The Providence news. (Providence [R.I.]) 1891-1906, 1901-03-21

A powell and interesting piece OF engi-
neeftng work II noted in lie Genie CIyir'
for January IT, 1901. This relates TO an in
crease In stored water and In the dry
weather now IN the. canalization OF the
river Neste. q tributary OF the river Car
ondc. not far from the Spanish border OF
France. Various small streams and lakes
had already been utilized for this pur-
pose; but the retrogradation OF the sla-
ciers OF the Pyrenees brought about
decrease OF the water available. and come
other source had TO be sought.
This source was found in the Lake OF
Caillaouas. situated In a bare and almost
savage section of the country, without
means OF access and presenting engineer
ing difficulties that mt first seemed insur-
mountable. But work upon tapping this
supply was commenced In 1891 and com
pieted In iscs; and a storage reservoir
was secured winch added o6oo,OOO cubic
meters TO the supply
This lake was fed by the Glacier Of
Gours Blancs. and by small intermediate
lakes. It's surface covered 1O6 acres and II
was situated In basin of solid granite
dominated by high mountains. 1t was di-
vided from the valley OF one of the
head streams OF the River Neste by a
granite ridge: and IL was determined to
pierce this ridge by a tunnel which should
be fitted with dam and controlling
valves.
This tunnel was G02 feet long, and its
bottom az the upper or lake end was To-
Gated at "A level sufficient to tap a layer OF
water 30 feet deep. The tunnel section
was rectangle 80 feet wide by 5.6 feet
high, surmounted by the arc OF circle
with foot rise. Its width was sufficient
10 permit Two miners 10 work on the
face; and while tunnel driving was COM
menced at first from the lower end IL
was continued from shaft sunk about
100 feet from the border OF the lake AT
the foot OF this shaft and above the
crown OF the tunnel chamber was ex-
cavated for the better manipulation OF
the controlling valves that were later
put in This chamber was 22xl7 feet by
&C feet high.
The driving of this tunnel required the
work OF loo men, working day and night.
for 3i2 working days. The greatest dlnfi-
Guilty naturally was at the upper end of
the tunnel which WAS eventually to tap
a large body OF water 60 feet below it's
and the exercise OF the most minute pre-
cautions on the part OF the engineers. the
heading was driven to- within SO feet of
the lake-surface of the rock; but at this
point the leakages became so considera-
bic that II was deemed prudent 10 stop.
But before leaving the heading fifteen
drill-holes were made and were charged
with total OF III pounds of dynamite.
These charges We're fired electrically
and an opening was made that.-admitted
a flow OF cubic metres OF wafer per sec
ond into the tunnel. AS IL was figured
that n flow of cubic metres per second
was necessary for the speedy emptying OF
the 6o-feet depth or lake, the hole was
enlarged by attaching TO "A cross made
with old rails. cartridge containing IL
pounds OF dynamite. This arrangement
was lowered from boat, and drawn by
the current into the hole and fired cleo
trically With this enlarged opening the
lake was emptled in q days.
After building a temporary dam at the
lake end of the tunnel for controlling
any rise I'm the lake, a strong dam was
built across the tunnel on the lake side
OF the shaft. This dam was q feet long
on the base. and was made of cut stone,
laid in Portland cement mortar; IL was
larger on all sides than the normal tun-
mel section by LEA feet. Into this mason
ry were built ~ iron pipes arranged I'm
three rows, with no one Immediately un-
der the other. or these pipes were II
inches in diameter and three OF inches
i'm diameter; the latter being put in To
permit the closer manipulation of the
gates and 10 better guard against any
dangerous waterman i'm closing the
pipes. The valve rods extended through
the arched roof of the tunnel into the
chamber mentioned; and a stone stair
way built in the shaft provided access
from the surface. Including the building
OF roads OF access, houses for the guards
and workmen, stelegraph line. etc, tho
total cost OF this work was $50, 400.