Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/248272
PLANT PROFILE Material can be run directly to the barge loadout from the tunnel or the additional hoppers. have three barges actively in use and one that is only used periodically. Two are sister barges, nearly identical, with just a few features that differ. Depending on water level, each will hold between 2,000 and 2,100 tons of material. The third barge holds 3,000 to 3,100 tons of material." A program in the computer tells the barge loadout operator which product is required and which feeder to run, so all he has to do is punch a button and make small adjustments. The operator can control the flow of the material if the wind is blowing. A series of cables running along the dock attach to the vents on the barge, allowing the loadout operator to pull the barge back and forth during the loading process. The plant employs three tug boat companies to push its barges. All of the barges are self-unloading hopper barges with a conveyor that swings out to the side. When the barge arrives at its destination, material is dumped from the bottom of the hoppers onto the conveyor and is offloaded onto a series of conveyors onshore. Unique challenges The self-unloading hopper barges feature a conveyor that swings out to the side. Upon arrival at its destination, the swing-out conveyor feeds the material onto a series of onshore conveyors. tunnel system is also used for blending. Seventeen feeders allow the operation to blend different materials to produce an assortment of products. "The crushing plant produces four sizes of material — quarter minus, half to quarter, inch and a half to three-quarter, and threequarter to half," Northway explains. "The crushing plant has the capacity to recirculate loads, so when we're long on inch and a half, we can shut it off and recirculate it through the system." Though the operation ships some of its product by truck, a vast majority of the material leaves by barge. "Material can be run directly to the barge loadout from the tunnel or the addditional hoppers," Northway says. "We have a barge canal that comes in off the Multnomah Channel, which feeds directly out into the Columbia River system. We "There are some unique aspects to what we do here," Northway says. "For one thing, there aren't many facilities that do the majority of their mining underwater. Mining underwater with a dragline is a whole different type of operation. There's no delineation between some of the pits because it's all water." The dragline is electric, so a sub-station is located right on the property. The electric cable is a certain length, so moving the dragline from one location to another can be a bit of a challenge. During one particular move, the dragline was walked out as far as the cable would reach and was shut down. The substation was then relocated, the dragline was hooked up again, and moved the rest of the distance. Conveying wet material is also challenging. "It's not like pushing it down the side AGGREGATES MANAGER February 2014 33