METHODS AND COST OF CULVERT CONSTRUCTION.
Culvert work is generally located on the line of a railway or a highway, so that the facilities for getting plant and materials onto the work are the best, and as culverts are in most cases through embankment, under trestle or in trench below the ground level the advantage of gravity is had in handling materials to mixer and to forms. Ordinarily individual culverts are not long enough for any material economy to be obtained by using sectional forms unless these forms are capable of being used on other jobs which may occasionally be the case where standard culvert sections have been adopted by a railway or by a state highway commission. Various styles of sectional forms for curvelinear sections are given in Chapter XXI, and centers suitable for large arch culverts are discussed in Chapter XVII. Figure 169 shows an economic form for box sections; it can be made in panels or with continuous lagging as the prospects of reuse in other work may determine. For curvelinear sections of small size some of the patented metal forms have been successfully used.
BOX CULVERT CONSTRUCTION, C., B. & Q. R. R.—Mr. L. J. Hotchkiss gives the following data. Box sections of the type shown by Fig. 169 are used mostly; they range in size from single 4×4-ft. to double 20×20-ft. and triple 16×20-ft. boxes. These boxes are more simple in design and construction than arches, and for locations requiring piles they are less expensive. The form work is plain and the space occupied is small as compared with arches, so that excavation, sheeting and pumping are less and the culvert can be put through an embankment or under a trestle with less disturbance of the original structure. Finally, less expensive foundations are required.
For small jobs where it does not pay to install a power mixer a hand power mixer mounted on a frame carried by two large wheels has been found at least as efficient as hand mixing; more convenient and easier on the men. The machine is turned by a crank driving a sprocket chain; it is charged at the stock piles and then hauled to the forms to be discharged. Local conditions determine the capacity of power mixer to be used. Difficulties in supplying material or in taking away the concrete may readily reduce the output of a large machine to that of one much smaller, and the small machine is cheaper in first cost and in installation and operation. Where the yardage is sufficient to justify the installation of equipment for handling the materials and output of a large mixer it is found preferable to a small one, as the increase in plant charges is not proportionately so great as the increase in the amount of concrete handled. Again it may occur on a small job that the concrete must be taken a long distance from the mixer, that a large batch can be moved as quickly and as easily as a small one and the time consumed in doing it is sufficient for the charging and turning of a large mixer before the concrete car or bucket returns to it. Here a large mixer, while it may stand idle part of the time, is still economic.
Fig. 169.—Box Culvert and Form, C., B. & Q. R. R.
The plant lay-outs vary with the local conditions, as the following will show. In one case of a culvert located under a high, short trestle the following arrangement of plant was employed: A platform located on each side of the approach embankment about 8 ft. below the ties was built of old bridge timbers. A track was laid on each platform and ran out over a mixer located on the end slope of the embankment. Two mixers, one for each platform, were used. From each mixer a track led out over the culvert form and a track along the top of this form ran the full length of the culvert. Gravel and sand were dumped from cars onto the side platforms and thence shoveled into small bottom dump cars, which were pushed out over the mixer and dumped directly into it. Cars on the short tracks from mixers to culvert form took the mixed concrete and dumped it into the distributing cars traveling along the form. The cars were all hand pushed.
An entirely different lay-out was required in case of a long box culvert located in a flat valley some 600 ft. from the track. A platform was built at the foot of the embankment with its outer edge elevated high enough to clear two tracks carrying 5 cu. yd. dump cars. The sand and gravel was dumped from cars onto the side of the embankment, running down onto the platform so that scraper teams moved it to holes in the platform where it fell into the dump cars. These cars were hauled by cable from the mixer engine and dumped at the foot of an inclined platform leading to a hopper elevated sufficiently to let a 1½ cu. yd. dump car pass under it. A team operating a drag scraper by cable moved the material up the inclined platform into the hopper, whence it fell directly into the car to which cement was added at the same time. The charging car was then pulled by the mixer engine up another incline, at the top of which it dumped into the mixer. The concrete car was hauled up another incline to a track carried on the forms and reaching the full length of the culvert work.
The placing of the reinforcement is given close supervision. When a wet concrete is used it is found necessary to securely fasten the bars in place to prevent them being swept out of place by the rush of the concrete. A method of supporting the invert bars is shown by Fig. 169; 2×2-in. stakes are large enough and they need never be spaced closer than 6 ft. The longitudinal bars are held on the stakes by wire nails bent over and the transverse bars are wired to them at intersections by stove pipe wire. The vertical wall bars are placed by thrusting the ends into the soft footing concrete and nailing them to a horizontal timber at the top; the horizontal wall bars are wired at intersections to the verticals. In the roof slab the stakes are replaced by metal chairs, or by small notched blocks of concrete.
