HYDRAULIC MODEL STUDIES OF THE

TRENTON DAM SPILLWAY- -FRENCHMAN­

CAMBRIDGE DIVISION- -MISSOURI

RIVER BASIN PROJECT

Hydraulic Laboratory Report No. Hyd-301

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CONTENTS

Purpose of Study . . . . . Conclusions . . . . . . . . . Recommendations . . . . . . . . . . . . . Acknowledgment . . . . . . . . . Introduction . . . . . . . . • . Description of Model . . . . . . . . . . . . . Initial Observations and Test Procedure . . . . . • . . . Investigation of the Spillway Overflow Section

Preliminary Upstream E:dension of the Two End Piers-Pier A . . . . . . . . . . . . . . . . . . . .

Determination of End Pier Shape . . . . . . End Pier B . . . . . . • End Pier C. . . . . . . . . . . . . . . . . . . . . End Pier D. . . . . . . . . End Pier E. . . . . . . . End Pier F-•Recommended .• Vortices . . . . . . . . . . . . . . Streamlining of Center Pier Trailing Edge

Investigation of Spillway Chute and Stilling Basin.

Spillway Chute . . . . . . . . . . . . . . . . . . . . Spill way Stilling Basin . . . . . . . . . . . . . . . . . Erosion of the Spillway Exit Channel with Sand and Riprap . . Erosion of the Spillway Exit Channel with Sand. Wing Wall to Reduce Erosion . . . . . . . . . Stilling Basin Velocity Measurements . . . . . . Sloping of Stilling Basin Floor . . . . . . . . .

Recom;n:�nded Spill way and Appurtenances

Flow Condition in Approach Channel and Overflow Section . . Overflow Section Pressures . . . . . . . . . . . River Outlets Through Overflow Section . . Outlet Flow Distribution on Spillway Chute. . . . . . . Outlet Capacity and Pressures . . ." . . Pressures at Float-Well Intakes . . . . Flow Conditions through Spillway . . . . Water Surface Profiles in Stilling Basin . Spill way Capa.:city . . . . . . . . . . .

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FIGURE LIST

Location Map . . . . . . . . . . . . . . . General Plan of Trenton Spillway . . . . . . 1: 54 Model of Preliminary Spillway Design . . Preliminary Spillway Design Discharge of 50, 000 cfs . Preliminary Spillway Design Discharge of 100, 000 cfs. Preliminary Spillway Design Discharge of 125, 500 cfs at

M.3.ximum Reservoir Elevation 2785 Upstream Extensions of End Piers. . . . . . . . . . . Spillway Entrance-- Erid Pier B . . . . . . . . . . . . Spillway End Pier B--Discharge 126, 000 cfs at Maximum

Reservoir Elevation 2785 . . . . . . . . . . . . . . . Spillway End Pier C--Discharge 126,000 cfs at Maximum

Reservoir Elevation 2785 . . . . . . . . . . . . . . Spillway End Pier D--Discharge 126, 000 cfs at M3.Ximum

Reservoir Elevation 2785 . . . . . . . . . . . . . . Spillway End Pier E--Discharge 126,000 cfs at Maximum

Reservoir Elevation 2785 . . ·. . . . . . . . . . . . Recommended Spillway End Pier F--Discharge 126, 500 cfs at

Maximum Reservoir Elevation 2785 . . . . . . . . . . . Spillway Flow with Streamlined .Trailing Edge of Center Piers Erosion in Sand and Riprap of Spillway Exit Channel. . . . . Erosion in Sand of Spillway Exit Channel . . . . . . . . . . Erosion in Sand of Spillway Channel--Wing Wall on Retaining

Walls. . . . . . . : . . . . . . . . . . Velocity Traverses at Spillway Stilling Basin . . . . . 1: 54 Model of Recommended Spillway Design . . . . . Water Surface Profiles in Overflow Section of Spillway Pressures on Overflow Section and River Outlets . . . River Outlets Discharging in Spillway Chute . . . . . Recom.mended Spillway--Discharge 25, 000 and 50, 000 cfs Recom::n,ended Spillway--Discharge 100,000 and 126,500 cfs . . Water Surface Profiles in Spillway Stilling Basin Spillway and River Outlets--Capacity Curves . . . . . . .

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UNITED STATES DEPARTMENT OF THE INTERIOR

BUREAU OF RECLAMATION

Division of Design and Construction Engineering Laboratories Branch . Denver, Colorado

Laboratory Report No. 301 Hydraulic Laboratory Written by: J. C. Schuster Checked and Reviewed by: March 7, 1952

W. C. Case J. W. Ball

Subject: Hydraulic model studies of the Trenton Dam spillway-­Frenchman-Cambridge Division--Missouri River Basin. Project

PURPOSE OF STUDY

(a) Investigate the flow conditions in the approach channel, the overflow section, the chute, and the stilling basin, and determine the capacity of the Trenton Dam spillway.

(b) Investigate the pressures in and the capacity of the river out�ets, which pass through the overflow section of the spillway.

CONCLUSIONS

1. The end pier upstream extension, Design F, Figure 7F, which is elliptical in section between elevation 2787. 8 and 2775. 0, will cause the least water surface contraction at the ends of the overflow section of the spillway for all discharges through the maximum design capacity of 126, 500 cfs, Figure 13.

2. Vortices occurr:µig on both sides of the spillway entrance under the roadway may cause noise but will not have any detrimental effect on spill way operation.

3. Flow conditions were improved in the spillway chute by stream­lining the trailing edges of the center piers (Figure 14) but improvement was not sufficient to justify structural changes.

4. Pressures on the overflow section of the recommended spillway � will be satisfactory as evidenced by a maximum recorded subatmospheric

pressure of 4. 5 feet of water (Figure 21).

5. Water will not overtop the spillway chute training walls at flows up to. and including the maximum discharge with the wall height shown on Figure 2.

6. The hydraulic jump will form satisfactorily in the stilling basin with the 1 to 42. 2 sloping apron.

7. Stilling basin free board is sufficient for all discharges including the maximum design discharge.

8. Protection of the riverbed by riprap of 1 cubic foot to 1 cubic yard size will prevent serious erosion without the aid of downstream wing walls (Figure 15).

9. Spillway capacity curves for free discharge and gate control are on Figure 26.

10. Water discharged from the river outlets into the spillway chute will spread and flow evenly to the stilling basin (Figure 22).

11. Pressures on the bellmouth entrance of the river outlets will be above atmospheric for all flows (Figure 21).

12. Capacity curves for the river outlets are on Figure 26.

RECOMMENDATIONS

1. Use End Pier F with an undercut upstream extension and an elliptical section between elevations 2787. 8 and 2775. 0, for the Trenton Dam spillway (Figure 7F).

2. Use the training wall with the top slopes and elevations shown on Figure 2.

3. Slope the stilling basin floor (1 on 42. 2) from elevation 2655. 50 at Station 37+75. 00 to elevation 2653. 0 at Station 38+80. 50.

