ML062850256
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| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 09/07/2006 |
| From: | Hamer M Entergy Nuclear Vermont Yankee |
| To: | Rowley J NRC/NRR/ADRO |
| References | |
| %dam200611, TAC MD2297 | |
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VHS reports Attached to this e-mail are additional reports for Seismic design consideration and inspection report on VY dam.
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-I, - Q~nipmiq de-irtn lvv) nrif Pag e 1 Il VERMONT YANKEE NUCLEAR POWER CORPORAT2ON SEISMIC DESIGN CONSIDERATIONS FME THE VERNON DAM AND THE VERMONT YANKEE REACTOR BUILDING AmENmNT No. 6 MAY 24, 1967
Page 2 JRichard Emch -seismic design (vy).pdf-P-...,
INTRODUCTION This document contains seismic design information requested by the Commission Staff.
The material presented herein consists of:
I Stability analysis of the Vernon Dam.
II An analysis of the extent of cracking of the reactor building which might result from the postulated earth-quake at the reactor site.
(
Richard Emch - seismic design (vy).pdf e
I STABILITY ANALYSIS OF TIM VERNON DAM A)
SfFIMARY
- 1)
PURPOSE AND SCOPE The purpose of this analysis was to determine the in-place stability of the Vernon Dam located on the Connecticut River at Vernon, Veinont.
This analysis was performed in conjunction with the Vermont Yankee Nuclear Power Project which will be constructed on the west shore of the Connecticut River approximately 2500 feet north of the da=.
Particular attention was given to dynamic stability of the dam when affected by the maximum hypothetical earthquake for this site.
The scope of this analysis included the following:
a)
Stability analysis and design review of the typical dam cross-section or block with a base elevation of 171.13 (USGS).
b) Stability analysis and design review of the dam. block crossing the original river channel, which has a varying cross-section and a minimum base elevation of 1W1+ (USGS).
Preliminary copies of the detailed stability computations have been submitted informally to Professor Newmark.
Minor modifications to the analysis of the sec-tion of the dam which bridges the old river channel resulted in a slight change in the static and dynamic overturning factors.
The modifications were as follows:
a)
Use of the full base width for tplift on the East portion of the deep dam section.
b)
The addition of the equivalent concrete pier load on the up-stream face of the deep dam section (East and West).
c)
Utilization of full tailwater pressure for the East portion of the deep dam section.
- 2)
RESULTS The results of this analysis, assuming 100 percent uplift are as follows:
Richard Emch - seismic design (vy).pdfPage4 1.2 Typical Dam Section Dam Block Section in Deep (base el 171.13)
Original River Channel Static D
Static Dynamic Overturning Factor V.-32 1.01 1.44 1.Ih Shear Friction Factor 12.44 8.48 9.50 6.56 Toe Compression 5.19 k/ft 2 67.29 k/ft 2 8.20 kYft 2 22.3 k/ft 2 (no bass Tension)
- 3)
CONCLUSIONS It is our belief that the Vernon Dam is a Class I structure in that it can withstand, without gross failure, the maximum hypothetical earthquake selected for this site.
The analysis indicates that the critical block section is that with a base elevation of 171.13 (USGS) and that the deeper block section filling the original river channel, will act as a plug with a substantially higher safety factor.
All block sections investigated remain stable under all of the loading con-ditions.
B)
DISCUSSION
- 1) DESCRIPTION Vernon Dam is located on the Connecticut River at Vernon, Vermont.
It is a gravity type dam of concrete construction with a crest length of 956 feet and a reservoir with a gross capacity of approximately 40,000 acre-feet.
It is pri-marily used for hydro-electric generation and has an installed capacity of approxi-mately 25 mw.
Construction of the dam was completed in 1909.
Normal head-water level for the dam is at the top of the flashboards at ele-vation 220.13 (USGS).
Minimum tailwater level is at elevation 178.13 (USGS).
During flood conditions, the dam is submerged and stability increases.
- 2)
DEVELOPMENT OF COMPUTATIONS a)
General Conditions and Assumptions
Richard Emch-seismic design_(vy).pdf_..
Page5 1.3 The details of the sections of the dam which were analyzed were ob-obtained from the New England Power Company which owns and operates the Vernon Hydroelectric facility.
For the analysis, headwater was taken at normal water level at the top of the flashboards (El 220.13 USGS) and tail-water. as. determined from the tailrace rating curve, was taken at a mini-mum (no flow) elevation (El 178.13 USGS).
Uplift was investigated using a gradient extending from tailwater to headwater.
It is believed that the actual effect of the uplift would be best approximated by use of a 2/3 factor on the base area.
However, as an additional factor of safety, uplift was calculated and used in the compu-tations as affecting 100 percent of the base area.
Earthquake factors of 0.1"g horizontal and 0.O93gverticaj, acting simua-taneously, were used in the dynamic analysis in each case.
These factors are based on the maximum earthquake ever expected at this site.
Earthquake for-ces were considered to affect the headwater above El 171.13 and the dam it-self.
Dynamic headwater force was computed using "Bureau of Reclamation Engineering Monograph No. 19" with a pressure coefficient (c) equal to 0.735 and assuming a parabolic curve of increased water pressure.
Because of the transitory nature of the earthquake forces, the uplift and water pressure between the dam and the backfill material were not affected.
Also, earth-quake effect was not added to the tailwater as it would improve stability.
b) Specific Conditions and Assumptions
- 1) Typical Dam Section *(Base E2 171.13) - (See Sketch 1)
The static headwater force against the dam was computed between normal water level (El 220.13) and base elevation (El 171.13).
Tail-water calculations were computed between minimum tailwater (El 178.13) and base elevation (El 171.13).
Richard Emch - seismic designr(vy).pdf Page, 6.11 "r.4 The Shear Friction Factor was determined using l!Bureau of Reclama-tion Engineering Monograph No. 19" and assuming a coefficient of inter-nal friction (tan 0) of 0.7 and a cohesion (c) of.15 k/in. 2 which is half the minimum shearing strength normally used by. the Bureau of Re-clamation.
Compression tests of rock cores from the Vernon Nuclear site have shown a minimum strergth of 15,700 psi.
The rock at the dam is geologically similar to these cores and the shear values assumed are therefore extremely conservative.
- 2)
Deep Dam Section Since the dam cross-section varies through this deeper portion, it was decided to analyze a section at each end of the block which crosses this zome and to average the results to obtain the actual overturning safety factor for the block in question.
The length of this block is approximately 55 feet.
The original river channel crosses the dam axis on a skew in this area and therefore provides an excellent key.
The passive resistance of the material adjacent to the dam (as shown in the attached sketches) was neglected.
Including the effect of this material would improve the safety factor.
a)
East-End Section-(See Sketch 2)
The static headwater force against the dam was computed between normal water level (El 220.13) and El 153.13 which is the minimm elevation at the heel of the dam.
Tailwater forces against the dam were computed between minimum tailwater (El 178.13) and El 146.13.
This same depth of 32 feet was used in determining uplift.
b)
West-End Section -
(See Sketch 3)
The static headwater force against the dam was computed between normal water level (El 220.13) and El 149.13 which is
Page 7,
Richard Emch - seismic design (vy).pdf the minim=n elevation at the heel of the dam.
