From the very first the water power of the St. Louis river has been recognized as one of Duluth’s great assets. The early promoters of the Lake Superior and Mississippi Railroad had it in view, and of all the precious things from Lake Superior to Puget Sound Jay Cooke himself marked out the water power of the St. Louis for his very own and clung to it through all the vicissitudes of his house.
Riparian rights on both banks of the stream were acquired covering the chief power sites, and held by Jay Cooke and the Jay Cooke estate until the formation of the Great Northern Power Company. Bidders frequently appeared, but none reached the mark set by the Cooke family.
Early plans had necessarily contemplated a row of factory sites all along the river, but the introduction of electric transmission changed the face of things entirely, and the development plans which were finally successful were on the modern basis.
Meanwhile a beautiful splash was made in 1895 by a rival power company, anticipating in part the designs of the Great Northern, fathered by a stranger of pleasing address and gentle manners, Henry Curtis Spalding. He proposed to tap the St.
Louis above Cloquet, bring its water across country by a highland canal system, deliver it to turbines at Duluth, and circumvent the sites of the St. Louis. He also proposed that the county vote $600, 000 bonds in aid of his venture, which would surely bring back to the county threefold return in increased valuation. His way was so persuasive that the county board consented to a special election, but at the last moment opposition arose and the project was voted down.
Upon the formation of the Great Northern Power Company by C. C. Cokefair and his associates, the long deferred enterprise took on form. Riparian rights were acquired from the Cooke estate and others and flowage lands were purchased for the vast reservoir. At an outlay of above $5, 000, 000 the electric power plant was installed to utilize the energy of the St. Louis river, which had idly been spent for years.
527 5IISTORY OF ST. LOUIS COUNTY With 30, 000 electrical horse-power available for present use and 50, 000 additional available upon the installation of the added machinery and equipment necessary, Duluth is prepared to attract manufacturing enterprises of any magnitude. The extraordinary facilities for shipping, either by rail or water, combined with an abundance of cheap power, make the city an especially desirable location for almost any line of manufacturing.
This has been made possible by the tremendous undertakings carried out by the Great Northern Power Company.
It is little more than five years since the actual construction was commenced, but the engineering plans had been thoroughly worked out, and the men who took charge of the different features of the project were experienced, practical and energetic.
The immense dam at Thomson, the two and three-fourths miles of canal, the erection of the great power house and the installation of the ponderous machinery therein was accomplished at an enormous expense of wealth and labor.
The mathematical computations by which the available power was arrived at were based on the following fundamental facts: The drainage area of the St. Louis river basin approximates 3, 700 square miles. The average annual rainfall of this basin for the last thirty-five years, as determined by the government weather bureau gauge, is thirty inches, and the mean annual run-off is twelve inches. One inch of water on 3, 700 square miles equals 16, 344 cubic feet continuous flow per minute for one year. With the proper combination of pipe line, water wheels and generators, and a fall of 375 feet, two cubic feet of water flow per minute is equivalent to one electrical horse power. The immense service reservoir at Thomson, and several storage reservoirs at points above that place, make it practicable to conserve and utilize the entire run-off of the river.
The first great work was the construction of the main dam at the village of Thomson, fourteen miles above the main part of the city of Duluth, and about four miles from the city limits.
It is built of concrete, and is thirty-eight feet high and forty-two feet thick at the base, and the crest of the dam is 485 feet above Lake Superior. The overfall section is 356 feet long, and with the retaining wall at either end the total length of the structure is 1, 120 feet, or more than one-fifth of a mile. It is built upon a foundation of solid rock, and connects the natural walls of rock which flank the river on both sides at that point, forming an impregnable barrier to the current, which, when pursuing its natural course, in the next few miles plunges over a series of precipices, until it descends to the level of Lake Superior.
There are three sluice gates, each 7 by 9 feet in the main dam in the construction of which, together with a number of smaller dams built by the company, 60, 000 barrels of cement was used. The service reservoir, formed by the construction of this dam, constitutes a beautiful artificial lake, with an area of several hundred acres. The available Water stored in this reservoir is sufficient to operate the power house for twentyfour hours without receiving any water from the river.
