lbs., or 1,260 sq. ft., of expanded metal required for 63 lin. ft. of
conduit per day, which is equivalent to ½c per lb., or 3 cts. per sq.
ft., for the labor of shaping, placing and fastening the metal.

~CIRCULAR SEWER, SOUTH BEND, INDIANA.~--In building 2,464 ft. of 66-in.
circular reinforced concrete sewer at South Bend, Ind., in 1906, the
method of construction illustrated in Figs. 257, 258 and 259 was
employed. The sewer has a 9-in. shell buttressed on the sides and is
reinforced every 12 ins. by a 3/16×1-in. peripheral bar in the sides and
roof and 3 ins. in from the soffit. Each bar is composed of three
pieces, two side pieces from 15 ins. below to 6 ins. above springing
lines and a connecting roof bar attached to the side bars by cotter
pins. Two grades of concrete were used, a 1-3-6 bank gravel concrete for
the invert and a 1-2-4 bank gravel concrete for the arch. The invert was
given a ½-in. plaster coat of 1-1 mortar as high as the springing lines.

[Illustration: Fig. 257.--Form for South Bend Sewer (First Stage).]

[Illustration: Fig. 258.--Form for South Bend Sewer (Second Stage).]

[Illustration: Fig. 259.--Form for South Bend Sewer (Third Stage).]

Forms and Concreting.--In constructing the sewer the trench was
excavated so as to give a clearance of 1 ft. on each side and was
sheeted as shown by Fig. 257. The sewer was built in 12 ft. sections as
follows: The bottom of the trench was shaped as nearly as possible to
the grade and shape of the base of the sewer. Four braces to each 12 ft.
section were then nailed across the trench between the lowest rangers on
the trench sheeting. A partial form consisting of a vertical row of
lagging was set on each of the outside lines of the sewer barrel as
shown by Fig. 257. Each section of this lagging was held by stakes
driven into the trench bottom and nailed at their tops to the cross
braces as shown by Fig. 258. A template for the invert was then
suspended from the cross braces by pieces nailed to the four ribs of the
template and to the cross braces as shown by Fig. 257. The concrete was
now placed and carried to the top of the template, which was then
removed. The side pieces of the reinforcing bars were then set and
fastened as shown by Fig. 258. The side forms extending up to the
springing lines were then placed. They were held in position by braces
nailed to their ribs at the tops and by other braces fitting into
notches in the ends of their ribs at the bottom. The concrete was then
carried up to the springing lines, the arch centers in two pieces were
placed; the arch bar of the reinforcement was placed and the extrados
forms erected up to the 45° lines, all as shown by Fig. 259. The placing
of the arch concrete completed the sewer barrel. The outside forms and
bracing were removed about 24 hours after the completion of the arch and
back filling the trench was begun immediately, but the inside forms were
left in place for two weeks; they were then removed by the simple
process of knocking out the notched braces. By building several lengths
of invert first and following in succession by the side wall
construction and then by the arch construction, the form erection and
the concreting proceeded without interruption by each other. It was also
found that, by making bends in the form of polygons with 10 ft. sides
instead of in the form of curves, there was a material saving in
expensive form work. To overcome the friction of the angles in such
bends an additional fall was provided at these places. All concrete was
made in a Smith mixer mounted on trucks so that it could be moved along
the bank of the trench and discharging into a trough leading to the
work.

_Labor Force and Cost._--With a gang of 12 men from 24 to 36 ft. of
sewer was built per 10-hour day, working only part of the time on actual
concreting. The disposition of the force mixing and laying concrete and
the wages were as follows:

  Item.                                Per day.
Six wheelers, at 18.5 cts. per hour      $11.10
One mixer, at 22.5 cts. per hour           2.25
One dumper, at 18.5 cts. per hour          1.85
Four placers, at 22.5 cts. per hour        9.00
  Total                                  $24.20

There were 0.594 cu. yd. of concrete per lineal foot of sewer and its
cost is given as follows:

Item.                                     Per cu. yd.
Cost of gravel                                $0.774
Cost of sand                                   0.36
Cost of cement                                 1.50
Cost of steel reinforcement                    0.84
Cost of labor, mixing and placing concrete     1.094
Cost of moving forms, templates, etc.          0.757
Cost of forms, templates, etc.                 0.589
Cost of finishing, plastering, etc.            0.639
Cost of tools and general expenses             0.841
Total                                         $7.394

~SEWER INVERT, HAVERHILL, MASS.~--In constructing sewers with concrete
inverts at Haverhill, Mass., in 1905, use was made of the traveling form
or mold shown by Fig. 260. The form consists of an inner and an outer
shell, the annular space between which forms the mold; in operation the
annular space is filled with concrete, then the outer shell is pulled
ahead from underneath, leaving the inner shell in place. A second inner
shell is then adjusted to the outer shell in its new position, the
annular mold is concreted and the outer shell again pulled ahead.
Continued repetition of the operations described completes the invert.
The merit of the device lies in the fact that the inner shell is not
moved until the concrete has attained some degree of rigidity; when, in
such devices, the inner mold is slid ahead on the green concrete it is
likely so to "drag" forward the material that a rough and pitted surface
results.

_Mold Construction._--Referring to the drawings of Fig. 260, A is the
outer mold of sheet steel bent to the required shape of the outer
surface of the conduit to be constructed. A rib, or angle, B, is
riveted to the inside of the mold at its front end and a diaphragm C
of plank is securely fastened to the rear side of the rib. The opposite
or rear end of the mold is open. Angles D forming tracks are riveted
inside the mold a short distance below the edges and reaching their full
length. The inner mold comprises a steel shell E curved to the form of
the inside of the conduit; inside this steel shell is a reinforcing
lagging, and at each end there is a wooden diaphragm F. Passing
through both end diaphragms and having its ends flush with the end
planes of the mold is a timber G. Rearward projecting lips e are
secured to the lagging at the rear end of the mold and on each side of
the timber G. The diaphragms F have each two arms f which project
horizontally beyond the surface of the inner mold and engage the tracks
D; locking dogs H are pivoted to the arms f so as to hook under
the track angles D and hold the inner form from rising. Setting on the
inner mold is an inverted V-shaped deflector I; its edges are flush
with the sides of the mold and its purpose is to facilitate the placing
of the concrete. There is also a movable diaphragm K, fitting loosely
inside the outer mold A and bearing against the end of the inner mold
E. The length of the inner mold E is about one-half that of the
outer mold A; as a rule several inner molds are provided with one
outer mold.

[Illustration: Fig. 260.--Traveling Invert Form for Sewer Construction.]

_Mode of Operation._--In using the device described the outer mold A
is first placed in the trench with its rear end at the end of the
trench. An inner mold E is then suspended on the tracks of the outer
mold and locked therein by the dogs H, with its rear end flush with
the rear end of the outer mold. The partition K is then placed in
position against the forward end of the inner mold and a jack J of any
suitable form is interposed between diaphragms K and C, the jack
being extended sufficiently to press diaphragm K firmly against the
front end of the inner mold. The deflector I is next placed in
position on the inner mold and the concrete is forced down with an iron
rammer between the two molds, so as to fill completely the annular
space. The deflector aids in directing the concrete into this space, as
will be obvious. After the mold has been filled and the concrete
compacted as much as possible, the jack is operated to separate the
diaphragms K and C, and as the partition K is pressed against one
end of the mass of concrete which has been laid, the opposite end of
which abuts against the end of the trench, it follows that any backward
movement of the diaphragm K will compress the concrete. This movement
will be practically inappreciable in distance, but enough to compact
thoroughly the concrete and fill any voids. The action of the jack will
also push forward the diaphragm C and the outer mold A, the latter
being withdrawn from beneath the inner mold and the newly laid concrete,
the tracks D of the outer mold being drawn from beneath the arms f
of the inner mold, leaving the latter behind resting on the freshly laid
concrete. Further compression of the concrete after it has been left by
the outer mold will fill the spaces between the inner mold and the
surface of the trench. The outer mold is moved forward in this manner a
distance equal to the length of the inner mold, and then the diaphragm
K is drawn forward and another inner mold is lowered into the outer
mold exactly as was the first one. The jack is then placed, the concrete
deposited and the outer mold again advanced exactly as before. As the
outer mold advances, the inner molds become disengaged one after another
and are set ahead; in practice, enough inner molds are provided to
enable the concrete to harden sufficiently to keep its position when it
becomes necessary to take up successively the rearmost molds and place
them ahead.

_Haverhill Sewer Work._--The work at Haverhill, Mass., previously
mentioned in which the form just described was used, was a 24-in.
circular sewer with 6-in. walls. The outer form was 36 ins. in diameter
and 6 ft. 2 ins. long; the inner form was 24 ins. in diameter and 3 ft.
long. Angle B was 3 ins. and the track angles D were 1½ ins.; diaphragm
K was made of two thicknesses of 3-in. plank and diaphragm C of one
thickness of 3-in. plank, the other diaphragms were of 2-in. plank. The
shells of the molds were of ¼-in. steel plate; the jack was an ordinary
screw jack. Eight inner molds were used.

The form used at Haverhill was built by the city carpenter, the metal
portions being made in a boiler shop. Its cost was not ascertained, but
was, it is thought, about $75. The concrete used was a 1-3-5 stone
mixture, with cement costing $2 per barrel, sand $1.50 per load of 36
cu. ft., and stone $2.50 per load of 36 cu. ft. The men were paid 25
cts. per hour. Records kept on 265 ft. of invert, or, theoretically,
19.3 cu. yds. of concrete, gave the following figures:

                                      Per       Per
                                    lin. ft.  cu. yd.
Labor, setting and moving
  forms, 42 hours, at 25 cts.          $0.05    $0.67
Labor, mixing, placing and wheeling
  concrete, 179 hours, at 25 cts.       0.16     2.19
                                       -----    -----
  Total labor cost                     $0.21    $2.86

With the ordinary 1-3-5 mixture the cost of materials would run about as
follows:

                                 Per cu. yd.
Cement, 0.96 bbl., at $2.           $1.92
Sand, 0.47 cu. yd., at $1.13         0.53
Stone, 0.78 cu. yd., at $1.88        1.47
                                    -----
  Total cost materials              $3.92

Two men were worked in the trench, one alternately ramming the concrete
into place and working the jack, and the other shaping the trench ahead
and assisting in bringing the rear forms ahead.

The form described was invented by Mr. Robert R. Evans, of Haverhill,
Mass., and has been patented by him.

~29-FT. SEWER, ST. LOUIS, MO.~--The following account of the method and
cost of constructing 162 ft. of very large sewer section at St. Louis,
Mo., is compiled from information furnished by Mr. Curtis Hill.

The cross-section of the sewer is given by Fig. 261, which also shows
the arrangement of the reinforcing bars. Johnson corrugated bars, old
style, are used for reinforcement. The sections of the various
reinforcing bars are: Longitudinal bars, 0.18 sq. in.; invert bars, 0.7
sq. in., and arch bars, 0.7 sq. in. The spacing of the bars and the
arrangement of the splices are indicated on the drawings of Fig. 261.
All splices have a lap of 36 ins. Some gravel concrete has been used in
the invert, but most of the concrete has been crushed limestone and
Mississippi River channel sand. The proportions were 1-3-6 in the invert
and 1-2-5 in the arch. The arch was computed by Prof. Greene's method.
The ultimate strength of concrete in compression was taken as 2,000 lbs.
per sq. in. and the working strength at 500 lbs. per sq. in. The elastic
limit of the reinforcing bars was taken at 50,000 lbs.

[Illustration: Fig. 261.--Harlem Creek Sewer, St. Louis, Mo.]

The trenching was done by wheel scrapers to the amount of waste. Then a
cableway was erected spanning the entire length of the section and the
remainder of the material taken out. The last 4 or 5 ft. in depth were
in limestone and the excavated rock was taken by cableway to dump carts
which took it to the crusher and returned with crushed rock to be used
for concrete. This rock foundation was taken advantage of to reduce the
amount of invert concrete.

In constructing the sewer proper the invert was first concreted to
template to the height shown in Fig. 262. The arch forms were then
placed as shown in Fig. 262, and the roof arch concreted. Both templates
and arch forms were constructed of wood. The arch forms were moved ahead
on iron rails and jacked into place. The ribs were 2×10-in. pieces and
were spaced 4 ft. on centers; the lagging was 2-in. tongue and grooved
stuff and was smeared with crude oil. The reinforcing bars shown in Fig.
261 were bent to proper radius by means of a wagon tire bender and were
held in place by templates. The concrete was all mixed by two Chicago
Improved Cube mixers operated by electric power.

[Illustration: Fig. 262.--Center for Harlem Creek Sewer.]

The cost records of constructing the section of 29-ft. sewer so far
built are not susceptible of complete analysis, but the following
figures can be given. The prices of materials were as follows:

Cement, per barrel               $1.80
Sand, per cubic yard              0.75
Broken stone, per cubic yard      1.00
Reinforcing bars, per pound       0.02
Vitrified brick, per 1,000       12.00

The wages paid different classes of labor were:

                  Per hour.
Firemen            $0.50
Laborers            0.175
Laborers            0.20
Laborers            0.25
Laborers            0.28
Laborers            0.3025
Bricklayers         0.66 2/3
Helpers            $0.25
Carpenters          0.55
Engineers           0.50
Timekeepers         0.25
Watchmen           0.175
Hostlers           0.175
Teams               0.60

Taking up the several items of work in order, the excavation amounted to
21,400 cu. yds., of which 1,400 cu. yds. were rock excavation. The cost
of excavation was as follows:

                              Total.    Per cu. yd.
Earth, excavation             $7,640        $0.38
Earth bracing                  2,000         0.10
Rock excavation                1,400         1.00
Rock, dynamite, tools, etc.      560         0.40

The cost of crushing the excavated rock and returning it to the mixer
was $1 per cu. yd.