Tailwater forces against the dar were computed between minimum tail-water (El 178.13) and El 166.13.
Uplift was computed using this 12 foot height of tailwater.
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Richard Emch - seismic design (vy).pdf Page 111 31.1 II REACTOR BU]IDI!M2 CRACK ANALYSIS UNDER MAXIMUM POSTULATED EARTHQUAKE The design earthquake at the Vearmont Yankee site has a ground acceleration of 0.07g.
An analysis has been performed to determine the extent of cracking of the concrete walls of the reactor building which would result from a seismic dis-turbance with a ground acceleration twice that of the design earthquake or O.14g.
With a ground acceleration of 0.14g, it is expected that diagonal cracks will develop in the lower exterior concrete walls of the reactor building.
The estimated total length of these cracks is 1300 linear feet.
It is assumed that 5C% of the cracks would close after the earthquake transient.
It has also been conservatively assumed that the average cracks width of those cracks which re-main open is 20 mills.
With 650 linear feet of cracks with a 20 mill opening and a negative pressure of 0.25 inches of water within the reactor building, the inflow leakage rate would be 50 cfm.
Since the standby gas treatment system has a capacity of 1500 cfm, the es-timated inflow leakage rate is not considered significant.
The leakage computations used in this analysis were based on AEC research and development report NAA-SR-10100, "CONVENTIONAL BUILDING FOR REACTOR CON-TAINMENT" and the techniques employed are the same as those applied to pre-vious analysis of BWR reactor buildings.
Richard Emch -- seismic design (vy).pdf Pa qe 12 I Richard Emch-seismic design (vy).pdf Page 12:
VYNPS 8.0-1 8.1-1 STATEMENT 8.0 The following information is required to assess the adequacy of the site and building design criteria.
QUESTION
- 8. 1 Please state the sea level elevation of the station service water intake.
If this is higher than the Connecticut River low-flow elevation at this point without the Vernon Dam, please provide the justification.
ANSWER The station service water intake has a deck El. 237.0 ft MSL (Mean Sea Level - USGS datum) and the bottom of the intake is at El. 190.0 ft MSL.
The elevation of the Connecticut River at this point is controlled by the Vernon Dam located approximately 2500 feet downstream from the site.
By coordinating the operation of the Vernon Hydroelectric Station, adjacent to the dam, with the upstream hydroelectric stations, the Vernon pond water level is normally maintained between El. 218 ft MSL and El. 220 ft MS.L.
The crest of the darn is at El. 212 ft MSL while the flash-board is El. 2Z0 ft MSL. llashboard replacement requires that the pond level be temporarily reduced to El. 211.5 ft MSL; however, this operation is performed very infrequently, usually once a year.
In one instance, the pond level has been lowered to El. 210 it MSL for gate repairs. Even at this level the Vermont Yankee service water pump suction would remain submerged.
I Richard Emch -"seismic design (vy).pdf Paoe 13 I L
- 8. 1-2 With all units in operation at the Vernon Hydroelectric Station, under maximum head conditions and with no discharge from the upstream Bellows Falls Hydroelectric Station, the Vernon Pond drawdown rate would be 1. 3 ft/hr. Administrative controls exercised by the New England Power Company in the operation of the Vernon Hydroelectric Station, how-ever, limit the drawdown rate to 0. 3 ft/hr. If this drawdown rate were sustained for as long as 60 liours (assuming the pond to be at El. 218 ft IVISL initially and with no inflow) the station service water pump suction would still be submerged.
Operating in this mode for such a long period of time is not expected.
The Vernon Hydroelectric Station's standard operating practices will result in pond levels that ensure submergence of the Vermont Yankee service water pump suction. In addition, the Vermont Yankee Nuclear Power Station operators will be able to communicate directly with the Vernon Hydroelectric Station operators and thereby reduce the likelihood of inadvertent reductions in pond level below prescribed limits.
In order to provide submergence for the service water pumps it is necessary to assure a minimum river level of approximately El. 200.0 ft MSL.
This minimum level can be assured from an operations stand-point.
In addition, to be consistent with the design criteria for the struc-tures and equiprhent required for a safe shutdown of the Vermont Yankee Nuclear Power Station, the Vernon Dam should be analyzed for the maximum
- 0. 14g earthquake.
Ultimate stability is all that is required under this maximum earthquake, the same as is required for the Class I structures and equipment at the Vermont Yankee Nuclear Power Station.
The Vernon Dam is a gravity, concrete overflow type dam which was constructed in 1907.
This dam is approximately 600 feet long and
Hichard Emch - seismic design (vv).pdf 0...-, -f, I VYNPS 8.1-3 about 41 feet high except for a narrow section which bridges the old river channel.
This deeper section is limited in extent, approximately 60 feet long, and reaches a maximum depth of some 65 feet.
A powerhouse approximately 320 feet long is constructed directly to the west of the over-flow section of the dam.
The dam and powerhouse are founded on com-pact rock which is believed to be a granite gneiss, as determined from the borings taken at the Vermont Yankee site, approximately 2500 feet from the dam.
In the analysis of the dam for the maximum earthquake the head-water was taken at El. 220 ft MSL and a minimum tailwater El. 178 ft MSL was used.
Uplift on the base of the dam was assumed as varying from full headwater at the head of the dam to full tailwater at the toe of the dam acting on 2/3 of the base area. Calculations were also made to determine the stability with uplift acting on 100% of the base area.
The attached sketch, entitled Vernon Dam, shows the dam and loadings used for the analysis.
Results of the analysis are also shown in Figure 8. 1-1.
The overturn factor is equal to the summation of the horizontal earthquake and head-water moment plus the uplift moment divided into the summation of the dead weight moment of the dam, the tailwater moment and the moment due to the water on the dam, all moments taken about the toe of the dam.
The shear friction factor is equal to the summation of the horizontal forces divided into the sum of an allowable shear stress of 150 psi times the base area plus the summation of the vertical forces times a coefficient of friction equal to 0.70.
The compression on the toe of the dam was com-puted assuming no tension at the heel. If tension at the heel were to exist it would reduce the computed values.
The results show the dam to be stable under the maximum earth-quake loading.
Richard Emch-seismic-design (Vy).pdf..
Page 15]
I FrichardEmch - seismic design (vv),Pdf
-Page1_6,1 I Richard Emch - seismic desian (vv).pdf Page 16 I VYNPS 8.2-1 QUESTION 8.2 In Appendix H, dealing with the seismic design criteria, it is recom-mended that the earthquake spectra corresponding to the N69 0 W compon-ent of the 1952 Taft earthquake normalized to 0. 07 g be used for design.
Please justify the selection of this particular earthquake spectrum as being characteristic of this site.
ANSWER There are a number of past earthquake records which are available for use in design.
However, only three of these earthquake records are normally used in the analysis and design of structures for earthquake motions.
These three earthquakes are as follows:
- 1) 1957 Golden Gate Park earthquake, S80 0 E component.
- 2) 1940 El Centro earthquake north-south component.
- 3) 1952 Taft earthquake N69 0 W component.
The Golden Gate earthquake was recorded on competent rock, the El Centro earthquake on deep alluvium, and the Taft earthquake on shallower and firmer alluvium.
