Samuel M. Gray, M. Am. Soc. C. E., acting in the interest of some American capitalists (who had been induced by Col. J. A. Robertson, of Monterrey, to look into the merits of a concession acquired by him, for building these works), being guided by the Government's proposition to supply the city with water by damming the flood-waters of the Santa Catarina River in the narrow gorge through which the stream emerges from the Sierras, some eight miles from the city, had several soundings made and reservoir sites surveyed in the first two box canons up the river, and prepared and presented to the Government several alternative projects, besides the one mentioned by Mr. Schuyler. Several different dam sites were designated by Mr. Gray, whose investigations extended over some two years, and were finally abandoned after he had designed the general outlay for a complete network of water mains and sewers for the city, on account of the unwillingness of the Government at that time, about 1897, to grant any guaranties as to bonds or income to the concessionaire or his assigns. Mr. Gray did not favor the general scheme of storing flood-waters as a water supply, but strongly recommended to the attention of the Government the greater advantages of deriving the supply from subterranean flow in the river, by an infiltration gallery driven into the water-bearing gravels in the Santa Catarina Canon (only a short distance above the place where Mr. Binckley afterward established his bore-holes across the river). He proposed to take advantage of the steep slope of the river at a turn in the canon, and from the lower end drive a tunnel through a projecting rock spur, which tunnel, though starting well above the ordinary reach of floods, would terminate in water-bearing gravel, at a sufficient depth below the surface of the river-bed to intercept part of the underflow. Mr. Gray, through investigations made under his direction, by Nathaniel Turner, M. Am. Soc. C. E., had ascertained that there was an abundant subterranean flow, and work had actually been started on the proposed tunnel. The results of Mr. Gray's investigations were put at the disposal of Messrs. Mackenzie, Mann & Co. by Mr. Robertson, at whose offices Mr. Binckley prepared the first plans submitted by him for the approval of the Government.