Medford mail tribune., February 19, 1961, Image 10

MEDFORD MAIL TRIBUNE, MEDFORD. ORE.
Emigrant Dam Is Constructed on Scientific Principals
SUNDAY. FEBRUARY 19. 1961
SLIDING OUTCROP Ono of the fours lake are responsible. However, bureau of
' expressed coneerning Emigrant dam last reclamation engineers say the outcrop was
week by E. M. Tucker Sr., of the Tucker undercut by action of rising and falling
Sno-Cat Corp., concerned a sandstone out- water on soft formation beneath it. They
: crop several hundred feet from the dam on say it probably will drop into the lake
the east side. It is shown jutting into the eventuully, but if it did, no harm would
water in picture above, and arrow points, result. Picture was taken from crest of
to the "crevasses" Tucker has mentioned, dam, which shows in foreground.
He fears that the weight of the dam nnd the
' ? '.' 4 ,j "l. , ..-.V"
HAa PACKING This construction
wor;;c is packing dirt next to the old
concre:e dam at Emigrant lake. The ma
chine was used along the rock abutments
of the clam to pack the material where
faff fjzy x M-
5 1 1 JSC rxfZTs- Jr . 7-s
MACHINE PACKED This machine was oroject. It was the first time this machine
specially designed and made for earth-fill had been used in dam construction. When
dam packing by Wagner of Portland for this picture was taken, the earth-fill was
the R. A. Hointz Construction company, about 10 feet above the top of the old" con
Portland, contractors for tho Kmigrant dam cretc dam. (Whilland Locke Photo)
machines could not travel. All the material
used was constantly checked for the correct
water content so there would be no void
places In the packing where water could
accumulate. (Whlthmd Locke Photo)
Material Is Not
Loose Dirt, Rock,
Engineers Report
By ERIC W. ALLEN JR.
Mail Tribune Managing Editor
E. M. Tucker Sr., the re
spected inventor of the Tuck
er Sno-Cat, and president of
the firm that manufactures it,
believes that Emigrant dam,
located southeast of Ashland
is unsafe.
The Bureau of Reclama
tion's engineers declare that it
is as safe as human experi
ence, ingenunity, skill and
modern construction methods
can make it.
Who is right?
Like Tucker, this writer is
a layman in geological and en
gineering matters. And Tuck
er Is a persuasive man, par
ticularly when he waves his
arms and talks about a "wall
of water" sweeping down the
valley. '
Inspects Dam Closely
Last week end I visited the
dam, and inspected it closely,
with both Tucker and James
A. Callan, Bureau of Reclama
tion engineer in charge of the
Talent project, under whose
direction the entire project,
including Emigrant, has been
built over the past five years
at a cost approaching $25 mil
lion.
As a result, I am personally
convinced that the dam is just
as safe as it can be made, and
that Tucker's fears, no matter
how sincere, are without foun
dation. What are Tucker's specifics?
He has alleged: '
Uam in Danger
1. That the dam Itself is in
danger of washing away, due
either to earthquake action, or
because of waves blown up by
tornado-like winds, and that
the "loose dirt and rocks" ol
the dam are not adequate to
hold back the reservoir water.
2. That "crevasses" in a
nearby formation indicate that
the formation might be unsta
ble, and might stretch around
the hill to the dam itself, thus
endangering it.
The engineers reply, in ef
fect: 1. The dam is built on scien
tific principles, with the old
concrete dam as a core, the
center portion of the dam is
of highly compacted clay-type
earth which is impervious to
water, and that the next layer
is of heavy rock, gravel and
cobbles, with a final layer of
rip-rap on heavy rocks, no
less than five feet thick and in
most areas far thicker than
that. (See diagram.)
Earthquake-Resistant
...They add that this type of
construction, of natural mate
rials, is far more earthquake
resistant than unyielding con
crete, although the principal
reasons concrete was not used
included cost, convenience
and use factors. The dam is
for an entirely different pur
pose than the great power
generation dams on the Co
lumbia or Colorado and is far,
far less costly.
The materials used cannot
be accurately called "loose
dirt and rocks," they point
out.
As to wind action causing
waves to go over the top, they
point out that an open spill
way some distance from the
dam will keep the water level
12 feet below the crest of the
dam even at high water; that
additional water releases are
available if necessary; that
the lake is too small to permit
waves of any appreciable size
forming, and that even If they
did for a period of time, the
solid construction of the dam
would not be affected.
'Crevasses' Evident
2. The "crevasses" Tucker
fears are, indeed, evident. But
they are a local phenomenon,
a good distance from the dam,
and are not part of a fault for
mation running to the area of
the dam.
The outcrop of concern to
Tucker (see photos) is some
200 or more feet from the
dam itself, and is one of a
number noted in early geolog
ical surveys of the area.