4. Use riprap of 1 cubic foot to 1 cubic yard size immediately down­stream from the stilling basin ( Figure 2).

5. Discharge equal amounts of water through each qf the three radial gates to assure even flow distribution through spillway chute and stil_ling basin and to prevent overtopping of the training walls and undue erosion of the river channel.

ACKNOWLEDGMENT

The design of the hydraulic features of the Trenton Dam spill­way were evolved jointly by engineers of the Dams Branch and the Hydrau­lic Laboratory of the Engineering Laboratories Branch.

INTRODUCTION

Trenton Dam and Reservoir are located near Trenton, Nebraska, on the Republican River (Figure 1) . The res�rvoir is linked with Enders, Red Willow, and Medicine Creek reservoirs for flood control and irriga­tion storage. The dam is a compacted earth structure having a length of

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approximately 9, 000 feet and a height of 103 feet above the stream bed.

Water from the res'ervoir is passed through the spillway at the left abutment of the dam or through the canal outlet works located ap­proximately 6, 300 feet to the right of the spillway. Flood discharges are released by three 42-foot wide by 30-foot high float-controlled radial gates over a 126-foot wide spillway crest at elevatiog. 2743, Figure 2. The 126, 500 cfs maximum discharge from the overflow sec-

,. tion of the spillway will flow through the spillway; chute into a concrete­lined stilling basin having a constant width of 266 feet. The 133, 000 cfs discharge given in Figure 2 was a preliminary design criteria. Chute blocks 5 feet high by 5 feet wide were placed at the upstream end of the stilling basin, and a dentated sill 9 feet high was used at the downstream end. The floor elevation of the stilling basin was 2653 with a training wall height of 57 feet to provide 9 . 4 feet of freeboard above normal tail.-water elevation of 2700. 6 for the maximum design discharge.

Normal river discharges flow through two 6- by 7-foot 6-inch river outlets with an invert elevation of 2710 which pass under the over,.. flow section on the longitudinal. center line of the two 8-foot-wide center piers. The river outlet entrance is a rectangular bellmouth 14 feet wide by 14. 5 feet high which reduces in 15 feet by elliptical. curves to the 6-by 7-foot 6-inch conduit. The fl(?w through the river outlets is controlled by two 6-foot by 7-foot 6-inch high pressure slide gates. The top of the river outlet exit coincides with the downstream end of the center piers at Station 30+54. 18 and the bottom blends into the spillway chute 26. 5 feet downstream: The two river outlets discharge a maximum of 4, 100 cfs which flows through the spillway chute to the stilling basin.

Irrigation water from the reservoir passes to the canal outlet works through a 56-inch pipe. A 4- by 4-foot high pressure slide gate controls the discharge into a 16-foot hexagonally-shaped vertical stilling­well. A report of the hydraulic studies of the canal outlet works is pub­lished separately as Hydraulic Laboratory Report No. Hyd. 300.

DESCRIPTION OF MODEL

The hydraulic model of Trenton spillway was built to a scale of -i: 54 (Figure 3). The model. consisted of a portion of the reservoir, the upstream approach channel, all of the spill way including the stilling basin, and a section of the channel downstream. Topography upstream of the spillway was constructed of concrete mortar and the topography downstream was formed_ in sand. The spillway crest, chute, and stilling basin apron were formed of mortar using metal templates for profile guides. The radial gates were inad� of metal and the piers of wood. Water for the model was supp�ied by a 12-inch centrifugal pump and mea�ured by venturi meters. The flow approaching the cresf was uniformly distributed by passing it through a. rock baffle. A point gage with vernier graduations to thousandths of a foot was used to measure the reservoir elevation and a staff gage scaled

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in feet prototype for tail-water elevations. Piezometers were located in both the overflow section and in the river outlets to determine water pressures.

INITIAL OBSERVATIONS AND TEST PROCEDURE

When the model of the preliminary design was placed in opera­tion, the over-all hydraulic action of the spillway was generally good but the overflow section and the stilling basin indicated possible improvement. At the inside of both end piers a water surface depression (pier contrac- ., tion) occurred which resulted in unequal flow per foot width across the two outside overflow sections. Heavy fins of water formed downstream from each of the two center piers which indicated streamlining to be de-sirable. The flow through the spillway chute topped the training wall in the vicinity of Station 36+15 (Figure 2), but the efficiency of the stilling basin indicated that the floor could be raised to require less excavation.

As a result of the initial observations and consultations with the designers, it was agreed that the two end pier upstream extensions should be studied for the purpose of increasing the capacity of the overflow sec­tion and of obtaining equal lateral distribution of the flow entering the spill way chute. After a solution had been obtained for the overflow sec­tion! the stilling basin was studied in regard to depth and to the elimina­tion of erosion occurring at the exit corners. On the completion of the spillway revisions, calibration of the overflow section including the radial gates and river outlets concluded the tests.

INVESTIGATION OF THE SPILLWAY OVERFLOW SECTION

Preliminary Upstream Extension of the Two End Piers--End Pier A

A calibration of the spillway overflow section (Figure 3A) with the two preliminary end piers (End Pier A Figure 7A) showed a maximum flow of 125, 500- cubic feet per second at the maximum reservoir eleva­tion of 2785. This was below the preliminary design maximum of 133, 000 cfs. Flow contractions at the end piers were responsible for a part of the deficiency in discharge. The flow disturbance for discharges of 50, 000, 100, 000, and 125, 500 cfs, which originates with the contrac­tions and passes through the overflow section of the spillway, is shown in Figures 4, 5, and 6. Water spilled over the walls immediately down­stream from the end piers where a fin was formed by the flow contraction (Figure 6A and B). It was apparent that if the flow contractions were re­duced or eliminated, the water surface along the pier wall would be lowered and a more uniform flow distribution without overtopping of the walls would be obtained.

The foundation material in the approach channel to the spillway beyond the upstream end of the concrete of the overflow section was not suitable for supporting the weight of either an end-pier extension ,or a wing wall. Thus, the use of a wing wall for Trenton Dam spillway was not feasible and consideration was_ given to the use of pier extensions

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supported by the cresi and kept even with the two center piers at Station 29 +6 7. 44 ( Figure 2). Based on a similar flow distribution problem whose solution resulted in wing walls extending into the reservoir where approach velocities were low (see Report Hyd. -279 on Medicine Creek Dam spillway), above restrictions imposed a more difficult flow distri­bution problem.

Determination of End Pier Shape

For determining the size and the shape of the end pier extension, end pier A was removed and a series of thin sheet-metal plates were attached in a vertical position to the side-wall of the overflow section (Fig­ure 8A). The flow distribution in the spillway with these plates was sim­ilar to that which would occur for the end pier. Metal and modeling clay were used to form ,the general shape of the flow contraction void as the water flowed past the plate. A series of plates having a vertical leading edge (not shown in Figure 8A) were extended into the reservoir 5, 10, 15, and 22. 25 feet measured from Station 29+89. 69. This type of end pier was unsatisfactory for improving the flow disturbance.

