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HYDRAULICS BRANCH OFFICIAL FILE COPY

UNITED ST A TES DEPARTMENT OF THE INTERIOR

BUREAU OF RECLAMATION

OFF I CE

f ll[ COPY BUREAU OF RECLAMATION HYDRAUL IC LABORATORY

COMBINATION ROAD CB,OSSING,

CHECK DROP, AND OUTLET STRUCTURE

MADERA DISTRIBUTION SYSTEM

C E N TR A L VA L LE Y PRO J E CT , CA LI F ORN I A

Hydraulic Laboratory Report No. Hyd. 361

ENGINEERING LABORATORIES BRANCH

DESIGN AND CONSTRUCTION DNISION DENVER, COLORADO

N ov ember 12, 195 2

CONTENTS

Page

Purpose . 0 . . . . • . . 0 0 . . • . 1 Conclusions • 0 . . . • • • . • • . . • 1 Recommendations . . . -. • . . . • • • . . . . 2 Acknowledgment . . . . . . . • • . . 0 2 Introduction . • . . . • . . • . . . 2 Preliminary Investigation . . 0 0 . 0. 0 . • . • . . • • 2

The Problem . 0 • . . • • . • • 0 . . . 2 The Model • . . • . • . . . . . • • . 3 Tests , . • • • . • . . • • . . • . . . • . 0 . 3 Conclusions . . 0 . . • • . 0 • • • 0 . . 0 . . _3

Secondary Investigation . . • • . . • • . • . 4

The Model • • 0 • . • . • . • • • • • • • . • . • • 4 Test Facilities • . . • • • • . • • . • . . . • 4 Performance . . • . • . • • • • 0 . • • • . 0 . . . • 5

Stilling basin • • • • • • . • • • • • • • • . 5 Forebay • • • • • • . • • • . • • . . • • 5

Turnouts . • • • • • • • . • • • . • . • • 6

Figure

Sketch for Model Study . • . • • • • • • . • 0 . 1 Drawing, Combination Road Crossing Check Drop and Outlet . . 2 Recommended Stilling Basin. • • • • . . . 3 Recommended Stilling Basin with High Tailwater. • . • . • • • 4 Stilling Basin with ffBroken Backff Transition. . • • • • . . . 5 Stilling Basin with ffBroken Backff Transition and Sloping

Floor. • • • • • • • • • • • • • • • • • • • 6 Recommended Forebay Designs . • • • .. • • • • • • • • 7 "Tee~shaped" and "In Line" Forebays • • • • • • • • • • 8

. UNI'l'EP. STATES . _ DEPARTMENT or· THE INTERIOR

BUREAU OF RECLAMATIOi

Design and Construction Division Engin,ering Laboratories Branch

-.: Laboratory Report. No. Hytt.:.361 Hydraulic Laboratory ·Section Compiled by: . t. v .• Wil~on Denver, Colorado · . ·

November 12, i9·52 · Checked arid . . .. . _ _ . reviewed by:". w. c.· Case

J. W. Ball

Subject: Combination road crossing, cneck drop, 1am outlet structure-­_Madera Distribu~ion System-Central Valiey Project, California

PURPOSE

. ,_. Detendne· the min:i.mum sl~e ~f st:i.ucture· that combines a.~~ road crossing, vertical check drop, and i~rigation turnout.··

.CQNCLUSIONS. ·.

- ., ' . ,: . ;::,i·- .·, .... -_··.·; .- ' . .\ .. · . ,. . . . ' : ..

.. The following coniclusions _ apply to a structure. having __ a 2: l. upward slope on the pipe entering the head wall. · · · · ·

\ l

1. The recommended design (Figure 2) gives the best all-around performance. ·

·· 2 •. No flQ" straigbt~ner is. requi~d .. in :the. turnouts ahead or the totali.zing. meter-,-witb ~he ,,rec011Dl8nded cle_si~. '' ;, ·. . . '

.. . ,.-., -· ,·. _.,•· .,.:.<°'' _., : .. . ·. j ·:·' . . .

.3 •. _ The "in, line"_ forebq. (Figure 1). wo~, be, adequate under . conditions where· -no, regu4ting gate -is· used on the_ ~urnout or where -a: flow straightener. is used . ahe.,cl · of. the flow. meter.. · .