The form construction is shown by Fig. 169. It is not generally made in panels, since, as the work runs, the locations of boxes of the same size are usually so far apart that transportation charges are greater than the saving due to use a second time. No general rule is followed in removing forms, but they can usually be taken down when the concrete is a week old.
The boxes are built in sections separated by vertical joints, one section being a day's work. The vertical joints are plain butt joints; tongue and groove joints give trouble by the tenons cracking off in the planes of the joints. A wet mixture is used and smooth faces obtained by spading.
ARCH CULVERT COSTS, N. C. & ST. L. RY.—The cost of arch culvert construction for the Nashville, Chattanooga & St. Louis Ry. is recorded in a number of cases as follows:
18-ft. Arch Culvert.—Mr. H. M. Jones is authority for the following data: An 18-ft. full-centered arch culvert was built by contract, near Paris, Tenn. The culvert was built under a trestle 65 ft. high, before filling in the trestle. The railway company built a pile foundation to support a concrete foundation 2 ft. thick, and a concrete paving 20 ins. thick. The contractors then built the culvert which has a barrel 140 ft. long. No expansion joints were provided, which was a mistake for cracks have developed about 50 ft. apart. The contractors were given a large quantity of quarry spalls which they crushed in part by hand, much of it being too large for the concrete. The stone was shipped in drop-bottom cars and dumped into bins built on the ground under the trestle. The sand was shipped in ordinary coal cars, and dumped or shoveled into bins. The mixing boards were placed on the surface of the ground, and wheelbarrow runways were built up as the work progressed. The cost of the 1,900 cu. yds. of concrete in the culverts was as follows per cu. yd.:
| 1.01 bbls. Portland cement | $2.26 |
| 0.56 cu. yds. of sand, at 60 cts. | .32 |
| Loading and breaking stone | .25 |
| Lumber, centers, cement house and hardware | .64 |
| Hauling materials | .04 |
| Mixing and placing concrete | 1.17 |
| Carpenter work | .19 |
| Foreman (100 days at $2.50) | .13 |
| Superintendent (100 days at $5.50) | .29 |
| ——— | |
| Total per cu. yd. | $5.29 |
It will be seen that only 19 cu. yds. of concrete were placed per day with a gang that appears to have numbered about 21 laborers, who were negroes receiving about $1.10 per day. This was the first work of its kind that the contractors had done. It will be noticed that the cost of 42 cts. per cu. yd. for superintendence and foremanship was unnecessarily high.
Six Arch Culverts 5 ft. to 16 ft. Span.—All these arches were built under existing trestles, and in all cases, except No. 2, bins were built on the ground under the trestle and the materials were dumped from cars into the bins, loaded and delivered from the bins in wheelbarrows to the mixing boards, and from the mixing boards carried in wheelbarrows to place. Negro laborers were used in all cases, except No. 5, and were paid 90 cts. a day and their board, which cost an additional 20 cts.; they worked under white foremen who received $2.50 to $3 a day and board. In culvert No. 5, white laborers, at $1.25 without board, were used. There were two carpenters at $2 a day and one foreman at $2.50 on this gang, making the average wage $1.47 each for all engaged. The men were all green hands, in consequence of which the labor on the forms in particular was excessively high. The high rate of daily wages on culverts Nos. 1 and 3 was due to the use of some carpenters along with the laborers in mixing concrete. The high cost of mixing concrete on culvert No. 2 was due to the rehandling of the materials which were not dumped into bins but onto the concrete floor of the culvert and then wheeled out and stacked to one side. The cost of excavating and back-filling at the site of each culvert is not included in the table, but it ranged from 70 cts. to $2 per cu. yd. of concrete.
