The San Francisco call., 1895-11-14

area, bounded on three SlueS ny apIupt
mountain slopes The snow drifts and
packs into this basin during the winter
and remains until late i'll July. Springs
issue at the lower edge of the basin at the
head of San Antonio Creek and form the
source of the water supply for the mines.
The water from these springs drops into
the gulch at the head of this stream and
sinks into the debris that fills the gorge.
To catch this water and turn it into the
head of the pipe line a small reservoir was
built.
The debris was leveled off across the
gulch for width of sixty feet. leaving
bottom of finely broken granite rock. with
the rock walls of the hill on three sides. A
pine log dam six feet high was built across
the gulch, and lined with double thick
ness of plank sunk into trench In the
debris, the fine rock fragments being filled
back against the plank. Owing to the fact
that the gravel in the mine was OF limited
extent, all the work done on this reservoir
and other parts of the water system was of
a temporary nature. There were five diff
ferent materials in this small basin to be
joined by water-lght lining; shattered
slate to be joined to solid granite and to
the plank dam; the broken stone bottom
to be joined to slate, granite and planking,
and the planking to be joined to the end
OF the iron pipe line.
This was done by covering the whole
inner surface with two coats of hot asphalt
paste, which was not over half an inch
thick after the crevlces were filled. The
paste was MADE of four parts of the best
refined California asphaltum and one part
OF crude petroleum without sand. These
were boiled together until, when abso-
lutely cold, it was brittle under the ham,
mer, while elastic and pliable with the
least warmth. This lining is in good con-
dltlon after two summers and a severe win
ter, the only repairs made being the ap-
plication of a few quarts Of asphalt last
spring.
The pipe line is two miles long from the
collecting reservoir to the pressure reser-
yoir, and runs along very steep, rough
and sinuous mountain side, where it
would be impracticable to maintain ditch
or tlume on account of the snow and rock
slides from the mountains. The pipe
was made Of No. 16 sheet iron; it was boiled
in asphalt and had driven joints. The
first 1900 feet is II inches in diameter;
then comes 1000 feet of 10 inches, and the
remainder is inches. The first 500 feet is
on a grade OF 40 feet per mile, and the re-
mainder 16 feet per mile. Air valves are
located about 1900 feet apart along the
whole line, and cross and waste valves are
provided at the upper and lower ends and
at the head of the S-inch section. 1t was
decided to be cheaper to lay the
pipe on these continuous grades than
to cross the gulches by descend
ing into them and the pipe line could
be emptied of water in winter without the
use OF so many expensive valves. The
size of the pipe line was not so large as
recommended by the author, but was de-
termined upon to save the extra cost of
larger sections. At three places the line
is carried over gulches by wooden lattice
spans, the timber for which had to be car
ried up the mountain on mems backs, like
all the pipes, valves, asphaltum and other
materials. The laying of the pipe was
very difficult where an immense rockslide
had to be crossed. Here the loose top
material would move without jarring.. and
only one 20-feet length of pipe could be
laid at time, as a longer trench could not
be kept open. 1t was dangerous work, for
in driving the joints the heavy blows of
the maui shook the whole side.
The pressure reservoir was built for two
purposes First, as penstock at the head
of the pressure pipe leading to the mines; ;s
second, as a reservoir to hold water for
some hours during the latter part of the
season, when the supply is limited. 1t has
a capacity of $50, 900 gallons, but as origin
ally designed it was to hold 3000,00O
gallons. The depth at the bottom portion
is 1875 feet. 1t is located at the head of
gulch on thickly timbered part of a
ridge above the mines. A semi-circular
dam was built across the gulch of single
thickness of large pine logs, with ends
sawed on radial lines and butted close
together, forming an arch with
slight batter up stream. Each row of logs
is separated with, and bound together by,
small logs laid at right angles to the dam
and extending up into the reservoir. AS
these were put in place bank was formed
on the upper side of the timber of earth
and broken rock we'll tamped around the
logs. The slope on the upper side of this
filling is ~ to !.
There is no material in the neighborhood
that could be used i'll any way as puddle
for dam, and the bottom and sides of the
reservoir are OF earth, rotten granite and
shattered slate. To make the basin water
tight, lining was formed OF asphalt con-
crete. This is not what is known in the
street paving business by that name which
is composed of asphaltum and sand, for
clean, sharp sand would have cost $50 a ton
delivered on the mountain, but is true
concrete Of broken stone and asphaltum.
The stone was obtained from q porphyry
dixie near by and was broken into pieces
two inches or less in size. All the fine
material was left and enough more added
to have the entire mass free from all but
the smallest voids.
This concrete was prepared IN two street.
paving pans. The rock was heated and
well mixed in one pan and the mixture of
four parts of refined California asphaltum
and one part OF crude petroleum was boiled
in the other. The boiling paste was poured
with ladies over the hot rock and the
whole mixed over the fire until every
particle OF stone, sand and dust was thor
oughly covered with the paste. The con-
crete was then taken in hot iron wheeIbar-
rows to the site of the work and put IN
place in the usual manner, being rammed,
rolled and smoothed down with hot irons
1t was put op in four-inch layer, in
strips from four to SIX feet wide,
and where the strips were Joined, the
old edge was well coated with hot paste.
After the lining was finished it was
painted with hot paste mixed in the same
proportions, but boiled much longer
time, until, when entirely cold. it was
hard and brittle, breaking under the ham
mer like glass, yet tough, pliable and elias
tic when warm. This coat was applied
while the paste was very hot and should
not be over one.eighth of an inch thick,
although, through the fault of the con-
tractor, it exceeded this amount at some
places in the reservoir mentioned. The
lining cost Is cents per square foot.
In spite Of the faulty manner in which
the material was laid in places by the con-
tractor it has stood so well that the author
has advised its use on a rock-fill dam 100
feet high, to be built in Southern Califor-
MIA. After clearing the site of the dam to