Chapter III: Part 3

_Outlet Tunnel and Valve-House._--The outlet tunnel is at the north end of the reservoir, and was excavated in hard sillar rock. The tunnel is lined with concrete 30 cm. thick, the finished internal dimensions being 1.52 by 0.91 m. The length of the tunnel is 22.5 m. to the point where it enters the outlet-house. This house is divided by a wall 45 cm. thick, which supports a 76-cm. (30-in.) penstock-valve. The supply pipe to the city leaves this chamber in the west wall, and is also fitted with a 76-cm. penstock-valve. The supply pipe has a copper screen of the same design and dimensions as those in the inlet-house. A 30-cm. (12-in.) scour-out pipe in this chamber provides for draining the contents of the reservoir to a neighboring irrigation ditch, when necessary.

The superstructure of the valve-house is of concrete, and at the floor level there are bevel-geared head-stocks to raise the valves, etc.

_By-Pass and Supply Pipes._--The by-pass and supply pipes are carried below the reservoir embankment to join the main 76-cm. (30-in.) cast-iron distributing pipe to the city. For this short distance they were constructed of concrete, 76 cm. in internal diameter, 10 cm. (4 in.) thick, reinforced with 6-1/2-mm. square steel longitudinal rods, 30 cm. from center to center in the circumference, and hooped with 6-1/2-mm. square steel rods spaced 30 cm. apart. The concrete forming these pipes was a 1:1-1/2:2-1/2 mixture.

_Parapet Walls._--The parapet walls have 12 piers at each side and 8 at each end. In these piers there are ventilating openings branching at the top to each side of the parapet, with outlets provided with cast-iron screens. This arrangement gives 4 sq. m. of ventilating space (exclusive of that provided in the central tower), equally distributed at 40 points around the walls of the reservoir.

_General Construction Scheme._--The concrete mixing plant, which consisted of two No. 1 Smith mixers, was arranged in connection with the bins and hoppers for the rock and sand on the high ground to the west, and from there the material was conveyed on a framed timber gangway carried right across the center of the reservoir, as shown by Fig. 1, Plate XVII. From this central platform the concrete for the columns was filled from stages placed on the top of traveling towers, 5 m. high, which were run between two rows of columns on standard-gauge rails laid on the floor of the reservoir. By this arrangement 24 columns could be filled from each length of track. A main narrow track was also laid right around the reservoir, with the necessary turn-outs.

The forms for the columns, primary and secondary beams, are shown on Plate XIV. The side forms for the primary beams were struck in 24 hours, so as to economize lumber; but the bottom lumber was left in position for 28 days. To avoid much unnecessary timber, the secondary beam forms were supported at the ends on reinforced concrete corbels cast on the primary beams.

For placing the side-walls, a special traveling form was used, the details of which are shown clearly on Plate XIV. At the end of each form an expansion joint of 25 cm. was left to be filled after the roof was placed in position. The concrete was delivered to the wall through stove-pipe chutes, and carefully spaded by workmen in the limited space between the forms and the embankment. The wall form was removed after 36 hours, by loosening the jacks and pulling forward the hooked tie-rods. This form is also shown on Fig. 2, Plate XVI.

The concreting of the roof slab was carried on continuously, and, when partly completed, the floor was laid in the shade. The bottom layer of the floor, 13 cm. thick, was laid in continuous panels between the columns, and brought to a fairly smooth surface. On this surface, after keeping it wet for 10 days and then allowing it to dry thoroughly, a layer of asphaltum, supplied by the American Asphaltum and Rubber Company, of Chicago, was placed. The work was done by ordinary Mexican laborers after they had received a few days' instruction from one of the Asphaltum Company's superintendents. The surface of the lower layer was kept perfectly clean, and then received one coat of "Pioneer" paint. The asphaltum, heated in a boiler inside the reservoir to a temperature of approximately 425 deg. Fahr., was then poured over the floor from buckets, in a layer approximately 4 mm. thick. Where the floor joined the column pedestals, and at each new panel section, a double thickness was used. The labor cost of water-proofing, including superintendence, etc., amounted to 3.3 cents (Mexican) per sq. m. for painting with "Pioneer" paint, and 5.4 cents for the asphaltum coating, or a total labor cost of 8.7 cents per sq. m. for the complete water-proofing. This cost is based on a rate of 8.00 pesos per day for a foreman, and 1.00 peso for each laborer. It required 50 U. S. gal. of the paint to cover 265.2 sq. m., and an average of about 6 lb. of asphaltum for 1 sq. m.

The upper concrete layer of the floor, 10 cm. thick, was placed so as to break joint with the lower, and was brought to a smooth surface with wooden floats sheathed with steel and reaching across the panels. In this way a perfectly smooth surface was obtained without any plastering.

The concrete for the beams, columns, side-walls, and floor, was a 1:2-1/2:4 mixture, crushed sand and stone being used throughout. In the roof slab the mixture was 1:2:3.

The whole of the concrete work of the reservoir was completed in 6 months, by the Company's own administration, and the reservoir was first put into service a few days after the great flood of August 27th, when the Estanzuela supply main, crossing the Santa Catarina River, was partly destroyed. Since that time frequent examinations of the inspection pit, which is connected by a pipe to the rubble drains under the floor, have never revealed the slightest leakage.

_Lay-Out of the Reservoir Roof and Grounds._--The Company owns about 11-1/2 hectares of land, which includes that occupied by the reservoir and its surroundings, and as this property is in an attractive situation, commanding fine views of the Sierra Madre Mountains, the whole of the works have been given a pleasing architectural character, and the grounds laid out to form a public park for the citizens of Monterrey.

The general plan of the scheme is shown by Fig. 14 and Fig. 2, Plate XVIII. The roof, which has an area of 1 hectare, has been laid out with walks and grass plots, and the surrounding embankments have been converted into driveways. Above the reservoir a small plazuela of 1/2 hectare has been laid out with a space above it for a band-stand. The whole of the ground has been encircled with carriage drives, on which it is the intention to plant shade trees. The lay-out of this land also embraced the scheme for protecting the reservoir by draining the surface-water away to the irrigation ditches.

COMPARISON OF SOUTH AND OBISPADO RESERVOIRS.

The two reservoirs are practically of the same capacity, the only difference being the level of the overflows in their relationship to the roof, which gives the Obispado Reservoir a slightly greater capacity. Some comparative figures may be of interest, owing to the differences in type and construction. Table 7 gives the comparative quantities of material in each reservoir proper, that is to say, exclusive of the valve-houses, lay-out of grounds, etc.

