+---------------------------------------------+--------------------+ | | Pesos, | | | Mexican currency. | +---------------------------------------------+--------------------+ | ESTANZUELA SUPPLY : | | | Aqueduct and dam | 502,000 | | South Reservoir | 429,000 | | | ------- 931,000 | | | | | SAN GERONIMO GRAVITY SUPPLY : | | | Aqueduct, tunnel, and infiltration gallery | 223,000 | | Obispado Reservoir | 436,000 | | | ------- 659,000 | | | | | SAN GERONIMO PROVISIONAL SUPPLY , | | | including boring operations, etc. | 130,000 | | | | | CITY WATER DISTRIBUTION SYSTEM | 1,195,700 | | | | | CITY SEWER SYSTEM | 1,036,000 | | | | | OUTFALL : | | | Main outfall sewer | 425,000 | | Sewage purification works | 75,000 | | | ------- 500,000 | +---------------------------------------------+--------------------+ | Total 4,451,700 | +---------------------------------------------+--------------------+ As a general statement, the actual cost of labor is about 33-1/3% of the total cost of the construction work, including materials. Fig. 20 shows in graphic form the amount of the labor pay-rolls and the progress of the work during the whole construction period from 1906 to 1909, inclusive, comprising also that done under contract. [Illustration: FIG. 20.--PROGRESS DIAGRAM SHOWING MONTHLY LABOR PAY-ROLLS DURING THE CONSTRUCTION PERIOD.] TARIFFS AND SANITARY REGULATIONS. _Tariffs._--The tariffs charged for the water and drainage service (Table 17) were approved by the State Government (which accepts the responsibility for their collection), under a compulsory State law which came into force on March 1st, 1910, for the southern portion of the city, and on July 1st, for the northern half, the penalty for non-compliance being a tax of 10% on the monthly rental value of the property, as assessed by the State officials.