End Pier B

A study of the flow distribution and conditions in the immediate vicinity of End Pier A and the sheet-metal plates led to the following con­clusions: The water entering at the ends of the overflow section of the spillway flowed at right angles to the spillway center line and caused flow contractions because of the abrupt change of direction, and conversion of pressure head to velocity head. If the velocity and pressure reduction were grad.ual, as is the case for wing walls that are uniformly curved and ex­tended into the reservoir, the flow contraction would be reduced. Applica­tion of this knowledge to the Trenton end pier extensions led to an under­cutting of the end pier as shown in Figures 7B and 8.

A comparison of Figures 6 and 9, end pier A and end pier B, shows a 500 cfs increase in spillway capacity and some improvement of the flow conditions through the spillway even though end pier B was roughly shaped in metal. The undercutting caused the water acceleration and pressure reduction to occur along the sloping upstream end of the extension instead of occurring at the vertical upstream end of end pier A. A further re­duced flow, contraction was thought possible by proper shaping and sloping this type of extension. Further tests were made to accomplish this.

End Pier C

Since there was a decrease in the flow contraction for end pier B, a second extension with the outside face at 30° with respect to the spillway center line was constructed of metal (Figure 7C and l0A). Approximate dimensions taken from the metal end pier are shown on Figure 7C. A com• parison of the water surfaces on End Pier B (Figure 9) and on End Pier C (Figure 10) shows the decrease in flow contraction and the decrease in water surface height as the flow enters the chute .

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Two factors were responsible for this improvement, (1) the 30°

angle which decreased the required change of direction for the water to enter the spillway, and (2) the decrease of slope from top to bottom of the end pier. However, End Pier C was not used for Trenton spill way because it was believed that the pier extension could be reduced in size and the outer side could be maintained parallel to the spillway center line.

End Pier D

In determining the shape for the end pier extension, it was de­cided to make the end pier no more than 8 feet wide and to maintain the outer side parallel to the spill way center line to facilitate construction. Several shapes were formed in metal from which dimensions were taken to shape the wooden End Pier D { Figures 7D and 1 lA}.

The plan view of the end pier at elevation 2787. 79 was defined by 1/ 4 of the ellipse X2/ (22. 25)2 + 'YJ./ (7)2 = 1,. and a 1-foot radius arc which was tangent to the upstream end of the ellipse and to the outer side of the pier. The maximum width of the pier was 8 feet, with 7 feet rep­resenting one half the ellipse minor axis. One half the ellipse major axis, 22. 25 feet, was the maximum allowable because of the location of the 5-feet wide by 8-feet 8-inch long radial gate float wells in the end piers. The center of the float well is at Station 29+93. 40. The section through the end pier was constant from elevation 2787. 79 to 2785 where the nose was sloped toward the spillway on a 1 to 1. 7 slope to elevation 2754. At elevation 2754, the shape of the end pier was a semicircle of 4-foot radius which was extended down below the floor of the approach channel. Sections through the end pier between elevations 2785 and 2754 were defined by the trace of the ellipse on the spillway side. An arc with a radius, which varied from 1. O foot at elevation 2785 to 4. 0 feet at elevation 2754, was tangent to the ellipse and to the fiat, outer side of the end pier. The arc also intersected the 1 to 1. 7 slope.

Flow distribution (Figures llB and C) through the overflow sec­tion was improved for all discharges except from approximately 120, 000 to 126, 000 cfs. Through this range, the flow past the extension became unstable. Water flowing from the reservoir into the spillway did not continuously follow the curve of the end pier. The water was springing clear of the inside face of the end pier for short periods of time and then moved back in contact, which would cause vibration. The primary source of this instability was found to be the 1 to 1. 7 slope of the end pier exten­sion. With the upper end of the sloped portion of the pier at elevation 2785, the water change of direction was still too abrupt on the upper por­tion of the sloped section. The upper end of the slope of the end pier was lowered in elevation by using modeling clay, to begin at elevation·2775 and end at 2745, which kept the slope approximately the same as on end pier D but at a different elevation. The flow past this revised extensidh was stable.

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End Pier E

Using the revised End Pier D as a model, End Pier E was built of wood (Figure 7E and 12A) . Flow distribution at the spillway cre st was stable and better but the flow contraction was increased (Figure 12B and C) . This was attributed to the increased submergence of the slope . Therefore, the slope portion of the extension was begun at elevation 2775 and Station 29 +67 . 44 and ended at elevation 2754 and Station 29+85 . 69 .

End Pier F--Recommended

The shape of this end pier, End Pier F, Figures 7F and 1 3A, was essentially the same as end pier D. The ellipse equation of End Pier C defined the cross section through End Pier F from elevation 2787 . 8 to elevation 2775 . The pier was now sloped from elevation 2775 to elevation 27 54 on a 1 to 1 . 1 5 slope . Flow conditions at the entrance and in the over­flow section are shown in Figure 1 3B and C for the maximum discharge which was increased to 126, 500 cfs for reservoir elevation 278 5 . The in­stability of flow for End Pier D was not encountered at any discharge for End Pier E .

, A comparison of the water surface profiles for the preliminary

End Pier A, End Pier E, · and End Pier F (Figure 7) have been plotted in Figure 20 . These profiles were taken on the end pier inside wall for the maximum discharge and reservoir elevation. A difference in elevation of the water surfaces of approximately 2 feet for End Piers E and F may be noted upstream of the spillway crest (Figure 20C) . Since flow condi­tions were stable for both End Piers E and F and only a small difference in the water surfaces existed, the slope could not be too critical . The water surface elevation of End Pier F shows an improvement of 9 feet over that of End Pier A . It is believed that this type of undercut end pier could be satisfactorily used on other spill ways where the approach conditions are similar to that of the Trenton s pillway, and possibly, on center piers to reduce the water surface draw-down. The water surface contraction on Trenton ' s center piers with a vertical leading edge (no undercut) was acceptable .

Vortice s

During the study of the end piers, vortices occurred on both sides of the spill way entrance under the roadway at a distance of approx­imately 1 4 feet from the inside of the end piers. (Figure 2) . The vortices did not decrease the spillway capacity nor did --they cause erosion, since they formed above a portion of the dam which was protected by concrete . The vortices may cause slight noise . Model tests showed that the vor­tices can be prevented by placing two 1 -foot thick horizontal shelves at elevations of 27 6 1 . 3 and 2784. 4 between the end piers and the first coun­terforts at the abutments (Figure 20, Profile Stations) .

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Streamlining of Center Pier Trailing Edge

Impingement of the water flowing through adjacent sections of the overflow portion of the spillway resulted in fins of water downstream. of the two center piers (Figure 13C). Because of structural considerations, the downstream edges of the piers could not be readily streamlined. As noted from Figures 2 and 3, the center piers bridge the river outlets, and any tapering of the downstream •=nd of the piers would require added reinforcement in the top of the outlet conduits. Moreover, the radial gate counterbalances with guides ma.de of steel I-beams operate up and down the ends of the piers and tapering of the pier ends would make it more difficult to attach the steel I-beam guides.

