HomeMy WebLinkAboutEmail - Oroville Emergency Spillway Capacity Menchaca, Clarissa
From: Snyder,Ashley
Sent: Monday,April 3' 2O1782OAK4
To: B(]S
Cc: Menchaca, Clarissa
Subject: FW: Revised — DVVR's (]rov||e Emergency Spillway Capacity of36Q'OOO [FS is Bogus! —
byHenry VV. Burke 3.31.17
Please see the below correspondence.
Ash[CN N. SwU�er
Assistant Clerk of the Board
T: 530.538.2867 | F: 530.538.7120
11 VV F������� | ���T��� | Pi�t���t
From:ted ryan [mai|to:tedryan@monzom]
Sent: Friday, March 31, 20173:S2 PM
To: Connelly, Bill <BConne||y@buttecounty.net>; Clerk ofthe Board <derkotheboard@buttecounty.net>
Subject: FW: Revised --DWR's Oroville Emergency Spillway Capacity of 369,000 CIFS is Bogus! --by Henry W. Burke
3.31.17
FYI,from HW Burke...please read. Forward to Bill Connelly and fellow Supervisors.This is important to have an
independent known Dam /Engineer focusing only on Dams to provide his input.
Thank you in advance.
Ted
Sent from Mail for Windows 10
From: Henry W. Burke
Sent: Friday, March 31, 2017 2:29 PM
To:Ted 1Ryan
Subject: Revised -- DWR's Oroville Emergency Spillway Capacity of 369,000 CIFS is Bogus! --by Henry W. Burke --3.31.17
Ted Ryan:
I sent this report to all of the key people with DWR, FERC, BOC, etc. I don't mind
stirring things up a bit. My ENR print edition article (April 3, 2017) will do more of the
I revised this report to highlight the various calculated discharge capacities for the
Oroville Dam Emergency Spillway. That information appears at the end (with the
calculations) and also at the beginning.
Henry W. Burke
bu,r.ke cx�co ®net
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DWR's Oroville Emergency Spillway Capacity of 369,000 CFS is Bogus!
By Henry W. Burke
3.31.17
The California Department of Water Resources should immediately correct all statements
referring tote design capacity (design outflow) of the Oroville Dam Emergency ill ay
as 369,000 cfs, and change it to 18,000 cfs (cubic feet per second).
To summarize, the calculated discharge capacities for the Oroville Emergency Spillway
are as follows:
Elev. of Lake Oroville Hydraulic Head Calculated Discharge
902.0 ft. 1.0 ft. 6,400 cfs
902.6 ft. 1.6 ft. 12,930 cfs
903.0 ft. 2.0 ft. 18,100
cfs
On March 17, 2017, the California Department of Water Resources (DWR) sent a
memorandum to the Federal Energy Regulatory Commission (FERC). In the letter, DWR
2
transmitted information on "FERC Project No. 2100 — Oroville Emergency Recovery —
Spillways, Independent Board of Consultants, Memorandum No. L"
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On page 6 of the DWR Memorandum, it states the following:
Restore both spillways to pass the Probable Maximum Flood(PMF)flows without
failing, and with damage below the Emergency Spillway to be expected. These include
the following estimated flows:
• Gated Spillway peak design outflow of 277,000 cfs
*Emergency Spillway peak design outflow of 369,000 cfs
Operational maximum release goals are as follows:
•Operate the reservoir to limit the Gated Spillway maximum design release to
100,000 cfs
*Operate the reservoir to prevent spillover the Emergency Spillway.
It is the BOC's understanding that peak outflows through the Gated Spillway will be
limited to about 150,000 cfs, which is consistent with historic peak releases, and are
designed to prevent overtopping of levees and flooding of communities downstream of
the dam.
The current inflow to the reservoir is about 13,000 cfs. Using the current snow pack,
and based on forecasts from historical snowmelt seasons, a conservative estimate of
inflows during the April and May months indicate inflows of the order of 25,000 cfs.
With the gates closed, current outflows through powerhouse are about 13,000 cfs,
resulting in a net inflow of about 12,000 cfs. Thus, the reservoir should be operated to
address the net inflow during the snowmelt season.
Please note that DWR lists the "Gated Spillway" (Main Spillway) peak design outflow of
277,000 cfs; and DWR lists the "Emergency Spillway" peak design outflow at 369,000 cfs.
3
Where did DWR get an Emergency Spillway design capacity of 369,000 cfs? I can only
guess, as explained below.
