We use a similar approach to dredge sludge from mine drainage treatment settling ponds. The settling basin has to be fairly large. Surface area is the key, and shaped right or baffled to prevent short circuiting. We use polymer blocks to help settle solids sometimes, just depends on how fast they drop out. Dewatering bags work sometimes, sometimes not so well if the solids plug the fabric or blow through. Figure pumping about 10% solids / 90% water to keep from plugging piping / hoses, but maybe get up around 15% if it moves well. Too much solids over too long a distance stalls the pump and makes for a real mess. It takes a good bit of water to move sludge, but if you have the time it can be done. We recirculate some of the pumped water to jet / hose down the solids to the pump intake (we're using large hydraulic powered submersible pumps hung off cranes and diesel shore power units, same idea, but larger scale). Some of the submersible pumps we rent have a nozzle setup using some of the water to continuously blast the sludge around the pump intake - potholing. Hope that helps. Dale
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