The Golden Gate earthquake recorded on rock would appear to be better suited geologically to the Vernon site. However this spectra peaks very sharply at periods of 0. 1 to 0.25 seconds and drops off very rapidly for longer periods.
By comparison, the Taft earthquake peaks at about 0.2 to 0.5 seconds which is within the range of the estimated period of
I ~r'hrn'd'Fmr4, - '~kmir~ dp~inn MA.ndf Page _i7 h r Pmnh - --eis ic design Ivy) ndf VYNPS 8.2-2 the reactor building.
The Taft earthquake is, therefore, a more severe test for the structure and was selected as the design basis earthquake.
The El Centro earthquake is not typical from a geologic standpoint and in addition is not as severe a spectra for periods under 0.5 seconds.
1'"
Richard Emch - seismic design (vy).pdf Page 181 VYNPS 8.3-1 QUESTION 8.3 A table of damping values is presented on Page XII-2-7, and it is noted therein that reinforced concrete structures are to be designed for 5 per-cent of critical damping.
For this particular plant, which is founded on rock, justification for 5 percent damping is necessary, especially for the design earthquake situation in which the entire structure is assumed to remain elastic.
Higher levels of damping are permissible when cracking occurs and, in general, are a function of the stress and deform-ation level resulting from the loading.
Are the same damping values to be employed for both the design earthquake and maximum earthquake conditions?
ANSWER The subject building is a massive reinforced concrete construction, 144 feet by 144 feet in plan up to elevation 343 feet where the width de-creases to about 110 feet.
The outside concrete walls and concrete floors comprise the secondary containment (the primary containment is effected by the steel containment vessel).
The building period is approximately 0.3 seconds.
The damping value assigned for this massive concrete structure was five percent of criteria for both the design and maximum earthquakes.
Using the assigned damping value, shear stresses in the resisting walls of the building are estimated to be approximately 80 pounds per square inch.
These values are without consideration of wall reinforcement.
Richard Emch - seismic design (vy).pdf Page 191 VYNPS 8.3-2 With regard to the assignment of a realistic damping value, it is well known that damping values for concrete structures will vary with stress level, but it must be pointed out that the stress level in the sub-ject reactor building is by no means low when compared to stress levels used in actual damping tests of structures. Furthermore, the subject building has many cross walls, and is filled with equipment, water, fuel elements, etc. - a condition which is far from that represented by a base frame building having low damping characteristics.
To our knowledge, no authority has assigned a damping value of less than 5 percent critical damping to a building such as the proposed Vermont Yankee reactor building.
Nuclear Reactor and Earthquakes (TID 4500) of the United States Atomic Energy Commission, assigns a damping value of 7 percent for such concrete structures.
Of the many earthquake design criteria for nuclear power plants written by other persons knowledgeable in earthquake engineering, none has assigned a value of less than 7.5 percent for similar concrete structures.
One very similar to the building in question was assigned 10 percent.
In addition, interaction with the foundation material must be considered in the building analysis.
This interaction will increase effective damping.
Many recent testing programs have attempted to measure damping in buildings.
None of these tests have been performed using stress levels as great as those estimated for the Vermont Yankee reactor building under design earthquake conditions.
Two of these programs, however, are of particular interest. Professors Bouwkamp and Clough of the University of California are studying dynamic properties of buildings.
Their work is not yet complete but for the concrete building tested, their paper in
" "Page 20.,
Richard Emch-seismic design (vy).pdf VYNPS 8.3-3 the 1965 Proceedings of the Structural Engineers Association of Cali-fornia states with reference to proper damping values to be used in the dynamic analysis of concrete structures:
although the experi-mental data havr not been evaluated completely a damping of at least 5 percent can be safely assumed".
They also point out that under larger deflections the damping will increase substantially.
The deflections obtained in the test structure were considerably less than estimated for the subject reactor building under the design earthquake loading.
In his thesis entitled Dynamic Response of Multi-story Buildings, (California Institute of Technology), Dr. N. Norby Nielsen has determined certain damping values for a five-story concrete building.
Longitudinally, the building is laterally supported by frames; in the transverse direction by shear walls.
For the transverse direction a statistical study made of the basic data within the Nielsen report indicates a probable damping of 6.6 percent of stresses corresponding to those in the subject reactor building. While the extrapolation of such data may be large, our statisti-cal studies indicates that the basic data conform to straight line represen-tation - the correlation function is approximately 0. 053 - and that there is a 95 percent probability that the damping corresponding to a stress of 80 psi will be equal to5. 7 percent + 1.4%.
(Refer to Figure 8.3-1.)
In other words, the damping will vary between 7. 1 percent and
- 4. 3 percent with a 95 percent probability. While it is true that this study extrapolates information well beyond the range of the basic data, the results confirm the apparent consensus of opinion that realistic damping values for concrete structures is in the range of 5 to 10 percent of criti-cal for the stress levels estimated for the Vermont Yankee reactor building
....Page 2111°J RchardEmch seismic designa(vy)gpdf VYNPS 8.3-4 under design earthquake conditions.
While damping values in excess of 5 percent might be expected under the maximum earthquake condition it was decided to use 5 percent damping for both ea'rthquakes.
If the concrete structure in question was needed for primary con-tainment or a prestressed thin shell structure, a much lower damping value would be in order.
The subject building is not of this type, and the assigned damping value of five percent appears to be realistic. In our research we have not found any test information indicating that lower damping values should be used for a building such as the subject building
Comparison of Vermont Yankee Spectrum with 1993 LLNL Median Uniform Hazard Spectra 50 0.3g NUREG/CR-0098 Spectrum 20
-6 S.....
E 0.14g Housner Spectrum 5
0 02 2.......
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2 3
5 10 20 30 Frequency (hz)
Richard Emch - Safety insp (Vernon Project).PDF Pagel 1 f
'I1 I.
Ii Ii FIFTH QUINQUENNIAL SAFETY INSPECTION VERNON PROJECT FERC Project No. 1904 October 30 1987
'1 I,
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Prepared for New England Power Company by GEl 1021 Main Street Winchester, MA 01890 (617) 721-4000 Project No.
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I TABLE OF CONTENTS
- 1.
SUMMARY
II.
DESCRIPTION OF PROJECT A.
General B.
Project Data C.* Powerhouse D.
Trash Sluice E.
Spillway F.
Vernon Neck G.
Standard Operational Procedures III.
CONSTRUCTION HISTORY IV.
GEOLOGY V.
MONITORING PROGRAMS A.
Powerhouse B.
Vernon Neck C.
Adequacy VI.
FIELD INSPECTION A.
General B.
Powerhouse C.
Trash Sluice D.
Spillway E.
Fish Ladder F.
Vernon Neck G.
Emergency Action Plan H.
Miscellaneous VII.
SPILLWAY ADEQUACY VIII.
STRUCTURAL STABILITY A.
Visual Inspection B.
Analysis IX.
MAINTENANCE AND OPERATION X.
CONCLUSIONS XI.
RECOMMENDATIONS XII.
CERTIFICATION Page Nos.
3 3
3 4
4 4
4 4
5 6
7 77 7
8 89 9
10 10 10 10 10 12 12 12 13 14 16 17 T..