Near the eastern extremity of the service reservoir is the head of the canal, or race, which conducts the water to the top of the bluff, near the foot of the rapids, a distance of two and three-fourths miles, though the natural course of the river would be considerably more.
The canal has a minimum depth of fifteen feet and is thirtysix feet wide at the bottom. Where excavated in earth the sides are sloped two to one, but, for 3, 500 feet of its length it was excavated through slate rock at a uniform width of thirtysix feet. The total excavation was 310,000 cubic yards of earth and 72,000 cubic yards of rock. The water which passes through this channel is equal to 2,900 cubic feet per second. At the foot of the canal is a forebay forty acres in extent with an available depth of twelve feet from which the water is drawn through pipes directly to the power house at the foot of the bluff, nearly 400 feet below. The head gates through which the water is drawn from the service reservoir and from the forebay are placed several feet below the surface to provide against clogging by ice. Provision is made at the head gates at the foot of the forebay for eight seven-foot pipes, but only three of these have been installed at present. The pipes are each one mile in length, the first 4, 000 feet being made of California redwood, the staves being built with interlocking joints and banded by steel hoops, and the pipes are buried in trenches. The lower 1, 000 feet of each pipe is built of riveted steel. Five hundred feet above the power house each of the pipes is connected with a standpipe surmounted by a tank thirty feet in diameter, the function of which is to regulate the pressure and flow of water when loads are suddenly thrown on or off at the power house.
The thirty-foot tank has sufficient capacity between the elevations 426 and 472 to supply water to the wheels to meet a sudden demand for power up to 10, 000 horse power, and maintain the head required by the water wheel governors for good regulation while the water in the penstocks is accelerating to the speed required to meet the added demand.
The standpipe and tank are kept from freezing by allowing warm air to rise in the air space between the pipe and the lagging.
The heat is supplied by steam from the heating plant in the power station 500 feet distant.
Here, at the end of the pipe line, the water, after a fall of 378 feet from the service reservoir, enters, with tremendous force, the power house. The latter is set in the valley of the St. Louis and one comes upon it very unexpectedly in going up the river. From out of the timbered bank of the stream it breaks suddenly upon the view-a really fine structure from the architectural standpoint. Here, with almost no perceptible influence upon the river, the flood that was taken from the stream three miles above is poured out from the power house, undiminished in volume, having served its purpose of producing 30, 000 horse power of energy. The building in which the hydraulic and electric apparatus is housed is built upon massive concrete foundations, a brick and steel superstructure with trimmings of concrete that add beauty to its lines. It is said to be one of the finest power houses in the country in its appointments and it is so economically adjusted to the requirements of its functions that in it can be produced more power per square foot than in any similar structure in the world.
Thus far the building has been completed for four 10, 000 horse power units and two exciters, but the plans provide for an extension up to eight units of the same capacity. The present building is 188 feet long, 85 feet wide and about 50 feet high, and it is beautifully finished within with tiling; the great generators lined up on one side and the transformers in the center.
The transformer compartments are fitted with steel doors and overhead, traveling on steel girders, there is a sixty-ton crane, by means of which the 7, 500 kilowatt machines may be rolled out upon the floor.
The penstocks enter the power house from the end of the pipe line and are reduced for coupling with 72-inch hydraulic valves, each of which connects with a 13, 000 horse-power wheel with vertical shaft, with a speed capacity of 375 revolutions a minute. This shaft, in each case, is twenty-eight feet in length, and its upper end carries the internal revolving field of a generator.
In this mechanism is involved the entire process by which the water, running at terrific speed from its recent descent of 378 feet, is transformed into hydraulic power to be presently converted by the electrical apparatus into electric power for transmission. The center of each water wheel is eleven feet above low water level in the river, and the draught tubes discharge directly into the stream.
