The contract includes the construction and subsequent operation of the world's largest waste water treatment plant, located in Atotonilco, in the state of Hidalgo.

The original G&AWS scheme was developed in 1895 when C. Y. O'Connor engineered a scheme to deliver 23 MLD of untreated water to the Goldfields region through the construction of the Mundaring Weir, 530 kilometres of 30” pipeline, and delivered using eight steam-driven pumping stations. A world class engineering feat of the era! Since then this water system has been progressively upgraded, the new Mundaring Water Treatment Plant and pumping stations being the latest of these improvements to be implemented.