TABLE 7.--COMPARISON OF MATERIALS IN SOUTH AND OBISPADO RESERVOIRS.

==========================+===============================+============
| SOUTH RESERVOIR. | _OBISPADO RESERVOIR._
+--------+-------------+--------+------------
| | Quantities, | | Quantities,
| No. | in cubic | No. | in cubic
| | meters. | | meters.
--------------------------+--------+-------------+--------+------------
_Earthwork:_ | | | |
Total excavation | ... | 34,000 | ... | 56,479
Placed in embankment | ... | 31,500 | ... | 7,255
Placed in spoil banks | ... | 2,500 | ... | 49,224
+--------+-------------+--------+------------
_Concrete:_ | | | |
Columns (including | | | |
foundations) | 135 | 1,240 | 356 | 543
Primary beams | 135 | 440 | 374 | 462
Secondary beams | 670 | 515 | 1,252 | 576
Side-walls | ... | 1,255 | ... | 710
| | | |
| Square | | Square |
| meters.| | meters.|
Roof slab | 5,140 | 520 | 10,206 | 1,020
Floor | 4,070 | 780 | 9,200 | 2,120
Parapet walls | ... | 90 | ... | 165
+--------+-------------+--------+------------
Total concrete | ... | 4,840 | ... | 5,596
+--------+-------------+--------+------------
| | Pounds. | | Pounds.
Reinforcing steel bars | ... | 387,000 | ... | 380,000
| | | |
| | Square | | Square
| | meters. | | meters.
Expanded metal in roofs, | | | |
slabs, etc. | ... | 5,691 | ... | 10,490
==========================+========+=============+========+============

The total cost of these reservoirs, including valve-houses, by-passes, and the length of supply pipe where the by-pass joins, and including all engineering expenses, etc., but exclusive of the cost of lands, planting, fencing, and special work in connection with the formation of parks, was as follows:

South Reservoir: 394,000 pesos, or 10,368 pesos per million liters.

Obispado Reservoir: 375,000 pesos, or 9,375 pesos[7] per million liters.

[7] Mexican currency.

These rates may be regarded as reasonable when taking into consideration the special difficulties of construction in Mexico, and the high cost of all imported material, on which heavy duties are levied.

The value of the materials alone in these reservoirs amounted to more than 70% of their total cost.

ANALYSES OF ESTANZUELA AND SAN GERONIMO WATERS.

Table 8 shows analyses of the Estanzuela and San Geronimo waters, made in February, 1910, by Messrs. Ledoux, of New York City. The Estanzuela sample was taken at the valve-house of the South Reservoir, while that of San Geronimo was taken in Shaft No. 1 of the infiltration gallery when flowing at the rate of about 450 liters per sec. Both waters are absolutely free from turbidity.

TABLE 8.--ANALYSES OF ESTANZUELA AND SAN GERONIMO WATERS.
In Parts per Million.

==================================+================+===============
| | San Geronimo
| Estanzuela. | Infiltration
| | Gallery.
----------------------------------+----------------+---------------
Total solid matter in solution | 209.00 | 305.00
Organic and volatile matter | Not weighable. | Not weighable.
| |
ANALYSIS OF SOLIDS: | |
Silica | 10.5 | 12.0
Iron and Alumina | Traces. | Traces.
Lime | 85.4 | 112.6
Magnesia | 3.8 | 22.6
Soda (Na_{2}O) | 13.3 | 20.2
Potash (K_{2}O) | 2.0 | 1.9
Sulphuric Acid | 24.4 | 11.5
Chlorine | 2.0 | 2.8
+----------------+---------------
PROBABLE COMBINATION OF BASES & | |
ACID RADICALS IN THE SOLIDS: | |
Silica | 10.5 | 12.0
Iron and Alumina | Traces. | Traces.
Sodium Chloride | 3.3 | 4.6
Potassium Sulphate | 3.7 | 3.5
Sodium Sulphate | 26.3 | 40.8
Calcium Sulphate | 13.3 | 22.1
Calcium Carbonate | 142.7 | 184.8
Magnesium Carbonate | 8.4 | 49.8
+----------------+---------------
| 208.2 | 317.6
| |
Nitrogen as Free Ammonia | 0.004 | 0.032
Nitrogen as Albuminoid Ammonia | 0.006 | 0.022
Nitrogen as Nitrites (N_{2}O_{3}) | 0.002 | 0.002
Nitrogen as Nitrates (N_{2}O_{3}) | 0.100 | 1.85
Total Hardness (as CaCO_{3}) | 155.0 | 220.0
Alkalinity (as CaCO_{3}) | 121.0 | 180.0
==================================+================+===============

CITY WATER DISTRIBUTION SYSTEM.

The distribution system was begun in September, 1906, but the general lay-out of the mains was modified in July, 1907, in view of the division of the system into two services, for high and low pressure. Plate XIX shows in skeleton form the lines of the cast-iron mains. These are laid at the present time along routes containing houses (excluding wooden shacks) which can be served immediately. The distribution system is arranged to serve as follows:

Estanzuela supply 4,150 houses.
San Geronimo supply 8,600 "
--------------
Total 12,750 houses.

This represents, at the present time, a division of the city of 32-1/2% for the Estanzuela, and 67-1/2% for the San Geronimo supply. Of the area of the supply district north of Santa Catarina River, 57% will be supplied from San Geronimo and 43% from Estanzuela. The real development of the city, however, is northward in the area of the low-pressure supply.

The static pressure over the city in the two sections varies as follows:

Estanzuela supply 85 to 50 lb.
San Geronimo supply 55 to 29 lb.

