+===========================================================+==========+
| Description. |Length, |
| |in meters |
+-----------------------------------------------------------+----------+
| | |
|Cast-iron pipes, 45.7 cm. (18 in.) in diameter, along | |
| the stream bed of the Estanzuela River | 110 |
| | |
|Concrete tubes, 55.9 cm. (22 in.) in diameter, | |
| to Mederos (including 281 m. of tunnel) | 4,473.81 |
| | |
|Cast-iron siphons, 45.7 cm. (18 in.) | |
| in diameter: Calabozos 239 m | |
| South Virgen 124 " | |
| North Virgen 177 " | |
| Mederos 426 " | |
| ----- | 966 |
| | |
|Concrete tubes, 63.5 cm. (25 in.) in diameter, | |
| Mederos to South Reservoir. |12,039.19 |
| | |
|Cast-iron siphons, 50.8 cm. (20 in.) in diameter: | |
| Necaxa 315 m.| |
| San Augustin 796 " | |
| ----- | 1,111 |
| | |
+-----------------------------------------------------------+----------+
| Total |18,700 |
+===========================================================+==========+
The gradient of the concrete pipes is 0.43% from Estanzuela to Mederos,
and 0.53% from Mederos to the South Reservoir. The calculated
discharging capacity of the conduit when running full is 364 liters (13
cu. ft.) per sec. for the upper, and 465 liters (16.4 cu. ft.) per sec.
for the lower section. For these pipes, the coefficient, _n_, in
Kutter's formula, was taken at 0.013. At present the line has been
limited by overflows to discharge three-quarters full.
The increase in the size of the pipes from Mederos is for the purpose of
receiving the waters of the Mederos River and other springs in the San
Pablo and Aqua Verde catchment areas, as shown on Plate II.
The invert of the concrete conduit where it leaves the Estanzuela River
is 684.25 m. above datum, and at the valve-house of the South Reservoir
it is 589.00 m.
The concrete pipes were manufactured and laid under contract with Mr.
Arthur S. Bent, of Los Angeles, Cal., the Company providing all
materials, labor, etc. The contractor was paid 10 cents per lin. ft. of
pipe manufactured and 10 cents per lin. ft. laid. He was also
responsible for the satisfactory completion of the work.
[Illustration: FIG. 9.--ESTANZUELA PIPE LINE STEEL FORMS FOR THE
MANUFACTURE OF CONCRETE PIPE.]
Fig. 9 shows the details of the joint recommended by Mr. Schuyler and
adopted for these pipes. The 63.5-cm. (25-in.) pipes were 61 cm. long
and 76 mm. (3 in.) thick. The 55.9-cm. (22-in.) pipes were of the same
length, but 70 mm. (2-3/4 in.) thick. For the purpose of strengthening
these pipes while hauling them over very rough roads they were
reinforced with four rings of No. 6 galvanized-iron wire.
_Manufacture of Pipes._--The pipes were manufactured under the
Supervision of Mr. H. Stanley Bent, at a pipe yard established below
the crushing plant, from which the crushed rock and sand were delivered
by gravity in bogies run on narrow-gauge rails. The area of the pipe
yard was approximately 1-1/4 hectares, and it was laid out with parallel
lines of 76-mm. (3-in.) galvanized-iron piping with hose couplings for
sprinkling purposes. After trials with aggregates of various sizes, the
concrete for the pipes was proportioned by volume as follows:
Crushed rock broken to pass through a 19-mm. screen 0.136 cu. m.
Manufactured sand (run of rolls) 0.119 " "
Portland cement 0.090 " "
------------
Total 0.345 cu. m.=
(12.2 cu. ft.)
[Illustration: PLATE III, FIG. 2.--STEEL FORMS FOR MOULDING CONCRETE
TUBES, ESTANZUELA AQUEDUCT.]
The above quantity manufactured two 63.5-cm. pipes; a 55.9-cm. pipe
required 0.1415 cu. m. (5 cu. ft.) of the material, in the same
proportions. Fig. 9 shows the forms for these pipes, and Fig. 2, Plate
III, illustrates the process of moulding. The forms consist of cast-iron
bottom rings, to the proper section of the joint, and inner and outer
steel forms of 3-mm. plate, provided with inner and outer locking
arrangements. The concrete was poured through a cast-iron hopper which
fitted to the top of the outer form.
The concrete, which was mixed very dry, in a 1/2-cu. yd. batch, "Smith"
mixer, was thoroughly tamped with a 22-lb. tamper, and worked until it
was of a stiff jelly-like consistency, the wire rings being added as the
concrete was placed. The best results were obtained with the minimum
quantity of water. The upper joint was moulded with a heavy cast-iron
ring. The jacket and core forms were loosened immediately, and placed
over other rings, a sufficient number of bottom rings being used for a
day's work. For the pipes required for curves, special forms were used
to give the necessary bevel to the joint. After 24 hours the finished
pipes were lifted from the bottom ring with a special lifter, and ranged
in position for coating internally with a Portland cement grout to which
a little freshly slaked lime was added. The pipes were all numbered, and
were kept moist for 10 days by constant sprinkling. They were not hauled
to the work until 28 days after they were moulded, although this rule
was sometimes broken, to the detriment of the pipes. More than 32,000
pipes were manufactured, but some were used for purposes other than the
Estanzuela Aqueduct.
_Cost of Pipes._--The contractor brought with him experienced concrete
pipe makers from California, and these were afterward assisted by
Mexican labor. In a day two tampers could manufacture from 45 to 50
pipes of the larger (63.5-cm,), and from 55 to 60 of the smaller
(55.9-cm.) size.
The cost varied from 2.75 to 3.25 pesos per pipe for the smaller, and
from 3.50 to 4.00 pesos for the larger size.
The approximate cost of manufacturing is as follows: Taking, as a fair
example, one week's work during March, 1908, the wages paid to the 74
men comprising the total pay-roll (though part of this labor was
intermittent) amounted to 981 pesos. This includes a general foreman at
10 pesos per day, four American tampers at 7.50 pesos, and Mexican labor
varying from 4 to 1 peso, and all labor necessary to handle and finish
the pipes, including coating the interiors. During this week there were
made 1,126 of the 63.5-cm. and 1,095 of the 55.9-cm. size. The pay-roll
includes 520 pesos for the larger pipes (46 cents each) and 461 pesos
for the smaller pipe (42 cents each). Table 5 shows the quantities and
cost of the materials used in the manufacture of these pipes.