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5.5.3 The medium riprap size (D501 shall be as designated on the <br />Drawings. The minimum rock fragment size shall be 1-inch, and <br />the maximum size shall be approximately 1.75 times the D50 size. <br />The following table lists the approximate riprap gradation limits. <br />Riprao - D50 Size <br />Percent Smaller by Weight <br />Rock Size 10-inch <br />15-inch 100 <br />12-inch 70-100 <br />10-inch 50-70 <br />6-inch 35-50 <br />4-inch 2-10 <br />2-inch --- <br />5.5.4 Cobble material stockpiled in the Henderson Gravel Pit will require <br />processing by the contractor to meet the gradation requirements <br />stated above. Minimum riprap thickness shall be 1.75 times the <br />DSO rock size. <br />5.6 LEAN CONCRETE FILL <br />5.6.1 Lean concrete fill may be required as a filler material where <br />foundation conditions for pipes or structures are deemed unaccept- <br />able by the Engineer. <br />5.6.2 Lean concrete fill shall be batched concrete with a minimum 28-day <br />strength of 1,500 psi. Type V Sulfate Resistant cement or an <br />approved sulfate resistant alternate shall be used in the concrete <br />mixture. <br />5.6.3 The hatching, mixing, and placing procedures set forth in Specifica- <br />tion B Concrete shall generally apply to the placement of lean <br />concrete fill. <br />5.7 GEOTEXTILE FILTER FABRIC <br />5.7.1 Geotextile fabrics used as an underlayment for riprap and for <br />enveloping drain material shall be non-woven style synthetic fabric <br />with physical properties equivalent to Mirifi 180N. <br />SPEC. A -EARTHWORK <br />PAGE 7 <br />