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

DRAFT DOCUMENT
5.1 PREVIOUS STUDIES
5.0 DRAFT STUDY PLAN
Previous Studies Conducted
Stream gaging – the USGS installed a stream gage at the outlet of Connelly Lake
in July 1993 and collected data for slightly over one year. ADF&G is currently
gaging at or near the outlet of Chilkoot Lake for the past several years; which will
end in 2013. GLH installed a stream gage at the Connelly Lake outlet in
September 2011 and a stream gage just above the Connelly Creek confluence with
the Chilkoot River in May 2012.
Water temperature – a temperature datalogger was placed in the Chilkoot River
below Connelly Creek’s confluence with the river and with the stream gage at the
Connelly Lake outlet.
Fish habitat survey – conducted by ADF&G in 1995 through a contract with
Haines Light & Power, the utility at that time. No fish were found in Connelly
Lake or in the outlet stream down to the Chilkoot River. Fish surveys were
conducted between September 25 and September 28, 2011, by The Shipley
Group, a contractor for GLH. The surveys took place along the access road
streams and above Chilkoot Lake. At the time of these surveys ADF&G was also
surveying the Chilkoot River Valley above Chilkoot Lake.
Geotechnical survey – a preliminary geotech survey was conducted in 1993 and
found that:
o The dam axis is characterized by massive, relatively solid diorite bedrock
at each abutment. Between the abutments, an overburden of boulders,
peat, and sand were found to a depth of up to 36-inches.
o The powerhouse site (upper riverside site [Northerly]) is situated on an
inactive floodplain terrace. The upper 2’ of soil consists of clean sand,
which is underlain by sandy gravel and the terrace as seen in a riverbank
cut consists of dense course gravel in a sand matrix. The terrace soil abuts
steeply sloping diorite bedrock which would be a good source of borrow
for rip rap and embankment construction.
Hydrology evaluation – a preliminary evaluation to determine average annual
and average monthly stream flow for energy production was made in 1993.
Figure 8 above shows the difference between the Chilkoot River drainage and
Connelly Lakes drainage, which is significantly smaller. The PAD also contains a
table comparing the Connelly Lake USGS gage data with ADF&G gage data at
the river mouth and correlation with other nearby drainages. The hydrology
evaluation will continue until more gage data is collected.
Baseline environmental assessment – The USF&WS, 29 helped us narrow down
the TEC species we need to evaluate for this document. We were advised to
29 Personal e-mail communication with Steve Brockman, USF&WS, on March 8, 2012.
Draft Study Plan – June 2012 p. 40 Connelly Lake Hydroelectric Project