The cost of the concrete work was as follows:

Per cu. yd.
1.30 bbl. cement at $1.80        $2.34
.044 cu. yd. sand at 75 cts.      0.33
1 cu. yd. broken stone at $1      1.00
                                 -----
  Total concrete materials       $3.67

There were 1,600 cu. yds. of concrete placed at a cost of for:

                                Total.     Per cu. yd.
Mixing and placing              $1,180      $0.7375
Forms                            2,000       1.25
Moving forms                       400       0.25
                                ------      -------
  Total for forms and labor     $3,580      $2.2375

For reinforcing the concrete 86,600 lbs. of steel, or about 55 lbs. per
cu. yd. were used. The cost of placing and bending this steel was as
follows:

                   Total.      Per lb.
Cost of placing    $172      0.1986 ct.
Cost of bending      52      0.06   ct.

We can now summarize the cost of the concrete work proper of this sewer
as follows:

  Items.                         Per cu. yd.
Cement, sand and stone                 $3.67
55 lbs. steel at 2 cts.                 1.10
Forms, labor and materials              1.25
Mixing and placing concrete labor       0.74
Placing steel at 0.1986 ct. per lb.     0.11
Bending steel at 0.06 ct. per lb.       0.03
Moving forms                            0.25
                                       -----
  Total labor and materials            $7.15

To get the total cost of the sewer proper we must add the cost of the
vitrified brick invert paving. There were 71 cu. yds. of this paving and
its cost was as follows:

                                     Per cu. yd.
0.6 bbls. cement at $1.80                 $1.08
0.25 cu. yd. sand at 75 cts.              0.19
450 bricks at $12 per M.                  5.40
Labor laying, 71 cu. yds. at $180.33      2.54
                                         -----
Total                                    $9.21

None of the preceding figures includes the plant charges. The plant cost
$12,000 and the cost of running it during the work described was $2,000.
In explanation it should be noted that the plant served for building
some 1,340 lin. ft. of 27-ft. sewer as well as for the section
described.

~SEWER AT MIDDLESBOROUGH, KY.~--In constructing an oval sewer 4 ft. high
at Middlesborough, Ky., two steel forms in 10-ft. sections were used. As
shown in Fig. 263, T-iron ribs were spaced 5 ft. apart, fastened
together at the top by longitudinal angle irons, and at the bottom by a
sheet of steel 22 ins. wide, forming the bottom of the invert. The
lagging for the sides consists of movable 5-ft. lengths of channel iron,
secured by sliding bolts. After the bottom of the trench has been
roughly shaped with concrete, a 10-ft. section of invert forms is
lowered and suspended by the cross-beams, and the space beneath packed
with concrete; then a channel iron is slid into place and bolted, and
concrete packed behind it, and so on until the invert is made. The next
10-ft. section is then built while the first is hardening. Upon the
completion of the second section, the channel iron sides of the first
section are removed, and then the rib framework is lifted out. Wood arch
centers are then put in place and an inch of 1:2 plaster spread over the
lagging before placing the concrete for the arch, which is 6 ins. thick.

[Illustration: Fig. 263.--Invert Form for Sewer Construction.]

The cost per 100 ft. of this sewer was as follows (prices being assumed
for cement and labor):

  Bottom concrete.               Cost per 100 ft.
18.5 bbls. cement, at $1.50          $ 27.75
2.7 cu. yds. sand, at $1.00.            2.70
15 cu. yds. stone, at $1.00            15.00
17 days labor, at $1.50                25.50

  Bottom concrete.              Cost per 100 ft.
25.25 bbls. cement, at $1.50           37.85
7.5 cu. yds. sand, at $1.00             7.50
22 days labor, at $1.50                33.00

  Sewer Arch.
26 bbls. cement, at $1.50              39.00
3.9 cu. yds. sand, at $1.00             3.90
13.6 cu. yds. stone, at $1.00          13.60
21 days labor, at $1.50                31.50
                                     -------
  Cost per 100 ft.                   $237.30

[Illustration: Fig. 264.--Sewer at Cleveland, Ohio.]

~INTERCEPTING SEWERS, CLEVELAND, O.~--An intercepting sewer some 3½ miles
long, of the form and construction shown in Fig. 264, was built at
Cleveland, Ohio, in 1904. The construction consists of a plain concrete
invert lined with two courses of shale bricks, and having two rows of
anchor bars set in the side walls so that the bars of one row are
staggered with respect to those of the other row. The anchor bars are
2×½-in. steel, and are spaced 30 ins. apart in each row. To the anchor
bars are bolted arch reinforcing bars arranged as shown, and these arch
bars have bolted to them eight lines of 1½×¼-in. longitudinal bars. A
natural cement concrete is used for the invert and side walls. The arch
is Portland cement concrete of normally a 1-3-7½, 1½-in. screened stone
mixture, but where the voids in the broken stone exceeded 40 per cent.,
it is a 1-3-6 mixture. The invert bricks are laid in Portland cement
mortar and the arch has a mortar lining and is waterproofed with 1-in.
of mortar on top.

_Forms._--Separate forms were used for the invert and for the arch ring.
Regarding these, the engineer, Mr. Walter C. Parmley, remarks:

One of the first forms used in the sewer was like a piece of segmental
arch centering inverted, and with the lagging nailed fast to the ribs.
The trouble with this form is that it is difficult to tamp concrete
under the bottom portion of the form, and hence a very rough surface is
produced. Much better results were obtained by omitting the lagging
boards on the bottom and at the sides till a point was reached where the
inclination of the concrete surface was about 45°. The concrete for the
bottom could then be worked down between the ribs, thorough tamping
done, and a good surface obtained. The ribs serve as a guide, so that
the workman produces the proper shape. From this point up to the
vertical, good results can be secured with the ribs attached to the
lagging. Some contractors found it more convenient to use ribs that were
connected with each other by a skeleton framework only, and then to slip
the lagging in, one piece at a time. For some of the sewers, in which
the brick lining was not carried quite up to the spring line, a separate
side form of skeleton ribs and loose lagging was set upon brace legs
bearing on the bottom of the invert. This form carried the concrete from
about 2 ft. below to about 2 ft. above the springing line. The arch ribs
then became segmental and rested upon the middle braces. This method has
the advantage of using ribs that are lighter and more easily handled
than those that are semi-circular. For arch centering, it is necessary
and convenient to use independent ribs and loose lagging, for the
centers can then be carried forward piece-meal, the falsework upholding
the green arch and re-erected at the advance end of the work. In these
matters each contractor prefers to use his own ingenuity, and so long as
the work is properly built, the engineer can well give him considerable
latitude as to use of methods. One thing, however, the engineer must
insist upon--that all centering and falsework be as nearly rigid as
possible. Even a slight settlement of the centers at the crown under the
load of concrete and back-fill will cause the arch to kick out at the
quarters, and if the green concrete arch is not cracked at the crown, it
will be crushed on the inside, about half way between the crown and
springing line. A reinforced arch is no more immune to this danger than
is a plain concrete arch. However, with a few days of hardening,
although the damage may be serious, the danger of actual collapse is
less. A point to be guarded against, especially in reinforced
construction, is any foolish act on the part of contractor or workman,
due to his overconfidence in the strength of the structure because it
contains embedded steel.

The mode of procedure in constructing the arch ring was to erect the
centers with lagging complete. The lagging was then covered with
building paper waterproofed with paraffine. The arch reinforcing bars
were then bolted to the anchor bars and the longitudinals connected up.
The lining of Portland cement mortar was first laid on the lagging.
Before this mortar had set, concrete was rammed in between it and the
sheeting to a height of 18 ins. above the springing line, and then the
remainder of the concrete placed without outside forms. The top of the
arch ring was finally finished with a 1-in. mortar coat. In regard to
the concrete, Mr. Parmley remarks:

"Concrete will flush up to the forms and produce a better surface, and
the voids in the stone will be much better filled if it is so wet as to
require but little tamping; moreover there is less danger of obtaining a
weak, porous wall should a workman neglect thorough tamping, than there
is where only a moist mixture is used. It is also to the contractor's
interest to use wet concrete for much less labor is required in mixing
and placing it. Small broken stone or gravel is preferable in concrete
for sewers. The walls being comparatively thin, unless there be a
considerable excess of mortar, if coarse stones are used, the concrete
will be honeycombed with voids. The stones should be well graded in size
from large to fine, but the largest fragments should not exceed 1½ ins.
in greatest dimension."

_Cost._--A number of records of cost of constructing short sections of
the sewer described are given by Mr. Parmley, as follows:

  Labor placing anchor bars.                   Per day.
1 man, at $3.50                                   $3.50
1 man, at $1.75                                    1.75
4 hours carrying steel at 20 cts.                  0.80
                                                  -----
                                                  $6.05

The anchor bars were placed for 40 lin. ft. of sewer, or about 1,504
lbs. of metal at a cost of 0.4 ct. per lb.

The concreting gang for the sides consisted of:

5 men wheeling and mixing at $1.75                   $8.75
1 man tamping                                         1.75
2/3 time man lowering brick and concrete at $2.25     1.50
1 man carrying concrete                               1.75
                                                    $13.75

This gang built the side wall for 40 ft. of sewer daily, or 13 cu. yds.
Cost of labor per cu. yd. was, therefore, $1.06. The concrete was tamped
behind the brick lining as the latter was built up by the mason.

Cost of single ring brick lining at sides:

2 masons at 70 cents per hour                        $1.20
1 man mixing mortar                                   2.25
1/3 time man lowering at $2.25                        0.75
3 men wheeling sand, filling buckets and dumping      5.25
  Total labor for 40 lin. ft. of sewer              $19.45
Quantity of brick masonry laid, cu. yd.               6.38
Labor per cu. yd.                                     3.05

An account was kept of labor performed on 85 lin. ft. of arch work, or
14 1-6 ft. daily. The force was as follows:

1 man putting mortar lining on centering             $1.75
2 men mixing mortar, screening and wheeling sand      3.50
1 man tamping concrete                                1.75
8 men on mixing board at $1.75                       14.00
                                                    $21.00
No. cu. yd. placed daily                             25.64
Labor per cu. yd.                                     0.82
  Placing centering and arch bars:
2 men at $1.75                                       $3.50
1 man at $3.50                                        3.50
                                                     -----
                                                     $7.00

Costs, for 14 1-6 ft. daily, $0.49 per lin. ft.

As nearly as could be judged, about two-thirds of the labor was used in
erecting the centering and one-third in putting the steel in place. The
amount of steel placed daily was 785 lbs., at cost, therefore, of 0.3 of
a cent per lb., and the cost of erecting and moving centers, $0.33 per
lin. ft. of arch.

Another record of 39.27 ft. on a curve, gave for the cost of the brick
work at sides the same result as above, but the inspector's record of
men working on concrete backing at sides showed a less cost, as follows:

4 men mixing at $1.75                             $7.00
2/3 time man lowering at $2.25                     1.50
1 man in bottom                                    1.75
                                                  -----
                                                 $10.25

They placed 12.7 cu. yd. at a cost of $0.81 per cu. yd. This figure
probably more nearly represents the average cost than the $1.06 reported
in the first instance.

The cost of placing the anchor bars on straight sewer, representing
average progress, at another time, was found to be:

1 man                                             $3.50
1 man                                              1.75
                                                  -----
                                                  $5.25

They placed the steel for 44 ft. of sewer or 1,650 lb. at a cost of 0.32
of a cent per lb.

Further notes for 6 days' work, when it seemed to represent as nearly as
possible the general average for the whole were:

Labor on arch concrete:

Daily progress was 13 1-6 ft.

  The force employed was:
7 men making concrete, at $1.75      $12.25
1 man plastering the center            1.75
1 man mixing mortar                    2.00
1 man tamping                          1.75
                                      -----
                                     $17.75

On straight arch work they placed 24.1 cu. yd. daily at a cost of $0.74
per cu. yd. In three days' work on a curve, the same gang placed 26.37
cu. yd. daily at a cost of $0.675 per cu. yd.

On centering and steel for arch, three men kept up with the regular
progress of the arch-concreting gang. The cost, therefore, is:

1 man                             $3.50
2 men at $1.75                     3.50
                                  -----
                                  $7.00

They averaged 13 ft. daily, or at a total cost of about $0.54 per lin.
ft. of sewer.

Two-thirds of this labor was on the centering or $0.36 per lin. ft. of
arch; $0.18 per lin. ft. placed the steel ready for embedding, or about
55.5 lb. per ft. of arch, at a cost of 0.32 of a cent per lb.

For the double ring brick lining at the bottom, the regular daily rate
of progress was 28 ft. or 11.15 cu. yd. with:

2 bricklayers                    $11.20
5 men at $1.75                     8.75
1 man at $2.25                     2.25
                                  -----
                                 $22.20

or at a cost of $1.98 per cu. yd. This is given only because it is of
interest in connection with the cost of the concrete.

Other observations on cost of placing steel skeleton and concrete did
not vary materially from the figures given. It will be observed that no
charge for superintendence or anything for the general expenses is
included in the estimates of cost. These charges were, of course,
impossible to obtain. On another contract with machine mixing, as high
as 36 lin. ft. of 13 ft. 6 in. arch were built in a day, but no data as
to cost were taken, though it was evidently less than for the work with
hand-mixed concrete.