Attached to the housing of each of the water wheels are two relief valves which can be operated either by direct pressure or from the governors, and these governors, which were designed by the Escher-Wyss Company of Zurich, Switzerland, are similar to those used at Niagara Falls. The relief valves are set to discharge at a pressure equivalent to a head which will not overtop the standpipe. In case they are used in connection with the governors they reduce the waste of water. Pipe connections for the exciter wheels are made directly from the penstocks and the two water wheels for the exciters are similar to the main generators and each designed to drive a 250-kilowatt, 125-volt exciter at 500 revolutions per minute. The main generators are wound for 6,600 volts-8 phase, 25 cycles per secondand the water cooled oil transformers are furnished with taps so that the voltage can be varied between 30,000 and 60,000 volts.
The transformers, which are the largest ever built, embody several new and, to electrical engineers, interesting features of design, and are technically held to be the realization of the work of the advance school of electrical science. Each transformer is about twenty feet in height. The general scheme of wiring for the station is in the most modern practice. All main alternating- current switches are of the General Electric oil type, arranged to be electrically controlled from a distance. The utmost care has been taken in providing fireproof barriers, and the isolation is so complete that nothing but a widespread catastrophe will put all the plant out of commission. Accident is almost absolutely provided against. The switching apparatus is elaborate and extensive, the whole equipment being operated by remote control from a bench board. The entire switchboard is so compact that the control of 80, 000 horse power will be centered in a board less than nineteen feet in length.
The power is taken out of the power house at a voltage of 60,000 for transmission to Duluth. There are two circuits provided, either of which will carry the whole load in case of accident to the other. The wires are strung upon steel towers erected about 500 feet apart, which also carry a steel lightning arrester wire. Throughout the distance of fourteen miles the company has acquired a right of way 100 feet wide, from which the trees have been cleared and every possible provision made to prevent loss of power in transmission. The transmission line comes over the bluff at Duluth and is brought down to the substation at Fifteenth avenue west. In this building, which is of the same design as the power house, and fitted with similar elaborate care, transformers of the same design and capacity as those in the power station are used. Here the high voltage is stepped down for distribution. Here also are installed two 1, 500 kilowatt motor generator sets to supply power to the street railway system. In the Superior power station one 1, 500 kilowatt rotary is used. The current is transmitted across the Duluth- Superior harbor by means of submarine cables.
This entire development is based upon ultimately utilizing thirty per cent of the mean annual rainfall on the drainage area of 2.300 miles below the Duluth Heights system. The remainder of the drainage area (1,325 square miles) is reserved for the Duluth Heights development. This water that is reserved will be ultimately brought down from the Heights with a fall of 740 feet and will develop about 110, 000 horse power. As an engineering proposition this scheme is more desirable than to utilize the entire drainage area at Thomson, as twenty-five per cent more power, in the aggregate, can be developed this way than by using all the water to develop power at Thomson-and this aside from the important fact that it will permit the generation of this additional power on the edge of the district that will consume it.
Previous to the construction of the plant a number of contracts for furnishing power had been entered into. Among the uses thus anticipated were the operation of the street cars of both the cities of Duluth and Superior, as well as the electric lighting and pumping the city water of both cities. Besides these public utilities, a number of manufacturing establishments were waiting to make use of the power as soon as it was available, and others are constantly being established. The machinery at many of the elevators, and on the coal docks is operated by this electrical power, while its general use in the manufactories of the city obviates coal consumption and its cloud of smoke laden air.
The project to develop tie St. Louis river, according to the plans which have been followed, was conceived by F. A. Cokefair, chief engineer of the Great Northern Power Company, and it is largely due to his efforts that the project was carried out.
C. C. Cokefair, president of the Great Northern Development Company, organized the Great Northern Power Company and financed the project. Charles A. Duncan, of Duluth. is now president of the company, and W. M. Ryerson is general manager. Capt. Alexander McDougall is a director of the company and has been actively interested in it since its inception. F. O. Blackwell, of New York, was consulting engineer for the company.