Sacramento daily record-union. [volume] (Sacramento [Calif.]) 1875-1891, 1882-07-26

The Nevada City Tra,,sey1pt thus de-
scribes the recently.constructed debris-re-
straining dam of the North Bloomfield
Mining Company
The dam is located in Humbug creek,
few rods above its junction with the South
Yuba river, and ,, 600 feet below the point
where the tailings from the bloomfield
mine are dumped into the creek. Hereto
fore, each summer, the tailings from this
mine have formed dam 30 feet in hight
at the junction OF Humbug creek and the
Yuba, which dam held the tailings from
the mine in Humbug creek until the win
ter floods of the Yuba carried away the
dam and released the tailings III the creek.
The dam now constructedisa permanent one
and will prevent the tailiDgs leaving the
creek as heretofore. The structure consists
of heavy logs spanning the creek at mar.
row gorge Each stringer is bolted to the
rock at the end, and further held at inter.
walls of seven feet by course OF log ties
thirty to fifty feet long running up stream
These ties are notched on to the main
stringers aud held by heavy wrought iron
drift bolts. The upper end of the ties are
either bolted to the rock on the sides OF the
creek or yoked together by timbers. AS
the dam is raised the tallings are run into
the dam and packing around the ties holds
them firmly in place. When the taiings
reach the top course Of stringers another
course is added, and in this way the dam
will be increased In hight until the tailings
back to the mouth of the tunnel that dis
charges them into the creek. The total
hight of the dam will be seventy or eighty
feet
The first - feet of the dam filled as
rapidly as it could be built, but each foot
raised reduces the slope above and now the
filling goes on slowly. On Saturday the
dam was % feet in hight, and as the tim
Der work was getting too high above the
tailings to permit of convenient building,
construction was suspended until the tail
ings should reach near the top, and the
dam builders were at work procuring logs
for future addition. The face of the struc-
| ture Is nearly vertical, and the water falls
clear over the crest into the water below,
leaving no chance for wear of the dam ex-
cepting on the crest of the top log. When
the dam is raised to its full hight this will
! be protected with iron plates.
As to the safety and permauency of this
| dam there can be no question. The floods
of winter, which. by the way, are trifiing
on Humbug creek, can get no hold OF the
/ structure to tear it out, and as the logs are
kept wet by the seepage of water through
the sand they cannot decay. The perma.
nency of logs when buried in tailings that
are kept wet is plainly shown in the upper
portion of Humbug creek, where the
trees which formerly grew in the creek bed
have been buried for twenty-five years.
Mining in TIE upper creek has recently
been suspended and the winter floods have
washed away the old accumulation of tail
| ings, and the stumps of the trees are shown
to be perfectly sound. A crib dam similar
/ in construction TO that described, but only
I fifteen feet high, has been in Humbug creek
! for the past five years, and neither decay
/ nor the winter floods have had the slight.
| est effect upon it.
! After careful inspection of this dam we
can safely assert that the North Bloomfield
! Company have, in good faith, complied
with the decision of Judge Temple. They
| have constructed safe and permanent
structure that will, beyond question, hold
back the tailings from the mine. Muddy
water will, no doubt, pass it, and very fine
sand, such as is run into the river by
quartz and drift mines. The Bloomfield
Company has certainly placed itself beyond
the danger of an injunction until the dam
is filled to its full hight. Without care
full survey of the creek. bed it would be
difficult for an unprofessional man to make
even a good guess as to the quantity Of
tailings that can be held back by the Hum
bug creek dam, but rough inspection Of
4 - l =
structor's estimate OF storage capacity o.
l, 800, 900 yards or more, is not exagger
ated. This storage capacity would permit
the North Bloomfield to run their works
continually for six months, or more. Aftel
that it will be necessary to resort to the
construction of dams in the main Yuba.