. I 4._ ., The ~iia~e or th~. torebay has an err~ct. on the turnout -entrance loss.· · ·. · ·

. . .

and cli.8~~~:;s;:t:!!io:~:~; ::e~;:~:~n1:!~~:t:ii1!!=s~~:: -or the structure. ·

6. The energy is '~ot dia~ip~t.ed in the stilling basin when the tail water is above the crest of the check wall. High surface veloc­ities with considerable turbalence are present (Figure 4,A). The beam-·-·· baffie,ahown in.Figures,2 1 8'ni 4B,~ll,give_eatisf•ct~cy,conditions when the tail:. water .is: :at: or'.,&bc>,ve.,. ttie --\~P:· ot th!' o~eok ~! · .. • .~

7. The top or crest of the vertic~l c.heck .wall should not be lower than the crown of the.inlet~· ·

RECOMMENDATIONS

1. Use the design shown in Figure 2 tor a structure combining a· road crossing, check drop, and turnout. The dimensions given are considered minimum. ·

2. Use a minµium head-loss of 0.75 of the turnout velocity head for the turnout entrance. ·

3. Protect the canal bottom' and Bide slopes with riprap f'or a short distance below the stilling ba~in.

4. Place a beam battle across the stilling basin where high tail water will ex'ist. ·

The limiting dimensions of the recommended structure were dete~ined by members ot the Canals and the Engineering Laboratories Branches. · · · · ·

INTRODUCTION

Twenty road crossings were contemplated for construction at the time of this investigat:i.on, with perhaps twd or three times this· number anticipated for tuture construction in the Madera Sy-stem. It was proposed to combilie the road crossing, vertical cheak, and irrigation turnout into one structure where feasible. . This combination was expected to result in a savings in material and labor as ·com.pared to building three individual units. Four different size canal ro~ crossings were to be. constructed using 48-, 42-, 36-, and 30-inch concrete pipe. Some of the structures will contain two turnouts and the remainder single turnouts of either 30- or 24-inch concrete pipe. Dimensions, discharges, etc. given in this report refer to prototype unless stated. otherwise.

PRELIMDJARY DVESTIGATION

The Problem

The problem was to determine: the miniJlmm·, con11truction required between the head wall of the road crossing and the vertical check wall to prevent surging over the check wall. The preliminary design is shown on Figure l.

2

The Model -;t:·,_ .-

An existing laboratory model was used for the study. 1 - In this installation a 15-inch metergate discharged into a 3- by 3- by 11-:f'oot flume. A vertical-· check., whose -top eievation was identical -to the top _of' the gate opening., was placed in the flume -d~tream from- the gate to represent a 6;. by 6-:f'oot :f'orebay. No turn011ts were provided and the

, flume was_' too- ·narrow to provide a . geometrically similar ~tilling basin. The model represented the most-severe condition-which was the 48~inch road crossing discharging 60 cfs· at- 4.77-f'eet;.per:..second velocity.··. These conditions established, a model ratio of' 1:3.2. The discharge was measured through· an a.;;1nch venturi meter. .

Tests

_ The discharge representi_ng 60-'c:f's ·was passed over the ve'rtic~l check wall and. the tail-water elevation varied. water action in the :f'orebay was quite rough., piling up along the sides with reverse f'lcnl. There was no surging over the check wall. The disturbances in the fore­bay indicf:1,ted· that t)ie volume· was too· small. -Considering the narrow width of' the _fiume., the f'low-;eond:l.tioris ~n the pool were qu!ite·smooth un,til the tail water was· ··1evated higher than the top of' the check wall.. The high ;tail w~ter produ'ced an' undesi~ble' high;.velocity.: $ur:f'at3e stream.

