Draft Study Plan Vol 1 (PDF) - Alaska Power and Telephone Company

DRAFT DOCUMENT
Alternative 4 – Dam at Connelly Lake outlet, siphon intake, surface penstock,
downstream powerhouse location.
In the 1990’s, HL&P considered an alternative that placed the powerhouse about
2 miles downstream of the confluence of Connelly Creek and the Chilkoot River, with a
road and adjacent penstock up the hillside to the lake. They concluded that a road was
possible up to a bench at about the 1500 feet elevation, but that steep cliffs and boulder
fields precluded a road all the way to the lake. GLH has reviewed that information and
agrees that road access to the lake is not possible with the route considered by HL&P.
However, GLH believes that a different alignment for a road to the dam area may be
feasible, as shown in Figure 6.
Note that much of this alignment is based on the rather crude topography of the
USGS 15 minute quadrangles. GLH will obtain more detailed topographic mapping of
the proposed alignment if an initial evaluation and field reconnaissance determines there
is significant economy to be gained. GLH understands that the road may have a
substantial environmental impact.
Figure 6: Alternative Design 4
The preliminary road alignment shown in Figure 6 is 3.5 miles long, including 0.3
miles at a nearly level grade in the Chilkoot Valley from the existing road to the
powerhouse, 2.5 miles up the hillside at a nearly constant grade of 16%, and 0.7 miles at
a nearly level grade to the dam area. The penstock would be similar to Alternatives 1
and 2, with buried HDPE, ductile iron, or steel pipe in the upper section (about 6,000 feet
Draft Study Plan – June 2012 p. 8 Connelly Lake Hydroelectric Project