_General Construction Scheme._--The concrete mixing plant, which consisted of two No. 1 Smith mixers, was arranged in connection with the bins and hoppers for the rock and sand on the high ground to the west, and from there the material was conveyed on a framed timber gangway carried right across the center of the reservoir, as shown by Fig. 1, Plate XVII. From this central platform the concrete for the columns was filled from stages placed on the top of traveling towers, 5 m. high, which were run between two rows of columns on standard-gauge rails laid on the floor of the reservoir. By this arrangement 24 columns could be filled from each length of track. A main narrow track was also laid right around the reservoir, with the necessary turn-outs. [Illustration: PLATE XVII, FIG. 1.--FILLING PRIMARY BEAMS FROM TRAVELING TOWER, OBISPADO RESERVOIR.] [Illustration: PLATE XV, FIG. 1.--CONSTRUCTION OF WEST SIDE-WALL OF OBISPADO RESERVOIR.] [Illustration: PLATE XV, FIG. 2.--PRIMARY BEAMS AND COLUMNS, OBISPADO RESERVOIR.] [Illustration: PLATE XIV.--DETAILS OF FORMS FOR CONCRETE WORK, OBISPADO RESERVOIR.] The forms for the columns, primary and secondary beams, are shown on Plate XIV. The side forms for the primary beams were struck in 24 hours, so as to economize lumber; but the bottom lumber was left in position for 28 days. To avoid much unnecessary timber, the secondary beam forms were supported at the ends on reinforced concrete corbels cast on the primary beams. For placing the side-walls, a special traveling form was used, the details of which are shown clearly on Plate XIV. At the end of each form an expansion joint of 25 cm. was left to be filled after the roof was placed in position. The concrete was delivered to the wall through stove-pipe chutes, and carefully spaded by workmen in the limited space between the forms and the embankment. The wall form was removed after 36 hours, by loosening the jacks and pulling forward the hooked tie-rods. This form is also shown on Fig. 2, Plate XVI. [Illustration: PLATE XVI, FIG. 2.--TRAVELING SIDE-WALL FORM, OBISPADO RESERVOIR.] [Illustration: PLATE XVI, FIG. 1.--PREPARING FLOOR FOR CONCRETING, OBISPADO RESERVOIR.]