~REINFORCED CONCRETE SEWER AT WILMINGTON, DEL.~--Records of a notable job
of sewer construction at Wilmington, Del., in 1903, are furnished by Mr.
T. Chalkley Hatton. The sewer was built by day labor for the city; its
cross-section at various points is shown by Fig. 265. The cross-section
of sewers in trenches deep enough to cover the arch are marked "deep
cutting"; the sections where the arch projects above the ground surface
are marked "light cutting." The section through the marsh was 700 ft.
long, the cutting being 8 ft. deep, and at high tide the marsh was
flooded 1 to 4 ft. The material was a soft mud that would pull a tight
rubber boot from a workman's foot. The cost of this marsh excavation
including cofferdams, underdraining, pumping, etc., was $4.60 per cu.
yd. For 1,100 ft. the 9¼ ft. sewer was through a cut 22 to 34 ft. deep,
the material being clay underlaid by granite. A Carson-Lidgerwood
cableway was used. Although the crown of the arch was but 8 ins. thick,
it withstood the shock of dumping 1 cu. yd. buckets of earth and rock
from heights of 3 to 10 ft.; and the weight of 25 ft. of loose filling
caused no cracks in the concrete.

Concrete was placed in 4-in. layers (the depth of the lagging) and well
rammed, since it was found that "wet" concrete left small honeycombed
spaces on the inner surface. Concrete for the invert was 1-2-6, the
stone being 1½-in. and smaller, and the sand being crusher dust. The
arch was 1-2-5.

The reinforcing metal used in the 9½-ft. sewer was No. 6 expanded metal,
6-in. mesh, in sheets 8×5½ ft., supplied by Merritt & Co., of
Philadelphia. A single layer was placed around the sewer, 2 ins. from
the inner surface, its position being carefully maintained by the men
ramming, and with but little difficulty as the sheets were first bent to
the radius of the circle. Each sheet was lapped one mesh (6 ins.) over
its neighbor at both ends and sides, and no sheets were wired except the
top ones, which were liable to displacement by men walking over them.

[Illustration: Fig. 265.--Cross-Sections of Sewer at Wilmington, Del.]

The metal used on the rest of the work was a wire-woven fabric furnished
by the Wight-Easton-Townsend Co., of New York. This fabric comes in
rolls 5½ ft. wide and 100 ft. to the roll. The wire is No. 8, with a
6×4-in. mesh. This fabric was placed by first cutting the sheets to the
required length to surround the sewer entirely, embedding it in the
concrete as fast as concrete was placed, in the same manner as was done
with the expanded metal except over the center where, on account of its
pliability, the fabric was held the proper distance from the lagging by
a number of 2-in. blocks which were removed as the concrete was placed.
The wire cloth, being all in one sheet, can be placed a little more
expeditiously than expanded metal, but, on the other hand, the expanded
metal holds its position better in the concrete, since it is more rigid.

We quote now from Mr. Hatton's letter: "The major portion of concrete
was mixed by machine at a cost of 66 cts. per yard, including wheeling
to place, coal and running of mixing machine, wages being $1.50 per day
of 8 hrs, Stone was delivered alongside of machine and all material had
to be wheeled in barrows upon the platform, and after mixing to the
sewer. Placing and ramming concrete around the forms cost 39 cts. per
cu. yd., additional. Setting forms in invert cost 2 cts. per cu. yd.,
setting centers 7 cts. per cu. yd. Cost of setting forms and centers
includes placing steel metal. Each lineal foot of 9¼ ft. sewer contained
1 cu. yd. of concrete, although the section only calls for 0.94 cu. yd.
The excess was usually wasted by falling over sides of forms or being
made too thick at crown.

"This yard of 1-2-5 concrete cost in place as follows (record taken as
an average of several-days' run):

Cement, 1.31 bbls. at $1.30                            $1.703
Stone, 0.84 cu. yds. at $1.21                           1.016
Stone dust, 0.42 cu. yd. at $1.21                       0.508
Labor at 18¾ cts. per hour                              0.987
Labor setting forms and setting metal                   0.045
Cost of forms (distributed over 1,800 ft. of sewer)     0.082
40 sq. ft. expanded metal at 4¼ cts.                    1.700
Labor plastering invert                                 0.070
  Cost per ft., or per cu. yd.                         $6.111

"The forms for the invert were made of 2-in. rough hemlock boards cut
out 4 ins. less diameter than the diameter of the sewer, except for 18
ins. at the bottom of the form which coincided with the inside form of
sewer. The bottom of the sewers was laid to the bottom of this form
before it was set. Then the lagging, consisting of 2×6-in.×16-ft.
hemlock planed, was placed against each side of the form, one at a time,
and the concrete brought to the line of this top in 6-in. layers until
the whole invert was finished. These forms were set in 16-ft. sections,
five to each section.

"The centers consisted of seven ribs of 2-in. hemlock upon which was
nailed 1½-in. lagging, 2 ins. wide, tongued and grooved, and were 16 ft.
long, non-collapsible, but had one wing on each side, 9 ins. wide, which
could be wedged out to fit any inaccuracies in the invert. We used four
of these centers setting two at each operation and worked from two ends.
We left the centers in for 18 hours before drawing.

"The cost of the concrete on the smaller sewers was the same as are the
larger sewers, but the steel metal cost less, as it was wire woven metal
that cost 2½ cts. per sq. ft. It was much easier handled and cut to no
waste as it came in long rolls and was very pliable.

"After training our men, which occupied about one week or 10 days, we
had no difficulty in getting the concrete well placed around the metal,
preserving the proper location of the latter, which, however, bore
constant watching, as a careless workman would often take the temporary
supporting blocks and allow the metal to rest against the wooden center,
in which case the metal would show through the surface inside of the
sewer. The metal was kept 2 ins. away from the inside forms and the
arch. To keep it at this location we had several 2-in. wooden blocks cut
which were slipped under the wire or expanded metal and as soon as some
concrete was pushed under the wire at this point the block was removed.

"After the forms were removed the invert needed plastering, but the arch
was practically like a smoothly plastered wall except where it joined
the invert, where it frequently showed the result of too much hurry in
depositing the first loads of concrete on the arch. We remedied this by
requiring less concrete to be deposited at the start, thus giving the
rammers time to place the material properly.

"An interesting result was obtained in the smoothness of the inside
surface by using a mixture of different sized stones. When ¾-in. stones
or smaller were used in the arch, the inside was honeycombed; but, where
1 to 1½-in. stones (nothing smaller) were used, the inside was perfectly
smooth, and the same was true of the invert, showing that the use of
larger stones is an advantage and secures more monolithic work. When the
run of the crusher from 1½ to ¾-in. stones was used the work was not at
all satisfactory.

"The difference in cost of mixing by hand and machine is practically
nothing on this kind of work. As the moving of the machine to keep pace
with the progress of the work equals the extra cost of mixing by hand
when the mixing can be done close to the point where the cement is being
placed."

The total cost of the sewers, including excavation, etc., was:

                                         Cost per lin. ft.
9¼-ft. sewer through marsh                      $32.00
9¼-ft. sewer in cut averaging 24½ ft.            24.00
6½-ft. sewer in cut averaging 12 ft.             10.00
5-ft. sewer in cut averaging 11½ ft.              6.70

~SEWER WITH MONOLITHIC INVERT AND BLOCK ARCH.~--The following records of
construction for a sewer built at Coldwater, Mich., in 1901, are given
by Mr. H. V. Gifford. The sewer had a monolithic invert and a block
arch.

The sewer was circular, having an inner diameter of 42 ins., the
thickness of the invert and the arch alike was 8 ins. Figure 266 is a
cross-section. The concrete was 1 of Portland cement to 6 of gravel.
There were 11 concrete blocks in the ring of the arch, each block being
24 ins. long, 8 ins. thick, 8 ins. wide on the outside of the arch and
5¾ ins. wide on the inside of the arch. A block weighed 90 lbs. which
was too heavy for rapid laying; blocks 18 ins. long would have been
better. Some 8,500 blocks were made. Molds were of 2-in. lumber, lined
with tin, for after a little use it was found the concrete would stick
to the wood when the mold was removed. The four sides of the mold formed
the extrados, the intrados, and the two ends of the block; the other two
sides being left open. When put together the mold was laid upon a 1-in.
board, 12×30 ins., reinforced by cleats across the bottom. The sides of
the molds were held together with screws or wedge clamps. When the
blocks had set, the sides of the molds were removed, and the blocks were
left on the 12×30-in. boards for 3 days, then piled up, being watered
several times each day for a week.

A gang of 14 men made the blocks; 2 screening gravel through 1-in. mesh
screen; 4 mixing concrete; 4 molders; 3 shifting and watering blocks,
and 1 foreman. With a little practice each molder could turn out 175
blocks a day; and since each block measured ¾ cu. ft., the output of the
14 men was 19½ cu. yds. a day. Mr. Gifford informs us that the wages
were $1.50 a day for all the men, except the foreman. The daily wages of
the 14 men were $22, so that the labor of making the blocks was $1.10
per cu. yd.

[Illustration: Fig. 266.--Sewer with Monolithic Invert and Block Arch.]

Each batch of concrete, containing ½ bbl. of Portland cement costing
$1.35 per bbl., made 18 blocks. (1 bbl. per cu. yd.) Since the gravel
cost nothing, except the labor of screening it, the total cost of each
block was 11 to 12 cts., which includes 0.85 cent for use of molds and
mold boards, which were an entire loss. At 12 cts. per block the cost
was $4.32 per cu. yd.

The contract price was $3 per lin. ft. of this sewer, as against a bid
of $3.40 per ft. for a brick sewer.

When the trenching had reached to the level of the top of the invert,
two rows of stakes were driven in the bottom, stakes being 6 ft. apart
in each row, and rows being a distance apart ¼-in. greater than the
outer diameter of the sewer. These stakes were driven to such a grade
that the top of a 2×4-in. cap or "runner" set edgewise on top of them
was at the proper grade of the top of the invert. The excavation for the
invert was then begun, and finished to the proper curve by the aid of a
templet drawn along the 2×4-in. runners. In gravel it was impossible to
hold the true curve of the invert bottom. Concrete was then placed for
the invert. To hold up the sides of the invert concrete, a board served
as a support for the insides, but regular forms were more satisfactory
in every respect except that they were in the way of the workmen. A form
was tried, its length being 6 ft. It was built like the center for an
arch, except that the sheeting was omitted on the lower part of the
invert. It was suspended from the cross-pieces resting on the "runners."
After the concrete had been rounded in place, the form was removed and
the invert trued up. This form worked well in soil that could be
excavated a number of feet ahead, so that the forms could be drawn ahead
instead of having to be lifted out; but in soil, where the concreting
must immediately follow the excavation for the invert, the form is in
the way. The invert was trued up by drawing along the runners a
semi-circular templet having a radius of 21½ ins. Then a ½-in. coat of
1-2 mortar was roughly troweled on the green concrete. Another templet
having a 21-in. radius was then drawn along the runners to finish the
invert.

When the plaster had hardened, two courses of concrete blocks were laid
on each shoulder of the invert, using a 1-2-¼ mortar, the ¼ part
being lime paste. The lime made the mortar more plastic and easier to
trowel. Then the form for the arch was placed, and as each 8-ft. section
of the arch was built, a grout of 1-1 mortar was poured over the top
to fill the joints. Earth was thrown on each shoulder and tamped, and
the center moved ahead.

Common laborers were used for all the invert work, except the plastering
which was done by masons who were paid 30 cts. per hr. Masons were also
used to lay the concrete blocks in the arch. Mr. Gifford states that two
masons would lay at the rate of 100 lin. ft. of arch per day, if enough
invert were prepared in advance. As there were 11 blocks in the ring of
the arch, this rate would be equivalent to 7½ cu. yds. of arch laid per
mason per day.

[Illustration: Fig. 267.--Concrete Block Manhole.]

~COST OF BLOCK MANHOLES.~--The following costs of constructing concrete
block manholes for electric conduit at Rye, N. Y., were recorded by Mr.
Hugh C. Baker, Jr. The arrangement of the blocks, their size and shape
and the dimensions of the completed manholes are shown by Fig. 267. The
blocks were molded of 1-2-5¾-in. broken stone concrete in 30 wooden
molds made by a local carpenter at a cost of from $3.50 to $12 each. The
concrete was placed in the molds very wet, with very little tamping, and
was allowed to set for seven days before the blocks were moved to the
work. The molds were left in place from 24 to 36 hours. With the
facilities at hand six complete sets of top blocks were made each day by
four men, when no wall blocks were being made, and half a set (15) wall
blocks and two sets of top blocks were made each day by four men. The
cost of the block manholes complete was as follows, per manhole:

30 wall blocks, 2½ cu. yds.                        $21.00
6 cover blocks, 1½ cu. yds. reinforced               4.27
I-beams for cover, in place                          5.40
Supervision, freight, hauling 5.6 tons concrete      9.38
Labor placing cover, 3 hrs. at 15 cts.               0.45
Labor placing walls, 20 hrs. at 15 cts.              3.00
  Total, exclusive of iron cover                   $43.50

~CEMENT PIPE, CONSTRUCTED IN PLACE.~--In constructing 8-in. cement sewer
for the Foster Armstrong Piano Co.'s works at Rochester, N. Y., a gang
of seven men averaged 300 ft. of pipe per 10-hour day, using a Ransome
pipe mold. The mold is shown by Fig. 268. It is made of sheet steel,
with an inner core 10 ft. long, the front end of which is surrounded
with a sheet steel shell that serves as an outer form for the pipe. The
mortar mixed rather dry was packed into the annular space between core
and shell by one man, using a short wooden rammer. A second man kept the
mold slowly moving forward by operating the lever, which by means of a
ratchet and drum winds up a wire rope stretched ahead to a deadman in
the trench bottom. As the mold moves ahead it leaves behind it the
cement pipe. A third man carefully filled under the invert and over the
haunches of the green pipe with earth to give it support. The following
was the itemized cost per day, 300 ft. of pipe laid:

6 men at $1.70 per 10-hour day     $10.20
1 foreman                            3.00
3 bbls. cement at $1.25              3.75
3.3 cu. yds. sand at 85 cts.         2.80
Water                                0.15
  Total for 300 lin. ft.           $19.90

This is equivalent to 6.63 cts. per lin. ft. of pipe.

