Lower Granite Lock and Dam
Pertinent Data
General
Location:
State – Washington
County – Garfield and Whitman
River – Snake
River Mile – 107.5
Township – 14 N
Range – 43 E
Section – 32
Latitude – 46° 39' 37"
Longitude – 117° 25' 37"
River miles from mouth of Snake River - 107.5
River miles upstream from Little Goose Dam - 37.2
Owner - U.S. Army Corps of Engineers, Walla Walla District
Authorized Purpose - Power generation and inland navigation
Other Uses - Flood control (maintain levee freeboard at Lewiston), fishery, and recreation
Type of Project – Run-of-river
Real Estate:
Fee acquisition land above pool elevation 738 – 9,224 acres
Reservoir
Name - Lower Granite Lake1
Elevations (Feet Mean Sea Level):
Maximum at dam for spillway design flood – 746.5
Normal operating range at confluence gage (RM 139.5) – 738 to 733
Minimum at dam for standard project flood – 724
Length, miles:
Snake River (to Asotin damsite, RM 146.8) – 39.3
Clearwater River – 4.6
Length of shoreline - 91 miles
Average width - 0.3 miles
Maximum width - 0.6 miles
Surface area at elevation 738 (low flow, flat pool) - 8,900 acres
Storage below flat pool elevation 738 - 483,800 acre-feet
Storage below flat pool elevation 733 - 440,200 acre-feet
Storage between elevation 733 and 738 - 43,600
Height normal high pool to tailwater elevation 638 (low flow, 30,000 cfs or less) - 100 ft
Levees
Top width - 12 ft
Slopes, waterside and landside - 1V on 2H
Materials - Gravel and earth fill with impervious core
Top elevation - 5 feet above backwater profile for standard project flood
Embankment length:
Lewiston - 8.6 miles
Installed pumping capacity:
Lewiston levees 450.4 cfs
Dam (General)
Axis (Lambert) - N 32° 00'E
Length and Widths, feet:
Dam total length at crest – 3,200
North abutment embankment -1,435
South non-overflow monoliths – 32.2
Spillway overall length – 512
Spillway to powerhouse non-overflow – 43.4
Powerhouse overall length – 656
Spillway to navigation lock non-overflow – 43.4
Navigation lock overall width at foundation – 304
Navigation lock overall width at deck – 186
Concrete Heights, feet:
Maximum overall concrete height (powerhouse sump deck to deck)
Maximum non-overflow monoliths height:
North - 151
Central - 166
South - 181
Maximum lock wall monolith height (culverts to deck) - 191
Deck elevations, feet msl:
Intake, Spillway Bridge, non-overflow sections, and upstream end of navigation lock - 751
Downstream end of navigation lock - 746
South shore fish ladder - 656
Tailrace and fishwater intake - 656
North abutment embankment - 756
Spillway
Number of Bays - 8
Overall length (abutment centerlines) - 512 ft
Deck elevation - 751 ft msl
Ogee crest elevation - 681 ft msl
Flip lip elevation - 630
Control gates:
Type - Tainter
Size - 50'W x 60'H
Gantry crane (joint use with powerhouse) capacity - 100 tons
Stilling basin length - 188 ft
Stilling basin elevation - 580 ft msl
Maximum design capacity - 850,000 cfs
Powerhouse
Length overall - 656 ft
Spacing:
Units 1 through 5 – 90 ft
Unit 6 – 96 ft
Erection and service bay – 110 ft
Width overall, transverse section - 243.17 ft
Intake deck elevation - 751 ft msl
Tailrace deck elevation - 656 ft msl
Maximum height (draft tube invert to intake deck) - 228 ft
Turbines:
Type - Kaplan, 6-blade
Runner diameter – 312 in
Revolutions – 90 per min
Rating – 212,400 horsepower
Distributor centerline elevation – 599
Generators:
Rating (nameplates) – 135,000 kilowatts
Power factor – 0.95
