of the dam the buttresses were built in lifts of 12 feet, groups of three and four buttresses being built at one time according to the space which was available for this purpose. The deck and apron was usually placed on the buttresses soon after completion of each lift, so that in this way with the struts between the buttresses each buttress was properly supported as it was erected.

At the power house site after the whole chasm had been filled. up the foundations were erected to the point where the penstock elbows and draft tubes could be placed, then the additional concrete was placed up to the floor line. The end walls of the power

house formed protecting walls along the river bank on one side and the island on the other side. The reinforced concrete superstructure of the power house and gate house was further stiffened by structural steel framing to support the cranes and roof trusses. The work proceeded during the entire construction period, though its progress was somewhat interfered with by the heavy rains of the winter season. Fortunately, however, there were no excessive floods, and the cofferdam problems were not serious. The closing of the dam was effected after completion of the entire

structure with the exception of its temporary openings through the base of the spillway portion, which together with the three sluice gates carried the entire stream flow during the dry season just preceding the completion of the structure.

The installation of the machinery was pushed along as rapidly as the completion of he dam permitted. On account of the location of the power house with respect to the dam, it was necessary to lower the apparatus from the top of the bulkhead to the power house floor level, and the erection of the high tension apparatus inside the dam required that the buttress in back of the power house be completed and properly covered before installing this portion of the equipment. This was done, however, and as the transmission line was completed about the same time it was possible to transmit power to Portland very soon after the water was first passed over the spillway.

Mr. Frank R. Fisher, a member of your club, who was Resident Engineer in charge during the construction, kindly furnished much of the construction data given above.

PAPER NO. 1131

SUCTION GAS PRODUCER PUMPING ENGINE VS. COM

POUND CONDENSING CORLISS CRANK AND FLY WHEEL PUMPING ENGINE, GIVING COST OF OPERATION AND FIXED CHARGES, BASED UPON FIVE YEARS' OPERATING

EXPERIENCE

BY J. E. GIBSON AND S. H. WRIGHT

Read May 17, 1913.

We are all familiar with the cross compound connecting Corliss: engine, direct-connected to a pumping unit by having the piston rods extended back through cylinder heads, or by a set of trombone rods passing over crank and connected to the plungers of the pumps, and it is, we believe, generally conceded that this type of pump ng engine is about the best where efficiency, long life, simplicity of design and operation are considered.

On the other hand, we know comparatively little in this country about the gas or oil driven pumping engine. Among the principal reasons for this condition we may mention the following:

1st. The conservatism of the American engineer and owner against adopting something new and therefore different.

2nd. The early history and experience with the American built gas engine.

3rd. The difficulty of obtaining experienced help familiar with gas engines and producers.

4th. The low first cost of steam driven pumping engines as compared with the cost of gas engines.

5th. The abundance and low cost of fuel, making economy of secondary importance.

However, the increasing cost of fuel and the agitation for the conservation of our natural resources, together with the improvement in design and construction of the American gas engine, has caused a decided change in the attitude of the engineer and owner toward the gas and oil engine prime mover.

There is an abundance of engineering literature, technical and descriptive, on the gas engine, its thermodynamic and mechanical efficiency, reliability, first cost, maintenance, etc., but we do not recall anywhere a comparison of this type of prime mover with that of steam upon a commercial basis and especially one covering any considerable interval of time.

In the following we hope to present some figures that, while not technical nor bristling with B. T. U.'s, will be both useful and enlightening. Before proceeding to that portion of the paper, however, a brief description of the two plants to be considered will be given.

DELAWARE WATER COMPANY PLANT.

The Delaware Water Company was organized some seven years ago and supplies water to the P. B. & W. R. R. at its new shops and yards at Edge Moor and other points as far south as Newark, Delaware.

Its pumping station is located at the head of tide water on the Christiana Creek, where an old water power driven feed and flour mill is located. This property, especially the dam, had been allowed to decay, and, in fact, shortly after the water company purchased the site, a sudden freshet washed the old dam out. This was replaced by a new concrete dam 200 feet long by 12 feet high, built on heavy timber crib work and flanked upon each end with earth embankments.

Christiana Creek has a rather tortuous course through a sandy clay water-shed of 47.75 square miles, at site of dam, of which 85 is under cultivation. Generally speaking, the water is very turbid and high in suspended matter.

The impounding dam (10,000,000 gallons storage) is too small to permit of any material sedimentation, so mechanical filtration was resorted to.

The water flows from the impounding reservoir through an intake chamber, where a portion of the coagulant is fed, and a 16 inch main to a 500,000 gallon capacity sedimentation basin; from here it flows to the main suction well, where additional coagulant is added when found necessary. The pumps lift the water from the suction well and discharge it through mechanical pressure filters to the standpipe and storage reservoirs of the Railroad Company.

MECHANICAL PLANT.

Building.

The building for the plant is a neat, ornamental, brick structure, 130 feet long by 44 feet wide, concrete floors, slate roof on iron roof trusses, and divided by brick partition walls into producer, engine and filter rooms. Except for the producer room, which has a second or charging floor of rolled steel floor plate, the building is one story. Immediately to the rear of the producer room at the elevation of the second floor is located the coal storage bin. This is of concrete and rubble masonry walls, concrete floor and heavy wooden flat roof with coal holes. Coal is hauled from Bear Station on the Delaware Division of the P. B. & W. R. R. by wagons, which drive onto the roof and dump their load through the coal holes into the bin. Industrial tracks are laid in the bays of the bin, so that the operator loads the coal car in the bin and pushes it on a slightly descending grade to the producer room charging floor. This is a most admirable arrangement and dispenses with any form of mechanical elevator or lift. The ashes are taken from the producer at the lower floor and wheeled to the ash bin.

Gas Producer.

The gas producer plant as installed consists of two complete units of producers, pre-heaters, scrubbers, purifiers and their accompanying piping, drip wells, seals, etc. Each producer unit is equipped with a full set of manometers and a positive type of pressure blower for blowing up fires. This blower is belt-driven from a small water motor, or in case of insufficient water pressure can be operated by a hand crank attached to the extended shaft of the motor. Producers are the standard suction type and rated at 110 HP. by R. D. Wood & Company, their builders. The gas passes from the purifiers through a 16" cast iron gas main into engine room, where the branches are taken off to supply the engines. The far end of the gas main is provided with an opening to the atmosphere. In starting the plant, the purge valves at producers are closed and gas is blown through the gas main and out this bleeder until all of the air is displaced by gas.

Gas Engines.

There are two 13" diameter by 12" stroke three cylinder, single acting, type 3, vertical Westinghouse gas engines rated by their