Howard Hanson Dam Update

Seattle District U.S. Army Corps of Engineers

US Army Corps of Engineers

BUILDING STRONG® Howard Hanson Dam

Green River Landslide Debris

Existing Grout Small Depression Drainage Curtain Location Tunnel Spillway

Big Depression Location Sand and Gravel Blanket

Flood Control Eagle Gorge Tower Reservoir

Fish Passage Facility Excavation

BUILDING STRONG® Normal Project Operations

NOV MAR JUN NOV

1206 ft

Potential flood pools of Spring ramp-up for Summer and fall flow short duration augmentation augmentation

1167 ft

1075 ft

Pool elevation in feet above sea level

BUILDING STRONG® Grout Curtain Construction

BUILDING STRONG® Grout Curtain Construction

Landslide Materials Grouting Operations • Boulders • Drill casing • Primary Grout • Secondary Grout • Ancient Silt layer

Bedrock Lower Aquifer

BUILDING STRONG® Drainage Tunnel Improvement Construction

BUILDING STRONG® Green River Valley

. Blue and Purple shading is the FEMA mapped floodplain.

BUILDING STRONG® As of 20FEB09

US Army Corps Of Engineers Green River Levees Seattle District ID Levee Name Eligible 20 1 Tukwila, (Federal & Certified) X

2 Desimone-Briscoe School Working 19 3 Boeing X

4 Lower Russell Working

5 Upper Russell Working 18 6 Kent Shops - Narita X

7 Meyers Golf X 17 8 County Road 8 Working

9 Horseshoe Bend (Federal) X

10 Monk (abandoned) 16

11 Reddington X 15 12 Galli’s X

13 Dykstra X

14 Fenster 13 14 15 Muellen

16 Potter 11 12 17 Neeley

18 Hammakami

19 Turley 10 9 20 Loans

21 Imhoff (Not Shown)

8 1 2 7 6 Eligible 3 4 5 BUILDING STRONGIneligible® Tukwila Temporary Measures . Raise low areas using Hesco systems and supersacks to provide 13,900 cfs capacity. . Add a cut off levee . Add 3’ of freeboard to levee.

BUILDING STRONG® Kent Temporary Measures

. Raise low areas using Supersacks to provide 3,900 cfs containment. . Secondary Containment off of levees . Add 3’ Freeboard to right bank levees

BUILDING STRONG® Kent South

BUILDING STRONG® Kent North

BUILDING STRONG® Auburn Temporary Measures

•Raise low areas on the Dykstra levee to provide 13,900 cfs capacity.

•Secondary Containment using Hesco Systems to extend the Reddington Levee.

BUILDING STRONG® Green River Temporary Measures

Locations Deliveries

Hesco Super Sacks Sandbags

Auburn 10,500 100,000

Kent 21,000 500,000

Renton 11,000 250,000

Tukwila 10,500 9,000 100,000

King County 6,500 100,000

Seattle District 34,000 1,250,000

Totals 27,500 75,000 2,300,000

BUILDING STRONG®