Mohave County miner and our mineral wealth., 1921-07-15
MAIN CHA DAM ...'... ..... ~
 SLAB FINISHED

The main slab of the great Florence diversion dam was completed last | week and the race to finish the work to an extent that would make the structure safe against the frequently high waters of the Gila River was won. It is the only large Indian weir in the United States, following close ly the models of British engineers. The types of weirs in India have been adapted in several constructions in this country, but the Florence dam is purely Indian. The dam will serve the Florence, Casa Grande irrigation project, the oldest in Arizona.
 The work was begun in February by Maj. c. R. Olberg, under direction of the Indian Service officials. Light spring rains failed to interrupt the work, which went on with increasing intensity, latterly night and day. The construction of the superstructure will go on more leisurely because the foundation will prevent damage from flood waters.
 A permanent diversion headworks and irrigation system is provided by the dam and canal system. The pro- ject embraces 62,000 acres-35,000 acres of Indian lands on the Gila River Reservation, and 27,000 acres belonging to white men around Flor ence and Casa Grande. A total of 27,000 acres will be irrigated.
 Long Dap
 The dam itself is 40 feet long but with the shearing away of the rock wall on one side will provide for a discharge of water 800 feet wide. Counting the spillway aprons the dam is 240 feet wide, and the height is IA feet above the river bed.
 All the diversion gates will be To- cated on the south side, the north side canal being small and supplied through concrete bore in the main dam. The south-side canal will be forty feet wide at the bottom. Its capacity will be 10Oo second feet.
 The intake gates will be of the skimming type, hinged at the bottom and lying flat when fully opened. The current of the river will be kept to the south side by four sluiceways on that end, and these will provide for the discharge of loose silt. The set- ting basins and silt gates will be in the canal, just below the dam.
 Branch for Indians
 The canal will be run southwest to a point about seven miles southwest of Florence. At that point the branch canal to the Indian reservation will lead off through the Wentworth sec tion, past Casa ruins, nine miles west of Florence, and will empty into the Little Gila canal on the reservation to supply the Indian lands below.
 The main canal will continue south and empty into the Picacho reservoir, from which the Casa Grande lateral leads west by south, across the South ern Pacific Railway, and ends at a point few miles southwest of Casa Grande. This will irrigate the lands of the Casa Grande unit that are in cluded in the project.
 In 1887 there were a dozen ditches cut to the Gila, near Florence, by the settlers who thus provided irrigation for considerable acreage. In that year all the water rights were joined in the original Florence canal. This ran southwest across the desert to Mcclellan Wash, where a bank was thrown across the lowlands to form the Picacho reservoir. The canal on the west, toward Casa Grande, was next built, and a rock-fill dam install ed in the river at the heading of the canal. This was at almost the same location of the present dam.
 Store Flood Waters
 This system appeared satisfactory until a few years ago discussion be- gan of plan. to store the flood waters at the Buttes, three miles above the