1990-04-18_REVISION - M1977493 (4)

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6LAC K & V EAT. . n s Colorado Department of Health B&V Project 6913.007 Mr. Phil Hegeman 3 April 16, 1990 Assuming all 180 dry tons per year are applied to the tailings area, approximately seven acres per year can be reclaimed at the initial loading rate of 25 dry tons per acre. Once the vegetative cover is established, about 70 acres can be maintained at the annual loading of 2.5 dry tons per acre per year. ENVIRONMENTAL CONCERNS The overall environmental objective of the Climax Mine program is to establish a vegetative cover that will stabilize the soil and prevent erosion of the tailing area until such time as the tailing area may again be used for active tailing deposition. It is recommended that a large initial application of sludge be used to enhance the soil and prepare it for seeding. Once a vegetative cover has been established, lower application rates would be used to maintain the vegetation in a healthy condition. To be truly successful, however, this goal must be achieved without ground water contamination or the release of phosphorous, heavy metals, or other potentially harmful compounds to Ten Mile Creek and Dillon Reservoir. Ground Water Protection. The primary method for protecting ground water quality will be to prevent the leaching of any liquid sludge to the ground water table. Even though the ground water table is approximately 180 feet below the surface of the tailing area, distance alone should not be the sole barrier to ground water contamination. To prevent the percolation of any sludge liquid, the initial sludge application should be uniformly spread on the surface of the soil and then mixed with the soil via scarification using a short-tooth ripper. It is suggested that scarification be performed as soon as possible after the total design sludge loading has been applied to the soil. The mixing of sludge with the drier soil will create a sludge/soil mixture that will provide an excellent environment for seed growth without the release of sludge liquid to the ground water. For example, assuming thickened sludge at 7 percent solids and soil at 50 percent solids, mixing three dry tons of soil with one dry ton of sludge (3:1 ratio) will produce a soil/sludge mixture of 20 percent solids and there will be little or no seepage from material that has a solids content of 20 percent or greater. Assuming (1) the digested sludge is thickened to 7 percent solids, and (2) various solids concentrations for the soil, Figure 4 shows the required soil/sludge mixing ratios for any desired soil/sludge mixture. Figure 4A gives the required soil/sludge mixing ratio on a dry weight basis and Figure 4B presents the ratio according to the number of cubic yards of soil that must be mixed with each dry ton of sludge to achieve the desired soil/sludge mixture. The cubic yards shown on Figure 4B are on a wet, or in-situ (as is) basis. Table 1 summarizes the data presented on Figure 4 regarding the minimum soil/sludge mixing ratios required to achieve a 20 percent mixture. As