Common sense would suggest that a design discharge capacity of 369,000 cfs for an un-
gated overflow weir is way too high! Also what would 369,000 cfs of water do to an
unpaved steep slope between the Emergency Spillway and the Feather River diversion
pool? The answer lies in the events of February 11 and 12, 2017. The steep slopes were
severely eroded, portions of the boat ramp access road were destroyed, and the toe of the
concrete weir was partially undermined.
All of this occurred with only very light flows over the Emergency Spillway. DWR
estimates that 6,000 cfs to 12,600 cfs moved over the Emergency Spillway from Saturday,
Feb. 11 at 8:00 a.m. to Sunday, Feb. 12 at 8:00 p.m.
On 3.19.17, I sent the following short report to DWR:
----------------------
----------------------
Calculated Capacity of Oroville Dam Emergency Spillway
By Henry W. Burke
3.19.17
On February 11-12, 2017, the Emergency Spillway at Oroville Dam was used for the first
time in the dam's 50-year history. According to the California Department of Water
Resources (DWR), the flow over the Emergency Spillway was about 6,000 - 12,600 cubic
feet per second (cfs).
What is the rated capacity of the Oroville Dam Emergency Spillway? DWR does not
specifically list the Emergency Spillway capacity.
4
Why is the rated capacity of the Oroville Dam Emergency Spillway important? Some
sources have stated that the capacity is a whopping 450,000 cfs. Environmental groups
have advocated that the steep slope from the spillway to the Feather River should be
paved. Because there are practical and cost implications involved, the public needs to
know the Emergency Spillway capacity.
By comparison, the Oroville Dam Main Spillway is rated at 150,000 cfs (with up to 87-ft.
hydraulic head). The new Folsom Dam Auxiliary Spillway is rated at 312,000 cfs; this
huge spillway has radial gates 50-ft. lower than the dam proper. These figures point out
the ridiculous nature of figures like 450,000 cfs!
Based on my calculations, the rated discharge capacity of the Oroville Dam Emergency
Spillway is about 6, to 19,000 cubic feet per second (cfs).
Let me explain:
A. Background Information on Oroville Dam
Table 1 — Oroville Dam Crest Elevations
Description Crest Elevation
Material (Feet above
Mean Sea Level)
Oroville Dam Crest Earthfill 922 ft.
Emergency (Auxiliary) Spillway Crest Concrete 901 ft.
Main Spillway Ogee Crest Concrete 1 814 ft.
Table 2 — Oroville Dam and Reservoir: Elevation, Storage and Releases
Date Day Reservoir Distance Reservoir Available Reserv. Reserv.
Feb. of Elevation Below Storage Reservoir Inflow Outflow
Wk (ft.) Spillway (Acre-ft.) Storage (CFS) CFS)
5
Crest (Acre-ft.)
(ft.)
1 W 850.8 50 2,818,827 718,750 8,644 20,187
2 Th 849.1 52 2,796,832 740,745 9,381 20,463
3 F -- -- -- -- 20,210 25,772
4 Sat 849.2 52 2,797,635 739,942 36,027 30,014
5 Sun 849.4 52 2,799,641 737,931 30,856 29,911
6 M 850.9 50 2,819,768 717,809 48,795 38,741
7 T 862.3 39 2,976,908 560,669 106,845 27,425
8 W 874.8 26 3,155,684 381,893 101,841 11,687
9 Th 890.9 10 3,396,134 141,443 155,498 34,253
10 F 899.4 2 3,528,727 8,850 127,679 60,697
it Sat 902.6 -- 3,578,367 -- 84,437 59,472
12 Sun 899.8 1 3,533,936 3,641 69,167 69,131
13 M 891.7 9 3,408,430 129,147 14,441 100,000
14 T 882.4 19 3,266,396 271,181 28,388 100,000
15 W 872.2 29 3,117,546 420,031 25,032 100,000
16 Th 863.4 38 2,991,747 545,830 26,535 90,000
17 F 856.7 44 2,899,096 638,481 29,364 76,040
18 Sat 853.3 48 2,852,724 684,853 39,131 62,499
19 Sun 850.2 51 2,810,364 727,213 35,733 57,083
20 M 1 850.3 1 51 12,812,914 724,663 1 61,271 60,000
With the Main Spillway shut off on February 8, the reservoir took in a whopping 240,000
acre-feet in a 24-hour period (3,396,134 acre-ft. - 3,155,684 acre-ft. = 240,450 acre-ft.).