[Illustration: Fig. 268.--Ransome Continuous Mold for Concrete Pipe
Construction.]

In Trans. C. E., Vol. 31, 1894, p. 153, James D. Schuyler gives the cost
of cement pipe made by the Ransome system for the Denver Water Works.
There is a wrought iron shell of the size of the inner diameter of the
pipe forming the inner mold. To this shell is attached a "leader" and
"saddle" of larger diameter forming the outer mold. These molds are
drawn slowly along the trench by a cable and horse whim, and the
concrete is shoveled continuously into the core space between the molds
and rammed on a long incline. The top half, or arch, of the pipe is
supported by sheet iron plates (2 ft. wide), placed one after another on
the forward end of the mold; and, being clamped together at the top and
sides, remain in position after the mold is slid out from under them.
After the mold has passed along, these iron plates are supported by
upright sticks and by horizontal clamping rods. The plates are left in
place for 24 to 48 hrs. The concrete, made 1-3½, river sand and gravel,
was machine mixed. A gang of 30 men mixed, wheeled, shoveled and tamped
the concrete, attended to the plates, cleaning and greasing them, etc.
This gang would make short runs at the rate of 900 lin. ft. of pipe a
day, but counting stoppages, the average rate was 300 ft. a day. The
inner diameter of the pipe was 38 ins., and its bottom was molded flat
for a width of 18 ins. The concrete shell was 2½ to 3 ins. thick. The
pipe was washed with pure cement grout, applied with brushes after
removing the iron plates. With cement at $3.75 per bbl., gravel at $1.25
per cu. yd., and labor at $1.75 to $2 per day, the cost of this pipe was
$1.35 to $1.50 per ft., after the gang was well organized.

~PIPE SEWER, ST. JOSEPH, MO.~--In constructing extensions to 36-in.,
42-in., 48-in. and 72-in. sewers at St. Joseph, Mo., reinforced concrete
pipe of the form shown by Fig. 269 was employed. The thickness of shell
for the various sizes was 4 ins., 4½ ins., 5 ins., and 7 ins. All sizes
were made in 3-ft. lengths, one end of which is rebated and beveled to
form a spigot and the other end of which is chamfered on the inner edge
to receive the bevel of the spigot. This jointing leaves a
circumferential groove, into which the hooked ends of the longitudinal
reinforcing bars project in such a way that a circular hoop can be
threaded through them to connect successive lengths. The reinforcement
is of the same form for all sizes of pipe, but seven longitudinals were
used in the 72-in. size and five for all smaller sizes; the
circumferential bars were in all cases spaced one 9 ins. from each end.
The pipe, as described, is the standard pipe made by the Reinforced
Concrete Pipe Co., of Jackson, Mich., and is covered by patents. The
practice of this company is to manufacture the pipe itself on the ground
and furnish it to the contractor. It does not contract to build sewers
nor does it dispose of rights to manufacture to contractors.

[Illustration: Fig. 269.--Jackson Concrete Sewer Pipe.]

_Pipe Molding._--The pipe is molded endwise. A bottom plate so shaped as
to form the hub or receiving end of the pipe is set up. On the upper or
inner flange of this cast iron bottom plate is set the core defining the
inside diameter of the pipe; this core is in four segments of sheet
steel. The longitudinal reinforcing bars are next inserted in slots in
the bottom plate and the outside form of sheet steel is then set up on
the lower and outer flange of the bottom plate. Spacing clips on the top
edge of the outer shell hold the tops of the reinforcing bars in
position. The concrete is then shoveled into the annular mold and tamped
until it reaches the level for the first circumferential reinforcing
bar; this is then placed by removing the spacing clips, threading the
hoop over the longitudinal bars and sliding it down to position. Filling
and tamping then proceeds until the second hoop is to be placed; this is
placed exactly like the first, and filling and tamping then proceeds
until the mold is filled. At the St. Joseph work a 1-2-3 mixture, with
crushed limestone aggregate ranging from pea size to 1-in. stone was
used. The molding was done in tents which were heated by coke fires in
salamanders in freezing weather.

_Pipe Laying._--In laying, the pipes are handled and lowered into
position just as are cast iron water pipe. Successive lengths are placed
by inserting the spigot ends into the chamfered hub ends and then
threading the tie hoop through the hooked ends of the projecting
longitudinal reinforcing bars. A strip of galvanized iron is then passed
under the pipe and bent up so as to girdle the circumferential groove
except for a space at the top; the groove is then poured with a wet 1-2
cement mixture, which, when hardened, completes the joint.

~COST OF MOLDING SMALL CEMENT PIPE.~--Mr. Albert E. Wright gives the
following account of the method and cost of molding and laying 6 to
12-in. cement pipe for irregular work at Irrigon, Ore.: The pipe was 6
to 12 ins. inside, made of Portland cement and clean, sharp sand of all
sizes up to very coarse. The mortar was mixed rather dry, but very
thoroughly, using 14.1 cu. ft. of sand to 1 bbl. of cement, or very
closely a 1 to 4 mixture. From six to seven buckets of water were used
to each barrel of cement, except for the 6-in. pipe, for which the
mortar had to be made somewhat stiffer in order to remove the inner
form, which was not made collapsible as in the larger sizes.

The forms were sheet iron cylinders with a longitudinal lap joint that
could be expanded after molding the pipe, and removed without injuring
the soft mortar. The inner form was self-centering, so that there was
little variation in the thickness of the pipe.

Four men were required in making cement pipe by hand; one mixed the
mortar, and wheeled it to the place of work; another threw it into the
form a little at a time with a hand scoop; a third rammed it with a
tamping iron, and a fourth kept the new pipe sprinkled, and applied a
coat of neat cement slurry to the inside when it was sufficiently hard.
In molding, the form of the bell at the bottom was secured by an iron
ring that was first dropped into the form, and the reverse or convex
form at the top was made with a second ring. While still in its form
the pipe was rolled or lifted into its place in the drying yard, and the
form was then carefully removed. A very slight blow in removing the form
would destroy the pipe, and a considerable number, especially of the
larger sizes, collapsed in this way, and had to be remolded. To avoid
handling, the pipe was stacked on end a few feet from the place of
mixing, the form being moved as the yard filled with pipe. One crew of
four men could make about 250 joints or 500 lin. ft. of pipe a day.

As soon as hard enough, the pipe was turned end for end, and was then
kept wet for several weeks before being laid. The coating of neat cement
on the inside was applied with a short whitewash brush, and was a small
item in the cost.

In laying, the trench was carefully finished to grade in order to have
the joints close nicely, and the ends were well wet with a brush. The
mason then spread mortar, mixed 1 to 2, on the end of the pipe, and laid
a bed of mortar at the bottom of the joint. He then jammed the section
into place, and swabbed out the inside of the joint with a stiff brush,
to insure a smooth passage for the water. A band or ring of mortar was
spread round the outside of the joint as an additional reinforcement.
One barrel of cement would joint about 300 sections of pipe. The
materials cost as follows: Portland cement, per bbl., $4.45; labor, per
day, $2; foremen, per day. $2.50 to $3; hauling, per load mile (1 cu.
yd.), 20 cts.; sand, free at pit; water, free.

The pipe was all of a 1-4 sand and cement mortar, and the amount of
cement in one foot of pipe was arrived at by assuming that where the
sand has voids in excess of the cement used, the mortar will occupy 1.1
(see Chapter II) times the space of the dry sand, which yields the
following formula:

Where--

     c = cost per bbl. of cement, or $4.45.
     n = cu. ft. in one bbl. (taken at 3.5 here).
     s = ratio of sand to cement, or 4.
     d = inside diameter in inches.
     t = thickness of pipe in inches.
     l = length of pipe considered, or 1 ft. here.

Then:

                             c × l × [pi] × (dt + t²)
     Cement-cost per foot = --------------------------,
                                n × s × 1.1 × 144

         which gives here =

                4.45 × 1 × 3.142(dt + t²)
             -------------------------------   =  0.00631(dt + t²).
                  3.5 × 4 × 1.1 × 144

This gave the following cement costs per lineal foot:

Diameter, Thickness,    Cost
  ins.       ins.     per foot.
   6         1¼       $0.0571
   8         1¼        0.0730
  10         1-3/8     0.0998
  12         1½        0.1278

The sand cost was based on 15 cts. per cubic yard for loading, and a
haul of two miles of 1 cu. yd. to the load, making five trips per day,
at $4 for man and team. It bears a constant ratio to cement cost, being
11.2 per cent. of the cement cost. The labor cost of making was based on
the foreman's estimate that a foreman, tamper, mortar mixer, and water
man should finish 250 joints a day of 6 or 8-in. pipe. For the 10 and
12-in. pipe, the labor was assumed to be greater in proportion to the
material. The foreman was taken at $3, one man at $2.50 and two at $2.
The cement for painting the inside was neglected. Hauling the pipe to
place was taken at twice the cost of hauling the sand per mile, and a
haul of 4 miles was assumed. The cost of laying was based on a foreman's
estimate of 2 cts. per foot for trench, and that one man to lay, one man
to plaster the joints, one helper and one man to back-fill would lay 600
ft. per day of 6 or 8-in. pipe. The larger sizes were assumed to cost
more in proportion to their material.

These various costs gave the following results for small size pipe:

                               --Cost per foot for--
           6-in.    8-in.   10-in.   12-in.
           pipe.    pipe.    pipe.    pipe.

Cement    $0.057   $0.073   $0.099   $0.128
Sand       0.006    0.008    0.011    0.014
Labor      0.019    0.019    0.026    0.034
Hauling    0.024    0.032    0.044    0.056
Laying     0.024    0.024    0.032    0.042
Trench     0.020    0.020    0.020    0.020
          ------   ------   ------   ------
Totals.   $0.15    $0.176   $0.232   $0.294

The above costs show that the pipe in place costs about twice as much as
pipe in the yard, even with cement at $4.45.

[Illustration: Fig. 270.--Bordenave Pipe for Swansea, England, Water
Works.]

~MOLDED PIPE WATER MAIN, SWANSEA, ENGLAND.~--As a good example of foreign
practice in molded pipe conduit work a water main constructed at
Swansea, England, has been selected. This pipe line had to operate under
a head of 185 ft.; it was constructed under the patents of the French
engineer, Mr. R. Bordenave, who has built many miles of the same type of
conduit on the Continent.

Fig. 270 shows the construction of the pipe, the drawing being a part
longitudinal section through the shell at the joint. The pipe consists
of an inner and an outer reinforcement separated by a sheet steel tube
and all embedded in a 1-2 mortar. Both inner and outer reinforcements
consists of longitudinal bins of cruciform (+) section wound by a spiral
bar of the same section wired to them at every intersection. Only the
outer reinforcement and the steel tube are considered in calculating the
strength of the pipe, the inner reinforcement being considered as simply
supporting the mortar.

_Fabrication of Reinforcement_.--The steel tube is made of 1 mm. (0.04
in.) thick sheets of steel bent to a cylinder and jointed longitudinally
by welded butt joints, welded by a blow pipe using acetylene and oxygen.
Tests of this welded joint by R. H. Wyrill, Waterworks Engineer,
Swansea, showed it to be quite as strong as the unwelded steel cut from
the shell. The circumferential joints of the tube were made by turning
up the edges of the sheets and welding them; this gives a flexible
watertight joint. The tube was made in lengths of 9 ft. 9½ ins. and its
ends were turned up all around; just back from the turned-up ends a
vertical sheet steel collar was welded to the tube to form a strip end
for the external coating. These details are shown in Fig. 270. When the
tube for a length of pipe is completed the inside shell reinforcement
previously made is slipped into it and the outside shell reinforcement
is formed on it as a mandril, as shown by Fig. 271.

[Illustration: Fig. 271.--Applying External Reinforcement to Bordenave
Pipe.]

[Illustration: Fig. 272.--Casting Bordenave Pipe at Swansea, England.]

_Molding._--When the three positions of the steel skeleton were
completed, as shown by Fig. 271, they were set on curved wooden curbs
made to the exact shape necessary to center them and preserve the
correct thickness of cement coating. A collapsible core was lowered into
position in the inside, and a two-part sheet steel mold was erected
outside; the space between core and mold was then poured with a thin
mortar of one part Portland cement to two parts clean river sand. During
the process of pouring, the outer steel mold is sharply struck with
wooden mallets to facilitate the escape of air bubbles. The mortar was
mixed on an elevated traveling platform which is shown in Fig. 272,
which also shows a completed pipe, a core being withdrawn, a filled mold
and a section of reinforcement set up. The difficult feature of the
molding process was found to be the determination of the time for
withdrawing the core and removing the exterior mold; the time of setting
of the mortar was different in warm and in cool weather and varied with
the wetness of the mixture, the brand of cement, etc. By using a single
brand of cement that ran very uniform in quality and time of setting it
was possible, however, for the workmen, after a little practice, to gage
very accurately the correct time for removing the molds. With four sets
of molds a gang of eight men would curb 16 pipes per day under favorable
conditions, but when the temperature was low it was not possible to make
more than six or eight pipes. The pipes were allowed to stand four or
five days after the removal of the mold; they could then be removed by a
crane and laid in stock until used. It was found advisable to let the
pipes age about four weeks before laying; by this time, it is stated,
they would stand as much rough usage as cast iron pipe.

_Laying_.--The pipes were laid much in the same way as cast-iron pipes
are laid; they were each 9 ft. 9½ ins. long and weighed each about 12
cwt., and were handled by ordinary tackle. In laying, the pipes were
adjusted end to end and the joint enclosed by a temporary steel ring
inside which the bitumen seal, Fig. 270, was run and allowed to set when
the steel ring was removed. The joint was then encircled by a collar of
similar construction to the pipe itself and the space between collar and
pipe was poured with cement mortar. About ten lengths of pipe were laid
per day by one gang of men, one jointer and his assistant making all the
cement and bitumen joints as fast as the gang could lay the pipes.