Richar-d'Erch'- Safe~ty Insp (Vernon Projec~t).PDF Page 31 3
LIST OF FIGURES 1B.
General Layout of Plant 2B.
'Details of Spillway 3B.
Powerhouse & Switchyard 4B.
Section of Powerhouse Units 1 - 4 5B.
Section of Powerhouse Units 5 - 8 6B.
Section of Powerhouse Units 9 - 10 APPENDICES A.
References B.
Vernon Neck Cross-Section Surveys C.
Inspection Checklist, May 21, 1987 D.
Inspection Photographs, May 21, 1987 E.
Spillway Rating Curve F.
Spillway Gate Operation Report G.
Stability Analyses H.
Letter from FERC Accepting Independent Consultint 3~1
] IL' I.
1 i
I i
Ric-h-ard'Emch - Safety Insp (Vernon Project).PDF Page 4 II I RicharcPEmch - Safety Insp (Vernon Project).PDF Page 4Ij I I.
SUMMARY
The Vernon Project is located on the Connecticut River in the Towns of Vernon, Vermont, and Hinsdale, New Hampshire.
The licensed project consists of a 600-foot-long spillway and a powerhouse (Fig.
1).
The left abutment is a long natural soil ridge called Vernon Neck.
The project was constructed between 1907 and 1910.
A powerhouse addition was constructed between 1918 and 1921.
Previous Federal Energy Regulatory Commission (FERC) quinquennial safety inspections for this project performed in accordance with FERC Order No.
315 were dated November 1967, November 1972 and November 1977.
The 1982 quinquennial inspec-tion was conducted in accordance with FERC Order 122.
Findings of the fifth FERC Safety Inspection of the project required at five year intervals are presented.
The inspection was performed in accordance with Part 12 of FERC Order No.
122 effective March.1, 1981 and FERC letter dated May 15, 1987, Appendix H.
There have been no federal, state or independent consultant reports relating to safety of project structures since the last quinquennial safety inspection report.
The project structures are founded on hard massive gneiss.
There are no adversely oriented bedding planes or joints observed at the site and there are no known active faults in the area of the project.
Project instrumentation consists of an extensive power-house crack monitoring program.
There is no indication of changes or trends other than seasonal (thermal) cyclic variations in the crack dimensions.
-In our opinion, this program can be terminated; however, the gages should be main-tained and read after major floods, felt earthquakes and/or the next quinquennial safety inspection.
A survey.of four cross sections of Vernon Neck is conducted at five year intervals to detect upstream/downstream changes in cross section.
No changes indicating significant reduction in cross section have been detected to date.
This program should continue at five year intervals or after major floods.
In general, the project structures are in good condition and well maintained.
The powerhouse superstructure was in good condition and all mechanical equipment is well maintained and serviceable.
The project spillway structure and powerhouse intake have been extensively modified since the last inspection to improve spillway crest control, obtain access to Vernon Neck and to improve trash rack cleaning procedures.
The project spillway can pass up to 51 percent of the Probable Maximum Flood (PMF) at zero freeboard.
The flood of
I a f P a.g e S record is 185,000 cfs or 32 percent of the PMF in March 1936.
The estimated PMF is 567,100 cfs.
At PMF, significant damage to project structures would result due.to overtopping flows.
-n Stability analyses show the project powerhouse structure to be stable for all loading conditions including normal operating reservoir, ice loading, zero freeboard (References 2 and 4).
The studies in References.2 and 4 were extended in this inspection report to include 0.10g earthquake loading, and analysis of the modified spillway structures.
It is concluded that all structures are stable fdr the loading conditions investigated.
At PMF, the spillway structures become submerged weirs and the powerhouse will be heavily damaged.
1 Based on the information available from prior inspection i
reports and the observations made during this inspection, there 0
are no recommendations for emergency remedial actiofi or additional monitoring programs at this project.
It is recommendedthat rock scour downstream of the deep tainter gate be evaluated and stabilized.
It is also recommended that the heavy tree and brush growth on the Vernon INeck be selectively cleared.
I.i ui
Richard Emch - Safetyinsp (Vernon Project).PDF
........ ___-Fage 6_J II.
DESCRIPTION OF PROJECT A.
General The Vernon Project was constructed by the Connecticut River Power Company and is presently owned and operated by the New England Power Company (NEP).
Construction began in 1907 and was completed in 1910.
The power plant was put into commercial operation on December 1, 1909.
In 1910, the final three of the eight original generating units were placed in operation.
An addition to the generating station and the installation of two additional generating units was commenced.
in 1918 and completed in 1921.
These units were put. into commercial operation on March 12, 1921.
Effective date of FERC License. is June 1, 1979.
The date of expiration of the license is April 30, 2018.
The project is located on the Connecticut River in the towns of Vernon, Vermont, and Hinsdale, New Hampshire (Fig.
T).
The project structures include a gravity concrete spillway section equipped with flashboards, radial gates, and sluice gates, and a non-overflow section comprised of a trash sluice and the head works and powerhouse.
B.
Project Data The.following project data are taken from References I through 4.
The gross drainage area above the project is approximately 6266 square miles.
The reservoir extends upstream for approximately 30 miles above the project and has a surface area of 2550 acres at El. 220.13 NGVD (126.0).
For
- reference, elevations are given as NGVD with equfvalent project datum in parentheses.
- Project datum is 94.13 feet above NGVD (126.0 project Datum -
220.13 NGVD).
Other statistics are as follows:
Normal Maximum Reservoir Elevation 220.13 feet (126.00)
Normal Operating Reservoir Elevation 218.00 feet (123.87)
Normal Tailwater Elevation 184.80 feet (90.67)
Usable Storage (8 ft.
drawdown) 18,300 ac.
ft.
Spillway -
Length clear 542.50 feet Crest Elevation 10 x 50 gates (4) 212.13 feet (118.00) 10 x 10 panels (10),
212.13 feet (118.00) flashboards 3 (bays) 20 x 50 gates (2) 202.13 feet (108.00)
Discharge Capacity - W.S. El. 220.13 83,200 cfs W.S.
El. 228.13 127,600 cfs I
R~icha rd-Emch -,Safety Insp (VeýrnonProject.PDF a
Pae 7. C.
Powerhouse The project powerhouse contains ten generating units cohsisting of eight units rated at 2000 kw and two units rated at 4200 kw.
The installed capacity is 24,400 kw.
The powerhouse has an integral intake structure with intake gates, trash rack and trash rake.
An upstream trash boom protects the structures against floating debris, Figs.
2, 3, 4.and 5.
D.
Trash Sluice A trash sluice abuts the east (left) side of the powerhouse and is controlled by a motor-driven drop gate, Fig. 6.
E. Spillway The project spillway is 600 feet long.
During the period September 1985 through November 1986, the spillway was modified to install operable gates and an access bridge.
The modified spillway consists of the following from right (west) to left (east):
!e Number Height (ft)
Width (ft)
Tainter Gate 4
10.0 50.0 Hydraulic Steel 10 10.0 10.0 Flashboard Panels Pin Flashboards 2
8.0 50.0 Pin Flashboards 1
8.0 42.5 Tainter Gate 2
20.0 50.0 Sluice Gates 8
9.0 7.0 F.
Vernon Neck The Vernon Project is located on a bend.of the Connecticut River.
