or the
summit and upper slopes, of at least 180 inches, or four times the
rainfall in Tacoma or Seattle. The melting snows feed the White,
Puyallup and Nisqually rivers, large streams flowing into the Sound,
and the Cowlitz, an important tributary of the Columbia. The minimum
flow of these streams is computed at more than 1200 second feet, while
their average flow is nearly twice that total.

The utilization of this large water supply on the steep mountain
slopes began in 1904 with the erection of the Electron plant of the
Puget Sound Power Company. For this the water is diverted from the
Puyallup river ten miles from the end of its glacier, and 1750 feet
above sea level, and carried ten miles more in an open flume to a
reservoir, from which four steel penstocks, each four feet in
diameter, drop it to the power house 900 feet below. The plant
generates 28,000 horse power, which is conveyed to Tacoma, twenty-five
miles distant, at a pressure of 60,000 volts, and there is distributed
for the operation of street railways, lights and factories in that
city and Seattle.

[Illustration {p.109}: Mountain Climbers in Crevasse on Carbon
Glacier.]

A more important development is in progress on the larger White river
near Buckley, where the Pacific Coast Power Company is diverting the
water by a dam and eight-mile canal to Lake Tapps, elevation 540 feet
above tide. From this {p.111} great reservoir it will be taken
through a tunnel and pipe line to the generating plant at Dieringer,
elevation 65 feet. The 100,000 horse power ultimately to be produced
here will be carried fifteen miles to Tacoma, for sale to
manufacturers in the Puget Sound cities.

[Illustration]

[Illustration: Building Tacoma's Electric Power Plant on the Nisqually
Canyon. Upper view shows site of retention dam, above tunnel; middle
view, end of tunnel, where pipeline crosses the canyon on a bridge;
lower view, site of the generating plant (see p. 21).]

[Illustration]

Both these plants are enterprises of Stone & Webster, of Boston. A
competitive plant is now nearing completion by the city of Tacoma,
utilizing the third of the rivers emptying into the Sound. The
Nisqually is dammed above its famous canyon, at an elevation of 970
feet, where its minimum flow is 300 second feet. The water will be
carried through a 10,000-foot tunnel and over a bridge to a reservoir
at La Grande, from which the penstocks will carry it down the side of
the canyon {p.112