Kilovolt ampere rating – 142,100
Units installed complete initially – 3
Skeleton units provided initially – 3
Total units now installed – 6
Plant capacity, nameplate rating – 810,000 kilowatts
Crane capacities:
Intake (joint use with spillway) – 100 tons
Bridge – 600 tons
Draft tube gantry – 50 tons
Navigation Lock and Channels
Net clear length, lock chamber - 674 ft
Net clear width, lock chamber - 86 ft
Upstream gate:
Type - Submersible tainter
Height - 23
Downstream gate:
Type - Miter
Height - 122 ft
Operating water surface elevations in chamber - 633 to 738
Maximum operating lock lift - 105 ft
Lift (riverflow 300,000 cfs, practical navigation limit) - 88.2 ft
Length of guidewalls (from face of gate):
Upstream (floating) – 750 ft
Downstream – 700 ft
Downstream approach channel:
Width – 250 ft
Bottom elevation – 617
Minimum tailwater elevation - 633.0
Lower lock sill elevation - 618.0 ft
Upper lock sill elevation - 718.0 ft
Maximum depth over sills - 20.0 ft
Minimum depth over sills - 15.0 ft
Abutment Embankment
Embankment elevation - 756
Embankment top width - 45 ft
Material - Gravel fill with rock facing, impervious silt core
Upstream - Combination sand and gravel filters
Downstream - Gravel and sand filters
Slope, upstream - 1V on 2H
Slope, downstream - 1V on 2H
Fish Facilities2
Upstream migrants fish ladder:
Number of fish ladders - 1
Slope
Weir 634 to Weir 627 - 1V on 10H
Weir 728 to Weir 737 - 1 V on 32H
Ladder clear width – 20 ft
Design capacity – 75 cfs
Exit Channel:
Location - Width, feet Between weir 737 and pool in non-overflow section
Top of trashrack – El. 732
Invert – El. 727
Width – 6 ft
Alternative exit channel (pool elevation below 727):
Exit pipe to reservoir – 18-inch-diameter full plastic pipe down to El. 718,
and a half-round plastic pipe down to El. 710
Operating elevations:
Design range:
Pool elevations – 733 to 738
Tailwater elevations – 633 to 642
Riverflow – 0 to 225,000 cfs
Maximum operating range:
Pool elevations - 732 to 739
Tailwater elevations - 633 to 645.4
Riverflow - 0 to 340,000 cfs
Adult fish trap and handling facility - 1
Pumps for fishway system attraction water:
Number - 3
Capacity - 3,150 cfs
Downstream migrants bypass system:
Design pool range – 733 to 738
Design capacity – 200 to 250 cfs
Extended-length Submerged Bar Screens – 18
Vertical barrier fish screens – 18
Orifices from bulkhead and fish screen slots:
Number – 36, 36
Size (diameter in inches) – 10, 12
Fingerling collection gallery - 1
Fingerling transportation pipe – 1
Fingerling holding and sampling facility - 1
Fingerling transportation facilities:
Truck loading facility - 1
Barge loading facility - 1
Hydrologic Data
(Based on streamflow data for the Snake River near Clarkston, Washington)
Drainage area - 103,200 square miles
Period of Record - October 1915 to September 1972 (Discontinued in December 1972)
Discharges:
Instantaneous maximum of record, 29 May 1948 – 369,000 cfs
Instantaneous minimum of record, 2 September 1958 – 6,660 cfs\
Average annual flow – 50,300 cfs
Average annual mean daily peak flow – 188,300 cfs
Extreme outside period of record:
Flood of June 1894 – 420,000 cfs
Flood of June 1894, controlled by existing projects – 295,000 cfs
Standard project flood, controlled by existing projects:
Snake River below Clearwater River - 420,000 cfs
Snake River above Clearwater River - 295,000 cfs
Clearwater River above Snake River - 150,000 cfs
Spillway design flood - 850,000