(The 1D53 Bureau of Recla
mation report on the geology
of the reservoir area noted:
"On the sides of the reservoir,
overburden consists of as
much as 10 feet of residual
solid and slope -washed out
crops. Outcrops are numerous
at the lower end of the reser
voir, but practically disap
pear at the upper end. The
reservoir has been eroded in
the upper part of the Umpqua
formationf referring to the ge
ologic reference to the type of
formation). Bedrock through
out the basin consists of me
dium to coarse-grained sand
stone, shale or siltstone, con
glomerate, and intrusive igne
ous rock. Dips and strikes arc
errantic in the vicinity of the
intrusive rock. Numerous
aults throughout the area arc
filled with clay gouge and wa
ter tests indicate thev are
tight.")
The movement of this par
ticular outcrop, with the cre
vasses widening, has been not-
DIMENSIONS SHOWN The schematic diagram of a cross-section of
Emigrant dam, adapted from engineering plans for the structure, show its
"profile" and dimensions. The width at the base is approximately 1,100
feet, and at the top, about 35 feet. Total height is 190 feet. The old concrete
dam (A), which is an integral part of the new structure although buried by
the earth, clay and rock of the new one, is 110 feet high. Sections marked B
- f &t y .xr- yy
-Lirrf i ' ": yy
f--ff ;Jv,45 .-s.s , W14X ST"vJ
AERIAL OF LAKE This is an overall aerial view of Emigiant lake south
of Ashland. The earth-fill dam is at the upper -end of the lake, and the
highway saddle dike is at the
ed and watched for years by
irrigation district personnel,
and by bureau engineers and
geologists. It ' was marked,
measured, and studied for
movement for a long period.
The conclusion was that the
rising and falling action of
the water from season to sea
son, coupled with the wetting
and drying action, had eroded
and undercut soft formations
below the outcrop, causing it
to tip out.
It probably will fall Into
the lake some day, the bureau
men believe, but this would
cause no harm to the dam it
self. Comparing Tucker's fears
with the engineers' fact-packed
reassurances, having in
spected the site myself, and
having scanned the records of
the long and detailed engi
neering and geologic work
which preceded the construc
tion, T was forced to conclude
that the dam is safe, and that
Tucker is unduly alarmed.
11 Phoenix Students
At Speech Contest
Phoenix - Eleven Phoenix
High school students and
their coach, Bob Myrick, went
to McMinnville last weelt to
take part in the annual
Tournament of Champions
speech meet on the Linfield
college campus.
The three-day tournament
attracts hundreds of high
school students throughout
the state and features junior
and senior divisions for first
year and experienced speak
ers. All the members of this
year's Phoenix speech squad
are first year speakers and
were entered in junior men
and junior women divisions.
In addition to debate, each
student was entered in at
least two other individual
events including oratory, ex
temp, impromptu, interview,
after dinner, humorous read
ing and radio.
Those students making the
trip for Phoenix were Karen
Moeabee, Liz King. Pat Diede
rich, Nancey Pettitt, Penny
Simmonds, Shearon Poole,
Barbara Gysin, Chyrl Bow
man, Laura urimtn, Butch
Tompkins and Gene Holt.
The Phoenix squad trav
eled by bus with Ashland and
Eagle Point and returned
late Saturday night follow
ing a banquet and presenta
tion of awards.
left center of the picture. The
v
hits' - " w-N 1 vj'Sk -'Jrib ; . , r-, - L
p&- n h :
"CREVASS" SHOWN The slowly widening gap between
a sandstone outcrop and the side of the hill, mentioned bv
Tucker, is shown above. Dam is several hundred feet away
in background; lake water can be seen at left. One of the
SURFACE OF DAM The
dam is shown above. It is covered with rocks and boulders.
The level of the lake (at left) was several feet higher when
this was taken than the height of the old concrete dam
the lett side
the water is
spillway is on
lake-side surface of Emigrant
are of highly compacted clay-type earth, packed down inch by inch, with
sheeps-foot rollers. Sections marked C are compacted sand, gravel and
cobbles. Section D is rock and E is rip-rap over rock and gravel. Width of
the compacted earth section is 470 feet at the base, and the rocked sections
are each some 300 feet thick. At maximum pool, surface of Emigrant lake
will'be 12 feet below the top of the dam. -
1
between the highway saddle dike and the dam itself where
visible extending to a point behind a tree-covered knoll.
(Whitland Locke Photo)
- T . , 1
tracks or crevasses can be seen at right of picture. It was
measured at 20 feet deep, but may have been deeper before
loose dirt fell into it.
.urai rock abutment in shown in background. Base of
dam ,s several hunored feet to the left beneath the
ing water. v
-1