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• drainage of the road surface; dip spacing will be sufficient to minimize erosion of the <br />road surface. Insloped dips will discharge either into a culvert or drop inlet. <br />Outslope dips will discharge either onto natural ground or onto embankments if adequate <br />surface protection is provided to minimize erosion. <br />The road surface will be sloped as sufficient to prevent ponding of water and erosion of <br />the road surface. <br />Culverts and Bridges. Culverts with an end area of 35 square feet or less will be <br />designed to safely pass the 10-yea r, 24-hour precipitation event without a head of water <br />at the entrance unless suitable protection against erosion or fill saturation is in place <br />et the entrance and exit of the culvert. Culverts with an end area of greater than 35 <br />square feet, and bridges with spans of 30 feet or less will be designed to safely pass <br />the 20-year, 24-hour precipitation event. Bridges with spans of more than 30 feet will <br />be designed to safely pass the 100-year, 24-hour precipitation event or a larger event as <br />specified by the Division. <br />• Culverts will be designed, constructed and maintained to sustain the vertical soil <br />pressure, the passive resistance of the foundation, and the weight of vehicles to be used. <br />Drainage pipes and culverts will be constructed to avoid plugging or collapse and erosion <br />at inlets and outlets. <br />Trash racks end debris basins will be installed in the drainage area wherever debris from <br />the drainage area could impair the functions of drainage end sediment control structures. <br />Culverts will be installed to accommodate flow from small intersecting drainages end from <br />road surface drainage as necessary to control erosion. Design for culverts will be in <br />accordance with 4.03.2(4)(e) except where alternative specifications are utilized. <br />Alternative specifications may be utilized upon approval by the Division after a finding <br />that such specif itet ions will not result in an increase in erosion. Such findings will <br />be based on a demonstration by the applicant based at a minimum on consideration of <br />precipitation rates, percent of grade end soil properties appropriate to the site. <br />• culverts may be designed to carry less than the peak runoff from a 10-year, 24-hour <br />precipitation event if the ditch will not overtop and will remain stable. Culverts viii <br />13 <br />