:.,• • : '. <. • ' ~ I • ·, ;, • '. ' ', • ' ··,;_ • ·, •• ~ ... • ! • • ," ' . • \ : • • • ' • J • ;

The vertical.' check was 'moved to a distance equ·ivalent- of 12 -feet· downstream. The width was: maintained as 6 feet for a 'distance 'of. 6 feet upstream ·from' the check ~nd then widened to- 9:..1/2: feet -for the -· ·. remaining 6 ·reet to the head wall., to1'ming a "tee;.shapedlt :f'orebay. ·This chang~ hel~d eliminate the disturbances in the·fore'bay and'm&:l.ntained a quie't a:rea: of wat&r where the tµrnout~'wouli be located.,' ., , , , ,,,

Conclusions • • h • •

1_. The 6- by 6-foot-square forebay as originally c~_ntem~lated was 1~quate. · · · · · ·

2. The ·•tee-shaped .. forebay was ~ple with no surge over·- the ·

vertic:~; _,c~ck". .•. ·: , · _ .. : ;: __

3. Additional test would be ·required to obtain answers to the·-­

addi tional proble-9 voiced . by designers. These problems were: : .. ;

a. What' effect 'would a turnout have on the flow in the', forebay'l , .

b. W011ld flow in the turnout be uniform and without a spiral motlo11-T

C. Where should. the turnout.be located With respect to- the,

:f'orebay'l

3

d. What should be the size and shape of" the stilling basin below the drop'l

e. What effect would the 2:1 rise in the road crossing pipe. have on the forebay and turnout flows? ·

f. Could an adequate structure be designed in dimensionJ,.ess, terms that would meet all the requirements of the different diem­eters of' the road crossings and outlets?

The test results were too limited to answer the additional . questions so another model study.was proposed.

SECONDARY INVESTIGATION

The Model

A redesign of' the structure was made (Figure 2) by modifying. the preliminary design (Figure 1) on the basis of' information obtained from the preliminary tests. On Figure. 2 the numbers identified by a· bar are the prototype dimensions used in the model; e.g.,£• . The boxed dimensions (loJ) are the recommended design dimensions. A 1:4 model was fabricatec!'mainly of plywood and lumber. The road crossing was represented by a 12-inch pipe entering the f'orebay on a 2:1 slope. The only plastic pipe available for representing the t~rnouts was 8.11 inches in diameter which was somewhat oversize to represent a 30-inch turnout. Both a right and left turnout were provided. A tail box was placed at the end of.the turnout to adjust the downstream submergence. The water was conducted away from the tail box by a wooden waste flume.

Test Facilities

The discharge into the model was measured through an 8-inch venturi meter. A sheet-metal weir plate was placed at the end of the waste flume and calibrated to measure the discharge through the turnout. A point gage was used to measure the head on the weir. Because of the roughness of the water surface, accurate readings were not obtainable. so the turnout discharges were approximate only.

A piezometer tap was placed in the forebay floor, and one in the turnout pipe 6-3/4 diameters downstream from the inlet of the turn-out, for studying losses.

A point gage mounted on the stilling basin was used to maintain tail-water elevations. Flow characteristics in the stilling basin, fore-bay, and turnout were judged by visual observation.

4

Performance

'Stilling basin. Three variations of stilling pools were investigated. The first was the recommended design (Figures 2 and 3) ~, , The total discharge representing -60 cfs was passed over the-. vertical -- · •-­check wall without the turnouts operating, to study the effect of the

-maximum discharge in the stilling pool. Operation at normal-tail water or less was satisfactory, although a boil formed in the water _:_surface -at the intersection of the stilling basin and the canal. · 'Sand was placed in the model where the boil formed. The sand was displaced on the canal slope at the top corners only, and was not disturbed on the bottom of the canal. ·

A high-velocity surface stream was created when the tail water was raised above the top elevation of the vertical check wall. This·­condi tion was readily alleviated by using a vertical beam baffle down­stream from the check (Figure 4) •

The stilling basin was modified to the preliminary design by sloping the side walls to intersect the canal side slope, forming a "broken back• transition. This eliminated the corner disturbance of the recommended design but concentrated. the water in the center of the canal •. Studies with sand showed that the bottom of the canal was beirig consi,d;.. erably disturbed for some distanqe downstream. Figure 5 shows -the set-up and the pool in action.

The model-· was again modified by sloping the boj;tom of' the basin upward to the f''loor of the canal, This modification gave the best surface condition '(Figure 6) but gave the worst scouring effect on the canal sides and bottom. Large whirls were also formed in the downstream corners of' the pool.

