Gilpin observer., 1905-11-02
Cripple Creek DRAINAGE Tunnel.

'PP'S STScN drainage tunnel.
In his report to the committee on
drainage appointed by the Cripple
Creek Mine Owners Association, En-
gineer d. w. Brunton has quoted some
interesting facts and figures. He
says:
"A careful study shows conclusively
that the water in the district is what
Is commonly known as ground water
l. e., water that is stored in the pores,
crevices and assures in the rock, re-
plenished from the surface, and not by
springs from beneath. When the nat
ural water level is lowered, either by
pumping or tunnel drainage, the flow
toward the pumps or tunnel takes
place through every available opening
and even through the rocks them
selves. When the depth of drainage
below the natural water level is in
creased, the available drainage area is
proportionately enlarged and the flow
increased, as the velocity of the water,
either in an open tunnel, closed
crevice, or even through the pores Of
the rocks themselves, is in direct pro-
portion to the head; or, in other words,
the greater the pressure the greater
the fiow.'
A tabulation of the comparative
amounts of water taken from the
mines shows that at present it
amounts to 5,295 gallons a minute,
while in January, 1903, it was 1850.
Ihe amount at present carried off by
the tunnel is 4,117 gallons a minute,
leaving the amount being pumped at
present less than half of the amount
pumped in 1903.
In this connection he says:
AT that date the water level on the
western portion of the district was
somewhere about elevation 9,O2s,
which was approximately maintained Z
until the Cripple Creek drainage tun-
mel cut the water courses on Novem-
Der %, 1903, since which time the
water level has gradually fallen to
elevation 1891 feet, a distance of 1877
feet. The difference between the
number of mines pumping and the
quantity of water handled now and on
January II, 1903, affords, perhaps, the
most forcible illustration that can be
given to the effects of low level drain
age on the general water level of the
district
In the latter part of 1908 the
amount of water drained to lower the
water level one vertical foot was 25,-
2O4, 200 gallons. This amount rose
steadily as the drainage area in
creased until September. 1904, when it
had risen to 5S,109,000 gallons for one
vertical foot drained. since which time
the relation of discharge to drainage
area has remained practically con.
Stant
THE figures given show at a glance
that any attempt to drain the entire
district, even by the most modern cen
tralized pumping station, would prove
loo, Toll, -. Ii
amount of water for any considerable
distance would entail an expense
which would be prohibitive." Y
Referring to the former tunnels, he
says:
1T is n well-known fact that as
each successive tunnel struck the
water-bearing assures ii Immediately
drained the tunnel above II until at
the present time the FL Paso is the
only one discharging water. u
THE figures given show that the ef
feet of tapping the water by each sue
cessive tunnel was almost Immediately
felt in the mine workings over an i'm
mense area. and 1t seems probable
that the mines on the extreme south
and east, whose water level was ap-
parently unaffected. must have de-
rived considerable benefit by the low
ering of the water level to the north
and west of them, condition which is
borne out by the fact tina: each OF
these mines Is now pumping much
less water than before the Cripple
Creek drainage tunnel tapped the dis
trict, and in some instances. as at the
Portland and Independence, the pumps
have been entirely stopped.
THE expense of pumping is by no
means the measure of the increased
cost OF mining in wet ground. When
drifts, wines and raises are driven
where the miners can work in comfort,
wearing ordinary clothing. they can,
with ease and comfort to themselves.
do at least thirty-three per cent more
work than when weighed down with
rubber coats and boots, in addition TO
which, in ores like those Of Cripple
Creek, the amount of loss in fines is
certainty very much less in dry than
in wet mining. II is safe to say that
deep level drainage. and the conse-
quent draining OF the rocks woyld
show difference of at least twenty
per cent. in favor OF dry against wet
mining"
On the depth at which the tunnel
should be driven. he says: within
reasonable limits the greater the depth
at which the water-bearing rocks cam
be tapped the more rapidly and thSE
oughly will the eruptives be drained to
the outer edge of the rim, and no
great harm would be done II the dis
trict should be drained below a num-
ber Of the smaller veins, as 1t seems
probable that some at least OF the
stronger and more highly mineralized
assures will continue beyond the
depth at which 1t will be commercially
profitable to drive tunnel"
Largest Silver Producer.
The honor of being the largest pro-
ducer of silver in the world at the
present time rests between the Broken