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of the material was pulverized to determine the degree to which the particles may break down under <br />various degrees of compaction. While the material in the RPE was compacted during placement <br />(sample from the SE corner of the RPE), additional compaction was simulated using a standard <br />Proctor test, after which the gradations were compared. This additional compaction resulted in the <br />percent passing the #4 sieve increasing from 52.4 to 62.6 percent and the percent passing the #200 <br />sieve ranged from 17.8 to 22.3 percent. <br />Falling head hydraulic conductivity (permeability) tests were carried out on as -received material in <br />and on pulverized material to estimate the potential impact to saturated permeability due to long term <br />compaction, weather, and other effects. The initial test was performed on material at 90 percent of <br />standard Proctor dry density with a result of 9.9x10-6 cm/s. Then, only material passing the #200 <br />sieve was tested after compacting to 90 percent of estimated maximum dry density (using maximum <br />effort), resulting in a permeability of 3.1x10-6 cm/s. This same material was then compacted using the <br />maximum effort with a result of 9.8x10-7 cm/s. It can be seen that smaller particle sizes and increased <br />compaction may reduce the permeability of the refuse material by about one order of magnitude in <br />extreme conditions. <br />Due to the material's classification as a granular material (SM), and the low likelihood that the <br />material will become saturated to an appreciable depth in the field, the drained strength envelope was <br />measured in the laboratory using the direct shear apparatus. A sample of material finer than the #200 <br />sieve was ball -milled in the lab to break the material down to very fine particles. This approach was <br />used to represent anticipated worst-case conditions that may occur when the material is compacted <br />during placement, or if it breaks down over time due to freeze -thaw cycles and other weathering <br />phenomena. The sample was then subjected to a fully -softened direct shear test. The material used in <br />the testing classified as a silt (ML) after it was processed. The resulting fully -softened shear strength <br />envelope was 33.8 degrees with an apparent cohesion of 228 psf. Although the actual failure <br />envelope is non-linear, this linear approximation was used in the analysis for ease of computation. <br />Subsequent laboratory testing has shown that the refuse material produced by the CPP has changed <br />very little over time. Index testing such as moisture content, Atterberg limits, grain size (sieve and <br />hydrometer), and organic content was conducted on three rounds of samples. Standard Proctor testing <br />was also performed for each round of samples. To determine the shear strength of the refuse, direct <br />7 <br />P:\Mpls\06 CO\26\06261003 MCC Refuse Pile Site Review & Permit\WorkFiles\Permit Application\2014 Revision\Exhibit 82 2014-05- <br />29.docx <br />