Stretching for six and one-half miles along the Mahoning River, in the lowlands of Milton Township, the Milton Reservoir of the Youngstown, Ohio, water plant lies nearly ready for use as the source of the city’s supply. Only a comparatively small portion of work remains to be done before the gates can be closed. The reservoir, designed and built under the direction of F. M. Lillie, city engineer, took three years to complete. Throughout the Milton basin trees, houses, barns and structures of all kinds have been removed. A portion of the basin during the process of clearing is shown in Figure 1. Except for a few patches of corn yet to ripen and be reaped and some debris at the dam where last touches are due, the part adjacent to the dam is ready for filling.

Not only will the dam be used as a source of water supply, but the immediately surrounding territory will be fitted up as an amusement resort. Pleasure craft will be permitted to utilize the lake, and swimming will also be allowed. The dam is located seventeen miles east of Youngstown, but as the river to be dammed flows, the distance is about thirty-five miles, so that the water must flow this distance before reaching the filter plant. To take care of future automobile routes along the lake, three bridges have been constructed across the basin. The Palmyra bridge, shown in Figure 2, is the easterly structure and crosses some two miles west of the dam. The Fredericksburg bridge reaches across the lowland three miles farther west. Less than a mile beyond this, near the farthest extremity of the reservoir, the Schillings Mill bridge parallels the others. The viaducts are built of concrete and steel and are shaped along artistic lines.

The outstanding feature of the undertaking is the dam itself. It is 2,800 feet in length, curving slightly toward the southwest at the south end where the engineers have taken advantage of the topography of the land. It is earthen, except for the spillway, with concrete and stone reinforcement, and is 180 feet high, and will have a concrete promenade crest twenty feet in width, traversed on the west side by a concrete abutment to ward off spray and wages in windy weather. The soil, of which 200,000 cubic yards was used in the dam, is of a clay consistency and bolds well together. The spillway is situated in the northern section of the dam at the natural bed of the stream, as shown in Figure 3. It is 635 feet long, and tapers down from ten foot width at the crown to 50 foot width 63 feet below the surface. The spillway is of the cyclopean type, of solid concrete construction. Its top is rounded off instead of flat, with the back face slotting outward to the pool level below where an outward curve formation will deflect the water from the base, shown in Figure 4. This style of construction anticipates an overthrow of water at the crest. This type of construction eliminates the heavy wear on the supports just below the edge of the apron experienced when the water merely falls over without the gliding motion.

Fig. 3. Spillway in Northern Section of Dam, at Natural Bed of Stream.Fig. 2. Palmyra Bridge Across the Basin, Youngstown, Ohio, Water System.

There are 52,500 cubic yards of concrete in the spillway, over which it is expected the water will flow for the greater part of the year.’ With an area of 1,700 acres in which to hold the precipitation from a 290-square mile water-shed and with supplementary supply from Mosquity Creek, draining 125 miles, North Branch, 100 miles; West Branch, 75 miles, and Mill Creek, 90 miles, on the way to Youngstown, it is conceded the city can be provided with a minimum daily supply of seventy-five to one hundred million gallons. At present the minimum flow during extended hot weather is fifteen million gallons at Youngstown, nine million gallons of this supply coming from the confluent streams below Milton. As the minimum flow at Milton very often is as low as six million gallons, it is evident that there will be periods when the spillway will not have water flowing over it. During the dry periods the larger conductor pipes in the regulating section abutting the spillway at the northerly approach will be employed to give outlet to sufficient stored supply to maintain the requisite daily flow Four such pipes were installed, although two would have served the present needs.

Immediate benefits to be felt are three in number, the authorities state. First, the dam will act as a flood control; second, the temperature of the water in the city mains will be considerably lower. The column of water in the river channel here will be six times its present size, thereby lowering its temperature. Third, stream pollution will be lessened. A sweeping river will carry off filth that nowlags in the shallow waters and hazard from this source will be greatly lessened. The overall costs of the project are: Land rights, $243,000; dam, $544,000; new roads, $215,000; clearing the area to be inundated, $98,000; total, $1,100,000.

Fig. 4. Outward Curve Formation of Spillway.Inner Face of Dam, Youngstown, Ohio.

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