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<br />• Drain Systems <br />Drains are recommended at the base of all fills. Where multiple existing <br />drainages are present, then multiple branching drains will be required. The size of <br />the drains can vary. Drain sizes are specified by CDMG regulations for fills which <br />classify as Valley Fills. As discussed in the previous section PROPOSED DISPOSAL <br />AREAS, nine of the fills will likely classify as Valley Fills. As many as 16 of the 21 <br />fills could classify as Valley Fills depending on evaluation of more precise plans, and <br />CDMG interpretation of borderline conditions. Specifications for Valley Fill drains are <br />shown on Fig. 5. The regulations require a minimum height and width, resulting in <br />a minimum drain area. <br />For fills which do not classify as Valley Fills, smaller drain systems are <br />considered feasible (Fig. 5). The fill area, volume and drain configuration will need <br />to be reviewed on a case-by-case basis to confirm the required drain size and <br />gradation. For preliminary planning purposes triangular drains on the order of 3 to <br />• 8 feet in height with a base width of 6 to 16 feet are considered feasible. For the <br />smaller drains, smaller rock sizes will be necessary. For the 3 to 6-foot high drains, <br />rock sizes of 1-inch to 2 feet are considered appropriate. <br />The drain size selected will depend on conditions at each fill. If desired <br />because drain rock is readily available, the large Valley Fill drains can be used <br />without additional analysis for all Valley-like fills. Conversely, if suitable drain rock <br />is difficult to produce, then additional analysis can be performed for each fill to <br />attempt to justify smaller drains. We believe additional analysis will show that <br />smaller drains are appropriate even for fills which classify as Valley Fills. The use <br />of smaller drains will need to be approved by CDMG. <br />Considering the difficulty of generating filter material, we believe the use of <br />filter fabric will be a more practical choice. For the low gradient, intermittent types <br />of flows anticipated into the drains we believe filter fabric will perform satisfactorily. <br />. Filter fabric should be Mirafi 140 or equivalent. <br />LORENCITO COAL COMPANY <br />cTLR zs,zsi 13 <br />