Vernon Neck is a natural soil ridge that extends approximately 1,2 mile to the left (east) of the project spillway and is considered part of the water retaining struc-tures for the project, Fig. I and Appendix B.
G.
Standard Operational Procedures The Vernon Project is operated as a run-of-river hydrorelectric project.
Flows in excess of generation require-ments are released by operation of the project spillway crest control structures.
Richard Emch - SafetyfInsp(Vernon Proect).PDF Page8 111.
CONSTRUCTION HISTORY The Vernon Project was constructed between 1907 and 1910 with commercial operation beginning on December 1, 1909.
Two additional generation units were installed between 1918 and 1921 with commercial operation on March 12, 1921.
With the exception of regular maintenance, no significant changes were made to the project until the addition of a fish ladder between May 1979 and May 1981.
In September 1985, a'major construction program was initiated to add crest gates and hydraulic steel panels to the project spillway, to construct an access bridge across the spillway, and to improve the powerhouse intake structure by.
addition of an access bridge and hydraulic trash rake.- These facilities were effectively completed November 1986.
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'm
RJichardEmch -safety/Insp(Vernonproject).PDF Page~9t~ IV.
GEOLOGY The Vernon Dam is located on the Connecticut River between the states of Vermont and New Hampshire.
The'bedrock of this region consists of folded sediments and metasediments of the Silurian and Devonian Periods.
Older sediments and meta-sediments are exposed along intermittent stretches of the Connecticut River.
In general, the older sediments and meta-sediments are of the Ordovician Period.
Metavolcanic rocks of Ordovician Age and igneous intrusive rocks of the Paleozoic Era also outcrop along the Connecticut River.
West of the Connecticut River, in Central Vermont, the bedrock is generally older.
It consists of folded and faulted sediments, metasediments and igneous rocks of the lower Paleozoic Cambrian and Ordovician Periods.
In the vicinity of Vernon Dam, the bedrock consists of the lower Devonian intrusive igneous gneiss. of the Oliverian plutonic series.
This rock type forms the geologic structure referred to as the Vernon Dome.
The bedrock is hard and massive with no adversely oriented weak planes or joints evident, Photos 7, 8 and 9.
There are no known active faults near the project site.
-- 1
R ichard E m ch - S afety Insp (V ernon P roject).P D F Page1.. V.
MONITORING PROGRAMS A.
Powerhouse Numerous cracks in the project powerhouse are monitored for activity by use of trammel points and paper tapes.
New Avongard Calibrated Crack Monitoring gages were installed in 1980.
The Avongard Gage is a direct reading biaxial graphic movement monitoring device.
The two sections of the device are mounted on opposite sides of a crack and the crosshair on one element is aligned with the grid on the other element.
Changes in position over time can be interpreted to the nearest 0.1 millimeter.
To date, no significant changes or trends are discernible in the trammel points, paper tapes or Avongard gages other than seasonal (thermal) cyclic variations, Appendix B.
All crack monitoring devices were read following the 1982 New Brunswick and the Laconia, NH, earthquakes.
No detectable changes in crack widths were observed due to these earthquakes.
It was observed in Reference 4 that some of the powerhouse cracks in the downstream right corner were likely associated with the March 1936 flood which reached a headwater elevation of 231.4 (137.3),
or about 5 feet above the generator deck.
B.
Vernon Neck At periodic intervals, NEP conducts cross-section surveys at four locations on Vernon Neck.
The most recent surveys were conducted in July 15-17, 1987, Appendix B.
When superimposed on surveys taken since 1924, no significant changes could be detected in the main cross section of the neck.
Some con-tinuing minor changes at the.downstream toe caused by seasonal river erosion and deposition during flood flows is considered insignificant since the toe is protected by riprap.
The next survey of Vernon Neck should be conducted as part of the next quinquennial safety inspection or following a major flood (Q > 150,000 cfs).
C.
Adequacy The current program of instrumentation and monitoring of project structures is adequate, and no new or supplemental programs are required.
The. original data are on file at the project office.
It is our opinion the program of crack monitoring in the project powerhouse may be terminated.
The gages should be maintained so they can be read following major floods, felt earthquakes, and/or at the next quinquennial safety inspection.
Rfic'hardt h -c-Safety Insp (Verncn Project).PD
-*Pge1 VI. FIELD INSPECTION A.
General The project structures were inspected on May 21, 1987, by Messrs. Alton P. Davis, Jr., and Marvin Davidson of Geotechnical Engineers Inc. accompanied by Messrs.
Denton E.
Nichols of New England Power Service Company (NEPSCo),
and Hugh W. Sullivan, Charles M. Harrington, and George Webster of New England Power Company (NEP).
The water surface elevations at the time of the inspection were approximately as follows:
Headwater Elevation 218.2 (125.1)
Tailwater Elevation 183.2 (90.1)
An inspection checklist is included as Appendix C arrd inspection photographs are included as Appendix D.
In general, the various project features contain many detailed points of interest and significance relating to their current condition, such as cracks, seepage and spalling.
In previous inspection reports (References 1 through 4),
these conditions have been discussed in detail, and to avoid repeti-tion, only changes, or previously unreported conditions, will be high-lighted in the following subsections.
B. Powerhouse The powerhouse superstructure (Figures 3 through 6 and Photo No.
- 1) is in generally good condition with numerous cracks in the lower brickwork.
The elevation 226.88 (132.75) generator floor has numerous random cracki (Photo No. 2).
All accessible areas of the substructure were inspected and found to be in generally good condition.
The unit-wheel pits were in generally good condition.
The wheel pits appear unchanged from conditions noted in the 1982 Inspection Report (Reference 4).
The elevation 189.13 (95.0) walkway over the draft tubes was inspected.
To the left of Unit No.
1 draft tube, the downstream pier nose is eroded (Photo No.
10).
On the wall downstream of Unit Nos.
7 and 8, the concrete is heavily spalled with pattern ciacking.
These conditions have not changed significantly since noted in the 1967 inspection report (References 1 through 4).
Seepage discharge from the exciter unit area observed in 1982 (Reference 4) has been corrected.
The right abutment upstream training wall and earth back-fill are in good condition.
The powerhouse intake structure has been modified since*
the last inspection'to include installation of an access bridge
=ruuri!ru tmcn - batety insp (Vernon Project).PDFPae2 Page 12 and a new trash rake (Photo No.
1).
This is a major improve-merit for maintenance of the trash racks.
C.
Traih Sluice The elevation 226.38 (132.25) deck and piers are in good condition.
The ogee is generally in good condition with light to moderate surface spalling.
The concrete face under the stairway to the draft tube access walkway is spalled with heavy pattern cracking and is drummy.
This condition is generally unchanged from the 1982 inspection (Reference 4).
The trash sluice drop gate was undergoing repair at the time of the inspection.
D.
Spillway The spillway inspection tunnel and sluice gate operator gallery were inspected.
The two easterly gates (9 and 10) have been plugged.
NEP mobilized in June 1982 and rehabilitated the remaining 8 sluices including installation of new gate seals.
All eight sluice gates-were overhauled and completed in 1983.
At the west (right) end of the gallery is a room with storage tanks containing hydraulic fluid for operation of the sluice gates.