Cost of Six Concrete Culverts on the N., C. & St. L. Ry. & St. L. Ry.
| No. of culvert | 1 | 2 | 3 | 4 | 5 | 6 |
| Span of culvert | 5 ft. | 7.66 ft. | 10 ft. | 12 ft. | 12 ft. | 16 ft. |
| Cu. yds. of concrete. | 210 | 199 | 354 | 292 | 406 | 986 |
| Ratio of cement to stone | 1:5.5 | 1:6.5 | 1:5.8 | 1:5.8 | 1:6.1 | 1:6.5 |
| Increase of concrete over stone | 16.0% | 9.9% | 6.3% | 12.3% | 8.3% | 5.3% |
| Bbls. cement per cu. yd. | 1.02 | 0.90 | 1.06 | 1.01 | 1.00 | 1.09 |
| Cu. yds. sand per cu. yd. | 0.43 | 0.49 | 0.44 | 0.46 | 0.46 | 0.47 |
| Cu. yds. stone per cu. yd. | 0.86 | 0.90 | 0.95 | 0.89 | 0.94 | 0.94 |
| Total day labor (inc. foremen and supt.) | 702 | 607 | 784 | 726 | 768 | 1,994 |
| Av. wages per day (inc. foremen and supt.) | $1.61 | $1.33 | $1.59 | $1.19 | $1.47 | $1.46 |
| Cost per cu. yd.— | ||||||
| Cement | 2.18 | 1.94 | 2.27 | 1.82 | 2.11 | 2.01 |
| Sand | 0.17 | 0.20 | 0.18 | 0.18 | 0.19 | 0.14 |
| Stone | 0.52 | 0.52 | 0.47 | 0.54 | 0.47 | 0.58 |
| Lumber | 0.88 | 0.43 | 0.48 | 0.43 | 0.31 | 0.57 |
| Unload, materials | 0.23 | 0.17 | 0.18 | 0.18 | 0.16 | |
| Building forms | 1.07 | 0.33 | 0.62 | 0.47 | 0.72 | 0.41 |
| Mixing & placing | 1.59 | 1.74 | 1.69 | 1.35 | 1.23 | 1.26 |
| ——— | ——— | ——— | ——— | —— | —— | |
| Total per cu. yd. | $6.64 | $5.33 | $5.89 | $4.97 | $5.19 | $4.97 |
14-ft. 9-in. Arch Culvert.—Mr. W. H. Whorley gives the following methods and cost of constructing a 12-ft. full centered arch culvert 204 ft. long. The culvert was built in three sections, separated by vertical transverse joints to provide for expansion; the end sections were each 61 ft. long and the center section was 70 ft. long. Fig. 170 is a cross-section at the center; for the end sections the height is 14 ft. 9 ins., the crown thickness is 1 ft. 9 ins., and the side walls at their bases are 5 ft. thick. The concrete was a 1-3-6 mixture, using slag aggregate for part of the work and stone aggregate for a part. The culvert was built underneath a trestle which was afterwards filled in.
Mixing and Handling Concrete.—The height of the track above the valley permitted the mixing plant to be so laid out that all material was moved by gravity from the cars in which it was shipped until finally placed in the culvert. Sand and aggregate were received in drop bottom cars and were unloaded into bins in the trestle. These bins had hopper bottoms with chutes leading to a wheeling platform, which was placed between two trestle bents and extended over a mixer placed outside the trestle. The cement house was erected alongside the trestle at the wheeling platform level and a chute from an unloading platform at track level to the opposite end of the house enabled the bags to be handled directly from the car to the chute and thence run by gravity to the cement house. Sand and aggregate were chuted from the bins into wheelbarrows, wheeled about 23 ft., and dumped into a hopper over the mixer. Water was pumped by a gasoline engine from a well just below the trestle to a tank on the trestle, whence it was fed to the mixer by a flexible connection, a valve so regulating the flow that the necessary amount was delivered in the time required to mix a batch.
Fig. 170.—Section of Arch Culvert, N., C. & St. L. R. R.
The mixer was a No. 5 Chicago Improved Cube Mixer, operated by a gasoline engine; a larger size would have been preferable since a batch required only two-thirds of a bag of cement which had to be measured which required the services of an additional man. The mixer was in operation 194 hours and mixed 7,702 batches (1,217 cu. yds.), or a batch every 87 seconds, or 6.3 cu. yds. per hour. During the last ten days it mixed a batch every 78 seconds while running. The best short record made was 291 batches in five hours, or one batch every 63 seconds, this being at the rate of 58 batches equal to 9.2 cu. yds. of concrete in place per hour, or nearly 1/6 cu. yd. per batch. It took about ½ minute to mix the concrete and about the same length of time to charge and discharge the mixer.
