three-fourths
inch in diameter and five feet long. On these ribs a planked skin is
firmly spiked. This planking is of heart sugar pine, three inches thick
and eight inches wide, with planed edges fitted with an outgauge,
similar to ship planking. The plank was put on nearly thoroughly
seasoned, and swells sufficiently to make the face practically
water-tight without battening or calking the joints. The openings at
the joints made by the outgauge suck in small particles of vegetable
matter, which take the place of calking to a great extent. At the
bottom the plank is fitted to a firm bed-rock and calked with pine
wedges. There are three thicknesses (nine inches) on the lower
twenty-five feet, two thicknesses (six inches) on the next thirty-five
feet, and one thickness on the upper thirty-six feet.
From past experience it is believed that the planking will remain sufficiently sound for twenty years at least.
A
culvert extends through the dam, as shown by Fig. 5 B, through which
the water is drawn from the reservoir. This culvert is built with heavy
dry-rubble foundation and walls, and is covered with granite slabs
sixteen to eighteen inches thick and six and one-third feet long.
Three
wrought-iron pipes of No. 12 iron, each eighteen inches in diameter,
pass through the water-face of the dam. Their upper mouths are
protected by a strainer, formed of two-inch plank, anchored to the
bed-rock. A separate valve or gate is placed at the lower end of each
pipe ; the water passing through the gates, aggregating a flow of 280
cubic feet per second when the three are open, discharges into a
covered timber sluice, seven and one-half feet wide by one and
three-fourths feet high, passing to the lower edge of the dam, and
thence on to the solid rock of the creek bed. The gates are approached
by a walk way above the sluice. The crest of the dam is formed by a
coping of hewn heart-cedar timber, eight-