The main supply pipe from the South Reservoir is 61 cm. (24 in.) in internal diameter, and this size allows ample provision for future extensions. The supply pipe from the Obispado Reservoir is 76 cm. (30 in.) in internal diameter. On this main, in Calle de Cinco de Mayo, at a distance of 320 m. from the reservoir, has been placed a 76-cm. (30-in.) Venturi meter, the recording apparatus being in the house on the side of the road. Both these supply pipes are carried well into the city, and from them the distribution mains are laid; these are 45.7 and 30 cm. (18 and 12 in.) in internal diameter, with intermediate sections of 15 and 10 cm. (6 in. and 4 in.). Along Calle de Cinco de Mayo, where the division between the two services takes place, two lines are laid, a 30-cm. for high pressure and a 38-cm. (15-in.) for the low pressure. A duplicate pipe, 30 cm. (12 in.) in diameter, is also laid in Calle de Dr. Coss. On Calle de Alvarez the low-pressure pipe is 61 cm. (24 in.), and the high-pressure, 45.7 cm. (18 in.) in diameter. Provision is also made for extending the range of the two services to other districts. Practically every block is provided with gate-valves to cut off the supply in any direction. On the 76-cm. main, 61-cm. (24-in.) valves are used, and are connected by tapers to the pipe. On the 61-cm. mains, 45.7-cm. (18-in.) valves are used. The actual frictional loss by reducing the valve being small, this method permitted the use of valves of a more convenient size. On all the larger valves there are 15-cm. by-passes fitted with independent gate-valves.

Scour-out pipes, 10 cm. (4 in.) and 15 cm. (6 in.) in diameter, are placed in various parts of the system, draining to the sewers. Air-valves, both double and single, are also placed at high points in different parts of the system.

_Reducing Valves._--At four points in the system the mains are arranged so that the supply can be interchangeable. Fig. 15 shows the arrangement of the mains at the junction of Cinco de Mayo and Alvarez Streets, and is typical of the arrangement at the other points.

Each reducing valve is placed on a 30-cm. (12-in.) branch main between the two services. These valves adjust themselves automatically to the pressure required, after they have been properly regulated to the different pressures on either side. To allow repairs to be easily made, there are ordinary gate-valves at each end enclosed in the same pit. If necessary, as in case of fire, any part of the system can be changed into high pressure temporarily by closing the valves against the San Geronimo supply.

Table 9 gives the length of the mains as laid, and the number of valves.

TABLE 9.--LENGTH OF WATER MAINS.

=========================+=====================+=============
DIAMETER: | |
--------------+----------+ Length, in meters. | Number of
Centimeters. | Inches. | | gate-valves.
--------------+----------+---------------------+-------------
10.2 | 4 | 49,831.68 | 677
15.2 | 6 | 31,918.31 | 306
30.5 | 12 | 14,461.31 | 117
38.1 | 15 | 1,661.98 | 11
45.7 | 18 | 4,522.61 | 5
61.0 | 24 | 2,826.54 | 10
76.2 | 30 | 1,454.40 |
--------------+----------+---------------------+-------------
Totals | 106,676.83 | 1,126
=========================+=====================+=============

The pipes were all cast according to the British Standard Specification, in 3.65-m. (12-ft.) lengths, and were supplied by Messrs. D. Y. Stewart and Company, and Messrs. Dick, Kerr and Company, of Kilmarnock and London. The valves were all of standard design, faced with gun-metal, and were supplied by Messrs. Glenfield and Kennedy, Limited, of Kilmarnock, Scotland.

In the distribution system it is proposed to provide 200 fire-hydrants, by arrangement with the municipality, but only a few of these have been placed. The general type is a double hydrant for two 63.5-mm. (2-1/2-in.) streams. These are to be placed at the corner of every block in the business portion of the city; single-way hydrants will be used in the residential districts.

_Laying Cast-iron Pipes._--Table 10 has been prepared to show what can be accomplished with Mexican labor in laying pipes. In this kind of work the labor was particularly efficient; after the gangs were once drilled into shape, the work proceeded systematically, and at very good speed. All the pipes, after being laid, were tested to 150 lb. per sq. in. in the presence of the Technical Inspector.

Table 11 gives the details of the excavation, the material, and the average cost, of laying about 106.6 km. of pipes.

_House Connections._--The ordinary house connections, which are of 19-mm. (3/4-in.) galvanized-steel pipe, are connected to the mains by lead goosenecks and brass corporation cocks. The Company's obligation under the concession extended to the edge of the sidewalk, and at this point curb-boxes, chiefly of the Hays pattern, were placed; but, subsequently, owing to the metering of every house service in the city, the control of the Company extended to the meter, which, as a rule, is placed immediately inside of the house. Owing to the rapid deterioration of the house service pipes in some districts of the northern part of the city, where the soil is formed of decaying organic matter, it has been decided to use lead pipe entirely from the main to the meter.

_Damage Due to Floods._--During the night of August 27th, the main 61-cm. pipe, under the river bed of Santa Catarina, at the point where the main entered the city, was destroyed for a distance of 130 m., due to the scouring away of a whole block of city property. The Venturi meter register chart at the South Reservoir showed that the break occurred a few minutes before midnight. The location of this pipe is shown by Fig. 5; its broken end was in proximity to an old bridge pier. Fortunately, at the time of the flood, the Obispado Reservoir works were completed, and the whole city was supplied with water from San Geronimo within 48 hours. As only about 1,500 services had then been connected, this delay was not serious; in fact, in the lower part of the city, the water in the mains was sufficient until the San Geronimo supply could be connected. To make a temporary connection to conduct the high-pressure water to the city, a 15-cm. steel pipe was placed above ground, on the line of the main, for a distance of 100 m. This pipe was supported by a cable, 30 mm. in diameter, and by timber trestles. By limiting the supply district, this pipe was of sufficient capacity to serve until the large main could be safely restored.

TABLE 10.--COST OF LAYING AND JOINTING CAST-IRON PIPES, EXCLUDING
LOWERING AND TESTING.