This caused the lake level to jump 16 feet in one day! The reservoir level was 874.8 on
Feb. 8 and 890.9 on Feb. 9 (890.9 ft. - 874.8 ft. = 16.1 ft.). On Feb. 10, the lake moved up 9
feet. Over the course of six days from February 6 - 11, Oroville Lake levels rose a gigantic
52 feet!
On Feb. 11, the lake rose 3 feet and water started flowing over the Emergency Spillway
shortly after 8:00 a.m. This was the first time that water had moved over the Emergency
Spillway (Auxiliary Spillway) since Oroville Dam was built in 1967. Water continued
flowing over the Emergency Spillway until 8:00 p.m. on February 12.
B. Calculation of Oroville Emergency Spillway Capacity
6
The U.S. Bureau of Reclamation (BuRec) provides a reputable method of determining the
capacity of various spillways and overflow structures. Applicable portions of the
following publication are provided in the Appendix:
"Appurtenant Structures for Dams (Spillways and Outlet Works) Design Standard, U.S.
Bureau of Reclamation, August 2014.
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The BuRec publication provides this formula for determining the discharge capacity of an
ogee crest spillway:
Q = CLH312
Where:
Q is the total discharge in cubic feet per second (cfs)
C is the coefficient of discharge (suggested value for an ogee crest weir is 3.7)
L is the effected crest length (ft.)
H is the total hydraulic head above the spillway control structure (ft.)
Oroville Lake levels reached 901 ft. and 902.6 ft. on February 11 and 12 (1 ft. to 1.6 ft.
over the 901 ft. Emergency Spillway crest elevation). For Oroville Dam, L = 1,730 ft., and
H varies from 1 ft. to 1.6 ft. (about 2 ft.).
For various values of H31, the Oroville Emergency Spillway capacity equals:
Q = (3.7) (1,730 ft.) (1) = 6,400 cfs [H = 1.0]
Q = (3.7) (1,730) (2.02) = 12,930 cfs [H = 1.6]
Q = (3.7) 1,730) (2.83) = 18,100 cfs [H = 2.0]
Therefore, the Oroville Dam Emergency Spillway discharge capacity is about 6,000 cfs to
about 19,000 cfs. This is very close to the 6,000 to 12,600 cfs range reported by the
California Department of Water Resources for the February 11-12 flood event.
7
When compared with the Main Spillway releasing 100,000 cfs, "this is a drop in the
bucket." Never again should DWR rely on the Emergency Spillway for discharging water
from the reservoir. Instead, the department should use the damaged Main Spillway and
keep water levels in flood season below 825 ft. elevation.
Because the capacity of the Oroville Emergency Spillway is only about 13,000 cubic feet
per second, it would be a waste of money to pave the slope from the spillway to the
Feather River. Of course, this paved slope would be extremely ugly!
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----------------------------
Bio for Henry W. Burke
Henry Burke is a Civil Engineer with a B.S.C.E. and M.S.C.E. He has been a Registered
Professional Engineer (P.E.)for 37 years and has worked as a Civil Engineer in construction
for over 45 years.
Mr. Burke had a successful 27 year career with a large construction company.
Henry Burke has served as a full-time volunteer to oversee various construction projects. He
has written numerous articles on education, engineering, construction,politics, taxes, and
the economy.
Henry W. Burke
E-mail: h.wburke Kox®net
-------------------------
-------------------------
s
APPENDIX
Reclamation
Managing Water in the West
Appurtenant Structures for Dams (Spillways and Outlet Works) Design
Standard
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........//..................................................... ............ .............. ........................................................................ .................... ........................................................................................................................... ......................... ....................................1 .............. .....................................1 ..........
Chapter 3: General Spillway Design Considerations
Final: Phase 4
U.S. Department of the Interior
Bureau of Reclamation
August 2014
Chapter 3: General Spillway Design Considerations
(Page 3-60)
3.6 General Hydraulic Considerations
This section provides general hydraulic considerations for determining the type, location, and
size of a modified or new spillway. Detailed hydraulic analysis and design can be found in
Chapter 5, "Hydraulic Considerations for Spillways and Outlet Works," in this design standard.
As previously noted, unless otherwise specified, this chapter is applicable to the evaluation,
analysis, and design of reinforced concrete, high velocity, and high flow spillways.