To convey the concrete from the mixer to the culvert walls a 1 cu. yd. drop bottom car was used. This car ran on 30-in. gage tracks carried on a trestle straddling the culvert walls and having its floor high enough to clear the arch. A track ran lengthwise of the trestle over each culvert wall, and a cross track intersecting both with turntables ran to the mixer. Three men handled the car, a round trip to the extreme end of the trestle being made in about 3 minutes. In the meantime the mixer was discharging into a small hopper which unloaded into the car on its return. One only of the three sections, of the culvert was built at a time, both walls being brought up together. After a point had been reached about 2 ft. above the springing on both walls, one track was removed and the other was shifted to the center of the trestle.
Forms.—There was used in the forms 15,000 ft. B. M. of 2-in. dressed lagging for face work, 21,000 ft. B. M. rough lumber for back work, and old car sills for studding. No charge was made for studding except the cost of loading, the cost of the remaining lumber was $16 per M. for dressed and $12.50 per M. for rough. A credit of one-third the cost was allowed for the old material recovered. The total cost of the labor of erecting the material in forms, bins and platforms was $666. The work was done by a bridge crew of white men, the average rate of wages per man, including the bridge foreman's time, being $2.20 per day. In addition a mason at $3.50 per day and a carpenter at $2.25 per day worked with the bridge crew in erecting forms.
Cost.—The cost of the 1,217 cu. yds. of concrete in the culvert was as follows:
| Item. | Per cu. yd. |
| 1.08 bbls. cement at $1.72 | $1.85 |
| 0.47 cu. yd. sand at 30 cts. | 0.14 |
| 0.25 cu. yd. broken stone at 51 cts. | 0.13 |
| 0.8 cu. yd. slag at 26 cts. | 0.21 |
| Lumber in forms, etc. | 0.30 |
| Miscellaneous materials | 0.05 |
| Labor, unloading materials | 0.11 |
| Labor, mixing and placing concrete | 0.42 |
| Labor, building forms | 0.55 |
| Labor, not classified | 0.18 |
| Labor, excavating 40 cts. per cu. yd. | 0.28 |
| Labor, back filling and tearing down forms | 0.10 |
| —— | |
| Total | $4.32 |
CULVERTS FOR NEW CONSTRUCTION, WABASH RY.—The following data relate to culvert work carried out in constructing the Pittsburg extension of the Wabash Ry. in 1903. All the work was done by contract.
Plant I: This plant was located on a hillside with the crushing bins above the loading floor or platform which extended over the top of the mixer, so that the crushed stone could be drawn directly from the chutes of the bins and wheeled to the mixer. The sand was hauled up an incline in one-horse carts and dumped on this floor, and was also wheeled in barrows to the mixer. The proportions used were 4 bags of cement, 4 barrows of sand and stone dust and 7 barrows of crushed stone. A ⅞-cu. yd. mixer was used and it averaged 40 cu. yds. per 10-hour day at the following cost for labor:
| Item. | Per day. | Per cu. yd. |
| 1 foreman | $ 3.00 | $0.08 |
| 3 men charging with barrows | 4.50 | 0.11 |
| 1 man attending engine and mixer | 2.50 | 0.06 |
| 2 men loading concrete barrows | 3.00 | 0.08 |
| 4 men wheeling concrete barrows (100 ft.) | 6.00 | 0.15 |
| 4 men ramming concrete | 6.00 | 0.15 |
| 4 men wheeling and bedding rubble stones | 6.00 | 0.15 |
| ——— | —— | |
| Totals | $31.00 | $0.78 |
Assuming ⅓ ton of coal per day at $3 per ton, we have 2 cts. more per cubic yard for fuel.
Plant II.—At this plant a Smith mixer was used with a loading floor 4 ft. above the ground, this low platform being made possible by having a hole or sump in which the skip receiving the concrete was set. A derrick handled the skips between the sump and the work. The batch was made up of 2 bags of cement, 2 barrows of sand and 4 barrows of stone. The output was 50 cu. yds. per day of 10 hours at the following cost:
| Item. | Per day. | Per cu. yd. |
| 1 man feeding mixer | $1.50 | $0.03 |
| 1 mixer runner | 2.50 | 0.05 |
| 1 derrick engineman | 2.50 | 0.05 |
| 2 tagmen swinging and dumping | 3.00 | 0.06 |
| 6 men wheeling materials | 9.00 | 0.18 |
| 2 men tamping concrete | 3.00 | 0.06 |
| 1 foreman | 3.00 | 0.06 |
| ——— | —— | |
| Totals | $24.50 | $0.49 |
The cost of fuel would add about 3 cts. per cubic yard to this amount.
