96 HALIFAX WATER WORKS. JOHNSTON. 



The main dam at Spruce Hill Lake is an earthen structure 

 1,200 feet long, 12 feet wide on top the slopes, both inner and 

 outer, being built of granite about 16 inches thick. There is 

 no puddle or core-wall through it, but it was built by simply 

 compacting layers of the best available material. There are two 

 smaller dams about 300 feet and 250 feet long respectively, of 

 the same section as the main dam. The dams were constructed 

 in 1868 and the granite face wall in front of the dam was 

 built in 1891-3 and the dams raised at that time. The present 

 waste- weir was built in 1883 at an elevation of 362.79. It is 

 constructed of granite with four openings of 9 feet 3 inches 

 each in the clear, separated by cast-iron standards to receive 

 stop logs to retain the surplus water. There are three such 

 timbers in place, each 6 inches square, thus raising the level to 

 364.29. 



Gate-Houses. 



There are two gate-houses at Chain Lakes. The north one, 

 originally built in 1857, is located at the north part of the dam 

 at the toe of the outer slope, and consists of an iron tank built in 

 sections, bolted together and caulked. The water is drawn 

 from the lake to this chamber by a 24-inch pipe. It was raised 

 in 1894 by bolting a section to the existing chamber: The 24- 

 inch supply main is connected with this house. 



The south gate-house was built in 1894, over the channel 

 which led to the old south pipe house, which was the original 

 one built in 1848 and destroyed when the new one was com- 

 pleted. The new one is built of concrete and is 16 feet deep by 

 12-J feet wide by 16^ feet long with walls 4 feet thick. It is 

 drained by a 12-inch pipe. Both the 24-inch and the 27-inch 

 mains connect in this house, but may be separated should 

 occasion arise. There is a straining wall about 100 feet long in 

 front of this gate-ihouse built of loose stones, 4 feet 6 inches 

 thick on top with slopes of 1 to 4. The new house is ample in 

 size and avoids the difficulty always had with the north house 

 which is too small to vent the water freely, and was always in 