Nevertheless, reshaping of the downstream ends of the piers was studied to determine the influence on the flow distribution in the spill­way chute. Some improvem,ent of the distribution immediately below the overflow section was obtained by tapering the downstream ends of the piers to 1 foot, Figure 14A and B. The fins at the ends of the tapered piers . were approximately one-eight the width of those with square pier ends, although rising to the same height. A second fin occurring at Station 13+ 95 in the chute downstream was ithin although at times rising above the top of the training wall. Flow distribution downstream of the disturbance caused by the fins was essentially the same for both the square and the tapered pier ends. Slightly more wave action at the training walls through­out the spillway chute was noted for the tapered ends. Because no out­standing .fmprovement was accomplished with the tapered pier ends and they introduced structural problems, the designers decided in favor of the pier without the taper.

INVESTIGATION OF SPILLWAY C HUTE AND STILLING BASIN

Spillway Chute

Satisfactory flow conditions were established through the over­flow section by using the recom::nended end pier, design F, Figure 7. The flow was nearly equal per foot width within the spillway chute except for the fins that form,-=d downstream of the center piers. There was slight evidence of the water overtopping the training walls of the model which had not been increased in height. With a 5-foot increase in training wall height at Station 36+15 . 00, near the point of intersection of the chute slope and the vertical curve that enters the stilling basin (Figure 2) , no over­topping will occur. A decision was made by the designers to increase the height of the spillway training wall at this station, from ,�levation 2718 . 64 to elevation 2724. 04. This change in the training wall height decreased the slope of the training wall top from Station 31+65. 00 to Station 36+15. 00 and increased the training wall slope from the latter station to the stilling basin, Station 37+75 . 00.

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Spill wa;y Stilling Basin

Preliminary inspection of the fiow conditions for various dis­charges into the stilling basin showed satisfactory operation. Forma­tion of the jump started well up on the sloping floor to the basin and the chute blocks remained covered for all discharges. At maximum dis­charge the jump used the full length of the basin, with the surface rough­ness caused by the jump extending approximately 30 feet downstream. Eddies were formed on both sides of the basin exit near the 2 to 1 sloped bank and the retaining wall. A maximum water velocity of approximately 7 feet per second was attained by these eddies at a point 5 feet downstream of the retaining wall and at elevation 2660, which was approximately the top of the dentated sill.

Erosion of the Spill way Exit Channel with Sand an.d Riprap

Specifications for Trenton spillway require riprap for a distance of 1 10 feet downstream of the stilling basin and includes the 2 to 1 slopes to elevations above maximum tail-water elevation, 2700, on both sides of the basin exit. The riprap blanket is 3 feet thick and composed of rock varying from 1 cubic foot to 1 cubic yard in size. The model channel was formed according to Figure 2 in sand representing an erodible material with a 5/8-inch and smaller screened gravel for riprap ( Figure 15A). Operation of the model for 4 hours at a maximum discharge of 126, 500 cfs and at the maxim'.llll tail-water elevation, 2700. 6, resulted in the erosion pattern of Figure 15B. An erosion depth of 2 feet occurred on the right side of the basin near the training wall but without seriously disturbing the gravel. A general downstream movement of the gravel occurred across the channel width, but som,� gravel was moved upstream by the ground eddy and deposited on the downstream side of the dentated sill. Riprap on the 2 to 1 slopes adjacent to the retaining walls (at the end and at right angles to the spillway training walls) was not moved except that at the downstream ,�dge of the blanket on the left side of the basin. The riprap material ' in this area was moved upstream toward the erosion pocket by the eddy. The eddy tended to carry gravel down the slope op­posite the end of the training wall. The extent and depth of the riprap blanket was considered sufficient, and the design was satisfactory. For com:r,arison the same test was made using only sand as a riverbed mate­rial.

Erosion of the Spill way Exit Channel with Sand

Channel contours were re-formed in sand after screening out the majority of the gravel. Two erosion tests were made with the use of sand, one for 2 hours (Figure 16A) and one for 4 hours (Figure 16B) at 126, 500 cfs and a tail-water elevation of 2700. 6. The erosion pattern formed at the end of 2 hours showed a maximum erosion depth of 9 feet which pro­gressed to a depth of 13 feet at the end of 4 hours, both depths referred to the elevation of the basin floor 2653. The eddy velocity was great enough to erode away the 2 to 1 side slopes (sand) in both the 2 and 4 hour tests . Without the use of rip rap this amount of erosion was considered un­satisfactory for safety of the structure.

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Wing Wall to Reduce Erosion

In the past, several ways have been determined to reduce the type of erosion described in the previous paragraph. The best way when feasible, is to gradually expand the stilling basin width by m,�an.s of wing walls downstream of the sill. These walls have proved costly in spill­ways the size of Trenton when they must be 50 to· 60 feet long and must be of the sam,= height as the basin training wall. Therefore, a relatively small wing wall similar to a buttress was set at right angles to the re­taining wall (Figure 17). The position selected in Trenton was 11 feet 6 inches from the stilling basin corner. A test was made with the wing wall extended downstream 20 feet which was the convenient length to per­mit the wall to rest on the sam,= footings as the retaining wall. The wing wall reduced the erosion at the corners of the basin but it did little to pro­tect the slope. The maximum depth of erosion at 126, 500 cfs and a tall­water elevation of 2700 . 6 was 8 feet, located at the end of the downstream wing wall (Figure 17A) . Sand completely covered the cut-off wall at the end of the basin, and with the exception of the extreme corners sand covered the downstream side of the sill. The 2 to 1. slopes near the retaining walls were eroded to approximately 5 to 1. A second wall of 15-f oot length was added at a distance of 24 feet 6 inches from the basin corner without mate­rial improvement to the erosion pattern (Figure 17B) , although the depth of erosion was reduced from 8 to 5 feet. The buttress wing wall reduced the amount of riprap required since only the slopes need be covered but the additional cost of the wall for Trenton was not considered warranted. Therefore, a spillway exit channel protected by 1-cubic-foot to 1-cubic­yard riprap and with retaining walls at right angles to the spillway center line was recommended (Figure 2) .

Stilling Basin Velocity Measurements

Concurrent with the sand erosion tests, maximum velocities were measured at several locations in the stilling basin and spillway channel and plotted in Figure 18. The velocity profile at the end of the basin was good with the highest velocities near each training wall. The velocities across the basin exit were sufficiently equal that no recommendations were made in reshaping of the spillway chute training wall .

Sloping of Stilling Basin Floor

The prelim.i.nary stilling basin was designed for a horizontal floor at elevation 2653 . To withstand anticipated uplift pressures under the stilling basin floor, the designers increased the thickness of the concrete to approximately 2. 5 feet at Station 37+7 5 (upstream ,end). This was done by incorporating a 42. 2 to 1 slope up from ·�levation 2653 at the dentated sill to the intersection of the basin floor with the 3 to 1 slope of the spill­way chute (Figure 19B). Triangular fillets 5 feet high, 15 feet wide and full length of the basin were added to the basin training wall and floor junc­tion. An erosion test made with this change showed no appreciable differ­ences with the horizontal floor (Figure 16A) . Sand was used in this test because it is more easily moved by the water and therefore differences would be more readily apparent than by using rip rap. Since good. flow '

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conditions were obtained, the stilling basin was considered satisfactory and was recommended for Trenton spillway (Figure 2) .