The west wall of the room has'a heavy calcite buildup.
The flow coming from rock outcrops in the access.
stairwell from the powerhouse, noted in the 1982 inspection report (Reference 4), has been effectively sealed by a program of chemical grouting conducted by NEP and the flow is signifi-cantly diminished% Along the downstream crown of the gallery, a lift line makes slight seepage with heavy calcite buildup.
There is a 1/8-inch wide more-or-less continuous crack along the downstream gallery wall.
Much of the crack is calcified.
These conditions remain as reported since 1967 (References 1 through 4).
S.*
Between September 1985 and November 1986, NEPCo installed a major modification.to the project spillway.
Prior to this time, the crest was controlled by 8-foot-high pin supported timber flashboards.
At the time of the inspection, maintenance was being conducted on several of the hydraulic flashboard operators (Photo No.
6).
In Photo No.
6, the pin supported flashboards are installed as a cofferdam and the steel flash-boards supported'by struts to the access bridge during the
,1 maintenance period.
NEP reports that all gates were operated during the 1987 flood season.
Gates were operated during the 1986 flood
. season, as reported in Appendix F; Some plucking of rock and/or dental concrete downstream of the high head tainter gates was observed (Photo No.
9).
This should be investigated and additional dental concrete or a concrete apron should be installed to protect the rock in this area.
I RicharcEmch - Safety Insp (Vernon Project).PDF Page 13 An emergency. gasoline driven generator provides power for the No.
I and No.
2, 20 x 50 tainter gates.
Standby power for the spillway gates is any one of the ten project generators, which are capable of black start.
E.
Fish Ladder The Vernon fish ladder was placed in service in 1981 and has operated seasonally since that time.
F.
Vernon Neck Vernon Neck is a natural soil ridge of high ground between the reservoir and the downstream river channel and forms the left abutment of the spillway (Fig.
1).
The area is inspected regularly by NEP personnel and no significant changes have occurred to date (Photo No. 4).
The upstream and downstream slopes are heavily overgrown and need to be selectively cleared.
G.
Emergency Action Plan The Emergency Action Plan (EAP) was posted in the control room and the plant personnel receive an annual EAP training program.
The plan was updated in September 1987 and tested in December 1986.
The Vermont Yankee Nuclear Station is sited 1/2-mile upstream of the Vernon powerhouse.
The EAP has provision for evacuation in case of a declared radiological emergency condition at the Vermont Yankee Nuclear Station..
H.
Miscellaneous.
The reservoir shoreline as seen from the powerhouse has no obvious areas of distress or instability.---There are no significant changes in the river channel downstream of the dam.
There are no new developments in the reservoir flood zone or the downstream channel since the last inspection report.
There have been no state, federal or independent inspection reports since the 1982 FERC inspection.
ý...Pagý_IA]
Pir-hnrri.FmrCh - Safety Insn (Vernon Pro~iect).PDFPae1 VII.
SPILLWAY ADEQUACY The U.S.G.S. stream gaging station at Vernon Dam with a drainage area of 6266 square miles was used to obtain the hydrologic characteristics of the catchment.
The following information is reproduced from Reference 3.
A study of flow records which extend back to 1944 was made, and the major non-snowmelt flood events were selected and analyzed for use in deriving the unit hydrograph.
The flood of October 1959 was selected'to compute the six hour unit hydrograph for the basin at Vernon.
At the Vernon Project, the Probable Maximum Flood (PMF) with a peak inflow of 567,100 cfs would overtop the dam and appurtenant structures in attaining a maximum upstream water surface elevation of approximately. 251.0 (156.87) or 39 feet above the spillway crest.
A flood of this magnitude would likely destroy the generating capability of the Project and heavily damage the tainter gates of the spillway structures and the powerhouse superstructure.
The water would be 25 feet above the generator deck.
Reference 3 concluded that failure of any portion of the impounding structures which might release the total reservoir volume would.add less than one percent to the volume produced by the PMF.
The zero freeboard flood, elevation 237, (142.9) with a return period greater than 1,000 years, would reach a peak inflow estimated at 2B7,000 cfs, Appendix E.
The flood of record at the site occurred in March 1936 with a peak inflow of 185,000 cfs, causing an upstream water surface elevation of 231.4 (137.3).
Note that all preceding elevations are based on the original spillway configuration which has now been modified.
In Appendix E, a spillway rating curve is presented for the modified'spillway.
This rating curve assumes that all new tainter gates and hydraulic flashboards will be used as peiority gates to delay tripping of the pin supported flash-boards as long as possible.
It further assumes that once the head pond reaches elevation 240, the powerhouse superstructure will be effectively lost and discharge will occur through the powerhouse complex as a broad crested weir at approximately elevation 226.
At the PMF, Vernon Neck would have approximately 7 feet of freeboard upstream and up to 10 feet head-differential from headwater to tailwater in the downstream river channel.
The minimum width of Vernon Neck at elevation 251 is approximately 100 feet.
I L
RichardEmch - SafetyInsp (Vernon Pro'e T).PDF Page.15. ]/
VIII.
STRUCTURAL STABILITY A.
Visual Observation As noted in Section VI, the project structures are in good condition with no significant deterioration or structural distress observed.
B.
Analysis 1Stability analyses of all project water retaining structures were presented in the 1982 Inspection Report (Reference 4).
Since that report, major modifications to the spillway structures have been conducted to include addition of tainter gates, hydraulic flashboards and an access bridge.
Further, the design earthquake coefficient for the project area
]
has increased from 0.05g to 0.10g.
The powerhouse stability analysis in the 1982 Inspection Report has been revised to incorporate the new earthquake coefficient and the.results are summarized in Appendix G.
Stability analyses of the modified spillway structures 1have been, conducted as part of this inspection and the results are presented in Appendix G.
It is concluded that all project structures meet FERC criteria for stability.
Based on the studies presented in this section for the modified spillway, the previous recommendation to place back-fill concrete in the eroded toe areas downstream of the sluice gates is no longer considered critical.
The area should be monitored after major floods (greater than 150,000 cfs).
Remedial repairs need be made only if significant additional
]erosion is detected.
I:
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IX.
MAINTENANCE AND OPERATION Maintenance of the project facilities by the project staff is of a high level.* The project is operated for run-of-the-river hydropower.
Operational procedures are consistent with this goal.
Operational procedures are modified during the salmon spawning season in support of the anadromous fish restoration program for the Connecticut River.
Operation, maintenance and surveillance structures are considered satisfactory.
of the project o-.
.+
- 1
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~1 71
-j
~1
hi~cn!rd~rnch_.afety insp (Vernon Pmiroet1.PDFPae1
-1 &-" *r X.
CONCLUSIONS Based on this inspection, the results of stability analyses summarized herein, the results of monitoring programs
..and review of prior inspection reports, it is concluded that the project structures do not require any emergency remedial work at this time.
The spillway is adequate to pass approximately 51 percent of the PMF at zero freeboard.
The flood of record in March 1936 equaled 32 percent of the PMF.
The project spillway modification will add significantly to power generation by better controlling the reservoir water level to maintain maximum head.
The spillway, non-overflow and powerhouse structures are stable for all loading conditions investigated using procedures, formulations and criteria currently accepted by FERC.
