The piers of the Estanscia Bridge (Plate XXIII) were carried down through soft earth to a stiff clay from 4-1/2 to 6 m. below the surface, and the foundations were spread so that the pressure would not exceed 1 ton per sq. ft. The ends of the bridges were protected by rubble wing-walls supporting the embankment over the sewer. A 1:3:5 concrete was used for the upper part of the piers, and the lower part was of the same mixture with 30% of large boulders. There are 70 manholes (Fig. 19) along the line of the sewer, and they vary from 150 to 230 m. apart. The sewer is ventilated with 30 concrete towers (Fig. 18, and Fig. 2, Plate XXI), 2.9 m. high, having 20-cm. (8-in.) shafts. [Illustration: FIG. 18.--DETAILS OF VENTILATORS ON OUTFALL SEWER.] [Illustration: FIG. 19.--DETAILS OF MANHOLES ON OUTFALL SEWER.] The works for the outfall sewer were carried out satisfactorily under a contract with Mr. John Phillips, of Mexico City, the Company supplying the greater part of the materials. The work was begun on March 16th, and finished on November 12th, 1908. SEWAGE DISPOSAL WORKS AND IRRIGATION LANDS. For the purpose of disposing of the sewage and using it profitably, the Company purchased 909 hectares (2,246 acres) of land from the Community of San Nicolas de los Garzas, the outfall sewer being carried to the southwestern boundary of the land acquired. This area has a general fall in all directions to the northeastern boundary, with a gradual fall of about 25 m. across the diagonal of the land. The area purchased was practically virgin land, only small portions having been cultivated. The greater part was covered with a growth of mezquite trees and small shrubs. The quality of the land is excellent, if properly irrigated, and capable of yielding abundant crops of every description. The limits of this land are shown on Plate II.