+--------------+----------+----------------------------------------+
| | | 76 CM. (30 IN.) |
| | +-------+------------+--------+----------+
| Employees. | Rate for | Total | Total cost | No. of | Cost per |
| | 10-hour | No. | of labor. | pipes | linear |
| | day. | men. | Pesos. | laid. | meter. |
| | Pesos. | | | | Pesos. |
+--------------+----------+-------+------------+--------+----------+
| Foreman | 4.50 | 1 | 4.50 | ... | ... |
| Caulkers | 3.00 | 4 | 12.00 | ... | ... |
| Lead pourers | 2.00 | 2 | 4.00 | ... | ... |
| Lead melter | 1.50 | 1 | 1.50 | 20 | 0.498 |
| Pipe cutter | 2.00 | 1 | 2.00 | ... | ... |
| Peons | 1.00 | 12 | 12.00 | ... | ... |
| Water boy | 0.50 | 1 | 0.50 | ... | ... |
| | | | | | |
| | ... | 22 | 36.50 | ... | ... |
+--------------+----------+-------+------------+--------+----------+
| | | 61 CM. (24 IN.) |
| | +-------+------------+--------+----------+
| Employees. | Rate for | Total | Total cost | No. of | Cost per |
| | 10-hour | No. | of labor. | pipes | linear |
| | day. | men. | Pesos. | laid. | meter. |
| | Pesos. | | | | Pesos. |
+--------------+----------+-------+------------+--------+----------+
| Foreman | 4.50 | 1 | 4.50 | ... | ... |
| Caulkers | 3.00 | 5 | 15.00 | ... | ... |
| Lead pourers | 2.00 | 2 | 4.00 | ... | ... |
| Lead melter | 1.50 | 1 | 1.50 | 25 | 0.410 |
| Pipe cutter | 2.00 | 1 | 2.00 | ... | ... |
| Peons | 1.00 | 10 | 10.00 | ... | ... |
| Water boy | 0.50 | 1 | 0.50 | ... | ... |
| | | | | | |
| | ... | 21 | 37.50 | ... | ... |
+--------------+----------+-------+------------+--------+----------+
| | | 50 CM. (20 IN.) |
| | +-------+------------+--------+----------+
| | Rate for | Total | Total cost | No. of | Cost per |
| Employees. | 10-hour | No. | of labor. | pipes | linear |
| | day. | men. | Pesos. | laid. | meter. |
| | Pesos. | | | | Pesos. |
+--------------+----------+-------+------------+--------+----------+
| Foreman | 4.50 | 1 | 4.50 | ... | ... |
| Caulkers | 3.00 | 4 | 12.00 | ... | ... |
| Lead pourers | 2.00 | 2 | 4.00 | ... | ... |
| Lead melter | 1.50 | 1 | 1.50 | 35 | 0.287 |
| Pipe cutter | 2.00 | 1 | 2.00 | ... | ... |
| Peons | 1.00 | 12 | 12.00 | ... | ... |
| Water boy | 0.50 | 1 | 0.50 | ... | ... |
| | | | | | |
| | | 22 | 36.50 | ... | ... |
+--------------+----------+-------+------------+--------+----------+
| | | 45.7 CM. (18 IN.) |
| | +-------+------------+--------+----------+
| | Rate for | Total | Total cost | No. of | Cost per |
| Employees. | 10-hour | No. | of labor. | pipes | linear |
| | day. | men. | Pesos. | laid. | meter. |
| | Pesos. | | | | Pesos. |
+--------------+----------+-------+------------+--------+----------+
| Foreman | 4.50 | 1 | 4.50 | ... | ... |
| Caulkers | 3.00 | 4 | 12.00 | ... | ... |
| Lead pourers | 2.00 | 2 | 4.00 | ... | ... |
| Lead melter | 1.50 | 1 | 1.50 | 40 | 0.221 |
| Pipe cutter | 2.00 | 1 | 2.00 | ... | ... |
| Peons | 1.00 | 8 | 8.00 | ... | ... |
| Water boy | 0.50 | 1 | 0.50 | ... | ... |
| | | | | | |
| | | 18 | 32.50 | ... | ... |
+--------------+----------+-------+------------+--------+----------+
| | | 38 CM. (15 IN.) |
| | +-------+------------+--------+----------+
| | Rate for | Total | Total cost | No. of | Cost per |
| Employees. | 10-hour | No. | of labor. | pipes | linear |
| | day. | men. | Pesos. | laid. | meter. |
| | Pesos. | | | | Pesos. |
+--------------+----------+-------+------------+--------+----------+
| Foreman | 4.50 | 1 | 4.50 | ... | ... |
| Caulkers | 3.00 | 4 | 12.00 | ... | ... |
| Lead pourers | 2.00 | 2 | 4.00 | ... | ... |
| Lead melter | 1.50 | 1 | 1.50 | 45 | 0.196 |
| Pipe cutter | 2.00 | 1 | 2.00 | ... | ... |
| Peons | 1.00 | 8 | 8.00 | ... | ... |
| Water boy | 0.50 | 1 | 0.50 | ... | ... |
| | | | | | |
| | | 18 | 32.50 | ... | ... |
+--------------+----------+-------+------------+-------------------+
| | | 30.5 CM. (12 IN.) |
| | +-------+------------+--------+----------+
| | Rate for | Total | Total cost | No. of | Cost per |
| Employees. | 10-hour | No. | of labor. | pipes | linear |
| | day. | men. | Pesos. | laid. | meter. |
| | Pesos. | | | | Pesos. |
+--------------+----------+-------+------------+--------+----------+
| Foreman | 4.50 | 1 | 4.50 | ... | ... |
| Caulkers | 3.00 | 4 | 12.00 | ... | ... |
| Lead pourers | 2.00 | 2 | 4.00 | ... | ... |
| Lead melter | 1.50 | 1 | 1.50 | 60 | 0.147 |
| Pipe cutter | 2.00 | 1 | 2.00 | ... | ... |
| Peons | 1.00 | 8 | 8.00 | ... | ... |
| Water boy | 0.50 | 1 | 0.50 | ... | ... |
| | | | | | |
| | | 18 | 32.50 | ... | ... |
+--------------+----------+-------+------------+--------+----------+
| | | 15 CM. (6 IN.) |
| | +-------+------------+--------+----------+
| Employees. | Rate for | Total | Total cost | No. of | Cost per |
| | 10-hour | No. | of labor. | pipes | linear |
| | day. | men. | Pesos. | laid. | meter. |
| | Pesos. | | | | Pesos. |
+--------------+----------+-------+------------+--------+----------+
| Foreman | 4.50 | 1 | 4.50 | ... | ... |
| Caulkers | 3.00 | 4 | 12.00 | ... | ... |
| Lead pourers | 2.00 | 2 | 4.00 | ... | ... |
| Lead melter | 1.50 | 1 | 1.50 | 100 | 0.082 |
| Pipe cutter | 2.00 | 1 | 2.00 | ... | ... |
| Peons | 1.00 | 6 | 6.00 | ... | ... |
| Water boy | 0.50 | 1 | 0.50 | ... | ... |
| | | | | | |
| | | 16 | 30.50 | ... | ... |
+--------------+----------+-------+------------+--------+----------+
| | | 10 CM. (4 IN.) |
| | +-------+------------+--------+----------+
| Employees. | Rate for | Total | Total cost | No. of | Cost per |
| | 10-hour | No. | of labor. | pipes | linear |
| | day. | men. | Pesos. | laid. | meter. |
| | Pesos. | | | | Pesos. |
+--------------+----------+-------+------------+--------+----------+
| Foreman | 4.50 | 1 | 4.50 | ... | ... |
| Caulkers | 3.00 | 4 | 12.00 | ... | ... |
| Lead pourers | 2.00 | 2 | 4.00 | ... | ... |
| Lead melter | 1.50 | 1 | 1.50 | 150 | 0.0574 |
| Pipe cutter | 2.00 | 1 | 2.00 | ... | ... |
| Peons | 1.00 | 6 | 6.00 | ... | ... |
| Water boy | 0.50 | 1 | 0.50 | ... | ... |
| | | | | | |
| | | 16 | 30.50 | ... | ... |
+--------------+----------+-------+------------+--------+----------+

TABLE 11.--CAST-IRON WATER PIPES.--COST
OF MATERIALS AND LAYING AT MONTERREY.

