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Soo River HydroIntake Sediment Management
by
Stuart CroftVice President
GENERATE 2014 – Operators Workshop
15 October 2014
The Summit Power Group
The Summit Power Group
Soo River Hydro
A brief background
Soo River Project:
14 MW run-of-river development 15 km
north of Whistler on the Soo River
Develops 103.5 m of head; design flow
of 15 m3/s
Consists of a inflatable diversion weir
and intake, 960 m long tunnel, 240 m
long 2 m DIA buried penstock, 2 x 7 MW
Francis units, powerhouse, and tailrace
Commissioned in May 1994
The Summit Power Group
Soo River Hydro
Diversion & Intake Design
Diversion situated on a low
gradient reach of a coastal
river draining 250 km2
glaciated basin
High flow period:
May thru October
Bedload predominantly silt
and sand, some pebbles
Floating and submerged
woody debris is common
Soo River Hydro – headworks, Autumn 2012
(photo: Brian Rode)
Setting …
The Summit Power Group
Soo River Hydro
Diversion & Intake Design
The Summit Power Group
Soo River Hydro
Diversion & Intake Design
The Summit Power Group
How to remove ~ 3,000 m3/yr
silt during fisheries window
with minimal disruption to
operations & environment?
Soo River Hydro
Sediment Removal Challenge
Annual build-up of silt
– sand clogging intake,
eroding runners
Fisheries Window
15 July to 15 September
High Flow (and High
Production) period
15 April to 15 October
Autumn storm events
The Summit Power Group
Soo River Hydro
Dewater & Excavate?
Process …
Complete plant shutdown
Lower headpond
Fish recovery
Excavate & haul away
Soo River Hydro – headpond excavation, 2006
Problems …
Loss of high value production
Difficult to dewater fully
Handling & disposal of
saturated materials
Operating equipment on
saturated sediments
The Summit Power Group
Soo River Hydro
Dredging?
Process …
Systematically suction silt and sand from the
intake channel
Discharge to impoundment pond,
Allow sediments to settle overnight
Water exfiltrates through base of pond, or
Clarified water is “decanted” by pumping from
surface of pond
“Over flow” is filtered, returned to River
Sand pile is allowed to dry, then loaded and
trucked from site
Considerations …
Turbidity from “excavation” is contained
Minimal site impact, footprint, equipment
requirements
Generation operations are not affectedExcerpt from
Cascade Environmental Resources Group Ltd., Environmental Monitoring Report for 2013 Soo River Intake Sediment Removal
The Summit Power Group
Soo River Hydro
Dredging Equipment & Layout
Construct settling pond / decant works
Assemble purpose-built floating dredge
platform, including
Toyo DL-20 - 20 H.P., 10” electric slurry pump
with agitator and cutter head
Pump hoisting winch
Electric capstan to move platform along cable
anchored to shore
6” discharge line
On-board electric panel
Dredge area systematically removing silt
and sand from the intake channel
Approximate dredging flow ~ 600 US gpm with
a maximum of 20% solids.
The Summit Power Group
Soo River Hydro
Dredging Equipment & Layout
4” slurry line from DT-20 discharging to settling basin
Floating “top draw” arrangement for pump to sand filter; note sediment wedge accumulated in opposite corner
The Summit Power Group
Soo River Hydro
Dredging Equipment & Layout
Sand filters treating “decant” water drawn from top of water column at settling basin (at left), with discharge back to Soo River mainstem (to right)
Dredge in action
The Summit Power Group
Soo River Hydro
Final Thoughts
Intake sediment removal has become part of
Soo River Hydro annual operations
Innovative, small-scale dredging has allowed
Soo River Hydro to address a serious
maintenance issue with relatively little impact
on vital late summer energy deliveries
Please contact
Stuart Croft – Summit Power
or
Nels Powell – SOR Site Operations Manager
FOR MORE INFO...