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Granite Rock Company
Logan Quarry Plant Renovation and Fines Handling
Aromas, California
 Roberts
& Schaefer provided engineering, procurement, and construction
management for the expansion of Granite Rocks' Logan Quarry, consisting
of dry screening, tertiary crushing, wet screening, sand classification,
reclaim, blending, rinse and loadout facilities. Plant design
rates are 1,550 TPH for the dry circuit, 1,500 TPH for the wet
circuit, and an average of 2,500 TPH for the reclaim and loadout.
Fractured granite from the open pit quarry is fed to a mobile
primary crushing unit in the pit and conveyed to the plant for
further crushing, screening, and washing. Sized materials produced
in the plant are reclaimed from storage piles and blended to produce
concrete, asphalt, drain, and fill specification products.
 Material
entering the plant is screened into fine and coarse rock fractions.
Coarse rock is secondary crushed and dry screened to produce sized
materials ranging from 2 inch ballast to number 8 mesh dust. Oversize
material from the dry screening moves to a tertiary closed circuit
crushing system. Gate positioning and crusher settings adjust
production rates of the various sizes to match sales and balance
inventory. A special dry screening line provides premium "chip"
products.
Fine rock is wet screened to produce sized materials ranging
from 1 inch down to one-quarter inch. The number 8 mesh screen
underflow is classified to produce specification grade sand. Feed
from the sand circuit can be supplemented with dust from the dry
screening.
Sized material is reclaimed from product stockpiles and proportionally
blended to produce ASTM, California state, and county specification-grade
products for concrete, asphalt, road base, railroad ballast, drain
rock, and sand. Some products are rinsed across screens to remove
dust and contaminants before shipping.
Blended products are conveyed to bin compartments elevated over
truck loading lanes and a rail loading conveyor. Bin compartments
are filled sequentially on demand. Truck scales running the length
of the loadout lanes allow accurate loading.
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