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L <br />f <br />DRAINAGE CONTROL <br />To provide surface drainage for the closed landfill, sheet flow over <br />vegetated final cover soil will be intercepted in grass- and asphaltic <br />concrete (AC) -lined V -ditches. Sitings and details for each ditch <br />type are shown on Drawing 1 and Drawing 3, respectively. These <br />V -ditches will ultimately discharge runoff away from the landfill <br />area. <br />In the unlikely event refuse is exposed during ditch construction, the <br />ditch will be overexcavated to 5 feet below the flowline of the ditch. <br />The overexcavated area will be earthfilled by spreading suitable soils <br />in uniform layers not over 8 inches thick. Each soil layer should be <br />watered or dried as needed to bring the soil as close as practicable <br />to the optimum moisture content, and then compacted with suitable <br />equipment to at least 90 percent relative compaction (ASTM Test <br />Designation D1557-70). Excavated refuse will be disposed of at the <br />working face. <br />The final landfill cover will be graded at 5 percent minimum slope to <br />prevent ponding. The runoff velocity on the vegetated surface of the <br />final landfill will minimize erosion. However, if erosion is detect- <br />ed, the area will be stabilized immediately using temporary berms or <br />straw mulch, and runoff will be temporarily redirected around the <br />problem area. The eroded area will be returned to the original grade <br />as soon as possible, and vegetation will be re-established. This <br />system has effectively prevented most erosion problems at other dis- <br />posal sites. The drainage control facilities details are shown on <br />Drawing 3. <br />A portion of the southern landfill slope's toe is within the 100 -year <br />flood zone. This area will be covered with 3 -inch -minimum AC lining <br />to protect the area from erosion (Drawing 1). <br />LEACHATE CONTROL <br />PJ9 9390310.00D 9 <br />rmirnn Gccn.rin+ne <br />