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VALUE ENGINEERING PROPOSAL NO 2

PROJECT: Black Rock Dam

COMPONENT: Outlet Works

Tower

FUNCTION: Control Water

ORIGINAL CONCEPT

VE CONCEPT

! Excavate the silt around the

existing tower at a 6(H):1(V) slope

to about a 40-foot depth.

! Remove existing tower and

replace with new two bay tower,

using existing pile foundation. Use

36-inch gates and tie into relined

pipe.

! Backfill silt around tower.

Notes:

! No estimate was included for

dewatering. Dewatering for this

concept may be necessary.

! The wood piles in the existing

foundation may have reached the end

of their useful life. If this concept is

carried to further design stages,

further study will be required.

! Insert a temporary bulkhead in existing outlet pipe

to prevent inflow of silt.

Simultaneously place 10-foot diameter precast

concrete caisson and excavate silt from inside

caisson.

! Break existing pipe with clamshell. Caisson will

extend pass pipe approximately 20 feet.

! At bottom of pipe elevation, jetting may be

possible to advance caisson. The other option would

possibly require excavation to bottom of caisson

elevation (20 feet below pipe elevation). If this

material is excavated out, it will need to be backfilled

after caisson installation.

! Caisson may be adequate as self-contained

foundation by using side friction or end friction; if

not, piles need to be installed inside of caisson or a

deeper caisson. Piles are included in this alternative.

! After caisson and piles are installed, install pilecap

and floor of tower. Two options: 1) without

dewatering, tremie concrete down to form a seal and

pile cap; or 2) dewater from inside or outside of

caisson, and work "in the dry." Dewatering is not

factored in the cost estimate.

IMPLEMENTATION COSTS (-)

$10,000

NET SAVINGS

$1,713,000

* CHOOSE ONE METHOD - USE NONRECURRING IF LIFE CYCLE COSTING DOES NOT

APPLY.

VEPROP.TAB