four out lets
above elevat ion 4407 , and the d ischarge over the crest only o As
one m ight ant ic ipate , the discharge through the outlets was
slightly larger in the f inal design b ecause of the revision to the
more effic ient entrance described in section 16 0 The flow over
the crest , however , wee unchanged .
The d ischarge over the c re st obtained from the model test s
may be slightly larger then actual prot otype discharges , espec ially
at low heeds on the crest o This was evident when the discharge
coeffic ient for the crest wes computed ( from Q : K L H3/2g where
Q • discharge , K = the c oeffic ient ; L = net length of crest 9 and
B = head on c rest ) and found to b e too large base d upon experience
wit h other crests . From the nature of t he data it was believed
t hat the gage for measuring heed was zeroed about 0 a0l foot too
high (model } which would account for this h igher coeffic ient . No
4 4 1 6
4 4 1 4
44 1 2
4 4 1 0
4 4 0 8
4 4 06 z 0 - 4-4 0 4-<l: > W 4 4 0 2 _J w W 4 4 00 u <( o:: 4- 3 9 8 :::i (f)
0:: 43 9 6
w t-<! 4 3 9 4 5
4 39 2
4 3 90
4 3 9 8
4-3 8 6
4-3 84
4382
v
-
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I "__; T O P O F PA R ,A P E T E_ I . + 4 1 9 �,/ I 1 , I j --_,
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I I / I I I I I I !
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W A Y C � E � T E l . 44 0 ; , • D a t a f r o m t e s t s o n f i n a l d e s i g n -� j I i ' I I I I ! I I I I I :
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I ---lL I - --- il7" '
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I 4 O u t l e ts D i s c ha r g i n g - ' t y p e d i s c h a r g e s at l o w h e a d s o n - - - O r i g i n a l D e s i g n ( C y l i n d e r G a t e s )
i-- · - - F i n a l , { I ,,, ' ··- -
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2 4 2 8 32 3t3 40
D I S C H A R G E I N T H O U S A N D S O F S E C O N D F E E T
R I O G R A N D E P R O J E C T - N E W !11 E X I C O - T E X A S E LE PH A N T B UTTE DA M
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I SP I LLWAY A L T E RAT I O N S B Y H YD R A U LIC MODEL 1 :40 S CALE
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data on the se coefficients are presented in this report because
they would not be of any velue P and further p the model had to be
dismantled before any checks on the coeffic ients could be obteined 0
In the model of the original des ign the disoharge through
t he cylinder gates may have been measured in an incorrect
manner e As t he reservoir water surfac� rose air pockets formed
below the elbows of the outlets so the outlets d id not fill . How
ever , there was some question as t o whether the outlet s would fill
in the prototype , for the air pockets could be eliminated by
moment arily sealing the outlet exits . This was done in the model o
While sealing the air pocket s may have not been a t rue condit ion
and would give a larger d ischarge through the outlets in the
model than in the ·p rototype it was not cons idered important be
cause t he cylinder gates were to be eliminated end the ent ire
outlet design changed. ,In the new design no air pockets would form.
19 0 Abstract of correepondenoe ,
December 7 � 1939 a
January 3 9 1940 .
July 10 9 1941 0
Memorandum to R a F . Blanks , f rom J o E a Warnock , request ing informat ion concerning the construction of the spillway at Elephant Butte Dam. To show available informat ion 1/l(a.rnock presents excerpts from letters dated from May 6 0 1915 p to April 9 0 1941 � from various engineers who describe the h istory of the oonstruot ion of the spillway at Elephant Butte Dem o
Letter from R . S . Lieurance and R . F . Blanks to Chief Engineer 9 d escrib ing condit ion at Elephant Butte Dam as they found it on inspect ion trip durin, week ot December lO p 1939 0
Telegram from L o R. Fiock to Chief Engineer stat ing that reservoir hes reached maximum elevat ion, and will test spillway under limited disoharge o
July 15 1l 1941 .
Sept . 4 , 1941 .
Sept • 1 9 , 1 941 .
Sept . 19 , 1941 .