MATERIALS PER STANDARD LENGTH OF PIPE .

Key: cm = centimeter in = inch mm = millimeter kg = kilogram m = linear meter +-----------+------+-------+--------+-------------+--------+--------+-------+ | PIPE | |Weight |Cost/ | LEAD | OAKUM |CHARCOAL| Total | | DIAMETER |Thick-| of |piece +------+------+--------+--------+ Ma- | +------+----+ ness | Pipe |fob Mon-|Weight| Cost | Cost | Cost |terial | | | | | |terrey | | | | | Cost | | cm | in | mm | kg | pesos | kg |pesos | pesos | pesos | per m | +------+----+------+-------+--------+------+------+--------+--------+-------+ | 10 | 4 | 10.3 | 109 | 11.65 | 2.0 | 0.37 | 0.025 | 0.0525 | 3.30 | | 15 | 6 | 11.1 | 163 | 15.74 | 3.7 | 0.67 | 0.0675 | 0.065 | 4.51 | | 30.5 | 12 | 15.8 | 463 | 76.50 | 7.9 | 1.44 | 0.1225 | 0.1 | 21.35 | | 38 | 15 | 17.4 | 680 | 79.36 | 10.6 | 1.94 | 0.175 | 0.12 | 22.30 | | 45.7 | 18 | 19.0 | 871 | 90.28 | 13.4 | 2.42 | 0.2375 | 0.1375 | 25.42 | | 61 | 24 | 22.2 | 1,261 | 117.60 | 18.8 | 3.42 | 0.335 | 0.175 | 33.20 | | 76 | 30 | 25.4 | 1,946 | 199.05 | 24.5 | 4.42 | 0.44 | 0.2125 | 55.77 | +------+----+------+-------+--------+------+------+--------+--------+-------+

LABOR.

Key: cm = centimeter, in = inch, m = meter
+-----------+------+------+------+------+-------+-------+----
| | | | | | |Total |
| DIAMETER | | | Cubic| Cost |Back- |cost, |
| OF PIPE: | Width|Depth |meters| of |filling|exca- |
| | of | | per |exca- |and re-|vation |
+------+----+trench| |linear|vation|moving |back- | Continues
| | | | | meter| per |surplus|filling|
| cm | in | m | m | |lin. m|Pesos |etc. |
| | | | | | | |Pesos |
+------+----+------+------+------+------+-------+-------+----
| 10 | 4 | 0.55 | 0.90 | 0.50 | 0.60 | 0.18 | 0.78 |
| 15 | 6 | 0.60 | 1.00 | 0.60 | 0.72 | 0.22 | 0.94 |
| 30.5 | 12 | 0.65 | 1.20 | 0.78 | 0.94 | 0.29 | 1.23 |
| 38 | 15 | 0.70 | 1.30 | 0.91 | 1.10 | 0.34 | 1.44 | Below
| 45.7 | 18 | 0.80 | 1.40 | 1.12 | 1.34 | 0.41 | 1.75 |
| 61 | 24 | 1.00 | 1.50 | 1.50 | 1.80 | 0.55 | 2.35 |
| 76 | 30 | 1.10 | 1.60 | 1.76 | 2.11 | 0.65 | 2.76 |
+------+----+------+------+------+------+-------+-------+----

--+----------------+--------+--------+--------+
| HAULING PER | Cost | Total | Total |
| | of |hauling |excava- |
| LINEAR METER | laying | and |tion and|
| | per |laying |laying, |
+--------+-------+ linear | per |labor, |
| Haul- | Misc. | meter |linear |complete|
| ing | Pesos | | meter | |
| Pesos | | Pesos | Pesos | Pesos |
--+--------+-------+--------+--------+--------+
| 0.0275 | 0.005 | 0.06 | 0.0925 | 0.8725 |
| 0.45 | 0.005 | 0.825 | 0.1325 | 1.0725 |
| 0.18 | 0.0075| 0.1475 | 0.335 | 1.565 |
| 0.2725 | 0.01 | 0.19 | 0.4775 | 1.9125 |
| 0.2725 | 0.01 | 0.245 | 0.5275 | 2.2775 |
| 0.825 | 0.08 | 0.41 | 1.315 | 3.665 |
| 0.83 | 0.10 | 0.53 | 1.46 | 4.22 |
--+--------+-------+--------+--------+--------+

NOTE.--The above costs of earthwork are based on the following rates and percentages over the whole city:

Earth, per cubic meter | 0.35 pesos | 50%
Soft sillar | 0.75 " | 20%
Hard sillar | 1.50 " | 20%
Rock (chiefly conglomerate) | 4.00 " | 10%

SUMMARY OF TABLE 11.

+------------------------+-------------+------------+------------+
| DIAMETER | Total labor | Materials. | Total cost |
| OF PIPE : | cost. | Pesos. | per linear |
+--------------+---------+ In pesos. | | meter, in |
| Centimeters. | Inches. | | | pesos. |
+--------------+---------+-------------+------------+------------+
| 10 | 4 | 0.8725 | 3.30 | 4.1725 |
| 15 | 6 | 1.0725 | 4.51 | 5.5825 |
| 30.5 | 12 | 1.565 | 21.35 | 22.915 |
| 38 | 15 | 1.9125 | 22.30 | 24.2125 |
| 45.7 | 18 | 2.2775 | 25.42 | 27.6975 |
| 61 | 24 | 3.665 | 33.20 | 36.865 |
| 76 | 30 | 4.22 | 55.77 | 59.99 |
+--------------+---------+-------------+------------+------------+

The flood destroyed about 1,200 houses in the neighborhood of the river. In a number of blocks the smaller mains were scoured away, but considerable salvage was done afterward, and, as it is the intention of the authorities not to permit rebuilding along the flood-path of the river, these mains do not require reconstruction.