CHAPTER XXII.

METHODS AND COST OF CONSTRUCTING RESERVOIRS AND TANKS.

Floor, wall and roof work of structurally very simple character sum up
the task of the constructor in reservoir and tank construction. The only
intricacy involved lies in form design and construction for cylindrical
tank work. Several examples of such work are given in this chapter, and
in each the construction and handling of the forms are described. To
repeat details here would serve no purpose, but one general instruction
may be enunciated. No care is too great which ensures rigidity and
invariable form, both in the construction of the individual form units
and in the assembling of these units into the complete form. This is
particularly true of cylindrical tank work and especially high
cylindrical tank work where the forms are moved upward as the work
progresses. To the designer it may be suggested that any beauty he may
gain by giving the walls of his standpipe a batter is paid in the extra
cost of form work.

Concreting in tank work is expensive. The reasons are two. The work has
to be done in a narrow space, commonly pretty well filled with a network
of steel rods or bars. Again the work has to be done uniformly well, not
only for appearance sake but because of the necessity of watertightness.
Making a reservoir watertight is, when all things are said, the one
difficult constructional task in tank work and the contractor who
accepts the task lightly courts trouble. Exceptionally good concreting
is essential in tank work if watertightness is to be secured.

The illustration of these general admonitions will be found in the
specific examples of tank and reservoir work which follow.

~SMALL COVERED RESERVOIR.~--The reservoir was designed to hold 75,000
gallons of water for fire purposes. As it is of a type which is certain
to be frequently constructed and as we have personal knowledge of the
costs recorded we describe the work in some detail. The specifications
stipulated that the reservoir must be absolutely watertight and that the
roof should be capable of sustaining a load of 300 tons evenly
distributed and a live load of 5,000 lbs. on two wheels. Figure 273
shows a plan, Fig. 274 a longitudinal section, Fig. 275 a transverse
section and Fig. 276 the column construction.

[Illustration: Fig. 273.--Sectional Plan of 75,000-Gallon Reservoir.]

_Quantities of Work._--The excavation called for the removal of 579 cu.
yds. of earth. There were 83 cu. yds. of concrete in the structure,
although the plans called for less, the additional amount being used in
increasing the two 4-in. walls to 6-in. and increasing the bottom and
top, on one end, so as to give perfect drainage. The yardage was
divided as follows:

                                                  Cu. yds.
Footings                                               3.5
Columns                                                6.8
Sides                                                 22.6
Girders                                               11.0
Top                                                   20.0
Floor                                                 19.1
                                                      ----
      Total                                           83.0

[Illustration: Fig. 274.--Longitudinal Section of 75,000-Gallon
Reservoir.]

A manhole had to be put in the top and a sump in the bottom. Several
pipes also had to be placed in the concrete. None of these details is
shown on the plan. The structure had to be waterproofed.

_Excavation._--The excavation was made with pick and shovel and the
material hauled away in carts, the distance to the dump being 700 ft.
The top was shoveled directly into the carts, while the rest was handled
two and three times. When the reservoir was finished dirt had to be
filled in around the sides and puddled.

_Wages._--The following rates of wages were paid on the job:

Foreman                                           $3.00
Carpenter                                          3.50
Carts and driver                                   3.50
Laborers                                           1.50

The carpenters worked 8 hours a day and were paid time and a half for
overtime. The rest worked ten hours per day and were paid regular rates
for overtime.

[Illustration: Fig. 275.--Transverse Section of 75,000-Gallon
Reservoir.]

_Forms._--Carpenters framed and erected the forms, but laborers did all
the carrying for them. Laborers also tore down the forms. For the
girders and columns 2-in. boards were used, but for the sides 1-in.
boards with 3×4-in. scantlings were used. The props for supporting the
girder and top forms were 3×4. Except for columns and girders and some
props, all the forming was used three times. The lumber cost:

400 ft. B. M. at $24      $ 9.60
8,000 ft. B. M. at $18    144.00
                         -------
  Total                  $153.60

[Illustration: Fig. 276.--Column Construction for 75,000-Gallon
Reservoir.]

This makes an average price per 1,000 ft. of about $18.30, which price
we shall use in giving costs.

The cost of framing and erecting the forms was $167.27 for the sides,
columns, girders and top. In the forms for the sides, forming was only
used on one side of the concrete for two sides, the earth bank being
used for the other side of the forms, but on the other two sides the
banks had caved in, and forming was used on both sides of the wall. The
cost per cubic yard for forms was:

Lumber                     $2.54
Framing and erecting        2.77
Tearing down                 .54
                           -----
  Total                    $5.85

This cost is for the yardage of 60.4 on which forms were actually used.
For the total yardage in the tank the cost was:

Lumber                     $1.85
Framing and erecting        2.01
Tearing down                 .40
                           -----
  Total                    $4.26

The common labor cost of assisting to erect the forms was 15 per cent of
the total. Nothing is allowed for foreman, for the contractor acted as
his own foreman.

The cost of forms per 1,000 ft. for the amount of lumber purchased was:

Lumber                    $18.30
Framing and erecting       19.90
Tearing down                4.00
Total                     $42.20

As the lumber was used three times, the cost per thousand for all work
and materials on the forms would be just one-third of this--namely:
$14.06.

Since the framing, erecting and tearing down cost $19.90 plus $4, or
$23.90 per M. ft. B. M. purchased, and since the lumber was used three
times, the labor cost nearly $8 per M. each time that the lumber was
used. It will be noted that 8,400 ft. B. M. were required for the 83 cu.
yds. of concrete, or a trifle more than 100 ft. B. M. per cubic yard.

It will be of interest to see the labor costs of forms for the various
parts of the structure.

For the sides the cost of framing and erecting the forms was $4.19 per
cubic yard. Of this cost 4 per cent. was for common labor and the rest
for carpenters. The tearing down cost 47 cts. per cubic yard. For the
columns the erecting was $2.35, of which 1 per cent. was for common
labor. The tearing down cost 47 cts. For the girders and top the
erecting cost $1.83, of which 35 per cent. was common labor. The tearing
down cost 61 cts. per cubic yard. A summary would show:

                                          Girders
                      Sides     Columns     and
                       per        per     top per
                     cu. yd.    cu. yd.   cu. yd.
Framing and erecting   $4.19      $2.35    $1.83
Tearing down             .47        .47      .61
                       -----      -----    -----
  Total                $4.66      $2.82    $2.44

The greater cost of the columns forms over the girders and top was due
to the fact that the columns forms were handled almost exclusively by
the carpenters, and also in setting them great care and much time had to
be used to get them plumb and in line. The cost of the forms for the
sides was about twice as great as that for the top and girders. The
reasons for this are evident. The walls had forms on both sides, while
the top needed forming only underneath it, the area covered on the forms
being about 2,200 sq. ft. as compared to 1,000 sq. ft. The side forms
had to be set plumb and kept so. The framing was done ahead, but nearly
half of the lumber in the sides was erected as the concrete was being
put in place. The forms for the top were all put in place before any
concreting was done on the top, and the carpenters discharged. A much
larger per cent. of common labor could be used in placing forms for top
and girders than on the sides. The props were nearly all put in place
by laborers. The extra cost of tearing down the forms for the top was
due to the fact that the lumber all had to be handled one piece at a
time through a small manhole in the top, and carried about 150 ft. to be
piled.

To all the costs for forming should be added 6 cts. per cubic yard for
nails, wire and lines used on the forms.

_Concrete._--The mixtures varied for the different members. The cost of
materials was as follows:

Cement, 110 bbls. @ $1.12           $123.20
¾-in. stone, 80 cu. yds., @ $1.86    148.80
Gravel, 3 cu. yds., @ $1.33            4.00
Sand, 42 cu. yds., @ $1.20            50.40

The sides were first put in place, then the center columns were built,
following which the bottom was placed. Then the forms were erected for
the top and the girders, and these cast. In building the sides, one side
and half of the two ends were built at one time, and then forms erected
for the other half of the sides. For the sides the mixing was done in
the bottom of the reservoir. For the rest of the structure it was done
on the ground, the mixing board being along side of the reservoir. The
labor cost of the concrete work for the various members and the average
per cubic yard was as follows:

                                   Columns
                                     and
                           Sides.  Footings.  Bottom.  Girders.  Top.  Average.
Cubic yards                 22.6     10.3      19.1      11      20.0    83.
Preparing and cleaning up  $0.166   $0.060             $0.095           $0.065
Handling materials          1.022     .306    $0.070     .198   $0.187    .404
Cleaning out forms           .040                        .070     .053    .032
Mixing and placing          1.542     .728      .353     .792    1.080    .952
Ramming                     1.090     .540      .455     .450     .597    .673
Handling steel               .890     .020               .395     .083    .324
                           ------   ------    ------   ------   ------  ------
Total                      $4.750   $1.654    $0.878   $2.000   $2.000  $2.450

The total cost of labor was $203.35. The mixing was done entirely by
hand. Some plastering was done to the walls after the forms were taken
off, and the sides and bottom were washed with a brush with cement and
water. The plastering cost $6.60, including a barrel of cement and the
washing or grouting, two coats, cost $9.10, including a barrel of
cement. This added a cost of 19 cts. per cubic yard to the concrete
work, making the total cost per cubic yard $2.65.

It was a mistake to have mixed the concrete for the sides in the bottom
of the reservoir, as it made two handlings of the materials and
compelled all the concrete to be raised by hand to place it in the
forms. This accounts for the high cost of these two items.

The handling of the steel was high for the side walls, as it was all
separated and put into piles for the different panels and members in
getting it out of the pile for the sides. The rammers not only rammed
the concrete but they also bent down the prongs of the steel to get them
in place in the narrow forms, and afterwards had to pull out these
prongs. This had to be done for every piece of steel used, and readily
doubled the cost of ramming. The high cost of ramming the top was caused
by the fact that the 6 ins. of concrete had to be placed in three layers
and each rammed. The steel handling was high on account of the prongs
entangling the pieces with others, making them hard to handle. The cost
of handling steel per ton was about $4, or 0.2 ct. per pound. The steel
was all handled by common laborers.

The stock piles of material had to be made along a street and alley and
thus caused the material to be handled in wheelbarrow several hundred
feet.

The preparing to mix concrete, the cleaning up afterwards and the
cleaning out of forms are items that are seldom kept separate from the
others.

The cost of mixing and placing is high, owing to the fact that working
space was small and the mixers had to wait until the concrete was taken
off the board and placed in the forms before starting another batch.
This also meant an increased cost in the ramming, as the rammers were
idle some time waiting for a new batch to be mixed.

The total cost of concrete, including labor and materials, per cubic
yard on a basis of the 83 cu. yds. was:

                               Per cu. yd.

Cement, 1-1/3 bbls., @ $1.12     $ 1.49
Stone, 1 cu. yd.                   1.86
Sand ½ cu. yd.                      .60
Steel                              4.76
Forms, 100 ft. B. M., @ $18.30     1.85
Labor on forms                     2.41
Labor on concrete and steel        2.65
  Total                          $15.62

The cost of a foreman is not included in this, as the contractor looked
after the men himself.

_Waterproofing._--The waterproofing of the structure proved a serious
problem. It was thought at first that the concrete itself would be
nearly water tight, but the tank leaked like a sieve. After considering
several methods, an agent of a European waterproofing mixture prevailed
upon those interested to try his compound. To apply it, the walls had to
be dry, so a large coal burning stove was put in the reservoir and a
fire kept up day and night. While this drying process was going on
several light falls of snow occurred, and this had to be cleared away to
make the walls and roof dry. Two coats of the mixture were applied
according to the agent's instructions, and the reservoir was tested. The
water fell nearly half a foot in an hour's time.

Then a waterproofing contractor agreed to make the reservoir water tight
with paper and tar, by applying it on the inside. Three thicknesses of
paper were laid on the bottom and run well up on the sides, each layer
of paper being well covered with a preparation of tar. Upon testing it,
it was found that the leaking had been reduced about 50 per cent. A
preparation of asphalt was then placed over this, but upon a third test
the tank still leaked. As the sub-contractor had verbally agreed to make
it water tight for $125, only this amount was paid him. After this last
test he refused to do any more work.

After these attempts the sides of the reservoir were exposed on the
outside by excavating around it, and a one-brick-wall built up a few
inches from the concrete. This space was filled in with rich cement
mortar and the ground once more filled in around the structure. This
work and the materials used in it cost $1,240. Upon a fourth test the
reservoir was found to be water tight. Thus more than a third of the
cost of the entire work was in waterproofing the structure, and this
made the contract a money losing one, as this heavy cost was not
anticipated.

Several items of miscellaneous work are listed in the total cost of the
reservoir, such as filling in and puddling around reservoir and
replacing cobble paving. The top of the structure was used as a bin for
the storage of coal. For this purpose eight I-beams were embedded in
concrete around the top to be used as posts for the sides of the bin.
The cost of placing these is given.

