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ashlar on the upstream face and partly with rubble and partly with dressed ashlar on the downstream face and is provided with an overflow 100 feet long about the centre of its length. The cement concrete, with the exception of the backing of the upstream ashlar face, tapering from 10 feet thick at the base of the dam to 5 feet thick at the crest, which is in the proportion of 4 to 1, is mixed in the proportion of 6 to 1 and contains displacers. The height of the dam above the original stream bed is 90 feet and, from the lowest foundation level to the crest, 110 feet. A valve-well, containing four 10-inch draw-offs, connected with a 12-inch stand-pipe, which is in direct communication with the 18-inch suction main to the pumping station, is constructed in the dam and is surmounted with a valve-house. A Venturi meter (with recorder in the valve-house) registers the amount of water passed down to the pumps. The contents of the dam are:--
Cement Concrete, 24,520 Cubic Yards. Ashlar Masonry, 47,755 Yards. Rubble Masonry, 451 Feet. 17(ii). Pumping Station. The pumping station has been erected on a site well below the proposed low level reservoir and excavated out of the hillside, the material so obtained being utilized to form a reclamation where junks can come alongside and discharge coal. The buildings are substantial structures and comprise a commodious engine house, boiler house, workshop and store. Quarters for a European overseer have been constructed on a site 100 feet above the station overlooking Tytam Bay, whilst those for the Chinese staff of engine drivers and stokers are situated close to the station. The main flue from the boiler house is carried up the hillside and terminates in a short shaft 61 feet in height, the total vertical height from the fire-grate to the top of the shaft being 135 feet.
Two sets of pumping engines and two boilers, supplied by Messrs. Tangye, Birmingham, have been installed. Each set is capable of raising 14 million gallons a day to the gauge basin at the inlet to the Tytam tunnel, 400 feet above Ordnance Datum; the engines have been so designed as to work alternatively from the proposed low-level reservoir or with a negative suction lift of from 100 to 200 feet when pumping water from the intermediate reservoir. The engines are triple-expansion, condensing, and run at 241 revolutions per minute with a steam pressure of 135 lb. per square inch. The pumps, three in number, have 12-inch diameter rams and 30-inch stroke and are placed immediately under each cylinder, being driven direct from the piston rod cross-head by side rods straddling the crank shaft. The boilers, two in number, are of the Lancashire type and are fitted with super-heaters in the smoke chamber. An engine, supplied with steam from the main boilers, and a direct-driven dynamo of ample capacity have been installed for lighting the station. An overhead 5-ton travelling crane, capable of lifting any portion of the engines, spans the engine room.
(iii). Road. The road, whilst taking the rising main already laid and containing provision for a duplicate main to be laid later, also supersedes the old road which will be submerged when the low-level reservoir is constructed. It is 1.4 miles in length and has a width of 20 feet for 1 mile, where the main is laid under it, and of 12 feet where it has only to accommodate the traffic. The road has a continuous rising gradient, varying from 1 in 240 to 1 in 8, and is free from sharp bends so as to avoid excessive friction in the main when pumping is in progress. There are four large bridges, (one with 3 spans of 50 feet, one with 3 spans of 20 and one of 30 feet, one with 6 spans of 20 feet and one with 2 spans of 20 and one of 30 feet), three cuttings over 60 feet deep and numerous massive retaining walls.
The bridges have a clear width of 13 feet between parapet walls. The piers, abutments and arches are constructed of cement concrete, faced throughout with granite. The spandrels and haunches are filled in with lime concrete.
Wherever the road is on embankment, masonry piers have been carried up from the solid ground to support the mains.
(iv). Access Roads.—These have been constructed to take the rising and suction mains. They are of an aggregate length of 1.33 miles and have widths of 6 and 12 feet.
(v). Rising Main.—The rising main is 3,406 yards in length and consists of cast iron pipes 18 inches in diameter, 1 inch thick and 12 feet in length. The weight of each pipe is 19 cwts., the pipes being of uniform section throughout the whole length of the main so that no confusion should arise in laying them. Three sets of reflux, sluice, air and by-pass valves and five washouts have been fixed at intervals in the rising main.
The rising main is laid in a trench 3 feet 6 inches deep, the joints being run with lead, 2.5 inches deep, after the insertion of a strand of yarn.
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