MAIN SEWERAGE SYSTEM.

The Company's obligations, as far as drainage is concerned, were limited to the removal and disposal of sewage, no provision being required for storm-water, which is allowed to find its way to the natural watercourses. Apart from that fact, however, the best system for a city like Monterrey, where rainfall for many months at a time is very scarce, is the strictly "separate system." In the design advantage was taken of the natural topography of the drainage district, which is almost an ideal one for a gravitation system of sewers, the general fall in all directions being northeast; it was also in this direction that the best available land could be obtained for disposal purposes.

Plate XX shows in skeleton form the general lay-out of the sewers. Two drainage districts are arranged, divided by Calle de Washington, which may be regarded as practically the center of the city, and each of these districts has an independent main collector connecting to the outfall sewer at the northeast extremity of the city.

The system has been designed so that extensions may be made and may cover any part within the city limits; the main collectors are large enough for the whole area when fully built up.

The sewers are designed on a very liberal basis, namely, on the assumption that when flowing half full the quantity to be dealt with will be 380 liters per capita per day, with a maximum rate of flow of 200 per cent. It was assumed that each house would be occupied by 7 persons and have a frontage of 12-1/2 m. The minimum velocities in the sewers, when running full, vary between 0.91 and 1.5 m. per sec., with the exception of a few blocks.

The minimum size adopted was 24.3 cm. (8 in.) in internal diameter. The sewers of diameters between 24.3 and 50 cm., are 0.91 m. (36 in.) long, and are of salt-glazed vitrified clay, imported from San Antonio, Tex.

Table 12 gives the details of the length of the various sewers laid.

TABLE 12.--LENGTH OF SEWERS.

+----------+------------------------------------------+-----------+
|DIAMETER: | | |
+-----+----+ Kind. | Length, |
| cm | in.| | in meters.|
+-----+----+------------------------------------------+-----------+
|24.3 | 8 | Fire-clay | 38,332.85 |
|25.4 | 10 | " | 16,400.69 |
|30.5 | 12 | " | 7,953.15 |
|38.1 | 15 | " | 4,850.56 |
|45.7 | 18 | " | 2,023.40 |
|50.8 | 20 | " | 1,450.53 |
|55.9 | 22 | Reinforced concrete tubes, 6.9 cm. thick | 3,134.20 |
|61.0 | 25 | " " " 7.6 " " | 357.40 |
|68.6 | 27 | Brick and concrete | 484.05 |
|76.2 | 30 | " " " | 662.69 |
| | | | |
| | | Total | 75,649.15 |
+-----+----+------------------------------------------+-----------+

The greater number of the manholes are of brickwork, 23 cm. thick, and have concrete inverts. They have a diameter of 1.2 m., which is reduced to 0.61 m. at the top, and each is provided with a heavy cast-iron frame and closed cover weighing about 190 kg. There are 521 manholes, and they are placed at every block and on long lines about 80 m. apart.

The sewers are flushed with 15-cm. (6-in.) automatic flushing siphons of the Miller pattern with 20-cm. (8-in.) discharge pipes. There are 278 of these siphons, and they are placed in flush-tanks (Fig. 16) built of brickwork and plastered with 1:1 cement mortar. Their capacity varies from 800 to 1,200 liters, and they discharge from 22-1/2 to 28-1/2 liters per sec. They are timed to flush once in 24 hours.

The system is at present ventilated by 23-cm. (9-in.) steel ventilating columns (Fig. 16), with ornamental cast-iron bases. There are 220 of these columns. Most of them are 7.85 m. above the level of the edge of the sidewalk, and are connected to special 15-cm. branch pipes leading from the sewer on the outside of the flush-tanks. In the center of the city they are provided with extension lengths, giving a total height of 12 m.

Table 13 gives the particulars of the average distributed cost of laying the 75.6 km. of sewers.

TABLE 13.--AVERAGE COST, PER LINEAR METER, FOR 75.6 KM.
OF SEWERS, FOR MATERIALS AND LABOR COMPLETE.

+----------+-----------+--------+-----------------------------+--------+
| | INTERNAL |Cost of | EARTHWORK AND LABOR: | Total |
| | DIAMETER | mater- |-------+------------+--------| cost of|
| | OF | ials | | Cost of |Cost of | sewer |
| | SEWERS. |includ- |Average| excavation,|labor |complete|
|Kind of +------+----+ ing | depth | including | in | per |
| Sewer. | | |10-cm. | of | back- |laying | linear |
| | | |(4-in.) | sewer | filling, |(includ-| meter. |
| | cm. | in.|branches| | removing | ing | |
| | | |every | m. | surplus, |hauling,| |
| | | |4-1/2 m.| | etc. | etc.). | |
| | | |Pesos. | | Pesos. | Pesos. | |
+----------+------+----+--------+-------+------------+--------+--------+
|Fire-clay | 24.3 | 8 | 2.00 | 2.10 | 3.46 | 0.21 | 5.67 |
| " | 25.4 | 10 | 2.78 | 2.25 | 3.97 | 0.2625 | 7.0125 |
| " | 30.5 | 12 | 3.64 | 2.50 | 4.705 | 0.305 | 8.65 |
| " | 38.1 | 15 | 6.14 | 2.75 | 5.50 | 0.4375 |12.0775 |
| " | 45.7 | 18 | 8.80 | 3.00 | 6.745 | 0.645 |16.19 |
| " | 50.8 | 20 | 11.30 | 3.50 | 8.275 | 0.815 |20.39 |
|Concrete | 55.9 | 22 | 5.93 | 3.50 | 9.19 | 1.325 |16.445 |
| " | 61.0 | 25 | 7.30 | 3.75 | 11.245 | 1.685 |20.23 |
|One brick}| | | | | | | |
|thick on }| 68.6 | 27 | 7.17 | 3.75 | 11.735 | 3.93 |22.835 |
|concrete }| 76.2 | 30 | 7.925 | 4.00 | 14.53 | 4.515 |26.97 |
|founda- }| | | | | | | |
|tions }| | | | | | | |
+----------+------+----+--------+-------+------------+--------+--------+

The house connections are chiefly of 10-cm. (4-in.) pipes, laid on a minimum gradient of 2-1/2%, from oblique branches on the sewer to siphon intercepting traps near the house, as shown by Fig. 17. From this trap a 10-cm. fire-clay inspection pipe is carried up and capped at the sidewalk level with a cast-iron box having a locked cover. From this inspection pipe a branch is connected to a cast-iron fresh-air inlet, in most cases set in the wall of the house, the inlet being 30 cm. above the level of the pavement.