_Total Cost._--The cost of the structure without any profits was:

579 cu. yds. excavation @ $.896                 $ 529.65
Steel                                             395.00
Crushed stone                                     148.80
Gravel                                              4.00
Sand                                               50.40
Cement                                            123.20
Lumber                                            153.60
Labor on forms                                    200.09
Labor on concrete                                 203.35
Plastering                                          6.60
Sides and bottom                                    9.10
Nails, wire, etc.                                   4.98
Bailing water                                      21.19
Building temporary fence                            1.65
Extra excavation for forms, footings, etc.         13.90
Setting I-beams in concrete                        17.65
Filling in and pudding around reservoir            34.47
Replacing cobble paving                             4.30
Hauling tools                                       3.60
Heating reservoir and handling snow                14.50
Waterproof mixture                                 29.00
Labor applying it                                   9.74
Applying paper and tar, labor and materials       125.00
Labor and materials of final waterproofing      1,240.00
Tools                                              48.75
General expense                                   210.00
                                               ---------
  Total                                        $3,602.52

~COVERED RESERVOIR, AT FORT MEADE, SOUTH DAKOTA.~--The following account
of the method and cost of constructing a 500,000-gallon reservoir is
compiled from information furnished by Mr. Samuel H. Lea, M. Am. Soc. C.
E. As shown by Fig. 277, the reservoir consists of two equal
compartments, each 50×60 ft. inside dimensions, with rounded corners.
Both compartments are covered with a 3-in. slab roof carried on the
walls and interior columns.

The concrete was a 1-2-4 Portland cement, sand and broken stone mixture,
mixed by hand on a movable platform. A concrete gang consisted of four
men who were each paid $2.75 per day. They wheeled the materials from
the supply piles to the mixing platform, mixed the concrete and
deposited it in place. During the construction of the footings and floor
two concrete gangs were employed, but after the walls were started, one
gang only was required for concrete work; the other gang was then put to
work assisting the carpenters.

[Illustration: Fig. 277.--Reservoir at Ft. Meade, S. D.]

The sand and stone were wheeled to the platform in iron wheelbarrows of
2½ cu. ft. capacity. The cement was in ¼-bbl. sacks and each sack was
taken as 1 cu. ft. Each batch of concrete contained the following
quantity of material:

2½ sacks of cement          2½ cu. ft.
2 wheelbarrows of sand        5 cu. ft.
4 wheelbarrows of stone     10 cu. ft.

The quantities of sand and stone were adjusted so as to form the proper
proportion for making a dense concrete. From time to time, as the work
progressed, experiments were made to determine the percentage of voids
both in the sand and the crushed stone; and, in this way, uniformity in
composition was secured. The mixture was made quite wet in order to
insure a free flow around the reinforcing bars. On account of the narrow
space inside the forms and the number of reinforcing bars therein care
was taken to cause the mixture to be well distributed throughout. The
wet concrete was well spaded in an effort to secure a smooth surface
next to the forms. This was generally accomplished, but some rough
places which showed after the removal of the forms required patching up.

In constructing the footings some concrete was first deposited in place
and the metal reinforcement was embedded therein. For the floor
reinforcement the lower bars were carefully embedded in the concrete
after it had been brought to a suitable height; the upper bars were then
placed crosswise upon the lower ones and kept in position until the
remainder of the concrete had been deposited around and over them. In
the wall footings a depression or groove, several inches deep, was left
under the wall space for its entire length. This ensured a good bond
between the wall proper and the footing.

The concrete floor in each compartment was built in one continuous
operation, the object being to secure a practically monolithic
construction. The lower reinforcing bars in the floor were embedded at
the proper depth in the fresh concrete and the upper bars were then
placed crosswise upon the lower ones; the two sets were then wired
together at a sufficient number of places to prevent displacement while
the remaining concrete was being deposited around and over them.

The reinforcement for the walls and columns was erected in place upon
the footings and formed a steel skeleton around which the forms were
erected. The upright bars in the walls were held together and at the
proper distance apart by means of templates consisting of wooden strips
in which holes were bored at suitable intervals to receive the bars. The
templates were maintained in a horizontal position and were moved upward
as the concrete advanced in height. The horizontal reinforcing bars
were wired in place to the upright bars; they were placed in position
ahead of the concreting as the wall was built up.

The corrugated bars in beam and girders were placed in position in the
forms and held up by blocks which were removed as the forms were filled
with concrete. The expanded metal reinforcement for the roof slab was
placed so as to be close to the lower face of the slab, but far enough
up to be entirely enveloped in the concrete.

The wall forms were made of 2-in. planks, surfaced on the inner side and
placed horizontally on edge. They were held in place by 4×4-in. posts
spaced at intervals of about 4 ft., in pairs on opposite sides of the
wall. The posts were firmly braced on the outside; they were prevented
from spreading by connecting wires passing through the wall space
between the edges of adjacent planks. At the rounded corners of the
reservoir the pairs of posts were spaced about two feet apart and the
curve was made by springing thin boards into place to fit the curve and
nailing them to the posts. The posts were high enough to reach to the
top of the wall; the siding was built up one plank at a time as the
concrete work progressed. Column forms were made of 2-in. planks on end,
extending from floor to girder. Three sides were enclosed and one side
was left open to receive the concrete; this side was closed up as the
concreting advanced in height.

The beam and girder forms were open troughs of the required dimensions,
made of 2-in. plank, surfaced on inner faces. The form of centering for
the roof slab consisted of a smooth, tight floor of 2-in. planks,
extending between the open tops of column, beam and girder forms over
the entire area between enclosing walls of the reservoir. The centering
and the beam and girder forms were supported by 6×6-in. posts resting
upon the floor below.

The regular carpenter gang consisted of a foreman carpenter at $5 per
day, a carpenter at $3.50 per day, and two helpers at $2.75 per day.
During the early concrete work of making footings and floor, where forms
were not required, the carpenter force was employed in erecting the
steel skeleton for the walls. The upright bars were placed in position
and secured by temporary wooden stays extending from the upper portion
of bars to the surface of ground outside of excavation. These stays were
removed after concreting had advanced to a sufficient height to hold the
steel securely in place.

The wages paid the concrete gang which mixed and placed all the concrete
and the carpenter gang which constructed and erected the forms and
placed the reinforcement have been given above. The costs of
construction materials on the site were:

Cement, per barrel            $2.57
Sand, per cu. yd.              1.80
Stone, per cu. yd.             3.15
Lumber, per M. ft. B. M.      27.50

The quantities in the completed concrete structure were as follows:

Total volume of concrete in reservoir                   704.71 cu. yds.
Total volume of steel reinforcement in reservoir.         5.57 cu. yds.
Total volume of material in completed structure.        710.28 cu. yds.

The steel was, therefore, about 0.8%.

Volume of material in structure exclusive of roof slab     648.35 cu. yds.
Volume of material in roof slab                             61.93 cu. yds.
  Total                                                    710.28 cu. yds.

The cost of the structure per cubic yard of concrete, exclusive of the
roof slab, was as follows:

  Item.                          Per cu. yd.
Crushed stone                        $ 3.168
Sand                                    .842
Cement                                 3.859
Reinforcement                          4.959
Labor, mixing and placing concrete     1.721
Forms, labor and material              2.960
                                     -------
  Total                              $17.509

In constructing the roof slab the expanded metal reinforcement raised
the unit cost. For this portion of the work the costs were:

  Item.                        Per cu. yd.
Expanded metal reinforcement    $ 5.241
Other items, same as above       12.550
                                -------
Total                           $17.791

The floor and the inside surface of reservoir walls were covered with a
coating of cement mortar composed of one part Portland cement and one
part sand. The wall plastering was from ½ in. to ¾ in. thick; it was
applied in two coats. The floor finish was laid in alternate strips
about 1 in. thick and 3 ft. wide. After the strips first laid had
hardened the remaining strips were laid, the edges being grouted to
ensure tight joints.

The outside of walls and roof was covered with a coating of tar which
was heated in an open kettle to a temperature of about 360º F. and then
applied with a brush or mop.

The cost of wall and floor plastering was 44.4 cts. per square yard,
itemized as follows:

Cement      26.4 cts.
Sand         2.6 cts.
Labor       15.4 cts.
            -----
  Total     44.4 cts.

The cost of outside waterproofing was 4 cts. per square yard,
distributed as follows:

Material    2.5 cts.
Labor       1.5 cts
            ---
  Total     4.0 cts.

While some of the cost items are apparently high when compared with the
cost of similar work in other places, it should be remembered that the
isolated locality and the local conditions were unfavorable for low
cost. Owing to the isolated location of the reservoir with respect to
large markets and also to local sources of supply the cost of material
and labor was quite high. All construction material, except some of the
stone for crushing, had to be hauled over a mountain road from 3 to 4
miles to the top of the hill selected for the reservoir site. Labor was
scarce and commanded a wage of $2.50 per day for ordinary work; the
laborers mixing concrete were paid $2.75 per day. Another source of much
relative expense was the high cost of lumber and carpenter work on the
forms. On account of the thinness of the walls and roof, the cost of
lumber and labor required per cubic yard of concrete was considerable. A
part of the lumber was used the second time in forms, but it was found
impracticable to delay the work by waiting for the concrete to harden
before beginning the new portions of the walls. This lumber was sold
after the completion of the work, but the salvage was inconsiderable,
amounting to less than 10 per cent. of the original cost.

[Illustration: Fig. 278.--Reservoir Forms. Bloomington, Ill.]

~CIRCULAR RESERVOIR, BLOOMINGTON, ILL.~--An open circular reinforced
concrete reservoir was constructed in 1905-6 for the water-works of
Bloomington, Ill. This reservoir is 300 ft. in diameter, 15 ft. deep at
the circular wall and 25 ft. deep at the center of the spherical bottom.
The wall construction is shown clearly by Fig. 278, and the floor is a
6-in. spherical slab reinforced by a mat of ¼-in. round rods placed 6
ins. on centers in both directions. The wall reinforcement is corrugated
bars. Neither the wall nor the bottom has expansion joints.

_Concrete._--The specifications required not less than 1 part Portland
cement to 2 parts sand and 5 parts clean gravel, and stipulated that
there should always be more than enough cement to fill the voids in the
sand more than enough mortar to fill the voids in the gravel. The
proportions were varied, depending on the character of the available
material and on the location the concrete was to occupy. The
stipulations regarding the minimum quantities of cement and mortar were,
however, always at least fulfilled. A 1-3-4 mixture of cement, broken
stone and gravel was largely used in the footing and wall. The gravel
was fine and contained 40 to 50% of sand; the broken stone was the
crusher-run, with the dust screened out, and the maximum-sized pieces
not larger than those which would pass a 2-in. screen. The mortar facing
on the front face of the wall was made of 1 part cement to 4 parts fine
gravel, containing sand. Some gravel from the excavation was used in the
concrete for the floor. This gravel was so fine that about one-quarter
of it was replaced with broken stone and the mixture made 1-6. Both
faces of the wall were painted with a 1-1 mixture of cement and sand;
the inner face was also painted with a 1-1 mixture of waterproof Star
Stettin Portland cement and sand. The sidewalk finish on the surface of
the floor consisted of 1-1½ mortar.

_Mixing and Handling._--The concrete mixing plant was set up outside of
the site of the reservoir along a side track from the railroad. The
concrete materials were delivered on the side track, except some gravel
from the excavation that was used. A Foote portable continuous mixer was
used in making the concrete for the wall footings and the wall. It was
mounted so it could discharge into dump cars on a service track laid on
the ground. A double hopper was built up over the mixer, one compartment
for sand and one for broken stone. The end of a service track leading
from the side track was laid on an inclined trestle up to a floor level
with the top of this double hopper, the materials being hauled in dump
cars from the side track to the hopper. The service track from the mixer
extended entirely around the wall, and 10 ft. from it, on the
embankment made there with earth from the trench for the wall-footing.
The concrete was dumped from the cars on the service track to portable
shoveling platforms near the point where work on the wall was in
progress. It was shoveled by hand from these platforms to place in the
forms as the presence of the reinforcement bars in the narrow forms
precluded dumping in large quantities. The footing was built without
forms up to the right-angle joint between it and the base of the wall at
the front, and to the top of the 45° slope on its rear face. A layer of
concrete 2.5 in. thick was first placed in the completed trench. The
reinforcement bars near the bottom were then laid on this green
concrete, the vertical bars near the front face of the wall usually
being erected at the same time. The concrete in the toe of the footing
and in the footing proper up to the top layer of reinforcement was then
laid. After the top layer of reinforcing bars had been laid, the footing
was completed, except for a top layer about 2 ins. thick at the base of
the front face of the wall and 15 ins. thick at the toe of the footing.
This left a strip of surface about 6 ft. wide, sloping at about 1 in 6
from the wall toward the center of the reservoir, and furnished the
widest and best possible bond for the joint which had to be made when
floor was laid.

_Location and Construction of Forms and Wall._--The design of the wall
of the reservoir, although simple in itself, required unusually accurate
work in the location and construction of the forms for it. The location
was made with very little difficulty, however, by an arrangement devised
by the contractor which enabled the foreman, without the aid of an
engineer, to set the necessary grade and reference stakes. A post, 10
ins. in diameter, was set very accurately and firmly in the ground at
the center of the reservoir. This post was sawed off squarely on top so
that the line of collimation of an engineer's transit set on it without
a tripod would be exactly at the grade of the top of the completed wall
of the reservoir. A 200-ft. steel tape was used to measure the radial
distance from a nail in the center post to the posts of the back, or
outside forms for the wall. In the form for the back face of the wall
2×6-in. posts, spaced one one-hundredth of the circumference apart, were
set considerably in advance of any concrete work, and were made the
basis of all measurement in building the forms. The forms as originally
planned are shown in Fig. 278.

The wall, when started, was built continuously in both directions from
the starting point. The back forms consisted of planks for lagging
nailed to vertical posts, which were accurately set and firmly braced.
The front forms were made in lengths equal to one one-hundredth of the
circumference of the reservoir, and when set up were fastened to the
back forms. Twenty-one of these front form sections were built and all
set up at once. Concrete was filled in between the front and back forms,
starting at the central form, and was rammed in inclined layers,
sloping, at about 1 on 6, both ways towards the end forms. This method
was adopted in order that the concrete might be laid continuously and
without joints. The lagging of 1-in. boards on the vertical portion of
the sections was nailed to the vertical posts, and was carried up just
ahead of the concrete filling.