9
3.6.1 Discharge Capacity
Once discharge capacity has been determined, it is usually presented in the form of drawings
(discharge curves) and/or tables with discharges (cubic feet per second [ft3 /s]) related to RWS
elevations (feet [ft]). Estimating discharge capacity is based on either analytical methods or
physical models. Analytical methods will typically be used for all levels of design (appraisal,
feasibility, and final design levels), while physical models are typically limited to final design
levels. Furthermore, physical models are usually employed for atypical designs involving
unusual topography, geometry, and/or discharges or velocities that exceed experience levels.
Key in the estimation of discharge capacity is determining the hydraulic control(s) for the full
range of spillway operation (i.e., full range of RWSs that would invoke spillway releases).
Hydraulic controls include those discussed in the following sections.
3.6.1.1 Crest Control (Uncontrolled or Free Flow)
Crest control occurs when there is a free (water) surface and subcritical flow conditions exist
upstream of the control structure (such as an ogee crest structure), then pass through a critical
state (i.e., when the Froude number is equal to unity or when the specific energy is at a
minimum for a given discharge) at the control structure to a supercritical flow condition
downstream of the control structure. The governing equation for crest control is the weir
equation (see figure 3.6.1.1-1 and table 3.6.1.5-118 for more details):
Subcritical flow conditions occur when the Froude number is less than unity with low velocity flow described
as tranquil and streaming. Froude number is defined as the ratio of inertial forces to gravity forces or average
flow velocity (V) divided by the square root of the product of gravity (g) and hydraulic depth (D), which is
typically the wetted area (A) divided by the top width (T) of the water surface. Specific energy is defined as
energy per pound of water. measured from the channel bottom or the sum of pressure head (y) and velocity
head (V 2/2g) Supercritical flow conditions occur when the Froude number is greater than unity with high
velocity flow described as rapid, shooting, and torrential. Table 3.6.1.5-1 appears later, in Section 3.6.1.5,
"Discharge Capacity Design Procedures," in this chapter.
Q= CLH3/2 (weir equation)
Where:
10
Q is the total discharge (ft3 /s).
H is the total hydraulic head above the spillway control structure crest (i.e.,RWS elevation
(zRWS) minus spillway control structure crest elevation (zCRT) (ft).
C is the coefficient of discharge (initial suggested values include: 2.62 for broad-crested weir
and dam overtopping, 3.3 for sharp-crested weir, and 3.7 for ogee crest). The coefficient of
discharge is variable, depending on factors such as head (H), crest shape (ogee, sharp-crested
weir, broad-crested weir, etc.), control structure entrance (inlet structure, piers, etc.),
approach channel depth (P) and geometry, and downstream conditions (suppression,
submergence).
L is the effected crest length. See following text for estimating effective crest length (ft).
(Figure not shown here.)
Figure 3.6.1.1-1. Crest control.
Design Standards No. 14: Appurtenant Structures for Dams (Spillways and Outlet Works)
Design Standards
3-62 DS-14(3)
August 2014
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On page 209 (Appendix page A-1) of the BuRec Document, Example No. 1 is
provided. This example is entitled:
Example No. l —Dam T Modifications (Existing Embankment Dam): Modify Existing
Service Spillway and Construct New Auxiliary Spillway
The key parameters for the Example Dam are:
11
Reservoir Water Surface (RWS) — Elev. 5,250.0 ft.
Design Maximum RWS — Elev. 5,250 ft.
Service Spillway uncontrolled crest— Elev. 5,234 ft.
New Auxiliary Spillway crest— 5,236 ft.
New Auxiliary Spillway length — 300 ft.
The calculated discharge capacity for this new Auxiliary Spillway is:
Q = CLH312
Where:
Q is the total discharge in cubic feet per second (cfs)
C is the coefficient of discharge (suggested value for an ogee crest weir is 3.7)
L is the effected crest length (ft.)
H is the total hydraulic head above the spillway control structure (ft.)
The Head calculations are:
5,250 ft.
- 5,236 ft.
14 ft.
Q = CLH312
= (3.7) (300 ft.) (14)32 [H = 14 ft.]
_ (3.7) (300) (52.38)
= 58,142 cfs
The designed discharge capacity for the Existing Service Spillway was stated as 10,500
cfs. Because the spillway crest length was not given, I calculated it as 44.34 ft. The
calculated discharge capacity for the Existing Service Spillway is:
12
5,250 ft.
- 5,234 ft.
16 ft.
Q = CLH312
_ (3.7) (44.34 ft.) (16)32 [H = 16 ft.]
