February 1, 2014
CalPortland’s Santosh Aggregate Plant continues to scoop up profits in Oregon, one dragline bucket at a time.
By Kerry Clines, Contributing Editor
Northwest of Portland, Ore., in the small town of Scappoose, is an area along the Columbia River that is situated adjacent to the Multnomah Channel. This area is rich with deposits of sand and gravel ideal for construction use. It is also the location of CalPortland’s Santosh Aggregate Plant, a sand and gravel operation that has managed to stay very busy during the last few years while other operations were struggling to stay afloat.
There are several theories about where the deposits of material in the area came from, but the predominant theory is that it was originally deposited by the Missoula Floods, a series of floods that occurred over a period of 50 to 60 years at the end of the last ice age. The theory suggests that the floods were the result of sudden breaks in the ice dam of Lake Missoula, a large prehistoric glacial lake formed when the southernmost edge of the Cordilleran Ice Sheet blocked the flow of the Clark Fork River in Idaho.
The lake, which covered much of the western part of Montana and the panhandle of Idaho, was 3,000 square miles in size and contained approximately 500 cubic miles of water, about half the water volume of Lake Michigan. During each flood, it is believed that the peak flow rate of the water was as much as 15 cubic miles per hour, and that it traveled at a speed of up to 80 miles per hour. The flood would pick up sediment, loess, and basalt found in Montana and Idaho and deposit them along the Columbia River Gorge in Oregon and Washington and throughout the surrounding valleys as it rushed toward the ocean.
“This facility has been around since the 1960s,” says Gene Northway, plant manager. The operation originally used a clamshell dredge to mine the area, but it wasn’t very successful. Other types of mining techniques were also tried — yarders, sourman buckets, and long-hoe excavators — but none were very successful, so the decision was made to use a dragline.
“In the ’90s, we purchased a used Marion dragline with a 16-yard bucket,” Northway says. “By dragline standards, it’s kind of mid-sized. It makes the small ones look tiny and the big ones look huge. The dragline allowed us to complete a lot of the mining out there that we hadn’t been able to do before.”
A big part of the machine’s time is spent doing preparation work. The dragline excavates the overburden, most of which is underwater, down to gravel. Then it excavates the gravel and places it where the overburden came out to create a bench area so that the dragline can move to that spot to dig. The rest of the machine’s time is spent digging production rock.
The dragline has a hoist cable and a drag cable. The operator swings the bucket out with the teeth of the bucket facing downward and drops it into the water. Once it hits the bottom, the operator pulls on the bucket to fill it up. When the bucket is full, the operator pulls it in until it is fairly close to the shore. Then he lifts it out of the water and dumps the material into a spoil pile. A front-end loader scoops up the material from the pile and loads it into the haul trucks, which carry it to a belt feeder. The belt feeder feeds the material onto a 48-inch-wide, 4,500-foot-long overland conveyor, where it dumps the material onto another 1,200-foot-long conveyor, and then another 2,200-foot-long conveyor. The conveyor system eventually carries the material to a portable processing plant that has been set up in a permanent location.
The processing plant has a 6 x16 vibratory screen and a jaw crusher. Larger material is sized through the screen and moved to a stockpile area. There, it is either stockpiled or sent on to a tunnel where it goes up a series of conveyors to a screening tower. The screening tower has two screens — a 7×20 JCI and a 7×20 Telsmith.
At this point, concrete aggregate is pulled out, and sand is filtered through a sump at the bottom of the tower and pumped through a tunnel that goes underneath all of the stockpiles. The sand is pumped through an HDPE sand line that runs out to an underground sand classifier system. At the classifier, the concrete sand can be blended with other products. The 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 three-quarter 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 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.
“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 of a slope with a dozer or picking up dry material and throwing it in a hopper,” Northway says. “All of the material comes up wet on the conveyors. Plus, it rains nine to 10 months out of the year, so we have to work with wet material all the time. It’s like trying to convey water at times.”
“We’ve actually been very fortunate during the economic downturn, particularly over the last three years, to have a fair amount of work out of this facility,” Northway says. “We’re supplying the lion’s share of the concrete aggregate for a large project in Hillsboro.”
There has also been quite a bit of work going on at the Portland airport. The Santosh plant specializes in that type of work and has been supplying rock to the airport for both asphalt and concrete paving.
Northway says they will eventually go back to using a dredge at the plant, but it will be a cutter-head dredge rather than the clamshell dredge that was originally used at the plant. The dragline can only reach a certain depth, which isn’t as deep as the operation’s permitted depth of 150 feet. But for now, all of the prep work and digging is done with the dragline.
Cat 992D wheel loader
Cat 988F wheel loaders (2)
Cat 988G wheel loader
John Deere 450 excavator
Cat D400 haul trucks (2)
John Deere 300D haul truck
Cat 980H wheel loader
Cat 1T 24F wheel loader
Marion 7450 dragline
Cat D9T dozer
Cat D8N dozer
John Deere 770B motor grader
Telsmith 57 cone crushers (2)
Universal 3042 jaw crusher
ISC 82 vertical shaft impact crusher
JCI 8×20 horizontal screens (4)
JCI 7×20 horizontal screen
Telsmith 7×20 incline screen
Cedarapids 6×20 incline screen
Simplicity 8×20 incline screen
Simplicity 6×16 incline screen
JCI 6×16 incline screen
48-inch overland conveyor (8,200 feet)
150-foot radial stackers (3)