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Much of the geotechnical exploration program was focused on the evaluation <br />of the strength and consolidation characteristics of the levee. Gradation test <br />results for samples of the levee indicate it is well graded and very cobbly (rocky). <br />By excavating test pits T -1 through TP-3 with a -inch diameter auger, the <br />occurrence of larger diameter particles could be examined. The cobbles were <br />closely spaced and surrounded by a matrix of dense sand and stiff clay. It was very <br />difficult to pry the cobbles loose by hand. Test pit walls in the levee stood vertically <br />after excavation by the auger and showed no tendency to care. <br />Sand core density te t and nuclear gauge tests were conducted in the three <br />large diameter test pits. Holes for sand cone tests were difficult to excavate due to <br />the extensive cobbles. The pilot hole for the nuclear gauge tests had to be <br />advanced by driving ar pointed steel rod into the ground with a sledge hammer. <br />Results of field density tests are given in Table 11. Of the 15 compaction tests two <br />of which were in the foundation soils at the bottom of the fill), percent compaction <br />ranged from 75 to 103 percent. The wide range in percent compaction and <br />particularly the lower results are believed to be due to error caused by the cobbles <br />interfering with proper test conduct. Effort required to dig the sand cone holes and <br />drive the pilot hole for the nuclear gauge are evidence that the levee is well <br />compacted. <br />Based on field testing, observed characteristics of the levee and its <br />resistance to penetration, the levee is judged to be well compacted. Field <br />compaction tests were given less weight in this judgment because the levee fill is <br />practically untestable due to the concentration of large diameter particles. The <br />Colorado Department of Transportation (CDOT) considers a material as `rock fill" <br />and "not testable" if it contains 50 percent or more particles of 114 -inch size or <br />larger. Samples of the levee contained up to 45 percent retained on the No. 4 <br />sieve. cobble size particles were scalped from these gradation test samples. <br />Adjustment of the gradation tests to account for the cobble size particles would <br />indicate the samples are classified as "not testable ". Review r of Fig. I attached to <br />our August 22, 1997 later in Appendix B shows for an "unscalped" sample (none <br />FLATIRON COMPANIES <br />LEVEE AT DEERE FARM PIT <br />TUT 25,385 <br />