Sacramento daily record-union. [volume] (Sacramento [Calif.]) 1875-1891, 1880-10-28
TIE ENGLISH BREAK.
How Engineers Propose to Build a Dam
and Escape Weir along River Bank.

is washout through the west bank Of tbs
Sacramento river, about four miles above th,
Sacramento and Yoio bridge. The levee il
destroyed for about 525 feet in length, and
crevasse "a LILO feet in depth is cut through
the natural bank for an average width of IS.
feet. Upon the plane Of the natural bank
level this break is about $50 feet in length
1t has been seriously feared that longer neg.
let of this break would result in the river
some day taking its course through the crew
asse and finding new channel through the
low lands on the west of the present river
bed, result which would entail vast damage
and be serious injury to the whole State:
The Board of Drainage Commissioners of
Drainage District No. l has resolved TO Sc
cure this crevasse from further enlargement,
and to bring its bottom line up to level
about five feet below full food stage IN the
river For this purpose a dam of small trees
and brush, built after the plans and specitica-
tons originally drawn for the dams contracted
for on the Yuba and Bear rivers. is to be
built across the opening on a line well behind
the deep cut and connected with the levee
above and below it by means of an embank-
ment of earth. The details of this work are
of interest, as indicating the approved
methods of building dams and escape weirs
In the main, the proposed structure
will consist of two sections of levee, to be
placed nearly at right angles to the main
levee upon the bank of the river, and termi-
mating in abutments with -bulkheads, to
protect the extremities from abrasion.
| hulkheads is to be filled with a brush
! dam of from four to six feet in hight
above the average level of the present
surface. the center of the crest of the dam to
be upon an arc of about 372 feet radius. The
| general character of the dam is to be the
| same as those specified and contracted for in
the Yuba and Bear rivers. The dam is to be
SO constructed that its crest, as represented
by the upper edges or corners of all the tree
butts which end at the top surface through
out the width, on completion of the
work, shall be within four-tenths of a
foot of one level plane. The over
fall face must be on uniform slope of about
40 degrees. The foundation of the dam is
| to be laid In level benches at depths below the
general surface of the adjacent ground. When
completed the crest will not vary more than
four tenths of a foot from a level plane across
| it. The trees on the upstream face of the
dam will lie in a plane within degrees of the
slope of one foot vertical to two feet hori-
zontal, and its downstream face will lie in a
plane within 5 degrees of slope of one foot
vertical to one foot horizontal. In making
| the excavation fer the foundation or subgrade
within which the brush laying will begin if
! it is found that suitable foundation cannot
be had at the estimated depth, the contract
ors are bound to go as much as twice the
depth originally designated, but it is provided
that they need not go down over 6 feet on the
average for any 100 feet of foundation. Tie
structure is to be built in this manner:
The lower apron will be first built and
laid entirely beneath the average
plane of the grounds surface. The
material to be used will consist of
small trees, ranging from 20 to 80 feet in
length in the average sized structure, and of
greater or less length, as may be required, in
the longer or smaller crcss-sections, and from
to inches in diameter at the butt, laid
closely together lengthways up and down the
stream, in horizontal layers, separated by
smaller poles, planted three feet apart and
parallel with the line of the dam, the whole
consolidated and filled in with smaller brush
and spare material that is being moved. The
poles of each set are to be spiked solidly
down upon the tree trunks below, and the
trees of each layer are to be spiked to the
poles upon which they rest. Heavy stakes
are to be driven as firmly as can be done with
a ten-pound sledge, FIVE feet apart, through
and along the upper edge of the apron, to
which the pole and trees are to be firmly Sc
cured. The upper apron, to be laid rsially
below and partially above the natural
surface of the ground, is to be
next built. This apron rests partly upon
the lower apron and partly upon the ground
above, and is to be composed of the same
class of materials as the lower apron, and
laid Ia the following manner: Small trees or
trunks Of trees, varying from ID to 20 feet in
length for the average sized structure, and Of
greater or less length for the larger or smaller
nd fraf1 CIV 20 uaxyara rhac
diameter at the butt. are to be laid closely
together leDgthways up and down stream, in
layers sloping downwards and retreating up
stream, the butts exposed in the down stream
edge of each layer, covered or buried at the
upstream edge for the greater portion OF
their length. Alternating with these layers
of trees, poles of a smaller diameter are to be
laid three feet apart, crossing the trees SUBJ
stantially at right angles. The Intervening
spaces are to be well filed and consolidated
with small brush and spare material that
is being moved. The poles of each set are to
be solidly spiked down as in the first instance,
and heavy stakes are to be driven as before.
THE DAM PROPER.
The dam, resting partly upon the upstream
edge Of the upper apron, partially upon the
grounds surface next above and partially in
pit at the upper edge, is to be next built.
In its composition it Is to be similar to the
upper apron. Small trees or trunks of trees
II to Is feet in length, and 6 to s inches in
| diameter at the butt, are to be laid closely
together lepgthways up and down stream, in
layers sloping downwards in an upstream
direction, the butts exposed on the down.
stream edge of each layer. Alternating with
these layers of trees, poles of q smaller diam
eter are to be laid, crossing the trees substan-
TALLY at right angles. The interyen-
ing spaces between the trees and
layers are to be well filed with
small brush and spare material. In this
manner the dam is to be built up to the in
tended elevation of its crest, and then trees
| of larger diameter, and % to 80 feet In
length. are to be used, with their butts in
rows forming the crest of the dam, their
trunks sloping downward upstream, their
| tops buried in the pit and Incorporated with
| brush and earth. On the up stream face of
the dam, and on the top, back of such ma
! terial as may have been excavated from the
pit beneath is to be placed. With the con-
| sent of the Board Of Directors layer Of
good secondhand grain sacks filed
| with sand and strongly closed, may be
used either to supplement, or as substitute
| for the earth backing to an extent OF at least
! three sand bags fer each linear foot Of dam.
| At each end Of the OVERALL of the dam, at the
junction with the projecting levee, will be
! constructed an abutraent of timber and plank,
| filled with sand bags, earth and brush. The
surface of the ground beneath each abutment
| is to be excavated to depth of feet below
the natural surface. The ends of the dam
! are TO be well built into the abutment and
! firmly secured to the timbers which comprise
/ its frame This frame is to be of SINGH
square timber. and the planking is to be 2
and 3-iuch plank. The interiors OF the abut-
ments are to be filed with sand bags. AZ
each end Of the dam are TO be built earth
| lsvees, feet on top, with slopes . to on
the river side, and p to l on the land side
The old levee crown, for 200 feet each
side the break, is to be reformed
and raised. To protect the levee
brush revetment is to be built
where needed on the water slope of the
leyee from its base to within three feet OF its
crown and will consist of layers OF brush
and cross layers of saplings, cross, pegged
down, thus making q mattress. Brush spurs,
at right angles to the embankment, are to be
| built from the face of the levee to the river
bank, distance of 90 feet The details of
this brush spur work are elaborate, and call
for very superior and strong structures.
There will be about 450 feet of this spur
work, averaging six feet in hight The spur.
work may be described as that OF inclined
open-work walls of brush, supported on a
string-piece or ridge pole resting in a crotch
of small, rough timber cross horses placed at
intervals The work thus ont