When the concrete had reached the top of the central one of the 21
sections of the forms, and the concrete in that section had set
sufficiently, the section was broken up and removed, leaving two sets of
10 sections of the forms. Subsequently the other forms could be removed
in turn as desired without being broken up. As the filling-in proceeded
between the two sets of 10 forms each, the form in each set nearest the
starting point was removed, carried forward, and put in place at the
other end of its set of forms. Twelve men were required to take down and
transport one of the front form sections.

In setting up a front form, its inner toe was firmly supported by a
stake driven into the ground and by the horizontal board, nailed
transversely under the bottom 4×4-in. horizontal stringers, which rested
on the ground. The upper part of the form was then securely fastened to
the 2×6-in. posts of the back forms by temporary wooden connecting
strips, which were removed as the concrete filling was carried up. The
sections of the front forms were also securely tied to each other.

A facing of gravel concrete, rich in cement and with no pebbles larger
than ½-in. was placed on the front face of the wall, extending from the
back edges of the vertical reinforcing bars to the surface. A sheet-iron
plate, about 8 ins. wide by 5 ft. long, was placed vertically just back
of those bars. The concrete was shoveled in loose to the top of these
iron plates, and then the mortar was poured in between the latter and
the front face forms from buckets. The iron plates were next drawn by
handles attached to them, and the mortar and concrete tamped together
before either had set. In making joints, the old concrete surfaces were
always brushed and wet down, and, if necessary slushed with a grout of
neat cement before new concrete was laid on them.

_Construction of Floor._--The excavation over the site of the reservoir
floor was brought accurately to grade 6 ins. below the surface of the
finished concrete by hand after the scoop-bucket excavator had passed
over. In making the excavation the levels were given on radial lines
drawn from the ends of the 10-ft. sections of the wall to the center. A
rod, on which the elevations of the sub-grade at every 10 ft. from the
wall to the center of the reservoir were clearly marked, was used in
connection with a transit on the center post in locating the elevations
of different points in the reservoir floor. By using this method the
elevations required were easily found by the foreman in charge without
the assistance of an engineer. When the work approached the center, the
post was removed and the transit was placed on a portable pedestal which
was set on points of known elevation on the finished concrete.

The slanting surface left on the top of the footing inside the wall
formed, together with the projecting reinforcement rods, an excellent
bond between the concrete of the wall and that of the floor, when the
latter was laid. A circular strip of the floor, 16 ft. wide, was put
down next to the wall first, and the remainder of the floor was laid
according to the progress of the excavation. The lower 3½ ins, of the
concrete was usually first spread out over an area 12 or 16 ft. square,
then the reinforcement was placed, and after that the top 2 ins. of
concrete and a ½-in. sidewalk finish surface were laid.

[Illustration: Fig. 279.--Standpipe at Haverhill, Mass.]

The ¼-in. rods in the bottom are 6-ins. on centers in both directions.
They were in 12 and 16-ft. lengths and were partly woven together in
mats before being placed. The rods in one direction were all laid out
and woven with four or five of those in the other direction, the joints
being tied with small wire. The remaining cross rods were laid after the
mat had been placed. The mats were overlapped 1 ft. This method of
placing proved economical and efficient, giving at the same time
something permanent on which to lay the remaining concrete.

~STANDPIPE AT ATTLEBOROUGH, MASS.~--The stand pipe was 50 ft. in diameter
and 106 ft. high inside, with walls 18 ins. thick at the bottom and 8
ins. thick at the top. Figure 279 shows the general arrangement of the
reinforcement. Round bars of 0.4 carbon steel were used; the bars came
in 56½-ft. lengths, so that three lengths with laps of 30 ins., made a
complete ring around the tank. The concrete was a 1-2-4 mixture of ¼ to
1½-in. broken stone with screenings used as portion of sand.

The floor was built first, and on it was erected a tower to a height of
60 ft. and a derrick with a 40-ft. boom was set on its top. The derrick
was operated by an engine on the ground which also had a revolving gear
attached. When the work had reached the top of this tower, the tower was
raised to 110 ft. in height and the derrick shifted to the new
elevation. The forms were convex and concave sections 7½ ft. high and
about 11 ft. long. The concave or outside forms were made in 16 panels,
with horizontal ribs and vertical lagging; two complete rings of panels
were used. The panels were joined into a ring by clamps across the
joints, this clamping action and the friction of the concrete holding
them in place. The inside forms consisted of vertical ribs carrying
horizontal lagging put in place a piece at a time as the filling
proceeded. They were supported by staging from the derrick tower. The
remaining plant comprised a Sturtevant roll jaw crusher feeding to
screens which discharged fines below ¼-in. into one bin, medium stone
into another bin and coarse stone into a third bin. These bins fed to
the measuring hopper of a Smith mixer, which discharged into the derrick
bucket.

The mode of procedure was as follows: The reinforcing rings were erected
to a height of 7½ ft. The bars were bent by being pulled through a tire
binder and around a curved templet by a steam engine. The bending gave
some trouble, due, it was thought, to the stiffness of the high carbon
steel. Vertical channels 4 ins. deep were set with webs in radial planes
or across wall at four points in the circumference. The flanges of these
channels were punched exactly to the vertical spacing of the reinforcing
rings. Through the punched holes were passed short bars on the opposite
ends of which the reinforcing rings were supported and wired. The three
sections of rod of which each ring was composed, were lapped 30 ins. and
connected by Crosby clips. Considerable difficulty was had in holding
the reinforcing rings in line by the method employed; it is stated by
the engineer that a greater number than four channels would have been
much better.

The reinforcement being in place, an inside and an outside ring of forms
was erected. Concreting was then carried on simultaneously from four
points on the circumference and a ring 7½ ft. high was concreted in one
operation. Several facts were brought out in the concreting; careful and
conscientious spading was necessary to get a smooth dense surface; a too
wet mixture allowed the stone to settle and segregate; care was
necessary in this thin wall containing two rings of bars to keep the
stone from wedging among and around the bars and thus causing voids. The
engineer states that for this reason the substitution of mortar for
concrete in tank walls is worth considering. He estimates that in this
work, costing $35,000, that the use of a 1-2 mortar in place of the
1-2-4 concrete would have increased the cost by $2,300, a 1-2½ mortar by
$1,500, and a 1-3 mortar by $750. It was also found that there was
danger from a movement of the reinforcement in the concrete and of the
forms in placing the concrete.

When a ring of wall 7½ ft. high had been concreted, the reinforcement
was placed as before described for another ring. The two rings of forms
below those just filled were removed from the wall, hoisted up and set
in place on top. These two operations of placing reinforcement and
setting forms for another ring of wall took three days, so that the top
surface of the wall to which new concrete was to be added, had become
hard. This hard surface was very thoroughly washed and then coated with
neat cement immediately before depositing the fresh concrete. Water was
admitted to the tank as the work progressed, being kept about 20 ft.
below the work in progress. Numerous small leaks developed, but only two
were large enough for the water to squirt beyond the face of the wall.
These leaks appeared to grow smaller as time went on. To do away with
them entirely, the inside wall was plastered. The first coat of plaster
was not successful in stopping the leaks, so the standpipe was emptied
and replastered, five coats being used in the lower 20 ft. This did not
serve so resort was had to a Sylvester wash. A boiling hot solution of
12 ozs. to the gallon of water of pure olive oil castile soap was
applied to the dry wall. In 24 hours this was followed with a 2 ozs. to
the gallon solution of alum applied at normal temperature. Four coats of
each solution were applied, which reduced the leakage to a small amount.
To do away with all leakage another four-coat application of Sylvester
wash was used.

Details of the cost of the work are not available. There were 770 cu.
yds. of concrete in the walls and 185 tons of steel bars. Altogether
3,000 Crosby clips, costing $1,100 were used. The cost of the concrete
in place was about as follows:

Cement, per cu. yd. of concrete          $ 4.80
Sand and stone, per cu. yd. of concrete    3.90
Mixing, per cu. yd. of concrete            0.40
Placing, per cu. yd. of concrete           2.20
Forms, per cu. yd. of concrete             2.65
  Total per cu. yd. of concrete          $13.95

~GAS HOLDER TANK, DES MOINES, IOWA.~--The tank was 84 ft. in diameter and
21 ft. 5 ins. deep. It had a horizontal floor 16 ins. thick 5 ft. below
ground level and a wall 21 ft. high, 18 ins. thick at base and 12 ins.
thick at top under coping and with alternate pilasters and piers around
the outside. The concrete for the floor was a 1-2½-5 2-in. stone mixture
and the concrete for the walls was a 1-2-4 1-in. stone mixture. The
floor was constructed first, with a circular channel for the wall
footing, and then the wall was constructed.

Piles were driven in the bottom and their heads cut to level and filled
around with tamped cinders. Two circumferential rows of posts were
driven around the edge so that a pair of posts, one inner and one outer,
came on each radius through a wall pilaster or pier. These posts served
primarily to carry the frames for the wall forms and secondarily for
holding the forms for the circular wall footing channel as shown by the
sketch Fig. 280. The floor concrete was put in in diamond-shaped panels
between forms, whose top edges were set to floor level. Each form was
designed to make a groove in the edge of the slab so that adjacent slabs
would bond with it. The concrete was wheeled to place in barrows,
thoroughly tamped, roughly floated to surface and finally given a trowel
finish.

[Illustration: Fig. 280.--Forms for Constructing Channel for Wall in
Reservoir Floor.]

To construct the walls, the posts before mentioned, were cut off to
exact level 6 ins. above the finished floor. A bent for the wall forms
was then erected on each radial pair as shown by Fig. 281. The bents
were erected by hand and carefully plumbed and lined up, both radially
and circumferentially. The pier and pilaster forms were then erected
across wall opposite each bent as shown by Fig. 281. The forms for the
wall between pilasters and piers consisted of panels 4 ft. high.

[Illustration: Fig. 281.--Frame for Forms for Circular Reservoir Wall.]

[Illustration: Fig. 282.--Form Panels for Circular Reservoir Wall.]

A panel for the inner face of the wall is shown by Fig. 282, the panel
for the outer face was similar in construction but was, of course,
concave instead of convex. Enough panels of each kind were made to reach
entirely around the tank. The inside panels were bolted at the ends to
the uprights of the bents; the outside panels were similarly lag screwed
to the uprights of the pier and pilaster forms; Fig. 281 shows the holes
for bolts and lag screws. The spaces between ends of inside panels in
front of the bents was closed by a ½×6-in. steel plate the full height
of the wall; this plate was bolted to the bents and had anchor bolts
every 3 ft., reaching into the wall. This anchoring of the plate to the
wall permitted the diagonal bracing of the bents to be removed to allow
runways to be laid on the cross-pieces, since the plate held firmly the
bent post to which it was bolted as indicated by Fig. 283. A complete
circle of inside and outside forms was erected and filled, then the
forms were raised 3 ft. by block and tackle from cross timbers across
wall between bent and pilaster form, and this depth concreted and the
forms raised again. The forms were oiled on the faces coming against the
concrete. It took about half a day to raise and set a complete circle of
forms. The concrete was mixed outside the tank and was wheeled up
inclines and dumped onto runways laid on the cross pieces of the bents
and then loaded and wheeled to place. The runway was raised to
successive horizontals as the work progressed.

[Illustration: Fig. 283.--Sketch Showing Filler for Joint Between Form
Panels.]

Only a few general cost figures are available. The labor for mixing and
placing concrete was as follows:

For floor, per cu. yd.      3.4 hrs.
For walls, per cu. yd.      5.2 hrs.
For cornice, per cu. yd.    5.4 hrs.

The cost of unloading the reinforcing steel from cars and placing it in
the structure was $7 per ton, or 0.35 ct. per lb. The cost of form
lumber, framing, erecting and taking down forms was 9 cts. per square
foot of wall covered.

~GAS HOLDER TANK, NEW YORK CITY.~--The tank for the Central Union Gas
Co.'s gas holder at 136th St. and Locust Ave. has an interior diameter
of 189 ft. and a depth of 41 ft. 6 ins. The exterior wall is 42 ft. 6
ins. deep, 5 ft. 6 ins. thick at the base and 4 ft. 6 ins. thick at the
top; concentric with it and 11 ft. 6 in. away is the interior wall 166
ft. in external diameter and 16 ft. 6 ins. high with a uniform
thickness of 2 ft. 6 ins. The bottom of the tank enclosed by the
interior wall is a truncated cone whose base is at the level of the wall
top. Fig. 284 shows the arrangement.

It was specified that the diameter of this tank should not vary more
than 2 ins. and that the exterior wall should not vary more than 1 in.
from the vertical. The main form was a circular drum whose exterior face
formed the inner face of the main wall. Its framework consisted of 40
vertical trusses or radial frames 6 ft. deep and 42 ft. high set
equidistant around the tank, these trusses being braced together on both
edges by circumferential timbers. Radial horizontal pieces nailed across
the radial frames and projecting beyond their faces carried vertical
iron guide strips against which the movable panels of lagging were
seated. These panels were cylindrical segments 5 ft. high and long
enough to span between two radial frames or 14 ft. 11-5/8 ins. The
panels were adjusted radially by wedges to give 1/8 in. clearance in
respect to inner face of wall; enough of them were made to form a
complete circle and they were set with 1-in. clearance between vertical
edges of adjacent panels to allow for swelling when wetted.

[Illustration: Fig. 284.--Section of Gas Holder Tank, New York City.]