At PMF, the project structures will experience over-topping-flows.of up to 18 feet above the top of the spillway piers*.
Heavy damage to the project structures is likely at PMF.
Project instrumentation consists of numerous crack monitoring gages in the powerhouse.
This program has shown no significant movements in crack widths to date except for seasonal (thermal) cycles.
There were no detectable changes 3
due to the 1982 New Brunswick or Laconia, New Hampshire, earth-quakes.
In our opinion, this program may be terminated; however, the gages should be retained to permit reading after high flood flows, felt earthquakes and/or during the next quinquennial safety inspection.
No additional instrumentation.
is required at this time.
The Vernon Neck surveys show no significant chan~es in the cross-section of the neck.
These surveys should continue on a
.jfive year basis and after any flood exceeding 150,000 cfs.
Project maintenance is very good.
Surveillance and opera-1 tional procedures a're adequate.
The Emergency Action Plan was J
posted in the control room and was updated in September 1987 and tested in December 1986.
Plant personnel receive an annual, EAP training program.
The plan includes a Radiological Response plan for the Vernon Nuclear Plant one-half mile upstream..
There are no changes in the downstream channel.
S'1 The spillway gates are operable and were used during the April 1987 flood.
Standby power is provided by any of the 10 powerhouse generators.
The eight sluice gates are operable.
An emergency generator provides power for the 20 x 50 feet tainter gates.
The exposed bedrock downstream of the new deep tainter J
gate section shows evidence of erosion.
This should be
[Richar&Ernch -Safety Insp (Vernon Project).PDF Page 1811 t.R£h,[;E~
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... P g *8* investigated starting with a survey in 1987 followed by a second survey after the 1988 flood season.
Remedial action should be based on evaluation of any changes observed.
The toe erosion previously observed downstream of the sluice gate sections is of less concern now that the spillway has been modified and post-tensioned to'the bedrock.
This area should be monitored after major floods and at five year intervals to detect any significantichanges that might warrant remedial work in the future.
All recommendations from prior inspection reports for the Vernon Project have been complied with by NEP.
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Ricpard Ernch-__Safe~ty Insp (Vernon Projeqt).PDýF
-Page 191 S.4 XI.
RECOMMENDATIONS Based on Ehe visual inspection reported herein and review of past inspection reports, we have the following recommen-dations for the Vernon Project:
o Evaluate the rock and dental concrete erosion downstream of the deep tainter gates and stabilize as required.
o Selectively clear the heavy tree and brush growth on Vernon neck to permit annual inspection of the upstream and downstream slopes.
The evalua.tion of dental concrete requirements downstream of the new deep tainter gates should begin with a survey in 1987 followed by a second survey after the 1988 flood season.
Action should be based on evaluation of any changes observed.
Z The Vernon Neck clearing should be completed in 1988.
.37.
1
- 1 ii 11111
NIcnardc mch - Safety Insp (Vernon Project).PDF p
20 4., XII.
CERTIFICATION The project structures were inspected on May 21, 1987, by Messrs. Alton P. Davis, Jr., and Marvin Davidson of Geotechnical Engineers Inc. accompanied by Mr.
Denton E.
Nichols of New England Power Service Company; and Messrs. Hugh W. Sullivan, Charles M. Harrington and George Webster of New England Power Company.
This'report covers our inspection of the project carried out in accordance with Part 12 of FERC Order No.
122.
The project inspection and preparation of this report was done under the direction of the undersigned.
The assistance of project staff in conducting the inspection and assembling project data is gratefully acknowledged.
We certify that all work performed in.connection with the inspection and investigation of this project and preparation of
_j this report has been done in compliance with Part 12 of FERC Order No.
122 dated March 1, 1981.
All conclusions and recom-mendations in this report have been made independently of the
- licensee, its employees, and its representatives as required by paragraph 12.37(c)(7) of that order.
. _i
- L *..
E D A V I S, P R
=
- 11
-t No.5421 Respectfully submitted, GEOTECHNICAL ENGINEERS INC.
I
- No. 4241 S-~:/
Alton P. Davis Jr.,
.E.
Project Manager
-I
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Appendix F Spillway Gate Operation Report L
R 'Emch - Safety (sp_(Vernon Project).PDF.
Page221 7?~ ~"'New England Power Mr. Martin Inwald, F Federal Energy Regul iNew York Regional 0 26 Federal Plaza, R New York, N.Y.
1027 RE:
A) iii MI
.,-.w crngiano r-ower *cmpany 33 West Lehanon Road P.O. Box 528 Lebanon, New Hampshire 037(
August 25, 1986 Regional Director
.atory Cornmission ffice oom 2207 78 4NUAL OPE3ATIONAL INSPECTION SPILL-GATE TEST AND MINIMUM FLOW REQUIRE-
- INT FOR L.P.
No.
1904-VT/N-i, VERNON T
Dear Mr. Inwald:
Thank you for your letter informing us of Mr.
Estenio Rosell's scheduled inspecion on September 16, 1986.
Our Mr.
Charles M. Harringccn, Superintendent of Hydro Maintenance has made arrangements to accompany Mr.
Rosell during his insspection.
Records will be available at.this location to Mr.
Rosell which should adequately demonstrate our compliance with the requirements of our 1icense concerning minimum flows at this location.
I I
-A]
- Ii II I
I ii
-I Since operation of spillway gates during this period may pose a problem, we have carefully checked our records and find that all spillway gates at this Project were operated within the preceding 12-month period.
At our Vdrnon Station, the power for a spillway gate operation is supplied by ten individual hydro-electric generating units operating together on any combination thereof.
These units were the source of power during the test of the flood gates at this location.
Since these ten generators routinely carry. load on*a-'dailv basis for other purposes, no specific load tests are performed.
We trust this information will preclude any gate operation during Mr. Rosell s inspection, however, if Mr.
Rosell should request the operation by performance in his presence, we stand ready to do so.
I HWS:tl c/c -
G. H.
Webster C. M. Harrington very truly yours, H. W. SULLIVAN, DIRECTOR HYDRO PRODUCTION A New England ElectIc System company
LIST OF.FIGURES G1.
Stability Summary G2. Stability Summary G3. Stability Summary G4.
Stability Summary, Sluice Gate Section G5.
Case 1, Normal Operating Pool, Sluice Gate Section S
G6.
Case V, Flood of Record, Sluice Gate Section G7. Stability Summary, Deep Tainter Gate G8.
Case 1:
Normal Operating Pool G9.
Case V:
Flood of Record
-1
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Richard-Emch -_Safety Insp (Vernon Project).PDF Page 24 11 1.
III.11 F11 fir Ii' Ii'
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La APPENDIX G STABILITY ANALYSIS Values and Assumptions for Stability Analysis of Concrete Sectlons" A.
Nomenclature:
Effective Length =uncracked portion of base FH = Summation of Horizontal Forces -. kips FV -
Summation of Vertical Forces - kips (including uplift)
Mr -
Summation of Resisting Moments - kip-ft Mo = Summation of Overturning Moments -
kip-ft Mr - Factor of Safety Against Overturning FH - Coefficient of Sliding B.
Unit Weight of Concrete:
150 lbs/cu ft C.
Unit Weight of Water: -62.4 lbs/cu ft D.