_Effect of the Flood on Sewers._--The flood of August 27th and 28th, 1909, partly destroyed one of the main collectors, which was laid along the banks of the river and encased in concrete. This has now been relaid farther north, and out of the way of any future floods. The total length of the new sewers replacing those damaged amounts to 1200 m., and they vary in internal diameter from 20 to 55.9 cm. (8 to 22 in.).

MAIN OUTFALL SEWER.

The direction of the main outfall sewer was determined after a thorough study of all the available land lying to the north and northeast of the city, as it was the intention of the Company to utilize for irrigation purposes the sewage and any surplus waters that might be developed. The best available site was found to be about 12 km. north of the city, a little northwest of the village of San Nicolas de los Garzas, as shown on Plate II. The long length of outfall required was justified by the cheap cost of the land and its excellent character for sewage irrigation. The sewer was designed for a capacity of 90,000,000 liters a day (36.76 cu. ft. per sec.) in order to allow for conveying surplus waters as well as sewage.

The outfall intercepts the two main branches of the city sewers at Calle de Allende and Calle de Tapia, and its total length is approximately 11,900 m. The chief type adopted is shown on Plate XXII. It is formed with an invert of radial bricks laid in 1:2 cement mortar, on a foundation of 1:3:5 concrete approximately 7 cm. thick. As the ground was chiefly in hard sillar, only a little concrete was required to mould the bottom to the correct shape. The arch was formed of special radial bricks, 15 cm. (6 in.) deep, laid in cement mortar. These bricks were adopted in preference to concrete, owing to the heavy cost of sand and rock, due to the long haul, and for the purpose of obtaining rapid work. Plate XXI shows the sewer arch, and one of the ventilating columns and manholes. The bricks were obtained from the local brick plant, and form a very satisfactory material for sewers, being well burnt, thoroughly hard, and absorbing not more than 7-1/2% of their weight of water. The contract prices for the labor on the brickwork were 1.25 pesos per sq. m., and 1.38 pesos for the arch.

The general route of the sewer is very direct, long straight lines of several kilometers being possible, and these were joined by curves of approximately 30 m. radius. The gradient of the sewer invert is 0.2% (1 in 500) which is approximately the general fall of the ground northward from Monterrey.

The total quantity of excavation was as follows:

No. 1, soft earth 8,960 cu. m.
No. 2, sillar 18,492 " "
No. 3, conglomerate rock 9,822 " "
------
Total 37,274 cu. m.

The contract prices for this excavation were: for No. 1, 32 cents; No. 2, 85 cents; and No. 3, 2.17 pesos per cu. m.

All the excavation was in perfectly dry ground. Where the sewer was partly out of the ground it had a foundation of concrete, 1.75 m. wide, from 15 to 23 cm. thick, below the bottom of the brickwork, and carried up to the springing of the arch, and a well-tamped embankment, with slopes of 1-1/2 to 1, to protect the sewer to a height of 30 cm. (12 in.) above the arch. For 342 m. at the Monterrey end of the line, the sewer was constructed in tunnel, from, the open end and from two intermediate shafts. The tunnel throughout was in sillar, and the contract price for excavation was 24.50 pesos per lin. m. This work was done without timbering of any kind, except at the shaft lengths. Plate XXII shows the lining of the tunnel, which was of concrete with a brick invert. At four places the sewer passes under main railway tracks, which at these points were carried on steel girders supported on concrete abutments, the sewer being carried under the tracks in the ordinary way.

_Bridges._--At three points the sewer was carried over arroyos on reinforced concrete girders. No. 1, at Station 5,600, consisted of four 10-m. spans; No. 2, at Station 8,365, over the Estanscia Arroyo, consisted of nine 10-m. spans; and No. 3, at Station 8,960, over the Topo Chico Arroyo, consisted of three 10-m. spans. One of these bridges is shown on Plate XXIII. They were designed as two parallel continuous girders with connecting top and bottom slabs. The concrete for the girders was a 1:2-1/2:3-1/2 mixture, the sand being from the crusher and the rock gauged to pass a 19-mm. (3/4-in.) screen. The inside was rendered with a coat of 1:1 cement mortar, 7 mm. thick, for water-tightness.

The piers of the Estanscia Bridge (Plate XXIII) were carried down through soft earth to a stiff clay from 4-1/2 to 6 m. below the surface, and the foundations were spread so that the pressure would not exceed 1 ton per sq. ft. The ends of the bridges were protected by rubble wing-walls supporting the embankment over the sewer. A 1:3:5 concrete was used for the upper part of the piers, and the lower part was of the same mixture with 30% of large boulders. There are 70 manholes (Fig. 19) along the line of the sewer, and they vary from 150 to 230 m. apart. The sewer is ventilated with 30 concrete towers (Fig. 18, and Fig. 2, Plate XXI), 2.9 m. high, having 20-cm. (8-in.) shafts.

The works for the outfall sewer were carried out satisfactorily under a contract with Mr. John Phillips, of Mexico City, the Company supplying the greater part of the materials. The work was begun on March 16th, and finished on November 12th, 1908.

SEWAGE DISPOSAL WORKS AND IRRIGATION LANDS.

For the purpose of disposing of the sewage and using it profitably, the Company purchased 909 hectares (2,246 acres) of land from the Community of San Nicolas de los Garzas, the outfall sewer being carried to the southwestern boundary of the land acquired. This area has a general fall in all directions to the northeastern boundary, with a gradual fall of about 25 m. across the diagonal of the land. The area purchased was practically virgin land, only small portions having been cultivated. The greater part was covered with a growth of mezquite trees and small shrubs. The quality of the land is excellent, if properly irrigated, and capable of yielding abundant crops of every description. The limits of this land are shown on Plate II.