The concrete bottom of the annular space between walls was first
constructed. On this floor were set 6×6-in.×8-ft. sills for the radial
frames; these were located accurately by transit. The radial frames were
then set on the sills by a derrick, adjusted to exact radial position by
a measuring wire swiveled to the center point of the tank and plumbed
by transit. A complete circle of lagging panels was then adjusted to the
frames at the bottom of the trench. For concreting, the wall was divided
circumferentially into three sections. These sections were separately
concreted to the top of the lagging panels, that is to a height of 5 ft.
After the concrete had set 48 hours the panels were hoisted 4 ft., so
that their lower edges still overlapped the concrete 12 ins., and
another ring of wall was concreted. This procedure was repeated until
the wall was completed. The back of the wall was formed against the side
of the trench where possible and in other places against rough board
lagging held in position in any convenient way.

For handling the concrete, four equidistant panels of the form framework
were converted into double compartment elevator shafts providing for two
balanced cars controlled by a sheave provided with a friction brake.
Three mixers supplied concrete to these elevators. Considering a single
elevator, two barrows of concrete were wheeled from the mixer onto the
car at the top of the elevator frame, the friction brake was released
and the loaded car descended to the work hoisting at the same time its
twin car loaded with two empty barrows. The elevators distributed to
wheeling platforms cantilevered out from the outer face of the framework
and located successively 5 ft., 15 ft., 20 ft., etc., above the bottom
of the trench. On these platforms the concrete was distributed as
required, the maximum wheeling distance being never over one-eighth the
circumference of the tank. The concrete was mixed very wet and deposited
in 6-in. layers.

The inner and outer surfaces of the wall were both painted with two
coats of stiff cement grout neat, and in addition the inner surface was
rubbed smooth by carborundum brick. Regarding this finishing work Mr.
Howard Bruce, Engineer of Construction, writes:

"The scouring was done on each section of the wall immediately after the
forms supporting these sections had been removed. The object was to rub
this interior surface with carborundum before the surface of the
concrete had taken its final set. By rubbing the concrete at this stage
and at the same time applying with a brush a coating of neat cement
grout, we believe the face of the concrete was made more or less
impermeable, as examination shows the pores of the concrete are very
largely filled up. We have no accurate figures as to the cost per square
yard of this treatment, but one can readily see that this cost would be
insignificant as compared with the possible improvement of the work. The
carborundum brick was selected on account of its hardness. I believe
practically any stone would answer the same purpose. In addition to
filling the pores of the concrete, this treatment gives the surface a
good smooth finish."

~LINING A RESERVOIR, QUINCY, MASS.~--The following methods and costs are
given by Mr. C. M. Saville, M. Am. Soc. C. E., for lining the Forbes
Hill Reservoir at Quincy, Mass. This reservoir is 100×280 ft. on the
floor, with side slopes of 1 on 1.75, and was built by contract in
1900-1901.

[Illustration: Fig. 285.--Section of Reservoir Lining, Quincy, Mass.]

Figure 285 is a section of the concrete lining; the bottom layer for the
floor was a 1-2-5 natural cement concrete, and for the sides a 1-2½-6½
Portland cement concrete; the top layer on both floor and sides was a
1-2½-4 Portland cement concrete; 2½-in. stone was the maximum size
allowed in any concrete and 1½-in. the maximum allowed in the top layer.
Smaller stone was used for special surface work, as noted further on.
The stone was cobbles turned up in the excavation work and had to be
gathered from scattered piles and washed before crushing. A 9×15 Farrel
crusher, operated by a 12 HP. engine did the crushing; it was rated at
125 tons a day, but averaged only about 40 tons. The fine dust was
screened out and the remainder discharged into a 30-cu. yd.,
three-compartment bin, one compartment for stone less than 1½ ins.,
another for 1½ to 2½-in. stone and a third for returns. The stone had 46
per cent. voids and weighed 95 lbs. per cu. ft. The sand was of
excellent quality. Atlas and Beach's Portland and Hoffman natural cement
were used.

All concrete was mixed and placed by hand, the concrete gang consisting
generally of 1 sub-foreman, 2 men measuring materials, 2 men mixing
mortar, 3 men turning concrete three times, 3 men wheeling concrete, 1
man placing concrete and 2 men ramming concrete. Two gangs were
ordinarily employed, each mixing and placing about 20 cu. yds. per day,
or 1.43 cu. yds. per man per day. The materials (sand and stone) were
measured in bottomless boxes, the following sizes being used:

                     --Sand Box--                --Stone Box--

Prop. of Mix.    Size.      Vol. cu. ft.       Size.     Vol. cu. ft.

1-2½-4[H]      2'9"×2'×1'8"       9.25        5'×4'5½"        14.8
1-3-6[H]       2'9"×2'×2'        11.1         5'×6'8"         22.2
1-2-5          2'9"×2'×1'4"       7.4         5'×6'6-5/8"     18.5
1-2½-6½        2'9"×2'×1'8"       9.25        5'×7'2½"        24.05

[Footnote H: These mixtures were used for gate house and standpipe
foundation work.]

The bottom layer was placed in a continuous sheet; the top layer was
laid in 10-ft. squares on the floor and in 8×10-ft. squares on the
sides; these squares alternated in both directions, one-half being first
laid and allowed to set. In laying the sides the surface was left 1 in.
low and then before the concrete had set was brought to plane by a 1-in.
layer of 1-2½-4 mixture using stone and stone dust less than 3/8 in. The
concrete for the floor was mixed rather wet and rammed until it quaked;
on the sides a drier mixture was necessary to prevent flow. The cost of
the lining concrete was as follows:

  Bottom Layer on Floor: 1-2-5 Mixture:
1.25 bbls. natural cement at $1.08           $1.350
0.34 cu. yd. sand at $1.02                    0.347
0.86 cu. yd. stone at $1.57                   1.350
4½ ft. B. M. lumber at $20 per M.             0.090
Labor, on forms                               0.100
Labor mixing and placing                      1.170
Labor general expenses                        0.080
  Total                                      $4.487

  Bottom Layer on Sides: 1-2½-6½ Mixture:
1.08 bbl. Portland cement at $1.53           $1.652
0.37 cu. yd. sand at $1.02                    0.377
0.96 cu. yd. stone at $1.57                   1.507
Lumber for forms (about 1 ft. B. M.) at $20   0.016
Labor, on forms.                              0.121
Labor, mixing and placing                     1.213
Labor, general expenses                       0.177
  Total                                      $5.063

  Top Layer on Floor and Sides: 1-2½-4 Mixture:
1.37 bbls. Portland cement at $1.53          $2.09
0.47 cu. yd. sand at $1.02                    0.48
0.75 cu. yd. stone at $1.57                   1.17
12½ ft. B. M. form lumber at $20 per M.       0.25
Labor, on forms                               0.26
Labor, mixing and placing                     1.530
Labor, general expenses                       0.150
  Total                                       $5.93

The side finish with 1-2½-4 concrete of 3/8-in. stone cost $0.154 per
sq. yd. 1 in. thick. This work was done by a gang of 3 plasterers and 3
helpers.

The layer of plaster between the concrete layers was put down on 4-ft.
strips and finished similarly to the surface of a granolithic walk. This
layer consisted of 1-2 mortar finished with a 4-1 mortar. To keep the
plaster from cracking it was covered with strips of coarse burlap soaked
in water; this precaution was not entirely successful, some cracks
appeared and had to be grouted. Three gangs, each consisting of 1
plasterer and 1 helper, did the plastering, each gang laying about 700
sq. yds. per day. The cost of the plaster layer was as follows:

  Item.         Per 100 sq. ft.   Per sq. yd.   Per cu. yd.
Cement at $1.53     $1.15           $0.103        $7.42
Sand at $1.02        0.13            0.012         0.86
Burlap               0.02            0.002         0.14
Labor                0.92            0.083         6.00
                    -----           ------       ------
  Totals            $2.22           $0.200       $14.42

It will be noted that it took over 5 bbls. of cement per cubic yard, and
that the labor cost was $6 per cubic yard.

~RELINING A RESERVOIR, CHELSEA, MASS.~--The following account of relining
the Powder Horn Hill Reservoir at Chelsea, Mass., is taken from a paper
by Mr. C. M. Saville. This reservoir which holds about 1,000,000 gallons
is oval in shape, 98×175 ft. at the top, 68×148 ft. at the bottom and 15
ft. deep, with side slopes about 1 on 1. The work was done by day labor.
For sake of completeness the costs of excavation and back-filling are
given here as well as the concrete costs.

The top of the bank was too narrow to allow the use of carts and an
18-in. gage railroad was decided upon as most convenient for handling
materials. A 65-ft. boom derrick with a 70-ft. mast was used for
removing the excavated material and for depositing concrete. The derrick
was operated by a 15-h.p. double drum hoisting engine, was held in place
by six wire guy ropes, and had a reach such that only one moving was
necessary after it was placed. The engine and derrick were set up on the
floor of the reservoir, and the work of excavation was begun at about
the middle of the south side. In order to facilitate the work, a
platform supported on A frames was set up. These frames were spaced
about 15 ft. apart and rested on the bottom and slope of the reservoir,
being held in place by bolts driven into the floor.

The paving blocks on the top of the slope were removed and piled up to
be taken away. The old lining and the material excavated from the bank
were shoveled into the scale pan of the derrick, hoisted to the cars on
the top of the bank, and then run by gravity to a dump a short distance
down the hillside. Here the cars were run out on a rough trestle, the
load dumped, and the empties hauled back to the work by a rope carried
through pulleys to the winch head on the hoisting drum of the engine.

For the storage of some of the materials, two small portable storehouses
were set up--one 8×10×7 ft., the other 11×16 x 7 ft. The bulky portions,
such as cement, sand, and stone, were delivered as necessary, a few
days' supply only being kept on hand. A branch from the railroad was so
arranged that it passed the storehouses and stone piles, while the sand
was piled close to the concrete mixing board. The intention on the work
was to do nothing by hand that could possibly be done by steam, except
that all of the concrete was mixed by hand. As great a proportion of
water was used as could be done without causing the material to slide
when rammed in place.

The lower layer of concrete was of the proportion by volume of 1 cement,
2½ sand, and 6½ crushed stone (sizes from ¾ to 1½ ins.). This was rather
a lean mixture, and as it could not be rammed enough to flush all over,
the surface was finished where necessary by a thick mortar made in the
proportion of 1 cement to 6 sand, and applied with heavy brushes. Before
placing any of the concrete, the bank back of the old concrete left in
place was thoroughly rammed with iron railroad tampers, and the edge of
the old concrete was scrubbed with water and a stiff brush and then
coated with 1 to 4 grout, which was allowed to fill in the angle between
the concrete and the slope. Just before placing the concrete the earth
bank was well wet in order that moisture might not be drawn from the
concrete while it was soft.

In order to make the new lining as waterproof as possible, a layer of
asphalt was placed on top of the lower layer of concrete and brought up
on the exposed edge of the old layer at the bottom of the new work.
This, it was expected would make an elastic and watertight joint between
the new and the old work.

Venezuela asphalt, "Crystal Brand," was used, being poured upon the top
of the concrete layer and allowed to run down the slope, care being
taken that the concrete was entirely and perfectly covered. After the
first layer of asphalt was cool, a second layer was similarly applied,
and the resulting sheet was about ¼ in. thick. Any inclination to crawl
down the slope when exposed to the sun was readily stopped by throwing
on a pailful of cold water. A most particular part of this work was to
get the asphalt as hot and liquid as possible and yet not burn it. All
of the concrete was protected from the sun and kept damp by being
covered with strips of burlap, which were moistened by sprinkling.

The upper layer of concrete was composed of a much richer mixture of
concrete than that used in the bottom layer, the proportions by volume
being 1 cement, 1¼ sand, 1¼ stone dust, and 4 broken stone of the sizes
mentioned above. On account of the steep slope it was possible to do
only a little ramming, and the material was laid as wet as possible. To
make this layer more impervious and also to obtain a smooth surface, the
concrete was left about an inch below and a finish coat applied by
expert granolithic finishers. This coating was applied as soon as it was
possible to do so after the main layer was in place, but on account of
the steepness and the liability of the wet concrete to flow, care had to
be taken not to begin work too soon.

The top finishing coat was made in the proportion of 1 part cement,
1-2/3 part sand, and 3-1/3 parts stone dust. In order to help in
bonding, the last ramming on the concrete was done with rammers studded
with pieces of iron about 1 in. long and ½ in. deep.

The finishing was done in three operations: The material was spread on
the concrete and thoroughly worked into it by the finishers, using rough
wooden floats; after this it was gone over and partially smoothed down
with a thin steel float; and finally it was worked to give the finished
appearance and an impervious surface.

The under layer of concrete was placed in a continuous sheet. The upper
layer was put down in alternate strips, 10 ft, long (the whole length of
the layer) and 5 ft. wide. These blocks were built up in forms, which
were not removed until the concrete had set. Finally, the back or edge
of the block toward the bank was well wet and thoroughly plastered, to
prevent, as far as possible, the infiltration of any water. The plaster
was mixed in the proportion of 1 part cement to 4 parts sand. When the
forms were wholly removed, the space between the concrete and the bank
was refilled, to within about 6 ins. of the top, with a clayey material
previously excavated, and the space was filled and graded to the top of
the bank with loam. During the work two holidays intervened; the men
were also transported to and from the work. Charges were made for these
items, amounting to $209.77, and this sum, together with the cost of
installing the plant ($716.03) are proportionally charged against the
work as follows:

                            Per cent.   Total.   Per cu. yd.
Excavation                     70.3      $651       $2.17
Lower concrete                 12         111        1.16
Upper concrete                 15.4       143        1.11
Back fill                       2.3        21         .28

The detailed cost of repairing the reservoir lining is given in the
following tabulations:

Excavation.

                                    Rate.   Per cu. yd.
Foreman                    9 5/9 days   $4.00   $0.13
Engineman                 12 3/9 days    3.00     .12
Carpenter                  2     days    2.67     .02
Laborers                   9 6/9 days    2.25     .07
Laborers                 110 2/9 days    2.00     .73
Laborers                  46 5/9 days    1.75     .27