SMALL ARCH CULVERT COSTS, PENNSYLVANIA R. R.—Mr. Alex. R. Holliday gives the following figures of cost of small concrete culvert work carried out under his direction. The culvert section used is shown in Fig. 171. This section gives a slightly larger waterway than a 36-in. cast iron pipe. Eight culverts, having an aggregate length of 306 ft. were built, using a mixture of Portland cement and limestone and screenings. Each culvert had a small spandrel wall at each end.
The work was done by a gang of six men, receiving the following wages:
| Foreman, | cents | per | hour | 27.5 |
| Assistant | " | " | " | 17.5 |
| Laborers | " | " | " | 15.0 |
| Teams | " | " | " | 35.0 |
The materials were hauled about 1 mile from railway to site of work. Cement, including freight and haulage, cost $1.97 per barrel. Limestone and screenings cost 50 cts. per cu. yd. f. o. b. at quarry. No freight charges are included in cost of any of the materials except cement. The cost of the 306 ft. of culvert was as follows:
| Item. | Total. | Per lin. ft. | Per cu. yd. |
| Labor | $443.14 | $1.45 | $3.35 |
| Stone and screenings | 78.50 | 0.25 | 0.60 |
| Cement | 307.53 | 1.01 | 2.34 |
| Forms | 12.00 | 0.04 | 0.09 |
| ——— | —— | —— | |
| Total | $841.17 | $2.75 | $6.38 |
Fig. 171.—Small Culverts, Pennsylvania R. R.
26-FT SPAN ARCH CULVERT.—The culvert was 62 ft. long and 26-ft. span and was built of 1-8 and 1-10 concrete mixed by hand. The wages paid were: General foreman, 40 cts. per hour; foreman, 25 cts. per hour; carpenters, 22½ to 25 cts. per hour, and laborers, 15 cts. per hour. The cost of the concrete in place, exclusive of excavation but including wing walls and parapet, was as follows:
| Per cu. yd. | |
| 0.96 bbl. cement, at $1.60 | $1.535 |
| 1.03 tons coarse gravel, at $0.19 | 0.195 |
| 0.40 tons fine gravel, at $0.21 | 0.085 |
| 0.32 tons sand, at $0.36 | 0.115 |
| Tools, etc. | 0.078 |
| Lumber for forms and centers | 0.430 |
| Carpenter work on forms (23 cts. hr.) | 0.280 |
| Carpenter work platforms and buildings | 0.050 |
| Preparing site and cleaning up | 0.210 |
| Changing trestle | 0.085 |
| Handling materials | 0.037 |
| Mixing and laying, av. 15½ cts. per hr. | 1.440 |
| ——— | |
| Total per cu. yd | $4.540 |
There were 1,493 cu. yds. of concrete in the work. The excavation cost $463 and the total cost was $7,243.
COST OF RAILWAY CULVERT.—The culvert was for a single track railway and contained 113 cu. yds. of concrete and required 36 cu. yds. of excavation. The figures are given by C. C. Williams as follows:
12-FT. CULVERT, KALAMAZOO, MICH.—A portion 1,080 ft. long of a new channel built in 1902-3 for a small stream flowing through the city of Kalamazoo, Mich., was constructed as an arch culvert of the form shown by Fig. 172. The concrete section is reinforced on the lines indicated by a double layer of woven steel wire fabric. The concrete was approximately a 1 cement, 6 sand and gravel mixture.
Fig. 172.—Cross-Section of Culvert at Kalamazoo, Mich.
The centers were built in sections 12½ ft. long of the form and construction shown by Fig. 173, and a sufficient number was provided to lay twelve sections of invert and six sections of arch. The arch centers were arranged to be uncoupled at the crown; this with the hinges at the quarter points permitted the two halves to be separated and each half to be folded so that it could be carried from the rear of the work through the forms still in place and erected again for new work. When in place the center ribs rested on the side forms which set on the invert concrete and are braced apart by the hinged cross-strut. This cross-strut was the key that bound the whole structure together; the method of removing this key is indicated by Fig. 174. From his experience with these centers the engineer of the work, Mr. Geo. S. Pierson, remarks:
"In work of this kind it is very important to have the centering absolutely rigid so it will not spring when concrete is being tamped against it and thus weaken the cohesion of the concrete. It is also important to have the arrangement such that all the centering can be removed without straining or jarring the fresh concrete. The centers were generally removed in about three or four days after the concrete arch was in place."
Fig. 173.—Center for Culvert at Kalamazoo, Mich.
