Aberdeen herald. [volume] (Aberdeen, Chehalis County, W.T.) 1886-1917, 1909-01-07

Purpose Of the Dam and ExpIana
ton Of Its Construction-No Lake
Under Its Site
Explaining the settling of the rock
toe" which started the rumor that
the foundation of the Gatun dam was
sinking and that subterrancan lake
had been discovered under the canal,
as an event that was expected. Il re-
port has been made to the authorities
mt Washington which. it is hoped. will
dispel any apprehension.
\ portion of this toe on the up
stream end Of the dam sank about
forty feet on Nov. n. During several
weeks prior to this date slide under
che high trestle Of the relocated Pan
Una railroad at Gatun made reccs-
Sary the dumping Of an additional
quantity of rock before the roadbcd
was brought up TO grade. On Nov. Is
the Chagres river flooded the tracks
At Gatun. At the same time the ru-
mean lake on the site of Gatun dam
and beneath it came out. The report
says in part
"The purpose of the dam at Gatun
is 10 inpouhd the waters OF the
tbagrcs IAN artiiiciah lake that Will
form in the valley of the Chagres riv-
or. This dam will extend from one
ridge of hills west across the valley
to the ridge on the hills east and will
be one and Il half miles long At the
extreme east end the locks are being
built through a small hill on which
abuts the dam. The dam itself is di-
vided into two parts. from the site of
the locks to the spillway. the other
from the spllway to the hills west
The spillway will he located through
small hill that rises in the middle
"f the dam. 4 temporary spillway
300 feet wide. which will let the
Chagres flow during the construction
Is completed and concrete laid there
early in January. There are three old
channels running through the dam
site.
'''rhe plan for constructing the dam
is to pump sand and clay upon the
site selected until the hill is 13, feet
above sea level and LOO feet wide
Hcrnss the valley. This sand and clay
have been found IN large quantities
down the ChagrrS valley. convenient
to the site and have proved to be
good material for dam. The dam
will be made by suction urcd.es.
which will pump the material mixed
with wafer upon the site. and the wa
ter running IF will leave Il closely
homogeneous material. For the pur-
pose Of adding weight to the dam aud
to prevent material from sliding north
and south. as great mass of earth
IS likely to do. two walls. or toes. are
hGing built across the valley.
''Thc north or downs'ream toe il
composed of rocks and earth taken ut
the site Of the locks The south or
upstream toe Is composed of hard
rock taken from the cut at Ha> Obs
pc. The ridge of Ras Obisro rock is
thirty feet broad at til" top and when
bias reached that HEIGHT I'M one place
ard has ono tn one ard y l'nlf Sl"p".
'Rc,wcen The north and Snu~h toes
2 100000 cubic Yards of clay and sand
from the Chagrcs valley will h" pump
Cd The object Of these toes is to hold
TIE material Of the hydrauli" fill until
The water has drained off.
.,f no tAn IN
lncn extended to the spllway. closing
the old channel Of thc Chagrcs and
east diversion beside thc old French
canal, the river finding an outlet
through the east diversion dug by the
French. The old French canal crosses
the Chacrcs at five different places he
tween Bohin and Gatuu. ard II Is
through that channel that the greatest
part of the ChagreS flows to Gatuu.
"a short distance above the dam the
Gatuncillo flows into the Chagres. Tho
building of the toe forces the water of
the Gatuncillo and that of the French
channel or canal to seek an outlet at
right angle to its natural course. and
II has caused the flats south Of Gatun
.
aS the diversion of the French canal
Is not wide enough to receive the
quantity of water that flows down the
valley and foods the lower parts. The
high water OF Nov II was simply the
repetition of what happened several
times during this rainy season. food
Ing the fats of Gatun on the south of
IT, and it WAS unusually high. rs the
water rose i'm some places as much as
eight inches above the rails.
Halfway between the foot of the
east hill and the spilway the old
French canal channel runs through
the dam site, but ii has been closed by
thc construction If the south toe. The
silt and soft mud that hHd collected
in the bottom of this channel for the
vast twenty years were not removed
when the construction If tl!e toe WAS
begun. and when the weight of tho
rock became great enough Il displaced
the soft bottom of the old channel
Gnd forced il M 2N feet north If llr
toe into the site If the dam.
This was autic ilatrd and desired