Forebay, Three f'oreba;ys were investigated., a "tee" shape, an "ell" shape, anCan "in line." Both turnouts were opened using the "tee" shape and the maximwn discharge· run through the model. Operation was satisfactory with quiet conditions in the forebay.

'fhe majority ot the turnouts in these structures will be single instead of double ·so the lef't turnout was closed. Figure 7A shows the single t~rnout'in operation in the "tee" f'orebay and Figure SB shows the over-all:model. conditions were good except tor a vortex that formed in the upstream corner near the turnout entrance. The vortex became more pronounced as the head on'the turnout was reduced and eventually·separated into several vortexes. ·

' The "'ell-shaped" f'orebay was evolved to save space and material where only one -- turnout was included. The operation of' this f'orebay iS shown in Figure 7B~ -Operation was satisfactory but a vortex formed as -in the "tee" shape.

5

The "in line" shape was tried. during head loss studies. The · forebay was mad.e the equivalent of 6 feet wide ~~-.the head -,,all to the vertical check. It is shown. in operation,_in Figure 8A; ·· Action in,the. forebay-was good, contrary to the same shape .in the prel:lminaey model. lo pile-up of water along the sides.or.reverse _flow occurred. The . . improved. performance was probably due to the upward veloci:ty. :l,n. the 2: l slope of the. ro$d crossing pipe which was.· not incorporated. into the .. preliminary model.

A study was made u~ing battles to eliDlinate the vortexes that formed in the fore bays. No simple solution was determined~ These vor-texes admitted an appreciable amount of air and created an unstable · water surface near the turnout, but no operational difficulties were indicated. ·

Turnouts

Irrespective of foreba;y shape., the water had a tendency toward spiral flow in the turnout. The spiral was clockwise in the right turn­out looking downstream and counterclockwise in the left turnout. . The. use of a propeller-type totalizing •ter is contemplated tor measuring turnout discharge in the Madera S1&tem. It was anticipated that the· spiral fl~ iµght affect the accuracy of the meter by speeding up with spiral flow in one direction and slowing down in the opposite.

A meter was installed and tested in the turnout having the "tee-shaped" forebay with and without a flow straightener upstream from. the meter. Bo difference was detec'ted in the measurement by the meter. The meter used had a 6-inch propeller.

The field structure wiU have regulating gates on the turnouts. Ro gates wen, installed on the model but a round sheet-metal disc was · placed on the turn011t entrance at different openings to represent a gate. In the "tee-" and "ell-shaped" f'orebays the gate helps to eliminate the spiral condition. The gate in the "in line" forebay increased the spira~ flow to a great extent.

An attempt was made to study tb,e turnout loss.. Two ·conditions handicapped the measurements and the results should be used Judiciously. The first condition was the locatio11 of thepiezometer tap. in the fore­bay. · · In studying losses in the "tee-shaped" toreba;y., the piezometer tap was located in the floor in the Qorner at the turnout.and head wall, and the average loss was found to be about 0.75 of the turnout velocity head. In the "in linen forebay the piezometer tap was loeated first in the floor in the a.enter of the torebay; this resulted in a loss of o.4 of the turnOllt velocity hed. ~ pj.ezometer was then located in the center of the extreme left outlet.wall., utilizing the space b~tween the inner

6

and outer wall as a stilling-well. The new loss was O. 5 of the turnout velocity head. Using this piezometer location for the "ell-shaped" forebay, the loss was one velocity head.

The second condition affecting the losses was the turnout discharge measurement. Head on the weir in the waste flume was meas­ured by a point gage. The water surface in the f'lume was too rough for accurate point gage readings.

The results indicate that the "tee-" and "ell-shaped" forebays introduce more loss than the "in line" fore bay. However, if the turnout inlet were moved closer to the road crossing jet than 1/4 diameter of the road crossing pipe, it is expected that the head loss would increase appreciably and would probably exceed that for the "tee-" and "ell­shaped" forebays. The "tee" and "ell" shape designs are recommended where open-f'low meters are to be used in the turnouts since the flow conditions in the turnout pipe are more-favorable as regards the accuracy of the meter •

7 Interior • Reclamation - Denver, Colo,

.;; a. .. . .. o_ ·o :..J rr-~--• .. __ :

Earth Transition, 10'-o" or as directed.·-----, ~a· ----5'-o" Min.

k-__ \ ___ .._ __ ,2'-0'!.-.Ji,,,-"'-'--: I I a I I I h I I _t_ !!