_Sewage Purification Tanks._--For the purpose of obtaining a satisfactory effluent to discharge on the land without causing nuisance, the Company built a system of detritus chambers and liquefying tanks at the end of the outfall sewer. One difficulty to be faced, in designing these works, was the fact that there were no data regarding the probable quantity of dry-weather sewage, nor any particulars as to its general character; there was also the probability that the outfall sewer would have to carry large quantities of surplus water. Therefore, the system was designed so as to be capable of extension if necessary, and the sizes of the various tanks were limited at present, because of the septic processes which would be set up in the long length of outfall sewer. The tanks were designed to deal with 10,000,000 liters of sewage proper per day, and the channels, etc., were proportioned to take the full flow of the sewer if necessary. Provision was also made for discharging large volumes of surplus water directly on the land, independent of the tanks. To do this a by-pass was taken from the sewer a short distance before reaching the site of the tanks. By properly timing the flow, arrangements could be made to discharge these waters in the early hours of the morning, by allowing the scour-pipes in the distribution system to be opened at night when the domestic sewage flow was at its minimum. As the area of land available is very great, the degree of purification in the tanks was relatively unimportant; the object to be obtained consisted chiefly in distributing on the land an effluent which would be innocuous and clear.

The general design of the works is shown on Plate XXIV, and they consist essentially of a screen chamber, duplicate detritus tanks, and three liquefying tanks. There is also a sludge-pit 629 m. from the tanks.

_Screen Chamber and Detritus Tanks._--Enlarged details of the screen chamber are shown on Plate XXV. The invert, where the sewer enters the screen chamber, is 489.45 m. above datum. This chamber has duplicate screens which are fully detailed on Plate XXX. For cleaning purposes the screens are raised by a steel-framed head-gear, which is arranged so that they may be lowered to a small traveling bogie, out of the way of the screen chamber.

From the screen chamber there are two main channels, 1.22 m. wide, branching to the two concrete detritus chambers. Each channel has a square penstock, so that the sewage can be diverted into either chamber when necessary.

The detritus chambers are octagonal in plan, 4 m. in diameter, and each is provided with an outlet weir 1.50 m. wide. At the weir level the chambers have a depth of 1.75 m., with drainage channels below that level. The coping is 1 m. above the outlet weir of the detritus tanks. To drain off these chambers, each has a scour-out pipe, 30 cm. in diameter, controlled from valves with spindles carried above the coping level. Each of these pipes is connected to a central chamber, and leads to a 56-cm. (22-in.) sludge-pipe. The chambers as designed are of smaller capacity than those usually provided, but, as all surface water is strictly excluded from the sewerage system, the quantity of detritus reaching the chambers may be small. The velocity through them when both are in use will be approximately 0.082 m. (0.27 ft.) per sec.

From these chambers the sewage is carried to the three liquefying tanks by a main channel, 11.5 m. long and 1.50 m. wide.

The tanks are of concrete and have reinforced concrete roofs. Each is 66 m. long and 6 m. wide; the minimum depth for the sewage is 1.50 m. at the outlet end, and 2.25 m. at the inlet, increasing to a maximum depth of 2.75 m. at the lowest depth at the scour-out channel. Their combined capacity is 2,500,000 liters, which is equivalent to 6 hours' flow of the quantity of sewage for which they were designed. The sewage passes from the main channel, through penstock-valves which control the flow, into one or the other of the tanks. From these valve openings it flows over concrete weirs, 5 m. long, and is deflected to the bottom of the tank by a reinforced concrete scum-plate, extending across each tank, with a clearance of 15 cm. at each end. This scum-plate is 1.5 m. deep and 10 cm. thick, and is placed 40 cm. from the end walls.

The details of the concrete division and outside walls are shown on Plate XXIX. The floor was constructed in two layers, and its surface is divided into 6 channels formed by small walls, 20 cm. wide and 15 cm. deep, the object of these channels being to facilitate the cleaning of the floor by scouring it out to a specially arranged channel at the deepest point of the tank, near the inlet end. Each scour-out channel has a 30-cm. (12-in.) gate-valve, controlled from the roof of the tank, the three scour-pipes meeting in a concrete chamber outside of the tanks, from which a 56-cm. (22-in.) concrete pipe discharges the contents of the tanks to the sludge-pit during cleaning operations. The velocity through the tanks, when they are used in combination, is 0.0253 m. (0.083 ft.) per sec., the tanks being made as long as economically possible, in order to obtain this low velocity and thus permit the proper sedimentation of the suspended matters. The roof of each tank is 1 m. above the weir level. Each tank has four ventilating columns, 3.7 m. high and 30 cm. in diameter, vitrified clay pipes, with an exterior casing of contrete, being used for the shafts. The roof is enclosed within parapet walls, and is covered with a layer of earth 25 cm. thick.

The outlet channel from the tanks leads to a measuring chamber, 3 m. square, as shown on Plate XXIX. This chamber is fitted with penstocks, 1.83 m. wide, and measuring weirs. From this chamber the sewage is delivered to two main irrigation ditches, which distribute the sewage in two directions, one northward and the other to the western extremity of the lands.

_Construction of Tanks._--The excavation for the tanks was in soft earth for a depth of 1-1/2 m.; the lower depths were in a firm foundation of sillar and calcareous clay. The total excavation in the tanks, channels, etc., was 8,335 cu. m., and the actual cost was 45-3/4 cents per cu. m. To facilitate the construction, about six-tenths of the concrete beams were cast as single monoliths and placed in position by sliding them across the tanks on temporary timbers. The remainder of the beams, the roof, and the slab were placed in position in the ordinary way with timber forms. The total quantity of concrete placed was 1,360 cu. m. A 1:2-1/2:4-1/2 concrete was used for the walls, channels, etc., and a 1:2:3 mixture for the roof slab and beams.

Table 14 gives the average cost per cubic meter for all the concrete work.

TABLE 14.--AVERAGE COST PER CUBIC METER FOR CONCRETE IN TANKS.

+-----------------------------------------+-----------+-----------+
| | Pesos per | Pesos per |
| | cubic | cubic |
| | meter. | meter. |
+-----------------------------------------+-----------+-----------+
| LABOR : | | |
| Mixing and placing | 5.20 | |
| Carpenter work in forms, framing, etc. | 4.20 | |
| | _____ | |
| Total labor cost | | 9.40 |
| | | |
| MATERIALS : | | |
| Screened gravel | 4.04 | |
| Sand (from neighboring arroyo) | 4.98 | |
| Cement (including hauling) | 15.19 | |
| Lumber, nails, and other supplies | 1.90 | 26.11 |
+-----------------------------------------+-----------+-----------+
| Total cost of concrete per cubic meter 35.51 |
+-----------------------------------------------------------------+