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

DRAFT DOCUMENT
powerhouse at the base of the hillside. After installation, this section would be buried to
protect the pipe from falling trees and rocks.
Figure 3: Alternative Design 1
Powerhouse
The powerhouse would be a pre-engineered metal building with a reinforced
concrete foundation, and would house either one or two generating units, depending on
the installed capacity. With one unit, the powerhouse dimensions would be
approximately 50 feet by 70 feet by 40 feet high above the top of the surrounding
backfill. With two units, the powerhouse dimensions would be approximately 50 feet by
100 feet by 40 feet high. The floor level of the powerhouse would be at about El 170.
The powerhouse would be located on the east side of the Chilkoot valley
approximately 1100 feet downstream of the confluence of Connelly Creek and the
Chilkoot River and approximately 300 feet upstream of Power Creek. There is a
floodplain terrace of varying width between the base of the hillside and the river channel.
The powerhouse would be located partially on this terrace and partially on an excavation
into the hillside. There are isolated bedrock exposures on the hillside, and GLH
anticipates founding the major portion of the powerhouse on bedrock.
Spoils from the powerhouse excavation would be used for backfill around the
powerhouse. The fill would be as much as 20 feet deep. The fill slopes would be
armored with riprap to protect it from erosion by floodwaters of the Chilkoot River.
Draft Study Plan – June 2012 p. 4 Connelly Lake Hydroelectric Project