,-·i 30" Dia. Form Turnout.

s'-o" Min.·--" e'!, r/ .. 8• · ,,--Earth Transition, 10'-o" t<---..i't-a.,../~----L ______ ...,. ____ t_ __ .,.. or as directed. I a II ~ 11 ,.,, 2 -1· , I 24-""'4 I~ '-2!.,4a. I I I w .. 1...___ ! :

! I·

Protection as directed:···' i;>

"·-----Protection as directed.

TYPICAL PROFILE OF ROAD CROSSING. TURNOUT a CHECK-DROP

--ie~-.--1-L ____ • . . · ,,--·Earth Transition, io'-o" : : t 1 ;t:··-lll,n.L2• 3d1 t 202----------------.i or as directed. ! I i j-i Ht-- : ---------4 M + M '--;_,:____ i ! I I

I I I • I

!

-T ---------1 ,--w.s. I ~

.:.-1 I

.... L_~ ---,-

LONGITUDINAL SECTION AT OUTLET END

,,-{ 30"Dio. Form Turnout.

_...,. __ Lz· I I I I I I

l"

l ' ~ ' ; I .. } i __ _t

;!

~Ill

' . : ! ' -.. r ~~ ' ! ..

·~------....L----------1 ---T

PLAN AT OUTLET END

Q

15

30

45

60

P.C.P. CANAL BELOW TURNOUT DROP SECTION CHECK SECTION Dia.

30°

36°

42°

48°

V w, d, V L, w, d, do Lo Do w, 3.05 6.0' 1.85' .92 6,0' .9':t .ft-3/i 6.0'

4.24 6.0° 2.66' 1.14 6.0' 1.5':t .5'-4.2° 6.0°

4.68 s.o' 2.891 1.26 6.0' 1.9':t 'i-3.5° 6.0°

4.77 s.o' 3.36' 1.38 6.0' 2.3°:t 1.5-3.5 6.0'

CENTRAL VALLEY PROJECT- CALIFORNIA

MADERA DISTRIBUTION SYSTEM

COMBINATION ROAD CROSSING CHECK DROP AND OUTLET

PRELIMfNARY DESIGN

. h,

3.5'

4.5°

4.83'

s·.,r ..

21

!;:"Tl o-21 G) ... C: :,:::U -< I'll ? .. !!!

.--Place wall here for / single outlet.

...-.......... :1-11--+111-'1...__,.,_

: , ______ ../~

I I

I I I

' I ! . H r;1 1 I al

r~l- L::&1-v L )~· I 11 --i~:~- --!£:~

Lr• 1:: : .. :

PLAN

6.0' 4.0' ,--===-, ,:::; !"---~.:~.!'_t-·-""j<-t.!!?J---+I I I· I

Lr' I

I I

I I I I I

X

' C).--1½:1 Slope

i

----f I

I ri, 131:rOI _ly L.T.J------

0

I I ____ i.

L. X

Beam Baffle

~ ro: f -----;:;! r.L~ l~ L~J L __ t_ __ _

·,,

',,_2: I Slupe SECTION- Y-Y

~ d L4-Nh'f'>.~ SECTION X-X

NOTES This sketch applies to inside dimensions only, and does

not reflect footings, wall thickness etc. Dimensions underlined with a bar l.2.l are prototype dimensions used in the model construction. Boxed dimensions ( [~ l are recommended design._

I 0 10 15

h.u1 L...J.......J.. L...J. I SCALE OF FEET

\

CENTRAL VALLEY PROJECT - CALIFORNIA

MADERA· DISTRIBUTION SYSTEM

COMBINATION ROAD CROSSING OHEOK DROP AND OUTLET

RECOMMENDED DESIGN

:II

"' 'II ,, -OG)

~c­:c :u -< ITI !=' .. "' ..