The invert concrete was brought to form by means of templates, Fig. 173, and straight edges. The side forms were then placed and braced apart by the struts and concreting continued to the skewback plane indicated in Fig. 173. The arch form was then placed; it rested at the edges on the side forms and was further supported by center posts bearing on boards laid on the bottom of the invert. A template, Fig. 175, was used to get the proper thickness and form of arch ring. Outside forms were used to confine the concrete at the haunches but nearer the crown they were not required.
Fig. 174.—Hinged Cross Strut for Center for Culvert at Kalamazoo, Mich.
Much of the work was done when the thermometer, during working hours, ranged from 12° to 25° above zero. When the temperature was below freezing, hot water was used in mixing the concrete and on a few of the coldest days salt was dissolved in the water. In addition each section of the work was covered with oiled canvas as soon as completed, and the conduit was kept closed so far as was practicable to retain the heat. Concreting was never stopped on account of cold weather.
Fig. 175.—Templet for Arch Ring for Culvert at Kalamazoo, Mich.
Account was kept of the cost of all work, and the figures obtained are given in the following tables:
The cost per cubic yard was thus $6.26. Wages were $1.75 per day.
METHOD AND COST OF MOLDING CULVERT PIPE, CHICAGO & ILLINOIS WESTERN R. R.—During 1906, the Chicago & Illinois Western R. R., Mr. O. P. Chamberlain, Chief Engineer, built a number of culverts of concrete pipe with an interior diameter of 4 ft., and 6-in. shells. Fig. 176 shows the forms in which the pipe was molded. Both forms are of ordinary wooden tank construction. The inner form has one wedge-shaped loose stave which is withdrawn after the concrete has set for about 20 hours, thus collapsing the inner form and allowing it to be removed. The outer form is built in two pieces with 2×⅝-in. semi-circular iron hoops on the outside, the hoops having loops at the ends. The staves are fastened to the hoops by wood screws 1¾ ins. long driven from the outside of the hoop. When the two sides of the outer form are in position, the loops on one side come into position just above the loops on the other side, and four ¾-in. steel pins are inserted in the loops to hold the two sides together while the form is being filled with concrete and while the concrete is setting. After the inner form has been removed, the two pins in the same vertical line are removed and the form opened horizontally on the hinges formed by the loops and pins on the opposite side. The inner and outer forms are then ready to be set up for building another pipe.
Fig. 176.—Form for Molding Culvert Pipe.
The concrete used in manufacturing these pipes was composed of American Portland cement, limestone screenings and crushed limestone that has passed through a ¾-in. diameter screen after everything that would pass through a ½-in. diameter screen had been removed. The concrete was mixed in the proportions of one part cement to three and one-half parts each of screenings and crushed stone. All work except the building of the forms was performed by common laborers. In his experimental work Mr. Chamberlain used two laborers, one of whom set the forms, and filled them and the other of whom mixed the concrete. The pipes were left in the forms till the morning of the day after molding. The two laborers removed the forms filled the day before, the first thing in the morning, and proceeded to refill them. The average time the concrete was allowed to set before the forms were removed was 16 hours. Mr. Chamberlain believes that with three men and six forms the whole six forms could be removed and refilled daily. Based on the use of only two forms with two laborers removing and refilling them each day, and on the assumption that a single set of forms costing $40 can be used only 50 times before being replaced, Mr. Chamberlain estimates the cost of molding 4-ft. pipes as follows:
| 2 per cent, of $40 for forms | $0.80 |
| 1.1 cu. yds. stone and screenings at $1.85 | 2.04 |
| 0.8 bbls. cement at $2.10 | 1.68 |
| 10 hours' labor at 28 cts. | 2.80 |
| —— | |
| Total per pipe | $7.32 |
This gives a cost of $1.83 per lineal foot of pipe or practically $7 per cu. yd. of concrete. The pipe actually molded cost $2.50 per lin ft., or $9.62 per cu. yd. of concrete, owing to the small scale on which the work was carried on—the laborers were not kept steadily at work.
The pipes were built under a derrick and loaded by means of the derrick upon flat cars for transportation. At the culvert site they were unloaded and put in by an ordinary section gang with no appliances other than skids to remove the pipes from the cars. As each four-foot section of this pipe weighs about two tons, it was not deemed expedient to build sections of a greater length than 4 ft., to be unloaded and placed by hand. On a trunk line, however, where a derrick car is available for unloading and placing the pipes, there is no reason why they should not be built in 6 or 8-ft. sections.