Posted on 02/12/2017 4:26:47 PM PST by janetjanet998
Edited on 02/12/2017 9:33:58 PM PST by Admin Moderator. [history]
The Oroville Dam is the highest in the nation.
I do not understand what that graph is trying to tell me.
It shows the elevation of the spillway from the gates to the foot of the spillway.
It’s not a flat slope but a convex slope. I think this contributed to the collapse.
Looks like it’s height vs length of the main spillway.
OK, I get it now.
Thanks!
At what length did the pothole/break occur?
Where it starts to slope down? At 1200, or further out?
What is that overall? ... A 13% slope?
The hole developed downstream from there. From the info in #1521 I estimate around 1970’
after trending north yesterday......models are tending back south with the heaviest rain track along I-80 vs the Oroville area
By topology matching of this early version "Wing Delta" Main Spillway Design, this blueprint lends credence to an "early" construction "grading" of the "saddle" area if this option moved forward (from hydraulic flow modeling testing & design). The left side "wing" follows the grading into where the 60FT high section of where the Emergency Spillway Wier now exists.
Replacing prior excavated material, even if fractured rock, would have been an unpopular choice. IT would have been easier to design a Tall Emergency Spillway Weir and then taper it. re: discussion on "origin of "focused wash basin". note: See post 1554 for original discussion of the "Wing Delta" Main Spillway Design.
HEAVY RAIN...Rainfall amounts of up to 3-6 inches are likely in
the Sierra through Tuesday morning, with 1-2 inches in the valleys
of northeast CA and western NV and 2-3 inches in the foothills
west of Highway 395. For northwest and west central NV, between
0.50 and 1 inch is probable north of US-50 with less than 0.50
inch south of US-50. Heavy rain is expected to bring widespread
flooding concerns to the region—including small stream flooding,
urban flooding, mud and rock slides, as well as increases to
mainstem rivers. See our hydrology section below for more details
on flooding.
.HYDROLOGY...
. Major flooding now expected for the Middle Fork of the Feather
River near Portola.
. Truckee River at Reno and Vista along with the Carson River near
Carson City and Susan River at Susanville forecast to reach
monitor stage.
. Flooding likely for creeks, streams, urban areas and drainage
basins in the Tahoe Basin, eastern Sierra, northeast California
and western Nevada early Monday through early Tuesday.
A strong atmospheric river will push into the region today through
through Tuesday morning bringing heavy rain and rising snow levels.
Currently, snow levels are expected to be around 6500 feet in
northeast California and around 7500 feet for much of the Sierra and
western Nevada. Precipitation totals in the Sierra could reach 3 to
6 inches, with 2 to 3 inches in the Carson Range and much of the
Susan, Pit, and Middle Fork of the Feather river basins. 1 to 2
US Weather Service Reno.
It started raining here in north Reno about an hour ago. Temp 38 degrees.
Inherent skepticism leads me to suspect that the financial interests of someone, or group of someones, might have played more of a role in siting at this location than engineering considerations.
I'll admit to being unfamiliar with the area's geology, but ER's research above hints at a sort of Rube Goldberg approach to making it all fit just here, as opposed to somewhere the topology might have been better suited.
/venality theory
https://archive.org/stream/zh9californiastatew2003calirich/zh9californiastatew2003calirich_djvu.txt
In the late 1940s, the State compared development
at the Oroville site with developments on the North
Fork at Big Bend and on the South Fork at Bidwell
Bar. The conclusion, quoting the August 1949 report
(see Bibliography), was that “major storage capacity
can most feasibly and economically be provided at the
Oroville site”.
Work then was concentrated on feasibility studies
for the State Water Project (then known as the
Feather River Project), which was authorized by the
State Legislature in 1951. A concrete gravity dam
similar to Shasta Dam was assumed at Oroville for
these studies.
In 1956, the State Legislature authorized the prepa-
ration of final designs, plans, and specifications for
Oroville Dam. First, the type of dam to be constructed
at the site had to be selected. Initially, gravity, multi-
ple-arch, straight-buttress, and arch-buttress concrete
dams were studied (Figure 58).
