+-----------------------------------------+-----------+-----------+ | | 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 | +-----------------------------------------------------------------+ _Sludge-pit._--The sludge-pit, used when cleaning out the tanks, is carried 639 m. northward, far enough to get the available fall to drain the bottom of the detritus chambers and liquefying tanks. The drainage pipe was formed of 56-cm. (22-in.) concrete tubes. The sludge-pit is merely an excavation in the earth 20 m. square and 2 m. deep, the sides having a slope of 1-1/2 to 1. An overflow drains the pit to an irrigation ditch, the solid matter being allowed to settle and the liquid to drain off. From time to time it is proposed to dig out the solids and plow them into the land. _General._--To the east of the tanks a 3-roomed house has been built for the inspector. In order to provide a good supply of water for cleaning operations, a well 22 m. deep has been sunk and is fitted with pumps operated by an Eclipse windmill, 4 m. in diameter, on a tower 22 m. high, which delivers the pump water to a circular wooden tank of 20,000 liters capacity. The work in connection with the purification tanks was carried out by the Company's own staff; it was begun on September 10th, 1908, and practically completed by the first week in January, 1909.