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<br />M-2000-158 TR Memo 5 May 17.2001 <br />maximum length far the working face, over and above the 500 foot commitment for final pit perimeters, and this <br />length plus the 500 feet should be used to determine the bond to be required for pit slope armoring. <br />The Division will require, in accordance with the language of the TR, that no more than 500 linear feet of erosion <br />sensitive final pit perimeter be exposed without armoring at any one time during the life of the mine. Further, the <br />Division suggests that the Operator make every reasonable effort to complete final lakeshore protection measures <br />for all such areas prior to April 1" of each year. (Lakeshore sensitive areas are those areas depicted in green on <br />the map included with the TR. The Division considers April I° to be the approximate onset of snowmelt flood <br />season on the South Platte). A cost for lakeshore armoring per linear foot is developed here, and may be applied <br />to the maximum length ofthe working face, plus 500 feet of unreclaimed pit perimeter, that will be committed to <br />by the Applicant. <br />/ Cost of riprap at the quarry: $10.50 per short ton. <br />/ Pit bank riprap required, per linear foot: 6 tons (d¢rived by ratio: Ajeet thick required in Divislotr guidance <br />compared to Applicant's proposed 3 foot thickness and a.5 tons per linear foot). <br />/ Approximate haul distance from Jefferson County riprap quarties to pit: 60 miles. <br />/ Hauling cost $i/mile @ 120 miles @ 15 tons per load: $8.00 per ton. <br />/ Installation cost of riprap: $I.00 per ton. <br />/ Riprap bedding @ I.5 tons per linear foot, cost: $3.50 per ton. <br />/ Bedding haul cost, assume source could be found within 10 miles, $I/mite @ 20 miles @ IO tons/load: <br />$2.OOton. <br />[$10.5/Tx6T//j]+[$8lTx6T/ f]+[$1/Tx6Tllj]+[$3.5/Tx1.5Tllj]+[$2/TxI.STIIf] <br />_ $125.25 per linear foot <br />As it turns out, this per linear foot cost will not be adequate to assure stable armoring of the lakeshores. <br />Additional armoring requirements are discussed in the next section, and another estimate of the cost per linear <br />foot is developed incorporating the additional requirements. The cost developed in the next section will be used <br />by the Division for bonding purposes unless the Applicant can providejustification for a lower cost. <br />Timetable jot Riprap Installation <br />The Applicant states in the TR that any armoring of the riverbank will be optional. It is the Division's position <br />that riverbank armor is required prior to mining for any portion of river bank where mining will occur within 400 <br />feet of the riverbank (DMG, 1998, page D-6, copy attached). However, the Division may waive this requirement <br />for those portions of riverbank that are currently stable, and are characterized by gentle bank slopes and well <br />established riparian vegetation. Prior to installing riprap into areas of cut bank, the bank must be graded to no <br />steeper than 2.5:1 and granular bedding and filter subgrade must be in place (DMG, 1998, figure D-S, copy <br />attached). Since the Applicant will be required to armor bank areas prior to mining within 400 feet, there is no <br />need to bond for the riverbank riprap installations. This is because the permit requirements will dictate that the <br />riprap be in place before it is actually needed. <br />The Division has reservations about the Applicant's proposal to_install the_pit slope_riprar onto the I:I min_ed_ <br />slopes, then fill and grade over the riprap to establish the finished 3:1 grade. The Division's guidance states that <br />side slopes for riprapped banks should be no steeper than 2.5:1 (DMG, 1998, p. D-3, copy attached). If the riprap <br />