AXTOFAGASTA RAILWAY WATERWORKS. 123 



At Palpana and Polapi the springs are collected into a central 

 chamber by means of covered channels, and the mains carry the 

 collected water to San Pedro. 



At Siloli a small dam has been built across the stream which 

 has a daily flow (with very slight variations) of 11,300 cubic 

 metres, or, say, 2,500,000 gallons. The draw-off for the main 

 to San Pedro is carried through the dam. The author believes 

 that this is probably the highest intake of any waterworks under- 

 taking in the world, although the Department has charge of a 

 small station supply on the Collahuasi branch of the railway, 

 where the intake is at an altitude of over 15,000 feet. 



On the San Pedro Eiver, which at the Company's intake is 

 in a narrow gorge, three contiguous chambers have been built 

 across the bottom of the gorge, and the river passes into the 

 centre chamber, and overflows a weir placed in the rear wall. 



In the division walls between the chambers, weirs have been 

 cut at a slightly lower level than the weir in the end wall, so 

 that these chambers are always maintained full. The photo- 

 graph (Plate I) shows the intake with the San Pedro volcano in 

 the distance. 



The storage reservoirs situated in San Pedro at a height of 

 10.680 feet above sea-level at Antofagasta are four in number, 

 and have a total capacity of 28,000 cubic metres. 



They are excavated in the solid rock, which, at this point, 

 comes up to ground level without any earth covermg whatever. 

 They are rectangular in plan and the walls are made smooth and 

 vertical with concrete. The draw-off arrangements have nothing 

 unusual to remark upon. 



It may be here mentioned that the rarefied atmosphere at 

 these altitudes, and more especially at Siloli, renders exertion 

 difTficult. Mountain sickness generally overcomes British people, 

 but the Bolivian Indian, who lives at altitudes between 12,000 

 and 17,000 feet, proves equal to the labour required in construc- 

 tion, and the amount of work which can be got out of him is 

 surprising. 



Pipe Lines. 



The waterworks department of the railway is responsible for 

 the water supply at all stations on the line, the sale of water 

 in the towns of Calama and Sierra Gorda in the interior, and the 

 ports of Antofagasta, Mejillones and Coloso on the coast, as well 

 as the sale of water in bulk to the nitrate oficinas which are 

 situated close to the railway. 



The total population in the region served by the waterworks 

 department is about 85,000. 



The stations beyond the reservoirs in San Pedro are supplied 

 from small independent works, by means of pipe lines carried 

 into the hills, where small springs fed from the melting snow 

 are sufficient to meet the locomotive and station requirements. 



