Sacramento daily record-union. [volume] (Sacramento [Calif.]) 1875-1891, 1881-07-29
THE YUBA DAM.
ITS Present Condition and What It Has
Accomplished Desirability of Repair
ing It-Views of Experts.


ing It-Views of Experts.
The following report of an examination Of
the brush dam on the Yuba river, will be
read with interest by all classes of people:
To the Miners Association of California
Gentlemen: have, at your request, made
professional examination of the dam built
by the Commissioners of Drainage District
Ne. ]. across the Yuba river in 1880, and now
beg leave to submit the following report:
PRESENT CONDITION OF DAM.
By the courtesy OF the State Engineer, have been
| furnished with copies OF crossseetions taken al
various points above and below the dam and across
the Yuha river These sections were first taken in
1880 just before the construction OF the dam, were
retraced during the present month, and show in de-
tail, with sufficient accuracy, the present condition
OF the dam and the amount OF material which has
been lodged Immediately above it since it was built.
The dam is u structure OF brush laid parallel with
the stream, with bending poles laid az right angles,
and tied together with wire. A brush mattress is
placed below the down.strea slope Of the dam to
protect it from upder- cutting the water passes
over; the upper slope was protected by tiers OF
sand bags. The largest trees used have diameter
| of about eight inches. Earth embaukments con-
nected the ends of the brush-work with the shore
lines.
The total length of the dam is nearly 10000 feet
its greatest hight, feet its cost in the neigh
| borhood of Sl20, 600
| The dam has broken in three places as follows
The earth embankment at the northern end has been
washed away nearly down to the original level, from
the end Of the brush-work to the shore, distance
OF 400 feet; the brush dam has been cut away en-
trely in two places-one 760 and the other $50 feet
| in length, measured on the CREST in two places
there are small gaps, but with the foundation un-
| disturbed. Out OF total length OF 10000 feet
there has, therefore, been destroyed about one
| seventh.
| a. :
slightly less than two feet; this apparent settle
ment is nearly in proportion the original height
of the structure-that is to say, it is generally
greatest where the dam was highest and has, with
out doubt been nearly altogether caused by the
compression of the loose brush into solid mass by
the pressure OF the water which has passed the
crest. Along the whole length Of the dam there are
evidences of the large stream which flowed over il
heavy water-soaked logs, of two feet or more in
diameter, still resting its crest and the pro-
lection mattress, where not covered with nd
shows signs OF the rush of the water.
Ia many places, both on the dam and on the pro-
lection mattress, willows are now sproutIng and
growing their roots will have very beneficial in
fiuence in mating or tying the whole structure
curely together II is q notable fact that none of
| the breaks occurred at the old river channels. The
southt IN break-230 feet in length-was old
Slough The bottom at the other breaks was not
! thought to be comparatively sof. or infirm. The
| brush mattress below the dam has very satisfac-
torily answered its purpose in protecting the lower
| slope of the work from under. cutting.
CAUSE OF THE BREAKS.
| The earth embankment which gave way was IN
all probability first attacked by water passing with
considerable pressure through the nterstiees OF the
| brush-work and washing away the earth inmedi-
ately next to the brush bulkhead. Alter the water
| had once commenced cutting, as matter Of course
the whole embankment soon crumbled away. This
supposition is confirmed by the statements OF eye
| Witnesses and by knowledge Of the iujudicous
manner in which the earth and brush-works were
| connected.
The breaks in the dana proper were probably
caused by strong currents OF water'sweeping along
| and undermining the upper or inner slope of the
| dam, the water escaping through the depres5ions
caused by the compression before alluded to- Small
brush buttresses projecting at right angles up from
| the dam, would have greatly lessened the danger
from any such undermining.
The flood Of the past winter which at its maxi
mum is thought to be greater than the memorable
food Of 1862, came upon the dam, soon after its
| completion, with great force. Had there been only
| the ordinary spring freshet, thus allowing the
| brush to be gradually filed and compacted nith
| sediment, there would have been much less subse-
| quent compression and very likely the whole work
| would have stood in its entirety.
The dam was commenced at late period in the
| season, and from the necessary haste in which it
| was built it was doubtless impossible to devote
that care in its const ucton which would have been
taken had there been more time in which to do the
| work.
BENEFITS RESULTING ALREADY FROM THE DAM.