RECOMMENDED SPILLWAY AND APPURTENANCES

Flow C ondition in Appr oach Channel and Overflow Section

With the completion of the stilling basin studies, the Trenton spillway was considered to be hydraulically satisfactory (Figure 1 9 ) . Further studies were made to record operational characteristics, such as water-surface profiles, pressures on the overflow section, and flow capacity of the spill way.

Figure 20 shows the water surface ·profiles on the pier walls of the recom.,mended overflow section (Figure 1 9A). With the recommended End Pier F, nearly equal flow per foot across the overflow section ex­isted with water surface contractions at the end piers only slightly greater than those on the center piers. These cont�actions were acceptable .

Overflow Section Pressures

Pressures on the overflow section were recorded at the maxi­mum reservoir elevation, 27 85 , at gate openings of 5, 10 , 1 5 feet and full gate opening (Figure 21) . Slight subatm':>spheric pressures were found for all flows. The maximum was minus 4 . 5 feet of water.

River Outlets Through Overflow Section

The previously described river outlets could not be studied in detail because of the small scale of the Trenton model. Since no opera­tion difficulties were anticipated up to and including the design head cor­responding to reservoir elevation 2773 , which is the elevation of the top of the radial gates when they are closed, .a larger model .was not con­sidered necessary. With the outlets closed at the entrances by m,?tal plates, water flowed from the gate air vents on the downstream .side of the two center piers at maximum discharge and reservoir elevation 2785 (Figure l l C). The flow was from water entrapped under pres sure within the outlet . The pressure source was apparently a pressure rise which accompanied the turning of water on the curve of the overflow section be­tween Station 30+54. 1 8 and Station 30+80 . 9 7. This c ondition will probably occur without detrim,.�ntal effect for maximum discharge with the outlet gates shut in the full size structure .

Outlet Flow Distribution on Spillway Chute

Outlet flow distribution across the spillway chute for reservoir elevation 2720 , and a discharge of 8 75 cfs, is shown in Figure 22A, and for rese rvoir elevation 27 52 and a discharge of 3 , 570 cfs is shown in Fig­ure 2 2B. The distribution was considered satisfactory.

1 1

Outlet C apacity and Pressures

C apacity of the two river outlet s has been plotted in Figure 2 6 and pressures oc curring in the bellmouth entrance have been plotted in Figure 21 . The model outlets were constructed without c ontrol gates which limited the calibration to full open gate s at various heads. The maximum discharge for the two outlets is 4, 28 0 cfs at reservoir eleva­tion 27 7 3 . Pressures in the bellmouth were positive and only slightly negative in the outlet downstream of the slide gates for the two r eser­voir elevations of 2773 and 2743 which cover the upp er range of opera­tion.

Pressures at Float..-Well Intakes

For radial-gate operation at Trenton Dam_. water is supplied from the reservoir to six float wells located in the four piers . Rate of water fl ow to the wells is dependent upon the pressure at t� well in­takes . With the rat e of gate opening proportioned to t he rate of reser­voir rise, the relationship of the pressure at the intakes to the reser ­voir elevation i s important . It is desired that the pres sure head at the intakes correspond to reservoir elevation. The intakes should b e lo­cated where velocity of flow does not reduce the intake pre ssure below reservoir head. Pre s sures were obtained for two intake proposals:

1 . Two intakes located on the outsides of the end piers at Station 30+0 1 . 00 and one intake on the right center pier at Station 29 +67 . 44, all at ele vation 27 66 . 3 6 . The se intakes were to supply water to all float wells .

2 . One intake on each of the center lines of the right and left c en­ter piers, and one five feet to the left of the center line of the right center pier, all at elevation 2 7 28 and over the entrances to the river outlet s at Station 29+67 . 44 . All of the se intakes were protected by the river -outl�t trashracks az:id supply water to all float wells .

For Proposal ( 1) , as the radial gate opening was increased, the reservoir elevation indicated by piezometers located at the fl_oat -well in­take positions deviated lineally from the actual re servoir elevations. This deviation varied from O at reservoir elevation 27 7 3 and the radial gates closed t o O . 5 foot of water at re servoir elevation 2 7 7 8 and the gates 25 feet open. This was c onsidered ac ceptable; howe ver Proposal ( 1) was considered unsatisfactory because debris c ould c olle ct under the roadway, co ver the intakes and this may cause improper re gulation of the radial gates . Als o, wave action with the reservoir at gate top elevation 2 773 could cause a pressure fluctuation at the intake elevation 2 7 6 6 . 36 that could open the gates and waste wat er .

For Proposal (2) , the deviation o f indicated reservoir elevation to that of the actual re servoir elevation varied from O with the gates closed to 0 . 1 foot at a 2 0 ... foot radial gate opening. With the intakes protect ed by the river outlet tras hracks and at an elevation low enough to eliminate wave effect, Proposal ( 2) was c onsidered satisfactory . It was planned that the

1 2

{

..

river outlets will be closed while the radial gates are operated; thus flow through the outlets does not enter the problem .

Flow Conditions Through Spill way

Figures 23 and 24 show satisfactory flow conditions in the spill­way chute and stilling basin for discharges ranging from 25, 000 cfs to the m aximum of 1 26, 500 cfs. Norm.al control of the flood discharge will b� maintained by the float-controlled radial gates . Entrance and exit flow distribution at the overflow section was shown in Figure 13B and C for the maximum discharge of 1 26, 500 cfs . With radial gate control of dis ­charges of 25, 000, 50, 000, and 1 00, 000 cfs, entrance conditions to the overflow section were tranquil except for the normal vortices that form ed. at the junction of the gates and piers. A discharge of 1 6 0, 000 cfs, 26 percent over design maximum, was passed through the spillway. Flow distribution at this discharge evidenced no serious overtopping of training walls . The jump remained in the stilling basin, moving to the middle of the basin only when the tail water was lowered 5 to 6 feet below elevation 2702, which is approximately the tail-water elevation corresponding to a discharge of 1 60, 000 cfs.

Water-Surface Profiles in Stilling Basin

Maximum .water-surface profiles in the stilling basin for a dis ­charge of 1 26, 500 cfs and tail-water elevation 2700. 6 have been plotted in Figure 25. The minimum freeboard on the basin walls is o. 5 feet.-

Spillway Capacity

The discharge capacity curves of Figure 26 are for the recom ­m ended spillway design shown in Figure 2 o Figure 26 includes capacity curves for the radial gates at various openings . The capacity of the spillway exclusive of the river outlets with the reservoir at elevation 2785 was 1 26 , 500 cfs, the designed value. The capacity of the spillway in­cluding river outlets with reservoir at elevation 2785 was approximately 1 30, 000 cfs.

1 3 Interior - Reclamation - Denver , C0lo.

..

D U N D Y

-------I N D E X M A P

V I C I N I T Y MAP .JL

E X P L A N A T I O N (VICINITY MAP ONLY)

----- OILED OR PAVED ROADS -=--- GRAVELED ROADS ---= IMPROVED ROADS

0 10 15 20 25

S C A L E OF MILES

UNITED STATES

DEPARTMENT OF THE INTERIOR

BUREAU OF RECLAMATION

MISSOURI RIVER BASIN PROJECT FRENCHMAN-CAMBRIDGE DIVISION - NEBRASKA

TREN TON DAM LOCA TION MAP

;:::;0;_ ·_::::;::::::_·_::::�:;�7;::D�;:�:::::.

