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A cross section of the dam showing the maximum height of masonry that had been placed by the end of 1913.
Front view of the dam showing areas excavated and masonry placed by the end of 1913.
By the end of 1913, excavation for the Kensico dam was 90% complete, and one-third of all masonry for the dam was placed. After masonry began to be placed on April 23, further excavation was done only at night, with the masonry then cleaned and readied for the concrete gang the next morning. The bedrock under the dam was gneiss, limestone, and schist. Building progressed so quickly that the quarry had to work 2 shifts to keep up. The ‘portable plant’ used to construct the dam in 1913 consisted of:
The deepest part of the dam called the gorge. I believe this picture is looking north at what will eventually be below the face of the dam. The picture caption says this is elevation 190 (about 50 feet underground today), but I think they mean the camera is at 190. So from the camera the dam will rise another 180 feet and the gorge descends 125 feet, the lowest point being excavated by hand. The deepest 50 feet of masonry was placed directly against the downstream bedrock.
The new dam slowly reaches ground level. The remains of the old 1885 dam can be seen on the right. The large buildings in the picture are the cement storage house (center) and machine shop (top left).
A similar view but taken closer to the dam after a little more progress had been made. It looks like a very busy construction site.
Looking west at the upstream face of the dam. The gorge is in the foreground and the remains of the old dam are in the background.
By the time work was stopped on the 20th of December, 293,350 cubic yards of cyclopean masonry had been placed, as well as 13,390 cubic yards of concrete blocks and 9350 cubic yards of mass concrete. The bottom 90 feet of the gorge was filled with a single masonry section. Above that level, the dam was divided into 79-foot sections, with an expansion joint between each section. Concrete blocks were used on the upstream face of the dam and on one side of each expansion joint. These concrete blocks were placed at night in warmer weather, and during the day at alternating parts of the dam in colder weather, with concrete placed against the blocks the following day. Stones used in the cyclopean masonry weighed between 1 and 16 tons. As work progressed the rising dam was backfilled, in some cases with the dirt being taken from the old 1885 dam.
A close-up of the concrete blocks placed on the upstream face and at one of the expansion joints. Also shown are the tracks for the derricks and the concrete pylons which were later embedded in the dam as it rose.
Further plans for the ornamental stonework on the downstream face of the dam were completed, and it was decided that the stone would come from local quarries. The ornamentation plans also covered the public highway across the dam and circular granite pavilions at each end. At the base of the dam would be a 30-foot wide terrace with a pair of “small” square pavilions surrounding steps up to the terrace at each end. Between the terrace at the base of the dam and the shallow rectangular pool (with fountains) would sit a strip for parking. The top of the dam was to be 1850 feet long, with the visible base 1025 feet long and the exposed height 133 feet. The maximum height of the dam, from its lowest foundation point, was 310 feet. Drawings were also completed for the lower gate chamber at the dam which would feed the original Bronx Conduit from the old dam.
All new highways had been completed except Westlake Drive from the dam to the aerators and the roads in front of the dam. Camp Kensico housed as many as 852 people during the year, 625 of them adult men. South of the Valhalla train station sat the main storage yard on a railroad siding. The storage yard included a blacksmith shop, storehouse, stables for 68 animals, a sick bay, an ice house, a granary, and a guy derrick with an 80-foot boom for unloading railroad cars. Beyond the siding 17 miles of railroad track built with 60-pound rail was in use, including two switchbacks to reach the top of the dam.
Casting concrete blocks for the upstream face of the dam, now hidden by the Kensico Reservoir. This plant, constructed in 1912, had 320 steel forms for casting the blocks.
On the west side of the reservoir, all concrete masonry for the by-pass aqueduct, upper and lower effluent gate chambers, and aeration basin was complete. The by-pass aqueduct was also covered with soil, although some drainage work was not yet complete. In the aeration basin 7774 out of a total of 10275 floor panels were placed during 1913. Nearly all concrete masonry on the influent gate chamber and weir was also complete. In Camp Columbus, 12 buildings were demolished during the year to allow for construction of new roads and grading around the aerators.
The Upper Effluent Gate Chamber – This is where the water flows out of the reservoir and into the aqueduct. To get some idea of the scale, notice the workmen just to the left of the second row of openings from the bottom. The Inlet channel in the foreground was still a little above final grade at the end of the year.
The 1911 drawing for this structure showing each opening is 10 feet tall.
On February 25, 1913 a contract to remove all of the chestnut trees around the Kensico reservoir was awarded as a result of the chestnut blight, and work began March 21. By the end of the year 478 acres of thickly-wooded and 41 acres of sparsely-wooded areas had been cleared of chestnut trees. Some of the wood was salvaged, primarily as railroad ties.
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Synopsis written by Robert Mortell, 2013.