One of these designs was of the concrete-buttress
65
Figure 58. Model of Multiple-Arch Concrete Don
66
type consisting of a series of massive head buttresses
60 feet thick and spaced 1 20 feet center to center across
Oroville Canyon. Later, to eliminate the extremely
high buttresses that would have been required in the
deeper part of the Canyon, an arch-buttress alterna-
tive was developed. The central deepest portion of the
Canyon was to be spanned by an inclined arch abut-
ting against a massive buttress on either side. The
remainder of the dam would have consisted of a mas-
sive head buttress similar to that proposed for the
straight-buttress dam. Preliminary design studies of
this hybrid dam showed it to be economically and
engineeringly attractive. Detailed design studies,
which included a structural model, were undertaken.
Designs for multiple-arch dams were suggested by the
foremost concrete dam designers in the world at the
time.
The Oroville Dam Consulting Board (discussed in
Appendix A) advised the Department of Water Re-
sources on these studies and on the final design and
construction of the Dam and appurtenant structures.
Concurrent with these design studies, extensive
damsite geologic and construction materials investiga-
tions were being undertaken. The materials investiga-
tions were centered in the vast fields of tailings located
10 to 15 miles downstream of the site that had been
produced by dredgers working over the flood plain of
the Feather River for gold. This gravelly cobbly
material originally was explored for a source of con-
crete aggregate and later proved to be an ideal material
for pervious shells for the earthfill dam. The dredger
tailings, consisting of washed sands and gravels, var-
ied in depth from IS to 50 feet. Normal dredger opera-
tion stacked the gravel and cobbly material on top of
the sand. The sand deposit was not usable for concrete
aggregate but could be used to blend with the tailings
to form transition zones for an earth or rockfill dam.
http://www.freerepublic.com/focus/news/3524221/posts?page=1391#1391
Gov. Moonbeam’s father lied about the cost of the dam to get the bond issue passed.
Thanks for the report !
Post from freedom_is_not_free, about the evac order last week; they’re in the area of the dam...
http://www.freerepublic.com/focus/f-news/3526696/posts?page=43#43
See pics at link in post #6 by gubamyster
http://www.freerepublic.com/focus/f-news/3526879/posts?page=6#6
Grabbed wrong post; pix are here
http://www.freerepublic.com/focus/f-news/3526879/posts?page=23#23
H/t blueplum
As I posted on the Central Valley thread:
Okay, good morning everyone. As one who has followed this event with interest it looks like Oroville is still holding on this morning.
Based upon Lake measurements, it appears inflow has fluctuated between 47k and 23k cubic feet per second. Operators have been holding outflow over the main spillway to 59,900 cfs or thereabouts. This has kept lake levels falling very slightly from 851.17 to 849.54 or a decline of 1’ 7 1/2”.
Rainfall in the tributary area continues with Brush Creek, Four Trees and Buck’s Lake showing 24 hour rainfall running 2.4, 2.7 and 2.9 on the main fork of the Feather. Quincy and Grizzly Ridge have received about 1.5 inches. Gauges at Buck’s Creek and Lake Davis are not reporting data but areas surrounding them are less than critical.
Beale AFB radar:
https://radar.weather.gov/radar_lite.php?rid=bbx&product=N0R&loop=yes
Shows the more intense storms in the Folsom Reservoir drainage but higher elevation hills shade out some readings east of Oroville.
Clicking the eastern link shows Reno radar showing even distribution of precipitation across the western Sierras.
San Francisco Bay radar
https://radar.weather.gov/radar_lite.php?rid=mux&product=N0R&loop=yes
Shows the storms making landfall to be heavier south of the main urban area with Flash Flood warnings south of Monterrey Bay. I believe the coast highway is still closed for the bridge problems at Pfeiffer Canyon so travel there is very limited.
A prayer is offered for the next 72 hours that the Rivers don’t rise and the dam holds.
Good report. It looks like the storm tracked South at the last minute, good news for the dam area. Still over two inches of rain in what is an already saturated area is a lot. Portola is getting hammered again. BTW the rain is now heavy in Reno. That means that the first storm has pushed over the Sierra’s and is moving East. The sat images of the next storm look like it is wet and colder. More snow less rain. Sacramento could still be in danger and there is going to be massive flooding around Stockton/Manteca.
Had a family member that lived in Manteca for a few years about 16 years back. Have friends in Sacramento and Modesto now. Just came back from driving the whole central valley south from Dublin to Barstow at New Years so I know what it is like.
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