Sept • 26 , 1941 .
Nov o 25 , 1 941 .
April 18, 1942
April 23 , 1942 .
April 23 , 1942 .
Letter from Superintendent t o the Commissioner , transmitt ing prints end negat ives of spillway discharging for f irst t ime July 12 ; and 13 0
Also , cl ippings from local newspapers .
Letter from Superintendent t o Chief Engineer P enclos ing chronological record of the spillwaygate operat ions , and photographs . In paragraphs 6 , ? , 8 , aild 9 the inadequacy of t he pre sent spillway c hannel is emphasized , and model studies are believed necessary to predict t he action of larger discharges o
Letter from Chief Enginee r to Superintendent 9 stat ing that hydraulic model of spillway was considered necessary , that des ign was started o Also requesting topography of t he river bottom for construction of the model downstream from the spillway .
Letter from Ch ief Enginee r to Superintendent , stat ing that model construct io.n ha s begun 9
test ing possible in three or four weeks and asking for interpretat ion of paragraph 7 of letter of September 4 .
Let ter from Superintendent to Chief Engineer, in answer to letters of September 1 9 , explaining meaning of paragraph of letters of Setpember 4 p and stating that topography or st illing pool is being obtained .
Letter from Superintendent t o Chief Engineer , enclosing drawings showing actual elevat ions of the floor and t op of t he walls of the spillway explaining d ifference s from original plans . Also condit ions of backfill along spillway . Also a drawing of topography of st illing pool .
Letter from Chief Engineer t o Superintendent , request ing drill holes to determine c ondit ions of spillwey in connection �1th sp illway alterations .
Telegr811l from Chief Engineer to Fiock stating that drilling me.y be deferre d unt il after flood see.son .
Lettx:i r from superintendent to Chief Engineer stat ing that spillway d ischarging 2 0 500 secondfeet with probab il ity of greater floods , end that drilling not advisable . Also rece ived
April 23 , 1942 ( cont inued )
April 24 , 1942 .
April 2 5 , 1942 .
April 28 , 1942 0
Mey 2 3 , 1942 0
June 16 P 1942 .
June 23 , 1942 .
le tter of April 2l p with Savage and Smith report , and states in connect ion with lowering apil1'918y gates not pract ical because existing wells may be submerged for several years o
Telegram r rom Chief Engineer to P'iock , stati ng that construct ion of t imber bulkheads on the spillway walls be started immediately .
Letter from Chief Engineer t o Superintendent , conf irming telegram of April 24 , and enclosing · sketch of proposed construotion o
Letter from Chief Engineer to Superintendent in reply to let ter of April 23, stat ing that drilling may be postponed , but that lowering of spillway gates and permanent changes ehould be made by next March o
Let ter from Chief Engineer to Superintendent , stat ing t �et the Denver office wee concerned with the sp illway capacity for t he 1943 flood seeeon , that there were d ifferences of opinion in the Denver office , end that the superintendent ' s views were wanted o
Memorandum for Mr . Keener by D o C . McConaughy 9 Inspection of Elephant Butte Spi llway and other structures . A report of an inspect ion trip to observe flow over the spillway up to 7 9 000 second-feet o Location of t imber walls was ind icated by the model correct , and that they would not be necessery for d ischarges less than 8, 000 second-feet also correct as water ca.me to the top of the channel walls at 7 9 000 secondfoot di scharge . Other works downstream from Elephant Butte Dam observed .
Letter from Superintendent to Chief Engineer 9 in reply to letter of May 23, and others , enclosing drawings showing the const ruction and present condit ions of the spillway , cre st , gat e s , end temporary repairs , to assist t he design department in connection with the sp illway revisions . Aleo , superintendent ' s view on the 1943 flood season is that it is unlikely that abnormal floods will occur , and that sp illway revisions should be delayed unt il better t imes Q
52
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•
l
Letter from Chief Engineer t o Superint endent0
in reply to letter of June 23 9 stating thet it is sat isfact ory to postpone alteretions to the spill�ayo Also that a diamond drill will be available to explore the rook under the spill�ay •
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