The sections before referred to, taken across the
river show that fifty feet below the dam there has
been average erosion OF $40 OF foot; fifty feet
| above the dam there has been an average fill Of
55-l00 OF foot; one half mile above the dam there
has been an average fill OF / $40 of q foot; one
mile above the dam there has been average fill of
| $40 Of a foot one and ahalf miles above the
dam there has been an average I'LL OF $40 OF a
foot two miles above the dam there has been an
average fill of 40 OF foot; two and a-haf miles
above the dam there has been average fill Of 10
OF foot. Stll higher up the river, just below
1880 The total fill since 1880, for distance of
three and half miles above tine dam, is estimated
at ISL 600 cubic yards.
To nv mind the foregoing facts show conclusively
that this filing restraint of nearly 5000 600 cubic
wards has been caused entirely by the presence OF
The dam. or, in other words, that had not the dam
been built all this material would have been washed
i'll further down the stream the larger portion
lodging on the sackenea grade near Marysville, the
residue passing into the Feather river.
The serious breaks in the dam did not occur until
the food had in measure, spent its force, so that
at the moment when MGrysyille was in greatest
danger Of inundation, notable quantity OF water
was held back, together with aiow of sand, which
would otherwise have materially increased the leve
of high water.
Judging from the accounts given me Of the food,
it seems clear that to this dam Marysve is IN
debted for its safety during the past winter.
COST AND ACCESSIBILITY OF REPAIRING THE
DAM.
Tie tests to which the work now standing have
been so severe, and the results the whole Sc
satisfactory in an engineering point of view, that
am convinced that the dam can and should be Sc
curely repaired. The breaks should be filed with
ush-work, similar in general character but more
carefully executed, to the old structure; the dan
should be, where settled compressed, raised to
little above the original hight. When thus re
paired, in my Judgment, the work will stand tht
hoods, nd fully answer the purposes for which il
was designed.
a contract can think, be made with responsible,
parties for sum not $4,000, who will agre'
| to put the dam IN good repair, and only receive
their pay in case it stands intact until the summer
| OF Is 2 Without such guaranty the repairs car
be executed for much less sum.
The estimated storage capacity OF the reservoir
| to be formed by the dam is 41,500,0G0 OF cubi
wards deductiDg the 5000 600 OF yards now il
capacity, which can be secured for the compare
lively small sum Of $4,000 or less.
The State Engineer estimates that the ann1la
flow of material which can be impounded down TIT
Yuba river averages about 10000, GOO yards, all th
mines being at work. This Yuba dam will there
fore, when restored, hold over two years supply.
is probable that the flow OF sand down the fuo
several years to come will be below the average
as the great food of the past winter has swept dow
very much more than the usual quantity
1t has been objected to this dam, that in case OF
break the impounded sands would pour out in
great flood on the lower lands. We're it reseryoi
of water such would be the case, but with film:
of comparatively compact material any break woul'
only result in the discharge Of the sand cut out b.
the narrow current of water passing through tn
breach. The large amount of debris held back b.
the dam in its present badly broken and incomplete
state is sufficient proof that this objection Is prae
tcay an uHsound one.
CONCLUSION.
Should this dam be .stored, and hold back from
the Yuba and Feather rivers the injurious flow o
sand and gravel all Of which believe that it vii
do-the bitter contest now pending between miner
and farmers can be brought to end, before tn
STRIFE has inflicted irreparAbe injury on either o
both sides.
There is no question but what there is ampl
room in the Yuba canyons in which to store the min
ing debris for very many years to come TIL
magnitude OF the mining interest is great, that
it be shown that this debris be stored will
safety, at a reasonable expense, then certainly way
and means will be found for the execution of tn
necessary engineering works.
Hence, especially hope that the mining commu
nifty will do all in Its power to have this dam
the Yuba thoroughly repaired, that its value ma
be determined with certainty.
1t may be well to add that, even surprising minin
to be discontinued, still the dam will be of grea
service in holding back the large deposits of sam
and gravel already placed above it in the beds of tn
, river and Us branches.
Colonel George II. Mendell, OF the United State
Engineers, has BEEN kind enough to give me tn
letter which is attached to this report. The view
of Colonel Mendell will doubtless receive the atten
ton which his high standing in the profession wal
rants. Very respectfully,
HAMILTON SMITH, JR.
, San Francisco, July 81, 1881.