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, 1⅔ part sand, and 3⅓ 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:
The cost of the concrete work in the lower and upper layers can be still further detailed as shown below:
| Lower Layer Concrete. | ||||
| 95.5 cu. yds., 1-2½-6½ concrete. | ||||
| Materials: | Rate. | Per cu. yd. | ||
| Atlas cement | 1.11 | bbl. | $1.35 | $1.50 |
| Sand | .39 | cu. yd. | 1.10 | 0.43 |
| Broken stone (.97 cu. yd.) | 1.23 | tons | 1.35 | 1.66 |
| Miscellaneous, plant, coal, etc. | 1.28 | |||
| Labor: | ||||
| Mixing and placing | $2.09 | |||
| Carpenter work on forms at $24.00 per M. | .34 | |||
| —— | ||||
| Total per cu. yd. in place | $7.30 | |||
| Upper Layer Concrete. | ||||
| 129.2 cu. yds., 1-1¼-1¼-4 concrete. | ||||
| Materials: | Rate. | Per cu. yd. | ||
| Atlas cement | 1.37 | bbl. | $1.35 | $1.85 |
| Sand | .24 | cu. yd. | 1.10 | 0.26 |
| Stone dust (.25 cu. yd.) | .32 | ton | 1.50 | 0.48 |
| Broken stone (.75 cu. yd.) | .96 | ton | 1.35 | 1.30 |
| Lumber | 0.31 | M. ft. | 21.00 | 0.65 |
| Miscellaneous, plant, etc. | 1.32 | |||
| Labor: | ||||
| Mixing and placing | 1.85 | |||
| Carpenter work on forms at $21.00 per M. | 0.66 | |||
| —— | ||||
| Total per cu. yd. in place | $8.37 |