If you’re going to build hydropower canals, you’ve got to have water. (We started to touch on this topic yesterday.) From the earliest days of the Cohoes Company’s canal operations, they had control of a wing dam that diverted water from the river into their canals. About 1866, they constructed a sophisticated gatehouse that exists to this day. In fact, the original equipment was still in place when the hydropower plant at the site was redeveloped just a few years ago, and a fellow by the name of Bruce G. Harvey was not only fortunate enough to document the site for HAER, he has shared a number of his photographs here. Click on through to see the beauty of 1866 mechanical works.
According to Mr. Harvey’s documentation, the original complex from the 1830s was upgraded in 1866 into a gatehouse that straddled the power canal, immediately downstream from a new dam they built that same year. The gatehouse allowed the Cohoes Company to control the flow into the canal. That gatehouse was expanded in 1922 by the Cohoes Power and Light Company, which developed hydroelectric power at the site.
Engineering News in 1915 described the impending redevelopment of the old hydraulic canal in Cohoes, which after 85 years was being redeveloped into use for hydro-electric generation. The article noted that the original system was designed by James B. Francis, “the father of modern hydraulic engineering,” a detail that seems to have eluded other accounts. It noted that the first power canal was completed in 1834, 1¾ miles long with a fall of 18 feet. In 1843, a second-level canal was added and the first one altered so both could make use of the old Erie Canal bed, which had been secured by an exchange of land during the enlargement. A third canal was built the same year using part of the old Erie Canal, half a mile long with a fall of 23 feet. The fourth and fifth levels, half a mile long and giving a drop of 20 feet, were added around 1880.
The article says that power was supplied at $20 per horsepower-year to tenants induced to settle on the Cohoes Company’s land. “As a result, the expenses for motive power and ground rent of the largest mills in the earlier stages scarcely exceeded $1000 per year.” The power of that water was not endless, however. “In recent years [to 1915] the land of the company has been largely occupied and the low-stage flow of the Mohawk has been practically all utilized. Indeed the largest mill, in order to obtain extra power required by the development of its business, was obliged to build a steam station.”
By 1915, of course, this style of hydropower was almost hopelessly obsolete; the 10,000 horsepower it could produce was equaled by one unit of the proposed new electric generation station. The wheels it turned were inefficient, water had to flow constantly without respect to the demands of the mills, there was considerable leakage, “and in winter considerable water was wasted in ridding the canal of ice.”
The plan for hydroelectric power described in Engineering News was substantially the plan that exists today, with a feeder canal bringing diverted river water into a series of penstocks feeding electric generators. The Erie Canal still existed (as did all of the Cohoes Company canals), but its replacement, the Barge Canal, was already being developed.
By the way, the generation station built there was considerably advanced for its time. It managed 96 feet of hydraulic head, and included three 10,000-horsepower generators at the outset, with room for the placement of two more. Power was generated at 12,000 volts without use of step-up transformers, as power was intended to be supplied within a radius of 10 miles; that created some efficiency at the outset.
By the way, what’s remarkable about these photographs from the Library of Congress (there are more) isn’t that they exist and show the relationship of the old Cohoes Company canal to the south (above) and the north (here) sides of the Harmony Mills complex – it’s that these photos were taken in 1969. These portions of the canals, at least, survived that long.