CHECKED:<f'..t(l,.._ �Cl,4,!:.. _ •. APPROVED: .. _ -PL-·l,�----· ... OEIVVER,COLORAOO, MAr 3, 1949 3 28-0-802

� t' ---->'- f'

...- - I I \

---12· 010 abutment ' surface drain outlet.

;1'

'Pe��'�:s backf,il outside the slopes of the dam embankment - ��--,._

--- - - - - - -: 0 -'-4''Min. screenea <jravel

around upper half drain SEC TI ON K-K

...,_,���-,--,--,-,-,-+,-+-,---,i--t � T :-,,

7"" . 'i

'--io" Oroin-cementedjainls C. t. 'SIQlfed dome strainer ' in lower half of perimeter

\4, Layer of bedding material ,I

I • ' 4" Drains with J �� cemented joints-' \

D E TA I L z 12' Min>

i ) :'f.24" A� :_2t" Min.

. --t8' Drain-cemented joints in

' 'Apply.protechve coating to freshly .,. .,/ exposed shale surface where directed - -

SECTION A -A 50 0 50 100

SEC TION G - G

Sta 36f/500- .

,9"Crushed : rock or qravel

SEC TION

--<J F

c:, C:,1 c:;• c:,• ..._ , "'' ...,, "' ' .,__, V, 1 '. I

,-s. 6s000 E.

I - 1-

(c i

FIGURE 2 REPORT HYD. 301

kf Spillway

! 1 11 I ' " I I " :

1----------,40- 6--- -- --- - - ---

1-- -- - - - - - --,s8

10 - -- ---- - -- ---

1- - -- - - ----,40-6-- -- --- --- --'1

c:, ,, 1Crest of dam E__t. 2793. 0 : : : �

I-.., .., "-

1 : � : I / _,p ___ _

\iri/Jly-protective coatinq to freshly exposed

excava fed surfaces where directed

RIVER OUTLETS DISCHARGE IN THOUSANDS OF C.F.S. 0

2790 -�--' I I

2 3 4 5

I I I Max WS Fl 2785.Q_P::: Tnp_ Qf,G,gtesr·o· unnl, ;::.aa-2780

2770

;jpJ/lwoy Discharge _

1 __ -t.• I

LH�..'.'.gqtes Sl.;:: __,_..- Toijwa�er �t ------::= stifling pool'"'t �

2760 I/

-,- ----I "' -

g _ � -

27 1 2

27.08 � �

2704 2: 0

2700 ;:: ,Max. T. W El. 2700. 6 ' Q = l33, 000 C. F. S.

'!c > .., 2750

'- --/

/

y <i - -" Spillway Gres:: I § . ..., 1•� El. 2743. 00 I �

' � ---1 -J- ;,,; � it= he � >i '-

� 2696 � .., --' �

tt. 2675 0 .., 2 740 ui ,:; 2 7 30

2720 /

fr 2710 O

CONCRETE FINISHES Surfaces covered by fill:

Formed; F-t, Unformed U-1. Exposed surfaces:

Formed F-2 Unformed, u-2. Concrele qutter, U-1 ; Stop loq seats U-3

-/

---Discharge 2-6-0 x 7-6 -;: � -'1 2692 ffi

1--I/ � - � -- RivPr nut'J!l+r; I I C) I

I I >< ' -- I I I I �

� Invert of R,ver Outlets El. 2710.00 20 40 EO 80 100 120 140

SPILLWAY DISCHARGE IN THOUSANDS OF C. F. S.

D I S CHARGE - TA I LWATER C U R V E S

UNI T£D STATES

DEPAR TMEN T OF THE IN TERIOR

B UREA U OF RECL AMA TION

2688 � --'

2684 �

1602680

For finishes of river outlets see Dwq. 328 -D- 949 MISSOURI RIVER BASIN PROJECT FRENCHMAN- CAMBRIDGE DI VISION - NEBR.

TRENTON DA M N O TE S SPIL L WA Y Reinforcement shown in Sec. G - G, H-H, and J-J, only. p L A N A No s E c TI ON s Structural desiqn based an a nJinimum compress·/l·�i---------------------------1

strenqth of 3D0D lbs. per sq. in. at 28 days. .,, 7�� Highway bridge designed far H-20 s 16-44 IIXldinq. � :::::����:���":"::: �:;:::::=��=---- � 1�� ��-� _ _ :: 0) CHECKEDf:_£ ____ %,{�� - APPROVEQ __ x,_12,,.::/t�- - - -:,; � DEN VER, COLORADO APRIL 21, 1950 3 28-0- 946

A . Spillway entrance

B. Spillway chute and stilling basin

1: 54 MODEL OF PRELIMINARY SPILLWAY DESIGN Trenton Dam

Figure 3 Report Hyd . 301

A . Spillway entrance

B . Spillway chute and stilling basin

Figure 4 Report Hyd . 301

PRELIMINARY SPILLWAY DESIGN - DISCHARGE OF 50, 000 CFS Trenton Dam

A . Spillway entrance

B . Spillway cute and stilling basin

Figure 5 Report Hyd . 301

PRELIMINARY SPILLWAY DESIGN - DISC HARGE OF 100, 000 CFS Trenton Dam

A . Flow distribution and flow contraction at spillway entrance ( Flow right to left)

B . Flow distribution and waves on end piers in overflow section

C . Spillway chute and stilling basin

PRELIMINARY SPILLWAY DESIGN - DISCHARGE OF 125, 000 CFS - AT MAXIMUM RESERVOIR ELEVATION 2785

Trent on Dani

Figure 6 Report Hyd. 301

/ .. ��_tt_-20·-·u �- ' : \ PLAN ', : .'1... ------Upstream end ot

n2ra1.79 :-------·�r"22·25�---� rodiol gate tloot well

El.2735.0

E N D P R D F I L E A.- E N D P I E R A - PR E L I M I N AR Y

E N D C . - E N D P I E R C

E N D P R OFI L E E . - E N D P I ER E

PROF I L E

F LO W

-U PSTREAM EXTE N S I O N S OF E N D P I E R S

S P I LLWAY O V E R F LO W S E CT I O N

T R E N T O N D A M

F I G U R E 7 REPORT HYO. 301

X2 Y2 c]J' 22.252+ 11 = 1 IAppro•:

�-.i,

1.0·- ' \ � . . • i , ' P L A N

-

E N D P RO F I L E B. - E N D P I E R B

z-- - ------

4.0'R- -

E N D P R O F I LE 0. - E N D Pl ER D

2:�,.+ �= I···--.

