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David Berry, Dan Hernandez, -2- February 15, 1994 <br />Harry Ranney <br />Secondly, it is clearly stated in the permit text that the so-called "contour furrows" (really <br />contour ditches) will be designed as temporary structures. Long ditches in parallel along contour <br />are not a stable, long-term configuration. Unless constructed to rigid specifications and grade <br />requirements, breaches are almost a guaranteed certainty and set off a chain reaction along the <br />fall line which destroys other ditches below. There is no detailed design plan for these ditches. <br />Rule 4.05.17 states, "before abandoning the area the operator shall renovate ponds, diversions, <br />etc., to the criteria in the detailed design plan." The contour ditches need to be removed. <br />Evaluation of Soil Erosion Analysis <br />The operator has chosen to attempt to model the sediment yield from a 10-year, 24-hour <br />precipitation event, comparing models from the reclaimed areas to the approved reference area. <br />The Division considers this a valid technique for sediment demonstrations given proper data <br />input. A number of assumptions or input data were determined to be inaccurate. A discussion <br />of those inadequacies is as follows: <br />1. The operator conducted a sieve analysis of material from the sediment trap, Pond 002 and <br />Pond 003. This site-specific information is then entered directly as a particle size <br />distribution, for which there are four for this model. The problems with this are as follows: <br />a) The particle size distribution is the eroded particle size prior to transport. Material size <br />analysis of pond sediment gives a size range after transport. Direct input of a sieve <br />analysis of pond material is inappropriate. <br />b) It is not clear when this material in the pond was analyzed. If storms exceeding the <br />10-year, 24-hour event were the cause of this material, then the analysis would be <br />invalid, regardless of the transport issue. <br />c) The consultant has inappropriately entered the percentages for the "percent finer" input <br />in the SEDCAD runs. Large particles (those exceeding 4mm1 should not be included in <br />the distribution. Remember, what needs to be entered is the eroded particle size and <br />the percent finer than 4mm as 100 percent. <br />2. The consultant chose to assume that the soil data pre-mining can be assumed equivalent to <br />the post-mining analysis. Soil information from the reference area should be collected in a <br />similar fashion as the sediment from the disturbed watershed. Setting numerous modeling <br />parameters equal in both pre-mine and post-mine conditions defeats the purpose of <br />comparison by limiting variability to a few discrete parameters. <br />Summary <br />In summary, my recommendation is to deny the Phase II Bond Release request for all areas. <br />Rule 3.03.1(3)(bl does not allow more than 60 percent of the applicable bond to be released so <br />