(A) No Discharge

CB) Norma.1 Ma::drn•IID Tailwater--Discharging 60 cfs

RECOMMENDED STILLING BASIN

Combination Road Crossing, Check-drop and Outlet Structure--Madera Distribution System

Central Valley Project--California

Figure 3 Report Hyd. 361

(A) No Discharge

(Bl Normal Maximum Tailwater--Discharging 60 cfs

RECOMMENDED STILLING BASIN

Combination Road Crossing, Check-drop and Outlet Structure--Madera Distribution System

Central Valley Project--California

Figure 3 Report Hyd. 361

Figure 4 Report 11yd. 361

(A) Recommended Stilling Basin--Discharging 60 cfs

(B) Recommended StiUing Basin--With Baffle--. Discbarlinl 60 eta

RECOMMENDED STILLING BASIN WITH HIGH TAILWATER

Combination Road Crossing. Check-drop and Outlet Structure- -Madera Distribution System

Central Vall~y Pr.oject--California

(A) Recommended Stilling Basin--Discharging 60 cfs

(B) Recommended Stilling Basin--With Baffle-­Discharging 60 cfs

RECOMMENDED STILLING BASIN WITH HIGH TAILWATER

Combination Road Crossing, Check-drop and Outlet Structure--Madera Distribution System

Central Valley Project--California

Figure 4 Report Hyd. 361

(A) No Discharge

(B) Discharging 60 cfs

STILLING BASIN WITH ''BROKEN BACK'' TRANSITION

Combination Road Crossing, Check-drop and Outlet Structure--Madera Distribution System

Central Valley Project--California

Figure 5 _Report Hyd. 361

(A) No Discharge

(B) Dischargmc 80 cfs

STILLING BASIN WITH "BROKEN BACK" TRANSITION

Combination Road Crossing, · Check-drop and Outlet Structure--Madera Distribution System.·

Central Valley Project--California

Figure 5 Report Hyd. 361

. . Figure~ Report Byc:t 361

(A) "Broken-Back" Stilling Basin with Sloping Floor

"Broken-Back" Stilling Basin with Sloping Floor and Discharging 60 cfs

STILLING B.Afi:..N WITH "BROKEN BACK" TRANSITION AND SLOPING FLOOR

Combination Road Crossing, Check-drop and Outlet Structure--Madera Distribution System

Central Valley Project--California

(A) "Broken-Back" Stilling Basin with Sloping Floor

"Broken-Back" Stilling Basin with Sloping Floor_ and Discharging 6 0 cfs

STILLING BASIN WITH '·'BROKEN BACK" TRANSITION AND SLOPING FLOOR

Combination Road Crossing, Check-drop and Outlet Structure--Madera Distribution System

Central Valley Project--California

Figure 6 Report Hyd. 361

(A) Tee-Shaped Forebay--60 cfs Total Discharge with Right Turnout Operating

(B) EU-shaped Forebay--60 cfs Total Discharge with Turnout at Right Operating

RECOMMENDED FOREBAY DESIGNS

Combination Road Crossing, Check-drop and Outlet Structure--Madera Distribution System

Central Valley Project--California

Figure 7 Report Hyd. 361

Figure 7 Report Hyd. 361

(A) Tee-Shaped Forebay--60 cfs Total Discharge with Right Turnout Operating

(B) Ell-shaped Forebay--60 cfs Total Discharge with Turnout at Right Operating

RECOMMENDED FOREBAY DESIGNS

Combination Road Crossing, Check-drop and Outlet Structure--Madera Distribution System

Central Valley Project--California

Figure 8 Report 11yd. 381

(A) In-Line Forebay--80 cfs Total Discharge with Rigid OuUet .Operating

(B) Over-all View with Tee-shaped Forebay--60 cfs Total Discharge with Ri~t Outlet Operating

"TEE-SHAPED" AND IN-LINE FOREBAYS

Combination Road Crossing, Check-drop and Outlet Structure- -Madera Distribution System

Central Valley Project--Californla

Figure 8 Report Hyd. 361

(A) In-Line Forebay--60 cfs Total Discharge with Right Outlet Operating

(B) Over-all View with Tee-shaped Forebay--60 cfs Total Discharge with Right Outlet Operating

11 TEE-SHAPED" AND IN-LINE FOREBAYS

Combination Road Crossing, Check-drop and Outlet Structure--Madera Distribution System

Central Valley Project--California