• . • _I:. - �-r 1.0'----�

-$ Sto. 29+67.44-.,, , p LA N

E N D

El.2]�?:_����----22.25' -------�

4.0'R-

EJ.2735.0 P R O F \ LE

F. - E N D P I E R F - R ECOMMEN DED

A . Sheet metal plate used for determining the end pier shape

B . End pier B

SPILLWAY ENTRANCE-END PIER B Trenton Dam

Figure 8 Report Hyd . 301

A . Flow distribution at spillway entrance for end pier B

B . Flow distribution in overflow section for end pier B

Figure 9 Report Hyd . 301

SPILLWAY END PIER B - DISC HARGE 126 , 000 C FS AT MAXIMUM RESERVOIR ELEVATION 2785

Trent on Dam.

A. End pier C

B . Flow distribution at spillway entrance for end· pier C

C . Flow distribution in overflow section for end pier C

SPILLWAY END PIER C - DISC HARGE 1 26, 0 0 0 C FS AT MAXIMUM RESERVOffi ELEVATION 2785

Trent on Dam

Figure 10 Report Hyd . 3 0 1

A . End pier D

B. Flow distribution at spillway entrance for end pier D

C . Flow distribution in overflow section for end pier D

SPILLWAY END PIER D - DISC HARGE 126, 000 C FS AT MAXIMUM RESERVOIR ELEVATION 2785

Trenton Dam

Figure 1 1 Report Hyd . 301

A . End pier E

B . Flow distribution at spillway entrance for end pier E

C . Flow distribution in overflow section for end pier E

SPILLWAY END PIER E - DISC HARGE 126, 000 C FS AT MAXIMUM RESERVOIR ELEVATION 2785

Trenton Dam

Figure 12 Report Hyd 301

A. End pier F - Recommended

B . Flow distribution at spillway entrance for end pier F

C . Flow distribution in overflow section for end pier F

REC OMMENDED SPILLWAY END PIER F - DISC HARGE 126 , 500 CFS AT MAXIMUM RESERVOIR ELEVATION 2785

Trenton Dam

Figure 13 Report Hyd . 301

A . Streamlining of trailing edge o f center piers

B . Flow distribution downstream of overflow section showing 3 fins of water, one from the end of each c enter pier and one at Station 3 1 +9 5 . 8 - Discharge 1 26, 000 cfs

Figure 14 Report Hyd . 3 0 1

SPILLWAY FLOW WITH STREAMLINED TRAILING EDGE OF CENTER PIERS Trenton Dam

A . Preliminary stilling basin and spillway exit channel with representative 1 cubic foot to 1 cubic yard riprap 3 feet in thickne ss

B . Erosion after a 4-hour discharge of 1 2 6 , 5 00 cfs at a tailwater elevation of 2700. 6 . Basin floor elevation 2653

EROSION IN SAND AND RIPRAP SPILLWAY EXIT C HANNEL Trenton Dam

Figure 1 5 Report Hyd . 3 0 1

A. Preliminary stilling basin and spillway channel after 2-hour sand erosion

Figure 16 Report Hyd . 301

B . Preliminary stilling basin and river channel after 4-hour sand erosion

EROSION IN SAND OF SPILLWAY EXIT C HANNEL DISCHARGE 1 26, 500 CFS

TAIL WATER ELEVATION 2700. 6 Trenton Dam

Figure 17 Report Hyd . 301

A . Four hour erosion results using one 2 0 foot long buttress at a distance of 1 1 . 5 feet from inside of training wall on both sides of spillway

B . F our hour erosion results using one 20 foot and one 1 5 foot lo1:1g buttress at re spe ctive distances of 1 1 . 5 and 24 . 5 feet from inside of training wall on both sides of spillway

EROSION IN SAND OF SPILLWAY C HANNEL - WING WALLS ON RETAINING WALLS - DISC HARGE 1 26, 500 C FS

TAIL WATER ELEVATION 2700 . 6 Trenton Dam

-

5C

,' -< - '

-

.

' 4 ' I / \ -

- - -- I � \ - I ---I -r -

N O T E \ -I. A l l veloc it ies ore ma x i m um 2. Bas i n floor length is 125 feet.

\ -4( 30 20 r o 0

FEET \ -1---- D

F L OW r-f �

rf------.:- ------ Traverse ot B

Elevation 2662 -

(STATION B -Traverse ot A-- -----, - I Elevation 2655 .

.-STA T I O N A -I - (

j C \

I/ -...... �

10 20 30 40 0 I 20 30

V E L O C I T Y - F E E T P E R S EC O N D P L A N

v--... :· -Wote) surto1ce

·-·uevor,on 27 10 -- -Mox. �ws - -� -- --� -� �--= sok--:::s �.£- ---==- a== ----

2693 - ,--Trove rs at C Discharge 126,SOOCFS � � _; ..........

� !rrave�se D 5 E<: ....___ 2673

't> El7vatio1 2661\ __ ,, --- ------ICSK

- .... ----1 to 42.2 slope ,--Eleva ion 2r53 -

,: ,-30

V E L OC I T Y - F E E T P E R S E C O N D P R O F I L E

V E LOCITY TRAV ERSES AT SPI LLWAY STILLING BASI N

TRE N TO N E> A M .

q

40

F I G U R E 1 8 REPORT HYO 301

A. Spillway entrance and abutments - recommended design

B . Spillway chute and stilling basin - rec ommended design 1 on 42 . 2 slope up in direction of arrow

1: 54 MODEL OF RECOMMENDED SPll..LWAY DESIGN Trenton Dam

Figure 19 Report Hyd. 301

2783 A.. � :::::.. �- �--C

/ 2773 � ¾ \ ,._ f:::_._, >--' 2763

>-

��-"" 1 21e3

z I'\ '\. 0

;: <( � 2743 .J / ---........_

I\', �' 2733 '

2723

271 :5

/ /

/ V /

I/

"--.,_

'� � � A. PROF I L E C ll D "'

�--El. 2784.4

1.2743 �- :,· ·· ..... Vortex prevention sh.elves

�

�� � u�� 2783 1

k I I Jt:::-i P�O F I L E,STAT I Oi"½.J I I I I I t station A ond I

""I !\J. �] 7 <f -,1.:::::j-_ �l.End oi;n A ( I I I I I I zm\ ' I' ' 3- � , .. · I

· · r ,,.: 1 JS«�-- F, I I I I

... L11�J+-�:_��--+--4--t-7__::1t�1"�1-r-- r7 ::: � 21e3

� . , .... , ... " I I I I I ----::::I I I I "�,;:.. �, I I I � 2743 ! k, I ....---_, "' 2733

I'! JiApproximote I elevation of

Dom inter­section

2723 t-+-.- --.+- -+- -- +- -- t--�- -�- -�-�'lc-- -t---i---+---+------,

C. P R O F I L E A 15 I 271 3 I I J/ I I I I I I I , --T- I I

A

� r-=::.:::.---� \ [-G �

"'s,.. s,.. '\

\, /v -� "

/ l"" /

/ "" / B. PROFI L E F ll G

V N O T E S

Un less othewise noted, pro fi les were Reservoir elevation 2785 Discharge 126,500 C FS token on recommended design- e n d Pier F.