Uplift Pressure:
The base pressure was assumed to vary linearly from full headwater pressure at the upstream side to full tailwater pressure at the downstream side taken over 100 percent of the base area for each case analyzed.
Uplift on any portion of the base or section not in compression is assumed to be 100 percent of the headwater pressure for any case~with no foundation drainage systems.
Due to the transient or short-term nature of earthquake loading, the uplift is not changed from the pre-earthquake condition due to further propagation of a tensile crack.
E.
Lateral Water Pressure:
Headwater pressures were computed using the full heights of water to headwater elevations over the projected height of the structures.
Tailwater pressures are taken at full tailwater elevation for non-overflow structures.
For overflow structures,.tailwater back pressures are based on Figs. 14 through 18, Ven T. Chow Open Channel Hydraulics, 1959.
Chas. T. Main, Iinc
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Richard Emch - Safety Insp(Vn Projec t).PDF age 25 F.
Ice Load:
5 kips per linear foot at normal water level.
G.
Earthquake:
Accelerations of 0.10g ýere applied in a horizontal direc-tion.
To obtain the worst case, the resultant force action on the structure due to earthquake is taken in the downstream direction.
The hydrodynamic force was determined using a method presented in Design of Small Dams, USBR, pages 336-337.
"H."
Resistance to Sliding:
Where the ratio of FH/FV is greater than 0.65, the shearing resistance of the foundation to horizontal movement must be investigated using the Shear Friction Formula.
The factor of safety against.sliding is determined by the Shear Friction Formula as:
Ss~f *f V + c A where:
f -
coefficient of the angle of internal friction of foundation material (Tan 0
.0.65)
V - summation of vertical forces c
, unit shearing strength at zero normal load on'
- ~
foundation material.(0.192 ksi)
A -
area of potential failure plane (area of base in compression)
H11 summation of horizontal forces Typical values of "f" and "c" were taken from "The Sliding Stability of Dams".by Harold Link in Water Power Magazine, March, April and May 1969.
I.
The following factors of safety are generally required for the calculated stress and shear-friction factor of safety within the structure and at the rock-concrete interface, assuming a planar failure surface.
High or Significant Hazard Potential Dams a
UnUsual Loading Combination 3.0 Unusual Loading Combination 2.0 I-b Extreme Loading Combination 1.0 Chas.
T. Main, It.
I Richard Emch - Safety Insp (Vernon Project).PDF Page 26 1t I Richard Emch - Saf ety Insp (Vernon Project).PDF Page 26 ~I A
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=1 21 2.
I CASE CASE CASE CASE CASE CASE Low Hazard Potential Dams Usual Loading Combination 2.0 Unusual Loading Combination 1.25 Extreme Loading Combination 1.0 Loading Conditions to be Investigated a)
Usual Loading Combination:
Normal Operating Condi tion b)
Unusual Loading Combination:
Flood Discharge Condition-c)
Extreme Loading Combination:
Normal Operating Condition with earthquake The applied loads should include the appropriate concrete, water, earth, silt, ice, earthquake, and uplift forces appli-cable to the loading conditions being investigated.
I.
Bearing Pressure:
Maximum bearing stress -
20 tsf on bedrock (278 psi)
J.
Factor of Safety Against Overturning:
The minimum factor of safety against overturning is 1.0.
K.
Strength of Vertical Connections:
For structures connected to adjacent structures via keyways, the maximum shear strength used across the key -
250 psi.
Cases Used in Stability Analysis I.
Normal Operating. Water Levels H.W.L.
218.0 (123.9)
T.W.L.
184.8 (90.7)
II Normal Operating Water Level with Earthquake
- H.W.I' 218.0".
.(123."9)
T.W.L.
184.8 (90.7)
III Normal Operating Water Level with Ice H.W.L.
212.1 (118.0)
T.W.L.
184.8 (90.7)
IV Normal Flood Conditions (3'
over flashboards and prior to flashboard collapse)
H.W.L.
=
223.1 (129.0)
T.W.L.
185.1 (91.0)
V Flood of Record Q -
185,000 cfs H.W.L.
=
231.4 (137.3)
T.W.L.
222.9 (128.8)
- VI Probable Maximum Flood Q -
567,100 cfs H.W.L.
251.0 (156.9)
T.W.L.
247.0 (152.9)
V Chas.
T. Main, Inc.
0.
STABI LI TY
SUMMARY
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.e 308 6.7.83D 12.5, 81.1, 96 l182*8 0.05 607.20 44.12 188,6195 608i.032 3.23 6.20 539u 8311 ik.2.,115 I¶UL3 (3174 02 F15 3
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- F-FH = -96.90
- CFV a 1828.32
- rFH/:CFV a 0.05 SSF = 607.10 RESULTANT AT X = 43.38 1*MR - 688678.75
- MO = -608021.75 CMR/CMO x 1.13 BASE STRESS (PSI) 6.20 AT X = 0.00 5.89 AT X = 87.50 VERNON STATION POWERHOUSE UNIT 5
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.52.5 1768 2695 0.66 15.8 23.4 194,021 131,000 1.48 13.3 26.2 Case 2 52.5 52.5 2365 2695 0.88 11.8 18.9 194,021 143,040 1.36 3.2 36.4 Case 3 52.5 52.5 1460 2785 0.52 19.1 25.9 190,124 117,755 1.61 19.6 21.3 Ce.. 4 52.5 52.5 2125 2830 0.75 13.2 19.4 203,575 146,640 1.37 4.5 37.0 Cose 5 52.5 52.5 550 2677 0.20 50.7 32.6 275,882 188,700 1.46 33.9 5.4 Case 6 a.
- Neadwater to 39 feet above optllvey crest.
Tstlvtter to 4 feet lower, 35 feet bovse *ptllway crest.
Spill..ey to fully eubmarJed duriS8 PMy sod stable by isp ctto".
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Power C.'apsny Weetbotough, HA Vernon Project STABILITY
SUMMARY
I SLUIC CATE SECTION Project 87123 sept. 30. 1987 fit. *4
Richard'Emch_- Safety Insp_(Vernon.Project).pDF Page 31
Richard4Emrch_ - Safety.Insp (Veqrnon Project).PDF Pg 2i NOTES
- 1) WlEIGKr OF BRIDGE, PIER AND G3ATE -9.4 /j". OFDAM.
- 2) SL!JCE GATE SECTION 1S la FEET LONG.
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ST R 15 root Unit stock Case 1 53.0 5340 550 994 0.55 14.5 25.7 33.021 7.494 4.41 23.6 28.5 Cse. 2 53.0 53.0 590 984 0.61 13.3 25.6 33.021 7800 4.23 23.1 28.4 C... 3 53.0 53.0 323 1029 0.51 15.3 25.2 33.021 7.111 4.64 22.9 31.0 Cape 4 53.0 53.0 907 955 0.95 8.7 21.6 31.021 0 t15.40 2.66 I1.1 38.9 Case 5 53.0 53.0 104 1003 0.10 76.7 29.3 33.390 3°964 8.42 34.6 17.9 Cs. 6 53.0 53.0 I:
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53.0' UPLIFT PRESSURE ON PIER h'uI CASE Y: FLOOD OF PERIOD 0
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