Improvements at the Durham Water Plant
The plant of the water company at Durham. N. C., has been in operation since 1886, providing an ample supply of pure water during the entire period. The present population tributary to pipe lines, including such suburbs as receive their supply from this source, is 22,500. There are 40 miles of cast-iron pipe lines varying from 6 to 20 inches in diameter, 215 double-nozzle public fire hydrants and 75 private hydrants. The average distance between hydrants is approximately 610 feet. Total nuntber of taps for domestic and manufacturing purposes approximate 3,370, while there are 1,470 meters in use.
The average daily pumpage amounts, to 1,750,000 gallons and the average domestic pressure is 65 pounds. One 12-inch and one 20-inch cast-iron gravity line connect the 3,500,000-gallon masonry and earth-fill reservoir to the distribution system, the distance from reservoir to center of city being 21,800 feet. Eno river, rising about 25 miles northwest of Durham, provides the supply, which is soft and clear except after storms, when the clay turbidity is heavy. The area of the watershed above the intake is about 115 square miles, and the minimum gauged flow for the dryest year was about 4,500,000 gallons per day.
Future demands exceeding the minimum flow will be met by construction of a masonry dam 40 feet high and 350 feet long near the intake. At present the intake is located in a low masonry and timber dam formerly used for water power pumping plant. The low-lift service at the river raises the water 20 feet to a coagulating basin of 5,000,000 gallons capacity. Secondary coagulating tanks of wood are provided, having about 30minute period, though secondary coagulation is used only in emergencies. The filter equipment consists of Warren type low-head gravity filters, three 10-foot and three 13-foot, with mechanical agitation by rakes. These are driven by a 24-inch Pelton wheel, the discharge from which is used to supplement wash water. From here the high-lift service pumps against a 225-foot head to a gravity reservoir 8,300 feet distant. Recent additions have been made to the Durham system, including one Platt Iron Works centrifugal pump.
14-inch, direct-connected to a Harrisburg Foundry & Machine Works 9×9-inch side crank, self-oiling engine, with double piston valve gear with adjustable cut-off, permitting speed adjustment to meet variable demands of service. This outfit is used for the low-lilt service and exhausts to a new 400-horsepower heater. The pump has a rated capacity of 4,000 gallons per minute against a total head of 35 feet, at 400 revolutions per minute. The new Worthington boiler-feed pump,6x4x6 inches, outside packed, is of the ram pattern. with brass valves for hot water. A 78-inch by 20-foot. 150-pound pressure, horizontal return tubular boiler and a duplex compound engine, 16×26 by 16×24 inches, with a nominal capacity at 100-foot piston speed of 3,000,000 gallons per 34 hours, are also recent additions to the plant. The newly added equipment supplements the following apparatus, which is still in service: A 1,500,000-gallon Blake compound duplex steam pump, for low-lift service; a Worthington 8-inch centrifugal pump, belted to Lane and Bodyle 8xl0-inch side-crank engine, also for low-lift service; a 2,260,000-gallon Bethlehem beltdriven power pump and a Bethlehem 1,500,000gallon pump, belted from extended shaft of the 14×36-inch Hamilton Corliss Engine; one Blake 1,500,000-gallon duplex compound noncondensing pumping engine. The last three mentioned pumps are for high-lift service. The boiler equipment consists of two 100-horse-power horizontal return tubular boilers with independent steel stacks, connected to a W orthington 6x4x6-inch piston-pattern boiler-feed pump. The accompanying illustrations show a general view of the interior of the pumping station and the new duplex compound pumping engine of 3,000,000 gallons capacity daily. J. C. Michie is superintendent of the plant, and it is due to his management that the present high efficiency of the Durham water works is maintained.