Los Angeles herald., 1910-08-14

water over canyons and deep hollows.
Besides the tunnels and fumes there
are nine miles of conduit lined with
concrete. A concrete curb, six by
eight inches in size, with holes for re-
inforcing rods to permit the conduit
beng rooted, has also been constructed
on either side of the ditch.
The 10000 feet of tuneling is made up
of seventeen distinct tunnels, ranging
in length from forty feet to 2060 feet,
the latter being in the Cottonwood dis
trict of the county. The tunnels,
flume and conduit for the entire thir-
teen miles have uniform fall of four
feet in every 5000 feet.
The Chollas Heights balancing and
storage reservoir has a capacity of
60,OOOOO0 United States gallons, suffi-
cient to supply the city for twenty
days in it's present requirements. Its
dam is an embankment of earth de-
posted in layers and rolled. The cut
off consists of a concrete wall bullt
in a trench thirty inches wide at the
bottom extending across the valley
and a riveted steel plate diaphragm
having its lower edges and ends en-
bedded in the concrete. The dam IS
526 feet long. twenty feet wide at the
top and fifty-six feet high. 1t was
constructed during the summer OF
1901 Water is drawn from the reser-
voir through a twenty-four inch cast
iron pipe laid in a trench eXcaVated
in the natural earth beneath one END
of the dam about thirty-eight feet be-
low the top.
The Upper Otay dam, 500 feet above
the sea, was completed in 1901. II was
created by the construction of unique
arched dam in a V-shaped gorge bed
ded and resting on solid rock pOrphyry,
base and abutments. 1t is only four
feet thick on top and fourteen feet at
the bottom, rivaling for originality and
boldness of desi5n the celebrated Bear
Valley dam. The Tipped Otay dam IS
located about twenty-five miles south
east of San Diego and has a capacity
of 100000 gallons.
To pass surplus water from the Up
per into the Lower Otay dam a waste
way has been eXcavated in the hillside
around one end of the dam and seven
rectangular overflow notches formed in
the TOP of the dam. Water is drawn
from this reservoir through pipe
built into the masonry of the dam
about thirty-two feet below the top.
This pipe is controlled by a gate valve
on its downstream end and discharges
through a wooden box flume into the
river reservoir, which extends nearly
to the upper dam.
The Lower Otay at 400 feet eleva-
ton is also unique and peculiar IN
construction being the only dam in
existence of the rockhill type, relying
for tightness on a diaphragm of one
fourth inch steel plate imbedded in a
two-foot layer of concrete with a bur
lap and asphalt coating to avert dam
age from rust. 1t is $50 feet high ano
565 feet long and was considerably
larger than the upper dam, having a
capacity of II 696, 100000 gallons, suf-
ficient to supply the city with its pres
ent Requirements for eight years on a
basis of 100 gallons per head each
The water now in the dam would sup
ply the city for several years though
not a drop of rain fell.
During the past year the mammoth
University Heights reservoir was COM
pleted at a cost of about 100000. II
is of reinforced concrete and has a
capacity of more than 20,0OO,0 900 gallons
and is the largest reservoir of the kind
west of the Mississippi river.
In the mountain watersheds of Sar
Diego county the annual rainfall is
greater than in any other portion OF
the state south of the, Tehachapi, and
even in the years of greatest drouth
a total of more than twenty-five inches
rain is recorded. A considerable pOr-
tion of the shed which the san Diego
water system taps is covered with
snow a few months in the year.
The amount of clear mountain wa
ter to be caught annually by the Cot
tonwood and Pine creek watershed
portion which the water company is
developing is enormous. It's vastness