Wednesday, May 8, 2002
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Wednesday, May 8, 2002 |
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Why 'pump and pile'? Seek alternate methods Did you know that 22,000 cubic yards of silt will cover one acre of land to a height of 13 feet? I'm commenting on your May 1 article about Lake Peachtree dredging andthe statement by Jim Mallet,"We need an acre or so to pump this stuff out (silt) and let it dry out ... It's not going to look pretty." These remarks seem to indicate that Mr. Mallet and the county water department are still not considering all alternative methods. What about a mechanical clamshell bucket technique from a barge? The advantage of this method is that dredged silt can be loaded into transport barges then unloaded into lined trucks and hauled to a final disposal area. It's extremely cost efficient because dredging costs are calculated by the amount of cubic yards removed, not by an hourly dollar cost as charged by many "pumping" companies. Piling it up and letting it dry out may be a great way to do it on extremely large river projects where there is a lot more maneuverability with conventional pumping equipment, but not necessarily in Lake Peachtree. This project has delayed because of decisions about what to do with the silt. The silt removal method I'm referring to minimizes disturbance to the lake shore and surrounding property because it only requires one access point to the lake and silt is then hauled away. This type of dredging has been used on all the lakes of Callaway Gardens, the large lake at Stone Mountain, Lake Lanier for the city of Atlanta, St. Ives Country Club lakes in Duluth, and more recently, the city of Palmetto reservoir. As with Lake Peachtree there was no suitable place to pile up the silt and let it dry out. There was no "pump this stuff out and let it dry out" situation. For your reference, the Palmetto reservoir dredging cost was $200,000 to remove and haul off 10,000 cubic yards. So, it's reasonable to expect that the cost for Lake Peachtree should be under $500,000. Finding a solution to this dredging process seems to be a colossal undertaking between the Water Department and Peachtree City. In my opinion, with a little more research as was done by the Palmetto City engineers, we wouldn't have all this continuing endless discussion. The one bright spot about this ongoing process is that the county has considered an alternative method to dredging. The $1.4 million spent in 1986 to drain and excavate thousands of cubic yards of silt from one end of Lake Peachtree to build an island, which in itself displaces a significant amount of usable water, was a complete debacle. Finally, Peachtree City has to be careful if they do decide to "pile" up the silt next to City Hall. You shouldn't put it on a flood plain, and, you can't place the fill in any surrounding wetland areas as this would violate Section 404 of the Clean Water Act. Scott Powell Peachtree City rspnhp@bellsouth.net
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