Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/891178
16 AGGREGATES MANAGER / November 2017 Analyze the site and test reserves A s it becomes more diffi cult to permit additional land to open up greenfi eld projects, sand and gravel and aggregates operations are increasingly making the decision to dredge deeper. In the last 10 years, companies have discovered they have deeper reserves in areas they have already mined, explains Bob Wetta, president and CEO of Reserve, La.-based DSC Dredge. CalPortland now has a dredge designed for a depth of 155 feet and Vulcan Materials has a dredge in Florida that was designed to and has achieved 200 feet, although this is atypical. So how does a producer determine whether to abandon an existing site and move to a new location or dig deeper? There are obvious costs to starting up a new oper- ation such as stripping overburden, bringing in utilities, and moving or purchasing new equipment, Wetta says. "If you can stay at the same site, there are several costs that have already happened that you won't have to take on again," he says. One cost, though, is critical when deciding whether to dredge deeper or fi nd a new location – geological testing, such as boring analysis and compaction testing. "Think long term, educate yourself, and develop a mine plan," Wetta advises. "Don't be afraid of testing. It could be the cheapest information you ever pay for so you don't spend money on something that won't work. "You could have a great-looking dredge that can produce material, but you'll have a really expensive water pump, if you can't dig it," Wetta says. "If you can double the life of the deposit, you don't have to look for new land, but you want to make sure you don't put the dredge in a spot where it has to be moved several times and end up mining around the material instead of mining the material." J. (Jos) Clement, director of technical services for CEDA Dredging & Fluid Management in the Edmonton, AB, Canada offi ce, notes that producers/dredging contractors need to carefully examine all physical conditions and process requirements to ensure they have the correct equipment confi gurations for a deep excavation application. "You can potentially undersize and/or oversize sections that may ef- fectively destroy the viability of the dredge," Clement says. "The deeper you go, the more complicated it becomes. You can't afford to overlook the details." Seals on an underwater pump are one example. If the bearing housing seals are not correct and proper lube pressure is not applied, the seals will be destroyed in short order, Clement says. "Then lubricant is lost, putting the bearings at risk," he says. "All of a sudden, you are contam- inating the water because you are losing oil. Little things like this must be taken into account." Bob Woodington, owner and manager of Phoenix Pinelands Corp., says, if a producer is going to buy a new dredge and take it to depths such as 125 feet, it's absolutely critical that it's being purchased from a manufacturer who establishes a relationship beyond selling the equipment. "Good manufacturers have real experience in the fi eld – someone who has actually been out there and dredged," he says, "not just someone who just sits behind a desk and designs things." Mining in deep water may increase deposit life, but requires signifi cant planning and testing. Before taking the plunge to dredge deeper, conduct a boring analysis and compaction test to see if there are additional reserves available and the size and type of material that would be mined. Even if mate- rial is available, it's possible that it is too compact to dig up. A mine plan should also be developed prior to starting production for maximum effi ciency. This will help ensure a dredge doesn't need to be moved several times and is actually mining the material instead of mining around it. 1