I I A

l -� �"" y"•-H / '\ � � \ "' 9_,' � � -

'\I'\ �, '\ "-

. . � � / V I"-. '

� /

'� I/ V · � / D. PROFI L E B,E, ll H

/

/

� � � "'¾, ""-- -

'\

"\ ""'

i�

¾ -'--

-- ··. -'>

4 0 30 , o 10 . 0 10 20 F E E T

30 40 50 60 70 00 90 .. 40 ·-30 --20 ·-10 10 ·-20

F E E T

--30 ·-40 --,o --60 70 ·-00 90

W A T E R S U R F A C E P R O F I L E S

I N O V E R F LO W S E CT I O N O F S P I LLWAY

T R E N T O N D A M

cl G) C ., "' "' 0

50

45

40

35

a: w 30 ,_ <l 3: u. 0

� 25 w u. ' w a: :, "' 20 (/) w a: a.

1 5

10 '

0

-5

0 '

'10 )

D 20

0

.4 0

.

_/

� -50

\ \

F IGURE 21 R E PORT HYO. 301

\ OUTLET PRESSURES M EASURED W ITH RAD IAL GATES CLOSED

\ �

,-·Reservoir Elevation 2773 ,, Discharge 4280 CFS

\ a,

\ '

I �. ,-Reservoir Elevation 2743 I ,,., , Discharge 3170 CFS I

' ' ' I,

PI EZOMETERS

: f � 4

I

,,---Elevation 2743 Gote opening

V /

V ,:�levation 2723.5 /

N 3 4 .._:._ '

/v

--40 30 20 10

\ \

\ \ K,\

I� \, �

-�� �� \ � ,, � \"---r:r-7

1 1

-·Gote position

I\ ', ' --,._ 8 '

9 � 10

FULL GATE OPEN ING D I SCHA RGE 1 26, 500 CFS

RESERVOIR ELEVATION 2785

F

/ I

25.0 Feet 94, 200 CFS 2785

I ., i /

) / ,'

I5 .0 Feet 6 1 , 500 CFS 2785

i/ I / I j / p __ _1· 5.0 Feet

2 1 , 500 CFS

[,/ / / 2119. 5 I / ,,d1/a

. I O RESERVOIR ELEVATION 2773

4 RESERVO IR ELEVATION 2743

- --4"'

"'

12 6 13 Il l I I

Piezometers on spil lway centerline

� I I "..,

Piezometers 5 ond 6 o� river outlet centerline

,I'-. 5 � I 3

�

t

r4;'-o" by 7'-6" river outlet '--

,t .,,-Elevation 2710 -----,__

0 FEET

10 20 30 40 50 60

P R E SSURES ON OVER FLOW S ECT ION OF SPI LLWAY

AN D R I VER O U T L E T S

TR E N TON D A M

A. Flow distribution in spillway chute with river outlets discharging 875 cfs at re servoir elevation 2720

B . Flow distribution in spillway chute with river outlets discharging 3570 c fs at reservoir elevation 2752

RIVER OUTLETS DISC HARGING IN SPILLWAY C HUTE Trenton Dam

Figure 22 Reoort Hyd . 301

•

Figure 23 Report Hyd . 301

A. Flow in spillway chute and stilling basin - Discharge 25, 000 cfs - Reservoir elevation 2781 - Gate opening 5. 2 feet

B . Flow in spillway chute and stilling basin - Discharge 50, 000 cfs - Reservoir elevation 2785 - Gate opening 1 1 . 9 feet

RECOMMENDED SPILLWAY--DISCHARGE 25, 000 AND 50, 000 CFS Trenton Dam

•

Figure 24 Report Hyd . 301

A . Flow in spillway chute and stilling basin - Discharge 1 00, 000 cfs - Reservoir elevation 2785 - Gate opening 2 6 . 8 feet ,,

B . Flow in spillway chute and stilling basin - Discharge 1 26, 50(, c fs - Reservoir elevation 2785 - Free Discharge

REC OMMENDED SPILLWAY--DISCHARGE 1 0 0, 0 0 0 AND 126, 500 CFS Trenton Dam

,... "' "' IL

z

27

269

267

265

271

z 269 2

>

� 3

3

l

"

--=, � -r:-----

LEFT A B ' I '

r---r:-----r--r--r---

"' ...J .-· !Station 35 t 55.17 LiJ 267

265

27 -r---r----r---269 ;

267

265 ... 0 --20 --40 --60

=::::..:::..-: ----..::::..:::. P'-:::::.: ---t-----._ -.::::--

i----._ ---.::: ------t---..

31 8 IL

1 1 D i I

D I S C H A R G E 1 26,500 CFS

---· ,-......._ 1---------- ...___ ----- ---------r---...

---,-......._ ------ -------------------- �

r----.

--80 ---100 - --120

i----� ---;:::?

p---� �- // ----- � / ---- � --- ----

El

R I G H T ----t--..

r---...

--- ,__..... ---- --.,,--r---... ------

---- ----------------r----

------ I

---- 1.,-----' i---------

1-----------r---r---- ------t---..

------7 140 160 180 200 220

F E E T WAT E R SURFACE PROFI LES

IN SPI LLWAY STI LLING BAS I N TRENTQN DAM

..

Top of stil l ing basin wal l elevation 2710·-, . E· ,_.. - 1----- - �- -- , _ TYi. El.

2700.6 ---- A-' s--�='

t >-----___

2 7 1 0--. V

B·· -- - ---- _ _, t:::-:==r ..--=--- - 0-·'

--

r-= I>-.. I

Station 39t00·-, I I ... "'Sj

2 7 1 0 ·-. I • C·· . i---

--., -

r: r>--.. ---240 ---260 ---280 ---300 320 340

,, "' ,, "Tl 0 -,, Gl ..., c

� ;%) 0 !Tl

<,, N . 0 "'

2 7 8 8

2 7 8 3

2 7 7 8

I- 2 7 7 3 w w LL

z O 2 7 6 8 I-<( > w ...J w o::: 2 7 6 3

0 > 0::: w (/) w 0::: 2 7 5 8

2 7 5 3

2 748

I I

2743 0

I I I I I I I I I I I I Ma x i m u m rese rvo i r e l e v a t i o n )

,i-' -� � ..

F I G U R E 2 6 R E PORT HYO. 301

3 - 4 2 '- o " x 30'- o " g a tes /,,. ,J

I ' I J J I,;"" Ope n i n gs

J I I I

j

I I I

I I I

'

I I .v I �v

' � V

IV • -V V

-1-- f--

i/ /

I/ S p i l l wa y c re st

1 0

ref e r red to c rest, ' I .v V '- J ' j I I/ . V .....

"-"hi I/ I V ' I I I/ / '

I G AT E OPEN I NG - F E ET I/ /

5 . 0 / 1 0.0/ 1 5.0/ 20.0/ 2 5 .�V

7 I II" , I,;"" j I �

I !/ / I,"' 1 ...... '

I J I I/ I,"'

I/ I i....... ..... -J ) I V ...... I,"""

J

I I I V ...... ,,,,,,..

I I ) / V �

I I I � ,,,, 2 7 60 I I ,J

V

I < I .... v '

I I/ / �' -Free d i scharge - net crest -- w J i ......

... f--

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