_ (3.7) (44.34) (64)
= 10,500 cfs
When the calculated lake level is raised to 5,252 ft., H becomes 18 ft. and the calculated
discharge capacity for the Existing Service Spillway is:
Q = CLH312
_ (3.7) (44.34) (18)32 [H = 18 ft.]
_ (3.7) (44.34) (76.37)
= 12,500 cfs
These calculated capacities for the Existing Service Spillway of 10,500 cfs and 12,500 cfs
agree with the BuRec Example No. 1. BuRec plotted this information on a graph on page
A-6 (page 214). On this graph, the new Auxiliary Spillway with an ogee crest of 300-ft.-
long is also plotted.
How did the Department of Water Resources get a bogus figure of 369,000 cfs for the
Emergency Spillway discharge capacity? I will provide some guesses.
If DWR "Person A" glanced at the graph of the "New ogee crest auxiliary spillway — 300
ft." at 5,250 ft. elevation, the person could get a discharge figure of 60,000 cfs (not very
exact). (The hydraulic head for this spillway is 14 feet.) Then some simple math would
suggest the following:
13
60,000 cfs = 200 cfs per foot of spillway length
300 ft.
The Oroville Emergency Spillway has a crest length of 1,730 ft. If Person A multiplied the
above factor by the Oroville Emergency Spillway length, the result is 346,000 cfs, which is
reasonably close to the 369,000 cfs figure.
Q = (200 cfs per ft. of spillway length) (1,730 ft.)
= 346,000 cfs
There is only one slight problem with the 200 cfs per ft. figure. It was based on a spillway
that has a Head of 14 feet!
The ogee crest elevation of the Oroville Emergency Spillway is 901.0 ft. The Oroville
Emergency Spillway has virtually no hydraulic head; it is the top surface of Lake
Oroville. As such, the Oroville situation has a Head ranging from 0.00 ft. (Lake Oroville
at 901.0 ft.) to about 1.6 ft. (lake at 902.6 ft. on Sat., Feb. 11).
The correct calculated discharge capacity for the Oroville Emergency Spillway is shown
for various hydraulic heads.
For a Head of 1.0 ft. (reservoir at 902.0 ft. elev.), the calculated discharge capacity is:
Q = CLH312
_ (3.7) (1,730 ft.) (1.0 ft.)3/2 [H = 1.0 ft.]
_ (3.7) (1,730) (1.0)
= 6,400 cfs
For a Head of 1.6 ft. (reservoir at 902.6 ft. elev.), the calculated discharge capacity is:
14
Q = CLH312
_ (3.7) (1,730 ft.) (1.6 ft.)3/2 [H = 1.6 ft.]
_ (3.7) (1,730) (2.02)
= 12,930 cfs
For a Head of 2.0 ft. (reservoir at 903.0 ft. elev.), the calculated discharge capacity is:
Q = CLH3/2
_ (3.7) (1,730 ft.) (2.0 ft.)3/2 [H = 2.0 ft.]
_ (3.7) (1,730) (2.83)
= 18,100 cfs
To summarize, the calculated discharge capacities for the Oroville Emergency Spillway
are as follows:
Elev. of Lake Oroville Hydraulic Head Calculated Discharge
902.0 ft. 1.0 ft. 6,400 cfs
902.6 ft. 1.6 ft. 12,930 cfs
903.0 ft. 2.0 ft. 18,100
cfs
These calculated figures of 6,400 cfs to 12,930 cfs agree very closely with DWR's statement
that the flow over the Emergency Spillway was 6,000 cfs to 12,600 cfs on Feb. 11 - 12,
2017. Lake Oroville elevation on Saturday, Feb. 11 was 902.6 feet. At most, the discharge
capacity could be 18,000 cfs (corresponding to Lake Oroville at 903.0 ft.).
The California Department of Water Resources should immediately correct all statements
referring tote design capacity (design outflow) of the Oroville Dam Emergency ill ay
as 369,000 cfs, and change it to 18,000 cfs (cubic feet per second).
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15
Bio for Henry W. Burke
Henry Burke is a Civil Engineer with a B.S.C.E. and M.S.C.E. He has been a Registered
Professional Engineer (P.E.)for 37 years and has worked as a Civil Engineer in construction
for over 45 years.
Mr. Burke had a successful 27 year career with a large construction company.
Henry Burke has served as a full-time volunteer to oversee various construction projects. He
has written numerous articles on education, engineering, construction,politics, taxes, and
the economy.
Henry W. Burke
E-mail: hwl urke a�eo .nel
16