SOME DIFFICULTIES IN OBTAINING A WATER SUPPLY
CAHABA river in a stream of great fluctuations—its daily average winter flow, including East Cahamba creek, being estimated at from 150 000,000 to 200,000,000 gallons, while its dry weather flow is estimated at less than 15,000,000 gallons daily. Its vertical rise and fall it was difficult to determine, but one noted freshet in 1872, known among the natives as the “July fresh.” was said to have risen forty feet above low water. A pump house was designed to meet these conditions, circular in form, fifty-four feet in internal diameter. An excavation was made in earth and rock to about the level of the bed of the stream and the entire surface covered with four feet of concrete, extending to the outside of the wall The wall, which is of brick, laid in cement, is double, with a core of concrete five inches thick. It is fifty inches thick at bottom, and reduced by offsets to forty inches at the doorsill of the first opening, which is at the level of the boiler room floor, thirty-two feet above the bottom. Above this level the wall extends fifteen feet, ami is surmounted by a conical roof. Ample light and ventilation are afforded by windows above high water. It is well provided with ventilating fans and an electric light plant. A masonry inlet, three and one-half by four feet, extends from the river to the pump well just outside the building. The machinery is of the horizontal type, and consists of one Worthington high duty pump, cylinders twenty-eight and threequarter-inch and fifty-seven and one-lmlf-inch. plungers nineteen-inch, and stroke forty-eight-inch, with combiued air pump, and having a capacity of 5,000,000 gallons daily; and one Knowles, directacting, duplex-compound-condensing pump, with outside packed plungers and independent air pump, cylinders thirty-inch and sixty-inch, plungers twentyfour-inch, and stroke thirty-six-inch, and having a capacity of 8,000 000 gallons daily. There are twelve return tubular steel boilers, sixty inches diameter and sixteen feet long, each with separate setting, so that any one may be cut out for repairs or cleaning. Coal is supplied from the company’s own mine, situated less than a half a mile away; whence a little narrow gauge locomotive of about five tons’ weight brings the coal cars os they are loaded in the mine to the boiler room door. After being weighed, they are tlien caught up on an overhead track and dumped directly in front of the boiler doors. A separate swinging car returns the cinders by means of the same overhead track to a dumping car just outside the door. Does any one know of a water company that mines its own coal and gets it delivered so cheaply and conveniently?
From the lumping station the pipe line ascends abruptly, rising 380 feet in the first half mile. To this point two twenty-inch mains, one for each engine, are extended, and connected to a standpipe fifty-five feet in height and six feet in diameter. From the standpipe a thirty-inch cast iron main extends, over rugged ground by an undulating grade, 12,500 feet to the reservoir. Blow-offs are provided at the depressions and air-cocks at the summits. Much of the excavation is in rock. There are two reservoirs located iu a gup upon Shades mountain, at an elevation of 400 feet above the river, and 220 feet above, and nearly five miles from the city. These reservoirs are natural basins, formed simply by building three dams across a valley, and removing the vegetable matter from the bottom. The dams are constructed of clay, with a small natural admixture of sand and gravel, moistened and thoroughly rolled with a grooved roller, in layers from five to six inches in thickness, of uniform texture, without any core wall of either puddle or masonry. The slopes are two to one on both sides, and are protected by a riprapping of sandstone. They are eighteen feet on top. and their maximum heights are respectively forty-three, thirty-two. and eighteen feet
The first reservoir—that is. the one nearest the pumping station – covers an area of seventeen acres, and has a capacity exceeding 110,000,000 gallons. The other—the two being separated by a dam—covers five acres, and has a capacity of 28,000,000gallons. This reservoir is paved throughout with riprapping of sandstone. The delivery and outlet pipes of these reservoirs are arranged so that the water may be pumped into, or drawn from cither or both reservoirs, or it may be pumped round them, direct into thecity. Usually it is delivered near the bottom of the first reservoir, and is drawn out near the top into the bottom of the second, from which it is drawn near the surface into the main, thus securing the full benefit of circulation and sedimentation. From the reservoir the pipe line is about at right angles to the trend of the mountains
On the line are one large creek and two tunnels, one of the latter 150 feet and the other 2,100 feet in length. The latter is through Bed mountain, and in its construction great difficulties were encountered. The northwest portal is in hard limestone, while the other is in stiff, waxy, blue clay. Between the two were encountered chert, shale, sandstone, and iron ore. Slides of slushy material from the top were very troublesome and greatly enhanced the cost. In rock the section is seven by twelve feet. Inearth the excavation was sufficient to admit outside of the masonry, a timber arch of twelve-inch timbers From the reservoir to the north west portal of the tunnel, which is substantially the corporate limits, adistance of 1(5,200 feet, the main is thirty-inch diameter, and is laid to an hydraulic grade of one and one-half per 1,000, being calculated for a delivery of about 11,000,000 gallons daily. From this point 9,400 feetof t weuty-four-inch pipe extends to the centre of the city»being connected to the lateral mains at all street crossings. The distribution system consists of about sixty-six miles of mains of all sizes.
This, briefly, is the physical plant. The quality of the water is excellent, though at times somewhat roiled. The effect of this improved supply is apparent in the health statistics. Mr. Mason, in his book above referred to, cives the death rate from typhoid fever, prior to 1890, at twenty-six and four-tenths per 10.000 Last year the total deaths from typhoid fever originating in the city, out of a population of 4(»,000. was only eight, and of these eight, only five were using hydrant water—another palpable evidence of the value of good water to a community.
Some other statistics may be suggestive, and sj>eei ally interesting to our friends who sell meters, since only about eleven per cent, of attachments are metered.
The daily average consumption for the months of Septeml>er and October for several years past has been as follows:
* Paper read at the eighteenth annual convention of the American Water Works association. Buffalo. N. Y„ Bcptem her. 1899.